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Chunshan Song - One of the best experts on this subject based on the ideXlab platform.
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MCM-41-supported Co-Mo Catalysts for deep hydrodesulfurization of light cycle oil
Catalysis Today, 2003Co-Authors: Uday T. Turaga, Chunshan SongAbstract:Abstract Light cycle oil (LCO), a by-product of the fluid catalytic cracking (FCC) process in a petroleum refinery, can be used as a blendstock for the production of diesel and jet fuels. Regulatory and operational issues result in need for new and more active Catalysts for the deep hydrodesulfurization (HDS) of diesel feedstocks, such as LCO. This paper reports the activity of a mesoporous molecular sieve MCM-41-supported Co-Mo Catalyst in comparison to a commercial γ-alumina (Al2O3)-supported Co-Mo Catalyst for the desulfurization of a LCO with a sulfur content of 2.19 wt.%. The HDS of dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene—polyaromatic sulfur compounds present in LCO—and their relative reactivities in terms of conversion were examined as a function of time on stream in a fixed-bed flow reactor. The MCM-41-supported Catalyst demonstrates consistently higher activity for the HDS of the refractory dibenzothiophenic sulfur compounds, particularly 4,6-dimethyldibenzothiophene. The presence of a large concentration of aromatics in LCO appears to inhibit the HDS of the substituted dibenzothiophenes.
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Influence of nitrogen compounds on deep hydrodesulfurization of 4,6-dimethyldibenzothiophene over Al2O3- and MCM-41-supported Co-Mo sulfide Catalysts
Catalysis Today, 2003Co-Authors: Uday T. Turaga, Chunshan SongAbstract:Abstract The present work focuses on the effect of nitrogen compounds on the activity of MCM-41- and γ-Al 2 O 3 -supported Co-Mo Catalysts for the deep hydrodesulfurization of 4,6-dimethyldibenzothiophene (4,6-DMDBT) in a fixed-bed flow reactor. Sulfur removal to the depths required by new specifications will require knowledge of the influence of non-sulfur diesel fuel components on deep hydrodesulfurization. The main objective of this paper is to examine the activity of hydrodesulfurization Catalysts during and, most importantly, after exposure to basic and non-basic nitrogen. Quinoline (basic nitrogen) inhibits catalytic activity of both γ-Al 2 O 3 - and MCM-41-supported Catalysts. It strongly inhibits hydrogenation and hydrogenolysis activity as evidenced by decreased selectivity for cyclohexylbenzene and biphenyl derivatives, respectively. To a certain extent, the long-term effects of quinoline are reversible. Carbazole (non-basic nitrogen) has little effect on the γ-Al 2 O 3 -supported Co-Mo Catalyst but significantly inhibits the activity of the MCM-41-supported Co-Mo Catalyst. The inhibition of the MCM-41-supported Catalyst is reversible following removal of carbazole from the feedstock. Molecular modeling was also conducted to derive the bond order and electron charges of the nitrogen and sulfur compounds, which are helpful to understanding the experimental results.
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Mesoporous molecular sieve MCM-41 supported Co–Mo Catalyst for hydrodesulfurization of dibenzothiophene in distillate fuels
Applied Catalysis A: General, 1999Co-Authors: Chunshan Song, Kondam Madhusudan ReddyAbstract:Abstract A mesoporous aluminosilicate molecular sieve with MCM-41 type structure was synthesized using aluminum isopropoxide as the Al source. Supported Co–Mo/MCM-41 Catalysts were prepared by co-impregnation of Co(NO3)2·6H2O and (NH4)6Mo7O24 followed by calcination and sulfidation. For comparison, conventional Al2O3-supported sulfided Co–Mo Catalysts were also prepared using the same procedure. These two types of Catalysts were examined at two different metal loading levels in hydrodesulfurization of a model fuel containing 3.5 wt% sulfur as dibenzothiophene in n-tridecane. At 350–375°C under higher H2 pressure (6.9 MPa), sulfided Co–Mo/MCM-41 Catalysts show higher hydrogenation and hydrocracking activities at both normal and high metal loading levels, whereas Co–Mo/Al2O3 Catalysts show higher selectivity to desulfurization. Co–Mo/MCM-41 Catalyst at high metal loading level is substantially more active than the Co–Mo/Al2O3 Catalysts.
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Mesoporous molecular sieve MCM-41 supported Co–Mo Catalyst for hydrodesulfurization of petroleum resids
Catalysis Today, 1998Co-Authors: Kondam Madhusudan Reddy, Boli Wei, Chunshan SongAbstract:Abstract In this work, we explored the potential of mesoporous zeolite-supported Co–Mo Catalyst for hydrodesulfurization of petroleum resids, atmospheric and vacuum resids at 350–450°C under 6.9 MPa of H 2 pressure. A mesoporous molecular sieve of MCM-41 type was synthesized; which has SiO 2 /Al 2 O 3 ratio of about 41. MCM-41 supported Co–Mo Catalyst was prepared by co-impregnation of Co(NO 3 ) 2 ·6H 2 O and (NH 4 ) 6 Mo 7 O 24 followed by calcination and sulfidation. Commercial Al 2 O 3 supported Co–Mo (criterion 344TL) and dispersed ammonium tetrathiomolybdate (ATTM) were also tested for comparison purposes. The results indicated that Co–Mo/MCM-41(H) is active for HDS, but is not as good as commercial Co–Mo/Al 2 O 3 for desulfurization of petroleum resids. It appears that the pore size of the synthesized MCM-41 (28 A) is not large enough to convert large-sized molecules such as asphaltene present in the petroleum resids. Removing asphaltene from the resid prior to HDS has been found to improve the catalytic activity of Co–Mo/MCM-41(H). The use of ATTM is not as effective as that of Co–Mo Catalysts, but is better for conversions of >540°C fraction as compared to noncatalytic runs at 400–450°C.
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Mesoporous zeolite-supported Co-Mo Catalyst for hydrodesulfurization of petroleum resids
Preprints-American Chemical Society Division of Petroleum Chemistry, 1997Co-Authors: Kondam Madhusudan Reddy, Boli Wei, Chunshan SongAbstract:In this paper we present the preliminary results on our attempts to upgrade two types of petroleum resids (atmospheric and vacuum), particularly with regard to the removal of sulfur and the reduction of the molecular weight of the feedstocks to material with boiling points below 540°C.
Kondam Madhusudan Reddy - One of the best experts on this subject based on the ideXlab platform.
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Mesoporous molecular sieve MCM-41 supported Co–Mo Catalyst for hydrodesulfurization of dibenzothiophene in distillate fuels
Applied Catalysis A: General, 1999Co-Authors: Chunshan Song, Kondam Madhusudan ReddyAbstract:Abstract A mesoporous aluminosilicate molecular sieve with MCM-41 type structure was synthesized using aluminum isopropoxide as the Al source. Supported Co–Mo/MCM-41 Catalysts were prepared by co-impregnation of Co(NO3)2·6H2O and (NH4)6Mo7O24 followed by calcination and sulfidation. For comparison, conventional Al2O3-supported sulfided Co–Mo Catalysts were also prepared using the same procedure. These two types of Catalysts were examined at two different metal loading levels in hydrodesulfurization of a model fuel containing 3.5 wt% sulfur as dibenzothiophene in n-tridecane. At 350–375°C under higher H2 pressure (6.9 MPa), sulfided Co–Mo/MCM-41 Catalysts show higher hydrogenation and hydrocracking activities at both normal and high metal loading levels, whereas Co–Mo/Al2O3 Catalysts show higher selectivity to desulfurization. Co–Mo/MCM-41 Catalyst at high metal loading level is substantially more active than the Co–Mo/Al2O3 Catalysts.
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Mesoporous molecular sieve MCM-41 supported Co–Mo Catalyst for hydrodesulfurization of petroleum resids
Catalysis Today, 1998Co-Authors: Kondam Madhusudan Reddy, Boli Wei, Chunshan SongAbstract:Abstract In this work, we explored the potential of mesoporous zeolite-supported Co–Mo Catalyst for hydrodesulfurization of petroleum resids, atmospheric and vacuum resids at 350–450°C under 6.9 MPa of H 2 pressure. A mesoporous molecular sieve of MCM-41 type was synthesized; which has SiO 2 /Al 2 O 3 ratio of about 41. MCM-41 supported Co–Mo Catalyst was prepared by co-impregnation of Co(NO 3 ) 2 ·6H 2 O and (NH 4 ) 6 Mo 7 O 24 followed by calcination and sulfidation. Commercial Al 2 O 3 supported Co–Mo (criterion 344TL) and dispersed ammonium tetrathiomolybdate (ATTM) were also tested for comparison purposes. The results indicated that Co–Mo/MCM-41(H) is active for HDS, but is not as good as commercial Co–Mo/Al 2 O 3 for desulfurization of petroleum resids. It appears that the pore size of the synthesized MCM-41 (28 A) is not large enough to convert large-sized molecules such as asphaltene present in the petroleum resids. Removing asphaltene from the resid prior to HDS has been found to improve the catalytic activity of Co–Mo/MCM-41(H). The use of ATTM is not as effective as that of Co–Mo Catalysts, but is better for conversions of >540°C fraction as compared to noncatalytic runs at 400–450°C.
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Mesoporous zeolite-supported Co-Mo Catalyst for hydrodesulfurization of petroleum resids
Preprints-American Chemical Society Division of Petroleum Chemistry, 1997Co-Authors: Kondam Madhusudan Reddy, Boli Wei, Chunshan SongAbstract:In this paper we present the preliminary results on our attempts to upgrade two types of petroleum resids (atmospheric and vacuum), particularly with regard to the removal of sulfur and the reduction of the molecular weight of the feedstocks to material with boiling points below 540°C.
Uday T. Turaga - One of the best experts on this subject based on the ideXlab platform.
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MCM-41-supported Co-Mo Catalysts for deep hydrodesulfurization of light cycle oil
Catalysis Today, 2003Co-Authors: Uday T. Turaga, Chunshan SongAbstract:Abstract Light cycle oil (LCO), a by-product of the fluid catalytic cracking (FCC) process in a petroleum refinery, can be used as a blendstock for the production of diesel and jet fuels. Regulatory and operational issues result in need for new and more active Catalysts for the deep hydrodesulfurization (HDS) of diesel feedstocks, such as LCO. This paper reports the activity of a mesoporous molecular sieve MCM-41-supported Co-Mo Catalyst in comparison to a commercial γ-alumina (Al2O3)-supported Co-Mo Catalyst for the desulfurization of a LCO with a sulfur content of 2.19 wt.%. The HDS of dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene—polyaromatic sulfur compounds present in LCO—and their relative reactivities in terms of conversion were examined as a function of time on stream in a fixed-bed flow reactor. The MCM-41-supported Catalyst demonstrates consistently higher activity for the HDS of the refractory dibenzothiophenic sulfur compounds, particularly 4,6-dimethyldibenzothiophene. The presence of a large concentration of aromatics in LCO appears to inhibit the HDS of the substituted dibenzothiophenes.
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Influence of nitrogen compounds on deep hydrodesulfurization of 4,6-dimethyldibenzothiophene over Al2O3- and MCM-41-supported Co-Mo sulfide Catalysts
Catalysis Today, 2003Co-Authors: Uday T. Turaga, Chunshan SongAbstract:Abstract The present work focuses on the effect of nitrogen compounds on the activity of MCM-41- and γ-Al 2 O 3 -supported Co-Mo Catalysts for the deep hydrodesulfurization of 4,6-dimethyldibenzothiophene (4,6-DMDBT) in a fixed-bed flow reactor. Sulfur removal to the depths required by new specifications will require knowledge of the influence of non-sulfur diesel fuel components on deep hydrodesulfurization. The main objective of this paper is to examine the activity of hydrodesulfurization Catalysts during and, most importantly, after exposure to basic and non-basic nitrogen. Quinoline (basic nitrogen) inhibits catalytic activity of both γ-Al 2 O 3 - and MCM-41-supported Catalysts. It strongly inhibits hydrogenation and hydrogenolysis activity as evidenced by decreased selectivity for cyclohexylbenzene and biphenyl derivatives, respectively. To a certain extent, the long-term effects of quinoline are reversible. Carbazole (non-basic nitrogen) has little effect on the γ-Al 2 O 3 -supported Co-Mo Catalyst but significantly inhibits the activity of the MCM-41-supported Co-Mo Catalyst. The inhibition of the MCM-41-supported Catalyst is reversible following removal of carbazole from the feedstock. Molecular modeling was also conducted to derive the bond order and electron charges of the nitrogen and sulfur compounds, which are helpful to understanding the experimental results.
Arumugam Manthiram - One of the best experts on this subject based on the ideXlab platform.
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Nafion–Imidazole– H3PO4 Composite Membranes for Proton Exchange Membrane Fuel Cells
Journal of The Electrochemical Society, 2007Co-Authors: Yongzhu Fu, Arumugam ManthiramAbstract:Water in Nafion 115 membranes was replaced by imidazole and then doped with H 3 PO 4 to form imidazole-H 3 PO 4 complexes as proton solvent. Both the Nafion-imidazole and Nafion-imidazole-H 3 PO 4 composite membranes exhibited higher proton conductivity than the plain Nafion membrane under anhydrous conditions at T > 100°C. Although the Nafion-imidazole membranes with Pt Catalyst exhibit poor performance in proton exchange membrane fuel cells (PEMFCs) at low temperatures (60 and 80°C) due to the poisoning of the Pt Catalyst by imidazole, doping with H 3 PO 4 improves the fuel cell performance significantly due to the suppression of imidazole poisoning through the formation of imidazolium salt with H 3 PO 4 . The imidazole poisoning could also be suppressed further by replacing the Pt Catalyst with a newly developed Pd-Co-Mo Catalyst. The Nafion-imidazole-H 3 PO 4 membranes with the Pd-Co-Mo Catalyst show performance superior to that of Nafion membrane with the Pt or Pd-Co-Mo Catalyst in PEMFCs at 100°C.
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Pd-Co-Mo electroCatalyst for the oxygen reduction reaction in proton exchange membrane fuel cells.
The journal of physical chemistry. B, 2005Co-Authors: V. Raghuveer, Arumugam Manthiram, Allen J. BardAbstract:The catalytic activity of carbon supported Pd−Co−Mo for the oxygen reduction reaction (ORR) in a single cell proton exchange membrane fuel cell (PEMFC) has been investigated at 60 °C and compared with data from commercial Pt Catalyst and our previously reported Pd−Co−Au and Pd−Ti Catalysts. The Pd−Co−Mo Catalyst with a Pd:Co:Mo atomic ratio of 70:20:10 exhibits slightly higher catalytic activity like the Pd−Co−Au Catalyst than the commercial Pt Catalyst, but with excellent chemical stability unlike the Pd−Co−Au Catalyst. The Pd−Co−Mo Catalyst also exhibits better tolerance to methanol poisoning than Pt. Investigation of the catalytic activity of the Pd−Co−Mo system with varying composition and heat treatment temperature reveals that a Pd:Co:Mo atomic ratio of 70:20:10 with a heat treatment temperature of 500 °C exhibits the highest catalytic activity. Although the degree of alloying increases with increasing temperature from 500 to 900 °C as indicated by the X-ray diffraction data, the catalytic activity ...
Adesoji A. Adesina - One of the best experts on this subject based on the ideXlab platform.
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Alumina-supported cobalt-molybdenum Catalyst for slurry phase Fischer–Tropsch synthesis
Catalysis Today, 2007Co-Authors: Cyrus G. Cooper, Tuan-huy Nguyen, Y.j. Lee, Kelfin M. Hardiman, Tomasz Safinski, Frank P. Lucien, Adesoji A. AdesinaAbstract:Abstract An evaluative investigation of the Fischer–Tropsch performance of two Catalysts (20%Co/Al2O3 and 10%Co:10%Mo/Al2O3) has been carried out in a slurry reactor at 2 MPa and 220–260 °C. The addition of Mo to the Co-Catalyst significantly increased the acid-site strength suggesting strong electron withdrawing character in the Co-Mo Catalyst. Analysis of steady-state rate data however, indicates that the FT reaction proceeds via a similar mechanism on both Catalysts (carbide mechanism with hydrogenation of surface precursors as the rate-determining step). Although chain growth, α, on both Catalysts were comparable (α ≅ 0.6), stronger CH2 adsorption on the Co-Mo Catalyst and lower surface concentration of hydrogen adatoms as a result of increased acid-site strength was responsible for the lower individual hydrocarbons production rate compared to the Co Catalyst. The activation energy, E, for Co (96.6 kJ mol−1), is also smaller than the estimate for the Co-Mo Catalyst (112 kJ mol−1). Transient hydrocarbon rate profiles on each Catalyst are indicative of first-order processes, however the associated surface time constants are higher for alkanes than alkenes on individual Catalysts. Even so, for each homologous class, surface time constants for paraffins are greater for Co-Mo than Co, indicative that the adsorption of CH2 species on the Co-Mo surface is stronger than on the monometallic Co Catalyst.
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A statistical evaluation of preparation conditions on the performance of Ce-promoted Co-Mo Fischer-Tropsch Catalyst
Korean Journal of Chemical Engineering, 2000Co-Authors: K. Eisenacher, Adesoji A. AdesinaAbstract:This paper describes a statistical approach to the optimal selection of preparation conditions for a ceria-promoted Co-Mo Catalyst used during CO hydrogenation. Eight Catalyst samples based on a full factorial design were prepared via incipient wetness method. Evaluation was carried out in laboratory packed bed reactor using synthesis gas containing H_2:CO=2 at 280 °C and 110 kPa. BET was unaffected by pH although increased calcination temperature induced only a small drop in total surface area. More significantly, Catalysts calcined at low temperature (350 °C) suffered a 3-fold loss in metal surface area when treated at high temperatures (550 °C) while an increase in pH improved the metal area value. pH values above the isoelectric point (IEP=5.65) and low calcination temperature favoured activity and alkene selectivity. High reduction temperature, however, appeared to enhance methane suppression. Additionally, 2-factor interactions were statistically more significant than 3-factor interactions at 95% confidence level. Optimisation of the polynomial models describing the response data was also consistent with qualitative inferences.
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Improved alkene selectivity in carbon monoxide hydrogenation over silica supported cobalt-molybdenum Catalyst
Applied Catalysis A: General, 1994Co-Authors: Hong Chen, Adesoji A. AdesinaAbstract:Abstract The Fischer-Tropsch synthesis performance of a Co-Mo bimetallic Catalyst containing 6Co:lMo:4K:100SiO 2 has been studied and compared with a similar monometallic cobalt Catalyst. The bimetallic system showed nearly 100% improvement in alkene-alkane ratio at the experimental conditions of 101 kPa and 280°C (553 K) and CO-H 2 ratio of 1:19 to 19:1. Ethylene-to-methane ratio (EMR) over the Co-Mo Catalyst was about 70-100% better than the cobalt Catalyst over the wide composition range studied. The kinetics over the Co-Mo Catalyst also followed conventional Anderson-Schulz-Flory (ASF) polymerisation kinetics suggesting that there is no fundamental change in the reaction mechanism. The increase in chain growth probability and alkene content was attributed to substantial methane suppression caused by the introduction of molybdenum to the Catalyst. Activation energy values for the light hydrocarbons over the bimetallic Catalyst were in the range 85–120kJ/mol and about 10-15% lower than the corresponding estimates over the monometallic system.