Bio-oil Upgrading Process Research Articles

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.

Catalytic hydrodeoxygenation of benzoic acid as a bio-oil model compound: Reaction and kinetics using nickel-supported catalysts

The development of technologies for the bio-oil upgrading process is a crucial step towards achieving sustainable energy production. This study investigates the effects of support properties during the hydrodeoxygenation (HDO)...

Multicomponent graphene based catalysts for guaiacol upgrading in hydrothermal conditions: Exploring "H2-free" alternatives for bio-compounds hydrodeoxygenation

Catalytic hydrodeoxygenation (HDO) is a critical technique for upgrading biomass derivatives to deoxygenated fuels or other high-value compounds. Phenol, guaiacol, anisole, p-cresol, m-cresol and vanillin are all monomeric phenolics produced from lignin. Guaiacol is often utilised as a model lignin compound to deduce mechanistic information about the bio-oil upgrading process. Typically, a source of H2 is supplied as reactant for the HDO reaction. However, the H2 supply, due to the high cost of production and additional safety precautions needed for storage and transportation, imposes significant economic infeasibilities on the HDO process's scaling up. We investigated a novel H2-free hydrodeoxygenation (HDO) reaction of guaiacol at low temperatures and pressures, using water as both a reaction medium and hydrogen source. A variety of Ni catalysts supported on zirconia/graphene/with/without nitrogen doping were synthesised and evaluated at 250 °C and 300 °C in a batch reactor, with the goal of performing a multi-step tandem reaction including water splitting followed by HDO. The catalysts were characterised using H2-TPR, XRD, TEM and XPS to better understand the physicochemical properties and their correlation with catalytic performance of the samples in the HDO process. Indeed, our NiZr2O/Gr-n present the best activity/selectivity balance and it is deemed as a promising catalyst to conduct the H2-free HDO reaction. The catalyst reached commendable conversion levels and selectivity to mono-oxygenated compounds considering the very challenging reaction conditions. This innovative HDO approach provides a new avenue for cost-effective biomass upgrading.

Synergetic effect of steam and activated tyre char on the selective production of levoglucosan-rich bio-oil from catalytic pyrolysis of wood chips

The catalysts used in the pyrolytic bio-oil upgrading process are either expensive or not efficient enough. This research aims to investigate and improve the catalytic capability of tyre char (TC), an otherwise low-value waste, as an effective catalyst for upgrading bio-oil derived from the pyrolysis of eucalyptus wood chips. Efforts were specifically made to tailor the TC properties to improve the selectivity of levoglucosan (LGA), a value-added bio-chemical in bio-oil. Experiments were carried out in a two-stage fixed-bed reactor in the absence and presence of steam (30 vol%) at different heating rates (10 °C/min and 110 °C/min). By using 3-Flex, SEM-EDX, XRD, XRF, CHNS, and synchrotron XAS analyses, it was found that zinc and sulphur added during the tyre manufacturing process were mainly present in the form of ZnS nanoparticles with a crystallite size less than 1 nm in the TC matrix. An overall deoxygenation extent of 31.7 wt% was achieved with original TC catalyst and slow heating rate of 10 °C/min. However, this number was increased to 49.2 wt% with steam activated TC and fast heating rate of 110 °C/min, and adding steam to the reactor at the optimum temperature of 500 °C. More specifically, the introduction of steam and activated TC to the pyrolysis reactor enhanced the transformation of heavy hydrocarbons to light species and value-added chemicals such as LGA and furfural, reaching 34.9 wt% and 11.3 wt% on the mass basis of bio-oil, respectively. The high catalytic performance can be attributed to the large porosity and better exposure of ZnS nanoparticles on the surface of the activated TC, and the influence of steam in shifting the reactions toward more selective production of light hydrocarbons.

Study the effect of zeolite pore size and acidity on the catalytic pyrolysis of Kraft lignin

In this study, three zeolites with different pore sizes and acidity, H-Beta, HY and HZSM-5, were used for the preparation of bio-oil by catalytic pyrolysis of Kraft lignin at 600 °C. The three-dimensional sizes and kinetic diameters of the bio-oil components were calculated using quantum chemical calculations, and the bio-oil was analyzed by heteronuclear single quantum coherence nuclear magnetic resonance (HSQC-NMR). The effects of zeolite acidity and pore size on the bio-oil upgrading process were studied for the pyrolysis products of Kraft lignin. The results showed that optimum pore size of the zeolites ranged from 6.500 Å–8.400 Å during the catalyzed pyrolysis of lignin. Among the zeolites, the H-Beta zeolite is the most effective in the lignin pyrolysis. The results also showed that the pore size and acidity of the zeolites had a significant effect on the product yields, coking and deoxygenation. The pore size affects the coking and dehydration reactions, while the acidity can promote the rearrangement of ether bonds or the breaking of lignin side chains and deoxygenation reactions. This study would be beneficial to improve the zeolite catalytic activity and minimize the oxygen content in bio-oil produced from the pyrolysis of Kraft lignin.

Analyzing esterification kinetics of model bio-oil with ethanol catalyzed by a green catalyst

Fast pyrolysis of biomass is a potential method for the production of bio-oils as a renewable liquid fuel. Bio-oils contain a large number of organic compounds, particularly carboxylic acids, which cause corrosiveness and instability that are troublesome for storage and for the transportation of fuel. Upgrading is an important process to transform bio-oils into high-quality biofuels. Contained organic acids are treated with alcohol to convert them into esters by esterification which may be considered as a good intermediate bio-oil upgrading method. This work presents a kinetic study for 12-tungstosilicic acid (a type of heteropoly acid, HPA) catalyzed esterification of a model bio-oil with ethanol. The main compound of the agro-residue-derived bio-oil was illustrated by oleic acid. The kinetic study was investigated under the molar ratio between ethanol to oleic acid of 9.11:1 and catalyst loading of 10 wt% condition with the varied reaction temperature in the range of 35-75°C. The result showed that a pseudo-first-order was suitable to represent the kinetic model for esterification of the model bio-oil. By fitting between the experimental results and kinetic model, the activation energy (Ea) and the pre-exponential factor (A) were found to be 31.5 kJ/mol and 432 min−1, respectively. This comparatively low activation energy equated to other catalytic esterification proved that the HPA catalyst (12-tungstosilicic acid) considered here was an assured green catalyst for esterification in the bio-oil upgrading process.

Process Simulation and Economic Evaluation of Bio-Oil Two-Stage Hydrogenation Production

Bio-oil hydrogenation upgrading process is a method that can convert crude bio-oil into high-quality bio-fuel oil, which includes two stages of mild and deep hydrogenation. However, coking in the hydrogenation process is the key issue which negatively affects the catalyst activity and consequently the degree of hydrogenation in both stages. In this paper, an Aspen Plus process simulation model was developed for the two-stage bio-oil hydrogenation demonstration plant which was used to evaluate the effect of catalyst coking on the bio-oil upgrading process and the economic performance of the process. The model was also used to investigate the effect of catalyst deactivation caused by coke deposition in the mild stage. Three reaction temperatures in the mild stage (250 °C, 280 °C, and 300 °C) were considered. The simulation results show that 45% yield of final product is obtained at the optimal reaction condition which is 280 °C for the mild stage and 400 °C for the deep stage. Economic analysis shows that the capital cost of industrial production is $15.2 million for a bio-oil upgrading plant at a scale of 107 thousand tons per year. The operating costs are predicted to be $1024.27 per ton of final product.

Composition-structure-function correlation of Ca/Zn/AlOx catalysts for the ketonization of acetic acid

Abstract Ketonization can efficiently convert carboxylic acids into ketones, promising in bio-oil upgrading. For economic-sustainable bio-refining, Ca/Zn/AlOx (CZA) metal oxides with various Ca/Zn/Al ratios have been prepared by the low-cost and natural abundant metals and are applied in the process here. Mechanistic study on the ketonization of acetic acid revealed the reaction pathways strongly depends on “composition-structure-function” correlation of the Ca/Zn/AlOx catalysts. The reaction is mainly performed on strong base sites (e.g. CaO and ZnO) via thermal decomposition of carboxylates at high temperature (≥375 °C), but depends on acid-base pairs (e.g. amorphous calcium aluminates) significantly at low temperature (≤350 °C). CZA(331) (Ca/Zn/Al = 3/3/1) obtained the highest acetone yield of 97.1% at 425 °C hitherto and retained for over 100 h with simple regeneration process. Adding major bio-oil model compounds (e.g. phenol) into the reaction mixture has minor effect on the CZA catalysts. Therefore, current highly active and stable CZA catalysts are promising in boosting the efficiency and economy of bio-oil upgrading process in future.

Reusable Amberlyst 16 catalyst for acetic acid esterification relevant for pyrolysis bio-oil upgrading process

The current research article addresses the ability of heterogeneous Amberlyst 16 to catalyze the esterification reaction between acetic acid and ethanol, as well as the modelling of the chemical kinetics. The effects of pretreatment, reaction temperature, ethanol-to-acid molar ratio, catalyst dose and time on the rate of ethyl acetate production were systematically investigated. Furthermore, the recyclability of Amberlyst 16 to accelerate the esterification reaction was carefully examined. Amberlyst 16 was found to be a suitable catalyst for this process giving a final acid conversion of 93.3% using reaction temperature of 60 °C, ethanol-to-acid molar ratio of 6:1, catalyst dose of 10 wt% and 200 rpm stirring intensity after 1680 min, and can be successfully utilized for 4 recycle tests. A detailed kinetic model has been developed and tested for the described process, which was based on a four-step mechanism equivalent to the Langmuir–Hinshelwood one. It was found that that the esterification reaction occurred between ethoxide ions and acetic acid chemisorbed on the neighboring catalytic surfaces, whereas, the overall process was controlled by the surface reaction step.

Synthesis of Renewable Diesel Range Alkanes by Hydrodeoxygenation of Palmitic Acid over 5% Ni/CNTs under Mild Conditions

Recently, the catalytic upgrading of bio-oil to renewable diesel has been attracting more and more attention. In the current paper, carbon nanotube (CNT)-supported nickel catalysts, namely, 5% Ni/CNTs, were prepared for liquid hydrocarbon production through the deoxygenation of palmitic acid, the model compound of bio-oil under a mild condition of 240 °C reaction temperature and 2 MPa H2 pressure. The experimental results revealed that the main reaction product was pentadecane (yield of 89.64%) at an optimum palmitic acid conversion of 97.25% via the hydrodecarbonylation (HDC) process. The deoxygenation mechanism for palmitic acid conversion was also investigated. This study provides technical parameters and a theoretical basis for further industrialization in the bio-oil upgrading process.

Research on Non-Thermal Plasma assisted HZSM-5 online catalytic upgrading bio-oil

In order to improve the quality of bio-oil and reduce the coking and deactivation of HZSM-5 molecular sieve catalyst in the catalytic cracking of bio-oil upgrading process, Non-Thermal Plasma (NTP) assisted HZSM-5 technical scheme was proposed, online upgrading of rape straw vacuum pyrolytic vapors were conducted in a fixed bed reactor to verify the effectiveness of the technology. In the research, the influence of catalyzing temperature, catalyst bed height, discharge power on the physicochemical properties of refined bio-oil were studied, and the yield of refined bio-oil was regarded as evaluation index, response surface methodology was adopted to optimize upgrading processing parameters. Chemical composition of the refined bio-oil which was obtained under optimized parameters was analyzed by GC–MS, and using thermogravimetric analysis, the impact of NTP on catalyst anti-coking property was evaluated. Research results indicates that catalyzing temperature, catalyst bed height and discharge power have significance effect on yield and physicochemical properties of refined bio-oil. With the optimized processing parameters of 392 °C catalyzing temperature, 34 mm catalyst bed height and 23.7 W discharge power, the oxygen content, high heating value and pH of refined bio-oil were respectively 19.79%, 33.14 MJ/kg and 4.98. Compared with original HZSM-5 catalytic upgrading method, the quality of refined bio-oil was improved obviously, and the amount of catalyst coke deposit reduced from 5.88% to 2.14%, the feasibility of NTP assisted HZSM-5 online upgrading bio-oil was confirmed.

Hydrodeoxygenation upgrading of pine sawdust bio-oil using zinc metal with zero valency

Abstract Hydrodeoxygenation (HDO) is an effective method for bio-oil upgrading. However, the high hydrogen consumption resulted in high bio-oil upgrading cost. In this study, an novel method of hydrogen generation from water for bio-oil HDO was reported. Zinc metal with zero valency was used to generate hydrogen through zinc hydrolysis reaction in the bio-oil HDO process. The effects of different temperatures (20 °C, 250 °C, 300 °C, 350 °C, 400 °C) on in situ bio-oil HDO was investigated. The results showed that high temperatures resulted in high hydrogen yield that led to promoted HDO activity over zinc metal-based materials. Although 20 °C bio-oil HDO process generated the highest oil phase yield at 14.07%, 400 °C bio-oil upgrading process produced upgraded bio-oil with highest hydrocarbons content at 68.95%. Physicochemical properties of raw bio-oil improved significantly after bio-oil HDO upgrading at higher temperatures (250 °C, 300 °C, 350 °C and 400 °C). The pH of upgraded bio-oils (5.70–6.49) increased significantly compared to raw bio-oil (3.24). The higher heating value of upgraded bio-oils (28.67–33.43 MJ/kg) increased significantly compared to raw bio-oil (15.54 MJ/kg), and valuable hydrocarbons content improved significantly from 16.94% in raw bio-oil to 37.86%–68.95% in upgraded bio-oils.

Hydrotreatment of fast pyrolysis oil: Effects of esterification pre-treatment of the oil using alcohol at a small loading

Aiming to retard the self-polymerization of the reaction intermediates during bio-oil upgrading process, a large amount of alcohol (e.g., 50wt% with respect to bio-oil) was used in the stabilization of fast pyrolysis oil by esterification before hydrotreatment by the authors in a previous work. In order to reduce the amount of alcohol use and hence improve the process economy, effects of stabilizing fast pyrolysis oil by esterification with methanol, ethanol or glycerol at a small loading (5wt% w.r.t. bio-oil) in the presence of Amberlyst-35 DRY – a solid acid catalyst on the subsequent hydrotreatment of the oil were investigated. The bio-oil hydrotreatment experiments were carried out at 300 and 350°C in a combined batch and semi-batch operation mode with Ru/C catalyst. The results demonstrated that, although stabilization of the pyrolysis oil by esterification with a small alcohol loading had least effects on the mass and carbon distribution in the hydrotreatment products and the elemental composition of the hydrotreated oil products, it could effectively reduce the molecular weight of the feed, prevent self-polymerization and decrease the overall molecular weight of the hydrotreated oil products.

Analysis of coke precursor on deactivated catalyst in bio-oil upgrading process

ABSTRACTCharacterization of coke precursor on deactivated catalyst in bio-oil upgrading under CO atmosphere was analyzed with thermogravimetry, X-ray diffraction, infrared analysis, scanning electron microscopy, and nuclear magnetic resonance. The results showed that the deposition of coke precursor on a catalyst surface was mainly low-boiling point of saturated hydrocarbon compounds and the coke precursor of internal channels of deactivated catalyst were major aromatic hydrocarbon compounds. The coke precursor was in an amorphous state, which was highly dispersed on the catalyst surface or into the catalyst micropore. In addition, the catalyst deactivation mechanism was speculated that the small molecule aromatic compounds entered the internal channels of a catalyst and formed macromolecular aromatic hydrocarbons by aromatization gradually, further condensed to form coke and obstructed the channels of the catalyst.

Impact of solvent type and condition on biomass liquefaction to produce heavy oils in high yield with low oxygen contents

Bio-oils produced by processes such as slow or fast pyrolysis typically contain high water and oxygen contents, which make them incompatible with conventional fuels. It is therefore necessary to upgrade the bio-oils to reduce their oxygen and water contents. The bio-oil upgrading process can consume up to 84wt% of the initial bio-oil it is therefore important to develop other alternative approaches to generate high quality bio-oil. Thermolytic liquid solvent extraction (LSE) has been considered as a potential viable process due to the high liquid yield, better product quality and water free nature of the final products.In this study, a novel LSE process of biomass liquefaction has been studied under various conditions of solvent type, temperature, and biomass species. Compared to currently available commercial pyrolysis approaches, this process using tetralin as a solvent is shown to be capable of generating high quality bio-oil with low oxygen contents (ca. 5.9%) at extremely high overall conversions of up to 87 and 92 (%) dry and ash free basis (DAF) from Scotch pine and miscanthus, respectively. Overall, the study has demonstrated the advantages of LSE for bio-oil generation from biomass, in terms of producing high conversions to liquid products that are compatible with existing petroleum heavy feedstocks.

Environmental life cycle assessment of bio-fuel production via fast pyrolysis of corn stover and hydroprocessing

A comparative life cycle assessment (LCA) of biofuel production from corn stover fast pyrolysis and subsequent hydrotreating and hydrocracking was conducted based on the Greenhouse gases Regulated Emissions and Energy use in Transportation (GREET) model. Three different cases were investigated as a result of different hydrogen treatment in bio-oil upgrading process. Environmental impacts such as non-renewable energy demand and Global Warming Potential (GWP) were primarily evaluated for 1MJ biofuel produced. All the results showed obvious environmental benefits compared with conventional gasoline and diesel based on the year of 2010. The results of Case 1 in which hydrogen was provided by external natural gas reforming displayed a reduction of 67.5% in net non-renewable energy demand and a reduction of 69.1% in net GWP in contrast to conventional gasoline and diesel. Net non-renewable energy demand was lowered by 76.6% and net GWP was reduced by 73.0% in Case 2 where 35% of bio-oil aqueous phase was consumed by steam reforming for hydrogen production. Case 3 gained an obvious advantage on both environmental aspects over the others, in which surplus hydrogen from steam reforming of whole aqueous phase of bio-oil was obtained as a coproduct. The results displayed a significant net non-renewable energy reduction of 147.5% and a net GWP reduction of 119.4%. However, the outcomes indicated decreasing biofuel yields from Case 1 to Case 3 compared with increasing environmental benefits. The biofuel yields of three cases were 31.2%, 23.7% and 11.5% respectively in this work.

Development of on-line comprehensive two-dimensional liquid chromatography method for the separation of biomass compounds

Comprehensive on-line two-dimensional liquid chromatography (on-line LC×LC) was used for the characterization of bio-oils obtained by fast pyrolysis of lignocellulosic biomass. The resulting bio-oil contains a large number of oxygenated chemical families and must therefore be upgraded before being used as drop-in transportation biofuels. The good knowledge of its complex composition is essential for optimizing the mandatory bio-oil upgrading process to biofuels, thereby requiring powerful separation techniques designed to be hyphenated to mass spectrometry detection (LC×LC–MS). In this study, reversed phase conditions were optimized in both dimensions for the RPLC×RPLC separation of the aqueous fraction of bio-oils. The first step of method development consisted in searching for a suitable set of RP-conditions via the screening of a large number of RP-systems (made up of different stationary phases and/or mobile phases and/or temperature). The practical peak capacity and the degree of orthogonality were calculated for a sample of 38 representative compounds, both descriptors having been considered as selection criterion. Two different couplings were chosen and evaluated for the RPLC×RPLC separation of the 38 representative compounds. The best of both, in terms of real practical peak capacity, was further successfully applied to the separation of the aqueous phase of a partially dehydroxygenated bio-oil.

System Analysis of <i>in situ</i> Bio-Oil Hydrodeoxygenation

An in situ bio-oil upgrading process employing two circulating fluidized beds (CFBs) in series is proposed. One CFB allows the rapid pyrolysis of biomass and the other CFB facilitates bio-oil upgrading in the presence of a catalyst. In bio-oil upgrading CFBs, bio-oil is deoxygenated with hydrogen which is known as the hydrodeoxygenation (HDO) process. A system analysis was carried out on this process with respect to heat and mass balance to optimize the process efficiency and operating conditions. The product distribution of the pyrolysis CFB was experimentally obtained using a fluidized-bed reactor. According to the experimental results, a pyrolysis temperature of 823 K produced the highest bio-oil yield of 66 mass%. Based on the analysis of the bio-oil upgrading process, the maximum energy conversion from biomass to bio-oil was determined to be as high as 70% with respect to the biomass lower heating value (LHV). The energy conversion was strongly affected by the amount of hydrogen that was introduced to the bio-oil upgrading CFB. The bio-oil upgrading CFB produced a large amount of heat owing to the exothermic reaction of the HDO process. Heat elimination from the bio-oil upgrading CFB was required to maintain the catalyst temperature. It was found that the thermal utilization of unreacted hydrogen and an increased bio-oil yield during pyrolysis are required to further improve the energy conversion.

The Effect of Support on the Catalytic Performance for Bio-Oil Upgrading

Catalysts play critical roles in hydrotreating and hydrocracking processes of upgrading biomass-derived bio-oil to drop-in fuels. The selectivity and deactivate of catalysts, however, still remain biggest challenge. By using ZSM-5, alumina, and activated carbon as supports, different catalysts made up with Ru were prepared and tested in a bio-oil upgrading process. The effect of supports were investigated and compared in term of surface properties. The results showed that the ZSM-5 based catalysts got more water phase because of its highest surface acidity. The alumina changed to aluminum hydroxide in the presence of water at the reaction conditions. Activated carbon based catalysts showed good catalytic performance with more hydrocarbons and less water phase content in the upgraded bio-oil. All of upgraded bio-oils were verified by chemical analysis using a GC-MS. Nevertheless, further study for the kinetics of catalytically upgrading bio-oil is recommended.