Alkanes propylene oxide selectivity

The direct oxidation of propane has fewer restrictions on plant location since the alkane is easier to ship over long distances as the compressed liquid. Its oxidation to acrolein, acrylic acid and acrylonitrile is the subject of numerous studies. The synthesis of acrylonitrile has already been developed to the stage of a demonstration plant. Catalysts are based on V-Sb mixed oxides, with additional metal promoters. Propylene is generally recognized as the intermediate through which acrylonitrile is obtained. Selectivities are close to 50-60% at ca. 20% propane conversion. 

Alkane oxidation to alcohols, aldehydes and ketones has been extensively studied and it was found that the smaller linear alkanes show higher turnovers than the longer linear, branched and cyclic alkanes [81]. Although the turnover numbers are found to increase with the addition of methanol as a co-solvent, the general role of the co-solvent in selectivity is still not clear. Catalytic epoxidations of relatively inert alkenes such as propylene and allyl chloride were found to be facile under mild... 

Control of reactivity by catalysis provides the capability to shift to lower cost feedstocks. In the twentieth century, advances in catalysis have allowed the substitution of acetylene with olefins and subsequently with synthesis gas as primary feedstocks. For example, production of acrylic acid, traditionally produced by the Reppe process from acetylene and CO, has now been replaced by catalytic oxidation of propylene. The emergence of paraffins, the hydrocarbon feedstock of the future, will depend on development of catalysts for selective alkane C-H activation (2). 

Accordingly, we need to design new catalysts in which the active sites for the alkane oxidative activation are less effective in the deep oxidation of olefins or, in the case of 0-insertion reactions, to favor a fast selective transformation of olefin to O-containing partial oxidation products. At the moment there are only two examples in which the catalyst shows an extremely low activity for olefin oxidation with respect to that for alkane oxidation, i.e. MoVTeNbO and Ni-modified catalysts " for the ODH of ethane to ethylene (which will be further discussed in Section 24.1.4). This can be explained by the absence of allyl hydrogen in ethylene and the low achvity of the catalyst in the abstraction of the vinyl hydrogen. Conversely, the interachon between longer olefins (such as propylenes and butenes) and catalysts with allyl abstraction affinity leads to further oxidized products which will depend on the nature and reactivity of the corresponding olefin. 

Supported metal oxide catalysts are widely employed in industrial applications alkane dehydrogenation, olefin polymerization, olefin metathesis, selective oxidation/ammoxida-tion/reduction of organic molecules (alkyl aromatics and propylene), and inorganic emissions (N2O, NO , H2S, SO2, and VOC) [1,3,7,11-13]. The initial industrial applications of supported metal oxide catalysts were limited to hydrocarbon dehydrogenation/hydro-genation and olefin polymerization/metathesis reactions. In more recent years, the number of applications of supported metal oxide catalysts for oxidation reactions has grown significantly due to their excellent oxidation characteristics in the manufacture of certain... 

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