Preparation and Characterization of Pd Modified Nanofiber...

Research ArticlePreparation and Characterization of Pd ModifiedTiO2 Nanofiber Catalyst for CarbonndashCarbon CouplingHeck Reaction

Leah O Nyangasi12 DicksonM Andala3 Charles O Onindo1 Jane C Ngila4

Banothile C E Makhubela5 and Eric M Ngigi4

1Chemistry Department Kenyatta University PO Box 43844-00100 Nairobi Kenya2Natural Science Department Catholic University of Eastern Africa PO Box 62157-00200 Nairobi Kenya3Chemistry Department Multimedia University of Kenya PO Box 30305-00100 Nairobi Kenya4Department of Applied Chemistry University of Johannesburg PO Box 17011 Corner Beit and Nind StreetDoornfontein Johannesburg 2028 South Africa5Department of Chemistry University of Johannesburg PO Box 17011 Kingsway Campus Auckland Park 2006 South Africa

Correspondence should be addressed to Leah O Nyangasi lnyangasigmailcom

Received 27 June 2017 Revised 12 September 2017 Accepted 12 October 2017 Published 9 November 2017

Academic Editor Sherine Obare

Copyright copy 2017 Leah O Nyangasi et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

TiO2fibers were prepared through electrospinning of polymethylmethacrylate (PMMA) and titanium isopropoxide (TIP) solution

followed by calcination of fibers in air at 500∘C Cetyltrimethylammonium bromide (CTAB) protected palladium nanoparticles(Pd NPs) prepared through reduction method were successfully adsorbed on the TiO

2nanofibers (NF) Combined studies of

X-ray diffraction (XRD) scanning electron microscope (SEM) and transmission electron microscope (TEM) indicated that thesynthesized PdTiO

2had anatase BET indicated that the synthesized TiO

2and PdTiO

2had a surface area of 534 and 434m2g

respectivelyThe activity and selectivity of 1mol PdTiO2in the Heck reaction have been investigated towards theMizoroki-Heck

carbonndashcarbon cross-coupling of bromobenzene (ArBr) and styrene Temperature time solvent and base were optimized andcatalyst was recycled thrice 1H NMR and 13C NMR indicated that stilbene a known compound from literature was obtained invarious Heck reactions at temperatures between 100∘C and 140∘C but the recyclability was limited due to some palladium leachingand catalyst poisoning which probably arose from some residual carbon from the polymer The catalyst was found to be highlyactive under air atmosphere with reaction temperatures up to 140∘C Optimized reaction condition resulted in 897 conversionswith a TON of 19934 and TOF value of 3322 hrminus1

1 Introduction

The Heck coupling reaction (HR) is a single operational stepreaction involving an aryl halide and an olefin (Scheme 1)in the presence of palladium catalyst a solvent and a baseHR can be used to produce fine chemicals such as deter-gents plastics pharmaceuticals and polymers [1ndash4] Theherbicide Prosulfuron the sunscreen agent 2-ethylhexylp-methoxycinnamate and Naproxen antiasthma agentSingulair are examples of compounds that have beenproduced on large scale [1] 1ndash5mole palladium species has

commonly been used in homogenous system with palladiumbeing generated by Pd2+ salts with ligands such as ClminusPPh3 dba N-heterocyclic carbenes [5 6] phosphorus andor

oxygen based ligands [1 7] thiosemicarbazones [7] andbis(thio)urea ligands [8] in the presence of organic andorinorganic bases for neutralization of the reaction

Homogenous catalysis efficiency has been limited byformation of black palladium precipitate unstable catalystsnonrecyclability of the catalyst and use of expensive andhazardous reagents all leading to low percentage yields [1 25 8] To help address the problem of recovery and recycling

HindawiJournal of NanomaterialsVolume 2017 Article ID 8290892 13 pageshttpsdoiorg10115520178290892

2 Journal of Nanomaterials

A+ +B

X

A

+

A

+

R Rcis or trans

Pd

Terminal product

Internal productA Ph OR COOR CON２

CN

R H alkyl CO２COH N2 Halide (o p m)

（+８

minus

X Halide OS2C3 COCＦ2

B －23 MOAc (M alkali metal) ＋3０4 ２3

Scheme 1 General Heck reaction

of the catalyst different support materials have been and arestill being investigated The most attractive is Pd on carbonor carbon nanotubes [9ndash11] Pd on metal oxide such as MgOAl2O3 ZnO ZrO

2 and TiO

2[5 12ndash15] Pd on zeolites [16]

Pd encapsulated in large organic structures (dendrimers) [17]and Pd on block copolymer micelles [18] The supports tendto arrest Pd on the surface of a solid material or in an organicmatrix making it possible to stabilize the catalytically activepalladium species and prevent sintering

Metal oxides have become the most lucrative Pd supportsfor heterogeneous catalysis due to their availability lowproduction costs and photoinduced electron hole pairs onthe surfaces ofmetal oxidewhich can be harvested to enhanceelectron transfer and their chemical reactivity [22 23] Thefirst paper on heterogenousHeck catalysis of Pd supported onan inorganic support was reported in 1990 [19 21] reportingthe coupling of chlorobenzene and styrene in the presence ofPdMgOmethanol solvent and sodiumcarbonate as a base at150∘C Several other reports have since beenmade and Table 1summarizes the literature on metal oxide support and Heckreaction

Titania a semiconductor has attracted more researchinterest due to its large band gap sim30ndash32 eV From litera-ture PdTiO

2catalyst for HR was previously prepared by

impregnation of Titania followed by hydrogen reduction ofpalladium precursor In 2011 Obuya and coworkers photo-deposited Pd NPs of diameters within 2ndash5 nm on electrospunTiO2NF In 2014 Nasrollahzadeh and his group dispersed

40 nm PdNPs on commercial TiO2using simple drop drying

process The catalyst was used in ArI-styrene system at 140∘Cfor 10 h In a different method Li and his team synthesizedPdTiO

2through adsorption method by pH control and

applied it in the Heck system of and methyl acrylate inthe presence of 01ndash05 PdTiO

2catalyst and KOAc base

and DMA solvent [12] Generally the reported results bythe separate groups showed variation in products yield Thiscould probably be attributed to variation in bases and solventsused percentage mole of palladium and the method ofpreparing the support The method of synthesizing Pd NPsfor C-C coupling reactions has also remained an area ofinterest [5]

This paper reports a simple and inexpensive method forpreparation of heterogenous and reusable PdTiO

2through

electrospinning to produce high surface area fibers followedby palladium deposition-reduction The efficiency of thesynthesized catalyst was evaluated in a styrene-ArBr modelHeck C-C coupling reaction

2 Experimental Methods

21 Materials The synthesis and reactions were carriedout using commercially available reagents Poly methylmethacrylate (PMMA) Mw 996000 by GPC crystallinetitanium isopropoxide (TIP) sodium acetate (NaOAc) bro-mobenzene (ArBr) styrene (990) hydrazine monohydrate(N2H464-65 reagent grade (98) palladium acetylace-

tonate (Pd(acac)2) (999) dimethyl formamide (DMF)

ethanol 998 and methyl acrylate (99) were purchasedfrom Sigma and Aldrich Anhydrous sodium carbonate(Na2CO3) 995 was purchased from Promark Chemicals

Cetyltrimethylammoniumbromide (CTAB)Molecular Biol-ogy Grade (990) was purchased from Calbiochem Allchemicals were used without any further purification

22 Structural Characterizations of Catalyst The morphol-ogy of the nanoparticles of TiO

2and PdTiO

2was observed

using a scanning electron microscope (SEM Tescan Japan)at an accelerated voltage of 20 kV Prior to scanning byelectron microscope the samples were sputter-coated withcarbon using a Jeol JFC-1200 fine coater Elemental analysisor chemical characterization was done by X-ray powderdiffractometer (XRD PANalytical X-Pert diffractometer withCu-K120572 radiation 154060 A PANalytical BV Netherlands)BrunauerminusEmmettminusTeller (BET) surface areas of the pow-ders were determined by nitrogen adsorption atminus196∘C in therange of a relative pressure 1198751198750 from 005 to 1 Samples weredegaussed at 120∘C for 7 h prior to nitrogen adsorption mea-surements The surface area and pore size were analyzed onmicromeritics ASAP 2020 The pore size distributions wereobtained from the desorption branch of the isotherm usingthe Barret-Joyner-Halenda (BJH) procedure TEM imageswere taken using JOEL JEM 2100 Transmission EmissionMicroscope (TEM) The samples were sonicated in ethanolplaced on a copper grid and left in the air for the solventto evaporate IR spectra were recorded on PerkinndashElmer100 spectrophotometer FTIR series (Tokyo Japan) measuredas KBr pellets (1 10 sampleKBr) The instrument was setto scan from 400 cmminus1 to 4000 cmminus1 and the spectra wereobtained Concentrations of styrene and ArBr in the Heckreaction were determined using a Varian 3900 GC modelNetherlands with a flame ionization detector (FID) anda Megabore column (length 25m with 023mm id) Theprogramme ran from 80∘C to 240∘C at a flow of 10mL permin and a velocity of 24 cmminminus1

Journal of Nanomaterials 3

Table1Selected

Heckreactio

nof

palladium

supp

ortedon

inorganico

xides

Catalyst

ArX

Alkene

Base

ArX

alkenebasePd

Molm

olm

olm

olSolvent

T ∘ CTime

hYield

Selectivity

Ref

Reg

Chem

oPd

MgO

ArC

lStyrene

Na 2CO3

710

332times10minus4

Methano

l150

532

42[19

]

PdA

l 2O3606

4-Nitrob

enzoyl

chlorid

eVBA

Et3N

121225times10minus3

Dioxane

100

471

1039

[20]

PdSiO212

24-Nitrob

enzoyl

chlorid

eVBA

rEt3N

121225times10minus3

Dioxane

100

451

1032

[20]

PdA

l 2O35

ArI

Acrylonitrile

Et3N

111

1times10minus2

Aceton

itrile

140

1472

33

20[21]

PdM

gO5

ArI

Acrylonitrile

Et3N

111

1times10minus2

Aceton

itrile

140

1478

35

10[21]

PdM

gO5

ArBr

Styrene

NaO

Ac11

5121times

10minus3

DMA

140

20365

125

112

[14]

PdZnO

45

ArBr

Styrene

NaO

Ac11

5121times

10minus3

DMA

140

20333

118

101

[14]

PdTiO243

ArBr

Styrene

NaO

Ac11

5121times

10minus3

DMA

140

20412

127

95[14

]Pd

ZrO255

ArBr

Styrene

NaO

Ac11

5121times

10minus3

DMA

140

20491

123

112

[14]

PdTiO21

ArBr

Styrene

Et3N

112210

DMF

140

2491

[13]

PdTiO2026

ArBr

Methylacrylate

KOAc

0506065times10minus1

DMA

140

2479

[12]

PdTiO25

ArI

Styrene

NaO

Ac444

66972

35times10minus2

NMP

160

90[22]

PdTiO21

ArBr

Styrene

NaO

Ac11

22times10minus2

DMF

140

6897

Thispaper

PdTiO21

ArBr

Methylacrylate

NaO

Ac11

22times10minus2

DMF

140

6806

Thispaper

Et3Ntrie

thylam

ineArBrbrom

obenzeneA

rIiod

obenzeneV

BAvinylbu

tyletherD

MAdim

ethylacetamideNMP

N-m

ethyl-2

-pyrrolid

one


1H and 13C NMR spectra were recorded on Bruker Mag-netic system 400MHz spectrometer at room temperature(298K) equipped with a 5mm BBO probe at the Universityof Johannesburg (400MHz for 1H and 100MHz for 13C)The 1H and 13C spectra were referenced internally usingthe residual CDCl

3and reported relative to the internal

standard tetramethylsilane (TMS) and chemical shift valuesgiven in ppm Inductively coupled plasma-optical emissionspectrometer (ICP-OES) Spectro Arcos (Germany) wasused to quantify the amount of Pd in the catalyst after thereaction

23 Synthesis of TiO2Nanofibers 100mgmL of PMMA in

2 3DCMDMFwasmagnetically stirred until a homogenoussolutionwas obtained TIPwas added to the polymer solutionin the ratio of 1 2 (PMMA TIP) and the mixture stirredfor 10 minutes The resulting PMMATIP solution wasthen electrospun at 18 kV and 18 cm using electrospinningequipment model Holmarcrsquos HO-NFES-040 The spun fiberswere then allowed to stand for 4 h at room temperature to dryoff the solvents and to allow the hydrolysis of titanium (IV)hydroxide Ti(OH)

4 to go to completion The dried material

was then peeled off the aluminum foil and transferred toa ceramic boat for annealing in a LindbergBlue M modelnumber TF55035C-1 furnace The fibers were annealed at500∘C for 3 h in a continuous flow of air at a ramp rate of10∘Cmin

24 Synthesis of PdTiO2Nanofibers CTAB protected and

stabilized Pd NPs were prepared by modified Brust method[24] 10 g of TIP and 11 g of CTAB were mixed with 40mLof Toluene sonicated for 20 minutes transferred to a two-neck round bottomed flask and refluxed at 40∘C for 1 h In aseparate beaker 1 of Pd(acac)

2with respect to TIP and 10 g

of CTAB were dissolved in 20mL of Toluene and sonicatedfor 30 minutes to make the precursor solution Hydrazinemonohydrate N

2H460ndash65 was added dropwise to reduce

Pd2+ to Pd0 as shown in

2Pd2+ + 4OHminus +N2H4997888rarr Pd0 +N

2+ 4H2O (1)

The mixture turned from cream yellow to cream and finallyformed a grey precipitate The precipitate was immediatelyadded to the TiO

2solution and refluxed further for 1 h at

40∘CThe mixture was then cooled to room temperature and

the sample dried overnight in an oven at 70∘CThedry samplewas then washed with ethanol water and acetone to removethe organic materials The cleaned sample was then calcinedin air at 500∘C for 3 h to obtain PdTiO

2

25 Test of the Catalytic Activity of PdTiO2 The Heck

reactions of ArBr with styrene (Scheme 2) were carried outin a carousel (Radleyrsquos UK) 12-port reaction under magneticstirring at 600 rpm

26 General Procedure for the Catalytic Tests 1 molar equiv-alent of a base with respect to ArBr was transferred to a tube

followed by 4mL solvent and 025mL of n-decane as a GCinternal standard 12mmol 138mL of styrene was addedfollowed by (10mmol 1053mL) of bromobenzene 01mL ofthe mixture was withdrawn and added to 1mL of the solventforGC-FID analysis at119879

0 PdTiO

2(005mmolwith respect

to ArBr) was added and the mixture placed on the carousel at140∘C for 6 h After completion of reaction at time 119879

6 01mL

of the crude product in 10mL of the solvent was identifiedusing GC-FID Varian CP 3900 Aliquots were removed fromthe reaction mixture with a filtering syringe and analyzedwith an Agilent gas chromatograph (GC) equipped with a 30-mtimes 032mm 025120583mfilmHP-5 capillary column and a FIDdetectorTheGC programwas as follows initial temperature100∘C dwell time 2min ramp 10∘Cminminus1 final tempera-ture 300∘C and dwell time 5min Conversion and selectivitywere represented by product distributions (=relative areaof GC signal) and GC yields (=relative area of GC-FIDsignals) referred to n-decane internal standard calibrated tothe corresponding pure compound (Δrel lt plusmn10) and hencethe percentage yield TON andTOF calculated relative to arylhalide In separate control experiments TiO

2and Pd(acac)

2

were used as catalysts

27 Purification of the Product After completion of thereaction 10mL EtOAc was added to the vessel and thecatalyst separated by simple filtration Water 3 times 15mL wasadded to the EtOAc phase and separated using a separatingfunnel The organic layer was dried under low pressureand vacuum The resulting crude product was purified bycolumn chromatography using hexane EtOAc (30 70) givingthe pure product which was analyzed by NMR spectro-scopy

28 Catalyst Optimization

Temperature Effects on Heck Reaction A temperature range of80ndash140∘C was used based on reported reaction temperaturevalues obtained from literature [5]

Base Effect on Heck Reaction Na2CO3 NaOAc KOH and

Et3N were selected for screening as they were found to be

the most commonly used bases from literature Selection of abase is necessary to ensure high turnover frequency for thecatalyst and high product yields Another experiment wascarried out in the absence of a base

Solvent Effects on Heck Reaction The olefination of ArBr withstyrene using PdTiO

2and Et

3N as base at 100∘C was used to

study the effect of various solvents DMF Toluene MeOHand EtOH were screened for the activity and selectivity inHeck reactions

Effect of Catalyst Loading The coupling of ArBr with styreneusingDMF as solvent andNaOAc as base at 140∘Cwas used tostudy the effect of various catalyst loadingThe volume of thesolvent base temperature and time were kept constant Theexperiments were repeated using 005 001 02 and 03molPd and the conversion was measured using GC-FID In thecontrol experiment no catalyst was added


+

Br

+

cis or trans

+ （+Ｌ

minusPdTi2

Ｎ3N 100∘CSolvent

Scheme 2 Heck reaction

29 Recycling and Heterogeneity of the Catalyst

Recycling After the reaction was completed the solid catalystPdTiO

2was first washed with dichloromethane to remove

organic components It was then with water to remove thebase and saltsThe catalyst was separated by centrifuging andfinally washed with acetone to remove any adsorbed organicsubstrate followed by drying at 120∘C for 4 h as reported byLi and coworkers [12 25]

Heterogeneity Test To confirm whether the reaction tookplace on the surface or it leached a hot filtration wascarried out after 1 h and the progress of reaction was furthermonitored using GC-FID up to 6 h

In an alternative method the clear filtrate was collectedin a glass vessel immediately after hot filtration with carefulevaporation to expel the organic compoundsThe sample wasthen dissolved in 3mL aqua regia diluted to 10mL and thesolution was filtered The palladium content in solution wasdetermined by ICP-OES Spectro Arcos (Germany) Multipleanalyses were applied for each sample for better accuracy

210 Percent Conversion of ArBr as Time Increases Thegeneral procedure described under Section 26 was followed2ml samples were drawn from the reaction vessel after 10 2030 40 50 60 120 180 240 300 and 360 minutes and theproduct yields were analyzed using GC-FID

3 Results and Discussion

Inspired by the reports of Obuya and her team in 2011we electrospun TiO

2NF and adsorbed Pd NPs on the

fibers Information about the surface was obtained from SEMimages shown in Figure 1

31 SEMAnalysis Figure 1(a) shows the PMMATIPNF afterelectrospinning Figure 1(b) after hydrolysis and Figure 1(c)after calcination The fibers appeared smooth and had adiameter of 350 plusmn 50 nm On calcination in air at 500∘C theNF diameters reduced to 180plusmn60 nm On adding PdNPs theSEM images revealed small spots on the fibers representingpalladium nanoparticles (Figures 1(d) and 1(e))

32 Elemental Analysis Using EDX The elemental composi-tion of the as-synthesized PdTiO

2was investigated by EDS

and elemental mappingThe presence of various well-definedpeaks of Pd oxygen (O) and Ti confirmed the formation

of PdTiO2(Figure 2(a)) The presence of the carbon peaks

could be attributed to residual organics from the incompletecombustion of PMMAduring calcination and the carbon thatwas coated on the fibers

To confirm the distribution of Pd O and Ti ions ontothe lattice surface elemental mapping of the area is shownin Figure 2(b) The analysis shows that Pd O and Ti aredistributed over the whole material which further confirmedthe formation of a moderately dispersed PdTiO

2 (yellow for

Pd and blue for TiO2)

33 Confirmation of Absence of Organic Polymer in TiO2

Nanofibers Using FTIR Figure 3 shows the FT-IR spectraof the PMMA PMMA-TIP and calcined TiO

2recorded on

PerkinndashElmer 100 spectrophotometer FTIR series (TokyoJapan)

The PMMA spectrum Figure 3(b) showed peaks at1140 cmminus1ndash1270 cmminus1 (CndashOndashC str) 1385 cmminus1 and 741 cmminus1(120572-CH

3) 836 cmminus1 (acrylate carboxyl group) and 3436 cmminus1

and 1634 cmminus1 (ndashOH str) indicating PMMAThe PMMATIP fibers Figure 3(c) showed peaks at

593 cmminus1 (TindashO str) sim987 cmminus1 (OndashO str) the sharp1443 cmminus1 (latt vibrations of TiO

2) 1627 cmminus1 OH bend for

H2O and TindashOH and 3436 and 1634 cmminus1 (H

2O and TindashOH)

indicating TiO2[26] This confirmed the presence of TIP in

PMMA Figure 3(b) shows the TiO2spectrum The removal

of PMMA during calcination was confirmed by the absenceof CH

119909bending and stretching modes and presence of TindashO

stretch at sim600 cmminus1 in the TiO2spectrum

34 TEM Analysis of PdTiO2Catalyst Further morpholog-

ical characterization of the synthesized catalyst was doneusing TEM The deposition of Pd on TiO

2was as shown in

Figure 4The surface of the NF has dark shades representing the

denser Pd NPs with estimated diameters of between 10 nmand 40 nmwhile the light shade is for the less dense TiO

2The

calcined fibers had a diameter of 180 plusmn 60 nm On zoomingin on Pd NPs at lower magnification the Pd NPs were notwell resolved A few of the Pd particles were completely insidethe NF while some others were partially inside and partiallyoutside the NF to some extent TEM images were a proof ofthe successful nucleation and particle deposition on porousTiO2surface

35 XRD Analysis Figure 5 shows the XRD pattern of thecalcined sample at 500∘C in air for 4 h ICDD database


(a) (b) (c)

Pd

Ti2 NF

(d) (e)

Figure 1 SEM images for (a) PMMA (b) PMMATIP before calcination (c) PMMATIP after calcination (d) PdTiO2at 120 kV and (e)

PdTiO2at 80 kV

Spectrum 7

TiPd

O

TiC

0 2 4 6 8 10 12 14 16 18 20

(keV)Full scale 3230cts cursor 0000

(a) (b)

Figure 2 (a) EDAX image for PdTiO2 (b) distribution of Pd O and Ti on to the lattice surface

was used to identify the phases in the sample materialThe diffraction patterns of the phase correlate well with thestandard peaks (ICDD 01-075-2547) The peaks at 253 (101)480 (200) 539 (105) and 624 (204) confirm the structureof anatase The crystal structure was tetragonal with 141amdspace group [13 27]

The average crystal size was significantly changed dueto the addition of Pd NPs The XRD reveals a Pd peak at2120579 404∘ and some PdO at 335∘ [27] Comparing TiO

2to

PdTiO2 the peak widths in PdTiO

2increased implying

particle size reduction due to formation of PdTiO2

36 BET Analysis The BET surface area calculated from themonolayer of the nitrogen gas adsorbedwas determined to be534m2g for TiO

2and 434m2g for PdTiO

2 the difference

indicating the filling up of the pores The isotherm plotsrevealed a type IV hysteresis loopwith capillary condensationoccurring in the pores Per IUPAC classification the results


Table 2 Pd-TiO2catalyzed Heck reaction of bromobenzene and styrene

Entry Base Solvent Cat (Pd mol) Temp (∘C) Time (h) Conversion(1) Et

3N Toluene 005 140 6 19

(2) Et3N MeOH 005 140 6 11

(3) Et3N EtOH 005 140 6 17

(4) Et3N DMF 005 140 6 339

(5) K2CO3

DMF 005 140 6 301(6) NaOAc DMF 005 140 6 419(7) Na

2CO3

DMF 005 140 6 273(8) NaOAc DMF 005 140 6 419(9) NaOAc DMF 01 140 6 612(10) NaOAc DMF 02 140 6 897(11) NaOAc DMF 02 100 6 563(12) NaOAc DMF 02 120 6 730(13) NaOAc DMF 02 140 6 890(14) NaOAc DMF 03 140 6 890(15) mdash DMF 02 140 6 0(16) NaOAc DMF mdash 140 6 0(17) NaOAc DMF TiO

2140 6 3

(18) NaOAc DMF Pd(acac)2

140 6 14Reaction conditions styrene (12mmol) bromobenzene (10mmole) base (10mmole) and solvent (4mL) based on average results (reaction carried out thricefor reproducibility)

OH strTindashOH

593

741836

1634

1140

1270

138598729573000

3436

1725

1443

(a)

(b)(c)

3500 3000 2500 2000 1500 1000 5004000Wavelength (cＧminus1

)

Tran

smitt

ance

()

570ndash850cＧminus1

Figure 3 IR spectra of TiO2(a) PMMA (b) and PMMATIP (c)

TiO2

gave a typical type IV isotherm Figure 6(b) The hysteresisloop suggests mesoporous structure with pore condensationat high pressure

The BJH single point pore volume was 0170926 cm3gand pore size was 127873 nm (Figure 5(a))

The porosity and total intrusion volume for the synthe-sized 1 wt PdTiO

2sample were 3452 and 017mLg A

comparison between these values and porosity (4427) andtotal intrusion volume (019mL) for TiO

2doped indicates

a decrease in porosity and total intrusion volume Thisindicates that the catalysts were mostly dispersed on thesurface of the TiO

2instead of also being embedded within

the pores of TiO2

In comparison with what was reported by Wojcieszakand his group the BET surface area obtained was much

higher Wojcieszakrsquos group prepared PdTiO2using different

methods (wet-impregnation sol-gel hydrazine reductionand reverse microemulsion) and obtained very low surfaceareas (8-9m2g) [28] Obuya and her team did apply elec-trospinning in preparing the same catalyst and obtained acatalyst with a surface area of 93m2g which was quite highcompared to the one reported in this thesis This impliedthat electrospinning is a superior method for preparing highsurface area NF The difference between the surface areaobtained by Obuya and her group and what is reported herecould have resulted from local improvisations made on theelectrospinning apparatus lack of a pump and use of glassPasteur pipettes Another reason could have been because ofPd NP preparation method and average molecular weight ofthe polymer [22]

37 Catalyst Application Coupling reaction between ArBrand styrene was chosen as a model reaction (Scheme 2)The PdTiO

2supported catalyst was prepared as described in

the experimental section and was used as-synthesized Thecatalytic data for PdTiO

2are displayed in Table 2

38 Effect of Base Et3N an organic liquid base was used

with variable solvents (Toluene MeOH EtOH and DMF)in the presence of 005 Pd loading Et

3N gave a higher

conversion [12] with DMF as the solvent (Table 2 entry(4)) This is in agreement with what is reported in literaturethe rates of reaction have been found to be faster in polaraprotic solvents (DMF) than in polar protic (MeOHH

2Oand

EtOH) and nonpolar solvents like Toluene [29]This could beattributed to the fact that polar protic solvents are favourablefor SN1 substitution reactions and hence will consume the


PdTi2 NF

Figure 4 TEM images for PdTiO2

Inte

nsity

(au

)

253

274 37

8

481

540

550

404

750

827627

689

703

335

30 40 50 60 70 80 90202 theta (degrees)

Ti2

PdTi2

Figure 5 XRD spectra for TiO2and PdTiO

2calcined samples at

500∘C

strong bases in a side reaction On the other hand polaraprotic solvents are favourable for SN2 substitution reactionsbelieved to be taking place in the proposedmechanism hencehigher product yields [22]

39 Effect of Bases Based on literature survey K2CO3

NaOAc Na2CO3 and Et

3Nbases were selected for screening

NaOAc improved yields in the presence of the polar DMF(Table 2 entry (6)) Inorganic bases recorded poor yieldsdue to relative insolubility effects of the inorganic bases inthe organic reaction matrix [13] There was no conversionachieved when the reaction was carried out in the absence ofa base This indicates that removal of base from the reactionmedia inhibits the HR mechanism It was suggested froman early point of HR mechanism that bases were needed todeprotonate the hydridopalladium complex formed at the 120573-elimination step in order to regenerate Pd(0) Li and his groupused NaOAc as a base in their experiments and obtained 78conversion [12]

310 Effect of Catalyst Loading The catalytic activity of thesystem was investigated by varying the amount of catalystIt was observed that 02mol (with respect to ArX) wassufficient for near completion giving a yield of 897 (Table 2entry (13)) The effect of TiO

2and Pd(acac)

2as individual

catalyst for the same reaction was also carried out and theresult showed formation of a coupling reaction product inlow yields (Table 2 entry (17) and entry (18)) This provesa synergistic effect of Pd and TiO

2(PdTiO

2) NPs for

enhancement of coupling yields in heterogenous system Noconversion was achieved when no catalyst was added to thereaction vessel

311 Effect of Temperature No conversion was achievedwhen the reaction was carried out at room temperaturebut as the temperature increased the reaction rate increased(Table 2 entries (11)ndash(13)) The conversion increased from563 to 890 under the same reaction time An increase intemperature was accompanied by an increase in the reactionrate due to increase in average kinetic energy of moleculesand more collisions per unit time The catalyst exhibitedstability at high reaction temperatures up to 140∘C This canbe attributed to the thermal stability of TiO

2support and

thus enhanced catalyst activity at high reaction temperaturesHomogenous Pd complexes will not be thermally stable atthese temperatures [30]

312 Catalytic Properties The synthesized PdTiO2catalyst

exhibited high activity and selectivity in the Heck reaction ofArBr with styrene (Scheme 1) E-stilbene was observed as themain product in all cases

A typical spectrum is given in Figure 6 The retentiontime of the chemical compounds in this experiment is STY(123min) ArX (135min) and stilbene (267min) (Fig-ure 7) The products were identified by GC-FID Varian 3900series

The catalyst was found to be highly active under airwith reaction temperatures up to 140∘C Optimized reactioncondition resulted in 897 conversions with a TONof 19934and TOF value of 3322 hrminus1


0 20 40 60 80

0000

0002

0004

0006

0008

0010

0012

0014

Pore diameter (nm)

Pore

vol

ume (

cＧ3gmiddotn

m)

(a)

Qua

ntity

adso

rbed

(＝Ｇ

3g

STP

)PdTi2

Ti2

02 04 06 08 1000Relative pressure (PPo)

(b)

Figure 6 (a) BJH pore volume plot (b) Nitrogen adsorptiondesorption isotherms

27527

26526

25525

24524

23523

22522

21521

20520

19519

18518

17517

16516

15515

14514

13513

125

9000085000800007500070000650006000055000500004500040000350003000025000200001500010000

50000

RT (min)

G2T6DATA

(uV

)

STY

ArX

Stilb

ene

Solv

ent

Figure 7 GC spectrum of reaction mixture

313 Heck Product Identification All the products are knowncompounds and the spectral data and melting points wereidentified by comparing with those reported in literature

314 E-Stilbene Analytical data mp 118∘C 1H NMRCDCl

3 400MHz 752 (d 3119869 = 70Hz 4H ortho-vinyl-

C6H5) 736 (t 3119869 = 75Hz 4H meta-vinyl-C

6H5) 727

(t 3119869 = 70Hz 2H para-vinyl-C6H5) 712 (s 2H CH-

vinyl) 13C NMR CDCl3 400MHz 13736 (C-vinyl-C

6H5)

12867 (meta-vinyl-C6H5) 12867 (CH-vinylic) 12761 (para-

vinyl-C6H5) 12653 (ortho-vinyl-C

6H5) C14H12-elemental

analysis Found (calc) C 9201 (9329) H 664 (671)

50 100 150 200 250 300 350 4000Time (min)

0

20

40

60

80

100

Con

vers

ion

()

PdTi2 solv

Figure 8 Product yield per given time

315 Percent Conversion of ArBr as Time Increases Timedependence of the yield under the optimized condition wasstudied The reaction of ArBr with styrene came to nearcompletion after 100 minutes (Figure 8)

The conversion was a bit slow in the first 15 minutesduring induction period after which there was a gradual risein the conversion up to about 83The conversion improvedto 897 in the second hour and remained almost the samefor the next 4 hThis implies that the conversion occurs in thefirst 60 minutes

316 Separation Recycling andReuse Generally the recycledcatalyst PdTiO

2showed high activity as in the first run


89785 80

20

Recycling

0

Con

vers

ion

2 3 41

Run

102030405060708090

100

Figure 9 Recycling and reuse of selected PdTiO2catalysts in the

Heck reaction of bromobenzene with styrene

(Figure 9) and even a slightly increased activity after tworuns

In the first cycle the coupling product was obtained witha yield of 897 After the products and residual reactantswere extracted new starting materials were added to theremnant that contained the catalyst from the first reactionAfter stirring for another 6 h at 140∘C the product yield was85 in the second cycle Similarly the third cycle affordeda yield of 80 and the subsequent fourth cycle afforded a20 yield The yield of the fourth cycle decreased greatlywhen comparing with the first cycle probably due to theconglomeration of particles and loss of the catalyst Therecycling could have also been hampered by partial structuraldamage to support and deactivation by coke deposition asalso reported by Dams and his team (Dams et al 2002)There was also observed increase in mass of the solid dueto the presence of the catalyst solid base and salt makingreproducibility difficult after every run In addition to thatwashingwithwater after separation reduced the activity of thecatalysts Filtering also leads to loss of some catalyst material

317 Pd Leaching Using Hot Filtration Test Figure 10 showsthe progress of the reaction after removal of the catalyst

There is very minimal noticeable change in the conver-sion as the reaction progresses This implied that minimal orno leaching occurred in the reaction The activity reportedin this paper could therefore be assumed to have arisen fromthe adsorbed Pd metal particles on the exterior surface of theTiO2NF with more effective filling of the pores within the

TiO2support A hot filtration test proved the heterogenous

nature of the supported catalyst and without a measurablehomogenous contribution

318 Metal Leaching and the Nature of Catalysis Table 3 givesthe results of catalyst leaching in the Heck coupling reactionof ArBr and styrene with 16 Pd at 140∘C According tothe ICP-OES analysis the Pd content of the heterogenouscatalyst was determined to be 187mmolgminus1 The solublePd amount was found to range within 19ndash25 ppm in thereaction mixture which meets the requirements of less than5 ppm residual heavy metal in product streams in the phar-maceutical industry [31] The percentage of Pd leachingPdloading was around 12 The soluble leached Pd could

Conversion before filtration ()Conversion after hot filtration ()

50 100 150 200 250 300 3500Time (minutes)

0

50

100

Con

vers

ion

()

Figure 10 Effect of removing Pd catalyst from reaction after 100minutes

Table 3 Results of catalyst leaching

Catalyst Cycles Conversion () Pd leaching (ppm)

PdTiO2

1 87 252 87 223 86 19

likely be responsible for catalysis in Heck coupling reactionof ArBr and styrene Pd leaching correlates significantlywith the progress of the reaction the nature of the startingmaterials and products solvent base and atmosphereTheseresults agree with Shmidt and Mametovarsquos observation of theoxidative attack of the halide to themetal crystallites yieldingdirectly Pd(II) in solution [32] As indicated in previousliterature reports presence of Pd(II) ions in the reactionmixture indicates the PdTiO

2catalyst is quasi-homogenous

[11]Comparable results were obtained by Nasrollahzadeh

and coworkers in 2014 Nasrollahzadehrsquos group prepared1 PdTiO

2from commercial TiO

2 Pd NPs of diameter

40 nm were dispersed on the TiO2using simple drop drying

process The catalyst was found effective in ArI (10mmol)-STY (15mmol)HR coupling using Et

3Nbase (20mmol) and

DMF solvent (4mL) at 140∘C for 24 h giving 93 conversion02 ppm Pd was leached during the reaction However thedispersion of the Pd NPs was not reported by the groupTheyalso carried their experiment under nitrogen

In this paper TiO2NF were prepared through electro-

spinning and Pd(acac)2precursor was used to deposit PdNPs

of sim12 nm on the NF through deposition-reduction methodThe catalyst was found effective in ArCl (02mmol)-STY(12mmol) HR coupling using NaOAc base (20mmol) andDMF solvent (4mL) at 140∘C for 6 h giving 897 conversion22 ppm Pd was leached during the reaction


The differences in the conversion for the experimentscould have been attributed to the differences in the basesused the atmosphere in which the experiment was carriedout the hours the reaction took the method of preparing thecatalyst the catalyst loading and moles of styrene used withrespect toArXWhile our team carried out the reaction underair Nasrollahzadehworked under nitrogen inert atmosphereThis probably hindered the recycling of the catalyst due toease in agglomeration of Pd NPs It is noted that the amountof Pd leached in our experiment was higher Less Pd wasleached in theNasrollahzadeh probably due to effective fillingof the pores in the catalyst than the one reported in this paperLastly Nasrollahzadehrsquos group allowed the reaction to run forlonger hours (24 h) allowing more time for more Pd NPs tobe reused in the mechanism

In 2011 Obuya and coworkers used photo-deposited PdNPs of diameter 2ndash5 nmon electrospunTiO

2NFof diameters

150 plusmn 50 nm The product yield was 93 at optimizedconditions and it had a TOF of 785minminus1 [22] Although ourgroup used an approach almost like the approach of Obuyaand her team the percentage conversion obtained for thecoupling of ArBr-STY in this paper was slightly lower (93versus 897)This was probably due to the catalyst preparedby Obuya and her group having TiO

2NF having a higher

surface area (93m2g versus 53m2g) and use of a phasetransfer salt during the coupling reaction Another reasoncould be the differences in Pd particle size (2ndash5 nm versus10ndash40 nm) and the distribution of Pd NP on the TiO

2NF In

this paper it was observed that the Pd NPs were not as evenlydistributed as in Obuyarsquos case

319 Mechanism Upon heating electrons from TiO2NF

are excited from the valence band into the unoccupiedconduction band and positive holes are formed in theconduction band These electrons from the conduction bandcan easily transfer to the Pd NPs surface generating electronheterogeneity at the PdTiO

2surface Thus it is reasonable

to expect the Pd sites with the energetic electrons at thePdTiO

2surface will exhibit superior catalytic activity to that

of palladium salt or TiO2aloneTheArBr is oxidatively added

to the palladium to form a coordinatively unsaturated Pdcomplexmdasha characteristic of many coupling reactions A _-complex is then formed by association with the electron richalkene leading to the formation of a new CndashC bond 120573-hydride elimination occurs to form product The catalyticactive Pd species is regenerated in the presence ofNaOAcbaseand is recycled in a similar reaction cycle

320 Heck Cross-Coupling Reaction of ArBr and MethylAcrylate The optimum conditions identified were employedin the coupling reaction of ArBr with methyl acrylate in thepresence of the synthesized catalyst PdTiO

2(see Scheme 3)

ArBr and methyl acrylate went to completion giving a conversion of 806 The product was identified as E-methylcinnamate

E-Methyl Cinnamate 1HNMR (400MHz CDCl3) 120575 763 (d

119869 = 160Hz 1H) 745 (dd 119869 = 66 30Hz 2H) 731 (dd

Br+ 2Me

2MePdTi2 140∘C

Bromobenzene Methyl acrylate Trans-methyl cinnamate

ET3N DMF

Scheme 3 Heck coupling of ArBr and methyl acrylate

119869 = 65 37Hz 2H) 718 (s 1H) 637 (d 119869 = 160Hz 1H) 374(s 3H)13C NMR (101MHz CDCl

3) 120575 16640 14385 13344

12927 12788 12705 11682 5066As seen in Table 1 Li and his coworkers are the only

group that carried out this reaction using PdTiO2 In the

2010 Li and his coworkers synthesized 01 to 05 PdTiO2by

adsorption method by pH control and applied it in the Hecksystem of ArBr and methyl acrylate in the presence of 026PdTiO

2catalyst loading in the presence of KOAc and DMA

gave 79yield of product Comparing the percent conversionfor Li and his group and our group there is only a slightincrease in percentage conversion (79 versus 806) Ourresults are in agreement with Li and his group [12]

4 Conclusions

PdTiO2

catalyst prepared by electrospinning exhibitscomparable activity and selectivity in the formation ofcarbonndashcarbon bonds by Heck reaction when comparedto similar heterogeneous HR Activated aryl bromidesshow a higher turnover at 140∘C after few hours using theheterogeneous catalysts when compared to aryl chloridesThe activity of the catalysts can somehow be correlatedwith the nature of the support and the palladium dispersionand size The catalysts can be recycled and reused withsome significant loss of activity The observed residualactivity of the homogeneous solution after separation ofthe solid catalyst is found to be dependent on the filtrationprocedure reaction condition and dispersion of the metalon the support Although there are several indications fora heterogeneous reaction mechanism the participationof resolved Pd species (colloids or complexes) cannot beexcluded

These results reveal the potential of synthesized PdTiO2

as efficient catalyst for industrial applications The couplingreactions of aryl bromides with different olefins requiredhigher temperature and extended reaction times Optimizedreaction condition resulted in 897 conversion with a TONof 19934 andTOF value of 3322 hrminus1 for ArBr-styrene systemand 79 TON 1044 and TOF 174 hrminus1 for ArBr-methylacrylate system

Themethod has the advantage of high yields eliminationof ligand and homogenous catalyst simple methodology andeasy work up The catalyst is eco-friendly and stable becauseit produces little waste and can be recovered and successfullyreused without the significant loss of activity

On atom economy it is observed that all reagents andmaterial used were incorporated into the final product Sec-ondly we worked at relatively lower temperature and ambientpressure which are both a factor for energy efficiency Finallyunnecessary derivatization was avoided


Conflicts of Interest

The authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

The authors are grateful to the NACOSTI for the STampI Grant5th CALL PhD043 University of Johannesburg (UJ)-DFCand APK for laboratory use and material characterizationAfrican-GermanNetwork of Excellence in Science (AGNES)the FederalMinistry of Education and Research (BMBF) andAlexander von Humboldt Foundation (AvH) for the grant toUJ and the Catholic University of Eastern Africa (CUEA)and Kenyatta University (KU) for offering the laboratoryspace

References

[1] J G De Vries ldquoThe Heck reaction in the production of finechemicalsrdquo Canadian Journal of Chemistry vol 79 no 5-6 pp1086ndash1092 2001

[2] R FHeck R FHeck andE-UChimistePalladiumReagents inOrganic Syntheses vol 179 Academic Press London UK 1985

[3] J Tsuji Palladium Reagents and Catalysts Wiley and Sons 1995[4] X-F Wu P Anbarasan H Neumann and M Beller ldquoFrom

noble metal to Nobel Prize palladium-catalyzed couplingreactions as key methods in organic synthesisrdquo AngewandteChemie International Edition vol 49 no 48 pp 9047ndash90502010

[5] A BiffisM Zecca andM Basato ldquoPalladiummetal catalysts inHeck C-C coupling reactionsrdquo Journal of Molecular Catalysis AChemical vol 173 no 1-2 pp 249ndash274 2001

[6] W A Herrmann ldquoN-heterocyclic carbenes A new conceptin organometallic catalysisrdquo Angewandte Chemie InternationalEdition vol 41 no 8 pp 1290ndash1309 2002

[7] R N Prabhu and R Ramesh ldquoCatalytic application of din-uclear palladium(II) bis(thiosemicarbazone) complex in theMizoroki-Heck reactionrdquo Tetrahedron Letters vol 53 no 44pp 5961ndash5965 2012

[8] W Chen R Li B Han et al ldquoThe design and synthesisof bis(thiourea) ligands and their application in Pd-catalyzedheck and suzuki reactions under aerobic conditionsrdquo EuropeanJournal of Organic Chemistry no 5 pp 1177ndash1184 2006

[9] A Corma H Garcia and A Leyva ldquoCatalytic activity of pal-ladium supported on single wall carbon nanotubes comparedto palladium supported on activated carbon study of the Heckand Suzuki couplings aerobic alcohol oxidation and selectivehydrogenationrdquo Journal of Molecular Catalysis A Chemical vol230 no 1-2 pp 97ndash105 2005

[10] I Janowska K Chizari J-H Olivier R Ziessel M J Ledouxand C Pham-Huu ldquoA new recyclable Pd catalyst supportedon vertically aligned carbon nanotubes for microwaves-assistedHeck reactionsrdquo Comptes Rendus Chimie vol 14 no 7-8 pp663ndash670 2011

[11] K Kohler R G Heidenreich J G E Krauter and J PietschldquoHighly active palladiumactivated carbon catalysts for heckreactions Correlation of activity catalyst properties and PdleachingrdquoChemistry - A European Journal vol 8 no 3 pp 622ndash631 2002

[12] Z Li J Chen W Su and M Hong ldquoA titania-supportedhighly dispersed palladium nano-catalyst generated via in situreduction for efficient Heck coupling reactionrdquo Journal ofMolecular Catalysis A Chemical vol 328 no 1-2 pp 93ndash982010

[13] M Nasrollahzadeh A Azarian A Ehsani and M Kha-laj ldquoPreparation optical properties and catalytic activity ofTiO2Pd nanoparticles as heterogeneous and reusable catalysts

for ligand-free Heck coupling reactionrdquo Journal of MolecularCatalysis A Chemical vol 394 pp 205ndash210 2014

[14] M Wagner K Kohler L Djakovitch S Weinkauf V Hagenand M Muhler ldquoHeck reactions catalyzed by oxide-supportedpalladium - Structure-activity relationshipsrdquoTopics in Catalysisvol 13 no 3 pp 319ndash326 2000

[15] L Yin and J Liebscher ldquoCarbon-carbon coupling reactionscatalyzed by heterogeneous palladium catalystsrdquo ChemicalReviews vol 107 no 1 pp 133ndash173 2007

[16] G Durgun O Aksin and L Artok ldquoPd-loaded NaY zeolite asa highly active catalyst for ligandless Suzuki-Miyaura reactionsof aryl halides at low Pd loadings under aerobic conditionsrdquoJournal of Molecular Catalysis A Chemical vol 278 no 1-2 pp189ndash199 2007

[17] J M Calatayud P Pardo and J Alarcon ldquoHydrothermal-mediated synthesis of orange Cr Sb-containing TiO2 nano-pigments with improved microstructurerdquo Dyes and Pigmentsvol 139 pp 33ndash41 2017

[18] S Ogasawara and S Kato ldquoPalladium nanoparticles capturedin microporous polymers A tailor-made catalyst for heteroge-neous carbon cross-coupling reactionsrdquo Journal of the AmericanChemical Society vol 132 no 13 pp 4608ndash4613 2010

[19] K Kaneda M Higuchi and T Imanaka ldquoHighly dispersed Pdon MgO as catalyst for activation of phenyl-chlorine bondsleading to carbon-carbon bond formationrdquo Journal ofMolecularCatalysis vol 63 no 3 pp L33ndashL36 1990

[20] R L Augustine and S T OrsquoLeary ldquoHeterogeneous catalysisin organic chemistry Part 8 The use of supported palladiumcatalysts for the Heck arylationrdquo Journal of Molecular Catalysisvol 72 no 2 pp 229ndash242 1992

[21] A Wali S Muthukumaru Pillai V K Kaushik and S SatishldquoArylation of acrylonitrile with iodobenzene over PdMgOcatalystrdquo Applied Catalysis A General vol 135 no 1 pp 83ndash931996

[22] E A Obuya W Harrigan D M Andala J Lippens T CKeane and W E Jones Jr ldquoPhotodeposited Pd nanoparticlecatalysts supported onphotoactivatedTiO2nanofibersrdquo Journalof Molecular Catalysis A Chemical vol 340 no 1-2 pp 89ndash982011

[23] S J Tauster S C Fung R T K Baker and J A HorsleyldquoStrong interactions in supported-metal catalystsrdquo Science vol211 article 4487 1981

[24] S Chen K Huang and J A Stearns ldquoAlkanethiolate-protectedpalladium nanoparticlesrdquo Chemistry of Materials vol 12 no 2pp 540ndash547 2000

[25] K KohlerMWagner and LDjakovitch ldquoSupported palladiumas catalyst for carbon-carbon bond construction (Heck reac-tion) in organic synthesisrdquo Catalysis Today vol 66 no 1 pp105ndash114 2001

[26] P Gupta C Elkins T E Long and G L Wilkes ldquoElectro-spinning of linear homopolymers of poly(methyl methacry-late) exploring relationships between fiber formation viscositymolecular weight and concentration in a good solventrdquo PolymerJournal vol 46 no 13 pp 4799ndash4810 2005


[27] B C E Makhubela A Jardine and G S Smith ldquoPd nanosizedparticles supported on chitosan and 6-deoxy-6-amino chitosanas recyclable catalysts for Suzuki-Miyaura and Heck cross-coupling reactionsrdquo Applied Catalysis A General vol 393 no1-2 pp 231ndash241 2011

[28] RWojcieszak RMateos-Blanco DHauwaert S RGCarrazanE M Gaigneaux and P Ruiz ldquoInfluence of the preparationmethod on catalytic properties of PdTiO

2catalysts in the

reaction of partial oxidation of methanolrdquo Current Catalysisvol 2 no 1 pp 27ndash34 2013

[29] L Djakovitch and K Koehler ldquoHeterogeneously catalysedHeck reaction using palladium modified zeolitesrdquo Journal ofMolecular Catalysis A Chemical vol 142 no 2 pp 275ndash2841999

[30] F Zhao K Murakami M Shirai and M Arai ldquoRecyclablehomogeneousheterogeneous catalytic systems for heck reac-tion through reversible transfer of palladium species betweensolvent and supportrdquo Journal of Catalysis vol 194 no 2 pp479ndash483 2000

[31] C E Garrett and K Prasad ldquoThe art of meeting palladiumspecifications in active pharmaceutical ingredients producedby Pd-catalyzed reactionsrdquo Advanced Synthesis amp Catalysis vol346 no 8 pp 889ndash900 2004

[32] H Schmidt G Jonschker S Goedicke and M Mennig ldquoTheSol-gel process as a basic technology for nanoparticle-dispersedinorganic-organic compositesrdquo Journal of Sol-Gel Science andTechnology vol 19 no 1-3 pp 39ndash51 2000

Submit your manuscripts athttpswwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of



A+ +B

X

A

+

A

+

R Rcis or trans

Pd

Terminal product

Internal productA Ph OR COOR CON２

CN

R H alkyl CO２COH N2 Halide (o p m)

（+８

minus

X Halide OS2C3 COCＦ2

B －23 MOAc (M alkali metal) ＋3０4 ２3

Scheme 1 General Heck reaction

of the catalyst different support materials have been and arestill being investigated The most attractive is Pd on carbonor carbon nanotubes [9ndash11] Pd on metal oxide such as MgOAl2O3 ZnO ZrO

2 and TiO

2[5 12ndash15] Pd on zeolites [16]

Pd encapsulated in large organic structures (dendrimers) [17]and Pd on block copolymer micelles [18] The supports tendto arrest Pd on the surface of a solid material or in an organicmatrix making it possible to stabilize the catalytically activepalladium species and prevent sintering

Metal oxides have become the most lucrative Pd supportsfor heterogeneous catalysis due to their availability lowproduction costs and photoinduced electron hole pairs onthe surfaces ofmetal oxidewhich can be harvested to enhanceelectron transfer and their chemical reactivity [22 23] Thefirst paper on heterogenousHeck catalysis of Pd supported onan inorganic support was reported in 1990 [19 21] reportingthe coupling of chlorobenzene and styrene in the presence ofPdMgOmethanol solvent and sodiumcarbonate as a base at150∘C Several other reports have since beenmade and Table 1summarizes the literature on metal oxide support and Heckreaction

Titania a semiconductor has attracted more researchinterest due to its large band gap sim30ndash32 eV From litera-ture PdTiO

2catalyst for HR was previously prepared by

impregnation of Titania followed by hydrogen reduction ofpalladium precursor In 2011 Obuya and coworkers photo-deposited Pd NPs of diameters within 2ndash5 nm on electrospunTiO2NF In 2014 Nasrollahzadeh and his group dispersed

40 nm PdNPs on commercial TiO2using simple drop drying

process The catalyst was used in ArI-styrene system at 140∘Cfor 10 h In a different method Li and his team synthesizedPdTiO

2through adsorption method by pH control and

applied it in the Heck system of and methyl acrylate inthe presence of 01ndash05 PdTiO

2catalyst and KOAc base

and DMA solvent [12] Generally the reported results bythe separate groups showed variation in products yield Thiscould probably be attributed to variation in bases and solventsused percentage mole of palladium and the method ofpreparing the support The method of synthesizing Pd NPsfor C-C coupling reactions has also remained an area ofinterest [5]

This paper reports a simple and inexpensive method forpreparation of heterogenous and reusable PdTiO

2through

electrospinning to produce high surface area fibers followedby palladium deposition-reduction The efficiency of thesynthesized catalyst was evaluated in a styrene-ArBr modelHeck C-C coupling reaction

2 Experimental Methods

21 Materials The synthesis and reactions were carriedout using commercially available reagents Poly methylmethacrylate (PMMA) Mw 996000 by GPC crystallinetitanium isopropoxide (TIP) sodium acetate (NaOAc) bro-mobenzene (ArBr) styrene (990) hydrazine monohydrate(N2H464-65 reagent grade (98) palladium acetylace-

tonate (Pd(acac)2) (999) dimethyl formamide (DMF)

ethanol 998 and methyl acrylate (99) were purchasedfrom Sigma and Aldrich Anhydrous sodium carbonate(Na2CO3) 995 was purchased from Promark Chemicals

Cetyltrimethylammoniumbromide (CTAB)Molecular Biol-ogy Grade (990) was purchased from Calbiochem Allchemicals were used without any further purification

22 Structural Characterizations of Catalyst The morphol-ogy of the nanoparticles of TiO

2and PdTiO

2was observed

using a scanning electron microscope (SEM Tescan Japan)at an accelerated voltage of 20 kV Prior to scanning byelectron microscope the samples were sputter-coated withcarbon using a Jeol JFC-1200 fine coater Elemental analysisor chemical characterization was done by X-ray powderdiffractometer (XRD PANalytical X-Pert diffractometer withCu-K120572 radiation 154060 A PANalytical BV Netherlands)BrunauerminusEmmettminusTeller (BET) surface areas of the pow-ders were determined by nitrogen adsorption atminus196∘C in therange of a relative pressure 1198751198750 from 005 to 1 Samples weredegaussed at 120∘C for 7 h prior to nitrogen adsorption mea-surements The surface area and pore size were analyzed onmicromeritics ASAP 2020 The pore size distributions wereobtained from the desorption branch of the isotherm usingthe Barret-Joyner-Halenda (BJH) procedure TEM imageswere taken using JOEL JEM 2100 Transmission EmissionMicroscope (TEM) The samples were sonicated in ethanolplaced on a copper grid and left in the air for the solventto evaporate IR spectra were recorded on PerkinndashElmer100 spectrophotometer FTIR series (Tokyo Japan) measuredas KBr pellets (1 10 sampleKBr) The instrument was setto scan from 400 cmminus1 to 4000 cmminus1 and the spectra wereobtained Concentrations of styrene and ArBr in the Heckreaction were determined using a Varian 3900 GC modelNetherlands with a flame ionization detector (FID) anda Megabore column (length 25m with 023mm id) Theprogramme ran from 80∘C to 240∘C at a flow of 10mL permin and a velocity of 24 cmminminus1


Table1Selected

Heckreactio

nof

palladium

supp

ortedon

inorganico

xides

Catalyst

ArX

Alkene

Base

ArX

alkenebasePd

Molm

olm

olm

olSolvent

T ∘ CTime

hYield

Selectivity

Ref

Reg

Chem

oPd

MgO

ArC

lStyrene

Na 2CO3

710

332times10minus4

Methano

l150

532

42[19

]

PdA

l 2O3606

4-Nitrob

enzoyl

chlorid

eVBA

Et3N

121225times10minus3

Dioxane

100

471

1039

[20]

PdSiO212

24-Nitrob

enzoyl

chlorid

eVBA

rEt3N

121225times10minus3

Dioxane

100

451

1032

[20]

PdA

l 2O35

ArI

Acrylonitrile

Et3N

111

1times10minus2

Aceton

itrile

140

1472

33

20[21]

PdM

gO5

ArI

Acrylonitrile

Et3N

111

1times10minus2

Aceton

itrile

140

1478

35

10[21]

PdM

gO5

ArBr

Styrene

NaO

Ac11

5121times

10minus3

DMA

140

20365

125

112

[14]

PdZnO

45

ArBr

Styrene

NaO

Ac11

5121times

10minus3

DMA

140

20333

118

101

[14]

PdTiO243

ArBr

Styrene

NaO

Ac11

5121times

10minus3

DMA

140

20412

127

95[14

]Pd

ZrO255

ArBr

Styrene

NaO

Ac11

5121times

10minus3

DMA

140

20491

123

112

[14]

PdTiO21

ArBr

Styrene

Et3N

112210

DMF

140

2491

[13]

PdTiO2026

ArBr

Methylacrylate

KOAc


DMA

140

2479

[12]

PdTiO25

ArI

Styrene

NaO

Ac444

66972

35times10minus2

NMP

160

90[22]

PdTiO21

ArBr

Styrene

NaO

Ac11

22times10minus2

DMF

140

6897

Thispaper

PdTiO21

ArBr

Methylacrylate

NaO

Ac11

22times10minus2

DMF

140

6806

Thispaper

Et3Ntrie

thylam

ineArBrbrom

obenzeneA

rIiod

obenzeneV

BAvinylbu

tyletherD

MAdim

ethylacetamideNMP

N-m

ethyl-2

-pyrrolid

one
















2+ 4H2O (1)





2





0 PdTiO



6 01mL


2and Pd(acac)

2









2and Et





+

Br

+

cis or trans

+ （+Ｌ

minusPdTi2





















2 (yellow for




2recorded on








2O and TindashOH)








2was as shown in



2The




(a) (b) (c)

Pd

Ti2 NF

(d) (e)


PdTiO2at 80 kV

Spectrum 7

TiPd

O

TiC

0 2 4 6 8 10 12 14 16 18 20


(a) (b)




2to


2increased implying




2 the difference





3N Toluene 005 140 6 19

(2) Et3N MeOH 005 140 6 11

(3) Et3N EtOH 005 140 6 17

(4) Et3N DMF 005 140 6 339

(5) K2CO3

DMF 005 140 6 301(6) NaOAc DMF 005 140 6 419(7) Na

2CO3


2140 6 3



OH strTindashOH

593

741836

1634

1140

1270

138598729573000

3436

1725

1443

(a)

(b)(c)


)

Tran

smitt

ance

()



TiO2






2doped indicates



the pores of TiO2










3N gave a higher


2Oand



PdTi2 NF


Inte

nsity

(au

)

253

274 37

8

481

540

550

404

750

827627

689

703

335

30 40 50 60 70 80 90202 theta (degrees)

Ti2

PdTi2



500∘C



NaOAc Na2CO3 and Et




2and Pd(acac)

2as individual


2(PdTiO

2) NPs for



2support and







0 20 40 60 80

0000

0002

0004

0006

0008

0010

0012

0014

Pore diameter (nm)

Pore

vol

ume (

cＧ3gmiddotn

m)

(a)

Qua

ntity

adso

rbed

(＝Ｇ

3g

STP

)PdTi2

Ti2


(b)


27527

26526

25525

24524

23523

22522

21521

20520

19519

18518

17517

16516

15515

14514

13513

125

9000085000800007500070000650006000055000500004500040000350003000025000200001500010000

50000

RT (min)

G2T6DATA

(uV

)

STY

ArX

Stilb

ene

Solv

ent






6H5) 727



6H5)





50 100 150 200 250 300 350 4000Time (min)

0

20

40

60

80

100

Con

vers

ion

()

PdTi2 solv







89785 80

20

Recycling

0

Con

vers

ion

2 3 41

Run

102030405060708090

100











50 100 150 200 250 300 3500Time (minutes)

0

50

100

Con

vers

ion

()




PdTiO2

1 87 252 87 223 86 19









3Nbase (20mmol) and








2NFof diameters


2NF having a higher


2NF In










2(see Scheme 3)



119869 = 160Hz 1H) 745 (dd 119869 = 66 30Hz 2H) 731 (dd

Br+ 2Me

2MePdTi2 140∘C


ET3N DMF



3) 120575 16640 14385 13344







4 Conclusions

PdTiO2









Acknowledgments


References































2catalysts in the













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



Table1Selected

Heckreactio

nof

palladium

supp

ortedon

inorganico

xides

Catalyst

ArX

Alkene

Base

ArX

alkenebasePd

Molm

olm

olm

olSolvent

T ∘ CTime

hYield

Selectivity

Ref

Reg

Chem

oPd

MgO

ArC

lStyrene

Na 2CO3

710

332times10minus4

Methano

l150

532

42[19

]

PdA

l 2O3606

4-Nitrob

enzoyl

chlorid

eVBA

Et3N

121225times10minus3

Dioxane

100

471

1039

[20]

PdSiO212

24-Nitrob

enzoyl

chlorid

eVBA

rEt3N

121225times10minus3

Dioxane

100

451

1032

[20]

PdA

l 2O35

ArI

Acrylonitrile

Et3N

111

1times10minus2

Aceton

itrile

140

1472

33

20[21]

PdM

gO5

ArI

Acrylonitrile

Et3N

111

1times10minus2

Aceton

itrile

140

1478

35

10[21]

PdM

gO5

ArBr

Styrene

NaO

Ac11

5121times

10minus3

DMA

140

20365

125

112

[14]

PdZnO

45

ArBr

Styrene

NaO

Ac11

5121times

10minus3

DMA

140

20333

118

101

[14]

PdTiO243

ArBr

Styrene

NaO

Ac11

5121times

10minus3

DMA

140

20412

127

95[14

]Pd

ZrO255

ArBr

Styrene

NaO

Ac11

5121times

10minus3

DMA

140

20491

123

112

[14]

PdTiO21

ArBr

Styrene

Et3N

112210

DMF

140

2491

[13]

PdTiO2026

ArBr

Methylacrylate

KOAc


DMA

140

2479

[12]

PdTiO25

ArI

Styrene

NaO

Ac444

66972

35times10minus2

NMP

160

90[22]

PdTiO21

ArBr

Styrene

NaO

Ac11

22times10minus2

DMF

140

6897

Thispaper

PdTiO21

ArBr

Methylacrylate

NaO

Ac11

22times10minus2

DMF

140

6806

Thispaper

Et3Ntrie

thylam

ineArBrbrom

obenzeneA

rIiod

obenzeneV

BAvinylbu

tyletherD

MAdim

ethylacetamideNMP

N-m

ethyl-2

-pyrrolid

one
















2+ 4H2O (1)





2





0 PdTiO



6 01mL


2and Pd(acac)

2









2and Et





+

Br

+

cis or trans

+ （+Ｌ

minusPdTi2





















2 (yellow for




2recorded on








2O and TindashOH)








2was as shown in



2The




(a) (b) (c)

Pd

Ti2 NF

(d) (e)


PdTiO2at 80 kV

Spectrum 7

TiPd

O

TiC

0 2 4 6 8 10 12 14 16 18 20


(a) (b)




2to


2increased implying




2 the difference





3N Toluene 005 140 6 19

(2) Et3N MeOH 005 140 6 11

(3) Et3N EtOH 005 140 6 17

(4) Et3N DMF 005 140 6 339

(5) K2CO3

DMF 005 140 6 301(6) NaOAc DMF 005 140 6 419(7) Na

2CO3


2140 6 3



OH strTindashOH

593

741836

1634

1140

1270

138598729573000

3436

1725

1443

(a)

(b)(c)


)

Tran

smitt

ance

()



TiO2






2doped indicates



the pores of TiO2










3N gave a higher


2Oand



PdTi2 NF


Inte

nsity

(au

)

253

274 37

8

481

540

550

404

750

827627

689

703

335

30 40 50 60 70 80 90202 theta (degrees)

Ti2

PdTi2



500∘C



NaOAc Na2CO3 and Et




2and Pd(acac)

2as individual


2(PdTiO

2) NPs for



2support and







0 20 40 60 80

0000

0002

0004

0006

0008

0010

0012

0014

Pore diameter (nm)

Pore

vol

ume (

cＧ3gmiddotn

m)

(a)

Qua

ntity

adso

rbed

(＝Ｇ

3g

STP

)PdTi2

Ti2


(b)


27527

26526

25525

24524

23523

22522

21521

20520

19519

18518

17517

16516

15515

14514

13513

125

9000085000800007500070000650006000055000500004500040000350003000025000200001500010000

50000

RT (min)

G2T6DATA

(uV

)

STY

ArX

Stilb

ene

Solv

ent






6H5) 727



6H5)





50 100 150 200 250 300 350 4000Time (min)

0

20

40

60

80

100

Con

vers

ion

()

PdTi2 solv







89785 80

20

Recycling

0

Con

vers

ion

2 3 41

Run

102030405060708090

100











50 100 150 200 250 300 3500Time (minutes)

0

50

100

Con

vers

ion

()




PdTiO2

1 87 252 87 223 86 19









3Nbase (20mmol) and








2NFof diameters


2NF having a higher


2NF In










2(see Scheme 3)



119869 = 160Hz 1H) 745 (dd 119869 = 66 30Hz 2H) 731 (dd

Br+ 2Me

2MePdTi2 140∘C


ET3N DMF



3) 120575 16640 14385 13344







4 Conclusions

PdTiO2









Acknowledgments


References































2catalysts in the













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of

















2+ 4H2O (1)





2





0 PdTiO



6 01mL


2and Pd(acac)

2









2and Et





+

Br

+

cis or trans

+ （+Ｌ

minusPdTi2





















2 (yellow for




2recorded on








2O and TindashOH)








2was as shown in



2The




(a) (b) (c)

Pd

Ti2 NF

(d) (e)


PdTiO2at 80 kV

Spectrum 7

TiPd

O

TiC

0 2 4 6 8 10 12 14 16 18 20


(a) (b)




2to


2increased implying




2 the difference





3N Toluene 005 140 6 19

(2) Et3N MeOH 005 140 6 11

(3) Et3N EtOH 005 140 6 17

(4) Et3N DMF 005 140 6 339

(5) K2CO3

DMF 005 140 6 301(6) NaOAc DMF 005 140 6 419(7) Na

2CO3


2140 6 3



OH strTindashOH

593

741836

1634

1140

1270

138598729573000

3436

1725

1443

(a)

(b)(c)


)

Tran

smitt

ance

()



TiO2






2doped indicates



the pores of TiO2










3N gave a higher


2Oand



PdTi2 NF


Inte

nsity

(au

)

253

274 37

8

481

540

550

404

750

827627

689

703

335

30 40 50 60 70 80 90202 theta (degrees)

Ti2

PdTi2



500∘C



NaOAc Na2CO3 and Et




2and Pd(acac)

2as individual


2(PdTiO

2) NPs for



2support and







0 20 40 60 80

0000

0002

0004

0006

0008

0010

0012

0014

Pore diameter (nm)

Pore

vol

ume (

cＧ3gmiddotn

m)

(a)

Qua

ntity

adso

rbed

(＝Ｇ

3g

STP

)PdTi2

Ti2


(b)


27527

26526

25525

24524

23523

22522

21521

20520

19519

18518

17517

16516

15515

14514

13513

125

9000085000800007500070000650006000055000500004500040000350003000025000200001500010000

50000

RT (min)

G2T6DATA

(uV

)

STY

ArX

Stilb

ene

Solv

ent






6H5) 727



6H5)





50 100 150 200 250 300 350 4000Time (min)

0

20

40

60

80

100

Con

vers

ion

()

PdTi2 solv







89785 80

20

Recycling

0

Con

vers

ion

2 3 41

Run

102030405060708090

100











50 100 150 200 250 300 3500Time (minutes)

0

50

100

Con

vers

ion

()




PdTiO2

1 87 252 87 223 86 19









3Nbase (20mmol) and








2NFof diameters


2NF having a higher


2NF In










2(see Scheme 3)



119869 = 160Hz 1H) 745 (dd 119869 = 66 30Hz 2H) 731 (dd

Br+ 2Me

2MePdTi2 140∘C


ET3N DMF



3) 120575 16640 14385 13344







4 Conclusions

PdTiO2









Acknowledgments


References































2catalysts in the













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



+

Br

+

cis or trans

+ （+Ｌ

minusPdTi2





















2 (yellow for




2recorded on








2O and TindashOH)








2was as shown in



2The




(a) (b) (c)

Pd

Ti2 NF

(d) (e)


PdTiO2at 80 kV

Spectrum 7

TiPd

O

TiC

0 2 4 6 8 10 12 14 16 18 20


(a) (b)




2to


2increased implying




2 the difference





3N Toluene 005 140 6 19

(2) Et3N MeOH 005 140 6 11

(3) Et3N EtOH 005 140 6 17

(4) Et3N DMF 005 140 6 339

(5) K2CO3

DMF 005 140 6 301(6) NaOAc DMF 005 140 6 419(7) Na

2CO3


2140 6 3



OH strTindashOH

593

741836

1634

1140

1270

138598729573000

3436

1725

1443

(a)

(b)(c)


)

Tran

smitt

ance

()



TiO2






2doped indicates



the pores of TiO2










3N gave a higher


2Oand



PdTi2 NF


Inte

nsity

(au

)

253

274 37

8

481

540

550

404

750

827627

689

703

335

30 40 50 60 70 80 90202 theta (degrees)

Ti2

PdTi2



500∘C



NaOAc Na2CO3 and Et




2and Pd(acac)

2as individual


2(PdTiO

2) NPs for



2support and







0 20 40 60 80

0000

0002

0004

0006

0008

0010

0012

0014

Pore diameter (nm)

Pore

vol

ume (

cＧ3gmiddotn

m)

(a)

Qua

ntity

adso

rbed

(＝Ｇ

3g

STP

)PdTi2

Ti2


(b)


27527

26526

25525

24524

23523

22522

21521

20520

19519

18518

17517

16516

15515

14514

13513

125

9000085000800007500070000650006000055000500004500040000350003000025000200001500010000

50000

RT (min)

G2T6DATA

(uV

)

STY

ArX

Stilb

ene

Solv

ent






6H5) 727



6H5)





50 100 150 200 250 300 350 4000Time (min)

0

20

40

60

80

100

Con

vers

ion

()

PdTi2 solv







89785 80

20

Recycling

0

Con

vers

ion

2 3 41

Run

102030405060708090

100











50 100 150 200 250 300 3500Time (minutes)

0

50

100

Con

vers

ion

()




PdTiO2

1 87 252 87 223 86 19









3Nbase (20mmol) and








2NFof diameters


2NF having a higher


2NF In










2(see Scheme 3)



119869 = 160Hz 1H) 745 (dd 119869 = 66 30Hz 2H) 731 (dd

Br+ 2Me

2MePdTi2 140∘C


ET3N DMF



3) 120575 16640 14385 13344







4 Conclusions

PdTiO2









Acknowledgments


References































2catalysts in the













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



(a) (b) (c)

Pd

Ti2 NF

(d) (e)


PdTiO2at 80 kV

Spectrum 7

TiPd

O

TiC

0 2 4 6 8 10 12 14 16 18 20


(a) (b)




2to


2increased implying




2 the difference





3N Toluene 005 140 6 19

(2) Et3N MeOH 005 140 6 11

(3) Et3N EtOH 005 140 6 17

(4) Et3N DMF 005 140 6 339

(5) K2CO3

DMF 005 140 6 301(6) NaOAc DMF 005 140 6 419(7) Na

2CO3


2140 6 3



OH strTindashOH

593

741836

1634

1140

1270

138598729573000

3436

1725

1443

(a)

(b)(c)


)

Tran

smitt

ance

()



TiO2






2doped indicates



the pores of TiO2










3N gave a higher


2Oand



PdTi2 NF


Inte

nsity

(au

)

253

274 37

8

481

540

550

404

750

827627

689

703

335

30 40 50 60 70 80 90202 theta (degrees)

Ti2

PdTi2



500∘C



NaOAc Na2CO3 and Et




2and Pd(acac)

2as individual


2(PdTiO

2) NPs for



2support and







0 20 40 60 80

0000

0002

0004

0006

0008

0010

0012

0014

Pore diameter (nm)

Pore

vol

ume (

cＧ3gmiddotn

m)

(a)

Qua

ntity

adso

rbed

(＝Ｇ

3g

STP

)PdTi2

Ti2


(b)


27527

26526

25525

24524

23523

22522

21521

20520

19519

18518

17517

16516

15515

14514

13513

125

9000085000800007500070000650006000055000500004500040000350003000025000200001500010000

50000

RT (min)

G2T6DATA

(uV

)

STY

ArX

Stilb

ene

Solv

ent






6H5) 727



6H5)





50 100 150 200 250 300 350 4000Time (min)

0

20

40

60

80

100

Con

vers

ion

()

PdTi2 solv







89785 80

20

Recycling

0

Con

vers

ion

2 3 41

Run

102030405060708090

100











50 100 150 200 250 300 3500Time (minutes)

0

50

100

Con

vers

ion

()




PdTiO2

1 87 252 87 223 86 19









3Nbase (20mmol) and








2NFof diameters


2NF having a higher


2NF In










2(see Scheme 3)



119869 = 160Hz 1H) 745 (dd 119869 = 66 30Hz 2H) 731 (dd

Br+ 2Me

2MePdTi2 140∘C


ET3N DMF



3) 120575 16640 14385 13344







4 Conclusions

PdTiO2









Acknowledgments


References































2catalysts in the













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of





3N Toluene 005 140 6 19

(2) Et3N MeOH 005 140 6 11

(3) Et3N EtOH 005 140 6 17

(4) Et3N DMF 005 140 6 339

(5) K2CO3

DMF 005 140 6 301(6) NaOAc DMF 005 140 6 419(7) Na

2CO3


2140 6 3



OH strTindashOH

593

741836

1634

1140

1270

138598729573000

3436

1725

1443

(a)

(b)(c)


)

Tran

smitt

ance

()



TiO2






2doped indicates



the pores of TiO2










3N gave a higher


2Oand



PdTi2 NF


Inte

nsity

(au

)

253

274 37

8

481

540

550

404

750

827627

689

703

335

30 40 50 60 70 80 90202 theta (degrees)

Ti2

PdTi2



500∘C



NaOAc Na2CO3 and Et




2and Pd(acac)

2as individual


2(PdTiO

2) NPs for



2support and







0 20 40 60 80

0000

0002

0004

0006

0008

0010

0012

0014

Pore diameter (nm)

Pore

vol

ume (

cＧ3gmiddotn

m)

(a)

Qua

ntity

adso

rbed

(＝Ｇ

3g

STP

)PdTi2

Ti2


(b)


27527

26526

25525

24524

23523

22522

21521

20520

19519

18518

17517

16516

15515

14514

13513

125

9000085000800007500070000650006000055000500004500040000350003000025000200001500010000

50000

RT (min)

G2T6DATA

(uV

)

STY

ArX

Stilb

ene

Solv

ent






6H5) 727



6H5)





50 100 150 200 250 300 350 4000Time (min)

0

20

40

60

80

100

Con

vers

ion

()

PdTi2 solv







89785 80

20

Recycling

0

Con

vers

ion

2 3 41

Run

102030405060708090

100











50 100 150 200 250 300 3500Time (minutes)

0

50

100

Con

vers

ion

()




PdTiO2

1 87 252 87 223 86 19









3Nbase (20mmol) and








2NFof diameters


2NF having a higher


2NF In










2(see Scheme 3)



119869 = 160Hz 1H) 745 (dd 119869 = 66 30Hz 2H) 731 (dd

Br+ 2Me

2MePdTi2 140∘C


ET3N DMF



3) 120575 16640 14385 13344







4 Conclusions

PdTiO2









Acknowledgments


References































2catalysts in the













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



PdTi2 NF


Inte

nsity

(au

)

253

274 37

8

481

540

550

404

750

827627

689

703

335

30 40 50 60 70 80 90202 theta (degrees)

Ti2

PdTi2



500∘C



NaOAc Na2CO3 and Et




2and Pd(acac)

2as individual


2(PdTiO

2) NPs for



2support and







0 20 40 60 80

0000

0002

0004

0006

0008

0010

0012

0014

Pore diameter (nm)

Pore

vol

ume (

cＧ3gmiddotn

m)

(a)

Qua

ntity

adso

rbed

(＝Ｇ

3g

STP

)PdTi2

Ti2


(b)


27527

26526

25525

24524

23523

22522

21521

20520

19519

18518

17517

16516

15515

14514

13513

125

9000085000800007500070000650006000055000500004500040000350003000025000200001500010000

50000

RT (min)

G2T6DATA

(uV

)

STY

ArX

Stilb

ene

Solv

ent






6H5) 727



6H5)





50 100 150 200 250 300 350 4000Time (min)

0

20

40

60

80

100

Con

vers

ion

()

PdTi2 solv







89785 80

20

Recycling

0

Con

vers

ion

2 3 41

Run

102030405060708090

100











50 100 150 200 250 300 3500Time (minutes)

0

50

100

Con

vers

ion

()




PdTiO2

1 87 252 87 223 86 19









3Nbase (20mmol) and








2NFof diameters


2NF having a higher


2NF In










2(see Scheme 3)



119869 = 160Hz 1H) 745 (dd 119869 = 66 30Hz 2H) 731 (dd

Br+ 2Me

2MePdTi2 140∘C


ET3N DMF



3) 120575 16640 14385 13344







4 Conclusions

PdTiO2









Acknowledgments


References































2catalysts in the













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



0 20 40 60 80

0000

0002

0004

0006

0008

0010

0012

0014

Pore diameter (nm)

Pore

vol

ume (

cＧ3gmiddotn

m)

(a)

Qua

ntity

adso

rbed

(＝Ｇ

3g

STP

)PdTi2

Ti2


(b)


27527

26526

25525

24524

23523

22522

21521

20520

19519

18518

17517

16516

15515

14514

13513

125

9000085000800007500070000650006000055000500004500040000350003000025000200001500010000

50000

RT (min)

G2T6DATA

(uV

)

STY

ArX

Stilb

ene

Solv

ent






6H5) 727



6H5)





50 100 150 200 250 300 350 4000Time (min)

0

20

40

60

80

100

Con

vers

ion

()

PdTi2 solv







89785 80

20

Recycling

0

Con

vers

ion

2 3 41

Run

102030405060708090

100











50 100 150 200 250 300 3500Time (minutes)

0

50

100

Con

vers

ion

()




PdTiO2

1 87 252 87 223 86 19









3Nbase (20mmol) and








2NFof diameters


2NF having a higher


2NF In










2(see Scheme 3)



119869 = 160Hz 1H) 745 (dd 119869 = 66 30Hz 2H) 731 (dd

Br+ 2Me

2MePdTi2 140∘C


ET3N DMF



3) 120575 16640 14385 13344







4 Conclusions

PdTiO2









Acknowledgments


References































2catalysts in the













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of



89785 80

20

Recycling

0

Con

vers

ion

2 3 41

Run

102030405060708090

100











50 100 150 200 250 300 3500Time (minutes)

0

50

100

Con

vers

ion

()




PdTiO2

1 87 252 87 223 86 19









3Nbase (20mmol) and








2NFof diameters


2NF having a higher


2NF In










2(see Scheme 3)



119869 = 160Hz 1H) 745 (dd 119869 = 66 30Hz 2H) 731 (dd

Br+ 2Me

2MePdTi2 140∘C


ET3N DMF



3) 120575 16640 14385 13344







4 Conclusions

PdTiO2









Acknowledgments


References































2catalysts in the













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of





2NFof diameters


2NF having a higher


2NF In










2(see Scheme 3)



119869 = 160Hz 1H) 745 (dd 119869 = 66 30Hz 2H) 731 (dd

Br+ 2Me

2MePdTi2 140∘C


ET3N DMF



3) 120575 16640 14385 13344







4 Conclusions

PdTiO2









Acknowledgments


References































2catalysts in the













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of





Acknowledgments


References































2catalysts in the













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of





2catalysts in the













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of









CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Preparation and Characterization of Pd Modified Nanofiber...

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