Selective synthesis of 3-picoline via the vapor-phase methylation of pyridine with methanol over Ni1-xCoxFe2O4 (x=0, 0.2, 0.5, 0.8 and 1.0) type ferrites

A series of Ni-Co ferrites with the general formula Ni1-xCoxFe2O4 (x = 0, 0 .2, 0.5, 0.8 and 1.0) was prepared by a low-temperature hydroxide coprecipi tation route. The catalyst systems were characterized by adopting various p hysico-chemical techniques. Alkylation of pyridine with methanol was carrie d out in a down-flow vapor-phase reactor. The influence of surface acid-bas e properties, cation distribution in the spinel lattice and various reactio n parameters are discussed. It was observed that the systems possessing x v alues greater than or equal to 0.5 are selective for 3-picoline formation, whereas the ones with x values 0 and 0.2 give a mixture of 2- and 3-picolin es. Pyridine conversion increased with the progressive substitution of Ni2 ions by Co2+ ions. Cation distribution in the spinel lattice influences th eir acidic and basic properties, and these factors have been adequately con sidered as helpful to evaluate the activity of the systems.