HOMOGENEOUS REACTION OF CARBON DISULFIDE AND o-PHENYLENE DIAMINE IN THE PRESENCE OF POTASSIUM HYDROXIDE

ABSTRACT

The reaction of carbon disulfide and o-phenylene diamine catalyzed by tertiary amine in the presence of potassium hydroxide is investigated. The role of KOH on the reaction is tested by conducting several independent experiments that included reaction of carbon disulfide and potassium hydroxide for a period, and further reaction of o-phenylene diamine in various sequential orders. Based on experimental data, a kinetic model that take into account the reaction of carbon disulfide and o-phenylene diamine in the presence of KOH catalyzed by tertiary amines is proposed. A reaction mechanism is proposed in which carbon disulfide and tertiary amine first reacted to produce the active intermediate CS₂-R₃N. This intermediate further reacts with o-phenylene diamine to produce mercaptobenzimidazole (MBI). The reaction is greatly accelerated in the presence of both tertiary amine and potassium hydroxide, but this enhancement in the reaction of carbon disulfide and o-phenylene diamine with tertiary amine exceeded that with potassium hydroxide. An optimum amount of KOH is obtained in the reaction. Satisfactory explanation accounts for the effect of KOH on the conversion.     

铜尾矿浮选明矾石精矿中有价元素直接碱浸动力学及过程强化

作为一种多元素矿物,紫金山铜尾矿浮选明矾石精矿有望成为铝、钾和镓等元素的替代资源。相对于传统工艺,KOH溶液直接浸出明矾石精矿可以避免高能耗的热分解过程,同时降低杂质离子的干扰。本工作研究了铜尾矿浮选明矾石精矿在KOH溶液中的直接浸出行为特性,重点研究了不同碱浓度和温度下精矿中多元素浸出率随时间的变化规律,并结合动力学分析阐明了精矿直接碱浸反应的控制步骤;在此基础上,引入机械活化促进精矿中有价元素的高效浸出。结果表明,在实验条件下精矿直接碱浸过程中仅发生明矾石相的分解;提高KOH浓度和浸出温度可使元素浸出速率快速增加;根据经典的液-固反应收缩核模型的动力学理论,分析发现浸出反应符合化学反应步骤控制。机械活化使精矿粒径降低、比表面积增加、非晶化程度提高,从而使精矿的反应活性增强,使铝、钾和镓的浸出速率提高。     

Biogas from lignocellulosic feedstock: A review on the main pretreatments,inocula and operational variables involved in anaerobic reactor efficiency

Research focused on reusing lignocellulosic waste has been gaining ground, both for the purpose of obtaining energy from renewable sources, as well as for reducing feedstock costs and preventing environmental pollution. Despite being currently evaluated as a promising feedstock, large-scale application of lignocellulosic waste to obtain bioenergy is still scarce. One of the obstacles in terms of reusing it is its recalcitrant composition, often requiring pretreatment applications to break its fibers, increasing its bioavailability. In addition to the type of substrate, there are many operational parameters that may affect the process efficiency, including the type of reactor, temperature, pH, inoculum source, among others. Considering this, it is interesting to consider using statistical tools instead of “one-factor-at-a-time” methods for simultaneous optimization of these variables to increase the production of value-added compounds, such as Plackett-Burman screening design and Central Composite Rotational Design. In this context, this review aimed at compiling data regarding obtaining value-added compounds, focusing on bio-H₂ and bio-CH₄, from different lignocellulosic waste, such as sugarcane bagasse, citrus peel waste, coffee and cereal husks, brewer's spent grain, cocoa processing waste, sawdust, among others, considering the main operational parameters involved (temperature, pH, inoculum) and the type of pretreatment applied (physical, chemical and/or biological). The results described here may support future research on reusing residual lignocellulosic waste, in addition to elucidating the importance of different operational parameters to convert this waste into H₂ and/or CH₄.