Biomass to Chemicals

We proposed that gamma-valerolactone, a frequently used food additive, exhibits the most important characteristics of a sustainable liquid including the possibility to use it for the production of energy or carbon-based consumer products [1]. It is renewable, easy and safe to store and move globally in large quantities, has low melting (-31 °C), high boiling (207 °C) and flash (96 °C) points, low vapor pressure, a definitive but acceptable smell for easy recognition of leaks and spills, low toxicity, and high solubility in water to assists biodegradation. We have been investigating the selective conversion of carbohydrates to various C5-oxygenates including levulinic and formic acids, gamma-valerolactone, 2-methyl-THF, and alkanes [2]:

bm2chem_img1[1] Horváth, I. T.; Mehdi, H.; Fábos, V.; Boda, L.; Mika, L. T. Gamma-valerolactone: A Sustainable Liquid for Energy and Carbon-based Chemicals. Green Chem. 2008, 10, 238.

[2] Mehdi, H.; Fábos, V.; Tuba, R.; Bodor, A.; Mika, L. T. Horváth, I. T. Integration of Homogeneous and Heterogeneous Catalytic Processes for a Multi-step Conversion of Biomass: from Sucrose to Levulinic acid, gamma-Valerolactone, 1,4-Pentanediol, 2-Methyl-tetrahydrofuran, and Alkanes. Top. Catal. 2008, 48, 49.

 

Our recent valorization strategy [3] of C6-polysaccharide containing agricultural residues and food wastes involves the production of levulinic and formic acids in the presence of sulfuric acid in GVL followed by the addition of ammonium hydroxide in equimolar amounts of the H2SO4. The resulting biphasic system contains most of the levulinic and formic acids in the organic phase and (NH4)2SO4 in the aqueous phase, which can be readily separated due to the salting out effect of the concentrated (NH4)2SO4 solution. After the catalytic conversion of levulinic and formic acids to gamma-valerolactone in the organic phase, the catalyst is separated from the gamma-valerolactone/water system and recycled [4]. In the case of C5– polysaccharide containing agricultural residues and food wastes, furfural is the dehydration product, which can be hydrogenated to furfuril alcohol. The latter can be converted to levulinic acid in the presence of acid catalyst and water. In this case, the addition of formic acid or hydrogen is required to convert furfural to furfuril alcohol as well as levulinic acid to gamma-valerolactone. The conversion of carbohydrates is generally accompanied by the formation of humins, which can be used as the renewable energy sources for the processes involved. The separation of heterogeneous or immobilized homogeneous catalysts from insoluble solid products and/or side products could be cumbersome. An attractive approach is the use of magnetic solid supports including magnetic iron cores with porous silica layers which can be removed from non-magnetic solids by a magnet [5].

bm2chem_img2[3] Lui, M. Y.; Wong, Y. Y.; Choi, W.-T.; Mui, Y. F.; Qi, L.; Horváth, I. T. Valorization of carbohydrates of agricultural residues and food wastes: a key strategy for carbon conservation. ACS Sustainable Chem. Eng. 2019, 7, 17799 – 17807.

[4] He, D.; Horváth, I. T. Application of Silica Supported Shvo’s Catalysts for Transfer Hydrogenation of Levulinic Acid with Formic Acid. J. Organomet. Chem. 2017, 847, 263 – 269

[5] He, D.; Horváth, I. T. Molecular Engineering in Catalysis: Immobilization of Shvo’s Ruthenium Catalyst to Silica Coated Magnetic Nanoparticles. Periodica Polytechnica Chemical Engineering, 2021, 65, 1–11.