Ethanol distillation technology

The current ethanol dehydration technology - two-stage distillation followed by a molecular-sieve dryer, as shown in Figure 8.18(a) - uses approximately 16 000-20 000 Btu of energy/gal of ethanol produced. This is about 20% of the energy value of the ethanol produced. There is a considerable interest in membrane technology that would be lower in cost and less energy intensive. 

IFP Ethyl tertiary butyl ether (ETBE) FCC and steam-cracker C4 cuts and ethanol CATACOL technology ensures hirjt ETBE yields by combining catalysis and distillation separation 3 1996... 

Ethanol is the most successful biofuel and, for example, already supplies 40% of Brazil s transportation fuel needs. Its main advantage is that there is a well-established infrastructure for its production and use. Techniques for its production by the fermentation of sucrose are in place, large-scale distillation technologies have been developed, and it can be used in so-called flexible-fuel vehicles. In addition, the logistics for its distribution are well-established. Every gas station in Brazil supplies it, with gasoline being provided in a commercial blend containing up to 24% ethanol. 

Just as interest in ethanol has driven the development of chemical models, distillation technology, and the field of metabolic engineering, it has also driven the development of the field of biomass deconstruction. Given that the focus of this book series is on biotechnology, this chapter will place more emphasis on the metabolic engineering aspect. However, key examples are briefly discussed in Section 18.3. 

The catalytic esterification of ethanol and acetic acid to ethyl acetate and water has been taken as a representative example to emphasize the potential advantages of the application of membrane technology compared with conventional distillation [48], see Fig. 13.6. From the McCabe-Thiele diagram for the separation of ethanol-water mixtures it follows that pervaporation can reach high water selectivities at the azeotropic point in contrast to the distillation process. Considering the economic evaluation of membrane-assisted esterifications compared with the conventional distillation technique, a decrease of 75% in energy input and 50% lower investment and operation costs can be calculated. The characteristics of the membrane and the module design mainly determine the investment costs of membrane processes, whereas the operational costs are influenced by the hfetime of the membranes. 

The three current applications of pervaporation are dehydration of solvents, water purification, and organic/organic separations as an alternative to distillation. Currently dehydration of solvents, in particular ethanol and isopropanol, is the only process installed on a large scale. However, as the technology develops, the other applications are expected to grow. Separation of organic mixtures, in particular, could become a major application. Each of these applications is described separately below. 

During corn dry mill ethanol manufacturing, the most common method for ethanol production in North America, the primary byproduct is dried distiller s grain (DDG). As production increases to meet demand, the supply of DDG will significantly increase. Thus, ethanol producers need to modify their processes for the sake of profitability. Technological... 

The catalytic dehydration of ethanol to ethylene in SC water may be commercially important (16). Although high quality commercial alumina catalysts exist for the vapor phase dehydration of ethanol, the commercial processes require the ethanol feedstock to be relatively free of water. Hence the ethanol must be distilled from the ethanol-water mixture which is the product of fermentation processes. By avoiding this distillation step, and securing phase separation of the ethylene product from the ethanol-water reactant, SC dehydration of ethanol could enjoy advantages over existing commercial technologies. 

Methanol. As is the case with ethanol, the concept of producing methanol from wood is not new. Methanol obtained from the destructive distillation of wood represented the only commercial source until the 1920s. The yield of methanol from wood by this method is low, only about 1-2 percent or 20 L/metric ton (6 gal/ton) for hardwoods and about one-half that for softwoods. With the introduction of natural gas technology, the industry gradually switched to a synthetic methanol formed from a synthesis gas (syngas) produced from reformed natural gas. Two volumes of H2 and one volume of CO are reacted in a catalytic converter at pressures of 1500-4000 psi to produce methanol. Presently, 99 percent of the methanol produced in the United States is derived from natural gas or petroleum. 

The methacryloyloxymethyl alkoxysilanes are easily available starting from methyl trichlorosilane, dimethyl dichlorosilane, or trimethyl chlorosilane (1), respectively (Scheme 1). Photochlorination of these precursor silanes almost exclusively leads to the chloromelhyl silanes. Alkoxylation with methanol or ethanol leads to the chloromethyl(methyl)alkoxysilanes (2). Nucleophilic substitution under phase transfer catalysis conditions and distillative isolation finally yields the methacryloyloxymethylsilanes (3), making the production independent of expensive hydrosilation technology. 

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