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.
A robust sample workup protocol is described that allows quantification of acidic components in complex biomass-derived process streams. This protocol is shown to have application in the field of lignin conversion.
Aliphatic polyamides, or nylons,
are typically highly crystalline
and thermally robust polymers used in high-performance applications.
Nylon 6, a high-ceiling-temperature (HCT) polyamide from ε-caprolactam,
lacks expedient chemical recyclability, while low-ceiling temperature
(LCT) nylon 4 from pyrrolidone exhibits complete chemical recyclability,
but it is thermally unstable and not melt-processable. Here, we introduce
a hybrid nylon, nylon 4/6, based on a bicyclic lactam composed of
both HCT ε-caprolactam and LCT pyrrolidone motifs in a hybridized
offspring structure. Hybrid nylon 4/6 overcomes trade-offs in (de)polymerizability
and performance properties of the parent nylons, exhibiting both excellent
polymerization and facile depolymerization characteristics. This stereoregular
polyamide forms nanocrystalline domains, allowing optical clarity
and high thermal stability, however, without displaying a melting
transition before decomposition. Of a series of statistical copolymers
comprising nylon 4/6 and nylon 4, a 50/50 copolymer achieves the greatest
synergy in both reactivity and polymer properties of each homopolymer,
offering an amorphous nylon with favorable properties, including optical
clarity, a high glass transition temperature, melt processability,
and full chemical recyclability.
A ring-fused γ-butyrolactone can be selectively ring-open polymerized at room temperature by N-heterocyclic carbenes to cyclic polyester or by bifunctional (thio)urea and base pairs in a living fashion to high molecular weight linear polyester that can be organocatalytically and quantitatively recycled at 120 °C.
Nylon-6 is selectively depolymerized to the parent monomer ɛ-caprolactam by the readily accessible and commercially available lanthanide trisamido catalysts Ln(N(TMS) 2 ) 3 (Ln = lanthanide). The depolymerization process is solvent-free, near quantitative, highly selective, and operates at the lowest Nylon-6 to ɛcaprolactam depolymerization temperature reported to date. The catalytic activity of the different lanthanide trisamides scales with the Ln 3 + ionic radius, and this process is effective with post-consumer Nylon-6 as well as with Nylon-6 + polyethylene, polypropylene or polyethylene terephthalate mixtures. Experimental kinetic data and theoretical (DFT) mechanistic analyses suggest initial deprotonation of a Nylon terminal amido NÀ H bond, which covalently binds the catalyst to the polymer, followed by a chain-end back-biting process in which ɛcaprolactam units are sequentially extruded from the chain end.
Carboxylic
acids are common products produced from the bioconversion
of renewable feedstocks. In these processes the separation of the
acid product from fermentation broth is the most energy and cost intensive
unit operation. Thus, the development of robust, scalable separation
approaches that can be applied to a variety of carboxylates is of
critical importance to the development of processes that utilize carboxylic
acids as platform chemicals. Here we report a batch separation method
that includes cell and particulate removal, cation exchange, activated
carbon treatment, dewatering with a polymer resin, and product recovery.
This method is demonstrated on two unique fermentation broths both
derived from corn stover hydrolysate to separate neat succinic and
propionic acid. For succinic acid, a crystallization yield of 91%
with a product purity of 99.93% was achieved. To our knowledge this
is the highest reported crystallization yield and purity for the recovery
of succinic acid. Additionally, the method requires approximately
50% less energy compared to standard evaporative crystallization approaches.
For propionic acid, neat liquid product was obtained with a distillation
yield of 80% and purity of 98%. These excellent results achieved in
terms of yield and purity for succinic and propionic acid, two acids
with widely different physical properties, from chemically complex
hydrolysate broth demonstrates the effective and robust nature of
this approach.
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