Integrated Process of Coal Pyrolysis with Steam Reforming of Ethane for Improving the Tar Yield

A new process to integrate coal pyrolysis with steam reforming of ethane (CP-SRE) using Ni/Al2O3 as a catalyst was proposed to improve the tar yield of coal. Coal tar of the CP-SRE process was compared to that of pyrolysis in atmospheres of nitrogen (CP-N-2), hydrogen (CP-H-2), and steam reforming of methane (SRM). The results showed a high tar yield in CPSRE; it is 15.34% on a dry and ash-free basis at a temperature of 600 degrees C, which is 1.42, 1.09, and 1.04 times the tar yield of CPN2, CP-H-2, or CP-SRM, respectively. To understand fraction distribution and structural information on tar in CP-SRE, coal tar was characterized by simulated distillation, H-1 and C-13 nuclear magnetic resonance, and gel permeation chromatography. It indicated that the tar from CP-SRE presents a lower molecular weight distribution, higher light oil content, lower asphaltene content, and slightly higher amount of uncondensed aromatic protons and quaternary aromatic carbons than that from CP-N-2. The coal tar formation mechanism in CP-SRE was investigated using the isotope trace method with deuterium oxide (D2O) and deuterated ethane (C2D6) as tracer agents. The results indicated that D2O and C2D6 contribute to coal tar formation in the form of activated free radicals, including D-center dot, (CD3)-C-center dot, (C2D5)-C-center dot, etc.