Toxic feedstocks

As a possible chemical process for distributed manufacture, the production of toxic feedstock gases is claimed [1,139]. Benson and Ponton were among the first... 

Dimethyl carbonate new methods for synthesis and use of dimethyl carbonate could greatly reduce the use of highly toxic feedstocks such as phosgene other waste streams (such as HC1) would be reduced as well. 

Each year over a thousand new chemical substances are manufactured or imported in the United States. While some of these substances will replace other more toxic substances, each new substance has the potential to increase the levels of pollution in our air, water and land. Even substances that are themselves innocuous may be manufactured using highly toxic feedstocks or may result in significant generation of hazardous waste. The U.S. Environmental Protection Agency has regulatory authority over new chemical substances as well as the mandate to champion pollution prevention in all aspects of our environment. 

PD is currently produced commercially in small quantities by chemical synthesis using the toxic feedstock acrolein. Although 1,3-PD has not been produced on a large scale, there are dozens of potential uses in polymer synthesis and as a chemical intermediate (26), Cameron has also been involved in studies on strains of Clostridium thermosaccharolyticum that produce R(-)-1,2-propanediol, a useful chiral building block in organic synthesis (27),... 

The only significant use of 1,1,2,2-tetrachloroethane is as a feedstock in the manufacture of trichloroethylene, tetrachloroethylene, and 1,2-dichloroethylene. Although it is an excellent solvent, its use should be discouraged in view of its high toxicity. 

Oxidation and reduction reactions can be carried out usiag reformer hydrogen and oxygen from the air. To decide when electroorganic synthesis is likely to be a viable option for a desired product, some opportunity factors are use of cheaper feedstock elimination of process step(s) or a difficult reaction avoidance of waste disposal, toxic materials, and/or abiUty to recycle reagent and abiUty to obtain products from anode and cathode. 

Polymerization Exothermic reaction which, unless carefully controlled, can run-away and create a thermal explosion or vessel overpressurization Refer to Table 7.20 for common monomers Certain processes require polymerization of feedstock at high pressure, with associated hazards Many vinyl monomers (e.g. vinyl chloride, acrylonitrile) pose a chronic toxicity hazard Refer to Table 7.19 for basic precautions... 

Toxicity and Environmental Fate Information for Propylene CAS 115-07-1 Sourtes. Propylene (propene) is one of the light ends formed during catalytic and thermal cracking and coking operations, it is usually collected and used as a feedstock to the alkylation unit. Propylene is volatile and soluble in water making releases to both air and water significant. 

Feedstock Toxicity Fire Hazard Explosion Hazard... 

Use of some biomass feedstocks can increase potential environmental risks. Municipal solid waste can contain toxic materials that can produce dioxins and other poisons in the flue gas, and these should not be burned without special emission controls. Demolition wood can contain lead from paint, other heavy metals, creosote, and halides used in presen a-tive treatments. Sewage sludge has a high amount of sulfur, and sulfur dioxide emission can increase if sewage sludge is used as a feedstock. 

Desulfurization of FCC feedstocks reduces the sulfur content of FCC products and SOX emissions. In the United States, road diesel sulfur can be 500 ppm (0.05 wt%). In some European countries, for example in Sweden, the sulfur of road diesel is 50 ppm or less. In California, the gasoline sulfur is required to be less than 40 ppm. The EPA s complex model uses sulfur as a controlling parameter to reduce toxic emissions. With hydroprocessed FCC feeds, about 5% of feed sulfur is in the FCC gasoline. For non-hydroprocessed feeds, the FCC gasoline sulfur is typically 10% of the feed sulfur. 

Both new catalysts and new processes need to be developed for a complete exploitation of the potential of CO2 use [41]. The key motivation to producing chemicals from CO2 is that CO2 can lead to totally new polymeric materials and also new routes to existing chemical intermediates and products could be more efficient and economical than current methods. As a case in point, the conventional method for methanol production is based on fossil feedstock and the production of dimethyl carbonate (DMC) involves the use of toxic phosgene or CO. A proposed alternative production process involves the use of CO2 as a raw material (Figure 7.1)... 

Two options are being developed at the moment. The first is to produce 1,2-propanediol (propylene glycol) from glycerol. 1,2-Propanediol has a number of industrial uses, including as a less toxic alternative to ethylene glycol in anti-freeze. Conventionally, 1,2-propanediol is made from a petrochemical feedstock, propylene oxide. The new process uses a combination of a copper-chromite catalyst and reactive distillation. The catalyst operates at a lower temperature and pressure than alternative systems 220°C compared to 260°C and 10 bar compared to 150 bar. The process also produces fewer by-products, and should be cheaper than petrochemical routes at current prices for natural glycerol. The first commercial plant is under construction and the process is being actively licensed to other companies. 

Biodiesel is a fuel derived from renewable natural resources such as soybean and rapeseed and consists of alkyl esters derived from transesterification of triglycerides with methanol. In spite of all the advantages of biodiesel, such as low emissiotts, biodegradability, non-toxicity, and lubricity, the major hurdle in penetration of biodiesel is its high cost because of the expensive food grade refined vegetable oil feedstock. 

Carbamate, RNHCOOR, produced from carbonylation pathways can be selectively converted to isocyanate (1.4). Carbonylation pathways offer a number of advantages (i) the environmentally benign nature of the reactants, (ii) the high selectivity of the reaction processes, (iii) the stability and low toxicity of carbamate products and (iv) the wide range of applications of carbamate as chemical feedstock. 

An important parameter that has to be considered during desulfurization as well as for subsequent biocatalyst separation and recycle is the impact of the oil phase on the biocatalyst activity and half-life. Additionally, the effect of the biocatalyst on forma-tion/breakage of the oil-water emulsions is also important. The latter will be discussed in Section 2.3.3. It becomes important for lower boiling feedstocks such as gasoline, which offers the most toxic solvent environment for the biodesulfurization catalyst. The effect of solvents on biocatalysts has been investigated in very few reports. A study by the Monot group reported effect of two solvents on several Rhodococcus strains [254], The strains contacted with the solvents and their desulfurization activity, growth, and... 

Unprotected feedstock (e.g., hay or grain) should be destroyed. Leaves of forage vegetation could still retain sufficient vesicant agent, or toxic decomposition products, to produce effects for several weeks post release, depending on the level of contamination and the weather conditions. 

TSCA poses a new challenge to universities. While toxics are uniquely a chemical problem, their impacts extend to involve other disciplines as well. The life cycle of a toxic substance starts with chemical feedstocks. It continues through the myriad steps of manufacture and processing, through use, and ends only after end-product disposal. During this cycle there are many chances for "leaks" into the environment. Risks posed may appear primarily as risks to occupational safety and health, to general human health, or to particularly sensitive or important... 

Pollution associated with petroleum refining typically includes volatile organic compounds (volatile organic compounds), carbon monoxide (CO), sulfur oxides (SO c), nitrogen oxides (NO ), particulates, ammonia (NH3), hydrogen sulfide (H2S), metals, spent acids, and numerous toxic organic compounds (Hydrocarbon Processing, 2003). Sulfur and metals result from the impurities in crude oil. The other wastes represent losses of feedstock and petroleum products. 

Methanol, CH3OH, the simplest alcohol, is made by reacting CO and H2 at high pressures over a catalyst. Methanol is a liquid at room temperature and is highly toxic. It is used to make formaldehyde, acetic acid, and other chemical intermediates. It is also used as a feedstock for MTBE (methyl tertiary butyl ether), a gasoline-blending component. 

Shaw selected a combination of polyolefin resins as the base polymer of choice for its substitute, EcoWorx . Due to the low toxicity of its feedstocks, superior adhesion properties, dimensional stability, and its ability to be recycled, EcoWorx meets all of the design criteria necessary to satisfy the needs of the marketplace from a performance, health, and environmental standpoint. Research also indicated that the post-consumer carpet tile had a positive economic value at the end of its useful life. The cost of collection, transportation, elutriation, and return to manufacturing processes is less than the cost of using virgin raw materials. This is a truly recyclable (or Cradle to Cradle) product and is a good example of how substitution through innovation can make economic as well as environmental sense. ... 

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