Platinum promoted nickel

He became intimately familiar with a wide range of catalytic materials—including aluminum oxide, silica, and clay, as well as nickel, platinum, zinc, and copper—and their role individually and as mixtures 111 effecting chemical transformation. One of Ipatieffs most important lines of research was his breakthrough work on the nature and mechanisms of catalytic promoters on organic reactions. 

Although the action of most additives on a catalytic surface is somewhat obscure, it seems safe to assume that the action of platinic chloride is a promoter action through the formation of metallic platinum under these reductive conditions. The platinum is plated out on the nickel surface. Promoter action has been observed when platinic chloride in amount sufficient to provide only 0.4 mg. of platinum is mixed with as much as 3 g. of Raney nickel catalyst (41). 

A comparative study of other catalysts showed that the action of cobalt was similar to that of nickel but required a higher temperature while negative results were obtained with platinum, palladium, copper, aud iron. The discovery of the catalytic activity of finely divided nickel in promoting the synthesis of methane found immediate application in the various methods which were devised or suggested for the preparation of water-gas having a high methane content.10... 

There are five dihydropyrimidines. The 1,4- and the 1,6-dihydropyrimidines can readily interconvert by tautomerism because of the mobile NH proton. The common metals to effect hydrogenation can be used . Platinum has been the catalyst of choice for the reduction of the 5,6-double bond of uracils, for example, in the addition of deuterium to uracil to produce [5,6- H2]5,6-dihydrouracil. But in the reduction of 2(l/f)-pyrimidinone and its iV-methyl derivative it is the 1,6-dihydro derivatives which are formed. The addition of hydrogen to the 5,6-bond of thymidine and other 5-substituted uridines is stereospecific with rhodium-on-alumina as catalyst. Rhodium-on-charcoal has been useful for hydrogenation of the 5,6-double bond in uracils, uridine, and isocytosine. Raney nickel readily promotes saturation of the 5,6-double bond. Thio derivatives may either be dethiated or taken further to reduced forms by Raney nickel catalysts . 

Tlhe catalytic removal of nitrogen oxides from automotive exhaust gases has been the subject of many studies. Catalysts containing at least 20 different metals, alone and in combination, have been tested. We found that the support used in catalyst preparation is as important as the metal, particularly in catalyst selectivity toward nitrogen rather than ammonia in strongly reducing streams. This paper is a report on some of the effects of support chemistry in a fairly well known system, platinum-promoted nickel (I). We also elucidate the pathways of ammonia removal in this system. 

Catalysts used for preparing amines from alcohols iaclude cobalt promoted with tirconium, lanthanum, cerium, or uranium (52) the metals and oxides of nickel, cobalt, and/or copper (53,54,56,60,61) metal oxides of antimony, tin, and manganese on alumina support (55) copper, nickel, and a metal belonging to the platinum group 8—10 (57) copper formate (58) nickel promoted with chromium and/or iron on alumina support (53,59) and cobalt, copper, and either iron, 2iac, or zirconium (62). 

Hydrogenation Catalysts. The key to catalytic hydrogenation is the catalyst, which promotes a reaction which otherwise would occur too slowly to be useful. Catalysts for the hydrogenation of nitro compounds and nitriles are generally based on one or more of the group VIII metals. The metals most commonly used are cobalt, nickel, palladium, platinum, rhodium, and mthenium, but others, including copper (16), iron (17), and tellurium... 

In past years, metals in dilute sulfuric acid were used to produce the nascent hydrogen reductant (42). Today, the reducing agent is hydrogen in the presence of a catalyst. Nickel, preferably Raney nickel (34), chromium or molybdenum promoted nickel (43), or supported precious metals such as platinum or palladium (35,44) on activated carbon, or the oxides of these metals (36,45), are used as catalysts. Other catalysts have been suggested such as molybdenum and platinum sulfide (46,47), or a platinum—nithenium mixture (48). 

Metals in the platinum family are recognized for their ability to promote combustion at lowtemperatures. Other catalysts include various oxides of copper, chromium, vanadium, nickel, and cobalt. These catalysts are subject to poisoning, particularly from halogens, halogen and sulfur compounds, zinc, arsenic, lead, mercury, and particulates. It is therefore important that catalyst surfaces be clean and active to ensure optimum performance. 

Platinum, especially as platinum oxide, has been used by many investigators. If this catalyst contains residual alkali, it is apt to be ineffective for aromatic ring reduction unless an acidic solvent is used (1,3,19) or unless the compound also contains a carbonyl group, as in acetophenone, where 1,4-and 1,6-addition are possible (46). Nickel, unless especially active, requires vigorous conditions—conditions that may promote side reactions. 

In contrast to phenolic hydroxyl, benzylic hydroxyl is replaced by hydrogen very easily. In catalytic hydrogenation of aromatic aldehydes, ketones, acids and esters it is sometimes difficult to prevent the easy hydrogenolysis of the benzylic alcohols which result from the reduction of the above functions. A catalyst suitable for preventing hydrogenolysis of benzylic hydroxyl is platinized charcoal [28], Other catalysts, especially palladium on charcoal [619], palladium hydride [619], nickel [43], Raney nickel [619] and copper chromite [620], promote hydrogenolysis. In the case of chiral alcohols such as 2-phenyl-2-butanol hydrogenolysis took place with inversion over platinum and palladium, and with retention over Raney nickel (optical purities 59-66%) [619]. 

Aqueous phase reforming of glycerol in several studies by Dumesic and co-workers has been reported [270, 275, 277, 282, 289, 292, 294, 319]. The first catalysts that they reported were platinum-based materials which operate at relatively moderate temperatures (220-280 °C) and pressures that prevent steam formation. Catalyst performances are stable for a long period. The gas stream contains low levels of CO, while the major reaction intermediates detected in the liquid phase include ethanol, 1,2-pro-panediol, methanol, 1-propanol, propionic acid, acetone, propionaldehyde and lactic acid. Novel tin-promoted Raney nickel catalysts were subsequently developed. The catalytic performance of these non-precious metal catalysts is comparable to that of more costly platinum-based systems for the production of hydrogen from glycerol. 

FCC units that use antimony to passivate the deleterious impacts of nickel poisoning can also passivate the platinum (Pt) in the CO promoter. Antimony use can lead to an increase in afterbum or higher amounts of promoter. 

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... 

In having a low activity with respect to C-C bond fission and in promoting isomerization, the Ni-Cu alloys are more reminiscent of platinum than nickel. The explanation given is similar to that proposed for the suppression of ethane hydrogenolysis. Hydrogenolysis requires multicenter adsorption and is therefore more sensitive to alloying than reactions needing fewer centers. This was examined in detail by Ponec et al. (60) in a study of the... 

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