Chapter 3 SYNTHESIS OF ACROLEIN BY DEHYDRATION OF GLYCEROL...
Transcript of Chapter 3 SYNTHESIS OF ACROLEIN BY DEHYDRATION OF GLYCEROL...
Synthesis of acrolein by dehydration of glycerol
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© Suraj Onkar Katole, Institute of Chemical Technology (ICT), Mumbai, India
CHAPTER 3
SYNTHESIS OF ACROLEIN BY DEHYDRATION OF GLYCEROL IN FIXED
BED CATALYTIC REACTOR
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© Suraj Onkar Katole, Institute of Chemical Technology (ICT), Mumbai, India
3.1. INTRODUCTION
As stated in previous chapter, fossil fuel based economy has many drawbacks
with regard to sustainability and global warming and thus it becomes necessary to shift
from the non renewable to the renewable feedstock based chemical and allied industries.
In the 21st century, utilization of renewable biomass into the conversion of industrially
important chemical substances has been intensely pursued by using principles of green
chemistry. Plant derived sugars and other compounds should be used to synthesize the
necessary compounds for the production of pharmaceuticals, agricultural chemicals,
plastics, and transportation fuels. The biorefinery concept is analogous to today’s
petroleum refinery, which produce multiple fuels and product from petroleum.
Biorefinery is a facility that integrates biomass conversion process and equipment to
produce fuels, power and chemicals from biomass (Dubois et al. 2006).
Glycerol, one of the potential renewable resources, is obtained as a by-product/co-
product in hydrolysis of fat, soap-manufacturing process and production of biodiesel. In
the biodiesel production processes the ratio of biodiesel to crude glycerol produced are
about 9:1. It is predicted that as the biodiesel production increases, supply of the glycerol
will be excess than the market demand and glycerol cost will further decrease. Therefore,
a new application of glycerol needs to be found. Dehydration of glycerol produces two
important commodity chemicals, 3-hydroxypropionaldehyde and acrolein. Acrolein is an
important bulk chemical used as a feedstock for acrylic acid production, pharmaceuticals
intermediates, fibre treatments, and methionine (used in animal feed) (Hess et al. 1978).
The most significant application of acrolein is an herbicide to control the growth of
aquatic plants. It kills the plant cells by reaction with biological molecules and
destruction of the cell membrane integrity, as well as by its affinity for sulfydryl groups,
causing the denaturation of vital enzymes (Corma et al. 2007).
Acrolein is the simplest unsaturated aldehyde. The primary characteristic of
acrolein is its high reactivity due to conjugation of the carbonyl group with a vinyl group.
Acrolein is a highly toxic material with extreme lacrimatic properties. At room
temperature, acrolein is highly volatile, respiration inhibitor and flammable liquid.
Special care in handling is required because of the flammability, extraordinary high
reactivity, pungent order and high toxicity of acrolein (Mcketta et al. 2006).
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© Suraj Onkar Katole, Institute of Chemical Technology (ICT), Mumbai, India
3.1.1 Commercial value of acrolein
Acrolein is a commercially important product which is having a key role as an
intermediate in various value added chemicals in a chemical industry. Acrolein is used in
the synthesis of following chemicals and compounds:
Polyester resin
L-methionine
Polyurethane
Propylene glycol
Glycerin (when biodiesel concept was not practiced; now it is exactly opposite as
will be discussed in this chapter)
Acrylic acid
The principal use of acrolein is an intermediate in the synthesis of numerous
chemicals, in particular acrylic acid and its lower alkyl esters and DL-methionine, an
essential amino acid used as feed supplement for poultry and cattle. In the past, ~91 to
93% of the total quantity of acrolein produced was converted to acrylic acid and its
derivatives (esters), and 5% to methionine. However, more than 80% of the refined
acrolein that is produced goes into synthesis of methionine (Liu et al. 2012). Other
derivatives of acrolein including are: 2-hydroxyadipaldehyde, 1, 2, 6-hexanetriol, lysine,
glutaraldehyde, tetrahydro-benzaldehyde, pentanediols, 1, 4-butanediol, allyl alcohol,
quinoline, homopolymers, and copolymers. Among the direct use of acrolein, its
application as a biocide is the most important one. Acrolein at a concentration of 6-10
ppm in the water is used as an algaecide, molluscicide, and herbicide in re-circulating
process water system, irrigation channels, cooling water towers, and water treatment
ponds. Acrolein can also be used as a tissue fixative, warming agent in the methyl
chloride refrigerants, leather tanning agent, and for immobilization of enzyme via
polymerization (Gerhartz et al. 2008).
3.1.2 Various routes for the synthesis of acrolein
There are two major routes to produce acrolein, one is based on a non-renewable
resource like petroleum feedstock and, another one is on a renewable resource like
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© Suraj Onkar Katole, Institute of Chemical Technology (ICT), Mumbai, India
glycerol. Acrolein is commercially produced by gas phase oxidation of propylene in the
presence of Bi-Mo mixed oxide catalyst (Beauchamp et al. 1985, Bowmer and Sainty
1977, Carrazan et al. 2006). The second route is the oxidation of propane to
acrolein/acrylic acid. This is also gas phase oxidation reaction using molybdenum and
vanadium based catalysts (Zhao and Wachs 2008, Wu et al. 2007).
Production of acrolein by dehydration of glycerol is not yet commercialized. Some of the
important papers and patents based on glycerol are discussed below. Bo-Qing Xu et al.
(2007) reported gas-phase dehydration of glycerol to produce acrolein at 315 °C over
Nb2O5 catalyst. They achieved 51 mol% acrolein selectivity; also observed deactivation
after using this catalyst. Tsukuda et al. (2007) found that silicotungustic acid supported
on silica with mesopores of 10 nm showed stable catalytic activity with the highest
acrolein selectivity of greater than 85 mol%. The catalyst showed gradual deactivation
after 5 h. Ning et al. (2008) reported activated carbon supported silicotungustic acid
catalysts to produce acrolein from glycerol dehydration. They found that 10%
silicotungustic acid exhibited the space time yield of acrolein 68.5 mmol/ (g.h). Reaction
was carried out at 330 °C under atmospheric pressure for 5 h. Watanabe et al. (2005) have
reported glycerol dehydration reaction at high temperature and high pressure water (573
to 673 K, saturated pressure or 34.5 MPa) using a batch and flow apparatus. Glycerol
conversion was 90% and acrolein selectivity was 80% with H2SO4 in supercritical
condition (673 K and 34.5 MPa).
Ott et al. (2006) conducted the reaction in a high pressure plug flow reactor from
300-390 °C, 25-34 MPa, 10-60 s residence time and varying amount of zinc sulfate. They
have reported that near sub-critical temperature, increase in the amount of salt enhances
the glycerol conversion. The maximum acrolein selectivity was 75 mol% at 360 °C, 25
MPa, 470 ppm zinc sulfate and a conversion of 50%. Neher et al. (1995) describe the
process for the production of acrolein by dehydration of glycerol in the liquid phase or in
the gaseous phase with solid acid catalysts. They used glycerol-water mixture with 10 to
40 wt. % of glycerol content. Reaction phase was liquid as well gaseous. Reaction
temperature was in the range from 180 – 340 °C for liquid phase and 250- 340 °C for
gaseous phase. The solid catalysts consisted of H3PO4/Al2O3 or H3PO4/TiO2 for liquid
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phase and H-ZSM5 or H-Y Catalyst, mordenite, montmorillonite or acidic zeolite, oxide,
mixed oxide or heteropolyacids for gaseous phase. According to this patent, the gas phase
process is preferable since it enables a degree of conversion of the glycerol of close to the
100% to be obtained.
Heteropolyacids are less harmful to the environment than mineral sulfuric acid. It
was reported that supported heteropolyacid effectively work in the dehydration reaction
(Izumi et al. 1983).
Since it was reported that heteropolyacids give better selectivity to acrolein (Atia
et al. 2008, Tsukuda et al. 2007, Ning et al. 2007), dodeca-tungustophoric acid (DTP) as
heteropolyacid was targeted in this work for dehydration of glycerol to acrolein process.
The present work deals with use of DTP/HMS (dodeca-tungustophoric acid (DTP)
supported on hexagonal mesoporous silica (HMS)) for dehydration of glycerol to acrolein
in vapour phase fix bed catalytic reactor (Yadav et al. 2009). Scheme.3.1 shows the
dehydration of glycerol with acrolein as major product.
Scheme 3.1: Dehydration of glycerol to acrolein
Synthesis of acrolein by dehydration of glycerol
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© Suraj Onkar Katole, Institute of Chemical Technology (ICT), Mumbai, India
3.2. EXPERIMENTAL
3.2.1 Chemicals
The following chemicals were procured from reputed firms and used without any
further purification: Glycerol (LR), ethanol, dodeca-tungustophoric acid (DTP) (AR),
methanol (M/s. s.d. Fine Chemicals ltd, Mumbai, India), tetraethyl orthosilicate (TEOS)
(Fluka, Germany), hexadecyl amine (Spectrochem Ltd., Mumbai, India).
3.2.2 Catalyst preparation
Hexagonal mesoporous silica (HMS): The ordered hexagonal mesoporous silica
(HMS) was prepared using the following procedure. 5 g Dodecyl amine was dissolved in
41.8 g of ethanol and 29.6 g of distilled water. 20.8 g of tetraethyl orthosilicate (TEOS)
was added under vigorous stirring. The addition of ethanol improved the solubility of the
template. The reaction mixture was aged for 18 h at 30 °C. The clear liquid above the
white colored precipitate was decanted and the precipitate HMS was dried on a glass
plate. The template was removed by calcination by keeping the resultant material at 650
°C in air for 3 h.
20% w/w DTP/HMS: It was prepared by incipient wetness technique for which
2 g of dry dodecatungstophosphoric acid was weighed accurately. This was dissolved in 8
ml of methanol. The solution was added in small amount of 1 ml each time to the silica
molecular sieve with constant stirring using a glass rod. The solution was added at time
intervals of 2 min. At the outset of addition of DTP solution on HMS was in powdery
form but on complete addition it formed a paste. The paste on further kneading for 10
minutes resulted in a free flowing powder. The performed catalyst was dried at 120 °C
for removal of water and other occluded volatiles materials. Then it was subsequently
calcined at 300 °C temperature for 3 h. to get active catalyst (Yadav and Manyar 2003,
Yadav and Lande 2006). 20% w/w DTP/K-10 (Yadav and Kirthivasan 1995; Yadav and
Krishnan 1998; Bokade and Yadav 2012), 20% Cs-DTP/K-10 (Yadav et al. 2003; Yadav
and Asthana 2003) and 20% w/w DTP/OMS (octahedral molecular sieves) were prepared
as the method reported in literature (Yadav and Mewada 2012; Yadav and Mewada
2013). 20% w/w NiO/HMS, 20% w/w CoO/HMS, 20% w/w CuO/HMS, and 20% w/w
Synthesis of acrolein by dehydration of glycerol
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Fe2O3/HMS were prepared by adding nitrate solution of respective metal precursor to
HMS by wet incipient technique and further calcination was done at 650 0C for 3 h.
3.2.3 Experimental set up and analytical method
Dehydration of glycerol was carried out at atmospheric pressure in a fixed bed
catalytic reactor, with a down flow fixed bed equipped with as upstream vaporizer and
downstream condenser. The liquid feed was fed by double piston pump (Well Chrom
HPLC-pump K-120) to the vaporizer by using N2 as a carrier gas. The catalyst was
loaded in the form of powder to form catalytic bed. Inert glass bead were used as packing
material and placed above and below the catalyst bed. The temperature of the bed was
maintained with the help of PID controller. Flow rate of the gas was measured and
controlled by mass flow controllers (MFC). Reaction samples were collected in liquid
form, from the bottom of the condenser. Catalyst was activated under nitrogen flow for 2
h prior to use at the reaction temperature. The schematic diagram of the fixed bed
catalytic reactor was shown in Figure 3.1. The analysis of reaction products was carried
out using GC (Chemito 1000) equipped with a BPX-50 capillary column (length: 30m,
ID: 0.25mm) and with FID detector. Confirmation of products was done by GC-MS
using same capillary column.
Synthesis of acrolein by dehydration of glycerol
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Figure 3.1 Schematic diagram of fixed bed catalytic reactor
Notations: 1. Pump, 2. Vaporizer, 3. Reactor, 4. Condenser, 5. Phase Separator, 6.
Receiver.
3.3 RESULTS AND DISCUSSION
3.3.1 Catalyst characterizations of 20 %( w/w) DTP supported on K10, HMS and OMS.
The three different supports K10, HMS and OMS were used to incorporate
dodecatungstophosphoric acid. The total acidity measurement of K10 and HMS were
carried using NH3-TPD were found to 0.139 mmol/g and 0.021 mmol/g, respectively
while basicity measurement of OMS was carried out by CO2-TPD was measured to be
4.76 mmol/g. 20% (w/w) DTP/K10 and 20% (w/w) DTP/HMS are completely
characterized again during this work for both virgin and used catalysts by NH3-TPD,
FTIR, XRD, SEM, and BET surface area, and the some characterization was published
by our group (Yadav and Kirthivasan 1995; Yadav and Krishnan 1998; Yadav and
Asthana 2003). 20% (w/w) DTP/OMS was characterized similarly. Only a few salient
features are reported here. The acidity of 20% w/w DTP/K-10 catalyst was measured by
NH3-TPD and found to be 0.423 mmol/g. The IR spectrum of 20% (w/w) DTP/K10, 20%
(w/w) DTP/HMS and 20% (w/w) DTP/OMS catalyst exhibits bands at 3450, 1652, 1092,
990.7, 893, 817, and 466 cm-1. The XRD analysis confirmed that 20% w/w DTP/K-10 is
crystalline in nature. The BET surface area of 20% w/w DTP/K-10 was found to be 135
m2/g. The preparation of 20% w/w DTP/HMS and its application is also reported by our
group (Yadav and Manyar 2003). The acidity of 20% w/w DTP/HMS was measured by
NH3-TPD and found to be 0.130 mmole/g. 20% w/w DTP/HMS characterized by XRD
and no crystalline phase was detected which indicates, the uniform distribution of DTP in
HMS. Hence, these materials are completely amorphous in nature. The BET surface area
of 20% w/w DTP/HMS was found to be 299.7 m2/g and is a type-IV isotherm, indicates
mesoporosity is retained after DTP loading. The OMS-2 catalyst has a one-dimensional
tunnel structure formed by 2 ×2 edge shared MnO6 octahedral chains. X-ray diffraction
patterns show d-spacing values which match with the reported data of OMS-2 and the
corresponding (h k l) values are (1 0 1), (0 0 2), (3 0 1), (2 1 1), (3 1 0), (1 1 4) and (6 0
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© Suraj Onkar Katole, Institute of Chemical Technology (ICT), Mumbai, India
0) at 2 theta values of 12.7, 18.0, 28.7, 37.4, 41.8, 50.0, 55.3. When DTP is dispersed in
OMS-2, there is a linear decrease in surface area from 69.4 to 42.4 m2/g.
Keggin type heteropoly acid (HPA) catalysts are strong Bronsted acids. HMS is neutral.
The active species in DTP/HMS are Bronsted acids arising from the
doedcatungstophosphoric acid was reported by us earlier (Yadav and Manyar 2003) and
(Bardin et al. 1998). There are abundant silanol groups (#Si-OH) on the surface of
mesoporous silica owing to its amorphous wall structure. With these reactive silanol
groups, one can effectively immobilize organic functional groups onto a silica surface
through either covalent bonding or hydrogen bonding (Rouxhet and Sempels 1974). On
silica, only H-bond formation occurs indicating a rather weak acidity of the silanol
groups, quantitatively characterized by pKa = 7. (Tsyganenko et al. 2000) Hexagonal
mesoporous silica is neutral and does not create acidity by steam generated in situ during
dehydration, particularly at the reaction temperature of 225 oC.
3.3.2 Catalysts characterization (20% DTP-HMS)
3.3.2.1 Surface area analysis
The specific surface area, pore volume and pore diameter were determined by N2
adsorption-desorption isotherm at low temperature (77 K) using a Micromeritics ASAP
2010 instrument of fresh and used 20% (w/w) DTP/HMS. The catalyst samples were
degassed under vacuum at 200ºC for 3 h. The measurements were made using N2 gas as
the adsorbent and with a multipoint method. Isotherms were measured at liquid nitrogen
temperature. Surface area, pore volume and pore diameter were calculated from N2
adsorption-desorption isotherm using conventional BET method. Figures 3.2 and 3.3
show the isotherm of fresh and used catalyst. According to results it can be concluded
that surface area of the fresh catalyst was decreased because of the coke deposition
occurred inside the pore of the catalyst. In support of these results elemental analysis was
carried out and it was found that 3.87% carbon was deposited on the catalyst. Results
were shown in Table. 3.1.
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Table 3.1 Surface areas, pore volume and pore diameter of fresh and used catalyst
Catalyst (20% DTP-HMS) Fresh Used
BET Surface Area 299.7 m2/g 1.32 m2/g
Pore Volume 0.204 cm3/g 0.002 cm3/g
Pore Diameter 27.16 A0 ----
Figure 3.2 Adsorption desorption isotherm of fresh 20%DTP-HMS catalyst
Synthesis of acrolein by dehydration of glycerol
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© Suraj Onkar Katole, Institute of Chemical Technology (ICT), Mumbai, India
Figure 3.3 Adsorption desorption isotherm of used 20%DTP-HMS catalyst
3.3.2.2 Temperature programmed desorption (NH3-TPD)
Acidic sites of the catalyst were determined with temperature programmed
desorption (TPD) analysis using Autochem II 2910 (Micromeritics, USA) with ammonia
as probe molecules. A quantity of 30 mg of the catalyst was taken in a quartz tube and
degassed up to 300 0C under the flow of nitrogen. Then ammonia was passed for 30 min
to adsorb the ammonia over the surface of the catalysts at room temperature. Physisorbed
gas was removed by passing inert nitrogen at room temperature. Chemisorbed ammonia
was desorbed by using temperature programmed desorption and detected by TCD. NH3-
TPD data of fresh and used 20% DTP-HMS catalyst are shown in Figures 3.4 and 3.5.
NH3-TPD data of used catalyst indicate that acidity of the used catalyst has completely
decreased. This is because of deposition of the coke during reaction and also leaching of
DTP during the process of washing of the used catalyst.
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Fig.3.4. NH3-TPD of fresh 20% (w/w) DTP/HMS catalyst
Figure 3.5 NH3-TPD of used 20% (w/w) DTP/HMS catalyst
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© Suraj Onkar Katole, Institute of Chemical Technology (ICT), Mumbai, India
3.3.2.4 Elemental analysis by EDX
Elemental analysis of fresh and used catalyst was also done by EDX and it was
found that the used catalyst contain 3.87% carbon present on the catalyst. These carbons
are due to coke deposition inside the catalyst during reaction, results were shown in Table
3.2.
Table 3.2 Elemental analysis by EDX
3.3.3 Efficacies of different support and catalyst screening
20% w/w DTP was loaded on different support like K-10 (acidic), HMS (neutral)
and OMS (basic) to evaluate the effect of support on glycerol conversion and acrolein
selectivity. Although, all the catalysts have the same 20% w/w DTP loading, it was
observed that neutral support (HMS) showed better selectivity for acrolein as compared
with other support (Table 3.3). The increase in selectivity also can be due the presence of
free hydroxyl group which make the catalyst more hydrophilic in nature. Therefore,
various HMS supported catalysts such as 20% w/w CoO/HMS, 20% w/w CuO/HMS,
20% w/w NiO/HMS, 20% w/w Fe2O3/HMS, 20% w/w CsDTP/HMS and 20% w/w
DTP/HMS were prepared and screened for vapor phase glycerol dehydration reaction.
Recently, the redox active metals such as copper, iron and nickel were used in the
catalyst composition for dehydration of glycerol to acrolein (Miranda et al. 2014; Lei et
Elements % Mass of fresh
20%(w/w) DTP/HMS
% Mass of used
20%(w/w) DTP/HMS
C ---- 3.87
O 41.53 40.97
Si 29.90 30.25
W 28.57 24.91
Total 100 100
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© Suraj Onkar Katole, Institute of Chemical Technology (ICT), Mumbai, India
al. 2013). Therefore, copper, iron, nickel and cobalt were supported on HMS and their
activity for acrolein preparation was evaluated. However, it was observed that HMS
supported copper, iron, nickel and cobalt catalysts showed poor acrolein selectivity as
compared to heteropoly acid based catalysts such as 20% w/w CsDTP/HMS and 20%
w/w DTP/HMS, which can be due to redox properties of these metals (Figure 3.8).
Typical reaction conditions were: 1.0 g of catalyst loading, 225 0C of reactor bed
temperature, 225 0C of preheator temperature, 20% (w/w) glycerol solution, 10.2 ml/h of
feed flow rate (glycerol solution), 1.5 lit/h of N2 flow rate, 4 h reaction duration and
10.74 h-1 of WHSV. 20% w/w DTP/HMS was found to be the best catalyst as compared
to other catalysts. The increase in activity can be due to the synergistic effect of DTP and
hydrophilic nature of HMS support which has high surface area and mesoporosity.
Hence, further, experiments were carried out by using 20% w/w DTP/HMS catalyst.
Table 3.3 Efficacy of different support
Catalyst % Conversion
(glycerol)
% Selectivity
Acrolein Hydroxyacetone Others*
20% w/w DTP/K-10 89 50 10 40
20% w/w DTP/HMS 94 80 9 11
20% w/w DTP/OMS 62 45 14 41
*acetaldehyde, propionaldehyde, acetone, allyl alcohol
Reaction conditions: 20% (w/w) glycerol solution, 1.0 g of catalyst weight, 225 0C, 1.5
L/h of N2 flow rate, 10.2 ml/h of glycerol flow rate, 10.74 h-1 of WHSV, 4 h.
Synthesis of acrolein by dehydration of glycerol
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© Suraj Onkar Katole, Institute of Chemical Technology (ICT), Mumbai, India
Figure 3.8 Catalysts screening
Reaction conditions: 20% (w/w) glycerol solution, 1.0 g catalyst weight, 225 °C
temperature, 1.5 lit/h N2 flow rate, 10.2 ml/h feed flow rate (glycerol solution), 10.74 h-
1WHSV, 4 h.
3.3.4 Effect of temperature
The glycerol conversion as a function of temperature was studied in the range of
200 to 325°C under similar reaction conditions over 20% w/w DTP-HMS catalyst. It was
observed that conversion of glycerol increased with increasing temperature from 200 to
325°C. At 200°C conversion was 61% which increased up to 96% at 325°C. It was found
that after 225°C there is a marginal increase in conversion up to 325°C from 94 to 96.0%
respectively. But selectivity of acrolein was highest at 225°C and found that 80%. Above
225°C, selectivity of acrolein decreased up to 325°C; which can be attributed to carbon
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© Suraj Onkar Katole, Institute of Chemical Technology (ICT), Mumbai, India
after 10, 13, 15 and 19 h (Figure 3.10). 50% w/w DTP/HMS has more catalyst active
sites and hence it takes longer time to deactivate as compared to 20% w/w DTP/HMS.
The deactivation of 20% w/w DTP/HMS catalyst was further studied by NH3-TPD, BET-
surface area, SEM and EDX analysis.
0
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40%(w/w) DTP/HMS 50%(w/w) DTP/HMS
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© Suraj Onkar Katole, Institute of Chemical Technology (ICT), Mumbai, India
Figure 3.10 Effect of DTP loading on HMS
Reaction conditions: 20% (w/w) glycerol solution, 1.0 g of catalyst weight, 225 0C, 1.5
L/h N2 of flow rate, 10.2 ml/h of feed flow rate, 10.74 h-1 of WHSV.
3.3.6 Effect of glycerol concentration
Different concentrations of glycerol such as 10%, 20% and 50% (w/w) were used
to evaluate the activity of the catalyst. It was observed that 10% and 20% (w/w) of
glycerol solution gave almost similar results. However, 50% (w/w) of glycerol solution
resulted into a decrease in glycerol conversion as well as acrolein selectivity. This is due
to the fact that as concentration of glycerol increases on sites; it leads to cracking and
coking of the catalyst. Hence there is decrease in selectivity and conversion. Hence, 20%
w/w of glycerol solution was used for further optimization (Figure 3.11).
0
20
40
60
80
100
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Sel
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)
Time (h)
20%(w/w) DTP/HMS 30%(w/w) DTP/HMS
40%(w/w) DTP/HMS 50%(w/w) DTP/HMS
R
3.3.7
glyce
incre
decre
does
glyce
© Suraj
Reaction cond
temp
7 Effect of fe
Glycerol
erol flow rat
asing glycer
eased. The d
not get en
erol flow rate
0
20
40
60
80
100
Per
cen
tage
(%
)
Onkar Katole
Figure
ditions: 10-5
perature, 1.5
eed flow rate
flow rate w
te 5.1, 10.2
rol flow rate
ecrease in ca
nough time
e was chosen
10%
e, Institute of
3.11 Effect
50% (w/w) g
5 lit/h N2 flow
e
was optimize
, 20.4 and 4
from 10.2 t
atalyst activ
to convert
n for further
Conv
Synthesis o
64
Chemical Tec
t of glycerol
glycerol solu
w rate, 10.2
ed by condu
40.8 mL/h a
to 40.8 mL/h
ity is due to
glycerol to
r optimizatio
20%
version S
of acrolein b
chnology (ICT
l concentrat
ution, 1.0 g c
ml/h feed fl
ucting the r
at 225°C. It
h, both the c
increase in
acrolein. T
on (Figure 3.
50
Selectivity
y dehydratio
T), Mumbai, In
tion
catalyst weig
ow rate, 4 h
reaction at f
t was observ
conversion an
WHSV valu
Therefore, 1
12).
%
on of glycero
ndia
ght, 225°C
.
four differen
ved that wit
nd selectivit
ues and henc
0.2 mL/h o
ol
nt
th
ty
ce
of
3.3.8
on re
select
carrie
flow
© Suraj
Reaction co
Effect of N
Effect of
eaction. It wa
tivity of acr
ed away by N
rate was fou
0
20
40
60
80
100
Per
cen
tage
(%
)
Onkar Katole
Fig
onditions: 20
tem
N2 Flow rate
N2 flow rate
as observed
rolein decre
N2 gas, and
und to be opt
5.1
e, Institute of
gure 3.12 E
0% (w/w) gly
mperature, 1.
es 0.72, 1.5,
that with in
ased. This i
did not get
timized and
10.2
Con
Synthesis o
65
Chemical Tec
ffect of feed
ycerol soluti
5 L/h N2 flo
, and 3.0 L/h
ncrease in N
is because a
enough time
used for furt
20
version S
of acrolein b
chnology (ICT
d flow rate
on, 1.0 g cat
ow rate, 4 h.
h were selec
2 flow rate f
at higher N2
e to get cond
ther study (F
0.4
Selectivity
y dehydratio
T), Mumbai, In
talyst weight
cted to estab
from 0.72 L
2 flow rate,
densing. Hen
Figure 3.13)
40.8
on of glycero
ndia
t, 225°C
blish its effec
/h to 3.0 L/h
acrolein wa
nce 1.5 l/h N
.
ol
ct
h,
as
N2
Reac
3.3.9
loadin
expec
due t
found
© Suraj
tion conditio
Effect of ca
Effect of
ng the reac
cted that wit
to proportion
d optimum a
0
20
40
60
80
100
Per
cen
tage
(%
)
Onkar Katole
Fi
ons: 20% (w
atalyst loadin
f catalyst lo
tor with 0.2
th increase i
nal increase
and used furt
0.72
e, Institute of
igure 3.13 E
w/w) glycerol
weight, 225
ng
oading with
25, 0.5, 1.0
in catalyst lo
in catalyst a
ther for reusa
Conv
Synthesis o
66
Chemical Tec
Effect of N2
l solution, fe
°C temperat
the conver
, and 2.0 g
oading, the
active sites.
ability study
1.5
version Se
of acrolein b
chnology (ICT
Flow rate
eed flow rate
ture, 4 h.
rsion of gly
g of 20%DT
life of cataly
Hence 1.0 g
y (Figure 3.1
3
electivity
y dehydratio
T), Mumbai, In
e 10.2 ml/h,
ycerol was
TP-HMS cat
yst can also
g of catalyst
4).
3
on of glycero
ndia
1.0 g catalys
evaluated b
talyst. It wa
be increase
t loading wa
ol
st
by
as
ed
as
Rea
3.3.1
After
with
surfa
befor
filtrat
than
found
© Suraj
action condit
0 Reusabilit
Catalyst r
r the comple
water and m
ce of the ca
re using in t
tion. Hence,
the previou
d that after
0
20
40
60
80
100
Per
cen
tage
(%
)
Onkar Katole
Fig
ions: 20% (w
fl
ty study of c
reusability s
etion of react
methanol tw
atalyst. Then
he next batc
, actual amo
us batch. Th
completion
2
e, Institute of
ure 3.14 Eff
w/w) glycero
flow rate, 225
atalyst
study was c
tion, the cata
wo three tim
n it was filt
ch of reactio
ount of catal
he loss of ca
n the reactio
1
Conv
Synthesis o
67
Chemical Tec
fect of catal
ol solution, f
5°C tempera
arried out u
alyst was co
mes to remov
ered and dr
on. There wa
lyst used in
atalyst was
on catalysts
0
version S
of acrolein b
chnology (ICT
lyst loading
feed flow rat
ature, 4 h.
using optimi
ollected from
ve adsorbed
ried at 120 °
as predictab
the next ba
made-up wi
s undergo d
0.5
Selectivity
y dehydratio
T), Mumbai, In
te 10.2 ml/h
ized reaction
m the reactor
d material pr
°C for 2 h,
le loss of ca
atch, was alm
ith fresh cat
deactivation
0.25
on of glycero
ndia
, 1.5 lit/h N2
n parameter
r, and washe
resent on th
and weighe
atalyst durin
most 5% les
talyst. It wa
due to cok
ol
2
s.
ed
he
ed
ng
ss
as
ke
depos
leach
reuse
Reac
© Suraj
sition. In reu
hing of DTP
e this catalys
tion conditio
0
20
40
60
80
100
Per
sen
tage
(%
)
Onkar Katole
use study co
at the time
st (Figure 3.
Figu
ons: 20% (w
weight, 1.5
e, Institute of
onversion an
of catalyst
15).
ure 3.15 Cat
w/w) glycerol
5 lit/h N2 flo
Fresh
Conv
Synthesis o
68
Chemical Tec
nd selectivity
washing aft
talyst reusa
l solution, fe
w rate, 225°
version S
of acrolein b
chnology (ICT
y is drastica
er first use.
ability study
eed flow rate
°C temperatu
Used
Selectivity
y dehydratio
T), Mumbai, In
ally decrease
Hence it wa
y
e 10.2 ml/h,
ure, 4 h.
on of glycero
ndia
ed because o
as planned t
1.0 g catalys
ol
of
to
st
Synthesis of acrolein by dehydration of glycerol
69
© Suraj Onkar Katole, Institute of Chemical Technology (ICT), Mumbai, India
3.4 CONCLUSION
Continuous synthesis of acrolein by dehydration of glycerol was investigated in a
fixed bed catalytic reactor using several solid acid catalysts. Out of them 20% w/w DTP-
HMS catalyst gives high glycerol conversion and selectivity towards acrolein. 98%
conversion of glycerol and 80% selectivity towards acrolein were obtained at optimized
reaction conditions. The various process parameters, such as effects of temperature,
glycerol concentration, feed flow rate, N2 flow rate and catalyst loading were studied and
optimized. This catalyst shows extremely good result at lower temperature at 225 °C as
compared to other published literature so far. Catalyst was well characterized before and
after use using NH3-TPD, BET-surface area, SEM image and EDX analysis, to find out
exact reason for catalyst deactivation. Deposition of carbon on the surface of the catalyst
is major concern of this reaction, so development of reusable catalyst for this process was
the emphasis for further study. In next chapter, a new catalyst development is presented
to overcome these entire problems.