两种介孔分子筛动态吸附VOCs的研究

采用模板剂法制备了孔道规整、大比表面积的2种介孔分子筛MCM-41和SBA-15,并以甲苯、二甲苯、三甲苯为吸附对象,考察了介孔分子筛动态吸附VOCs的性能.结果表明,增加VOCs分子尺寸和浓度,降低床层温度可大幅提高介孔分子筛吸附性能.SBA-15由于介孔壁上的微孔结构适合吸附低浓度、小分子VOCs;MCM-41更适合吸附高浓度、大分子VOCs.TPD脱附试验表明,VOCs在介孔材料表面150℃下就能基本脱附完全.     

ZSM-5沸石分子筛吸附-脱附VOCs的性能研究

以不同Si/Al比的ZSM-5分子筛为吸附剂,考察了硅铝比对其疏水性和吸附性能的影响.结果表明,随着Si/Al比的增加,其微孔孔体积和微孔表面积变大,当Si/Al100时,ZSM-5分子筛均具有良好的疏水性和对甲苯的选择性吸附能力,但脱附温度随之升高.同时,以4类VOCs(醇类、酯类、烃类、酮类)为吸附质,研究了ZSM-5分子筛吸附-脱附不同VOCs的性能.发现ZSM-5分子筛由于具有丰富的微孔结构更适合吸附小分子VOCs,对于同类VOCs分子,随着碳数的增加,分子大小和极性均增大,其与分子筛的作用力越强,热脱附温度越高,但VOCs在ZSM-5分子筛表面300℃左右就能脱附完全.     

金属有机框架ZIF-8/聚二乙烯基苯纳米复合材料的合成及其吸附VOCs的性能

在常温常压下的甲醇溶液体系中,将COOH功能化的介孔材料聚二乙烯基苯(PDVB)与微孔材料金属有机框架(MOFs)ZIF-8进行复合,获得了一种新型的多孔纳米复合材料ZIF-8/PDVB,采用XRD、FTIR、SEM和氮气吸附-脱附等方法对ZIF-8/PDVB进行表征,并考察了其吸附甲苯、乙酸乙酯的性能.XRD谱图表明,所合成的ZIF-8以晶体形式存在;FTIR和XRD的结果表明,ZIF-8与PDVB的复合是通过Zn2+与PDVB上的COOH形成配位,未配位饱和的Zn~(2+)再与2-甲基咪唑进行配位,从而形成纳米复合材料ZIF-8/PDVB;SEM结果显示,ZIF-8晶体分散在PDVB的表面上;氮气吸附-脱附表征结果显示,ZIF-8/PDVB的比表面积达到1301 m~2·g~(-1),材料同时具有介孔与微孔结构.吸附性能评价结果表明,ZIF-8/PDVB对甲苯、乙酸乙酯均具有优良的吸附性能,ZIF-8/PDVB在吸附VOCs性能上显示出潜在的巨大优势.     

水雾协同微波脱附再生树脂吸附剂

以溶剂热法合成的聚二乙烯苯（PDVB）树脂为吸附剂,苯、甲苯、二氯甲烷为典型的非极性吸附质,对比单一微波和超声雾化水协同微波条件下树脂的脱附再生效果,考察微波功率、水雾量、吸附质种类等对树脂脱附效果的影响.结果表明,PDVB 树脂在单一微波作用下对非极性有机分子的脱附率约为50%,而在超声雾化水协同作用下,PDVB 对苯、甲苯、二氯甲烷的脱附率均可达到90%以上.同时脱附床层的温度始终保持在40℃以下,不会造成树脂高温老化,多次吸附/脱附循环再生后,树脂结构仍能保持稳定,表明在微波条件下引入超声雾化水可强化体系的微波吸收能力,实现树脂吸附剂的快速脱附再生.     

蜂窝活性炭与沸石分子筛对涂装VOCs废气的吸脱附性能对比

选取工业涂装VOCs废气作为试验对象,以蜂窝活性炭和沸石分子筛为吸附剂,设计固定床小试装置进行VOCs吸脱附试验。结果表明：蜂窝活性炭的碘值、比表面积、总孔容及微孔孔容均大于沸石分子筛,分别是沸石分子筛的1.79,2.93,1.55,2.02倍;相同脱附温度、进气风速条件下,VOCs从蜂窝活性炭表面脱附更容易,其脱附时间远低于沸石分子筛;相同反应条件下,蜂窝活性炭对VOCs的饱和吸附量明显高于沸石分子筛,但沸石分子筛的饱和吸附量受反应温度和VOCs浓度的影响相对较小;循环吸脱附10次后,蜂窝活性炭和沸石分子筛对VOCs的吸附率分别下降为第1次时的71.35%和81.15%,沸石分子筛的吸脱附性能更为稳定;蜂窝活性炭饱和吸附量大、脱附时间快,适用于宽负荷、低风量、中高浓度VOCs废气处理;沸石分子筛空气动力学及循环吸脱附性能较好,适用于处理初始温度相对较高、中低浓度VOCs废气。     

疏水改性ZSM-5的优化制备及其在高湿度下的VOCs吸附性能研究

针对分子筛在高湿度条件下VOCs吸附容量急剧下降的问题,通过优化液相沉积法合成了疏水改性的ZSM-5分子筛.实验选用更加经济环保的乙醇替代甲苯作为改性溶剂,并对两种溶剂的改性效果进行比较,优选出最佳改性条件制备疏水改性ZSM-5,考察了该吸附剂对模拟高湿度有机废气的吸附性能,并采用了SEM、XRD、FTIR、氮气吸脱附、水接触角等方法进行表征.结果表明,作为分散剂,相较于甲苯,无水乙醇更能显著提高分子筛疏水性.在最佳改性条件下,无水乙醇改性的ZSM-5-E₀在90%相对湿度下对甲苯的饱和吸附量可达81.9 mg·g^-1,远高于原样,是甲苯改性的ZSM-5-T₀的3倍,循环吸脱附4次后的吸附容量仍在90%以上,对甲苯的吸附符合Langmuir等温吸附模型.实验证明,无水乙醇改性的ZSM-5-E₀有优异的VOCs吸脱附性能,具有应用前景.     

孔径调变对MCM-41分子筛吸附VOCs性能的影响

采用3种不同碳链长度的季铵盐表面活性剂C_nTAB(n=8,12,16)为模板剂,分别合成8-MCM-41、12-MCM-41和16-MCM-41介孔分子筛,并以甲苯、邻二甲苯、均三甲苯为吸附对象,考察了介孔分子筛动态吸附VOCs的性能.结果表明,通过减少表面活性剂的碳链长度,可以成功地把MCM-41分子筛的孔径调变为4.1、3.2和2.4 nm.吸附实验结果表明,当MCM-41孔径减小时,其对低浓度甲苯、邻二甲苯的吸附量大幅上升,均三甲苯存在孔道扩散效应,其吸附量增加不明显.吸附等温线表明,在2.4 nm孔道内,3种芳烃分子均属于典型的Langmuir单分子层吸附;当孔径大于2.4 nm时,芳烃分子出现明显的多层吸附和毛细凝聚现象.     

壳聚糖改性竹制粉末活性炭吸附剂对微囊藻毒素的吸附特性研究

研究了壳聚糖改性的竹制粉末活性炭吸附剂对饮用水中微囊藻毒素Microcystin-RR(MCRR)的吸附效果和机理.结果表明,这种新合成的吸附剂具有一定的孔结构,比表面积为203.63m·2g-1,平均孔径为7.23nm,并且具有较高比例的介孔分布,这种特性使得其对最长分子尺寸为2.86nm的MCRR具有较好的捕捉效果.吸附动力学实验表明,接触时间达到100min后,吸附趋于稳定,该吸附剂对MCRR的吸附行为可以用Langmuir模型(Ce/Qe=0.014Ce+0.81,R2=0.99)和Freundlich模型(lnQe=0.61lnCe+1.04,R2=0.99)较好地描述;在中性条件下该吸附剂对MCRR的最大吸附量达到69.93μg·g-1,具有较强的吸附能力.受吸附剂本身等电点及MCRR分子带电性能的影响,吸附剂对MCRR的吸附受pH影响较大,在pH=3时吸附能力最强;此外,天然有机物(NOM)的存在会对MCRR的吸附产生明显的竞争作用.脱附实验表明,改变脱附溶液的pH对提高脱附效率影响不大,甲醇作为脱附剂具有较好的脱附效果,脱附率可达到96%.     

挥发性有机物在活性炭纤维上的吸附和电致热脱附

采用3种不同的活性炭纤维,考察了VOCs种类、VOCs浓度以及床层温度对活性炭纤维吸附VOCs性能的影响,并采用电致热脱附技术进行再生研究.结果表明,甲苯浓度对吸附推动力影响较大,在高浓度下,可使吸附容量达到434.8mg/g.活性炭纤维吸附甲苯受温度影响较小,在60℃下仍然具有288.6mg/g的吸附容量.电致热脱附电压越大,活性炭纤维升温速率越快,脱附效率越高,经过100min即可完全脱附.经过4次吸脱附循环,活性炭纤维仍有较好的吸附效果,饱和吸附量能达到原有吸附量的80%以上.     

活性炭热氮气循环脱附甲苯性能实验研究

以GAC-1和GAC-2两种商业活性炭颗粒为吸附剂,甲苯为吸附质,考察活性炭孔道结构、脱附温度对热氮气脱附效率的影响,分析了活性炭再生性能。结果表明:两种活性炭对甲苯均表现出良好的吸附性能,GAC-1具有更大的比表面积、孔容和孔径,更有利于甲苯有机废气的吸附;热氮气循环脱附实验中,相比于90℃和120℃,150℃的脱附温度可以达到更高的脱附率(67.3%);经过5次循环吸附-脱附,GAC-1仍保持原有的吸附容量,脱附率仅下降2.1%。     

挥发性有机物(VOCs)吸附材料的研究进展

目前,我国面临严重的挥发性有机物（VOCs）污染问题。吸附法是研究与应用最为广泛的VOCs治理技术。主要介绍了吸附净化VOCs原理和几种常见的VOCs吸附材料,包括活性炭、新型多孔炭材料、沸石分子筛、黏土基吸附剂、金属有机框架和介孔硅。详述了各吸附材料的VOCs吸附能力和优缺点,判断了其应用价值,并指出了为提升大规模工业化应用潜力,后续研发的VOCs吸附材料应满足高吸附量、高疏水性、高热稳定性和再生能力强4个特征。     

锚定金属离子-螯合物的介孔硅除磷性能研究

采用3种介孔硅分子筛制备了锚定金属离子-螯合物的介孔硅吸附剂。系统研究了硅分子筛、螯合剂、金属离子和吸附时间等因素对吸附剂磷吸附性能的影响。结果表明,硅分子筛、螯合物和金属离子对吸附剂的磷吸附性能有显著的影响,其对介孔硅吸附剂磷吸附量影响的顺序分别为:SBA15>MCM41>MCM48,Fe-SH-MCM41<相似文献   

Adsorption of benzene,cyclohexane and hexane on ordered mesoporous carbon

Ordered mesoporous carbon (OMC) with high specific surface area and large pore volume was synthesized and tested for use as an adsorbent for volatile organic compound (VOC) disposal. Benzene, cyclohexane and hexane were selected as typical adsorbates due to their different molecular sizes and extensive utilization in industrial processes. In spite of their structural differences, high adsorption amounts were achieved for all three adsorbates, as the pore size of OMC is large enough for the access of these VOCs. In addition, the unusual bimodal-like pore size distribution gives the adsorbates a higher diffusion rate compared with conventional adsorbents such as activated carbon and carbon molecular sieve. Kinetic analysis suggests that the adsorption barriers mainly originated from the difficulty of VOC vapor molecules entering the pore channels of adsorbents. Therefore, its superior adsorption ability toward VOCs, together with a high diffusion rate, makes the ordered mesoporous carbon a promising potential adsorbent for VOC disposal.     

Adsorption of benzene, cyclohexane and hexane on ordered mesoporous carbon

Ordered mesoporous carbon(OMC) with high specific surface area and large pore volume was synthesized and tested for use as an adsorbent for volatile organic compound(VOC)disposal. Benzene, cyclohexane and hexane were selected as typical adsorbates due to their different molecular sizes and extensive utilization in industrial processes. In spite of their structural differences, high adsorption amounts were achieved for all three adsorbates, as the pore size of OMC is large enough for the access of these VOCs. In addition, the unusual bimodal-like pore size distribution gives the adsorbates a higher diffusion rate compared with conventional adsorbents such as activated carbon and carbon molecular sieve. Kinetic analysis suggests that the adsorption barriers mainly originated from the difficulty of VOC vapor molecules entering the pore channels of adsorbents. Therefore, its superior adsorption ability toward VOCs, together with a high diffusion rate, makes the ordered mesoporous carbon a promising potential adsorbent for VOC disposal.     

纳米片层状ZSM-5分子筛制备及其对室内环境VOCs吸附性能

合成了1种新型分子结构的bola型表面活性剂,并以其为模板,以正硅酸乙酯、偏铝酸钠为硅源和铝源,按n（NaOH）∶n（NaAlO₂）∶n（SiO₂）∶n（SDA）∶n（H₂O）为30∶2.5∶120∶5∶4800进行配比,采用水热法制备出具有纳米片层结构的ZSM-5分子筛（H-ZSM-5）。采用扫描电镜、透射电镜、X射线和N₂吸脱附等技术表征所制备的片层ZSM-5分子筛。对传统ZSM-5、H-ZSM-5进行了甲醛分子静态吸附实验,发现H-ZSM-5分子筛静态吸附量显著高于传统微孔ZSM-5。采用较大分子直径的甲苯蒸汽分子评价吸附性能发现,纳米片层状H-ZSM-5分子筛具备吸附较大分子直径VOCs的能力,可以用于室内较大分子VOCs的净化去除。     

Comparison of dynamic adsorption/desorption characteristics of toluene on different porous materials

Four different types of adsorbents, SBA-15, MCM-41, NaY and SiO₂, were used to study the dynamic adsorption/desorption of toluene. To further investigate the influence of pore structure on its adsorption performance, two SBA-15 samples with different microspores were also selected. It is shown that microporous material NaY has the largest adsorption capacity of 0.2873 mL/g, and the amorphous SiO₂ exhibits the least capacity of 0.1003 mL/g. MCM-41 also shows a lower break through capacity in spite of the relatively small pore diameter, because it can not provide the necessary small geometric confinement for the tiny adsorbates. However, the mesoporous SBA-15 silica with certain micropore volume shows relatively higher adsorption capacity than that of MCM-41 silica. The presence of micropores directly leads to an increase in the dynamic adsorption capacity of toluene. Although NaY has the highest adsorption capacity for toluene, its complete desorption temperature for toluene is high (>350℃), which limits its wide application. On the contrary, mesoporous silica materials exhibits a good desorption performance for volatile organic compounds at lower temperatures. Among these materials mesoporous SBA-15 samples, with a larger amount micropores and a lower desorption temperature, are a potentially interesting adsorbent for the removal of volatile organic compounds. This behavior should been related with the best synergetic effect of mesopores and micropores.