甲烷单加氧酶催化反应的研究进展

介绍了甲烷单加氧酶的组成,催化作用、性能、机理、载体及其影响因素,以及甲烷单加氧酶的化学模拟初步的发展状况.综述了甲烷单加氧酶(简称MMO)在甲烷催化合成反应中的重要作用及其发展前景.     

矿化垃圾中兼性营养菌原位强化甲烷氧化

引言好氧甲烷氧化菌在新陈代谢上具有独一无二的特性:它们能够利用甲烷和其他一碳化合物作为唯一碳源和能源。这类微生物最典型的特点是利用甲烷单加氧酶(MMO,methane monooxygenase)     

端羟基聚丁二烯改性喷涂聚脲弹性体的制备及性能

以端羟基聚丁二烯(HTPB)和端羟基聚醚(DL-2000)与二苯甲烷二异氰酸酯反应合成A组分;以端氨基聚醚、交联剂聚醚胺和扩链剂3,3'-二氯-4,4'-二胺基二苯甲烷(MOCA)在有机铋或有机锡二月桂酸二丁基锡催化剂的作用下制备B组分;然后A、B 2组分等体积喷涂制备HTPB改性聚脲弹性体.研究了有机铋和有机锡2种催...     

玉米秸秆木质素的漆酶/介体活化处理

采用漆酶配以不同的介体对玉米秸秆木质素进行活化处理,利用红外光谱(FTIR)、紫外光谱、凝胶渗透色谱(GPC)、热失重(TG)、示差扫描量热(DSC)等分析方法研究了介体对漆酶活化降解木质素的影响。结果表明,漆酶会使木质素发生脱甲基作用,降低木质素的相对分子质量,增加酚羟基的含量,但在解聚木质素的同时也伴随着再聚合作用。在漆酶活化木质素的过程中,介体作为传递电子的中间体,能够促进木质素的氧化降解,降低木质素的相对分子质量,提升羟基的反应活性。不同的介体,活化效果不同,HBT、香草醛和紫丁香醛三种介体中,HBT介体的活化效果最佳。     

一氧化碳甲烷化反应的研究进展

介绍了甲烷化反应的发展历程,分析了CO甲烷化的反应机理,详细综述了国内外甲烷化催化剂载体、活性组分和助剂的研究现状,最后提出了催化剂的发展趋势和甲烷化反应面临的机遇和挑战。     

美研究甲烷制甲醇催化反应机理

美国西北大学研究了甲烷制甲醇反应用的具有膜囊结构的金属酶。他们将分解结构为2．8A的颗粒甲烷单氧酶(pMMO)(即主要的甲烷氧化酶)溶入在甲烷消耗细茵中。该酶由三个单体组成，并且聚集成束而形成膜囊的微元。每个单体在其可溶区域内含两个金属中心(其中一个为单个铜离子，另一个为一对铜离子)，     

部分甲烷化生产中热值煤气的研究

含高浓度CO和CO_2的气体的甲烷化,在工程上碰到几个主要的问题:(1)是反应强烈放热,使催化剂床产生剧烈温升,可能使催化剂烧结;(2)是反应气体中H_2/CO克分子比较低,增加了板结的可能性;(3)是反应气体中存在的对催化剂有害的毒物使催化剂失活。因此,对煤气甲烷化过程的研究通常包括两个方面:甲烷化工艺(包括反应器)的研究和甲炕化催化剂的研究。本报告简要地介绍了有关煤气部分甲烷化工艺及两种类型的甲烷化催化剂的研究结果。     

CO、CO_2及其共存体系的甲烷化反应

介绍了甲烷化的反应体系,CO、CO2甲烷化反应的机理;比较了CO体系、CO2体系和CO、CO2共存体系的甲烷化反应特点以及三种反应体系对催化剂的要求;综述了适用于不同体系催化剂的研究进展,并重点介绍了多种催化剂的载体、助剂与活性组分之间的相互作用方式以及几种催化剂对碳氧化物甲烷化反应的催化机理;甲烷化反应的应用方向逐步从合成氨、合成气制天然气向燃料电池、焦炉煤气等方向扩展,对反应体系的研究也由CO甲烷化体系向CO2甲烷化体系和共存体系方向发展;复合载体负载的多金属催化剂成为现在甲烷化催化剂的主要研究方向,纳米颗粒催化剂、等离子体等技术开始应用于甲烷化催化剂。     

二氧化碳甲烷化催化剂及反应机理研究进展

在“双碳”目标的背景下，明确碳处理路径至关重要。利用可再生能源制得的氢，将二氧化碳(CO₂)通过甲烷化反应制备合成天然气(SNG)被广泛认为是一种高效、有前景的碳捕集利用技术，有望实现碳循环利用。近年来，二氧化碳甲烷化催化剂及相关反应机理均取得了许多新进展。鉴于此，本工作对该反应进行了系统的综述。首先，介绍了CO₂甲烷化反应的热力学研究中不同反应条件的影响；随后从活性金属、载体、制备方法及辅助技术等四方面介绍了CO₂甲烷化催化剂的研究进展，其中活性组分包括非贵金属基(Ni,Fe,Co和Mo)和贵金属基(Ru,Rh,Pt和Pd)，载体包括传统氧化物(Al₂O₃,SiO₂,TiO₂,ZrO₂和CeO₂)和新型载体材料(金属有机框架和碳基材料)，催化剂制备方法包括传统制备方法(浸渍法、共沉淀法、水热法、溶胶-凝胶法和固相合成法)和合成辅助技术(超声波、微波和等离子体等)；总结了CO₂     

煤制天然气催化剂研究进展

甲烷化催化剂是甲烷化工艺开发的基础,综述了甲烷化催化剂的活性组分、载体和助剂的研究进展以及影响甲烷化催化剂活性的因素,分析了国内外甲烷化催化剂现状。     

Isothermal, non‐oxidative, two‐step CH4 conversion over unsupported and supported Ru and Pt catalysts

The isothermal, non‐oxidative, two‐step conversion of CH₄ to C₂₊ hydrocarbons was investigated over unsupported and supported Pt and Ru catalysts at moderate temperatures and elevated pressures. The single‐cycle specific activity (μmol C₂₊/g_cat) and total product yield (μmol C₂₊/μmol surface metal) for Ru powder at 430 K were significantly higher than for Pt powder at 503 K. The activity and total product yield for mixed metal oxide (MMO)‐supported Ru were significantly less than for Ru powder; however, Pt/MMO exhibited similar activity and product yield in comparison to Pt powder. The formation of methylbutane and methylpentane increased with increasing pressure over Ru/MMO. However, increasing pressure favored the formation of C₄ species over Pt/MMO. This revised version was published online in July 2006 with corrections to the Cover Date.     

纳米复合金属氧化物/聚酰胺6复合纤维的制备及性能

用共沉淀法制备了锌铝、锌镁铝及镁铝层状双氢氧化物(LDHs),将LDHs经过500℃煅烧后,得到相应的纳米复合金属氧化物(MMO)。MMO经偶联剂表面改性后,与聚酰胺6(PA6)切片共混造粒、熔融纺丝制备MMO/PA6复合纤维,并织造了MMO/PA6织物。用差示扫描量热仪(DSC)、扫描电子显微镜(SEM)以及红外成像仪等研究了MMO/PA6复合纤维的热性能、横截面形貌及MMO/PA6织物的红外辐射性能。结果表明:MMO/PA6复合纤维的可纺性好;加入MMO后,PA6复合纤维的强度下降约10%,但对PA6纤维的熔融温度没有影响;MMO的加入显著提高了PA6纤维的红外辐射性能,60℃保温的MMO/PA6织物,当MMO的质量分数为2.0%时,其温度高于空白PA6织物约2.0℃,具有优异的远红外辐射性能。     

Thermal stability of solutions of cellulose in methylmorpholine-N-oxide and systems based on it

Conclusions The thermal stability of MMO and of cellulose solutions in MMO has been investigated by the methods of viscosimetry, thermogravimetric analysis, and mass-spectrometric analysis.The thermoxidative nature of the degradation of cellulose in MMO solutions has been oxidation and reduce the melting point of the solutions obtained.Translated from Khimicheskie Volokna, No. 3, pp. 30–32, May–June, 1987.     

Optical Properties and Structure of Highly Concentrated Solutions of Cellulose in N-Methylmorpholine N-Oxide

The nature of the anisotropy of highly concentrated solutions of cellulose in MMO was investigated. The temperature-concentration intervals of the existence of nonequilibrium and thermodynamically equilibrium anisotropic states of cellulose in solutions of MMO were detected and determined. The proposed explanation of the specific features of the reaction of cellulose with MMO, which results in the formation of a mesophase, does not exhaust the group of problems of the mechanism of ordering of highly concentrated cellulose solutions and the structural characteristics of the liquid-crystalline phase formed. An examination of these questions requires conducting further detailed studies.     

水系镁离子电池正极材料MgMn2O4的制备

采用溶胶-凝胶法制备得到了主相为四方结构的MgMn2O4。研究了煅烧温度对产物的相演化和表面形貌的影响,比较了电化学循环稳定性。结果表明,550℃烧结得到了表面呈现多孔通道和孔洞的MgMn2O4 (MMO550),在40 mA/g电流密度下,最大放电比容量为54.0 mAh/g; 与碳纳米管于400℃复合2 h后,CNT形成的导电网格有效地将MgMn2O4颗粒连接起来,得到MMO/CNT样品的首次放电比容量可达118.0 mAh/g,是未复合MMO550最大放电比容量的2.2倍,循环30周后容量保持在88.1 mAh/g。     

Synthesis of Ni-Al layered double hydroxide via coprecipitation: Formation mechanism,synthesis intensification,and catalytic application

Herein, the formation mechanism of Ni-Al layered double hydroxide (NiAl-LDH) synthesized by coprecipitation was explored. Moreover, NiAl-LDH was prepared in a rotating packed bed (RPB) under different rotation speeds, which shows that increasing the rotation speed decreases the lateral size and thickness of NiAl-LDH, since high rotation speed accelerates the nucleation of NiAl-LDH. Additionally, the Ni/mixed metal oxides (MMO) catalysts derived from NiAl-LDH were prepared for maleic anhydride (MA) hydrogenation. Result shows that Ni/MMO catalyst obtained from NiAl-LDH prepared under a higher rotation speed exhibits higher MA conversion due to its larger surface area and smaller nickel particle size. The Ni/MMO catalyst obtained from NiAl-LDH prepared under 500 rpm exhibits 100% MA conversion and 100% succinic anhydride selectivity under 30°C and 2 MPa within 1 h. This work provides fundamental insight to understand the formation of NiAl-LDH. Moreover, RPB as an effective technique to synthesize NiAl-LDH and Ni-based catalysts was validated.     

A binder‐free Ir0.4Ru0.6‐oxide/functionalized multi‐walled carbon nanotube electrode for possible applications in supercapacitors

An initial study on a simple and inexpensive method to form an Ir_0.4Ru_0.6‐oxide (MMO) coating onto high‐area plasma functionalized multi‐walled carbon nanotubes (f‐MWCNTs) at the bench‐scale for possible supercapacitor (SC) applications is presented. f‐MWCNT electrodes are prepared in a two‐step process combining the growth of MWCNTs directly onto a 316 stainless steel mesh by thermal‐chemical vapour deposition (t‐CVD), followed by the addition of oxygen‐containing functionalities to their surface by plasma functionalization. The plasma functionalization step is done to: (i) improve electrode wettability and (ii) improve capacitive properties through the addition of pseudocapacitive oxygen functionalities. A simple dip‐dry method is then employed to coat the f‐MWCNTs with the desired MMO coating (Ir_0.4Ru_0.6‐oxide) prepared initially in a liquid precursor mixture. f‐MWCNT electrodes are suspended and dipped into the precursor then heated in air to evaporate the solvent while building the oxide layer. The resulting MMO/f‐MWCNT electrode exhibits excellent stability in 4 mol/L KOH electrolyte, yielding larger specific capacitance values than those obtained on bare f‐MWCNT electrodes; at a charging/discharging current density of 0.5 mA cm^?2, the MMO/f‐MWCNT and f‐MWCNT electrodes achieve specific capacitances of 664 ± 7 and 190 ± 30 F g^?1 in a 3‐electrode cell, respectively. The MMO/f‐MWCNT electrodes show good rate capability performance up to 10 mA · cm^?2 and excellent stability.

     

Highly dispersed and confined Ni/MMO catalyst synthesized in a rotating packed bed for hydrogenation of maleic anhydride

Catalytic hydrogenation of maleic anhydride (MA) into succinic anhydride (SA) is one of the most important transformations in synthetic organic chemistry. Herein, we firstly synthesized well-dispersed nickel particles confined by mixed metal oxides (Ni/MMO) derived from in situ transformation of Ni-Al hydrotalcite in a rotating packed bed (RPB) to catalyze this process. A series of Ni/MMO catalysts (63 wt%–89 wt% Ni) were effectively fabricated and the structure–activity relationship was established. Results showed that a Ni/MMO catalyst (82 wt% Ni) with substantial surface defect sites and the highest Ni surface area among the prepared Ni/MMO catalysts, demonstrates the highest activity with ~100% MA conversion and ~100% selectivity to SA under 25°C within 77 min. This is, to our knowledge, the highest conversion and selectivity under room temperature to date. Moreover, the Ni/MMO catalyst prepared by RPB has higher specific surface area and Ni surface area, therefore possessing a higher hydrogenation rate compared to that by stirred tank reactor (1.69 vs. 1.36, 10⁻³·mol_MA/g_cat/min). These results will provide an attractive option of the catalysts for MA hydrogenation, and a novel strategy for synthesizing nickel catalyst derived from Ni-Al hydrotalcite.     

Temperature dependence of vapor pressure in the system N-methylmorpholine-N-oxide-water system

Conclusions The temperature dependence of vapor pressure over the MMO-water and dehydrated MMO has been obtained.It has been shown that crystal hydrates of MMO affect the character of the temperature dependence.Translated from Khimicheskie Volokna, No. 5, pp. 26–27, September–October, 1985.     

Superior overall water splitting performance in polypyrrole photoelectrode by coupling NrGO and modifying electropolymerization substrate

We prepare photoelectrodes with mixed metal oxides (TiO₂-RuO₂), polypyrrole (PPy) and N-doped reduced graphene oxide (NrGO) on titanium (Ti) substrate for overall water splitting and methylene blue degradation during two steps; including a sol–gel deposition of mixed metal oxide (MMO) and electrodeposition of PPy or PPy-NrGO films. The as-prepared photoelectrodes are characterized by physical and photoelectrochemical measurements. Ti/MMO/PPy-NrGO photoelectrode exhibit a considerably photocurrent density of −6.97 mA cm⁻² (at 0 V vs. reversible hydrogen electrode [RHE]) and 12.89 mA cm⁻² (at 1.23 V vs. RHE) for hydrogen and oxygen generations, respectively. However, promotion in the H⁺/H₂ efficiency (40.25%) is about 28 orders of magnitude while in the case of H₂O/O₂ (13.77%) is 10 times. The electrochemical impedance spectroscopy and Mott–Schottky measurements reveal that the simultaneous incorporation of MMO and NrGO nanosheets in PPy coating leads to the lowest charge transfer resistance at the photoelectrode/electrolyte interface and an improvement in charge carrier density.