Chloride ions enhance furfural formation from d-xylose in dilute aqueous acidic solutions

• Published in: Green chemistry : an international journal and green chemistry resource : GC 2010-01, Vol.12 (1), p.1739-1746
• Main Authors: Marcotullio, Gianluca, De Jong, Wiebren
• Format: Article
• Language: English
• Subjects: Acidic wastes; Carbohydrates with 4, 5, 6, ... C atoms, dissacharides and oligosaccharides; Carbohydrates. Nucleosides and nucleotides; Catalysis; Catalysts: preparations and properties; Chemistry; Exact sciences and technology; General and physical chemistry; Heterocyclic compounds; Heterocyclic compounds with o, s, se, te hetero atom and condensed derivatives; Kinetics and mechanisms; Organic chemistry; Preparations and properties; Reactivity and mechanisms; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/b927424c

Furfural production through traditional processes is accompanied by acidic waste stream production and high energy consumption. Modern furfural production process concepts will have to consider environmental concerns and energy requirements besides economics, moreover will have to be integrated within widened biorefinery concepts. In this paper, some particular aspects of the chemistry of d -xylose reaction to furfural are addressed, with the aim to clarify the reaction mechanism leading to furfural and to define new green catalytic pathways for its production. Specifically, reducing the use of mineral acids is addressed by the introduction of alternative catalysts. In this sense, chloride salts were tested in dilute acidic solutions at temperatures between 170 and 200 °C. Results indicate that the Cl − ions promote the formation of the 1,2-enediol from the acyclic form of xylose, and thus the subsequent acid catalyzed dehydration to furfural. For this reason the presence of Cl − ions led to significant improvements with respect to the H 2 SO 4 case. The addition of NaCl to a 50 mM HCl aqueous solution gave 90% selectivity to furfural. Among the salts tested FeCl 3 showed very interesting preliminary results, producing exceptionally high xylose reaction rates. The reaction mechanism leading from xylose to furfural in acidic solutions is deeply explored, in particular, the remarkable effect brought about by the presence of chloride ions. The simple addition of NaCl to an aqueous acidic solution significantly improved the yield and selectivity of furfural.