Coproduct generation

Accounting for multifunctionahty is particularly important for animal-derived fibres due to the larger amounts of coproducts generated. In the case of silk, total dry matter conversion finm mulberry biomass to raw silk is less than 5% (Dai-Gang, 2013). ISO standards recommend using the system expansion or avoided burden approach, with allocation a less preferred option. In this study we employed both approaches and provide both results for comparison. 

Coproduct generation is frequently encountered in process chains for bioproducts. Procedures for expansion of the product system as well as allocation are very different. Larson enumerates six approaches to allocate coproduct credits found from a review of more than 30 LCA studies and concludes that allocation is the main methodological factor for divergent results from LCA [17]. 

Early demand for chlorine centered on textile bleaching, and chlorine generated through the electrolytic decomposition of salt (NaCl) sufficed. Sodium hydroxide was produced by the lime—soda reaction, using sodium carbonate readily available from the Solvay process. Increased demand for chlorine for PVC manufacture led to the production of chlorine and sodium hydroxide as coproducts. Solution mining of salt and the avadabiHty of asbestos resulted in the dominance of the diaphragm process in North America, whereas soHd salt and mercury avadabiHty led to the dominance of the mercury process in Europe. Japan imported its salt in soHd form and, until the development of the membrane process, also favored the mercury ceU for production. 

Simply looking at the feedstock prices or price ratios is iasufficient to accurately identify the most attractive feedstock because the values of all of the co-products and by-products must also be taken iato account. This is usually accompHshed by calculating the cost to produce ethylene with all other coproduct and by-product yields credited against the cost of ethylene. An example of the cost of ethylene is presented ia Table 4. The cash costs of ethylene from various feedstocks are compared for the months of July and November of 1991. Cash costs reflect all plant manufactufing costs except depreciation and are a measure of the out-of-pocket cash costs generated by the operation. 

Over 90% of the HCl produced ia the United States origiaates as a coproduct from various chlorination processes direct generation of HCl from and CI2 accounts for only about 8% of the total production. Table 11 describes the production contribution of HCl from significant sources through the period 1980 to 1992 (72). Figure 6 illustrates the historical production growth of HCl ia the United States (73). The growth rate, about 5—6% from 1955 to 1975, slowed to - 1% because of disparity between supply and demand (see Table 12). The production capacity ia 1993 was about 2.92 million metric tons, down 9.6% from the 1992 production of 3.24 million metric tons (74). 

In the second proposed alternative process, tert-huty hypochlorite, formed from the reaction of chlorine and tert-huty alcohol, reacts with propylene and water to produce the chlorohydrin. The alcohol is a coproduct and is recycled to generate the hypochlorite (114—116). No commercialisation of the hypochlorous acid and tert-huty hypochlorite processes for chlorohydrin production is known. 

The generated chlorine dioxide must be air stripped from the anode compartment in order to achieve high chlorite conversion efficiency. Sodium ions from the anode compartment are transported into the cathode compartment, forming sodium hydroxide [1310-73-2] and hydrogen gas coproducts ... 

The only preparative limitation to this method is the occasional coproduction of alkenyl-boronates that presumably arise via a-elimination pathways of the ate complex generated upon addition of the organometallic reagent to the a-haloalkylboronate4,29-30. This problem is illustrated in the synthesis of 5-(rm-butyldimethylsilyloxy)-2-pentenyl-substituted dioxaborolane30. 

As chemical companies rely more heavily on ethane and propane feeds to their olefins plants to generate their ethylene and propylene supplies, the coproduction of butadiene in olefins plants has not kept up with demand. Industry has resorted to building plants that make on-purpose or swing supply butadiene. The processes involve catalytically dehydrogenating (removing hydrogen from) butane or butylene. 

The development of versatile and efficient methods for the synthesis of amines has long been an active area of research, mainly because a wide variety of amines play important roles in many fields of organic chemistry. The N-alkylation of amines with alcohols represents an attractive method for synthesizing various amines because it does not generate any wasteful byproducts (H2O is the only stoichiometric coproduct). Although several catalytic systems for this process have been studied using transition-metal catalysts [53-57], most of these require a high reaction temperature (>150°C). 

This paper touches on the chemistry of coal gasification and liquefaction comments on the current status of conversion processes and the influence of coal properties on coal performance in such processes and examines the contributions which coal conversion could make towards attainment of Canadian energy self-sufficiency. Particular attention is directed to a possible role for the medium-btu gas in long-term supply of fuel gas to residential and industrial consumers to linkages between partial conversion and thermal generation of electric energy and to coproduction of certain petrochemicals, fuel gas and liquid hydrocarbons by carbon monoxide hydrogenation. 

The Laux process is a very important method for producing iron oxide because of the coproduction of aniline it does not generate byproducts that harm the environment. 

The generation of these reactive species was supported by trapping experiments and the dimerization of the silene to E/Z isomeric 1,3-disilacyclobutanes 264. The coproduct, 1,2-dimesityltetramethyldisilane 265, of the Me2S extrusion is also photolabile. Silene... 

Polycondensation reactions that are equilibrium controlled, such as polyesters, could benefit from the thin films generated in the RPB or spinning disc. In these reactions, removal of the coproduct of polymerization, e.g., ethylene glycol, is necessary in order to advance the polymerization, a task that becomes increasingly difficult as the reaction proceeds. The thin films and short residence time of high-gravity devices aid the evaporation and may permit operation at higher temperatures than conventional reactors (50). 

In some experiments, carbon dioxide was generated without coproduction of hydrogen sulfide. However, treatment of the solid remaining after the experiment with HCa, evolved hydrogen sulfide stoichiometrically consistent with carbon dioxide production. This implies that under the experimental conditions, CaS was probably formed. The importance of this observation is that lack of hydrogen sulfide generation does not necessarily mean no sulfate reduction. This should be kept in mind for future experiments, or indeed for interpreting published results. 

The market price for DDG has ranged between 80 and 100/t in recent years (13,15). Assuming that 6.5 lb of DDG is generated per gallon of ethanol produced (15,16), the estimated coproduct value is 0.26/gal of ethanol using the conservative price of 80/1 of DDG. 

Prevent waste Design chemical syntheses to prevent waste, leaving no waste to treat or clean up. As com-monsensical as this sounds, many chemists do not consider the waste generated by the syntheses they design. Coproducts (substances that are formed in stoichiometric amounts during a reaction) and byproducts (substances that are formed unintentionally, usually in side reactions) are an inconvenience with which others are expected to deal. 

Similarly, zeolites can catalyze the addition of ammonia to an olefinic double bond, as is exemplified by the BASF process for the production of tert-butylamine by reaction of isobutene with ammonia, in the vapor phase, over a rare earth exchanged ZSM-5 or Yzeolite (Fig. 2.20) [58, 59]. This process has an atom efficiency of 100% and replaced a conventional synthesis via a Ritter reaction, which employs HCN and sulfuric acid and generates formate as a coproduct. 

Economics The conversion of EO to glycols is essentially complete. The reaction not only generates the desired MEG, but also produces DEG and TEG that can be recovered as coproducts. The production of more DEG and TEG may be desirable if the manufacturer has a specific use for these products or if market conditions provide a good price for DEG and TEG relative to MEG. A catalyzed process will produce less heavy glycols. The ability to operate in catalyzed or uncatalyzed mode provides flexibility to the manufacturer to meet changing market demands. 

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