氨基修饰微孔/介孔复合材料AM-5A-MCM-41对CO2吸附分离的分子模拟

构建了氨基修饰微孔/介孔复合材料AM-5A-MCM-41的全原子模型,采用巨正则Monte Carlo（GCMC）方法研究了它的CO₂吸附分离性能,采用加权混合规则来描述氨基和CO₂分子的弱化学作用。模拟结果表明,CO₂分子优先吸附在复合材料介孔表面的氨基附近,CO₂纯气体的吸附量和吸附热有了显著提高,而N₂的吸附量和吸附热则基本不受影响。对于CO₂和N₂的混合气分离,由于复合材料对CO₂的弱化学吸附作用,显著提高了CO₂吸附量和吸附选择性,在573 K和100 kPa时CO₂/N₂的选择性达到了87.0。通过分子模拟研究可以从微观角度了解CO₂在氨基修饰的微孔/介孔复合材料中的吸附分离的细节和机理,为实验设计和合成高效CO₂吸附剂提供指导。     

含有MCM-41分子筛的混合基质复合膜用于CO2分离

为了提高CO₂分离膜的性能,将接枝了氨基的MCM-41分子筛(MCM-NH₂)添加到聚乙烯基胺(PVAm)水溶液中配制涂膜液,并将PVAm-MCM-NH₂涂膜液涂覆到聚砜(PSf)超滤膜上制备PVAm-MCM-NH₂/PSf混合基质复合膜。复合膜分离层较薄,有利于CO₂渗透速率的提高。接枝的胺基提高了分子筛与聚合物的相容性和膜内胺基含量,有利于膜渗透选择性能的提高。使用CO₂/N₂混合气(15% CO₂ + 85% N₂,体积分数)考察了不同MCM-NH₂添加量的PVAm-MCM-NH₂/PSf膜的渗透选择性能。当涂膜液中m_MCM-NH2/m_PVAm为0.2、湿涂层厚度为50 μm,测试温度为22℃ 、进料气压力为0.11 MPa时,膜的CO₂渗透速率可达4.66×10^-7 mol·m^-2·s^-1·Pa^-1,CO₂/N₂分离因子可达150。较高的CO₂/N₂分离性能表明PVAm-MCM-NH₂/PSf膜在烟道气碳捕集领域具有良好的应用前景。此外,考察了湿涂层厚度、热处理、添加小分子胺等条件对膜渗透选择性能的影响。     

Effects of water vapor on gas permeation and separation properties of MFI zeolite membranes at high temperatures

Understanding the effects of water vapor on gas permeation and separation properties of MFI zeolite membranes, especially at high temperatures, is important to the applications of these zeolite membranes for chemical reactions and separation involving water vapor. The effects of water vapor on H₂ and CO₂ permeation and separation properties of ZSM‐5 (Si/Al ～ 80) zeolite and aluminum‐free silicalite membranes were studied by comparing permeation properties of H₂ and CO₂ with the feed of equimolar H₂/CO₂ binary and H₂/CO₂/H₂O ternary mixtures in 300–550°C. For both membranes, the presence of water vapor lowers H₂ and CO₂ permeance to the same extent, resulting in negligible effect on the H₂/CO₂ separation factor. The suppression effect of water vapor on H₂ and CO₂ permeation is larger for the less hydrophobic ZSM‐5 zeolite membrane than for the hydrophobic silicalite membrane, and, for both membranes, is stronger at lower temperatures and higher water vapor partial pressures. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Synthesis and characterization of MCM-41-type composite materials prepared from ZSM-5 zeolite

Micro/mesoporous composite materials with microporous and mesoporous double pores-size distribution were hydrothermally synthesized by using slurry or filtrate of alkali-treated ZSM-5 zeolite and were characterized by XRD, N₂ adsorption, FT-IR, TEM and so on. The XRD and TEM patterns indicate the composite materials possess ordered hexagonal structure. The sample MZ-B using filtrate of alkali-treated ZSM-5 zeolite hardly contains raw ZSM-5 particles. However, sample MZ-A originated from the slurry of alkali-treated ZSM-5 zeolite may contain some ZSM-5 crystallites, owing to the differences in concentration and time of alkaline treatment for ZSM-5 zeolite.     

疏水微／介孔材料的合成及其对苯及其同系物的吸附

以含氢聚甲基硅氧烷(PMHS)、正硅酸乙酯(TEOS)为硅源,在室温、无模板剂条件下合成了一种疏水微孔/介孔材料,通过调节PMHS/TEOS的比例,获得了3种具有不同微孔,介孔比例的多孔材料.并通过N2吸附,脱附、HRTEM、热重等手段对上述3种材料的结构特征及热稳定性进行了表征.结果发现,所得材料均具有微孔和介孔两种孔隙结构,且具有良好的热稳定性和疏水性,在500℃以下不会发生热分解.进一步利用脉冲色谱技术研究了上述3种材料对苯及其同系物的热力学吸附行为.结果表明,上述3种材料均能够实现苯及其同系物的完全分离,相应的亨利常数、吸附热、分离因子的大小顺序为:正丁基苯>正丙基苯>乙苯>甲苯>苯,且随着PMHS/TEOS比例的增加,亨利常数、吸附热以及分离因子都增加.     

MgO/MCM-41对二氧化碳的吸/脱附性能的研究

采用等体积浸渍法制备MgO/MCM-41作为吸附剂,通过静态吸附法对其吸附性能进行了测定。结果表明,制得的吸附剂只存在一个碱性位,二氧化碳吸附后主要以碳酸氢盐的形式存在。当MgO的负载量为20%的时候,对二氧化碳的吸附量最大,在30℃条件下,其对二氧化碳的吸附量为46.6 mg/g。     

氨改性的介孔二氧化硅的直接合成和CO2吸附

Amine-functionalized mesoporous silica was prepared by using lauric acid and N-stearoyl-l-glutamic acid as structure directing agents via the SN+-I mechanism and applied to CO2 adsorption at room temperature. With γ-aminopropyltriethoxysilane as co-structure directing agent and due to the direct electrostatic interaction with anionic surfactant, most of the amino groups were uniformly distributed at the inner surface of pores and the performance was stable. The amine-functionalized mesoporous silica was characterized by Fourier transform infrared spectrometer, X-ray diffraction, nitrogen physisorption and thermogravimetric analysis. The CO2 adsorption capacity was measured by digital recording balance. At the room temperature and under the atmospheric pres-sure, the adsorption capacity of LAA-AMS-0.2 for CO2 and N2 is 1.40 mmol•g1 and 0.03 mmol•g1, respectively, indicating high separation coefficient of CO2/N2.     

CO2 separation performance by chitosan/tetraethylenepentamine/poly(ether sulfone) composite membrane

CO₂ separation from CO₂/N₂ (20:80) gas mixture has been demonstrated by tetraethylenepentamine blended with chitosan (CS‐TEPA) membrane. Optimization of CS and TEPA weight ratio were carried out based on characterization details involving thermogravimetric analysis, Fourier transform infrared spectroscopy, X‐ray diffraction, atomic force microscope, and field emission scanning electron microscope. Effects of water flow rate, pressure, and temperature were concurrently studied on CS‐TEPA membranes through gas permeation. Almost twofold increase in CO₂ permeance (24.7 GPU) was detected in CS blend with 30% (w/w) of TEPA (CS70) as compared to pure CS membrane (12.5 GPU). CS70 yielded CO₂/N₂ selectivity of 80 whereas CS demonstrated a maximum of 54 at 90 °C. The membrane also exhibited improved stability at temperatures less than 120 °C which was evident from TGA isotherm trace. The proposed composite membrane can be a promising candidate for flue gas separation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45206.     

Al-SBA-15介孔分子筛及其吸附脱氮研究

采用嫁接法制备了Al-SBA-15介孔分子筛,并对硅铝比、焙烧温度等影响产物的制备因素进行了考察。通过XRD,BET,FT-IR,NH3-TPD等分析手段对所得样品进行了分析。将所得产物Al-SBA-15与SBA-15在相同条件下进行了吸附脱除碱性氮化物对比实验。结果表明:Al-SBA-15保留了SBA-15高度有序的二维六方介孔结构。AlSBA-15具有比SBA-15更好的吸附脱氮能力,在焙烧温度550℃、硅铝比(原子比)为50的条件下,Al-SBA-15(50)介孔分子筛最高脱氮率为68.02%,此时饱和吸附量为30.6 mg/g。     

真空变温吸附捕集干烟道气中CO2的模拟研究

为减缓气候变化,减少CO₂的排放,对真空变温吸附(TVSA)从干烟道气中捕集CO₂进行了系统的研究。以沸石13X为吸附剂,设计了实验室规模的4塔连续进料的TVSA工艺,并建立数学模型进行数值模拟。模拟结果表明,通过四塔TVSA可获得纯度为97.54%,回收率为96.79%的CO₂产品气,其产率为1.7 mol· ( \mathrm{k} \mathrm{g} \text{?} \mathrm{a} \mathrm{d} \mathrm{s} ) ^-1·h^-1,能耗为3.14 \mathrm{M} \mathrm{J} · ( \mathrm{k} \mathrm{g} \text{?} \mathrm{C} {\mathrm{O}}_{\mathrm{2}} {)}_{}^{-\mathrm{1}} 。此外,考察了进料量、循环回流步骤时间、真空度对产品气纯度、回收率、吸附剂产率和工艺能耗的影响,并且分析了塔内压力与温度变化,详细探讨了塔内气固相浓度随轴向的分布。良好的工艺效果表明,TVSA有潜力成为一种能够生产高纯度高回收率的CO₂产品气,并具有良好经济效益的捕碳工艺。     

面向烟气NOx净化与回收的新型吸附工艺

合理高效的吸附工艺是决定吸附法净化和回收烟气中NO_x工业可行性的关键工艺环节。提出一种通过外部补充气体实现固定床循环体空间内多次循环解吸NO_x的新型吸附工艺（GVTSA）。基于该工艺,采用Na-ZSM-5分子筛作为吸附剂,以某钢厂烧结机脱硫后烟气为原料（组分）进行了NO_x吸附回收实验研究。结果表明,GVTSA工艺相较传统吸附工艺（TSA工艺、VSA工艺）可获取更高的NO_x回收量,在优选条件下（220℃,-50 kPa）,NO_x回收率达到90%,解吸气中NO₂浓度由原料气的36 mg·m^-3提升到2%以上,NO_x循环吸附量可达0.10 mmol·g^-1,16次吸脱附循环稳定。研究结果可为烟气NO_x治理与资源化工业应用提供参考。     

CO_2,CH_4在全硅MFI型沸石中吸附的分子模拟

采用巨正则蒙特卡洛(GCMC)分子模拟方法研究了CO2,CH4分子在全硅MFI型沸石中的吸附行为,计算得到了纯组分和两组分的混合物在不同温度时的吸附等温线;分析了全硅MFI型沸石对混合组分的选择性吸附;模拟还得到了CO2,CH4分子在全硅MFI型沸石中的吸附位。     

应用于烟气中CO2捕集的固体吸附材料研究进展

固体吸附法捕集二氧化碳技术具有吸/脱附性能优良、设备轻便灵活、环保和低成本的优势，被认为是实现电厂烟气中碳捕集最具前景的技术之一。国内外学者对于可应用于电厂烟气中二氧化碳捕集的固体吸附材料开展了大量的研究并取得一定进展。该文综述了近些年沸石分子筛、金属有机框架材料（MOFs）和活性炭（ACs）等吸附材料的研究现状；归纳并分析了各类吸附材料的应用优势和在工程应用中存在的问题；总结了各类材料吸附性能的主要影响因素和吸附机理等。最后，展望了固体吸附材料的发展方向。     

Y分子筛/介孔Al-SBA-15复合材料与脱铝Y分子筛的表征和重油加氢裂化性能

采用两步法和水热-化学方法制备了具有高水热稳定性的Y分子筛/介孔Al-SBA-15复合材料和含有介孔的脱铝Y分子筛,用浸渍法制备了加氢裂化催化剂,并利用XRD、N2 吸附、SEM、XRF和TEM等分析手段对Y分子筛/介孔Al-SBA-15复合材料、含有介孔的脱铝Y分子筛及其催化剂的物化性质进行了对比分析。相同条件下催化剂的重油加氢裂化性能对比评价结果表明,以Y分子筛/介孔Al-SBA-15复合材料为载体的加氢裂化催化剂的中间馏分油收率和中油选择性高达66.21%和84.5%,比以脱铝Y分子筛为载体的催化剂分别提高了5.68%和5.7%。     

介微孔HY/MCM-41复合分子筛的合成及应用

以微孔HY浆液为母液,合成了介-微孔复合分子筛HY/MCM-41。通过XRD、BET和NH₃-TPD等手段对复合分子筛进行表征,并考察其水热稳定性。结果表明,复合分子筛同时具有中孔分子筛MCM-41和微孔HY型沸石的特点,与纯MCM-41分子筛相比,酸性明显增强,水热稳定性提高。利用一段串联加氢裂化工艺,考察了复合分子筛的催化性能。200 mL固定床加氢装置评价结果表明,在控制原料>350 ℃馏分油转化率为75%的条件下,加氢裂化生成油C₅⁺液收98.51%,最大量柴油馏分［(140~370) ℃］收率69.09%,＜370 ℃中馏分油选择性80.5%,能满足工业装置最大量生产柴油的需要。     

NaA/MCM-41微介复合分子筛的合成与表征

按n(SiO2)∶n(Na2O)∶n(Al2O3)∶n(H2O)=1∶1.5∶0.5∶100加料,在90℃下水热晶化3 h合成NaA微孔分子筛,再按n(SiO2)∶n(NaOH)∶n(CTAB)∶n(H2O)=1∶0.3∶0.3∶90依次添加到NaA微孔分子筛中,于110℃下水热晶化24 h合成NaA/MCM-41微介复合分子筛,并采用XRD、SEM(EDS)和TEM等方法对其进行了表征。吸附阳离子红X-5GN模拟染料废水结果表明,在50 mLρ(阳离子红X-5GN)=20 mg/L的水溶液中,NaA/MCM-41微介复合分子筛的投加量为0.6 g/L、pH=6、振荡时间为60 min时,脱色率可达到96.4%,比NaA分子筛和MCM-41介孔分子筛独自吸附脱色效果要好。     

对硝基氯苯在HZSM-5沸石中的吸附和扩散行为研究

通过静态吸附实验,研究水体中对硝基氯苯在HZSM-5沸石中的吸附和扩散行为.研究结果表明,对硝基氯苯在HZSM-5沸石中的吸附等温线存在2个平台,其最大吸附量与温度无关.对硝基氯苯优先吸附在沸石孔道的交点位置,其吸附过程由内扩散控制.对硝基氯苯在HZSM-5沸石中的扩散性与温度和对硝基氯苯的吸附量密切相关,其扩散系数在高温与吸附量小于2 mol/u.c.时较高.     

水中Ni~(2+)在粒状沸石/活性炭复合材料上的吸附研究

采用廉价的煤矸石为主要原料,添加一定量的沥青粉制备了沸石NaA/活性炭粒状复合材料,并以此作为吸附剂,研究了水溶液中Ni~(2+)在该复合材料中的吸附行为,考察溶液的初始浓度、吸附时间和pH对吸附的影响.结果表明溶液较高的pH值有利于Ni~(2+)在吸附剂上的吸附;随Ni~(2+)初始浓度的增大复合材料的吸附量增大,而Ni~(2+)的去除率随之减小;Ni~(2+)在复合材料上的吸附接近Langmuir-Freundlich等温吸附模型,反映了吸附表面的多相性及两类吸附中心在复合材料上的共存性;吸附速率遵循准二级吸附动力学模型.     

Preparation and characterization of Beta/MCM-41composite zeolite with a stepwise-distributed pore structure

A Beta/MCM-41 composite zeolite with a stepwise-distributed pore structure was prepared with a silica-alumina source originated from alkaline treatment of zeolite Beta. The material was characterized by various techniques. The results indicated that this composite possesses a mesopore system of MCM-41 and the microporous structure of Beta zeolite. Hydrothermal stability and acidity was improved over MCM-41 due to the introduction of Beta building units into the mesopore walls. The composite was used as the support of a Pd-Pt catalyst for the hydrogenation of naphthalene in the presence and absence of 4, 6-dimethyldibenzothiophene. It was demonstrated that the catalyst has an enhanced activity and sulfur tolerance during naphthalene hydrogenation.     

真空变压吸附捕集烟道气中二氧化碳的模拟、实验及分析

采用工业硅胶作为吸附剂,利用两塔变压吸附装置进行了烟道气变压吸附碳捕集实验。利用gPROMS软件建立两塔变压吸附模型对实验过程进行模拟,对比了实验和模拟的结果,验证了模型的准确性。通过两塔变压吸附可将15%的CO₂富集到74%,收率为91.52%。在模型基础上考察了变压吸附碳捕集过程中进料量、吸附时间、顺放压力与二氧化碳收率、纯度和能耗的关系,定性分析了吸附塔压力和进料量对压缩机能耗的影响。结果表明:增大进料量、延长吸附时间、降低顺放压力,可以有效提高产品气中CO₂浓度,但同时也导致收率的下降,前两者还会造成单位能耗的增加;吸附压力越高,进料流量越大,压缩机能耗越大。