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Hydrogenation of Levulinic Acid to γ- in a Continuous Packed Bed ReactorValerolactone

Haan, J.E. de (2013) Hydrogenation of Levulinic Acid to γ- in a Continuous Packed Bed ReactorValerolactone. Master's Thesis / Essay, Chemistry.

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Levulinic acid (LA), derived from lignocellulosic biomass, is recently selected as one of the 15 most promising carbohydrate-derived platform chemicals by the US Department of Energy. The presence of a ketone and carboxyl group makes it a versatile component, which can be converted to a number of derivatives. Among the derivatives of LA, γ-valerolactone (GVL) is identified as a sustainable platform chemical for the production of carbon-based chemicals and fuels. A significant amount of literature is available about the production of GVL in batch set-ups with the use of different solvents and catalysts. Nevertheless, limited literature is available about studies using continuous set-ups. For eventual scaling up to industrial level, continuous processes are preferred above batch processes for a bulk chemical like GVL. This study is focused on the catalytic hydrogenation of LA in water to produce GVL through the intermediate 4-hydroxypentanoic acid (4-HPA) in a continuous packed bed reactor. A catalyst screening study with heterogeneous catalysts was performed using ruthenium on different supports (typical conditions: 90°C, 1 mL/min feed flow, 30 mL/min H2 flow, 2 gram catalyst, column pressure 45 bar). Ru/Al2O3 was found to be unstable under the applied hydrothermal conditions and acid environment and dissolved slowly. Ru/TiO2 showed high stability, but a low conversion of LA was achieved. The best performance of all tested catalysts was demonstrated by Ru/C. The catalyst showed high activity (almost full conversion of LA) and stability over 6 hours on stream. Because of its excellent performance, Ru/C was chosen as base catalyst for further process studies. The effect of LA feed concentration on the conversion of LA and reaction rate was investigated by using feed streams of different LA concentrations under the same reaction conditions. It was found that the initial LA concentration has a significant influence on the LA conversion. The conversion of LA in concentrated LA solution was increased by alteration of the process conditions and using higher catalyst intakes. This showed that Ru/C is able to convert concentrated streams of LA to GVL. Finally, a long duration test was performed with diluted LA (1 mol/L), using Ru/C (0.5 wt.% of Ru) as catalyst. A slow decrease in conversion of LA was observed over 52 hours on stream. The initial conversion of LA was 95%, and after 52 hours on stream 82% of LA conversion was observed. A significant decrease in specific surface area of the catalyst (BET) was observed, from 1108 m2/g to 391 m2/g after 52 hours on stream. This was most likely the cause of decrease in activity, since no measureable leaching of ruthenium was detected during the experiment.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Chemistry
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 07:54
Last Modified: 15 Feb 2018 07:54

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