Activity group VIII metals supported

The catalytic activities of group VIII metals supported on activated carbon for methanol carbonylation were in the order as follows ... 

Activities of Group VIII Metal Catalysts. Methanol conversions to methyl acetate and acetic acid on group VIII metals supported upon activated carbon are illustrated in Figure 1, The yield was calculated as methanol conversion to acetyl group. For each catalyst, acetic acid formation is predominant at high temperature while methyl acetate has a point of maximum yield. 

The preparation of OPDA from CNA requires two different catalytic steps, i.e. dechlorination and reduction. Both of these reactions requires hydrogen and are catalyzed by Group VIII metals. Supported palladium is considered as one of the most active catalyst both for hydrodehalogenation [2,3] and reduction of the nitro group [2]. 

Group VIII metals supported on silica are known to hydrogenate preferentially the C=C double bond of a,B-unsaturated aldehydes (as e.g. crotonaldehyde). Only for a few metals, like Os and Co, a significant activity for the hydrogenation of the C=0 group was reported [1]. Improved selectivity for carbonyl group hydrogenation was described for platinum catalysts modified by Sn [2,3,4], Fe... 

The classic catalyst consists of Co-Th02-MgO mixtures supported on Kieselguhr (see Ref. 269) group VIII metals, especially Ni, generally are active,... 

To Illustrate the utility of the technique, we have addressed the question of the anomalous chemlsorptlve behavior of tltanla-supported group VIII metals reduced at high temperatures. The suppression of strong H2 chemisorption on these catalysts has been ascribed to a strong-metal-support Interaction (SMSI) ( ). It has also been found that the reaction activity and selectivity patterns of the catalysts are different In normal and SMSI states... 

Conversions obtained in the hydrogenation of RCN in CH on alumina supported Group VIII metals indicated the lower activity of these catalysts compared to the Raney type catalysts (see Table 3). Almost complete conversion (except Co/A1203) was achieved on M/A1203 catalyst at 140 °C for 9 h instead of... 

It is a matter of speculation as to whether or not the activity would pass through a significant maximum at a surface composition between 0 and 30% Rh. It is interesting to note in this connection that the magnetic susceptibility (156, 157) and the electronic specific heat coefficient (156) increase from low values at 60% Ag-Pd through pure palladium and reach a maximum at - 5% Rh-Pd, thereafter decreasing smoothly to pure rhodium. Activity maxima have also been reported for reduced mixed oxides and supported alloys of group VIII metal pairs. For example, in the... 

Catalysts. - Group VIII metals, conventional base metal catalysts (Ni, Co, and Fe) as well as noble metal catalysts (Pt, Ru, Rh, Pd) are active for the SR reaction. These are usually dispersed on various oxide supports. y-Alumina is widely used but a-alumina, magnesium aluminate, calcium aluminate, ceria, magnesia, pervoskites, and zirconia are also used as support materials. The following sections discuss the base metal and noble metal catalysts in detail, focusing on liquid hydrocarbon SR for fuel cell applications. 

All Group VIII metals, as well as Mn, Cr, and Cu, exhibit some activity in hydroformylation.6 11 Cobalt, the catalyst in the original discovery, is still used mainly in industry rhodium, introduced later, is one of the most active and studied catalysts. The metal catalysts may be applied as homogeneous soluble complexes, heteroge-nized metal complexes, or supported metals. 

Throughout these studies, no product other than propane was observed. However, subsequent studies by Sinfelt et al. [249—251] using silica-supported Group VIII metals (Co, Ni, Cu, Ru, Os, Rh, Ir, Pd and Pt) have shown that, in addition to hydrogenation, hydrocracking to ethane and methane occurs with cobalt, nickel, ruthenium and osmium, but not with the other metals studied. From the metal surface areas determined by hydrogen and carbon monoxide chemisorption, the specific activities of... 

Arrhenius parameters for the methanation reaction on alumina-supported Group VIII metals (227b) were close to the line for cracking reactions on several metals (Table III, A). Activity was based on the numbers of surface metal atoms and a compensation relation was described from these data we calculate c = 0.1185 0.0117, B = 15.216 1.068, and oL = 0.491. 

The catalytic activity of zeolites in alkane to olefin reactions, photochemical conversion reactions, Fischer-Tropsch hydrogenation, isocyana-tion, carbonylation, and related chemistry make up the last theme. An important focus of this is to explore the utility of zeolites as selective heterogeneous catalysts for reactions that involve Group VIII metals. The mechanistic nature of some of this chemistry is presented, along with the characterization of supported organometallic transition metal complexes. 

Vannice, M.A., The catalytic synthesis of hydrocarbons from Ha/CO mixtures over the group VIII metals (I. The specific activities and product disthbutions of supported metals), J. Catal. 37 (1975) 449-461. 

The high temperatures and low pressures needed for this endothermic reaction are conditions conducive to deactivation due to coke deposition through the Boudouard reaction and the decomposition of CH4 [12]. Current research has focused on Group VIII metals [13] on a variety of supports. Most of the work has been on Rh and Ni supported on AI2O3, Ti02, Si02, and MgO [1, 8, 14-17] with some interest in Pt and Pd [5, 10, 18-19]. High activity and low carbon deposition have been observed on Rh catalysts [20-23], but the limited supply of this metal when compared to others reduces the potential for it to be commercially feasible [6]. Many studies have been done on Ni [24-28] which show that the support has a profound effect on the activity and deactivation of the catalyst. Severe deactivation due to carbonaceous deposits was found to... 

Although the most well established function of the support is to disperse the metal and to retard the sintering, recent works on metal-support interaction collected in (1) have shown that the chemi-sorptive and catalytic activity of group VIII metals were considerably lowered when the metal was supported on reducible oxide, such as Ti02, and reduced at high temperature. The objective of the work reported in this paper was to further investigate the role of the support on the adsorptive and on the catalytic properties of platinum. 

In general, inclusion of a Group IB metal with a Group VIII metal markedly decreases the hydrogenolysis activity of the latter but has a much smaller effect on the activity for reactions such as the dehydrogenation and isomerization of hydrocarbons (1,2,5-8). These observations have been supported by the work of other investigators (9-11). 

Direct experimental verification of very highly dispersed bimetallic clusters is complicated by limitations in the ability of physical methods to obtain structural information on such systems. In such a system, however, a catalytic reaction can serve as a sensitive probe to obtain evidence of interaction between the atoms of the two metallic components. For supported bimetallic combinations of a Group VIII and a Group IB metal, the hydrogenolysis of ethane to methane is a useful reaction for this purpose. In the case of unsupported bimetallic systems of this type, as discussed previously, the interaction between the Group VIII metal and the Group IB metal results in a marked suppression of the hydrogenolysis activity of the former. 

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