Preparation of Biowax Esters in Continuous Flow Conditions

Abstract

Biowaxes synthesized from vegetable fatty acids are an alternative to petrochemical paraffins. A simple way of access to these compounds involves Fisher-type esterification of long-chain acids and alcohols under acidic conditions, but long reaction times and harsh conditions are commonly required. In this study, for the first time in the literature, biowax esters are prepared under flow conditions cutting dramatically both reaction times (from 12 h to 30 min) and temperature conditions, with respect to batch procedures (from 90–120 °C to 55 °C). This approach brings substantial improvements to the biowax synthesis process from an economic and environmental point of view, thus making the method up-scalable to the industrial level.

Synthesis of Acid Hydrazides from Carboxylic Acids in Continuous Flow

“…Although esterification in continuous flow has been achieved using a variety of techniques, such as alternative sulfonic acid ion-exchange resins, 26−28 vortex fluidic devices, 29 and diazotization of amines, 30 most require prolonged residence times and specialized reactors or are limited to monofunctionalized substrates. 31 In this context, we aimed to identify a set of reaction conditions using standardized flow chemistry equipment that would be amenable to difunctionalized substrates and easily translatable to scale. Gratifyingly, we found that standard Fischer esterification conditions (i.e., catalytic H 2 SO 4 in methanol) could be directly adapted to continuous flow.…”

“…Even at an elevated temperature of 120 °C and with extended residence times, little to no diester was obtained under relevant flow conditions (see the Supporting Information for details). Although esterification in continuous flow has been achieved using a variety of techniques, such as alternative sulfonic acid ion-exchange resins, − vortex fluidic devices, and diazotization of amines, most require prolonged residence times and specialized reactors or are limited to monofunctionalized substrates . In this context, we aimed to identify a set of reaction conditions using standardized flow chemistry equipment that would be amenable to difunctionalized substrates and easily translatable to scale.…”

An Ionic Liquid Promoted Clean and Direct Conversion of Triglycerides into Bio‐Based Thermal Energy Storage Materials

“…In these studies, free fatty acids and fatty alcohols were generally used as starting compounds to synthesize the related esters. [23,49,58,59] Moreover, in some of these studies, transition metal-containing catalysts were used to accelerate the esterification reactions. In this study, we used triglycerides directly as the starting material and successfully converted them into the desired wax esters in a solvent-free environment with a metal-free BAIL catalyst.…”

“…For instance, Caputo et al reported the synthesis of related wax esters from some fatty acids and fatty alcohols under continuous flow conditions with methane sulfonic acid and chloroform. [49] In their study, the esterification time was short, but the esters were prepared using free fatty acids in a toxic solvent environment. On the other hand, there are many studies showing that IL can play a role as effective green catalysts in esterification and/or transesterification reactions.…”