Continuous flow hydrogenation of methyl and ethyl levulinate: an alternative route to γ -valerolactone production

Abstract

Heterogeneous continuous transformation of methyl levulinate (ML) and ethyl levulinate (EL) to γ -valerolactone (GVL), as a promising C 5 -platform molecule was studied at 100°C. It was proved that the H-Cube ® continuous hydrogenation system equipped with 5% Ru/C CatCart ® is suitable for the reduction of both levulinate esters. While excellent conversion rates (greater than 99.9%) of ML and EL could be achieved in water and corresponding alcohols, the selectivities of GVL were primarily affected by the solvent used. In water, 100% conversion and ca 50% selectivity that represent ca 0.45 mol GVL g metal −1 h −1 productivity towards GVL, were obtained under 100 bar of total system pressure. The application of alcohols as a solvent, which maintained high conversion rates up to 1 ml min –1 flow rate, resulted in lower productivities (less than 0.2 mol GVL g metal −1 h −1 ) of GVL. Therefore, from a synthesis point of view, the corresponding 4-hydroxyvalerate esters could be obtained even at a higher reaction rate. The addition of sulfonated triphenylphosphine ligand (TPPTS) allowed reduction of the system pressure and resulted in the higher selectivity towards GVL.

γ-Valerolactone Production from Levulinic Acid Hydrogenation Using Ni Supported Nanoparticles: Influence of Tungsten Loading and pH of Synthesis

“…For this Ni/ATW1 A nickel monometallic catalyst (See Figure 20), methyl levulinate signals were elucidated by finding the characteristic triplets generated by the vicinal CH 2 with their displacements for each proton (#2CH 2 , δ = 2.55 ppm and #3CH 2 , δ = 2.78 ppm); a singlet was observed for the methyls (#5CH 3 , δ = 2.19 ppm) and (#6CH 3 , δ = 3.70 ppm). In the case of the GVL, the multiplicity of the neighboring protons were generated for (#4CH 2 δ = 1.88 ppm and 2.38 ppm) and (#3CH 2 δ = 2.45 ppm), the multiplicity of (CH, δ = 4.66 ppm), and finally the doublet (CH 3 , δ = 1.41 ppm) generated from its neighbor CH [128]. The strong signals for methyl levulinate correspond to the excess percentage.…”

Quantitative Sustainability Assessment of Flow Chemistry–From Simple Metrics to Holistic Assessment

“…Biomass-derived solvents have gained a great deal of attention in recent years, and consequently, different synthetic procedures have been reported to exploit these new chemicals for improving the safety and/or the sustainability of a chemical process. − Among the different types of biomasses utilized to access valuable platform chemicals, lignocellulosic biomass is the most used and abundant, and it is mainly composed of lignin, cellulose, and hemicellulose. To date, a plethora of batch and flow protocols have been defined − to achieve the valorization of this biomass and access chemicals such as levulinic acid, gamma-valerolactone (GVL), and 2-Me-THF. In addition, several of these processes include the use of molecular hydrogen or formic acid as a safer biomass-derived hydrogen source .…”

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

“…It has been utilised for the reduction of amides [239], nitro compounds [240][241][242], nitriles [243][244][245], azides [246,247], diazo compounds [248], and for carrying out reductive aminations [249][250][251] on a laboratory scale, while the H-Cube ® midi, has been designed specifically to be used in larger scale processes [252][253][254]. Recently, the H-Cube ® apparatus has also found use in the evaluation for biomass-derived chemicals recovery, such as Ru-catalysed hydrogenation of methyl levulinate (262) from lignocellulosic biomass to γ-valerolactone (263) [255], and scrap waste recovery, such as the scrap ceramic-cores of automotive catalytic converters (CATs) employed in the chemoselective hydrogenation of cinnamaldehyde to hydrocinnamyl alcohol [256,257].…”