Ca2+交换的几种分子筛的氮氩分离性能

采用水溶液离子交换法制备了Ca2+交换的4A,13X和LSX分子筛,并在25 ℃下测定了它们的静态吸附等温线和动态穿透曲线.研究发现, Ca2+交换的4A,13X和LSX分子筛对氮的吸附性能都明显优于其相应的钠型分子筛,而它们对氩的吸附量变化不大,说明Ca2+交换的这三种分子筛是较好的氮氩分离吸附剂.从动态吸附的结果来看,所研究的各种分子筛都有一个最优的吸附分离压力,在本论文研究的压力范围内,这个最优压力在0.6 MPa附近.由穿透曲线可推算出混合气体的吸附量,通过氮和氩在混合气体中的吸附量和相应纯气体吸附量的对比可以得出,对于氮氩吸附选择性较高的分子筛,氮的存在对氩的吸附量有较大的影响.     

Li＋交换的几种分子筛的氮氩分离性能

采用水溶液离子交换法制备了高Li＋交换度的4A、13X和LSX分子筛,并在25 ℃下测定了它们的静态吸附等温线和动态穿透曲线.研究发现,高Li＋离子交换度的4A、13X和LSX分子筛都具有较大的氮吸附容量和较高的氮氩分离选择性,说明高Li＋离子交换度的4A、13X和LSX分子筛是较好的氮氩分离吸附剂.从动态穿透曲线结果来看,所研究的三种分子筛都有一个最优的吸附分离压力,在本文研究的压力范围内,这个最优压力在0.6 MPa附近.对比高锂交换度的三种分子筛,以高锂交换度的LSX分子筛的氮氩吸附分离性能最好.     

不同分子筛的氮氩分离性能

采用水溶液离子交换法制备了不同离子交换的13X和4A分子筛,并在25℃下测 定了它们的静态吸附等温线和动态穿透曲线。研究发现,Ca~(2+)离子和Li~+离子 交换的13X和4A分子筛对氮的吸附性能都明显优于其相应的钠型分子筛,而它们对 氩的吸附量变化不大,说明这两种离子交换的分子筛是较好的氮氩分离吸附剂。从 动态吸附的结果来看,所研究的各种分子筛都有一个最优的吸附分离压力,在本论 文研究的压力范围内,这个最优压力在0.6MPa附近。通过穿透曲线推算出的混合气 体吸附量和纯气体吸附量的对比可以得出,对于氮氩吸附选择性较高的分子筛,氮 的存在对氩的吸附量有较大的影响。     

N2和Ar在改性的NaA分子筛上的吸附分离

采用水溶液离子交换法分别制备了不同Li^ 和Ca^2^ 交换度的A型分子筛,并在25℃下测定了各分子筛吸附剂的氮和氩的吸附等温线及穿透曲线．研究发现,锂交换和钙交换的两种分子筛的氮吸附量和氮氩分离选择性都随分子筛中阳离子交换度的增加而增大;在阳离子交换度较高时,锂离子和钙离子交换的A型分子筛的氮氩分离能力均优于NaA分子筛．穿透曲线的结果显示,所研究的各种吸附剂都存在一个最优的吸附分离压力,大约在0．6MPa．在0．6MPaT,接近100％阳离子交换度的CaNaA分子筛的动态氮氩分离性能优于相同交换度的LiNaA分子筛。     

氮、氩在5A^。分子筛上的低温吸附分离

测定了不同温度下氮、氩在5分子筛上的吸附等温线,其中三参数的Langmuir-Freundlich方程和Toth方程在不同温度下都能获得较好的拟合结果;计算了不同温度下氮、氩在5分子筛上吸附的亨利常数,获得了氮、氩选择性和温度的关系.测定了125K温度下氮、氩混合气体在5分子筛吸附柱上的穿透曲线.结果表明:最先流出的5L气体中含有约70%的氩,通过收集5L气体即可实现混合气体中氩的初步分离.     

几种二价阳离子的交换对13X分子筛氮氩分离性能的影响

采用水溶液离子交换法分别制备了不同二价阳离子(Mg²⁺、Zn²⁺和Ca²⁺)交换的13X型分子筛，并在25 ℃下测定了各分子筛吸附剂的氮和氩的吸附等温线。研究发现，13X分子筛经Mg²⁺和Zn²⁺交换后，吸附剂的吸氮能力及氮氩分离能力降低；13X分子筛经Ca²⁺交换后，吸附剂的吸氮能力及氮氩分离能力随分子筛中钙离子交换度的增加而增大。对常压氮氩分离性能较好的CaNaX系列分子     

氮、氩在5分子筛上的低温吸附分离

测定了不同温度下氮、氩在5分子筛上的吸附等温线,其中三参数的Langmuir-Freundlich方程和Toth方程在不同温度下都能获得较好的拟合结果;计算了不同温度下氮、氩在5分子筛上吸附的亨利常数,获得了氮、氩选择性和温度的关系。测定了125K温度下氮、氩混合气体在5分子筛吸附柱上的穿透曲线。结果表明:最先流出的5L气体中含有约70%的氩,通过收集5L气体即可实现混合气体中氩的初步分离。     

低温变压分子筛动态分离CH_4/CO_2实验研究

在低温变压条件下测量了5A和13X沸石分子筛对CH_4/CO_2混合气体的分离能力。实验研究了CH_4/CO_2气体流量、吸附压力、填料高度和吸附温度对穿透曲线和分离能力的影响。研究结果表明,增大气体流量、增加吸附压力会降低分离效果,减小混合气体的分离系数;降低吸附温度、增加填料高度有利于CH_4/CO_2分离,提高混合气体的分离系数;在相同实验条件下,13X沸石分子筛对CH_4/CO_2混合气体吸附分离能力高于5A分子筛。     

13X分子筛去除水中重金属离子的研究

以人工合成的13X型分子筛为吸附剂,研究了水中Pb2 、Cd2 和Cu2 在分子筛上的吸附行为,讨论了Pb2 、Cd2 和Cu2 共存条件下的竞争吸附,并考察了水中存在的Na 、Mg2 、Ca2 等离子对分子筛吸附去除重金属的影响.实验结果表明,13X分子筛对Pb2 、Cd2 和Cu2 3种离子的吸附符合Langmuir模型,最大吸附量分别为2.47mmol/L、2.0mmol/L和1.78mmol/L.在竞争吸附条件下,13X分子筛对3种重金属离子的选择性依次为pb2 ＞Cd2 ＞Cu2 .水中存在的Na 、Mg2 、Ca2 等对分子筛吸附重金属效率有一定的影响,其中Ca2 对Cu2 在分子筛上的去除影响最为显著.     

晶种法高效合成低硅铝比LSX型分子筛

分别以工业级的偏铝酸钠和水玻璃为铝源和硅源,氢氧化钠为主要碱源,氢氧化钾为辅助碱源,采用LSX晶种法制备了LSX型分子筛。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线荧光(XRF)、傅里叶变换红外光谱(FTIR)和N2吸附-脱附等表征方式考察了有无晶种、钾钠物质的量之比、晶化条件对合成LSX型分子筛的影响。结果表明,加入LSX晶种不仅能显著缩短晶化时间,提高分子筛的结晶度,还可有效抑制方钠石和A型杂晶的伴生;钾钠比过高或过低均会造成A型或方钠石型杂晶的伴生;直接进行高温晶化会导致亚稳态的LSX型分子筛向热力学稳定相转变;延长老化时间或高温晶化处理降低了产物中的硅铝比;样品的比表面积和N2吸附量随老化时间的延长和高温晶化处理而逐渐下降。     

Hydrothermal Stability of the Novel Zeolite Type LSX in Comparison to the Traditional 13X Modification

Ion‐exchanged LSX (Si/Al = 1.02) and 13X (Si/Al = 1.18) zeolite series (Li, Na, K, Rb, Ca, Sr, Ba exchanged) were hydrothermally treated at temperatures between 423 K and 513 K in liquid water under autogeneous water vapour pressure. Beside X‐ray powder diffraction, the molybdate method and the water sorption uptake have been used to characterize the treated samples. The LSX and 13X zeolites show a similar hydrothermal behaviour in spite of their different framework Si/Al ratios depending only on the type of introduced cations. Significant destabilizing effects were observed especially in presence of K and Rb cations as well as the bivalent Sr and Ba cations. The LSX zeolites are hydrothermally more stable than LTA zeolites of same cations despite their same chemical framework composition.     

Separation of CO_2–N_2 using zeolite NaKA with high selectivity

The adsorption method based on solid adsorbents is one of feasible ways to capture and store CO_2. Using the ion exchange method, different zeolites Na KA varying in K+content were produced. The adsorption isotherms and kinetic uptakes were measured. The experimental results show that the optimal NaKA could adsorb significant quantities of CO_2 and little N_2. On the zeolite Na KA with 14.7 at.% K+, the adsorption capacity for pure CO_2 is over 3.10 mmol g~(-1) and the CO_2–N_2 selectivity is about 149 at ambient pressure and temperature. The kinetic CO_2–N_2 selectivity could also achieved 200 within 3 min according to the uptake data. To demonstrate the separation effectiveness, breakthrough curves of pure components and binary mixtures were investigated experimentally and theoretically in a fixed bed. It is found that the breakthrough points of CO_2 and N_2 are almost at the same time under the atmospheric pressure at 348 K with the raw gas composition CO_2/N_2(20:80, v/v). If the pressure has been increased higher than 0.1 MPa, CO_2 would break through the bed much slower than N_2. Therefore, the pressure may become the limiting factor for the separation performance of zeolites NaKA.     

沸石中阳离子对氮/氧吸附性能影响的研究进展

基于制氧吸附剂在变压吸附空分制氧工业应用的重要性，从沸石分子筛的氮／氧吸附性能方面，介绍了低硅沸石LSX、钙沸石、锂沸石、锂银沸石等的研究进展。讨论了沸石分子筛骨架结构和其中阳离子的种类、位置、数量与其吸附特性的关系，探讨其在变压吸附空分制氧中的应用前景。     

自粘结低硅铝X型沸石的结构、吸附和N_2/O_2分离比

用原位合成方法直接将高岭土转化为所需形状的低硅X型沸石(PLSX),经X衍射,~(29)Si,~(27)AI MAS NMR谱证实PLSX的结构硅铝比接近1,它含LSX的组成为40.40%,含4A的组成为17.92%,其余为无定形硅、铝氧化物.LSX的骨架硅铝比接近1,是骨架负电荷分配最均匀的X型沸石,293K时静态法测定和推算ISX的饱和吸附水达39.80wt%,LSX的组成为Na(96-x)K_x(Al_(96)S_i(96)O_(384))·310H_2O,是吸附量高、价廉的吸水剂.PLSX对空气中氮氧的分离系数为α(N_2/O_2)=3.15,高于用于PSA的商品5A的α(N_2/O_2)=2.33和已报道的13X的α(N_2/O_2)=2.36.PLSX也是一种极好的吸附分离剂.     

Hydrogen storage in low silica type X zeolites

Low silica type X zeolites (LSX, Si/Al = 1) fully exchanged by alkali-metal cations (Li(+), Na(+), and K(+)) were studied for their hydrogen storage capacities. Hydrogen adsorption isotherms were measured separately at 77 K and <1 atm, and at 298 K and <10 MPa. It was found that the hydrogen adsorption capacity of LSX zeolite depended strongly on the cationic radius and the density of the cations that are located on the exposed sites. The interaction energies between H(2) and the cations follow the order Li(+) > Na(+) > K(+), as predicted based on the ionic radii. Oxygen anions on zeolite framework were minor adsorption sites. Li-LSX had an H(2) capacity of 1.5 wt % at 77 K and 1 atm, and a capacity of 0.6 wt % at 298 K and 10 MPa, among the highest of known sorbents. The hydrogen capacity in LSX zeolite by bridged hydrogen spillover was also investigated. A simple and effective technique was employed to build carbon bridges between the H(2) dissociation catalyst and the zeolite to facilitate spillover of hydrogen atoms. Thus, the hydrogen storage capacity of Li-LSX zeolite was enhanced to 1.6 wt % (by a factor of 2.6) at 298 K and 10 MPa. This is by far the highest hydrogen storage capacity obtained on a zeolite material at room temperature. Furthermore, the adsorption rates were fast, and the storages were shown to be fully reversible and rechargeable. Further optimization of the bridge building technique would lead to an additional enhancement of hydrogen storage.     

Monte Carlo simulation of adsorption of binary and quaternary alkane isomers mixtures in zeolites: Effect of pore size and structure

Grand canonical Monte Carlo and configurational bias Monte Carlo techniques were employed to simulate the adsorption of binary mixtures of butane isomers and quaternary mixtures in nine zeolites at 300 K. For binary mixtures the results show there is a critical pore size, which is 10-membered-ring about 5.6 Å. The channel sizes of BEA, ISV, MOR and CFI are larger than this critical pore size, they prefer i-butane than n-butane, whereas TON with smaller channel size than critical pore size prefers n-butane than i-butane, but its selectivity decreases with pressure increasing. MFI, MEL and TER prefer i-butane than n-butane at low pressure, but with pressure increasing, the selectivity is reversed. BOG prefers i-butane than n-butane but the selectivity decreased with pressure increasing. It demonstrates that the adsorption and selectivity are controlled by both pore size and pore structure. The n-butane–i-butane–n-pentane–2-methylbutane quaternary mixtures adsorbed in these nine zeolites were studied, and the results show alkane chain length dependence at low pressure, but the adsorption is controlled by pore size and structure with pressure increasing in all the zeolites except for TON and BOG.     

Synthesis,characterization and CO2 adsorption of NaA,NaX and NaZSM-5 from rice husk ash

NaA, NaX and NaZSM-5 zeolites were prepared by using silica extracted from rice hull ash as a raw material, and they were investigated for CO₂ adsorption performance as an adsorbent in order to solve the problem of suppressing the global warming. Three zeolites were synthesized by hydrothermal methods with seed technology, and a series of characterization methods, including XRD, FTIR, nitrogen adsorption-desorption and SEM, were used to demonstrate their advantages compared to traditional hydrothermal methods. The maximum equilibrium adsorption capacity of NaA-RS, NaX-RS and NaZSM-5-RS was 1.46, 3.12 and 2.20 mmol/g at 0 °C and 101.3 kPa, respectively. The CO₂ and N₂ adsorption isotherms recorded at different temperatures were perfectly fitted by the Dual-site Langmuir model. The CO₂/N₂ selectivity and Henry's law constants were calculated to demonstrate that the samples have a stronger affinity for CO₂, especially at low pressures. The isosteric heat of CO₂ and N₂ adsorption of the three zeolites was calculated, which was indicated that they were in an excellent potential for adsorption and separation of CO₂ in industrial flue gas.     

吸附法脱除乙烯中少量氮气的研究

采用重量法在电子天平上，研究了C2H4和N2单组分在5A、13X、丝光沸石和炭分子筛不同吸附剂上的吸附平衡性质和扩散动力学性质。单柱模拟变压吸附评价了炭分子筛吸附脱除C2H4-N2（N2为4．7％）混合组分中N2的性能，并对流速和压力的影响进行了考察。研究表明，该炭分子筛是吸附脱除C2H4中少量N2的理想吸附剂。