Biofuels–Renewable Energy Sources: A Review

Biodiesel is biodegradable and nontoxic, and it significantly reduces toxic and other emissions when burned as a fuel. The advantages of biodiesel as diesel fuel are its portability, ready availability, renewability, higher combustion efficiency, non-toxicity, higher flash point, and lower sulfur and aromatic content, higher cetane number, and higher biodegradability. The major disadvantages of biodiesel are its higher viscosity, lower energy content, higher cloud point and pour point, higher nitrogen oxide (NO_x) emissions, lower engine speed and power, injector coking, engine compatibility, high price, and greater engine wear. The technical disadvantages of biodiesel/fossil diesel blends include problems with fuel freezing in cold weather, reduced energy density, and degradation of fuel under storage for prolonged periods. The sources of biodiesel are vegetable oils and fats. The direct use of vegetable oils and/or oil blends is generally considered to be unsatisfactory and impractical for both direct injection and indirect type diesel engines because of their high viscosities and low volatilities injector coking and trumpet formation on the injectors, higher level of carbon deposits, oil ring sticking, and thickening and gelling of the engine lubricant oil, acid composition. Biodiesel is obtained by transesterifying triglycerides with methanol. A popular variation of the batch transesterification process which needs high alcohol/acid ratio (several separation problems and high corrosivity and toxicity) is the use of continuous stirred tank reactors in series. This continuous process is heterogeneous and is based on reactive distillation. The key factor is the selection of the right and effective solid catalyst which leads to reduction of energy consumption and investments at all.     

Ultra Moisturizing Anti-Wrinkle Lotion Enriched with Tocotrienols

A stable palm-based anti-wrinkle lotion enriched with tocotrienols was successfully prepared. The stability of the product was due to the presence of liquid crystalline structure in the emulsion system. It helps in bringing the active to the dermis layer. Functionality active ingredients such as tocotrienols and anti-wrinkle were added in the formulation. A commercial plant extract was used to strengthen the collagen seated at the dermis layer. The product was formulated to pH 5.5 which is suitable for the skin. The mean droplet size is 10.2 µm with a monomodal distribution pattern which prevents agglomeration. This will decrease Brownian motion, thus prolonging its stability. Long-term acute moisturizing tests show a significant increase of between 24% and 17% hydration for five and six weeks respectively. The efficacy testing on 12 subjects confirmed a reduction in natural fine wrinkles on faces during aging or premature aging at ?7.6%.     

碳酸钾催化的铁基氧载体煤催化化学链燃烧

研究了K₂CO₃催化剂及惰性担体对铁基氧载体煤化学链燃烧的影响.实验结果表明,K₂CO₃的添加可明显促进铁基氧载体与煤之间的反应速率,其原因可归结为从氧载体上迁移到煤颗粒上的K₂CO₃对煤-CO₂气化步骤的催化作用(该步骤为整个还原过程的速率控制步骤);由于K₂CO₃本身的促熔效果及加入K₂CO₃后导致的剧烈氧化还原反应,可以发现,K₂CO₃会增大铁基氧载体的烧结;不同惰性担体对铁基氧载体与煤的反应性影响不大,这是由于惰性担体对还原速控步没有影响;K₂CO₃在多循环化学链燃烧过程中依然可以保持一定的催化活性,另外由于催化剂的流失与失活,使得氧载体的反应活性有所下降.     

铜基载氧体与可燃固体废弃物化学链燃烧特性研究

采用机械混合法制备了铜基载氧体,利用两段式管式炉反应平台和磁悬浮热重分析仪分别研究了铜基载氧体与石墨、可燃固体废弃物典型组分及可燃固体废弃物热解气模型物CH₄的化学链燃烧特性。结果表明,机械混合法制备的Cu80Si950载氧体强度高,具有良好的转化率和循环稳定性,是实现可燃固体废弃物化学链燃烧的一种比较理想的载氧体。利用扫描电镜(SEM)、X射线衍射仪(XRD)和颗粒强度测定仪对各个反应阶段载氧体进行分析。结果表明,Cu80Si950载氧体参与反应后表面结构发生巨大改变,机械强度骤降。多次循环之后载氧体结构趋于规则均匀化,形成类似球棒形状的大孔隙率结构,强度保持不变,使得载氧体在长时间使用过程中反应性能得以维持。     

两相流中煤粉的燃烧机理及动力学特征

利用微型流化床动力学分析仪研究了两相流条件下无烟煤粉的燃烧反应机理和动力学特征,并与热重法所得结果进行比较分析。结果表明,当温度大于850℃时,煤粉燃烧机理发生了变化,燃烧气态产物的生成比例也随之改变;当气速大于0.10 m/s时,气体扩散限制基本被消除,煤粉燃烧反应速率主要受界面化学反应控制;煤粉燃烧反应速率随着氧气分压的增大呈幂函数形式增长,且氧气分压对煤粉静置燃烧的影响更加显著。煤氧两相流燃烧的表观活化能与静置燃烧相比降低了49 kJ/mol,相同温度条件下两相流燃烧的界面化学反应阻力也明显小于热重法测试结果。     

Cu-V-O氧化物催化燃烧甲苯的活性和抗硫性

采用溶胶-凝胶法制备一系列不同Cu/V比例的Cu-V-O催化剂,利用XRD、BET、H₂-TPR等手段对催化剂进行了表征,并考察其催化燃烧甲苯的活性和抗硫性。结果表明,适量的Cu掺杂会提高催化剂比表面积,而且Cu-V可以形成Cu₃V₂O₈晶型结构,使V₂O₅晶格氧活动增加,提高催化剂氧化-还原能力。其中,Cu_0.15V_0.85催化剂表现出最佳的活性和抗硫性;通过TiO₂负载可以进一步提高催化剂对甲苯的催化燃烧活性和抗硫性。     

Fe2O3/Al2O3氧载体用于甲烷化学链燃烧：负载量与制备方法的影响

以不同方法制备了系列Fe₂O₃/Al₂O₃氧载体,采用XRD、H₂-TPR、CH₄-TPR、O₂-TPD和BET等分析技术对氧载体进行了表征。研究了不同Fe₂O₃负载量氧载体的甲烷化学链燃烧性能,考察了不同制备方法对Fe₂O₃/Al₂O₃氧载体结构、反应性和产物选择性的影响。结果表明,Fe₂O₃负载量对氧载体活性及产物中CO₂选择性的影响较大,负载量较低时氧载体活性较低且引起甲烷部分氧化产物CO含量增加。制备方法亦对氧载体与甲烷的反应活性有所影响,整体上共沉淀法制备的质量分数60％Fe₂O₃/Al₂O₃氧载体具有较高的氧化活性和化学链循环稳定性。其在反应温度850℃、反应时间15 min、30次循环后甲烷转化率及产物中CO₂选择性均未见明显降低。     

Application of the Combustion Method in a Closed Flask to the Lead Determination in Atmospheric Aerosols

Abstract

The destruction of the filter for metal determination in atmospheric aerosols is an important step in the analysis. Nowadays the decomposition of this kind of sample has not been completely solved, so it is interesting to study new methods for filter sample attack. In the present work the application of the combustion method in a closed flask for mixed cellulose esters filter decomposition for lead determination is proposed. For this purpose optimum operating conditions as stopper flask design, sample size, flask volume, shaking time and volume and concentration of absorbing solution are established, and accuracy and precision of the proposed method using AAS for the measurements is given. The results obtained by the closed flask combustion are compared with those found by wet attack with HNO₃. The method proposed is rapid, has low reagent contamination and no loss of lead by volatilization or by amalgamation occurs. This method shows an accuracy and a precision in good agreement with the standard method.     

Determination of chlorophenols in environmental water samples using directly suspended droplet liquid-liquid-liquid phase microextraction prior to high-performance liquid chromatography

A new sample preparation method named directly suspended droplet liquid-liquid-liquid phase microextraction was used in this research for determination of three chlorophenols in environmental water samples. The analytes (2-chlorophenol, 3-chlorophenol and 4-chlorophenol) were extracted from 4.5?mL acidic donor phase, (pH 2, P1) into an organic phase, 350?µL?of benzene/1-octanol (90?:?10 v/v, P2) and then were back-extracted into a 7?µL droplet of an basic (pH 13) aqueous solution (acceptor phase, P3). In this method, contrary to the ordinary single drop liquid-phase microextraction technique, an aqueous large droplet is freely suspended on the surface of the organic solvent, without using a microsyringe as supporting device. This aqueous microdroplet is delivered at the top-centre position of an immiscible organic solvent which is laid over the aqueous donor sample solution while the solution is being agitated. Then, the acceptor phase containing chlorophenols was withdrawn back into a HPLC microsyringe and neutralised by adding of 7?µL HCl 0.1?M. The total amount was eventually injected into the HPLC system with UV detection at 225?nm for further analysis. Parameters such as the organic solvent, phases volumes, extraction and back-extraction times, stirring rate and pH values were optimised. The calibration graphs are linear in the range of 10–2000?µg?L^?1 with r?≥?0.9973. The enrichment factors were ranged from 115 to 170, and the limit of detection (LOD, n?=?7) varied from 5 to 10?µg?L^?1. The relative standard deviations (RSDs, n?=?5) were found 6.8 to 7.4 at S/N?=?3. All experiments were carried out at room temperature, (22?±?0.5°C).     

Strong Morphological Effect of Mn3O4 Nanocrystallites on the Catalytic Activity of Mn3O4 and Au/Mn3O4 in Benzene Combustion

Gold nanoparticles (3–4 nm) were deposited on Mn₃O₄ nanocrystallites with three distinct morphologies (cubic, hexagonal, and octahedral). The resulting structures were characterized, and their activities for benzene combustion were evaluated. The dominant exposed facets for the three kinds of Mn₃O₄ polyhedrons show the activity order: (103)≈(200)>(101). A similar activity order was derived for the interfaces between the Au and the Mn₃O₄ facet: Au/(200)≈Au/(103)>Au/(101). The metal–support interactions between the Au nanoclusters and specific facets of the Mn₃O₄ polyhedrons lead to a unique interfacial synergism in which the electronic modification of the Au nanoparticles and the morphology of the Mn₃O₄ substrate have a joint effect that is responsible for a significant enhancement in the catalytic activity of the Au/Mn₃O₄ system.