GAS-PHASE OXYGEN OXIDATIONS OF ALKYLAROMATICS OVER CVD FE/MO/BOROSILICATE MOLECULAR-SIEVE .2. THE ROLE OF CARBON-DIOXIDE AS A COOXIDANT

In the course of studying carbon dioxide as a burning suppressing agent for the gas-phase oxygen oxidation of alkylaromatics, it was unexpectedly found that the oxygen oxidation reaction was promoted in the presence of carbon dioxide over the CVD Fe/Mo/DBH catalyst. The substrates included p- and o-xylene, and p-ethyltoluene. The conversion of these substrates to aldehydes and other oxygenates was dramatically increased in the gas stream containing oxygen in carbon dioxide at low temperatures. The selectivity to aldehydes and oxygenates was also improved by suppressing substrate burning in carbon dioxide. The carbon dioxide molecules may be activated on the surface of CVD Fe/Mo/DBH catalyst to form the peroxocarbonate intermediate, which serves as a promoter for the gas-phase oxygen oxidation reactions.