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The treatment of biomass-derived fast pyrolysis vapors with solid acid catalysts (in particular HZSM-5 zeolite) improves the quality of liquid bio-oils. However, due to the highly reactive nature of the oxygenates, the catalysts deactivate rapidly due to coking. Within this study, the deactivation and product yields using steam-treated phosphorus-modified HZSM-5/γ-Al2O3 and bare γ-Al2O3 was studied with analytical Py-GC. While at a fixed catalyst temperature of 450 °C, a rapid breakthrough of oxygenates was observed with increased biomass feeding, this breakthrough was delayed and slower at higher catalyst temperatures (600 °C). Nevertheless, at all (constant) temperatures, there was a continuous decrease in the yield of oxygen-free hydrocarbons with increased biomass feeding. Raising the reaction temperature during the vapor treatment could successfully compensate for the loss in activity and allowed a more stable production of oxygen-free hydrocarbons. Since more biomass could be fed over the same amount of catalyst while maintaining good deoxygenation performance, this strategy reduces the frequency of regeneration in parallel fixed bed applications and provides a more stable product yield. The approach appears particularly interesting for catalysts that are robust under hydrothermal conditions and warrants further investigations at larger scales for the collection and analysis of liquid bio-oil. [ABSTRACT FROM AUTHOR]

• HZSM-5/γ-Al 2 O 3 was modified with 18 different metals and tested in He and H 2 /He. • Comparison of product yields and catalyst deactivation using wheat straw biomass. • Limited to no benefits of metal modification with inert carrier gas. • In H 2 /He, catalytic activity enhanced by Co, Fe, Pd and even more by Ni, Mo, Pt. • Lower coke yields in H 2 /He suggests hydrogenation of coke precursors. Screening of catalysts for deoxygenation and atmospheric hydrodeoxygenation of fast pyrolysis vapors from biomass (wheat straw) was performed using a micro-scale setup. Steam-treated HZSM-5/Al 2 O 3 extrudates were impregnated with metals by incipient wetness impregnation. 18 different metal modifiers (Pt, Pd, Ru, B, Li, Nb, Ga, Ca, Mg, Ce, Zn, Fe, Ni, Cu, Mo, Co, La, Zr) were tested, of which 14 were tested under inert atmosphere and 10 were tested in H 2 containing atmosphere. The catalysts were evaluated based on the yield of individual product groups (incl. gas and coke), the oxygen content of the vapors, and the yield of vapor compounds containing, zero, one, and two-or-more oxygen atoms. The deactivation was monitored during 16 consecutive vapor pulses and cumulative product properties at B:C ∼4 were compared. In He atmosphere, a slight improvement of the deactivation behavior and the resulting cumulative vapor properties was observed for impregnation with Mg, B, Fe and Zr, but generally, the benefits were moderate or absent. Ga, Co, Ni, Fe, Cu, Mo, Nb, Pt, Ru, and Pd-modified HZSM-5/Al 2 O 3 were tested in H 2 -containing atmosphere. A clear enhancement in catalytic activity resulted for Co, Fe, and Pd, achieving 21–26 % lower oxygen content compared to the unmodified HZSM-5/Al 2 O 3. Even higher deoxygenation activity resulted for Ni, Mo, and Pt impregnated HZSM-5/Al 2 O 3 , achieving 35 %, 40 %, and 46 % lower oxygen content compared to HZSM-5/Al 2 O 3. The results are attributed to a more favorable reaction chemistry such as hydrodeoxygenation and hydrogenation of coke precursors. Coke yields were clearly decreased compared to the parent HZSM-5/Al 2 O 3 for the majority of the metal modifiers under H 2 atmosphere, while under He atmosphere coke yields tended to be higher. Based on the high yields of gasoline-range hydrocarbons and considering catalyst costs, Mo-promoted HZSM-5/Al 2 O 3 appears to be a promising catalyst that should be tested in hydrogen-containing atmosphere at larger scale allowing for further assessment of the liquid yield and properties. [ABSTRACT FROM AUTHOR]

• Comparison of HDO performance of (supported) MoO 3 , WO 3 , and Pt catalysts. • Vapor (hydro-)deoxygenation using red mud and bug iron as cheap iron-oxide catalysts. • Comparison of deactivation rates and cumulative carbon yields of products. • Grouping of vapor products containing zero, one, or two + oxygen atoms. Catalyst screening at micro-scale was performed for atmospheric hydrodeoxygenation (HDO) of fast pyrolysis vapors from biomass (wheat straw). The performance of TiO 2 -supported Pt and MoO 3 catalysts and ZrO 2 and TiO 2 -supported WO 3 catalysts was compared to industrial Mo- and NiMo based catalysts. In addition, the HDO activity of an industrial HZSM-5/γ-Al 2 O 3 extrudate promoted by MoO 3 was investigated. In comparison with unpromoted acidic catalysts such as HZSM-5/γ-Al 2 O 3 , decreased deactivation rates and coke yields were obtained with catalysts that are active in HDO. Mo-based catalysts showed a higher selectivity to aromatics compared to aliphatics, while vapor upgrading with Pt/TiO 2 favored aliphatics, thereby achieving the highest effective hydrogen index of the non-condensed vapors amongst the tested catalysts. Bulk WO 3 was active for deoxygenation (23 % oxygen removal), albeit to a lesser extent compared to bulk MoO 3 (37 % oxygen removal). Compared at the same mass of bulk transition metal oxide, the TiO 2 -supported WO 3 and MoO 3 catalysts obtained nearly complete deoxygenation (86–96 % oxygen removal), again with the supported MoO 3 being more active than the supported WO 3 catalyst. For the production of renewable fuels and/or chemicals from biomass via HDO of pyrolysis vapors the catalyst cost directly influences the economy and sustainability of the process. Therefore, this study further investigated red mud, an abundantly produced industrial waste from aluminum industries, and bog iron as two low-cost transition metal catalysts that are rich in iron. These two catalysts were tested at 4 times higher loading (8 mg) than the high-performing catalysts (2 mg). Under these conditions, an oxygen removal of 51 % and 61 % at vapor carbon yields of 22 wt% C and 14 wt% C were obtained for bog iron and red mud, respectively. Both catalysts showed a high selectivity to monoaromatics and ketones. However, bog iron obtained a higher yield of ketones compared to red mud. In addition, phenolics were converted completely by red mud, indicating a higher activity compared to bog iron. [ABSTRACT FROM AUTHOR]

• Deoxygenation of biomass fast pyrolysis vapors with micro-pyrolyzer and at bench scale. • Na promoted γ-Al 2 O 3 effectively converts acids via ketonization, yielding bio-oil with low TAN. • Na-Al 2 O 3 active up to high B:C ratios and stable through six reaction/regeneration cycles. • Na promotion lowered the coke combustion temperature by ~100 °C. Catalytic upgrading of pyrolysis vapors from wheat straw over Na 2 CO 3 impregnated γ-Al 2 O 3 was studied as a promising route to biofuels. The Na species were homogenously distributed on the support and created a basicity of ~0.02 mmol CO 2 /g catalyst, at 80% lower catalyst acidity. Analytical pyrolysis using a micro-pyrolyzer showed that Na-Al 2 O 3 particularly decreased the yield of acids via ketonization, which was confirmed by feeding carboxylic acid model compounds. The presence of Na decreased the coke yield and catalyzed the coke combustion, decreasing the combustion temperature by ~100 °C. Subsequently, 100 g Na-Al 2 O 3 catalyst was tested in an ablative bench scale fast pyrolysis unit where ~5 kg of wheat straw was pyrolyzed and the vapors passed the catalytic reactor during six reaction/regeneration cycles. In agreement with the micro-pyrolyzer results, Na-Al 2 O 3 was highly effective in reducing the acidity of the bio-oils. Total acid numbers (TAN) as low as ~1–4 mg KOH/g could be maintained up to high B:C ratios of ~13. For a given TAN, this allowed operating to higher B:C ratios and provided higher oil yields compared to using acidic catalysts such as γ-Al 2 O 3 and HZSM-5 zeolite for vapor treatment. At bio-oil energy recoveries of ~60–70% relative to raw bio-oil, the deoxygenation was comparable to the acidic catalysts. Operation to higher B:C ratios allowed increasing the energy recovery to ~85% relative to the non-treated bio-oil while still obtaining a good deoxygenation performance of ~60%. Despite the hydrothermal conditions during reaction and oxidative regeneration, the activity of Na-Al 2 O 3 was regained by coke combustion, the Na remained well dispersed on the support, and the catalyst maintained its capacity for CO 2 adsorption at 500 °C after six reaction/regeneration cycles. [ABSTRACT FROM AUTHOR]

Steam treated HZSM-5 with different Si/Al ratios were tested as catalysts for the upgrading of wheat straw pyrolysis vapors and their performance was compared to hierarchical counterparts, which were prepared by desilication followed by acid washing. Pyrolysis vapors were generated in an ablative system, hot gas filtered, and upgraded in an ex-situ catalyst bed to remove oxygen functionalities and reduce the oils' total acid number (TAN). Besides elemental analysis and TAN, the collected liquids were analyzed for water, chemical composition by gas chromatography mass spectrometry with flame ionization detection (GC–MS/FID), size exclusion chromatography (SEC), thermogravimetric analysis (TGA), and selectively by 1H nuclear magnetic resonance (NMR), 13C NMR, and two-dimensional heteronuclear single-quantum correlation (2D HSQC) NMR. Hierarchical and conventional catalysts were analyzed with X-ray fluorescence (XRF), ammonia temperature-programmed desorption (NH 3 -TPD) and ethylamine TPD, N 2 and Ar-physisorption, transmission electron microscopy (TEM) and X-ray diffraction (XRD) to investigate changes induced by the desilication process. In addition, samples were analyzed after several reaction and regeneration cycles to investigate catalyst stability. The hierarchical samples showed an increased coking propensity compared to their parent version. The introduction of mesopores after desilication of HZSM-5 with molar Si/Al ratios of 29 and 39 lead to prolonged activity in deoxygenation and improved carbon recovery in the collected oil fractions compared to the parent counterparts. The results indicate that mild deoxygenation may be a viable way of pretreating pyrolysis oil before co-processing with fossil oil in refineries. • Catalytic deoxygenation of wheat straw fast pyrolysis vapors • Bio-oil properties correlated with catalyst deactivation • Enhanced coking propensity of mesoporous HZSM-5 • Mesoporous HZSM-5 obtained improved carbon recovery of liquid product. • Best deoxygenation performance achieved with moderate mesoporosity. [ABSTRACT FROM AUTHOR]