A product comprising a lower alkyl ester of a lower aliphatic carboxylic acid is produced by a process comprising reacting under substantially anhydrous conditions a lower alkyl ether with carbon monoxide in the presence of a zeolite catalyst having an 8-member ring channel which is interconnected with a channel defined by a ring with greater than or equal to 8 members, the 8-member ring having a window size of at least 2.5 Angstroms×at least 3.6 Angstroms and at least one Brønsted acid site and the zeolite having a silica:X2O3 ratio of at least 5, wherein X is selected from aluminum, boron, iron, gallium and mixtures thereof.