Gasoline catalytic oxidation

Locap A process for removing mercaptans from gasoline by catalytic oxidation to disulfides, using a fixed bed of catalyst that is continuously treated with aqueous sodium sulfide. Commercialized by Petrolite Corporation in 1963. 

Another limitation on the use of catalytic oxidation is the susceptibility of the catalysts to various deactivators or poisons, although according to the vendor the phase out of the use of volatile lead alkyls as antiknock agents in U.S. gasoline, catalyst poisoning is today rarely encountered. 

Gasolines contain a small amount of sulfur which is emitted with the exhaust gas mainly as sulfur dioxide. On passing through the catalyst, the sulfur dioxide in exhaust gas is partially converted to sulfur trioxide which may react with the water vapor to form sulfuric acid (1,2) or with the support oxide to form aluminum sulfate and cerium sulfate (3-6). However, sulfur storage can also occur by the direct interaction of SO2 with both alumina and ceria (4,7). Studies of the oxidation of SO2 over supported noble metal catalysts indicate that Pt catalytically oxidizes more SO2 to SO3 than Rh (8,9) and that this reaction diminishes with increasing Rh content for Pt-Rh catalysts (10). Moreover, it was shown that heating platinum and rhodium catalysts in a SO2 and O2 mixture produces sulfate on the metals (11). 

Mitsubishi Rayon in Japan has commercialized a three-step process on the basis of a two-step catalytic oxidation of isobutene, preferentially through f-butanol as primary intermediate. This process suffers not only from a relatively moderate overall MMA yield ( 80%), but also from increasing isobutene cost due to its alternative use for MTBE (methyl fert.-butyl ether) production as a gasoline additive. 

Use Polymer and alkylate gasoline polybutenes butadiene intermediate for C4 and C5 aldehydes, alcohols, and other derivatives production of maleic anhydride by catalytic oxidation. 

Methanol to olefins Benzene reduction Olefins to gasoline Isophthalonitrile Catalytic oxidation... 

The process can be modified to give predominandy or solely /-butyl alcohol. Thus, /-butyl hydroperoxide (and /-butyl alcohol) produced by oxidation of isobutane in the first step of the process can be decomposed under controlled, catalytic conditions to give gasoline grade /-butyl alcohol (GTBA) in high selectivity (19—22). 

The mechanism of poisoning automobile exhaust catalysts has been identified (71). Upon combustion in the cylinder tetraethyllead (TEL) produces lead oxide which would accumulate in the combustion chamber except that ethylene dibromide [106-93-4] or other similar haUde compounds were added to the gasoline along with TEL to form volatile lead haUde compounds. Thus lead deposits in the cylinder and on the spark plugs are minimized. Volatile lead hahdes (bromides or chlorides) would then exit the combustion chamber, and such volatile compounds would diffuse to catalyst surfaces by the same mechanisms as do carbon monoxide compounds. When adsorbed on the precious metal catalyst site, lead haUde renders the catalytic site inactive. 

Several other important commercial processes need to be mentioned. They are (not necessarily in the order of importance) the low pressure methanol process, using a copper-containing catalyst which was introduced in 1972 the production of acetic add from methanol over RhI catalysts, which has cornered the market the methanol-to-gasoline processes (MTG) over ZSM-5 zeolite, which opened a new route to gasoline from syngas and ammoxidation of propene over mixed-oxide catalysts. In 1962, catalytic steam reforming for the production of synthesis gas and/or hydrogen over nickel potassium alumina catalysts was commercialized. 

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