Catalytic Reforming Of Characteristics Of Dust-containing Coal Pyrolysis Volatiles

In the volatiles from coal pyrolysis, the heavy tar components and a small amount of dust can form tar residue, which adversely effects the transportation and clean utilization of energy. At present, catalytic cracking is one of the effective ways to solve this problem. The tar cracking catalysts are divided into two categories, synthetic catalysts and natural mineral catalysts. In this paper, Ni-Al₂O3 catalysts and dolomite catalysts were selected from these two kinds of catalysts as the research subjects. Four kinds of Ni-Al2O3 catalysts with different additives and a kind of modified dolomite catalysts were prepared. The tar catalytic reforming experiment was performed on a fixed-bed reaction equipment using model tar compounds as reactants to study the effect of operating conditions on the catalytic activity to determine the preferred operating conditions for each kind of catalysts. The activity, stability and reaction-regeneration performance of different catalysts were compared.The effect of deposition of the different oxides on the surface of 2%NiO/1 %CeO2/2%ZrO2-Al2O3 and 10%NiO/1%La2O3-dolomite catalysts on the catalytic activity were conducted.The optimal operation conditions of four kinds of Ni-based catalysts with K2O, MgO, CeO2, and ZrO2 , which are 2%NiO/1%CeO2-Al2O3 catalysts, 2%NiO/1 %CeO2/2%ZrO2-Al2O3 catalysts,1%NiO/0.1%MgO-Al2O3 catalysts and 3%NiO/5%K2O-Al2O3 catalysts respectively, are reaction temperature 800?, space velocity 11000h-1,water ratio 3:1; reaction temperature 800?, space velocity 16000h-1,water ratio 5:1; reaction temperature 800?, space velocity 16000h-1,water ratio 4:1; and reaction temperature 800?, space velocity 12000h-1,water ratio 4:1. The 2% NiO/1% CeO2/2% ZrO2-Al2O3 catalysts have the highest activity and stability among the four Ni-based catalysts. The NH3-TPD results show that MgO and K2O reduce the amount of acids.XRD analysis show that the CeO2 and ZrO2 additives form stable?Zr0.85Ce0.15?O2 solid solution which could improve the stability of the catalyst. The optimum operating condition for 10%NiO/1%La2O3-dolomite catalysts is reaction temperature 800?,space velocity 300h-1, the ratio of water and ingredient 5:1. The optimum regeneration condition is regeneration temperature 700?, regeneration time 1h. XRD results show that MgO-NiO solid solution and La?NiO3?crystalline phase are converted in the modified dolomite catalysts.The yield H2 and CO is higher over 10%NiO/1%La2O3-dolomite catalysts, but the yield of CH4, C2+ and macro-molecular hydrocarbon gases is higher over 2%NiO/1%CeO2/2%ZrO2-Al2O3. The stability and reaction-regeneration performance of 10%NiO/1%La2O3-dolomite catalysts are worse than those of 2%NiO/1%CeO2/2%ZrO2-Al2O3. XRD results show that MgO-NiO solid solution and La?NiO3? crystalline phase are converted in 10%NiO/1%La2O3-dolomite catalysts, and?Zr0.85Ce0.15?O2 solid solution in 2%NiO/1%Ce02/2%Zr02-Al2O3. XPS results show that the shift of the binding energy of Ni 2p3/2 on the two catalysts are different. The introduction of MgO and CaO reduces the C content on the 2%NiO/1%CeO2/2%ZrO2-Al2O3 catalysts surface. The introduction of CaO can improve the activity of the two catalysts.However, due to the different composition of the two catalysts, the effect of MgO on the catalyst activity of the two catalysts varies greatly. With The introduction of Fe2O3, the catalytic activity of both catalysts has little effect but declined slightly, because Fe also has catalytic activity.The introduction of SiO2 and Al2O3 reduces the activity of the two catalysts.