Catalysts industrial examples

Nickel is a moderately lustrous, silvery metal, and is extensively used in alloys (for example coinage, stainless steel) and for plating where a durable resistant surface is required. It is also used as an industrial catalyst, for example in the hydrogenation of unsaturated organic compounds. It is attacked by dilute aqueous acids but not by alkalis it combines readily with many non-metals on heating. 

Catalysts. Nearly aU. of the industrially significant aromatic alkylation processes of the past have been carried out in the Hquid phase with unsupported acid catalysts. For example, AlCl HF have been used commercially for at least one of the benzene alkylation processes to produce ethylbenzene (104), cumene (105), and detergent alkylates (80). Exceptions to this historical trend have been the use of a supported boron trifluoride for the production of ethylbenzene and of a soHd phosphoric acid (SPA) catalyst for the production of cumene (59,106). 

Catalysis by Metal Oxides and Zeolites. Metal oxides are common catalyst supports and catalysts. Some metal oxides alone are industrial catalysts an example is the y-Al202 used for ethanol dehydration to give ethylene. But these simple oxides are the exception mixed metal oxides are more... 

Oxychlorination of methane can yield significant amounts of methylene chloride. A number of patents were obtained by Lummus in the mid-1970s on a high temperature, molten salt oxychlorination process (22,23). Catalyst development work has continued and generally consists of mixtures of Cu, Ni, Cr, or Fe promoted with an alkah metal (24—27). There are no industrial examples of this process at the present time. 

Hydrogenation of Carbon Tetrachloride. Carbon tetrachloride can be hydrogenated, ie, hydrodechlorinated, to chloroform over a catalyst (25,26) or thermally (27). Although there are no industrial examples of this process at this time, it will receive more attention as more carbon tetrachloride becomes available as the CFC-11 and -12 markets decline (see, Chlorocarbons and chlorohydrocarbons, carbon tetrachloride). Chloroform can be further hydrodechlorinated to methylene chloride (28,29). 

Many applications of novolacs are found in the electronics industry. Examples include microchip module packaging, circuit board adhesives, and photoresists for microchip etching. These applications are very sensitive to trace metal contamination. Therefore the applicable novolacs have stringent metal-content specifications, often in the low ppb range. Low level restrictions may also be applied to free phenol, acid, moisture, and other monomers. There is often a strong interaction between the monomers and catalysts chosen and attainment of low metals levels. These requirements, in combination with the high temperature requirements mentioned above, often dictate special materials be used for reactor vessel construction. Whereas many resoles can be processed in mild steel reactors, novolacs require special alloys (e.g. Inconel ), titanium, or glass for contact surfaces. These materials are very expensive and most have associated maintenance problems as well. 

Although most industrial catalysts are heterogeneous, a growing number of industrial reactions use homogeneous catalysts. One example is the production of acetic acid. Most of the 2.1 billion kilograms of acetic acid produced annually is used in the polymer industry. The reaction of methanol and carbon monoxide to form acetic acid is catalyzed by a rhodium compound that dissolves in methanol ... 

Gezdhmte Chemie im Mikroreaktor, VDI Nachrichten, June 2000 Micro-reactor enterprises shape and material variety of micro reactors selectivity gains and new project regimes direct fluorination faster process development BASF investigations safety increase speed-up of catalyst development production for fine chemistry and pharmacy numbering-up first industrial examples for micro-reactor production [215]. 

There are two basic types of packed-bed reactor those in which the solid is a reactant, and those in which the solid is a catalyst. Many examples of the first type can be found in the extractive metallurgical industries. 

The studies discussed above deal with highly dispersed and therefore well-defined rhodium particles with which fundamental questions on particle shape, chemisorption and metal-support interactions can be addressed. Practical rhodium catalysts, for example those used in the three-way catalyst for reduction of NO by CO, have significantly larger particle sizes, however. In fact, large rhodium particles with diameters above 10 nm are much more active for the NO+CO reaction than the particles we discussed here, because of the large ensembles of Rh surface atoms needed for this reaction [28]. Such particles have also been extensively characterized with spectroscopic techniques and electron microscopy we mention in particular the work of Wong and McCabe [29] and Burkhardt and Schmidt [30], These studies deal with the materials science of rhodium catalysts that are closer to the ones used in practice, which is of great interest from an industrial point of view. 

Wakao and Smith [20] originally developed the random pore model to account for the behaviour of bidisperse systems which contain both micro- and macro-pores. Many industrial catalysts, for example, when prepared in pellet form, contain not only the smaller intraparticle pores, but also larger pores consisting of the voids between compressed particles. Transport within the pellet is assumed to occur through void regions... 

Vanadium pentoxide (V203)-based catalysts, for example, are extensively used in industry for a number of catalytic processes including the selective oxidation of aromatic hydrocarbons and transformation of SOj into SO3 [14,15]. The vanadium pentoxide catalysts are usually prepared in supported form on a proper... 

The importance of catalysts in chemical reactions cannot be overestimated. In the destruction of ozone previously mentioned, chlorine serves as a catalyst. Because of its detrimental effect to the environment, CFCs and other chlorine compounds have been banned internationally. Nearly every industrial chemical process is associated with numerous catalysts. These catalysts make the reactions commercially feasible, and chemists are continually searching for new catalysts. Some examples of important catalysts include iron, potassium oxide, and aluminum oxide in the Haber process to manufacture ammonia platinum and rhodium in the Ostwald synthesis of nitric... 

The remaining chapters each deal with a property or a special class of solid. Chapter 4 covers low-dimensional solids, the properties of which are not isotropic. Chapter 5 deals with zeolites, an interesting class of compounds used extensively in industry (as catalysts, for example), the properties of which strongly reflect their stracture. Chapter 6 deals with optical properties and Chapter 7 with magnetic properties of solids. Finally, Chapter 8 explores the exciting field of superconductors, particularly the relatively recently discovered high temperature superconductors. 

The modern industrialized world would be inconceivable without catalysts. Catalysis is a multidisciplinary area of chemistry, particularly industrial chemistry where around 85% of all products pass through at least one catalytic stage. Anyone who is involved with chemical reactions will eventually have something to do with catalysts. For example, the contact process for the production of sulfuric acid was introduced as early as 1880. After World War II, some catalysts for crude oil processing appeared on the US and European markets and, from an environmental standpoint, they became crucial from 1970 onwards because of their contribution to the protection of the environment and thus to a generally higher standard of living. 

The mixed-addenda atoms affect the redox properties mixed-addenda heteropoly compounds are used as industrial oxidation catalysts. For example, the rate of reduction by H2 is slower and less reversible for solid PMO 2-,VJto m+, than for solid PM012O40, although the former are stronger oxidants than the latter in solution (279, 280). The effects of substituting V for Mo on the catalytic activity are controversial (279, 281-284). Differences in redox processes between solutions and solids, the thermal or chemical stability of the heteropoly compounds, and the effects of countercations in solids have been suggested to account for the discrepancies. 

Oxyfunctionalization of lower paraffins such as methane, ethane, propane, and butanes has recently attracted much attention (5, 330, 331, 347-350). Oxidation of -butane to maleic anhydride is an industrial example (346, 351). The oxidation of propane and isobutane with heteropoly catalysts was first reported in 1979 (352). Ai (324a) and Centi et al. (324b, 324c) reported that heteropoly compounds catalyze the oxidation of lower paraffins, especially propane, isobutane, and pentane (324). 

Immobilization often leads to much improved activity or lifetime of the catalyst. For example, the microenvironment of the catalytic center can be chosen to have the proper polarity, ionic strength, etc. for the catalytic activity (367). Prevention of bimolecular deactivation is the key to enhanced stability (115,128). Unprecedented activities have been discovered by immobilization of catalytic centers, as is the case for Mn-catalyzed cis dihy-droxylation (81). Another tantalizing reaction is the selective oxidation of primary carbon atoms, the industrial implementation of which is eagerly awaited (163). 

The catalytic activity of amorphous silica-alumina ([Si—Al]) in reactions via carbonium ions is due to the existence of Bronsted acid sites on their surface. Consequently, amorphous [Si-Al] acid catalysts provide acid sites and transport to the active sites easily. As a result, amorphous [Si-Al] acid catalysts have been widely operated as cracking catalysts. Acid zeolites have been successfully applied as cracking catalysts. However, in some industrial applications of acid catalysts, for example, in the cracking of hydrocarbons of high molecular weight, zeolites are not useful, since... 

This reaction is, however, strongly endothermic and is thermodynamically unfavourable at temperatures below 1500°C [6], With catalysts, for example M0S2, the reaction yield can be much improved, but a maximum reaction yield of about 30% at temperatures of about 1100°C does not offer very good perspectives for industrial use. 

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