Terminal Oxidation of n-Octane over ZSM-5 and Silicalite Catalysts in the Liquid Phase

Siyabonga Ndlela
2016 unpublished
Three types of zeolites namely ion-exchanged ZSM-5 (Si/Al ratio of 47), framework substituted ZSM-5, and silicalite were synthesized. The synthesis of zeolite ZSM-5 was conducted using sol-gel method and modified using ionic exchange method to yield Fe-ZSM-5(47,IE), V-ZSM-5(47,IE), Cr-ZSM-5(47,IE) and Mn-ZSM-5(47,IE). In addition, 1.1Fe0.8V-ZSM-5(IE) and 0.4Fe1.2V-ZSM-5(IE) catalysts were synthesized to evaluate the activity of a bimetallic catalyst. Furthermore, the synthesis of Fe-ZSM-5(62),
more » ... s of Fe-ZSM-5(62), 1.6Fe-silicalite, 1.8V-silicalite, 0.9Fe0.8V-silicalite and 0.3Fe1.3V-silicalite was carried out by an isomorphic substitution. The numbers represent the metal Wt%, while the number in bracket represents Si/metal ratios. Powder XRD results showed that only the ZSM-5 phase was obtained for all the prepared catalysts and the optical density ratio of all the catalysts was above 0.7 confirming the catalysts' crystalline nature. All synthesized catalysts were tested in the oxidation of n-octane with H 2 O 2 as the oxidant in MeCN at 80 °C for 8 hours. Fe-ZSM-5(47,IE), V-ZSM-5(47,IE), Cr-ZSM-5(47,IE), Mn-ZSM-5(47,IE), 1.1Fe0.8V-ZSM-5(IE) and 0.4Fe1.2V-ZSM-5(IE) produced selectivities of 38, 12, 10, 6, 21 and 17 % respectively to terminal products. Furthermore, 1.6Fe-silicalite, 1.8V-silicalite, 0.9Fe0.8V-silicalite and 0.3Fe1.3V-silicalite achieved terminal selectivities of 17, 12, 16 and 22 % respectively while Fe-ZSM-5(62) showed 20 % terminal selectivity. The terminal selectivities were found to increase with the decrease in the amount of vanadium used in ZSM-5 while the opposite was true for silicalite catalysts. iii