Sustainable polyesters via direct functionalization of lignocellulosic sugars.

The development of sustainable plastics from abundant renewable feedstocks has been limited by the complexity and efficiency of their production, as well as their lack of competitive material properties. Here we demonstrate the direct transformation of the hemicellulosic fraction of non-edible biomass into a tricyclic diester plastic precursor at 83% yield (95% from commercial xylose) during integrated plant fractionation with glyoxylic acid. Melt polycondensation of the resulting diester with a range of aliphatic diols led to amorphous polyesters (Mn = 30-60 kDa) with high glass transition temperatures (72-100 °C), tough mechanical properties (ultimate tensile strengths of 63-77 MPa, tensile moduli of 2,000-2,500 MPa and elongations at break of 50-80%) and strong gas barriers (oxygen transmission rates (100 µm) of 11-24 cc m-2 day-1 bar-1 and water vapour transmission rates (100 µm) of 25-36 g m-2 day-1) that could be processed by injection moulding, thermoforming, twin-screw extrusion and three-dimensional printing. Although standardized biodegradation studies still need to be performed, the inherently degradable nature of these materials facilitated their chemical recycling via methanolysis at 64 °C, and eventual depolymerization in room-temperature water.

Renewable acrylonitrile production.

Acrylonitrile (ACN) is a petroleum-derived compound used in resins, polymers, acrylics, and carbon fiber. We present a process for renewable ACN production using 3-hydroxypropionic acid (3-HP), which can be produced microbially from sugars. The process achieves ACN molar yields exceeding 90% from ethyl 3-hydroxypropanoate (ethyl 3-HP) via dehydration and nitrilation with ammonia over an inexpensive titanium dioxide solid acid catalyst. We further describe an integrated process modeled at scale that is based on this chemistry and achieves near-quantitative ACN yields (98 ± 2%) from ethyl acrylate. This endothermic approach eliminates runaway reaction hazards and achieves higher yields than the standard propylene ammoxidation process. Avoidance of hydrogen cyanide as a by-product also improves process safety and mitigates product handling requirements.