Search Results (44)

This study aims to assess the by-products generated through the thermal and catalytic pyrolysis of the organic matter and paper fractions of municipal solid waste (MSW) in different socioeconomic regions, through the yields of reaction products (bio-oil, biochar, H₂O, and gas), acid value and chemical composition of bio-oils, and characterization of biochar, on a laboratory scale. The organic matter and paper segregated from the gravimetric composition of the total waste sample were subjected to drying, crushing, and sieving pre-treatment. The experiments were carried out at 450 °C and 1.0 atmosphere, and at 400 °C and 475 °C and 1.0 atmosphere, using a basic catalyst, Ca(OH)₂, at 10.0% by mass, in discontinuous mode. The bio-oil was characterized by acidity value and the chemical functions present in the bio-oil identified by FT-IR, NMR, and composition by GC-MS. The biochar was characterized by SEM/EDS and XRD. The bio-oil yield increased with the addition of the catalyst and the pyrolysis temperature. For catalytic pyrolysis, bio-char and gas yields increased slightly with the Ca(OH)₂ content, while bio-oil and H₂O phases remained constant. The GC-MS of the liquid reaction products identified the presence of hydrocarbons and oxygenates, as well as nitrogen-containing compounds, including amides and amines. The acidity of the bio-oil decreased with the addition of the basic catalyst in the process. The concentration of hydrocarbons in the bio-oil appeared with the addition of the catalyst in the catalytic pyrolysis process as the catalytic deoxygenation of fatty acid molecules occurred, through decarboxylation/decarbonylation, producing aliphatic and aromatic hydrocarbons, introducing the basic catalyst into the thermal process. Full article

This research contributes to advance the sustainable production of biofuels and provides insights into the energy and exergy assessment of bio-oil, which is essential for developing environmentally friendly energy production solutions. Energy and exergy analyses were performed to evaluate the pyrolysis of beech wood biomass at 500 °C in an Auger reactor. To improve the quality of the obtained bio-oil, its catalytic deoxygenation was performed within an in-line fluidized catalytic bed reactor using a catalyst based on HZSM5 zeolite modified with 5 wt.% Iron (5%FeHZSM-5). A thermodynamic analysis of the catalytic and non-catalytic pyrolysis system was carried out, as well as a comparative study of the calculation methods for the energy and exergy evaluation for bio-oil. The required heat for pyrolysis was found to be 1.2 MJ/kg_biomass in the case of non-catalytic treatment and 3.46 MJ/kg_biomass in the presence of the zeolite-based catalyst. The exergy efficiency in the Auger reactor was 90.3%. Using the catalytic system coupled to the Auger reactor, this efficiency increased to 91.6%, leading to less energy degradation. Calculating the total energy and total exergy of the bio-oil using two different methods showed a difference of 6%. In the first method, only the energy contributions of the model compounds, corresponding to the major compounds of each chemical family of bio-oil, were considered. In contrast, in the second method, all molecules identified in the bio-oil were considered for the calculation. The second method proved to be more suitable for thermodynamic analysis. The novelties of this work concern the thermodynamic analysis of a coupled system of an Auger biomass pyrolysis reactor and a fluidized bed catalytic deoxygenation reactor on the one hand, and the use of all the molecules identified in the oily phase for the evaluation of energy and exergy on the other hand. Full article

Bio-oil is a potential source for the production of alternative fuels and chemicals. In this work, Ni-V bimetallic zeolite catalysts were synthesized and evaluated in in situ catalytic hydrodeoxygenation (HDO) of pyrolysis volatiles of pine nut shell for upgraded bio-oil products. The pH and lower heating value (LHV) of the upgraded bio-oil products were improved by in situ catalytic HDO, while the moisture content and density of the oil decreased. The O/C ratio of the upgraded bio-oil products decreased significantly, and the oxygenated compounds in the pyrolysis volatiles were converted efficiently via deoxygenation over Ni-V zeolite catalysts. The highest HDO activity was obtained with NiV/MesoY, where the obtained bio-oil had the lowest O/C atomic ratio (0.27), a higher LHV (27.03 MJ/kg) and the highest selectivity (19.6%) towards target arenes. Owing to the more appropriate pore size distribution and better dispersion of metal active sites, NiV/MesoY enhanced the transformation of reacting intermediates, obtaining the dominant products of phenols and arenes. A higher HDO temperature improved the catalytic activity of pyrolysis volatiles to form more deoxygenated arenes. Higher Ni loading could generate more metal active sites, thus promoting the catalyst’s HDO activity for pyrolysis volatiles. This study contributes to the development of cost-efficient and eco-friendly HDO catalysts, which are required for producing high-quality biofuel products. Full article

The main goal of this study is to investigate the possibility of using residual materials (biomass derived from used cooking oils and lignocellulosic biomass from plant waste) on a large scale for producing renewable fuels and, in particular, the best way to collect them. The methodology of Geographic Information Systems (GIS) as well as spatial analysis (SA) techniques were used to investigate the Greek case for this. The data recorded in the geographic database were quantities of waste cooking and household oils as well as quantities of lignocellulosic biomass. The most common global and local indices of spatial autocorrelation were used. Concerning the biomass derived from used cooking oils, it was found that their quantities were important (163.17 million L/year), and these can be used to produce green diesel in the context of the circular economy. Although the dispersion of the used cooking oils was wide, there is no doubt that their concentration in large cities and tourist areas is higher. This finding suggests a collection process that could be carried out mainly in these areas through the development of small autonomous collection units in each neighborhood and central processing plants in small regional units. The investigation of the geographical–spatial distribution of residual lignocellulosic biomass showed the geographical fragmentation and heterogeneity of the distributions. The quantities recorded were significant (4.5 million tons/year) but widely dispersed, such that the cost of collecting and transporting the biomass to central processing plants could be prohibitive. The “geography” of the problem itself suggests solutions of small mobile collection units in every part of the country. The lignocellulosic biomass would be collected and converted in situ into bio-oil by rapid pyrolysis carried out in a tanker vehicle. This would transport the produced bio-oil to the nearest oil refineries for the conversion of bio-oil into biofuels through deoxygenation processes. Full article

Lignin is considered a renewable source for the production of valuable aromatic chemicals and liquid fuel. Solvent depolymerization of lignin is a fruitful strategy for the valorization of lignin. However, Kraft lignin is highly prone to produce char (a by-product) during the hydrothermal depolymerization process due to its poor solubility in organic solvents. Therefore, the minimization of char formation remains challenging. The purpose of the present study was to fractionate Kraft lignin in methanol to obtain low-molecular-weight fractions that could be further depolymerized in supercritical methanol to produce aromatic monomers and to suppress char formation. The results showed that the use of methanol-soluble lignin achieved a bio-oil yield of 45.04% and a char yield of 39.6% at 280 °C for 2 h compared to 28.57% and 57.73%, respectively, when using raw Kraft lignin. Elemental analysis revealed a high heating value of 30.13 MJ kg⁻¹ and a sulfur content of only 0.09% for the bio-oil derived from methanol-soluble lignin. The methanol extraction process reduced the oxygen content and increased the hydrogen and carbon contents in the modified lignin and bio-oil, indicating that the extracted lignin fraction had an enhanced deoxygenation capability and a higher energy content. These findings highlight the potential of methanol-soluble Kraft lignin as a valuable resource for sustainable energy production and the production of aromatic compounds. Full article

This study investigates a continuous deoxygenation of bio-oil vapor in a catalytic fixed-bed reactor coupled to a continuous drop tube reactor (DTR) for biomass pyrolysis. Beech wood pyrolysis was initially examined without catalysts at various temperatures (500–600 °C). The products were characterised using GC-MS, Karl Fischer titration, GC-FID/TCD, and thermogravimetric analysis. The highest bio-oil yield (58.8 wt.%) was achieved at 500 °C with a 500 mL/min N₂ flow rate. Subsequently, ex situ catalytic pyrolysis was performed using an HZSM-5 catalyst in a fixed-bed reactor at a DTR outlet, operating at 425 °C, 450 °C, and 500 °C. The HZSM-5 catalyst exhibited declining deoxygenation efficiency over time, which was evidenced by decreasing conversion rates of chemical families. Principal component analysis was employed to interpret the complex dataset, facilitating a visualisation of the relationships between the experimental conditions and product compositions. This study highlights the challenges of continuous operation as experimental durations were limited to 120 min due to clogging issues. This research contributes to understanding continuous biomass pyrolysis coupled with catalytic deoxygenation, providing insights into the reactor configuration, process parameters, and catalyst performance crucial for developing efficient and sustainable biofuel production processes. Full article

Aiming at problems such as low energy utilization efficiency and the high oxygen content of liquid products in the process of conventional biomass conversion to prepare liquid fuels, the deoxygenation pyrolysis technology route of larch based on microwave heating was proposed in this paper. Two kinds of calcium–iron composite oxygen carriers, including Ca₂Fe₂O₅ with iron ore structure and CaFe₂O₄ with spinel structure, were successfully synthesized. The results showed that the selectivity of ideal products was improved under the action of single iron-based oxygen carriers; however, the deoxygenation effect was undesirable. Under the action of CaFe₂O₄, the selectivity of aromatics was increased to 27.17% and the selectivity of phenols was decreased to 36.46%, which mainly existed in the form of O₁P with low oxygen content. The oxygen content of bio-oil was reduced to 27.70% and the calorific value was increased to 29.05 MJ/kg, thus leading to a great improvement in the quality of liquid products. After the pyrolysis reaction, the Fe2P_3/2 XPS peak of CaFe₂O₄ shifted to a higher binding energy and was characterized as higher valence of iron oxide, which proved its “oxygen grabbing” capacity in microwave pyrolysis. The deoxygenation conversion of larch without an external hydrogen supply was achieved. Full article

The goal of this research work was to investigate the improvement of bio-oil issued from beechwood biomass through catalytic de-oxygenation. Pyrolysis was conducted in an auger reactor and the catalytic treatment was performed in a fluidized catalytic bed reactor. Lab-synthesized Fe-HZSM-5 catalysts with different iron concentrations were tested. BET specific surface area, BJH pore size distribution, and FT-IR technologies were used to characterize the catalysts. Thermogravimetric analysis was used to measure the amount of coke deposited on the catalysts after use. Gas chromatography coupled to mass spectrometry (GC-MS), flame ionization detection (GC-FID), and thermal conductivity detection (GC-TCD) were used to identify and quantify the liquid and gaseous products. The pyrolysis temperature proved to be the most influential factor on the final products. It was observed that a pyrolysis temperature of 500 °C, vapor residence time of 18 s, and solid residence time of 2 min resulted in a maximum bio-oil yield of 53 wt.%. A high percentage of oxygenated compounds, such as phenolic compounds, guaiacols, and the carboxylic acid group, was present in this bio-oil. Catalytic treatment with the Fe-HZSM-5 catalysts promoted gas production at the expense of the bio-oil yield, however, the composition of the bio-oil was strongly modified. These properties of the treated bio-oil changed as a function of the Fe loading on the catalyst, with 5%Fe-HZSM-5 giving the best performance. A higher iron loading of 5%Fe-HZSM-5 could have a negative impact on the catalyst performance due to increased coke formation. Full article

Bio-oil produced via fast pyrolysis, irrespective of the biomass source, faces several limitations, such as high water content, significant oxygenated compound concentration (35–40 wt.%), a low heating value (13–20 MJ/kg), and poor miscibility with fossil fuels. These inherent drawbacks hinder the bio-oil’s desirable properties and usability, highlighting the necessity for advanced processing techniques to overcome these challenges and improve the bio-oil’s overall quality and applicability in energy and industrial sectors. To address the limitations of bio-oil, a magnetic bimetallic oxide catalyst supported on activated rice straw biochar (ZrO₂-Fe₃O₄/AcB), which has not been previously employed for this purpose, was developed and characterized for upgrading rice straw bio-oil in supercritical butanol via esterification. Furthermore, the silica in the biochar, combined with the Lewis acid sites provided by ZrO₂ and Fe₃O₄, offers Brønsted acid sites. This synergistic combination enhances the bio-oil’s quality by facilitating esterification, deoxygenation, and mild hydrogenation, thereby reducing oxygen content and increasing carbon and hydrogen levels. The effects of variables, including time, temperature, and catalyst load, were optimized using response surface methodology (RSM). The optimal reaction conditions were determined using a three-factor, one-response, and three-level Box-Behnken design (BBD). The ANOVA results at a 95% confidence level indicate that the results are statistically significant due to a high Fisher’s test (F-value = 37.07) and a low probability (p-value = 0.001). The minimal difference between the predicted R² and adjusted R² for the ester yield (0.0092) suggests a better fit. The results confirm that the optimal reaction conditions are a catalyst concentration of 1.8 g, a reaction time of 2 h, and a reaction temperature of 300 °C. Additionally, the catalyst can be easily recycled for four reaction cycles. Moreover, the catalyst demonstrated remarkable reusability, maintaining its activity through four consecutive reaction cycles. Its magnetic properties allow for easy separation from the reaction mixture using an external magnet. Full article

Biomass can be converted into energy/fuel by different techniques, such as pyrolysis, gasification, and others. In the case of pyrolysis, biomass can be converted into a crude bio-oil around 50–75% yield. However, the direct use of this crude bio-oil is impractical due to its high content of oxygenated compounds, which provide inferior properties compared to those of fossil-derived bio-oil, such as petroleum. Consequently, bio-oil needs to be upgraded by physical processes (filtration, emulsification, among others) and/or chemical processes (esterification, cracking, hydrodeoxygenation, among others). In contrast, hydrodeoxygenation (HDO) can effectively increase the calorific value and improve the acidity and viscosity of bio-oils through reaction pathways such as cracking, decarbonylation, decarboxylation, hydrocracking, hydrodeoxygenation, and hydrogenation, where catalysts play a crucial role. This article first focuses on the general aspects of biomass, subsequent bio-oil production, its properties, and the various methods of upgrading pyrolytic bio-oil to improve its calorific value, pH, viscosity, degree of deoxygenation (DOD), and other attributes. Secondly, particular emphasis is placed on the process of converting model molecules and bio-oil via HDO using catalysts based on nickel and nickel combined with other active elements. Through these phases, readers can gain a deeper understanding of the HDO process and the reaction mechanisms involved. Finally, the different equipment used to obtain an improved HDO product from bio-oil is discussed, providing valuable insights for the practical application of this reaction in pyrolysis bio-oil production. Full article

Transition metal carbides have emerged as an attractive alternative to conventional catalysts in hydrodeoxygenation (HDO) reactions due to surface reactivity, catalytic activity, and thermodynamic stability similar to those of noble metals. In this study, the impact of varying Mo concentration in carbon nanofiber-supported catalysts for the supercritical ethanol-assisted HDO of bio-oils in an autoclave batch reactor is discussed. Raw bio-oils derived from agave bagasse and corncob through solar hydrothermal liquefaction were treated at 350 °C. Our findings indicate that the presence of Mo has a strong impact on both product yield and chemical properties. Thus, a Mo concentration of 10 wt.% is enough to obtain high deoxygenation values (69–72%), resulting in a yield of upgraded bio-oil ranging between 49.9 and 60.4%, depending on the feedstock used, with an energy content of around 35 MJ/kg. A further increase in the Mo loadings (20 and 30 wt.%) reduced the loss of carbon due to gasification and improved the bio-oil yields up to 62.6 and 67.4%, without compromising the product quality. Full article

This study aims to investigate the catalytic co-pyrolysis of beech wood with polystyrene as a synergic and catalytic effect on liquid oil production. For this purpose, a tubular semi-continuous reactor under an inert nitrogen atmosphere was used. Several zeolite catalysts were modified via incipient wetness impregnation using iron and/or nickel. The liquid oil recovered was analyzed using GC-MS for the identification of the liquid products, and GC-FID was used for their quantification. The effects of catalyst type, beechwood-to-polystyrene ratio, and operating temperature were investigated. The results showed that the Fe/Ni-ZSM-5 catalyst had the best deoxygenation capability. The derived oil was mainly constituted of aromatics of about 92 wt.% for the 1:1 mixture of beechwood and polystyrene, with a remarkably high heating value of around 39 MJ/kg compared to 18 MJ/kg for beechwood-based bio-oil. The liquid oil experienced a great reduction in oxygen content of about 92% for the polystyrene–beechwood 50-50 mixture in comparison to beechwood alone. The catalytic and synergetic effects were more realized for high beechwood percentages as a 75-25 beechwood–polystyrene mix. Regarding the temperature variation between 450 and 600 °C, the catalyst seemed to deactivate faster at higher temperatures, thus constituting a quality reduction in the pyrolytic oil in high-temperature ranges. Full article

The catalytic potential of Na and LiNa fly ash (FA) obtained through a simple solid-state synthesis was investigated for the pyrolysis of Isochrysis sp. microalgae using a fixed bed reactor at 500 °C. While both LiNa-FA and Na-FA catalysts reduced the bio-oil yield and increased char and gas production, LiNa-FA was found to enhance the quality of the resulting bio-oil by decreasing its oxygen content (−25 wt.%), increasing paraffins and olefins and decreasing its acidity. The deoxygenation activity of LiNa-FA was attributed to the presence of weak and mild base sites, which enabled dehydration, decarboxylation, ketonisation, and cracking to form olefins. The bio-oil generated with LiNa-FA contained higher amounts of alkanes, alkenes, and carbonated esters, indicating its capacity to chemisorb and partially desorb CO₂ under the studied conditions. These findings suggest that LiNa-FA catalysts could be a cost-effective alternative to acidic zeolites for in situ deoxygenation of microalgae to biofuels. Full article

This review provides insights into the current research on pyrolytic bio-oil obtained from different feedstock regarding upgrading techniques and applications such as energy, fuels, chemicals, and carbon materials. Raw bio-oil is not appropriate for transportation and ignition due to undesired properties; therefore, several challenges have been reported regarding its suitable market application. For liquid biofuel production, thermochemical pathways, particularly hydrogenation and deoxygenation, must be carried out, and for chemical production, liquid solvents are mostly used via physical separation. The main issues related to downstream processes with environmental and economic assessment are also covered. The analysis indicates that the major bottlenecks for commercial applications of upgraded bio-oil are the initial stage (upgrading techniques), high production costs, and pilot scale production. Finally, future directions are addressed for the improvement of bio-oil upgrading. Full article

Because of the global necessity to decrease CO₂ emissions, biomass-based fuels have become an interesting option to explore; although, bio-oils need to be upgraded, for example, by catalytic hydrodeoxygenation (HDO), to reduce oxygen content. This reaction generally requires bifunctional catalysts with both metal and acid sites. For that purpose, Pt-Al₂O₃ and Ni-Al₂O₃ catalysts containing heteropolyacids (HPA) were prepared. HPAs were added by two different methods: the impregnation of a H₃PW₁₂O₄₀ solution onto the support and a physical mixture of the support with Cs_2.5H_0.5PW₁₂O₄₀. The catalysts were characterized by powder X-ray diffraction, Infrared, UV-Vis, Raman, X-ray photoelectron spectroscopy and NH₃-TPD experiments. The presence of H₃PW₁₂O₄₀ was confirmed by Raman, UV-Vis and X-ray photoelectron spectroscopy, while the presence of Cs_2.5H_0.5PW₁₂O₄₀ was confirmed by all of the techniques. However, HPW was shown to strongly interact with the supports, especially in the case of Pt-Al₂O₃. These catalysts were tested in the HDO of guaiacol, at 300 °C, under H₂ and at atmospheric pressure. Ni-based catalysts led to higher conversion and selectivity to deoxygenated compound values, such as benzene. This is attributed to both a higher metal and acidic contents of these catalysts. Among all tested catalysts, HPW/Ni-Al₂O₃ was shown to be the most promising, although it suffered a more severe deactivation with time-on-stream. Full article