Hydrogenation catalytic performance, selectivity

The preparation of iron impregnated activated carbon as catalysts and the catalytic performance of these catalysts were studied in benzene hydroxylation with hydrogen peroxide as oxidant. 5.0Fe/AC catalyst containing 5.0 wt% iron on activated carbon yielded about 16% phenol. The addition of Sn on 5.0Fe/AC catalyst led to the enhancement of selectivity towards phenol. 

PICA) show excellent activity and enantioselectivity for reaction of such bulky ketones.Selection of alcoholic solvent is important to achieve high catalytic performance. Thus, hydrogenation of pinacolone with the (5)-TolBINAP/PICA-Ru catalyst (S/C = 100,000) in C2H5OH quantitatively gives (5)-3,3-dimethyl-2-buta-nol in 98% ee (Figure 1.21). The reaction in conventional 2-propanol with the same catalyst results in the S alcohol in only 36% ee. 

In the field of selective hydrogenation two important properties are used to describe the catalytic performance the activity and the selectivity of the catalysts. Their values have to be optimized. The simplest approach is to fix the desired conversion level and ranking the catalysts according to their selectivity data. An alternative way for catalyst optimization is the use of the so called "desirability function" d. Upon using this function different optimization parameters can be combined in a common function Dj. In the combination different optimization parameters (often called as objective functions) can be taken into account with different weights [21]. The single desirability function for the conversion (a) can be described by the following formula ... 

In this paper, principles and potential of the catalytic performance profiling is introduced and illustrated with respect to the identification of a suitable Pd/C catalyst for selective hydrogenation of a hydroxy-olefm from a library of diverse palladium catalysts. 

Because of the pure performance of traditional Cu catalysts in the hydrogenation of C02, efforts have been made to find new, more effective catalysts for direct C02 hydrogenation. The problem is to improve selectivity, specifically, to find catalysts that display high selectivity toward methanol formation and, at the same time, show low selectivity in the reverse water-gas shift reaction, that is, in the formation of CO. It appears that copper is the metal of choice for methanol synthesis from C02 provided suitable promoters may be added. Special synthesis methods have also been described for the preparation of traditional three-component Cu catalysts (Cu-ZnO-A1203 and Cu-Zn0-Cr203) to improve catalytic performance for C02 reduction. 

Certain molybdenum complexes, such as MoO(02)(PhCONPhO)22 and the peroxo-molybdenum compound derived from tris(cetylpyridinium) 12-molybdophosphate and hydrogen peroxide (PCMP),28 are able to selectively oxidize secondary alcohols. PCMP is able to perform selective oxidations in catalytic amounts in the presence of hydrogen peroxide as secondary oxidant.29... 

Velu S, Suzuki K. Selective production of hydrogen for fuel cells via oxidative steam reforming of methanol over CuZnAl oxide catalysts effect of substitution of zirconium and cerium on the catalytic performance. Top Catal. 2003 22(3-4) 235-44. 

The hydrogenation of fatty acids or fatty esters is of industrial importance for the production of fatty alcohols. Usually, the hydrogenation is performed in slurry-phase or fixed-bed reactors over copper-chromium oxide catalyst at elevated temperature and pressure.37 Rieke et al. investigated the hydrogenation of methyl dodecanoate over copper-chromium oxide at 280°C and 13.8 MPa H2, in order to study the side reactions that occur during hydrogenation.37 On the basis of the potential reaction routes described by Rieke et al., the pathways leading to C12 alcohol and various byproducts are summarized in Scheme 10.2, with exclusion of the formation and reactions of acetals. It has been found that both catalytic activity and selectivity correlated well with the crystallinity of the copper-chromium ox-... 

Besides Ga, other metals such as Zn (11, 12) and Pt (13) have also been used in combination with ZSM-5 zeolite for C2-C4 aromatization. However, besides aromatization, Pt also catalyzes other undesired reactions, such as hydrogenolysis, hydrogenation and dealkylation that leads to excessive formation of methane and ethane, and limits the selectivity to aromatics. Therefore, Ga- and Zn-ZSM-5 catalysts are preferred over Pt-ZSM-5 except, perhaps, in the case of the more refractory ethane, in where a higher dehydrogenating function is needed to activate the reactant. The catalytic performance of Ga and Zn/ZSM-5 for propane aromatization is compared in Table 2.2. The results obtained on the purely acidic H-ZSM-5 are also included in the table. As observed, a higher conversion and yield of aromatics is obtained for the Ga/ZSM-5 catalyst. 

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