Population balance modeling and simulation of liquid–liquid–liquid phase transfer catalyzed synthesis of mandelic acid from benzaldehyde
Mandelic acid has cosmetic, pharmaceutical, and antibacterial activities and is used in urinary antiseptic medicines. An attractive process for the production of mandelic acid is through reaction between benzaldehyde, sodium hydroxide, and chloroform in the presence of polyethylene glycol 4000 as a phase transfer catalyst. The liquid–liquid phase transfer catalyzed (L–L PTC) reaction can be intensified by converting it into three-liquid phases (L–L–L PTC). We address the modeling of a well-stirred reactor for the foregoing process, in which organic droplets surrounded by a thin film of catalyst-rich phase are suspended in the aqueous phase. A population balance model is formulated for the L–L–L PTC reaction and solved by Monte Carlo simulation using interval of quiescence technique. Transport processes and intrinsic reaction kinetics are extracted from the experiments. This population balance model serves to assess and interpret the relative roles of various processes in L–L–L PTC reaction, such as diffusive transport, reaction, and interaction between dispersed phase droplets. The model is expected to be an effective tool for reactor design and scale up. © 2012 American Institute of Chemical Engineers AIChE J, 2012
Selective engineering in O-alkylation of m-cresol with benzyl chloride using liquid–liquid–liquid phase transfer catalysis
Abstract Selective O-alkylation or etherification of phenolic substances is attractive to make pharmaceuticals and fine chemicals. Liquid–liquid phase transfer catalysis (L–L PTC) is used to make such ethers but it always leads to byproduct formation and wastage of catalyst. On the contrary, liquid–liquid–liquid (L–L–L) PTC is an excellent strategy for waste reduction and improving profitability, in which a catalyst-rich middle (or third) phase is formed between aqueous and organic phases. The reaction takes place in the middle phase, which intensifies the rates and offers better selectivity including catalyst reusability unlike the bi-liquid PTC. Selective O-benzylation of m -cresol was studied with benzyl chloride by using L–L–L PTC at 50 °C. It gives 100% selectivity to 3-benzyloxytoluene. The catalyst-rich third phase was recycled many times, thereby leading to profitability and waste minimization. A kinetic model is developed and validated against experimental data. The reaction follows a pseudo-first order rate law. The studies were also extended to the benzylation of o - and p -cresol. The energy of activation for the benzylation of o -, m - and p -cresols were found to be 12.84, 10.00 and 12.12 kcal/mol, respectively. The results are novel.
Exopolysaccharide biosynthesis and related enzyme activities of the medicinal fungus, Ganoderma lucidum, grown on lactose in a bioreactor
Exopolysaccharide (EPS) production and biosynthesis were studied in Ganoderma lucidum, a fungus used in traditional Chinese medicine, grown with lactose in a bioreactor. β-Galactosidase activity, which implies the existence of a lactose permease system, was induced by lactose. Lactose feeding also increased α-phosphoglucomutase activity and EPS accumulation but decreased phosphoglucose isomerase activity and lactate concentration in the culture broth. A maximum cell density of 22 g l−1 and EPS at 1.25 g l−1 were obtained in fed-batch bioreactor culture.