The use of polyurethanes and, therefore, the quantity of its scrap are increasing. Considering the thermoset characteristic of most polyurethanes, the most circular recycling method is by means of chemical depolymerization, for which glycolysis is finding its way into the industry. The main goal of polyurethane glycolysis is to recover the polyols used, but only limited attempts were made toward recovering the aromatic dicarbamate residues and derivates from the used isocyanates. By the split-phase glycolysis method, the recovered polyols form a top-layer phase and the bottom layer contain transreacted carbamates, excess glycol, amines, urea, and other side products. The hydrolysis of carbamates results in amines and CO2 as the main products. Consequently, the carbamates in the bottom layer of polyurethane split-phase glycolysis can also be hydrolyzed in a separate process, generating amines, which can serve as feedstock for isocyanate production to complete the polyurethane material cycle. In this paper, the full recycling of polyurethanes is reviewed and experimentally studied. As a matter of demonstration, combined glycolysis and hydrolysis led to an amine production yield of about 30% for model systems. With this result, we show the high potential for further research by future optimization of reaction conditions and catalysis.
A chemical method was developed for low-temperature synthesis of DAG from MAG followed by an easy purification procedure in order to obtain high-purity DAG. Solvent-assisted and solvent-free reaction conditions were used, combined with different catalysts (sodium methoxide, p-toluenesulfonic acid, methanesulfonic acid, and sulfuric acid). All reactions were performed at 35 and 70 °C. By increasing both acidity and polarity of the catalyst the equilibrium shifts towards the formation of DAG. When using sulfuric acid in solvent-assisted condition at 70 °C, 88% conversion was obtained after 20 min of reaction (77% w/w DAG in the reaction mixture after evaporation of the solvent). After purifying by means of column chromatography, 96% pure DAG were obtained. The overall yield of DAG was 81%.
The purpose of this study was to form new dispersion systems based on chemically interesterified waste turkey fat containing sesame oil (2:3 wt./wt.) and to evaluate effectiveness of synthetized diacylglycerols stabilizing these emulsions. Sesame oil was used to enrich and improve turkey fat's composition with unsaturated fatty acids derived from oil. Physical properties of raw fats and fat blends (before and after the reaction) were determined. Increase of acid value and crystallization point was noted after the reaction, and no changes occurred in the fatty acid composition of the sesame oil and turkey fat blends. Diacylglycerols were synthesized from specified monoacylglycerols, then purified, and analyzed by means of Gel Permeation Chromatography (GPC) and Thin-Layer Chromatography (TLC). The role of the amount of synthetically obtained diacylglycerols (DAG) as emulsifiers in obtaining the stable emulsion product was examined. 6% (wt./wt.) was found to be the smallest amount of DAG emulsifier needed to properly stabilize the prepared emulsions. The proposed new emulsion products could be applied as new food product formulations like mayonnaise sauces or dressings. Such formulations containing beneficial fats like turkey fat or sesame oil, as well as new structured diacylglycerols could meet customer requirements.
We provide a new method to source
fatty alcohols from poly(ethylene)
(PE) pyrolysis oil. To this end, we have developed a new one-pot process
to obtain fatty alcohols from a mixture of long chain alkenes and
alkanes (C10–C20) that is obtained from pyrolyzed PE. Hydroboration–oxidation
methods with and without an isomerization step were investigated for
converting all types of alkenes present in the PE pyrolysis oil to
primary alcohols only, following the anti-Markovnikov rule. Our process
showed 91%–98% conversion of the alkenes to alcohols in a one-pot
reaction at a scale of 50 g at low temperature (10–25 °C)
under ambient pressure. In addition, the efficiency of the process
was confirmed by testing several types of pyrolysis oil derived from
commercial waste PE where alcohol recovery reached 83%–92%
based on the amount of alkenes in the PE pyrolysis oil. As fatty alcohols
are commodity chemicals, our study can pave the way for converting
waste plastics into high value chemicals, a welcome energy and materials
saving shortcut to the specialty chemicals market.
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