Direct conversion of syngas to DME as a green fuel in a high pressure microreactor: Influence of slurry solid content on characteristics and reactivity of washcoated CuO–ZnO–Al2O3/HZSM-5 nanocatalyst

Abstract

Microchannels of a stainless steel microreactor were successfully washcoated with slurry of Cu–ZnO–Al2O3/HZSM-5 (CZAZ) nanocatalyst with different concentrations (10, 20 and 30wt.%). The properties of nanocatalyst and the washcoated microchannels were investigated by XRD, FESEM, N2 physisorption, FTIR, EDX-Dot mapping and EDX-Line mapping analysis. The best adherence was observed for 20wt.% catalyst which has a uniform coating, almost no cracks and homogenous dispersion of copper and zinc. Trend of weight gain during 10 soaks in catalyst slurry was very slow for 10wt.% but faster for 20 and 30wt.%. Low amount of weight gain was observed for the last soaks of catalyst slurry in the case of 30wt.% washcoating. The performance of microreactor with different slurry concentrations were evaluated in direct synthesis of DME at 200–300°C, 60–150cm3/min and 40bar. Regardless of slurry concentration, the microreactor exhibited a better reactivity in comparison to fixed-bed reactor performance. Among three different slurry concentrations, 20wt.% catalyst slurry revealed the best reactivity in direct DME synthesis. The reduction in reactor performance at higher flow rates was significant in the fixed-bed reactor while microreactor, particularly 20wt.% washcoated channels, revealed less drastic reduction.