Vapor phase methylation of pyridine with CO–H2 over metal catalysts Original Research Article

The title reaction was carried out over Ni, Ni/SiO2, Ni/Al2O3, Ni/ZrO2, Ni/MgO, Co/SiO2, Ru/SiO2, Rh/SiO2, Pt/SiO2 and Pd/SiO2 catalysts. Over Ni, Ni/SiO2, Ni/Al2O3, Ni/ZrO2 and Ni/MgO, 2-methylpyridine is produced with high selectivity along with small amounts of 2,6-dimethylpyridine and methane. Methylation occurs selectively at carbon atoms adjacent to a nitrogen atom. The order of the catalytic activity is Ni/Al2O3 > Ni/ZrO2 > Ni > Ni/SiO2 > Ni/MgO. It was found that 2,6-dimethylpyridine is produced via methylation of 2-methylpyridine, and that methylation of pyridine with CO–H2 and CO methanation are parallel reactions. CHx species produced from CO–H2 are consumed effectively for methylation of pyridine. Over Co/SiO2 and Ru/SiO2, although methylation occurs, the yield is very low. Over Rh/SiO2, Pt/SiO2 and Pd/SiO2, methylation is not observed. Differences in the yields of the catalysts are discussed.