Catalytic coal hydrogasification by cobalt-calcium catalyst in a pressurized fluidized bed: Role of hydropyrolysis and catalysis process

摘要

Coal pyrolysis, hydropyrolysis and hydrogasification were performed in a lab-scale pressurized fluidized bed with or without cobalt-calcium bimetallic catalyst (Co-Ca) to preliminarily discern the role of hydropyrolysis, Co-Ca catalyst and H-2 in the course of coal catalytic hydrogasification (CCHG). The hydrogasification reactivity and chemical structure of the coal chars generated after hydropyrolysis were also analyzed by means of pressurized thermogravimetric analyzer (P-TGA), FT-Raman and FT-IR, etc. Results indicate that Co-Ca catalyst possesses catalytic depolymerization and hydrogenation effect on coal during hydropyrolysis, which resulted in the promoted yield of CH4, tar and the high hydrogasification reactivity of the generated char. Co-Ca catalyst alone and H-2 alone are hardly to fracture the C=C bonds in condensed aromatic rings of coal, but the union of them yields a superior bonds cleavage ability. The catalytic cleavage of C-C bonds is the crucial step of CCHG at the temperature above 800 degrees C with the hydrogen pressure above 1 MPa. Moreover, the CCHG process over Co-Ca catalyst is discussed and the probable pathways of the catalytic cleavage of C-C bonds are proposed.