频率响应法研究噻吩在CeY分子筛上的吸附行为

以NaY、液相Ce离子交换改性的Y型分子筛(L-CeY)为研究对象,运用N2吸附、XRD、NH3-TPD和Py-FTIR等实验方法表征两种Y型分子筛的物化性能。采用频率响应技术(FR)和智能重量分析仪(IGA)研究噻吩在两种分子筛上的吸附行为,并考察噻吩在稀土离子改性Y型分子筛上的不同吸附作用模式。结果表明,频率响应技术能够有效识别分子筛孔道内发生的不同传质过程。噻吩在NaY分子筛上的吸附行为较为简单,存在孔道吸附和π电子相互作用两种吸附过程;而在L-CeY分子筛上吸附行为较为复杂,同时存在孔道吸附和"S-M"吸附等多种吸附过程,另外,在高温条件下,还存在复杂的催化反应过程。     

V_2O_5-沸石-活性炭-凹土脱硝催化剂的研制及脱硝性能

稻壳炭化后添加碱液和铝源分别合成了A型、A+X型和X型沸石-活性炭复合材料,加入凹凸棒石黏土成型,采用浸渍法负载V2O5制备V2O5-沸石-活性炭-凹土复合脱硝催化剂。采用XRD、SEM、N2吸附和EDX对样品进行表征,考察载体类型、V2O5含量和反应温度对催化剂低温脱硝活性的影响。结果表明,二元载体和V2O5协同催化脱硝,其脱硝率高于纯凹土制备的脱硝催化剂。催化剂脱硝活性随V2O5含量的增加而降低。反应温度越高,催化剂脱硝活性越高,最佳的反应温度为250℃,温度大于280℃后活性炭被氧化。     

钒对USY型分子筛的影响及氧化镧在钒捕集中的作用

模拟催化裂化高温水热再生环境,采用X射线衍射、N₂物理吸附、高分辨电子透射显微镜与NH₃-程序升温热脱附等方法,研究了重金属元素钒(V)对催化剂活性组分水热超稳Y型分子筛(USY型分子筛)的破坏行为;在此基础上,研究了稀土氧化物氧化镧(La₂O₃)对重金属V的捕集作用。结果表明：当分子筛负载较高质量分数的V时,分子筛的晶体结构遭到严重破坏;与未负载V的催化剂相比,负载质量分数为0.5%的催化剂,转化率降低了16.3个百分点,目标产物(液化气和汽油)收率显著降低,副产物干气、焦炭收率大幅增加;向模型催化剂中添加La₂O₃可以提高催化剂的重金属V捕集能力,在V负载质量分数为0.6%的情况下,含有La₂O₃的模型催化剂的原料油转化率和目标产物收率大幅增加。     

Fabrication of Pebax/SAPO mixed matrix membranes for CO2/N2 separation

Mixed matrix membranes (MMMs) were prepared by solvent evaporation method using Pebax-1074 polymer as matrix and inorganic zeolite SAPO-23 as dopant. The morphology, surface functional groups, microstructure, thermal stability, and separation performance of MMMs were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and gas permeation, respectively. The effects of dopant loading amount, permeation temperature, and permeation pressure on the structure and properties of MMMs were investigated. The results showed that the introduction of SAPO zeolite reduced the crystallinity of the MMMs and improved the CO₂/N₂ selectivity. Under the conditions of 30°C and 0.15 MPa, the MMMs prepared by incorporating with 5% SAPO zeolite in content exhibited the highest CO₂/N₂ selectivity of 72.0 together with the CO₂ permeability of 98.2 Barrer.     

Phi zeolite synthesized by template-free method for selective catalytic reduction of NO

Nitrogen oxide (NO_x) is one of the major air pollutants. Using a copper-based zeolite with a chabazite structure (CHA) as a catalyst, the selective catalytic reduction (SCR) technology can effectively remove NO_x. This work introduces a low silica CHA type zeolite with structural defects (zeolite Phi, with Si/Al of 4.7). The zeolite Phi is synthesized through a hydrothermal method without adding any template, which is low-cost and environment-friendly. The Cu-exchanged Phi is abundant of surface acidity and isolated Cu²⁺, showing a superior low-temperature activity, a wide work temperature window and a good hydrothermal stability. The presence of Na or Mg decreases the surface acidity and isolated Cu²⁺. The hydrothermally aged Na,Cu/Phi and Mg,Cu/Phi present different levels of framework collapse, which correspondingly induces catalyst deactivation.     

基于13X沸石分子筛/MgCl_2的复合吸附剂性能实验研究

复合吸附剂的吸附性能是吸附制冷循环过程中的一个重要参数,基于测试整体成型复合吸附剂吸附性能的需要,本文设计搭建了一种整体成型吸附剂性能测试装置,对复合吸附剂MgCl_2-13X进行了吸附性能测试实验。结果表明:该实验装置中吸附床外侧底部的温度变化速率较接近吸附床内部底部吸附剂的温度变化速率,二者温度变化速率相差0.01~1.9℃/min,整个吸附和脱附过程二者温度的平均值相差约3.24%,能够满足吸附剂性能测试实验的要求。吸附剂性能测试实验及电镜下吸附剂的微观结构表明:浸泡法制备的复合吸附剂的吸附性能与MgCl_2溶液的浓度有关,MgCl_2能够改善13X沸石分子筛的吸附性能,本实验测得当MgCl_2溶液的浓度为15%时所制得复合吸附剂MX3性能最优,其最大吸附量为0.32 g/g,最大吸附速率0.59 g/min,相比单一吸附剂13X沸石分子筛提高了20%。     

陶瓷中空纤维内表面动态水热合成NaA分子筛膜及其表征

采用动态水热法在氧化铝陶瓷中空纤维内表面原位合成了NaA分子筛膜。利用X射线衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)表征了分子筛膜的物相及微观形貌,通过渗透汽化测试考察了膜的乙醇/水分离性能,研究了合成工艺参数对成膜过程及膜质量的影响。结果表明,动态下合成的分子筛膜,晶体交联紧致,膜层薄且连续性好,厚度约4μm;提高动态速度有利于降低载体内外合成液的温差和浓度差,缩短晶化时间。在温度343K下,分离质量分数90%的乙醇/水体系,膜的渗透通量和分离因子可达1.03kg/(m2·h)和3 781,对乙醇/水表现出良好的分离效果和可重复性。     

三元离子交换平衡的表达与计算

利用Ｐｉｔｚｅｒ电解质溶液模型和Ｆｒａｎｋｉｌｎ三元交换体系的表达方法,对ＷＱＤ １沸石的Ｋ＋ Ｎａ＋ ＮＨ４＋交换平衡进行了定量描述。计算结果表明：在海水提钾等交换前后离子浓度变化不大的情况下,液相活度校正项可近似为１。经过简化后的离子交换平衡商可代替交换选择商Ｋｋ＋／Ｎａ＋。     

Preparation of acidic or bifunctional catalysts by means of straightforward calcination of as-synthesized [Ga]-ZSM-5 zeolites obtained from alkali-free media. Propane aromatization

Propane aromatization (530°C, 1 atm) was used as a reaction model to evaluate the effect of the calcination temperature on the catalytic properties of an as-synthesized [Ga_1.3]-ZSM-5 zeolite obtained from alkali-free media and calcined at two different temperatures: 530°C (C-530) and 750°C (C-750). Results show that in spite of its lower acidity, C-750 is more active and selective toward aromatics than C-530. This is probably due to the fact that at higher temperature the decomposition of organic compounds used during the zeolite synthesis is accompanied by a partial degalliation of the zeolitic support leading to the production of a bifunctional xGa₂O₃ /H-[Ga_y-ZSM-5(2x+y=1.3)catalyst.     

Identification of Pd3+ ions in zeolite L by temperature programmed reduction and electron paramagnetic resonance spectroscopy

Pd supported on KL zeolite has been studied by temperature programmed reduction (TPR) and electron paramagnetic resonance (EPR) spectroscopy. It has been found that upon calcination in pure oxygen Pd³⁺ and Pd²⁺ ions are formed; the Pd³⁺ ions are identified by their EPR signal. As Pd³⁺ ions in the cancrinite cages are difficult to reduce, the H₂ consumption in conventional TPR is below the stoichiometric amount.