Catalyst economic importance 425 - producers

In the second step, the synthesis gas and additional steam are passed over a metal oxide catalyst at about 400°C. Under these conditions, the carbon monoxide component of the synthesis gas and the steam are converted to carbon dioxide and more hydrogen. This reaction of CO with H20 is called the water-gas shift reaction because it shifts the composition of synthesis gas by removing the toxic carbon monoxide and producing more of the economically important hydrogen ... 

Catalysts are used in the production of a large variety of chemicals and fuels, as demonstrated by the fact that catalyst-based manufacturing accounts for about 60% of chemical products and 90% of processes (Senkan 2001). These numbers will likely increase in the future, considering all the advantages of a catalytic process it requires only small amount of a smart molecule to produce a large quantity of the desired compound the catalyst usually allows operation under mild reaction conditions also the economic benefits of an efficient catalytic process are enormous since it is less capital-intensive, has lower operating costs, produces products of higher purity and fewer by-products. In addition, catalysts provide important environmental benefits. 

Heterogeneous catalysis is widely used in the chemical industry to produce thousands of different products in massive amounts. On a global scale, the technological and economic importance of heterogeneous catalysis is immense because it provides the backbone of the world s chemical and oil industries. This is the reason for intense research in both academic and industrial laboratories. Depending on the particular compounds to be synthesized, the chemical active constituents of a catalysts can be metals ". ... 

Up to the early 1980s VCM was produced by addition of hydrogen chloride to acetylene. In this process the gaseous reactants are brought into contact with the catalyst at slightly increased pressure and 100-250 °C [1]. Mercury(II) chloride on activated carbon is used as a catalyst in this heterogeneous process. Today, however, this reaction has no economical importance. Nowadays, VCM is exclusively produced by thermal decomposition of DCE. 

The second period is closely related to the development of the so-called three-way catalysts (TWC). As is known, TWCs constitute the current technology of election for the abatement of exhaust emissions (Unbumed hydrocarbons, CO, and NOx) from gasoline-fuelled vehicles [10,18,19,246,247]. More than 95% of the gasoline vehicles nowadays produced in the world are equipped with a TWC converter [247]. The economic importance is also extraordinary, the TWC sales representing about one fourth of global catalyst market [246]. 

Since the special properties of the catalysts decisively influence the economics of a process, their true economic importance is considerably higher than their. qnarket value . The value of the products that are produced with catalysts is 500 billion EUR p.a. Also market estimates vary widely - for example, there are no figures available for the considerable internal consumption of the chemical industry - the key importance of industrial catalysts can be recognized from the above data. In this chapter we shall treat the catalysts according to their area of use. 

The formation of aromatic isocyanate trimers is of economic importance, because rigid insulation foams, having isocyanurate structures built into their network structure, are produced from aromatic diisocyanates. Triphenyl isocyanurates with hydroxyl or carboxyl groups in their p-positions can be obtained on hydrolysis of McsSiO- and McsSiOCO-groups, respectively, with hydrochloric acid °. Such trifunctional compounds are of use in the construction of network polymers. The mechanism of the phenyl isocyanate trimer-ization, using Pd(o) diimide catalysts was elucidated recently. The initial steps of this trimerization reaction involve a chain growth process as encountered in the anionic homopolymerization of isocyanates. 

The choice of catalyst is based primarily on economic effects and product purity requirements. More recentiy, the handling of waste associated with the choice of catalyst has become an important factor in the economic evaluation. Catalysts that produce less waste and more easily handled waste by-products are strongly preferred by alkylphenol producers. Some commonly used catalysts are sulfuric acid, boron trifluoride, aluminum phenoxide, methanesulfonic acid, toluene—xylene sulfonic acid, cationic-exchange resin, acidic clays, and modified zeoHtes. 

This in itself draws attention to one of the artistic aspects of the industrial catalyst designer s job. Money values are neither absolute, invariant, nor always logically desirable entities. For example, resource producing nations can increase feedstock prices and they may do so for political rather than for hard, technological reasons. One very important consequence is the fact that a catalytic process that is economic in one year but not in the next is not as attractive as one that can adapt. 

The ageing and decay characteristics of catalysts are of immense importance in defining the economics of processes. The simplest criterion that can be applied is that of total productivity during the life of the catalyst and also loss of productivity during the shut down required for catalyst replacement. Figure 2 illustrates notional performances for two catalysts A and B in hypothetical processes in which productivity is simply a measure of quantity of product produced. Catalyst A has a lower initial productivity but is more stable in use and dies off at a much lower rate than catalyst B, which has a high initial productivity which falls relatively... 

Heterogeneous catalysts have been used industrially for well over 100 years. Amongst the first processes was the catalytic hydrogenation of oils and fats to produce margarine using finely divided nickel. It is quite likely that when this process was first operated in the late nineteenth century unhealthy amounts of nickel remained in the product. The issue of leaching and the avoidance of trace catalyst residues are still important aspects of research from both economic and environmental points of view. 

As already mentioned, the most important industrial application of homogeneous hydrogenation catalysts is for the enantioselective synthesis of chiral compounds. Today, not only pharmaceuticals and vitamins [3], agrochemicals [4], flavors and fragrances [5] but also functional materials [6, 7] are increasingly produced as enantiomerically pure compounds. The reason for this development is the often superior performance of the pure enantiomers and/or that regulations demand the evaluation of both enantiomers of a biologically active compound before its approval. This trend has made the economical enantioselective synthesis of chiral performance chemicals a very important topic. 

A catalyst is a substance that increases the rate of a chemical reaction without being consumed by the reaction. Catalysts are of tremendous importance in all facets of chemistry, from the laboratory to industry. Many industrial reactions, for example, would not be economically viable without catalysts. Well over three million tonnes of catalysts are produced annually in North America. 

However, in contrast to fuels, petrochemicals intermediates must be produced at extremely high purities. For example, CO at ppm levels will poison polyethylene catalysts, and acetylene in ethylene at this level will produce a crosslinked polymer that will have unsatisfactory properties. Therefore, the chemical engineer must produce these intermediates with extremely high purities, and this requires both careful attention to minor reactor products and to efficient separation of them from the desired product. These factors are also important in the economics of petrochemicals. 

Ethanolamines became available commercially in the early 1930s they assumed steadily growing commercial importance as intermediates after 1945, because of the large-scale production of ethylene oxide. Since the mid-1970s, economical production of very pure, colourless ethanolamines has been possible. Ethanolamines are produced on an industrial scale exclusively by reaction of ethylene oxide (see I ARC, 1994) and excess ammonia. This reaction takes place slowly, but is accelerated by water. An anhydrous procedure uses a fixed-bed ion-exchange resin catalyst (Hammer et al., 1987). 

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