Catalysis Today 63 (2000) 471–478 Methylation of benzene with methanol over zeolite catalysts in a low pressure flow reactor Moses O. Adebajo, Russell F. Howe ∗ , Mervyn A. Long School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia Abstract Previous studies in this laboratory have shown oxygen to be a crucial requirement for the reaction of methane with benzene over zeolite catalysts at 400 ◦ C in a high pressure batch reactor. Thus, a two-step mechanism involving the intermediate formation of methanol by partial oxidation of methane followed by the methylation of benzene with methanol in the second step, was postulated. This paper now shows clearly that there is excellent correlation between the performance of the zeolite catalysts used for the methylation of benzene with methanol in a low pressure flow reactor and the methylation of benzene with methane in the presence of oxygen in a high pressure batch reactor. This finding therefore gives further support to the two-step mechanism for the oxidative methylation reaction at 400 ◦ C. © 2000 Elsevier Science B.V. All rights reserved. Keywords: Methylation; Benzene; Methanol; Methane; Zeolites’ performance; Excellent correlation 1. Introduction It has previously been demonstrated by Long and co-workers [1] that the direct methylation of benzene with methane occurred over zeolite cat- alysts at 400 ◦ C in a high pressure batch reactor. The methyl groups incorporated into the methy- lated products were shown through the use of 13 C labelled methane to originate from the methane reac- tant. Such direct methylation of aromatic molecules with methane is not thermodynamically feasible under normal conditions but significant yields of methylated products are feasible if the reaction is carried out in the presence of sufficient excess of methane. In contrast to the observation by Long et al., earlier studies by Lunsford et al. [2] failed to show the pres- ∗ Corresponding author. Tel.: +61-2-9385-4693; fax: +61-2-9385-6141. E-mail address: r.howe@unsw.edu.au (R.F. Howe). ence of any detectable 13 C in the toluene and xylenes formed when benzene was reacted with methane at 400 ◦ C over acidic H-beta zeolite catalyst in a high pressure flow reactor. These workers concluded that the methylated products were formed by cracking of the benzene reactant, and found that the activity for this reaction was only present in strongly acidic zeo- lites. A more recent investigation in this laboratory [3,4] has now demonstrated that oxygen is required in the methylation of benzene with methane at 400 ◦ C over ZSM-5 zeolite catalysts in a high pressure batch re- actor. The reaction was therefore postulated to go through a two-step mechanism involving the interme- diate formation of methanol by partial oxidation of methane in the first step and methylation of benzene with methanol in the second step. In addition to this oxidative methylation reaction, it was observed that in the case of H-beta zeolite catalyst, methyl aromatics can also be formed in the absence of oxygen, consis- tent with the earlier report [2] that these products are 0920-5861/00/$ – see front matter © 2000 Elsevier Science B.V. All rights reserved. PII:S0920-5861(00)00493-4