Role of shaping in the preparation of heterogeneous catalysts: tableting and slip-casting of oxidation catalysts
(2015) Catalysis Today — Vol. 246, p. 81-91 (2015)
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- tThe process and impact of shaping mixed vanadium aluminum (hydr)oxides, VAlOH and VAlO, respec-tively, and BiMo catalysts by tableting and slip-casting were examined. Graphite (G) was employed asa shaping agent for tableting. Without it tableting was impracticable. Graphite was found to enhancethe mechanical resistance of VAlOH-xG and BiMo-xG and changed the surface area by increasing it forthe non-porous BiMo and by decreasing it for the mesoporous VAlOH. In addition, graphite modified thecatalytic performance despite changing neither the chemical nor the structural state of the base VAlO(H)and BiMo catalysts. A positive effect on the performance of VAlO-xG in propane oxidative dehydrogena-tion was found. It was proposed that catalytic active sites are formed on graphite during calcination.Conversely, graphite was harmful for non-calcined VAlOH-xG and BiMo-xG. On the other hand, thepreparation of chemically and physically stable VAlO(H) suspensions for slip-casting was accomplished.Chemical stability was achieved at pHs near the isoelectric point of these catalysts. For physical stability,the use of a dispersing agent, poly(acrylic acid), combined with a control of the solids concentration wasnecessary. A simple and reliable method for preparing VAlOH and BiMo pellets by slip-casting was thusdeveloped with the use of colloidal silica as binding agent. The so prepared pellets were mechanicallyresistant and kept the surface area of the base materials. A decrease in the surface concentration of theactive metals due to surface active site masking by silicon for VAlOH-xSi and BiMo-xSi led to an inferiorcatalytic performance.
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Baldovino Medrano, V., Le, M. T., Van Driessche, I., Bruneel, E., Alcazar, C., Colomer, M. T., Moreno, R., Florencie, A., Farin, B., & Gaigneaux, E. (2015). Role of shaping in the preparation of heterogeneous catalysts: tableting and slip-casting of oxidation catalysts. Catalysis Today, 246, 81-91. https://doi.org/10.1016/j.cattod.2014.08.030 (Original work published 2015)