A review on selective production of value-added chemicals via catalytic pyrolysis of lignocellulosic biomass

Benzenoid Aromatics from Renewable Resources

In this Review, all known chemical methods for the conversion of renewable resources into benzenoid aromatics are summarized. The raw materials that were taken into consideration are CO2; lignocellulose and its constituents cellulose, hemicellulose, and lignin; carbohydrates, mostly glucose, fructose, and xylose; chitin; fats and oils; terpenes; and materials that are easily obtained via fermentation, such as biogas, bioethanol, acetone, and many more. There are roughly two directions. One much used method is catalytic fast pyrolysis carried out at high temperatures (between 300 and 700 °C depending on the raw material), which leads to the formation of biochar; gases, such as CO, CO2, H2, and CH4; and an oil which is a mixture of hydrocarbons, mostly aromatics. The carbon selectivities of this method can be reasonably high when defined small molecules such as methanol or hexane are used but are rather low when highly oxygenated compounds such as lignocellulose are used. The other direction is largely based on the multistep conversion of platform chemicals obtained from lignocellulose, cellulose, or sugars and a limited number of fats and terpenes. Much research has focused on furan compounds such as furfural, 5-hydroxymethylfurfural, and 5-chloromethylfurfural. The conversion of lignocellulose to xylene via 5-chloromethylfurfural and dimethylfuran has led to the construction of two large-scale plants, one of which has been operational since 2023.

Straw Tar Epoxy Resin for Carbon Fiber-Reinforced Plastic: A Review

The massive consumption of fossil fuels has led to the serious accumulation of carbon dioxide gas in the atmosphere and global warming. Bioconversion technologies that utilize biomass resources to produce chemical products are becoming widely accepted and highly recognized. The world is heavily dependent on petroleum-based products, which may raise serious concerns about future environmental security. Most commercially available epoxy resins (EPs) are synthesized by the condensation of bisphenol A (BPA), which not only affects the human endocrine system and metabolism, but is also costly to produce and environmentally polluting. In some cases, straw tar-based epoxy resins have been recognized as potential alternatives to bisphenol A-based epoxy resins, and are receiving increasing attention due to their important role in overcoming the above problems. Using straw tar and lignin as the main raw materials, phenol derivatives were extracted from the middle tar instead of bisphenol A. Bio-based epoxy resins were prepared by replacing epichlorohydrin with epoxylated lignin to press carbon fiber sheets, which is a kind of bio-based fine chemical product. This paper reviews the research progress of bio-based materials such as lignin modification, straw pyrolysis, lignin epoxidation, phenol derivative extraction, and synthesis of epoxy resin. It improves the performance of carbon fiber-reinforced plastic (CFRP) while taking into account the ecological and environmental protection, so that the epoxy resin is developed in the direction of non-toxic, harmless and high-performance characteristics, and it also provides a new idea for the development of bio-based carbon fibers.

Influence of anionic species on the low temperature pyrolysis performance of heated tobacco sheets catalyzed by sodium salts

Development of low temperature catalytic pyrolysis technology for heated tobacco sheets is expected to increase the aroma of heated tobacco products and improve their overall smoking quality. In this study, the low temperature pyrolysis performances of heated tobacco sheets catalyzed by various anionic sodium salts were investigated using TG-DTG, Py-GC-MS technology and smoke routine chemical composition analysis. The results showed that the total weight loss between 100°C and 300°C increased by 7.8%-13.15% after adding various anionic sodium salts, among which, sodium acetate and sodium tartrate showed a relatively higher weight loss. The relative content of free hydroxyacetone, furfuryl alcohol, butyrolactone and megastigmatrienone in the pyrolysis gas increased, while the relative content of free nicotine decreased. With the change of anionic species, the catalytic decomposition ability of cellulose, lignin, and other substances may change, resulting in the distribution alteration of compounds in the pyrolysis gas. After adding sodium acetate and sodium citrate, the release of total particulate matter (TPM), glycerol, and nicotine in flue gas increased. Overall, the addition of sodium acetate and sodium citrate showed a higher low temperature pyrolysis performance of heated tobacco sheets. The research results in this paper provide data support for changing the low temperature catalytic pyrolysis performance of heated tobacco sheets by adjusting the type of anions in sodium salts.

Preparation and Structural Analysis of a Water-Soluble Aminated Lignin

Lignin is insoluble in water, thereby limiting its use in the synthesis of adhesives. Therefore, in this study, an aminated lignin compound was prepared through a lignin amination reaction to increase the amount of raw lignin material that can be used in the synthesis of adhesives; moreover, structural analysis was conducted. The main result of this was the introduction of amino groups into phenolic hydroxyl groups in the hydrolyzing lignin from the raw lignin materials, thus generating the product of aminated lignin. The resulting particle sizes were about 100 nm, the average molecular weight was 57,627 g/mol, and the water solubility of the aminated lignin was about 0.45 g/100 mL. Therefore, the water solubility of raw lignin was greatly improved. The proposed reaction mechanism of phenolic hydroxyl groups and carboxylic acid groups in lignin is a reaction with ammonia molecules; thus, the successful introduction of amino groups generated the aminated lignin compounds. Hence, this article enriches the scientific theory of lignin reactions and provides a reference for the widespread application of raw lignin materials in the field of adhesives.

Design and Advanced Manufacturing of NU-1000 Metal-Organic Frameworks with Future Perspectives for Environmental and Renewable Energy Applications

Metal-organic frameworks (MOFs) represent a relatively new family of materials that attract lots of attention thanks to their unique features such as hierarchical porosity, active metal centers, versatility of linkers/metal nodes, and large surface area. Among the extended list of MOFs, Zr-based-MOFs demonstrate comparably superior chemical and thermal stabilities, making them ideal candidates for energy and environmental applications. As a Zr-MOF, NU-1000 is first synthesized at Northwestern University. A comprehensive review of various approaches to the synthesis of NU-1000 MOFs for obtaining unique surface properties (e.g., diverse surface morphologies, large surface area, and particular pore size distribution) and their applications in the catalysis (electro-, and photo-catalysis), CO2 reduction, batteries, hydrogen storage, gas storage/separation, and other environmental fields are presented. The review further outlines the current challenges in the development of NU-1000 MOFs and their derivatives in practical applications, revealing areas for future investigation.

Catalytic pyrolysis of liquor-industry waste: Product and mechanism analysis

The effects of three catalysts, namely Ni/γ-Al2O3, Fe/γ-Al2O3, and Mg/γ-Al2O3, on the three-phase products of liquor-industry waste pyrolysis were investigated in this study. Results indicated that the catalytic performance of Ni/γ-Al2O3 outperformed those of Fe/γ-Al2O3 and Mg/γ-Al2O3 significantly. The application of Ni/γ-Al2O3 facilitated the reformation of pyrolysis volatiles, leading to increased yields of H2 (174.1 mL/g), CH4 (80.7 mL/g), and CO (88.2 mL/g) by 980.00 %, 133.24 %, and 83.37 %, respectively. compared to catalyst-free conditions. The Ni/γ-Al2O3 also increased the low-level calorific value of biogas by 109.3 % compared to that under non-catalyst conditions. Moreover, Ni/γ-Al2O3 enhanced the relative concentrations of hydrocarbons in tar by 23.15 % while reducing the relative concentrations of O-species by 15.73 % compared to catalyst-free conditions through induced deoxygenation, decarboxylation, decarbonylation reactions as well as efficient steam reforming processes for tar and syngas upgrading purposes. Thus, incorporating Ni/γ-Al2O3 into the pyrolysis process represents a renewable approach for waste-to-energy conversion.

Green chemical and hybrid enzymatic pretreatments for lignocellulosic biorefineries: Mechanism and challenges

The greener chemical and enzymatic pretreatments for lignocellulosic biomasses are portraying a crucial role owing to their recalcitrant nature. Traditional pretreatments lead to partial degradation of lignin and hemicellulose moieties from the pretreated biomass. But it still restricts the enzyme accessibility for the digestibility towards the celluloses and the interaction of lignin-enzymes, nonproductively. Moreover, incursion of certain special chemical treatments and other lignin sulfonation techniques to the enzymatic pretreatment (hybrid enzymatic pretreatment) enhances the lignin structural modification, solubilization of the hemicelluloses and both saccharification and fermentation processes (SAF). This article concentrates on recent developments in various chemical and hybrid enzymatic pretreatments on biomass materials with their mode of activities. Furthermore, the issues on strategies of the existing pretreatments towards their industrial applications are highlighted, which could lead to innovative ideas to overcome the challenges and give guideline for the researchers towards the lignocellulosic biorefineries.

Understanding the multifunctionality of pyroligneous acid from waste biomass and the potential applications in agriculture

Efforts have been directed to the development of environmentally friendly processes and manufacturing of green products, use of renewable energy and more sustainable agricultural practices. Pyroligneous acid (PA) is a byproduct of biomass pyrolysis that consists of a complex mixture of bioactive substances. The complexity and richness of PA composition have opened a window for PA application in agriculture and mitigation of environmental pollution. This review brings a brief historical on the use of PA and regulatory policies adopted in Brazil, China, Japan and Thailand for PA application in agriculture. The composition and stability of PAs of several origins are presented, together with a discussion of the use of PA to boost plant growth and crop productivity, remove toxic metals from soil, inhibit soil ureases, mitigate the emission of greenhouse gases, control phytopathogen proliferation and weed dissemination. A great variety of biomass types are reported as feedstock to produce PA with distinct chemically diverse and active substances at wide-ranging concentrations. PA has been shown to successfully improve farming practices in a more sustainable fashion. The disclosure of the mechanisms of action that drive the PA's effects, together with the pursue of safety and efficacy data in a case-by-case way to address toxicity and shelf stability, will be valuable to expand the use of PA worldwide for food production.

A review on co-pyrolysis of agriculture biomass and disposable medical face mask waste for green fuel production: recent advances and thermo-kinetic models

The Association of Southeast Asian Nations is blessed with agricultural resources, and with the growing population, it will continue to prosper, which follows the abundance of agricultural biomass. Lignocellulosic biomass attracted researchers' interest in extracting bio-oil from these wastes. However, the resulting bio-oil has low heating values and undesirable physical properties. Hence, co-pyrolysis with plastic or polymer wastes is adopted to improve the yield and quality of the bio-oil. Furthermore, with the spread of the novel coronavirus, the surge of single-use plastic waste such as disposable medical face mask, can potentially set back the previous plastic waste reduction measures. Therefore, studies of existing technologies and techniques are referred in exploring the potential of disposable medical face mask waste as a candidate for co-pyrolysis with biomass. Process parameters, utilisation of catalysts and technologies are key factors in improving and optimising the process to achieve commercial standard of liquid fuel. Catalytic co-pyrolysis involves a series of complex mechanisms, which cannot be explained using simple iso-conversional models. Hence, advanced conversional models are introduced, followed by the evolutionary models and predictive models, which can solve the non-linear catalytic co-pyrolysis reaction kinetics. The outlook and challenges for the topic are discussed in detail.

Catalytic co-pyrolysis of oil palm trunk and polypropylene with Ni-Mo/TiO2 and Ni/Al2O3: Oil composition and mechanism

Pyrolysis oil from oil palm biomass can be a sustainable alternative to fossil fuels and the precursor for synthesizing petrochemical products due to its carbon-neutral properties and low sulfur and nitrogen content. This work investigated the effect of applying mesoporous acidic catalysts, Ni-Mo/TiO₂ and Ni/Al₂O_3, in a catalytic co-pyrolysis of oil palm trunk (OPT) and polypropylene (PP) from 500 to 700 °C. The obtained oil yields varied between 12.67 and 19.50 wt.% and 12.33-17.17 wt.% for Ni-Mo/TiO₂ and Ni/Al₂O₃, respectively. The hydrocarbon content in oil significantly increased up to 54.07-58.18% and 37.28-68.77% after adding Ni-Mo/TiO₂ and Ni/Al₂O₃, respectively. The phenolic compounds content was substantially reduced to 8.46-20.16% for Ni-Mo/TiO₂ and 2.93-14.56% for Ni/Al₂O₃. Minor reduction in oxygenated compounds was noticed from catalytic co-pyrolysis, though the parametric effects of temperature and catalyst type remain unclear. The enhanced deoxygenation and cracking of phenolic and oxygenated compounds and the PP decomposition resulted in increased hydrocarbon production in oil during catalytic co-pyrolysis. Catalyst addition also promoted the isomerization and oligomerization reactions, enhancing the formation of cyclic relative to aliphatic hydrocarbon.

Heterogenization of a Tungstosilicic Acid Catalyst for Esterification of Bio-Oil Model Compound

Based on a prior demonstration of the high activity of a homogeneous tungstosilicic acid catalyst for the esterification of acetic acid as bio-oil model compound, a further study has been undertaken in an attempt to heterogenize the catalyst. Tungsten oxide was supported on amorphous silica (W/A150) using incipient wetness impregnation and incorporated into the structure of structured silica (W-KIT-5) via a one-step hydrothermal synthesis. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), physisorption (BET), and temperature-programmed desorption of ammonia (NH3-TPD). Both series were evaluated for the esterification of acetic acid with ethanol and compared with the homogeneous 12-tungstosilicic acid catalyst. The result of XRD analysis suggests the average crystallite size of the W oxide nanoparticles on both supports to be less than 2 nm, while XPS analysis revealed that all W existed in the W 6+ oxidation state. From the BET and NH3-TPD analyses, it was shown that the KIT-5 series had higher surface area and acidity than the W/A150 catalyst. The 10% W-KIT-5 was shown to be the best heterogeneous catalyst with the highest activity and acid conversion of about 20% and 93% of the homogeneous catalyst. Significant leaching of tungsten from both the supports occurred and will have to be solved in the future.

Current Challenges and Perspectives for the Catalytic Pyrolysis of Lignocellulosic Biomass to High-Value Products

Lignocellulosic biomass is an excellent alternative of fossil source because it is low-cost, plentiful and environmentally friendly, and it can be transformed into biogas, bio-oil and biochar through pyrolysis; thereby, the three types of pyrolytic products can be upgraded or improved to satisfy the standard of biofuel, chemicals and energy materials for industries. The bio-oil derived from direct pyrolysis shows some disadvantages: high contents of oxygenates, water and acids, easy-aging and so forth, which restrict the large-scale application and commercialization of bio-oil. Catalytic pyrolysis favors the refinement of bio-oil through deoxygenation, cracking, decarboxylation, decarbonylation reactions and so on, which could occur on the specified reaction sites. Therefore, the catalytic pyrolysis of lignocellulosic biomass is a promising approach for the production of high quality and renewable biofuels. This review gives information about the factors which might determine the catalytic pyrolysis output, including the properties of biomass, operational parameters of catalytic pyrolysis and different types of pyrolysis equipment. Catalysts used in recent research studies aiming to explore the catalytic pyrolysis conversion of biomass to high quality bio-oil or chemicals are discussed, and the current challenges and future perspectives for biomass catalytic pyrolysis are highlighted for further comprehension.

Sustainable biopolyol production via solvothermal liquefaction silvergrass saccharification residue: Experimental, economic, and environmental approach

With the rising environmental concern, sustainable chemistry should be accomplished by considering technical, economic, and environmental factors that guarantee the successful implementation of new alternative products. Hence, we performed the integrated techno-economic and life cycle assessment for two-step solvothermal liquefaction (two-pot synthesis) and simplified solvothermal liquefaction (one-pot synthesis) based on experiment results. Based on the itemized cost estimation, the unit biopolyol production costs obtained from the two-pot synthesis and one-pot synthesis were 10.0 $ kg^-1 and 2.89 $ kg^-1, respectively. To provide techno-economic guidelines for biopolyol production, profitability analysis, and uncertainty analysis were used to identify the economic feasibility of the proposed processes. In addition, the life cycle assessment results indicated that biopolyol production via the two-pot synthesis leads to a slightly lower greenhouse gas emission compared with the one-pot synthesis, which further required the use of an analytic hierarchy process to determine the best process for biopolyol production depending on the different weight points in the economic and environmental aspects. From these results, we can provide the technical performance, economic feasibility, and environmental impact of lab-scale biopolyol production from silvergrass residue, a low-cost waste of biomass saccharification.

Removal of micropollutants through bio-based materials as a transition to circular bioeconomy: Treatment processes involved, perspectives and bottlenecks

The recent increase in micropollutant levels in water bodies is a growing concern globally. The generation of new materials and techniques for wastewater treatment often involves the release of hazardous wastes and the utilization of energy related to it. This can be resolved by the synthesis of bio-based materials through the use of already released wastes and naturally occurring components, adding their value as reusable resources. These bio-based materials find wide applications for micropollutant elimination and energy tapping due to the presence of various functional groups, large surface area, high stability, and reusability. The processes involved in micropollutant elimination through biomaterials generally include adsorption and degradation. These treatment processes are suggested to depend on various operational parameters like pH, temperature, dose, reaction time, presence of other contaminants, ions, etc. in the system, which may influence the process efficiency. Understanding the potential of bio-based materials many steps can be taken towards its large-scale application to upgrade wastewater treatment plants for micropollutant elimination. Furthermore, the recent advances of bio-based materials in energy storage and conversion have widened its scope for implementation in a circular bioeconomy. The bottlenecks towards such a transition and future recommendations are also presented and discussed.

Production of biochar from rice straw and its application for wastewater remediation - An overview

The valorization of biochar as a green and low-cost adsorbent provides a sustainable alternative to commercial wastewater treatment technologies that are usually chemical intensive and expensive. This review presents an in-depth analysis focusing on the rice straw-derived biochar (RSB) for removal of various types of contaminants in wastewater remediation. Pyrolysis is to date the most established technology to produce biochar. Subsequently, biochar is upgraded via physical, chemical or hybrid activation/modification techniques to enhance its adsorption capacity and robustness. Thus far, acid-modified RSB is able to remove metal ions and organic compounds, while magnetic biochar and electrochemical deposition have emerged as potential biochar modification techniques. Besides, temperature and pH are the two main parameters that affect the efficiency of contaminants removal by RSB. Lastly, the limitations of RSB in wastewater remediation are elucidated based on the current advancements of the field, and future research directions are proposed.

Steam Gasification of Torrefied/Carbonized Wheat Straw for H2-Enriched Syngas Production and Tar Reduction

Torrefaction/carbonization integrated with steam gasification of agricultural biomass for gas production and tar reduction was not investigated. The aim of this study was to evaluate the influence of the torrefaction/carbonization severity on H₂-enriched syngas production and tar reduction during steam gasification of wheat straw (WS). The torrefaction/carbonization experiments were initially performed at 220-500 °C to examine the effect of pretreated temperature on the fuel properties of torrefied/carbonized WS. Then, the gasification temperature (700-900 °C) was optimized at 900 °C in terms of gas formation behaviors. Afterward, steam gasification of raw and torrefied/carbonized WS feedstocks was conducted. WS carbonized at 500 °C (WS-500) possessed the highest H₂ concentration (54.21 vol%) and syngas purity (85.59%), while the maximum H₂/CO molar ratio (1.83), high carbon conversion efficiency (90.33 C%) and cold gas efficiency (109.24%) were observed for WS torrefied at 280 °C. Notably, the cumulative gas yield, H₂ yield, and syngas yield respectively reached 102.68 mmol/g, 55.66 mmol/g, and 87.89 mmol/g from steam gasification of WS-500. In addition, the carbonized WS feedstocks, especially WS-500, revealed a lower tar content. Simply put, integrating torrefaction/carbonization with steam gasification provided a novel and effective route to manufacture H₂-enriched syngas with extremely low tar content from agricultural biomass.

Cr/13X Zeolite and Zn/13X Zeolite Nanocatalysts Used in Pyrolysis of Pretreated Residual Biomass to Produce Bio-Oil with Improved Quality

By loading Cr and Zn on 13X zeolite, efficient nanocatalysts were prepared; they were characterized by different techniques and used for corn cobs pyrolysis to produce bio-oil. The corn cobs biomass (CCB) was washed with sulfuric acid 0.1 M, and the characteristics of the pretreated biomass (PTCCB) were analyzed. Pyrolysis was performed at different catalyst-to-biomass ratios (C/B), and the composition of the obtained bio-oil was determined. The results showed that the crystallinity of the nanocatalysts was slightly lower than that of the pattern 13X zeolite. The surface observation of the nanocatalysts showed the presence of pores and particles, which are quite evenly dispersed on the surface, and no difference was observed in the morphology of the Zn/13X zeolite and Cr /13X zeolite nanocatalysts. In comparison to 13X zeolite, the morphological changes, metal dispersion, and surface area decrease of both Zn/13X and Cr/13X zeolite nanocatalysts could be observed. Pyrolysis tests demonstrated that the use of Zn/13X zeolite and Cr/13X zeolite nanocatalysts could be very profitable to obtain a high conversion to hydrocarbons of the compounds containing oxygen, and consequently, the quality of the bio-oil was improved.

Effective Biotransformation of Variety of Guaiacyl Lignin Monomers Into Vanillin by Bacillus pumilus

Biotransformation has gained increasing attention due to its being an eco-friendly way for the production of value-added chemicals. The present study aimed to assess the potential of Bacillus pumilus ZB1 on guaiacyl lignin monomers biotransformation for the production of vanillin. Consequently, isoeugenol, eugenol, and vanillyl alcohol could be transformed into vanillin by B. pumilus ZB1. Based on the structural alteration of masson pine and the increase of total phenol content in the supernatant, B. pumilus ZB1 exhibited potential in lignin depolymerization and valorization using masson pine as the substrate. As the precursors of vanillin, 61.1% of isoeugenol and eugenol in pyrolyzed bio-oil derived from masson pine could be transformed into vanillin by B. pumilus ZB1. Four monooxygenases with high specific activity were identified that were involved in the transformation process. Thus, B. pumilus ZB1 could emerge as a candidate in the biosynthesis of vanillin by using wide guaiacyl precursors as the substrates.

Thermal Conversion of Sugarcane Bagasse Coupled with Vapor Phase Hydrotreatment over Nickel-Based Catalysts: A Comprehensive Characterization of Upgraded Products

In the present work, we compared the chemical profile of the organic compounds produced in non-catalytic pyrolysis of sugarcane bagasse at 500 °C with those obtained by the in-line catalytic upgrading of the vapor phase at 350 °C. The influence over the chemical profile was evaluated by testing two Ni-based catalysts employing an inert atmosphere (N2) and a reactive atmosphere (H2) under atmospheric pressure with yields of the liquid phase varying from 55 to 62%. Major changes in the chemical profile were evidenced in the process under the H2 atmosphere, wherein a higher degree of deoxygenation was identified due to the effect of synergistic action between the catalyst and H2. The organic fraction of the liquid phase, called bio-oil, showed an increase in the relative content of alcohols and phenolic compounds in the GC/MS fingerprint after the upgrading process, corroborating with the action of the catalytic process upon the compounds derived from sugar and carboxylic acids. Thus, the thermal conversion of sugarcane bagasse, in a process under an H2 atmosphere and the presence of Ni-based catalysts, promoted higher deoxygenation performance of the pyrolytic vapors, acting mainly through sugar dehydration reactions. Therefore, the adoption of this process can potentialize the use of this waste biomass to produce a bio-oil with higher content of phenolic species, which have a wide range of applications in the energy and industrial sectors.

Thermal kinetic analysis of mustard biomass with equiatomic iron-nickel catalyst and its predictive modeling

Mustard waste briquettes are commercially used as a fuel for power production in boilers, whereas the thermal kinetics of the biomass plays a vital role in deciding the process parameters. The pyrolysis process converts biomass to value-added products such as biochar, bio-oil, and hydrocarbon gases based on the heating rates and temperature. To enhance the pyrolytic activity of mustard biomass, magnetically separable and reusable FeNi alloy catalyst is investigated. The thermo-conversion properties are studied under variable heating rates with 2 and 10% FeNi particles prepared through a facile chemical reduction technique. Thermal kinetics is computed using Flynn-Wall-Ozawa (FOW) and Kissinger-Akahira-Sunose (KAS) methods. The activation energies calculated using FOW and KAS methods increase with FeNi addition in mustard while the calorific value decreases. The FeNi alloy particles with the spike-like morphology provide better metal-biomass binding resulting in higher activation energy and facilitates the easy decomposition of lignin. The 10% FeNi -mustard shows uniform conversion independent of heating rates, suitable for magnetically recoverable catalytic pyrolysis. Response surface methodology analysis predicts optimum conversion for 10% FeNi added mustard and less significance for the heating rates in concurrence with the experiments. Artificial neural network utilized to predict and validate mass loss for mustard biomass exhibits best fit for the three neural hidden layer and one output layered topology.

Lignocellulosic biomass-based pyrolysis: A comprehensive review

The efficacious application of lignocellulosic biomass for the new valuable chemicals generation curbs the excessive dependency on fossil fuels. Among the various techniques available, pyrolysis has garnered much attention for conversion of lignocellulosic biomass (encompasses cellulose, hemicellulose and lignin components) into product of solid, liquid and gases by thermal decomposition in an efficient manner. Pyrolysis conversion mechanism can be outlined as formation of char, depolymerisation, fragmentation and other secondary reactions. This paper gives a deep insight about the pyrolytic behavior of the lignocellulosic components accompanied by its by-products. Also several parameters such as reaction environment, temperature, residence time and heating rate which has a great impact on the pyrolysis process are also elucidated in a detailed manner. In addition the environmental and economical facet of lignocellulosic biomass pyrolysis for commercialization at industrial scale is critically analyzed. This article also illustrates the prevailing challenges and inhibition in implementing lignocellulosic biomass based pyrolysis with possible solution.

Selective direct conversion of aqueous ethanol into butadiene via rational design of multifunctional catalysts

The highly efficient multifunctional 3% Y–Zn0.02Zr0.02/Si-beta catalyst possessed superior butadiene selectivity and ethanol conversion in direct conversion of aqueous ethanol into butadiene.

Comparative studies on thermochemical behavior and kinetics of lignocellulosic biomass residues using TG-FTIR and Py-GC/MS

In the present study, similarities and variances in thermochemical behavior and composition of degradation products among cellulose, lignin, and agricultural residues (sawdust, black tea, barley, bagasse, rice husk, and corncob) were assessed using TG analysis, DSC, TG-FTIR, and Py-GC/MS. The experimental results indicated the temperature range of maximum mass loss between 295-430 °C for cellulose, 155-600 °C for lignin, and 150-500 °C for agricultural residues representing the feedstock's active pyrolysis region. The FTIR analysis established the presence of CO, CC, CO₂, CO, CO, and CH₄ gaseous functional groups with a strong synergistic effect. The CO₂ was the primary product in gaseous mixtures, and their yield enhanced at elevated temperature. The characteristically dependent pyrolysis product groups were anhydro-sugars (84.9%-90.1%) and furans (4.1%-5.6%) in cellulose; phenols (69.6%-77.4%) and aldehydes (5.9%-7.9%) in lignin; furans (1.4%-47.7%) and acids (15.8%-37.3%) in agricultural residues, respectively. Bagasse and corncob trailed similar thermal behavior with furans (30.8%-47.7%) as major pyrolysis products, whereas acids (83.1%-88.7%) were prevalent in rice husk. The mean values of apparent activation energy evaluated by the isoconversional Friedman method were 174.8, 123.1, 160.7-217.3 kJ mol^-1, respectively, for cellulose, lignin, and agricultural residues. The results presented comprehensive data in elucidating the influence of individual biomass components at optimized temperatures for higher selectivity of value-added chemicals and bioenergy.

Progress of the Pyrolyzer Reactors and Advanced Technologies for Biomass Pyrolysis Processing

In the future, renewable energy technologies will have a significant role in catering to energy security concerns and a safe environment. Among the various renewable energy sources available, biomass has high accessibility and is considered a carbon-neutral source. Pyrolysis technology is a thermo-chemical route for converting biomass to many useful products (biochar, bio-oil, and combustible pyrolysis gases). The composition and relative product yield depend on the pyrolysis technology adopted. The present review paper evaluates various types of biomass pyrolysis. Fast pyrolysis, slow pyrolysis, and advanced pyrolysis techniques concerning different pyrolyzer reactors have been reviewed from the literature and are presented to broaden the scope of its selection and application for future studies and research. Slow pyrolysis can deliver superior ecological welfare because it provides additional bio-char yield using auger and rotary kiln reactors. Fast pyrolysis can produce bio-oil, primarily via bubbling and circulating fluidized bed reactors. Advanced pyrolysis processes have good potential to provide high prosperity for specific applications. The success of pyrolysis depends strongly on the selection of a specific reactor as a pyrolyzer based on the desired product and feedstock specifications.

Synthesis of graphene oxide from agave fiberTequilana Weberby hydrothermal method

Lignocellulosic residues are an important biomass source in Mexico, which can be considered as starting materials for obtaining carbon materials. In this work, carbon materials were produced by pyrolysis of agave fiber (AF). The results obtained revealed that the hydrothermal process was successfully used for the synthesis of carbon fibers and subsequently potentiate the production of graphite sheets and graphene oxide (GO), after determining and optimizing the reaction conditions. The formation of graphite and GO was indicated by XRD, Raman spectroscopy and TGA thermal analysis, the latter evaluated the carbon oxidation range. Scanning electron microscope showed the samples morphology and microstructure of the AFTequilana Weberand the synthesized products (Graphite-600 °C, GO-800 °C and GO-1000 °C), being all of them carbon allotropes, they presented size and variable thickness, with potential surface characteristics useful in various industrial applications. The hydrothermal and thermal processes were considered an economic and environmental way of obtaining materials under inert conditions, especially to produce GO, which is a material that has many useful properties and a plethora of new applications, like a more affordable support for catalysts, absorbent, semiconductor.

Biochar-driven simplification of the compositions of cellulose-pyrolysis-derived biocrude oil coupled with the promotion of hydrogen generation

The corn stover originated biochar was developed to catalyze and simplify the compositions of biocrude oil from cellulose pyrolysis. The generation of common species such as furans and (anhydro)-sugars in the biocrude oil from cellulose pyrolysis was weakened remarkably in the presence of biochars, while the formation of phenol and alkylphenols was enhanced. The formation of hydrogen was favored when the biochar was presented. For example at the temperature of 600 °C and biochar to cellulose ratio of 3, about 78 vol% of hydrogen was detected, increased from around 48 vol% for non-catalytic pyrolysis. Despite 10 cycles of reuse, the biochar remained a good activity towards promoting the generation of hydrogen and monomeric phenols. This work relates to a new access to simplify the compositions of biocrude oil and produce renewable hydrogen energy through the low-cost, simple, and highly stable biochar catalyst.

Quantification of Cellulose Pyrolyzates via a Tube Reactor and a Pyrolyzer-Gas Chromatograph/Flame Ionization Detector-Based System

Pyrolysis of cellulose primarily produces 1,6-anhydro-β-d-glucopyranose (levoglucosan), which easily repolymerizes to form coke precursors in the heating zone of a pyrolysis reactor. This hinders the investigation of primary pyrolysis products as well as the elucidation of cellulose pyrolysis mechanisms, particularly because of the significant buildup of coke during slow pyrolysis. The present study discusses the applicability of a pyrolysis-gas chromatography/flame ionization detection (Py-GC/FID) system using naphthalene as the internal standard, with the aim of substantially improving the quantification of pyrolyzates during the slow pyrolysis of cellulose. This method achieved quantification of levoglucosan with a yield that was 14 times higher than that obtained from offline pyrolysis in a simple tube reactor. The high yield recovery of levoglucosan was attributed to the suppression of levoglucosan repolymerization in the Py-GC/FID system, owing to the rapid escape of levoglucosan from the heating zone, low concentration of levoglucosan in the gas phase, and rapid quenching of levoglucosan. Therefore, this method facilitated the improved quantification of primary pyrolysis products during the slow pyrolysis of cellulose, which can be beneficial for understanding the primary pyrolysis reaction mechanisms. This method can potentially be applied to other polymeric materials that produce reactive pyrolyzates.

Producción de acetinas (aditivos para combustibles) a partir de glicerol

La elevada producción de glicerol, un subproducto de bajo costo proveniente de la industria del biodiésel, ha supuesto una amenaza tanto para el medio ambiente como para la economía. La transformación de glicerol en productos de valor agregado contribuiría positivamente a la economía del biodiésel. En este artículo de revisión se describen las rutas de valorización del glicerol y se presenta la esterificación como una de las más prometedoras para la transformación de glicerol en aditivos para combustibles; igualmente, se describen los resultados más relevantes entre 2010 y 2020 relacionados con las condiciones experimentales (temperatura, relación molar y tiempo de reacción), los catalizadores heterogéneos y la actividad catalítica (en términos de la conversión del glicerol y la selectividad) para la transformación de glicerol en acetinas (monoacetina, diacetina y triacetina). Se espera que esta revisión permita abordar esta técnica de valorización de manera rentable y ambientalmente sostenible.

A comprehensive review on the factors affecting thermochemical conversion efficiency of algal biomass to energy

Algae are one of the most viable feedstock options that can be converted into different bioenergies viz., bioethanol, biobutanol, biodiesel, biomethane, biohydrogen, etc. owing to their renewable, sustainable and economic credibility features. Algal biomass to fuel biorefining process is generally classified into three categories as chemical, biochemical and thermochemical methods. The present article aims to provide a state-of-the-art review on the factors affecting the thermochemical conversion process of algal biomass to bioenergy. Further, reaction conditions of each techniques (torrefaction, pyrolysis, gasification and hydrothermal process) influence biochar, bio-oil and syngas yield were discussed. Reaction parameters or factors such as reactor temperature, residence time, pressure, biomass load/feedstock composition, catalyst addition and carrier gas flow affecting process efficiency in terms of product yield and quality were spotlighted and extensively discussed with copious literature. It also presents the novel insights on production of solid (char), liquid (bio-oil) and gaseous (syngas) biofuel through torrefaction, pyrolysis and gasification, respectively. It is found that the energy intensive drying was more efficient mode involved in thermochemical process for wet algal biomass. However other modes of thermochemical process were having unique feature on improving the product yield and quality. Among the various factors, reaction temperature and residence time were relatively more important factors which affected the process efficiency. The other factors signposted in this review will lay a roadmap to researchers to choose an optimal thermochemical conditions for high quality end product. Lastly, the perspectives and challenges in thermochemical conversion algae biomass to biofuels were also discussed.

Selectively Producing Acetic Acid via Boric Acid-Catalyzed Fast Pyrolysis of Woody Biomass

Boric acid is recently proved to be a good substitute for conventional acidic catalytic materials. However, few studies used boric acid as a catalyst in biomass pyrolysis. This study focused on the catalytic effects of boric acid (BA) on pyrolysis behaviors of woody biomass. The birch wood flour (WF) was used as feedstock and treated by impregnation of boric acid solution. Both untreated and boric acid-treated samples (BW) were characterized by FTIR and SEM. Thermogravimetry (TG) and pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC/MS) techniques were used for studying mass loss, composition, and distribution of evolved volatiles formed from pyrolysis process. Additionally, a small fixed-bed pyrolyzer with an amplificated loading amount was used to prepare liquid products, and further, GC/MS were used to analyze the composition of these liquid products. Different pyrolysis temperatures and boric acid/wood flour mass ratios were also studied. The main results are as follows. Boric acid infiltrated into both cell cavity and cell wall through impregnation treatment. FTIR analysis showed that boric acid reacted with wood flour to form B-O-C bond during the treatment. After the treatment of boric acid, the initial degradation temperatures and residual carbon contents were increased, while the maximum weight loss rates were decreased. Boric acid significantly altered the composition and distribution of volatile pyrolysis products of wood flour. It significantly increased the contents of small molecule compounds such as acetic acid and furfural but, decreased the contents of phenol derivatives with high molecular weights. And these changes became more pronounced as the temperature increased. When mass ratio of boric acid (BA) to wood flour (WF) was 2, the acetic acid accounted for 91.28% of the total product in the pyrolysis liquid, which was 14 times higher than that of untreated wood flour. Boric acid effectively catalyzed fast pyrolysis of woody biomass to selectively produce acetic acid

Experimental study on light volatile products from thermal decomposition of lignin monomer model compounds: effect of temperature, residence time and methoxyl group

In order to investigate the effects of temperature, residence time (RT) and methoxyl (OCH₃) on the product distribution and vapor phase reactions during pyrolysis of complex solid fuels, three model phenolic representatives, phenol, guaiacol and syringol, were pyrolyzed at a residence time of 0.7 s, over a temperature range of 400 °C–950 °C, and at temperatures of 650 °C and 750 °C, in a RT region of 0.1 s–4.2 s. Increasing yields of CO and C₁–C₅ light hydrocarbons (LHs) with RT at 650 °C and 750 °C indicated that ring-reduction/CO elimination of phenolic compounds happened at 650 °C, and dramatically at 750 °C. The addition of OCH₃ affects the product distribution and ring-reduction pathways: C₅ LHs from phenol, C₂ LHs, C₄ LHs and C₅ LHs from guaiacol, and C₁–C₂ LHs from syringol. CO₂ yields increase with the addition of OCH₃. CO₂ was formed via benzoyl and a four-membered ring, which would compete with the CO formation. The addition of OCH₃ promotes the formation of coke and tar. The decomposition pathways are discussed, based on the experimental data, focusing on ring-reduction reactions and the formation of CO/CO₂ and C₁–C₅ LHs.

Effects of temperature, residence time and methoxyl on the decomposition of phenol, guaiacol and syringol, were investigated. Thermal decomposition pathways of the three model compounds were discussed based on ring reduction/CO elimination reactions.