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为提高Y分子筛对可挥发性有机废气的选择性吸附能力,采用高温水热处理技术对NaY分子筛进行骨架脱铝制备超稳Y分子筛(USY),并在固定床反应器中考察了USY在水汽存在下动态吸附低浓度甲苯的性能。结果表明,随着USY分子筛骨架Si/Al比的增加,虽然其微孔孔体积和比表面积发生了下降,但形成了较多的中孔结构。并且骨架硅含量增加后,USY对非极性的甲苯分子选择性吸附能力明显增加,当Si/Al为22左右,在相对湿度50%下,单位面积甲苯吸附量要比水吸附量大5.6倍。热重脱附研究表明,经过改性后,甲苯脱附温度可从NaY的300℃下降到超稳Y分子筛的160℃,具有优良的热再生性能。 相似文献
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采用不同后处理手段(碱处理、水汽处理以及碱处理-水汽处理)对HZSM-5沸石的孔结构和酸性质进行了调变,并对其丁烯裂解性能进行了研究。运用N2吸脱附、扫描电镜(SEM)、X射线衍射(XRD)以及吡啶吸附红外(Py-IR)对后处理改性前后的沸石样品的物理化学性质进行了表征。碱处理后HZSM-5的质子酸量增加,在5~20 nm处具有分布较宽的介孔,其反应活性升高,丙烯选择性下降,但失活速率没有加快。单独水汽处理在2~4 nm处产生介孔,但介孔体积较小。碱处理-水汽处理在2~4和5~20 nm处具有双分布介孔,前者分布较集中,后者分布较宽。单独水汽处理和碱处理-水汽处理的样品可以提高HZSM-5的丙烯选择性,主要归功于酸量的降低;反应2.5 h后具有较稳定的丙烯收率(高碱浓度处理-水汽处理的样品除外)。 相似文献
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将P改性用于甲醇制丙烯(MTP)反应ZSM-5分子筛的改性研究,以提高丙烯选择性和分子筛活性稳定性。采用XRD、SEM和NH_3-TPD表征催化剂物化性能。对不同硅铝比ZSM-5分子筛P改性研究发现,3种不同硅铝物质的量比(50、150和300)ZSM-5分子筛进行P改性时,在n(P)∶n(Al)=0.5~0.7时,ZSM-5分子筛改性后丙烯选择性和寿命得到提升。研究分子筛晶粒尺寸与P负载量关系时发现,随着分子筛晶粒尺寸的增大,位于分子筛表面的P含量逐渐增加,并且分子筛晶粒越小,最佳的P负载量越小。 相似文献
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《Inorganic chemistry communications》2003,6(6):623-625
Phthalocyaninatozinc(II) with cationic substituents was adsorbed on natural zeolites, clinoptiolite and mordenite, while it was not adsorbed on synthetic zeolites. The complex might be intercalated into a small amount of clay contained in the natural zeolites as an impurity. The complex-loaded zeolites acted as a sensitizer for photooxidation of bilirubin ditaurate in an aqueous solution. 相似文献
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采用水热原位法合成了不同硅铝比的ZSM-5分子筛,研究了硅铝比对ZSM-5分子筛结构和疏水性的影响。以典型的挥发性有机物甲苯为对象,在动态吸附实验装置上评价了ZSM-5分子筛吸附有机物的性能,并拟合了甲苯在疏水ZSM-5上的吸附等温线方程。结果表明,高硅铝比ZSM-5具有良好的疏水性,其静态水吸附容量为0.014 g·g-1,在高湿度条件下,甲苯浓度为1800 mg·m-3,GHSV为25000 ml·h-1·g-1,温度为35℃,甲苯穿透吸附容量为0.041 g·g-1,甲苯饱和吸附容量为0.075 g·g-1。吸附等温线的拟合显示,甲苯在疏水ZSM-5分子筛上的吸附符合Langmuir-Freundlich复合模型。 相似文献
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Fe改性HZSM-5分子筛上甲醇耦合C4烃制低碳烯烃反应性能研究 总被引:1,自引:0,他引:1
用等体积浸渍法制备Fe改性HZSM-5分子筛催化剂(Fe/HZSM-5)。考察了Fe/HZSM-5在不同温度下对甲醇耦合C4烃制低碳烯烃反应性能的影响,并利用紫外-可见漫反射光谱对Fe/HZSM-5进行了表征。结果表明,在低铁含量条件下,Fe改性HZSM-5分子筛上Fe(Ⅲ)主要以高分散隔离的形式存在于HZSM-5分子筛的表面,Fe改性提高了催化剂上的原料转化率以及乙烯和丙烯选择性,从而获得了较高的乙烯和丙烯总收率。在反应温度为550 ℃时,在Fe(Ⅲ)处理的HZSM-5分子筛上,乙烯和丙烯总收率最高可达42.1%,比未改性的HZSM-5提高了7%。 相似文献
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在常压、空速为1.5 h-1、反应温度为450℃条件下,考察了4种具有不同拓扑结构的分子筛(SAPO-34、ZSM-48、ZSM-5和beta)在甲醇转化制丙烯(MTP)反应中的催化性能,并对催化剂的积炭失活行为进行了研究。结果表明,从8元环到12元环,分子筛孔口尺寸越小,低碳烯烃(乙烯+丙烯)选择性越高,积炭失活速率也越快。孔道尺寸越大,丙烯/乙烯(P/E)比越高,但产物分布向C4以上组分偏移,丙烯选择性降低。10元环分子筛具有较高的丙烯选择性,但催化剂的积炭失活速率随孔道体系的不同有很大差异。一维直通孔道的ZSM-48容易积炭失活,而具有三维交叉孔结构的ZSM-5表现出了优异的抗积炭失活性能。不同结构分子筛在MTP反应中催化性能的差异主要归因于分子筛的过渡态择形和产物择形作用的不同。 相似文献
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To increase the light olefins selectivity of catalytic pyrolysis catalyst for heavy oil processing, the effects of large pore zeolite additions on the selectivity to light olefins (ethylene and propylene) were studied in a micro-activity test (MAT) unit at 625 °C by using Daqing heavy oil and n-decene/n-decane as feedstocks. Rare earth containing ultra-stable Y, Hβ and four types of alkali-treated Hβ with different pore size distributions were employed as the large pore zeolite components. The yields of C2–C3 light olefins showed a volcano trend with the increasing amount of large pore zeolite additions. They reached up to 24.5 and 26.7 wt%, respectively, when an optimum combination of zeolites ZSM-5 and RE-USY or ZSM-5 and alkali-treated Hβ was used. Moreover, increasing the pore size of large pore zeolites also led to the increases in the yields of light olefins, the maximum total yields of ethylene and propylene reached up to 26.7 wt% when the total pore volume of the zeolite Hβ added was 0.452 cm3 g−1. 相似文献
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采用密度泛函理论研究金属离子(La~(3+),Ce~(3+),Y~(3+),Ga~(3+),Cr~(3+),Zn~(2+),Cu~(2+))改性Y型分子筛的水热化学。结果表明,金属离子取代Y型分子筛骨架Al的能力较弱,以M(OH)(Z-1)+形式存在的金属离子能够进入分子筛β笼,且更倾向定位于β笼Ⅰ'位,增强分子筛Al和相邻骨架O原子之间的作用力,提高分子筛的结构稳定性。探讨制备金属离子改性Y型分子筛应考虑金属离子性能和金属离子与分子筛骨架元素的作用。 相似文献
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以碳酸二乙酯和乙二胺为原料,气固相催化合成N-乙基乙二胺。考察了不同催化剂(丝光沸石、β沸石、Y分子筛)、碱金属(Li、Na、K)离子改性的催化剂和反应条件对该烷基化反应的影响。结果表明,在实验所用的催化剂中,Y分子筛具有最高的催化活性;Y分子筛用不同阳离子改性后对反应有显著影响,其中,NaY分子筛催化效果最好;在反应温度为240℃,n(乙二胺)/n(碳酸二乙酯)=2,质量空速为15.8 h-1,氮气流速为120 mL/min的反应条件下,N-乙基乙二胺的产率可达93.1%。 相似文献
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E.O. Edney D. J. Driscoll W. S. Weathers T. E. Kleindienst T. S. Conver C. D. McIver 《Aerosol science and technology》2013,47(6):998-1008
A laboratory study was carried out to investigate the formation of polyketones in secondary organic aerosol from photooxidation of the aromatic hydrocarbon toluene, a major constituent of automobile exhaust. The laboratory experiments consisted of irradiating toluene/propylene/NO x /air mixtures in a smog chamber operated in the dynamic mode and collecting submicron secondary organic aerosol samples on Zefluor filters and on stainless steel disks in a low pressure cascade impactor. Carbonyl oxidation products in methanol extracts of the filters were derivatized using O-(2,3,4,5,6,-pentafluorobenzyl)-hydroxylamine, and the oxime derivatives were detected with a positive chemical ionization gas chromatography ion trap mass spectroscopy (GC-ITMS) system. Infrared spectra of the cascade impactor samples were used to determine the chemical functional group concentrations of the aerosol. The results of the GC-ITMS and infrared spectral analyses were consistent with the formation of multifunctional oxygenates, including hydroxy diones as well as triones, tetraones, and pentaones. 相似文献
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Fuping Tian Xin Sun Xinyi Liu Hongluan Zhang Jiaxu Liu Hongchen Guo Yifu Zhang Changgong Meng 《中国化学工程学报》2020,28(2):414-419
The adsorption removal of indole and quinoline in octane with and without toluene over zeolites NaY and Yttrium Ion-exchanged Y(YY) using batch adsorption experiments was studied at 25 ℃ and 0.1 MPa. YY was prepared by treating NaY with Y(NO_3)_3 solution twice via liquid ion-exchange method. NaY and YY were both characterized by XRD, SEM, N_2 adsorption, XRF, NH_3-TPD, and pyridine-FTIR techniques. Adsorption isotherms of indole, quinoline and toluene in octane were conducted at 25.0 ℃ to explain the influence of toluene on nitrogen removal over NaY and YY. The partial destruct of the crystalline structure of NaY was observed after the introduction of yttrium ion, which led to an evident decline in BET surface area and pore volume of YY. Strong Br?nsted acidity and medium Lewis acidity were introduced by yttrium ion-exchange. Though the specific surface area and pore volume of YY were much lower than those of NaY, YY exhibited equivalent adsorption capacities for indole and quinoline as NaY in model fuels without toluene. In the presence of 20 vol% toluene, however,YY exhibited much higher adsorption capacities for indole and quinoline than NaY, especially in the case of quinoline. The improved toluene-tolerant of YY was ascribed to the strong acid–base interaction between YY and quinoline and the decreased adsorption strength between YY and toluene. 相似文献
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本文详尽地讨论了几种典型超稳Y型分子筛的制备过程、特点及工业应用情况,并对我国今后的工作提出自己的看法。 相似文献
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Significant progress has been made in recent years regarding the photooxidation of olefin copolymers, but questions still remain. This paper reviews the progress and probes the photooxidative chemistry of ethylene–propylene (EP) and ethylene/propylene/diene monomer (EPDM) copolymers. Both stabilized and unstabilized polymer plaques were irradiated in a xenon are and the surface chemistry followed using infra-red spectroscopy. Model compounds were used to help elucidate the chemistry caused by unique structural features present in the copolymers. Volatile products evolved during photooxidation were determined giving valuable insight into the degradation chemistry. 相似文献