Redispersion Microreactor System for Phase Transfer Catalyzed Esterification

Abstract

Redispersion Microreactor System for Phase Transfer Catalyzed EsterificationAn interdigital mixer -redispersion capillary assembly was applied to prevent the liquid-liquid bubbly flow coalescence in microreactors. The redispersion capillary consisted of 1 mm long and 0.25 mm inner-diameter constrictions placed every 0.50 m along the channel length. The system was tested on the phase transfer catalyzed esterification to produce benzyl benzoate. The application of constrictions to prevent coalescence resulted in a better reproducibility compared to a capillary without the constrictions. By controlling the total flow rate and the aqueous-to-organic ratio the bubbly flow surface-volume ratio could be increased up to 230 700 m 2 m -3. Compared to the conventional phase transfer catalyzed esterification, the continuous operation in the interdigital-redispersion capillary assembly eliminated the use of solvents and bases, removing an energy intensive step of distillation, while increasing process safety.

The Use of Flow Chemistry for Two-Phase Dibromocyclopropanation of Alkenes

“…This is in accordance with the existence of an optimum flow ratio with a maximum productivity as described in the literature [31]. Using CHBr 3 as the solvent instead of CH 2 Cl 2 (Table 1, Entry 16) resulted in lower yields.…”

“…Jovanovic et al [31] successfully used a solution of 45% (w/w) KOH (aq) containing 0.12 wt.% TEBA (aq) for the PTC alkylation of phenylacetonitrile. They found that increasing the AO ratio increased the yield of alkylation product.…”

“…They found that increasing the AO ratio increased the yield of alkylation product. This can be attributed to the decreased organic slug size and increased average surfaceto-volume ratio yielding an increased rate of catalyst transfer across the liquid-liquid interface area, and also increasing the internal circulation of the organic interslug [31].…”

“…The catalyst (0.12 wt.% TEBA) was added to the water phase. The amount of TEBA relative to the cyclohexene was only 0.3 mol% (and 0.014 mol% relative to the KOH solution) which is close to the maximum amount (0.0157 mol% relative to the KOH solution) that is soluble in the 45% (w/w) KOH (aq) according to literature [31]. Different tube reactor lengths and flow rates were tried, giving reaction times from 6 to 50 min.…”

Scale-Up Investigation of the Continuous Phase-Transfer-Catalyzed Hypochlorite Oxidation of Alcohols and Aldehydes

“…The saturated bleach had a higher ionic strength, facilitating the extraction of organic salts from the aqueous phase to the organic phase. 36 Given the same residence time, the ratio of the aqueous and organic flow rates (Q A /Q O ) also played an important role in controlling the overall reaction rate as a result of the increase in surface to volume ratio and hence higher mass transfer rate with increasing Q A /Q O 37,30 (see Figure 3b). Since the amount of NaOCl was already in large excess at Q A /Q O = 1:1, the increased rates could be attributed to higher interfacial area, implying that the reaction is within the mass-transfer-limited region.…”