甲基单胞菌GYJ3催化环氧丙烷的半连续合成

利用含有甲烷单加氢酶（MMO）的甲烷氧化细菌整催化丙烷环氧化制取环氧丙烷,其产物抑制和辅酶NADH消耗是反应难以连续进行的主要原因,采用甲烷再生NADH,研究了丙烯和甲烷共氧化和氧物氧丙烷积累对甲基单胞菌GYJ3的环氧化活性的影响,并考察了在具有产物连续收系统的两段式生物反应器中用细菌胞悬浮液半连续生产环氧丙烷的可行性,将再生和环氧化过程分开进行,以减小甲烷和丙烯的竞争抑制,通过连续抽提产物环氧丙烷,克服了产物抑制,该半连续过程分别在不同的温度下共进行了70h,产生环氧丙烷438μmol。     

甲醇驱动的环氧丙烷连续生物合成

采用甲醇蒸气作为碳源对甲基弯菌IMV 3011进行驯化培养,然后逐渐增加液态甲醇的浓度使其适应,得到了能耐受甲醇(φ(MeOH)=1%)的甲基弯菌IMV 3011.对甲基弯菌IMV 3011进行甲烷-甲醇共培养可得到大量具有甲烷单加氧酶(MMO)活性的细胞.研究了添加甲醇对甲基弯菌IMV 3011生长和MMO活性的影响,发现甲醇能够促进甲基弯菌IMV3011的生长.在批式反应器中,添加甲醇能够提高甲基弯菌IMV 3011的催化环氧化能力,说明甲醇可以作为电子供体通过再生辅酶NADH驱动环氧丙烷合成.考察了在膜反应器中用细胞悬浮液连续合成环氧丙烷的可行性.结果表明,通过192 h连续抽提产物环氧丙烷,避免了其对环氧化反应的抑制,流出液中环氧丙烷的浓度仍保持在1.35 mmol/L左右.     

La2O3/BaCO3上甲烷氧化偶联反应动力学与历程

以8％La_2O_3/BaCO_3为催化剂,用无梯度反应器,在720～800℃温度范围内,通过改变甲烷与氧分压进行了一系列的甲烷氧化偶联反应动力学测量,确定了该反应的反应历程。乙烷和大部分CO_x(主要是CO_2)是甲烷氧化的一次产物。乙烯是乙烷串行反应的产物。用幂式动力学方程拟合动力学试验数据,估算了各步反应速度方程的动力学参数。还用脉冲反应技术与过渡应答技术证明了参与活化甲烷的是催化剂表面上的可逆吸附氧。     

脉冲电晕放电下的甲烷氧化偶联反应(英文)

研究了在常温,常压及惰性气体稀释的条件下,用脉冲电晕放电进行的甲烷氧化偶联（OCM）反应。在各种实验条件下,产物CZ烃由一6o／o乙烯,－70rk乙烷和一87％乙炔组成。甲烷的转化率及CZ烃的生成速率依赖于反应气中甲烷与氧气的比值,它们的流速及直流电源的电压等n通过调节这些实验条件,甲烷转化为C4烃的转化率可得到优化,在45kV高压,30ml。／min的流速下（反应气体组成为95％CHn与50／0O2）,CZ烃的最高选择性可达85O／O。当反应气体组成为80％CH4和20O／oOZ时,甲烷的最高转化率达23％。在间歇式反应器中,甲烷转化率随反应时间增长而提高,反应75分钟时甲烷转化率达7lO／O,而CZ烃的产物分布,尤其是乙炔的含量随反应时间增长而明显降低,这些实验结果支持了文献中提出的ZCH4～CZH6—CZH4～CZHZ～CO／COZ反应历程。     

甲烷氧化细菌催化二氧化碳生物合成甲醇的研究

甲烷氧化细菌中包含的甲烷单加氧酶(MMO)、甲醇脱氢酶(ADH)、甲醛脱氢酶(FaldDH)、甲酸脱氢酶(FateDH)经过一系列反应能够把甲烷深度氧化生成二氧化碳，并生成一定的能量物质．把二氧化碳还原为甲醇是一个需要能量的过程，目前还没有已知的有机体在温和条件下完成这一反应．研究发现，甲基弯菌Methylosi-nus trichosporium IMV 3011可以催化二氧化碳生物转化生成甲醇．在休眠的悬浮细胞中充人二氧化碳后，反应一段时间在反应液中检测到了甲醇．二氧化碳转化成甲醇是一个需要能量推动的反应，为了补充反应所消耗的能量．反应一段时间后需要用甲烷进行再生，以恢复细胞中的还原当量NADH．我们进行了反应再生的交替连续批式反应，甲醇积累量能够维持在一个比较稳定的水平．理论上，反应不会增加温室效应，这是一个有效的、环境友好的、可恢复的反应过程．     

甲烷氧化细菌的铜捕获机理

甲烷是大气中主要温室气体之一. 由于甲烷排放的增加, 近200年来其在大气中的含量以每年1%的速度急剧上升, 对温室效应贡献已达到15%～20%. 广泛存在于自然界中的甲烷氧化细菌 (Methanotrophic bacteria或 Methane-oxidizing bacteria) 能够以甲烷为唯一碳源和能源进行生长, 通过甲烷单加氧酶(Methane monooxygenase, MMO)开始的一个酶系将甲烷最终代谢成二氧化碳和水, 并在此过程中获得生长所需的碳骨架和能量.     

Ni基催化剂上甲烷与空气或O_2/水蒸气部分氧化制合成气(英文)

在固定床反应器中考察了Ni基催化剂上甲烷氧化与空气或O2/水蒸气部分氧化制合成气的反应。用空气取代纯氧同样能获得高甲烷转化率和产物选择性。水的添加主要发生水气变换反应,同时也能降低催化剂上积炭。在甲烷与纯氧500小时反应的稳定性考察中,甲烷转化率、CO及H2选择性分别保持在90％、95％和95％以上;反应后上层催化剂的Ni含量从新鲜催化剂的7.2％下降到5.2％,在反应后的催化剂上没有发现积炭和相变。     

NOx催化的甲烷气相氧化反应

 考察了没有固体催化剂时NOx对甲烷气相氧化的催化作用，并用原位红外光谱研究了CH4－O2－NOx体系随温度的变化．实验结果表明，NOx对甲烷气相氧化有很高的催化活性．在20％CH4－10％O2体系中加入0．05％～0．2％的NO后，反应温度可降低200～300℃，在650～700℃下反应时，CH4转化率和CO选择性可分别达到38％和90％，产物中的n（H2）／n（CO）比为0．4～0．7．反应产物中可观察到有甲醛、甲醇和乙烯等，通过改变反应条件可以控制各组分的相对浓度．     

微波场对固态氧离子导体上的甲烷氧化偶朕的影响

研究了微波场下甲烷在具有Bi2O3结构的固态氧离子导体上氧化偶联反应行为．与常规加热条件下的反应结果相比较,微波辐照下的反应有如下特点;（1）在达到相同甲烷转化率时,微波辐照下所需床层温度要远低于常规加热条件下所需床层温度;（2）微波辐照下,甲烷氧化偶联产物中C2烃的选择性普遍较高,在低温区尤为突出．微波场下甲烷偶联产物乙烷、乙烯的再氧化得到一定程度的抑制,致使微波场下的甲烷氧化偶联反应通常有较低的烯／烷比．     

反应器型式对甲烷低温等离子体转化制C2烃的影响

就不同反应器对甲烷常压低温等离子体转化制C2烃的影响进行了研究。结果表明,相同的甲烷停留时间和相同甲烷流率下,反应器A和B中反应的主要产物是乙炔,乙烯和乙烷的含量较少,积炭量较多;而反应器C和D中反应的主要产物为乙烷和丙烷,乙烯和乙炔含量较少,积炭量很少。反应积炭对反应器A中甲烷转化率影响很大,对于产物选择性影响不大,而对反应器C中的反应影响较小。根据产物分布可知,在反应器A和B中,由于电子具有很高的能量和密度,甲烷主要解离为碳原子;而在反应器C及D中,由于电子能量和密度较低,甲烷主要解离为CH3自由基。     

Control of the directions of oxidative transformation of methane over nickel-based catalysts by acid-base properties

Two completely different directions of the oxidative transformation of methane (OTM) were performed on nickel-based catalysts due to the different acid-base properties of those catalysts. The relatively acidic LaNiO_x and LiNiLaO_x/Al₂O₃ catalysts exhibit excellent Partial Oxidation of Methane to Syngas (POM) performance. However, the relatively basic LiNiLaO_x catalyst has a good Oxidative Coupling of Methane to C₂ Hydrocarbons (OCM) activity. The basic properties of the catalyst makes it difficult to reduce nickel and keeps it in the oxidized state. Reduced nickel is necessary for POM and oxidized nickel for the OCM reaction.     

Quantum chemical study of C—H bond activation in methane molecule by AuIII aqua chloride complexes

The mechanism of the reactions of methane with the gold(III) complexes [AuCl_x(H₂O)_{4− x} ]^3−x (x = 2, 3, or 4) was studied by the DFT/PBE method with the SBK basis set. High activation barriers obtained for the reactions of [AuCl₄]⁻ and [Au(H₂O)Cl₃] with methane suggest these reactions cannot proceed under mild conditions. The reaction of the [Au(H₂O)₂Cl₂]⁺ complex with methane has a rather low energy barrier and proceeds through the formation of an intermediate complex. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 191–201, February, 2006.     

NOx—Catalyzed Gas—Phase Activation of Methane： the Formation of Hydrogen

NOx-catalyzed oxidation of methane without a solid catalyst was investigated, and a hydrogen selectivity of 27% was obtained with an overall methane conversion of 34% and a free O2 concentration of 1.7% at 700℃.     

Calorimetric study of methane interaction with supported Pd catalysts

As supported palladium oxide catalysts present the best performances in methane combustion in lean conditions, microcalorimetric studies of the interaction between methane and palladium oxide or metallic palladium supported on Al₂O₃, ZrO₂ and BN have been performed at 673 K. At this temperature methane reduced the palladium oxide, and the heat of reduction of palladium oxide was shown to depend on the dispersion and on the support. The lowest heats of reduction corresponded to the highest rates of methane combustion. Moreover methane reforming occurred on metallic palladium, producing hydrogen, and again methane decomposition was shown to depend on the support. This revised version was published online in July 2006 with corrections to the Cover Date.     

Recent progress in methane dehydroaromatization: From laboratory curiosities to promising technology

Direct conversion of methane to benzene or other valuable chemicals is a very promising process for the efficient application of natural gas. Compared with conversion processes that require oxidants, non-oxidative direct conversion is more attractive due to high selectivity to the target product. In this paper, an alternative route for methane dehydrogenation and selective conversion to benzene and hydrogen without the participation of oxygen is discussed. A brief review of the catalysts used in methane dehydroaromatization (MDA) is first given, followed by our current understanding of the location and the active phase of Mo species, the reaction mechanism, the mechanism of carbonaceous deposit and the deactivation of Mo/zeolite catalysts are systematically discussed. Ways to improve the catalytic activity and stability are described in detail based on catalyst and reaction as well as reactor design. Future prospects for methane dehydroaromatization process are also presented.     

Role of iron and copper in particulate methane monooxygenase of Methylosinus trichosporium OB3b

The role of iron and copper in particulate methane monooxygenase (pMMO) of Methylosinus trichosporium OB3b is described, and an overview of the enzyme's properties is presented. The pMMO from M. trichosporium OB3b was solubilized in the detergent n-dodecyl--D-maltoside and purified by chromatographic techniques. The enzyme consists of 0.9 iron atoms and 12.8 copper atoms per molecule. The iron site in pMMO may be mononuclear non-heme iron. Copper exists as either copper ion coupled to four nitrogen atoms and/or trinuclear copper cluster wherein copper ions are ferromagnetically coupled.     

Interaction of Methane and Oxygen with the Surface of Manganese Oxide-Containing Catalysts

We used pulsed reduction and temperature programmed oxidation to study the interaction of methane and oxygen with the surface of manganese oxide-containing catalysts. We hypothesized that during oxidative dimerization of methane, the phase supplying strongly bound oxygen for selective methane coupling is an acceptor for weakly bound oxygen of the phase catalyzing exhaustive oxidation.     

Coke formation during high pressure catalytic partial oxidation of methane to syngas

Summary Carbonization of the surface of alumina-based catalysts has been studied with respect to the composition of the catalysts and conditions of the propionitrile ammonolysis. It was shown that the surface concentration of carbon increases with the increase in temperature and with time of the reaction and depends on the catalysts nature in the order: Al-Zr(5)-O < Al-Zr(40)-O < Al-O < Al-Mg-O. The surface concentration of the Brönsted acidic sites follows the same sequence.     

Selective methane oxidation to formaldehyde using polymorphic T-, M-, and H-forms of niobium(V) oxide as catalysts

The investigations of selective methane oxidation to formaldehyde over T-Nb₂O₅, the mixture of M-Nb₂O₅ and H-Nb₂O₅ as well as H-Nb₂O₅ were carried out. The tests were conducted under atmospheric pressure, in the temperature range 420–750°C, using oxygen as the oxidizing agent. T-Nb₂O₅ samples were examined at the contact time 0.7–1.8 s (GHSV 2000–5143 h⁻¹). Other polymorphic forms of niobium(V) oxide were examined at the contact time 0.9 s. Various polymorphic forms of Nb₂O₅ displayed various formaldehyde and carbon dioxide yield. Using H-Nb₂O₅ and M-Nb₂O₅ phases with a block type structure, made it possible to obtain higher formaldehyde selectivity (78 % at 0.9 s) as compared to T-Nb₂O₅ (47 % at 0.9 s), a polymorphic form which does not have a block type structure. However, the highest space time yield of formaldehyde (46 g per kg of catalyst per h) was obtained over T-Nb₂O₅ supported on SiO₂. Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May 2007.     

Samarium Based High Surface Area Perovskite Type Oxides SmFe1-XAlXO3 (X=0.00, 0.50, 0.95). Part II, Catalytic Combustion of CH4

The catalytic combustion of methane with stoichiometric amounts of oxygen to CO₂ and H₂O has been studied over samarium based high surface area perovskite type oxides SmFe_1-xAl_xO₃ (x=0.00, 0.50 0.95) prepared via a new sol-gel method. A comparison to other lanthanum perovskites prepared by the ceramic method shows higher catalytic activity for SmFeO₃ and SmFe_0.5Al_0.5O₃ samples.