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Hydrothermal liquefaction (HTL) can thermochemically transform sewage sludge into a biocrude with high energy content, high chemical complexity, and high O and N content. The development of an efficient upgrading process for such complex feedstocks necessitates detailed knowledge of the molecular composition and the specific heteroatom-containing compounds to understand and optimize the hydrotreating reactions. In this study, we present the upgrading of sewage sludge-derived HTL biocrude via a two-stage hydrotreatment process and perform advanced chemical characterization of the feedstock, intermediate, and final upgraded products with gas chromatography-mass spectrometry (GC-MS) and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). We show that hydrotreatment significantly improves the quality of the oil, primarily succeeding in cracking the heavy molecules and removing the sulfur- and oxygen-containing components. FTICR-MS analysis shows that the HTL biocrude has a high concentration of fatty acid amides that readily lose their oxygen and nitrogen during hydrotreating and are converted into saturated hydrocarbons, whereas the aromatic O

The catalytic performance of a set of technical, zeolite ZSM-5 extruded materials have been studied in a bench scale unit for the ex-situ Catalytic Fast Pyrolysis (CFP) of lignocellulosic biomass. The set of catalysts include micro- and mesoporous materials, with and without ZrO2-promotion, with different Si/Al ratios and with micro- and nanosized zeolite crystals. Mesoporosity, acidity and crystal size play a key role on the overall catalytic performances in terms of activity and selectivity (i. e., in their ability to obtain the highest bio-oil fraction with the lowest oxygen content), and also importantly, stability. Detailed post-mortem bulk and micro-spectroscopic studies of the solid catalysts complement the catalytic testing. The obtained results point towards coke deposits as the main cause for catalyst deactivation. Details of the nature, formation and evolution of these coke deposits revealed essential insights, which serve to evaluate the design of catalysts for the ex-situ CFP of biomass. In particular the mesoporous catalysts are overall better preserved with increasing time-on-stream and deactivate later than their microporous counterparts, which suffer from pore blockage. Likewise, it was seen that ZrO2-promotion contributed positively in the prevention against deactivation by hard coke spreading, thanks to its enhanced Lewis acidity. The zeolite's crystal size is another important characteristic to combine the different components within catalyst bodies, ensuring the proper interaction between zeolite, promoter and binder. This is illustrated by the nanocrystalline ZrO2/n-ZSM-5-ATP material, which shows the best catalytic performance.

The catalytic performance of a set of technical, zeolite ZSM-5 extruded materials have been studied in a bench scale unit for the ex-situ Catalytic Fast Pyrolysis (CFP) of lignocellulosic biomass. The set of catalysts include micro- and mesoporous materials, with and without ZrO2-promotion, with different Si/Al ratios and with micro- and nanosized zeolite crystals. Mesoporosity, acidity and crystal size play a key role on the overall catalytic performances in terms of activity and selectivity (i. e., in their ability to obtain the highest bio-oil fraction with the lowest oxygen content), and also importantly, stability. Detailed post-mortem bulk and micro-spectroscopic studies of the solid catalysts complement the catalytic testing. The obtained results point towards coke deposits as the main cause for catalyst deactivation. Details of the nature, formation and evolution of these coke deposits revealed essential insights, which serve to evaluate the design of catalysts for the ex-situ CFP of biomass. In particular the mesoporous catalysts are overall better preserved with increasing time-on-stream and deactivate later than their microporous counterparts, which suffer from pore blockage. Likewise, it was seen that ZrO2-promotion contributed positively in the prevention against deactivation by hard coke spreading, thanks to its enhanced Lewis acidity. The zeolite's crystal size is another important characteristic to combine the different components within catalyst bodies, ensuring the proper interaction between zeolite, promoter and binder. This is illustrated by the nanocrystalline ZrO2/n-ZSM-5-ATP material, which shows the best catalytic performance.

Additional file 1: Figure S1. Study for the optimum solids and enzyme loading conditions. Figure S2. The color gained by the solutions after: A blank experiments in a H2O and b DMSO:H2O (4:1) mixture and B in pure aqueous solution of sugars in the presence of (a) sodium tetraborate decahydrate and NaOH, (b) buffer citrate phosphate (5 mM) and NaOH and (c) sodium tetraborate decahydrate, buffer citrate-phosphate (5 mM) and NaOH. Table S1. Composition for each lignocellulosic biomass sample. Table S2. Sugars (glucose and fructose, 2.5 wt. %) conversion to HMF in the absence of any additional catalyst (150 °C, 60 min). Table S3. Effect of homogeneous and heterogeneous catalysts on the decomposition reactions of sugars (glucose and fructose 2.5 wt. %) to organic acids (150 °C, 60 min).