升温速率对CO2在13X分子筛上脱附性能的影响

Impact of Heating Rate on Desorption Performance of CO2 Attached to 13X Zeolite

采用程序升温脱附技术研究了升温速率对CO2在13X上脱附性能的影响,基于Polanyi-Wigner方程在无假定条件的情况下计算了不同升温速率下的脱附活化能（Ed）.结果表明,13X分子筛在常温下吸附CO2后,脱附时会产生两个脱附峰（低温峰和高温峰）;改变升温速率β会影响Ed,随β升高,低温峰的脱附活化能Ed,L呈对数规律减小,高温峰的脱附活化能Ed,H基本不变,且Ed,L〈Ed,H,无假设情况下Ed的计算结果比升温速率变化法计算结果更具合理性和准确性;吸附量相同时,随β升高,CO2的低温脱附量Qd,L逐渐增大而高温脱附量Qd,H逐渐减小,且Qd,L〉〉Qd,H;物理吸附与化学吸附作用力的差异造成两峰吸脱附机理存在根本差别.

Temperature programmed desorption（TPD）was used to investigate the impact of heating rate on desorption performance of CO2 attached to 13X zeolite.Based on the Polanyi-Wigner equation,the desorption activation energy Ed under different heating rates（b）was calculated without any assumed conditions.The results showed that two desorption peaks on TPD curve were produced while heating 13X molecular sieve full of CO2 at room temperature,one was located at low temperature,called as low-temperature peak,the other was at high temperature,called as high-temperature peak.Ed changed with β.The low-temperature peak related to the desorption activation energy Ed,L decreased logarithmically with respect to increasing β,while Ed,H remained the same,and the value of Ed,L was smaller than that of Ed,H.So Ed calculated without assumptions were more reasonable and accurate than the value calculated by variable heating rate method.For the same adsorption capacity,desorption capacity of CO2 at low temperature called Qd,L increased gradually with the growth of β,while at high temperature Qd,H decreased,and Qd,L was far greater than Qd,H.The different acting force of physisorption and chemisorption was the key factor that resulted in a difference between high-temperature peak and low-temperature peak on adsorption mechanism.