Oxidation, gas-phase of Hydrocarbons

Heterogeneous catalysis is widely used in technology for gas-phase oxidation of hydrocarbons to alcohols, aldehydes, epoxides, anhydrides, etc. Homogeneous catalysis predominates in the liquid-phase oxidation technology. Nevertheless, a series of experimental studies was devoted in the 1970s to 1990s to heterogeneous catalysis. The main objects of study were metal oxides and metals as catalysts. 

Oxo-metal complexes also intervene as active species in the heterogeneous gas-phase oxidation of hydrocarbons over metal oxide or mixed metal oxide catalysts at high temperatures. Characteristic examples are the bismuth molybdate-catalyzed oxidation of propene to acrolein and the V205-catalyzed oxidation of benzene to maleic anhydride (equations 17 and 18).SJ... 

The selective oxidation of organic molecules is one of the most important processes used in the chemical industry. Its reactions fall into two broad categories (i) gas-phase oxidation of hydrocarbons (alkanes, alkenes) to oxygenated products and (ii) further oxidation of molecules containing one or more oxygen atoms (mainly in the liquid phase). 

Investigations of the mode of termination by studying the effect of surface on the ovarall kinetics of the gas-phase oxidation of hydrocarbons cannot lead to unequivocal conclusions, because under certain conditions the major propagation steps may also be heterogeneous (see Sect. 5.2). However, Lucquin and co-workers have thrown considerable light on some of these reactions. 

V. Ya Shtern, The Gas Phase Oxidation of Hydrocarbons, Pergamon, London, 1964. 

We are not aware of any significant study of autoxidation of polypropylene at elevated temperatures, i.e. oxidative pyrolysis. On the other hand, much is known about gas-phase oxidation of hydrocarbons at high temperatures and the cool-flame limit (25,26,27,28). The reactions are recognized as free radical chain reactions propagated by peroxy radicals and hydroperoxides which was essentially a development of Backstrom s scheme for the oxidation of aldehydes (29). These mechanisms may be adapted to the oxidative pyrolysis of polypropylene. 

Shtern, V. Ya. Gas-Phase Oxidation of Hydrocarbons. Oxford—London, Pergamon 1964, p. 724. 

Coronas, J., Menendez, M. and Santamaria, J. (1995). The Porous-Wall Ceramic Membrane Reactor An Inherently Safer Contacting Device for Gas-Phase Oxidation of Hydrocarbons, J. Loss Prevent. Proc., 8, pp. 97—101. 

FIGURE 11.2 Scheme of the installation for the gas-phase oxidation of hydrocarbons used by the Celanese firm [263] (1) mixer, (2) heater, (3) reactor, (4) formaldehyde scrubber, (5) water scrubber, (6) distillation coiumn, (7) heat exchanger. (I) Hydrocarbon gas (11) air (111) cycle gas (IV) gas for the hydrocarbon recovery unit (V) gas for light products purification unit (VI) recycled formalin solution (VII) crude formalin for purification (VIII) formaldehyde from chemical products purification unit (IX) caustic soda to adjust the pH value. 

There are reports on the gas-phase oxidation of C5—Cg saturated hydrocarbons. For example, the gas-phase oxidation of hexane gives a-oxides and derivatives of oxacyclobutane and tetrahydrofuran. There is evidence of the possibility using the gas-phase oxidation of hydrocarbons to increase the octane number of gasoline without changing their boiling limits... 

INNOVATIVE TECHNOLOGIES BASED ON THE GAS-PHASE OXIDATION OF HYDROCARBON GASES TO OXYGENATES... 

Enikolopyan NS, Konoreva GP. Homogeneous catalysis in the gas-phase oxidation of hydrocarbons. Russ Chem Bull 1960 9 389-95. 

This reaction occurs much more slowly that the addition reaction. It plays a noticeable role in the high-temperature gas-phase oxidation of hydrocarbons with weak C—H bonds. This results in the parallel formation of ROOH and H2O2 through RO2 and HO2... 

Coronas, I, Menendez, M. and Santamarfa, J. (1995) The porous-wall ceramic membrane reactor an inherently safer contacting device for gas-phase oxidation of hydrocarbons./oama/ of Loss Prevention in the Process Industries, 8,97-101. 

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