Production of Synthesis Gas via Dry Reforming of Methane over Co-Based Catalysts: Effect on H 2 /CO Ratio and Carbon Deposition The effect of support type on synthesis gas production using Co-based catalysts supported over TiO 2 -P25, Al 2 O 3 , SiO 2 , and CeO 2 was investigated. The catalysts were prepared by the incipient wet impregnation method and characterized by various techniques for comparison. Experiments were performed in a micro tubu- lar reactor. The results revealed that all Co-supported catalysts produced synthesis gas ratios of 1 and below and, thus, proved to be well-suited for methanol and Fischer-Tropsch syntheses. Co catalysts supported over TiO 2 -P25 and Al 2 O 3 pro- vided better synthesis gas ratios and stability performances. The promotion of a Co/TiO 2 -P25 catalyst with Ce had a substantial influence on its catalytic activity and the amount of carbon deposit. A Ce-promoted catalyst diminished markedly the extent of carbon deposition and thus boosted the performance towards better activity and stability. Keywords: Carbon formation, Cerium promoter, Cobalt catalyst, Synthesis gas, TiO 2 -P25 Received: November 17, 2014; revised: January 08, 2015; accepted: May 19, 2015 DOI: 10.1002/ceat.201400690 1 Introduction The emissions of greenhouse gases, e.g., CO 2 and CH 4 , pose environmental concerns such as global warming and, therefore, their limitations are of paramount importance [1–5]. Catalysts based on transitional elements like Ni and Co can play dramat- ic roles in alleviating these problems by consuming and trans- forming greenhouse gases into synthesis gas through reforming processes [6–11]. Synthesis gas has found many industrial ap- plications. In principle, any hydrocarbon feedstock can be used to produce synthesis gas. However, the incurred cost of cooling and purification of syngas, removal of soot, and handling of materials jeopardizes the conversion of such feedstock by gasi- fication. Therefore, looking for an appropriate technology like CO 2 reforming of CH 4 (CRM) is worth considering. The main CO 2 reforming of CH 4 reaction and the associated side reactions are as follows: CH 4 + CO 2 fi 2CO + 2H 2 CO 2 reforming of CH 4 (1) CO 2 +H 2 O fi CO + H 2 reverse water-gas shift reaction (2) CH 4 fi C + 2H 2 methane cracking reaction (3) 2CO fi C + CO 2 disproportionation reaction (4) C+H 2 O fi CO + H 2 carbon gasification (5) The reforming process is frequently hampered by coke for- mation and loss dispersion of the active catalyst [12–16]. Gen- erally, there are two primary coke formation side reactions that could occur during the CRM process: methane dissociation ac- cording to Eq. (3) and disproportionation of CO according to Eq. (4). The former is endothermic and favored at higher tem- peratures and under lower pressures, while the latter is exother- mic and favored at lower temperatures and higher pressures. The carbon formation rate over Ni-based catalysts was the highest among the transitional element-based catalysts. Deacti- vation due to carbon restricted the industrial application of Ni-based catalysts for the CRM process. The size, shape, struc- ture, and surface composition have significant effects on the coke resistance of Ni-based catalysts. Thus, numerous efforts have been made to establish coke-resistant Ni-based catalysts suitable for long-term catalytic performance [10, 11, 17]. Nevertheless, the need for efficient catalysts is indispensable to achieve long-term operation of the process. Co-based cata- lysts showed considerable activity for the CH 4 reforming reac- tions which suggests that Co could be a suitable metal for the CRM process [18]. However, the occurrence of strong surface Chem. Eng. Technol. 2015, 38, No. 8, 1397–1405 ª 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.cet-journal.com Ahmed A. Ibrahim Muhammad Awais Naeem Anis H. Fakeeha Wasim Ullah Khan Ahmed S. Al-Fatesh Ahmed E. Abasaeed Chemical Engineering Department, College of Engineering, King Saud University, Riyadh, Saudi Arabia. – Correspondence: Dr. Ahmed S. Al-Fatesh (aalfatesh@ksu.edu.sa), Chemical Engineering Department, College of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia. Research Article 1397