Journal of the Nigerian Society of Chemical Engineers, 35(1), 2020 17 IMPROVED SELECTIVITY EFFECT OF COBALT, NICKEL CO-METAL IMPREGNATION WITH ZINC ON ZSM-5 FOR AROMATIZATION OF PROPANE G.G. Oseke 1* , A. Y. Atta 1* , B. Mukhtar 1 , B. J. El-Yakubu 1 and B. O. Aderemi 1 1 Chemical Engineering Department, Ahmadu Bello University, Zaria. *Corresponding author: osechemtechy@gmail.com Sub-theme: Research Development and innovation in chemical engineering ABSTRACT Conversion of light alkanes catalytically to aromatic compounds is an important research area of interest. This is because aromatic compound are the major feedstocks for petrochemical industries. Zn/ZSM-5 has been found to improve aromatic selectivity of HZSM-5 but unstable. Hence the need for stabilizing Zn with another metal. The interaction of Zn with Co and Ni on ZSM-5 shows a higher selectivity towards aromatics over 85%. This improved Zinc stability on ZSM-5 as compared to only Zinc with dwindling selectivity to 50% and HZSM-5 of 10% at ten hours TOS. Catalyst physicochemical properties were analysed with XRD, BET, N2-adsorption, FTIR, FTIR-Pyridine, SEM, and TEM. The XRD and FTIR characterization showed that the modified catalysts were still crystalline after metal impregnation. The products distribution also showed reduced light gases formation and formation of more aromatics. The synergistic interaction between Ni and Co with Zn metal improved the catalytic performance of Zn-Co/ZSM-5 and Zn-Ni/ZSM-5 catalysts by promoting and sustaining the dehydrogenation step and suppressing protolytic cracking step in the reaction series resulting in the recorded significant improvement in aromatic yield over the monometallic Zn/ZSM-5 catalyst. Keywords: Propane conversion, bimetallic, toluene selectivity, co-impregnation, Metal modified Zn/ZSM-5 1. INTRODUCTION The conversion of propane to aromatics has been a subject of interest to industrialists and academia within the last two decades. This is closely related to increasing demand for aromatic compounds (mainly, benzene, toluene, ethylbenzene and xylene) which are used as feedstocks for the production of chemicals, polymers, detergents, pharmaceuticals, agricultural inputs and explosives from petrochemical industries. Nigeria among many nations has been declared to be more of gas rich nation which are substrates for production of aromatic compounds. It is becoming more important and imperative to start considering ways to transform these abundant gas resources (light alkanes such as propane) to aromatic compound which are building block and feedstock to petrochemical and chemical process industries. Propane exists in large deposits in natural gas reservoirs, gas condensate, and refinery gases (Derouane et al., 2006: Asaftei et al., 2009). A number of researches have been conducted over time to understudy the kinetics and mechanism of propane transformation to aromatics (Fechete et al., 2012: Armor, 2011). It was found that reaction steps majorly includes: Protolysis, hydride transfer, beta-scission, alkylation-dealkylation, dehydrogenation, oligomerization, olefin adsorption and desorption, alkanes adsorption and desorptions, cyclization and aromatization. Most related researches from kinetic and thermodynamic views have revealed that propane protolytic cracking step is the rate limiting step and the hydride transfer which is recombination of the abstracted hydrogen with the radical intermediates further limits the progression of the reaction to form aromatics (Lindström and Lars, 2003: Bhattacharya and Sivasanker, 1996: Rane et al., 2006: Xu et al., 2013). Modification of catalyst by metal anchoring on ZSM-5 catalyst had made up part of the efforts applied to produce aromatic compounds as parent HZSM-5 had been found to be low on aromatic selectivity. These include developments of monometallic zeolitic catalysts i.e. Pt/ZSM-5, Ga/ZSM-5, Zn-ZSM-5, Mo/ZSM-5 aimed at promoting protolytic scission over C=C cracking and improve cyclization to aromatization (Bhan and Nicholas, 2008: Choudhary et al., 1996: Choudhary et al., 2006: Guisnet et al., 1992: He, 2015) Zn/ZSM-5 emerged as the most promising catalyst considering cost effectiveness, selectivity toward