Total Syngas Methanation to Synthetic Natural Gas

This process has been recently carried out over a Ni-supported catalyst in a microchannel reactor resulting in an excellent catalytic performance in milliseconds (50 ms) contact time. Liu et al. developed a new method to manufacture the metal (FeCralloy)-ceramic (Y-AI2O3) complex substrate needed as catalyst support, called improved thermal spray. Due to the dual function of this substrate, a CO conversion value of above 98% and 92% CH4 selectivity and reliability were found operating at 550 °C, 30 atm, and 71000 h [41]. 

This reaction provides a wide variety of hydrocarbons (Ci to 50-200) from synthesis gas, becoming a very attractive route for the production of clean fuels (LPG, gasoline, kerosene, and diesel) and a source of chemicals (namely, linear olefins) [42]. However, it is important to ensure an appropriate size and type of reactor due to its exothermicity (Af/R = -165kJ/mol). Mass transfer effects are also significant since catalyst pores are filled with liquid products (waxes and water) limiting the diffusion rate. Despite the gas phase of reactants, selectivity to C5+ seems to decrease notably for diffusion lengths exceeding 0.1-0.3mm. Therefore, MSRs have been proposed as a suitable alternative. 

Concerning possible scale-up of this process, MSRs showed highest productivity per unit of catalyst volume [51], while milli-fixed bed reactors were found to provide better temperature management compared with a conventional fixed bed and a slurry reactor [52]. Consequently, Lerou et al. [53] reported an increase of productivity by 50-300% to 12 bpd/t reactor, which supposes excellent economics at much smaller scale (500 bpd versus lOOOObpd). Deshmukh et al. [54] also described a feasible scale-up yielding 72% conversion and 85% C5+ selectivity within 290 ms, by means of a reactor characterized by 150 g proprietary catalyst (Co, Oxford Catalysts, Ltd (OCL)) on 276 microchannels 

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