KF/CaO固体碱催化剂对酯交换工艺影响的研究

碱催化酯交换反应速度快、收率高但是后续处理复杂,易于造成环境污染,而固体碱催化剂易于分离,不会造成环境污染;用等体积浸渍法制备了不同浓度KF浸渍KF/CaO固体碱,并考察了KF/CaO固体碱对酯交换反应的催化性能;通过测定酯交换反应过程中产生的甘油与Cu(OH)2悬浊液反应生成绛蓝色溶液的吸光度,计算酯化率;利用均匀设...     

分子筛微波辐射负载CaO催化合成生物柴油

研究微波辐射法制备固体碱催化剂CaO/NaY在合成生物柴油中的应用。结果表明,该催化剂在醇油摩尔比9∶1,催化剂质量分数3%,反应温度65℃,反应时间3 h等条件下,以精制大豆油为原料制备的生物柴油得率可达95%;而以酸值(以KOH计)为4 mg/g和含水质量分数为1.5%的油脂为原料,生物柴油得率可分别达到92.4%和84.8%。催化剂结构表征表明:微波辐射改善了CaO在载体NaY上的分散,其总碱量(H-27)达到3.798mmol/g,是一种固体超强碱。     

制备生物柴油的负载型催化剂KF/CaO/陶土的研究

以共混/浸渍法制备复合负载型固体碱催化剂KF/CaO/陶土,考察了催化剂制备条件对催化活性的影响,以SEM、TEM、BET等手段对催化剂进行了表征。结果表明：焙烧温度为600 ℃,焙烧时间为4 h,陶土与CaO质量比为3∶7,浸渍剂KF占陶土与CaO总质量的20%时,催化乌桕籽油制备生物柴油的收率可达96%以上。催化剂结构表征显示,该催化剂呈多孔网状结构,粒径主要分布在30～100 nm,平均孔径分布为43 nm,表面积为113.9 m2/g。     

NaF/CaO固体碱催化制备生物柴油

采用等体积浸渍法制备了NaF/CaO催化剂,用于催化大豆油与甲醇酯交换反应制备生物柴油。考察了催化剂制备条件和反应条件对酯交换反应的影响。结果表明,通过等体积浸渍法、500℃焙烧4h和NaF与CaO的质量比6:1制得的催化剂,在70℃、催化剂用量为油质量的8%、醇油物质的量比9:1和反应2 h条件下,生物柴油收率可达95%。与单纯的CaO相比,NaF/CaO催化剂的催化活性明显提高。用共聚焦拉曼光谱考察了催化剂的表面特征。     

不同工艺制备的CaO固体催化剂对生物柴油性能的影响

用菜籽油为原料,以CaO为非均相催化剂,通过酯交换反应制备生物柴油。对比不同工艺下制备的4种CaO系列固体催化剂对制备的生物柴油黏度、酸值及得率的影响,发现催化效率高低顺序为:煅烧CaO>CaO/MgO(Ⅰ)>CaO/MgO(Ⅱ)>原料CaO。经700℃煅烧所制得的锻烧CaO固体催化剂使用效果最佳,在反应4h后得到黏度为4.37 mm²/s、酸值为0.79 mg/g的生物柴油,达到国家标准,得率为94.30%。     

固体碱催化油脂甘油酯化降酸值的研究

高酸值油脂的甘油酯化降酸值是降低油脂中脂肪酸含量的一种有效方法,本文比较了固体超强碱Na/NaOH/γ-Al2O3、固体碱NaOH/γ-Al2O3以及氢氧化钠在甘油与脂肪酸酯化反应中的催化作用。结果表明固体碱NaOH/γ-Al2O3是一种高效的甘油酯化催化剂,通过优化反应条件,酯化率可以达到99.3%以上,得到油脂的酸值可降至0.3mgKOH/g以内,该工艺可用于食用油脂的降酸值,也可用于生物柴油的预酯化,具有一定的工业应用前景。     

硫酸改性金属氧化物超强酸的合成及其催化麻疯树籽油酯交换反应性能的研究

基于H2SO4溶液浸渍法改性氢氧化钛(Ti(OH)4)和氢氧化锆(Zr(OH)4)制备了SO42-/TiO2和SO42-/ZrO2固体超强酸催化剂.利用XRD、N2-物理吸附、FT-IR和NH3-TPD技术对催化剂的微观结构及酸性质进行了表征.并将其用于麻疯树籽油酯交换生产生物柴油反应,测试其催化活性和产物选择性.结果 表明,硫酸改性后的催化剂表现出更高的催化活性,主要归功于催化剂的强酸性和大比表面积促进了酯交换反应.     

固体碱催化制备生物柴油的研究

近些年来,生物柴油已成为重要的新兴可再生能源之一。简要列举了一些固体碱的合成及其催化制备生物柴油催化性能的研究,并简单预测了今后此类催化剂可能的发展方向。     

非均相催化剂两步法催化潲水油制备生物柴油

对取自餐饮的潲水油进行一系列预处理,脱去其中的胶类、色素、水分等杂质,然后用自制的固体酸、固体碱催化剂经"两步法"工艺将其转化为生物柴油。结果发现,在预酯化反应中,催化剂A用量为6%、醇油摩尔比为12∶1,反应2.5 h后,潲水油的酸值由50 mg KOH.g-1降至2 mg KOH.g-1。通过正交实验得到碱催化酯交换反应最佳条件为:反应时间2 h、反应温度100℃、催化剂B用量6%、醇油摩尔比9∶1,在此条件下转化率达96.4%。表明所制备的固体酸、固体碱催化剂能有效将潲水油转化为生物柴油。     

负载型固体碱催化合成甲酯生物柴油的研究

采用浸渍法制备了Na2CO3/高岭土负载型固体碱催化剂,用于催化大豆油与甲醇酯交换反应制备甲酯生物柴油。考察了反应时间、催化剂用量、反应温度和醇油摩尔比对酯交换反应转化率的影响,并通过单因素试验确定了最优工艺条件。结果表明:反应时间4 h、反应温度60℃、催化剂用量3%和醇油摩尔比12∶1条件下,酯交换反应转化率达到90.5%。     

柴油空气催化氧化脱硫的探索研究

为克服柴油加氢脱硫技术投资大、操作条件苛刻及污染严重等问题，提出一种空气催化氧化脱硫方法。考察了催化剂种类及其用量、催化氧化温度、时间、空气流速等因素对脱硫效果的影响。实验结果表明，选用粉状白土作脱硫催化剂，在空气流量为1600 ml/min和160 ℃下反应30 min，可将原料油中硫的质量分数从1033×10^－6降到381×10^－6，脱硫率达63.12%。     

Effect of strontium doping on catalytic behaviour of lanthanum oxide on oxidative coupling of methane

The doping of lanthanum oxide with strontium maintains the good selectivity of the oxidative methane coupling for the catalysts prepared or calcined at high temperature (> 800 °C) by preserving the platelet shape of oxide particles.     

Solid acidity of metal oxide monolayer and its role in catalytic reactions

Such metal oxide as SO₄²⁻, MoO₃, WO₃, and V₂O₅ spread readily on supports like SnO₂, ZrO₂, and TiO₂ due to the different properties between acid and base oxides to generate the acid site on the monolayer. Number, strength, and structure of the acid site were characterized by temperature-programmed desorption (TPD) of ammonia principally, together with various physico-chemical techniques, and its role for catalytic reactions was studied. Approximately, one to two acid sites were stabilized on 1 nm² of the surface, which consisted of four to eight metal atoms. The limit in surface acid site density was estimated on the monolayer based on the concept of solid acidity on zeolites. Sequence of the metal oxide to show the strong acidity was, SO₄²⁻>WO₃>MoO₃>V₂O₅, and for the support oxide to accommodate the monolayer, SnO₂>ZrO₂>TiO₂>Al₂O₃. From these combinations, the metal oxide monolayer to show the adequate strength of acid site could be selected. Brønsted acidity was observed often, however, the Lewis acidity was prevailing on the reduced vanadium oxide. The structure of acid site, Brønsted or Lewis acid site, thus depended on the oxidation state. Relationship of the profile of solid acidity with various catalytic activities was explained. The solid acid site on the monolayer will possibly be applied to environment friendly technologies.     

Transesterification of soybean oil to biodiesel using CaO as a solid base catalyst

In this study, transesterification of soybean oil to biodiesel using CaO as a solid base catalyst was studied. The reaction mechanism was proposed and the separate effects of the molar ratio of methanol to oil, reaction temperature, mass ratio of catalyst to oil and water content were investigated. The experimental results showed that a 12:1 molar ratio of methanol to oil, addition of 8% CaO catalyst, 65 °C reaction temperature and 2.03% water content in methanol gave the best results, and the biodiesel yield exceeded 95% at 3 h. The catalyst lifetime was longer than that of calcined K₂CO₃/γ-Al₂O₃ and KF/γ-Al₂O₃ catalysts. CaO maintained sustained activity even after being repeatedly used for 20 cycles and the biodiesel yield at 1.5 h was not affected much in the repeated experiments.     

Recycling of waste lubricant oil into chemical feedstock or fuel oil over supported iron oxide catalysts

The recycling of waste lubricant oil from automobile industry was found to be best alternative to incineration. Silica (SiO₂), alumina (Al₂O₃), silica-alumina (SiO₂-Al₂O₃) supported iron oxide (10 wt% Fe) catalysts were prepared by wet impregnation method and used for the desulphurisation of waste lubricant oil into fuel oil. The extent of sulphur removal increases in the sequence of Fe/SiO₂-Al₂O₃<Fe/Al₂O₃<Fe/SiO₂ and this might be due to the presence of smaller crystalline size (7.4 nm) of Fe₂O₃ in Fe/SiO₂ catalyst. X-ray diffraction results suggest the presence of iron sulphide in the used catalyst. Gas chromatography with thermal conductivity detector analysis confirms the presence of H₂S in gaseous products. In addition, Fe/SiO₂ catalyst facilitated the formation of lower hydrocarbons by cracking higher hydrocarbons (≈C₄₀) present in waste lubricant oil.     

Solid oxide derived from waste shells of Turbonilla striatula as a renewable catalyst for biodiesel production

Biodiesel production via transesterification of mustard oil with methanol using solid oxide catalyst derived from waste shell of Turbonilla striatula was investigated. The shells were calcined at different temperatures for 4 h and catalyst characterizations were carried out by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), Fourier transform infrared spectrometer (FT-IR), thermogravimetric analysis (TGA)/differential scanning calorimetry (DSC) and Brunauer-Emmett-Teller (BET) surface area measurements . Formation of solid oxide i.e. CaO was confirmed at calcination temperature of 800 °C. The effect of the molar ratio of methanol to oil, the reaction temperature, catalyst calcination temperature and catalyst amount used for transesterification were studied to optimize the reaction conditions. Biodiesel yield of 93.3% was achieved when transesterification was carried out at 65 ± 5 °C by employing 3.0 wt.% catalyst and 9:1 methanol to oil molar ratio. BET surface area indicated that the shells calcined in the temperature range of 700 °C-900 °C exhibited enhanced surface area and higher pore volume than the shells calcined at 600 °C. Reusability of the catalysts prepared in different temperatures was also investigated.     

Effect of alkali doping on catalytic properties of alumina-supported nickel oxide in the selective oxidehydrogenation of cyclohexane

The influence of alkali metal (Na, K, Cs) doping on the surface and catalytic properties of γ-Al₂O₃ supported nickel oxide in the selective oxidehydrogenation of cyclohexane was investigated. Among the organic products quantified were cyclohexene, 1,3-cyclohexadiene, benzene, and CO, CO₂, and H₂O as inorganic products, respectively. Cyclohexene selectivities of up to 75% were achieved. Doping of the catalyst with alkali was found to have no promoting effect. Selectivity to cyclohexene increased in the following order: NiO/Cs-Al₂O₃ < NiO/K-Al₂O₃ < NiO/Na-Al₂O₃ < NiO/Al₂O₃.     

Effect of doping graphene oxide on the structure and properties of SiO2 based high emissivity coatings

High emissivity coatings have received a great attention due to their energy saving capability for using in spacecraft and industrial furnaces applications. In this study, a feasible spray deposition method was employed to prepare a high emissivity coating on Kovar alloy substrate with porous structure after heat treatment. Graphene oxide was used to dope coating to improve its emissivity. The emissivity enhancement mechanisms of the graphene oxide doped SiO₂ coatings have been investigated. Results show that coating emissivity can be significantly improved (6.41 and 9.64% of coating emissivity at 500 and 800°C, respectively) by doping graphene oxide. Thus, this study proposed a feasible and effective method to prepare high emissivity coatings. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48794.     

Modelling the impact of creep on the probability of failure of a solid oxide fuel cell stack

In solid oxide fuel cell (SOFC) technology a major challenge lies in balancing thermal stresses from an inevitable thermal field. The cells are known to creep, changing over time the stress field. The main objective of this study was to assess the influence of creep on the failure probability of an SOFC stack. A finite element analysis on a single repeating unit of the stack was performed, in which the influence of the mechanical interactions, the temperature-dependent mechanical properties and creep of the SOFC materials are considered. Moreover, stresses from the thermo-mechanical simulation of sintering of the cells have been obtained and were implemented into the model of the single repeating unit. The significance of the relaxation of the stresses by creep in the cell components and its influence on the probability of cell survival was investigated. Finally, the influence of cell size on the failure probability was investigated.