Catalyst synergy

A new explanation for catalyst synergy between two solid phases of a catalyst has recently been advanced by Delmon (174) in studies of hydrodesulfurization (HDS) with mixtures of MoS2 and Co9S8. Both the activity and the selectivity of the HDS reaction increased if the contact between the admixed phases was improved. Spiltover hydrogen from the Co9S8 partially reduces the MoS2 modest reduction creates hydrogenation sites and further reduction creates HDS sites. 

Ji M, Zhang X, Wang J, Park SE (2013) Ethylbenzene dehydrogcmatirai with CO2 over Fe-doped MgAl204 spinel catalysts synergy effect between and Fe L J Mol Catal A Chem 371 36-41... 

In this work we present results obtained both with batch and continuous flow operation of the gas-recycle reactor-separator utilizing Ag and Ag-Sm203 electrocatalysts and Sr(lwt%) La203 catalysts, in conjunction with Linde molecular sieve 5A as the trapping material, and discuss the synergy between the catalytic and adsorption units in view of the OCM reaction network. 

The ethylene selectivity (Fig. 5) and thus the ethylene yield depend strongly on the adsorbent mass (Fig. 5). For fixed catalyst mass, oxygen supply I/2F and methane conversion there is an optimal amount of adsorbent for maximizing ethylene selectivity and yield (Fig. 5). Excessive amounts of adsorbent cause quantitative trapping of ethane and thus a decrease in ethylene yield according to the above reaction network. This shows the important synergy between the catalytic and adsorbent units which significantly affects the product distribution and yield. 

A Molecular Approach to Synergy Generation in Co Mo Binary Sulfide Catalysts for Hydrodesulfurization... 

Xu et al. have obtained similar results with n-butyl bromide using TBAB (10 mol%) and alumina (4 1 ivjxv) as the catalyst [13]. Benzyl acetate was also conveniently prepared from sodium acetate and benzyl halide by use of microwave irradiation and PTC in synergy [14]. 

Iglesia, E., Soled, S. L., Fiato, R. A., and Via, G. H. 1993. Bimetallic synergy in cobalt-ruthenium Fischer-Tropsch synthesis catalysts. J. Catal. 143 345-68. 

W. C. SCHATTENMANN, M. SpiEGLER, et at, Angew. Chem. 1998, 110, 2631-2633 Angew. Chem. Int. Ed. 1998, 37, 2490-2493 (b) Highly Active Ruthenium Catalysts for Olefin Metathesis The Synergy of N-Heterocyclic Carbenes and Coordi-natively Labile Ligands, T. Weskamp,... 

Dow Chemical has launched a range of foams which are said to exceed industry standards for softness and toughness. This article supplies brief details of the foams which are based on Dow s Insite catalyst technology. Synergy Soft Touch Foams are produced using Dow s Index Interpolymers, a new thermoplastic polymer family based on the copolymerisation of ethylene and styrene. The foams are offered in three grades of softness, and other properties include shock absorption, vibration damping and insulation. 

The oxidation of propene to acrolein has been one of the most studied selective oxidation reaction. The catalysts used are usually pure bismuth molybdates owing to the fact that these phases are present in industrial catalysts and that they exhibit rather good catalytic properties (1). However the industrial catalysts also contain bivalent cation molybdates like cobalt, iron and nickel molybdates, the presence of which improves both the activity and the selectivity of the catdysts (2,3). This improvement of performances for a mixture of phases with respect to each phase component, designated synergy effect, has recently been attributed to a support effect of the bivalent cation molybdate on the bismuth molybdate (4) or to a synergy effect due to remote control (5) or to more or less strong interaction between phases (6). However, this was proposed only in view of kinetic data obtained on a prepared supported catalyst. 

In a recent work we were able to show that an electronic effect was detected between Bi2Mo30i2 and a mixed iron and cobalt molybdate with an enhancement of the electrical conductivity of the cobalt molybdate with the substitution of the cobaltous ions by the ferrous ions (7). However this effect alone cannot explain the synergy effect and we have investigated the influence of both the de ee of subtitution of the cobalt with the iron cations in the cobalt molybdate and the ratio of the two phases (for a given substituted cobalt molybdate) on the catalytic propert cs of the mixture.We have tried to characterize by XPS and EDX-STEM the catalysts before and after the catalytic reaction in order to detect a possible transformation of the solid. The results obtained are presented and discussed in this study. 

These results and the comparison between the catalyst particles before and after catalytic run point out the ability for these particles both to exchange electrons and oxygen anions and to change morphology under the conditions of the catalytic reaction with spreading of the oxides one over the other. These two phenomena should be at the basis of the explanation of synergy effect in molybdates based catalysts. The fact that some FexCoi.xMo04 particles remain free (i.e. not deposited on bismuth molybdate particles) show that even more active and selective catalysts may be obtained in more reliable preparation conditions. 

Figure 6. Schematic representation of the catalysts particles for explaining synergy effect for mixtures of Bi2Mo30j2 and 67 0 33 4 ...

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