Ethanol production?

Reply 1# liupta: The current production methods for ethanol include biological fermentation and the ethylene hydration method. The acetic acid hydrogenation process is still in the development stage; it seems that Celanese Corporation has applied for patents related to the catalysts used in this process!

Industrially, ethanol is generally produced by starch fermentation or direct hydration of ethylene: 1. Fermentation method The production of ethanol via fermentation evolved from winemaking, and for a long time it was the only industrial method for producing ethanol. The raw materials for the fermentation method can be starch-containing agricultural products, such as grains, tubers, or fruits of wild plants ； Waste molasses from sugar mills can also be used ； Or use wood chips containing cellulose, plant stems, and the like. After certain pretreatment, these substances can be converted into ethanol through hydrolysis (this step is carried out using waste honey as the raw material) and fermentation. The mass fraction in the fermentation broth is approximately 6% to 10%, and it contains other organic impurities; 95% industrial ethanol can be obtained through distillation. 2. Ethylene hydration method: The direct hydration of ethylene involves the direct reaction of ethylene with water under conditions of heating, pressure, and in the presence of a catalyst to produce ethanol: CH2═CH2 + H—OH→C2H5OH. This reaction takes place in two steps; in the first step, organic mercury compounds are formed with mercury salts such as mercuric acetate in an aqueous-xylene solution, and then these compounds are reduced using sodium borohydride. The raw material for this method, ethylene, can be obtained in large quantities from petroleum cracking gases, making it cost-effective and allowing for high yields. This helps to save a significant amount of grain, which is why this method has seen rapid development. There are two methods for the hydration process; one is the indirect hydration method using sulfuric acid as an absorbent ； Another is the ethylene-catalyzed direct hydration method. ①The indirect hydration method, also known as the sulfate method, proceeds in two steps. First, ethylene is introduced into concentrated sulfuric acid under certain temperature and pressure conditions to form a sulfate ester; this sulfate ester is then heated in a hydrolysis tower to undergo hydrolysis, yielding ethanol while ether, as a by-product, is formed. The indirect hydration method can use ethanol of low purity as a raw material, features mild reaction conditions and a high ethylene conversion rate, but it causes severe equipment corrosion and has a long production process; as a result, it has been replaced by the direct hydration method. ②Direct hydration: Under certain conditions, ethylene reacts directly with water in the presence of a solid acid catalyst to produce ethanol: CH2=CH2 + H2O → CH3CH2OH