二次生长法合成SAPO-34沸石膜及其气体渗透性能

以四乙基氢氧化铵(TEAOH)为模板剂,采用二次生长法在α-Al_2O_3多孔陶瓷管上合成了SAPO-34沸石膜.利用X射线衍射(XRD)、扫描电镜(SEM)以及气体渗透对合成的膜进行了表征.XRD结果表明合成的膜具有典型的CHA型沸石特征峰,无其它杂相存在.SEM显示膜厚大约为5 μm,膜表面晶粒交织共生完好,且连续、致密,没有发现明显的针孔和裂纹.室温下, 当膜两侧压降为0.1 MPa时,CO_2/CH_4的理想选择性和混合气体分离选择性分别为7和40.     

生物模板法制备SAPO-34分子筛及其对CO2/CH4吸附分离性能的研究

采用生物质模板（茶花粉）掺杂制备SAPO-34分子筛,研究了SAPO-34分子筛对CO₂和CH₄的静态吸附性能,同时考察了水热晶化时间、硅铝摩尔比（SiO₂/Al₂O₃摩尔比）和有机模板剂对茶花粉掺杂合成SAPO-34分子筛的影响。结果表明,茶花粉的加入可以制备性能良好的SAPO-34分子筛并降低其尺寸在1～2μm之间;晶化时间（24～36 h）的延长有利于分子筛结晶;当硅铝比为0.6、有机模板剂摩尔比为2时,SAPO-34分子筛的晶化效果最佳。茶花粉清液合成的SAPO-34分子筛在静态吸附实验压力为100 kPa时,CO₂和CH₄的总吸附量分别为2.92 mmol/g和0.58 mmol/g, CO₂/CH₄的理想分离系数为5.05。     

微波辅助高效水热合成SAPO-11分子筛

采用微波辅助的方法,以拟薄水铝石、硅溶胶等为原料,合成出纯相SAPO-11分子筛,大大减少了晶化时间,节约了合成成本。通过X射线衍射（XRD）,扫描电子显微镜（SEM）对合成的样品进行表征,详细考察了硅源、模板剂、硅铝比及晶化条件（晶化时间、晶化温度、pH）对合成的影响。结果表明,pH及晶化时间的影响较为显著,以硅溶胶为硅源,以二正丙胺为模板剂,在n(SiO2)∶n(Al2O3)=0.6、pH=5.7、晶化温度为185 ℃、晶化时间为10 h的条件下,采用微波辅助可以高效地合成纯相的SAPO-11分子筛。     

微波辅助二次生长法合成SAPO-34分子筛膜与关键影响因素

采用微波辅助二次生长法在α-Al2O3载体上合成了SAPO-34分子筛膜,并将其应用于CO_2/CH4分离。通过扫描电镜、X射线衍射和傅里叶变换红外光谱等表征方法,系统考察了加热方式、晶种粒径、老化时间和晶化时间对SAPO-34分子筛膜表面形貌和结构的影响。实验结果表明,以0.4μm分子筛作为晶种,在老化24 h,然后微波加热晶化4 h后可制备出厚度约为1.5μm的致密、无缺陷SAPO-34分子筛膜,其平均CO_2/CH4分离因子和CO_2渗透率分别达到81和6.6×10-7 mol·m-2·s-1·Pa-1,制备方法可靠,重复性高。     

硅源与磷源对合成SAPO-34分子筛结构和形貌的影响

采用水热合成法制备了小晶粒SAPO-34分子筛,主要考察了不同硅源(硅溶胶,二氧化硅纳米粉和正硅酸乙酯)和磷源(磷酸,多聚磷酸)对合成SAPO-34分子筛的影响.实验结果表明:在合成液配比为1.0 Al2O3∶2.0 P2O5∶0.6 SiO2∶4.0 TEAOH∶105.0 H2O以及晶化温度为180 ℃晶化时间为48 h的条件下,二氧化硅纳米粉是较为理想的硅源,所合成的SAPO-34分子筛具有较高的结晶度,晶体呈现典型的立方体结构,晶粒大小为300 nm左右;而将多聚磷酸取代磷酸作为磷源后可以有效缩短合成时间至36 h,同时晶型由立方体结构转变为片状结构,但晶粒增大至为500 nm左右.     

纳米SAPO-34分子筛粒径的影响因素研究

纳米SAPO-34分子筛因其颗粒尺寸小和比表面积大等特性,使其在吸附分离和工业催化等领域表现出更好的性能.本文主要阐述了常规水热合成法中硅源、模板剂等因素对合成的纳米SAPO-34分子筛颗粒尺寸的影响规律,并进一步评述了两种合成纳米SAPO-34分子筛的新方法.最后对这类材料的未来发展做了展望.     

SAPO-34分子筛晶粒大小和形貌的影响因素及其控制研究进展

SAPO-34分子筛被认为是甲醇催化转化制低碳烯烃(MTO)最适用的催化剂。然而,传统的SAPO-34分子筛催化剂极易发生积碳失活,寿命较短。研究表明,小晶粒SAPO-34分子筛可以有效地提高催化剂使用性能。文章介绍了小晶粒SAPO-34分子筛具有的特性以及晶粒大小和形貌的影响因素及其控制,进一步分析了催化剂晶粒大小和形貌对MTO反应的影响,并提出改善MTO催化剂使用性能的建议。     

SAPO-34分子筛形貌和粒径的影响因素考察

以四乙基氢氧化铵为模板剂,水热合成法制备SAPO-34分子筛,采用XRD和SEM进行表征,考察硅铝比、晶化温度、晶化时间和陈化时间对分子筛形貌和粒径的影响。结果表明,在硅铝物质的量比为0.8、晶化温度200℃、晶化时间24 h和陈化时间4 h条件下,可合成晶粒均匀和晶体表面光滑的粒径仅为2μm的SAPO-34分子筛。     

高岭土微球离子热法原位合成SAPO-34分子筛

在季戊四醇和四乙基氯化铵低共融混合物中,采用离子热法将苏州高岭土为主要原料的微球原位晶化制备了SAPO-34分子筛微球。考察了晶化条件和晶化液对原位合成的影响。通过XRD和SEM等手段对合成的微球进行了表征。实验结果表明,在晶化温度为180 ℃下,晶化液物质的量比为n（二氧化硅）∶n（氧化铝）∶n（五氧化二磷）∶n［N-甲基咪唑（2-甲基咪唑）］∶n（氟化氢）∶n（水）=2.26∶1∶0.5∶0.66∶0.3∶26.4时,晶化20 h可以合成出SAPO-34分子筛微球。加入导向剂N-甲基咪唑和2-甲基咪唑有利于SAPO-34分子筛的合成。     

煤矸石微波辅助合成沸石分子筛的研究

为探究煤矸石合成沸石分子筛的最优工艺,以煤矸石为主要原料,采用传统水浴加热与微波辅助加热的方法,合成4A型沸石分子筛与P型沸石分子筛,利用电子显微镜和X射线衍射,对其形貌和结构进行分析表征。实验通过制备相同的沸石分子筛,得出制备沸石分子筛的煤矸石需要高岭石含量较高、有害杂质含量较低及较为合适的粒径(3μm～50μm)。相较于传统水浴加热,微波辅助加热得到的沸石分子筛纯度低,但加热时间仅需30 min～40 min,而传统水浴加热合成需要24 h,同时微波辅助加热还提高了沸石分子筛反应速率和分散度。     

Hydrophobic modification of SAPO-34 membranes for improvement of stability under wet condition

SAPO-34 zeolite membranes show high efficiency for CO₂/CH₄ separation but suffer from the reduction of separation performance when exposed to humid atmosphere. In this work, n-dodecyltrimethoxysilane (DTMS) was used to modify the hollow fibers supported SAPO-34 membranes to increase the external surface hydrophobicity and thus sustain their performance under moisture environment. The modified membranes were fully characterized. Their separation performance was extensively investigated in both dry and wet gaseous systems and compared with the un-modified ones. The un-modified SAPO-34 membrane exhibited a high separation selectivity of 160 and CO₂ permeance of 1.18×10^-6 mol·m^-2·s^-1·Pa^-1 for separation of dry CO₂/CH₄ at 298 K. However, its separation selectivity declined to 0.9 and the CO₂ permeance was only about 1.7×10^-8 mol·m^-2·s^-1·Pa^-1 for wet CO₂/CH₄ at same temperature. High temperature (e.g. 353 K) could reduce the effect of moisture to improve SAPO-34 separation selectivity, but further increasing temperature (e.g. 373 K) led to decrease in CO₂/CH₄ separation selectivity. A significant decrease of selectivity was observed at higher pressure drop. The modified SAPO-34 membrane showed decreased CO₂ permeance but increased separation selectivity for dry CO₂/CH₄ gas mixture, and super performance for wet CO₂/CH₄ gas mixture due to the improved hydrophobicity of membrane surface. A separation selectivity of 65 and CO₂ permeance of 4.73×10^-8 mol·m^-2·s^-1·Pa^-1 for wet CO₂/CH₄ mixture can be observed at 353 K with a pressure drop of 0.4 MPa. Furthermore, the modified membrane exhibited stable separation performance during the 120-hour test for wet CO₂/CH₄ mixture at 353 K. The hydrophobic modification paves a way for SAPO-34 membranes in real applications.     

双模版剂法制备SAPO-5和SAPO-34分子筛

以二乙胺和四乙基氢氧化铵为混合模版剂,采用水热法合成了SAPO6和SAPO-34分子筛,并用XRD,SEM,XRF,NH3-TPD等手段对其表征,以氧化苯乙烯重排反应为探针反应评价其活性.分别讨论了加料顺序和晶化升温模式对合成SAPO-5和SAPO-34的影响.结果表明,改变加料顺序和晶化升温模式时,在原料和合成物料配比不变的条件下可以分别合成出纯相的SAPO6和SAPO-34分子筛.在氧化苯乙烯重排反应中,由于SAPO-34含有强酸位,会产生大量聚合物,使得苯乙醛的选择性较低,而只含有弱酸位的SAPO-5表现出较好的活性和选择性.     

Simultaneously tuning dense skin and porous substrate of asymmetric hollow fiber membranes for efficient purification of aggressive natural gas

Highly permeable, selective, and stable asymmetric membranes are required to replace the traditional separation approaches for natural gas purification with higher energy efficiency and smaller footprints. Herein, we report on the design and engineering of defect-free asymmetric hollow fiber membranes with a thin dense skin and highly porous substrate to effectively deal with aggressive natural gas. A crosslinkable polymer with rigid molecular structure and high molecular weight was synthesized for developing spinning dope with desirable solution properties. Phase separation behavior of the polymer was carefully controlled by systematic formulation of the dope composition and optimizing spinning conditions, thereby realizing simultaneously tuning dense skins and porous substrates of the spun asymmetric hollow fiber membranes. The crosslinked hollow fiber membrane, with well-preserved delicate asymmetric nanostructures, exhibited unprecedentedly high and stable separation performance for long-term processing extremely aggressive CO₂/CH₄ mixtures (with pressure up to 820 psi containing C6⁺ hydrocarbons), thereby showing great potential for practical application of natural gas purification. This work offers a new platform to create hollow fiber membranes with both high permeance and plasticization resistance in natural gas service. © 2019 American Institute of Chemical Engineers AIChE J, 65: 1269–1280, 2019     

SAPO-34 membranes for CO2/CH4 separations: Effect of Si/Al ratio

Silicoaluminophosphate (SAPO) membranes with Si/Al gel ratios from 0.05 to 0.3 were synthesized by in situ crystallization onto porous, tubular stainless steel support. Pure SAPO-34 membranes were obtained when the Si/Al ratio was 0.15 or higher. The adsorbate polarizability correlated with the adsorption capacity on SAPO-34, and the amounts of gases adsorbed were in the order: CO₂ > CH₄ > N₂ > H₂. The Si/Al ratio did not affect the pore volume significantly, but it changed the CO₂ and CH₄ adsorption equilibrium constants. The SAPO-34 membranes effectively separated CO₂ from CH₄ for feed pressures up to 7 MPa. At 295 K, for a pressure drop of 138 kPa and a 50/50 feed, the CO₂/CH₄ selectivity was 170 for a membrane with a Si/Al gel ratio of 0.15. At 7 MPa, the CO₂/CH₄ selectivity was 100 and the CO₂ permeance was 4 × 10⁻⁸ mol/(m² · s · Pa) at 295 K. This membrane was also separated CO₂/N₂ (selectivity = 21) and H₂/CH₄ (selectivity = 32) mixtures at 295 K and a pressure drop of 138 kPa. Competitive adsorption and difference in diffusivities are responsible for CO₂/CH₄ and CO₂/N₂ separations, whereas the H₂/CH₄ separation was due to diffusivity differences. For a membrane with Si/Al gel ratio of 0.1, a mixture of SAPO-34 and SAPO-5 formed, and the CO₂/CH₄ selectivity was lower.     

SAPO-34分子筛应用研究进展

综述了SAPO-34分子筛催化低碳物转化制低碳烯烃(甲醇、二甲醚、卤化烷烃制烯烃、乙醇脱水制乙烯)、C_4～C_8直链烯烃/烷烃裂解制低碳烯烃、烷烃氧化或直接脱氢反应制烯烃、催化烃类或H_2选择性还原NO_x、制备膜分离材料以及在发光体材料等领域中的应用。系统分析sAPO-34分子筛在各领域应用进展,有利于理解材料的物化性能对其催化性能、热稳定性及水热稳定性、选择性渗透和分子筛分离性能的影响,有利于实现对SAPO-34分子筛的认识取得突破性进展,拓展SAPO-34分子筛应用领域,并为其他催化材料的设计提供借鉴。     

纳米SAPO-34分子筛的制备与表征

本文采用水热合成法制备纳米SAPO-34分子筛,并考查了晶化时间、陈化时间、水含量对纳米SAPO-34分子筛合成的影响,进一步采用XRD、SEM对合成的分子筛进行表征.实验结果表明,在一定范围内,当物料摩尔配比为1(Al2O3)∶2(P2O5)∶0.6(SiO2)∶4(TEAOH)∶107(H2O),室温陈化72 h,200℃晶化时间为24 h时,合成的纳米SAPO-34分子筛相对结晶度较高,平均粒径约为255 nm.     

CuO-ZnO/(SAPO-34)-高岭土催化CO2加氢合成低碳烯烃

以廉价的高岭土为原料,三乙胺为模板剂,采用水热法制备了负载型催化剂(SAPO-34)-高岭土。通过将CuO-ZnO负载于(SAPO-34)-高岭土表面制备了双功能催化剂CuO-ZnO/(SAPO-34)-高岭土,用XRD、SEM、EDS、BET、H_2-TPR及NH_3-TPD对合成的催化剂进行了表征,将其用于催化CO_2加氢制备低碳烯烃,在反应温度为673 K、反应压力为3 MPa、空速为1 800 m L/(g_(cat)·h)、V(CO_2)∶V(H_2)=1∶3的条件下,CO_2单程转化率为43.5%,低碳烯烃的选择性和产率分别为63.8%和27.8%。在连续8 h的催化性能测试中,低碳烯烃的产率最低为18.7%。     

多级孔SAPO-34分子筛的合成及催化性能

利用磷酸硅铝分子筛的晶化母液合成SAPO-34分子筛,采用XRD、SEM和N_2吸附-脱附进行表征。结果表明,合成的样品为具有多级孔结构的SAPO-34分子筛,该分子筛催化剂在甲醇制烯烃反应中表现出高低碳烯烃选择性及较长的寿命。     

Investigation of slowing-down and speeding-up effects in binary mixture permeation across SAPO-34 and MFI membranes

Permeation experiments for Ar/CH₄ and CO₂/H₂ mixtures across a SAPO-34 membrane were performed with the objective of highlighting their distinct diffusion characteristics. For the Ar/CH₄ mixture, the effective transport coefficients of the individual components in the mixture were found to be practically the same as those obtained from unary permeation experiments, when compared at the same total loading at the upstream face of the membrane. There is no speeding-up of the tardier CH₄. Only at the high loadings is there evidence of a small, about 10%, slowing-down of the more mobile Ar.

A different picture emerges for permeation of CO₂/H₂ mixtures across SAPO-34 membrane. While the transport coefficient of CO₂ is practically identical to those obtained from unary experiments, there is a significant slowing-down of the more mobile H₂. At the highest loading, the transport coefficient of H₂ is about a third of the value of the pure component.

Permeation of CO₂/CH₄ mixtures across an MFI membrane showed that there is a significant slowing-down of the more mobile CH₄ with concomitant speeding-up of the tardier CO₂.

The incorporation of the Vignes interpolation formula for the exchange coefficient Ð₁₂ in the Maxwell–Stefan equations does not adequately reflect the slowing-down and speeding-up phenomena for either SAPO-34 or MFI membranes.