活性炭孔结构对甲苯及丙酮吸附性能的影响

采制3种活性炭样品进行甲苯、丙酮吸附实验,以重量法计算活性炭对甲苯、丙酮气体的饱和吸附率,并将活性炭物性参数与其关联。结果表明,活性炭物性与其对有机物的吸附性能密切相关,活性炭碘吸附值、总比表面积与甲苯吸附率成明显的负相关,较高中孔与总孔比(V_(mes)/V_t)会促进对甲苯的有效吸附;微孔比表面积和孔容积越大,活性炭对丙酮的吸附效果越好。此外,线性回归分析的结果表明,活性炭中孔径小于1.4 nm的微孔及合理的孔径分布对甲苯的吸附起主要作用,孔径1.67～2.22 nm是吸附丙酮的有效孔径。     

VOCs在分子筛上吸附性能的研究进展

简单介绍了一些常见分子筛的构型及特点,讨论了不同构型分子筛对各种VOCs废气吸附效果的研究进展。总结了各类分子筛对VOCs的吸附特性,发现立方构型的分子筛对VOCs废气的吸附效果最佳。小结了影响分子筛吸附性能的因素,发现分子筛的比表面积、孔容、硅铝比、表面官能团等自身性质都会对吸附VOCs废气的性能产生一定的影响。另外,分子筛的吸附容量还与吸附时的进气流速、入口气体浓度、吸附剂床层高度等工况有关。最后,对现有研究做了总结与展望,为分子筛吸附VOCs的合理应用提供了理论支持。     

MFI型纯硅分子筛的表面Si—OH及其对VOCs的吸附性能

运用原位IR和N_2等温吸脱附法对不同方法制备MFI型S-1纯硅分子筛进行表征,考察S-1分子筛焙烧温度和后处理对S-1分子筛表面Si—OH的影响及VOCs吸附性能。结果表明,提高焙烧温度,可有效除去部分硅羟基,显著改变其表面亲水亲油性能。不同酸强度的处理剂(NH_4F相似文献   

Ti掺杂NaP分子筛的合成及其吸附性能

以粉煤灰分级提取的硅酸钠与偏铝酸钠为原料,提出了水热合成与络合法协同制备Ti掺杂NaP分子筛(Ti-NaP)的方法。采用X射线衍射、扫描电子显微镜、X射线光电子能谱和固体硅铝核磁(MAS NMR)对Ti掺杂NaP分子筛前后产物进行了晶相、形貌和元素赋存状态研究,并对Ti-NaP吸附性能进行评价。结果表明,当n(Al₂O₃):n(TBOT)摩尔比为6:1时,Ti-NaP结晶度可达98.2%,且Ti在NaP分子筛中有两种主要的赋存状态:即与骨架硅原子同晶取代和平衡骨架负电荷。与未掺杂Ti的NaP分子筛相比,Ti-NaP比表面积约增大3.6倍(从27 m²/g增大至123 m²/g)。Zn(Ⅱ)吸附测试表明,Ti-NaP对Zn(Ⅱ)吸附去除率可达97.71%,经再生循环使用5次,仍具有良好的吸附稳定性。     

4A分子筛的吸附性能与孔结构研究

多孔材料的吸附性能与其独特、复杂的孔结构有关.为探究低温低压下4A分子筛的吸附性能,采用静态膨胀法获得了其在77 K下对N2、O2、空气的吸附曲线,分析了分子筛对不同吸附质的吸附量存在差异的原因.以N2、CO2、Ar为吸附质,利用气体吸附法来表征4A分子筛的微孔结构.研究结果表明:4A分子筛对O2的吸附量达到1 ×104Pa·L/g,高出N2、空气两个数量级;对于4A分子筛,273 K时,CO2是气体吸附法表征其微孔结构的理想吸附质;采用D-R法计算4A分子筛的比表面积更为合理,其比表面积为533.148 m2/g;基于最大吸附量计算的4A分子筛微孔孔容与文献值较为接近;与DFT法相比,H-K法更能准确表征具有微孔的4A分子筛的孔径分布,孔径在1 nm以下的孔体积比例占85.42％.     

分子筛吸附甲基丙烯酸甲酯中微量水分的研究

研究了3A，4A，5A和13X4种型号分子筛对甲基丙烯酸甲酯中微量水分的静态吸附的动力学性能，做出了4种型号分子筛的吸附动力学曲线；对其结果进行了分析讨论。并进一步研究了13X型分子筛的吸附温度和吸附剂用量对其饱和吸附量的影响。结果表明，13X型分子筛的吸附效果优于3A，4A和5A型分子筛；其在25℃时吸附效果最好，饱和吸附量最大，吸附速率也最快，分子筛的最佳用量为0．4g／mL。FTIR证明13X分子筛同时还吸附了一定量的对苯二酚。     

4种分子筛对VOCs静态吸附与脱附性能研究

采用干燥器-静态吸附法测定3A、4A、5A、10X四种分子筛对甲醇、苯、正己烷等VOCs的吸附性能。结果表明,10X分子筛在吸附量上明显高于其它3种分子筛,对苯、甲醇、正己烷的吸附量分别达到了96,88,75 mg/g。微波脱附和热脱附的脱附能力差别甚微,微波脱附时间短。分子筛再生率>95%,与之前吸附量相当,未对分子筛的内部结构产生影响。     

介孔分子筛MCM-48对果胶酶吸附研究

利用水热合成法制备得到纳米介孔分子筛MCM-48,并研究了其对果胶酶的吸附固载性能和吸附条件及过程特点,测定了固载果胶酶的活性。动力学研究表明,MCM-48与果胶酶间的吸附符合准二阶动力学方程。热力学计算表明,该吸附过程ΔH=-68.94kJ/mol,ΔS=-197.90J·mol~(-1)·K~(-1),说明MCM-48对于果胶酶的吸附是一个放热的、熵减的吸附过程。通过对比游离酶(酶活力14 569U)和固定化果胶酶(酶活力13 345U)的酶活力,说明固载在MCM-48中的果胶酶依然具有良好的活性,这对于保持果胶酶的天然结构以及生物活性非常有益。     

银基分子筛对放射性碘的吸附性能研究

以具有代表性的放射性单质碘和甲基碘作为吸附质,考察了银基分子筛对其的静态吸附容量和吸附热、动力学,通过SEM、EDX mapping、XPS测试材料的微观形貌、元素组成,对吸附机理进行了分析。结果表明,该材料在常温下对单质碘和甲基碘吸附容量分别可达1 000,380 mg/g,对甲基碘的吸附过程符合准二级动力学方程和Langmuair吸附等温模型。银基分子筛通过化学吸附处理痕量的放射性碘,而对于较高浓度的放射性碘主要的吸附方式为物理吸附。     

4种分子筛对VOCs静态吸附与脱附性能研究

采用干燥器-静态吸附法测定3A、4A、5A、10X四种分子筛对甲醇、苯、正己烷等VOCs的吸附性能。结果表明,10X分子筛在吸附量上明显高于其它3种分子筛,对苯、甲醇、正己烷的吸附量分别达到了96,88,75 mg/g。微波脱附和热脱附的脱附能力差别甚微,微波脱附时间短。分子筛再生率>95%,与之前吸附量相当,未对分子筛的内部结构产生影响。     

2,2-Dimethylbutane adsorption and diffusion in MFI zeolite

Adsorption rates of 2,2-dimethylbutane (DMB) from the liquid phase into MFI zeolite crystals were measured by a volumetric/gravimetric method. Desorption rates in the presence of liquid n-hexane were measured by a non-adsorbing solvent (isooctane) method. Dimethylbutane desorbed, and was replaced by n-hexane, approximately three orders of magnitude faster than it adsorbed. Adsorption was slow and reached only 40% of saturation loading in 6-μm crystals after 45 days at 295 K, but this DMB loading desorbed into n-hexane in less than 1 h. Desorption may be faster due to slight expansion of the MFI unit cell by n-hexane adsorption. Although DMB diffused slower than n-hexane in MFI crystals, its transient time through a silicalite-1 membrane was an order of magnitude shorter than the n-hexane time at 313 K because DMB diffused through defects, whereas n-hexane diffused mainly through zeolite pores. The n-hexane transient time was longer because n-hexane: (1) expanded the MFI crystal size slightly and shrank non-zeolitic pores, and (2) adsorbed in the zeolite as it moved through the remaining non-zeolitic pores. A silicalite-1 membrane saturated with DMB at 423 K was sealed so effectively, and DMB desorbed slowly enough, that the helium permeation flux at 313 K was below the detection limit.     

Effect of substrate curvature on microstructure and gas permeability of hollow fiber MFI zeolite membranes

Literature data show that gas permeability of MFI zeolite membrane varies depending on the geometry of supports. The present work investigates the effects of the surface curvature of substrates on the microstructure and the gas permeation property of supported zeolite membranes. MFI zeolite membranes were grown on porous alumina hollow fibers with different diameters (surface curvature) by the secondary growth method. Single gas permeation and H₂/CO₂ binary gas separation from 25 to 300 were conducted to study the membrane quality. The zeolite membranes on supports of larger surface curvature have higher permeability and lower selectivity due to the presence of more inter‐crystalline gaps in the zeolite layer formed during the template removal step. The effects of the support surface curvature (and geometry) on zeolite membrane microstructure and gas permeation characteristics are semi‐quantitatively analyzed by a transport model considering both structural change and gas diffusion in micropores. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3419–3428, 2018     

水中丙酮在活性炭上吸附平衡与动力学研究

研究了水中丙酮在活性炭上的吸附平衡与动力学曲线,对在20、30、40℃下的吸附等温线用Freundich方程拟合,得出了满意的结果。选择合适的实验条件,在消除了外膜阻力的条件下,表明颗粒内扩散中的表面扩散占主要地位,考察了初始浓度、温度、活性炭粒径等因素对丙酮吸附的影响,并用间歇搅拌槽吸附的表面扩散模型拟合出扩散时间常数。     

Pure H2 production through hollow fiber hydrogen‐selective MFI zeolite membranes using steam as sweep gas

Hollow fiber MFI zeolite membranes were modified by catalytic cracking deposition of methyldiethoxysilane to enhance their H₂/CO₂ separation performance and further used in high temperature water gas shift membrane reactor. Steam was used as the sweep gas in the MR for the production of pure H₂. Extensive investigations were conducted on MR performance by variations of temperature, feed pressure, sweep steam flow rate, and steam‐to‐CO ratio. CO conversion was obviously enhanced in the MR as compared with conventional packed‐bed reactor (PBR) due to the coupled effects of H₂ removal as well as counter‐diffusion of sweep steam. Significant increment in CO conversion for MR vs. PBR was obtained at relatively low temperature and steam‐to‐CO ratio. A high H₂ permeate purity of 98.2% could be achieved in the MR swept by steam. Moreover, the MR exhibited an excellent long‐term operating stability for 100 h in despite of the membrane quality. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3459–3469, 2015     

Atomistic simulations for adsorption and separation of flue gas in MFI zeolite and MFI/MCM-41 micro/mesoporous composite

Adsorption of pure CO₂ and N₂ and separation of CO₂/N₂ mixture in MFI zeolite and MFI/MCM-41 micro/mesoporous composite have been studied by using atomistic simulations. Fully atomistic models of MFI and MFI/MCM-41 are constructed and characterized. A bimodal pore size distribution is observed in MFI/MCM-41 from simulated small- and broad-angle X-ray diffraction patterns. The density of MFI/MCM-41 is lower than MFI, while its free volume and specific surface area are greater than MFI due to the presence of mesopores. CO₂ is preferentially adsorbed than N₂, and thus, the loading and isosteric heat of CO₂ are greater than N₂ in both MFI and MFI/MCM-41. CO₂ isotherm in MFI/MCM-41 is similar to that in MFI at low pressures, but resembles that in MCM-41 at high pressures. N₂ shows similar amount of loading in MFI, MCM-41 and MFI/MCM-41. The selectivity of CO₂ over N₂ in the three adsorbents decreases in the order of MFI>MFI/MCM-41>MCM-41. With increasing pressure, the selectivity increases in MFI and MFI/MCM-41, but decreases in MCM-41. The self-diffusivity of CO₂ and N₂ in MFI decreases as loading increases, while in MFI/MCM-41, it first increases and then drops.     

沸石改性及其吸附性能研究

对沸石进行降低硅铝比改性，改性沸石对H2O，H2S，NH3的饱和吸附量分别为16.8％，18．2mg/g，71．1mg/g，而只进行过焙烧的沸石为9．3％，11．7mg/g,38.4mg/g，表明沸石经降低硅铝比改性后，对H2O，H2S，NH3的吸附量大大提高。     

沸石分子筛吸附性能的测定方法

介绍了沸石分子筛吸附性能常用的测定方法,综述了近年来沸石分子筛吸附性能的研究进展。认为在众多方法中,气相色谱法、智能重量分析技术、频率响应法、分子模拟技术等以其方便有效的优点,是测定沸石分子筛吸附性能的重要手段。     

沸石的改性处理及吸附性能研究

介绍了沸石改性的方法,讨论了影响沸石吸附性能的因素.实验表明,在废水温度为25℃,pH为6,Cd2 的初始质量浓度为50 mg/L,吸附剂的用量为20g/L,吸附时间为120 min的条件下,改性沸石对镉离子的去除率达到99.12%.     

MFI沸石中Maxwell-Stefan扩散系数与覆盖率的关系

基于描述多孔介质中表面扩散的Maxwell-Stefan（M-S）方程,结合本文动力学Monte Carlo（KMC）模拟及文献中分子动力学（MD）模拟数据,提出了MFI沸石中M-S扩散系数与覆盖率依赖关系的新表达式.该关系式考虑了分子间相互作用以及饱和吸附覆盖量对扩散系数与覆盖率依赖关系的影响,用于预测强受限组分CF₄、弱受限组分CH₄以及中度受限组分Xe等7种单组分在MFI沸石中的M-S扩散系数时,结果较现有其他关系式更为合理.     

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.