Activated alumina physical properties

Layered crystalline titanates (CT) [Anthony and Dosch, U.S. Patent 5 177 045 (1993)] are pillared with tetraethyl orthosilicate, 3-aminopropyltrimethoxysilane, and aluminum(III) acetylacetonate to prepare porous and high surface area supports for sulfided NiMo catalyst. Tetraethyl orthosilicate or aluminum(III) acetylacetonate intercalated CT are prepared by stepwise intercalation. First, the basal distance is increased by n-alkylammonium ions prior to intercalation with inorganic compounds. However, an aqueous solution of 3-aminopropyltrimethoxysilane can directly pillar CT without first swelling the titanate with n-alkylamine. The catalytic activities for hydrogenation of pyrene of sulfided NiMo supported silica or alumina pillared CT are higher than those of commercial catalysts (Shell324 and AmocatlC). The silicon and aluminum contents of the pillared CT, used as supports, have considerable effects on the catalytic activities and physical properties of the supports. 

Table 2 summaries overall attrition rate constants (Ka) and physical properties for each dry sorbent. As shown in Table 2, Ka of activated alumina was the lower than any other sorbent, but was similar to activated carbon. However, we used activated carbon as dry sorbent to control CO2 because it is the most cost-effective among others.

Hervey H. Voge and Charles R. Adams The Physical-Chemical Properties of Chro-mia-Alumina Catalysts Charles P. Poole, Jr. and D. S. MacIver Catalytic Activity and Acidic Property of Solid Metal Sulfates... 

Microwave irradiation also shows a beneficial effect in the preparation of solid-supported palladium catalysts for hydrogenation reactions. Thus, alumina- and silica-supported palladium catalysts were synthesised by conventional and microwave heating, and their physical properties and catalytic activity in the hydrogenation of benzene were compared. The alumina-based system prepared under microwave conditions showed turnover numbers an order of magnitude higher than the conventionally prepared catalysts28. 

A large number of heterogeneous catalysts have been tested under screening conditions (reaction parameters 60 °C, linoleic acid ethyl ester at an LHSV of 30 L/h, and a fixed carbon dioxide and hydrogen flow) to identify a suitable fixed-bed catalyst. We investigated a number of catalyst parameters such as palladium and platinum as precious metal (both in the form of supported metal and as immobilized metal complex catalysts), precious-metal content, precious-metal distribution (egg shell vs. uniform distribution), catalyst particle size, and different supports (activated carbon, alumina, Deloxan , silica, and titania). We found that Deloxan-supported precious-metal catalysts are at least two times more active than traditional supported precious-metal fixed-bed catalysts at a comparable particle size and precious-metal content. Experimental results are shown in Table 14.1 for supported palladium catalysts. The Deloxan-supported catalysts also led to superior linoleate selectivity and a lower cis/trans isomerization rate was found. The explanation for the superior behavior of Deloxan-supported precious-metal catalysts can be found in their unique chemical and physical properties—for example, high pore volume and specific surface area in combination with a meso- and macro-pore-size distribution, which is especially attractive for catalytic reactions (Wieland and Panster, 1995). The majority of our work has therefore focused on Deloxan-supported precious-metal catalysts. 

Physical Properties. Physical properties of importance include particle size, density, volume fraction of intraparticle and extraparticle voids when packed into adsorbent beds, strength, attrition resistance, and dustiness. These properties can be varied intentionally to tailor adsorbents to specific applications (See Adsorption liquid separation Aluminum compounds, aluminum oxide (alumina) Carbon, activated carbon Ion exchange Molecular... 

A new class of hi alumina silica-aluminas has been prepared with hi pore volume and with controllable pore size. For 20 wt % Si02 content materials steam treatment at 760°C serves to substantially increase the gas oil cracking activity. Steam stability at 870°C has also been demonstrated for these unique materials. These samples are prepared by recrystallization of co-gels of aluminum and silicon alkoj compounds losing a two-step procedure. AmorjAious alumina shows similar physical properties to those of the silica-alumina co-gels vhen re-crystallized in an analogous manner. 

For the overall performance of potential catalysts in practical application additional factors, such as number of active sites, physical form, and porosity must also be taken into account. The classical commercial iron catalyst is an unsupported catalyst. First of all iron is a cheap material and secondly by the incorporation of alumina a surface area similar to that attained in highly dispersed supported catalysts can be obtained. Of course, for an expensive material such as the platinum group metals, the use of a support material is the only viable option. The properties of the supported catalyst will be influenced by several factors [172]... 

Table 1 lists some of the physical properties of several commercially produced activated aluminas. It shows the available variety of structural properties. These values were obtained from the manufacturer s literature. 

Activated alumina, prepared from aluminium sulphate, exhibited excellent physical parameters, conversion and selectivity at 3so c and were superior to the imported catalyst. The indigenous catalyst showed resistance to carbon deposition, a property which imparts longer life of the catalyst. The catalyst could be regenerated at 400 C, atleast three times, without any significant loss of activity or selectivity. A stream of 100% pure ethylene could be produced at 350 C. 

The activity and selectivity for various products of cinnamaldehyde hydrogenation on Pt/Al catalysts are dependent on the physical properties and the make of the support alumina. 

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