Isopropyl alcohol dehydrogenation

Until World War 1 acetone was manufactured commercially by the dry distillation of calcium acetate from lime and pyroligneous acid (wood distillate) (9). During the war processes for acetic acid from acetylene and by fermentation supplanted the pyroligneous acid (10). In turn these methods were displaced by the process developed for the bacterial fermentation of carbohydrates (cornstarch and molasses) to acetone and alcohols (11). At one time Pubhcker Industries, Commercial Solvents, and National Distillers had combined biofermentation capacity of 22,700 metric tons of acetone per year. Biofermentation became noncompetitive around 1960 because of the economics of scale of the isopropyl alcohol dehydrogenation and cumene hydroperoxide processes. 

Simultaneous Activation and Deactivation Phenomena in Isopropyl Alcohol Dehydrogenation on a Cu/SiO Catalyst... 

SIMULTANEOUS ACTIVATION AND DEACTIVATION PHENOMENA IN ISOPROPYL ALCOHOL DEHYDROGENATION ON A Cu/Si02 CATALYST... 

A kinetic model for simultaneous activation and deactivation processes in solid catalysts has been applied to kinetic data obtained in isopropyl alcohol dehydrogenation on a Cu/Si02 catalyst. The influence of different catalyst pretreatments on the relevant kinetic parameters of the system has been investigated. 

It was stated earlier that, on a surface with one type of site, if more than a single active site is involved in a unimolecular step, as indicated by reactions 7.7-7.10, then the denominator is no longer L -order, as shown in equation 7.6, but it is raised to an appropriate power, such as that given in equation 7.12. A recent example of such a decomposition reaction is isopropyl alcohol dehydrogenation to produce acetone, and this is discussed in Illustration 7.2. 

Isopropyl alcohol dehydrogenation over copper catalysts has been studied by Rioux and Vannice [11], and a detailed kinetic study was conducted of this reaction over a 0.98% Cu/carbon catalyst between 433 and 473 K and at a total pressure of 1 atm. The support was an activated carbon that had been given a high temperature treatment at 1223 K under H2 to remove S impurities (1300 ppm), and it had a surface area of 1140m g k After a pretreatment in H2 at 573 K, CO and N2O adsorption showed that only metallic Cu (Cu ) was present at the surface of the metal crystallites, in agreement with the XRD pattern, and the Cu dispersion was 0.11, indicating an average Cu crystallite size of about 9.8 nm. 

Table 7.2. Reaction Orders for Isopropyl Alcohol Dehydrogenation over 0.98% Cu/Activated Carbon (Reprinted from ref. 11, copyright 2003, with permission...

Production of acetone by dehydrogenation of isopropyl alcohol began in the early 1920s and remained the dominant production method through the 1960s. In the mid-1960s virtually all United States acetone was produced from propylene. A process for direct oxidation of propylene to acetone was developed by Wacker Chemie (12), but is not beheved to have been used in the United States. However, by the mid-1970s 60% of United States acetone capacity was based on cumene hydroperoxide [80-15-9], which accounted for about 65% of the acetone produced. 

Dehydrogenation of isopropyl alcohol accounts for most of the acetone production not obtained from cumene. The vapor is passed over a brass, copper, or other catalyst at 400—500°C, and a yield of about 95% is achieved (1.09 unit weight of alcohol per unit of acetone) (13). 

Dehydrogenation of Isopropyl Alcohol. In the United States about 4% of the acetone is made by this process, and in Western Europe about 19% (22). Isopropyl alcohol is dehydrogenated in an endothermic reaction. 

Although the selectivity of isopropyl alcohol to acetone via vapor-phase dehydrogenation is high, there are a number of by-products that must be removed from the acetone. The hot reactor effluent contains acetone, unconverted isopropyl alcohol, and hydrogen, and may also contain propylene, polypropylene, mesityl oxide, diisopropyl ether, acetaldehyde, propionaldehyde, and many other hydrocarbons and carbon oxides (25,28). 

Direct oxidation yields biacetyl (2,3-butanedione), a flavorant, or methyl ethyl ketone peroxide, an initiator used in polyester production. Ma.nufa.cture. MEK is predominandy produced by the dehydrogenation of 2-butanol. The reaction mechanism (11—13) and reaction equihbtium (14) have been reported, and the process is in many ways analogous to the production of acetone (qv) from isopropyl alcohol. 

Dehydrogenation. Before the large-scale availabiUty of acetone as a co-product of phenol (qv) in some processes, dehydrogenation of isopropyl alcohol to acetone (qv) was the most widely practiced production method. A wide variety of catalysts can be used in this endothermic (66.5 kj/mol (15.9 kcal/mol) at 327°C), vapor-phase process to achieve high (75—95 mol %) conversions. Operation at 300—500°C and moderate pressures (207 kPa (2.04 atm)) provides acetone in yields up to 90 mol %. The most useful catalysts contain Cu, Cr, Zn, and Ni, either alone, as oxides, or in combinations on inert supports (see Catalysts, supported) (13-16). 

Worldwide propylene production and capacity utilization for 1992 are given in Table 6 (74). The world capacity to produce propylene reached 41.5 X 10 t in 1992 the demand for propylene amounted to 32.3 x 10 t. About 80% of propylene produced worldwide was derived from steam crackers the balance came from refinery operations and propylene dehydrogenation. The manufacture of polypropylene, a thermoplastic resin, accounted for about 45% of the total demand. Demand for other uses included manufacture of acrylonitrile (qv), oxochemicals, propylene oxide (qv), cumene (qv), isopropyl alcohol (see Propyl alcohols), and polygas chemicals. Each of these markets accounted for about 5—15% of the propylene demand in 1992 (Table 7). 

The reaction scheme is rather complex also in the case of the oxidation of o-xylene (41a, 87a), of the oxidative dehydrogenation of n-butenes over bismuth-molybdenum catalyst (87b), or of ethylbenzene on aluminum oxide catalysts (87c), in the hydrogenolysis of glucose (87d) over Ni-kieselguhr or of n-butane on a nickel on silica catalyst (87e), and in the hydrogenation of succinimide in isopropyl alcohol on Ni-Al2Oa catalyst (87f) or of acetophenone on Rh-Al203 catalyst (87g). Decomposition of n-and sec-butyl acetates on synthetic zeolites accompanied by the isomerization of the formed butenes has also been the subject of a kinetic study (87h). 

A similar difference in the adsorption coefficients of the starting reactant of branched reactions was also found in the parallel dehydration and dehydrogenation of isopropyl alcohol on some oxide catalyst (123) here, of course, the chemical nature of both branches is clearly different. It is of interest, however, to note that for the series of catalysts with varying... 

Ratios of Rate Constants and of Adsorption Coefficients in Parallel Dehydrogenation (1) and Dehydration (2) of Isopropyl Alcohol on Some Oxide Catalysts (123)... 

Dehydrogenation of Isopropyl Alcohol to Acetone Nonporous Pd membranes Mikhalenko, Khrapova and Gryaznov (1986)... 

Mikhalenko, N. N., E. V. Khrapova and V. M. Gryaznov. 1986. Influence of hydrogen on the dehydrogenation of isopropyl alcohol in the presence of a palladium membrane catalyst. Kinet. and Catal. 27(1) 125-128. 

Ketones.have the characteristic -C- signature group imbedded in them. Acetone, CH3COCH3, comes from two different routes. It is a by-product in the cumene to phenol/acetone process. It is the on-purpose product of the catalytic dehydrogenation of isopropyl alcohol. Acetone is popular as a solvent and as a chemical intermediate for the manufacture of MIBK, methyl methacrylate, and Bisphenol A. 

In the minor route isopropyl alcohol, obtained from the hydrolysis of propylene, is converted into acetone by either dehydrogenation (preferred) or air oxidation. These are catalytic processes at 500°C and 40-50 psi. The acetone is purified by distillation, bp 56°C. The conversion per pass is 70-85% and the yield is over 90%. 

While alcohols and acids are considered to be primary products (see Figure 4) ketones are probably formed in secondary reactions which only occur at higher temperatures 2). In Table II it can be seen that as the temperature increases, ketone production increases at the expense of alcohols up to a point after which both decrease (due to hydrogenation to hydrocarbons which under FT conditions are thermodynamically more stable (2), It has been suggested (2) that ketones result from the direct reaction between alcohols and surface carbon atoms and/or from the dehydrogenation of secondary alcohols (eg under high temperature FT conditions acetone and isopropyl alcohol are in thermodynamic equilibrium (2). 

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