JOURNAL OF FUEL CHEMISTRY AND TECHNOLOGY Volume 44, Issue 7 July 2016 Online English edition of the Chinese language journal Received: 11-Mar-2016; Revised: 05-May-2016. Foundation item: Supported by Short Term Internal Research Fund Universiti Teknologi PETRONAS (0153AA-D06) and the Ministry of Education (Higher Education Department) under MyRA Incentive Grant for CO2-Rich Matural Gas Value Chain Program. *Corresponding author. Tel: +605-3688222, Fax: +605-3658214, E-mail: zahra.gholami@petronas.com.my. Copyright  2016, Institute of Coal Chemistry, Chinese Academy of Sciences. Published by Elsevier Limited. All rights reserved. RESEARCH PAPER Cite this article as: J Fuel Chem Technol, 2016, 44(7), 815821 Synthesis and characterization of niobium-promoted cobalt/iron catalysts supported on carbon nanotubes for the hydrogenation of carbon monoxide Zahra Gholami 1, *, Noor Asmawati Mohd Zabidi 2 , Fatemeh Gholami 3 , Mohammadtaghi Vakili 4 1 Centralized Analytical Laboratory, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Tronoh 32610, Perak, Malaysia 2 Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Tronoh 32610, Perak, Malaysia 3 Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia 4 School of Industrial Technology, Universiti Sains Malaysia, Penang 11800, Malaysia Abstract: Bimetallic Co/Fe catalysts supported on carbon nanotubes (CNTs) were prepared, and niobium (Nb) was added as promoter to the 70Co:30Fe/CNT catalyst. The physicochemical properties of the catalysts were characterized, and the catalytic performances were analyzed at the same operation conditions (H2:CO (volume ratio) = 2:1, p = 1 MPa, and t = 260°C) in a tubular fixed-bed microreactor system. The addition of Nb to the bimetallic catalyst decreases the average size of the oxide nanoparticles and improves the reducibility of the bimetallic catalyst. Evaluation of the catalyst performance in a Fischer-Tropsch reaction shows that the catalyst results in high selectivity to methane, and the selectivity to C5+ increased slightly in the bimetallic catalyst unlike that in the monometallic catalysts. The addition of 1% Nb to the bimetallic catalyst increases CO conversion and selectivity to C5+. Meanwhile, a decrease in methane selectivity is observed. Keywords: Fischer-Tropsch synthesis; bimetallic catalyst; niobium promoter; carbon nanotubes Conventional energy resources, such as coal, petroleum, and natural gas, are fulfilling the major energy demands; however, these resources are on the verge of being exhausted, and fossil oil sources are estimated to be depleted by 2050 [1] . The increasing population, economic development, and limited supplies of fossil fuels led to the development of new approaches to produce renewable liquid fuels [2] . Fischer-Tropsch synthesis (FTS) gained popularity as an alternative approach to transform different non-petroleum carbon resources, such as coal, natural gas, and biomass, into valuable chemicals from syngas (H 2 and CO) or clean transportation fuels [3] . FTS is a process that catalytically converts syngas into clean hydrocarbon fuels, whereas syngas can be derived from non-petroleum feedstock, such as coal, natural gas, or biomass. Increasing the quality of products by developing novel catalysts with high activity and selectivity is desirable in FTS reactions [4] . In FTS reactions, syngas is transformed into liquid fuel through catalytic polymerization, which results in various products, such as paraffins, olefins, alcohols, and aldehydes. Some challenges still remain in catalyzing FTS reactions. From a fundamental perspective, one of the important difficulties is the control of selectivity. CO undergoes dissociative or hydrogen-assisted dissociative chemisorption on the surface of active metal phases to produce CH x (x = 0–3) intermediates as monomers for polymerization. The connection between CH x monomers results in chain growth and provides C n H m intermediates. C n H m intermediates with different carbon numbers can undergo hydrogenation or dehydrogenation to produce paraffins or olefins as final products [5,6] . Ni, Fe, Co, and Ru are known to be the most active elements for FTS reactions [7–9] because of their ability to dissociatively adsorb CO and H 2 [10] . One of the parameters that affect the activity of a catalyst is the chemical composition of the catalyst [11–13] . However, other parameters, including appropriate physical properties and high surface area, are also important for the catalytic activity in FTS