微介孔Ni/ZSM-5分子筛对甲苯催化重整的影响

文章通过水热法结合使用淀粉模板剂和碱处理合成了3种微介孔ZSM-5分子筛,并以Ni为活性组分制备了一系列Ni/ZSM-5催化剂用于甲苯(生物质气化焦油模型化合物)水蒸气催化重整实验。采用N2吸附-脱附、NH3-TPD和XRD对分子筛和催化剂进行表征,研究了催化剂酸性和孔结构对甲苯催化重整效果的影响,并深入分析了介孔体积以及孔径分布与碳转化率的相关性。研究结果表明:合成的ZSM-5分子筛具有较大的介孔体积,主要分布在2~4,4~8 nm和16~45 nm,其中2~4 nm的介孔体积与甲苯碳转化率有很好的相关性(R^(2)>0.99);模板法合成的ZSM-5(ST)具有最大的2~4 nm介孔体积,相应的碳转化率接近100%;碱处理制得的ZSM-5(AT)的酸性增强,4~8 nm孔容大幅增加,但碳转化率仅有约70%;模板法改性可提升镍基催化剂的性能。

碱酸改性处理方案对介孔β沸石孔分布和织构性质的影响

采用水热碱蚀-碱溶滤-酸洗逐级处理方法对Hβ沸石进行介孔改性研究。借助XRD、N2吸附-脱附、SEM、TEM等技术考察了改性方法对改性沸石的介孔形成、介孔孔分布和织构性质的影响;建立了半经验粒内介孔体积分率模型,分析了织构介孔在基质结晶性和体积构成上的差异。实验结果表明,改性沸石具有较高的比表面积和介孔率及倾向于均一化的介孔分布。水热碱蚀导致介孔孔分布趋于均一化;碱溶滤脱硅是沸石产生介孔的关键步骤;酸洗脱铝具有拓孔作用。当Na OH溶液浓度由0.1 mol/L增至0.3 mol/L时,经水热碱蚀-碱溶滤-酸洗-铵交换处理得到的改性沸石的粒内介孔体积比率均保持在70%以上。

多级孔SAPO-11的制备及其临氢异构性能

在低温下通过两步水热结晶法制备了多级孔SAPO-11分子筛(S-H-T_0,T_0为再结晶温度),采用浸渍法合成了0.5%(w)Pt/S-H-T_0催化剂,利用XRD、N_2吸附-脱附、SEM、TEM、XRF、NH_3-TPD和Py-FTIR等分析手段对合成的催化剂进行表征,并以正十六烷的临氢异构反应评价了催化剂的性能。表征结果显示,分子筛的制备方法对SAPO-11的孔道结构和酸量有显著影响,与传统水热法制备的SAPO-11(S-T)相比,S-H-T_0具有微-介孔结构、更大的比表面积和介孔体积、更多的B酸酸量。实验结果表明,Pt/S-H-T_0的正十六烷转化率和异构十六烷选择性均高于Pt/S-T催化剂,其中,Pt/S-H-120催化剂的催化性能最优,在340℃、1 MPa、重时空速1.5 h^(-1)、氢气和正十六烷体积比为1 000的条件下,Pt/S-H-120的正十六烷转化率和异构十六烷选择性分别为85%和88%,连续稳定运行60 h催化剂的活性未见明显下降。

BISQ model based on a Kelvin-Voigt viscoelastic frame in a partially saturated porous medium

Taking into account three important porous media mechanisms during wave propagation （the Biot-flow, squirt-flow, and solid-skeleton viscoelastic mechanisms）, we introduce water saturation into the dynamic governing equations of wave propagation by analyzing the effective medium theory and then providing a viscoelastic Biot/squirt （BISQ） model which can analyze the wave propagation problems in a partially viscous pore fluid saturated porous media. In this model, the effects of pore fluid distribution patterns on the effective bulk modulus at different frequencies are considered. Then we derive the wave dynamic equations in the time-space domain. The phase velocity and the attenuation coefficient equations of the viscoelatic BISQ model in the frequency-wavenumber domain are deduced through a set of plane harmonic solution assumptions. Finally, by means of numerical simulations, we investigate the effects of water saturation, permeability, and frequency on compressional wave velocity and attenuation. Based on tight sandstone and carbonate experimental observed data, the compressional wave velocities of partially saturated reservoir rocks are calculated. The compressional wave velocity in carbonate reservoirs is more sensitive to gas saturation than in sandstone reservoirs.