Ethanol, environmentally benign production

Ethanol is produced as a more environmentally benign fuel. The systematic effect of ethyl alcohol differs from that of methyl alcohol. Ethyl alcohol is rapidly oxidized in the body to carbon dioxide and water, and in contrast to methyl alcohol no cumulative effect occurs. Ethanol is also a preferred alcohol in the transportation sector compared to methanol because it is derived from agricultural products and is renewable and biologically less objectionable in the enviromnent. 

The need to address the issue of global warming and fossil resource depletion has prompted research on the sustainable production of environmentally benign fuels and chemicals [ 1]. A biorefinery, which utilizes biomass as the starting material for the production of fuels and chemicals, can not only generate sustainable energy but also reduce CO2 emitted by fossil fuel combustion. For instance, bioethanol is one of the most promising alternatives to conventional petroleum-based transport fuels. The United States produced 52.6 billion liters of ethanol fuel in 2011, an increase from 49.2 billion liters in 2010 [2]. 

Ethyl lactate (ethyl 2-hydroxypropionate) is a nontoxic biodegradable compoxmd naturally found in a variety of food and industrially produced via esterification of lactic acid with ethanol [149]. Both of the components for the production of ethyl lactate are derived from renewable raw material (including low-cost agricultural waste) mainly by the fermentation process. This environmentally benign solvent with high boiling point (154 °C) and low volatility has properties superior to many conventional petroleum-based solvents and can substitute them as an eco-friendly alternative in many reactions [150,151]. The applications of ethyl lactate as a medium for the multicomponent heterocyclic synthesis are exemplified below. 

This metric is an attempt to define yield in terms of the mass of the product that is made from non-toxic materials. This was one of the first times that reagent and reactant toxicity were included as an important part of determining what is considered to be green, and it is something that was absent from traditional yield measures. Hudlicky et al. did make an attempt to define benign (i.e. those byproducts, reagents, or solvents that have no known environmental risk associated with them, for example, water, low-concentration saline, dilute ethanol, autoclaved cell mass, etc. ), but the explanation suffers from a lack of definitional clarity. 

Table 8.5 shows that as conditions change from ethanol to water, time reduces and yield increases. The use of water gives environmental benefits, i.e., no atmospheric pollution by escaping solvents and easy waste treatment. For this reason, this methodology represents an important improvement for the production of this kind of fine chemicals following enviroiunentally benign procedmes. 

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