Integrated coal pyrolysis with steam reforming of propane to improve tar yield

•Integrated coal pyrolysis with steam reforming of propane (CP-SRP) improved tar yield.•Benzenes, phenols and naphthalene content of tar improved effectively by CP-SRP.•Isotopic tracer experiments confirm that C3H8 and H2O participate in tar formation. An integrated process of coal pyrolysis with steam reforming of propane (CP-SRP) to improve tar yield was studied using Ni/Al2O3 as reforming catalyst. Comparing with coal pyrolysis under N2 atmosphere (CP-N2), the CP-SRP and the integrated coal pyrolysis with steam reforming of methane (CP-SRM) or methane with a few propane (CP-SRMP) show higher tar yield. Tar yield reaches its maximum at 600 °C in CP-SRP, which is 1.17, 1.14, and 1.11 times that in CP-N2, CP-SRMP and CP-SRM, respectively. Simulated distillation and GC–MS were used to characterize the fraction distributions and compositions of tar, which indicated the tar from CP-SRP has higher light oil, phenols and naphthalenes content than that from CP-N2. Isotopic tracer agents like C3D8 and D2O were used to study the tar formation mechanism in CP-SRP. The radicals like D, CD3 generated by activated C3D8 and D2O in SRP combine with radicals formed from coal pyrolysis to improve tar yield and change the product distribution.