Levulinic acid (LA) is a promising renewable platform compound derived from biomass for the manufacture of various valuable chemicals, among which levulinate esters have been demonstrated to be good fuel additives. Many previous studies have focused on the production of short-chain levulinates for biofuels such as methyl and ethyl levulinates, but these esters suffer from some essential issues including a high oxygen content, low energy density (or heating value) and water solubility. Long-chain levulinate esters have similar structures to biodiesel. The long carbon chain may provide a higher carbon content and strong hydrophobicity, therefore improving the energy density and water insolubility. In this work, the synthesis of a long-chain levulinate ester, n-hexyl levulinate (HL), has been fast and efficiently achieved by the catalytic esterification of LA and 1-hexanol at low temperature. Tungsten hexachloride (WCl₆) showed the most superior activity among the tested metal salt catalysts under mild conditions. A HL yield of ∼85% with almost complete LA conversion could be obtained at 50 °C after only 30 min. Other hexanols that have larger steric hindrances, such as 2-ethyl-1-butanol, 2-hexanol, 3-hexanol and cyclohexanol, could also promote efficient esterification with LA over the WCl₆ catalyst, resulting in excellent product yields of ∼82–91%. The strategy applies to the efficient synthesis of longer chain levulinate esters such as n-octyl levulinate (OL) as well. The WCl₆ catalyst was reusable several times in a consecutive batch reaction mode. The method reported herein offers a strategy for the efficient production of liquid fuels from LA, potentially bridging raw biomass feedstocks and terminal utilization of biobased products.

Converting saccharides into 5-hydroxymethylfurfural (5-HMF) has attracted more and more research interest under the background of global energy shortage. A lot of effort has been devoted to the conversion of fructose and glucose. However, other underused sugars receive very limited attention, although some of them have considerable reserves in nature as well. In this work, mannose, a major component from hemicellulose, was effectively converted into 5-HMF under mild conditions. AlCl₃·6H₂O exhibited superior activity among the tested catalysts, achieving a maximum 5-HMF yield of 60% in a dimethyl sulfoxide (DMSO)/water mixed solvent at 130 °C within 45 min. Adding an appropriate amount of water in DMSO could suppress some side reactions while preserving the reactivity of mannose dehydration. Mannose showed a comparable reactivity to fructose in the employed catalytic system. The studied system was also effective in the conversion of di/trisaccharides such as cellobiose and melezitose into 5-HMF. A number of control experiments with different catalysts and additives were conducted to elucidate the preliminary mechanism.

The Sn/MCM-41 catalyst was demonstrated to be effective for the conversion of mannose into 5-HMF, with comparable performances to those of reported heterogeneous catalysts. The Sn/MCM-41 catalyst was reusable without significant loss of activity after eight consecutive runs.

The additive Ga₂O₃improved the catalytic performance of CuO–ZnO/HZSM-5 catalysts for hydrogenation of CO₂to DME.

A double walled hafnium-based metal–organic framework with ultra-microporous structure was successfully constructed and displayed high chemical stability and commendable CO ₂ adsorption and separation ability.