Manufacturers, materials, recycling chemical processes

Recycle. A large number of manufacturing facilities, especially chemical plants, have internal recycle streams that are considered part of the process. In this case, recycle refers to the external recycle of materials, such as polyester film and bottles, Tyvek envelopes, paper, and spent solvents. 

The manufacture of food chemicals, whether it involves chemical or biological synthesis and purification, or recovery from natural materials, has a number of characteristics that must be taken into account in establishing a system of good manufacturing practice. For example, in the production of many chemicals, recycling of process liquors and recovery from waste streams are necessary for reasons of quality, economics, and environmental protection. In addition, the production of some food chemicals involves processes in which chemical and biochemical mechanisms have not been fully elucidated, and thus the methods and procedures for materials accountability usually will differ from those applicable to the manufacture of other classes of materials. 

Renewable raw materials can contribute to the sustainability of chemical products in two ways (i) by developing greener, biomass-derived products which replace existing oil-based products, e.g. a biodegradable plastic, and (ii) greener processes for the manufacture of existing chemicals from biomass instead of from fossil feedstocks. These conversion processes should, of course, be catalytic in order to maximize atom efficiencies and minimize waste (E factors) but they could be chemo- or biocatalytic, e.g. fermentation [3-5]. Even the chemocatalysts themselves can be derived from biomass, e.g. expanded com starches modified with surface S03H or amine moieties can be used as recyclable solid acid or base catalysts, respectively [6]. 

A related issue is decreased quality of some streams of recycled materials. Manufacturers of recycled paper seem to have the most problems, reporting that the additional contamination causes economic harm to their operations. Not only must the receiving facilities pay for unusable material, they also have to do more processing and use more chemicals to remove the contaminants. It has been estimated that mUl operation costs increase by about 8 per ton when fiber from single-stream rather than dual-stream MRFs is used. ... 

In 1966, the process we proposed (Table VI) was too complex to fit the technology of the varnish plants of that era recycle, reflux, extraction,fractionation, etc. The process costs were uncertain. The marketing futures were uncertain. The only thing that was certain was that the use of the traditional natural and refined drying oils was waning. New materials were coming up. The new materials were coming less and less out of the varnish plants of the formulator industry, and more and more out of the chemical process industry. It was not at all certain whether, if the chemical process industries, who were now vendors, should capture all the vehicle manufactures, would expand also into the final products. 

Melamine was synthesized early in the history of organic chemistry but remained a chemical curiosity until it was found to react with formaldehyde to form a useful amino resin. Melamine was first manufactured from dicyan-diamide, but it is now made from urea, a much lower-cost starting material. In this process the urea is dehydrated to cyanamid which terminates to melamine. The reaction is carried out at high pressure in the presence of ammonia to suppress the formation of deamination products. Ammonium carbamate is also formed in the reaction and must be recycled to convert it back to urea. 

Toray (1) A large Japanese chemicals manufacturer, perhaps best known for its process for synthesizing /-lysine for use as a dietary supplement. The starting material is cyclohexene which is converted in five steps to racemic lysine. An enzymic process isolates the desired optical isomer, the other is recycled. 

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