Propene epoxidation catalytic performance

The effect of chain length on the catalytic performance was investigated using a series of co-bromo-2-methylalkenes. In all cases the predominant enantiomer produced had the -configuration except for 3-bromo-2-methylpropene oxide, which was predominantly in the S-form due to the priority switch [274], The short propene and butene derivatives were converted quantitatively whereas the longer pentene, hexene and heptene substrates failed to convert completely. Many other functional groups such as carboxylic ester, methoxy, acetoxy and carbonic ester are accepted by the system. The epoxidation fails, however, for 4-hydroxy-2-methyl-l-butene as substrate [270]. 

Table 6.2 Comparison of catalytic performance with EBHP versus different heterogeneous Ti-based catalytic systems in propene epoxidation.

Table 6.3 Catalytic performance in propene epoxidation with H P in the Degussa/Uhde process [20].

Duma and Honicke were the first to report the successful use of N2O in propene epoxidation. A PO yield of 5% was obtained over silica-supported iron oxide catalysts promoted with Na ions [43bj. The pore shape and diameter of the support as well as iron oxide dispersion are crucial parameters in the reaction [43b,cj. Doping vdth alkali metal may also considerably affect the Fe dispersion, and favor epoxidation over allylic oxidation [43fj. Further modification by boron can also significantly enhance the catalytic performance of the K-doped FeO /SBA-lS catalyst [43gj. 

A flow reactor was used to determine the catalytic performance of the different catalysts. The experiments were carried out with typically 0.30 g of catalyst and a gas flow of 50 Nml/min (GHSV 10,000 h ). In the epoxidation experiments, a gas mixture was used similar to that in most research in the literature 10% of oxygen, 10% of hydrogen, and 10% of propene in helium (all gas compositions given in vol.%). The pressure was 1.1 bar. In this study, the activity was determined at 323, 373,423, and 473 K the lowest temperature being most appropriate for the titania-supported catalyst, the higher temperatures being more optimal for the Ti-silica-supported catalysts. 

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