碳五烯烃裂解制取丙烯/乙烯热力学分析及反应性能的研究

Thermodynamics Analysis and Reaction Performance for Production of Propylene and Ethylene from C_5 Olefins by Catalytic Cracking

采用最小吉布斯自由能法对C2~5烯烃构成的热力学网络进行平衡状态计算,并与ZSM-5催化剂上C5烃催化裂解过程的实验结果进行比较。研究结果表明,乙烯平衡收率随反应温度的升高而增大,尤其在温度高于500℃时增幅增大。压力为0.03 MPa时,在560~580℃内丙烯平衡收率达到最大值42.3%;压力为0.10 MPa时,在630~650℃内丙烯平衡收率达到最大值41.7%。0.03 MPa和0.10 MPa时,C4烯烃平衡组成均在400℃附近达到最大值,分别为43.0%和42.2%。ZSM-5催化剂上C5烃催化裂解产物中C2~5烯烃质量分数随温度的变化表现出与热力学一致的变化规律。C5烯烃裂解过程中热力学因素起主导作用,建议反应压力为0.03 MPa时反应温度选取450~620℃;反应压力为0.10 MPa时反应温度选取480~650℃。

The equilibrium state of thermodynamics reaction net constituted by C2-5 olefins was calculated by means of the minimum Gibbs free energy method and the results were compared with the experimental data from the catalytic cracking of C5 hydrocarbons over ZSM-5 catalyst. The investigation results showed that the equilibrium yield of ethylene increased with temperature rise at constant pressure,and increased rapidly above 500 ℃,and the equilibrium yield of propylene reached maximum 41.7%（w） in the range of 630-650 ℃ at 0.10 MPa and 42.3%（w） in the range of 560-580 ℃ at 0.03 MPa,respectively. At 400 ℃,the equilibrium yield of total C4 olefins reach maximum 43.0%（w） at 0.03 MPa and 42.2%（w） at 0.10 MPa,respectively. It was indicated that the thermodynamics equilibrium data based on the reaction net of C2-5 olefins were in accord with the experiment results obtained from the production of propylene and ethylene by the catalytic cracking of C5 hydrocarbons over the ZSM-5 catalyst in the temperature range of 450-620 ℃. It was obvious that the effect of thermodynamics factors on the product distribution was dominant in the catalytic cracking of C5 hydrocarbons over the ZSM-5 catalyst. In order to obtain desired propylene yield,it was suggested that the appropriate reaction temperature was in the range of 450-620 ℃ at 0.03 MPa and 480-650 ℃ at 0.10 MPa,respectively.