Alumina crushing strength

Granular and extruded carbon supports are stable to hydrothermal conditions as measured by crush strength unlike silica or alumina. There are certain metal oxides, such as mtile titania that are also stable. The data shown in Figure 34.5 shows the retention of original crush strength following 24 h soak in pH adjnsted... 

For regeneration to be technically viable, it must be able to remove deposited vanadium and nickel quantitatively as well as the carbonaceous coke which was co-deposited. The catalyti-cally active metals should remain unaffected in amount, chemistry, and state of dispersion. The alumina support should remain intact, with the surface area, pore-size distribution and crush strength after treatment comparable to that of the original. To be economically viable, the process should be accomplished in a minimum of steps at nearly ambient temperatures and preferably in aqueous solution. The ultimate proof of any such scheme is for the catalytic activity of the regenerated catalyst to be equal to that of a fresh one. 

Through a series of round robin tests conducted by participating laboratories, ASTM Committee D-32 on Catalysts has characterized a variety of catalyst materials using standard test methods. Materials include fluid cracking catalysts, zeolites, silicas, aluminas, supported metals, and a gas oil feedstock. Properties characterized include surface area, crush strength, catalytic microactivity, particle size, unit cell dimensions and metal content. These materials are available from the National Institute of Standards and Technology as reference materials. 

Although several standard test methods have been developed for the chemical analysis of catalysts only small samples of supported platinum and palladium reference materials are available. Zeolites have been characterized for zeolite area, unit cell dimensions, and relative x-ray diffraction intensity. The crush strength of alumina pellets has also been determined. As the needs of catalyst users and producers change so will the materials characterized. To the extent that adequate amounts of material can be donated, standard test methods developed, and round robin tests performed Committee D-32 on catalysts will continue to make them available through NIST as reference materials. 

Binder is needed for forming extrudates. Besides water, colloidal alumina, silica, or cellulose are frequently used as binding material. The crush strength of the extrusion is normally weaker than the products granulated by compaction or compression. However, the advantages of extruding are high capacity and low cost. 

Table 4 Comparison of crush strength and attrition rate of sol-gel-derived y-alumina xerogel granules with commercial sorbents...

An alumina based catalyst, suitable for vapour phase dehydration of ethyl alcohol to ethylene, has been developed. Different physico- chemical parameters viz. bulk density surface area, pore volume, crushing strength, attrition loss, activity, selectivity, coking and regenerative properties, were evaluated and compared with an imported commercial catalyst. Indigenously developed catalyst was superior to the imported commercial catalyst in all respects. 

Fresh alumina or after 24-hr calcination at 1000°C. b Crushing strength measured on individual balls. c Attrition % of fines formed after vibration in a steel container. 

Concerning the mechanical strength measurements, it is observed in Table 1 that phosphorus slightly improves the mechanical strength of alumina extru-dates, while molybdenum seems to have no influence on these properties. The preparation procedures (P->Mo) and (Mo+P) produce catalysts with similar crushing strength values. 

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