树枝状大分子催化剂的研究进展

回顾了功能树枝状大分子在催化作用领域的研究成就，重点就活性中心在核附 近的树枝状大分子和表面含催化官能团的树枝状大分子的结构与催化作用进行了讨 论，并对其应用前景进行了展望。     

钬对铂重整催化剂改性作用的研究

采用脉冲微反应技术研究了一系列Pt-Ho催化剂催化甲基环戊烷及环己烷的重整反应,应用Faraday磁天平研究了催化剂的磁性,用氢氧滴定法测定了催化剂上铂的分散度与平均粒径.结果表明,钬能改善活性组分铂的分散度,降低铂的平均粒径,从而增加铂催化剂的活性中心数,提高了铂重整催化剂的活性,进而增强了铂催化剂的抗硫稳定性.Pt-Ho催化剂的活性与磁性有对应关系.     

Steam Reforming of Methanol Over Pd-Zn Catalysts

Heating the physical mixtures of Pd and Zn selectively yielded PdZn or Pd_3.9Zn_6.1 alloy. These alloys were highly selective for the steam reforming of methanol.     

Scientific Foundations of the Theory of Catalytic Processes and Reactors

The problems of the theory of heterogeneous catalysis are discussed based on mathematical modeling of catalytic reactions, processes, and reactors. The combination of actual and computational experiments are used to develop mathematical models. The role of mathematics and especially qualitative methods for the analysis of nonlinear mathematical models is discussed.     

用于甲烷水蒸气重整的镍基催化剂的失活和再生

The deactivation of nickel catalysts used in Arak and Razi petrochemical complexes followed by catalyst regeneration was evalu-ated. The characterization of the different structures was made by powder X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),transmission electron microscopy(TEM),and carbon & sulfur analyzer. The Ni particle size was estimated from XRD patterns and TEM graphs. The agglomeration of nickel particle and the poison by sulfur components were recognized as the main reasons in deactivation of Arak and Razi catalysts,respectively. The activity of the used catalysts before and after regeneration was measured on methane steam reforming at a CH4:H2O ratio of 1:3 at 850 oC. The regeneration processes for Arak and Razi samples were performed with CO2 as an oxidative atmosphere and steam as a regenerating agent,respectively. The results show that,(1) no residual sulfur components were on the regenerated Razi catalyst surface without changing the structure of the catalyst and the regenerated catalyst has gained 80% of its catalytic activity,and that(2) the nickel particle size of regenerated Arak specimen decreased remarkably as measured by Debye-Scherrer equation from XRD patterns. TEM images were in agreement with the XRD results and indicated a decrease in nickel particle size of regenerated catalyst. Additionally,in both regenerated catalysts all the coke on the surface of the support was eliminated after regeneration.     

钙钛矿材料在固体氧化物燃料电池燃料重整中的应用

固体氧化物燃料电池（solid oxide fuel cell,SOFC）是通过电化学反应将化石燃料（煤、石油和天然气等）、生物质燃料或其它碳氢燃料中的化学能直接转换为电能的发电装置,能量转换效率更高、污染更低,被公认为21世纪高效绿色能源技术. 但直接以碳氢化合物为燃料时,镍基阳极中容易产生积碳,从而失去电化学催化活性. 在阳极外侧进行一次燃料的预重整是一种行之有效的解决办法,其中高效稳定的重整催化剂至关重要. 本文将结合本课题组的研究进展对钙钛矿催化剂在燃料重整中的应用进行概述,并提出自己相应的观点和展望.     

Steam Reforming Reactions of Methanol Over Nickel and Copper Catalysts

Steam-reforming reactions of methanol over NiO/Al₂O₃ and CuO/ZnO have been investigated. Over the nickel catalyst, the reaction rate is of zero kinetic order with respect to either methanol or steam, and the activation energy is 12.4 kJmol^?1, whereas with copper catalyst, the rate is expressed according to the literature as kP_a/(1 + K_aP_a + K_b+P_b) in which “a” and “b” are methanol and steam, respectively. The rate-controlling step of the reaction is assigned to the dissociation of O-H bond with dehydrogenation of C-H bond proceed rapidly to form carbon oxides. With copper catalyst the intrinsic participation of a water molecule during the dehydrogenation of C-H bond leads to the formation of carbon dioxide. With nickel catalyst, the dehydrogenation proceed more rapidly than the migration of a water molecule from an alumina site to a nickel site and causes almost exclusively the formation of carbon monoxide and hydrogen at a lower reaction temperature.     

Promotion Effects of Nickel Catalysts of Dry Reforming with Methane

The promotion effects of nickel catalyst of dry reforming with methane were extensively investigated by means of XRD, SEM, EDX, N₂‐adsorption and H₂‐adsorption. XRD characterization indicated that good dispersion of nickel oxide and MgO promoter is achieved over γ‐Al₂O₃ support. Addition of MgO promoter effectively retards the formation of NiAl₂O₄ phase. SEM and EDX analysis exhibited that the addition of rare‐earth metal oxide CeO₂ effectively promotes the Ni metal dispersion on the surface of the catalysts despite of undesirable self‐dispersion of CeO₂ promoter. Furthermore, the nickel component is gradually dispersed on the surface of the support following the exposure to reaction gas mixture for a period of time. The addition of MgO inhibited the self‐dispersion and promotion effect of CeO₂ on Ni dispersion on the catalysts. H₂ chemisorption revealed that the addition of the alkaline oxide MgO promoter significantly prohibits the metal dispersion on the catalyst. Inappropriate promoter addition can result in sharp decrease of the metal dispersion, N₂‐adsorption indicated that oxide promoter was mostly concentrated on the outer layer of the alumina support while the nickel metal was generally dispersed in the support pores. Addition of promoters contributed to more reduction in mesopore volume.     

用于甲烷分解和甲烷二氧化炭重整的碳材料催化剂研究进展

The decomposition and CO2 reforming of methane,respectively,are promising alternatives to industrial steam methane reforming. In recent years,research has been focused on the development of catalysts that can operate without getting deactivated by carbon deposition,where,in particular,carbon catalysts have shown positive results. In this work,the role of carbon materials in heterogeneous catalysis is assessed and publications on methane decomposition and CO2 reforming of methane over carbon materials are reviewed. The influence of textural properties(BET surface area and micropore volume,etc.) and oxygen surface groups on the catalytic activity of carbon materials are discussed. In addition,this review examines how activated carbon and carbon black catalysts,which are the most commonly used carbon catalysts,are deactivated. Characteristics of the carbon deposits from methane are discussed and the influence of the reactivity to CO2 of fresh carbon and carbonaceous deposits for high and steady conversion during CO2 reforming of CH4 are also considered.     

NiO/LaMnO3催化剂用于乙醇水蒸气重整反应

采用柠檬酸络合-浸渍法制备了NiO/LaMnO3钙钛矿型复合氧化物催化剂并将其应用于乙醇水蒸汽重整制氢反应, 考察了NiO含量、焙烧温度对催化剂性能的影响, 采用XRD、TPR和热分析等手段对催化剂进行了表征. 结果表明, 该催化剂具有高活性、高选择性和良好的稳定性. 催化剂中的NiO含量和焙烧温度对催化性能有显著影响. 在原料气体积组成为20%(体积分数, φ) C2H5OH 和水以及80%(φ)N2, 其中水醇摩尔比为3:1, 空速为80000 mL·h-1·g-1 cat, 反应温度为400 ℃时, 15%(质量分数, w)的NiO/LaMnO3上, 乙醇转化率接近100%. 关联催化剂活性和TPR及XRD实验结果, 发现催化剂的高活性源于由催化剂前驱体中进入钙钛矿型复合氧化物晶格中的镍离子被还原所得的金属镍.     

Characterization of Acid-Modified Alumina as a Support for Reforming Catalysts

The textural and acid–base characteristics of initial alumina and alumina modified with acetic acid at different concentrations (from 0.83 to 17.4 mol/L) were studied. It was found that treatment with acetic acid did not influence on the texture characteristics and phase composition of the supports. According to the IR-spectroscopic data on adsorbed CO, an increase in the concentration of medium-strength Lewis acid sites and an increase in the total acidity of the modified supports were observed, as compared with those of the initial alumina. Among the Pt‒Re systems, a catalyst based on the support treated with acetic acid at a concentration of 1.67 mol/L exhibited the highest activity in n-heptane reforming due to an optimal composition of the acid sites of the support.     

乙醇水蒸气重整Co/CeO2催化剂

 采用共沉淀法制备了Co/CeO2催化剂并将其应用于乙醇水蒸气重整制氢反应,考察了活性组分含量和焙烧温度对催化剂性能的影响. 结果表明,在原料气水∶乙醇∶N2摩尔比为3∶1∶16, 空速为40 L/(g·h)和反应温度为350～600 ℃的条件下, 经650 ℃焙烧的10%Co/CeO2催化剂对乙醇水蒸气重整制氢反应具有高活性和高选择性. 在500 ℃下进行的40 h稳定性测试中,该催化剂上的乙醇转化率始终接近100%, 反应后气体中的H2含量保持在65%左右. X射线衍射表征结果显示,焙烧后催化剂的主要物相组成为Co3O4和CeO2, 二者之间存在相互作用. Co/CeO2催化剂中钴的主要存在形式包括小晶粒的钴氧化物、大晶粒Co3O4和进入CeO2晶格的钴,Co3O4含量和焙烧温度的改变可影响催化剂中钴的存在形式. 由催化剂中高分散小晶粒的钴氧化物还原所得的金属钴是关键的活性组分.     

Dry Reforming of Methane Over Cobalt Catalysts: A Literature Review of Catalyst Development

Dry reforming of methane produces syngas with desirable H₂/CO ratio. Besides noble metal catalysts, the cobalt catalyst performs good activity in this reaction. However, carbon deposition and catalyst deactivation are becoming the main problems inhibiting the scale up of this process into industrial application. Recently, many scientists were trying to increase the activity as well as the stability toward coking by using variants of support, promoter, and combination of metal series catalyst. This paper presents a recent technology of methane dry reforming over cobalt metal-base catalyst, covering the catalyst activity and their resistance of catalyst deactivation.     

Electron‐rich O=PR3 compounds: Catalysts for alcohol silylation

The catalytic effect of a group of R₃P=O compounds was studied in a mild procedure for the silylation of primary alcohols, secondary alcohols, hindered secondary alcohols, and of hindered phenols in the presence of t‐butyldimethylsilyl chloride (TBDMSCl) and t‐butyldiphenylsilyl chloride (TBDPSCl). It was found that R₃P=O is an efficient catalyst in such reactions when R is a good electron‐donating group, such as Me₂N or n‐Bu and as an NMe(CH₂) moiety in N(CH₂CH₂NMe)₃P=O ( 3 ). However, R₃P=O is a weak or ineffective catalyst when R is a poor electron‐donating group, such as Ph or O‐n‐Bu or as a CH₂N‐o‐CH₂C₅H₄N moiety in N(CH₂CH₂N‐o‐CH₂C₅H₄N)₃P=O. Compound 3 , synthesized by oxidation of commercially available N(CH₂CH₂NMe)₃P, displayed the best catalytic properties for alcohol silylation in terms of efficiency, stability, and safety. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:21–26, 2001     

二甲醚水蒸气重整制氢的ZSM-5和Cu-Zn的复合催化体系

二甲醚水蒸气重整制氢反应是燃料电池理想的供氢方式之一.探讨了二甲醚水蒸气重整过程中的反应与反应、反应与传热的耦合协同效应.采用二甲醚水解催化剂ZSM-5(硅铝比为25)和甲醇水蒸气重整催化剂(Cu-Zn系列及商用Cu-Zn-Al催化剂)混合制得二甲醚水蒸气重整的复合催化剂.在固定床反应装置中评价了催化剂活性并对催化剂进行了透射电镜、X射线衍射及N2吸附表征.结果表明,复合催化剂的活性除了受催化剂组成和铜含量的影响外,还与Al和Zr的量有关.在Cu:Zn摩尔比为60:30时,Al和Zr的同时加入使催化剂中Cu晶粒分散最好,催化剂具有较高的低温活性,二甲醚在空速为4 922 ml/(g·h)和260℃下的转化率达到72%.     

二甲醚部分氧化重整制氢中的部分氧化催化剂的考察

采用浸渍法制备了一系列负载型贵金属催化剂,与Ni/Al2O3构成双床层催化剂,在连续流动固定床反应器中,进行了二甲醚(DME)部分氧化重整制氢的研究,系统地考察了贵金属类型及其负载量、载体以及还原温度与反应温度的影响.结果表明,Pd/Al2O3催化性能不及Pt/Al2O3和Rh/Al2O3,而Pt/Al2O3和Rh/Al2O3催化性能相当,考虑到价格因素,选择了Pt/Al2O3作为本反应催化剂.对Pt负载量的考察表明,0.5%Pt/Al2O3催化性能最佳,且Al2O3又比MgO和ZrO2更适合作载体.通过对工艺条件的考察,确定适当的还原温度与反应温度均为700℃.在上述最佳催化剂与反应条件下,DME转化率保持在100%,H2收率可达80%.     

Pathways to Better Stability of Catalysts for Reforming of Gasoline Fractions

Adsorbents AS-31 and AKD-981 based on zinc oxide and alumina are described. They are used in the purification of hydrogen-containing gas of reforming from hydrogen sulfide at 20–120°C and pressures up to 4 MPa. The second of these adsorbents is capable of forming weak adsorption complexes with hydrogen sulfide and can be recovered 2–3 more times than the first one. To remove sulfur-containing compounds from the gaseous feed of reforming at 350–450°C, the KAS-50 catalyst/adsorbent is proposed, which is prepared by mixing manganese dioxide and aluminum hydroxide. The sulfur capacity of this catalyst is 20%. New platinum–rhenium reforming catalysts KR-200 and KR-201 are proposed, which have higher stability when they work with purified feedstock. The concentration of the active catalyst is the same or lower, and these catalysts show better activity than their predecessors. All catalysts and adsorbents are tested and work in industry.     

CuO-ZnO-ZrO2催化甲醇水蒸汽重整反应机理和中间态

应用质谱在线技术,对CuO-ZnO-ZrO2催化甲醇水蒸汽重整（SRM）反应进行程序升温脱附（TPD）和程序升温表面反应（TPSR）研究.结果表明:在反应态催化剂表面,甲醇以分子吸附态形式存在,甲醇水蒸汽重整反应经历甲酸根中间物种.分别用CuO、CuO-ZnO、CuO-ZnO-ZrO2作催化剂,甲醇在气流中的摩尔分数分别高于5.4％、0.37％和0.17％时,甲酸根中间态的分解产物为CO2和H2;而甲醇在气流中的摩尔分数分别低于5.4％、0.37％和0.17％时,甲酸根中间态的分解产物为CO、CO2和H2.