| dc.description.abstract | The increasing human population and it’s associated economic, environment and geopolitical demands towards sustainable transport energy have advanced research onto renewable liquid fuel production and aviation fuel range in particular. The aviation sector is deemed as difficult-to-decarbonize and thus vigorous investigations on promising biomass conversion pathway is timely. Lignocellulose biomass upgrading via pyrolysis is considered one of the most promising route to convert biomass to jet-fuel range aromatics. Several renewable processing steps for the production of jet-fuel range hydrocarbons have been reported but bio-derived aromatics production has receive less attention, even though the role of aromatics in jet fuel composition is indispensable.
In this study, a multi-scale experimental approach was applied to decouple the complexity of biomass to bio oil-aviation fuel cascading process. The complexity of biomass pyrolysis was simplified using analytical pyrolysis-gas chromatography/mass spectrometer (Py-GC/MS) for online monitoring of thermal and catalytic ex situ upgrading vapors from several biomass resources, heavy organic fraction of bio oil, levoglucosan and model compounds derived from cellulose pyrolysis. Herein, biomass sample weight within 0.1-0.6 mg was studied and semi-quantitative analysis was done via normalized area yield. The process was further up scaled using one single fixed bed reactor with dual bed to study in vapor phase the carbon coupling and oxygen removal reactions of bio-derived light oxygenates (model compounds) into aviation fuel pool. The catalyst mass applied herein was within 1-2 grams. Finally, a new class of multifunctional catalyst, Ru-MoFeP/Al2O3 was synthesized using modified pechini method. The catalyst was tested under fixed bed reactor conditions for hydrodeoxygenation activity of simulated bio oil. The prepared simulated bio oil has similar O/C and H/C ratio in compares to actual woody bio oil. Finally, the simulated upgrading was upscaled using the mini-pilot plant conditions with catalyst weight of 20-40 grams. In addition, tandem catalytic approach was also applied to increase the liquid transport fuel-range carbon number via tandem reaction.
The physical and chemical properties for the tested catalysts (HZSM-5, Ni/HZSM-5, Cu/SiO2, TiO2, and Ru-MoFeP/Al2O3) were studied using multiple characterization techniques such as XRD, BET, CO2/NH3-TPD, TPR, SEM-EDS, TEM, FTIR, CO2-NH3/DRIFTS, XPS and TPO. In addition, DFT was used to calculate the adsorption energy of propanal and propanol. Finally, under fixed bed laboratory reactor and pilot plant investigations, liquid and gas phase products were analyzed using GC/TCD/FID-MS setup for online gas and bulk liquid analysis. The parameters studied are effects of space velocity, catalyst dependent activity and yield relationship, deactivation, reaction pathway and mechanism for the production of jet-fuel range aromatics using feedstock such as biomass, bioderived light oxygenates and simulated bio oil.
The thermal analysis of six biomass types, soft wood (pine, spruce), hard wood (poplar, chestnut), mix wood and herbaceous plant (sweet sorghum) displayed variable product distribution under analytical PyGCMS analysis. The results reveal oxygenates and phenolic compounds as the main detected products of pyrolysis of biomass. The yield and product distribution depend significantly on the biomass properties. The pyrolysis of hardwood chestnut resulted in the highest yield and levoglocosan as the main product, while the pyrolysis of softwood pine resulted in a relatively low yield and phenolic compounds as the main product. The tandem catalytic upgrading on Ni/HZSM-5 effectively converted pyrolysis vapor to aromatics at 500 oC. Moreover, four tandem catalytic strategies with (i) HZSM-5, (ii) Ni/HZSM-5, (iii) 5Cu/SiO2 +TiO2 and (iv) double-layered: 5Cu/SiO2-TiO2 (upstream) + 20Ni/ZSM-5 (downstream) at catatyst:pine weight ratio of 3 were tested. 5Cu/SiO2+TiO2 resulted in high content of ketones and CO2, via ketonization reactions involving intramolecular oxygen removal. The double layer catalytic bed by combined ketonization and zeolite catalysts resulted in a significantly higher yield and shifted product towards higher carbon numbers compared to other strategies.
Furthermore, a significantly enhanced production of aromatics by ex-situ catalytic co-pyrolysis of lignocellulosic biomass and heavy fraction of bio-oil (HFB) on Ni-ZSM-5 was obtained. The mechanism for the synergy in thermal and ex-situ catalytic copyrolysis is due to the enhanced secondary reaction of levoglucosan assisted by hydroxyl groups as the hydrogen donor resulted from pyrolysis of HFB. A reaction pathway and mechanism has been proposed for the synergistic effects.
Moreover, Tandem conversion of bio-derived light oxygenates to jet fuel range aromatics with high yield (>83%) and purity (> 90 %) and also remarkably enhanced stability in one single continuous-flow reactor was achieved by integrating aldol condensation and hydrodeoxygenation using nonprecious dual bed catalyst system. Instead of conventional pathway (i.e., olefin generation following oligomerization), we report a new route mediated by C9 cyclic ketone formation via C=C bond coupling and ring closure reactions on upstream Cu/SiO2-TiO2 catalyst, and subsequent hydrogenation-dehydration-aromatization chain reactions to jet-fuel range aromatics and H2O on the downstream Ni/HZSM-5 catalyst at relatively low temperature (300 oC) and atmospheric pressure.
In addition, the active site requirement and mechanistic pathway for the above reaction over Cu/SiO2+TiO2-Ni/HZSM-5 has been proposed. An optimum TiO2 (p25) passivation temperature of 350 oC led to higher C9-cyclic formation rate. The probed Ti-O and Ti-O-Ti site are required for C3-enolate formation and surface reaction between C3-enolate and adsorbed C6-intermediate, 2-methyl-2-pentenal stabilization, respectively. Lewis sites/Ti were found to be responsible for the cyclization of linear C9 to cyclic ketone. Furthermore, the active site for hydrodeoxygenation of the C9-cyclic ketone to jet-fuel range aromatics involves Lewis acid sites via Ni-coordination. Thus, the newly created Ni catalyzed hydrogenolysis activity than the inherent Brønsted acid sites from HZSM-5. In addition, coke formation and sintering were identified as the main deactivation mechanism for the decline in the jet-fuel range aromatics yield.
Finally, the synthesis of promoted and supported bimetallic phosphide catalyst at industrially relevant conditions with a remarkable hydrodeoxygenation (HDO) selectivity was achieved. The 1Ru-20MoFeP/Al2O3 multifunctional catalyst had hydrocarbon yield of > 70% at hydro-processing temperature of 400 oC and industrially low pressure (14.7 bar H2) for obtaining 100 % conversion of acetic acid, acetol, furfural, guaiacol, eugenol but ca. 86 % for phenol. The tandem approach using Au/TiO2 and Ru-MoFeP/Al2O3 as upstream and downstream respectively led to 43.6 % reduction in light gases (C1-C4). The degree of deoxygenation observed was, 99.4, 99.3, 98.8, 97.6 and 97.1 % for Ru-TiO2-RuMoFeP/Al2O3>RuMoFeP/Al2O3 > Pd-TiO2-RuMoFeP/Al2O3 > Au-TiO2+RuMoFeP/Al2O3 > TiO2+RuMoFeP/Al2O3, respectively. Therefore, higher oxygen removal activity was achieved via intramolecular condensation and hydrodeoxygenation reactions using the versatile tandem catalytic strategy to high yield jet fuel range aromatics. | nb_NO |
