甲烷低温活化制甲醇研究进展

简要评述了当前国内外在甲烷直接部分氧化合成甲醇和甲烷经卤代后合成甲醇领域的研究进展。众多研究表明,甲烷多相催化氧化制甲醇是最具有工业化应用前景的技术,其中钼系催化剂的效果较好;以Pt、Pd配合物为催化剂的甲烷液相催化氧化法制甲醇方法具有较高的甲烷转化率和甲醇选择性,但是催化剂价格昂贵、反应条件苛刻、环境污染严重;甲烷气相均相氧化属于非催化反应,在高温高压下进行,且反应器须具备特殊的形式,结构复杂;虽然酶催化氧化法的选择性较高,但是生物酶的制备有一定难度,不适用于大范围应用,该路线目前仅限于实验室研究阶段;光催化氧化是一种环境友好的技术,反应条件温和、避免氧化剂应用,但是该类催化剂局限于半导体和盐类,还有待于进一步开发新型高效的催化剂。同时,甲烷经卤代后合成甲醇的方法对解决甲烷活化的难题具有独特优势,是一种比较有开发前景的路线,正在受到研究者们的密切关注。     

SYNTHESIS OF DIALKOXYMETHANE AT HIGH ALKALINE CONCENTRATION VIA PHASE TRANSFER CATALYSIS

The phase-transfer catalytic reaction (PTC) of 2,4,6-tribromophenol and dibromomethane by quaternary ammonium salt was carried out in a high alkali content of KOH/dibromomethane two-phase medium. A large conversion of 2,4,6-tribromophenol is obtained at a region of high KOH content. Dibromomethane acts both as the organic-phase reactant and the organic solvent; thus, no extra organic solvent is required. Two main products, i.e., α -bromomethyl 2,4,6-tribromophenyl ether (mono-substituted product) and bis-(2,4,6-tribromophenoxide)methane (bis-substituted product), were detected in the solution during the phase-transfer catalytic reaction. The active catalyst (tetrabutylammonium 2,4,6-tribromophenoxide, ArOQ), which was produced from the reaction of 2,4,6-tribromophenol, potassium hydroxide, and tetrabutylammonium bromide (TBAB or QBr), is purified as the crystalline product from the reaction solution. A kinetic model is developed to describe the behaviors of the two organic-phase reactions on the basis of the experimental observation. The two intrinsic rate constants of the two organic-phase reactions, which are the rate-determining steps of the whole reaction system, are determined. Effects of the reaction conditions, such as agitation speed, amount of water, amount of TBAB catalyst, temperature, and amount of dibromomethane, quaternary ammonium salts, and inorganic salt KBr, on the conversion of 2,4,6-tribromophenol and the reaction rate are investigated in detail.     

介质阻挡放电常压低温等离子体转化甲烷制C2及高碳烃的研究

对介质阻挡放电(DBD)反应器用于甲烷常压低温等离子体转化过程,分别就停留时间、输入功率、内电极材料及温度、介质厚度等对反应的影响进行了研究。实验结果表明,甲烷转化率随停留时间、输入功率的增加而增加,但增加的幅度逐渐减小。内电极材料对反应积炭有很大的影响。紫铜和紫铜(镀银)材料能够有效地抑制积炭的产生,从而可以增加反应寿命,还对甲烷转化率有很大的影响。较低的内电极温度可以抑制积炭,但是甲烷转化率有所降低,同时液态高碳烃选择性增加。在甲烷流量较低时介质厚度对反应的影响很小,但随着甲烷流量的提高会逐渐增大,并且介质厚度越小,甲烷转化率越高。     

Non-oxidative conversion of methane to aromatics over modified Mo/HZSM5 catalysts

The effects of HZSM5 Si/Al ratio, cobalt additive and HCl-acidified pretreatment on methane conversion and selectivity to aromatics have been investigated for non-oxidative conversion of methane to aromatics. The HZSM5 (E) with low Si/Al ratio (Si/Al=20) has better methane conversion and benzene selectivity than HZSM5 (D) (Si/Al=55). The synergistic effect is exhibited in 3% Mo-1% Co-HCl/HZSM5 (E) catalyst, on which a high methane conversion of 10.7% can be achieved, in comparison with 5.3% methane conversion on 3% Mo/HZSM5 (E). The catalysts have been characterized by XPS and the reaction mechanism is discussed.     

CuZnTiO2/SAPO-34双功能催化剂的设计、制备及其用于CO2加氢制烯烃性能

CO₂加氢经甲醇（含氧中间体）制低碳烯烃工艺路线，可实现成醇、脱水两步反应串联协同进行，打破费托合成产物Anderson-Schulz-Flory（ASF）分布限制，高选择性地制取低碳烯烃。传统甲醇合成Cu基催化剂加氢能力较强，在两步反应中产物以CH₄、低碳烷烃为主。实验设计、制备了CuZnTiO₂/(Zn-)SAPO-34复合催化剂，实现了CO₂加氢在Cu基复合催化剂上高选择性合成C₂～C₄烯烃（约60%）。研究表明，两步反应过程中甲醇体积分数较低（＜6%），且高温下逆水煤气变换反应严重，导致催化剂酸性变化对产物分布的影响较大。调变两类活性位点比例发现，CH₄的产生与串联反应存在竞争关系，SAPO-34酸量的增加抑制了CH₄的生成，促进串联反应正向进行；合适的酸性有助于生成C₂～C₄烯烃。控制成醇、脱水两类活性位点接触距离可调变烯烃的二次反应，降低加氢能力，改善产物分布。     

Alkane metathesis by tandem alkane-dehydrogenation-olefin-metathesis catalysis and related chemistry

Methods for the conversion of both renewable and non-petroleum fossil carbon sources to transportation fuels that are both efficient and economically viable could greatly enhance global security and prosperity. Currently, the major route to convert natural gas and coal to liquids is Fischer-Tropsch catalysis, which is potentially applicable to any source of synthesis gas including biomass and nonconventional fossil carbon sources. The major desired products of Fischer-Tropsch catalysis are n-alkanes that contain 9-19 carbons; they comprise a clean-burning and high combustion quality diesel, jet, and marine fuel. However, Fischer-Tropsch catalysis also results in significant yields of the much less valuable C(3) to C(8)n-alkanes; these are also present in large quantities in oil and gas reserves (natural gas liquids) and can be produced from the direct reduction of carbohydrates. Therefore, methods that could disproportionate medium-weight (C(3)-C(8)) n-alkanes into heavy and light n-alkanes offer great potential value as global demand for fuel increases and petroleum reserves decrease. This Account describes systems that we have developed for alkane metathesis based on the tandem operation of catalysts for alkane dehydrogenation and olefin metathesis. As dehydrogenation catalysts, we used pincer-ligated iridium complexes, and we initially investigated Schrock-type Mo or W alkylidene complexes as olefin metathesis catalysts. The interoperability of the catalysts typically represents a major challenge in tandem catalysis. In our systems, the rate of alkane dehydrogenation generally limits the overall reaction rate, whereas the lifetime of the alkylidene complexes at the relatively high temperatures required to obtain practical dehydrogenation rates (ca. 125 -200 °C) limits the total turnover numbers. Accordingly, we have focused on the development and use of more active dehydrogenation catalysts and more stable olefin-metathesis catalysts. We have used thermally stable solid metal oxides as the olefin-metathesis catalysts. Both the pincer complexes and the alkylidene complexes have been supported on alumina via adsorption through basic para-substituents. This process does not significantly affect catalyst activity, and in some cases it increases both the catalyst lifetime and the compatibility of the co-catalysts. These molecular catalysts are the first systems that effect alkane metathesis with molecular-weight selectivity, particularly for the conversion of C(n)n-alkanes to C(2n-2)n-alkanes plus ethane. This molecular-weight selectivity offers a critical advantage over the few previously reported alkane metathesis systems. We have studied the factors that determine molecular-weight selectivity in depth, including the isomerization of the olefinic intermediates and the regioselectivity of the pincer-iridium catalyst for dehydrogenation at the terminal position of the n-alkane. Our continuing work centers on the development of co-catalysts with improved interoperability, particularly olefin-metathesis catalysts that are more robust at high temperature and dehydrogenation catalysts that are more active at low temperature. We are also designing dehydrogenation catalysts based on metals other than iridium. Our ongoing mechanistic studies are focused on the apparently complex combination of factors that determine molecular-weight selectivity.     

Methanol formation from methane partial oxidation in CH4–O2–NO gaseous phase at atmospheric pressure

The reaction condition for high yield of methanol in a gaseous reaction between methane and oxygen in the presence of NO at atmospheric pressure was explored. Methane partial oxidation without NO (CH₄–O₂) gave only 1% conversion of methane at 966 K. The addition of NO led to a remarkable increase in methane conversion and to high selectivity to C₁-oxygenates. The conversion of methane attained 10% at 808 K in the presence of NO (0.5%) where the selectivities to methanol and formaldehyde were 22.1 and 24.1%, respectively. Nitromethane and carbon oxides were also observed in the product gas. The amount of nitromethane was almost equal and/or near to that of initial NO. The carbon monoxide produced was several times higher than carbon dioxide. Influences of NO concentration, ratio of methane to oxygen, water vapor, and dilution with helium gas on product distribution were measured. Low concentration of NO (0.35–0.55%) was favorable for methanol formation. High selectivity to methanol was obtained at low value of the ratio of methane to oxygen (2.0–3.0) or low concentration of dilution gas (<16%). The NO₂ added promoted methane partial oxidation and selectivity to methanol. Therefore, it was assured that NO_x promoted the formation of CH₃√ and CH₃O√ in the gas phase reaction for CH₄–O₂–NO.     

二（1-咪唑基）甲烷的合成研究

以二溴甲烷和咪唑为原料合成了二(1-咪唑基)甲烷.确定适宜的合成条件为:在乙腈溶液中,咪唑、二溴甲烷、氢氧化钾投料摩尔比为1∶0.45∶1.20,60℃反应3.5 h后再回流反应1.5 h,经重结晶提纯,产率可达83.2%.通过熔点测试和1HNMR谱图分析对产物结构进行了确证.本法具有耗时短、副反应少、产率高等特点.     

Rh负载的整体型催化剂甲烷催化部分氧化过程

采用负载Rh的泡沫独石整体型催化剂研究了甲烷催化部分氧化过程，考察了外界温度、空速和甲烷与氧气进料比例对反应转化率和选择性的影响，并对过程控制条件和调控参数进行了分析。研究结果表明该过程为毫秒级超短接触过程，反应可以在自热条件下进行，高空速条件下（8×10⁵ h^-1），甲烷与氧气进料比（体积比）为1.8，甲烷转过率超过90%，CO选择性接近95%，H₂选择性超过90%。外界加热对过程有利，可获得更高的转化率和选择性。     

Low temperature FTIR spectroscopic study of ozone interaction with phenol adsorbed on silica and ceria

Electrochemical conversion of methane has been studied over a Pt electrode in a solid oxygen conducting electrolyte cell at 800°C. It was found that the Pt electrode is an active electrode-catalyst in the partial oxidation of methane to syngas. Carbon mon-oxide selectivity and yield of 85 and 65% respectively were reached. Potentialities of the electrochemical route for production of syngas from methane against the conventional catalytic way are briefly discussed.     

己内酰胺类离子液体催化合成N-单烷基苯胺

  在己内酰胺类Brønsted酸离子液体催化下,苯胺和溴丙烷发生N-烷基化反应,高选择性地制备N-单烷基苯胺。考察了苯胺和溴丙烷摩尔比、缚酸剂用量、反应温度、反应时间、催化剂用量和催化剂类型等因素对反应结果的影响。确定其最佳反应条件为：n(苯胺)∶n(溴丙烷)∶n(催化剂)∶n(三乙胺)= 1.0∶1.0∶0.05∶2.0,反应温度60 ℃,反应时间为1.0 h,在上述反应条件下,苯胺的转化率可达到92.40%,N-单烷基苯胺的选择性可达到93.40%。     

Acetylene synthesis by methane pyrolysis on a tungsten wire

Acetylene synthesis conditions in methane pyrolysis on a tungsten wire heating element have been investigated. At high temperatures, methane pyrolysis yields a large amount of carbon black as small particles and carbon filaments. Carbon black practically does not form when methane is diluted with helium. At methane concentrations of 10–15% and coil temperatures of 1800–2000°C, 80% methane conversion and 80% acetylene selectivity have been attained at a contact time of a few hundredths of a second. Changing from pure methane to natural gas in the specified temperature range exerts no effect on the methane conversion and acetylene selectivity. It has been experimentally demonstrated that the reaction ceases on the gas temperature is decreased below 800°C.     

流化床中甲烷芳构化过程

在石英流化床反应器中研究了无氧条件下甲烷直接催化转化制备芳烃的过程.发现催化剂的诱导期长短、甲烷的总转化率与温度、甲烷分压及甲烷空速相关.在973 K下,液体产品中苯的选择性与萘的选择性随着催化剂的失活呈现不同的变化趋势.所得主要技术指标（甲烷转化率、苯的收率与选择性等）与固定床微型反应器中的结果相近.还研究了催化剂上的积炭对甲烷转化率、催化剂失活的影响,为将来的进一步研究提供了基础.     

Synthesis of halogenated phenyl glycidyl ethers and their use for flame retardancy of polymeric materials

This study deals with the synthesis of halogenated derivatives of phenyl glycidyl ether and with possibilities of their use as flame retardants and reactive diluents of epoxy resin. The best reaction conditions optimized by Nelder-Mead simplex method were found. The products of very high quality were prepared. They were mixed with a lowmolecular epoxy resin and cured by diamino diphenyl methane. The viscosity of the resin mixtures and limiting oxygen index of cured systems were determined. It was found that a higher content of halogen, both chlorine and bromine, causes increasing viscosity and reduced flammability of the epoxides.     

Low-temperature conversion of methane to oxygenates by supported metal catalysts:From nanoparticles to single atoms

Direct cost-effective conversion of abundant methane to high value-added oxygenates (methanol,formic acid,acetic acid,etc.) under mild conditions is prospective for optimizing the structure of energy resources.However,the C-H bond of products is more reactive than that of high thermodynamic stable methane.Exploring an appropriate approach to eliminate the "seesaw effect" between methane conver-sion and oxygenate selectivity is significant.In this review,we briefly summarize the research progress in the past decade on low-temperature direct conversion of methane to oxygenates in gas-solid-liquid phase over various transition metal (Fe,Cu,Rh,Pd,AuPd,etc.) based nanoparticle or single-atom catalyst.Furthermore,the prospects of catalyst design and catalysis process are also discussed.     

甲烷制卤代甲烷研究进展

甲烷的化学性质很不活泼,需经中间体才能将其转变成高附加值的化工产品。以卤代甲烷为中间体具有能耗低的优势,是一种潜在的甲烷活化方式。综述国内外甲烷制卤代甲烷研究进展,主要介绍不同卤素源条件下的反应机理及催化剂性质、反应条件对单卤代甲烷选择性的影响。甲烷经氯代甲烷活化时,产物中一氯甲烷选择性与催化剂性质密切相关,亲电型催化剂能高选择性生成一氯甲烷;甲烷经溴代甲烷活化时,贵金属和非贵金属均可作为催化剂活性中心,且该反应可以根据后续产物的需要,调节产物组成和比例。甲烷溴代反应单卤代产物选择性高于甲烷氯代反应,但溴代反应需在较高温度进行。     

Catalytic skeletal isomerization of linear butenes to isobutene

The increased demand for isobutene, used for the production of the octane-enhancer methyl tert-butyl ether, has generated tremendous interest in the catalytic conversion of the linear butenes to isobutene. In this review we survey the progress made since the late 1970s in implementing the catalytic skeletal isomerization reaction of these linear alkenes. Halogenated catalysts, especially those based on alumina, and prepared using a variety of compounds of fluorine, chlorine or bromine, have been shown to exhibit both high conversions and selectivities for the reaction, resulting in high yields of isobutene, when water is added to the feed stream. Elution of the halogen from the catalyst leads to the loss of catalytic activity and necessitates the continuous or discontinuous addition of the halogen compound. As a consequence, environmental and other considerations are most likely to weigh against the industrial usage of these catalysts. Another class of catalysts exhibiting high activities and selectivities, again in the presence of water, are the silicated aluminas. No information is, however, available on their long-term stability. Even alumina on its own displays high activity and selectivity, provided water is co-fed with the hydrocarbon stream. More recent results obtained over other types of catalysts such as zeolites and molecular sieves are also presented. Most promising are the results obtained with the zeolite ferrierite which gives high yields of the branched isomer in the absence of any other additive or diluent. The catalyst also appears to be fairly stable showing no decrease in the yield of isobutene after 14 days on-stream. The high yields of isobutene can be ascribed to the small channel diameters which prevent the extensive dimerization or oligomerization of the linear butenes or of the product isobutene. Plans for the first large-scale demonstration plant to produce isobutene from n-butenes using ferrierite as catalyst have already been announced in the United States.     

Effects of acceptor level on chemically synthesized polypyrrole-halogen complexes

Electrically conductive polypyrrole (PPY)-halogen complexes have been synthesized by simultaneous chemical polymerization and oxidation of pyrrole. The ratio of pyrrole monomer to halogen (chlorine, bromine, or iodine) used in the synthesis was varied and the physicochemical and electrical properties of the resulting complexes were studied in detail. With all three halogens, the yield of the complex is affected by the initial amount of halogen used, with the properties of the polypyrrole-bromine complex showing the strongest dependence on the acceptor level. For this complex, both the percentage of bromine incorporated and the ratio of covalent to ionic bromide increase upon increasing the initial bromine concentration, while the electrical conductivity shows a maximum. Experimental evidence suggests that some halogen substitution at the pyrrole ring must have occurred in the PPY–Br₂ and PPY–Cl₂ complexes, but not in the PPY–I₂ complex.     

Methane Steam Reforming in Hydrogen-permeable Membrane Reactor for Pure Hydrogen Production

Steam reforming of methane over a ruthenium catalyst has been carried out at 500 °C in a membrane reactor equipped with a palladium membrane supported on a porous stainless steel tube. Hydrogen and carbon dioxide are mainly produced in the reaction, while hydrogen is selectively permeated through the membrane. Since equilibrium-shift takes place by hydrogen separation from the reaction mixture, the methane conversion significantly exceeds the equilibrium value, which is low at 500 °C. The selectivity to carbon monoxide by-produced in the reaction is lower than that expected from the equilibrium. Although the equilibrium conversion decreases with an increase in the reaction pressure, the conversion with the membrane reactor can increase because the hydrogen separation is promoted by the pressure increase. The catalytic activity is an important factor to produce a sufficiently high methane conversion and it is enhanced at a high reaction pressure.     

甲烷低温催化直接合成乙酸的新途径

对甲烷经合成气路线间接制乙酸的现状及在温和条件下直接转化制乙酸的研究进展作了述评．通过对间接与直接路线的比较．以及在直接路线中,甲烷低温氧化羰化和直接羧化制乙酸均相与非均相催化体系的分析。指出了CH4-CO2低温直接合成乙酸在工艺过程上的显著优势,尤其是采用非均相催化体系．该工艺为乙酸合成和CH4与CO2的绿色化学利用开辟了新途径。其研究将会丰富C1化学化工的理论与实践．并为实现热力学不利反应提供实验方法和理论依据。