固定化Methylomonas Z201细胞：甲烷单加氧酶的活性和稳定性

分别以海藻酸钙和砂子为载体，采用包埋和吸附技术固定化ＭｅｔｈｙｌｏｍｏｎａｓＺ２０１细胞．以丙烯环氧化为指标反应，系统研究固定化对ＭｅｔｈｙｌｏｍｏｎａｓＺ２０１细胞ＭＭＯ活性和稳定性的影响．结果表明，对包埋细胞，合适的负载量和粒径为保留较高ＭＭＯ活性所必需．砂子对细胞的吸附能力中等．外源性电子给体甲酸钠对游离和固定化细胞的ＭＭＯ活性影响不同．固定化细胞的最适ｐＨ值和温度与游离细胞相同，但活化能降低．固定化细胞保留游离细胞ＭＭＯ活性的６０—７０％，操作稳定性、热稳定性、贮存稳定性均有所提高．     

丙烯酶催化氧化制取环氧丙烷—活细胞包埋法制备、再生固定化生物催化剂

采用海藻酸钙包埋法制备固定化细胞,将这种固定化的活细胞培养85h后,测其环氧化活性。催化剂经反应约6h失活,用甲烷/空气=1的混合气培养再生16h,催化剂完全恢复活性,经7次再生后的催化剂活性依然不变。文中还考察了催化剂活性与再生时间的关系,发现当再生时间为6.5h时,催化剂活性最高。用2％的甲醇培养再生16h,催化剂完全失活。用0.5％的甲醇培养基溶液再生30min,其活性可超过新制备的催化剂。还作了甲醛、甲酸钠使整细胞中NADH再生的试验。发现甲烷和空气是使细胞内NADH再生的最好方法。     

固定化酵母非水相催化羰基不对称还原反应的研究

用海藻酸钙包埋法对增殖培养的酵母细胞进行了固定化,并用于催化有机溶剂中乙酰乙酸乙酯的不对称还原反应。考察了固定化时所用缓冲溶液的pH、催化剂颗粒大小与用量、辅助底物种类、底物浓度、以及重复利用批次等因素对反应产物（S）-3-羟基丁酸乙酯的浓度和光学纯度的影响。结果表明,固定化时应采用pH为7的Tris-HCL缓冲溶液,颗粒的直径以2mm左右为较佳;反应时应以正已烷为溶剂,正已醇为辅助底物,固定化酵母颗粒的最适用量为6g/20ml反应液;底物的初始浓度以100mmol/L为佳,浓度过高对反应有一定的抑制作用;固定化细胞重复利用三次对映选择性基本保持不变。     

固定化乳杆菌细胞的离子交换吸附发酵生产乳酸

本文提出了固定化乳杆菌细胞的离子交换吸附发酵生产乳酸的新方法，该法以海藻酸钙凝胶为载体包埋固定化细胞用于生产乳酸，将离子交换树脂填充柱与发酵反应器相连接，用于从发酵液中及时地分离出产物乳酸。这种新方法成功地消除了产物乳酸对乳酸菌生长和产物形成的抑制作用。与常规的发酵法相比，利用离子交换树脂吸附发酵使糖转化率和乳酸生产速率分别由８６．２％和０．３２８ｇ／Ｌ·ｈ提高到９４．７％和０．４８２ｇ／Ｌ·ｈ。     

甲烷直接氧化制甲醇Ⅲ．反应气吹扫催化膜反应器（RSCMR）

用溶胶－凝胶法制备了“ＳｉＯ＿２／陶瓷”非对称无机膜，并用该膜制备了反应气吹扫催化膜反应器（ＲＳＣＭＲ）装置。在ＲＳＣＭＲ上考察了甲烷一步催化氧化制甲醇反应。结果表明，在研究的范围内，增加氧气或甲烷的浓度和吹扫气的流速（即总的反应气流量）有利于提高甲醇的收率；甲醇在反应条件下的热不稳定性是影响目标反应选择性的重要原因。ＲＳＣＭＲ较膜反应器（ＣＭＲ）系统能更有效地抑制甲醇的热分解，因而可得到较ＣＭＲ更高的甲醇收率。当反应温度为７００℃时，甲醇的收率在ＣＭＲ中为０．５ｇ／ｍ￣２ｈ，在ＲＳＣＭＲ中可达０．９ｇ／ｍ￣２ｈ。     

甲烷直接氧化制甲醇：Ⅱ.催化膜反应器（CMR）

采用溶胶－凝胶（Ｓｏｌ－Ｇｅｌ）法制备了微孔结构均匀的“ＳｉＯ２／陶瓷”膜和“Ｍｏ－Ｃｏ－Ｏ／ＳｉＯ２／陶瓷”催化功能膜，并用ＸＲＤ、ＳＥＭ和孔径测定等技术进行了表征。在常压，５００～７００℃的条件下，在催化膜反应器（ＣＭＲ）中考察了甲烷氧化制甲醇的反应。在相似的反应条件下（转化率为１．０％），用ＣＭＲ（甲醇选择性１?．２％）可获得较固定床反应器（甲醇选择性４．５％）高得多的甲醇选择性。     

甲烷直接氧化制甲醇Ⅱ．催化膜反应器（CMR）

采用溶胶－凝胶（Ｓｏｌ－Ｇｅｌ）法制备了微孔结构均匀的“ＳｉＯ＿２／陶瓷”膜和“Ｍｏ－Ｃｏ－·Ｏ／ＳｉＯ＿２／陶瓷”催化功能膜，并用ＸＲＤ、ＳＥＭ和孔径测定等技术进行了表征。在常压、５００～７００℃的条件下，在催化膜反应器（ＣＭＲ）中考察了甲烷氧化制甲醇的反应。在相似的反应条件下（转化率为１．０％），用ＣＭＲ（甲醇选择性１１．２％）可获得较固定床反应器（甲醇选择性４．５％）高得多的甲醇选择性。     

溶胶-凝胶固定化多酶催化二氧化碳转化为甲醇反应初探

 为了探索温室气体CO2的固定和利用的新途径，以正硅酸乙酯为\r\n前驱体，用改进的溶胶－凝胶法对甲酸脱氢酶、甲醛脱氢酶和乙醇脱氢\r\n酶进行了包埋共固定化，并以包埋的三种酶为催化剂，以还原型烟酰胺\r\n腺嘌呤二核苷酸（NADH）为电子供体，在低温低压下将CO2转化为甲醇\r\n．初步研究了反应温度、pH值、酶含量及NADH用量对甲醇收率的影响．\r\n实验结果表明，在37℃和pH7．0的条件下，甲醇的收率可达92．4％．\r\n由于酶空间构型的微小变化和空间位阻效应的存在，与液相酶反应结果\r\n相比，包埋后的酶活性略有降低．     

固定化对恶臭假单胞菌腈水合酶催化特性的影响

酶法代替铜催化法使丙烯腈转化制内烯酰胺的研究,70年代起在国外开始进行.近年来,国内也相继开展了这方面的工作.他们筛选得到的恶臭假单胞菌JP-1具有较高腈水合酶活力,其完整细胞的腈水合酶催化特性也已进行了研究.本文研究了采用海藻酸钙包埋法制备的恶臭假单胞菌固定化细胞的酶学性质.     

甲烷直接氧化制甲醇：Ⅲ.反应气吹扫催化膜反应器（RSCMR）

用溶胶－凝胶法制备了“ＳｉＯ２／陶瓷”非对称无机膜，并用该膜制备了反应气吹扫催化膜反应器（ＲＳＣＭＲ０装置。在ＲＳＣＭＲ上考察了甲烷一步催化氧化制甲醇反应。结果表明，在研究的范围内，增加氧气或甲烷的浓度和吹扫气的流速（即总的反应气流量）有利于提高甲醇的收率；甲醇在反应条件下的热不稳定性是影响目标反应选择性的重要原因。ＲＳＣＭＲ较膜反应（ＣＭＲ０系统能更有效地抑制甲醇的热分解，因而可得到较ＣＭＲ更高     

甲烷氧化偶联催化剂的研究

甲烷氧化偶联是化学工作者十分重视的新课题,并做了许多研究工作,Benson以氯为氧化剂在1700℃高温下反应^[1],Keller等使甲烷在金属氧化物格子氧上反应^[2],Hinsen等以PbO/Y-Al₂O₃做催化剂,氧做氧化剂进行偶联^[3],但乙烯和乙烷的选择率很低,J. H. Lunsford等则用Li₂O/MgO做催化剂,氧为氧化剂把乙烯和乙烷的总收率提高到19.4％^[4],但乙烯的收率低于乙烷。     

Tuning methane content in gas hydrates via thermodynamic modeling and molecular dynamics simulation

Storage and transportation of natural gas as gas hydrate (“gas-to-solids technology”) is a promising alternative to the established liquefied natural gas (LNG) or compressed natural gas (CNG) technologies. Gas hydrates offer a relatively high gas storage capacity and mild temperature and pressure conditions for formation. Simulations based on the van der Waals–Platteeuw model and molecular dynamics (MD) are employed in this study to relate the methane gas content/occupancy in different hydrate systems with the hydrate stability conditions including temperature, pressure, and secondary clathrate stabilizing guests. Methane is chosen as a model system for natural gas. It was found that the addition of about 1% propane suffices to increase the structure II (sII) methane hydrate stability without excessively compromising methane storage capacity in hydrate. When tetrahydrofuran (THF) is used as the stabilizing agent in sII hydrate at concentration between 1% and 3%, a reasonably high methane content in hydrate can be maintained (∼85–100, v/v) without dealing with pressures more than 5 MPa and close to room temperature.     

甲烷分子在碱性催化剂上的吸附与酸碱活化机理

以碳酸锶为甲烷吸附活化的模型催化剂，用切换变应答、ＣＨ４（ＣＯ２）－ＴＰＤ等技术，对甲烷的吸附、碱性对催化剂性能的影响进行了研究，结果表明，甲烷在碳酸锶上的活化显示出明显的酸碱活化机理特征，瞬变应答及ＴＰＤ结果均证明，甲烷在碳酸锶表面有较强的吸附，其脱附温度约３１０℃，关联结果表明，甲烷转化率及Ｃ２烃收率与催化剂表面ＳｒＯ碱性中心浓度有非常一致的顺变关系，因此催化剂表面的酸碱中心可能是甲烷的选择活     

Selective oxidation of light alkanes under mild conditions

Methanotrophs mediate the conversion of methane (CH₄) into methanol selectively and efficiently near ambient conditions so we can learn from microbes to develop biomimetic catalysts capable of performing this difficult chemistry. This review highlights the development of a tricopper cluster catalyst that functions similar to the particulate methane monooxygenase enzyme in methanotrophic bacteria. The performance of this catalytic system formulated for quasi-heterogeneous catalysis is compared with other heterogeneous catalysts derived from Cu- and Fe-based zeolites and Cu mordenites known to activate CH₄ stoichiometrically near 200 °C. We also highlight a unique catalytic system, in which the oxidizing power of both O atoms of the O₂ molecule can be harnessed for oxidation of toluene to yield benzaldehyde at room temperature.     

Kinetics of Methane Partial Oxidation to Syngas over a LiLaNiO/γ -Al2O3 Catalyst

The kinetic behavior of partial oxidation of methane to syngas over a LiLaNiO/γ -Al₂O₃ catalyst was investigated under steady-state conditions. Under kinetic control, syngas, to a large extent, is formed via a direct partial oxidation (DPO) scheme. CO and CO₂ are formed in parallel by oxidation reaction over the catalyst. The active sites in the kinetically controlled regime are different from those in the non-kinetic regime, thus the CO selectivity in the former may not increase with temperature. This revised version was published online in June 2006 with corrections to the Cover Date.     

An investigation of the promotional effect of propylene or propane traces on the activity of sulfatedPt/g-Al2O3andPt-Sn/g-Al2O3inCH4combustion

Summary A strong promoting effect of the presence of C₃H₈or C₃H₆was determined for the combustion of CH₄in excess oxygen, over pre-sulfated 1%Pt/g-Al₂O₃and pre-sulfated 1%Pt-2%Sn/g-Al₂O₃catalysts.</o:p>     

The synthesis and thermal degradation products of the C–H bond activating complex [(diimine)Pt(Me)(OSO2CF3)]

Design of a selective homogeneous methane functionalizing catalyst based on [(ArN=CRCR=NAr)Pt(Me)(L)]⁺ requires knowledge of its stability in various reaction media, particularly water. Reaction of (diimine)PtMe₂ (1) (diimine = ArN=CRCR=NAr, Ar = 2, 6-Me₂C₆H₃, R = Me) with HOTf (OTf = OSO₂CF₃) gives the methane activating compound (diimine)Pt(Me)OTf (3). When varying amounts of H₂O are added during the synthesis of 3, competing degradation pathways lead to two different characterizable products. With only trace amounts of water, two dimeric species, [(diimine)Pt(μ-Cl)(μ-OH)Pt(diimine)](OTf)₂ (6) and [(diimine)Pt(μ-OH)₂Pt(diimine)](OTf)₂ (7), are isolated, in addition to an uncharacterized dark brown precipitate. When an excess of H₂O is added, the aquo species [(diimine)Pt(Me)(H₂O)][OTf] (5) is first observed, which then reacts further to give a dark brown precipitate and 7. The structures of 1, 6, and 7 are presented. Both 6 and 7 exhibit unusual conformations for their respective classes. Compound 6 has a rarely observed planar conformation, while 7 has an unusual bifurcated H-bonding motif between the bridging OH-groups and a triflate anion, with a highly bent conformation.     

锂在甲烷氧化偶联催化剂中的助催化作用

自Lunsford等首次报道在Li/MgO催化剂上的甲烷氧化偶联(OCM)以来,许多研究者相继报道了添加碱金属对该反应的影响,其中以Li的添加最受关注。Li在OCM反应中对提高C_2烃选择性的作用最为明显,因而弄清Li在这一反应中的作用十分必要。本文讨论了Li在几个有代表性的碱土(CaO)及稀土(La_2O_3)中的存在形式与生成C_2产物的关系。     

Catalytic combustion of methane over iron- and manganese-substituted lanthanum hexaaluminates

A series of hexaaluminates, LaMnFe _x Al_11−x O_19−δ samples (x = 1, 2, 4, 6, 8) as new catalysts were prepared by carbonate precipitation and calcined at high temperature. Fe and Mn ions were used as active components to replace part of aluminum ions in the hexaaluminate lattices. The structures and properties of these samples were characterized by XRD, BET, and XPS. The series of hexaaluminates exhibited significant catalytic activity and stability at high temperature. The LaMnFe₂Al₉O_19−δ retains a larger surface area and shows a good activity in methane combustion.     

Monolithic reactors for experimental studies of the catalytic partial oxidation of methane to synthesis gas

Monoliths containing 0.1 wt.% Pt and Rh have been used for the partial oxidation of methane to synthesis gas. Two different impregnation methods for making Pt and Rh (and Ni) monoliths are described and discussed. The studies were carried out at conditions with incomplete conversion of O₂ and with product distributions far from equilibrium. The two metals show different activities.