• Verberckmoes, An
• Saegher, Tibo De
• Lauwaert, Jeroen
• Atanasova, Boyana
• Clercq, Jeriffa De

Abstract

Due to the timely issue of climate change, continuously rising CO2 emissions, and the depletion of fossil fuel reserves, it is imperative to focus on the development of new, CO2-neutral, and renewable sources as an alternative feedstock for base chemicals. Currently, the mixture of benzene, toluene and xylene (BTX), which originates from fossil fuels, is the main feedstock for production of nearly all aromatic chemicals[1]. Thus, to achieve a CO2-neutral economy, finding an alternative and sustainable feedstock for aromatic chemicals is paramount. The complex biopolymer lignin is the largest indigestible renewable source of aromatic compounds in nature [2]. However, lignin valorization is challenged by the development of successful depolymerization techniques that result in both high product yields and high selectivity towards functionalized aromatic chemicals [3]. Amongst numerous depolymerization strategies, mild reductive depolymerization is characterized by superior selectivity to the desired products but is currently still hindered by low yields. [4]. The use of a performant redox catalyst and reductive agent can compensate for the latter, ultimately providing a successful lignin depolymerization pathway to functionalized aromatic chemicals. This project focuses on the relationship between the catalytic properties of supported (bimetallic) nanoparticles (NPs) and the obtained product pool after mild reductive depolymerization of Soda-extracted lignin. Gaining insight into this interaction will advance the development of high yield reductive lignin depolymerization (Figure 1). Firstly, the effect of bimetallic configurations is studied by testing 5 w% bimetallic Pd nanocatalysts, in 1:1 stoichiometric ratio with Cu, Ni, Fe, Co, and Mo, at 200oC and 10 bar H2 in a 70/30 (vol%/vol%) ethanol-water mixture for 6 and 20 hours. The best performing combinations are also tested in 1:3 and 3:1 stoichiometric ratio.The results are compared with monometallic 5 w% Pd. Secondly, calcined and reduced catalysts are used to study the effect of metal oxidation state. Lastly, the synergy between NPs and support material is studied on multiple supports: γ-Alumina, active carbon, SiO2, and CeO2.3 factors are considered for evaluating the catalytic performance: hydrogenation rate, product selectivity, and depolymerization rate. By combing both noble and base metal sites, less hydrogenation with no decrease in depolymerization rate is observed, thereby increasing the selectivity towards aromatic components. Calcination shows slight superiority in depolymerization rate while tendency for less polydispersity is detected for the reduced catalysts. Firmer conclusions are to be made once all reactions sets have been performed and analyzed with GPC, GC-MS and 2D GPC-HPLC.

Topics

• nanoparticle
• impedance spectroscopy
• compound
• Carbon
• laser emission spectroscopy
• lignin
• gas chromatography
• polydispersity
• High-performance liquid chromatography
• gas chromatography-mass spectrometry