Simulated Bio-oil Research Articles

Synergistic effect of transition metals substitution on the catalytic activity of LaNi0.5M0.5O3 (M = Co, Cu, and Fe) perovskite catalyst for steam reforming of simulated bio-oil for green hydrogen production

Hydrogen is considered an excellent source of renewable and sustainable energy which can be produced from inexpensive starting materials such as biomass. The present study aims at developing a stable catalytic system for bio-oil steam reforming process to produce green hydrogen. The perovskite catalysts LaNi0.5M0.5O3 (M = Co, Cu, and Fe) were synthesized using sol-gel method and their catalytic performance towards hydrogen production and bio-oil conversion was evaluated in a fixed bed tubular reactor. A wide array of techniques such as XRD, BET, NH3 and CO2 -TPD, FE-SEM, XPS, TGA and pyridine-FTIR were used to analyze the material properties of the synthesized catalysts. The results of these analyses verified the successful formation of the highly sought-after perovskite structure with good amount of surface oxygen vacancies as well as medium-strength acidic and basic sites. To establish an efficient catalytic system, process parameter (space-time and reaction temperature) optimization and time on stream (TOS) studies were conducted. The TOS results displayed that LaNi0.5Co0.5O3 perovskite catalyst is stable up to 12 h at 700 °C for space-time of 17.4 kgcat. h/kgmolbio-oil. In-depth characterizations (FE-SEM, TGA, RAMAN spectroscopy and XRD) of spent catalyst after the reaction not only gave further insights about the excellent activity exhibited by the chosen catalyst but also revealed information about the nature of the coke deposited on the surface.

Hydrogenation of bio-oil in a needle-plate dielectric barrier discharge reactor

A needle-plate dielectric barrier discharge reactor was constructed to achieve bio-oil hydrogenation under low temperature and normal pressure. According to the composition and content of rice husk bio-oil, seven model compounds were mixed up to prepare simulated bio-oil, and effects of operating voltage, gas flow rate and reaction time on the deoxygenation rate and high calorific value of simulated bio-oil were investigated. The results showed that the maximum deoxidation rate of 31.62% was achieved, with the high calorific value of bio-oil increased from 25.78 MJ/kg to 32.69 MJ/kg, and the pH value increased from 3.67 to 4.83, which confirmed the feasibility of using dielectric barrier discharge reaction to hydrogenate bio-oil under low temperature and normal pressure conditions. With energy consumption and energy conversion rate as indexes, the operation economy of bio-oil hydrogenation process in the needle-plate dielectric barrier discharge reactor was evaluated, calculation results showed that under the optimized operation conditions, energy consumption of 2.44 kW·h/kg and energy conversion rate of 40.87% were achieved.

Catalytic performance of Ni-Co/HZSM-5 catalysts for aromatic compound promotion in simulated bio-oil upgrading.

Bio-oil can be used as a substitute for fossil fuels after it is upgraded. Bimetal-modified HZSM-5 catalysts with various Ni-to-Co ratios were prepared to address catalysis problems, including deactivation of the catalysts and low hydrocarbon yields. The catalytic performance of Ni-Co/HZSM-5 in upgrading the simulated bio-oil was investigated with a fixed-bed reactor, and the influence of the loaded duplex metal ratio was also discussed. The new moderately strong/strong acid sites of Ni-Co/HZSM-5 changed according to the Ni/Co loading ratios, which substantially affected the acidity, catalytic activity and selectivity of the Ni-Co/HZSM-5. However, incorporating Co and Ni into the zeolite did not alter the structure of the HZSM-5. The interactions of the loaded bimetallic oxides reached equilibrium in 6Ni-4Co/HZSM-5, in which moderately strong acid sites and strong acid sites were formed after loading with Co3O4 and NiO. With a suitable acid site ratio, 6Ni-4Co/HZSM-5 exhibited excellent performance, with a lower coke deposition of 3.29 wt% and stable catalytic activity, and the conversion remained at 83-73% during 360 min of uninterrupted catalysis. Periodic changes in the acid sites and interfacial protons were the critical factors that improved the properties of the 6Ni-4Co/HZSM-5 and enhanced its selectivity for aromatic compounds.

Catalytic steam reforming of simulated bio-oil for green hydrogen production using highly active LaNixCo1−xO3 perovskite catalysts

LaNi0.5Co0.5O3 perovskite catalysts displayed excellent catalytic activity for hydrogen production via steam reforming of simulated bio-oil.

Tandem Hydrodeoxygenation Catalyst System for Hydrocarbons Production from Simulated Bio-oil: Effect of C–C Coupling Catalysts

Research in the sustainable conversion of biomass to fuels and chemicals is a necessity for the reduction of the carbon footprint in transport energy. Herein, we demonstrate an efficient tandem catalyst to selectively convert (simulated) bio-oil to hydrocarbons with enhanced C4+ fuel yield in a fixed bed reactor of a small pilot plant. The tandem catalytic system is a multifunctional dual bed system; carbon coupling catalysts (0.2 wt % X-TiO2(X: Ru, Pd, Au) at the upper layer and hydro-deoxygenation (Ru-MoFeP/Al2O3) at the bottom layer in a single fixed bed reactor. The upper-bed catalysts facilitated the carbon coupling reaction of C2–C4 light oxygenates and significantly reduced the light gases yield (C1–C5) to ca. 40% and increased the organic (C4+) phase ca. 15%. The analysis of the organic phase suggests that among the screened upstream catalysts, 0.2 wt % Ru/TiO2||Ru-MoFeP/Al2O3 recorded the optimum activity. The coupled light oxygenates (acetone) alkylated with the phenolic compounds and sequentially hydro-deoxygenated to yield higher C4+ hydrocarbons. This versatile tandem catalytic approach has a potential application in the emerging biorefinery concept.

Comparison of novel olivine supported catalysts for high purity hydrogen production by CO2 sorption enhanced steam reforming

Abstract Seven Ni-based catalysts were prepared over different supports (conventional Al2O3, non-conventional olivine and hydrotalcite) with Co and Pd addition. Their catalytic performance was studied in hydrogen production by Steam Reforming (SR) and CO2-Sorption Enhanced Steam Reforming (SESR) with two different feeds: I) acetic acid as model compound and II) a mixture of acetic acid, acetone, phenol, furfural and 1-butanol as a simulated bio-oil. Two dolomites were employed and compared as CO2 sorbents. The so-called Arctic dolomite showed better characteristics for CO2 sorption than raw dolomite. High purity hydrogen (99.89 %) was generated during the CO2-SESR process without CO or CH4 detection, before the breakthrough curve, even during the complex mixture reforming. The olivine supported novel and cheap catalysts showed very high activity, with TOF values as high as 75 s−1, high hydrogen purity and yields, and good stability during 20−50 h under reforming conditions.

Influence of CoAl2O4 spinel and Co-phyllosilicate structures derived from Co/sepiolite catalysts on steam reforming of bio-oil for hydrogen production

Extensive attentions have been paid to develop steam reforming of bio-oil, which was considered as one of the sustainable technologies for producing eco-friendly next-generation energy sources, such as syngas and hydrogen. In this work, the novel catalysts consisted of CoAl2O4 spinel and Co-phyllosilicate are facilely manufactured from xCo/Sepiolite (xCo/SEP) precursors and their catalytic performance has been studied in steam reforming of simulated bio-oil (SRSB). The effects of Co content on the microstructures and physicochemical properties of catalysts are analyzed by various characterizations such as N2 adsorption-desorption, XRD, FTIR, H2-TPR, HRTEM and XPS. The results reveal that the CoAl2O4 phases in these catalysts are evolved gradually from Co-lean nonstoichiometric Co1−xAl2O4−x to Co-rich CoAl2O4 structure with increasing Co loading, subsequently accompanying with the formation Co-phyllosilicate species (CPS) when the Co content exceeds 10 wt%. Among them, calcined 15Co/SEP sample with optimal configuration of Co-Al spinel and CPS leads to its reduced-counterpart possesses fine Co metal nanoparticles, abundant defective Co-Al-spinel and metal-support interface sites. It therefore presents the highest carbon conversion (95.7%) and H2 yield (68.8%) in activity experiment and a slight deactivation in 50 h of stability test during SRSB. The analyses of TG-DSC, XRD and HRTEM are conducted on used catalysts and discover xCo/SEP-derived catalysts exhibit promising coke resistance and metal sintering is the major issue for catalyst deactivation, which mainly caused by particle migration and coalescence mechanism due to the further reduction of CPS.

Are the typical organic components in biomass pyrolyzed bio-oil available for leaching of alkali and alkaline earth metallic species (AAEMs) from biomass?

In this study, six dominant organic compounds in biomass pyrolyzed bio-oil, composed of acidic compound (acetic acid) and non-acidic compound (furfural, hydroxyacetone, ethylene glycol, phenol, and guaiacol) were used to remove AAEMs from different lignocellulosic biomass (rice husk, cotton stalk, and fir sawdust) by leaching pretreatment. Other four conventional solutions (deionized water, hydrochloric acid solution, aqueous phase bio-oil, and simulated bio-oil) were selected as control eluents. Results showed that the removal rate of AAEMs was highly affected by the types of immersion solutions, pH values, and the species of biomass. Majority of K in biomass could be removed by leaching of acetic acid. Ca was more difficult to be removed by leaching of water and acetic acid, but could be removed by leaching of HCl. In general, the removal rate of K was highest among the four species of AAMEs by using five non-acidic components, followed by Na, Mg, and Ca. The use of five non-acidic solutions was significantly benefit for the remove of K, Mg, and Na, but, was less useful in removal of Ca in rice husk and fir sawdust. However, the removal rates of Ca in cotton stalk by leaching of phenol, guaiacol, and hydroxyacetone were increased to nearly three times than water leaching. A synergistic effect for removing AAEMs occurred between acetic acid and non-acidic components in bio-oil, indicating that the non-acidic compounds also play an important role in leaching of AAEMs.

Renewable hydrogen production via steam reforming of simulated bio-oil over Ni-based catalysts

The production of hydrogen via steam reforming (SR) of simulated bio-oil (glycerol, syringol, n-butanol, m-xylene, m-cresol, and furfural) was investigated over Ni/CeO2-Al2O3 and Me-Ni/CeO2-Al2O3 (Me = Rh, Ru) catalysts. Monometallic (Ni) and bimetallic (Rh-Ni and Ru-Ni) catalysts were prepared by the wetness impregnation technique of the CeO2-Al2O3 support previously synthesized by the surfactant-assisted co-precipitation method. The as-prepared powders were systematically characterized by N2-physisorption, XRD, H2-TPR, and TEM measurements to analyze their structure, morphology, and reducibility properties. Experiments were performed in a continuous fixed-bed reactor at atmospheric pressure, temperature of 800 °C, steam to carbon (S/C) ratio of 5, and WHSV of 21.15 h−1. Then, the temperature was decreased to 700 °C and increased afterwards to 800 °C. After the experiments TPO and TEM analysis were performed on the spent catalysts to check any evidence of catalyst deactivation. The results showed that the incorporation of noble metal (Ru or Rh) promoter positively affected the activity of the Ni/CeO2-Al2O3 catalysts by enhancing the reducibility of Ni2+ species. Ni-based catalyst deactivated under the studied conditions, whereas Ru- and mainly Rh-promoted systems showed increased resistance to carbon deposition by favouring the gasification of adsorbed carbon species. Between all tested catalysts, the Rh-Ni/CeO2-Al2O3 provided the highest H2 yield and coking-resistance in SR of simulated bio-oil.

Phenolics isolation from bio-oil using the metal-organic framework MIL-53(Al) as a highly selective adsorbent.

By using flexible metal organic frameworks such as MIL-53(Al), the selective uptake of 4-methylguaiacol was achieved from a simulated bio-oil (40 wt%). Similar high uptake capacity of phenolics (27 wt%) was observed from a real pyrolysis bio-oil, with good selectivity towards a variety of phenolics, e.g. guaiacol, 4-methylguaiacol and catechol.

Improved catalytic upgrading of simulated bio-oil via mild hydrogenation over bimetallic catalysts

The bio-oil, produced via fast pyrolysis of biomass, can be used as substitute for transportation fuels after its subsequent upgrading. However, conventional upgrading of bio-oil faces serious problems of rapid catalyst deactivation and low conversion efficiency, due to the high unsaturation degree of bio-oil. In this study, the mild hydrogenation of simulated bio-oil over monometallic catalysts (Pd and Pt) and bimetallic catalysts (Pt-Fe, Pd-Fe, Pt-Ni and Pd-Ni) was performed, in order to increase the saturation degree. It was found that the addition of Ni could significantly facilitate the conversion of phenols. The maximum conversion of guaiacol and phenol over Pt-Ni/SiO2 catalyst reached 97.8% and 99.6%, respectively. The introduction of Fe improved the conversion of AcOH by promoting the protonation of carbonyl group. Complete conversion of AcOH was achieved over Pt-Fe/SiO2 catalyst. The upgraded product, of which the activity was significantly improved, was ready for subsequent upgrading for liquid fuel production.

Simulation of Oil Palm Shell Pyrolysis to Produce Bio-Oil with Self-Pyrolysis Reactor

A new self-pyrolysis reactor was designed to reduce the utilization of electric heater due to the energy saving for the production of bio-oil from oil palm shell. The yield of the bio- oil was then evaluated with the developed mathematical model by Sharma [1] with the characteristic of oil palm shell [2]. During the simulation, the temperature on the combustion chamber on the release of the bio-oil was utilized to determine the volatile composition from the combustion of the oil palm shell as fuel. The mass flow was assumed constant for three experiments. The model resulted in a significant difference between the simulated bio-oil and experiments. The bio-oil yields from the simulation were 22.01, 16.36, and 21.89 % (d.b.) meanwhile the experimental yields were 10.23, 9.82, and 8.41% (d.b.). The char yield varied from 30.7 % (d.b.) from the simulation to 40.9 % (d.b.) from the experiment. This phenomenon was due to the development of process temperature over time which was not considered as one of the influential factors in producing volatile matters on the simulation model. Meanwhile the real experiments highly relied on the process conditions (reactor type, temperature over time, gas flow). There was also possibilities of the occurrence of the gasification inside the reactor which caused the liquid yield was not as high as simulated. Further simulation model research on producing the bio-oil yield will be needed to predict the optimum condition and temperature development on the newly self-pyrolysis reactor.

Steam reforming of simulated bio-oil on K-Ni-Cu-Mg-Ce-O/Al2O3: The effect of K

Steam reforming of simulated bio-oil (ethanol, acetone, phenol, and acetic acid) and phenol has been studied on K-Ni-Cu-Mg-Ce-O/Al2O3 composite catalysts. Complementary characterization techniques, such as nitrogen sorption, XRD, H2-TPR, H2-TPD, CO-TPD, CO-DRIFTS, and in situ XPS, were used to correlate surface structure and functionality to catalytic performance of potassium (K) doped catalysts. K doping of the Ni-Cu-Mg-Ce-O/Al2O3 catalyst created a Ni°/Ni2+ mixed active phase, which not only enhanced steam reforming activity, but also suppressed the methanation reaction. In addition, K doping changed the surface acid-basic properties of the catalyst, which instead favor the gasifcation and water-gas shift reactions. With the combination of these effects, K doping of Ni-Cu-Mg-Ce-O/Al2O3 catalysts led to higher C1 yield and much lower methane formation, favoring hydrogen production in steam reforming of both phenol and simulated bio-oil.

Mild hydrogenation of simulated bio-oil based on molecular distillation

A mild hydrogenation of simulated bio-oil was carried out in a fixed-bed reactor. Based on the experimental results, 300 °C/4 MPa was chosen as an optimum condition for the mild hydrogenation, the simulated bio-oil was nearly completely converted. Besides, the liquid product selectivity achieved 85.0% and its (H/C)eff was significantly promoted from 1.266 to 1.554. The liquid composition was greatly improved and a notable decrease of phenols and acids contents was observed. In this case, the product activity was significantly enhanced and then the subsequent catalytic cracking was favored.

Aromatic Hydrocarbon Generation from a Simulated Bio-oil Fraction by Dual-stage Hydrogenation-cracking: Hydrogen Supply and Transfer Behaviors

The improvement of the hydrogen-poor composition of bio-oil is important for its cracking to produce aromatic hydrocarbons. In this work, a mild hydrogenation pre-treatment and methanol cocracking were combined to implement proper hydrogen supplementation for cracking. Acetic acid (HAc), hydroxypropanone (HPO), and cyclopentanone (CPO) were selected as model compounds and mixed to prepare a simulated distilled fraction (SDF) of bio-oil. The hydrogen supply and transfer behaviours in hydrogenation-cracking were investigated. For the conversion of individual components: HAc was difficult to be hydrogenated, and therefore in the cracking stage, the conversion and oil phase yield were low; ketones were successfully hydrogenated to alcohols, and thus high aromatic hydrocarbon yields were achieved. Hydrogenation-cracking of SDF showed that the inferior performance of HAc was improved by an internal hydrogen transfer, namely the alcohols produced from ketones supplied hydrogen for HAc conversion. However, because of the high HAc content in SDF, this hydrogen supplement was not sufficient. Therefore, methanol (MeOH) was used as the coreactant for secondary hydrogen supply. The integral efficient conversion of SDF and MeOH to aromatic hydrocarbons was achieved when the MeOH blending ratio was 30%. Finally, a reaction mechanism of hydrogenation-cocracking was proposed.

Initial Reaction Mechanism of Bio-oil High-Temperature Oxidation Simulated with Reactive Force Field Molecular Dynamics

The high-temperature reaction pathways of bio-oil oxidation were investigated by simulations of a 24-component bio-oil model using reactive force field (ReaxFF) molecular dynamics. Evolution profiles of fuel, O2, and major products, including radicals, with time and temperature during the initial stage of bio-oil oxidation were obtained. Major products generated during the simulations are consistent with observations reported in the literature. A kinetic model obtained from the simulated bio-oil oxidation is able to predict a long-time evolution trend of fuel consumption. Reaction networks of five representative components of the bio-oil model were revealed. The bio-oil oxidation is initiated by a series of homolysis and H-abstraction reactions and then propagation reactions involving H-shift, H-abstraction, and β-scission reactions. Oxidation of the unsaturated C–C bond, ring reduction of the phenolic radical, and abscission of the −CO structure (decarbonylation) appear frequently. Reaction pathways obtained from the comprehensive observations of simulation results employing VARxMD are in broad agreement with the literature. This work demonstrated a methodology that ReaxFF molecular dynamic simulations combined with the capability of VARxMD for reaction analysis can provide useful insights into the reaction pathway of bio-oil combustion.

Upgrading of the Acid-Rich Fraction of Bio-oil by Catalytic Hydrogenation-Esterification

The complex composition, high degree of unsaturation, and strong corrosiveness of bio-oil make direct catalytic upgrading problematic due to coking and device corrosion, and therefore, proper pretreatment is required. In this study, catalytic hydrogenation-esterification was identified as an efficient pretreatment method for bio-oil upgrading, and the hydrogenation-esterification behavior of typical compounds found in the acid-rich fraction of bio-oil over Cu/SBA-15 catalyst was investigated. It was found that furfural, hydroxyacetone, and guaiacol could be synergistically transformed with acetic acid (AcOH) during hydrogenation-esterification. Meanwhile, a higher reaction temperature promoted AcOH conversion and increased the degree of hydrogenation. On the basis of the quantification of the main products, the reaction pathways in the presence of furfural, hydroxyacetone, or guaiacol were proposed. Finally, the hydrogenation-esterification of simulated bio-oil was performed at 300 °C. The results showed ...

Effect of Coal Ash on the Steam Reforming of Simulated Bio-oil for Hydrogen Production over Ni/γ-Al2O3

An improved system for hydrogen production by the steam reforming of simulated bio-oil was developed. The coal ash was packed in front of nickel-based catalysts, acting as a guard catalyst. The model compounds passed through coal ash and were preliminarily reformed to smaller molecular intermediates containing more CO and CH4, which were then further reformed over the following nickel-reforming catalyst. The improved reaction system succeeded in effectively converting the complex simulated bio-oil into hydrogen and exhibited high activity. For 15 wt.% Ni/γ-Al2O3 catalyst with coal ash packing, the catalyst lifetime was extended to 8 h, with simulated bio-oil almost completely converted into hydrogen. In addition, coke deposition was suppressed.

Thermodynamic comparison between bio-oil and ethanol steam reforming

The thermodynamic analysis of the steam reforming (under catalytic steam reforming conditions) of a simulated bio-oil (composed of model compounds of components in a real bio-oil) and of ethanol is performed by minimization of Gibb's free energy method with Pro II-Simsci® 8.3 software, and their results are compared. At the equilibrium conditions both oxygenated feeds are completely converted, with H2, CO2, CO and CH4 being the only significant gaseous products. Coke formation is observed below 700 °C for low steam/carbon (S/C) molar ratios (below the stoichiometric value). H2 yield, which is very similar for both reforming processes (with small differences only for S/C < 2), increases with S/C ratio and goes through a maximum with temperature, being higher than 90% for S/C > 5 and in the 540–640 °C range. Above 600–650 °C (depending on the S/C molar ratio), the energy requirement for steam reforming of ethanol is slightly higher that for bio-oil steam reforming. These results evidence the viability of the joint valorisation of bio-oil and bio-ethanol by means of steam reforming.

Hydrogen production via steam reforming of bio-oil model compounds over supported nickel catalysts

The steam reforming of four bio-oil model compounds (acetic acid, ethanol, acetone and phenol) was investigated over Ni-based catalysts supported on Al2O3 modified by Mg, Ce or Co in this paper. The activation process can improve the catalytic activity with the change of high-valence Ni (Ni2O3, NiO) to low-valence Ni (Ni, NiO). Among these catalysts after activation, the Ce-Ni/Co catalyst showed the best catalytic activity for the steam reforming of all the four model compounds. After long-term experiment at 700 °C and the S/C ratio of 9, the Ce-Ni/Co catalyst still maintained excellent stability for the steam reforming of the simulated bio-oil (mixed by the four compounds with the equal masses). With CaO calcinated from calcium acetate as CO2 sorbent, the catalytic steam reforming experiment combined with continuous in situ CO2 adsorption was performed. With the comparison of the case without the adding of CO2 sorbent, the hydrogen concentration was dramatically improved from 74.8% to 92.3%, with the CO2 concentration obviously decreased from 19.90% to 1.88%.