Abstract—NaZSM-5 zeolite was synthesized by a hydrothermal method using rice husk silica and modified by desilication with NaOH solution to generate mesopores. The removal of silicon atoms was confirmed by the Si/Al ratio, analyzed by ICP-MS showing that the Si/Al ratio of the desilicated NaZSM-5 was lower than that of the parent. Both the parent and desilicated NaZSM-5 were used as support materials for Fe for phenol hydroxylation. All the supports and catalysts were characterized by XRD, TEM, and N2 adsorption- desorption to confirm the zeolite structure, observe morphology and determine surface area and pore size distribution. Desilication did not change the zeolite structure but generated non-uniform mesopores with a broad range of mesopore size and increased surface area. The form of Fe, analyzed by XANES was in the oxidation state 3+. Catalytic performance of 5Fe/NaZSM-5 and 5Fe/NaZSM-5(D) for phenol hydroxylation in a batch reactor using H2O2 as an oxidant, gave phenol conversion of ca. 67% at 70˚C [phenol:H2O2= 1:3]. The 5Fe/NaZSM-5(D) showed a faster phenol conversion to reach equilibrium. Products from both catalysts were catechol and hydroquinone with mole ratio about 2:1.
Index Terms—Phenol hydroxylation, Rice husk silica, ZSM-5, iron
M. Pimsuta, S. Prayoonpokarach, and J. Wittayakun are with Material Chemistry Research Group, School of Chemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand (email: oob_mus@hotmail.com, sanchaip@sut.ac.th, jatuporn@sut.ac.th).
A. Neramittagapong is with Department of Chemical Engineering, Faculty of Engineering, Khon Kaen University, Khon Kaen 40002, Thailand (email: artner@kku.ac.th ).
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Cite: M. Pimsuta, A. Neramittagapong, S. Prayoonpokarach, and J. Wittayakun, "Desilication of NaZSM-5 and Utilization as Support of Fe for Phenol Hydroxylation," International Journal of Chemical Engineering and Applications vol. 3, no. 2, pp. 86-91, 2012.
