Comparison of the adsorption dynamics of air on zeolite 5A and carbon molecular sieve beds

Adsorption and desorption in zeolite 5A and CMS beds were compared by using a ternary mixture (N₂/ O₂/Ar; 78 : 21 : 1 vol%). Because the breakthrough curves for both beds show a tail by temperature variance, a non-isothermal mathematical model was applied to the simulation of adsorption dynamics. The LDF model with a constant rate parameter was enough to predict the experimental breakthrough and temperature curves of an equilibrium separation bed, while the modified LDF model with a concentration-dependent parameter should be applied to a kinetic separation bed. In the CMS bed initially saturated with He, Ar was the first breakthrough component with N₂ following after a short interval. Then, after a long interval, the breakthrough of O₂ occurred with a broad roll-up due to its fast diffusion rate and the relatively slow diffusion rate of N₂. In the CMS bed initially saturated with O₂, the breakthrough curves of O₂ and N₂ showed a very broad shape because of the slow diffusion of N₂ into CMS. In the zeolite 5A bed, the breakthrough time sequence was Ar, O₂, and N₂ at very close time intervals. After the sharp roll-ups of O2 and Ar, the variation of the breakthrough curves was negligible. The inflection of the temperature profile in the zeolite 5A bed was caused by the crossover of the O₂ and N₂MTZs, while in the CMS bed it was caused by the difference in the diffusion rates of O₂ and N₂.     

13X沸石分子筛对低浓度CO2动态吸附

目前对于吸附分离技术应用于高压、低浓度CO₂脱除的研究还较少,在进行相应吸附脱碳工艺设计时也缺少相关的参考数据。为探究13X沸石分子筛对低浓度CO₂的动态吸附性能,本文利用动态吸附实验的方法,探究不同条件下低浓度（摩尔分数3%）CO₂气体在13X分子筛上的动态吸附性能,得到不同压力、温度、气体流量、填料高度及分子筛规格（尺寸、形状）等因素影响下的13X分子筛对于CO₂气体的动态吸附规律及相应的性能指标参数。结果表明：随着吸附压力的升高,13X分子筛的CO₂吸附量增加但增量逐渐减小;降低吸附温度、减小气体流量和增加填料高度均有利于增强13X分子筛的动态CO₂吸附性能,提高吸附脱碳效果,其中温度及填料高度的变化对于CO₂吸附的影响程度最大;实验还发现小尺寸及条状13X分子筛的动态吸附脱碳性能优于其他规格,并根据其特定条件下的出口CO₂浓度为50mL/m³时的CO₂吸附量指标,给出吸附剂用量与液化天然气（LNG）脱碳工艺处理量的关系系数。     

Dielectric and electromagnetic interference shielding properties of zeolite 13X and carbon black nanoparticles based PVDF nanocomposites

In the present work, Zeolite 13X and carbon black nanoparticles (CBNPs) reinforced polyvinylidene fluoride (PVDF) nanocomposites were obtained by a simple solvent casting technique. The structural, morphological and thermal properties of PVDF/Zeolite 13X/CBNPs nanocomposites with various loadings of Zeolite 13X and CBNPs were investigated using Fourier-transform infrared spectroscopy, X-ray diffraction, Scanning electron microscopy and thermo-gravimetric analysis. The dielectric studies were carried out in the 50 Hz–10 MHz frequency range at room temperature. The electromagnetic interference (EMI) shielding effectiveness (SE) of PVDF/Zeolite 13X/CBNPs nanocomposite was investigated in the 8–18 GHz frequency region (X-band and Ku-band). The maximum EMI SE of approximately −11.1 dB (8–12 GHz) and −11.5 dB (12–18 GHz) was observed for PVDF/CBNPs nanocomposites with 10 wt% loading of CBNPs. These findings emphasize the application of PVDF/Zeolite 13X/CBNPs nanocomposites as a potential EMI shielding material.     

发泡剂对沸石分子筛吸附/脱附性能的影响

采用XRD和SEM等手段分别测定了添加发泡剂处理前后的13X沸石分子筛的晶体结构和微观形貌的变化,并用容量法考察了发泡处理对13X沸石分子筛-乙醇吸附/脱附性能的影响.发现在空气氛围中,500℃下对13X沸石分子筛进行发泡处理,能提高沸石的渗透性,而并不破坏其晶体结构.     

Adsorption equilibrium and kinetics of H2O on zeolite 13x

The adsorption characteristics of H₂O on zeolite 13X were measured by a gravimetric method. The adsorption isotherm showed type II isotherm and was fitted by using both the excess surface work (ESW) model and Langmuir-Freundlich model. The results predicted by the Langmuir-Freundlich model were much smaller than the experimental results at higher-pressure region. However, the ESW model agreed well with the experimental data over the whole pressure region. In this case, a plot of the change in chemical potential versus the amount adsorbed gave two linear regions due to secondary effects such as capillary condensation. The experimental uptake curves were well fitted by several LDF models and solid diffusion model with the error range of 1.5-3.5%. Unlike the expectation that the more rigorous solid diffusion model would fit better, Nakao-Suzuki model showed the best agreement with experimental uptake data.     

A study on the thermal behavior of low silica X-type zeolite ion-exchanged with alkaline earth cations

Pure and high crystalline low silica X-type zeolite with Si/Al ratio of 1 was synthesized under specific hydrothermal conditions. After preparation and characterization of Na form of the zeolite (Na-LSX) from the synthesized zeolite, Na cations were exchanged by three alkaline earth cations. The amount of the exchanged cations per 1 g of the zeolite for each cation was determined by wet chemical method. Among the various prepared samples, those containing approximately equal amount of different cations were selected and characterized by XRD, IR, and XRF techniques. TGA/DTG/DTA and XRD techniques were employed to investigate thermal behavior of the cation exchanged zeolites.     

Stellerite-seeded facile synthesis of zeolite X with excellent aqueous Cd2+ and Ni2+ adsorption performance

Zeolite X was synthesized by a two-step hydrothermal method using natural stellerite zeolite as the silicon seed, and its adsorption performance for Cd²⁺ and Ni²⁺ ions was experimentally and comprehensively investigated. The effects of pH, zeolite X dosage, contact time, and temperature on adsorption performance for Cd²⁺ and Ni²⁺ ions over were studied. The adsorption process was endothermic and spontaneous, and followed the pseudo-second-order kinetic and the Langmuir isotherm models. The maximum adsorption capacitiesfor Cd²⁺ and Ni²⁺ ions at 298 K were 173.553 and 75.897 mg·g^-1, respectively. Ion exchange and precipitation were the principal mechanisms for the removal of Cd²⁺ ions from aqueous solutions by zeolite X, followed by electrostatic adsorption. Ion exchange was the principal mechanisms for the removal of Ni²⁺ ions from aqueous solutions by zeolite X, followed by electrostatic adsorption and precipitation. The zeolite X converted from stellerite zeolite has a low n(Si/Al), abundant hydroxyl groups, and high crystallinity and purity, imparting a good adsorption performance for Cd²⁺ and Ni²⁺ ions. This study suggests that zeolite X converted from stellerite zeolite could be a useful environmentally-friendly and effective tool for the removal of Cd²⁺ and Ni²⁺ ions from aqueous solutions.     

AgCo13X改性分子筛的制备与吸附脱硫性能

采用液相离子交换法制备了以金属离子Co2+和Ag+共同改性的AgCo13X分子筛吸附剂,并用XRD、NH3-TPD、BET和TG等技术对其结构进行表征。在模拟柴油中考察了吸附剂对二苯并噻吩(DBT)的脱硫性能。结果表明:AgCo13X分子筛的脱硫性能优于单一离子改性的Co13X和Ag13X分子筛;而Co13X和Ag13X分子筛的脱硫性能又明显高于未改性的13X分子筛。当Ag+离子交换浓度为0.1 mol/L时制备的Co2+和Ag+共同改性的AgCo13X分子筛具有最好的脱硫性能,其脱硫率为99.91%。剂油比为0.02 g/mL,当吸附时间为1 h即可达到吸附平衡;吸附剂具有良好的稳定性和再生性,再生后的脱硫率达到98.21%。     

Molecular dynamic simulation of carbon dioxide,methane, and nitrogen adsorption on Faujasite zeolite

Removing impurities such as carbon dioxide and nitrogen from natural gas is a technical challenge and one of the major concerns in natural gas treatment process. In this study, adsorption of CH₄, N₂, and CO₂ on the Faujasite(FAU) zeolite has been studied using molecular dynamics simulation at temperatures of 293, 308, and 323 K and pressures up to 1 MPa. COMPASS force field was used to model the interactions between zeolite and guest molecules. Ewald and atom-bas...     

载金属离子的13X分子筛对噻吩的吸附性能研究

采用Zn2+,Cu2+,N i2+,Ag+分别负载到13X分子筛制得吸附剂,考察了它们对噻吩的吸附能力,发现Ag+-13X吸附效果最好,与软硬酸碱理论解释的结果一致。测定了噻吩在Ag+-13X上的吸附动力学数据,并测定了其不同温度下的吸附平衡数据,采用Langmu ir模型进行拟合,与平衡数据吻合得很好,说明Langmu ir模型能够描述本体系的特征,从微观上探讨了其吸附机理,是分子尺寸和化学键的共同作用;考察了Ag+-13X对真实汽油的脱硫性能,结果表明对汽油中的噻吩类硫化物都有脱除效果,为其工业设计提供基础数据。     

Cu~+-13X上噻吩与苯并噻吩的竞争吸附

以噻吩(TP)、苯并噻吩(BT)和正己烷配制模拟汽油,就如何提高Cu+-13X分子筛对噻吩的选择性进行了一系列的静态吸附及动力学吸附研究。结果表明:增加模拟汽油中噻吩的初始质量分数,可以增大Cu+-13X对噻吩的吸附量,提高噻吩对苯并噻吩的竞争吸附性能。当模拟汽油中苯并噻吩、噻吩的初始质量分数分别为500,700μg/g时,Cu+-13X对噻吩的吸附量就大于苯并噻吩;当模拟汽油中苯并噻吩、噻吩的初始质量分数分别为350,850μg/g时,Cu+-13X对噻吩的选择性大于苯并噻吩,噻吩在竞争吸附中占优势。     

Effects of zeolite structure and aluminum content on thiophene adsorption, desorption, and surface reactions

The adsorption and desorption of thiophene and the reactions of thiophene-derived adsorbed species in He, H₂, and O₂ were examined on H-ZSM5, H-Beta, and H-Y with varying Si/Al ratios. Thiophene adsorption uptakes (per Al) were independent of Al content, but were above unity and influenced by zeolite structure (1.7, 2.2, and 2.9 on H-ZSM5, H-Beta, and H-Y). These data indicate that thiophene oligomers form during adsorption and that their size depends on spatial constraints within zeolite channels. Adsorption and oligomerization occur on Brønsted acid sites at 363 K. Thiophene/toluene adsorption from their mixtures show significant thiophene selectivity ratios (10.3, 7.9, and 6.4, for H-ZSM5, H-Beta, and H-Y zeolites), which exceed those expected from van der Waals interactions and reflect specific interactions with Brønsted acid sites and formation of toluene–thiophene reaction products. Treatment of thiophene-derived adsorbed species above 363 K in He or H₂ led to depolymerization of thiophene oligomers and to the formation of unsaturated adsorbed species with a 1:1 thiophene/Al stoichiometry on all zeolites and at all Si/Al ratios. These unsaturated species desorb as stable molecules, such as H₂S, hydrocarbons, and larger organosulfur compounds, formed via ring opening and hydrogen transfer from H₂ or co-adsorbed species, and also form stranded unsaturated organic deposits. Smaller channels and higher Al contents preferentially formed H₂S, benzotiophenes, and arene products during treatment in He or H₂, as a result of diffusion-enhanced of secondary reactions of desorbed thiophene molecules with adsorbed thiophene-derived species. Only oxidative regeneration treatments led to full recovery of thiophene uptake capacities. A preceding treatment in H₂, however, led to the partial recovery of thiophene-derived carbon atoms as useful hydrocarbons and decreased the amount of CO₂ and SO₂ formed during subsequent oxidative treatments required for regeneration.     

超声法制备Ce^4＋/13X分子筛的吸附脱硫性能

采用在离子交换过程中引入超声的方法制备了Ce4 /13X分子筛,考察了超声法对分子筛的制备及脱硫性能的影响,并考察了静态吸附条件对Ce4 /13X在低硫模型汽油(硫含量为23 mg/kg)中的脱硫性能影响。结果表明,超声法可显著缩短分子筛离子交换平衡的时间,提高离子交换度,且能有效地提高活性组分Ce在分子筛表面的含量,脱硫实验结果也显示吸附容量有明显的提高。常温常压,吸附时间为2.5 h,剂油质量比为0.0072的条件下,Ce4 /13X对噻吩的脱硫效果最好,吸附量为0.07653mmol/g,脱硫率可达到76.5%。Freundlich等温式能很好地关联噻吩在Ce4 /13X上的吸附平衡数据。450℃空气气氛中焙烧4 h的方法,可较好地再生Ce4 /13X。     

噻吩在Cu+-13X上吸附平衡和动态数据测定

对噻吩在Cu -13X分子筛上的吸附平衡和动态数据进行了测定。对噻吩的吸附平衡数据用Langmuir模型进行拟合,得到了303、323 K下噻吩在Cu -13X上的饱和吸附量分别为232.86、74.78 mg/g;采用固定床测定了不同停留时间及不同初始浓度下的动态透过曲线,结果表明,在透过点以前动态吸附可以实现噻吩的零含量,缩短停留时间和增加初始浓度会影响吸附的透过曲线,实验结果为吸附工艺设计提供了一定的基础数据。     

升温速率对CO2在13X分子筛上脱附性能的影响

采用程序升温脱附技术研究了升温速率对CO2在13X上脱附性能的影响,基于Polanyi?Wigner方程在无假定条件的情况下计算了不同升温速率下的脱附活化能(Ed). 结果表明,13X分子筛在常温下吸附CO2后,脱附时会产生两个脱附峰(低温峰和高温峰);改变升温速率?会影响Ed,随?升高,低温峰的脱附活化能Ed,L呈对数规律减小,高温峰的脱附活化能Ed,H基本不变,且Ed,L>Qd,H;物理吸附与化学吸附作用力的差异造成两峰吸脱附机理存在根本差别.     

载铜13X的制备及其对噻吩的吸附动力学

研究了载铜13X的制备以及吸附噻吩的动力学性能.实验考察了负载溶液、还原时间、还原温度以及预处理等方面对吸附剂制备的影响,得到了制备载铜13X吸附剂所需要的最优化条件.采用Crank单孔模型对测定的吸附动力学数据进行拟合,确定了不同温度下的噻吩在载铜13X上的扩散系数.实验结果表明,Crank单孔模型可很好地描述噻吩在载铜13X分子筛上的吸附过程.     

13X沸石吸附处理水中苯胺的性能及应用

用天然岩石矿物为原料，经过较简单的工艺过程合成13X沸石去除水中苯胺，模拟废水的实验结果表明：沸石对苯胺的吸附速率非常快，吸附时间为10min时，吸附基本达饱和；一般当沸石用量为10g/L时，水蝇苯胺的吸附率达95％，随着pH值的增加，苯胺在沸石上的吸附率较小；温度增加，吸附率有所增加。但常温下，苯胺的吸附率也能达到93％，13X沸石对苯胺的最大吸附量可达10mg/g，其吸附规律较好地符合Freundlich吸附等温式，饱和了苯胺的沸石，用质量分数为20％，温度为60℃的氯化钠溶液洗脱，解吸率近于100％，且解吸后的沸石在未经任何处理的情况下仍能吸附苯胺；对实际苯胺废水的处理结果，也表明13X沸石不仅可有效地去除苯胺，还可以有效地去除废水中的SS，CODCr，氨氮及油等。     

Polymer nanocomposites using zinc aluminum and magnesium aluminum oleate layered double hydroxides: Effects of LDH divalent metals on dispersion, thermal, mechanical and fire performance in various polymers

Oleate-containing layered double hydroxides of zinc aluminum (ZnAl) and magnesium aluminum (MgAl) were used to prepare nanocomposites of polyethylene, poly(ethylene-co-butyl acrylate) and poly(methyl methacrylate). The additives and/or their polymer composites were characterized by X-ray diffraction, FTIR, elemental analysis, thermogravimetric analysis, mechanical testing, and cone calorimetry. The unusual packing of the monounsaturated oleate anions in the gallery of these LDHs facilitates the dispersion of these nanomaterials. The inorganic LDH protects the polymer from thermal oxidation, shown by enhancement of the thermal and fire properties of the corresponding polymer nanocomposites. There is a qualitative difference in the morphology of the two LDHs in PE and PMMA. ZnAl is better dispersed in PE while MgAl is better dispersed in PMMA. The zinc-containing material led to a large reduction in the peak heat release rate in polyethylene, while the magnesium-containing material led to enhancement of the fire properties of the more polar poly(methyl methacrylate). These fire properties are consistent with the morphological differences. Neither of these LDHs shows efficacy with poly(ethylene-co-butyl acrylate), which indicates a selective interaction between the LDH and the various polymers.     

氯化镁/沸石复合材料的吸附特性及储热性能

制备了一种以13X沸石分子筛为多孔基质材料、氯化镁为反应盐的高性能复合吸附储热材料,并对其吸附性能和储热密度进行了深入研究。使用扫描电子显微镜（SEM）对复合材料的微观结构和形态特征进行了表征;使用全自动比表面积与孔隙度分析仪（ASAP 2460）测试了复合材料的孔体积;使用恒温恒湿箱对复合吸附材料的吸附性能进行了测试,其中含盐量29%（质量分数）的复合吸附材料达到了0.75 g·g^-1的平衡吸附量,探讨了含盐量和相对湿度对复合吸附材料吸附性能的影响规律;利用激光热导仪（LFA）测试了纯沸石以及复合吸附材料的热扩散系数;利用同步热分析仪（STA）测试了复合吸附材料的储热密度,其中含盐量最高的复合吸附材料质量储热密度达到1628 kJ·kg^-1,体积密度高达412 kW·h·m^-3,定量地分析了氯化镁/沸石复合材料耦合物理吸附、化学吸附与吸收过程的多形态储热密度。     

Analysis of dynamic CO2 capture over 13X zeolite monoliths in the presence of SOx,NOx and humidity

In this investigation, the CO₂ capture performances of zeolite 13X monoliths with 600 and 800 cells per square inch (cpsi) in the presence of SO₂/NO impurities under dry and humid conditions were evaluated and compared with that of 13X beads. Dynamic breakthrough tests demonstrated a drastic reduction in CO₂ capture capacity and deterioration of kinetics under dry-clean conditions, whereas, upon switching the feed from a clean gas to contaminated gas which contained SO₂ and NO, different adsorption performance was observed. Specifically, in dry-contaminated mode, the adsorbents retained their capture capacities with comparable kinetics to that of dry-clean feed conditions, however, in humid-contaminated mode, the adsorbents experienced improved CO₂ uptake and CO₂/N₂ selectivity, albeit at the expense of deteriorated kinetics. These findings indicate that the presence of SO₂ and NO contaminants, especially SO₂ contaminants, lead to dramatic changes in the adsorption performance of zeolite 13X monoliths, indicating the importance of evaluating adsorbent materials under realistic conditions.