This disclosure provides improved processes for converting benzene/toluene via methylation with methanol/dimethyl ether for producing, e.g., p-xylene. In an embodiment, a process utilizes a methylation catalyst system comprising a molecular sieve catalyst and an auxiliary catalyst. The auxiliary catalyst comprises a metal element selected from Group 2, Group 3, the lanthanide series, the actinide series, and mixtures and combinations thereof. The auxiliary catalyst may comprise the oxide of the metal element. Deactivation of the molecular sieve catalyst can be reduced with the inclusion of the auxiliary catalyst in the methylation catalyst system.

This disclosure provides improved processes for converting benzene/toluene via methylation with methanol/dimethyl ether for producing, e.g., p-xylene. In an embodiment, a process utilizes a methylation catalyst system comprising a molecular sieve catalyst and an auxiliary catalyst. The auxiliary catalyst comprises a metal element selected from Group 2, Group 3, the lanthanide series, the actinide series, and mixtures and combinations thereof. The auxiliary catalyst may comprise the oxide of the metal element. Deactivation of the molecular sieve catalyst can be reduced with the inclusion of the auxiliary catalyst in the methylation catalyst system.

The oxidative coupling of methane (OCM) and the oxidative dehydrogenation (ODH) of ethane and higher hydrocarbons is described using SO.sub.3 and sulfate, sulfite, bisulfite and metabifulfite salts as oxygen transfer agents in the presence of one or more elements selected from Groups 3 to 14 of the periodic table, optionally further in the presence of alkali or alkaline salts and/or sulfur-containing compounds.

The oxidative coupling of methane (OCM) and the oxidative dehydrogenation (ODH) of ethane and higher hydrocarbons is described using SO.sub.3 and sulfate, sulfite, bisulfite and metabifulfite salts as oxygen transfer agents in the presence of one or more elements selected from Groups 3 to 14 of the periodic table, optionally further in the presence of alkali or alkaline salts and/or sulfur-containing compounds.