碱改性介-微孔HZSM-5分子筛催化乙醇脱水制乙烯性能

对两种不同硅铝比的HZSM-5分子筛进行碱处理,制备介-微孔复合HZSM-5分子筛,研究乙醇脱水制乙烯的催化性能,并考察碱溶液浓度和处理温度对HZSM-5分子筛孔结构和表面酸性的影响。结果表明,适宜的碱处理条件有利于分子筛发生骨架脱硅和脱铝,从而形成介孔。碱处理对硅铝比低的HZSM-5分子筛酸性质影响明显,而硅铝比高的HZSM-5分子筛在碱处理过程中酸性质变化不明显,更易发生脱硅和脱铝而形成更多介孔。碱改性介-微孔HZSM-5分子筛催化剂使乙醇脱水制乙烯催化性能得到改善,尤其低温催化活性提高,这主要归功于碱处理中介孔的形成和表面酸性的调变。     

中大孔催化裂化催化剂研究进展

发展中大孔型催化剂是催化裂化催化剂的主要发展方向之一,催化裂化催化剂中引入中大孔的主要方法有高岭土酸碱改性法、引入大孔硅铝基材料法、引入介孔分子筛法、原位晶化法和模板法。酸碱改性高岭土的孔结构受原料影响较大,孔径一般小于10 nm;制备大孔硅铝基材料替代拟薄水铝石可有效改善催化剂的孔结构,但应关注对催化剂强度的影响;分子筛中引入介孔又包括水热处理法,酸、碱处理法和引入不稳定位点法,工业应用范围广,但处理过程中易造成Y型分子筛结晶度下降,并缺乏连续、贯通型孔道;原位晶化法是工业上较成功的中大孔催化剂制备方法,但能耗相对高,流程长;模板法可通过改变模板类型、含量对催化剂孔结构调变,但应关注环保及催化剂强度问题。     

负载氧化铜的硅基分子筛的催化性能研究

通过浸渍法获得负载氧化铜的硅基介孔分子筛催化剂。通过XRD、TEM等手段对所合成的样品进行表征,并评价了所合成的催化剂在选择性氧化DMM合成DMC过程中的催化活性。研究结果表明:氧化铜为该探针反应的有效活性组分,其负载于硅基介孔分子筛所制备的催化剂与NHPI具有协同催化的效果。     

β分子筛催化剂的多异丙苯烷基转移性能研究

运用比表面分析、孔径分布、NH₃-TPD等方法测定了分子筛催化剂的孔结构及表面酸性质,采用固定床反应器对改性β分子筛催化剂的烷基转移性能进行了研究。结果表明,催化剂的酸性质及孔结构决定了其烷基转移性能。针对不同的烷基化反应,研究了用不同方法改性的β分子筛催化剂的烷基转移性能。     

液相硅沉积对乙醇制乙烯催化剂结构和稳定性的影响

利用XRD、NH3-TPD和TGA等方法考察了硅沉积处理对改性ZSM-5分子筛催化剂晶体结构、酸性和积碳的影响,并评价了处理前后催化剂在乙醇脱水制乙烯反应中的活性和稳定性.结果表明,硅沉积对改性ZSM-5分子筛预处理后,其晶体结构未发生明显变化;催化剂的总酸量有所下降,主要是强酸下降比例为原分子筛的53.7%;催化剂的乙醇转化率和乙烯产率分别维持在98%和90%;其催化活性和稳定性增强,并进一步表明过多的强酸位存留在催化剂上会引起积碳的生成,降低催化剂的稳定性,而硅沉积能除去了分子筛外表面的部分酸位.     

不同硅铝比HZSM-5催化正己烷耦合甲醇芳构化

在温度为400℃,压力为0.50 MPa,质量空速为1 h~(-1),甲醇与正己烷质量比为7/3的条件下,在50 mL固定床反应器中考察了5种不同硅铝比HZSM-5分子筛催化正己烷耦合甲醇芳构化反应的活性和稳定性,并对HZSM-5分子筛进行了X射线衍射(XRD)、N_2吸-脱附、NH_3程序升温脱附(NH_3-TPD)、扫描电镜(SEM)和吡啶吸附红外光谱(Py-IR)表征。研究结果表明:硅铝比低的HZSM-5分子筛作为催化剂时,产物中芳烃的选择性较大;硅铝比高的HZSM-5分子筛作为催化剂时,其反应稳定性较好。硅铝比为15时,芳烃选择性为49.7%,催化剂寿命为144 h;硅铝比为75时,芳烃选择性为27.7%,催化剂寿命为384 h。表征结果显示:不同硅铝比HZSM-5分子筛是由纳米尺寸的小晶粒构成,均具有MFI晶型结构,比表面积和孔体积相近;高硅铝比HZSM-5分子筛的中强酸量和Br?nsted酸量较小,反应温和,催化剂稳定性较好,不同硅铝比HZSM-5分子筛的酸量差异可能是造成催化性能不同的主要原因。     

环己酮肟贝克曼重排制己内酰胺绿色催化研究进展

己内酰胺是一种重要的有机化工原料,其传统的环己酮肟贝克曼重排制己内酰胺是以发烟硫酸为催化剂的生产工艺,存在污染环境、设备腐蚀以及成本高等缺点。综述了环己酮肟贝克曼重排反应制己内酰胺的绿色催化研究进展;介绍了氧化物催化剂、钛硅分子筛催化剂,及离子液体在催化中的应用;氧化物催化剂具有较好的催化活性,但存在寿命短、再生性差的缺点;TS-1型分子筛催化剂成本高,重现性差,工业化生产有待进一步研究;S-1型分子筛催化剂催化性能好,但反应条件较苛刻,使用寿命短;离子液体作为催化剂选择性不高。指出气相重排工艺绿色催化的高硅分子筛,特别是S-1型分子筛,具有较理想的催化效果,进一步提高全硅分子筛催化剂的选择性、延长使用寿命是今后研究的重点。     

含Ni介孔分子筛的合成及其对苯加氢催化性能

采用水热法合成出不含镍和含镍的硅基介孔分子筛.利用XRD、FT-IR、TPR、TEM和比表面孔径测定等手段对样品进行了表征.结果表明：合成出有序性好的介孔分子筛（MCM-41）,550 ℃焙烧可以将模板剂有效去除,所合成介孔分子筛负载Pt后介孔有序性降低,但是介孔结构仍然存在.苯催化加氢反应研究表明：不含Ni的介孔分子筛不具有加氢活性,当将其负载Pt后具有苯加氢催化活性;含Ni介孔分子筛本身具有苯加氢活性,含Ni介孔分子筛负载Pt后苯加氢催化活性有较大的提高,所有样品的环己烷选择性都接近100 %,说明含Ni介孔分子筛可以直接作为苯加氢反应的催化剂或作为苯加氢催化剂良好的载体.     

废聚苯乙烯裂解回收苯乙烯研究进展

对近年来国内外废聚苯乙(烯PS)的化学解聚制备苯乙烯单体的方法与工艺研究进展进行了综述,指出催化裂解是废PS裂解回收苯乙烯单体的有效途径,并对碱性中孔分子筛催化PS裂解进行了分析与展望,认为碱性中孔分子筛有望成为废PS裂解回收苯乙烯单体的有效催化剂,建议今后应在改善中孔分子筛催化剂的稳定性及酸碱性方面做进一步研究。     

Fe-ZSM-5@SiO_2的制备及脱硝性能研究

本文首先使用水热法合成的纳米Fe-ZSM-5分子筛,随后用聚二基二甲基氯化铵(PDDA)对分子筛表面进行预处理或直接加入到全硅的晶化体系中,得到核壳结构分子筛Fe-ZSM-5@Si O2。通过X射线衍射(XRD)、透射电镜(TEM)、扫描电镜(SEM)对样品的形貌结构进行分析,并在固定床反应器中对催化剂在NH3-SCR反应中的催化活性进行测试。     

废塑料化学转化制燃料的催化剂研究进展

在简要介绍和比较热裂解、催化裂解、热裂解-催化改质和催化裂解-催化改质4种废塑料化学转化制燃料基本方法的基础上,综述了近年来国内外在废塑料裂解催化剂和废塑料裂解产物改质催化剂的研究进展,重点讨论了催化剂酸性、比表面积、孔径以及负载金属离子的类型等对废塑料催化裂解和催化改质反应性能的影响,并介绍了聚烯烃（包括聚乙烯和聚丙烯）废塑料和聚苯乙烯废塑料热裂解和催化裂解的反应机理。最后对废塑料化学转化制燃料技术的研究与开发提出了一些建议,指出采用催化裂解-催化改质组合技术是未来废塑料化学转化制燃料过程的发展趋势,其今后的研究重点将是开发具有较强酸性和有利于大分子扩散与传质性能孔道结构的分子筛催化剂。     

Evaluation of various types of Al-MCM-41 materials as catalysts in biomass pyrolysis for the production of bio-fuels and chemicals

MCM-41, is one of the latest members of the mesoporous family of materials. They possess a hexagonal array of uniform mesopores (1.4–10 nm), high surface areas (>1000 m²/g) and moderate acidity. Due to these properties the MCM-41 materials are currently under study in a variety of processes as catalysts or catalyst supports. The objective of this study was to evaluate different types of MCM-41 materials as potential catalysts in the catalytic biomass pyrolysis process. We expected that the very high pore size and the mild acidity of these materials could be beneficial to reformulate the high molecular weight primary molecules from biomass pyrolysis producing useful chemical (and especially phenolic compounds) and lighter bio-oil with less heavy molecules. Three different samples of Al-MCM-41 materials (with different Si/Al ratio) and three metal containing mesoporous samples (Cu–Al-MCM-41, Fe–Al-MCM-41 and Zn–Al-MCM-41) have been synthesised, characterized and tested as catalysts in the biomass catalytic pyrolysis process using a fixed bed pyrolysis combined with a fixed catalytic reactor and two different types of biomass feeds. Compared to conventional (non-catalytic) pyrolysis, it was found that the presence of the MCM-41 material alters significantly the quality of the pyrolysis products. All catalysts were found to increase the amount of phenolic compounds, which are very important in the chemical (adhesives) industry. A low Si/Al ratio was found to have a positive effect on product yields and composition. Fe–Al-MCM-41 and Cu–Al-MCM-41 are the best metal-containing catalysts in terms of phenols production. The presence of the Al-MCM-41 material was also found to decrease the fraction of undesirable oxygenated compounds in the bio-oil produced, which is an indication that the bio-oil produced is more stable.     

生物质与废轮胎共热解及催化对热解油的影响

生物质稻壳与废轮胎以不同比例组成的均匀混合物在管式固定床内共热解,MCM-41和SBA-15作为催化剂,对产生的热解油性质进行了研究。结果表明,随着废轮胎在混合物中比例增加,热解油产率和热值在增加,而黏度和密度在降低。当稻壳占到60%（质量）时,热解液体产率为44.5%（质量）,热解油热值为40 MJ·kg-1,热值与柴油接近;温度对热解油的产率和组分柠檬精油的生成影响较大。对组成一定的混合物,在热解温度500℃时二者均达到最大。通过对热解油主要组分柠檬精油和氧含量的分析说明,共热解过程中组分间可以产生一定的相互作用,并具有协同效果,体现在柠檬精油组分的含量低于加权后的浓度,氧含量大于加权后的数值;与没有催化剂存在情况相比,MCM-41和SBA-15的存在能显著降低热解液体的黏度和密度,其中,SBA-15的降低效果更为明显。     

MCM-22沸石催化剂的苯与长链烯烃烷基化性能

用NH3-TPD法研究了4种不同硅铝摩尔比的MCM-22沸石的酸性质,在常压间歇式反应器中考察了它们在苯与长链烯烃烷基化反应中的催化性能,并与HY和HZSM-5沸石催化剂进行了比较。实验结果发现MCM-22的催化活性与其强酸量有一致的关系,与其硅铝摩尔比无对应关系;MCM-22的活性比HY低,但对2-P的选择性远远高于HY,这说明了MCM-22对2-P具有形状选择作用。     

Enhanced CuCl dispersion by regulating acidity of MCM-41 for catalytic oxycarbonylation of ethanol to diethyl carbonate

CuCl supported on molecular sieves has attracted increasing attention in catalyzing oxidative carbonylation of ethanol to diethyl carbonate. Mesoporous MCM-41 has been widely used as catalyst support due to its large surface area and well defined mesoporous structure. Considering its intrinsic weak acidity, MCM-41 was modified by a simple impregnation method to incorporate Al. The incorporation of Al components resulted in the high dispersion of Cu species and the increase of acid sites without changing the mesoporous structure of MCM-41, and thus enhanceed the catalytic activity of CuCl/MCM-41for diethyl carbonate synthesis.     

Esterification of bioplatform molecules over 12-tungstophosphoric acid anchored to MCM-41

The catalytic conversion of bio-platform molecules into desired products can be an important unit for the future biorefinery. The present contribution consists of synthesis of solid acid catalyst comprising 20 % 12-tungstophosphoric acid (TPA) and MCM-41 and its characterization by various physico-chemical techniques such as fourier transform infrared, X-ray diffraction surface area measurement (BET method), transmission electron microscopy and total acidity. The use of synthesized catalyst was explored for esterification of bio-platform molecules such as succinic acid and malonic acid with different alcohols. The catalyst shows high activity in terms of higher yields towards all diesters. The product selectivity towards the mono and diester was found to be the same for TPA alone and supported system, TPA₂/MCM-41, that also confirms the uniform distribution of the TPA on MCM-41. The excellent catalytic performance is attributed to the large surface area and pore diameter of the mesoporous support, MCM-41 as well as the Bronsted acid strength of TPA, as active sites. The catalyst shows the potential of being used as a recyclable catalytic material after simple regeneration without significant loss in activity.     

Preparation of mesoporous MCM-41 from natural sepiolite and its catalytic activity of cracking waste polystyrene plastics

Mesoporous MCM-41 was prepared by leaching of sepiolite and sequent hydrothermal synthesis in NaOH solution with hexadecyltrimethylammonium bromide as template. Small-angle X-ray diffraction patterns, Scanning electron microscopy, transmission electron microscopy and Brunauer–Emmett–Teller were performed to characterize the resulting compounds. The results showed that the crystallinity and pore size of MCM-41 increased with increase of crystallization time, ratios of surfactant to SiO₂ and decrease of Mg content. The experimental results of catalytic cracking of polystyrene waste showed that the MCM-41 with MgO from natural sepiolite had high catalytic activity and good selectivity to monomer styrene for the catalytic cracking of polystyrene when the ratio of waste plastics to MCM-41 was 200. The side reactions yielded ethylbenzene, isopropylbenzene, isopropenylbenzene and secondary cross-linking were suppressed by basic species MgO in MCM-41.     

Short Vapour Residence Time Catalytic Pyrolysis of Spruce Sawdust in a Bubbling Fluidized-Bed Reactor with HZSM-5 Catalysts

Catalytic pyrolysis of spruce sawdust was carried out in a bubbling fluidized-bed reactor using HZSM-5 catalysts. The effects of space velocity, catalyst deactivation, catalyst acidity and catalyst regeneration were studied. The use of catalysts decreased the yield of organic liquids compared to non-catalytic yields while the yields of pyrolytic water and gases increased. Decreasing the space velocity enhanced these effects. The rate of catalyst deactivation depended on the acidity of the catalyst, with more acidic catalysts deactivating more rapidly. Using a catalyst with a Si/Al ratio of 140 resulted in the largest changes in bio-oil properties. Periodic regeneration of the catalyst in the fluidized-bed reactor was also demonstrated using varying regeneration times and temperatures. It was shown that compared to BFB reactors, CFB reactor types would offer better operating characteristics for commercial scale catalytic pyrolysis processes in regard to vapour residence times, and catalyst activity and regeneration.     

Mesoporous silicas containing carboxylic acid: Preparation,thermal degradation,and catalytic performance

The calcination and thermal degradation behaviors of surfactants in mesoporous silicas SBA-15 and MCM-41 were investigated by FT-IR, ¹³C CP/MAS NMR, TG/DTA, and GPC. It was found that carboxylic acid-containing products were generated as active components in the mesopores of SBA-15 and MCM-41 from the triblock copolymer (PEO)₂₀(PPO)₇₀(PEO)₂₀ and cetyltrimethylammonium bromide (CTAB), respectively; the latter materials were used as templates. The carboxylic acid-containing mesoporous silica obtained showed a catalytic activity for hydrolysis of sucrose. The acidity was evaluated by means of NaOH titration. The acidity sensitively depended on both the calcination temperature and the atmosphere; the maximum appeared at 150 °C in air for SBA-15 where the highest activity was observed. However, the product in MCM-41 showed a lower catalytic activity than that in SBA-15. The SBA-15 product was easily leached from the mesopores of SBA-15 into the solution, but the degree of leaching for MCM-41 was considerably smaller than that for SBA-15.