Effect of sodium cation on the electrochemical reduction of CO<Subscript>2</Subscript> at a copper electrode in methanol

The electrochemical reduction of CO₂ with a Cu electrode in methanol was investigated with sodium hydroxide supporting salt. A divided H-type cell was employed; the supporting electrolytes were 80 mmol dm⁻³ sodium hydroxide in methanol (catholyte) and 300 mmol dm⁻³ potassium hydroxide in methanol (anolyte). The main products from CO₂ were methane, ethylene, carbon monoxide, and formic acid. The maximum current efficiency for hydrocarbons (methane and ethylene) was 80.6%, at −4.0 V vs Ag/AgCl, saturated KCl. The ratio of current efficiency for methane/ethylene, r _f(CH₄)/r _f(C₂H₄), was similar to those obtained in LiOH/methanol-based electrolyte and larger relative to those in methanol using KOH, RbOH, and CsOH supporting salts. In NaOH/methanol-based electrolyte, the efficiency of hydrogen formation, a competing reaction of CO₂ reduction, was suppressed to below 4%. The electrochemical CO₂ reduction to methane may be able to proceed efficiently in a hydrophilic environment near the electrode surface provided by sodium cation.     

含钒杂多酸催化发烟硫酸中甲烷液相部分氧化反应

 以H5PV2Mo10O40 为催化剂,在发烟硫酸中进行了甲烷液相部分氧化,考察了催化剂用量、反应温度、反应时间和发烟硫酸浓度等工艺条件对反应收率的影响. 甲烷在反应中首先转化为硫酸甲酯,硫酸甲酯随后水解为甲醇. 对于甲烷液相部分氧化反应,发烟硫酸中游离的SO3是非常重要的影响因素. 在工艺条件为催化剂用量7.0 mmol, 反应温度473 K, 反应压力3.5 MPa, 反应时间3 h和发烟硫酸中SO3含量50%时,甲烷转化率可达48.5%, 目的产物甲醇收率为41.5%.     

Effects of tetrazolium chloride concentration,O<Subscript>2</Subscript>, and cell age on dehydrogenase activity of <Emphasis Type="Italic">Aspergillus niger</Emphasis>

The effects of triphenyl tetrazolium chloride (TTC) concentration, cell age, and presence of O₂ on the dehydrogenase activity of Aspergillus niger as measured by triphenyl formazan (TF) yield were investigated. The results indicated that increasing TTC concentration initially increased the TF yield and then decreased it. The maximum TF yield was observed at a TTC concentration of 30 g/L for young cells (4 d old) and 20 g/L for old cells (12 d old). Conducting the test under anaerobic conditions increased the TF yield. About 18% of the TF produced was converted back into TTC in the presence of oxygen. The relationship between dehydrogenase activity of A. niger (as measured by TF yield) and cell mass was found to be linear. A kinetic model describing the relationship between reaction rate (micromoles of TF formed per hour) and TTC concentration while accounting for substrate inhibition was developed, and the model constants were calculated. The optimum TTC-test conditions for dehydrogenase activity measurement of A. niger were a TTC concentration of 20 g/L, a pH of 9.0, a temperature of 55°C, an incubation time of 3 h, and anaerobic conditions.     

Biosynthesis of poly-β-hydroxybutyrate and exopolysaccharides on azotobacter chroococcum strain 6B utilizing simple and complex carbon sources

Coproduction of poly-β-hydroxybutyrate (PHB) and exopolysaccharides (EPS) was investigated with Azotobacter chroococcum strain 6B isolated from soil samples. The bacterium was cultured using various carbon sources solely or with 0.1 g/L of ammonium sulfate. Ammonium addition resulted in reduced PHB and EPS production with glucose, fructose, and sucrose media, but cellular mass remained constant except for sucrose. Protein was nearly twofold higher in ammonium-grown cultures. Glucose and fructose alone biosynthesized high amounts of EPS (maximum 2.1 and 1.1 g/L, respectively, at 72 h), whereas PHB was accumulated only in glucose-grown cells. Sucrose almost did not produce EPS. Conversely, PHB content was the highest obtained from all experimented conditions (1.1 g/L at 48 h, 40% cell dry wt). When a complex carbon source such as sugar cane molasses was utilized, PHB was accumulated concomitant with EPS production from the initial time to 48 h (0.75 g/L, 37% cell dry wt and 0.6 g/L, respectively), and then PHB decayed at 72 h (0.2 g/L). On the other hand, EPS continued to be biosynthesized (1.1 g/L, 72 h). PHB fractions of total intra- and extracellular biopolymers were calculated. Sucrose-modified Burk’s medium without ammonium addition is suggested as a medium capable of diverting the carbon source for the production of intracellular PHB rather than EPS with A. chroococcum 6B.     

Biosynthesis of methanol from methane by <Emphasis Type="Italic">Methylosinus trichosporium</Emphasis> OB3b

Methanol has recently attracted significant interest in the energetic field. Current technology for the conversion of methane to methanol is based on energy intensive endothermic steam reforming followed by catalytic conversion into methanol. The one-step method performed at very low temperatures (35°C) is methane oxidation to methanol via bacteria. The aim of this work was to examine the role of copper in the one-step methane oxidation to methanol by utilizing whole cells of Methylosinus trichosporium OB3b bacteria. From the results obtained it was found that copper concentration in the medium influences the rate of bacterial biomass growth or methanol production during the process of methane oxidation to methanol. The presented results indicate that the process of methane oxidation to methanol by Methylosinus trichosporium OB3b bacteria is most efficient when the mineral medium contains 1.0 × 10⁻⁶ mol dm⁻³ of copper. Under these conditions, a satisfactory growth of biomass was also achieved. Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May 2008.     

MFC逆转化CO2合成甲醇研究

微生物燃料电池(MFC)反应器是利用附着在阳极上的产氢微生物,在吸收烟气CO2的同时将CO2逆转化合成高附加值的生物合成燃料的装置。试验选用从牛粪中分离筛选出的梭状芽孢菌(Clostridium.sp)作为合成生物燃料的合成菌,将MFC反应装置接入电化学工作站进行CV测试,当发生还原反应时,在-0.5 V时出现还原峰,利用直流稳压电源恒电压电解,检测到合成的生物燃料为甲醇。在24 h时甲醇的积累量达到最大3.13 mmol/L;当CO2气体比例为15%时甲醇积累量最大,为2.98 mmol/L。在细菌接种量为1 mL时,甲醇积累量达到最大,为2.76 mmol/L。,最适条件下的CO2转化率为7.5%。     

Evaluation of cell recycle on Thermomyces lanuginosus xylanase a production by Pichia pastoris GS 115

This work aims to evaluate cell recycle of a recombinant strain of Pichia pastoris GS115 on the Xylanase A (XynA) production of Thermomyces lanuginosus IOC-4145 in submerged fermentation. Fed-batch processes were carried out with methanol feeding at each 12h and recycling cell at 24, 48, and 72 h. Additionally, the influence of the initial cell concentration was investigated. XynA production was not decreased with the recycling time, during four cell recycles, using an initial cell concentration of 2.5 g/L. The maximum activity was 14,050 U/L obtained in 24h of expression. However, when the initial cell concentration of 0.25 g/L was investigated, the enzymatic activity was reduced by 30 and 75% after the third and fourth cycles, respectively. Finally, it could be concluded that the initial cell concentration influenced the process performance and the interval of cell recycle affected enzymatic production.     

滑动弧放电等离子体分解甲醇制氢

对常温常压下滑动弧放电等离子体直接分解甲醇进行了研究,探讨了载气流量、甲醇浓度、电极间距、输入电压和气化室温度等实验参数的影响。结果表明,不同操作条件导致甲醇转化率由51%升高到81.7%,氢气和一氧化碳的选择性之比基本保持一个固定值。除了氢气和一氧化碳,产物中还检测到了少量的甲烷和C₂不饱和烃以及痕量二氧化碳。不同于传统的甲醇热分解机理,提出了滑动弧放电等离子体甲醇分解的制氢路径。     

Biosynthesis of poly-3-hydroxybutyrate with a high molecular weight by methanotroph from methane and methanol

Poly-3-hydroxybutyrate （PHB） can be produced by various species of bacteria. Among the possible carbon sources, both methane and methanol could be a suitable substrate for the production of PHB. Methane is cheap and plentiful not only as natural gas, but also as biogas. Methanol can also maintain methanotrophic activity in some conditions. The methanotrophic strain Methylosinus trichosporium IMV3011 can accumulate PHB with methane and methanol in a brief nonsterile process. Liquid methanol （0.1%） was added to improve the oxidization of methane. The studies were carried out using shake flasks. Cultivation was performed in two stages： a continuous growth phase and a PHB accumulation phase under the conditions short of essential nutrients （ammonium, nitrate, phosphorus, copper, iron （Ⅲ）, magnesium or ethylenediamine tetraacetate （EDTA）） in batch culture. It was found that the most suitable growth time for the cell is 144 h. Then an optimized culture condition for second stage was determined, in which the PHB concentration could be much increased to 0.6 g/L. In order to increase PHB content, citric acid was added as an inhibitor of tricarboxylic acid cycle （TCA）. It was found that citric acid is favorable for the PHB accumulation, and the PHB yield was increased to 40% （w/w） from the initial yield of 12% （w/w） after nutrient deficiency cultivation. The PHB produced is of very high quality with molecular weight up to 1.5 × 10^6Da.     

Selective flow-injection determination of methanol in the presence of ethanol based on a multi-enzyme system with chemiluminescence detection

A highly selective flow-injection system was developed for the determination of methanol. The system consisted of three immobilized enzymes with luminol chemiluminescence detection. First, methanol was oxidized in the presence of alcohol oxidase to yield formaldehyde and hydrogen peroxide. The hydrogen peroxide produced was then destroyed by catalase. The formaldehyde formed in the first stage was further oxidized by NAD⁺-formaldehyde dehydrogenase. The NADH formed was oxidized by 1-methoxy-5-methylphenazinium methylsulphate (1-MPMS), and finally the reduced 1-MPMS was spontaneously oxidized and hydrogen peroxide was produced. The concentration of the hydrogen peroxide produced, which was proportional to the initial concentration of methanol, was determined by luminol chemiluminescence. The determination range was from 0.1 to 100 mg l⁻¹ and the response time was less than 2 min per sample with a relative standard deviation of less than 3%. The system showed good selectivity for methanol; the response was ca. 50 times higher than for ethanol.     

造纸白泥催化花生油与甲醇酯交换的特性研究

从催化剂用量、酯交换温度及时间、醇油物质的量比等影响因素出发,并借助热重、X射线荧光光谱、X射线衍射、氮气吸附与哈米特指示剂等催化剂表征手段,研究造纸白泥催化花生油与甲醇的酯交换特性.造纸白泥通过800 ℃煅烧-常温水合-600 ℃活化处理后,成分以CaO为主、比表面积为7.28 m²/g、碱性强度为9.8相似文献   

醋酸溶液中Pd-CuPc/Y催化甲烷选择氧化制甲醇

以氯化铜、钼酸铵、苯酐、氯化铵、尿素和NaY分子筛为原料,采用苯酐-尿素法制备了酞菁铜/分子筛复合物CuPc/Y.采用等体积浸渍法将金属钯担载在CuPc/Y上制备了Pd-CuPc/Y催化剂,并在醋酸水溶液中考察了其催化甲烷选择氧化合成甲醇反应的性能,结果表明,催化性能与反应温度、溶剂中CH₃COOH与H₂O的混合比例、对苯醌用量、反应时间等因素有关,在0.5%Pd-0.5%CuPc/Y添加量0.5 g、CH₃COOH与H₂O体积比4∶1、对苯醌用量1 000 μmol、反应时间3 h、反应温度150 ℃的条件下,甲醇的最佳生成量为1 840 μmol.Pd-CuPc/Y催化剂可以多次循环使用,但由于催化剂流失和催化剂表面的钯粒子聚集的原因,循环使用后的催化剂催化活性有所下降.Pd-CuPc/Y在醋酸溶液中催化甲烷选择氧化合成甲醇是亲电取代反应和活性氧物种氧化共同作用的结果.     

Effect of immobilization on the main dynamic characteristics of the enzymatic oxidation of methane to methanol by bacteria <Emphasis Type="Italic">Methylosinus sporium</Emphasis> B-2121

The main dynamic characteristics of biochemical methanol formation by the oxidation of methane using a biocatalyst were studied. The biocatalyst is based on cells of bacteria Methylosinus sporium B-2121, both suspended in a medium and immobilized in the poly(vinyl alcohol) cryogel. The change in the methane concentration and the biocatalyst amount affects the productivity of the system, the maximal concentration of methanol in the cultural liquid, and the rate of methanol accumulation. The most part of the dynamic characteristics are described by extremal curves. The experimental conditions were optimized prior to experiments. The use of the immobilized biocatalyst makes it possible to enhance the productivity of the process more than fivefold compared to that of the free cells and to achieve the highest methanol concentration in the medium: 62±2 mg L⁻¹. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1603–1606, August, 2008.     

Effects of Oxygen Limitation on Xylose Fermentation, Intracellular Metabolites, and Key Enzymes of Neurospora crassa AS3.1602

The effects of oxygen limitation on xylose fermentation of Neurospora crassa AS3.1602 were studied using batch cultures. The maximum yield of ethanol was 0.34 g/g at oxygen transfer rate (OTR) of 8.4 mmol/L·h. The maximum yield of xylitol was 0.33 g/g at OTR of 5.1 mmol/L·h. Oxygen limitation greatly affected mycelia growth and xylitol and ethanol productions. The specific growth rate (μ) decreased 82% from 0.045 to 0.008 h⁻¹ when OTR changed from 12.6 to 8.4 mmol/L·h. Intracellular metabolites of the pentose phosphate pathway, glycolysis, and tricarboxylic acid cycle were determined at various OTRs. Concentrations of most intracellular metabolites decreased with the increase in oxygen limitation. Intracellular enzyme activities of xylose reductase, xylitol dehydrogenase, and xylulokinase, the first three enzymes in xylose metabolic pathway, decreased with the increase in oxygen limitation, resulting in the decreased xylose uptake rate. Under all tested conditions, transaldolase and transketolase activities always maintained at low levels, indicating a great control on xylose metabolism. The enzyme of glucose-6-phosphate dehydrogenase played a major role in NADPH regeneration, and its activity decreased remarkably with the increase in oxygen limitation.     

基于氯化镁饱和溶液中固定化脂肪酶Lipozyme TL IM催化光皮树油脂合成生物柴油

基于氯化镁饱和溶液反应体系中,对采用固定化脂肪酶Lipozyme TL IM催化光皮树油脂转化为生物柴油的工艺进行了研究。考察了固定化脂肪酶Lipozyme TL IM催化光皮树油转酯化的工艺中甲醇的用量、固定化脂肪酶的添加量、摇床的转速和反应时间对生物柴油产率的影响。实验结果表明,采用氯化镁饱和溶液反应体系,在醇油摩尔比为3∶1,固定化酶Lipozyme TL IM用量为光皮树油质量的20%,摇床转速为150 r/min,反应8 h时,生物柴油产率最高,达到86.5%。与传统的三步甲醇醇解或者有机溶剂反应体系比较,采用的氯化镁饱和溶液体系的酶稳定性更好,反应效率更高,有效地解决了酶在甲醇中失活的问题,生产成本低,可成为生产生物柴油的新工艺。     

Biodiesel Production from Various Oils Under Supercritical Fluid Conditions by Candida antartica Lipase B Using a Stepwise Reaction Method

In this study, we evaluate the effects of various reaction factors, including pressure, temperature, agitation speed, enzyme concentration, and water content to increase biodiesel production. In addition, biodiesel was produced from various oils to establish the optimal enzymatic process of biodiesel production. Optimal conditions were determined to be as follows: pressure 130 bar, temperature 45 °C, agitation speed 200 rpm, enzyme concentration 20%, and water contents 10%. Among the various oils used for production, olive oil showed the highest yield (65.18%) upon transesterification. However, when biodiesel was produced using a batch system, biodiesel conversion yield was not increased over 65%; therefore, a stepwise reaction was conducted to increase biodiesel production. When a reaction medium with an initial concentration of methanol of 60 mmol was used and adjusted to maintain this concentration of methanol every 1.5 h during biodiesel production, the conversion yield of biodiesel was 98.92% at 6 h. Finally, reusability was evaluated using immobilized lipase to determine if this method was applicable for industrial biodiesel production. When biodiesel was produced repeatedly, the conversion rate was maintained at over 85% after eight reuses.     

生物质气催化合成甲醇的研究

在高压微型反应装置上进行了生物质气合成甲醇的研究。利用组成为H2/CO/CO2 /N2(体积比)=52.5/21.5/22.8/3.2 的富CO2原料气考察了不同温度、压力和空速条件时甲醇的时空产率和质量分数。结果表明,在所考察的范围内,甲醇的产率和质量分数在260 ℃达到最大。产率和质量分数随反应压力升高而增大,空速增加使产率增大,甲醇的质量分数降低。当p=4 MPa,t=260 ℃,WHSV=5 280 h-1时, 甲醇的时空产率为0.79 g·（mL·h）－１,质量分数为96.2%,与工业合成气相比,分别下降25.8％和1.64％。     

Independent exponential feeding of glycerol and methanol for fed-batch culture of recombinant Hansenula polymorpha DL-1

As a novel feeding strategy for aptomizing human epidermal growth factor (hEGF) production with a recombinant Hansenula polymorpha DL-1 using the methanol oxidase (MOX) promoter in H. polymorpha DL-1, independent exponential feeding of two substrates was used. A simple kinetic model considering the cell growth on two substrates was established and used to calculate the respective feeding rates of glycerol and methanol. In the fedbatch culture with methanol-only feeding, the optimal set point of specific growth rate on methanol was found to be 0.10 h⁻¹. When the fed-batch cultures were conducted by the independent feeding of glycerol and methanol, the actual specific growth rate on glycerol and methanol was slightly lower than the set point of specific growth rate. By the uncoupled feeding of glycerol and methanol the volumetric productivity of hEGF increased from 6.4 to 8.0 mg/(L·h), compared with methanol-only feeding.     

Production of biosurfactant from a new and promising strain of Pseudomonas aeruginosa PA1

The Pseudomonas aeruginosa PA1 strain, isolated from the water of oil production in Sergipe, Northeast Brazil, wasevaluated as a potential rhamnolipid type of biosurfactant producer. The production of biosurfactants was investigated using different carbon sources (n-hexadecane, paraffin oil, glycerol, and babassu oil) and inoculum concentrations (0.0016–0.008 g/L) The best results were obtained with glycerol as the substrate and an initial cell concentration of 0.004 g/L. AC:N ratio of 22.8 led to the greatest production of rhamnolipids (1700 mg/L) and efficiency (1.18 g of rhamnolipid/g of dry wt).     

纤维素在亚/超临界甲醇中液化条件对主要化合物产物的影响

在反应温度240-320 ℃、甲醇用量0-200 mL、反应时间0-200 min的条件下,采用间歇式高温高压反应釜对玉米秸秆纤维素在亚/超临界甲醇中进行液化实验,结合GC-MS分析,研究不同液化反应条件下,生物油中轻油、重油产率及液化产物中烃类、醇类、酯类、酸类等主要化合物的组分分布及其变化规律。结果表明,反应温度和甲醇用量对化合物的分布与含量影响较大,反应温度和甲醇用量增加,促进纤维素向烃类、醇类、酯类转化,各化合物含量随之增加,并使轻油、重油产率升高,当反应条件为：甲醇用量160 mL,温度320 ℃,反应时间30 min时,生物油产率达到最高25.1%。生物油中组分含量顺序为：烃类>醇类>酯类>酸类,各化合物最高相对含量分别为77.2%、19.0%、30.9%、20.8%。初步分析发现,随着温度的升高和甲醇量的增加,自由基活性逐渐增强,当甲醇用量超过160 mL、温度超过300 ℃时,醇类以及酯类等化合物进一步发生氧化、缩合等反应形成酸类等化合物,造成化合物产率减小,进而使生物油产率降低。