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Role of shaping in the preparation of heterogeneous catalysts: Tableting and slip-casting of oxidation catalysts

Paper ID Volume ID Publish Year Pages File Format Full-Text
54218 47001 2015 11 PDF Available
Title
Role of shaping in the preparation of heterogeneous catalysts: Tableting and slip-casting of oxidation catalysts
Abstract

•Shaping of bismuth molybdate and vanadium–aluminum mixed (hydr)oxide catalysts was investigated.•Graphite was demonstrated to be an effective shaping agent for tableting.•Graphite can have a promotional effect in ODHP.•A method to prepare catalyst pellets by slip-casting was developed.•Colloidal silica, used as a slip-casting binder, had a masking effect on catalyst active sites.

The process and impact of shaping mixed vanadium aluminum (hydr)oxides, VAlOH and VAlO, respectively, and BiMo catalysts by tableting and slip-casting were examined. Graphite (G) was employed as a shaping agent for tableting. Without it tableting was impracticable. Graphite was found to enhance the mechanical resistance of VAlOH-xG and BiMo-xG and changed the surface area by increasing it for the non-porous BiMo and by decreasing it for the mesoporous VAlOH. In addition, graphite modified the catalytic 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 dehydrogenation 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, the preparation 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 was necessary. A simple and reliable method for preparing VAlOH and BiMo pellets by slip-casting was thus developed with the use of colloidal silica as binding agent. The so prepared pellets were mechanically resistant and kept the surface area of the base materials. A decrease in the surface concentration of the active metals due to surface active site masking by silicon for VAlOH-xSi and BiMo-xSi led to an inferior catalytic performance.

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Keywords
Catalyst shaping; Tableting; Slip-casting; VAlO(H); BiMo; Selective oxidation
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Role of shaping in the preparation of heterogeneous catalysts: Tableting and slip-casting of oxidation catalysts
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Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Today - Volume 246, 15 May 2015, Pages 81–91
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us