Thermochemical Routes Research Articles

Mechanochemical Synthesis of Carbazole Isomer Phosphors.

The 1H-benzo[f]indole (Bd[f]), a carbazole (Cz) isomer is first reported as the source of Cz-based phosphors in 2020. In this work, the novel carbazole isomers, 1H-benzo[g]indole (Bd[g]) based derivatives, are synthesized by a one-step solvent-free mechanical ball milling reaction, establishing a facile, efficient, and environmentally friendly method for the synthesis of new Cz isomer phosphorescent derivatives with high yields compared to previously reported multi-step solvent-based thermochemical synthesis routes of Bd[f] derivatives with low yields. Six Bd[g] derivatives with different substituents, namely OCH3-Bd, In-Bd, Bn-Bd, F-Bd, Cl-Bd, and Br-Bd, are synthesized, which exhibit distinctly different single-crystal structures and phosphorescent properties. After irradiation with 365nm UV light, Bd[g] derivatives-doped poly (methyl methacrylate) (PMMA) films exhibit photoactivated green room-temperature phosphorescence with ultra-long lifetimes up to 1.65s. Interestingly, the phosphorescence is stable in seawater along with good bactericidal properties, which also provide new candidates for indole-based marine antifoulants. This study demonstrates that mechanical ball milling is an efficient method for the synthesis of benzoindole heterocycles. Bd[g], as new members of the benzoindole family, are new building units to construct carbazole isomer phosphorescent molecules besides Bd[f].

The Impact of Biomass Composition Variability on the Char Features and Yields Resulted through Thermochemical Processes.

This paper explores the intricate relations between biomass polymeric composition, thermochemical conversion routes, char yields and features in order to advance the knowledge on biomass conversion processes and customize them to meet specific requirements. An exhaustive characterization has been performed for three types of biomasses: (i) spruce bark, a woody primary and secondary residue from forestry and wood processing; (ii) wheat straws-agricultural waste harvest from arable and permanent cropland; and (iii) vine shoots, a woody biomass resulting from vineyard waste. Chemical (proximate and ultimate analysis), biochemical, trace elements, and thermal analyses were performed. Also, Fourier transform infrared spectroscopy, Scanning Electron Microscopy, and thermogravimetric analysis were conducted to establish the compositional and structural characteristics of feedstock. The main polymeric components influence the amount and quality of char. The high hemicellulose content recommends wheat straws as a good candidate especially for hydrothermal carbonization. Cellulose is a primary contributor to char formation during pyrolysis, suggesting that vine shoots may yield higher-quality char compared to that converted from wheat straws. It was shown that the char yield can be predicted and is strongly dependent on the polymeric composition. While in the case of spruce bark and wheat straws, lignin has a major contribution in the char formation, cellulose and secondary lignin are main contributors for vine shoots char.

Algal-based biochar and hydrochar: A holistic and sustainable approach to wastewater treatment

Biochar and hydrochar are carbon-rich solid products of algal and terrestrial biomass obtained through various thermochemical processes, mainly hydrothermal liquefaction, pyrolysis, and hydrothermal carbonization. Both are regarded as economical, potent, and environmentally friendly adsorbents for wastewater remediation. The versatile applicability of biochar and hydrochar, which is due to their enhanced surface physicochemical properties, includes efficient metal biosorption, soil fertility enhancement, and carbon sequestration. Consequently, there has been an increase in research for producing and exploiting biochar and hydrochar from algae. Both micro- and macro-algal biomass have strong potential due to their sustainability footprint and distinct properties. This review focuses on a comprehensive account of the synthesis of algal biochar and hydrochar and use in wastewater treatment to develop innovative solutions for efficient mitigation of several aqueous pollutants and heavy metal ions. The review discusses the various thermochemical production routes, biophysical characterization techniques, and modes of mechanism for wastewater bioremediation. Algal-based biochar and hydrochar are reported to have higher porosity and more diverse functional groups such as amines, hydroxyl, and carboxyl compared to their cellulosic and waste-derived counterparts, demonstrating an increased wastewater remediation efficiency. In addition, presence of inorganic metal including sodium, potassium, magnesium, and phosphorus in algal chars facilitates the formation of mesopores and graphite structures, improving their cation exchange capacity. Moreover, algal chars may exhibit pH buffering capacity, which could help stabilize the pH during wastewater treatment processes. Notably, the low O/C content of algal hydrochars enhances the binding and removal of organic pollutants including toxic dyes and antibiotics. The review highlights the development of modified algal chars to enhance the porosity, surface area, structural integrity, and adsorption capacity enabling a higher bioremediation potential.

Ammonia production from microalgal biosystem: Present scenario, cultivation systems, production technologies, and way forward

Recent advancements in renewable energy technologies have increased the demand for ammonia production from a variety of biomasses due to biomass’s abundant availability. Many types of biomass are used to generate biofuels by thermochemical and biochemical methods. These include residues from farming and forests, municipal solid waste, energy crops, food processing residues, industrial organic effluents, and algae. Microalgae, among the biomasses, are a valuable resource for ammonia and hydrogen production because they have a higher biomass production rate than others. It is possible to use steam gasification, pyrolysis, catalytic pyrolysis, and steam catalytic gasification to move nitrogen from algal biomass to NH3. However, intensive investigation is required in new directions to develop a mature and cost-effective technology. This article closely examines the current production of ammonia and the feasibility of utilizing algal biomass for the production of hydrogen and ammonia through various biochemical and thermochemical routes. The study comprehensively addressed the characteristics of ammonia and the current status of its production across multiple countries. The subsequent section discusses the cultivation systems and life cycle assessment of algal biomass production for fuels. Furthermore, the ammonia/hydrogen production methods utilizing algal biomass are also listed and discussed.

Exploratory DSC investigation on the solvolytic depolymerization of PET in varied solvent systems and in the presence of model additives and contaminants

Solvolytic depolymerization of polyethylene terephthalate (PET) is a thermo-chemical recycling route that valorizes plastic waste by recovering monomers and chemicals that can be reused for the synthesis of new polymers. This study focuses on neutral hydrolysis due to the potential environmental and economic benefits of water as depolymerization agent compared to alternative organic solvents. High-pressure crucibles were used as batch reactors in differential scanning calorimetry (DSC) to perform real-time monitoring of the thermodynamic phenomena taking place during solvolytic depolymerization of PET in varied solvent systems. PET melting point depression was found to be the main identified phenomena, with PET melting point exhibiting a drop of almost 30 °C in water and 50 °C in monoalcohol solvents like methanol and ethanol. Moreover, PET only underwent significant depolymerization prior to melting in NaOH containing systems. Gas Chromatography and Mass Spectrometry were used to study the fate of model additives and contaminants under solvolytic conditions. The uncertainty concerning these foreign substances poses a challenge for the development of PET solvolytic technologies, and the methods here provided proved to be a fast-screening technique to quantify the conversion and identify potential degradation products of model additives like 2-(2-hydroxy-5-methylphenyl) benzotriazole UV-stabilizer, 1-(methylamino) anthraquinone dye, and model contaminant (R)-(+)-limonene under hydrothermal conditions.

Assessment and modeling of mercury adsorption on carbon-based adsorbents prepared from Jacaranda mimosifolia and guava biomass via pyrolysis and hydrothermal carbonization

Abstract The mercury adsorption properties of carbon-based materials prepared from jacaranda (Jacaranda mimosifolia) and guava (Psidium guajava) seed wastes are reported and compared in this paper. These adsorbent samples were obtained via pyrolysis and hydrothermal carbonization. Mercury adsorption equilibrium was studied at pH 4 and 20–40 °C, and the adsorption enthalpy changes were calculated for all adsorbent samples. The results showed that jacaranda-based materials contained a higher amount of acidic functional groups than guava seed-based adsorbents, and consequently, their mercury adsorption properties were better. The surface area of these adsorbents was <10 m2/g thus being classified as low-porosity materials. Elemental analysis indicated that all adsorbents were mainly composed of oxygen (4–25%) and carbon (75–95%). The calculated adsorption capacities at saturation of the best adsorbent were 18.05–30.09 mg/g under the tested experimental conditions. Statistical physics calculations also indicated that the adsorption mechanism of HgCl2 species was multi-molecular and endothermic. Ligand exchange and van der Waals forces were involved in generating the mercury–adsorbent interface. These results highlight the importance of comparing and optimizing biomass thermochemical conversion routes to tailor the surface properties of adsorbents used for water purification.

Production of sugars from lignocellulosic biomass via biochemical and thermochemical routes

Sugars are precursors to the majority of the world’s biofuels. Most of these come from sugar and starch crops, such as sugarcane and corn grain. Lignocellulosic sugars, although more challenging to extract from biomass, represent a large, untapped, opportunity. In response to the increasing attention to renewable energy, fuels, and chemicals, we review and compare two strategies for extracting sugars from lignocellulosic biomass: biochemical and thermochemical processing. Biochemical processing based on enzymatic hydrolysis has high sugar yield but is relatively slow. Thermochemical processing, which includes fast pyrolysis and solvent liquefaction, offers increased throughput and operability at the expense of low sugar yields.

Assessment and comparison of thermochemical pathways for the rice residues valorization: pyrolysis and gasification.

Lignocellulosic biomass conversion applying thermochemical routes has been postulated as an alternative for generating renewable energy. This research compares energy-driven biorefineries based on two thermochemical routes addressed to upgrade rice husk and rice straw produced in the Department of Sucre-Colombia. Initially, this research analyzes the physico-chemical and structural characterization of the rice residues. Four different scenarios were proposed to compare the energy-driven biorefineries based on fast pyrolysis and gasification considering technical, economic, and environmental metrics. These biorefineries were simulated using the Aspen Plus V.14.0 software. The novelty of this research is focused on the identification of the biorefinery with the best techno-economic, energetic, and environmental performance in the Colombian context. Economic and environmental analyses were done by using economic metrics and emissions. From an economic perspective, the stand-alone gasification process did not have a positive economic margin. In contrast, the fast pyrolysis process has the best economic performance since this process has a positive profit margin. Indeed, scenario 1 (fast pyrolysis of both rice residues) presented an economic margin of 13.75% and emissions of 2170.92 kgCO2eq/kg for 10years. However, this scenario was not energetically the best, holding second place due to the feedstock requirements, compared to gasification. The biorefinery scenario 1 has the best performance.

A Critical Review of the Sustainable Production and Application of Methanol as a Biochemical and Bioenergy Carrier

There is a growing interest in the production of biofuels and biochemicals from renewable biomass. Biomass in the form of woody and agricultural residues, municipal solid waste and other organic refuse is becoming popular as a feedstock for biofuel and biochemical production through thermochemical and biological routes. Methanol, a widely used industrial chemical, also has clean fuel properties due to its high-octane number, low flammability, low emissions and high engine performance. This paper performs a comprehensive review of different thermochemical and biological processes able to sustainably convert waste biomass to methanol. This article also evaluates the techno-economic assessment and lifecycle analysis of different processes used for methanol production. The article discusses the effects of process parameters and biomass properties on methanol production and utilization. Finally, the article concludes with recommendations on the eco-friendly aspects of methanol for use as a clean fuel and chemical derived from renewable organic bioresources.

Biomass and bioenergy potentials of bioresidues: assessment methodology development and application to the region of Lafões

AbstractBioenergy research aims to uncover the potentials of biological residues. Regional-specific characterization of such potentials is needed to improve the use of local resources, decisions on bioenergy conversion routes, and services within global efforts against climate change. The definition and calculation of the theoretical and technical biomass and bioenergy potentials are keys for developing sustainable use pathways at a regional level. The present work develops a methodology where theoretical framework, quantification methods, and values for the necessary parameters, to assess regional biomass and bioenergy potentials, are considered. The region of Lafões (Portugal) is the case study to illustrate the application of the methods, resulting in three bioresidue categories (agricultural by-products, forestry residues, and municipal waste) and two bioenergy conversion routes (biochemical and thermochemical). The biochemical conversion route revealed a technical energy potential of 765 TJ yr−1, comparing favourably with the 543 TJ yr−1 achieved by the thermochemical route. Also, the environmental and economic performances, associated with the implementation of bioenergy technologies, are possibly better achieved through the biochemical route, to be assessed through life cycle analyses and life cycle costing. Regardless of action priorities, the two conversion routes combined can potentially cover the entire current electrical energy demand of the region. This should also be appraised with expectations in mind for both flexible bioenergy services (with other renewables) and for bioenergy usage in applications which are difficult to defossilize.

Low-temperature upcycling of polypropylene waste into H2 fuel via a novel hydrothermal tandem process.

Plastic waste is a promising and abundant resource for H2production. However, upcycling plastic waste into H2fuel via conventional thermochemical routes requires relatively considerable energy input and severe reaction conditions, particularly for polyolefin waste. Here, we report a tandem strategy for the selective upcycling of polypropylene (PP) waste into H2fuel in a mild and clean manner. PP waste was first oxidizedinto small-molecule organic acids usingpure O2as oxidantat 190 °C, followed by the catalytic reforming of oxidation aqueous products over ZnO-modified Ru/NiAl2O4catalysts to produce H2at 300 °C. A high H2yield of 44.5 mol/kgPPand a H2mole fraction of 60.5% were obtained from this tandem process. The entire process operated with almost no solid residue remaining and equipment contamination, ensuring relative stability and clean of the reaction system. This strategy provides a new route for low-temperature transforming PP and improving the sustainability of plastic waste disposal processes.

Electrochemical Valorization of Glycerol via Electrocatalytic Reduction into Biofuels: A Review.

Electrochemical conversion of underutilized biomass-based glycerol into high-value-added products provides a green approach for biomass and waste valorization. Plus, this approach offers an alternative to biofuel manufacturing procedure, under mild operating conditions, compared to the traditional thermochemical routes. Nevertheless, glycerol has been widely valorized via electrooxidation, with lower-value products generated at the cathode, ignoring the electroreduction. Here we study and establish a review of the efficient glycerol reduction into various products via the electrocatalytic reduction (ECR) process. This review has been built upon the background of glycerol underutilization and theoretical knowledge about the state-of-the-art ECR. The experimental understanding of the processing parameter influences towards electrochemical efficiency, catalytic activity, and product selectivity are comprehensively reviewed, based on the recent glycerol ECR studies. We conclude by outlining present issues and highlighting potential future research avenues for enhanced ECR application.

Investigation on bio-oil pyrolysis with Ni/Al2O3 blending: Influence of the blended catalyst on coke formation

Bio-oil can be converted into syngas, chemicals, and carbon materials via thermochemical and/or catalytic conversion routes. However, coking remains a significant challenge during the heating of bio-oil. In this study, we investigated the influence of pre-blending Ni/Al2O3 and bio-oil in an in-situ catalytic pyrolysis process on the coking behaviours of bio-oil. Our results indicate that the presence of Ni/Al2O3 significantly reduces coke yield and increases gas yield (for example, by a 14.2 % reduction in coke and a 44.1 % increase in gas at 700 °C). This is attributed to the suppression of the cross-linking reactions responsible for coke formation through the pre-elimination of O-containing groups into CO and CO2. Additionally, pre-blending of Ni/Al2O3 is highly desirable for transforming or stabilising the highly reactive substances in the early pyrolysis stage of bio-oil, minimising their tendency to polymerise. Furthermore, the presence of Ni/Al2O3 facilitates the cracking of C–H bonds and self-reforming of bio-oil, increasing H2 production (which is increased by 42.3 % at 700 °C), thereby promoting the breakage of side chains of lignin-derived aromatics and the hydrogenation of unsaturated structures, suppressing the formation of small aromatic systems in coke (<6 rings). Nevertheless, enhanced formation of alkyl-aryl C–C bonds during aromatisation leads to more condensed coke structures.

Recent advances in green hydrogen production, storage and commercial-scale use via catalytic ammonia cracking

Sustainable societal growth relies on the efficient storage, transportation, and use of renewable energies. Considerable progress has been made in sustainable hydrogen production via water electrolysis and biomass conversion, but hydrogen storage and transportation remain major challenges for commercial-scale applications. Owing to its high hydrogen content and energy density, ammonia is a promising zero-carbon energy carrier for large-scale energy storage. Therefore, the transformation of renewable hydrogen into ammonia is a promising strategy for effective hydrogen transportation and storage. Unlike the direct combustion of ammonia, which can produce NOx, catalytic cracking into nitrogen and hydrogen provides an environmentally friendly method for hydrogen regeneration. Herein, recent advances in effective ammonia decomposition via various processes, including electrochemical, photochemical, and, particularly, thermochemical routes, are summarized. In addition, hydrogen separation techniques and techno-economic analyses of the ammonia and hydrogen economy are discussed. The main objective of this review is to provide a conceptual framework for effective ammonia cracking to yield pure hydrogen as a clean fuel for developing futuristic and sustainable energy solutions.

Screening and characterization of waste lignocellulosic biomass as a potential substrate for energy recovery

AbstractThe world is facing a severe energy crisis due to rapid industrialization, population explosion, and modern lifestyle. Conventional energy sources are running out of stock and accordingly, an ardent need for the search for alternative feedstock for energy recovery has been the research focus for the past few decades. In context to this energy turmoil, the lignocellulosic biomasses have emerged as an excellent surrogate antecedent for energy procreation in this present scenario of the energy crisis. Among numerous feasible biomass energy recovery methods, the biochemical route and the thermochemical route are the most prevailing. Accordingly, several biomass characteristics require well understanding to access the extent of possible energy recovery. The compositional features assessed (in terms of cellulose, hemicellulose, extractives, and lignin content) as well as the ultimate analysis carried out (in terms of the carbon, hydrogen, oxygen, sulfur, and nitrogen content) as one of the major parameters for evaluating the energy recovery potential and subsequently, a Van Krevelen diagram was obtained to define their energy recovery potential. The calorific value of the three biomass specimens obtained by using an adiabatic bomb calorimeter and subsequently, their oil equivalence was presented. A tariff and budgetary analysis evaluated to define their respective economic incentives and their potential scope to meet the energy crisis scenario. Finally, a scoring matrix analysis conducted parallelly by evaluating the various parameters by adopting the rank correlation method to screen out the best biomass category. The overall scheme of study adopted for screening a particular waste biomass category from three widely available agriculture waste biomass samples (rice husk, corn cob, and nutshell) through multiple criteria and thereby evaluating the most ideal biomass as the surrogate source to meet the ever‐increasing energy demand which are prevalent in the state of Jharkhand, India.

Unveiling environmental impacts of methanol production via electrocatalysis against conventional and thermochemical routes by life cycle assessment

A comparative life cycle assessment is performed to understand the environmental sustainability of methanol production via electrochemical CO2 reduction (EC), thermochemical CO2 hydrogenation (TC), and conventional processes. At the midpoint and endpoint levels, three processes present significant results in global warming (GW), terrestrial ecotoxicity (TE), human non-carcinogenic toxicity (HNC), and fossil resource scarcity (FS). TC and EC pathways have higher scores in these selected impact potentials, and the EC pathway is the least sustainable with a highest impact contribution of around 76%. This research also highlights the significance of integrating the recycling streams in the process flows to effectively reduce the environmental burden. Out of the several, it is meaningful to observe a total reduction of 87.53 kg CO2 eq and 718.28 kg CO2 eq for the GW potential of TC and EC pathways, respectively. In view of the uncertainty analysis, the NHC indicator demonstrates the highest uncertainty for all three processes, which can be traced back to its higher environmental relevance to the impact indicators. In the primary midpoint and midpoint analysis, TC and EC pathways indicate inferior positions in terms of sustainability, but once changing the electricity mix to 100% renewable sources-based (hydropower, solar power, and wind power), a large reduction of 41%–88% in impact potentials is realized. Among all, electricity mix optimization based on a 100% hydropower source gives the best result. In this way, the TC pathway has a lowest environmental impact potential, standing out among the three processes. As a whole, this study highlights the importance of developing emerging technology for sustainable fuel production and enlightens the future direction of developing emerging thermochemical and electrochemical methanol production from CO2.

Synthesis, characterization and optimization of gasification products from Aegle Marmelos Correa shell in a downdraft gasifier using ANN and RSM

Biomass has demonstrated how it is likely to be an excellent energy source equipped to meet the rising global need for clean and unceasing power sources to better our society. The gasification process is among the most viable thermochemical routes of bioenergy production. Gasification of Aegle Marmelos Correa shell was conducted in a portable downdraft fixed-bed reactor to assess the impact of moisture content and particle size on syngas composition. The artificial neural network (ANN) technique predicted gasification performance and compared it with response surface methodology (RSM) for forecasting their abilities. Syngas composition at optimum conditions of 10% (wt.) moisture and 2.6 mm particle size was 19.2 vol.% H2, 15.3 vol.% CO, 18 vol.% CO2, and 6.4 vol.% CH4. The results reveal that moisture content plays a more significant role than particle size in gasification reaction rate. It can be concluded that ANN has been more accurate and superior to the RSM model for forecasting gasification performance.

Conceptualizing novel CH3OH-based thermochemical energy storage routes via a modeling approach

Conceptualizing novel CH3OH-based thermochemical energy storage routes via a modeling approach

Study on the reaction mechanism of C8+ aliphatic hydrocarbons obtained directly from biomass by hydropyrolysis vapor upgrading

Aviation fuel production is an important direction for biomass utilization, however, the direct transformation of biomass into aviation fuel is a bottleneck in this field. Among all the biomass-to-liquid thermochemical routes, the pyrolysis process can directly produce bio-oil in a continuous industrial manner. Herein, Ni-Mo/γ-Al2O3 catalyst was used to investigate the hydropyrolysis (HP) vapor upgrading (VU) process of lignocellulosic biomass to obtain bio-oil with high selectivity of aviation fuel components. The VU temperature of 300–350℃ was conducive to generating liquid fuel with C8+ aliphatics as the main component of jet fuel. It was indicated that the yield of the oil phase was 6.4 wt% with an HHV of 46.2 MJ/kg, while the selectivity of aliphatics reached 72.6% with C8+ aliphatics was 59.9%. Moreover, it was found that all three components of biomass could be transformed into long-chain aliphatics by coupling reaction. The hydroxyalkylation is the main way and the aldehyde group is the directing group of the carbon-increasing, which was supported by the results of the quantum chemical calculation. Further, the reaction network for the HP-VU process of lignocellulosic biomass with C8+ aliphatics as the main product was proposed to provide a theoretical understanding of the carbon-increasing in biomass hydropyrolysis.

Biomass to H2: Evaluation of the Impact of PV and TES Power Supply on the Performance of an Integrated Bio-Thermo-Chemical Upgrading Process for Wet Residual Biomass

The last Intergovernmental Panel on Climate Change (IPPC) assessment report highlighted how actions to reduce CO2 emissions have not been effective so far to achieve the 1.5 C limit and that radical measures are required. Solutions such as the upgrading of waste biomass, the power-to-X paradigm, and an innovative energy carrier such as hydrogen can make an effective contribution to the transition toward a low-carbon energy system. In this context, the aim of this study is to improve the hydrogen production process from wet residual biomass by examining the advantages of an innovative integration of anaerobic digestion with thermochemical transformation processes. Furthermore, this solution is integrated into a hybrid power supply composed of an electric grid and a photovoltaic plant (PV), supported by a thermal energy storage (TES) system. Both the performance of the plant and its input energy demand—splitting the power request between the photovoltaic system and the national grid—are carefully assessed by a Simulink/Simscape model. The preliminary evaluation shows that the plant has good performance in terms of hydrogen yields, reaching 5.37% kgH2/kgbiomass, which is significantly higher than the typical value of a single process (approximately 3%). This finding demonstrates a good synergy between the biological and thermochemical biomass valorization routes. Moreover, thermal energy storage significantly improves the conversion plant’s independence, almost halving the energy demand from the grid.