Direct Catalytic Conversion of Cellulose to 5-Hydroxymethylfurfural Using Ionic Liquids

Abstract

Abstract:Cellulose is the single largest component of lignocellulosic biomass and is an attractive feedstock for a wide variety of renewable platform chemicals and biofuels, providing an alternative to petrochemicals and petrofuels. This potential is currently limited by the existing methods of transforming this poorly soluble polymer into useful chemical building blocks, such as 5-hydroxymethylfurfural (HMF). Ionic liquids have been used successfully to separate cellulose from the other components of lignocellulosic biomass and so the use of the same medium for the challenging transformation of cellulose into HMF would be highly attractive for the development of the biorefinery concept. In this report, ionic liquids based on 1-butyl-3-methylimidazolium cations [C 4 C 1 im] + with Lewis basic (X = Cl − ) and Brønsted acidic (X = HSO 4 − ) anions were used to investigate the direct catalytic transformation of cellulose to HMF. Variables probed included the composition of the ionic liquid medium, the metal catalyst, and the reaction conditions (temperature, substrate concentration). Lowering the cellulose loading and optimising the temperature achieved a 58% HMF yield after only one hour at 150 • C using a 7 mol % loading of the CrCl 3 catalyst. This compares favourably with current literature procedures requiring much longer reactions times or approaches that are difficult to scale such as microwave irradiation.

Challenges and opportunities of hydrothermal carbonisation in the UK; case study in Chirnside

“…For example, alkaline conditions give the highest reaction rates for hydrolysis whereas further degradation reactions of simple mono-or disaccharides are highly enhanced under acidic conditions 43 using most commonly mineral acids such as sulphuric and hydrochloric acids. 44 3.2.3 Decarboxylation. IR spectroscopy graphs for hydrochar demonstrate no peak detection around wavenumber 1725 cm À1 .…”

Metal-Catalyzed Degradation of Cellulose in Ionic Liquid Media

“…In the case of the tungsten oxide-based POM, prolonging the reaction time at 100 • C improved the glucose yield up to 24 h and then a plateau was achieved. The HMF yield increased slowly for 72 h. Eminov et al [7] reported that the highest HMF yield with CrCl 3 •6H 2 O as a catalyst in [BMIM]Cl was obtained at 120 • C and it was 5 times higher than the yield obtained at 100 • C. In this work, the temperature was also increased by 20 • C, yet the ability to convert glucose to HMF was not improved. Instead, the opposite effect was observed: glucose was not present in any sample and the maximum HMF yield was achieved at 8 h, remaining 81.4% lower than the result obtained at 100 • C. According to the literature the lower yield could be caused by humin formation at higher temperatures [36].…”

“…Moreover, ILs have an ability to solubilize low-toxicity metal catalysts for the direct conversion of cellulose to value-added chemicals. However, most published papers focus mainly on the advantages of ionic liquids in the separation of cellulose from lignocellulosic biomass over traditional methods [6][7][8][9]. From previous studies it appears that when using cellulose as a feedstock for HMF formation, the key steps are the dissolution and depolymerisation of cellulose to glucose monomers and not the isomerization to fructose and subsequent dehydration of fructose to HMF.…”

“…Cellulose has an abundant number of intra-and intermolecular hydrogen bonds that make it intrinsically recalcitrant to depolymerize which is why ionic liquids as solvents can provide a solution due to their specific ability to dissolve the compound [10]. ILs appear to be even more advantageous in overcoming these problems as they can act as both solvents and catalysts [7]. The catalytic conversion of biomass-derived carbohydrates to value-added chemicals is a commercially important reaction and requires the use of both Lewis and Brønsted acids.…”

Role of Brønsted and Lewis acidic sites in sulfonated Zr-MCM-41 for the catalytic reaction of cellulose into 5-hydroxymethyl furfural

“…However, they have reported some issues such as lack of separation of the catalyst, corrosion, and toxicity. These can be overcome by the use of solid acid catalyst [12][13][14][15][16][17].…”