下Pd/C催化剂催化 松香加氢反应的研究

在超临界CO₂条件下采用Pd/C催化剂进行催化松香加氢反应的研究。超临界CO₂条件与常规条件下反应产物相比较,产品中枞酸、去氢枞酸含量都较常规条件下的氢化松香产品低。详细考察了反应温度、反应时间、催化剂用量、催化剂重复使用对反应的影响。结果表明Pd/C催化剂中Pd的流失是造成催化剂失活的主要原因。     

超临界二氧化碳介质中的催化加氢反应

综述了超临界二氧化碳（SCCO2）介质中的催化加氢反应，包括不对称加氢、不饱和醛／酮加氢、油脂加氢、CO加氢（氢甲酰化反应）、CO2加氢和硝基化合物加氢。     

CO2催化加氢制备烯烃的研究进展

利用CO2作为碳源合成增值的化学品和燃料,特别是低碳烯烃,既可以减少大气中CO2浓度,又可以生产具有经济价值的化学原料,设计具有活性、选择性和稳定性的烯烃催化剂至关重要,本文综述了CO2热催化加氢的现状和研究进展.     

Heterogeneously Catalyzed Hydrogenation of Supercritical CO2 to Methanol

Interest in energy storage technologies is still increasing in times of excess of electricity generated by wind farms or solar plants. A key part of the energy storage technologies plays the efficient conversion of H₂ and CO₂ from renewable resources. Here, the process conditions for continuous catalytic hydrogenation of CO₂ to CH₃OH under supercritical conditions over lab‐synthesized Cu/ZnO/Al₂O₃ catalysts were investigated. A possible in situ phase separation of reaction products within the reactor due to the higher densities of the reaction mixture by the higher pressure could affect the kinetics and simplify downstream processing. The combination of thermodynamic studies and catalytic performance tests for CO₂ hydrogenation under supercritical conditions is discussed and a process concept is presented.     

SiO_2为载体负载Pd催化加氢合成3-三氟甲基苯胺

用浸渍法制得0.2%铁元素改性的SiO2为载体负载5%Pd催化剂,用于3-硝基三氟甲苯常压催化加氢合成3-三氟甲基苯胺,用沸点、元素分析、IR和1 H NMR对它的结构表征为目标产物;确定优化工艺条件为:0.1mol硝基物,0.26g催化剂,80mL无水乙醇作溶剂,反应温度为50℃,0.1MPa下加氢反应3h,收率为97.8%,产物的纯度达98.2%。     

Pd/C催化加氢法合成3,3’-二氯联苯胺

在碱性介质中,以Pd/C为催化剂,对邻硝基氟苯催化加氢制备2,2’-二氯氢化偶氮苯(DHB)进行研究,采用正交法对加氢还原进行了条件优化,优化条件为:反应温度65℃氢氧化钠质量浓度为:538g/l;Pd/C用量为4.0%;助催化剂NQON用量为2.67%。在该条件下催化剂可重复使用6次,所得产物DHB质量分数大于94.5%。在强酸性条件下,将DHB重排得5,3’二氯联苯胺盐酸盐,重排反应收率为90.0%,总收率85.0%。     

CO2加氢合成乙醇热力学分析及催化研究进展

综述了CO2的分子结构及性质、CO2加氢合成乙醇催化剂的催化性能和该反应的反应机理;还对CO2加氢合成乙醇反应进行了热力学分析,计算出不同反应条件下系统的平衡组成和CO2平衡转化率,并讨论了反应温度、压力及进料比对CO2平衡转化率的影响。结果表明,CO2平衡转化率随温度的升高而下降,增大反应体系的压力和采用高的氢碳比,对提高CO2平衡转化率有利。     

负载钯的磁性复合纳米颗粒的制备及其催化性能研究

本文首先合成SiO2包覆的磁性Fe3O4纳米颗粒(Fe3O4@SiO2),再通过硅烷偶联剂得到氨基修饰的纳米颗粒(Fe3O4@SiO2-NH2),该纳米颗粒再与Na2[Pd Cl4]反应将Pd负载在磁性纳米颗粒上,最后通过Na BH4还原得到了磁性纳米复合物Fe3O4@SiO2-NH2-Pd。利用红外、TEM和XRD技术对产物进行了表征。用UV-Vis对其催化4-硝基苯酚还原反应的性能进行了研究。结果表明,该纳米颗粒具有很好的催化性及重复利用性。     

CO Oxidation and Toluene Hydrogenation by Pt/TiO2 Catalysts Prepared from Dendrimer Encapsulated Nanoparticle Precursors

Generation 4 hydroxyl terminated polyamidoamine (PAMAM) dendrimer encapsulated nanoparticles (DENs) were examined as precursors for Pt/TiO₂ catalysts. In this preparation method, the dendrimers were initially used to template and stabilize Pt nanoparticles in solution. DENs were then deposited onto titania, and activation conditions for dendrimer thermolysis were examined. The interactions between PAMAM dendrimers and the titania were found to differ from previous reports of dendrimer-support interactions with silica, alumina, and zirconia. In the case of titania, the amide bonds were found to shift 100 cm^?1, indicating adsorption occurs primarily through amide–titania interactions. Infrared spectroscopy, CO oxidation catalysis, and toluene hydrogenation catalysis were used to evaluate protocols for removing the dendrimer. Thermal decomposition of the DENs in O₂ or CO/O₂ atmospheres led to the formation of surface isocyanates that were preferentially bound to the metal nanoparticles. CO oxidation catalysis was insensitive to the activation protocol used, and infrared spectroscopy of adsorbed CO showed only small differences in the basic surface properties of the resulting Pt catalysts. Toluene hydrogenation catalysis was more sensitive to different activation pretreatments. The most active hydrogenation catalysts resulted from short, low temperature (150 °C) hydrogen treatments while longer treatments at higher temperature (300 °C) resulted in slightly less active catalysts.     

超临界CO2中CO2参与的化学反应

超临界CO2中的化学反应是目前的研究热点之一。超临界CO2既为反应介质又为反应物的化学反应的主要优势是将萃取与反应相耦合形成均相体系,排除了传质阻力,提高了反应的速率和选择性;产物与催化剂易于分离;同时CO2作为反应原料无毒、不燃、易得,不但可以代替有机溶剂和有毒原材料,而且可有效利用CO2。介绍了超临界CO2作为反应原料所参与化学反应的类型及特点,简单综述了这些化学反应的研究进展,并对未来的发展提出展望。     

Development of a Novel Catalytic Membrane Reactor for Heterogeneous Catalysis in Supercritical CO2

A novel type of high-pressure membrane reactor has been developed for hydrogenation in supercritical carbon dioxide (scCO₂). The main objectives of the design of the reactor are the separate feeding of hydrogen and substrate in scCO₂ for safe reactions in a continuous flow process, and to reduce the reaction time. By using this new reactor, hydrogenation of cinnamaldehyde into hydrocinnamaldehyde has been successfully carried out with 100% selectivity at 50 °C in 10 MPa (H₂: 1 MPa, CO₂: 9 MPa) with a flow rate of substrate ranging from 0.05 to 1.0 mL/min.     

Pd/C催化加氢法制备DSD酸

用水作反应介质,Pd/C为催化剂,研究了液相催化加氢法还原4,4′ 二硝基二苯乙烯 2,2′ 二磺酸(DNS)制备4,4′ 二氨基二苯乙烯 2,2′ 二磺酸(DSD酸)。通过一系列条件实验,确定的最佳工艺条件是:原料DNS10g,质量浓度为180g/L;Pd/C催化剂0 8g;助催化剂OVN80mg;反应体系pH=6;反应温度65℃;压力0 8MPa。在此工艺条件下,制得产品的质量分数大于99%,产品收率可达95%。     

超临界CO2萃取鹤草芽浸膏的研究

研究利用超临界CO2从鹤草芽中萃取鹤草芽浸膏的工艺条件,考察了温度,压力,萃取剂用量等对浸膏收率的影响,结果表明,用超临界CO2从鹤草芽中萃取鹤草芽浸膏的最佳萃取工艺条件为：温度35－40℃,压力16MPa,萃取剂用量,每组实验300L左右。     

超临界二氧化碳中的分散聚合

在介绍以超临界二氧化碳(Sc-CO2)为介质的分散聚合的成粒机理的基础上,阐明分散剂在分散聚合中的稳定作用,着重综述分散剂的结构组成及用量对分散聚合树脂颗粒特性、聚合速率、产物分子量及分布等的影响,并展望Sc-CO2中分散聚合的研发和应用。     

Characteristics and Catalytic Properties of Pd/SiO2 Synthesized by One-step Flame Spray Pyrolysis in Liquid-phase Hydrogenation of 1-Heptyne

In this study, Pd/SiO₂ catalysts with 0.5–10 wt.% Pd loadings were prepared by one-step flame spray pyrolysis (FSP) and characterized by N₂ physisorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), CO chemisorption, and X-ray photoelectron spectroscopy (XPS). The average cluster/particles size of Pd as revealed by TEM were ca. 0.5–3 nm. The turnover frequencies (TOFs) of the flame-made catalysts decreased from 66.2 to 4.3 per s as Pd loading increased from 0.5 to 10 wt.%, suggesting that the catalytic activity was dependent on Pd particle/cluster size. However, there were no appreciable influences on 1-heptene selectivity. The flame-made Pd/SiO₂ showed better properties than the conventional prepared catalysts. Their advantages are not only the presence of large pores that facilitates diffusion of the reactants and products, but also the high-catalytic activity of as-synthesized catalysts so that further pretreatment is not necessary.     

Catalytic Olefin Epoxidation With H2O2 in Supercritical CO2. Synergic Effect by Hexafluoroacetone and Manganese‐Porphyrins

The heterogeneous oxidation of cyclooctene with hydrogen peroxide catalyzed by manganese 5,10,15,20‐tetrakis(2′,6′‐dichlorophenyl)porphyrinate, in the presence of hexafluoroacetone hydrate as co‐catalyst, has been studied in supercritical carbon dioxide, at 40 °C and 20 MPa. Under proper conditions, a complete olefin conversion may be obtained with the formation of cyclooctene oxide as the sole product. Fixation by hexafluoroacetone into its perhydrate derivatives provides a useful system to solubilize hydrogen peroxide in supercritical carbon dioxide, and to hamper catalyst bleaching and oxidant decomposition. Moreover, in the presence of both manganese‐porphyrin and hexafluoroacetone, the reaction rates are enhanced. Among the factors that may increase yields and rate of conversion, the use of a Teflon‐coated steel reactor rather than an uncoated one proved to be quite relevant, thus indicating the occurrence of a parasite radical decomposition of hydrogen peroxide promoted by steel reactor walls.     

液相催化加氢制备2-氨基苯甲醇

以2-硝基苯甲醇为原料,乙酸乙酯为溶剂,负载型Ni为催化剂,采用液相催化加氢制备了2-氨基苯甲醇,考察了溶剂种类、温度、压力和催化剂用量对反应的影响。结果表明,该反应的最优化的工艺条件是：以乙酸乙酯为溶剂,反应温度50～60℃,反应压力1．5MPa,m（催化荆）／m（2-硝基苯甲醇）=1：10。在此条件下,产品收率可达...     

以Pd/C为催化剂的松香加氢本征动力学

在温度403~433K,压力3.0～7.0MPa下,研究了以Pd/C为催化剂的松香催化加氢本征动力学,为工业反应过程的开发和操作提供了理论依据.通过减少催化剂粒度和提高搅拌转速,以消除内外扩散的影响,在松香加氢反应过程中,在线跟踪了反应物和产物浓度随反应时间的变化关系.根据实验数据,采用EVIEWS软件对10个可能的反应机理模型进行筛选,认为最可几的反应机理为松香中的主要成分枞酸分子不吸附,枞酸分子与催化剂表面上被吸附的氢原子进行反应,氢原子的吸附为控制步骤;其反应动力学方程为, 据此导出反应速率常数和吸附平衡常数分别为 (Hk =5.695exp((2498.5/T), bs =9.4(10(3exp(1920.8/T).