Reaction alumina-supported nickel

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. 

Platinum, ruthenium, and mixed platinum-ruthenium species supported on silica Various alumina-supported nickel complexes Dispersion of metallic species during treatments in 02 and H2 at temperatures up to 473 K Reaction of nickel complexes and interaction with support at temperatures... 

The nature of the carbon deposits formed on an alumina-supported nickel catalyst have been characterized by their reactivity with H2 and H 0 during temperature-programmed surface reaction (TPSR). 

Carbon Deposited on Nickel via 02 Exposure TPSR with 1-atm H2 Carbon deposited on alumina-supported nickel (17 wt%) following ethylene exposure at various temperatures has a wide range of activity for reaction with H2 (Figure 2). Different states of carbon are identified by maxima in the rate of CH production. The temperature of the rate maximum (T ) for a particular carbon state was generally found to he independent of both the amount of carbon in that state and the temperature of deposition. Thus T will be taken as characteristic of the reactive state of... 

Surface-science studies using nickel single-crystal surfaces revealed that the methanation reaction is surface-structure-insensitive. Both the (111) and (100) crystal faces yield the same reaction rates over a wide temperature range. These specific rates are also the same as those found for alumina-supported nickel, further proving the structure insensitivity of the process. This is also the case for the reaction over ruthenium, rhodium, molybdenum, and iron. 

Hydrogenolysis of triphenylarsine (AsPh ) on alumina supported nickel (Ni/Al Oj) has been studied as model reaction for metallic catalyst poisoning. The hydrogenolysis of AsPh on Ni/Al Oj occurs at temperature ranging from 303 to 443 K under 12 bars of hydrogen and in n-heptane solution. It has been followed by kinetics analysis of the AsPh consumption and Benzene and cylohexane evolution as well as XRD measurements of the metallic and intermetallic phase(s). 

Triphenylarsine (AsPhs) hydrogenolysis on Ni/AlaOs can be used as a model for metallic poisoning by organometallic compounds. The aim of this work is to study the process of the Ni/A Oa deactivation by AsPhs in the model reaction of benzene hydrogenation and to describe the mechanism of AsPhs reaction with various alumina supported nickel solids. 

Several hydrogenations of olefins and aromatics are performed at relatively low temperature using supported metal catalysts, mostly alumina-supported nickel, cobalt, palladium, or platinum. For example, Pt/Al203 catalysts are applied in various vapor-phase benzene hydrogenation technologies, to produce cyclohexane or to reduce benzene content in gasoline. The benzene hydrogenation reaction is carried out at temperatures of... 

EP.12 A fuel cell system aims to produce 6.5 x lO kWh/month. It is fed with hydrogen at a rate of 1.5 x 10 kg/h. This hydrogen is generated by steam reforming with the 15% of alumina-supported nickel catalyst (MgAl204). The main reactions are described below ... 

Decreasing of the active surface by sintering and recrystallization processes. Example is the decrease of the active nickel surfaces through recrystallization on alumina-supported nickel catalysts in hydrogenation reactions. 

Nickel. As a methanation catalyst, nickel is presently preeminent. It is relatively cheap, it is very active, and it is the most selective to methane of all the metals. Its main drawback is that it is easily poisoned by sulfur, a fault common to all the known active methanation catalysts. The nickel content of commercial nickel catalysts is 25-77 wt %. Nickel is dispersed on a high-surface-area, refractory support such as alumina or kieselguhr. Some supports inhibit the formation of carbon by Reaction 4. Chromia-supported nickel has been studied by Czechoslovakian and Russian investigators. 

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]. 

The sulfidation mechanisms of cobalt- or nickel-promoted molybdenum catalysts are not yet known in the same detail as that of M0O3, but are not expected to be much different, as TPS patterns of Co-Mo/A1203 and Mo/Al203 are rather similar [56J. However, interactions of the promoter elements with the alumina support play an important role in the ease with which Ni and Co convert to the sulfidic state. We come back to this after we have discussed the active phase for the hydrodesulfurization reaction in more detail. 

Among the early systemmatic studies of the metal-catalysed hydrogenation of acetylene were those of Sheridan et al. [158,168—170] who investigated the kinetics and product distributions over pumice-supported metals. Subsequently, the reaction has been extensively studied by Bond et al. [9,165,171—175] over pumice- and alumina-supported metals and metal powders. The reaction of acetylene with deuterium over nickel [91, 163] and alumina-supported noble Group VIII metals [164,165] has also been investigated. 

One of the characteristic features of the metal-catalysed reaction of acetylene with hydrogen is that, in addition to ethylene and ethane, hydrocarbons containing more than two carbon atoms are frequently observed in appreciable yields. The hydropolymerisation of acetylene over nickel—pumice catalysts was investigated in some detail by Sheridan [169] who found that, between 200 and 250°C, extensive polymerisation to yield predominantly C4 - and C6 -polymers occurred, although small amounts of all polymers up to Cn, where n > 31, were also observed. It was also shown that the polymeric products were aliphatic hydrocarbons, although subsequent studies with nickel—alumina [176] revealed that, whilst the main products were aliphatic hydrocarbons, small amounts of cyclohexene, cyclohexane and aromatic hydrocarbons were also formed. The extent of polymerisation appears to be greater with the first row metals, iron, cobalt, nickel and copper, where up to 60% of the acetylene may polymerise, than with the second and third row noble Group VIII metals. With alumina-supported noble metals, the polymerisation prod-... 

The reaction of acetylene with deuterium has been studied over alumina-supported noble Group VIII metals [164,165], whilst over nickel-pumice catalysts the reaction of perdeuteroacetylene with hydrogen has been investigated [163]. In both of these studies, the deuteroethylene distributions have been interpreted in terms of the steady state analysis discussed in Sect. 4.4. Typical deuteroethylene distributions together with the values of p, q and s are shown in Table 16. 

In the nickel- and cobalt-catalysed reactions [166,207] it was observed that the butene distribution depended upon the temperature of reduction of the catalyst. For both powders and alumina-supported catalysts prepared by reduction of the oxides, reduction at temperatures below ca. 330° C gave catalysts which exhibited so-called Type A behaviour where but-2-ene was the major product and the frans-but-2-ene/cis-but-2-ene ratio was around unity. Reduction above 360° C (Ni) or 440° C (Co) yielded catalysts which gave frans-but-2-ene as the major product (Type B behaviour). It is of interest to note that the yield of cis-but-2-ene was not significantly dependent upon the catalyst reduction temperature with either metal. 

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... 

Supported nickel catalysts catalyze steam-methane reforming and the concurrent shift reaction. The catalyst contains 15-25 wt% nickel oxide on a mineral carrier. Carrier materials are alumina, aluminosilicates, cement, and magnesia. Before start-up, nickel oxide must be reduced to metallic nickel with hydrogen but also with natural gas or even with the feed gas itself. 

It is also clear that double-bond-shift is relatively facile on the nickel-silica-alumina catalysts. Double-bond shift may occur on the nickel cation centers or on the silica-alumina support or on both14. The hexene products formed from ethene are as expected for a reaction sequence involving (1) dimerization of ethene to but-l-ene etc, (2) double-bond-shift of but-l-ene to a but-2-ene mixture, and (3) reaction of but-2-ene with a further ethene... 

Steam reforming was the primary reaction over these nickel catalysts. The presence of hydrocarbons (G2 to G5) which would indicate cracking reactions occurred to the extent of less than 10% in the reaction products. The presence of methane, which would indicate partial reforming, did not exceed 5% in the reaction products. There does not appear to be any significant difference in product selectivity for the n-hexane steam reforming reaction over nickel on the 2 quite different supports—zeolite vs. alumina. Carbonaceous residues accumulated in the case of all the nickel catalysts where reforming activity was sustained and the carbon deposition on the zeolite catalysts compared favorably with G56. 

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