Bio-oil Upgrading Research Articles

Towards Achieving Circular Economy in the Production of Silica from Rice Husk as a Sustainable Adsorbent

The growing concern over water pollution and waste management requires innovative solutions that promote resource efficiency within a circular economy. This study aims to utilize rice husk (RH) as a sustainable feedstock to develop highly porous silica particles and generate valuable by-products, addressing the dual challenges of waste reduction and water contamination. We hypothesize that optimizing the production of amorphous silica from acid-washed RH will enhance its adsorptive properties and facilitate the concurrent generation of bio-oil and syngas. Amorphous silica particles were extracted from acid-washed RH with a yield of 15 wt% using a combination of acid washing at 100 °C, pyrolysis at 500 °C, and calcination at 700 °C with controlled heating at 2 °C/min. The optimized material (RH2-SiO2), composed of small (60–200 nm) and large (50–200 µm) particles, had a specific surface area of 320 m2/g, with funnel-shaped pores with diameters from 17 nm to 4 nm and showed a maximum cadmium adsorption capacity of 407 mg Cd/g SiO2. Additionally, the pyrolysis process yielded CO-rich syngas and bio-oil with an elevated phenolic content, demonstrating a higher bio-oil yield and reduced gas production compared to untreated RH. Some limitations were identified, including the need for bio-oil upgrading, further research into the application of RH2-SiO2 for wastewater treatment, and the scaling-up of adsorbent production. Despite the challenges, these results contribute to the development of a promising adsorbent for water pollution control while enhancing the value of agricultural waste and moving closer to a circular economy model.

Insights into the oxygen vacancies in titanium-aluminum composite oxides for Ru-catalyzed bio-oil upgrading using guaiacol as a model compound

Insights into the oxygen vacancies in titanium-aluminum composite oxides for Ru-catalyzed bio-oil upgrading using guaiacol as a model compound

A Critical Review of the Synthesis and Applications of Spinel-Derived Catalysts to Bio-Oil Upgrading.

The transformation of renewable bio-oil into platform chemicals and bio-oil through catalytic processes embodies an efficient approach within the realm of advancing sustainable energy. Spinel-based catalysts have garnered significant attention owing to their ability to precisely tune metals within the framework, facilitating adjustments to structural, physical, and electronic properties, coupled with their remarkable thermal stability. This review aims to provide a comprehensive overview of recent advancements in spinel-based catalysts for upgrading bio-oil. Its objective is to shed light on their potential to address the limitations of conventional catalysts. Initially, a comprehensive analysis is conducted on different metal oxide composites in terms of their similarity and dissimilarity on properties. Subsequently, the synthesis methodologies are scrutinised and potential avenues for their modification are explored. Following this, an in-depth discussion ensues regarding the spinels ascatalysts or catalyst precursors for catalytic cracking, ketonisation, catalytic hydrodeoxygenation, steam and aqueous-phase reforming, andelectrocatalytic upgrading of bio-oil. Finally, the challenges and potential prospectsare addressed, with a specific focus on the machine learning - based approaches to optimise the structure and activity of spinel catalysts. This review aims to provide specific directions for further exploration and maximisation of the spinel catalysts in the bio-oil upgrading field.

Preparation of metal-modified carbon-based catalyst and experimental study on catalytic pyrolysis of distillers dried grains with solubles

Distillers dried grains with solubles (DDGS) offer high calorific value, suited for catalytic rapid pyrolysis for energy and chemical applications, yet tar and coke formation during bio-oil upgrading necessitates exploration of cost-effective, durable biocarbon-based catalysts for tar removal. In this study, a carbon-based catalyst was prepared by metal modification of alkaline biochar for catalytic pyrolysis with Distillers dried grains with solubles (DDGS) biomass. Brunauer–Emmet–Teller (BET), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) were used to characterized the morphology and microstructure of the metal-modified carbon-based catalysts. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was used to analysis the pyrolysis-gas of catalytic pyrolysis. Furthermore, the effects of the loading and metal mass ratio of carbon-based monometallic catalysts (Fe and Co) and carbon-based bimetallic catalysts (Fe-Co) on the distribution of the DDGS pyrolysis products were further investigated. The results showed that the 8 wt% of loading rate of bimetallic catalyst significantly reduced the oxygenated compounds but increased the aromatic hydrocarbons. Compared with pyrolysis without catalyst, when the catalyst was 2Fe6Co (mass ratio of Fe/Co 1:3), the hydrocarbons increased from 36.42 % to 44.53 %, the oxygen-containing compounds decreased from 60.36 % to 52.35 %, and the aromatics increased significantly from 0.73 % to 25.37 %. This study provides a new route of increasing the aromatic hydrocarbon content of catalytic pyrolysis to offer theoretical basis for carbon-based catalysts of biomass conversion.

Investigation of ruthenium loaded beta zeolite catalyst performance in vanillin hydrodeoxygenation yielding both monomeric and dimeric cycloalkanes

The valorization of lignin-derived bio-oil is studied extensively due to its promising contribution to sustainability. Among these studies, many have focused on the hydrodeoxygenation (HDO) of phenolic model compounds as it is a crucial process in obtaining valuable oxygen-free hydrocarbons. In this work, vanillin HDO was performed on various bifunctional ruthenium-based zeolite catalysts with different zeolite supports (Y, ZSM-5, and beta) in a batch reactor. Ru-loaded beta zeolite catalysts (Ru/Hβ) exhibited the highest HDO activity among them, and the formation of dimeric cycloalkanes of high value were also observed specifically when using the Ru/Hβ catalyst. Due to their benefits of direct use in blending of biofuel, factors promoting the dimerization of phenolic monomers were extensively examined through a series of experiments using a mix of phenolic model compounds as HDO reactants. Specific oxygen containing functional groups contributed to the aldol condensation of aromatic species, and the structure and kinetic diameter of the monomers had a profound effect on the ability to participate in dimerization. Additionally, the metal loading of the catalyst and reaction conditions such as temperature and hydrogen pressure were varied to observe each of their effects on the product distribution. The change in metal loading had a remarkable impact on the preferred reaction pathway and product selectivity, while a high temperature of 200 °C and hydrogen pressure of 50 bar was determined to be necessary to fully achieve HDO to cycloalkanes. Consequently, this study has provided useful information on the production of both monomeric and dimeric cycloalkanes and has contributed to the development of the bio-oil upgrading process.

Highly efficient lignin depolymerization and enhanced bio-oil upgrading via in-situ hydrogenation: Impact of lignin structure

The inherent structural rigidity of lignin poses a significant challenge to its direct hydrogenation to produce aromatic compounds, requiring harsh reaction conditions. In this study, microwave-assisted hydrothermal liquefication was employed to rapidly generate raw bio-oil under mild conditions, coupled with an in-situ hydrogenation strategy to upgrade its quality. A series of lignin substrates were characterized to establish the relationship between lignin characteristics and aromatic products. Grass lignin can produce low molecular weight bio-oil in high yields (50.4–60.7 %) within 30 min at 180 °C, which is attributed to the abundance of cleavable β-O-4 linkages in its uniform structure. In contrast, softwood lignin with abundant guaiacyl (G) units possessed a robust thermal stability, resulting in a low monomer yield, but a high selectivity to G-type products (97 %). The raw bio-oil was further upgraded through in-situ hydrogenation with Pd catalysts. Low reaction temperatures (60–100 °C) favored the hydrogenation of aromatic aldehydes and ketones to their alcohol products, while high temperatures (100–220 °C) promoted the deep hydrogenation of aromatic side chains to alkyl products. Besides, an upgraded bio-oil with a higher heating value (29.8 MJ/kg) was obtained. Furthermore, the hydrogenation mechanism was investigated through the kinetics of simulated bio-oils. The activation energy follows the order: dimer β-O-4 linkage < monomer aldehyde group < ketone group < CC linkage, which is consistent with the hydrogenation kinetics observed in real lignin bio-oil. Overall, this study highlights the impact of lignin characteristics on subsequent conversion and alsoenhances our understanding of the complex depolymerization/hydrogenation mechanisms during lignin upgrading.

Upgrading of Pyrolysis Bio-Oil by Catalytic Hydrodeoxygenation, a Review Focused on Catalysts, Model Molecules, Deactivation, and Reaction Routes.

Biomass can be converted into energy/fuel by different techniques, such as pyrolysis, gasification, and others. In the case of pyrolysis, biomass can be converted into a crude bio-oil around 50-75% yield. However, the direct use of this crude bio-oil is impractical due to its high content of oxygenated compounds, which provide inferior properties compared to those of fossil-derived bio-oil, such as petroleum. Consequently, bio-oil needs to be upgraded by physical processes (filtration, emulsification, among others) and/or chemical processes (esterification, cracking, hydrodeoxygenation, among others). In contrast, hydrodeoxygenation (HDO) can effectively increase the calorific value and improve the acidity and viscosity of bio-oils through reaction pathways such as cracking, decarbonylation, decarboxylation, hydrocracking, hydrodeoxygenation, and hydrogenation, where catalysts play a crucial role. This article first focuses on the general aspects of biomass, subsequent bio-oil production, its properties, and the various methods of upgrading pyrolytic bio-oil to improve its calorific value, pH, viscosity, degree of deoxygenation (DOD), and other attributes. Secondly, particular emphasis is placed on the process of converting model molecules and bio-oil via HDO using catalysts based on nickel and nickel combined with other active elements. Through these phases, readers can gain a deeper understanding of the HDO process and the reaction mechanisms involved. Finally, the different equipment used to obtain an improved HDO product from bio-oil is discussed, providing valuable insights for the practical application of this reaction in pyrolysis bio-oil production.

Electrocatalytic Conversion of Phenol to Cyclohexane Using Pt and Ru-Based Catalysts

The production of renewable fuels has become necessary as fossil fuels continue to deplete.1 Pyrolysis of biomass to liquid fuels has emerged as a promising solution due to the possibility of conversion of high carbon content feedstocks into fuel. Pyrolysis oils, however, struggle from low yields and increased heteroatom content.2 In order to solve this problem a second upgrading step is needed to increase the fuel’s hydrogen content and remove heteroatoms. Conventional oil upgrading through thermochemical processes is an option using high temperatures (>300 °C) and high-pressure hydrogen (10-20MPa).3 Electrochemical upgrading of bio-oils represents a novel avenue for the conversion of bio-oils to usable fuels or commodity chemicals under mild condition which requires milder temperatures (30-80 °C) and generates the hydrogen in situ through the water splitting reaction.3 Though initial results on electrocatalytic upgrading have been promising, few studies report appreciable yields of fully deoxygenated products and the efficiency remains low at high current densities.3 This work focuses on the upgrading of phenol as a bio-oil model compound. ECH of phenol was investigated in a custom electrochemical cell (H-Cell), with a solvent trap for the collection and quantification of volatile organic products. Efficient ECH conversion of phenol to cyclohexane was demonstrated and the primary factors impacting the selective production of cyclohexane were studied. Multiple variables, including catalyst type, electrolyte composition and concentration, and cathodic potential were investigated to determine their influence on ECH reaction rate, selectivity, and efficiency. The results obtained show that lab-synthesized, bi-metallic PtRu-C catalyst results in the highest specific ECH rate of 23.52 mol h-1 g-1 metal in comparison to 19.92 mol h-1 g-1 metal, 15.84 mol h-1 g-1 metal and 4.64 mol h-1 g-1 metal, measured with a commercial PtRu-C and mono-metallic Pt-C and Ru-C catalysts, respectively. In addition, the lab synthesized PtRu-C catalyst achieved > 30% selectivity towards cyclohexane, which is among the highest reported in literature to date. Constant potential experiments showed that the cyclohexane was 4.6% higher at -0.46 V vs Ag/AgCl than -0.28 V vs Ag/AgCl indicating cyclohexane selectivity is weakly dependent on cathodic potential. To improve the mechanistic understanding of phenol ECH, operando Raman spectroscopy was explored, finding strong evidence for cyclohexanone reaction intermediates.References(1) Zhang, X.; Lei, H.; Chen, S.; Wu, J. Catalytic Co-Pyrolysis of Lignocellulosic Biomass with Polymers: A Critical Review. Green Chemistry. 2016. https://doi.org/10.1039/c6gc00911e.(2) Zhang, B.; Zhong, Z.; Min, M.; Ding, K.; Xie, Q.; Ruan, R. Catalytic Fast Co-Pyrolysis of Biomass and Food Waste to Produce Aromatics: Analytical Py-GC/MS Study. Bioresour. Technol. 2015, 189. https://doi.org/10.1016/j.biortech.2015.03.092.(3) Chen, G.; Liang, L.; Li, N.; Lu, X.; Yan, B.; Cheng, Z. Upgrading of Bio-Oil Model Compounds and Bio-Crude into Biofuel by Electrocatalysis: A Review. ChemSusChem. 2021. https://doi.org/10.1002/cssc.202002063. Figure 1

Biofuel from wastewater-grown microalgae: A biorefinery approach using hydrothermal liquefaction and catalyst upgrading

Third-generation biofuels from microalgae are becoming necessary for sustainable energy. In this context, this study explores the hydrothermal liquefaction (HTL) of microalgae biomass grown in wastewater, consisting of 30% Chlorella vulgaris, 69% Tetradesmus obliquus, and 1% cyanobacteria Limnothrix planctonica, and the subsequent upgrading of the produced bio-oil. The novelty of the work lies in integrating microalgae cultivation in wastewater with HTL in a biorefinery approach, enhanced using a catalyst to upgrade the bio-oil. Different temperatures (300, 325, and 350 °C) and reaction times (15, 30, and 45 min) were tested. The bio-oil upgrading occurred with a Cobalt-Molybdenum (CoMo) catalyst for 1 h at 375 °C. Post-HTL, although the hydrogen-to-carbon (H/C) ratio decreased from 1.70 to 1.38–1.60, the oxygen-to-carbon (O/C) ratio also decreased from 0.39 to 0.079–0.104, and the higher heating value increased from 20.6 to 36.4–38.3 MJ kg−1. Palmitic acid was the main component in all bio-oil samples. The highest bio-oil yield was at 300 °C for 30 min (23.4%). Upgrading increased long-chain hydrocarbons like heptadecane (5%), indicating biofuel potential, though nitrogenous compounds such as hexadecanenitrile suggest a need for further hydrodenitrogenation. Aqueous phase, solid residues, and gas from HTL can be used for applications such as biomass cultivation, bio-hydrogen, valuable chemicals, and materials like carbon composites and cement additives, promoting a circular economy. The study underscores the potential of microalgae-derived bio-oil as sustainable biofuel, although further refinement is needed to meet current fuel standards.

Energy assessment and heat integration of biofuel production from bio-oil produced through fast pyrolysis of sugarcane straw, and its upgrading via hydrotreatment

Sugarcane processing is one of the most important economic activities in Brazil, producing ethanol and sugar for domestic and international markets. Utilising the lignocellulosic residues of this industry, specifically bagasse and straw, would increase the second-generation biofuel production without increasing the sugarcane planted area. Among the processes available, the fast pyrolysis is a thermochemical conversion process that produces mainly bio-oil, a liquid with several advantages over solid biomass, regarding transportation, pumping, storage, and handling. Moreover, the bio-oil can be upgraded to obtain biofuels of higher added-value. Among feasible upgrading technologies, the hydrotreatment is one of the most promising methods for eliminating the reactive functionalities of the bio-oil by removing oxygen or cracking large molecules in the presence of hydrogen; however, this comes at the expense of a significant hydrogen consumption. Thus, the aim of this study is to evaluate the biofuel production through the fast pyrolysis of sugarcane straw, followed by the upgrading of the produced bio-oil via hydrotreatment. The evaluation is carried out by way of energy and mass balances of the processes, performed using the software Aspen Plus. Furthermore, the possibilities of integrating the bio-oil production and upgrading into the conventional ethanol and sugar production process will also be assessed through heat integration, applying the Pinch analysis. Results showed the potential for renewable gasoline and diesel production with yields of 0.086 kg/kg of dry straw and 0.08 kg/kg of dry straw, respectively. Additionally, integrating the pyrolysis process, including the bio-oil upgrading, into the ethanol production process can achieve a liquid fuel production (ethanol, gasoline and diesel) of 2289.8 MJ/t cane, which represents an increase of 29 %, while the surplus electricity increases in 5.3 %, when compared to the conventional ethanol production plant.

Synthesis of metal-free heteroatom (N, P, O, and B) doped biochar catalysts for enhanced catalytic co-pyrolysis of walnut shells and palm oil fatty acid distillate to produce high-quality bio-oil

In the current study, sugarcane bagasse-derived biochar catalysts were synthesized by doping with metal-free heteroatoms including nitrogen, phosphorus, oxygen, and boron and their efficacy was tested for catalytic co-pyrolysis of walnut shells (WS) and palm oil fatty acid distillate (PFAD) using Py-GC/MS. The biochar catalysts’ properties and their effectiveness on co-pyrolytic bio-oil (overall product distribution, selectivity towards aliphatic and aromatic hydrocarbons, and carbon number ranges) were extensively examined. Among the various catalysts considered, boron-doped biochar (BCB) demonstrated effective performance due to an improved surface area, porosity, and acidity and resulted in a significantly increased hydrocarbon yield, particularly in the gasoline and diesel range, and preference for aromatic over aliphatic hydrocarbons. The optimum bio-oil quality was achieved at a feedstock-to-catalyst ratio of 2:1 and a pyrolysis temperature of 750 °C, with a hydrocarbon yield of 90.8 % and aromatic hydrocarbon selectivity of 63.5 %. Overall, the study underscores the role of BCB in fostering deoxygenation, decarboxylation, and aromatic selectivity via thermal and catalytic pathways, highlighting the potential of non-metallic doped biochars for bio-oil upgrading.

Selective production of high-value fuel via catalytic upgrading of bio-oil over nitrogen-doped carbon-alumina hybrid supported cobalt catalysts

Bio-oil derived from biomass fast pyrolysis can be upgraded to gasoline and diesel alternatives by catalytic hydrodeoxygenation (HDO). Here, the novel nitrogen-doped carbon–alumina hybrid supported cobalt (Co/NCAn, n = 1, 2.5, 5) catalyst is established by a coagulation bath technique. The optimized Co/NCA2.5 catalyst presented 100 % conversion of guaiacol, high selectivity to cyclohexane (93.6 %), and extremely high deoxygenation degree (97.3 %), respectively. Therein, the formation of cyclohexanol was facilitated by stronger binding energy and greater charge transfer between Co and NC which was unraveled by density functional theory calculations. In addition, the appropriate amount of Lewis acid sites enhanced the cleavage of the C–O bond in cyclohexanol, finally resulting in a remarkable selectivity for cyclohexane. Finally, the Co/NCA2.5 catalyst also exhibited excellent selectivity (93.1 %) for high heating value hydrocarbon fuel in crude bio-oil HDO. This work provides a theoretical basis on N dopants collaborating alumina hybrid catalysts for efficient HDO reaction.

Pyrolysis and catalytic upgrading of pine wood sawdust over modified biochar catalyst in a tandem microreactor

A series of novel catalysts were prepared by modifying biochar (BC) with different metal loading (Fe, Zn) and thermal activation in different atmospheres (CO2, H2O). The catalysts were further used to upgrade the pyrolysis vapor from pine wood sawdust, aiming to produce high-quality bio-oil. The modified biochar catalyst exhibited strong deoxygenation ability to acids and ketones in bio-oil and effectively converted lignin-derived compounds into aromatic hydrocarbons and phenols. Subsequently, the catalyst (BC-Fe-CO2) demonstrating the highest yields of phenols and aromatics was selected for condition optimization. Different catalytic temperatures and biomass-to-catalyst ratios were compared to determine the optimal conditions for producing high-quality bio-oil. Phenolics and aromatic hydrocarbons content in the bio-oil reached 70 % at the optimal condition and the selectivity of monocyclic aromatic hydrocarbons in aromatic hydrocarbons reached 77 %. The properties of the biochar catalysts were characterized using BET, SEM, XRD, and XPS. The superior performance of the modified BC catalysts not only relied on its enhanced surface area and porous structure but also due to active Fe sites. The detail reaction pathways of the bio-oil catalytic upgrading were also proposed. These findings underscore the potential of modified biochar in pyrolysis and catalytic upgrading for bio-oil with improved quality.

N-doped MOF-lignin hybrid catalyst for highly selective hydrodeoxygenation of lignin-derived phenols

Upgrading of lignin-derived bio-oil to value-added biofuel was of great significance for efficient utilization of renewable resources and reducing the use of fossil fuels. Hydrodeoxygenation (HDO) was considered to be a promising technology for the conversion of lignin-derived bio-oil. Herein, we reported a novel method for the preparation of lignin-MOF derived N-doped catalysts, which was then successfully introduced into the upgrading of lignin-derived phenols and lignin depolymerization. All catalysts were well characterized and Co/CN-0.5–750 exhibited excellent performance during the catalytic HDO process. The optimized catalyst demonstrated highly efficient active hydrogen generation from isopropanol. Moreover, it could afford the best vanillin (VAN) conversion (100 %) and highest 2-Methoxy-4-methylphenol (MMP) yield (92 %) under the mild reaction conditions (180 °C, 0.5 MPa nitrogen, 2 h). It was confirmed that the excellent performance was related to nitrogen doping. This study could provide some useful insights for the hydrodeoxygenation of lignin and its derivative.

Optimized catalytic stepwise pyrolysis for converting cotton straw into hydrocarbon-rich bio-oil in N2 and CO2

Stepwise pyrolysis is recognized as a promising method in converting biomass into sustainable bio-oils. However, a systematic study on the stepwise parameters (e.g., low- and high-pyrolysis temperatures, duration, atmosphere) is still lacking. Herein, the stepwise catalytic fast pyrolysis (CFP) of cotton stove over ZSM-5 was conducted, aiming to reveal the impact of aforementioned parameters on bio-oils production. Results showed that the low-temperature pyrolysis benefitted the decomposition of biomass, while the high-temperature counterpart favored the upgrading of bio-oil. The combination of a low-temperature pyrolysis (400 ℃ for 2 min) and high-temperature pyrolysis (600 ℃ for 3 min) led to a satisfied hydrocarbons selectivity (35.8 area%) and bio-oil yield (11.4 wt%). This was superior to the one-step pyrolysis conducted at 600 ℃ for 5 min, which decreased the values to 32.2 area% and 11.2 wt%, respectively. The CO2 introduction into N2 atmosphere in stepwise pyrolysis further enhanced the hydrocarbon-rich bio-oil production, and a maximum bio-oil yield of 15.9 wt% was obtained in 100 vol% CO2, while the highest hydrocarbons selectivity of 51.8 area% was reached in 80 vol% CO2. This work confirmed the advantages of stepwise pyrolysis for producing high-quality bio-oils and provided a reference for pyrolysis in CO2 atmosphere.

Vapour phase hydrodeoxygenation of Guaiacol using Ni/SBA-15 for bio-oil upgrading

Vapour phase hydrodeoxygenation of Guaiacol using Ni/SBA-15 for bio-oil upgrading

Exploring molecular composition of upgraded pyrolysis bio-oil using GC×GC-(EI/PI)-TOF MS with different column set-ups

Bio-oils produced from the pyrolysis of lignocellulosic biomass are rich in oxygen, which causes instability and corrosion problems. Therefore, dedicated post-pyrolysis treatments such as hydrotreatment are required to increase the H/C ratio of the products to be used as fuel or chemicals. Here, a characterization method based on two-dimensional gas chromatography (GC×GC) was developed to highlight the evolution of the volatile fraction during hydrotreatment. Six samples obtained at different times of the hydrotreatment were analyzed. In this way, information on catalyst deactivation was obtained. The combination of information from normal and reversed phase GC×GC analysis provides a detailed characterization of the hydrotreated bio-oils. Furthermore, the use of soft photoionization (PI), in addition to conventional electron impact ionization (EI), yields a better understanding of the compound structures present in the sample. Identification and semi-quantification of the sample components indicate that the concentration of paraffins, cycloalkanes, and monoaromatics have largely decreased during hydrotreatment, while the concentration of oxygenated species and polycyclic aromatic hydrocarbons have increased. Using complementary GC methods highlights changes in the molecular composition of volatile species that correlate with catalyst performance. This approach can be used to follow the decrease in hydrodeoxygenation activity as a function of time on stream to estimate the catalyst aging during the hydrotreating process.

Promoting Effect of Ce and La on Ni-Mo/δ-Al2O3 Catalysts in the Hydrodeoxygenation of Vanillin.

A crucial aspect of adding an economical and environmental dimension to the upgrading of bio-oils is to develop catalysts with enhanced and prolonged activity. In the present study, the effect of doping δ-alumina (Al2O3) with oxides of cerium (Ce) and lanthanum (La) before thermal treatment was investigated. The performance of such an Al2O3-supported nickel-molybdenum (Ni-Mo) catalyst was evaluated by studying the selectivity for the direct hydrodeoxygenation (HDO) of vanillin to cresol under continuous-flow conditions. In addition, the effect of adding H2S during catalyst activation and/or performance tests was also evaluated. Overall, enhanced performance of the doped NiMo catalyst in the HDO process has been demonstrated and an increased selectivity for cresol via direct HDO observed. The advantage of adding La and Ce is supported by the characterization results, where less sintering and enhanced pore diameter of the doped Al2O3 were observed after thermally inducing the transformation from the δ to θ phases. The improved characteristics and prolonged activity of the doped Al2O3 were also deduced by the lower acidity of the catalyst, which resulted in reduced coke formation during the HDO process.

Characterization and mechanism elucidation of high-quality bio-oil production from co-pyrolysis of waste low-rank coal fines and de-oiled microalgae biomass using bimetallic (Cu-Cr) ZSM-5 catalyst

The present study provides a cleaner co-pyrolysis strategy for high-quality bio-oil production by utilizing low-cost residues such as low-rank coal (CL), de-oiled microalgae (ALG), and their blends (CLALG). The heavy metal-loaded Cu-Cr-ZSM-5 catalyst is synthesized by using ion-exchange method and investigated in the CL, ALG and CLALG pyrolysis bio-oil upgradation at different catalyst feed ratios (0.5:1, 1:1, 2:1). The synthesized catalyst was characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and brunauer-emmett-teller (BET) analysis. The synthesized catalyst is nano-crystalline of average size 7 nm. The microstructure of the synthesized catalyst shows stacked nanorods packing with connected intercrystal and intracrystal mesopores. The catalytic and non-catalytic pyrolysis of CL, ALG and CLALG are performed at 600 °C, 10 °C/min for 60 min. The non-catalytic ALG pyrolysis has shown maximum bio-oil yield (35.7%). The synergistic effect of nanorod morphology, active acid sites and excess mesoporosity of catalyst facilitates efficient deoxygenation, denitrogenation and aromatization of pyrolysis bio-oil with oxygen content from 2.1⎼3.1%, nitrogen content 3.5⎼5.1% and aromatic content 49.4⎼54.4% at catalyst feed ratio of 1:1. The maximum obtained higher heating value (HHV) of bio-oil from catalytic pyrolysis of CL (40.1 MJ/kg) followed by CLALG (38.6 MJ/kg) and ALG (36.5 MJ/kg) is very close to diesel oil with HHV (42⎼46 MJ/kg). Further, a co-pyrolysis mechanism is proposed to systematically investigate possible catalytic action sites to yield high-quality bio-oil. Thus, outcomes of the present study enrich information regarding catalyst development, catalyst feed interaction, and thermocatalytic cracking as emerging efforts towards industrial-scale upgradation of bio-oil to engine fuels.

Tandem hydrogenation/hydrogenolysis of furfural to 2-methylfuran over multifunctional metallic Cu nanoparticles supported ZIF-8 catalyst

Catalytic transfer hydrogenation (CTH), that employs protic solvents as hydrogen sources to alleviate the use of molecular hydrogen H2, has gained great attention. This work, reports multifunctional, metallic Cu nanoparticles supported ZIF-8 material for CTH of furfural to a highly valued fuel additive, 2-methylfuran (2-MF) using 2-propanol. Of all as-synthesized xCu(yM)/ZIF-8 catalysts with varied NaBH4 concentration (yM) and Cu loading (x), 11Cu(1.5 M)/ZIF-8 exhibited higher catalytic activity with > 99 % FAL conversion and 93.9 % 2-MF selectivity. This is ascribed to its high specific surface area, and existence of optimum amount of Lewis acid-base sites along with Cu0 species, which are responsible for hydrogenation of furfural to furfuryl alcohol and subsequent hydrogenolysis to produce 2-MF. The present work reports a highly efficient and stable, metal-MOF hybrid material for CTH of FAL to 2-MF, which is one among the best reports available in literature, therewith suggests a promising approach for bio-oil upgradation.