Biodiesel production from refined sunflower vegetable oil over KOH/ZSM5 catalysts

ZSM5 zeolite was impregnated with different KOH loadings (15 wt.%, 25 wt.% and 35 wt.%) to prepare a series of KOH/ZSM5 catalysts. The catalysts were calcined at 500 °C for 3 h and then characterized by N₂ adsorption–desorption and X-ray diffraction (XRD) techniques. The catalysts were tested in the transesterification reaction in a batch reactor at 60 °C and under atmospheric pressure. It was found that KOH/ZSM5 with 35 wt.% loading showed the best catalytic performance. The best reaction conditions in the presence of KOH/ZSM5 (35 wt.%) were determined while modifying the catalyst to oil ratio and the reaction time. The highest methyl ester yield (>95%) was obtained for a reaction time of 24 h, a catalyst to oil ratio of 18 wt.%, and a methanol to oil molar ratio of 12:1. The properties of produced biodiesel complied with the ASTM specifications. The catalytic stability test showed that 35KOH/ZSM5 was stable for 3 consecutive runs. Characterization of the spent catalyst indicated that a slight deactivation might be due to the leaching of potassium oxides active sites.     

A simple thermal oxidation technique and KOH wet etching process for fuel cell flow field fabrication

The relatively inexpensive SiO₂ layer was studied as the silicon etch mask in a KOH etching process for the fabrication of a flow field pattern that consists of channels as well as through-holes on the substrate of a fuel cell. The SiO₂ layer was grown in a wet thermal oxidation process to obtain a thickness of up to 6.5 μm and the growth was predicted using the Deal-Grove model. The flow fields on the cathode and anode sides were done using a wet etch process with KOH as etchant. Etching time was utilized to control the depth of the required pattern and the pattern shape was found to have an influence over the etch rate. With constant monitoring of the conditions and parameters used throughout the micro-fabrication process, the thick SiO₂ layer was found to be a reliable masking material for a long KOH etching.     

KOH-activated multi-walled carbon nanotubes as platinum supports for oxygen reduction reaction

In the present investigation, multi-walled carbon nanotubes (MWCNTs) thermally treated by KOH were adopted as the platinum supporting material for the oxygen reduction reaction electrocatalysts. FTIR and Raman spectra were used to investigate the surface state of MWCNTs treated by KOH at different temperatures (700, 800, and 900 °C) and showed MWCNTs can be successfully functionalized. The structural properties of KOH-activated MWCNTs supported Pt were determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and their electrochemical performance was evaluated by the aid of cyclic voltammetry (CV) and rotating disk electrode (RDE) voltammetry. According to the experimental findings of the present work, the surrface of MWCNTs can be successfully functionalized with oxygen-containing groups after activation by KOH, favoring the good dispersion of Pt nanoparticles with narrow size distribution. The as-prepared Pt catalysts supported on KOH treated MWCNTs at higher temperature, possess higher electrochemical surface area and exhibit desirable activity towards oxygen reduction reaction (ORR). More precisely, it has been found that the electrochemical active area of Pt/MWCNTs-900 is approximately two times higher than that of Pt/MWCNTs. It can be concluded that KOH activation is an effective way to decorate MWCNTs’ surface with oxygen-containing groups and bigger surface area, which makes them more suitable as electrocatalyst support materials.     

Feasibility of recycling KOH in chemical activation of oil‐sands petroleum coke

Although potassium hydroxide (KOH) is known to be effective in generating highly porous activated carbons, the mechanism of KOH activation has not been well elucidated. To develop porosity in carbon, a high KOH/carbon mass ratio must be maintained. Consequently, KOH, as the activating agent, represents a major part of the cost of the activation process. Focusing on the mechanism, particularly the activation products, the present work attempted to establish the technical feasibility of recycling KOH. Experiments revealed that the major products of KOH activation at 600–900°C are metallic K, K₂CO₃, CO and H₂, which is supported by thermodynamic analysis. The overall reaction may be written as 6KOH + 4C = K₂CO₃ + 4K + 3H₂ + 3CO. At temperatures over 900°C, K₂CO₃ becomes unstable and participates in activation reactions with carbon; a more suitable overall reaction would be KOH + C = CO + K + 0.5H₂. As potassium ion is reduced to metallic K which is readily converted into KOH and hydrogen gas upon reacting with water, KOH recycling is feasible. The reuse of KOH in chemical activation could substantially reduce the cost of activation process. © 2011 Canadian Society for Chemical Engineering     

KOH各向异性腐蚀中预处理对硅表面粗糙度的影响

通过实验研究表明:不同预处理方法对KOH腐蚀后硅片表面粗糙度的影响不同,分别用35℃的BOE(7:1氟化铵腐蚀液)、常温BOE、10:1 HF、50:1 HF含HF成分的腐蚀液对硅片进行预处理,再和未做预处理的硅片在同等条件下进行KOH腐蚀,实验结果发现预处理后硅片表面粗糙度比未做处理的硅片表面粗糙度增加约1 nm左右,即经过含HF成分的腐蚀液预处理后的硅片再进行KOH腐蚀,其表面粗糙度将变差.     

Impact of synthesis conditions of KOH activated carbons on their hydrogen storage capacities

39 activated carbons (ACs) were prepared by KOH activation of anthracite, using weight ratios KOH/anthracite (W) ranging from 1.5 to 7, activation temperatures (T) from 973 to 1073 K, and heating rates (Hr) from 1 to 5 K min⁻¹. ACs with high apparent surface areas (>3400 m² g⁻¹), high micropore volumes (>1 cm³ g⁻¹) and high hydrogen storage capacities (up to 6.6 wt. %) were obtained. A statistical study was carried out to clarify the impact of synthesis conditions on hydrogen storage capacities of the resultant ACs. Analysis of variance (ANOVA) showed that both W and T have a significant impact on hydrogen storage capacity, whereas Hr has not. A quadratic model was used to correlate W², W, T² and T to hydrogen storage capacities. The model adequately evaluated the impact of synthesis conditions on hydrogen storage capacities of the resultant ACs.     

Low boiling point organic amine-catalyzed transesterification of cottonseed oil to biodiesel with trace amount of KOH as co-catalyst

The effect of addition of trace amount of KOH as co-catalyst on low boiling point organic amine-catalyzed transesterification for biodiesel production was investigated. Three different organic amines, tri-ethylamine, di-ethylamine and tert-butylamine, were used as catalysts, and the maximum amount of KOH that could be added to these organic amine-catalyzed systems was 367.1 mg/kg oil. Under such circumstance, KOH could be left in the resultant biodiesel and no washing was needed to remove it as the concentration of K⁺ in the biodiesel met EN 14214 standards. Addition of trace amount of co-catalyst KOH with an amount of 367.1 mg/kg oil resulted in the organic amine-catalyzed transesterification under milder reaction conditions than those without addition of KOH to achieve >90% yield of methyl ester. Furthermore, side reactions that occurred in the pure organic amine-catalyzed systems could not be detected after addition of trace amount of KOH, as evidenced by the NMR results.     

用KOH Al2O3催化合成月桂氮艹卓酮

采用ＫＯＨ Ａｌ２Ｏ３催化合成月桂氮艹卓酮，可在较低的温度６５℃下和较短的时间４～５ｈ内进行反应。此法操作简便，收率达９０％以上，经纯化后产品的含量达到９８２％     

固相法合成氮掺杂碳纳米管及其二氧化碳吸附性能研究

以二乙烯苯(DVB)和1-乙烯基-3-丁基咪唑溴盐([VBIm]Br)共聚物为原料,铁氰化钾为催化剂前驱体,在600~1000℃下固相碳化制备了掺氮纳米碳管(NCNT)块体。利用SEM、TEM、Raman、XPS、物理吸附等对样品进行了表征。采用KOH在600~800℃下对NCNT进行活化,发现处理温度和时间是影响其孔结构的关键因素。CO_2吸附实验表明,单位孔容的微孔吸附量与碳材料表面氮含量之间存在明显的线性关系。     

浸渍KOH研制煤基高比表面活性炭

研究了在煤基活性炭生产工艺中浸渍ＫＯＨ方法对煤基活性炭吸附性能的影响，试验发现：采用竞争吸附剂加ＫＯＨ浸渍可显著提高煤基活性炭的比表面及吸附性能，利用水蒸汽活化法制得比表面＞１５００ｍ２／ｇ的煤基活性炭