Methanol Selective Oxidation to Formaldehyde over Iron-Molybdate Catalysts

This review deals with the important industrial reaction of formaldehyde manufacture by methanol oxidation over iron molybdate catalysts. Detailed reference is made to the used catalyst, preparation techniques (coprecipitation, sol-gel like, mechanical mixing, etc.) including unsupported and supported catalysts, promoters and characterization methods. The controversial active phase assignment (stoichiometric versus Mo rich iron molybdate) is discussed. The proposed reaction mechanisms and kinetic laws for the main and side reactions are examined. The catalyst deactivation processes are reviewed and the role of Mo excess on these processes is underlined. Finally conclusions and perspectives are presented.     

Partial Oxidation of Methanol to Formaldehyde on Molybdenum Based Mixed Oxide Catalyst

Molybdenum based mixed oxide containing Mo_0.65V_0.25W_0.10 was investigated for the partial oxidation of methanol. The structural property and catalytic activity of the mixed oxide catalyst was studied by surface area (BET), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infra-red spectroscopy (FTIR) and X-ray diffraction (XRD). The thermal activation of the catalyst resulted increase in the conversion of methanol and the selectivity to formaldehyde. The thermal activation of the MoVW mixed oxide in nitrogen atmospheres induces partial crystallization of a Mo₅O₁₄-type oxide at 813 K. The SEM images of the thermally activated catalyst show needle like particles. These particles were agglomerates of platelet-like crystallites of a few hundreds of nanometers in size. SEM and EDX techniques show that the mixed oxide is characterized by an inhomogeneous elemental distribution on the length scale of a few microns. XRD of the thermally activated catalyst showed a nanocrystalline material identified as a mixture of Mo₅O₁₄, MoO₃ and MoO₂-type MoVW oxides. The catalytic activity of the MoVW mixed oxide show a good conversion of methanol and selectivity to formaldehyde.     

甲烷部分催化氧化合成甲醇和甲醛

本文综述了由甲烷部分催化氧化制甲醇和甲醛研究中所用催化剂的制备条件及催化反应条件,并对用于该反应的催化剂开发和最佳合成工艺条件的选择指出了方向。     

The Selective Oxidation of Methanol to Formaldehyde on Iron Molybdate Catalysts and on Component Oxides

The reaction of methanol with an industrial iron molybdate catalyst, and with Fe₂O₃ and with MoO₃, has been investigated with a pulsed flow reactor and temperature-programmed desorption (TPD). The molybdena-based samples show only formaldehyde in TPD as the carbon-containing product, arising from the decomposition of a surface methoxy species. In contrast, haematite yields no formaldehyde, only CO₂ and H₂, which evolve coincidently at 290 °C, and indicates the presence of a formate intermediate on the surface. In turn, the reactor work shows high selectivity to formaldehyde for the molybdate materials and zero for haematite. The iron molybdate sample is more active than the molybdena, conversion beginning at 150 °C for the former and 270 °C for the latter. These data are discussed in terms of a global mechanism for the reaction and a tentative reaction enthalpy profile is proposed. The main differences between the iron and molybdenum samples arise from the stronger binding of oxygen in the former and the higher concentration of cation sites.     

粗甲醇生产甲醛

采用粗甲醇直接为原料生产甲醛，就可以节省精馏能耗，简化操作，降低生产成本，达到提高经济效益的目的。     

发泡银对甲醇空气氧化为甲醛的催化性能研究

研究了新型发泡银催化剂对甲醇空气氧化制备甲醛的催化作用 ,考察了催化反应温度、甲醇进料速率、进料体积分数及空气流量对甲醛产率的影响 ,得到了较好的催化反应工艺条件 :反应温度为 6 70℃、甲醇进料速率为 0 8mL·min-1、甲醇进料体积分数为 85 %、空气流量为 10 0 0mL·min-1,在此工艺条件下 ,甲醛的产率可达 85 %以上。对发泡银催化剂的稳定性进行了考察 ,结果表明在 5～ 6 0h内 ,其催化活性无明显变化。     

甲醇直接氧化制备二甲氧基甲烷催化剂研究进展

作为一种新型的高性能柴油添加剂,二甲氧基甲烷的研究与生产受到越来越多的关注。论述了气相法甲醇部分氧化直接制备二甲氧基甲烷的机理,通过对甲醇部分氧化直接制备二甲氧基甲烷反应所用的Re、Ru、Mo、V等不同系列的催化剂的研究进展的综述,比较了各催化体系的特点;介绍了液相法甲醇直接氧化制二甲氧基甲烷的研究进展。最后对甲醇直接氧化制备二甲氧基甲烷提出了建议。     

改进生产条件 降低甲醛中的醇含量

介绍了巨化公司在甲醛生产中开展的以提高甲醇转化率，降低甲醛中甲醇含量，提高经济效益及保障季戊四醇正常生产目的的质量攻关活动。通过对生产工艺中诸因素的正交试验，优化节生产条件，结果使甲醛中甲醇含量自原来的平均７％降低到２％左右，获得较显著的经济效益和社会效益。     

Methanol Oxidation over Iron-Molybdate Catalysts: Optimization of the Process

This research aims to shed more light on the possibilities to optimize the process of selective oxidation of methanol over oxide catalysts using an adiabatic layer by determining border values of basic parameters of the process in the adiabatic layer that ensure a maximum rate of methanol oxidation at high selectivity. Laboratory experiments were performed to clarify the influence of the most important parameters of the process (temperature, space velocity and methanol concentration) on the efficiency of the adiabatic layer. An industrial experiment was carried out to verify the results obtained.     

Catalytic Performance of the Sb–V Mixed Oxide on Sb–V–O/SiO2 Catalysts in Methane Selective Oxidation to Formaldehyde

Sb–V–O/SiO₂ catalysts were prepared and investigated in methane selective oxidation with O₂ as oxidant. Sb–V–O/SiO₂ catalysts are active and selective in methane selective oxidation. The formaldehyde yield obtained on Sb–V–O/SiO₂ catalysts is clearly higher than that for VO_X/SiO₂ and SbO_X/SiO₂ catalysts. A one-pass formaldehyde yield up to 3% was obtained on Sb–V–O/SiO₂ catalysts at 650 °C. XRD and UV Raman studies showed that the phase of Sb–V mixed oxide on Sb–V–O/SiO₂ catalysts transformed with decreasing Sb/V ratio from Sb₂VO₅ to SbVO₄/VSb_1-XO_4-1.5X phase. The Sb–V mixed oxide in Sb₂VO₅ phase is more active and selective than that in SbVO₄/VSb_1-XO_4-1.5X phase.     

甲醇氧化生产甲醛装置的工艺查定及分析(Ⅰ)

对湖北省宜化股份有限公司 3 .5万t·a-1甲醛生产装置进行了物料查定 ,以工厂生产参数和分析结果为依据 ,计算了反应原料的氧醇比、水醇比、配料浓度 ,校核了反应器的选择性、转化率、收率 ,列出了物料衡算表     

锰氧化物催化剂催化氧化甲醛的研究进展

锰氧化物具有活性高、毒性低、资源丰富、合成方法多样等优点,常作为许多催化反应的催化剂或载体材料。该文综述了近年来锰氧化物催化剂的研究进展,主要介绍了单一锰氧化物、掺杂改性的锰氧化物以及锰氧化物复合材料在甲醛催化氧化反应中的催化性能;讨论了形貌、晶型结构以及其他因素对催化性能的影响;并归纳了一部分甲醛催化氧化的反应机理;最后指出要发展高效、经济、环保的锰氧化物催化剂,通过构建更多的缺陷、添加助剂、掺杂改性等方法,增加活性面和活性位的数量,来提高锰氧化物的催化性能是未来的主要研究方向。     

Selective Methanol Conversion to Methylal on Re-Sb-O Crystalline Catalysts: Catalytic Properties and Structural Behavior

Three crystalline compounds, SbOReO₄·2H₂O, Sb₄Re₂O₁₃ and SbRe₂O₆, and several supported Re catalysts were employed as catalysts for the selective oxidation of methanol to methylal (3CH₃OH+1/2O₂ CH₂(OCH₃)₂+2H₂O). A high selectivity of 92.5% to methylal at a conversion of 6.5% under conditions of GHSV = 10000 mL h^-1g^-1 _-cat and 573 K was obtained on the new SbRe₂O₆ catalyst, while no significant formation of methylal was observed with the other two catalysts. No structural change in the bulk and surface of SbRe₂O₆ and Sb₄Re₂O₁₃ occurred after methanol oxidation below 593 K, but SbOReO₄·2H₂O was transformed to Sb₄Re₂O₁₃, as characterized by XRD, Raman spectroscopy, XPS and SEM. The high performance of SbRe₂O₆ for the selective methylal synthesis was ascribed to Re oxide species stabilized by a specific connection with Sb oxides at the crystal surface.     

Mechanistic Aspects of Hydrogen Production by Partial Oxidation of Methanol Over Cu/ZnO Catalysts

In this work, mechanistic aspects of the partial oxidation of methanol (POM) to hydrogen and carbon dioxide over Cu/ZnO catalysts have been investigated. The data obtained with different catalyst compositions and different Cu^o metal surface areas showed that the reaction depends on the presence of both the phases ZnO and Cu^o. On the other hand, for catalysts with Cu concentrations in the range 40-60 wt%, the copper metal surface area seems to be the main factor determining the reaction rate. Kinetic isotope effects using CH₃OH and CH₃OD showed that both C–H and O–H bonds are at least partially involved in the rate-limiting step. TPD experiments with pure Cu^o, pure ZnO and the catalyst Cu/ZnO showed that methanol can be activated by both ZnO and copper. On the ZnO surface methanol can form intermediates which in the presence of copper might react and desorb more easily probably via a reverse spillover process. The isotopic product distribution of H₂, HD, D₂, H₂O, HDO and D₂O in the temperature-programmed reaction of CH₃OD revealed a slight enrichment of the products with H, suggesting that during methanol activation on the ZnO some of the D atoms might be retained by the support. The effect of oxygen partial pressure suggests that oxygen atoms on the copper surface strongly promote methanol activation and H₂ and CO₂ formation. It is proposed that oxygen atoms participate in methanol activation by the abstraction of the hydroxyl H atom to form methoxide and OH_surf. This OH_surf species rapidly loses H to the surface regenerating the O_surf.     

金属催化剂选择性催化氧化甘油及其衍生物的研究

阐述了甘油氧化的路径,利用Pd、Pt和Au等金属催化剂,选择性催化氧化甘油及其衍生物制备甘油酸、1,3-二羟基丙酮、羟基丙酮酸、丙醇二酸和丙酮二酸等一系列重要化学品的研究,此方法选择性高,反应温和,对环境友好,前景广阔。     

Selective Oxidation of Toluene to Benzaldehyde Using Co-ZIF Nano-Catalyst

Nanometer-size Co-ZIF (zeolitic imidazolate frameworks) catalyst was prepared for selective oxidation of toluene to benzaldehyde under mild conditions. The typical characteristics of the metal-organic frameworks (MOFs) material were affirmed by the XRD, SEM, and TEM, the BET surface area of this catalyst was as high as 924.25 m²/g, and the diameter of particles was near 200 nm from TEM results. The Co metal was coated with 2-methyl glyoxaline, and the crystalline planes were relatively stable. The reaction temperatures, oxygen pressure, mass amount of N-hydroxyphthalimide (NHPI), and reaction time were discussed. The Co-ZIF catalyst gave the best result of 92.30% toluene conversion and 91.31% selectivity to benzaldehyde under 0.12 MPa and 313 K. The addition of a certain amount of NHPI and the smooth oxidate capacity of the catalyst were important factors in the high yield of benzaldehyde. This nanometer-size catalyst showed superior performance for recycling use in the oxidation of toluene. Finally, a possible reaction mechanism was proposed. This new nanometer-size Co-ZIF catalyst will be applied well in the selective oxidation of toluene to benzaldehyde.     

Efficient Copper-bisisoquinoline-based Catalysts for Selective Aerobic Oxidation of Alcohols to Aldehydes and Ketones

The selective oxidation of alcohols with molecular oxygen was efficiently completed in high conversion and selectivity using copper-bisisoquinoline-based catalysts under mild reaction condition. The effects of various parameters such as reaction temperature, reaction time, oxidant, ligands, etc, were studied. Solvent effect has been as well studied in ionic liquids [bmim]PF₆, [omim]BF₄ and [hmim]BF₄, comparing to traditional volatile organic solvent. The use of ionic liquids was found to enhance the catalytic properties of the catalysts used.     

复合氧化物催化剂上异丁烯选择氧化的研究进展

异丁烯选择氧化制备甲基丙烯醛是异丁烯法制备甲基丙烯酸甲酯的关键步骤. 本工作系统地综述了异丁烯选择氧化制备甲基丙烯醛复合氧化物催化剂的组成、微观结构、助剂作用以及催化机理的研究进展,认为具有实际应用意义的催化剂组成元素众多,各组分在立体结构和基元反应上高度协调,共同促进了催化剂的高效和稳定. 因此,多组分间的协同作用、活性位的形成机制及各种添加剂实际作用的进一步深入研究对改进催化反应性能具有重要意义.     

Selective Oxidation of Methanol to Dimethoxymethane over Mesoporous Al‐P‐V‐O Catalysts

The synthesis and application of bifunctional mesoporous Al‐P‐V—O catalysts with both acidic and redox sites for selective oxidation of methanol to dimethoxymethane (DMM) is described. The catalysts were characterized by N₂ adsorption/desorption, X‐ray diffraction, temperature‐programmed desorption, X‐ray photoelectron spectroscopy, and infrared spectroscopy. It is shown that porosity; redox property and surface acidity of the catalysts were greatly influenced by the Al/V/P ratio. The synergistic effect of phosphorus and vanadium was investigated. Al‐P‐V—O catalysts exhibited good catalytic activity because of the controlled reducibility and the acidic sites. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2587–2593, 2013