Modification of HZSM-5 by metal surfactant for aromatization

Zinc valerate and magnesium valerate were used to modify HZSM-5 for aromati zation of methylcyclohexane. Before and after the modification the pore str ucture and surface area of the zeolite were characterized and ammonia TPD m easurement was carried out. Methylcyclohexane aromatization reaction over t he zeolite was evaluated using a pulse quartz minireactor. The results indi cated that both the conversion and the aromatic selectivity were increased by zinc valerate modification but were decreased by magnesium valerate. The latter modification also caused increases in C1-C4 hydrocarbon selectivity and in its yield. The former modification resulted in an improvement in sh ape selectivity of the zeolite. There existed an optimal zinc ion ratio of external surface/internal surface of the zeolite for aromatization and the ratio could be obtained by a combination of zinc valerate modification and zinc ion exchange. Metal surfactant modification can be used to study the e xternal and internal surfaces of a zeolite separately. (C) 1998 Elsevier Sc ience B.V. All rights reserved.