The integrated process of CO2 reforming of methane with co-pyrolysis of Naomaohu coal and elm to improve tar yield

Co-pyrolysis of coal and biomass is an effective route to replace coal utilization with alternative biomass resource. However, it is crucial to acquire high tar yield during co-pyrolysis. To improve tar yield during co- pyrolysis of Naomaohu coal and elm, in this work, a new process was constructed by integrating co-pyrolysis with CO2 reforming of methane over 10Ni/gamma-Al2O3 catalyst (CP-CRM) on an infrared-heated fixed-bed reactor, and the effect of pyrolysis temperatures on the integrated process was investigated. The comparison of co- pyrolysis behaviors under N2 (CP-N2) or CH4/CO2 (CP-CH4/CO2) atmosphere was conducted to reveal the reaction mechanism during CP-CRM. Result revealed that the CP-CRM showed higher tar yield than co-pyrolysis under CP-N2, and the maximum tar yield of 21.68 wt% was achieved at 500 degrees C during the integrated process, which was 1.13 times as that under CP-N2. In comparison, tar yield in co-pyrolysis under CH4/CO2 mixture gas was between those of CP-N2 and CP-CRM, indicating that CH4 and CO2 themselves could facilitate the formation of tar, which could further be strengthened under the action of 10Ni/gamma-Al2O3 catalyst. The analyses of co- pyrolysis tar by simulated distillation, GC/MS, 1H-NMR and 13C-NMR showed that the pitch content in co- pyrolysis tar from CP-CRM was higher than those in CH4/CO2 and N2 atmospheres, and high phenols content up to 60.05% was obtained, higher than 51.61 % in tar from CP-N2. Additionally, the tar from CP-CRM possessed more aromatics with short side chains compared than those from pyrolysis under N2 and CH4/CO2, which was mainly ascribed to the participation of active free radicals from CO2 reforming of CH4. This work provides a simple route to improve tar yield and phenols content in tar during co-pyrolysis.