Catalysis commercial processes

A thkd method utilizes cooxidation of an organic promoter with manganese or cobalt-ion catalysis. A process using methyl ethyl ketone (248,252,265—270) was commercialized by Mobil but discontinued in 1973 (263,264). Other promoters include acetaldehyde (248,271—273), paraldehyde (248,274), various hydrocarbons such as butane (270,275), and others. Other types of reported activators include peracetic acid (276) and ozone (277), and very high concentrations of cobalt catalyst (2,248,278). 

The most widely used process for the production of phenol is the cumene process developed and Hcensed in the United States by AHiedSignal (formerly AHied Chemical Corp.). Benzene is alkylated with propylene to produce cumene (isopropylbenzene), which is oxidized by air over a catalyst to produce cumene hydroperoxide (CHP). With acid catalysis, CHP undergoes controUed decomposition to produce phenol and acetone a-methylstyrene and acetophenone are the by-products (12) (see Cumene Phenol). Other commercial processes for making phenol include the Raschig process, using chlorobenzene as the starting material, and the toluene process, via a benzoic acid intermediate. In the United States, 35-40% of the phenol produced is used for phenoHc resins. 

Table 3.12 surveys current industrial applications of enantioselective homogeneous catalysis in fine chemicals production. Most chiral catalyst in Table 3.12 have chiral phosphine ligands (see Fig. 3.54). The DIP AMP ligand, which is used in the production of L-Dopa, one of the first chiral syntheses, possesses phosphorus chirality, (see also Section 4.5.8.1) A number of commercial processes use the BINAP ligand, which has axial chirality. The PNNP ligand, on the other hand, has its chirality centred on the a-phenethyl groups two atoms removed from the phosphorus atoms, which bind to the rhodium ion. Nevertheless, good enantio.selectivity is obtained with this catalyst in the synthesis of L-phenylalanine. 

Under the operating conditions, the reaction intermediates (w-hexenes and i-hexenes in n-hexane isomerization) are thermodynamically very adverse, hence appear only as traces in the products. These intermediates (which are generally olefinic) are highly reactive in acid catalysis, which explains that the rates of bifunctional catalysis transformations are relatively high. The activity, stability, and selectivity of bifunctional zeolite catalysts depend mainly on three parameters the zeolite pore structure, the balance between hydrogenating and acid functions, and their intimacy. In most of the commercial processes, the balance is in favor of the hydrogenation function, that is, the transformations are limited by the acid function. 

The contact process was invented by Phillips in England in 1831 but was not used commercially until many years later. Today 99% of all sulfuric acid is manufactured by this method. It was developed mainly because of the demand for stronger acid. All new contact plants use interpass absorption, also known as double absorption or double catalysis. This process will be described in detail in Fig. 2.3. 

It can be expected that solid bases could be successful for commercializing the alkylation of toluene with methanol as a route to styrene, or for selective alkene coupling. There is no doubt that achieving success in several important commercial processes will boost the field of solid base catalysis. Because it appears to be difficult to achieve superbasic organic resins, much more attention should be paid to enhancement of the base strengths of solid superbases. Further work should be done on supported alkali metals and mixed metal oxides. Development of new solid superbases will be improved by increasing our understanding of how alkali metal clusters (302-304) interact with supports and become stabilized. 

A recent literature report described a green procedure for the condensation of arylacetonitriles with cyclic ketones using phase-transfer catalysis. This process was applied to the synthesis of venlafaxine, which was realized in overall 30% yield in two steps from commercially available 14. The condensation step was run in aqueous sodium hydroxide in the presence of tetrabutylammonium sulfate, to provide quantitative yield of intermediate 15. Hydrogenation in a formalin-methanol mixture provided the final product venlafaxine (1) in 30% overall yield. This protocol did not necessitate intermediate purification steps, making it attractive from the commercial standpoint. 

The important commercial process of sulfur dioxide oxidation has been studied by a number of investigators. A set of steps that has been proposed for both platinum and vanadium oxide-based catalysis by Horiuti (7) for the overall reaction 2SOz + 02 2SOs is as follows ... 

It should be emphasized here that there is a vast difference between the microenvironment of the catalyst surface as examined by the type of analytical techniques mentioned in Section 9.1 and the overall surface that influences commercial processes. Until the modern techniques became available, however, catalyst preparation was mostly a matter of trial and error we have now entered an era in which science has a chance to catch up with technology. It seems fairly safe to predict that a greatly increased understanding of heterogeneous catalysis will emerge as modern surface chemistry matures. 

We have seen previously shape-selective catalysis by ZSM-5 in the conversion of methanol to gasoline (Chapter 15).-7 Other commercial processes include the formation of ethylbenzene from benzene and ethylene and the synthesis of p-xylene. The efficient performance of ZSM-5 catalyst has been attributed to its high acidity and to the peculiar shape, arrangement, and dimensions of the channels. Most of the active sites are within the channel so a branched chain molecule may not be able to diffuse in, and therefore does not react, while a linear one may do so. Of course, once a reactant is in the channel a cavity large enough to house the activated complex must exist or product cannot form. Finally, the product must be able to diffuse out. and in some instances product size and shape exclude this possibility. For example, in the methylu-uon of toluene to form xylene ... 

T he six years since the first Advances in Chemistry Series volume, Homogeneous Catalysis—Industrial Applications and Implications, (Number 70) have been a period of mushrooming activity in the field. Not only has this activity been marked by the discovery of new types of catalysts and new insights into reaction mechanisms, but several major commercial processes based on homogeneous catalysts have been developed. 

DuPont has developed another commercial process, based on catalysis by a nitrilase (E.C. 3.5.5.1), to the solvent l,5-dimethyl-2-piperidone (1,5-DMPD) (Xolvone ) with applications in electronics and coatings (Thomas, 2002). The raw material is 2-methylglutaronitrile (MGN), a by-product during the manufacture of adipodinitrile (ADN) for nylon 6,6 discussed in the previous section. Such a raw material situation leads to coupling of nylon-6,6, 5-cyanovaleramide, and l,5-dimethyl-2-piperidone production, a situation that most likely is specific to DuPont and thus not prone to much competition. 

INDUSTRIAL CATALYSIS is the commercial process of finding and enhancing the performance of substances that increase the rate at which a chemical reaction reaches equilibrium. Industrial catalysis is vitally concerned with the activity, selectivity, lifetime, and environmental impact of... 

In 1905 Haber reported a successful experiment in which he succeeded in producing NH3 catalytically. However, under the conditions he used (1293 K) he only found minor amounts of NH3. He extrapolated his value to lower temperatures (at 1 bar) and concluded that a temperature of 520 K was the maximum temperature for a commercial process. This was the first application of chemical thermodynamics to catalysis, and precise thermodynamic data were not then known. At that time Haber regarded the development of a commercial process for ammonia synthesis as hopeless and he stopped his work. Meanwhile, Nernst had also investigated the ammonia synthesis reaction and concluded that the thermodynamic data Haber used were not correct. He arrived at different values and this led Haber to continue his work at higher pressures. Haber tried many catalysts and found that a particular sample of osmium was the most active one. This osmium was a very fine amorphous powder. He approached BASF and they decided to start a large program in which Bosch also became involved. 

A breakthrough occurred in the mid-seventies when Union Carbide and Celanese introduced Rh/phosphine catalysts in commercial processes. This catalyst is based on the work by Wilkinson s group he received the Nobel prize for his work in 1973. Rhodium-based catalysts are much more active than cobalt catalysts and, under certain conditions, at least for 1-alkenes, they are also more selective. The processes for the hydroformylation of higher alkenes (detergent alcohols) still rely on cobalt catalysis. A new development is the use of water-soluble complexes obtained through sulphonation of the Ligands (Ruhrchemie). 

As already discussed in Chapter 1, the commercialization, by Sumitomo [GO-64], of a vapor phase Beckmann rearrangement of cyclohexanone oxime to caprolactam over a high-silica MFI (ZSM-5 type) zeolite (Fig. 2.21) is another benchmark in zeolite catalysis. The process, which currently operates on a 90000 tpa scale, replaces a conventional one employing stoichiometric quantities of sulfuric acid and producing ca. 2 kg of ammonium sulfate per kg of caprolactam. 

Salts of the perrhenate anion (including perrhenic acid) are not only the single most important group of starting materials for the synthesis of other rhenium compounds but are also of importance in catalysis and other commercial processes. Although they are formally coordination complexes of Revn and they appear quite extensively in the chemical literature (e.g. see Chemical Abstracts), much of the interest in them is outside the confines of the topic of coordination chemistry as it is commonly accepted. Accordingly, an effort has been made here to keep the coverage of their chemistry to a minimum. 

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