Catalysts carbon alumina

Alkali moderation of supported precious metal catalysts reduces secondary amine formation and generation of ammonia (18). Ammonia in the reaction medium inhibits Rh, but not Ru precious metal catalyst. More secondary amine results from use of more polar protic solvents, CH OH > C2H5OH > Lithium hydroxide is the most effective alkah promoter (19), reducing secondary amine formation and hydrogenolysis. The general order of catalyst procUvity toward secondary amine formation is Pt > Pd Ru > Rh (20). Rhodium s catalyst support contribution to secondary amine formation decreases ia the order carbon > alumina > barium carbonate > barium sulfate > calcium carbonate. 

At temperatures of 300—600°C in the presence of an activated alumina catalyst, carbon dioxide and hydrogen sulfide are formed in almost quantitative yields (29) ... 

Hydrogenation. Hydrogenation is one of the oldest and most widely used appHcations for supported catalysts, and much has been written in this field (55—57). Metals useflil in hydrogenation include cobalt, copper, nickel, palladium, platinum, rhenium, rhodium, mthenium, and silver, and there are numerous catalysts available for various specific appHcations. Most hydrogenation catalysts rely on extremely fine dispersions of the active metal on activated carbon, alumina, siHca-alumina, 2eoHtes, kieselguhr, or inert salts, such as barium sulfate. 

A great many materials have been used as catalyst supports in hydrogena-tion, but most of these catalyst have been in a quest for an improved system. The majority of catalyst supports are some form of carbon, alumina, or silica-alumina. Supports such as calcium carbonate or barium sulfate may give better yields of B in reactions of the type A- B- C, exemplified by acetylenes- cjs-olefins, apparently owing to a weaker adsorption of the intermediate B. Large-pore supports that allow ready escape of B may give better selectivities than smaller-pore supports, but other factors may influence selectivity as well. 

The key elements that characterize chemical composition of the catalyst rre alumina, sodium, metals, and carbon on the regenerated catalyst. 

Park PW, Ledford JS (1998) The influence of surface structure on the catalytic activity of cerium promoted copper oxide catalysts on alumina oxidation of carbon monoxide and methane. Catal Lett 50(1—2) 41 48... 

Usually all alcohols undergo such reactions, forming their alkyl halides and eliminating a molecule of water. The reaction is catalyzed by metal chlorides deposited on carbon, alumina or silica gel or by silica-alumina catalysts. 

Rh > Ir > Ni > Pd > Co > Ru > Fe A plot of the relation between the catalytic activity and the affinity of the metals for halide ion resulted in a volcano shape. The rate determining step of the reaction was discussed on the basis of this affinity and the reaction order with respect to methyl iodide. Methanol was first carbonylated to methyl acetate directly or via dimethyl ether, then carbonylated again to acetic anhydride and finally quickly hydrolyzed to acetic acid. Overall kinetics were explored to simulate variable product profiles based on the reaction network mentioned above. Carbon monoxide was adsorbed weakly and associatively on nickel-activated-carbon catalysts. Carbon monoxide was adsorbed on nickel-y-alumina or nickel-silica gel catalysts more strongly and, in part, dissociatively,... 

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. 

Catalyst particles generally consist of a metal deposited onto the surface of a support and are denoted by metal/support, e.g. Pd/C indicates palladium metal on a carbon support. Among the metals used for catalysis, Pd is often found to be the most active metal. (Augustine 1965) For example, in the aqueous hydrodechlorination of 1,1,2-trichloroethane, Pd catalysts achieved significantly more conversion than Pt or Rh catalysts. (Kovenklioglu et al. 1992) Catalyst supports can vary in shape, size, porosity and surface area typical materials include carbon, alumina, silica and zeolites. 

The influence of varying amounts of the active component in Mo-Ni catalysts on alumina is shown in Fig. 11. The prehydrogenation tests were made with a bituminous-coal middle oil (aniline point—12°C., 17% tar acids, 0.75% N2) with the addition of 1% CS2. Carbon bisulfide is... 

Styrene (phenyl ethylene, vinyl benzene freezing point -30.6°C, boiling point 145°C, density 0.9059, flash point 31.4°C) is made from ethylbenzene by dehydrogenation at high temperature (630°C) with various metal oxides as catalysts, including zinc, chromium, iron, or magnesium oxides coated on activated carbon, alumina, or bauxite (Fig. 1). Iron oxide on potassium carbonate is also used. 

The catalyst is a palladium-on-carbon catalyst or alumina (A1203) with promoters such as germanium compounds suspended in a phosphate buffer solution46. 

Reforming Catalytic reforming is the process of increasing the number of double bonds on a petroleum product but maintaining the same number of carbon atoms. This process is done at high temperatures in the presence of a platinum or rhenium catalyst on alumina [1],... 

Cu-Cr combination on supports like carbon, alumina and monolith were found to be highly active and stable(5,6). Copper has been proposed as the main active species and chromium as a promoter which reduces the deactivation rates(6). However some contradictions still exist about the nature of active sites in copper based catalyst(7,8). 

This catalyst gave significantly lower LB formation than molybdena-alumina or carbon-alumina but appeared to be more prone towards aromatics formation when compared at similar conversion levels. 

The dehydrogenation catalyst must be sufficiently active to allow for very short contact times and the use of low temperatures, to minimize thermal cracking reactions. Carbon deposits are eliminated by beating in the presence of a gas containing oxygen. -This means that the catalyst must be thermally stable to avoid being deactivated during the oxidation of the deposits. The best catalysts contain alumina and chromium oxide, but these cannot be employed in the presence of steam. Operations are conducted at a temperature between 550 and 700 0, and low pressure, less than 0.1.10 Pa absolute. 

For example, a secondary alcohol of an average molecular weight of 202, containing 12—14 carbon atoms, is introduced into a reaction tube packed with a cobalt promoted zirconium catalyst on alumina at a rate of 60 mL/h along with liquid ammonia (90 mL/h) and hydrogen (5 L/h) to produce an amine mixture composed of 92.2% primary amine, 2.15% secondary and tertiary amines, and 5.7% unreacted alcohol (52). The reaction, at 180-190 0 and 24 MPa ( 5 3500 psig), is run by withdrawing the liquid reaction product from the bottom of the reactor. 

The nickel dispersion of the catalyst on alumina support was less than that on silica support. This may be due to the strong interaction between nickel and alumina and undeveloped support pore structure than that of silica support. However, high catalytic activity and resistance to carbon deposition were obtained on the nickel catalyst supported on alumina. This indicated that metal dispersion was not the decisive factor that influenced the catalyst performance. Actually, the catalytic performance of the catalysts were integrative effect of nickel loading, metal dispersion, support, promoter, preparation and activation. 

Many different catalysts have been used for catalytic hydrogenations they are mainly finely divided metals, metallic oxides or sulfides. The most commonly used in the laboratory are the platinum metals (platinum, palladium and, increasingly, rhodium and ruthenium) and nickel. The catalysts are not specific and may be used for a variety of different reductions. The most widely used are palladium and platinum catalysts. They are used either as the finely divided metal or, more commonly, supported on a suitable carrier such as activated carbon, alumina or barium sulfate. 

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