A New Method of Low Temperature Methanol Synthesis

Low temperature methanol synthesis is a promising technique for the practical methanol industry. New developments of a new kind of low temperature methanol synthesis were reviewed, including the effects of feed gas, reaction solvent, supercritical media and catalyst modification. The reaction mechanism and kinetics were also summarized primarily. Carbon dioxide played an important role in this new kind of low temperature methanol synthesis. It reacted with hydrogen adsorbed on catalyst surface to form HCOOM, an important reaction intermediate. Alcohol solvent in the low temperature methanol synthesis performed not only a media, but also a homogeneous catalyst. The reaction of the adsorbed formate species with alcohol on Cu/ZnO catalyst surface proceeded according to the Rideal mechanism rather than Langmuir–Hinshelwood mechanism to form alkyl formate. The formation of alkyl formate from alcohol solvent and hydrogenation of such an alkyl formate were the key steps in low temperature methanol synthesis reaction. These results provided new insights into low temperature methanol synthesis.     

PHOTOREACTIVATION ASSOCIATED WITH CHROMOSOMAL ABNORMALITY IN SEA URCHIN EGGS FERTILIZED WITH ULTRAVIOLET-IRRADIATED SPERM

Abstract— As a model for studies involving biologic systems, rates of hematoporphyrin and protopor-phyrin-sensitized photooxidation of tryptophan were measured in water-methanol mixtures. Absorption and fluorescence-emission spectra associated with solutions of porphyrins in different water-methano! mixtures were also examined. The optimal rate of photooxidation by hematoporphyrin occurred in 30% methanol; by protoporphyrin, in 60% methanol. Absorption spectra were examined to characterize dispersion of hematoporphyrin into monomeric form in 90% methanol, and the dimer formation which predominates in 30% methanol. With the more hydrophobic protoporphyrin, an absorption spectrum characteristic of drug monomer was seen in 100% methanol, a dimer spectrum was observed in 60% methanol. At methanol concentrations < 60%, we observed impaired photooxidation and another alteration in the absorption pattern apparently reflecting drug aggregation beyond the dimer stage. Fluorescence emission maxima of both porphyrins were blue-shifted with increasing solvent dielectric constant, but an additional blue shift was detected in an aqueous environment which was apparently related to porphyrin aggregation. Absorption and fluorescence-emission spectra appear helpful for characterizing environmental determinants of porphyrin-sensitized photooxidation.     

Optimization of methanol biosynthesis byMethylosinus trichosporium OB3b: An approach to improve methanol accumulation

Methylosinus trichosporium OB3b is a methanotrophic bacterium containing methane mono-oxygenase, catalyzing hydroxylation of methane to methanol. When methane is oxidized, the product is subsequently oxidized by methanol dehydrogenase contained in the same bacterium. To prevent further oxidation of methanol, the cell suspension was treated by cyclopropanol, an irreversible inhibitor for methanol dehydrogenase, leading to extracellular methanol accumulation. However, the reaction was terminated at approx 3 h with a final methanol concentration below 2.96 mmol/g dry cell. The methanol production efficiency (the ratio of the produced methanol per methane consumption) was 2.90%. By selecting the culture conditions and the reaction conditions, the reaction continued for 100 h, resulting in a methanol concentration of 152 mmol/g dry cell. This level was 51 times higher than that of the conventional reaction, and the methanol production efficiency was 61%.     

直接甲醇燃料电池甲醇传质过程分析及浓度控制策略

甲醇溶液浓度对于直接甲醇燃料电池(DMFC)的性能具有重要影响。 本文旨在建立一种能在电源系统中有效控制甲醇浓度的策略。 通过构建电池内甲醇物料守恒和热守恒方程,确定了基于电量和温度这两个参数的甲醇浓度控制策略。 通过测试温度-浓度关系验证了控制策略的可行性。 结果表明,采用该策略,DMFC电源系统稳定运行超过420 min;合适的甲醇浓度范围为0.70~0.87 mol/L。 该策略完成了甲醇浓度控制的目标,并将在电源系统中发挥重要作用。     

Pervaporation membranes in direct methanol fuel cells

The membranes in direct methanol fuel cells must both conduct protons and serve as a barrier for methanol. Nafion, the most common fuel cell membrane, is an excellent conductor but a poor barrier. Polyvinyl alcohol pervaporation membranes are good methanol barriers but poor conductors. These and most other pervaporation membranes offer no significant advantages over Nafion in methanol fuel cell applications. However, polybenzimidazole membranes have demonstrated characteristics that suggest up to a 15-fold improvement in direct methanol fuel cells. This improvement may be due to an alternate form of proton conduction in which protons travel via a Grotthus or “hopping” mechanism.     

Effect of methanol quality on the ionisation of herbicides,insecticides and fungicides using gradient elution liquid chromatography

This paper explores the changes in the electrospray signal response of 39 structurally different compounds caused by the quality of the methanol, when used as a component in a gradient elution mobile phase. When three batches of LC–MS grade methanol from one manufacturer were evaluated, the largest variation in the electrospray signal responses of the 39 compounds examined was 18%. However, significant enhancement of the electrospray signals of up to 106% were observed among different brands of LC–MS grade methanol from different manufacturers. The effect of methanol quality on signal response was found to be compound dependent. This study also demonstrated that the senescence of the methanol was important. Using an expired batch of LC–MS grade methanol, electrospray signals were suppressed by as much as 95% for all compounds measured using positive mode electrospray. Conversely, the negative mode electrospray signals of compounds such as 4-octyl benzoic acid showed an enhancement of up to 96% when using the same batch of methanol. Linuron was used as a model compound to examine the change in the electrospray response, during gradient elution, when the proportion of an expired batch of methanol was varied. An infusion experiment showed that the linuron signal intensity decreased as the proportion of expired methanol increased in the mobile phase, which was in direct contrast to the increase in linuron signal observed with a non-expired batch of methanol. A series of isocratic experiments also showed that the linuron signal decreased as the proportion of expired methanol increased in the mobile phase. The ion ratios of several of the compounds studied changed significantly when using the expired batch of LC–MS methanol. The change in the ion ratios accentuates the difficulty of identifying compounds from in-source spectral libraries. A protocol is recommended for assessing the quality of methanol for LC–MS applications.     

甲醇与异戊烯醚化反应的研究

采用国产大孔磺酸树脂(NKC-9),在无梯度反应器对异戊烯与甲醇醚化反应进行了研究,在消除内扩散和外扩散的情况下,考察了甲醇浓度对醚化反应速度的影响,根据LHHW机理和均相反应机理推导出相应的模型方程,经模型筛选和参数估值,得出 LHHW模型为最佳模型.在该模型中反应速率的实验值与模拟值有较好的一致性.     

Nitrogen-rich Graphdiyne Film for Efficiently Suppressing the Methanol Crossover in Direct Methanol Fuel Cells

The inhibition of the methanol crossover is one of the intractable challenges in the direct methanol fuel cell.The graphdiyne(GDY)with atomic-level pores shows great potential in realizing the zero-permeation of methanol molecules.In this paper,an ultrathin layer of nitrogen-rich GDY film with a high nitrogen content is largely prepared and readily used for retarding the methanol permeation in the state-of-the-art commercial Nafion membrane.The high N-content in this porous GDY nanofilm remarkably increases the selective suppression in methanol transfer,and single-layer GDY film can efficiently prevent 43％methanol crossover and the value of the double-layer GDY film can be high up to 69％.The power performance and the long-term stability of the cell are obviously improved due to the reduced methanol crossover.     

A model for methanol transport through Nafion membrane in diffusion cell

The transport of methanol through Nafion^® membrane in diffusion cell is investigated using the open circuit potential method at different initial methanol concentration solutions. A simple mathematical model based on quasi-steady-state diffusion for the transport of methanol across the membrane in a diffusion cell is developed to simulate the experimental data in order to measure the methanol permeability. The influence of the diffusion cell parameters and thickness of the membrane on the methanol permeability measurement has been evaluated and analyzed. By means of Maclaurin expansion technique, this model can be used to predict the deviation of methanol permeability determined by steady-state diffusion model.     

聚异丙基丙烯酰胺高分子在甲醇水溶液中溶解性的拉曼光谱研究

通过测量-13℃(低于低临界溶解温度(LCST))时聚异丙基丙烯酰胺(PNIPAM)高分子在甲醇水溶液中的拉曼光谱非一致效应(NCE),试图从PNIPAM与溶剂分子间的相互作用角度理解PNIPAM的溶解性.通过比较甲醇水溶液中加入PNIPAM前后甲醇分子C-O伸缩所对应的NCE变化,我们认为:甲醇摩尔分数(x)在1.0-0.90范围内,PNIPAM优先吸附甲醇分子;x=0.80-0.50时,PNIPAM优先吸附水分子;而x=0.50-0.20时,PNIPAM破坏了甲醇与水所形成的三元环稳定结构.进一步比较加入PNIPAM或其单元结构--异丙基丙酰胺(NIPPA)对甲醇水溶液NCE的影响,发现PNIPAM通过链段间的疏水协同作用吸附了甲醇分子.我们认为在甲醇水溶液的低浓度区间,这种协同作用破坏了甲醇与水形成的三元环团簇结构,而当温度升高时这种结构又重新形成,导致了PNIPAM在甲醇水溶液中的混致不溶现象.     

Reaction of molecular and atomic deuterium with methanol on Pd(111)

Multiplexed thermal desorption spectroscopy was used to study the influence of preadsorbed and postadsorbed deuterium on a methanol monolayer on Pd(111). In particular, the effect of atomic deuterium exposure on the reaction products was examined in detail. Preadsorbed deuterium hinders the formation of chemisorbed methanol and favors physisorption of methanol. This leads to a strong reduction of methanol dehydrogenation during sample heating. Postadsorption of molecular deuterium also changes partially chemisorbed to physisorbed methanol. No deuteration of methanol is found under these conditions. With atomic deuterium exposure, however, significant amounts of deuterated methanol, from methanol-D1 through methanol-D4, can be produced. In addition, D exposure also causes an increased dehydrogenation probability during sample heating. The probabilities for methanol deuteration, for methanol dehydrogenation, and for D-atom bulk absorption have been determined quantitatively.     

Low water/methanol permeable Nafion/CHP organic-inorganic composite membrane with high crystallinity

High methanol crossover is one of the main issues of the polyelectrolyte in direct methanol fuel cells (DMFCs). In order to decrease methanol crossover, we introduced a new method that crystallinity control was performed with incorporating CHP (calcium hydroxyphosphate) into Nafion solution. As a result, crystallinity in the composite membranes increased with CHP content compared to cast Nafion accompanying the formation of new crystalline peaks in the original amorphous region of Nafion. On the other hand, water uptake content, methanol sorption/desorption permeability and methanol crossover in the composite membranes remarkably decreased. We conclude that an increase in crystallinity due to the strong interfacial adhesion between Nafion and CHP can suppress the methanol crossover.     

Highly selective adsorption of methanol in carbon nanotubes immersed in methanol-water solution

The systems of open-ended carbon nanotubes (CNTs) immersed in methanol-water solution are studied by molecular dynamics simulations. For the (6,6) CNT, nearly pure methanol is found to preferentially occupy interior space of the CNT. Even when the mass fraction (MF) of methanol in bulk solution is as low as 1%, the methanol MF within the CNT is still more than 90%. For CNTs with larger diameters, the methanol concentrations within CNTs are also much higher than those outside CNTs. The methanol selectivity decreases with increasing CNT diameter, but not monotonically. From microscopic structural analyses, we find that the primary reason for the high selectivity of methanol by CNTs lies on high preference of methanol in the first solvation shell near the inner wall of CNT, which stems from a synergy effect of the van der Waals interaction between CNT and the methyl groups of methanol, together with the hydrogen bonding interaction among the liquid molecules. This synergy effect may be of general significance and extended to other systems, such as ethanol aqueous solution and methanol/ethanol mixture. The selective adsorption of methanol over water in CNTs may find applications in separation of water and methanol, detection of methanol, and preservation of methanol purity in fuel cells.     

Hydrogen and methanol exchange processes for (TMP)Rh-OCH3(CH3OH) in binary solutions of methanol and benzene

Tetramesityl porphinato rhodium(III) methoxide ((TMP)Rh-OCH(3)) binds with methanol in benzene to form a 1:1 methanol complex ((TMP)Rh-OCH(3)(CH(3)OH)) (1). Dynamic processes are observed to occur for the rhodium(III) methoxide methanol complex (1) that involve both hydrogen and methanol exchange. Hydrogen exchange between coordinated methanol and methoxide through methanol in solution results in an interchange of the environments for the non-equivalent porphyrin faces that contain methoxide and methanol ligands. Interchange of the environments of the coordinated methanol and methoxide sites in 1 produces interchange of the inequivalent mesityl o-CH(3) groups, but methanol ligand exchange occurs on one face of the porphyrin and the mesityl o-CH(3) groups remain inequivalent. Rate constants for dynamic processes are evaluated by full line shape analysis for the (1)H NMR of the mesityl o-CH(3) and high field methyl resonances of coordinated methanol and methoxide groups in 1. The rate constant for interchange of the inequivalent porphyrin faces is associated with hydrogen exchange between 1 and methanol in solution and is observed to increase regularly with the increase in the mole fraction of methanol. The rate constant for methanol ligand exchange between 1 and the solution varies with the solution composition and fluctuates in a manner that parallels the change in the activation energy for methanol diffusion which is a consequence of solution non-ideality from hydrogen bonded clusters.     

Bioinduced Room‐Temperature Methanol Reforming

Imitating nature′s approach in nucleophile‐activated formaldehyde dehydrogenation, air‐stable ruthenium complexes proved to be exquisite catalysts for the dehydrogenation of formaldehyde hydrate as well as for the transfer hydrogenation to unsaturated organic substrates at loadings as low as 0.5 mol %. Concatenation of the chemical hydrogen‐fixation route with an oxidase‐mediated activation of methanol gives an artificial methylotrophic in vitro metabolism providing methanol‐derived reduction equivalents for synthetic hydrogenation purposes. Moreover, for the first time methanol reforming at room temperature was achieved on the basis of this bioinduced dehydrogenation path delivering hydrogen gas from aqueous methanol.     

Vacuum-ultraviolet (VUV) photoionization of small methanol and methanol-water clusters

In this work, we report on the vacuum-ultraviolet (VUV) photoionization of small methanol and methanol-water clusters. Clusters of methanol with water are generated via co-expansion of the gas phase constituents in a continuous supersonic jet expansion of methanol and water seeded in Ar. The resulting clusters are investigated by single photon ionization with tunable vacuum-ultraviolet synchrotron radiation and mass analyzed using reflectron mass spectrometry. Protonated methanol clusters of the form (CH3OH)nH(+) (n = 1-12) dominate the mass spectrum below the ionization energy of the methanol monomer. With an increase in water concentration, small amounts of mixed clusters of the form (CH3OH)n(H2O)H(+) (n = 2-11) are detected. The only unprotonated species observed in this work are the methanol monomer and dimer. Appearance energies are obtained from the photoionization efficiency (PIE) curves for CH3OH(+), (CH3OH)2(+), (CH3OH)nH(+) (n = 1-9), and (CH3OH)n(H2O)H(+) (n = 2-9) as a function of photon energy. With an increase in the water content in the molecular beam, there is an enhancement of photoionization intensity for the methanol dimer and protonated methanol monomer at threshold. These results are compared and contrasted to previous experimental observations.     

Photoelectron imaging of large anionic methanol clusters: (MeOH)n - (n approximately 70-460)

Electron solvation in methanol anion clusters, (MeOH)(n) (-) (n approximately 70-460), is studied by photoelectron imaging. Two isomers are observed: methanol I, with vertical binding energies (VBE) ranging from 2-2.5 eV, and methanol II, with much lower VBE's between 0.2 and 0.5 eV. The VBE's of the two isomers depend linearly on n(-1/3) with nearly identical slopes. We propose that the excess electron is internally solvated in methanol I clusters, whereas in methanol II it resides in a dipole-bound surface-state. Evidence of an excited state accessible at 1.55 eV is observed for methanol I.     

Sr掺杂对CaO(100)表面吸附甲醇影响的分子模拟

借助分子模拟手段,研究了锶掺杂对氧化钙表面甲醇吸附行为的影响。构建了甲醇在CaO(100)和CaO(100)-Sr表面吸附的模型,计算了甲醇在氧化钙表面的吸附能和解离活化能,分析了甲醇在氧化钙表面成键的态密度以及锶掺杂前后甲醇在氧化钙表面电荷布局和差分电荷密度,评估了锶掺杂量对氧化钙表面甲醇吸附性能的影响。结果表明,锶掺杂能够显著强化氧化钙对甲醇的吸附性能,降低甲醇的解离活化能,且吸附性能随锶掺杂量的增加而增强;甲醇在氧化钙表面吸附时活化,锶掺杂后活化程度增加。     

Ab initio study on the adsorption and dissociation process of methanol on a silver surface

The geometries of methanol adsorbed on an oxygen-free silver surface, a promoted silver surface and an oxygen preadsorbed silver surface were optimized at the MP2 level and the energies were calculated at the MP4 level. Our calculations showed that weak physisorption of methanol occurs on the clean silver surface, but stable molecular chemisorption occurs in the other two cases. The adsorption and dissociation process of methanol was postulated to occur via two pathways, i.e. the Eley-Rideal mode and the Langmuir-Hinshelwood mode. The calculations also showed that the presence of atomic oxygen at a silver surface is essential for the cleavage of the OH bond in the methanol. The dissociation of methanol in the Langmuir-Hinshelwood mode has a small energy barrier but has no energy barrier in the Eley-Rideal mode.     

Mechanism of the photochemical substitution of 6-membered ring monoazaaromatic compounds by methanol in neutral and HCl acidified medium

6-Membered ring monoazaaromatic compounds such as pyridine, quinoline, 4-methylquinoline, isoquinoline and 9-phenylacridine are converted to the corresponding semiquinone radicals when irradiated in methanol acidified with HCl, ether or neutral methanol. In a neutral medium the hydrogen photoabstraction occurs from an nπ^* excited state by a monophotonic process, but in methanol acidified with HCl, the photoreaction corresponds to a biphotonic process. In this case the photoreaction involves an electron transfer from methanol to a protonated upper excited triplet state of the solute (Scheme 2, path 2).