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
Third-Liquid Phase Transfer Catalysis for Horner–Wadsworth–Emmons Reactions of “Moderately Acidic” and “Weakly Acidic” Phosphonates
The Horner–Wadsworth–Emmons (HWE) reaction was investigated in a green third-liquid phase-transfer catalysis (TLPTC) system. With 6% equiv of the catalyst and 50% NaOH aqueous solution, the third phase was generated. In this TLPTC system, HWE reactions of benzaldehydes bearing an electron-donating group with “weakly” or “moderately” acidic phosphonates proceeded in high yield (>90%) with an all E-isomer product (stilbene). Teraoctyl ammonium bromide (TOAB) afforded a high yield of 93% for the HWE reaction of benzaldehydes with electron-withdrawing groups. It was found that the ratio of E-stilbene to Z-stilbene was also influenced by the steric hindrance of the achiral quaternary ammonium salt catalyst. The isolated yield and geometric selectivity for the HWE reaction remained unchanged in four consecutive runs of both the third and the aqueous phase. A highly efficient and practical hydroxide-initiated TLPTC system was developed for the HWE reaction.
EL TRATAMIENTO NEOPRAGMATISTA DE LA VERDAD EN RICHARD RORTY NEOPRAGMATIST TREATMENT OF TRUTH IN RICHARD RORTY
Richard Rorty, one of the most influential authors of our time, presents a critique of the philosophical concept of truth as correspondence. The conclusion of Rorty's neopragmatism is that the idea of truth as correspondence between language and facts is ineffective because it no longer works. The neopragmatist conception of truth indicates the only possible uses for the term «truthful,» revolving around the idea of jus - tification. In this article, the neopragmatist notion of truth is presented in order to