Propylene ammoxidation, reaction conditions

The surface transformations of propylene, allyl alcohol and acrylic acid in the presence or absence of NHs over V-antimonate catalysts were studied by IR spectroscopy. The results show the existence of various possible pathways of surface transformation in the mechanism of propane ammoxidation, depending on the reaction condition and the surface coverage with chemisorbed NH3. A surface reaction network is proposed and used to explain the catalytic behavior observed in flow reactor conditions. 

In spite of the accumulated mechanistic investigations, it still seems difficult to explain why multicomponent bismuth molybdate catalysts show much better performances in both the oxidation and the ammoxidation of propylene and isobutylene. The catalytic activity has been increased almost 100 times compared to the simple binary oxide catalysts to result in the lowering of the reaction temperatures 60 80°C. The selectivities to the partially oxidized products have been also improved remarkably, corresponding to the improvements of the catalyst composition and reaction conditions. The reaction mechanism shown in Figs. 1 and 2 have been partly examined on the multicomponent bismuth molybdate catalysts. However, there has been no evidence to suggest different mechanisms on the multicomponent bismuth molybdate catalysts. 

Typical Reaction Conditions for the Oxidation and Ammoxidation of Propylene on the Simple and Multicomponent Bismuth Molybdate Catalyst°... 

Process Chemistry. Much of the early work on propane ammoxidation had centered on the development of catalysts that can operate under process conditions similar to those currently used for the propylene-based process. The intent is simply to replace propylene with propane as the feedstock and change the catalyst with little or no major alteration in reactors or other process equipment. As in the case of propylene ammoxidation, a solid catalyst is used to kinetically direct the vapor phase reaction to the desired partial oxidation product, namely, acrylonitrile. Also like propylene ammoxidation, the major by-products of the reaction are CO and CO2 along with acetonitrile and HCN. 

For illustrative purposes, the following hydrodynamic model and correlations are used in the model calculation of catalytic reactions of propylene ammox-idation to acrylonitrile. These hydrodynamic models and correlations are appropriate for a high-density riser under propylene ammoxidation conditions. Specifically, the axial profiles of cross-sectional averaged solids concentration was obtained by fitting the cluster-based model proposed by Li and Kwauk (1980) with the experimental data from Wei et al. (1998). The axial profile of solids concentration obtained can be expressed as ... 

The direct ammoxidation of propane into acrylonitrile by its reaction with oxygen and ammonia is an alternative route to the conventional propylene ammoxidation catalytic reaction to acrylonitrile. The use of propane instead of propylene makes the reaction conditions more demanding because of the necessity of activating the propane C-H bond which is much stronger than the propylene methyl C-H bond. Different catalytic systems have been investigated for the ammoxidation of propane into acrylonitrile with vanadium-based catalysts proving particularly efficient, particularly the Sb-V-0 mixed oxide catalyst. ... 

Hydrogen cyanide is an important building block chemical for the synthesis of a variety of industrially important chemicals, such as 2 hydroxy-4 methylthiobutyric acid, adiponitrile, nitrilotriacetic acid, lactic acid, and methyl methacrylate. The primary commercial routes to hydrogen cyanide are the reaction of methane and ammonia under aerobic (Andrussow Process) or anaerobic conditions (Degussa Process), or the separation of hydrogen cyanide as a by-product of the ammoxidation of propylene < ) The ammoxidation of methanol could represent an attractive alternate route to HCN for a number of reasons. First, on a molar basis, the price of methanol has become close to that of methane as world methanol capacity has increased. However, an accurate long term pricing picture for these two raw... 

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