Bio-oil Feedstock Research Articles

Metal-Doped HZSM-5 Zeolite Catalysts for Catalytic Cracking of Raw Bio-Oil: Exploring Activity toward Value-Added Products

Catalytic cracking of bio-oil, conducted at atmospheric pressure without hydrogen supply, is a cost-effective and versatile approach for the targeted synthesis of biofuels and platform chemicals. The conversion of raw bio-oil follows intricate reaction pathways strongly influenced by the catalyst properties. In this work, we explore the use of various transition metals (Cr, Fe, and Zn) to modify the properties of HZSM-5 zeolite and assess their impact on the catalytic cracking of real raw bio-oil feedstock. The effect of metal loading on physical and chemical characteristics of metal-doped zeolite catalysts was studied through XRD, XRF, N2 physisorption, NH3-TPD, FTIR, H2-TPR. The behavior of each catalyst was evaluated in a continuous two-step catalytic cracking system (TS-CC) operating at 450 °C and space-time 0.7 gcatalysth/gfeed. The results highlight the importance of carefully selecting active metal species to optimize the performance of HZSM-5 in the catalytic cracking of bio-oil. Cr and Fe were found to be effective metals in increasing the selectivity of C2–C4 olefins in the gas product and mono-aromatics in the hydrocarbon liquid product, whereas the Zn-doped catalyst exhibits poor activity compared to bulk zeolite. Furthermore, a significant impact of the metal oxidation state on catalytic activity was observed, with reduced metals promoting the formation of H2, CO, and CO2 at the expense of hydrocarbon production.

Bifunctional Pt/Hβ catalyzed alkylation and hydrodeoxygenation of phenol and cyclohexanol in one-pot to synthesize high-density fuels

Synthesis of fuels from lignin bio-oil feedstock significantly alleviates energy crises and environmental pollution. Phenol is the simplest model compound for lignin bio-oil feedstocks, and the synthesis of fuel precursors from phenol through alkylation has received increasing attention. Here we report a one-pot strategy for preparing polycyclic alkane high-density fuels from phenol and cyclohexanol over bifunctional Pt/Hβ catalyst by combining alkylation with following hydrodeoxygenation (HDO). The activity of different zeolites for catalyzing the alkylation of phenol and cyclohexanol was explored. It was found that the larger pore size of alkali treated Hβ would not limit the production of polycyclic compounds, and good acid content in a particular mesoporous specific surface area can speed up the reaction rate. The one-pot reaction conditions were then optimized. When the alkali treatment concentration is 0.2 mol/L, the metal loading is 0.2 wt%, and the molar ratio of phenol and cyclohexanol is 1:1, the highest conversion of phenol can reach more than 83 %. The selectivity of alkylphenol can reach more than 97 %, and the yield of bicyclic and tricyclic rings in the final product after HDO can reach 83.42 %. The bifunctional catalyst can also realize the coupling of other acid-catalyzed carbon growth reactions and metal-catalyzed HDO reactions, which allows the direct synthesis of fuel from lignin oil or other biomass compounds.

The effect of temperature distillation on products distribution derived from wood pyrolysis bio-oil

Bio-oil from biomass pyrolysis can be converted to chemicals, solid carbon materials, and syngas by various thermochemical conversion technology methods. Because of the elevated temperature, bio-oil suffers drastic component changes as the first step in these processes. Understanding the impact of heating temperature on bio-oil transformation during the distillation process is critical for practical bio-oil usage. A bio-oil feedstock produced from the pyrolysis of lamtoro wood residue at 500 °C was used in distillation from this work. Complete temperature range analysis of 96, 97, 98, 99, and 100 °C was conducted. Eight typical compounds in bio-oil were precisely quantified by gas chromatography-mass spectroscopy (GC-MS) and FTIR analysis. The results revealed that a common critical point was widely present during the distillation process, which may be attributed to a stable system generated by hydrogen bonding. As a result, the content of acetic acid, 2-Propanone, and phenol was up to 38%, 12%, and 20%, respectively. The detailed distillation characteristics and product distribution provide a comprehensive insight into the reaction process and component enrichment patterns, assisting design and parameter optimization.

Selective extraction of monophenols from pyrolysis bio-oil based on a novel three-dimensional visualization model

Monophenols in pyrolysis bio-oil can be used to produce renewable fuels and various other materials; their clean separation, however, remains a great challenge. This study provides an economical and feasible strategy for efficiently extracting monophenols from bio-oil. In order to determine the interaction between bio-oil components and different solvents, Hansen solubility parameter theory was used to predict the dissolution trend of several model compounds (e.g., 6 monophenols and 2 dimeric phenols) with a relatively high concentration and/or typical dissolution characteristics in the bio-oil feedstock. A new three-dimensional graphical model was then established by observing the distribution of the extractant coordinate points (Hansen solubility parameters) to predict the selectivity of the extraction of monophenols in a specific extraction process. Under the guidance of this dissolution model, a multistep extraction process with a mono phenol yield of 88.2 wt% was established, and the mass percentage of mono phenols in the separation product was about 86.3%. We performed catalytic hydrodeoxygenation on the separation product, and results showed that the yield and aromatic selectivity of the product were significantly higher than those of water-washed bio-oil. Since the separation strategy proposed in this study does not involve acids or alkalis and the solvent is easily recyclable, the method is expected to find practical application in the efficient separation of bio-oil and its downstream value-added refinement.

Rice Husk and Its Pretreatments for Bio-oil Production via Fast Pyrolysis: a Review

Rice husk is a prospective bio-oil feedstock due to its plentiful supply, but its unfavorable characteristics like high moisture content, high ash content, and low energy density tend to jeopardize both the yield and quality of bio-oil produced by fast pyrolysis. Lately, various pretreatments, namely, washing, torrefaction (dry and wet), and their combined pretreatments, have been researched on rice husk with the aim of improving its unfavorable characteristics for bio-oil production. However, the influences of different pretreatments on pretreated rice husk and the subsequent bio-oil produced have not been compared. Hence, this review paper presents an overview of rice husk as a bio-oil feedstock and its pretreatment methods for bio-oil production via fast pyrolysis. Particular emphasis is placed on the rice husk characteristics and their impacts on the bio-oil production via fast pyrolysis, as well as the different types of rice husk pretreatment and their influences on the characteristics of pretreated rice husk, product yields of fast pyrolysis, and the composition and physical properties of the bio-oil produced. A comparison of the physicochemical properties of rice husk- and other biomass-based bio-oil alongside those of petroleum fuel oil is also outlined. Major challenges and future prospects towards the utilization of rice husk as a bio-oil feedstock and the integration of rice husk pretreatment with fast pyrolysis for large-scale applications are also discussed.

Cost and Profitability Analysis of a Prospective Pennycress to Sustainable Aviation Fuel Supply Chain in Southern USA

This study evaluates biorefinery bio-oil feedstock costs at the plant gate for a prospective field pennycress (Thlaspi arvense L.) to sustainable aviation fuel (SAF) supply chain. The biorefinery would supply SAF to the Nashville, Tennessee international airport. Supply chain activities include pennycress production, transporting oilseed to a crushing facility, processing of oilseed into bio-oil, and transporting bio-oil to the biorefinery. The analysis shows profit potential for economic agents in the prospective supply chain. Estimated breakeven cost (profit = 0) of growing, harvesting, and transporting oilseed to a crushing facility is 17.7 ¢ kg−1. A crushing facility can pay up to 23.8 ¢ kg−1 for pennycress oilseed during the first year of production and provide investors 12.5% annual rate of return. Therefore, a profit margin of up to 6.1 ¢ kg−1 is available for the crushing facility to induce prospective pennycress producers to supply oilseed for SAF production. However, the estimated profit margin was sensitive mainly to uncertain oilseed yields, changes in field production costs, and pennycress meal and bio-oil prices. A spatial biorefineries sitting model, the Biofuels Facility Location Analysis Modeling Endeavor, estimated that the least-cost supply chain configuration is to establish three crushing facilities located in Union City, Huntington, and Clarksville, TN, to supply bio-oil to the biorefinery, with the biorefinery sited in an industrial park about 24.14 km from the Nashville international airport aviation fuel storage. Estimated total costs of bio-oil at the biorefinery plant gate are between 83 and 109 ¢ kg−1 if crushing facility oilseed procurement costs are between 17.7 and 23.8 ¢ kg−1 for oilseed.

Characterization of Deactivated Bio-oil Hydrotreating Catalysts

Deactivation of bio-oil hydrotreating catalysts remains a significant challenge because of the poor quality of pyrolysis bio-oil input for hydrotreating and understanding their deactivation mode is critical to developing improved catalysts and processes. In this research, we developed an understanding of the deactivation of two-step bio-oil hydrotreating catalysts (sulfided Ru/C and sulfided CoMo/C) through detailed characterization of the catalysts using various analytical techniques. Severe fouling of both catalysts by carbonaceous species was the major form of deactivation, which is consistent with the significant loss of surface area and pore volume of both deactivated catalysts and the significant increase of the bulk density. Further analysis of the carbonaceous species by thermogravimetric analysis and X-ray photoelectron spectroscopy indicated that the carbonaceous species was formed by condensation reaction of active species such as sugars and sugar derivatives (aldehydes and ketones) in bio-oil feedstock during bio-oil hydrotreating under the conditions and catalysts used. Microscopy results did not show metal sintering of the Ru/C catalyst. However, X-ray diffraction indicated a probable transformation of the highly-active CoMoS phase in the sulfided CoMo/C catalyst to Co8S9 and MoS2 phase with low activity. Loss of the active site by transport of inorganic elements from the bio-oil and the reactor construction material onto the catalyst surface also might be a cause of deactivation as indicated by elemental analysis of spent catalysts.

Techno-economic comparisons of hydrogen and synthetic fuel production using forest residue feedstock

Mobile distributed pyrolysis facilities have been proposed for delivery of a forest residue resource to bio-fuel facilities. This study examines the costs of producing hydrogen or synthetic petrol (gasoline) and diesel from feedstock produced by mobile facilities (bio-oil, bio-slurry, torrefied wood). Results show that using these feedstock can provide fuels at costs competitive to conventional bio-fuel production methods using gasification of a woodchip feedstock. Using a bio-oil feedstock in combination with bio-oil steam reforming or bio-oil upgrading can produce hydrogen or petrol and diesel at costs of 3.25 $ kg−1 or 0.86 $ litre−1, respectively, for optimally sized bio-fuel facilities. When compared on an energy basis ($ GJ−1), hydrogen production costs tend to be lower than those for synthetic petrol or diesel production across a variety of bio-fuel production pathways.

Production of Bio-oil from Fast Pyrolysis of Macroalgae Enteromorpha prolifera Powder in a Free-fall Reactor

The use of non-food biomass for bio-oils production appears to be an important trend for renewable energy in China. Biomass, in the form of marine macro-algae, is becoming popular among new renewable energy sources. Fast pyrolysis is one of the most important thermal conversion processes from biomass to bio-fuel. In this work, the marine green tide macroalgae Enteromorpha prolifera was converted into bio-oil by fast pyrolysis in a free-fall reactor at different temperatures ranging from 100 to 750°C. The bio-oil obtained was analyzed by elemental, gas chromatography-mass spectrometer, and Fourier transform infrared spectroscopy analysis. The results showed that the average heat value was 25.33 MJ kg−1 and the oxygen content was 30.27 wt%. The results suggested that E. prolifera presents as a good bio-oil feedstock candidate.

Recent Advances in Hydrotreating of Pyrolysis Bio-Oil and Its Oxygen-Containing Model Compounds

Considerable worldwide interest exists in discovering renewable energy sources that can substitute for fossil fuels. Lignocellulosic biomass, the most abundant and inexpensive renewable feedstock on the planet, has a great potential for sustainable production of fuels, chemicals, and carbon-based materials. Fast pyrolysis integrated with hydrotreating, one of the simplest, most cost-effective, and most efficient processes to convert lignocellulosic biomass to liquid hydrocarbon fuels for transportation, has attracted significant attention in recent decades. However, effective hydrotreating of pyrolysis bio-oil presents a daunting challenge to the commercialization of biomass conversion via pyrolysis-hydrotreating. Specifically, the development of active, selective, and stable hydrotreating catalysts is problematic due to the poor quality of current pyrolysis bio-oil feedstock (i.e., high oxygen content, molecular complexity, coking propensity, and corrosiveness). Significant research has been conducted to address the practical issues and provide fundamental understanding of hydrotreating and hydrodeoxygenation (HDO) of bio-oils and their oxygen-containing model compounds, including phenolics, furans, and carboxylic acids. A wide range of catalysts have been studied, including conventional Mo-based sulfide catalysts and noble metal catalysts. Noble metal catalysts have been the primary focus of recent research because of their excellent catalytic performances and because they do not require the use of environmentally unfriendly sulfur. Recently, the reaction mechanisms of the HDO of model compounds on noble metal catalysts and their efficacy for hydrotreating or stabilization of bio-oil have been reported. This review provides a survey of relevant literature, published over the past decade, reporting advances in the understanding of the HDO chemistry of bio-oils and their model compounds, mainly on noble metal catalysts.

Steam Reforming of Model Compounds and Fast Pyrolysis Bio-oil on Supported Nickle Metal Catalysts for Hydrogen Production

Steam reforming of biomass derived bio-oil liquid products was an available low carbon technology to produce sustainable hydrogen fuel. In this article, a series of nickel-based catalysts have been prepared. To examine the catalytic steam reforming behaviors over these catalysts in a fixed bed reactor system, several typical oxygen-containing chemicals, including acetic acids, furfural, cyclopentanone, and meta-cresol, that were proved to be contained in the bio-oil feedstock, were first selected as model starting materials. In these tests, yields for hydrogen were taken as an index of the catalyst activity and the catalyst that exhibited the maximum activity by hydrogen yields was then used for the bio-oil steam reforming studies. In this work, it was concluded that the catalyst activity reached a maximum hydrogen yield of 90.56% and decreased in an order of Ni/MgO-La2O3-Al2O3 > Ni/MgO-Al2O3 ≈ Ni/La2O3-Al2O3 > Ni/Al2O3. The yield of hydrogen for steam reforming of the whole fraction of the bio-oil reached 70% under 800°C and it only lowered 10%, after 10 hours on stream in a stability test.

Life-Cycle Assessment of Pyrolysis Bio-Oil Production*

Abstract As part of the Consortium for Research on Renewable Industrial Materials' Phase I life-cycle assessments of biofuels, life-cycle inventory burdens from the production of bio-oil were developed and compared with measures for residual fuel oil. Bio-oil feedstock was produced using whole southern pine (Pinus taeda) trees, chipped, and converted into bio-oil by fast pyrolysis. Input parameters and mass and energy balances were derived with Aspen. Mass and energy balances were input to SimaPro to determine the environmental performance of bio-oil compared with residual fuel oil as a heating fuel. Equivalent functional units of 1 MJ were used for demonstrating environmental preference in impact categories, such as fossil fuel use and global warming potential. Results showed near carbon neutrality of the bio-oil. Substituting bio-oil for residual fuel oil, based on the relative carbon emissions of the two fuels, estimated a reduction in CO2 emissions by 0.075 kg CO2 per MJ of fuel combustion or a 70 percent reduction in emission over residual fuel oil. The bio-oil production life-cycle stage consumed 92 percent of the total cradle-to-grave energy requirements, while feedstock collection, preparation, and transportation consumed 4 percent each. This model provides a framework to better understand the major factors affecting greenhouse gas emissions related to bio-oil production and conversion to boiler fuel during fast pyrolysis.

Elucidation of Thermal Pretreatment Kinetics of Bio-oil Feedstock Premixed with Calcium Hydroxide and Glycerol for Reactive Biodiesel Production via Ethanolysis in Developing Countries

With rising prices for imported fossil fuel and growing concerns about global warming, the developing countries of Sub-Saharan Africa may no longer be able to depend upon fossil diesel as a reliable source of energy in the future. Fortunately, the availability of local resources such as ethanol (EtOH), bio-oils, and hydrated lime makes it feasible to introduce renewable sources of power such as biodiesel via ethanolysis. A previous paper from our group reported concentration changes of triglycerides (TG), diglycerides (DG), monoglycerides (MG), and the added glycerol (GL) in the pretreatment with glycerol, and identified the glycerolysis of TG as the mechanism behind the reaction rate enhancement of the following transesterification. It will also be important, for actual application to biodiesel production, to determine the reaction rates and equilibrium constants. In the present study we determined the thermal pretreatment kinetics of a groundnut (Arachis hypogaea) oil feedstock premixed with glycerol and calcium hydroxide (Ca(OH)2) at 100 °C over reaction times from 1 to 3 h, while measuring the concentration changes of TG, DG, MG, and GL over time to determine the rate constants. Next, we used the data obtained to calculate the equilibrium constants. Through this approach, we successfully determined the reaction rate of the catalytic TG glycerolysis, the process that yielded DG and MG as reactive intermediates for the ethanolysis reaction. A GL/TG molar ratio of 2.35 is recommended for optimal performance of TG glycerolysis.