共查询到19条相似文献,搜索用时 125 毫秒
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本文介绍了固体碱性催化剂,特别是无机固体碱性催化剂的特点、分类。由于无机固体碱性催化剂具有的独特的优点和发展前景,受到广泛重视。文中按金属氧化物型、稀土金属氧化物型、复合金属氧化物型和载体型(惰性和半导体性)固体碱进行了分类,并分别进行了讨论。在文章最后部分还对纳米型催化剂作了简要的论述,指出了纳米催化剂的特点和优势。 相似文献
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竹炭基固体酸催化剂的制备及其催化性能研究 总被引:3,自引:0,他引:3
以4年生慈竹为炭源制备新型碳基固体强酸催化剂,以油酸与甲醇的酯化反应为模型反应主要考察了炭化温度、炭化时间、磺化温度和磺化时间等因素对其催化剂性能的影响。研究结果表明,以竹子作为碳源,利用硫酸合成碳基固体酸催化剂的最佳工艺条件为:碳化温度650℃,碳化时间6h,磺化温度140℃和磺化时间10h,在此条件下油酸与甲醇的酯化反应的转化率达到94.70%。竹炭基固体酸催化剂制备简单,催化酯化反应条件温和,克服了传统液体酸催化剂的缺点,具有良好的稳定性,且通过简单的过滤即可回收重复利用具有很好的应用前景。 相似文献
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从萤石结构型氧化物和钙钛矿结构型氧化物两个方面综述了固体氧化物燃料电池(SOFC)中电解质的研究进展.有关研究表明,掺杂剂的组成和掺杂量以及不同氧化物的结构对固体电解质的电导率和稳定性有着直接的影响.尽管目前已经进行了大量的关于固体电解质电导率促进作用机理的研究工作,但还未形成共识.同时,LaGaO3基钙钛矿型氧化物固体电解质具有广阔的应用前景. 相似文献
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分子筛又称沸石,沸石的研究始于18世纪50年代.瑞典矿物学家Cronstedt发现有一类天然硅铝酸盐矿物在灼烧时会产生泡沸现象,就称之为沸石.1883年Eichhorn首先观察到沸石的离子交换性并进行了应用.1936年,人们用酸洗过的天然粘土作为石油裂化催化剂,这是分子筛催化剂的先导.随后,又使用无定形的氧化硅-氧化铝固体,获得较高的裂化效果.20世纪50年代,美国联合碳化物公司(UCC)首次开发出合成沸石分子筛,主要用作干燥剂、净化剂、烃类分离.随后,各种类型的分子筛催化剂被合成或发现,广泛应用于石油和化工行业.分子筛催化剂是一种绿色、高效、可控性的催化剂,在国民经济发展中有着重要的战略地位.然而,很长一段时间,分子筛催化剂的合成不环保、不经济、能耗高,热稳定性和水热稳定性较差,催化效率不高,合成方法研究主要凭经验,主要用途限定于炼油和化工合成方面,且分子催化剂的回收利用研究较少,极大地制约了分子筛催化剂的发展和应用.近年来,分子筛催化剂的研究取得了长足的发展,合成方法更加经济、环保、节能,采用了数字化、信息化手段,分子筛催化剂的研究和合成更加高效,应用范围空前拓展,广泛应用于医疗、环保、电子等新型领域.本文综述了分子筛催化剂的发展历程、制备方法及应用,同时对分子筛催化剂未来发展趋势进行了展望. 相似文献
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Crystalline frameworks including primarily metal organic frameworks (MOF) and covalent organic frameworks (COF) have received much attention in the field of heterogeneous catalysts recently. Beyond providing large surface area and spatial confinement, these crystalline frameworks can be designed to either directly act as or influence the catalytic sites at molecular level. This approach offers a unique advantage to gain deeper insights of structure–activity correlations in solid materials, leading to new guiding principles for rational design of advanced solid catalysts for potential important applications related to energy and fine chemical synthesis. In this review, recent key progress achieved in designing MOF‐ and COF‐based molecular solid catalysts and the mechanistic understanding of the catalytic centers and associated reaction pathways are summarized. The state‐of‐the‐art rational design of MOF‐ and COF‐based solid catalysts in this review is grouped into seven different areas: (i) metalated linkers, (ii) metalated moieties anchored on linkers, (iii) organic moieties anchored on linkers, (iv) encapsulated single sites in pores, and (v) metal‐mode‐based active sites in MOFs. Along with this, some attention is paid to theoretical studies about the reaction mechanisms. Finally, technical challenges and possible solutions in applying these catalysts for practical applications are also presented. 相似文献
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木质纤维素是最丰富的可再生资源之一,具有低污染,广泛分布等优点,在化石资源日益枯竭的背景下,将其转化为高附加值化学品,为工业原料和能源油料提供可替代的资源是当前研究的一个热点,具有广阔的发展前景。文中详细综述了近年来国内外在木质纤维素液化中使用的催化剂类型、作用和研究进展,主要介绍了以浓硫酸为代表的液体无机酸,以NaOH为代表的固体无机碱,以草酸为代表的有机酸,以AlCl_3为代表的盐类和以Cl-/Fe_2O_3为代表的固体杂多酸;同时,分析、对比了不同类型催化剂的优点和缺点,预测了未来木质纤维素液化催化剂的发展趋势和前景。 相似文献
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Dong Liu Liming Dai Xuanni Lin Jian‐Feng Chen Jian Zhang Xinliang Feng Klaus Müllen Xiang Zhu Sheng Dai 《Advanced materials (Deerfield Beach, Fla.)》2019,31(13)
Highly active and durable catalysts play a key role in clean energy technologies. However, the high cost, low reserves, and poor stability of noble‐metal‐based catalysts have hindered the large‐scale development of renewable energy. Owing to their low cost, earth abundance, high activity, and excellent stability, carbon‐based metal‐free catalysts (CMFCs) are promising alternatives to precious‐metal‐based catalysts. Although many synthetic methods based on solution, surface/interface, solid state, and noncovalent chemistries have been developed for producing numerous CMFCs with diverse structures and functionalities, there is still a lack of effective approaches to precisely control the structures of active sites. Therefore, novel chemical approaches are needed for the development of highly active and durable CMFCs that are capable of replacing precious‐metal catalysts for large‐scale applications. Herein, a comprehensive and critical review on chemical approaches to CMFCs is given by summarizing important advancements, current challenges, and future perspectives in this emerging field. Through such a critical review, our understanding of CMFCs and the associated synthetic processes will be significantly increased. 相似文献
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掺杂镧的固体碱MgO/SBA-15催化大豆油制备生物柴油 总被引:1,自引:0,他引:1
采用浸渍法制备了掺杂镧的固体碱MgO/SBA-15催化剂,将其用于大豆油酯交换制备生物柴油的反应。XRD表征结果显示,活性组分在载体SiO2骨架中高度分散。考察了不同镧镁物质的量比、焙烧温度和催化剂用量等因素对催化剂性能的影响,发现镧的引入有利于催化剂与反应物的接触,从而提高催化剂的活性;镧和镁物质的量之比为0.5∶1,催化剂焙烧温度700℃,焙烧时间3h,催化剂质量分数为3%,反应时间3h时,生物柴油的产率达到95%以上。 相似文献
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《Current Opinion in Solid State & Materials Science》2013,17(3):115-125
The activity, selectivity and stability of solid catalysts depend critically on the details of their structure at all relevant length scales. Electron tomography (or 3D-TEM) has emerged as a powerful technique for nanostructural characterization. In this review we highlight recent advances in the field of electron tomography for the analysis of solid catalyst. Several examples demonstrate how unique quantitative information can be derived on relevant structural properties such as pore connectivity and corrugation, particle size distributions, and the 3D location of metal nanoparticles in porous oxide or carbon supports. The development of high-resolution imaging and novel reconstruction algorithms is promising to obtain atomically resolved electron tomograms of single catalyst nanoparticles. New reconstruction algorithms allow reconstruction from only a few projections, and hold potential for analyzing beam sensitive samples, as well as for time resolved electron tomography. Element specific or ‘chemical’ electron tomography, using electron energy-loss (EELS) or energy-dispersive X-ray spectroscopy (EDX), is an emerging tool for obtaining both chemical and structural information at nanoscale resolution. The rapid progress in electron tomography over the past few years holds great promise for detailed and quantitative insight into relevant nanostructural properties, thus allowing us to further develop our understanding of the relation between nanostructure and performance for catalysts and related materials. 相似文献
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A comparative study of thermal and catalytic degradation of polyethylene wastes has been carried out with the aim of obtaining chemical compounds with potential use in the chemical industry and the energy production. Polyethylene wastes were obtained from polyethylene bags used in supermarkets. Catalysts utilized in the study were silica gel, 5A molecular sieve and activated carbon. The pyrolysis was performed in a batch reactor at 450, 500 and 700 °C during 2h for each catalyst. The ratio catalyst/PE was 10% w/w and the solid and gaseous products were analyzed by gas chromatography and mass spectrometry. The optimum operation temperature and the influence of the three catalysts are discussed with regards to the products formed. The best temperature for degradation with silica gel and activated carbon as catalysts was 450 °C and with 5A molecular sieve was 700 °C. Degradation products of PE (solid fraction and gas fraction) are depending on temperature and catalyst used. External surface and structure of catalysts were visualized by Scanning Electron Microscopy (SEM) and the contribution on product distribution is commented. All products from different degradations could be used as feed stocks in chemical industry or in energy production based on the value of heat of combustion for solid fraction (45000 J/g), similar to the heat of combustion of commercial fuels. 相似文献
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木质素是自然界中含量仅次于纤维素的天然有机高分子,它是以3种苯丙烷(芥子醇、松柏醇和香豆醇)为结构单元,通过C-C和C-O-C键连接形成的无定形网状大分子,是自然界唯一可再生的芳香类物质原料。木质素在生产大宗化学品和精细化学品方面有着巨大潜力。但是,木质素复杂的结构导致其难以高效、高选择性转化而被有效利用。近年来,有关木质素催化降解液化的研究成为一个备受关注的热点。概述了木质素催化降解液化的研究现状,基于溶液状态下木质素分子尺度和形态分析,设计与之匹配的负载酸和金属粒子的介孔催化剂,可实现木质素在有限孔道内催化降解以及抑制降解片段重聚,最后对其未来发展趋势进行了展望。 相似文献