Phenols In Bio-oil Research Articles

Leaching of alkali and alkaline earth metallic species (AAEMs) with phenolic substances in bio-oil and its effect on pyrolysis characteristics of moso bamboo

Acids present in bio-oil are considered to be effective agents to remove alkali and alkaline earth metallic species (AAEMs) from biomass, therefore affecting biomass pyrolysis. This study assessed whether phenols in bio-oil have a similar effect, with the pyrolysis characteristics of leached bamboo investigated using water and two typical phenolic compounds, phenol and guaiacol. Results confirmed that phenols have an important role in the removal of AAEMs, removing 96.4–96.6% of K, 84.6–85.4% of Mg, 77.2–81.9% of Na, and 66.7–69.1% of Ca. TG-FTIR results showed that phenolic leaching enhanced the pyrolytic release of volatile components of bamboo (H2O, CO2, CO, CH4, and carbonyl (C=O)-containing components), increased the temperature of pyrolysis peaks and decreased the activation energy, while increasing separation of the hemicellulose and cellulose pyrolysis zone. The results of Py-GC/MS showed that phenolic leaching reduced the production of acids but promoted the formation of anhydrosugars in bio-oil, indicating that phenolic leaching of AAEMs has a positive effect on the pyrolysis utilization of bamboo.

Comparative study on the pyrolysis behaviors of rice straw under different washing pretreatments of water, acid solution, and aqueous phase bio-oil by using TG-FTIR and Py-GC/MS

Washing pretreatment is a promising method for upgrading biomass by removing alkali metal and alkaline earth metals (AAEMs). In this study, three types of solution with different pretreatment severities (i.e., water (H2O), dilute hydrochloric acid (HCl) solution, and aqueous phase bio-oil (APBO)) were used to study the effects of the washing pretreatment on the pyrolysis behaviors and kinetics of rice straw. The pyrolysis experiments of raw and pretreated rice straw (Raw-RS, H2O-RS, HCl-RS, and APBO-RS) were carried out using TG-FTIR and Py-GC/MS. Results show that among the three types of washing pretreatment methods, the APBO washing pretreatment has the highest removal efficiency of AAEMs: 99.7% of K, 91.7% of Na, 96.6% of Mg, and 95.2% of Ca. According to TG-FTIR results, only one sharp mass loss peak was present in the DTG curves of Raw-RS and H2O-RS, whereas two mass loss peaks (one sharp peak and one shoulder peak) were observed in HCl-RS and APBO-RS. The evolution pattern of the volatile compounds (H2O, CH4, CO, CO2, and CO stretching) was thoroughly investigated, and the absorbance intensity of these components increased with the washing pretreatment of APBO and HCl. The APBO washing pretreatment had the highest activation energy in the conversion rate of 0.2–0.75, followed by HCl and H2O washing pretreatment. According to the Py-GC/MS results, the washing pretreatment reduced the relative contents of acids, ketones, furans, and phenols in bio-oil, whereas removing of AAEMs increased the relative contents of anhydrosugars (mainly levoglucosan). Among the three types of washing pretreatments, the APBO washing pretreatment had the most remarkable influence on the property of bio-oil, and this indicates that the APBO washing pretreatment is a promising method for upgrading biomass and its pyrolytic product.

Catalytic pyrolysis of poplar wood over transition metal oxides: Correlation of catalytic behaviors with physiochemical properties of the oxides

Metal oxides are frequently used in the formulations of the catalysts for catalytic pyrolysis of biomass. This study aims to investigate the catalytic behaviors of the transition metal oxides (CoO, Cr2O3, CuO, Fe2O3, Mn2O3, NiO, TiO2 and V2O5) as well as CeO2 for the catalytic pyrolysis of poplar wood. The metal oxides, especially TiO2 and NiO could suppress further cracking of primary products, increasing the tar yield and simultaneously decreasing the gas yield. The V, Mn, Ti or Co-based catalyst promoted the formation of the heavy bio-oil, while the Ce, Cr, Cu or Fe-based catalysts were the opposite. The metal oxides (except Fe2O3) promoted the formation of alcohols, furan, ketones, acetic acid and phenolics in bio-oil. Fe2O3 catalysts suppressed formation of the derivatives from cellulose and hemicellulose except hydroxyl acetone. Hydroxyl acetone formation was promoted by almost all the oxide catalysts while hydroxyl aldehyde formation was the opposite. Remarkable coke formed over the V, Mn, Cu and Co-based catalysts. These oxides contain multiple valences and could be partially reduced to generate oxygen vacancies, which played important roles in the polymerisation reactions. In addition, the coke species formed on the oxide catalysts were mainly polymeric with low thermal stability.

Process optimization of biomass liquefaction in isopropanol/water with Raney nickel and sodium hydroxide as combined catalysts

Liquefaction co-catalyzed by Raney nickel and NaOH in isopropanol (2-PrOH)/H2O is an efficient method for transforming lignocellulosic biomass into bio-oil. The present study investigated the effect of reaction temperature, residence time, and dosage of the catalysts on the yield and composition of bio-oil. To understand the liquefaction mechanism, the transformation of lignin and cellulose at the same conditions was investigated as well. The results indicated that 240 °C was the optimum temperature in terms of bio-oil yield. It was also found that residence time had a great effect on not only the bio-oil yield but also the composition and higher heating value (HHV) of the bio-oil. Increasing the dosage of the catalysts also improved the yield and HHV of bio-oil. Most phenols in bio-oil were originated from lignin, while most ketones and hydrocarbons were produced by cellulose.

Effects of the controllable mesostructure of nano-sized ZSM-5 on the co-cracking of phenolic bio-oil model compounds and ethanol

The mesopore shape and distribution of mesostructured ZSM-5 showed a major influence on aromatics production of co-cracking of phenolic bio-oil and ethanol.

Synthesis and Characterization of Bio-Oil Phenol Formaldehyde Resin Used to Fabricate Phenolic Based Materials.

In this study, bio-oil from the fast pyrolysis of renewable biomass was used as the raw material to synthesize bio-oil phenol formaldehyde (BPF) resin—a desirable resin for fabricating phenolic-based material. During the synthesis process, paraformaldehyde was used to achieve the requirement of high solid content and low viscosity. The properties of BPF resins were tested. Results indicated that BPF resin with the bio-oil addition of 20% had good performance on oxygen index and bending strength, indicating that adding bio-oil could modify the fire resistance and brittleness of PF resin. The thermal curing behavior and heat resistance of BPF resins were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Results showed that adding bio-oil had an impact on curing characteristics and thermal degradation process of PF resin, but the influence was insignificant when the addition was relatively low. The chemical structure and surface characteristics of BPF resins were determined by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The analysis demonstrated that adding bio-oil in the amount of 20% was able to improve the crosslinking degree and form more hydrocarbon chains in PF resin.

Combined pretreatment with torrefaction and washing using torrefaction liquid products to yield upgraded biomass and pyrolysis products

This study presented an approach to upgrade biomass and pyrolysis products using a process based on torrefaction liquid washing combined with torrefaction pretreatment. The torrefaction of cotton stalk was first conducted at 250°C for 30min and then the resulting torrefaction liquid products were collected and reused to wash cottonstalk. The pyrolysis of the original and pretreated cotton stalk was performed at 500°C for 15min in a fixed-bed reactor. The results indicated that the combined pretreatment obviously reduced the metallic species in cotton stalk, decreased the water and acids contents while promoted phenols in bio-oil, declined the ash content in biochar, as well as improved the heating value of non-condensable gas. Overall, the combined pretreatment did not only allow to reuse the liquid products issued from torrefaction pretreatment but also improved the quality of biomass and the pyrolysis products, making it a novel promising pretreatment method.

Fabrication of Glass Fiber Reinforced Composites Based on Bio-Oil Phenol Formaldehyde Resin.

In this study, bio-oil from fast pyrolysis of renewable biomass was added by the mass of phenol to synthesize bio-oil phenol formaldehyde (BPF) resins, which were used to fabricate glass fiber (GF) reinforced BPF resin (GF/BPF) composites. The properties of the BPF resin and the GF/BPF composites prepared were tested. The functional groups and thermal property of BPF resin were thoroughly investigated by Fourier transform infrared (FTIR) spectra and dynamic thermomechanical analysis (DMA). Results indicated that the addition of 20% bio-oil exhibited favorable adaptability for enhancing the stiffness and heat resistance of phenol formaldehyde (PF) resin. Besides, high-performance GF/BPF composites could be successfully prepared with the BPF resin based on hand lay-up process. The interface characteristics of GF/BPF composites were determined by the analysis of dynamic wettability (DW) and scanning electron microscopy (SEM). It exhibited that GF could be well wetted and embedded in the BPF resin with the bio-oil addition of 20%.

Characterization of phenolic compounds contained in bio-oil stemming from agricultural biomass wastes

Bio-oil is produced by biomass pyrolysis. It contains hundreds of chemical compounds including alkanes, aromatic hydrocarbons, esters, ethers, ketones, aldehydes, acids, alcohols, and phenols. Phenols are compounds of increasing interest; they can be used as feedstock in many industrial applications such as the production of fuel additives, chemical synthesis, or as food antioxidants. Therefore, the valorization of phenols stemming from bio-oil can be an appropriated alternative to reduce the dependence on petro-based phenols in the chemical industry. The most important phenols in biooil from agricultural wastes are phenol, guaiacol, cresols, syringol, and xylenol. These compounds were separated by silica gel column chromatography technique, using 3 different solvents: a dichloromethane—acetone mixture, ethyl acetate, and methanol. Column elution was followed by thin-layer chromatography (TLC). Phenolic fraction was obtained and not individual phenols. This fraction was analyzed using gas chromatography–f...

Catalytic hydrothermal liquefaction of rice straw in water/ethanol mixtures for high yields of monomeric phenols using reductive CuZnAl catalyst

This work investigated the yields of monomeric phenols in bio-oil derived from hydrothermal liquefaction of rice straw (RS) in water and ethanol mixtures using a reductive CuZnAl catalyst. Based on the results of an initial analysis, five monomeric phenolic compounds were selected for research due to their higher concentrations, namely phenol, 4-ethyl-phenol, 2-methoxy-phenol, 2-methoxy-4-ethyl-phenol and 2,6-dimethoxy-phenol. The optimized conditions for the production of monomeric phenols can be determined as: 2g of CuZnAl catalyst, a ratio of 50% ethanol/50% water (v/v), a temperature of 300°C and a reaction time of 30min. Results suggested that the maximum yield of total monomeric phenols could reach as high as ~26.8% (based on the mass of RS lignin), and that the aqueous phase yielded 95.5% of the monomeric phenols due to the solubilization of the ethanol. The CuZnAl catalyst was recycled five times, and a slight loss in activity was observed and examined using a number of technologies, including inductively coupled plasma, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and energy dispersive X-ray detection. The low-cost nature of the CuZnAl catalyst makes it an ideal catalyst for the enhancement of monomeric phenols yields in water and ethanol mixtures.

Quantification of Bio-Oil Functional Groups and Evidences of the Presence of Pyrolytic Humins

Quantification of functional groups (carbonyl, carboxyl, hydroxyl, phenolics) in biomass-derived pyrolysis oils is crucial to advance our understanding of bio-oil compositional changes during production, storage, aging, and upgrading. Traditionally, most of the methods reported in the literature on this subject are based on titration. There are very few studies on the use of spectroscopic techniques for the quantification of functional groups in bio-oils. The distribution of functional groups between the volatile and the heavy fraction is also very poorly understood. The content of functional groups in the volatile fraction estimated by GC/MS was compared with their content in the total oil determined by titration and 31P NMR. The carbonyl groups are almost equally distributed between the volatile and the oligomeric fractions. The content of total phenols varies between 1.6 and 3.1 mmol/g. It is important to note that between 85 and 95% of the phenols in bio-oil are in the form of oligomers. The content o...

Characteristics of bio-oil from the pyrolysis of palm kernel shell in a newly developed two-stage pyrolyzer

Pyrolysis of palm kernel shell was performed using a two-stage pyrolyzer consisting of an auger reactor and a fluidized bed reactor within the auger reactor temperature range of ∼290–380 °C at the fluidized bed reactor temperature of ∼520 °C, and with a variable residence time of the feed material in the auger reactor. The highest bio-oil yield of the two-stage pyrolysis was ∼56 wt%. The bio-oil derived from the auger reactor contained degradation products of the hemicelluloses of PKS, such as acetic acid, and furfural, whereas the fluidized bed reactor produced a bio-oil with high concentrations of acetic acid and phenol. The auger reactor temperature and the residence time of PKS in the auger reactor had an influence on the acetic acid concentration in the bio-oil, while their changes did not induce an observable trend on the phenol concentration in the bio-oil derived from the fluidized bed reactor. The maximum concentrations of acetic acid and phenol in bio-oil were ∼78 and 12 wt% dry basis, respectively. As a result, it was possible for the two-stage pyrolyzer to separately produce two different bio-oils in one operation without any costly fractionation process of bio-oils.

Using decalin and tetralin as hydrogen source for transfer hydrogenation of renewable lignin-derived phenolics over activated carbon supported Pd and Pt catalysts

Catalytic hydrogenation is considered as an efficient technique for upgrading pyrolysis bio-oil. High flammability of hydrogen gas in contact with air leads to difficult control of high pressurized hydrogen gas in large-scale systems. Meanwhile, molecular hydrogen production is a costly industrial process. Thus, hydrogenation study using hydrogen donor (H-donor) material as alternative for hydrogen gas could be useful in terms of cost and safety control. In this study, the potential of decalin and tetralin for use as hydrogen source was investigated in transfer hydrogenation of renewable lignin-derived phenolic compounds (phenol, o-cresol and guaiacol) and a simulated phenolic bio-oil over Pd/C and Pt/C catalysts. Reaction mechanisms of H-donor dehydrogenation and phenolics hydrogenation were studied. Catalytic activity of Pt/C for transfer hydrogenation of the phenolic compounds was higher than that of Pd/C at reaction temperature of 275 °C. Decalin as hydrogen source showed to be more efficient for hydrogenation of the phenolic compounds compared to tetralin. In addition, the influence of water content on transfer hydrogenation activity was studied by employing the water to donor ratios of 0/100, 25/75, 50/50 and 75/25 g/g. Maximum hydrogenation of phenol as bio-oil model compound was observed at water to donor ratio of 50/50 g/g.

Microwave-assisted catalytic pyrolysis of lignocellulosic biomass for production of phenolic-rich bio-oil

Catalytic microwave pyrolysis of peanut shell (PT) and pine sawdust (PS) using activated carbon (AC) and lignite char (LC) for production of phenolic-rich bio-oil and nanotubes was investigated in this study. The effects of process parameters such as pyrolysis temperature and biomass/catalyst ratio on the yields and composition of pyrolysis products were investigated. Fast heating rates were achieved under microwave irradiation conditions. Gas chromatography–mass spectrometry (GC–MS) analysis of bio-oil showed that activated carbon significantly enhanced the selectivity of phenolic compounds in bio-oil. The highest phenolics content in the bio-oil (61.19 %(area)) was achieved at 300°C. The selectivity of phenolics in bio-oil was higher for PT sample compared to that of PS. The formation of nanotubes in PT biomass particles was observed for the first time in biomass microwave pyrolysis.

Production of phenol-rich bio-oil during catalytic fixed-bed and microwave pyrolysis of palm kernel shell

Catalytic fixed-bed and microwave pyrolysis of palm kernel shell using activated carbon (AC) and lignite char (LC) as catalysts and microwave receptors are investigated. The effects of process parameters including temperature and biomass:catalyst ratio on the yield and composition of pyrolysis products were studied. The addition of catalyst increased the bio-oil yield, but decreased the selectivity of phenol in fixed-bed. Catalytic microwave pyrolysis of PKS significantly enhanced the selectivity of phenol production. The highest concentration of phenol in bio-oil of 64.58 %(area) and total phenolics concentration of 71.24 %(area) were obtained at 500°C using AC. Fourier transform infrared spectroscopy (FTIR) results indicated that concentration of OH, CH, CO and CO functional groups in char samples decreased after pyrolysis. Scanning electron microscopy (SEM) analysis clearly indicated the development of liquid phase in biomass particles during microwave pyrolysis, and the mechanism is also discussed.

Catalytic hydrodeoxygenation of simulated phenolic bio-oil to cycloalkanes and aromatic hydrocarbons over bifunctional metal/acid catalysts of Ni/HBeta, Fe/HBeta and NiFe/HBeta

Bifunctional metal/acid catalysts of 5wt% Ni/HBeta, 5wt% Fe/HBeta, 2.5wt% Ni-2.5wt% Fe/HBeta (NiFe-5/HBeta) and 5wt% Ni-5wt% Fe/HBeta (NiFe-10/HBeta) were used for hydrodeoxygenation (HDO) of a simulated phenolic bio-oil consisting of phenol (50wt%), o-cresol (25wt%) and guaiacol (25wt%). Nickel and iron metals were supported on hydrogen form Beta zeolite (HBeta) under similar ion-exchange conditions. BET surface area and acid sites density of Ni/HBeta, Fe/HBeta, NiFe-5/HBeta and NiFe-10/HBeta were 463, 445, 455, 417m2/g and 0.53, 0.48, 0.50, 0.38mmol/g, respectively. Cycloalkanes (21.39wt%) and aromatic hydrocarbons (20.21wt%) were the dominant hydrocarbons obtained over monometallic catalysts of Ni/HBeta and Fe/HBeta through reactions of hydrogenation and hydrogenolysis, respectively. It was revealed that both hydrogenation and hydrogenolysis mechanisms were effectively proceeded over the bimetallic catalyst of NiFe/HBeta which showed enhanced HDO efficiency compared to monometallic catalysts of Ni/HBeta and Fe/HBeta due to the synergistic effect between the two metals. The effect of reaction temperature on HDO efficiency of NiFe-10/HBeta catalyst was investigated at 220, 260, 300 and 340°C. Maximum catalytic activity and hydrocarbons selectivity was observed at 300°C. Replacement of water with methanol as solvent in HDO of the simulated phenolic bio-oil over NiFe-10/HBeta remarkably reduced the selectivity towards hydrocarbons.

Vapor phase hydrodeoxygenation and hydrogenation of m-cresol on silica supported Ni, Pd and Pt catalysts

Hydrodeoxygenation of m-cresol (a model compound of lignin derived phenolics in bio-oil) has been studied on silica supported Ni, Pd and Pt catalysts at 250°C and atmospheric pressure. Hydrogenation (to 3-methylcyclohexanone and 3-methylcyclohexanol) and hydrodeoxygenation (to toluene) are the primary reactions over all catalysts. The intrinsic hydrogenation activity follows the order of Ni<Pd<Pt, and the deoxygenation activity follows the order of Ni≪Pd≈Pt. The oxygen removal is mainly through a direct deoxygenation (DDO) route. The hydrogenation–deoxygenation (HYD) route is not important due to the lack of acidic sites to catalyze dehydration and a rather low hydrogenolysis activity of the C–OH bond of 3-methylcyclohexanol. At high conversions, the initial hydrogenation products are reversely dehydrogenated to m-cresol, making the deoxygenation to toluene and its subsequent hydrogenation to methylcyclohexane the major pathway. In general, increasing reaction temperature suppresses the hydrogenation reaction but promotes the hydrodeoxygenation as well as C–C bond hydrogenolysis. On Pd and Pt, increasing temperature improves deoxygenation to toluene over the C–C bond hydrogenolysis. In contrast, higher temperature favors the successive C–C hydrogenolysis to produce the low value methane on Ni.

Modification of natural clinoptilolite and ZSM-5 with different oxides and studying of the obtained products in lignin pyrolysis

In this work, different metal oxides (MO) supported on two types of zeolites: 1) natural clinoptilolite (NZ) and 2) synthetic zeolite, ZSM-5 were prepared and tested as catalysts in the fast pyrolysis of hardwood lignin. NZ was modified with the CaO and MgO by a simple two steps procedure consisting of an ion exchange reaction and a subsequent calcination at 773 K. The synthetic ZSM-5 was modified with several MO species (Ni, Cu, Ca, Mg) by a wet impregnation and calcination at 873 K. ?he prepared catalysts were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDS) and measurement of specific surface area (BET method). Acid sites were characterized and quantified by pyridine (py) absorption using Fourier transform infrared spectroscopy (FTIR). The catalysts exhibit catalytic activity depanding on modification, reaction temperature and of the MO contents. The highest yield of useful phenol in bio-oil was obtained with NiO/ZSM-5 (34.8 wt.%) which exhibits the highest specific surface area and the highest concetration of Br?nsted and Lewis acid sites. The studied catalysts did not increase significantly the content of polycyclic aromatic hydrocarbons (PAHs) and heavy compounds compared to non-catalytic experiment.

Catalytic transformations of acids, aldehydes, and phenols in bio-oil to alcohols and esters

Acids, aldehydes, and phenols have negative effects on the properties of bio-oil. In this paper, n-butanal, acetic acid, and phenol were selected as model compounds of aldehydes, acids, and phenols, respectively. To convert these compounds into stable and combustible oxygenated organics (alcohols and esters), separate hydrogenation–esterification (SHE) of n-butanal, phenol, and acetic acid was carried out. 100% conversions of n-butanal and phenol were achieved over C-supported catalysts (Ru/C, Pt/C, and Pd/C) with high selectivity to desired products. With the catalysis of SO42−/ZrO2/SBA-15, the yields of butyl acetate and cyclohexyl acetate were 75.89% and 30.97% respectively, which were higher than those over HZSM-5. Based on the results, one-pot hydrogenation–esterification (OHE) of n-butanal, phenol and acetic acid was tested. In OHE, yields of desired products (alcohols and esters) reached 95%, which were higher than those in SHE. Hydrogenation–esterification is a promising method to convert aldehydes, phenols, and acids in bio-oil to stable and combustible organics.

The Performances of Intimately Mix and Layer Methods in Microwave Assisted Pyrolysis System

The oil palm shell was subjected to multimode microwave pyrolysis at a fixed microwave power of 300W at 2.54GHz using intimately mix and layer microwave heating methods to observe process temperature, pyrolysis product and bio-oil composition at various levels of Coconut Activated Carbon (CAC). The results indicated that the layers method achieved higher bio-oil yield with complete uniformity of process temperature at high CAC loading compared to intimate mix method. The increased CAC loading increased selectivity towards phenol in bio-oil with maximum phenol 80.23 %area and 51.77%area under GC-MS at 75wt% CAC loading using intimately mix and layer method, respectively. The layer method produced a new product 1,1-dimethyl hydrazine of 11.24–13.01 %area in bio-oils which was not found of using intimately mix method. The 1,1-dimethly hydrazine is an important source of high energy fuel. Keywords: Oil palm shell; intimately mix method; layer method; coconut activated carbon; microwave assisted pyrolysis; heating profile; bio-oil