正庚烷和正辛烷在无黏结剂5A分子筛上的吸附动力学特性

摘要

Adsorption kinetics of n-heptane and n-octane on 5A molecular sieve pellets with/without binder was studied using gravimetric method.Diffusivities were derived from the simplified model and diffusion activation energies were evaluated.Results show that the diffusion time constants of n-paraffins on binder-free pellets are larger than those of adsorbates on pellets with binder.In the temperatures range of 300-480 K, the micropore diffusivities of n-heptane and n-octane on binder-free pellets are (20.84-85.77) × 10-14 and (3.80-23.44) × 10-14 cm2/s, respectively; the macropore diffusivities of n-heptane and n-octane on pellets with binder are (4.87-38.58) × 10-7 and (4.28-14.65) × 10-7 cm2/s, respectively.The diffusion activation energies of n-heptane and n-octane are 10.74 and 12.71 kJ/mol on binder-free 5A molecular sieve respectively, 14.16 and 16.35 kJ/mol on 5A molecular sieve with binder respectively.%采用重量法研究正庚烷和正辛烷在无黏结剂和有黏结剂5A分子筛上的吸附动力学,采用简化的扩散模型计算扩散系数,并估算扩散活化能.结果表明.正构烷烃在无黏结剂5A分子筛颗粒上的扩散时间常数大于有黏结剂的5A分子筛,黏结剂的存在降低了正构烷烃在5A分子筛卜的扩散速率.在吸附温度为300～480 K的条件下,正庚烷和正辛烷在无黏结剂5A分子筛上的微孔扩散系数分别为(20.84～85.77)×10-14、(3.80～23.44)×10-14cm2/s.在有黏结剂5A分子筛上的大孔扩散系数分别为(4.87～38.58)×10-7、(4.28～14.65)×107cm2/s.正庚烷和正辛烷在无黏结剂5A分子筛上的扩散活化能分别为10.74、12.71 kJ/mol,在有黏结剂分子筛上的扩散活化能分别为14.16、16.35 kJ/mol.