Catalytic Combustion of Ethyl Acetate over Nanostructure Cobalt Supported ZSM-5 Zeolite Catalysts

Gas phase catalytic combustion of ethyl acetate, as one of volatile organic compounds (VOC), was studied on nanostructure ZSM-5, HZSM-5 and Co-ZSM-5 with different cobalt loadings. Nanostructure of ZSM-5 was determined by XRD, SEM and TEM. Catalytic studies were carried out under atmospheric pressure in a fixed bed reactor. Results showed that the Co-ZSM-5 catalysts had better activity than others and at temperatures below 350 ℃, amount of Co loading was more effective on catalytic activity. The order of conversion of ethyl acetate over different Co loading is as follows: Co-ZSM-5 (0.75 wt%)＜Co-ZSM-5 (1.5 wt%)＜Co-ZSM-5 (15 wt%)＜Co-ZSM-5 (2.8 wt%). Besides the higher the inlet concentration of ethyl acetate, the lower the conversion yield, and oxygen concentration in catalytic oxidation conditions has not so large influence on conversion. Furthermore, the presence of water vapor in inlet gaseous feed has an inhibitive effect on ethyl acetate conversion and at the temperatures above 400˚C, the effect decreases.     

A Novel Method for Synthesis of ZSM‐5 Coatings on Monolithic Cordierite Substrate

ZSM‐5 coatings, have been synthesized onto a monolithic cordierite substrate by an environmental friendly and high coating selectivity method—Vapor Phase Transport (VPT). With this method, an aluminosilicate gel coated onto the monolithic cordierite substrate has been transformed into a ZSM‐5 layer under vapors of n‐butylamine and water, n‐Butylamine played a key role in the forming of ZSM‐5 layer on the cordierite substrate. The ZSM‐5/cordierite monolith composites prepared by this method were ion‐exchanged with Cu²⁺ and tested for the selective catalytic reduction of NO by propane. The deNO_x activities of Cu/ZSM‐5 monolith catalysts were not only dependent on the ion‐exchange methods, but also on the ZSM‐5 loading of the monolith catalysts. The best result was obtained over the Cu (B3)/ZSM‐5 monolith catalyst, which had a ZSM‐5 loading of about 13% and was prepared by a pressure exchange procedure. At a temperature of 723 K and a space velocity of 10,000 h^?1 (based on the monolith volume), 85% of NO conversion and 93% of C₃H₃ conversion were achieved over the Cu(B3)/ZSM‐5 monolith catalyst.     

分散法制备的CuCl/ZSM-5分子筛催化剂上C3H6选择性催化还原NO反应的研究

研究了由分散法制备的CuCl/ZSM-5分子筛催化剂上丙烯在过量氧存在下选择催化还原NO反应,发现该法能使活性组份高度分散于载体上,且所制备的高负载量CuCl/H-ZSM-5与离子交换法制备的Cu-ZSM-5相比在较低反应温度下具有更高的反应活性.     

SiO2-Al2O3玻纤载体负载CuO-CeO2对挥发性有机化合物催化燃烧性能研究

采用等体积共浸渍法制备了CuO-CeO₂整体式催化剂,评价了催化剂对乙酸乙酯、异丙醇及甲苯的催化燃烧性能。采用N₂吸附-脱附、X射线衍射（XRD）、氢气程序升温还原（H₂-TPR）、氨气程序升温脱附（NH₃-TPD）以及挥发性有机化合物脱附等手段对催化剂进行了表征。表征数据显示,氧化铜以高分散态均匀分散存在于载体表面,氧化铈则是小的纳米颗粒,氧化铈颗粒粒径随着Cu/Ce物质的量比的减小而增大。添加铈氧化物会显著增加总酸量,特别是路易斯酸酸位的量,同时增强了乙酸乙酯和异丙醇的吸附量,吸附量的增加提高了催化剂对乙酸乙酯和异丙醇的催化燃烧性能。从甲苯的催化燃烧实验可以看出,大量添加CeO₂稍微增加了甲苯的吸附容量,减弱了催化剂的还原性、降低了活性氧的含量,最终导致甲苯的低转化率。催化行为由氧化铜、氧化铈以及载体三者之间的共同作用决定,这三者的协同作用不仅影响着表面氧的活性同时影响着催化剂对甲苯的吸附能力。     

以金属氧化物及钙钛矿结构化合物为活性组分的ZSM-5催化剂上NOx选择性还原研究

研究了在水蒸汽存在条件下,以ＮＨ３为还原剂,金属／ＺＳＭ－５催化剂和负载于ＺＳＭ－５上的钙钛矿结构催化剂上的ＮＯｘ选择性催化还原（ＳＣＲ）性能。实验结果表明,当反应气中通入水蒸汽时,各样品的催化活性均下降,同时伴随着Ｎ２选择性的增加。而Ｃｕ－ＺＳＭ－５样品却表现出独特的性能,在所有测定样品中具有最高的ＮＯｘ转化率（在４５０℃时达到６９％）,当有水蒸汽存在时,其活性没有下降,反而有所增加,４５０℃时     

Effect of Hydrohalogenation of Metal/Zeolite Catalysts for Cyclohexene Hydroconversion ‐Part 3‐ Pd/H‐ZSM‐5 Catalysts

Cyclohexene (CHE) hydroconversion was performed in a flow reactor at atmospheric pressure and temperatures of 50–400 °C using: Pd/H‐ZSM‐5, Pd/H‐ZSM‐5(HCl), and Pd/H‐ZSM‐5(HF) catalysts. These catalysts were characterized for acid site strength distribution via NH₃ TPD, Pd dispersion via H₂ chemisorption, TPR via reduction of the metal oxide in the catalysts and XRD for tracing crystallinity The hydroconversion steps proceeded as follows: CHE → Cyclohexane (CHA); CHE → Methylcyclopentenes (MCPEs) → Methylcyclopentane (MCPA); CHE → Cyclohexadienes (CHDEs) → Benzene → Alkylbenzenes; CHE and others → Hydrocrackedproducts. The overall hydroconversion of CHE was achieved in the catalyst order: Pd/H‐ZSM‐5 > Pd/H‐ZSM‐5(HF) > Pd/H‐ZSM‐5(HCl). CHE hydrogenation step was the major reaction at low temperatures which significantly inhibited via HCl treatment, but slightly enhanced via HF treatment. At medium temperatures, on all catalysts, isomerisation to MCPEs and MCPA increase to a maximum then a decline with a further increase of temperature. The overall isomerisation of CHE was highest on the untreated catalyst. During the higher temperature range, dehydrogenation, alkylation and hydrocracking were increased with temperature. Dehydrogenation of CHE always yielded larger amounts of 1,3‐CHDE than 1,4‐CHDE. These cyclohexadienes were produced in the catalyst order: Pd/H‐ZSM‐5(HF) > Pd/H‐ZSM‐5(HCl) > Pd/H‐ZSM‐5. In general, benzene alkylation to toluene exceeded that of xylenes, indicating that the second methylation is more difficult than the first. However, the catalytic activities for benzene and toluene production were in the order: Pd/H‐ZSM‐5 » Pd/H‐ZSM‐5(HCl) > Pd/H‐ZSM‐5(HF), whereas for xylenes production, Pd/H‐ZSM‐5 » Pd/H‐ZSM‐5(HF) > Pd/H‐ZSM‐5(HCl). Intrapore diffusion plays an important role during the dehydrogenation reactions as well as during the interconversion of individual aromatic hydrocarbons.     

Comparison of Cu‐ZSM‐5 Zeolites and Cu‐MOF‐505 Metal‐Organic Frameworks as Heterogeneous Catalysts for the Mukaiyama Aldol Reaction: A DFT Mechanistic Study

The density functional theory (DFT) model ONIOM(M06L/6‐311++G(2df,2p):UFF was employed to reveal the catalytic activity of Cu^II in the paddle‐wheel unit of the metal‐organic framework (MOF)‐505 material in the Mukaiyama aldol reaction compared with the activity of Cu‐ZSM‐5 zeolites. The aldol reaction between a silyl enol ether and formaldehyde catalyzed by the Lewis acidic site of both materials takes place through a concerted pathway, in which the formation of the C? C bond and the transfer of the silyl group occurs in a single step. MOF‐505 and Cu‐ZSM‐5 are predicted to be efficient catalysts for this reaction as they strongly activate the formaldehyde carbonyl carbon electrophile, which leads to a considerably lower reaction barrier compared with the gas‐phase system. Both MOF‐505 and Cu‐ZSM‐5 catalysts stabilize the reacting species along the reaction coordinate, thereby lowering the activation energy, compared to the gas‐phase system. The activation barriers for the MOF‐505, Cu‐ZSM‐5, and gas‐phase system are 48, 21, and 61 kJ mol^?1, respectively. Our results show the importance of the enveloping framework by stabilizing the reacting species and promoting the reaction.     

铜离子的引入对甲烷无氧芳构化催化剂Mo/CuH-ZSM-5中Mo物种化学状态的影响

对比考察了Mo/CuH-ZSM-5和Mo/H-ZSM-5催化剂的甲烷无氧芳构化性能,并用XRD,XPS,ESR等多种测试手段对反应前后催化剂上的Mo物种及铜助剂的价态变化进行了详细研究,发现Cu(Ⅱ)部分取代H-ZSM-5交换位上的H⁺后,抑制了活性组分MoO₃的还原,而Cu物种自身被还原,进而将这种价态变化与催化剂的活性进行了关联.     

铜源对Cu-SAPO-34氨催化还原NO性能的影响

采用离子交换法制备3种不同铜前驱体的Cu-SAPO-34分子筛催化剂,考察铜源对催化剂氨催化还原NO_x性能的影响,同时通过ICP、XRD、BET、H_2-TPR、XPS、NH_3-TPD等表征技术进行分析.活性结果表明,不同铜源制备的Cu-SAPO-34分子筛催化剂的NH_3-SCR高温活性基本相同,但中低温活性有较大差别.3种催化剂的中低温活性顺序为Cu(醋酸铜)-SAPO-34Cu(硫酸铜)-SAPO-34Cu(硝酸铜)-SAPO-34,以醋酸铜为铜源制备的催化剂中低温活性最高,在209℃NO_x转化率达85.2%.表征结果表明,不同铜源导致所制备催化剂的铜物种形式和数量及酸性强度不同,以醋酸铜为铜源制备的Cu-SAPO-34催化剂的Cu~(2+)起始还原温度最低,Cu~(2+)含量较多,酸性最强,因此其中低温活性最好.     

碱金属化合物改性ZSM-5沸石的择形催化作用

经碱金属化合物改性的HZSM-5分子筛,能提高甲苯烷基化生成对二甲苯的选择性,降低二甲苯异构化活性。改性后沸石的表面总酸度下降,酸强度减弱,孔结构变化不明显。     

CeO2-Y2O3涂层和负载型Pd催化剂催化燃烧VOCs

制备了一种粘附在堇青石蜂窝陶瓷载体上的CeO_2-Y_2O_3(CeY)复合氧化物新涂层.以二氧化铈和柠檬酸钇为前驱体,制备过程中无有害物质产生,对环境友好.CeY涂层和Pd/CeY催化剂通过SEM、EDX、XRF和Raman光谱等表征.结果表明,此涂层的粘结强度高,对活性组分的吸附性能好,适合用来负载钯催化剂.Y_2O_3大部分进入了峰窝陶瓷的孔道内,CeO_2和Pd物种则富集在载体的表面.以CO、甲苯和乙酸乙酯的催化燃烧来评价Pd/CeY催化剂的性能,此催化剂具有较好的催化活性和热稳定性.500℃焙烧的催化剂,CO、甲苯和乙酸乙酯的T_(99)(转化率99%以上所需的最低反应温度)分别为150、220和310℃;1050℃焙烧的催化剂,它们的T_(99)分别为180、250和330℃.高温焙烧的催化剂,活性物种PdO的晶粒增大,这可能导致催化剂的活性下降.     

Effect of Calcination Temperature on Catalytic Activity and Textual Property of Cu/HMOR Catalysts in Dimethyl Ether Carbonylation Reaction

The effect of calcination temperature on the catalytic activity for the dimethyl ether (DME) carbonylation into methyl acetate (MA) was investigated over mordenite supported copper (Cu/HMOR) prepared by ion-exchange process. The results showed that the catalytic activ-ity was obviously affected by the calcination temperature. The maximal DME conversion of 97.2% and the MA selectivity of 97.9% were obtained over the Cu/HMOR calcined at 430 oC under conditions of 210 oC, 1.5 MPa, and GSHV of 4883 h^-1. The obtained Cu/HMOR catalysts were characterized by powder X-ray diffraction, N₂ absorption, NH₃ temperature program desorption, CO temperature program desorption, and Raman techniques. Proper calcination temperature was effective to promote copper ions migration and diffusion, and led the support HMOR to possess more acid activity sites, which exhibited the complete decomposing of copper nitrate, large surface area and optimum micropore structure, more amount of CO adsorption site and proper amount of weak acid centers.     

Au/ZSM-5催化剂催化裂化轻柴油多产丙烯

经过三十多年的研究与开发,金催化已应用到环境污染治理与控制、精细化工合成和能源等领域,涉及的化学反应从简单的 CO氧化和丙烯环氧化等扩展到加氢、羰化和缩合等各类有机合成反应,研究领域从多相催化到均相催化以及光催化等.然而金催化所探索的反应多在较温和的反应条件下进行,对于重油催化裂解这类高温和复杂混合反应物体系的研究几乎无人问津.催化裂化(FCC)过程由于具有能耗较低、原料低廉及装置适应能力强等优点,在增产丙烯方面发挥着重要作用.由于特殊孔结构的择形性、较强的酸性和低的氢转移活性以及良好的水热稳定性, ZSM-5分子筛是目前应用于 FCC多产丙烯催化剂和助剂最为广泛的重要组分.值得注意的是,目前国内外开发的改性 ZSM-5无论是对 C4烃类和石脑油等催化裂解或作为助剂用于 FCC增产丙烯均有积极作用,但反应温度较高(大于510oC);当降低反应温度后,其增产丙烯的能力将受到极大限制.本文利用纳米金低温催化活性高的特点,采用改进的沉积沉淀(DP)方法,通过调变制备参数和金载量,制备了系列金修饰的 ZSM-5催化剂,考察了其对轻柴油催化裂解多产丙烯的催化性能.采用 X射线衍射(XRD)、N2吸附-脱附、氨程序升温脱附(NH3-TPD)、透射电镜(TEM)和诱导耦合等离子体光谱(ICP-AES)等手段研究了纳米金的分散状况及其对 ZSM-5物理化学结构的调变.结果发现,在460oC的较低反应温度下,与微米 ZSM-5母体相比,采用常规 DP法制备的经过滤洗涤后未用 NaBH4还原而是在300oC下空气中焙烧,理论金载量分别为0.5,0.8和1.0 wt%的三个纳米金催化剂的微反活性和丙烯选择性均增加.其中丙烯选择性分别提高了8.8%,2.9%和23.2%,微反活性指数分别提高了7.1%,4.3%和4.5%.这表明少量金的引入有利于在较低反应温度下催化裂化轻柴油增产丙烯,反映了其催化裂解烃类化合物的能力. TEM观察表明, Au/ZSM-5催化剂中金粒径分布非常不均匀(<10 nm–<200 nm).然而其中一些金粒子与载体呈扁平式接触,显示了两者间较强的相互作用.另外一些较小的金粒子可能嵌入到狭缝片状 ZSM-5颗粒之间的孔隙中,这可能在一定程度上影响了母体 ZSM-5的孔结构分布及其催化裂化性能. XRD, N2吸附-脱附和 NH3-TPD结果表明,金引入制备参数及其载量的变化导致了母体 ZSM-5载体的 MFI结构、孔结构分布及强弱酸量的变化.上述丙烯选择性和微反活性因
　　金的修饰而同时提高的三个金催化剂,基本保持了完整的 ZSM-5的 MFI结构,并且其孔分布比 ZSM-5窄.金的引入明显提高了 ZSM-5母体的酸性尤其是低温弱酸的酸强度,然而,综合性能优良的催化剂其强弱酸量的比例相近.因此,金修饰导致微反活性和丙烯选择性的同时提高取决于改性催化剂的 MFI结构、孔分布以及强弱酸比例的协同作用,而金载量和金粒子尺寸的影响不明显.一般来讲,修饰的金属主要通过形成正碳离子而在 B酸位上生成轻烯烃.高温水汽老化试验后,金修饰的 ZSM-5比未修饰的ZSM-5保留了更多的酸位,说明金在一定程度上抑制了骨架铝的脱除.扁平状分布在母体上的金粒子与母体间较强的相互作用可能导致部分电子从金属态金转移到(SiAl)O(OH)m上,增加了羟基中质子的流动性而提高了改性分子筛的酸性,有利于正碳离子的形成.     

A Comparison of NO Reduction Over Mn–Cu/ZSM5 and Mn–Cu/MWCNTs Catalysts Assisted by Plasma at Ambient Temperature

Manganese–copper bimetal oxide catalysts supported on ZSM5 and acid-treated multi-walled carbon nanotubes (MWCNTs) were produced by incipient wetness impregnation for selective catalytic reduction of NO with dielectric barrier discharge plasma. Plasma can activate molecules even at ambient temperature, generating active oxygen species such as O, O₃, and HO₂ radicals, which can oxidize NO to NO₂ effectively. The SCR activity of Mn–Cu/MWCNTs was studied and compared to that of the Mn–Cu/ZSM5. The obtained samples were characterized by XRD, SEM, TEM, ICP, H₂-TPR, Raman spectroscopy, and XPS. The results show that Mn–Cu/MWCNTs catalyst possesses NO removal activity superior to that of the Mn–Cu/ZSM5 catalyst. MWCNTs-based catalyst attains NO removal efficiency of 88% at 480 J/L, while the ZSM5-supported catalyst achieves NO removal efficiency of 82% at the same energy density. The oxygen content increased from 3.33 to 19.07% on the nanotube surface after introducing Mn and Cu, which almost remained unchanged on ZSM5. The oxygen-containing functionalities are important for NO_x adsorption and removal. Moreover, the characterization revealed that CuO is the main phase of copper oxide, but copper dispersion decreases on Mn–Cu/ZSM5 surface because of the formation of copper dimer species. The manganese is well-dispersed on the catalysts, MnO₂ and Mn₂O₃ contents of Mn–Cu/MWCNTs are larger than that of Mn–Cu/ZSM5, MnO₂ is the predominant phase of manganese oxide.     

Electrocatalytic Production of C3‐C4 Compounds by Conversion of CO2 on a Chloride‐Induced Bi‐Phasic Cu2O‐Cu Catalyst

Electrocatalytic conversion of carbon dioxide (CO₂) has recently received considerable attention as one of the most feasible CO₂ utilization techniques. In particular, copper and copper‐derived catalysts have exhibited the ability to produce a number of organic molecules from CO₂. Herein, we report a chloride (Cl)‐induced bi‐phasic cuprous oxide (Cu₂O) and metallic copper (Cu) electrode (Cu₂O_Cl) as an efficient catalyst for the formation of high‐carbon organic molecules by CO₂ conversion, and identify the origin of electroselectivity toward the formation of high‐carbon organic compounds. The Cu₂O_Cl electrocatalyst results in the preferential formation of multi‐carbon fuels, including n‐propanol and n‐butane C3–C4 compounds. We propose that the remarkable electrocatalytic conversion behavior is due to the favorable affinity between the reaction intermediates and the catalytic surface.     

NH3-SCR反应中Fe-ZSM-5的Fe物种分布和酸性位对其水热稳定性及抗硫和抗碳氢性能的影响

以Na+型和H+型ZSM-5为载体制备了Fe-ZSM-5催化剂并用于氨选择性催化还原(NH3-SCR)氮氧化物. Fe-H-ZSM-5在新鲜时和750 oC含10%水的空气中老化后,其SCR活性均优于Fe-Na-ZSM-5.表征结果显示, Fe-H-ZSM-5和Fe-Na-ZSM-5的Fe物种分布和酸性位有所不同.高温水热老化后Fe-H-ZSM-5分子筛骨架的脱铝较Fe-Na-ZSM-5严重.水和硫的存在对Fe-H-ZSM-5和Fe-Na-ZSM-5的SCR活性的影响相似,即降低了低温活性,略提高了高温活性. Fe-Na-ZSM-5表现出比Fe-H-ZSM-5更好的抗碳氢中毒性能.这两种催化剂的SO2和碳氢中毒是可逆的.     

Cu-M/ZSM-S(M=Ce,La,Ag)催化剂的表征及其对NO直接分解催化活性的研究

考察了用分散法制备的Ｃｕ－Ｍ／ＺＳＭ－５（Ｍ＝Ｃｅ,Ｌａ,Ａｇ）催化剂对ＮＯ直接分解的催化活性,并且用ＸＲＤ、ＳＥＭ、ＴＰＲ、ＸＰＳ及ＩＣＡＰ等手段对催化剂进行了表征。结果表明添加Ｃｅ有利于增加催化剂的铜离子交换度,添加Ａｇ有可能使ＺＳＭ－５分子筛的骨架结构发生改变,从而对催化剂活性产生影响。     

Modulating catalytic activity of polymer‐based cuAAC “click” reactions

The copper(I)‐catalyzed azide–alkyne cycloaddition (CuAAC) reaction is used to synthesize complex polymer architectures. In this work, we demonstrate the control of this reaction at 25 °C between polystyrene (PSTY) chains through modulating the catalytic activity by varying the combinations of copper source (i.e., Cu(I)Br or copper wire), ligand (PMDETA and/or triazole ligand), and solvent (toluene or DMF). The fastest rate of CuAAC was found using Cu(I)Br/PMDETA ligand in toluene, reaching near full conversion after 15 min at 25 °C. For the same catalysts system, DMF also gave fast rates of “click” (95% conversion in 25 min). Cu(0) wire in toluene gave a conversion of 98% after 600 min, a much higher rate than that observed for the same catalyst system used in DMF. When the PSTY had a chemically bound triazole ring close to the site of reaction, the rate of CuAAC in toluene increased significantly, 97% in 180 min at 25 °C, in agreement with our previously published results. This suggests that rapid rates can be obtained using copper wire and will have direct applications to the synthesis of compound where air, removal of copper, and reuse of the copper catalyst are required. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Effect of weak base modification on ZSM‐5 catalyst for methanol to aromatics

The effect of weak base modification on the catalytic performance of ZSM‐5 catalyst for conversion of methanol to aromatics was investigated. The catalysts were characterized using X‐ray diffraction, X‐ray fluorescence, N₂ adsorption–desorption, NH₃ temperature‐programmed desorption, Fourier transform infrared spectroscopy, scanning electron microscopy and thermogravimetry. The results showed that catalysts treated with weak base (NaHCO₃, Na₂CO₃ and NH₃⋅H₂O) exhibited a pore structure with interconnected micropores and mesopores. The existence of mesopores was beneficial for improving the diffusion of reactants and products, and the coke deposition resistance capacity of treated catalysts was enhanced greatly. Meanwhile, compared to traditional ZSM‐5 zeolite, the ratio of Brønsted to Lewis (B/L) acid sites of ZSM‐5/NH₃⋅H₂O (B/L = 7.35) zeolite slightly increased but the amount of acid sites reduced, while those of ZSM‐5/NaHCO₃ (B/L = 0.127) and ZSM‐5/Na₂CO₃ (B/L = 0.107) significantly reduced. Further, the catalyst treated with NH₃⋅H₂O solution was evaluated in the methanol to aromatics reaction and led to an enhanced aromatization reaction rate. The liquid hydrocarbons product distribution exhibited higher aromatic hydrocarbons yield (56.12%) and selectivity (40.28%) of benzene, toluene and xylene (BTX) with isoparaffin content reducing to 26.17%, which could be explained by appropriate B/L acid sites ratio, higher pore volumes and higher surface area.     

Influence of Aging Time on the Properties of Precursors of CuO／ZnO Catalysts for Methanol Synthesis

The aging process of pure copper precursors and copper-zinc binary precursors were studied by XRD, TG-DTG and TPR techniques. The catalytic activity and stability of CuO/ZnO were tested using fixed-bed flow reactor, and the physical properties of the catalysts and Cu species were characterized with N2 adsorption and N2O passivation method, respectively. For the Cu-Zn binary system prepared at the precipitating condition of pH=8.0 and temperature=80℃, the initial phase was a mixture of copper nitrate hydroxide Cu2(NO3)(OH)3, georgeite and hydrozincite Zn5(CO3)2(OH)6. By increasing the duration of its aging time, the phase of Cu2(NO3)(OH)2 first transited to georgeite, and then interdiffused into Zns(CO3)2(OH)6 and resulted in two new phases: rosasite (Cu,Zn)2CO3(OH)2 and aurichalcite (Zn,Cu)5(CO3)2(OH)6. The former phase was much easier to be formed than the latter one, while the latter phase was more responsible for the activity of methanol synthesis than the former one. It is found that the composition and structure of the precursors altered obviously after the colour transition point. The experimental results showed that methanol synthesis is a structure-sensitive catalytic reaction.