Hydrotreatment of lignocellulose-derived molecules to renewable fuels and chemicals

Eveliina Mäkelä

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

Lignocellulose is an abundant, non-edible source of biofuels and biochemicals. It can be processed into several platform molecules, such as furfural, levulinic acid (LA), and phenols. In this thesis, the hydrotreatment of lignocellulose-derived molecules to obtain biofuels and renewable chemicals was studied using batch reactors. Instead of traditional hydrotreatment catalysts (sulfided NiMo and CoMo on γ-Al2O3) and toxic copper chromite (industrial furfural hydrotreatment), noble and base metal catalysts on metal oxides as well as on bio-based carbon supports were used. Furfural hydrotreatment to 2-methylfuran (MF) was conducted using Pt, Ru, and Ni catalysts on wood-based activated carbons (ACs) from spruce and birch and with Cu/Ni catalysts on bio-based activated carbon foams (ACFs) from tannic acid and pine bark extracts and on spruce-based AC. The highest MF yields of 49%–58% were obtained with 1.5–3 wt.% Pt and Ru catalysts and with 5/5 wt.% Cu/Ni catalyst on ACs in liquid phase at 230–240 °C and 40 bar H2 pressure. The suitability of ACFs as catalyst supports was also confirmed, and MF selectivity was increased by acid treatments. The important catalytic factors affecting the MF selectivity were metal particle size and dispersion as well as the support's porosity and surface groups. Hydrotreatment of LA dimers was first studied with a model compound, γ-nonalactone, using 3 wt.% Pt, Pd, Ru, and Rh catalysts on ZrO2 at 280 °C and at an average pressure of 57.5 bar H2. The highest selectivity to hydrocarbons (nearly 24%) was obtained with the Ru catalyst. The initial conversion of the catalysts (Rh >> Ru) correlated with the amount of detected surface metal atoms. Further, the hydrotreatment of LA dimers was demonstrated with a 3.6 wt.% Ru/ZrO2 catalyst at 250–300 °C and 47.5 bar average H2 pressure to obtain increased carbon-chain-length (>C6) products. Deoxygenation, the formation of volatile products, and the formation of aromatics increased at high temperature. The volatile products mainly comprised not only acids, esters, and ketones but also linear, branched, and cyclic hydrocarbons. Hydrotreatment of 4-propylphenol to propylbenzene was studied with 3 wt.% Pt catalysts on Nb2O5, TiO2, and ZrO2 supports in liquid organic phase at 350 °C and 20 bar H2 pressure. The highest selectivity of 77% at 98% conversion level was obtained with the Pt/Nb2O5 catalyst. Nb2O5- and TiO2-supported catalysts had activity superior to ZrO2-supported catalyst, which was thought to be attributable to oxophilic sites created during catalyst reduction. In this thesis, high MF yields were obtained using catalysts on wood-based ACs. To the best of the author's knowledge, AFCs were tested as catalyst supports, for the first time. Moreover, the hydrotreatment of LA dimers with Ru catalyst was demonstrated, which offers a new route from lignocellulosic sugars to increased carbon-chain-length products. Finally, high selectivity to propylbenzene was obtained from 4-propylphenol; this is among the best results reported in the liquid-phase hydrotreatment of phenols.
Translated title of the contributionLignoselluloosapohjaisten molekyylien vetykäsittely uusiutuviksi polttoaineiksi ja kemikaaleiksi
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Puurunen, Riikka, Supervising Professor
  • Karinen, Reetta, Thesis Advisor
  • Lindblad, Marina, Thesis Advisor, External person
Publisher
Print ISBNs978-952-64-0479-0
Electronic ISBNs978-952-64-0480-6
Publication statusPublished - 2021
MoE publication typeG5 Doctoral dissertation (article)

Keywords

  • catalyst
  • hydrotreatment
  • furfural
  • levulinic acid
  • 4-propylphenol
  • biofuel

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