Dehydrogenation, 2-propanol

Dehydrogenation activities of the oxides of selenium and tellurium were observed by the pulse technique.Thus, the zirconium oxides which are loaded with selenic acid or telluric acid and calcined in air can dehydrogenate 2-propanol to acetone and hexane to benzene.In a typical reaction of 2-propanol, the conversion into acetone decreases continuously after the third pulse, probably owing to a decrease in the amount of oxygen on the catalyst surface. Poisoning experiments with injection of CO2, H2O or butylamine at 523 K before reaction had no effect on the yield of acetone. Thus this dehydrogenation process appears to be an oxidative dehydrogenation. No studies on the acidic or basic character of oxides of selenium and tellurium oxides have been reported. 

In a widely used industnal process the mixture of ethylene and propene that is obtained by dehydrogenation of natural gas is passed into concentrated sulfunc acid Water is added and the solution IS heated to hydrolyze the alkyl hydrogen sulfate The product is almost exclusively a sin gle alcohol Is this alcohol ethanol 1 propanol or 2 propanoH Why is this particular one formed almost exclusively" ... 

The one-step route from 2-propanol coproduces diisobutyl ketone and acetone, and is practiced in the United States by Union Carbide (61). The details of a vapor-phase 2-propanol dehydrogenation and condensation process for the production of acetone, MIBK, and higher ketones have been described in recent patents (62,63). The process converts an a2eotropic 2-propanol—water feed over a copper-based catalyst at 220°C and produces a product mixture containing 2-propanol (11.4%), acetone (52.4%), MIBK (21.6%), diisobutyl ketone (6.5%), and 4-methyl-2-pentanol (2.2%). 

Worldwide, approximately 85% of acetone is produced as a coproduct with phenol. The remaining 17% is produced by on-purpose acetone processes such as the hydration of propylene to 2-propanol and the dehydrogenation of 2-propanol to acetone. The cost of production of 2-propanol sets the floor price of acetone as long as the acetone demand exceeds the coproduct acetone supply. However, there is a disparity in the growth rates of phenol and acetone, with phenol demand projected at 3.0%/yr and acetone demand at 2.0%/yr. If this continues, the coproduct supply of acetone will exceed the total acetone demand and on-purpose production of acetone will be forced to shut down the price of acetone is expected to fall below the floor price set by the on-purpose cost production. Projections indicate that such a situation might occur in the world market by 2010. To forestall such a situation, companies such as Mitsui Petrochemical and Shinnippon (Nippon Steel) have built plants without the coproduction of acetone. 

Cyclohexane can be dehydrogenated to benzene very cleanly under the same conditions with the same copper-silver catalyst, as can 2-propanol to acetone. These catalysts almost certainly act by virtue of an oxide layer on the metal. 

The proposed catalytic cycle for the dehydrogenation of alcohols to ketones is shown in Scheme 15. The initial reaction of 17 with H2O affords the hydride complex a and C02- Dehydrogenation of a by acetone gives the active species b and 2-propanol. The subsequent reaction of b with the alcohol yields the corresponding ketone and regenerates a to complete the catalytic cycle. 

Photocatalytic dehydrogenation of 2-propanol to acetone over An/Ti02 exhibited a higher activity for the generation of photogenerated electron than the photocatalytic inactive Pd/Ti02 and PCI/AI2O3 at 298 K. 

Thin-fdm was prepared from a slurry of catalyst powder which was prepared from 10 mg catalyst in 5 ml of 2-propanol. The catalyst slurry was sonicated for 30 min. and allowed to sit stagnant overnight. Before preparing the films, the slurry was sonicated for 15 min., 20 drops (0.1 ml) were added onto a ZnSe trough plate internal reflection element (022-2010-45, Pike Technologies). The solvent was allowed to evaporate, the procedure was repeated a total of five times. After drying in air at room temperature, the catalyst thin-film was ready for 2-propanol dehydrogenation studies. 

The Au/Ti02 catalyst shows activity for photocatalytic dehydrogenation of 2-propanol at 298 K. The activity of Au/Ti02 is attributed to its unique capability for producing photogenerated electrons evidenced by the featureless IR adsorption during UV-irradiation. 

Over Cu/MgO the transfer from 2-propanol is much faster than molecular H2 addition (entry 1, Table 2), thus excluding the dehydrogenation-hydrogenation mechanism. For the other donors, the reaction needs to carried out at 140°C to reach reasonable rates. 

A new oxidation-dehydrogenation-Heck coupling catalyzed by Pd on porous glass or Pd(OAc)2 also proceeded under microwave heating in the MBR (Scheme 2.18) [36]. With an excess of Phi, saturated alcohols including 1-propanol and 3-phenylpro-panol afforded 3,3-diphenylpropenal as the major product, and trans-2,3-diphenylpro-penal by a concerted process taking 10 min at 220 °C. The yields of this remarkable transformation were low, however, and further work into several aspects is required to make them more respectable. 

The microwave technique has been also found to be the best method for preparing strongly basic zeolites (ZSM-5, L, Beta, etc.) by direct dispersion of MgO and KF. This novel procedure enabled the preparation of shape-selective, solid, strongly base catalysts by a simple, cost-effective, and environmentally friendly process [11, 12]. New solid bases formed were efficient catalysts for dehydrogenation of 2-propanol and isomerization of cis-2-butene. 

Meng, N., S. Shinoda, and Y. Saito, Improvements on thermal efficiency of chemical heat pump involving the reaction couple of 2-propanol dehydrogenation and acetone hydrogenation. Int. J. Hydrogen Energ., 22, 361-367 (1997). 

Another common application of IR is to characterize reaction intermediates on the catalytic surfaces, often in situ during the course of the reaction [76,78,88,89], Figure 1.12 provides an example in the form of a set of transmission IR spectra obtained as a function of temperature during the oxidation of 2-propanol on Ni/Al203 [90], A clear dehydrogenation reaction is identified in these data above 440 Kby the appearance of new acetone absorption bands around 1378,1472, and 1590 cm L... 

In an enantiomer-differentiating oxidation at a poly-(L-valine)-coated Pb02 anode, rac-2,2-dimethyl-l -phenyl-1 -propanol was partially oxidized leaving 43% optically pure (5)-alcohol [371]. At a TEMPO-modified graphite felt anode rac-1-phenyl-ethanol has been enantioselectively oxidized in the presence of (-[-sparteine leaving 46% of the (/ [-alcohol with 99.6% ee [372]. However, under the same conditions, an exclusive dehydrogenation of (-[-sparteine to the iminium salt without oxidation of the alcohol was found [373]. 

Ito, E., Yamashita, M., Saito, Y. 1991. Acomposite Ru-Pt catalyst for 2-propanol dehydrogenation adaptable to the chemical heat pump system. Chem Soc Jpn Chem Lett 1 351-354. 

Ning, M., Ando, Y, Tanaka, T., Takashima, T. 1999. Study of photoeatalytie 2-propanol dehydrogenation for solar thermal eell. Ameriean Institute of Aeronauties and Astronauties, AIAA-2000-2863 (35th IECEC-2000 7.24-7.28). 

The dehydrogenative coupling of primary alcohols to indoylamides was effected by TPAP/NMO/PMS/CH3CN, e.g. of 3-phenyl-1-propanol with pratosine and hippadine [504]. 

Figure 1. First order plots based on hydrogen evolution for the oxidative dehydrogenation of ethanolamine (EA), 2-(2-aminoethylamino)ethanol (AEAE), 3-amino-1-propanol (AP), 2-(methylamino)ethanol (MAE) and benzyl alcohol (BA) over chromia-promoted copper.

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