在仲丁醇脱氢反应中负载型铜催化剂的研究

采用浸渍法制备Cu/SiO₂和Cu-ZnO/SiO₂催化剂.研究了活性物种Cu和助剂ZnO的担载量对催化剂的结构和性能的影响,同时考察该催化剂对仲丁醇脱氢活性和选择性的影响.借助XRD和TPR对催化剂进行了表征,结果表明,高分散的Cu⁰为反应的活性中心,ZnO起到分散和稳定铜物种的作用.铜-锌之间的某种相互作用导致了缩合产物增加.     

气相法合成偏二氯乙烯的高稳定CsNO3/SiO2催化剂

用浸渍法制备CsNO₃/SiO₂催化剂,用于气相催化裂解1, 1, 2-三氯乙烷(TCE)制偏二氯乙烯(VDC)反应,考察了反应温度对CsNO₃/SiO₂催化剂失活的影响。研究发现,在较低反应温度( < 350 ℃)时, CsNO₃/SiO₂催化剂容易失活,在较高反应温度(> 400 ℃)时催化剂的活性较高且不易失活。反应后CsNO₃/SiO₂催化剂中CsNO₃物种转变为CsCl,催化剂表面存在积炭。导致催化剂失活的主要原因不是Cs物种转变和积炭,而是含氯反应产物在低温反应时难以从催化剂表面脱附。这些含氯反应产物能够高温脱附,从而使低温反应失活的催化剂再生。CsNO₃/SiO₂催化剂在400 ℃下100 h寿命实验中, TCE转化率和VDC选择性分别稳定为98%和78%,具有较好的工业应用前景。     

WO3/SiO2催化剂上2-丁烯与乙烯歧化制丙烯

采用浸渍法制备了WO₃/SiO₂催化剂,对其进行了UV-Vis DRS和NH₃-TPD表征。将WO₃/SiO₂作为催化剂,以乙烯和2-丁烯为原料制备丙烯,考察了反应温度、质量空速等因素对歧化反应的影响。实验结果表明,催化剂的最佳WO₃担载量为8 %;以8%WO₃/SiO₂ 为催化剂,在反应温度473K~573K、压力3.0MPa、质量空速1.6h^-1下,2-丁烯的转化率可保持在80%以上,丙烯的选择性大于89.2%。经过140h的稳定性实验,2-丁烯的转化率和丙烯的选择性略有下降,适当的提高反应温度（由473K增加到513K）可以恢复催化剂的活性。新鲜催化剂表面存在四面体、八面体六价钨物种和体相WO₃,适当还原的W物种是歧化活性物种;W负载在催化剂表面引入了新的强酸中心,同时明显增加了总酸量。     

溶胶-凝胶和浸渍法制备的铜催化剂在仲丁醇脱氢反应中的研究

采用溶胶-凝胶和浸渍法制备Cu/SiO2催化剂, 研究了不同制备方法对催化剂表面Cu物种的存在状态和其催化性能的影响. 采用BET, XRD, EPR和TPR等手段对催化剂进行了表征, 结果表明, 溶胶-凝胶法可制备高分散铜催化剂, 该催化剂中存在孤立的不可还原的Cu2+和可还原的Cu2+簇两种物种. 浸渍法制备的催化剂中含有可还原的Cu2+簇物种. 反应活性测试结果表明, 不可还原的孤立Cu2+呈高分散状态, 但其对仲丁醇脱氢反应没有活性; 可还原的Cu2+在反应过程中被还原成Cu0, Cu0是反应稳定脱氢的活性中心.     

硅源对蒸氨法制备Cu/SiO2催化剂催化甲醇裂解制氢的影响

采用蒸氨法制备Cu/SiO₂催化剂,分别考察气相二氧化硅（SiO₂-aer）、硅胶（SiO₂-gel）和碱性硅溶胶（SiO₂-sol）对Cu/SiO₂催化剂催化甲醇裂解制氢性能的影响,并采用N₂吸附-脱附、N₂O化学吸附、电感耦合等离子体原子发射光谱法（ICP-AES）、X射线衍射（XRD）、H₂程序升温还原（H₂-TPR）、透射电子显微镜（TEM）和X射线光电子能谱（XPS）等方法对催化剂进行表征。结果表明,硅源对Cu/SiO₂催化剂的活性具有较大影响。以碱性硅溶胶作为硅源制得的Cu/SiO₂-sol催化剂比表面积较大,活性中心粒径较小且分散均匀,这些使得其制氢性能优于其他两种硅源为载体所制备的催化剂。在反应温度280 ℃,反应压力1 MPa,甲醇质量空速0.6 h^-1的条件下,相较于Cu/SiO₂-aer和Cu/SiO₂-gel催化剂,Cu/SiO₂-sol催化剂的甲醇转化率分别提高10％和7％,气相副产物CH₄和CO₂浓度也有所降低,该催化剂上的甲醇转化率和气体收率分别达到98.4%和96.7%。     

Ir/SiO2上甲烷部分氧化制合成气反应的原位时间分辨红外和原位Raman光谱表征

采用原位时间分辨红外光谱和原位显微Raman光谱技术对Ir/SiO₂上甲烷部分氧化(POM)制合成气反应的初级产物和反应条件下催化剂表面物种进行了跟踪考察,实验结果表明,在H₂预还原的新鲜Ir/SiO₂表面,CO是V(CH₄):V(O₂):V(Ar)=2:1:45混合气反应的初级产物,因而甲烷的直接氧化过程是CO生成的主要途径;而在稳态反应条件下,CO生成的途径可能主要来自CO₂和H₂O与催化剂表面积碳物种(CHx)和/或CH₄的反应.催化剂上生成的积碳可能是导致稳态条件下Ir/SiO₂上POM反应机理不同于H₂预还原的新鲜催化剂的主要原因.     

氧化铝载体对Pt-Sn-K/γ-Al2O3催化剂上异丁烷脱氢性能的影响

采用盐酸回流法和氨水沉淀法合成了氧化铝载体,并通过络合真空浸渍法制备了不同来源氧化铝负载的Pt-Sn-K/γ-Al₂O₃催化剂。利用N₂物理吸附、CO脉冲吸附、H₂程序升温还原、NH₃程序升温脱附、热重等手段对Pt-Sn-K/γ-Al₂O₃催化剂进行了表征,以异丁烷脱氢为探针反应研究了氧化铝载体对该催化剂脱氢性能的影响。结果表明,与由盐酸回流法合成的载体制备的催化剂相比,采用氨水沉淀法合成的氧化铝载体制备的Pt-Sn-K/γ-Al₂O₃催化剂表面具有较小的Pt颗粒和较弱的酸性分布,其脱氢活性及异丁烯选择性更优。14 d的连续运行数据显示,由氨水沉淀合成的载体制备的催化剂,其抗积炭能力更强,反应后催化剂的积炭石墨化程度更低,因而具有更好的稳定性;在该催化剂上,异丁烷初始转化率为56.67%,14 d后仍能达到34.71%,异丁烯初始选择性为80%,7 d后维持在94%左右。     

ZnO-ZrO2催化剂上CO2辅助乙烷氧化脱氢制乙烯的研究(英文)

以焙烧商用氢氧化锆(Zr(OH)₄)得到的ZrO₂为载体,通过沉积-沉淀法制备了ZnO-ZrO₂催化剂,并在873 K下对该催化剂上CO₂辅助的乙烷氧化脱氢反应(CO₂-ODHE)的催化性能进行了评价。利用X射线衍射(XRD)、扫描电镜(SEM)、拉曼光谱(Raman)、高分辨透射电镜(HRTEM)、X射线光电子能谱(XPS)、CO₂程序升温脱附(CO₂-TPD)等技术对ZnO-ZrO₂催化剂的表面物理化学性质和形貌进行了表征。结果表明,在5%ZnO-ZrO₂催化剂上,ZnO掺入到了ZrO₂的表面晶格之中,在催化剂表面产生了高度分散的ZnO物种和氧缺陷区域。5%ZnO-ZrO₂催化剂可以选择性地剪裁乙烷C-H键,抑制C-C键的断裂,具备良好的催化性能。210μmol/(gcat·min)的C2H₄形成率可以与贵金属和过渡金属碳...     

不同载体对负载型Cu-Fe催化剂CO加氢反应性能的影响

以不同的氧化物为载体,采用共浸渍法制备了一系列负载型的Cu-Fe催化剂Cu-Fe/MO_x(MO_x=ZnO、ZrO₂、TiO₂、SiO₂、MgO、Al₂O₃),并采用X射线衍射(XRD)、N₂吸附(N₂-adsorption)、程序升温还原(H₂-TPR)和一氧化碳程序升温脱附(CO-TPD)技术对催化剂进行了表征。在温度为250℃、压力为3 MPa和原料气空速为6 000 mL/(g·h)的反应条件下,在连续流动微型固定床反应装置上考察了其催化CO加氢合成低碳醇的反应性能。结果表明,与其他氧化物为载体的催化剂相比,Cu-Fe/SiO₂催化剂表面CuO的分散度较高,在较低的温度下容易被还原,具有较强的CO吸附能力,从而同时具有较高的活性和低碳醇选择性。     

糠醛气相加氢制备糠醇Cu/SiO2催化剂的失活机理研究

采用共沉淀法制备了Cu/SiO₂催化剂，在固定床反应器上评价其糠醛气相催化加氢制备糠醇的反应性能，并采用XRD、H2-TPR、ICP-OES、XPS、TG、Raman、TEM等手段对使用后的Cu/SiO₂催化剂进行表征，研究其在反应中的失活机理。在常压、反应温度140℃、质量空速2.4 h^-1、氢醛比9.7的条件下，反应5 h内糠醛转化率均高于97%；反应6-21 h，糠醛转化率从96%快速下降到32%，说明Cu/SiO₂催化剂在糠醛加氢反应中快速失活，失活的主要原因是活性组分铜的团聚烧结和催化剂表面上积炭覆盖了反应活性位。     

负载型ZnO/SiO2及ZnO-SiO2溶胶凝胶催化剂的表面结构研究

催化剂的表面结构不仅影响催化剂的催化活性, 而且还影响反应产物的选择性[1]. 制备催化剂的方法不同, 其表面结构及表面性质也不同[2~4]. 浸渍法简单实用, 有利于得到高分散、晶粒细小的高比表面催化剂, 而溶胶-凝胶法则由于其制备温度较低, 易于形成无定形的或介态的氧化物相[5]而可达到分子级的混合, 其活性组分能有效地嵌入网状结构中, 不易受外界的影响而聚集或长大, 因此对催化剂的稳定性更为有利[6,7].     

Metal oxide-modified ZnO/SiO <Subscript>2</Subscript> catalysts for cyclo-dehydrogenation of ethylenediamine with propyleneglycol to 2-methylpyrazine

Metal oxide-modified ZnO /SiO2 catalysts were studied for the cyclo-dehydrogenation of ethylenediamine with propyleneglycol to 2-methylpyrazine at 633 K. The ZnO/SiO₂ catalyst showed fairly good ethylenediamine conversion and quantitative propyleneglycol conversion with about 60 mol% of 2-methylpyrazine selectivity, which is due to the existence of large amount of unconverted intermediate, 2-methylpiperazine. Metal oxide (CuO, NiO, Co₃O₄)-modified ZnO/SiO₂ catalysts were prepared to facilitate the dehydrogenation of 2-methylpiperazine to 2-methylpyrazine. About 82 mol% of 2-methylpyrazine selectivity was achieved on CuO and Co₃O₄ modified ZnO/SiO₂ catalysts, with significant increases of pyrazine selectivity. The catalytic properties of the metal oxidemodified ZnO/SiO₂ catalysts, pretreated with hydrogen gas as in the cyclo-dehydrogenation, were compared using the well-known probe reaction, the dehydrogenation/ dehydration of cyclohexanol to cyclohexanone or phenol/cyclohexene. The selectivities of pyrazine in the cyclo-dehydrogenation on the metal oxide-modified ZnO/SiO₂ catalysts were correlated with the phenol selectivities of the probe reaction. It is proposed that the metallic site of catalyst is responsible for the formation of pyrazine from ethylenediamine dimerization. The improved 2-methylpyrazine yield on CuO/ZnO/SiO₂ catalyst was explained by the proper adjustment of catalytic properties, which could be differentiated by the phenol selectivity in the cyclohexanol probe reaction. Thus, the large enhancement of 2-methylpiperazine dehydrogenation to 2-methylpyrazine and the suppression of excess pyrazine formation are supposed to occur on the metallic Cu formed in situ during the reaction during the cyclo-dehydrogenation of ethylenediamine with propyleneglycol.     

2-Methyl-3-butyn-2-ol conversion on AlPO4-cesium oxide (20 wt.%) catalysts obtained by impregnation with cesium chloride

2-Methyl-3-butyn-2-ol underwent almost exclusively dehydration to 3-methyl-3-buten-1-yne (acid activity) on pure AlPO₄, whereas its modification with cesium oxide developed AlPO₄-based materials with increased basic properties and hence, high selectivities to the base-catalyzed cleavage of MBOH yielding acetone and acetylene. At the same conversion level, catalysts obtained from cesium chloride exhibit higher selectivities to the base-catalyzed process than those obtained from cesium acetate.     

引入SiO2对SO4^2—／ZrO2超强酸体系的影响

用共沉淀法和负载法制备了一系列SO4^2-/ZrO2催化剂,详细研究了添加SiO2对SO4^2-/ZrO2超强酸样品的晶化、比表面、硫含量、超强酸性和异丙苯裂解及异丙醇脱水反应的影响。引入SiO2会延迟ZrO2的晶化和晶相转变,减弱SO4^2-/ZrO2体系的超强酸性,但对提高样品的异丙苯裂解和异丙醇脱水反应活性有利。     

A theoretical study of the dehydration and the dehydrogenation processes of alcohols on metal oxides using MOPAC

Using a semi-empirical molecular orbital method, PM3, and 2-propanol as an example, the dehydration and the dehydrogenation processes of alcohol on oxide catalysts were studied. The catalysts addressed here were four kinds of oxides (Al₂O₃, SiO₂, ZnO, CdO) whose reaction selectivities had been experimentally determined. The usual models consisting of a surface metal ion, several oxide ions and an isopropoxy group were used in calculations. For the dehydration, heats of formation of the models were calculated at each point of the process where the distance between a β-hydrogen of the group and a basic site (i.e. oxygen of the group or a surface oxide ion) or a metal ion was gradually shortened, or where the length of the C–O bond of the group was gradually increased. A reasonable dehydration mechanism was estimated by comparing activation energies calculated from the transitions of the heats of formation. The most probable dehydrogenation mechanism was also estimated in a similar way by gradually making an -hydrogen close to a surface oxide ion, the metal ion or a surface proton. It was concluded that the dehydration proceeds by scission of the C–O bond of the group after its oxygen was attacked by some electrophile on the surface and that the dehydrogenation proceeds by a mechanism in which an -hydrogen of the group was extracted by the metal ion.

Based on the dehydration mechanism thus deduced, alkoxy groups generated by adsorption of the primary, secondary and tertiary alcohols on SiO₂ were calculated in order to estimate the activation energies of their decompositions. In result, the order of the energies was found to be in good agreement with that of the decomposition rates experimentally determined by Kitahara. This agreement gives support to the validity of the mechanism deduced for the dehydration of alcohol.     

镍含量对NiO/SiO2气凝胶性能的影响

A series of NiO/SiO₂ aerogel catalysts were prepared by sol-gel method. The effects of the nickel content on the structure and existing forms of NiO/SiO₂ aerogel catalysts were investigated by using XRD, TPR and FT-IR. The results showed that there were interactions between NiO and SiO₂. But as nickel content increased, the in-teraction decreased. The nickel oxide in the catalysts appeared in different forms as nickel content was changed. When the content was less than 13%, Ni(Ⅱ) entered into the SiO₂ structure completely and it became clusters after calcining. If the content altered from 20% to 50%, NiO existed as both microcrystal and clusters, the later spices was dominating. However, when the content increased to 70%, microcrystal became the primary components.     

Al2（SO4）3／SiO2催化甲醇脱水合成二甲醚

采用浸渍法制备了不同负载量的Al2（SO4）3／SiO2催化剂．使用BET、XRD、FT—IR、异丙醇探针反应、NH3吸附量热和NH3吸附红外等手段对催化剂进行了表征,并测试了其在甲醇脱水合成二甲醚反应中的活性．BET、XRD和FT-IR结果表明,载体SiO2的表面积较高,随着Al2（SO4）3负载量的增加,样品的表面积逐渐降低,当Al2（SO4）3负载量高于20％时,样品表面开始出现晶相Al2（SO4）3．NH3吸附量热和NH3吸附红外结果表明,载体SiO2的酸性很弱,负载了Al2（SO4）3后,样品酸性大大增强,且酸性随着Al2（SO4）3负载量的增加先增强后减弱．样品表面同时存在B酸中心和L酸中心,但以B酸中心为主．Al2（SO4）3负载量为3％的样品的表面酸性最强,因而在甲醇脱水反应中表现出最高的反应活性,533K,甲醇转化率为83．5％,二甲醚选择性100％．     

制备工艺对NiFe2O4分解CO2活性的影响

随着大气中CO2浓度的增加,温室效应日趋严重,促使人们对大气中CO2的转化与消除这一课题更加重视。1990年Yutaka Tamaura[1]发现氧缺位磁铁矿几乎可以100%分解CO2后,为解决温室效应提供了一条新的探索途径。通过对不同铁酸盐MFe2O4(M=Fe,Mn[2],Co[3],Zn[4],Ni[5]等)分解CO2活性的考察,发现铁酸镍在300℃分解CO2的活性比其它铁酸盐都好。NiFe2O4的制备最常采用的是共沉淀法、柠檬酸溶胶凝胶法和水热法,3种方法由于制备