Catalytic activity olefin selectivity

Some progress has been made in explaining the splendid catalytic performance of multicomponent bismuth molybdates that are used widely for the industrial oxidations and ammoxidations of lower olefin. We have seen that the catalytic activity and selectivity are greatly enhanced by the multifunctionalization of the catalyst systems. Many functions newly introduced are... 

Earlier work in this laboratory showed that chromium oxide supported on alumina is a good catalyst for the conversion of olefins (ref. 1) as well as paraffins (ref. 2) to nitriles with high selectivities, by reaction of NO with the hydrocarbons (nitroxidation). Recent work (ref. 3) reported preliminary results of the nitroxidation of paraxylene as an extension of the use of C Oj-Al Oj to the catalytic synthesis of aromatic nitriles. It should be mentioned that only few data are available in the literature related to the nitroxidation of aromatic hydrocarbons. Teichner et al (ref. 4 ) reported interesting results of selective synthesis of benzonitrile by nitroxidation of toluene on NiO-AlgO catalysts. Improvements of the catalytic activity and selectivity in this reaction were reached by use of C Og-Al. which also exhibits striking properties in the synthesis of paratolunitrile by contact of NO with paraxylene (ref. 3). 

Hayashi and Moffat (792) reported that the Al salt and the NH4 salt were effective catalysts for the conversion of methanol to hydrocarbons. They claimed that the NH4 salts show high catalytic activity and selectivity for the formation of saturated hydrocarbons rather than olefins. The salts of organic... 

The investigation of the mechanism of olefin oxidation over oxide catalysts has paralleled catalyst development work, but with somewhat less success. Despite extensive efforts in this area which have been recently reviewed by several authors (9-13), there continues to be a good deal of uncertainty concerning the structure of the reactive intermediates, the nature of the active sites, and the relationship of catalyst structure with catalytic activity and selectivity. Some of this uncertainty is due to the fact that comparisons between various studies are frequently difficult to make because of the use of ill-defined catalysts or different catalytic systems, different reaction conditions, or different reactor designs. Thus, rather than reviewing the broader area of selective oxidation of hydrocarbons, this review will attempt to focus on a single aspect of selective hydrocarbon oxidation, the selective oxidation of propylene to acrolein, with the following questions in mind ... 

In addition, the present results clearly show that y-alumina improves the catalytic activity and selectivity to long chain hydrocarbons. Particularly, when the Fe-K is supported on y-alumina, the selectivity to olefins is improved as well as the activity and chain growth ability. It is likely that the marked improvements achieved by using both K and alumina is due to well dispersed active phase Fe-K. The better dispersion of Fe and K should provide the efficient interaction of Fe and K as well more active sites for the CO2 hydrogenation. The improved dispersion seems to be the result of strong metal-support interaction. 

High Catalytic Activity and Selectivity in the Hydroformylation of Olefins... 

Prior investigations on enantioselective aldol additions by Wennemers and coworkers in 2007 demonstrated the crucial relevance of the secondary amine at the N-terminus, the carboxylic acid in the side chain and a well-defined p-turn conformation of H-Pro-Pro-Asp-NH2-type proteins for the high catalytic activity and selectivity Thus, the employment of tripeptides comprising this motive was expanded to the 1,4-addition of aldehydes to nitro-olefins and nitroethylene (Scheme 13.12a) ° Peptide 15a comprising D-proline at the N-terminus showed the best catalytical performance for the addition of a series of aliphatic and aromatic aldehydes to aliphatic and aromatic nitro-olefins with good to excellent yields and excellent enantioselec-tivity The proposed transition states for both 15a and the above-mentioned parent peptide predicts the formation of the enantiomeric products. 

Wang CM, Wang YD, Liu FIX, Xie ZK, Liu ZP Catalytic activity and selectivity of meth-ylbenzenes in HSAPO-34 catalyst for the methanol-to-olefins conversion from first principles, J Catal 271 386—391, 2010. 

The hydration of oleflns is important for the direct synthesis of alcohols from olefins in the pietroleum industry and has been extensively studied over various solid acid catalysts. In the case of ethanol synthesis from ethylene and water, silicotungstic acids, silicophosphoric acids, solid phosphoric acids, metal sulfates, " and metal oxides have been studied as solid acid catalysts. In its industrial process, a solid phosphoric acid catalyst (Shell patent) is widely used throughout the world. The nature of the active (acidic) sites which exhibit high catalytic activity and selectivity is discussed below together with the hydration mechanism involving the catalytic behavior. 

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