Chemical process industry, major commercial

Figure 6. Major commercial processing developments in the chemical process industry (through...

New applications of zeolite adsorption developed recently for separation and purification processes are reviewed. Major commercial processes are discussed in areas of hydrocarbon separation, drying gases and liquids, separation and purification of industrial streams, pollution control, and nonregenerative applications. Special emphasis is placed on important commercial processes and potentially important applications. Important properties of zeolite adsorbents for these applications are adsorption capacity and selectivity, adsorption and desorption rate, physical strength and attrition resistance, low catalytic activity, thermal-hydrothermal and chemical stabilityy and particle size and shape. Apparent bulk density is important because it is related to adsorptive capacity per unit volume and to the rate of adsorption-desorption. However, more important factors controlling the raJtes are crystal size and macropore size distribution. 

Petrochemical industries require many different types of catalysts and adsorbents in process applications. Major portions of such requirements are being met through purchases from commercial catalyst suppliers. The importance of catalysts to chemical and petrochemical industries cannot be overstated. Deviations in catalyst performance from expectations affect yields and feedstock utilization, generate undesirable side reactions and by-products, increase operating costs, and reduce capacity. The cost of such deviations from the expectations which were incorporated in the process design, are not always known and can easily exceed the cost of a new catalyst charge. 

Although there has been a rapid decline in commercial destructive distillation of wood, manufacture of activated carbon by the pyrolysis of cellulosic materials still constitutes a major commercial operation. Finally, the possibility of developing new processes for production of special chemicals by the pyrolysis of cellulose, or the adaptation of the old process to the economy of developing nations blessed with rich forest resources, cannot be overlooked. Controlled pyrolysis of cellulose and cellulosic materials to provide a totally impermeable carbon and other industrial products is an example of the former possibilities. 

One approach to increasing CO2 solvent strength relies on the fact that most volatile materials (such as alcohols, ketones, and hydrocarbons) are soluble in supercritical and near-critical CO2. This allows the employment of a wide range of cosolvents to enhance the C02 s solvation properties. The use of such cosolvent-modified CO2 as a solvent medium is most recognized in the Unicarb spray-coating process commercialized by Union Carbide (now with Dow Chemical, Midland, MI) in the early 1990s. In this process, the majority of traditional solvents used in the spray coatings are replaced by supercritical CO2. This process has been implemented in automotive and furniture industries. 

The commercial process for the production of nylon 6 starts with the oxidation of cyclohexane with oxygen at 160°C to a mixture of cyclohexanol and cyclohexanone with a cobalt(II) catalyst. The reaction is taken to only 4% conversion to obtain 85% selectivity. Barton and co-workers have called this the least efficient major industrial chemical process.240 They have oxidized cyclohexane to the same products using tort bu(ylhydroperoxide with an iron(III) catalyst under air (70°C for 24 h) with 89% efficiency based on the hydroperoxide. The oxidation of cyclohexanol to cyclohexanone was carried out in the same way with 99% efficiency. A cobalt catalyst in MCM-41 zeolite gave 38% conversion with 95% selectivity in 4 days at 70 C.241 These produce ferf-butyl alcohol as a coproduct. It can be dehydrated to isobutene, which can be hydro-... 

Polychlorinated biphenyls ( PCBs ) have been manufactured and used commercially for 50 years because of their chemical stability, fire resistance, and electrical resistance properties. PCBs are frequently used in electrical transformers and capacitors. However, concern has been expressed that PCBs may be toxic to humans and to wildlife. Because of these concerns, the major American manufacturer of PCBs limited its sales of PCBs after 1972 to manufacturers of transformers and capacitors and then in 1977 ceased all manufacture of PCBs and shipped the last of its inventory. Today, PCBs are produced in this country only as incidental byproducts of industrial chemical processes. There are known natural sources of PCBs. 

Heterogeneous catalytic oxidation is a well studied and industrially useful process. Industrial catalytic oxidation of vapors and gases is a very broad field and is dealt with in several texts and review articles. Catalytic oxidation, both partial and complete, is an important process for such reactions as the partial oxidation of ethene and propene, ammoxidation of propene to acrylonitrile, maleic anhydride production, production of sulfuric acid, and oxidation of hydrocarbons in automotive exhaust catalysts. By far, the majority of oxidation catalysts and catalytic oxidation processes have been developed for these industrially important partially oxidized products. However, there are important differences between the commercial processes and the complete catalytic oxidation of VOCs at trace concentrations in air. For instance, in partial oxidation, complete oxidation to CO2 and H2O is an undesirable reaction occurring in parallel or in series to the one of interest. Other differences include the reactant concentration and temperature, the type of catalyst used, and the chemical nature of the oxidizable compound. Approximate ranges of the major independent variables of interest in this review are shown in Table 1. 

The use of coupled onhne spectroscopies (ATR-FTIR/Raman) for the development and the monitoring of industrial chemical processes was demonstrated by Wiss and ZiUan [14], For the investigation of two types of reaction, respective fiber optical spectroscopic probes were installed in a commercial reaction calorimeter. The authors pointed out that such a setup is more appropriate for industrial applications than bypass systems for sampling, and can be used in a pilot plant or production plant without major modification of the available equipment. 

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