The behavior of catalysts in hydrogasification of sub-bituminous coal in pressured fluidized bed

The catalytic hydtogasification of the sub-bituminous coal was carried out in a lab-scale pressurized fluidized bed with the Co-Ca, Ni-Ca and Fe-Ca as catalysts at 850 degrees C and 3 MPa. The effect of different catalysts on the characteristics of gasification products was investigated, and the behavior of the catalysts was also explored by means of the X-ray diffraction (XRD), FT-Raman, Brunauer-Emmett-Teller (BET), etc. Experiment results showed that all the catalysts promoted the carbon conversion in the coal catalytic hydrogasification (CCHG), and the catalytic activity was in the order: 5%Co-1%Ca > 5%Ni-1%Ca > 5%Fe-1%Ca. Compared with the raw coal hydrogasification, the carbon conversion increased from 43.4 wt.% to 91.3 wt.%, and the CH4 yield increased from 23.7 wt.% to 77.3 wt.% within 30 min after adding the 5%Co-1%Ca catalyst into the coal. Co-Ca and Ni-Ca possessed catalytic effect on both processes of pyrolysis of coal and hydrogasification of coal char in CCHG, by which the graphitization of the coal was suppressed and methane formation rate was significantly accelerated. Fe/Co/Ni-Ca could penetrate into the interior of coal during CCHG, making the catalytic production of CH4 conduct in the pore structures. The activity difference of the catalysts was owing to the different ability of rupturing the amorphous C-C bonds in coal structure. The incomplete carbon conversion of the 5%Co-1%Ca loaded coal was due to the agglomeration of the catalyst and the blockage of the reactive sites by the sintered catalyst. This work will provide a straightforward method and reference data for the further industrial-scale production of 1.2 N m(3) CH4/kg-coal from CCHG by using pressured fluidized bed reactor.