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Short communication

Hydrodesulfurization and hydrodearomatization activities ofcatalyst containing ETS-10 and AlPO4-5 on Daqing FCC diesel

Ye Zhao a,b, Baojian Shen a,*, Wencheng Zhang b, Ran Tian b, Zhihua Zhang b, Jinsen Gao a

a State Key Laboratory of Heavy Oil Processing; The Key Laboratory of Catalysis of CNPC; and Faculty of Chemical Science and

Engineering, China University of Petroleum, Beijing, Changping 102249, Chinab Research Center of Daqing Chemical Engineering, Petrochina Company Limited, Daqing 163714, China

Received 1 March 2007; received in revised form 20 October 2007; accepted 26 October 2007Available online 20 November 2007

Abstract

A NiW loaded ETS-10/AlPO4-5/Al2O3composite support catalyst was optimized and used in hydrodesulfurization (HDS) and hyd-rodearomatization (HDA) of Daqing FCC diesel feedstock. The result indicated that ETS-10 and AlPO4-5 showed positive synergismeffect. The effects of operating conditions on its catalytic performance were investigated by using a 100 mL hydrotreating test unit. Thecatalyst showed a remarkable HDS conversion of 99.9% and a HDA conversion of 73.2%. A clean diesel product with ultra-low sulfurcontent (

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with the catalyst loading of 100 mL. The catalysts were pre-sulfided in situ with 2 vol.% CS2 in kerosene. The feed-stock, Daqing FCC diesel, have density of 0.8702 g/mL,sulfur content of 1052.0 lg/g and total aromatic content51.2 vol.%.

The total sulfur content was measured by a coulometric

sulfur analyzer. The total aromatic content analyses weredetermined by the standard method of fluorescence indica-tor adsorption by using Dalian TSY-1132 instrument. Thecomposition was analyzed by BOMEM MB-160 near infra-red (NIR) spectra.

3. Results and discussion

3.1. Effect of support composition on catalyst activity

The catalyst activities of C-Al2O3, C-AETS, C-AAP andC-ATSP at 8.0 MPa, 633 K, 1.0 h1 and 500:1 (H2/oil, v/v)

are listed inTable 1. It was obvious that the catalytic activ-ity of the catalysts containing ETS-10 or AlPO4-5 wasenhanced in comparison with that of C-Al2O3. In detail,compared with catalyst C-Al2O3, HDS and HDA conver-sions increased by 1.4% and 2.8% for catalyst C-AETS,and increased by 0.5% and 5.7% for catalyst C-AAP. Thisindicated that catalyst containing AlPO4-5 (catalyst C-AAP) showed better HDA activity than the catalyst con-taining ETS-10 (catalyst C-AETS), whereas, the HDSactivity of catalyst C-AETS was better than that of C-AAP. The difference of activity and selectivity for C-AETSand C-AAP may be resulted from the different characteris-

tic of molecular sieves ETS-10 and AlPO4-5[17,18]. Thus,when various amount of ETS-10 or AlPO4-5 were intro-duced to alumina to prepare the corresponding compositesupport, the different degree of influences on the dispersionof metal active component could be caused. The data inTable 1 indicates that the catalyst C-ATSP (containingboth AlPO4-5 and ETS-10) owns the highest HDS (conver-sion 99.7%) and HDA (conversion 72.9%) activities. Itreduced the sulfur content from 1052.0 lg/g to 2.7 lg/g,and aromatics from 51.2 vol.% to 13.9 vol.%. It was clearthat simultaneous introduction of ETS-10 and AlPO4-5at a proper ratio could not only take advantage of their

individual advantages (HDS or HDA), but also cause posi-tive synergism effects amidst them, which results in aremarkable enhancement in the catalytic activity of the cat-alyst C-ATSP.

The evaluation data showed that decreasing ETS-10/AlPO4-5 ratio would result in the increase of HDS and

HDA conversions and the highest HDS and HDA conver-sions achieved were 99.7% and 72.9% for catalyst C-ATSP,in which the ratio of ETS-10 to AlPO4-5 was 1:2 (wt/wt). Itwas found that the introduction of ETS-10 and AlPO4-5can also bring a certain amount of moderate Bronsted acidsites [19], which favor eliminating the refractory 4,6-DMDBT and its steric-hindered derivatives through theisomerization-hydrogenation pathway.

Table 2compares the NIR compositional analysis dataof Daqing FCC diesel before and after hydrotreating overC-ATSP catalyst. The content of alkanes in hydrotreateddiesel increased by 12%, which may mainly result from sat-uration of olefins, saturation and ring opening of monoaro-

matics with short side chain, and ring opening of single ringcycloparaffin. It is known that reaction rate constant ofdiaromatics and triaromatics was far greater than that ofmonoaromatics. In the present work, the content of poly-cyclic aromatics (diaromatics and triaromatics) decreasedfrom 33.1 wt.% to 4.6 wt.%, and accordingly, the calcu-lated Cetane Number increased from 26.7 to 47.7.

3.2. Effect of reaction conditions on HDS and HDA activities

HDS and HDA activities of C-ATSP catalyst wereinvestigated at various reaction temperatures (573 K,

593 K, 603 K, 613 K, 623 K, 633 K and 643 K) at8.0 MPa, 1.0 h1, 500:1 (H2/oil, v/v). HDA conversionincreased with temperature elevating from 19.8% (573 K)until 68.8% (633 K), after 633 K it turned to decrease.HDS conversion also increased with temperature elevatingfrom 99.2% (573 K) until 99.9% (603 K). No further HDSconversion increasing was observed when higher tempera-ture was used. The NIR compositional analysis data ofthe hydrotreated diesel products over catalyst C-ATSP attemperature range from 573 K to 613 K also suggest that

Table 1The HDS and HDA activities of C-Al2O3, C-AETS, C-AAP and C-ATSPunder conditions of 8.0 MPa, 633 K, 1.0 h1, 500:1 (H2/oil, v/v)

Catalyst HDS conversion (%)(Sulfur content, lg/g)

HDA conversion (%)(Aromatic content, vol.%)

C-Al2O3 97.6 (25.6) 56.4 (22.3)C-AETS 99.0 (10.2) 59.2 (20.9)C-AAP 98.1 (19.5) 62.1 (19.4)C-ATSP 99.7 (2.7) 72.9 (13.9)

Note: HDS conversion (%) = [(Sfeed Sproduct)]/Sfeed 100; HDA con-version (%) = [(Afeed Aproduct)]/Afeed 100. Where Sfeedand Sproductarethe total sulfur contents (m%) in the feedstock and liquid product,respectively, andAfeedand Aproductare the total aromatic contents (vol.%)

in the feedstock and liquid product, respectively.

Table 2

Comparison of the compositional NIR analysis of FCC diesel feed and thehydrotreated diesel over catalyst C-ATSP under the conditions of8.0 MPa, 633 K, 1.0 h1, 500:1 (H2/oil, v/v)

Item FCC diesel feed Product

Saturates (wt.%) 40.7 68.9Alkanes (wt.%) 27.9 39.7Cycloalkanes (wt.%) 13.0 26.5Monocycloalkanes (wt.%) 11.0 10.4Dicycloalkanes (wt.%) 1.8 10.3Tricycloalkanes (wt.%) 0.4 7.1Aromatics (wt.%) 58.6 31.2Monoaromatics (wt.%) 24.2 26.7Diaromatics (wt.%) 27.6 3.9Triaromatics (wt.%) 5.5 0.7

Calculated cetane number 26.7 47.7

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the aromatic content decreased from 45.8 wt.% to39.3 wt.% when the reaction temperature increased from573 K to 613 K, and most of diaromatics (decreased from27.6 wt.% in feed to 4.8 wt.% in product at 613 K) and tri-aromatics (decreased from 5.52 wt.% in feed to 0.32 wt.%in product at 613 K) were saturated to monoaromatics or

cycloparaffin. The aromatics accumulated in the productwere mainly monoaromatics, which is critical to deephydrogenation saturation for aromatics [3,20,21].

The effect of LHSV on hydrogenation reaction under thereaction condition of 6.0 MPa, 633 K, 500:1 (H2/oil, v/v) ofC-ATSP catalyst was evaluated. With the increase of LHSVfrom 1.0 h1 to 2.6 h1, the HDS conversions decreasedfrom 99.9% to 99.6% (HDS conversions decreased to94.8% at 593 K, 6.0 MPa, 2.6 h1, 450:1(H2/oil, v/v)), andthe HDA conversions decreased from 66.8% to 21.9%. Itwas interestingly found that most of triaromatics and diaro-matics disappeared even at a higher LHSV condition.

The effect of reaction pressure on hydrogenation reac-

tion under the reaction condition of 633 K, 1.0 h1, 500:1(H2/oil, v/v) of C-ATSP catalyst was also evaluated. Asreaction pressure increased from 6.0 MPa to 9.0 MPa theHDA conversions linearly increased from 42.4% to 75.0%obviously, however, the HDS conversion just decreasedslightly from 99.9% to 99.6%.

The HDS and HDA performance of catalyst C-ATSPunder the reaction condition of 8.0 MPa, 633 K, 1.0 h1

at various H2/oil volume ratios from 300 to 1400 were also

investigated. It showed that HDA conversions increasedfrom 43.2% to 74.6% markedly as H2/oil ratio increased,and the trend of the increment was not drastic as H 2/oilratio large than 500:1. HDS activities achieved the highestconversion of 99.9% when H2/oil was 500:1.

3.3. Performance of catalyst C-ATSP

To evaluate the activity of catalyst C-ATSP, a commer-cial catalyst, which consisting of same active metals ofmolybdenum and nickel as well as alumina support, wasselected as the reference catalyst.Table 3shows the evalu-ation results of catalyst C-ATSP and reference catalyst Aat the conditions of 8.0 MPa, 633 K, 1.0 h1, 500:1 (H2/oil, v/v). It indicated that HDS conversion of catalyst C-ATSP (99.8%) was higher than that of reference catalystA (98.6%). Also HDA conversion of catalyst C-ATSP(64.7%) significantly higher than that of reference catalystA (42.8%). Compared with feedstock, cetane number incre-

ment of catalyst C-ATSP was 9 unit, higher than that ofreference catalyst A (6 unit). At the same time, catalystC-ATSP also the shows the higher liquid yield of101.6 vol.%. The evaluation data at a relatively low conver-sion are also listed inTable 3, the new catalyst (C-ATSP)still showed a higher HDS and HDA conversions than thatof the reference catalyst under reaction conditions of8.0 MPa, 593 K, 2.6 h1, 450:1(H2/oil, v/v).

The evaluation results of the optimized catalyst C-ATSPare listed inTable 4. It shows that HDS and HDA conver-sions of diesel achieved 99.9% and 28.5%, respectively atthe reaction conditions of 6.0 MPa, 593 K, 1.0 h1, 500:1

(H2/oil, v/v), with sulfur content 1.3 lg/g and polyaromat-ics content less than 5.0 wt.% (NIR method) which satisfythe Europe IV diesel specifications. Furthermore, Underthe reaction condition of 8.0 MPa, 613 K, 1.0 h1, 500:1(H2/oil, v/v), HDS and HDA conversions achieved 99.9%and 73.2%, respectively, with sulfur content

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4. Conclusion

A novel NiW loaded hydrotreating catalyst with ETS-10 and AlPO4-5 composite support was developed toimprove HDS and HDA of FCC diesel. ETS-10 andAlPO4-5 showed positive synergism effect and the good

combination of ETS-10 to AlPO4-5 was 1:2 (wt/wt). TheHDS and HDA conversions were 99.9% and 73.2%, respec-tively, cetane number increased by 9 unit when DaqingFCC diesel was used as feedstock under conditions of8.0 MPa, 633 K, 1.0 h1, 500:1 (H2/oil, v/v).

Acknowledgement

The authors gratefully acknowledge the funding ofthis project by MOST 973 Project of China(2004CB217806) and by PetroChina Co.

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