Getting Alcohols: Methods and Raw Materials

Alcohols are used in very many industries and spheres of activity. They produce various synthetic polymers, plasticizers, rubbers, detergents and many other varieties of products. The production of alcohols is carried out by means of biochemical and chemical methods. Many of them are mass products of petrochemical synthesis. Chemical synthesis from hydrocarbons is a relatively inexpensive production method. Also one of the most important methods is the production of alcohols by hydration of olefins. Thus, isopropyl, tert- and sec-butyl and ethyl alcohols are obtained . The preparation of methyl alcohol (methanol) is based on dry distillation of wood.

The main processes by which alcohols are obtained:

• Alkaline hydrolysis of halogen derivatives: the production of glycerin, benzyl alcohol and others.
• Hydration of epoxides and alkenes: ethylene glycol, ethanol, etc.
• Hydroformylation: hexanol, methanol, etc.
• Oxidation methods: production of higher fatty alcohols.
• Methods of recovery: higher fatty alcohols, xylitol, etc.
• Biochemical methods: production of glycerin and ethanol.

One of the most widely produced products is ethyl alcohol (ethanol). On its basis, a method for manufacturing synthetic rubber was developed. Ethanol is obtained from the products of the hydrolysis of wood, ethylene, sulfite liquors and the enzymatic method from food raw materials.

Getting alcohols (ethanol and methanol) from food raw materials and wood is an expensive and time-consuming process. Ethyl alcohol is much more profitable and easier to produce from inexpensive hydrocarbon raw materials, for example, by hydration of ethylene. To get one ton of ethanol in an enzymatic way, you need to process four tons of grain or eight tons of sawdust. For comparison: one ton of ethanol is obtained from 2.5 tons of petroleum distillate or ethylene gas. Labor costs in man-hours in the production of ethyl alcohol from various raw materials: from grain - 160, from potatoes - 280, from ethylene - 10. Acquisition of alcohols from petrochemical raw materials is less expensive and labor-consuming.

Also a very important chemical product is methanol. Modern production of methyl alcohol is carried out by the method of organic synthesis based on carbon monoxide (II) or synthesis gas on an industrial scale. Technological schemes exist different. Conditionally they can be divided into the following three groups.

- Synthesis on zinc-chromium catalysts at high pressure. This process is obsolete and is replaced by various methods of synthesis at low pressure.

- Synthesis on copper-zinc-aluminum catalysts at low pressure. The use of synthesis methods at low pressure allows to significantly reduce energy costs for production. With this production method, a high degree of purification of the raw material from impurities adversely affecting the catalyst is required.

- Synthesis of methanol in a three-phase system, which is carried out in suspension from an inert liquid and a finely dispersed catalyst. This is a method that allows increasing the yield of the product, while reducing the cost of energy. Ways of obtaining alcohols are being improved. The three-phase system is a progressive production technology.