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
Process intensification and waste minimization using liquid-liquid-liquid tri-phase transfer catalysis for the synthesis of 2-((benzyloxy)methyl)furan
Abstract Applications of phase transfer catalysts in etherification reaction of benzyl chloride with furfuryl alcohol in the L-L-L tri-phasic system was investigated. Comparison between the L-L bi-phase system and L-L-L tri-phase system was studied to achieve significant conversion, better selectivity, and waste minimization. The biphasic and tri-phasic systems have reached 69 (in 4–h) and 82% (in 2–h) conversion, respectively. Moreover, the catalyst rich phase and aqueous phase could be reused thereby reducing waste and increasing profitability of the process in the tri-phasic system. Four different phase transfer catalysts were screened, namely, tetra-n-butylammonium bromide, benzyltriethylammonium bromide, tetramethylammonium bromide, and tetra-n-propylammonium bromide out of which tetra-n-butylammonium bromide was found to be the best catalyst with 82% conversion and 100% selectivity toward 2-((benzyloxy)methyl)furan. Several parameters such as the effect of different catalysts, speed of agitation, catalyst concentration, sodium hydroxide concentration, effect of mole ratio, temperature, and reusability of the catalyst rich middle phase and aqueous phase were studied. Aqueous and catalyst-rich phase were readily recovered and reused for three-times after the first use with the significant conversion. An appropriate kinetic model was developed, and experimental data fitted. The reaction follows second order kinetics, and the activation energy was calculated as 18.88–kcal/mol. The studies were also extended to different alcohols to prove its scope.
Synthesis of 2,4-dideoxy-.beta.-D-erythro-hexopyranosyl nucleosides
The synthesis of 1-(2,4-dideoxy-β-D-erythro-hexopyranosyl)thymine (12) 1 was accomplished using two different synthetic routes. It was obtained starting either from 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose or from tri-O-acetyl-D-glucal. The other modified nucleosides, with either a cytosine, guanine, or adenine moiety, were synthesized using the second reaction scheme. Deoxygenation reactions were accomplished with the (2,4-dichlorophenoxy)thiocarbonyl derivatives generated in situ