Manufacturing process acrylics

The yield of acrylonitrile based on propylene is generally lower than the yield of acryhc acid based on the dkect oxidation of propylene. Hence, for the large volume manufacture of acrylates, the acrylonitrile route is not attractive since additional processing steps are involved and the ultimate yield of acrylate based on propylene is much lower. Hydrolysis of acrylonitrile can be controUed to provide acrylamide rather than acryhc acid, but acryhc acid is a by-product in such a process (80). 

Liquid-Phase Oxidation of Acrolein. As discussed before, the most attractive process for the manufacture of acrylates is based on the two-stage, vapor-phase oxidation of propylene. The second stage involves the oxidation of acrolein. Considerable art on the Hquid-phase oxidation of acrolein (17) is available, but this route caimot compete with the vapor-phase technology. 

Acrylate and methacrylate polymerizations are accompanied by the Hberation of a considerable amount of heat and a substantial decrease in volume. Both of these factors strongly influence most manufacturing processes. Excess heat must be dissipated to avoid uncontrolled exothermic polymerizations. In general, the percentage of shrinkage decreases as the size of the alcohol substituent increases on a molar basis, the shrinkage is relatively constant (77). 

Fig. 3. An aqueous dispersion polymerization process used in the manufacture of acrylic and modacrylic fibers.

Pure polymeric acrylonitrile is not an interesting fiber and it is virtually undyeable. In order to make fibers of commercial iaterest acrylonitrile is copolymerized with other monomers such as methacrylic acid, methyl methacrylate, vinyl compounds, etc, to improve mechanical, stmctural, and dyeing properties. Eibers based on at least 85% of acrylonitrile monomer are termed acryHc fibers those containing between 35—85% acrylonitrile monomer, modacryhc fibers. The two types are in general dyed the same, although the type and number of dye sites generated by the fiber manufacturing process have an influence (see Eibers, acrylic). 

Such lenses may be made by machining from rod. More recently processes have been developed where the monomers are cast polymerised in tiny plastics moulds whose cavity corresponds to the dimensions of the lens and using procedures very reminiscent of those described for the manufacture of acrylic sheet (see Section 15.2.2). 

The Reppe process for manufacture of acrylic esters uses acetylene and carbon monoxide, with a nickel carbonyl catalyst having high acute and longterm toxicity, to react with an alcohol to make the corresponding acrylic ester ... 

In addition to the conventional dyeing of acrylic fibres, there is considerable interest in so-called gel dyeing of acrylic filaments during the manufacturing process after extrusion. From the viewpoint of auxiliary usage this is outside the scope of the present work, but a useful account of the factors involved is available [61]. 

Klein, J. A., and A. S. Balchan (1996). "Safe Formulation and Manufacture of Acrylic Resins." International Conference and Workshop on Process Safety Management and Inherently Safer Processes, October 8-11, 1996, Orlando, FL, 329-342. New York American Institute of Chemical Engineers. 

The technology of the acrylic acid manufacturing process developed in Japan has been disclosed.1354... 

In the presence of such catalysts as a solution of cuprous and ammonium chlorides, hydrogen cyanide adds to acetylene to give acrylonitrile (CH2=CHCN). However, this process has been replaced by processes involving ammoxidation of propylene. Similarly, the process for the manufacture of acrylic acid has been superseded by processes involving oxidation of propylene (Fig. 1) although, for some countries, acetylene may still be used in acrylate manufacture. 

This invention has its roots in Reppe chemistry. In the late 1930s, Reppe in Germany had developed a number of manufacturing processes for bulk chemicals, where acetylene was used as one of the basic building blocks. Even today BASF and Rohm Hass manufacture large quantities of acrylic acid and its esters by hydrocarboxylation of acetylene. This reaction, 4.12, is catalyzed by a mixture of NiBr2 and Cul. It involves high pressure (100 bar) and temperature (220°C), and mechanistically is not fully understood. 

Sources of ignition must be kept away from these materials, and adequate, reliable ventilation and means of removing vapors must be provided in storage and processing areas. Their exists with the manufacturer of acrylic castings the situations of toxicity, flammability,... 

Acrylic Acid, Acrylates, and Acrylonitrile. Acrylic acid [79-10-7], C3H402, and acrylates were once prepared by reaction of acetylene and carbon monoxide with water or an alcohol, using nickel carbonyl as catalyst. I11 recent years tliis process has been completely superseded in the United States by newer processes involving oxidation of propylene (2). I11 western Europe, however, acetylene is still important in acrylate manufacture (see Acrylic acid and derivatives Acrylic ester polymers). 

In 1957 Standard Oil of Ohio (Sohio) discovered bismuth molybdate catalysts capable of producing high yields of acrolein at high propylene conversions (>90%) and at low pressures (12). Over the next 30 years much industrial and academic research and development was devoted to improving these catalysts, which are used in the production processes for acrolein, acrylic acid, and acrylonitrile. All commercial acrolein manufacturing processes known today are based on propylene oxidation and use bismuth molybdate based catalysts. 

Although some very7 minor manufacturers of acrylic acid may still use hydrolysis of acrylonitrile (see below), essentially all other plants worldwide use the propylene oxidation process. 

Ethylene Cyanohydrin Process. This process, the first for the manufacture of acrylic acid and esters, has been replaced by more economical ones. During World War I, the need for ethylene as an important raw material for the synthesis of aliphatic chemicals led to development of dais process (16) in both Germany, in 1927, and the United States, in 1931. 

Acrylonitrile is the starting material used in the manufacture of acrylic fibers (U.S. annual production capacity is more than 2 million pounds). Three industrial processes for the production of acrylonitrile are given below. Using data from Appendix 4, calculate AS°, AH°, and AG° for each process. For part a, assume that T = 25°C for part b, T = 70.°C and for part c, T = 700.°C. Assume that AH° and AS° do not depend on temperature, a. CH2-CH2(g) + HCN(5)... 

Acrylamide monomer is an important chemical commodity produced on a multihundred thousand ton scale for the production of polymers and copolymers. The preferred manufacturing process is by the catalytic hydration of acrylonitrile at 70-120 °C using reduced Raney copper as the catalyst the initial concentration of acrylonitrile being around 4 m. There are several shortcomings to this process, among which are the high level of acrylic acid formed and byproduct formation12, 3). 

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