Production Of High-quality Bio-oil Research Articles

Lignin Extracted from Various Parts of Castor (Ricinus communis L.) Plant: Structural Characterization and Catalytic Depolymerization.

Castor is an important non-edible oilseed crop used in the production of high-quality bio-oil. In this process, the leftover tissues rich in cellulose, hemicellulose and lignin are regarded as by-products and remain underutilized. Lignin is a crucial recalcitrance component, and its composition and structure strongly limit the high-value utilization of raw materials, but there is a lack of detailed studies relating to castor lignin chemistry. In this study, lignins were isolated from various parts of the castor plant, namely, stalk, root, leaf, petiole, seed endocarp and epicarp, using the dilute HCl/dioxane method, and the structural features of the as-obtained six lignins were investigated. The analyses indicated that endocarp lignin contained catechyl (C), guaiacyl (G) and syringyl (S) units, with a predominance of C unit [C/(G+S) = 6.9:1], in which the coexisted C-lignin and G/S-lignin could be disassembled completely. The isolated dioxane lignin (DL) from endocarp had a high abundance of benzodioxane linkages (85%) and a low level of β-β linkages (15%). The other lignins were enriched in G and S units with moderate amounts of β-O-4 and β-β linkages, being significantly different from endocarp lignin. Moreover, only p-coumarate (pCA) incorporated into the epicarp lignin was observed, with higher relative content, being rarely reported in previous studies. The catalytic depolymerization of isolated DL generated 1.4-35.6 wt% of aromatic monomers, among which DL from endocarp and epicarp have high yields and excellent selectivity. This work highlights the differences in lignins from various parts of the castor plant, providing a solid theory for the high-value utilization of the whole castor plant.

High-quality bio-oil production via catalytic pyrolysis of biocrude oil from hydrothermal liquefaction of microalgae Spirulina

Hydrothermal liquefaction (HTL) is an effective method for the conversion of wet microalgae to fuels. However, the biocrude oil from direct HTL is inferior to fossil fuels in quality. Catalytic hydrogenation is normally used to upgrade the biocrude, but the cost-intensive hydrogen with high pressure is needed. In this study, the raw biocrude from HTL of Spirulina was upgraded through catalytic pyrolysis using Fe-HZSM-5 as the catalyst without hydrogen. The effects of temperature and reaction time on the yield and quality of the upgraded bio-oil were explored. The yield of upgraded bio-oil ranged from 75% to 86%. With the addition of the catalyst, the carbon content and higher heating value (HHV) of the upgraded bio-oil were improved obviously. The carbon, hydrogen contents and HHV of the upgraded bio-oil were 78.89%, 10.51% and 40.8MJ/kg at 320 °C for 3 h, respectively. The composition of the upgraded bio-oil changed evidently compared with the raw biocrude, the peak area of the nitrogen-containing compounds was reduced by 50%, while the peak area of the hydrocarbons in the upgraded bio-oil with catalyst was twice of that in the raw biocrude. The catalyst still retained certain activity after 5 cycles. The HHV and nitrogen content of the upgraded bio-oil were 41.52MJ/kg and 0.39%, respectively, when the feedstock was switched to high-lipid salad waste. Results of this study demonstrate that high-quality bio-oil could be produced through coupling catalytic pyrolysis and HTL.

Catalytic hydrothermal liquefaction of microalgae over reduced graphene oxide support Ni catalyst

In this study, a reduced graphene oxide (RGO) material loaded with nickel was prepared, and to the best of the authors' knowledge, it was the first time that RGO material used as a catalyst in the hydrothermal liquefaction (HTL) of microalgae. The effect of RGO support Ni catalyst on the yield and quality of bio-oil derived from HTL of Spirulina was studied in this research. The results showed that the catalyst could improve the yield of bio-oil, and the performance in improving the quality of bio-oil was significantly increased. GC–MS analysis showed that RGO catalyst could promote the formation of hydrocarbons. When the loading amount of Ni was 5%, the oxygen content of bio-oil was the lowest (14.79%), and when the loading amount of Ni was increased to 25%, the content of hydrocarbons was the highest (11.41%). In addition, RGO catalyst also increased the content of low boiling point components (<400°C) in bio-oil from 68% to 81%. This study can provide valuable information for the further application of graphene in microalgae HTL and the production of high-quality bio-oil in the future.

Supercritical ethanol liquefaction of bamboo leaves using functionalized reduced graphene oxides for high quality bio-oil production

The study investigated the supercritical ethanol liquefaction of bamboo leaves using a functionalized reduced graphene oxide catalyst (GOr). The ZrO2–SrO/GOr catalyst consisted mostly of mesopores (95%) with only 5% micropores, which enhances the reactant's accessibility to active sites. The supercritical ethanol liquefaction was carried out in a 150 mL reactor and optimised for bio-oil production using an experimental central composite design (CCD). At optimum operating conditions (375 °C, a catalyst-to-biomass ratio of 1:2.5 (wt:wt) and a biomass-to-ethanol ratio of 1:10 (wt/vol), the bio-oil yield derived from bamboo leaves was 47%, which was higher than hydrothermal process (27%). A model was developed from analysis of variance (ANOVA) and validated using experimental data. The predicted and experimental data agreed well with an R2 of 0.99. The bio-oil had a higher heating value of 35.3 MJ/kg, consisting mainly of esters, phenolic and hydrocarbon compounds.

Pyrolysis-GCMS of Spirulina platensis: Evaluation of biomasses cultivated under autotrophic and mixotrophic conditions.

Microalgae are autotrophs and CO2 fixers with great potential to produce biofuels in a sustainable way, however the high cost of biomass production is a challenge. Mixotrophic growth of microalgae has been presented as a great alternative to achieve economic sustainability. Thus, the present work reports the energetic characterization of S. platensis biomasses cultivated under autotrophic (A) and mixotrophic conditions using cheese whey waste at different concentrations, 2.5 (M2.5), 5.0 (M5) and 10.0% (M10), in order to analyze the potential production of valuable chemicals and bio-oil by TGA/DTG and Py-GC/MS. The biochemical compositions of the studied biomasses were different due to the influence of different culture mediums. As the whey concentration increased, there was an increase in the carbohydrate content and a decrease in the protein content, which influenced the elemental composition, calorific value, TGA and volatile compounds evaluated by Py-GC/MS at 450°C, 550°C and 650°C. Sample M10 had lower protein content and formed a smaller amount of nitrogenates compounds by pyrolysis at all temperatures evaluated. There was a reduction of 43.8% (450º), 45.6% (550ºC) and 23.8% (650ºC) in the formation of nitrogenates compounds in relation to sample A. Moreover, the temperature also showed a considerable effect in the formation of volatile compounds. The highest yields of nitrogenates compounds, phenols and aromatic and non-aromatic hydrocarbons were observed at 650ºC. The oxygenated, and N and O containing compounds decreased as the temperature increased. Hydrocarbons such as toluene, heptadecane and heneicosane were produced by S.platensis pyrolysis, which makes this biomass attractive for production of high quality bio-oil and valuable chemicals. Therefore, the results showed that it is possible to decrease the formation of nitrogen compounds via manipulation of growth conditions and temperature.

Hydrotalcite as a deoxygenation catalyst in fast pyrolysis of biomass for the production of high quality bio-oil

Commercially available MG70 hydrotalcite (HT) has been investigated for its influence on the in-situ catalytic fast pyrolysis of beechwood. The investigations were performed both with an analytical Py-GC/MS (pyroprobe) and on a bench scale fluidized bed reactor at a pyrolysis temperature of 500 °C. The semi qualitative pyroprobe analysis was carried out for different catalyst to biomass (C/B) ratios and a ratio of 4 was found to be optimum. At this C/B ratio, the acids, anhydro-sugars and methoxy phenolics were more or less eliminated and HT facilitated the formation of alkylated cyclopentenones, cresols, methly furans and hydrocarbons. The application of HT in the bench scale fluidized bed reactor allowed for further analysis of the pyrolysis products: bio-oil, char, and gas. The semi qualitative GCMS analysis of bio-oil was in general agreement with the volatiles detected from Py-GC/MS analysis. In addition the catalyst was characterized by BET, XRD and TGA analysis. Overall an organic rich bio-oil with a yield of 9.5 wt%, higher heating value of 29.3 MJ/kg (as received) was obtained. The pH of the bio-oil increased from 3.2 to 6.0 and oxygen content reduced from 46.3 to 20.5 wt% (as received). The substantial increase in CO2 concentration in the pyrolysis gas also supported these findings. Overall, HT facilitated the formation of moderately deoxygenated compounds and they are of interest as they can be further processed downstream to produce bio-fuels.

Supercritical Ethanol Liquefaction of Bamboo Leaves Using Functionalized Reduced Graphene Oxides for High Quality Bio-Oil Production

Supercritical Ethanol Liquefaction of Bamboo Leaves Using Functionalized Reduced Graphene Oxides for High Quality Bio-Oil Production

Effect of torrefaction and fractional condensation on the quality of bio-oil from biomass pyrolysis for fuel applications

This study evaluated the effects of the pyrolytic temperature, torrefaction, and fractional condensation alongside the combined efficiency of torrefaction and fractional condensation on the production of high-quality bio-oil from woody sawdust (WS) pyrolysis for the first time. The proportion of acids decreased gradually with increasing temperature from 300 to 600 °C, while the selectivity of phenolic compounds was enhanced. An increase in the torrefaction severity caused a significant decrease in the bio-oil yield at the pyrolysis stage but favorably increased the selectivity of phenolics and mitigated the fraction of oxygenated compounds. In fractional condensation, the proportion of total oxygenates was increased with decreasing condensing temperature from the first condenser (Con 1) (250 °C) to the fourth condenser (Con 4) (-20 °C). On the other hand, most phenolics were condensed in Con 1 and then showed a decreasing trend with a decrease in temperature. Integrating torrefaction and fractional condensation decreased the oxygenated content dramatically while increasing the selectivity of phenolic content significantly (up to 89.48%) under high- and mild- temperatures condensation, suggesting a functional improvement. Overall, the torrefaction of biomass combined with fractional condensation in biomass pyrolysis is a promising approach to produce biofuels.

Valorization of the spent catalyst from flue gas denitrogenation by improving bio-oil production from hydrothermal liquefaction of pinewood sawdust

Normally, the spent catalyst (V2O5-WO3/TiO2, denoted as VWTi) is dumped as a solid waste after denitrogenation of flue gas through selective catalyst reduction (SCR). However, this used catalyst contains an abundant amount of acid sites and thus can be potentially utilized as the catalyst in hydrothermal liquefaction (HTL) to produce bio-oil. Thus, in this study, the influences of operational variables on the main HTL products distribution and physicochemical properties of bio-oil were evaluated at 240–320 °C for 0–60 min and 0–20 wt% of catalyst dosage. The results demonstrated that the spent VWTi catalyst significantly promoted the production of bio-oil, yielding the highest bio-oil yield (33.9 wt%) at 300 °C for 30 min with a 10 wt% of catalyst loading. The bio-oil obtained with catalyst under the optimal conditions has a HHV of 28.69 MJ/kg, along with an energy recovery of 51.93%. In addition, the use of the spent VWTi catalyst in the HTL could obtain a higher fraction of phenolics compounds with lower boiling point and lower molecular weight, as identified by TGA and GPC analysis. Overall, this study provides an alternative route to valorize the spent catalyst from flue gas denitrogenation by applying as a catalyst to produce high quality bio-oil production in the biomass HTL process.

Catalytic solar hydropyrolysis of the Chlamydomonas reinhardtii microalgae

Hydrogen (H2) and bio-oil production from renewable sources are promising technologies in the energy sector. Particularly, the use of microalgae as a biomass source in the catalytic pyrolysis process in a hydrogen atmosphere is an encouraging approach in the production of high-quality bio-oil. This study combines two forms of harnessing renewable energy: (1) production of H2 through alkaline electrolysis with sunlight as the energy source, and (2) the production of bio-oil through catalytic hydropyrolysis of microalgae using solar energy as a thermal source in biomass degradation. The effects of catalyst (hydrotalcite precursor) percentage (C) and reaction time (t) on the product distribution and bio-oil content are analyzed. An average bio-oil yield of 45.77% is achieved using ex situ catalytic solar hydropyrolysis, which reaches up to 48.83% under optimal experimental conditions. The hydrogen atmosphere contributes to reducing oxygenated compounds and using a catalyst reduces nitrogenous compounds and raises the hydrocarbon level in the liquid fraction. The bio-oil composition is found to reach 37% of hydrocarbons.

Comparative chemical analysis of pyrolyzed bio oil using online TGA-FTIR and GC-MS

The present study proposed successfully TG-FTIR as a novel technique for high quality bio oil production having desirable concentration of targeted products especially phenols and acids. TG-FTIR analysis of pine waste was performed to calculate yield of desirable chemical compounds at different temperature ranged 350−600 °C. While, bio oil was produced at each corresponded temperatures and GC–MS analysis was carried out to support TG-FTIR analysis which showed high consistency. Additionally, efficient extraction of phenolic compounds was performed via complex method using Ca2+ as a complex agent under alkaline conditions which showed that 95 % phenols were extracted successfully. Meanwhile, production of calcium acetate in residue bio oil turns this study highly valuable for future scientific research.

Catalytic hydrothermal liquefaction of microalgae over mesoporous silica-based materials with site-separated acids and bases

In this study, four kinds of porous silica-based materials with site-separated acids and bases were prepared, the catalysts possess both micropores and mesopores with a specific surface areas ranging from 764 m2/g to 1016 m2/g. Moreover, the effects of the catalysts on the yield and quality of bio-oil derived from hydrothermal liquefaction (HTL) of microalgae Chlorella were investigated. The results showed that the catalyst had no obvious change on the bio-oil yield, but they exhibited good performance in the improving of bio-oil quality. Catalyst with acids inside and outside of the pores worked best in denitrification of the bio-oil while catalyst with bases inside and outside of the pores achieved the minimum sulfur content of the bio-oil (0.65%). GC–MS analysis indicated that the catalyst with site-separated acids and bases showed magnified selectivity to hydrocarbons (over 50% of peak area). Furthermore, the catalyst could increase the low boiling fraction (<400 °C) of the bio-oil to from 68% to 81%. At last, the plausible mechanism of catalyst on HTL was proposed. This study could provide valuable information for production of high quality bio-oil in future researches.

Potentiality of combined catalyst for high quality bio-oil production from catalytic pyrolysis of pinewood using an analytical Py-GC/MS and fixed bed reactor

The aim of this study was to investigate the potential of combined catalyst (ZSM-5 and CaO) for high quality bio-oil production from the catalytic pyrolysis of pinewood sawdust that was performed in Py-GC/MS and fixed bed reactor at 500 °C. In Py-GC/MS, the maximum yield of aromatic hydrocarbon was 36 wt% at biomass to combined catalyst ratio of 1:4 where the mass ratio of ZSM-5 to CaO in the combined catalyst was 4:1. An increasing trend of phenolic compounds was observed with an increasing amount of CaO, whereas the highest yield of phenolic compounds (31 wt%) was recorded at biomass to combined catalyst ratio of 1:4 (ZSM-5: CaO - 4:1). Large molecule compounds could be found to crack into small molecules over CaO and then undergo further reactions over zeolites. The water content, higher heating value, and acidity of bio-oil from the fixed bed reactor were 21%, 24.27 MJkg−1, and 4.1, respectively, which indicates that the quality of obtained bio-oil meets the liquid biofuel standard ASTM D7544-12 for grade G biofuel. This research will provide a significant reference to produce a high-quality bio-oil from the catalytic pyrolysis of woody biomass over the combined catalyst at different mass ratios of biomass to catalyst.

Experimental studies on high-quality bio-oil production via pyrolysis of Azolla by the use of a three metallic/modified pyrochar catalyst

In this study, the potential of the pyrolysis method to overcome the negative effects of Azolla-filiculoides in infected areas was thoroughly investigated. Non-catalytic pyrolysis experiments were conducted at a temperature range of 400–700 °C. The highest possible bio-oil yield (35 wt%) was attained at 500 °C. To achieve the best chemical composition of bio-oil and higher amount of synthesis gas the catalytic pyrolysis were conducted in a dual-bed quartz reactor at the optimum temperature (500 °C). Although, all three catalysts (pyro-char, modified pyro-char (MPC), and Mg-Ni-Mo/MPC) showed almost an impressive performance in promotion of the common reactions, Mg-Ni-Mo/MPC catalyst have illustrated the stunning results by increasing the percentage of furan compounds from 5.25% to 33.07%, and decreasing the acid compounds from 25.56% to 9.09%. Using GC–MS and GC-FID liquid and gaseous products were fully analyzed. The carbon-based catalysts were also evaluated via FTIR, FESEM, EDX, and BET analyses.

An overview of catalysts in biomass pyrolysis for production of biofuels

In-situ catalytic pyrolysis of biomass has been extensively studied in recent years for cost-competitive production of high quality bio-oil. To achieve that, numerous catalysts have been studied to facilitate in-situ upgrading of low-grade condensable vapors (bio-oil) by converting oxygenated compounds and large-molecule species. In this review, these catalysts are categorized in different families and a systematic evaluation of the catalyst effects on pyrolysis products and their characteristics is carried out with respect to the scale of the experimental setup. Among these catalysts, microporous zeolites are considered as most promising in terms of performance and the potential to tailor the desired bio-oil properties. More specifically, the prominent advantages of zeolites include efficient deoxygenation and molecular weight reduction of the resultant bio-oil, while the main drawbacks are decreases in the yield of bio-oil’s organic phase and catalyst deactivation by coke deposition. In addition to the zeolite-based catalysts, other catalysts including mesoporous aluminosilicates, a widely-applied class of catalysts used for deoxygenation of bio-oil as well as alkaline compounds are also reviewed and discussed herein. The research on the latter has not been extensive but the preliminary results have revealed their potential for deoxygenation of bio-oil, production of hydrocarbons, and reduction of undesired compounds. Nevertheless, these catalysts need to be further investigated systematically. Overall, further development of dedicated catalysts for selective deoxygenation and cracking of bio-oil would be essential for scaling up the existing pyrolysis technologies to achieve commercial production of biofuels through pyrolysis.

High quality bio-oil production from catalytic microwave-assisted pyrolysis of pine sawdust

The catalytic microwave-assisted pyrolysis of pine sawdust using SiC and Ni modified HZSM-5 as microwave absorbent and catalyst for high quality bio-oil production was investigated. The Ni modified HZSM-5 catalyst was successfully prepared through the co-precipitation method and further characterized by X-ray diffraction (XRD) and surface area and pore size analyses. The product yield results showed that Ni modified HZSM-5 catalyst decreased the bio-oil yield and increased the gas yield. Gas chromatography-mass spectrometry (GC-MS) analysis showed that the bio-oil mainly contained alcohols, aldehydes, ketones, carboxylic acids, furans, and phenolics. The Ni modified HZSM-5 catalyst dramatically decreased the carboxylic acids and ketones content, while it remarkably increased phenolics, especially the phenol content. The physical property analysis showed that the bio-oil with the Ni modified HZSM-5 catalyst had a higher calorific value. Therefore, under microwave-assisted pyrolysis conditions, Ni modified HZSM-5 catalyst had a remarkable effect for improving the quality of bio-oil.

Microwave assisted co-pyrolysis of biomasses with polypropylene and polystyrene for high quality bio-oil production

In this study, co-pyrolysis of five lignocellulosic biomass residues, viz. groundnut shell (G), bagasse (B), rice husk (RH), Prosopis juliflora (PJF) and mixed wood sawdust (MWSD), with two synthetic plastics, polypropylene (PP) and polystyrene (PS), was conducted to improve the quality of bio-oil. Equal composition of biomass and plastic was pyrolyzed at 450 W microwave power using graphite susceptor, and the yields of bio-oil, char and gas fractions were determined. The bio-oil yields from PS-biomass blends varied in the range of 51–60 wt%, with maximum yield obtained from PS-MWSD, while that from PP-biomass blends were 25–41 wt% with maximum yield obtained from PP-RH. The higher heating value of co-pyrolysis bio-oil was high (38–42 MJ kg−1) as compared to bio-oil obtained from only biomass pyrolysis (20–30 MJ kg−1). Energy yield of co-pyrolysis bio-oil was significantly higher with PS mixtures (73–81%) than PP mixtures (32–62%). Importantly, the bio-oil, char and gas yields, and organic composition of bio-oil were non-additive with respect to that obtained from pyrolysis of the individual feedstocks. The presence of PS boosted the production of aromatic hydrocarbons (48–54 wt%), while PP promoted aliphatic hydrocarbons (19–33 wt%) in co-pyrolysis bio-oil. Specifically, high selectivity towards alkanes in bio-oil was obtained from PP-RH mixture. Co-pyrolysis bio-oil contained less moisture with lower acidity compared to pyrolysis bio-oil. RH-PS and RH-PP mixtures were shown to be the better biomass-plastic combinations from the viewpoint of recovering high energy in bio-oil. The microwave co-pyrolysis process efficiency was also high (63–68%) and promising.

Bench scale catalytic fast pyrolysis of empty fruit bunches over low cost catalysts and HZSM-5 using a fixed bed reactor

The performance of HZSM-5 and low cost catalysts, such as the spent fluid catalytic cracking (FCC) catalyst, bentonite, dolomite, and olivine, on the production of high-quality bio-oil during the catalytic pyrolysis of empty fruit bunches (EFBs) was compared in a bench scale fixed bed reactor. The spent FCC and HZSM-5 catalysts showed higher cracking performance than bentonite, dolomite, and olivine. The catalytic pyrolysis of EFB over the spent FCC catalyst showed higher selectivity to phenol (31.5%) and alkyl phenols (26.0%) due to the effective dealkoxylation of guaiacols and syringols, whereas HZSM-5 provided the higher selectivity to aromatic hydrocarbons (40.4%). The catalytic pyrolysis of EFB over the spent FCC catalyst and HZSM-5 produced bio-oil with a higher heating value (28.44–31.18 MJ/kg) than other bio-oils obtained over bentonite (27.89 MJ/kg) and olivine (16.83 MJ/kg). The bio-oils obtained from the catalytic pyrolysis of EFB over the spent FCC and HZSM-5 catalysts also had a lower viscosity (7.0–13.5 mm2/s) than those (13.8–22.1 mm2/s) over the other catalysts, even after accelerated aging at 80 °C for 1 day.

Hydrothermal liquefaction of biomass: Influence of temperature and biomass composition on the bio-oil production

Hydrothermal liquefaction is a promising process for the production of high quality bio-oil from biomass. Aim of this study is to investigate the effect of temperature and biomass composition on the yield and quality of bio-oils produced from three different biomass such as natural hay, oak wood and walnut shell. The hydrothermal liquefaction of cellulose was also investigated. The experimental tests, conducted in water sub-critical conditions, were carried out in a microreactor in a temperature range of 240–320°C with a reaction time of 30min. All the products of the process were analyzed and characterized by elemental analysis and GC–MS. It was observed an increase of the bio-oil yields with the lignin content of biomass, being the maximum bio-oil yield obtained for walnut shell and the minimum one for cellulose. This trend is representative of the obtained bio-oils composition, where the phenolic compounds are the major constituents, while the other identified compounds were mainly alcohols, ketones and aldehydes.

Bio-oil production from sequential two-step catalytic fast microwave-assisted biomass pyrolysis

A sequential two-step fast microwave-assisted pyrolysis (fMAP) for high quality bio-oil production was investigated. In the process, fMAP was followed by catalytic cracking and upgrading using a packed bed catalyst reactor with HZSM-5 as the catalyst. Effects of pyrolysis temperature, catalyst loading, and catalyst bed temperature on the product distribution were investigated. Results showed that maximum bio-oil and aromatic hydrocarbons yields were obtained when pyrolysis temperature reached 550°C With the increase in the catalyst loading, the bio-oil yield decreased linearly while the aromatic hydrocarbons yield increased. The catalyst bed temperature also has a significant effect on the product chemical profiles. The aromatic hydrocarbons proportion of the bio-oil was found to increase with increasing catalyst bed temperature and reached its maximum of 26.20% at 425°C. In addition, coke yield increased with increasing catalyst to biomass ratio and decreasing catalyst bed temperature.