Liquid-phase degradation of HDPE over alkali-treated natural zeolite catalysts

Catalytic performance of alkali-treated natural zeolites was studied in the liquid-phase catalytic degradation of HDPE. Alkali treatment of natural zeolite with a moderate NaOH solution brought about the formation of mesopores and a decrease in acid site density, resulting in a considerable improvement of its catalytic activity. However, alkali treatment with highly concentrated NaOH solutions induced zeolite structure destruction, resulting in lower activity. HDPE conversion and product selectivity of alkali-treated natural zeolites were discussed in terms of their pore structures, acidities and the diffusion properties of large molecules.     

Modified Beta Zeolite as Catalyst for Fries Rearrangement Reaction

Modified beta zeolites were applied as catalysts for the Fries rearrangement reaction. The properties of the modified zeolites were characterized by NH₃-TPD, n-hexane and 1,2,4-trimethylbenzene adsorption. Modification with SiO₂ did not block the pores of the beta zeolite but reduced the number of acid sites on the surface. However, when the beta zeolite was modified with Ce₂O₃, the number of acid sites determined by NH₃-TPD increased, which indicated that new acid sites are created by the interaction of cerium oxide and zeolite. Modified beta zeolites and H-beta were applied as catalysts for the Fries rearrangement of phenol acetate. Reaction over H-beta has low selectivity and the catalyst is easily deactivated. SiO₂ modification of the catalyst increases the selectivity of the reaction but decreases the conversion. Ce₂O₃-modified beta zeolites show higher catalytic activity and rearrangement selectivity in the reaction than other catalysts. The stability of the catalyst is also improved after Ce₂O₃ modification. About 70% selectivity and 60-80% conversion can be achieved over 16 wt% Ce₂O₃-modified beta zeolite.     

生物基乳酸(酯)制丙烯酸的工艺研究

以乳酸（酯）脱水反应为模型反应,分别考察了X、Y、ZSM-5和SBA等分子筛、硫酸盐、磷酸盐以及复配催化剂的催化性能。结果表明,适当调节分子筛催化剂的酸碱度,实现多种催化剂的复配应用,催化剂性能较好,丙烯酸及其酯的总选择性达80.3%。     

One-Step Synthesis of Dimethyl Ether from Syngas with Fe-Modified Zeolite ZSM-5 as Dehydration Catalyst

A number of Fe-containing ZSM-5 zeolites, such as HFeZSM-5 and HFeAlZSM-5 prepared by hydrothermal synthesis and Fe-modified ZSM-5 through solid-state ion-exchange, were adopted as methanol dehydration catalysts for syngas to dimethyl ether (STD) process. Their structures, acidic and basic properties were characterized by XRD, ESR, ICP-AES, TPD and FT-IR. Among these Fe-containing zeolites, the Fe-modified ZSM-5 displayed the highest dimethyl ether selectivity, least CO₂ production. Some correlations between catalytic performance and acidity and basicity of Fe-containing ZSM-5 zeolite were discussed.     

丁烯异构化催化剂镁碱沸石的合成研究进展

在丁烯异构化反应催化剂中,镁碱沸石分子筛由于具有十元环和八元环交错的独特的二维孔道结构、良好的水热稳定性和化学稳定性、较高的选择性等诸多优点受到广泛关注;但由于有机模板剂的影响,在环境友好方面有所欠缺。本文综述了镁碱沸石（FER）的合成方法：有机模板剂合成法、非模板剂合成法、层状前体合成法、乳化剂控制合成法,归纳比较了各种合成方法的优缺点,阐述了FER的合成后处理方式,指出采用无毒无害的原材料替代有机合成模板剂,从而提高镁碱沸石分子筛的催化性能,对环境友好大大改善,是未来研究镁碱沸石分子筛催化剂的发展方向之一。     

多级孔沸石分子筛的制备及其催化应用研究进展

多级孔沸石分子筛在保留了微孔沸石优异的催化活性与择形性的同时,能够从本质上大幅提升沸石分子筛的传质与扩散效率,改善催化剂因积炭问题失活较快的弊端。本文介绍了当前阶段多级孔沸石分子筛的研究现状,主要基于孔径大小的差异,重点综述了微孔-介孔、微孔-大孔以及微孔-介孔-大孔三类具有多级孔道结构的沸石分子筛在制备及催化应用方面的最新研究进展,综合分析了各种制备方法在性能、成本、可操作性及应用上的利弊关系,并且指出,设计并可控地制备出具有多级孔道结构且在三维空间高度贯通的多级孔沸石分子筛材料以最大限度地提高催化效率,将会是未来多级孔沸石分子筛领域的研究重点。     

磺酸化碳材料负载Ru催化剂催化纤维素水解/加氢反应

采用纤维素衍生碳、活性炭和介孔碳材料CMK-3为不同碳源前驱体,在不同磺酸化条件下制备磺酸化碳材料负载Ru的双功能催化剂,并用FTIR光谱、XRD、元素分析、热重分析、N₂物理吸附 脱附进行了表征,考察了其对纤维素加氢反应的催化活性。结果表明：相比于纤维素衍生化碳,活性炭和介孔碳CMK-3为碳源经过磺酸化后制备的催化剂具有较强的结合-SO₃H的能力和较高的催化活性,对多元醇具有良好的选择性,170 ℃下反应10 h六元醇的收率可高达84.0%。在循环使用时,磺酸化活性炭负载Ru催化剂催化活性有所降低,但可以保持对多元醇的选择性;而磺酸化介孔碳负载Ru催化剂存在少量S流失,转化率基本不变,但产物的选择性有所降低。     

Comparison of protonated zeolites with various dimensionalities for the liquid phase alkylation of i-butane with 2-butene

This study focused on the effects of structure on the catalytic performance of various three-, two-, and one-dimensional zeolites. The alkylation of isobutane with 2-butene was carried out under both mild and severe conditions with respect to the feed flow rate. It was observed that zeolite beta outperformed the other zeolites, exhibiting high olefin conversion and alkylate selectivity. For the olefin WHSV used in this work, LTL and USY deactivated rapidly. It is proposed that their fast deactivation was a result of the periodic expansions of their respective pore structures. In contrast to the behavior of other zeolites, the C₈ selectivities almost remained high and constant over LTL. The one-dimensional ZSM-12 was found to outperform in terms of activity many of the samples in this study because of its unique pore structure. A study of the carbonaceous material formed inside the zeolites pores discovered that their composition also depended on the zeolite pore structure. The results of this study indicate that the ability of certain zeolites to inhibit the formation of coke precursors because of their particular pore structures is an important parameter.     

硅源对ZSM-5分子筛合成和催化性能的影响

为了考察硅源对ZSM-5分子筛合成和催化性能的影响,分别采用白炭黑、硅胶、硅溶胶和单分散SiO₂为硅源合成ZSM-5分子筛,对合成的ZSM-5分子筛进行XRD、SEM、BET和NH₃-TPD表征,并以C₄烯烃为原料评价合成的ZSM-5分子筛的催化裂解性能。结果表明,以硅溶胶为硅源合成的ZSM-5分子筛具有较好的结晶度和催化活性。水热处理使分子筛酸量减少,孔容缩小,改善了分子筛的乙烯丙烯选择性。经600 ℃水热处理4 h的ZSM-5分子筛在常压、580 ℃和空速9 h^-1反应条件下,丁烯催化裂解为乙烯和丙烯平均转化率为90.2%,乙烯和丙烯总收率达61.1%。     

酸催化山梨醇脱水制异山梨醇的研究进展

异山梨醇是一种生物基功能性二元醇,近年来因其在聚合物工业中的潜在应用价值而备受关注。山梨醇脱水反应是生物质转化合成异山梨醇的关键步骤,目前普遍采用酸催化体系,且在酸性催化剂开发及工艺研究方面均取得了良好进展。本工作主要介绍了已报道的酸性催化剂结构与性质对催化活性及选择性的影响,指出强酸性均相催化剂具有高催化活性,但腐蚀性强,且不易循环利用;多相催化剂催化活性与酸性位点、酸度、酸容量、孔结构、表面性质和结构等都有关系,且这些性质随催化剂组成和结构改变而相互影响。针对目前山梨醇脱水反应催化剂均相催化腐蚀性强、催化剂循环性差,多相催化剂催化活性不高的现状,高催化活性可循环使用的离子液体催化剂是一种具有发展潜力的均相催化剂,对多相催化剂构效关系还应进行更多的研究以指导新型催化剂的开发。     

酸处理改性Hβ分子筛催化合成乙基蒽醌

采用微波辐射法,对Hβ分子筛进行酸处理改性,并通过NH₃-TPD、XRD和吡啶－IR对分子筛进行表征,考察改性前后分子筛酸性质和晶相变化,采用改性的Hβ分子筛催化乙苯和苯酐合成乙基蒽醌。结果表明,无机酸改性分子筛时,由于酸性太强,溶解了大量分子筛的铝物种,减小了分子筛固有的酸催化中心数,使分子筛的催化活性大幅度下降,不适合作为Hβ分子筛的改性试剂。有机酸对Hβ分子筛的改性效果较好,以0.1 mol·L^-1马来酸处理后的分子筛催化效果最好,苯酐转化率为51.53%,乙基蒽醌选择性为39.10%,乙基蒽醌收率最高可达20.15%。采用马来酸和Ce(NO₃)·6H₂O复合改性分子筛,乙基蒽醌选择性为54.0%,乙基蒽醌收率最高可达23.5%,选择性比马来酸单独改性时提高约15个百分点,催化效果明显提高。     

The effect of P/Ta ratio on sorbitol dehydration over modified tantalum oxide by phosphoric acid

A series of modified hydrated tantalum oxides (Ta₂O₅·nH₂O) with various contents of phosphoric acid were prepared and firstly used as the catalysts for sorbitol dehydration to isosorbide. The catalytic performance of Ta₂O₅ was improved significantly after modification, and the isosorbide selectivity over 0.8P/TaO was improved from 3.8 to 48.3% with nearly 100% sorbitol conversion. Characterization with NH₃-TPD, FT-IR, Raman and XRD demonstrated that the introduction of phosphate has transformed Ta₂O₅ into two kinds of new crystalline phases exhibiting various surface acidities. The P-OH species in TaH(PO₄)₂ were mainly responsible for the promotion of catalytic performance over modified oxides.     

甲醇气相脱水制二甲醚催化剂研究进展

甲醇气相脱水制二甲醚反应为固体酸催化反应,常用的固体酸催化剂有γ-Al₂O₃和分子筛类。γ-Al₂O₃表面存在弱酸中心或中等强度酸中心,催化剂有较好的初始催化活性,但活化所需的反应温度较高,耐水稳定性差;分子筛类催化剂表面有许多强酸性位,低温下催化活性较高,但在高温反应条件下易产生烃类副产物和积炭,热稳定性差。为改善这两类催化剂的催化性能,对催化剂进行了各种改性研究,改性后催化剂的活性、选择性和稳定性均有一定程度提高。综述了近年来在γ-Al₂O₃和分子筛催化剂上进行的改性研究,总结并展望了甲醇脱水催化剂的发展方向。     

H3PW12O40/SiO2 for sorbitol dehydration to isosorbide: High efficient and reusable solid acid catalyst

Tungstophosphoric acids (PW) supported on various metal oxides (SiO₂, γ-Al₂O₃, TiO₂, ZrO₂ and CeO₂) were synthesized and used as catalysts for sorbitol dehydration to isosorbide for the first time. 30% PW/SiO₂ exhibited the best catalytic performance for sorbitol dehydration, over which 56% isosorbide selectivity could be gained at a 95% sorbitol conversion at 250 °C. The catalytic performance of regenerated 30% PW/SiO₂ catalysts by dichloromethane elution showed no loss after recycling five runs. Characterizations with UV-Vis, XRD, NH₃-TPD and thermal analysis techniques revealed that PW had a good dispersion, and the primary Keggin structure was preserved after supporting PW on different supports. The interaction between PW and oxides resulted in different acidity of catalysts, which affected conversion of sorbitol and selectivity for isosorbide. The final acidity order of supported PW catalysts was the following: SiO₂>γ-Al₂O₃>TiO₂ ≈ ZrO₂>CeO₂.     

改性分子筛催化乳酸甲酯的脱水反应

通过生物基路线制备丙烯酸及酯具有潜在的经济效益.同时对化石资源的绿色替代具有重要意义.考察了X.Y.ZSM-5等沸石分子筛经过钾、钙、钻等金属离子交换改性后,在乳酸甲酯脱水制备生物基丙烯酸甲酯过程中的催化性能.试验结果表明K离子改性Y沸石分子筛对产物的选择性高,而ZSM-5类具有较高的转化率,但是选择性低.分析结果说明:Y分子筛催化剂的高选择性与其特有的骨架结构相关.沸石分子筛催化剂需要通过金属离子的交换才能调整到适当的酸碱性实现最佳催化的效果.在上述结论的基础上.以钾离子改性的NaY分子筛为催化剂,对反应温度.反应空适等反应条件进行了优化得到了较高的丙烯酸甲酯得率.     

不同结构分子筛的甲醇制丙烯催化性能

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。     

Sulfated tin oxide as an efficient solid acid catalyst for liquid phase selective dehydration of sorbitol to isosorbide

Sulfated tin oxides (STO) with different sulfur content (1–8 wt%) were prepared via straightforward thermal decomposition of stannous sulfate. The catalyst performances of STO were investigated in liquid phase dehydration of sorbitol under solvent free condition. The calcination temperature of STO affected sulfur content and isosorbide selectivity. The STO exhibited high catalytic activity compared to sulfated zirconia affording complete conversion of sorbitol with 65% isosorbide selectivity in 2 h at 180 °C. Effects of reaction temperature, catalyst amount and reaction time on conversion and selectivity were studied and the catalyst was also reused.     

Sn-Beta沸石合成研究进展

含强L酸中心的Sn-Beta沸石在生物质平台化合物转化中表现出独特的活性和选择性,具有广阔的应用前景。Sn-Beta沸石主要合成方法有干胶法、水热法和同晶取代法。不同方法制备的Sn-Beta沸石Sn活性位的微环境及酸性质存在差异,在反应中表现出不同的反应性能。主要介绍Sn-Beta沸石合成方法及控制合成的影响因素。     

Arenesulfonic acid functionalized ordered mesoporous silica as solid acid catalyst for solvent free dehydration of sorbitol to isosorbide

Organosulfonic acid functionalized ordered mesoporous silicas with different moieties have been synthesized and used as solid acid catalysts for solvent free dehydration of sorbitol to isosorbide. In screening experiments with distinct solid acids, the arenesulfonic acid functionalized SBA-15 (Ar/SBA-15) showed higher catalyst performance as compared to propyl and fluorosulfonic acid sites. Under optimum reaction condition, Ar/SBA-15 afforded 100% sorbitol conversion with 71% isosorbide selectivity in 2 h at moderate temperature of 170 °C. The high activity of catalyst ascribed to its ordered mesoporous structure and ease to access Brönsted acid sites with high acid strength.     

基于固体酸的纤维素非均相催化糖化的研究进展

作为纤维素水解产物,葡萄糖可进一步反应产生果糖、山梨醇、糠醛、乙酰丙酸等重要能源物质和基础平台化合物,因此高效催化纤维素定向转化为葡萄糖对获得高附加值化学品具有重要意义。本文从催化剂的物理化学结构与催化性能之间相互影响关系的角度,综述了磺化固体酸、氢型沸石、金属氧化物、负载金属和杂多酸5种主要非均相催化剂近年来的研究进展及未来的发展方向,分析得出以上催化剂具备易于与水解产物分离、高回收率、稳定的催化活性以及环境友好等明显优势,但仍存在与纤维素接触困难、活性组分容易损失等问题,指出通过引入活性官能团使催化剂兼有纤维素吸附、溶解和水解能力及利用官能团内部作用或固载使催化剂减少组分损失是纤维素非均相催化剂的发展方向。