Initial Coke Deposition on a NiMo/-Al2O3 Bitumen Hydroprocessing Catalyst
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- 作者：Susan M. Richardson ; Hiroshi Nagaishi ; and Murray R. Gray
- 刊名：Industrial & Engineering Chemistry Research
- 出版年：1996
- 出版时间：November 1996
- 年：1996
- 卷：35
- 期：11
- 页码：3940 - 3950
- 全文大小：274K
- 年卷期：v.35,no.11(November 1996)
- ISSN：1520-5045
文摘
Athabasca bitumen was hydrocracked over a commercialNiMo/
fchars/gamma.gif" BORDER=0 >-Al2O3 catalyst in tworeactors,a microbatch reactor and a 1-L continuous stirred tank reactor (CSTR).Coke deposition oncatalyst was measured as a function of hydrogen pressure, time onstream, and liquid compositionby measuring the carbon content of the cleaned spent catalyst. Thecarbon content ranged from11.3% to 17.6% over the pressure range 6.9-15.2 MPa in CSTRexperiments. Batch and CSTRexperiments showed a rapid approach to a constant coke content withincreasing oil/catalystratio. Coke deposition was independent of product composition forresidue concentrations rangingfrom 8% to 32% by weight. Removal of the coke by tetralin atreaction conditions suggestedreversible adsorption of residue components on the catalyst surface.A physical model based onclearance of coke by hydrogen in the vicinity of metal crystallites ispresented for the cokedeposition behavior during the first several hours of hydrocrackinguse. This model gives goodagreement with experimental data, including the effect of reactiontime, the ratio of total feedweight to catalyst weight, hydrogen pressure, and feed composition, andit agrees with generalobservations from industrial usage. The model implies that exceptat the highest coke levels,the active surfaces of the metal crystallites remain exposed.Severe mass-transfer limitationsare caused by the overall narrowing of the pore structure, which infchars/gamma.gif" BORDER=0 >-Al2O3 would give very loweffective diffusivity for residuum molecules inmicropores.
fchars/gamma.gif" BORDER=0 >-Al2O3 catalyst in tworeactors,a microbatch reactor and a 1-L continuous stirred tank reactor (CSTR).Coke deposition oncatalyst was measured as a function of hydrogen pressure, time onstream, and liquid compositionby measuring the carbon content of the cleaned spent catalyst. Thecarbon content ranged from11.3% to 17.6% over the pressure range 6.9-15.2 MPa in CSTRexperiments. Batch and CSTRexperiments showed a rapid approach to a constant coke content withincreasing oil/catalystratio. Coke deposition was independent of product composition forresidue concentrations rangingfrom 8% to 32% by weight. Removal of the coke by tetralin atreaction conditions suggestedreversible adsorption of residue components on the catalyst surface.A physical model based onclearance of coke by hydrogen in the vicinity of metal crystallites ispresented for the cokedeposition behavior during the first several hours of hydrocrackinguse. This model gives goodagreement with experimental data, including the effect of reactiontime, the ratio of total feedweight to catalyst weight, hydrogen pressure, and feed composition, andit agrees with generalobservations from industrial usage. The model implies that exceptat the highest coke levels,the active surfaces of the metal crystallites remain exposed.Severe mass-transfer limitationsare caused by the overall narrowing of the pore structure, which infchars/gamma.gif" BORDER=0 >-Al2O3 would give very loweffective diffusivity for residuum molecules inmicropores.