New reaction route for bio-based adiponitrile production: Towards the rational design of the reactants and reaction pathways

Abstract

<p indent=0mm>Adiponitrile is a key presursor to synthesize hexamethylenediamine that is specifically used for the production of nylon 66 and hexamethylene diisocyanate (HDI). Both nylon 66 and HDI are dispensible to chemical industries: Nylon 66 is widely used for chemical fibers and engineering plastics, towards clothing, electrical appliances, automobiles, and military industry; while HDI is important for the synthesis of high-grade polyurethane for automotive and coatings industries. In addition, HDI is also used as a curing agent for rocket propellant, highlighting the significance of adiponitrile production. Current production of adiponitrile mainly involves ammoniation-dehydration of adipic acid, electrolytic dimerization of acrylonitrile, or hydrocyanation of 1,3-butadiene. All of these involve high energy consumption processes that utilize highly toxic raw materials with unavoidable side reactions, leading to great concerns on cost, safety, environrment and sustainability. Therefore, it is urgent to develop a novel, safe and green method for the synthesis of adiponitrile. On the other hand, it is of equal importance for modern chemical industry to evaluate if a synthetic route is not only economic but also environmentally benigh, safe, and sustainable. Herein, a novel synthetic strategy is designed for adiponitrile preparation using biomass resource of 5-hydroxymethylfurfural through a conversion reaction of intermediate furandicarbonitrile. This strategy can avoid the safety risks and pollution issues in the present adiponitrile production industry. More importantly, it is a green and sustainable processs toproduce adiponitrile, especially considering the increasing shortage of petroleum resources. More specifically, when the furandicarbonitrile was synthesized from 5-hydroxymethylfurfural and nitrogen carrier compounds, hydroxylamine ionic liquid salts was the best served nitrogen carrier compounds, followed by ammonium carbonate, ammonium formate, ammonia and ammonium chloride. If the adiponitrile was synthesized from furandicarbonitrile and hydrogen carrier compounds, formic acid was the best-served hydrogen carrier compounds, followed by methanol, ethanol and hydrogen. The another one-step reaction route uisng 5-hydroxymethylfurfural and ammonium formate as raw materials was dominant. Besides, a “three-parameter evaluation system” is proposed for the first time and established, where Gibbs free energy, atom utilization efficiency, and intrinsic safety index determine the thermodynamic feasibility, atom economy, and reliability of chemical reactions, respectively. The synthetic strategy for bio-based adiponitrile production is evaluated by the “three-parameter evaluation system” and shows significantly reduced “three-parameter difference” value and is close to the ideal chemical reactions, when using hydroxylamine ionic liquid salts as the nitrogen carrier, formic acid as the hydrogen carrier, and integrating multi-reactions of 5-hydroxymethylfurfural and hydroxylamine ionic liquid salts and its further reaction with formic acid to produce adiponitrile. Such a novel synthesis of bio-based adiponitrile from 5-hydroxymethyl furfural, hydroxylamine ionic liquid salts and formic acid is green and safe, while the established “three-parameter evaluation system” is versatile and paves a new route towards validating efficient chemical productions.