Search

Microstructured reactors offer fast chemical engineering transfer and precise microfluidic control, enabling the determination of reactions' kinetic parameters. This review examines recent advancements in measuring microreaction kinetics. It explores kinetic modeling, reaction mechanisms, and intrinsic kinetic equations pertaining to two types of microreaction: esterification and transesterification reactions involving acids, bases, or biocatalysts. The utilization of a micro packed-bed reactor successfully achieves a harmonious combination of the micro-dispersion state and the reaction kinetic characteristics. Additionally, this review presents micro-process simulation software and explores the advanced integration of microreactors with spectroscopic analyses for reaction monitoring and data acquisition. Furthermore, it elaborates on the control principles of the micro platform. The superiority of online measurement, automation, and the digitalization of the microreaction process for kinetic measurements is highlighted, showcasing the vast prospects of artificial intelligence applications. [ABSTRACT FROM AUTHOR]

Abstract: Acid-catalyzed esterification and transesterification reactions, suitable for biodiesel production from high acid value oils, face a problem of long reaction time. In this study, we developed a two-step process for fast acid-catalyzed biodiesel production from high acid value oil in a microstructured reactor, which was assembled with an SIMM-V2 micromixer connected with a 0.6mm i.d. stainless steel capillary. Esterification of oleic acid and transesterification of cottonseed oil with methanol were separately carried out to find suitable reaction conditions. The influences of the residence time, the methanol to acid/oil molar ratio, the catalyst concentration, the water/acid concentration and the reaction temperature were examined. The highest oleic acid conversion was obtained when esterification of oleic acid with methanol was carried out at 100°C with the residence time of 5min, while the highest yield of fatty acid methyl ester (FAME) was achieved when transesterification of cottonseed oil with methanol was conducted at 120°C with the residence time of 20min. Thereafter, a two-step process was developed based on the above reaction conditions with the first and second steps separately conducted under the esterification and transesterification reaction conditions. The results indicated that the acid value of the acid oil was reduced from 160 to 1.1mg KOH/g with a methanol to acid molar ratio of 30, the H2SO4 concentration of 3wt%, a residence time of 7min at 100°C in the first step. The final FAME yield reached 99.5% with a methanol to triglyceride molar ratio of 20, the H2SO4 concentration of 3wt%, a residence time of 5min at 120°C in the second step. Therefore, biodiesel production from high acid value oil can be continuously achieved at high yields by acid-catalyzed transesterification in microstructured reactors with total reaction times of less than 15min. [Copyright &y& Elsevier]

Transesterification of cottonseed oil and methanol with KOH as the catalyst for biodiesel production was carried out in microstructured reactors at residence times of less than 1 min and high flow rates. The reaction system included a micromixer that was connected to either a stainless steel capillary (inner diameter of 0.6 mm) or a PTFE tube (inner diameter of 3 mm, packed with Dixon rings) where the reaction is supposed to take place. The influences of the type of the micromixer, the residence time, the methanol-to-oil molar ratio, the flow rate, the type of delay loop, and reaction temperatures below and above the boiling point of methanol were examined. Flow patterns under different conditions were also examined in transparent microtubes. The results indicated that multilamination micromixers exhibited higher efficiencies in biodiesel production than simple T- and J-type micromixers. A higher yield of biodiesel could be obtained at reaction temperatures above the normal boiling point of methanol. By using the stainless steel capillary as the delay loop, the yield of biodiesel reached 94.8% under the conditions of a methanol-to-oil molar ratio of 8:1, a flow rate of 2.5 mL/min, a residence time of 44 s, and a reaction temperature of 70 °C. Under such circumstances, the pressure drop was 0.8 MPa. By using the PTFE tube packed with Dixon rings as the delay loop, the yield of biodiesel reached 99.5% at the same methanol-to-oil molar ratio and reaction temperature, a flow rate of 10 mL/min, and a residence time of 17 s. The pressure drop was 0.7 MPa. Thus, very fast biodiesel production at high throughput can be achieved in microstructured reactors. [ABSTRACT FROM AUTHOR]

Abstract: 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 367.1mg/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 367.1mg/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. [Copyright &y& Elsevier]