Nickel catalyst, silica-supported

The currently practiced commercial process using nickel catalysts, either supported on kieselguhr or silica, has some disadvantages ... 

This paper describes the catalytic activity of nickel phosphide supported on silica, alumina, and carbon-coated alumina in the hydrodesulfurization of 4,6-dimethyldibenzothiophene. The catalysts are made by the reduction of phosphate precursors. On the silica support the phosphate is reduced easily to form nickel phosphide with hi catalytic activity, but on the alumina support interactions between the phosphate and the alumina hinder the reduction. The addition of a carbon overlayer on alumina decreases the interactions and leads to the formation of an active phosphide phase. 

An apparent particle size effect for the hydrodechlorination of 2-chlorophenol and 2,4-dichlorophenol was observed by Keane et al. [147], Investigating silica supported Ni catalysts (derived from either nickel nitrate or nickel ethane-diamine) with particles in the size range between 1.4 and 16.8 nm, enhanced rates for both reactions were observed with increased size over the full range (Figure 13). As electronic factors can be ruled out in this dimension, the observed behavior is traced back to some sort of ensemble effect, known from CFC transformations over Pd/Al203... 

A new isomerization catalyst can be prepared by the modification of silica-supported nickel with tetrabutyltin. This catalyst is capable of the selective isomerization of 3-carene to 2-carene.269... 

The work of Kikuchi et al. (123) with silica-supported catalysts also shows the high tendency of iron (370°-400°C), cobalt (330o-360°C) and nickel (330°-370°C) to catalyze fragmentation (of n-pentane) to methane. This work also showed that with cobalt and nickel, the extent of methane formation tended to decrease with increasing hydrogen partial pressure. Some data are listed in Table XII. 

In the cracking of benzene to acetylene over alumina- and silica-supported nickel catalysts it was observed that the selectivity of the reaction, expressed as the ethyne/ ethene ratio, was dramatically affected (from 1 9 to 9 1) by controlling the micro-wave energy input (i. e. 90% selectivity) [83]. 

Alstrup, I. and Tavares, T., Kinetics of carbon formation from CH4-H2 on silica-supported nickel and Ni-Cu catalysts, /. Catal., 139, 513,1993. 

Some nickel catalysts supported on phosphinated silica were shown to be superior to their homogeneous analogs (224). 

To develop effective catalysts for the C02 reforming of methane, other supports were also used for nickel catalysts, including perovskite (244), Y zeolite (245,246), 5A zeolite (247), high-silica ZSM-5 zeolite (248), and AIPO4 (tridymite) (249). 

Another large class of chemicals produced starting from ethanol are ethyl-amines. When heated to 150-220 °C over a silica- or alumina-supported nickel catalyst, ethanol and ammonia react to produce ethylamine. Further reaction leads to diethylamine and triethylamine. The ethylamines find use in the synthesis of pharmaceuticals, agricultural chemicals, and surfactants. 

Recently, silica supported nickel-boron catalyst was tested in the hydrogenation of cyclopentadiene and was found to be selective in giving cyclopentene47. 

The newest and most commercially successful process involves vapor phase oxidation of propylene to AA followed by esterification to the acrylate of your choice. Chemical grade propylene (90—95% purity) is premixed with steam and oxygen and then reacted at 650—700°F and 60—70 psi over a molybdate-cobait or nickel metal oxide catalyst on a silica support to give acrolein (CH2=CH-CHO), an intermediate oxidation product on the way to AA. Other catalysts based on cobalt-molybdenum vanadium oxides are sometimes used for the acrolein oxidation step. 

Table V shows the results obtained for the carbonylation of dimethyl ether and methyl acetate with molybdenum catalysts supported on various carrier materials. In the case of dimethyl ether carbonylation, molybdenum-activated carbon catalyst gave methyl acetate with an yield of 5.2% which was about one-third of the activity of nickel-activated carbon catalyst. Silica gel- or y-alumina-supported catalyst gave little carbonylated product. Similar results were obtained in the carbonylation of methyl acetate. The carbonylation activity occured only when molybdenum was supported on activated carbon, and it was about half the activity of nickel-activated carbon catalyst.

Sachtler s group (73) and Yasumori (64) studied the IR spectra of silica-supported Ni modified with amino acid and 2-hydroxy acid and the XPS of TA-MRNi. Both authors deduced almost the same model as proposed by Suetaka. Recently Sachtler s group proposed other models as shown in Fig. 22 from results obtained in enantio-differentiating hydrogenations of MAA with nickel catalysts modified with nickel and copper tartrates (74). The nickel tartrate adsorbs at the vacant coordination site of nickel in this model. 

Nickel, on the other hand, on alumina and on silica supports was found to have only five nearby sulfurs (square pyramidal) with Ni-Mo coordination numbers from 1 to 1.5. Ni-Mo-S supported on carbon was observed to have Ni-S coordination numbers of 6 in a trigonal-prismatic configuration. In addition, Ni (at low Ni concentrations) was found to have one nearby Ni, which could indicate that, in some catalysts, Ni is present as pairs on the MoS2 surface. The overall structure of the Ni-Mo-S was believed to be similar to that of millerite (i.e., Ni is located in the center of the MoS edge in a square-pyramidal configuration, with one sulfur extending perpendicular to the surface) (62-64). 

The co-existence of at least two modes of ethylene adsorption has been clearly demonstrated in studies of 14C-ethylene adsorption on nickel films [62] and various alumina- and silica-supported metals [53,63—65] at ambient temperature and above. When 14C-ethylene is adsorbed on to alumina-supported palladium, platinum, ruthenium, rhodium, nickel and iridium catalysts [63], it is observed that only a fraction of the initially adsorbed ethylene can be removed by molecular exchange with non-radioactive ethylene, by evacuation or during the subsequent hydrogenation of ethylene—hydrogen mixtures (Fig. 6). While the adsorptive capacity of the catalysts decreases in the order Ni > Rh > Ru > Ir > Pt > Pd, the percentage of the initially adsorbed ethylene retained by the surface which was the same for each of the processes, decreased in the order... 

Acetylene, when adsorbed on active nickel catalysts, undergoes self-hy-drogenation with the production of ethylene [91], although the extent of this process is less than with ethylene. Similar behaviour has been observed with alumina- and silica-supported palladium and rhodium [53], although with both of these metals ethane is the sole self-hydrogenation product some typical results for rhodium—silica are shown in Fig. 21. 

The metal-catalysed hydrogenation of cyclopropane has been extensively studied. Although the reaction was first reported in 1907 [242], it was not until some 50 years later that the first kinetic studies were reported by Bond et al. [26,243—245] who used pumice-supported nickel, rhodium, palladium, iridium and platinum, by Hayes and Taylor [246] who used K20-promoted iron catalysts, and by Benson and Kwan [247] who used nickel on silica—alumina. From these studies, it was concluded that the behaviour of cyclopropane was intermediate between that of alkenes and alkanes. With iron and nickel catalysts, the initial rate law is... 

Specific activities of silica-supported nickel catalysts for benzene hydrogenation (ftH) and exchange (ftE) at 298 K [39,282]... 

Ethylamines. Mono-, di-, and triethyl amines, produced by catalytic reaction of ethanol with ammonia (330), are a significant oudet for ethanol. The vapor-phase continuous process takes place at 1.38 MPa (13.6 atm) and 150—220°C over a nickel catalyst supported on alumina, silica, or silica—alumina.. In this reductive amination under a hydrogen atmosphere, the ratio of the mono-, di-, and triethyl amine product can be controlled by recycling the unwanted products. Other catalysts used include phosphoric acid and derivatives, copper and iron chlorides, sulfates, and oxides in the presence of acids or alkaline salts (331). Piperidine can be ethylated with ethanol in the presence of Raney nickel catalyst at 200°C and 10.3 MPa (102 atm), to give IV-ethylpiperidine [766-09-6] (332). 

Bouwman and Freriks (18.19) have also noted the advantages of FT spectroscopy and have used this technique to study the adsorption of CO on a silica-supported nickel catalyst at temperatures between 70 and 180°C. These authors point out that FT spectroscopy is particularly advantageous for in situ observation of heated samples since the radiation emitted by the sample is not modulated by the interferometer and hence does not contribute to the fluctuating portion of the interferogram. 

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