Propylene epoxide

The selective oxidation is catalyzed by silver, which is the only good catalyst. Other olefins are not converted selectively to the epoxides in the presence of silver. However, propylene epoxidation is appHed commercially the catalysts are either molybdenum complexes in solution or soHd Ti02—Si02 (see... 

In this article, a dynamic reaction kinetics for propylene epoxidation on Au/Ti02 is presented. Au/Ti02 catalyst is prepared and kinetics experiments are carried out in a tube reactor. Kinetic parameters are determined by fitting the experiments under different temperatures, and the reliability of the proposed kinetics is verified by experiments with different catalyst loading. 

Figure 24. Size of metal particles and support pores in silver and gold catalysts for gas-phase propylene epoxidation.

Figure 26. Effect of trimethylamine (TMA) addition to the reactant gases on propylene epoxidation [88].

Figure 27. Probable pathways for propylene epoxidation over surface modified Ti-Si02 catalysts [88].

Figure 29. In situ UV/Vis spectra for propylene epoxidation on Au/Ti-Si02 [88] (bottom BaS04 referenced, and top Ti-Si02 referenced) (a) under Ar at 298 K before propylene epoxidation, (b) under C3Hs/H2/02/Ar at 423 K for 120 min, (c) under C3H JH2/O2/ Ar at 423 K for 270 min, (d) under Ar at 298 K after propylene epoxidation. Offsets are used for clarity.

The catalysts which have been tested for the direct epoxidation include (i) supported metal catalysts, (ii) supported metal oxide catalysts (iii) lithium nitrate salt, and (iv) metal complexes (1-5). Rh/Al203 has been identified to be one of the most active supported metal catalysts for epoxidation (2). Although epoxidation over supported metal catalysts provides a desirable and simple approach for PO synthesis, PO selectivity generally decreases with propylene conversion and yield is generally below 50%. Further improvement of supported metal catalysts for propylene epoxidation relies not only on catalyst screening but also fundamental understanding of the epoxidation mechanism. 

The production of styrene and propylene epoxide from ethylbenzene (Halcon process) that includes the following three technological stages [234],... 

Gold clusters supported on a mixed Ti02-Si02 surface show activity for propylene epoxidation comparable to Ti02-supported Au catalysts but with enhanced stability.104 Therefore, it was decided... 

Buijink, J.K.F., van Vlaanderen, J.J.M., Crocker, M., and Niele, F.G.M. (2004) Propylene epoxidation over titanium-on-silica catalyst-the heart of the SMPO process. Catal. Today, 93-95,199-204. 

Synonyms 1,2-Epoxypropane propene oxide methyloxirane propylene epoxide... 

FIGURE 8. Geometrical parameters of the nearly symmetrical transition structure (a) for propylene epoxidation with peroxynitrous acid optimized at the QCISD/6-31G and CISD/6-31G (values are in parentheses) levels and unsymmetrical transition structures (b) and (c) resulting from the geometry optimizations at the B3LYP/6-311G and MP2(fuU)/6-31G levels, respectively... 

The activity and selectivity of propylene partial oxidation is very sensitive to the catalyst composition and reaction conditions (1, 2). Extensive studies have shown that Au supported on Ti02 is one of the most active and selective catalysts for CO oxidation in the presence of H2 and propylene epoxidation producing propylene oxide (i.e., PO) from propylene and oxygen in presence of hydrogen (3-8). 

In an earlier investigation by Le-Khac et al. (1) propylene epoxidation were prepared using the cation resin Amberlyst 36 and Pd(NH3)4Cl2. 

The evaluation and performance of similar propylene epoxidation catalysts using oxygen and hydrogen was performed by Kaminsky et al. (2) and is described. 

Gas-phase epoxidation of propylene with 02/H2 mixtures was accomplished over Ag1267 or Au1268 catalysts dispersed on TS-1 or other Ti-containing supports and Ti-modified high-silica zeolites.1269 Sodium ions were shown to be beneficial on the selectivity of propylene epoxidation with H202 over titanium silicalite.1270 A chromia-silica catalyst is active in the visible light-induced photoepoxidation of propylene by molecular oxygen.1271... 

Propylene epoxide, CHBCHOCH, contains a methyl group adjacent to a three-membered ring. Two of the bond brbitals of the ring carbon atom to which the methyl carbon atom is bonded can be described as bent toward each other, in such a way as to decrease somewhat the interaction energy restricting the rotation of the methyl group. The ob-... 

Because the petrochemical industry is based on hydrocarbons, especially alkenes, the selective oxidation of hydrocarbons to produce organic oxygenates occupies about 20% of total sales of current chemical industries. This is the second largest market after polymerization, which occupies about a 45% share. Selectively oxidized products, such as epoxides, ketones, aldehydes, alcohols and acids, are widely used to produce plastics, detergents, paints, cosmetics, and so on. Since it was found that supported Au catalysts can effectively catalyze gas-phase propylene epoxidation [121], the catalytic performance of Au catalysts in various selective oxidation reactions has been investigated extensively. In this section we focus mainly on the gas-phase selective oxidation of organic compounds. 

Scheme 3.1 The two main industrial processes for propylene epoxidation production.

Gas-Phase Propylene Epoxidation with Hydrogen-Oxygen Mixtures on Au/Ti02... 

Reaction pathways for propylene epoxidation over Au/Ti02 Sellers predicted that theoretically, on gold, H202 can be produced from 02 and H2 [132]. Later, Haruta and... 

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