氯化氢氧化反应催化剂研究进展

大量副产氯化氢的资源化高效利用是涉氯行业亟需解决的共性难题。氯化氢催化氧化循环制氯气是一个低能耗、可持续发展的有效途径，而催化剂的设计与制备是该过程的核心。本文重点介绍了铜基、钌基和铈基等催化剂，并对各类催化剂的作用机理及其活性、稳定性等性能进行了归纳。不同于铜基催化剂，钌基和铈基等催化剂主要按照Langmuir-Hinshelwood路径催化反应，具有更佳的反应活性及稳定性。基于该反应为放热过程，指出降低反应温度是增强氯化氢转化的关键。此外，活性组分烧结导致分散性变差是钌基和铈基催化剂的主要失活因素。高低温活性、高稳定性的复合氧化物催化剂将是未来本领域重点研究的方向。     

环己烯分子氧氧化多相催化剂研究进展

根据催化剂主组分的不同,综述了国内外环己烯分子氧氧化多相催化剂的研究进展;主要介绍了钴系、锰系、铁系及镍系催化剂在环己烯分子氧氧化中的应用及其优缺点.指出负载型纳米金催化剂与传统的钴、锰催化剂相结合制备双活性中心催化剂在环己烯分子氧氧化中有较好的应用前景.     

分子氧氧化环己烷制环己酮催化剂的研究进展

综述了分子氧氧化环己烷制取环己酮的催化剂的研究进展,重点介绍了光催化剂、纳米催化剂、仿生催化剂、分子筛催化剂和复合催化剂在环己烷催化氧化方面的应用,其中,负载在分子筛上的纳米金催化剂具有较高的催化活性、选择性及稳定性。     

Nanoscale Cu supported catalysts in the partial oxidation of cyclohexane with molecular oxygen

Cu supported catalysts (support: γ-Al₂O₃, Fe₂O₃, TiO₂) have been conveniently prepared by deposition of Cu particles from acetone solvated Cu atoms. The catalysts have been characterized by HRTEM analysis, showing a quite homogeneous Cu particle size distribution. They are active systems for the partial oxidation of cyclohexane to cyclohexanol and cyclohexanone. After the catalytic experiment the Cu/γ-Al₂O₃ and Cu/TiO₂ systems can be reused without valuable loss of activity, while the Cu/Fe₂O₃ system is quite inactive.     

环己烷分子氧氧化多相催化剂研究进展

综述了环己烷分子氧氧化多相催化剂最新研究进展;重点介绍了金系催化剂和钴系催化剂;指出环己烷分子氧氧化制环己酮和环己醇工艺存在选择性和转化率低、能耗高等缺点,解决问题的主要途径在于开发高效催化剂.金系催化剂在环己烷分子氧氧化中具有较好的应用前景.     

氯化氢氧化反应器的研究进展

从副产氯化氢中回收利用氯气是实现氯元素循环经济的有效途径.综述了近年来出现的各种由副产氯化氢多相催化氧化制备氯气的反应器类型,阐明了各种反应器的性能特点,探讨了新型反应器的研发方向.     

Internal recirculation reactor for the oxidation of sulphur dioxide on vanadium catalysts

A gradientless laboratory reactor for the study of heterogeneous gas phase catalytic reactions is described. The reactor operates by the principle of internal recirculation and is suitable for measurements of SO₂ oxidation rate on V₂O₅ catalysts in the industrial temperature range 400–600°C. The control of sufficient mixing in the reactor is discussed.     

Solvothermal synthesis of vanadium phosphate catalysts for n-butane oxidation

In this paper, we have developed a simple, low-cost, template-free and surfactant-free solvothermal process for synthesis of vanadyl hydrogen phosphate hemihydrate (VOHPO₄·0.5H₂O) with well defined crystal size. The synthesis was performed by reaction of VPO₄·2H₂O with an aliphatic alcohol (isobutyl alcohol, 1-pentanol, 1-hexanol, 1-heptanol or 1-decanol). This afforded well crystallized VOHPO₄·0.5H₂O by solvothermal methods at 120 °C temperature. This new method significantly reduced the preparation time and lowered production temperature (50%) of catalyst precursor (VOHPO₄·0.5H₂O) when compared to conventional hydrothermal synthesis methods. By varying the reducing agent, the solvothermal evolution process from layered tetragonal phase VOPO₄·2H₂O to orthorhombic phase VOHPO₄·0.5H₂O was observed. It was found that the length of carbon chain in an alcohol in the solvothermal condition had a great impact on chemical and physical properties of resulting catalysts. Interestingly, there was no trace of VO(H₂PO₄)₂ an impurity noted to be readily formed under solvothermal preparation condition. Therefore, this study introduces a more facile synthetic pathway to V(III) compounds. In addition, the microwave-synthesized catalysts exhibited some properties superior to those of conventionally synthesized catalyst such as better stability, crystallinity, and catalytic activity in the production of maleic anhydride. The characterization of both precursors and calcined catalysts was carried out using X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectrometer (ICP-AES), N₂ physisorption, temperature programmed reduction (H₂-TPR) and scanning electron microscopy (SEM). The XRD pattern of the active catalyst prepared by this solvothermal method confirmed the presence of smaller crystal size (between 6 and 13 nm along 0 2 0 planes) of vanadium phosphate catalyst with higher specific surface area. Finally, the yield of maleic anhydride was significantly increased from 29% for conventional catalyst to 44% for the new solvothermal catalyst.     

Copper-cationic salphen catalysts for the oxidation of cyclohexene by oxygen

The modified copper-cationic salphen catalysts were synthesized and used in the allylic oxidation of cyclohexene to 2-cyclohexen-1-ol and 2-cyclohexen-1-one with oxygen under mild conditions. Compared with their unmodified counterpart, the catalytic activities of modified catalysts are improved. The type of counteranion could affect the reactivity of catalyst, which offers an opportunity to improve the catalysts via changing counteranions to optimize the selectivity. The cation–anion interaction can be adjusted by different solvents, which in turn influences the catalyst reactivity. Furthermore, these novel catalysts can be reused without sacrificing the activity.     

Selective gas-phase oxidation of ethanol by molecular oxygen over oxide and gold-containing catalysts

The rapid increase in the production rates of bioalcohols (in particular bioethanol) gives grounds for regarding them as a promising renewable chemical raw material for obtaining a number of useful organic synthesis products. In order to develop new green technologies for processing ethanol into value-added products, a systematic study of selective conversion of ethanol under conditions of oxidation by molecular oxygen in the flow gas-phase mode over such catalysts as V₂O₅-TiO₂, mixed oxides V-Mo-Te, V-Mo-Nb and V-Mo-Te-Nb, and gold supported on oxide supports is performed. The catalytic activity is determined under conditions of temperature-programmed reaction under atmospheric pressure using a gas mixture (composition, mol %: EtOH, 2; O₂, 18; He, 80) at a hourly space velocity of the mixture of 3600 h^?1 over 0.25–0.5 mm catalyst fraction. The possibility of the efficient conversion of ethanol to products of partial oxidation and accompanying conversions (acetaldehyde, 90–99% yield; acetic acid, 92-98% yield; productive capacity >3 g g-cat^?1 h^?1) and acetic acid-ethyl acetate mixtures (1: 1 ratio, total yield >90%) in a number of cases is demonstrated.     

CO scrambling with reactive oxygen species on vanadium promoted rhodium catalysts

Well reduced silica-supported rhodium catalysts contain oxygen species that are able to participate in reactions. Adsorbed CO molecules were demonstrated to exchange their oxygen atoms with oxygen atoms from these catalysts. The amount of such reactive oxygen is increased by a vanadium promoter. Using infrared adsorption, the scrambling of¹³C¹⁸O to¹³C¹⁶O was studied as a function of the temperature. The vanadium promoter decreases the temperature for CO scrambling. Linear adsorbed CO is the preferred initial state for this process.     

氯化氢催化氧化制氯气技术进展

综述了在氯化氢催化氧化制氯气技术开发过程中,催化剂研究和反应器开发的进展情况。分析认为,采用催化氧化法生产的氯气将成为工业用氯气来源的重要组成部分。     

Dissolved oxygen removal by combination with hydrogen using wetproofed catalysts

Dissolved oxygen in water at parts per million levels could be reduced to a few parts per billion by reaction with hydrogen using Pt catalysts supported on carbon and stainless steel in random and structured bed configurations. The carbon supported catalyst was Teflon coated to wetproof it. Both gas phase and liquid phase reactions occurred simultaneously under trickle bed operation, resulting in higher oxygen removal efficiency for this mode of operation than for the liquid-filled condition. The structured catalyst bed yielded greater hydraulic capacity than the random bed, and with wetproofed catalyst it gave the best oxygen removal efficiency. Since the gas phase reaction rate could be increased by reducing the wetted fraction of the catalyst through wetproofing, wetproofed catalysts offer a unique advantage over conventional hydrophilic catalysts.     

Deep oxidation of light alkanes over titania-supported palladium/vanadium catalysts

The total oxidation of short-chain hydrocarbons has been studied using a titania-supported palladium catalyst modified with vanadium. A range of catalysts has been prepared by coimpregnation of the titania support with palladium (II) chloride and ammonium metavanadate. The addition of vanadium promoted the rates of oxidation at lower temperatures. Vanadium loadings between 0.5 and 3.0 wt% were investigated and the most active catalyst was 0.5% Pd1.5% V/TiO₂. The addition of vanadium decreased the palladium dispersion and the number of surface palladium sites. Microlaser Raman characterisation identified the supported vanadium species and the vanadium loading influenced these. The addition of palladium modified the vanadium species. In particular the presence of palladium increased the concentration of polymeric vanadium species. Temperature-programmed reduction studies showed that the addition of palladium to V/TiO₂ significantly increased the ease of catalyst reduction. Characterisation using electron paramagnetic resonance spectroscopy showed that the presence of palladium significantly increased the concentration of V⁴⁺ species. It is proposed that the increased catalyst activity is related to the modified redox properties of the catalysts.     

Copper-based efficient catalysts for propylene epoxidation by molecular oxygen

Among a series of SBA-15-supported transition metal oxides with and without modification, the CuO_x/SBA-15 after K⁺ modification exhibited the best catalytic performance for the epoxidation of propylene by molecular oxygen. Potassium was the best modifier among various alkali and alkaline earth metal ions examined, and potassium acetate was a superior precursor of K⁺ for propylene oxide formation. The highest propylene oxide selectivity was obtained over a catalyst with copper content of 1 wt.% and K/Cu molar ratio of 0.7. Kinetic studies reveal that the allylic oxidation mainly proceeds over the CuO_x/SBA-15 providing acrolein as the main partial oxidation product, and the K⁺ modification switches the main reaction route from allylic oxidation to epoxidation. The characterizations suggest that copper species with content of ≤5 wt.% are located in the mesoporous channels of SBA-15 existing mainly as CuO_x clusters and Cu²⁺ ions, and there exists an interaction between K⁺ and the copper species. This interaction is proposed to play pivotal roles in epoxidation of propylene. As compared with other reported Cu-based catalysts for propylene epoxidation, the present catalyst possesses several distinct features.     

Effect of hydrogen on the molecular weight of polypropylene with Ziegler-Natta catalysts

Summary Polymerization of propylene was conducted at 40 °C with the catalytic system of TiCl₄/MgCl₂/ Al (C₂H₅)₃/ethyl benzoate using hydrogen as a chain transfer agent, and the effect of hydrogen on the molecular weight was examined separately with the soluble and insoluble fractions in boiling n-heptane. It was found that the chain transfer reaction of the atactic and isotactic polymers took place via an atomic hydrogen and a molecular hydrogen, respectively. The result strongly supports the previous mechanism that there exist two types of polymerization centers, one having two vacancies which gives the atactic polymer and the other having one vacancy which gives the isotactic polymer.     

Tetralin oxidation over chromium-containing molecular sieve catalysts

A series of catalysts in which a transition metal (Fe, Co, and Cr) is incorporated into MCM-41, hexagonal mesoporous aluminophosphate (HMA), and AlPO₄-5 matrix was prepared and tested for liquid phase oxidation of tetralin using tert-butyl hydroperoxide as an oxidizing agent. In general, chromium-containing catalysts showed higher catalytic activity as well as higher α-tetralone selectivity than iron or cobalt-incorporated catalysts. In addition, HMA proved more effective as a support material than MCM-41. CrHMA was the most active (64.9% conversion) and selective (80% α-tetralone selectivity) catalyst, but developed metal leaching due to its amorphous pore walls. CrAlPO₄-5, having a crystalline structure, showed higher resistance to metal leaching than CrHMA.     

氯化氢氧化所用催化剂的研究进展

介绍了氯化氢转化成氯气的基本工艺方法,并从催化氧化法所用金属基催化剂出发,对反应过程中催化剂的稳定性进行总结,并对催化剂的未来发展方向做了展望。     

The catalysis of hydrogen oxidation with oxygen on molybdenum trioxide

The mechanism of the catalytic oxidation of H₂ with O₂ on pure MoO₃ was studied kinetically in a closed circulation and static system, by measuring the electric conductivity of the catalyst during the reaction. The kinetic isotope effect with respect to hydrogen and the isotope exchange reactions between ¹⁸O₂ and ¹⁶O₂ as well as between D₂ and H₂ during the catalysis were also measured to elucidate the details of the catalysis mechanism. The experimental results were compared with those of the catalytic oxidation of CO with O₂ on this oxide carried out previously. The activation energy and the rate constant of H₂ oxidation almost coincided with those of CO oxidation. Electric conductivity measurements indicated that the catalyst was in a slightly reduced state during the steady state of the catalysis of H₂ oxidation as well as in the case of CO oxidation. The active oxygen on the surface of the catalyst which was operative in the catalysis of CO oxidation was found to be also operative in the catalysis of H₂ oxidation. The reaction scheme of H₂ oxidation with O₂ on MoO₃ could be explained in a manner similar to that of CO oxidation on this oxide. From the fact that the activation energies for the oxidations of H₂ and D₂ were very close with each other on MoO₃, molecular hydrogen, weakly bound to the active oxygen on the surface of the catalyst, was assumed to enter into the active complex in the rate-determining step of this catalysis.