Industrial Organic Synthesis
Industrial Organic Synthesis
the large-scale production of organic compounds (the annual output of plants is tens and hundreds of thousands of tons). Products of industrial organic synthesis are used as intermediates in various branches of the chemical industry (production of synthetic rubbers and fibers, plastics, dyes, and biologically active compounds). They are also used in the national economy as chemical toxicants, solvents, and extradants.
The products of industrial organic synthesis are varied in their chemical nature; they include synthetic hydrocarbons (butadiene, isoprene, styrene, and alkyl aromatic compounds), oxygen-containing compounds (alcohols, aldehydes, ketones, carboxylic acids, aliphatic and aromatic ethers and esters, and olefin epoxides), halogen-containing and sulfur-containing compounds, and nitriles. The assortment of products of industrial organic synthesis is small and relatively constant compared to that of small-scale organic synthesis. The raw materials for industrial organic synthesis are alkanes and unsaturated hydrocarbons (mainly olefins and dienes), as well as aromatic hydrocarbons, synthesis gas, carbon monoxide, and various inorganic compounds such as halogens, acids and alkalies, oxygen, and hydrogen. The major sources of organic raw materials are petroleum, natural gas, casinghead gas, and petroleum refining gas. Solid natural fuels (coal, oil shale, and wood-chemical materials) still play a lesser role as raw materials for industrial organic synthesis. The simultaneous existence of several industrial processes for obtaining the most important products, which differ in their technology and raw materials, is characteristic of industrial organic synthesis. Many processes use a combination of several reactions proceeding simultaneously (oxidative ammonolysis and oxidative dehydrogenation).
The particular features of industrial organic synthesis are a function of the large scale of production and the high requirements for the purity of the products obtained. A main characteristic is the continuity of technological processes, which determines the production flow diagram as a whole. Sometimes, particularly in the case of batch processes, process flow diagrams with parallel connection of apparatus are used. The technological limitations resulting from physicochemical factors (the equilibrium yield of reaction products and the existence of azeotropic mixtures), as well as economic and safety requirements, necessitate the use of feedback coupling among the devices in the process flow diagram (mass and energy flows directed from later devices to earlier devices). Feedback coupling, or recycling, provides more complete use of raw material and an increase in the yield of final products, as well as output of products of the required purity, and use of heat.
Industrial organic synthesis is characterized by a high level of automation of the production processes. At industrial organic synthesis enterprises, automatic systems are used for the control of complex chemical-engineering complexes (plants and units) and systems for automated optimum designing are being designed. Cybernetic methods and equipment are also used in the design of process flow diagrams.
In industrial organic synthesis an attempt is made to minimize the number of reactor steps (one to three) in the chemical transformation by combining the operating functions of the reactors and using directionally integrated reaction-mass-exchange processes. Highly active catalysts are used to accelerate the chemical steps, and high temperatures and pressures or vacuum are used in a number of processes. The selectivity of catalysts is an important index that defines the efficiency of processes in industrial organic synthesis. Reactors in which there is contact between the gaseous and solid phases (with a fixed or fluidized catalyst bed) or between the gaseous and liquid phases (mainly column and airlift bubbler reactors) are most common in industrial organic synthesis.
Separation and purification processes play a large role in industrial organic synthesis. The average capital investment in distillation equipment alone is 20 percent of the estimated cost of enterprises, and expenditures for the energy required for separation processes reach 50 percent and more of the prime cost of production. In the 1960’s and 1970’s, in connection with the growth of unit output in primary petroleum-refining plants, several important products of industrial organic synthesis, such as butadiene, isoprene, and styrene, were produced directly by separation (mainly by special refining methods) from mixtures of pyrolysis products. Several additional steps are required in the production of these substances by ordinary (synthetic) methods. The requirement for the purification and use of considerable quantities of industrial wastes is a complex technological problem in industrial organic synthesis.
In the USSR, industrial organic synthesis was established during the first five-year plans, and its development has become especially rapid since the 1960’s. The rate of growth of the total volume of production may be seen in the following figures: in 1965 the total volume of production was 255 percent of the 1960 level; in 1970, 406 percent; in 1971, 427 percent; in 1972, 453 percent.
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