Isopropyl alcohol direct hydration

Figure 10.3a shows a simplified fiowsheet for the production of isopropyl alcohol by the direct hydration of propylene. Different reactor technologies are available for the process, and separation and recycle systems vary, but Fig. 10.3a is representative. Propylene... 

Figure 10.3 Outline flowsheet for the production of isopropyl alcohol by direct hydration of propylene. (From Smith and Petela, Chem. Eng., 513 24, 1991 reproduced by permission of the Institution of Chemical Engineers.)...

Fig. 2. Direct hydration process for the manufacture of isopropyl alcohol. The steps within the dashed box differentiate the direct from the indirect...

A Hquid-phase variation of the direct hydration was developed by Tokuyama Soda (78). The disadvantages of the gas-phase processes are largely avoided by employing a weakly acidic aqueous catalyst solution of a siHcotungstate (82). Preheated propylene, water, and recycled aqueous catalyst solution are pressurized and fed into a reaction chamber where they react in the Hquid state at 270°C and 20.3 MPa (200 atm) and form aqueous isopropyl alcohol. Propylene conversions of 60—70% per pass are obtained, and selectivity to isopropyl alcohol is 98—99 mol % of converted propylene. The catalyst is recycled and requites Htde replenishment compared to other processes. Corrosion and environmental problems are also minimized because the catalyst is a weak acid and because the system is completely closed. On account of the low gas recycle ratio, regular commercial propylene of 95% purity can be used as feedstock. 

Isopropyl Alcohol. Propylene may be easily hydrolyzed to isopropyl alcohol. Eady commercial processes involved the use of sulfuric acid in an indirect process (100). The disadvantage was the need to reconcentrate the sulfuric acid after hydrolysis. Direct catalytic hydration of propylene to 2-propanol followed commercialization of the sulfuric acid process and eliniinated the need for acid reconcentration, thus reducing corrosion problems, energy use, and air pollution by SO2 and organic sulfur compounds. Gas-phase hydration takes place over supported oxides of tungsten at 540 K and 25... 

Indirect hydration, the traditional route, took advantage of readily available refinery grade propylene and cheap sulfuric acid in a quick two-step to isopropyl alcohol. Persistent catalysis research has now resulted in a direct route involving a small amount of an arcane catalyst, less energy intensity, high conversion rate, and an overall cheaper process. 

You may wonder why boch these processes produce isopropyl alcohol instead of (normal) propyl alcohoL With the exception of ethylene, direct or indirect hydration of an aliphatic olefin always produces an alcohol with the hydroxyl group preferentially attached to the double-bonded carbon with the least number of hydrogen atoms. 

Synthesis gas is also the precursor to MTBE via methanol. The process requires isobutylene as well. Ethyl alcohol is made by direct, catalyzed hydration of ethylene. The route to isopropyl alcohol historically used to be solely indirect hydration of propylene, which occurs at much lower pressures and temperatures than the direct method, but advances in catalysis now make the direct route competitive. 

NEIER,W. and WOELLNER, J., "Isopropyl alcohol by direct hydration", Chemtechy p.95-99, Feb. 1973-... 

The hydration of olefins has long been practiced for the manufacture of amyl and isopropyl alcohol, and more recently for ethyl alcohol. Hydration is usually accomplished by a series of reactions involving the chlorides or alkyl sulfates, rather than the direct hydration reaction indicated here. 

Aliphatic Ethers. The aliphatic ethers used in industry are made usually by the action of sulfuric acid on an alcohol. Ethyl ether and isopropyl ether are thus prepared. However, more ethyl ether than the market usually absorbs is obtained as a by-product of the hydration of ethylene to alcohol. Alkyl halides react on a hydroxyl group either directly, in the presence of an alkali, or after the hydrogen of a hydroxyl group has been replaced by sodium. This is the Williamson synthesis which is particularly applicable to making mixed ethers ... 

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