以甲醇为碳源甲烷氧化细菌的高密度培养

分别考察了甲烷和甲醇对甲基弯菌IMV 3011生长的影响,并对甲醇添加方式对菌体生长的影响进行了比较。结果表明:甲醇可以代替甲烷作为碳源;当甲醇的最佳添加量为0.1%(V/V)时,间歇性添加甲醇发酵终止后的细胞密度为1.622g(dry wt).L-1,生长速率相对于甲烷提高到0.043h-1,但细胞生长的延滞期较长,为59.6254h;而相比较通过在线监测自动添加甲醇,发酵终止后的细胞密度为1.772g(dry wt).L-1,生长速率提高至0.056h-1,细胞生长的延滞期为37.1807h。说明在线监测自动添加甲醇缩短了细胞生长的延滞期即减少了发酵时间,促进了细胞的高密度生长。     

High methanol oxidation activity of electrocatalysts supported by directly grown nitrogen-containing carbon nanotubes on carbon cloth

The microstructure and electrochemical activity of the Pt-Ru supported by nitrogen-containing carbon nanotubes (CN_x NTs) directly grown on the carbon cloth have been investigated. The CN_x NTs directly grown on the carbon cloth (CN_x NTs-carbon cloth composite electrode) were synthesized using microwave-plasma-enhanced chemical vapour deposition first and then use as the template to support the Pt-Ru nanoclusters subsequently sputtered on. The ferricyanide/ferrocyanide redox reaction in cyclic voltammetry (CV) measurements showed a faster electron transfer on the CN_x NTs-carbon cloth composite electrode than the one with carbon cloth alone. Comparing their methanol oxidation abilities, it is found that the Pt-Ru nanoclusters supported by the CN_x NTs-carbon cloth composite electrode have considerably higher electrocatalytic activity than the carbon cloth counterpart. This result suggests high performance of the CN_x NTs-carbon cloth composite electrode, and demonstrates its suitability for direct methanol fuel cell applications.     

甲醇为碳源时C/N对反硝化过程中亚硝酸盐积累的影响

如何获得稳定的NO2--N作为厌氧氨氧化细菌的电子受体是城镇污水通过厌氧氨氧化途径脱氮的瓶颈问题。为此考虑利用反硝化途径获取稳定的NO2--N。以甲醇为碳源,采用小试装置的SBR反应器,通过控制进水C/N(COD与NO3--N质量浓度比)的策略,研究了反硝化过程中的NO2--N积累的状况。试验结果表明以甲醇为碳源且投加量不足时(C/N3.2),反硝化过程中和反硝化结束后会产生稳定的NO2--N积累;在C/N不足的前提下,NO2--N积累量随甲醇投加量的增加而增加;进水C/N为2.4～3.2时,可获得约25%的NO2--N积累率;进水C/N为0.8时,NO2--N积累率仅为5.6%;C/N1时,NO2--N与NO3--N的还原速率随着COD浓度的增加而增加;C/N≥1时,COD浓度不再影响NO2--N与NO3--N的还原速率。     

Development of electrochemical oxidase biosensors based on carbon nanotube-modified carbon film electrodes for glucose and ethanol

Functionalised multi-walled carbon nanotubes (MWCNTs) were cast on glassy carbon (GC) and carbon film electrodes (CFE), and were characterised electrochemically and applied in a glucose-oxidase-based biosensor. MWCNT-modified carbon film electrodes were then used to develop an alcohol oxidase (AlcOx) biosensor, in which AlcOx-BSA was cross-linked with glutaraldehyde and attached by drop-coating. The experimental conditions, applied potential and pH, for ethanol monitoring were optimised, and ethanol was determined amperometrically at −0.3 V vs. SCE at pH 7.5. Electrocatalytic effects of MWCNT were observed with respect to unmodified carbon film electrodes. The sensitivity obtained was 20 times higher at carbon film/MWCNT-based biosensors than without MWCNT.     

Influence of gas-mixture composition on yield,purity and morphology of carbon nanotubes grown by catalytic isobutane-decomposition

Present work concerns iron-catalyzed growth of multi-walled C nanotubes (MWCNTs) by decomposition of isobutane (C₄H₁₀). MWCNTs are prepared, by chemical vapor deposition (CVD) at 600 °C, in C₄H₁₀?H₂?He atmosphere over 29 wt.%Fe/Al₂O₃ catalysts. After purification, reaction products are analyzed by scanning electron microscopy (SEM), Raman spectroscopy (RS) and thermo-gravimetric analysis (TGA). The influence of the gas-mixture composition on the reaction issue is investigated by considering different gas-flowing setups: H₂ or C₄H₁₀ flow is varied in the range 15?90 cc/min while keeping hydrocarbon or H₂ constant. The total flow is kept at 120 cc/min by using He as a balance-gas. Owing to these changes, diverse selectivity towards nanotubes, morphologies, size distributions, purity degrees and crystallinity are obtained, as evidenced by the characterization results.     

Electrocatalytic oxidation of methanol and ethanol at carbon ceramic electrode modified with platinum nanoparticles

The use of carbon ceramic electrode (CCE) modified with platinum particles was studied for the electrocatalytic oxidation of methanol and ethanol by cyclic voltammetry and chronoamperometry. After preparation of a carbon ceramic as an electrode matrix by sol–gel technique, its surface was potentiostatically coated with Pt nanoparticles at −0.2 V vs. SCE in an aqueous solution of 0.1 M H₂SO₄ containing 0.002 M H₂PtCl₆. The electrocatalyst was characterized by XRD, SEM and cyclic voltammetry. The effective parameters on electrocatalytic oxidation of the alcohols, i.e. the amount Pt loadings, medium temperature and working potential limit in anodic direction were investigated and the results were discussed. This modified electrode showed an enhanced current density over the other Pt-modified electrodes making it more attractive for fuel cell applications.     

以葡萄糖为碳源不同碳化方式固体酸催化剂的制备与性能评价

以葡萄糖为碳源,发烟硫酸为磺酸化试剂,分别采用水热碳化法和热解碳化法制备碳基固体酸催化剂。使用扫描电镜、热重分析、X射线衍射和傅里叶变换红外光谱等对催化剂进行表征,并评价催化剂在纤维素水解反应中的性能。结果表明,两种碳化方式制备的碳基固体酸催化剂在形貌上具有很大差异,但结构上均含有—OH、—COOH和—SO_3H官能团,对于纤维素的水解反应,在150℃反应3 h,纤维素水解率超过60%。     

Effects of the ratio of carbon to nitrogen concentration on lipid production by bacterial consortium of sewage sludge using food wastewater as a carbon source

Food wastewater (FWW) and sewage sludge (SS) were used to control the C:N ratio in cultures as a method to increase lipid production by microbial species in SS. FWW and SS were mixed in volumetric ratios (FWW: SS) of 5: 0 (F5), 4: 1 (F4), or 3: 2 (F3). Compared to raw SS, total lipid content production was increased by 263% in F5, 142% in F4, and 111% in F3. These results were caused by increases in the concentrations of triglycerides (TAGs) during lipid enhancement. The fatty acid methyl ester content of TAGs (wt% of extract) was 25.3 in F5, 20.2 in F4 and 13.25 in F3; these were significant improvements over biodiesel production using raw SS. C16:0 fatty acid was mostly converted to C18:1 fatty acid; this is an important result because the proportion of C18:1 strongly influences the quality of biodiesel. This is the first effort to produce biodiesel using FWW instead of synthetic medium as a carbon source. Hence, this study provides a useful solution for treating organic wastes (SS and FWW) simultaneously; this strategy may be an economically viable method for producing biodiesel from organic wastes.     

剑麻皂甙元在甲醇和乙醇中溶解度的测定及应用

常压下,平衡法测定了剑麻皂甙元在甲醇(293~338K)和乙醇(293~353K)溶剂中的溶解度,并对溶解度数据进行关联拟合。结果表明:剑麻皂甙元在两种溶剂中的溶解度均随温度的升高而增大。温度293~323K时,甲醇溶解度高于乙醇溶解度,温度大于323K时,乙醇溶解度高于甲醇溶解度。甲醇和乙醇拟合方程校正决定系数分别为0.9961和0.9976,温度318~338K时,甲醇平均相对误差2.12%,温度328~353K时,乙醇平均相对误差2.56%,拟合方程基本可满足工程设计需要。对两种溶剂在剑麻皂甙元工业生产中的应用进行了研究,表明乙醇作为剑麻皂甙元的萃取溶剂优于甲醇。     

Oxygen to carbon atoms ratio effect on the size,morphology and purity of functionalized carbon nanoshells by using alcohol mixtures as carbon source

The effect of the ratio of oxygen to carbon atoms (O/C) on the morphology of carbon nanostructures has been studied by varying the methanol and ethanol ratio in the reaction mixtures. Notable morphological differences in the synthesized carbon nanostructures are observed as a function of the O/C ratio. At a high O/C ratio, i.e., using methanol (O/C = 1), the synthesized carbon nanoshells (CNS) are faceted. Moreover, other faceted nanostructures, such as triangular and hexagonal, are observed in this strong oxidative environment. Decreasing the O/C ratio in the mixture by adding ethanol induces changes in the CNSs morphology; they are less faceted and favor only the growth of single-walled carbon nanotubes mixed with the CNSs. The importance of the O/C ratio is corroborated by replacing ethanol (O/C = 0.5) with polyethylene glycol (O/C = 0.5) in the methanol:ethanol reaction mixture. Finally, at very low O/C ratios, i.e., methanol:octanol mixtures, CNS are obtained and no faceted nanostructures or SWCNT are found. Thus, adjusting the O/C ratio is a method for obtaining high purity samples of CNS. Moreover, the use of the alcohols during the synthetic process is a simple and green method of functionalizing CNS.     

Production of docosahexaenoic acid by Crypthecodinium cohnii grown in a pH-auxostat culture with acetic acid as principal carbon source

Crypthecodinium cohnii, a marine alga used for the commercial production of docosahexaenoic acid (DHA), was cultivated in medium containing sodium acetate as principal carbon source; the pH was maintained at a constant value by addition of acetic acid, which also provided an additional carbon source in a controlled manner. The accumulation of lipid by C. cohnii in this pH-auxostat culture was significantly greater than previously reported for batch cultures using glucose as principal carbon source. Of six strains tested in pH-auxostat cultures, C. cohnii ATCC 30772 was the best, with the cells reaching 20 to 30 g dry weight per liter after 98 to 144 h and containing in excess of 40% (w/w) total lipid, with DHA representing approximately half of the total fatty acids in the triacylglycerol fraction. A productivity of 36 mg DHAL⁻¹ h⁻¹ was achieved during cultivation for 98 h using a 5% (vol/vol) inoculum, and DHA production was in excess of 3 g per liter of culture. Most of the DHA was present in neutral lipids.     

甲醇合成影响因素与粗甲醇中乙醇含量超标研究

操作条件、入塔气组成以及催化剂性能是影响甲醇合成反应的主要因素。文章对甲醇合成反应的影响因素进行分析,找出甲醇装置开车初期粗甲醇中乙醇含量超标的具体原因,并在此基础上进行优化操作,粗甲醇中乙醇含量达到或优于设计指标。     

Chemical vapor deposition synthesis of graphene on copper with methanol, ethanol, and propanol precursors

Large area, high quality graphene was synthesized from different liquid alcohols by chemical vapor deposition on copper foils in a tube furnace. The quality of the synthesized graphene was systematically investigated with various growth conditions. Alcohol vapor exposure times of 5 min and an average growth temperature of 850 °C yield continuous graphene monolayer films, as inferred from Raman spectroscopy. X-ray photoelectron spectroscopy shows that the oxygen moieties found in the source molecules have no measureable doping or oxidation effect in the synthesized graphene. Raman spectroscopy indicates that graphene films transferred to insulating substrates are of high quality. The field effect mobility of large area graphene transistors was measured at room temperature to be in the range 1800–2100 cm²/V s at carrier densities between 10¹¹/cm² and 10¹²/cm².     

Pt–Ru nanoparticles supported on functionalized carbon as electrocatalysts for the methanol oxidation

Platinum–ruthenium alloy electrocatalysts, for methanol oxidation reaction, were prepared on carbons thermally treated in helium atmosphere or chemically functionalized in H₂O₂, or in HNO₃ + H₂SO₄ or in HNO₃ solutions. The functionalized carbon that is produced using acid solutions contains more surface oxygenated functional groups than carbon treated with H₂O₂ solution or HeTT. The XRD/HR-TEM analysis have showed the existence of a higher alloying degree for Pt–Ru electrocatalysts supported on functionalized carbon, which present superior electrocatalytic performance, assessed by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy, as compared to electrocatalysts on unfunctionalized carbon. It also was found that Pt–Ru alloy electrocatalysts on functionalized carbon improve the reaction rate compared to Pt–Ru on carbons treated with H₂O₂ solution and thermally. A mechanism is discussed, where oxygenated groups generated from acid functionalization of carbon and adsorbed on Pt–Ru electrocatalysts are considered to enhance the electrocatalytic activity of the methanol oxidation reaction.     

Measurement and prediction of high-pressure vapor-liquid equilibria for binary mixtures of carbon dioxide + n-octane, methanol, ethanol, and perfluorohexane

We report the measurement of high-pressure vapor-liquid equilibrium data for binary mixtures of carbon dioxide + n-octane, +methanol, and +ethanol systems at 313.14 K and carbon dioxide + perfluorohexane at 303.15-323.15 K. The experimental data were collected using a new simple apparatus for measuring high-pressure vapor-liquid equilibria and correlated using a modified SRK equation with the three-parameter conventional mixing rule proposed by Adachi and Sugie. The SAFT-VR equation of state has also been used to predict the phase behavior and found to be in good agreement with experimental data. For the carbon dioxide + methanol, carbon dioxide + ethanol and carbon dioxide + perfluorhexane systems simple Lorentz-Berthelot combining rules can be used to determine the cross interactions and predict the phase behavior. For the carbon dioxide + n-octane system cross interaction parameters fitted to experimental data are needed in order to capture the non-ideal phase behavior exhibited by this system.