Comparison on Non-isothermal Oxidation between Spent Catalytic Cracking Catalysts and Coal

China Petroleum Processing and Petrochemical Technology2010,vol.12,No.2,pp33-40Comparison on Non-isothermal Oxidation between SpentCatalytic Cracking Catalysts and CoalMen Xiujie; Zhan Shuhong; Li Yanjun; Wang Zijun; Wang Xieqing(Research Institute of Petroleum Processing, SINOPEC, Beijing 100083)Abstract: Oxidation of coke deposited on spent catalytic cracking catalysts was compared with that of coal andcoal char via the non-isothermal oxidation means, ie the thermal-gravimetric analysis(tGA)and the differentialthermal analysis(DTA). Oxidation kinetic parameters were further investigated by model-fitting methods. Thetest results showed that the oxidation of spent catalysts was a quite mild process, while coal and coal charexperienced sharp weight loss during oxidation. The temperature for commencement and termination of oxidationincreased in the following order: coal200 mesh, which was similar to the grain sizetesting instrument(EMIA-820V, made by the HORIBA Com- range of coked spent catalyst.pany of Japan). The coke content of the said catalyst wasequal to 2. 70% of carbon per gram of catalyst used in this3 Results and discussiostudy. The coal employed was a kind of washed coal ob- 3.1 TGA and DTA resultstained from the Shenhua coal mine in China. After theShenhua coal was subjected to vacuum carbonization for a The TGA results prdefinite period of time, its char was obtained. The propertiesal, coal char and coked spent catalyst all experienced someof both the coal and coal char are listed in Table Ieight loss at low temperature, which might be originatedfrom evaporation of humidity adsorbed by their porous2.2 Thermal analysisstructure Coal started to be oxidized into gaseous moleculesThermal analysis techniques, i e. thermal-gravimetric analy- at 290 C and its weight loss almost terminated at 512Csis(TGA)and differential thermal analysis(DTA)of thecoked spent FCC catalyst, coal and coal char were carried weight loss that increased sharply until its weight was re-out in a thermal analyzer( type SDT Q600 V20.5 Build 15 ), induced to about 8. 16% of the original value. However, coalwhich the sample under an air stream flowing at a rate of 60char showed a sharp weight loss from the beginning at 390ml/min was heated at a temperature rise rate of 10 C/min theC, and at 554 C its weight decreased to 16.72% of theweight loss and temperature difference during heating were original value. After oxidation of coal and coal char the re-Table 1 Properties and composition of coal and char tained inorganic elements. When the coked spent catalystItemsChar was subjected to oxidation, a quite mild process differentiated the coked catalyst from coal or coal char. with an increasing oxidation temperature a visible inflextion on theMoisture12.2TGA curve for the coked catalyst was identified when theweight of the coked catalyst was 96.72%o of its original value,103while another inflextion on the TGa curve appeared whenUltimate analysis, m%the weight of the coked catalyst was equal to 94.01% of its72.508581original value, wherein the weight difference of 2.71%wasH0.74coherently in agreement with a carbon content of 2. 70% in0.740.46the coked FCC catalyst determined previously. The tem-0.88 peratures for commencement and termination of oxidation14.23of tested samples increased in the following order: eMetal content, ppmchar