Dow and Süd-Chemie to collaborate on syngas-to-chemicals project

Abstract

The outer birch bark of Betula pendula Roth. was extracted using dry ethyl acetate, wet ethyl acetate (∼3.5% H2O) by the classical reflux boiling. The yields of the extracts, the content of triterpenoids and polar impurities were compared with the results of the extractions employing aqueous ethanol (5% H2O). A higher content of betulin and a lower content of polar impurities were found for ethyl acetate extractions compared with the ethanol-based experiments. Alkaline washing of betulin concentrates was proposed as an alternative cost-effective method for purifying extracts of polar impurities. The uptake of residual miscella on the depleted birch bark was assessed to be up to 200–300% relative to the bark charge. An efficient recovery of the residual ethyl acetate by hydrodistillation from the extracted bark was demonstrated. An assessment of stepwise energy consumption for the extraction, concentration of extract, solvent recovery established that the extractions using ethyl acetate are significantly energy-saving, compared with ethanol usage. Batch extraction of birch bark employing ethyl acetate (96.5%) with hydrodistillation of residual solvent from raw materials can be used for a small-scale process to obtain betulin concentrates. According to the scheme proposed, complete recycling of the organic and aqueous phases is carried out and extractant losses are practically excluded. Considering large-scale processes, the continuous extraction scheme with solvent separate recovery from waste materials in the special equipment is feasible with dry solvent application. Extracting birch bark with “green” extractant ethyl acetate is beneficial, since it provides extracts containing less polar impurities and significantly reduces energy consumption and extractant losses comparing with use of polar extractants.