共查询到19条相似文献,搜索用时 250 毫秒
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钙基负载型固体碱催化酯交换反应活性评价 总被引:4,自引:0,他引:4
动植物油脂与醇通过酯交换反应制备生物柴油,目前,工业上一般采用NaOH、KOH、NaOCH,等均相催化剂。均相催化剂的缺点是产品后处理复杂,产生大量含碱含油工业废水。而非均相固体碱催化酯交换反应,产品与催化剂分离容易,产品不需要水洗,避免了大量废液的排放。采用非均相固体碱制备生物柴油的文献报道较多,但固体碱的碱中心数、碱中心强度对酯交换反应影响的报道较少。本研究制备了钙基负载型固体碱催化剂,重点研究钙基负载型固体碱的制备工艺条件对碱强度、碱量分布的影响,考察碱强度、碱量分布对催化菜籽油与甲醇的酯交换反应制备生物柴油转化率的影响。 相似文献
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以共沉淀法制备了一系列不同价态过渡金属(Fe、Cu、Zr)改性的Mg-Al固体碱催化剂,考察了其对于甲醇与碳酸丙烯酯(PC)酯交换合成碳酸二甲酯的反应性能。采用XRD、N_2吸附-脱附、FT-IR、XPS、CO_2-TPD等手段对催化剂的物理化学性质进行了表征。结果表明,催化剂的碱强度、碱密度是影响催化活性的主要因素,不同价态过渡金属的加入可以调控Mg-Al固体催化剂的碱性。在考察的催化剂中,FeMgAl催化剂具有最高的表面碱密度,因此,表现出最好的催化性能。在温度为65℃、时间为4 h、甲醇与PC物质的量比为10∶1、催化剂用量为4%的反应条件下,PC转化率可达66.2%。 相似文献
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应可持续发展与绿色化学的需要,非均相催化剂替代传统的均相催化剂引起研究者的广泛重视。其中,金属基介孔固体碱具有比表面积大、腐蚀性小、传质速率快、易分离等优点,是一种理想的绿色催化剂。本文综述了近年来制备不同的金属基介孔固体碱(包括MgO、类水滑石(HTs)及改性的Al2O3、ZrO2、CeO2)的研究进展,重点讨论了软模板法、硬模板法、溶剂挥发自组装法、无模板剂法等制备各种金属基介孔固体碱的方法和机理。此外,还介绍了金属基介孔氧化物在催化、储能与环境领域中的实际应用。最后,简要分析了金属基介孔固体碱制备过程中存在的问题,并展望其在未来的发展趋势,为新型金属基介孔固体碱的构筑提供了新的思路。 相似文献
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采用共沉淀、高温焙烧及KF掺杂Zn-Al类水滑石的方法制备了KF/Zn-Al固体碱催化剂。 通过正交试验考察了制备条件对KF/Zn-Al固体碱催化活性的影响,得到的优化条件为:陈化温度353 K、陈化时间16 h、焙烧温度823 K、焙烧时间6 h及m(KF)/m(Zn-Al)=1。 以优化条件下制备的KF/Zn-Al固体碱为催化剂,在n(醇)/n(油)=9、m(催化剂)/m(油)=0.04、反应温度338 K、反应时间0.5 h的条件下,菜籽油转化率可达97.75%。 采用TG DTG、BET、XRD、SEM技术及Hammett指示剂法对催化剂及其前驱体进行了表征。 对催化剂结构及表面性质与其活性之间的关系进行了讨论。 相似文献
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负载型KNO3固体碱对环戊二烯甲基化反应的催化作用 总被引:4,自引:0,他引:4
考察了负载型KNO3固体碱对环戊二烯(CPD)和甲醇的甲基化制备甲基环戊二烯(MCPD)反应的催化性能. 通过X射线衍射和低温氮吸附等手段研究了载体的表面性质和KNO3在不同载体表面的分解情况,并用非水溶液Hammett指示剂法测定了各固体碱的碱强度. 结果表明, KNO3负载在不同的氧化物载体上后其碱强度表现出极大的差异,负载在ZrO2, γ-Al2O3, 水滑石(HT)和MgO上能检测到H-为27.0的碱强度,这些碱性位可视为固体超强碱; 而负载在SiO2和TiO2上仅检测到了H-为9.3的碱强度,这与载体本身的表面性质密切相关. 碱强度较低的KNO3/SiO2和KNO3/TiO2以及氧化物载体本身在CPD甲基化反应中表现出较差的活性,说明催化剂应具有一定的碱强度,但是催化剂的酸性和比表面积也会对其催化活性产生一定的影响. 在所考察的催化剂中, KNO3/γ-Al2O3和KNO3/HT的催化性能最好,在450 ℃时就能催化转化约32%的CPD, MCPD的选择性可达86%左右,高于传统固体碱MgO在500 ℃时的活性. 相似文献
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Rupankar PairaArindam Maity Shyamal MondalSubhendu Naskar Krishnendu B. SahuPritam Saha Abhijit HazraE. Padmanaban Sukdeb BanerjeeNirup B. Mondal 《Tetrahedron letters》2011,52(14):1653-1657
Basic alumina supported solvent-free one-pot synthesis of pyridine-fused polycyclic diazepaniums was achieved under microwave irradiation. The process was successfully extended to the synthesis of pyridine-fused bicyclic imidazolidiniums and tetrahydro-pyrimidiniums and also of tri- and tetracyclic diaza-heterocycle-fused quinoliniums. The dual characteristic of basic alumina, a solid support as well as a base, was successfully employed in the current investigation. The method emerged to be an effective route in terms of product yield, reaction time, and ease of purification and most importantly for environment friendly protocols. 相似文献
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Mohammadreza Shokouhimehr Mehdi Shahedi Asl Babak Mazinani 《Research on Chemical Intermediates》2018,44(3):1617-1626
In this study, mesoporous silica materials with tuned pores and surface areas were successfully synthesized by adjusting the amount of applied hexane and controlling the hydrothermal temperature. The synthesized silica materials were then functionalized by an amine group to produce solid base catalysts and be applicable as efficient heterogeneous base catalysts for the Henry reaction. The mesoporous silica catalysts possessing large-pores and surface area expose their active catalytic sites and thereby improve contacts with reactants fulfilling the reactions expeditiously in comparison with solid base catalysts possessing small-pores and surface area. The results indicated that the yield of the products is significantly dependent on the structure of the applied solid base catalysts. The modulated large-pore solid base catalysts presented high catalytic activity in Henry reactions and could be reused for five consecutive cycles. 相似文献
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The enantioseparation of basic compounds represent a challenging task in modern SFC. Therefore this work is focused on development and optimization of fast SFC methods suitable for enantioseparation of 27 biologically active basic compounds of various structures. The influences of the co-solvent type as well as different mobile phase additives on retention, enantioselectivity and enantioresolution were investigated. Obtained results confirmed that the mobile phase additives, especially bases (or the mixture of base and acid), improve peak shape and enhance enantioresolution. The best results were achieved with isopropylamine or the mixture of isopropylamine and trifluoroacetic acid as additives. In addition, the effect of temperature and back pressure were evaluated to optimize the enantioseparation process. The immobilized amylose-based chiral stationary phase, i.e. tris(3,5-dimethylphenylcarbamate) derivative of amylose proved to be useful tool for the enantioseparation of a broad spectrum of chiral bases. The chromatographic conditions that yielded baseline enantioseparations of all tested compounds were discovered. The presented work can serve as a guide for simplifying the method development for enantioseparation of basic racemates in SFC. 相似文献
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The heterogeneous base-catalyzed transesterification for biodiesel synthesis has been studied intensively over the last decade.
This review classifies the solid base catalysts for transesterification into the following six categories based on Hattori’s
classification: single metal oxides, mixed metal oxides, zeolites, supported alkali/alkaline earth metals, clay minerals (hydrotalcites),
and non-oxides (organic solid bases). The catalysts in each category have acceptable catalytic activities overall, and follow
specific catalyst design rules, although not completely systematically, thereby drawing the best activity from them. In parallel,
each catalyst is not versatile and has some limitations specifically related to its catalytic structure and properties. This
review focuses on the heterogeneous base-catalyzed transesterification in terms of catalyst development, based on the published
research, especially over the last decade. 相似文献
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Li-ion solid electrolytes, which are compatible with metallic lithium anodes, are the key component of all solid-state batteries. Recently, the garnet Li7La3Zr2O12 solid electrolyte has experienced booming development and shown great potential for its excellent overall performance. However, further understanding of its stability with lithium is required for a longer battery lifetime. In this review, latest research work on the interface between garnet-type solid electrolytes and lithium is presented, including both mechanisms governing interface stability and interface engineering methods. The development prospects and potential directions for following research are also discussed in the last section. 相似文献
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二甲胺乙基膦酸钡新型固体碱催化剂的研究 总被引:6,自引:0,他引:6
首次用二甲胺乙基膦酸与氯化钡在碱性溶液中制得二甲脘乙基膦酸钡载体,用5%NaOH溶液处理该载体,制得相应的固体碱,并用元素分析,IR、TG、DTA、DTG对其进行了表征,用指示剂法,测得固体碱碱强度(H-)为9.3~15.0;采用苯甲酸滴定法,测定了载体2和固体碱3在水中的游离碱量;讨论了载体制备中,驾流时间对载体2和固体碱3在水中游离碱量的影响。将固体碱用于催化Konevenagel缩合反应,产 相似文献
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Fred W. Mader 《Macromolecular Symposia》1992,57(1):15-31
Environmental concern about waste problems and regulatory measures from the governments have increased during the last decade. Plastics waste management has become a major strategic issue for the European plastics industry. A statistical study provides data on plastics consumption, post-users plastics waste arisings based on a life-time analysis and plastics recovery in the year 1989. An end-use sectorial split-up into sectors like municipal solid waste, automotive waste, agricultural waste, construction, as well as large distribution waste, will serve as a base for an integrated plastics waste management concept including recycling of mono-material and co-mingled waste, chemical recycling, energy recovery and landfill. An overview gives examples for ongoing plastics recycling activities in Western Europe and an outlook to the year 2000 is presented. 相似文献
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Parezhati Pataer Turghun Muhammad Yunusjan Turahun Wenwu Yang Sailemayi Aihebaier Muyasier Wubulikasimu Lingxin Chen 《Journal of separation science》2019,42(8):1634-1643
We describe a stoichiometric approach to the synthesis of molecularly imprinted polymers specific for auramine O. Using the stoichiometric interaction in molecular imprinting, no excess of binding sites is necessary and binding sites are only located inside the imprinted cavities. The free base of the template was obtained to facilitate the interaction with the monomers. Itaconic acid was selected as the functional monomer, and stoichiometric ratio of the interaction with the free base was investigated. The molecularly imprinted polymer preparation conditions such as cross‐linker, molar ratio, porogen were optimized as divinylbenzene, 1:2:20 and chloroform/N,N‐dimethylformamide, respectively. Under the optimum conditions, a good imprinting effect and very high selectivity were achieved. A solid‐phase extraction method was developed using the molecularly imprinted polymers as a sorbent and extraction procedure was optimized. The solid‐phase extraction method showed a high extraction recovery for auramine O in its hydrochloride form and free form compared to its analogues. The results strongly indicated that stoichiometric imprinting is an efficient method for development of high selectivity molecularly imprinted polymers for auramine O. 相似文献