Thermochemical Transformations Research Articles

Thermochemical transformation of CO2 for CH4 production using metal hydride and carbonates as portable sources

The thermochemical reaction between MgH2 and Li2CO3 is investigated for the first time for the CO2 transformation into fuels with and without nickel as a catalyst. Successful production of CH4 with high yields is reached depending on different reaction conditions such as microstructural refining, MgH2:Li2CO3 molar ratio, temperature and time. In absence of a catalyst, a methane yield of 68.2% was achieved by heating the milled MgH2:Li2CO3 mixture at 450 °C for 5 h. The global mechanism involves the reduction of CO2 from Li2CO3 by MgH2/Mg, producing CH4 and Li2O/MgO. For the Ni-catalyzed system, the highest methane yield of >90% was reached at 400 °C after 5 h of thermal treatment. The global process responds to a Sabatier reaction, with a contribution of a direct reduction of CO2 depending on the starting mol ratio. The results demonstrate that thermochemical activation of the Ni-catalyzed MgH2:Li2CO3 mixture is a powerful process for the generation of CH4 and CO2 utilization.

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.

First experimental characterization of CaCl2 coated heat exchanger for thermochemical heat transformer applications in industrial waste heat recovery

This study aims at evaluating the performance of a heat exchanger coated with CaCl2 (PVA polyvinyl alcohol used as binder) for Thermochemical Heat Transformers (THT) applications in industrial waste heat recovery.For this purpose, an experimental test bench has been built allowing to test operating temperatures up to 160 °C. A model heat exchanger plate is used to test two configurations: a thick layer of CaCl2 to model a packed bed reactor (used as reference) and a CaCl2-PVA deposit to model a coated reactor.For the packed bed configuration, results comparable to that of the literature are obtained with a specific power of 180 W/kg obtained for a temperature lift of 60 K. A high sensitivity to temperature lift is identified with a decrease of the specific power down to 38 W/kg for a lift of 77 K. The coated heat exchanger configuration achieves significantly higher performance with a specific power up to 341 W/kg for a temperature lift of 63 K. However, the analysis of the repeatability tests highlights a rapid change in temperature profiles highlighting a change in properties of the CaCl2/PVA compound material. Next steps will consist in enhanced material formulation and change in deposit protocol and to move to work at small reactor scale to assess system performance.

Insight into the structural feature, ash transformation behavior, and alkali metal heat release characteristic of industrial lignin via experimental and equilibrium evaluation

The release characteristics of inorganic minerals during the thermochemical transformation of organic solid wastes are one of the key issues for their resource utilization. This study concentrated on the chemical structure of three kinds of industrial lignin and the release pattern and mechanism of alkali metal elements during heat treatment by means of 13C NMR, FTIR, XRD, SEM, and chemical thermodynamic equilibrium simulation. The microstructures of the three lignin samples were studied using 13C NMR and FTIR. The three lignin samples contained much more aliphatic and aromatic carbon than carbonyl carbon, and the aliphatic carbon moieties contained the most oxygenated carbon. The lignin samples mainly had aromatic molecular structures with aromaticity (fa) of 55.76% (sodium lignin sulfonate, SL), 52.62% (calcium lignin sulfonate, CL), and 63.93% (de-alkalized lignin, DL), respectively. Carbonyl content in DL was lower than lignin sulfonate SL and CL. The benzene ring content of SL was lower than the other two lignin samples. Na+ metal salts promoted the pyrolysis of lignin samples, while Ca2+ metal salts inhibited the pyrolysis of lignin samples. Microstructural studies showed that the structure of SL evolved from columnar and granular coexistence breaking into filamentous protrusions and lamellar structures with the increase of pyrolysis temperature. The CL and DL samples became ash presented in granular state and the particle size continued to become smaller with increasing temperature as the distribution gap became larger. The chemical thermodynamic equilibrium calculations showed that the variation in the initial concentrations of Na+ and Ca2+ in the three lignin samples led to different release characteristics of the three lignin samples. Na+ release rate was higher than that of Ca2+, and the valence state of the metal ions was an important reason for this phenomenon. This study provides data support and theoretical basis for the migration and release pattern of alkali metal during the thermal conversion reaction of organic solid waste applications.

Thermo-economic assessment of salt hydrate-based thermochemical heat transformer system: Heat upgrade for matching domestic hot water production

Efficient energy storage technology is a crucial step in achieving the broad deployment of renewable energies. Thermochemical heat transformer (THT), which rely on reversible gas–solid reactions, can provide an option for efficient energy storage and heat upgrade. In this article, a pressurisation-assisted sorption THT system driven by low-grade solar thermal energy is proposed to meet the heat demand of domestic hot water (DHW) production, and different temperature rises can be realised by regulating the water vapour pressure. The thermodynamic and economic performances of the THT systems employing ten kinds of salt hydrates are investigated under various operating conditions. The results indicate that most salts-based THT systems enable output temperatures higher than 60 °C. Two-stage pressurisation systems can further elevate the temperature lift but at the cost of thermodynamic performance. SrBr2·6H2O, K2CO3·1.5H2O, and LiOH·H2O are more promising hydrates for the THT system by taking energy density, temperature lift, and thermo-economic performance into account. Compared to the classical TCES cycle, the temperature lifts attained by the above salts-based single-stage and two-stage pressurisation THT systems are 17.6–19.9 °C and 32.2–37.8 °C, respectively. Multi-objective optimisation results suggest that the optimum exergy efficiency for the SrBr2-, K2CO3-, and LiOH-based systems are 82.47%, 55.08%, and 63.97%, and the corresponding levelized energy costs (LECs) are 0.3549, 0.7132, and 0.5721 $/kWh, respectively. The results of this study demonstrate the significant potential of developing such pressurisation-assisted THT system for heat upgradation targeting DHW production.

Thermodynamic modeling of the reaction of simultaneous interaction of nickel (II), cobalt (II) and iron (III) oxides with carbon

This paper considers thermodynamic modeling of electric smelting of Allarechenskoye deposit dumps for nickel, cobalt, and iron extraction. Thermochemical transformations in the reaction of interaction of carbon with oxides of nickel (II), cobalt (II) and iron (III) are considered. The investigations of thermochemical transformations of the chemical-phase composition of the system were carried out using the software complex “Astra-4” developed by a team of scientists at the Bauman Moscow State Technical University. Thermochemical transformations and chemical-phase composition of the system as a function of T (temperature) and P (pressure) were studied. In particular, the temperature was in the range from 973K to 1773K and the pressure range was taken from 0.001 MPa to 0.1 MPa. According to the results, it was found that iron in the system transitions to condensed iron, with the degree of transition (αFe) from 29.0% at T = 1173K to 99.1% at 1773K, the degree of transitions of nickel to condensed nickel is 100% before T = 1273K, and with an increase in temperature from 1273K to 1773K decreases to 99,98%; the transition of cobalt to the gas phase is distributed similarly to nickel.

Substantiation of Practical Recommendations on the Organization of Optimal Modes of Preliminary Heat Treatment and Combustion of Coal in a Pulverized State

Based on the data on the reactivity of coal, a calculated justification of the requirements for the organization of its preparation and combustion processes was carried out, taking into account the initial quality and operating modes of the preparation systems and combustion devices of power steam boilers. The relationship between such operating parameters of the device for preliminary heat treatment of coal as the size of pulverized coal particles, temperature and duration of treatment with the quality of the source fuel has been established in order to ensure stable ignition and completeness of burnout of the products of thermochemical transformation of coal in the conditions of the furnace chamber of the boiler unit. The results of the cycle of analytical studies are summarized and brought to the level of engineering methodology (in the form of a nomogram), which allows determining the optimal values of temperature and time of the process of preliminary heat treatment of coal before combustion in the furnace chamber of a steam boiler based on the known characteristics of the initial fuel (reactivity and particle size). The found operating parameters of the device for preliminary heat treatment of coal ensure the performance of verification (thermal) and design calculations of real fuel-using installations, for example, fuel-free kindling and dust preparation systems. It is established that the most optimal mode of preliminary heat treatment of brown Kansk-Achinsk coals polyfraction, in terms of the efficiency of ignition and combustion of heat treatment products, is 800–850°C with a processing time of 0.6–1.2 s. The results of the calculated studies were confirmed during experimental work on a special laboratory stand, which provides a mode of preliminary heat treatment of coal in a pulverized state in a wide temperature range and afterburning of dust and gaseous heat treatment products under various conditions.

Method for calculating the pyrolysis zone in the production unit activated carbon

Activated charcoal can be obtained in many ways. The most promising in terms of resource saving and economic benefits is the method of obtaining activated carbon from organic waste by slow conductive pyrolysis. As a result of such thermochemical conversion, biochar and volatile products - condensable and non-condensable are formed, which are used as fuel for the operation of pyrolysis reactors. Modeling of slow thermal decomposition is carried out using finite difference schemes for heat and mass processes described by differential equations and equations of chemical kinetics. The pyrolysis process equipment is a complex and expensive mechanism, therefore, when developing equipment for pyrolysis, it is necessary to carry out calculations related to the optimization of the equipment design. In this work, as applied to an energy- and resource-saving plant for the production of activated carbon, analytical calculations were carried out and a universal calculation method was developed for the zone of conductive pyrolysis of crushed waste. A mathematical model of the process of conductive slow pyrolysis is presented, which consists of heat and mass transfer equations and equations of chemical kinetics. An algorithm for calculating the pyrolysis zone has been developed. A kinetic dependence of the specific gravity of the solid residue of wood particles during pyrolysis is obtained, which characterizes mass transfer during the thermochemical transformation of waste into a carbonaceous residue, this dependence shows the dynamics of the change in the mass of the solid fraction over time during the decomposition of waste, the kinetic curves show: the rate of chemical reactions occurring during pyrolysis, as well as the final specific gravity of coal.

Hot carrier photochemistry on metal nanoparticles

The last decade has seen a growing number of reports utilizing illuminated metal nanoparticles to drive chemical reactions of industrial and societal importance. Putting light to use in chemical reactions is an important alternative to petroleum, given its ubiquity as a sustainable energetic medium. Light also unlocks electronic contributions to chemical reactions through the generation and action of hot carriers on molecular adsorbates that are unavailable in traditional thermochemical transformations. In this Perspective, we will provide a pedagogical overview of important techniques and results from decades of surface science research that have built the foundation of modern studies on hot carrier photochemistry. Advances in nanoscience and heterogeneous catalysis have since introduced new materials, particularly metal nanoparticles that sustain collective electronic oscillations under illumination (plasmon resonances), to be exploited as potent photocatalysts. Plasmonic photocatalysts have strong optical absorption and, through Landau damping, can be engineered to maximize hot carrier generation within a given volume and applied to reactions of interest. Plasmonic hot carriers can induce excited electronic, vibrational, and rotational states in adsorbates that promote unexpected surface reactivities in the presence of light. We will address open questions regarding energy transfer, catalyst design, and possible implementation beyond laboratory scales. Throughout this Perspective, reactions critical to sustainability will be addressed given the urgent need to decarbonize the energy and chemical industries.

Identifying the fate of nitrogenous species during sewage sludge pyrolysis via in-situ tracing of protein-sludge inherent components interactions

The effect of interactions between different components in sewage sludge on the thermochemical transformation of nitrogenous species is usually neglected, which is important to explain the generation mechanism of some key nitrogenous by-products. Here, we investigated the distribution, form, and chemical properties of the products from sludge-extracted protein (PR) under different pyrolysis scenarios using several in-situ probe techniques, to elucidate the critical role of typical sludge organics/inorganics on the evolution of nitrogenous intermediates and by-products. The results suggested that Ca/Fe/Si/Al-containing inorganics significantly affected the pyrolytic behavior of PR and the thermal transformation of nitrogenous species, while sludge organics, including humic acids and polysaccharides, had limited effects on the temperature-dependent evolution of nitrogenous species in PR. Among them, calcium oxide catalyzed the ring-opening reaction of heterocyclic-N with aromatic-like structures, resulting in a 21.1 %–68.8 % reduction in nitrogen fixation efficiency in the char. At lower temperatures (350–450 °C), calcium oxide caused more nitrogen to be transferred to the gas/tar phases in the form of NH3 and heterocyclic-N, and it also enhanced the conversion of nitrile-N → HCN → NO at temperatures above 450 °C. In contrast, polyferric salts inhibited the devolatilization of mono-heterocyclic-N and enhanced the thermal stability of poly-heterocyclic-N, resulting in a maximum increase of 18.5 mg·g−1 of nitrogen content in the char, while reducing the release of NH3 and HCN by 71.1 % and 32.0 %. This work elucidated the interaction between PR and inherent components in sludge, providing key information for the control of nitrogenous volatiles and NOx.

Brewer’s Spent Grain Biochar: Grinding Method Matters

The present work is based on the principle of biomass waste valorization. Brewer’s spent grains (BSG) come from breweries as by-products. Their huge amount of production on an industrial scale should focus our attention on their valorization, which creates challenges as well as opportunities. One way to valorize BSG by-products is to convert them into biochar, a functional material with multiple potential applications. With an emphasis on sustainable development and the circular economy, in this work, we focused on a comparative study of the different mechanical processes of BSG grinding and their effect on the resulting biochar formed after pyrolysis. Home appliances such as blenders, coffee mills, and mortar and pestles were used for this purpose. FESEM images confirmed the successful creation of five different morphologies from the same BSG under the same pyrolysis conditions. Interestingly, a novel Chinese tea leaf egg-like biochar was also formed. It was found that a series of physical pretreatments of the biomass resulted in the reduced roughness of the biochar surface, i.e., they became smoother, thus negatively affecting the quality of the biochar. XRD revealed that the biomass physical treatments were also reflected in the crystallinity of some biochar. Via a Raman study, we witnessed the effect of mechanical pressure on the biomass for affecting the biochar features through pressure-induced modifications of the biomass’s internal structure. This induced enhanced biochar graphitization. This is a good example of the role of mechanochemistry. DSC revealed the thermochemical transformation of the five samples to be exothermic reactions. This study opens up an interesting possibility for the synthesis of biochar with controlled morphology, crystallinity, degree of graphitization, and heat capacity.

Mathematical Modelling of Marine Power Plants with Thermochemical Fuel Treatment

Abstract The article considers the methodological aspects of the theoretical investigation of marine power plants with thermochemical fuel treatment. The results of the study of the complex influence of temperature, pressure, and the ratio of steam / base fuel on the thermochemical treatment efficiency are presented. The adequacy of the obtained regression dependences was confirmed by the physical modelling of thermochemical fuel treatment processes. For a gas turbine power complex with a thermochemical fuel treatment system, the characteristics of the power equipment were determined separately with further merging of the obtained results and a combination of material and energy flow models. Algorithms, which provide settings for the mathematical models of structural and functional blocks, the optimisation of thermochemical energy transformations, and verification of developed models according to the indicators of existing gas turbine engines, were created. The influence of mechanical energy consumption during the organisation of thermochemical processing of fuel on the efficiency of thermochemical recuperation is analysed.

Activated carbon manufacturing via alternative Mexican lignocellulosic biomass and their application in water treatment: Preparation conditions, surface chemistry analysis and heavy metal adsorption properties

The preparation and functionalization of activated carbons from different biomass of Mexico and their application in the adsorption of heavy metal ions is reported in this paper. Jacaranda seeds, guava seeds, grape pomace and sugarcane bagasse were utilized as lignocellulosic precursors to obtain activated carbons via the chemical activation of biomass and its pyrolysis. The best conditions to prepare the activated carbons were identified with ZnCl2, NaOH, HNO3 and H3PO4 as activating agents. A systematic analysis of the biomass chemical activation and thermochemical transformation via pyrolysis was performed to maximize the Hg2+, Zn2+ and Pb2+ adsorption properties of activated carbons. These adsorbents showed maximum adsorption capacities from 0.014 to 0.84 mmol/g at 25–40 °C where the best adsorbent was obtained from the Jacaranda fruit activated with 0.5 M ZnCl2 for 2 h and pyrolyzed at 800 h for 4 h. This adsorbent was effective for the Hg2+ removal in single, binary and ternary systems thus suggesting its potential application for industrial wastewater treatment where several heavy metal ions could be present. The removal of these heavy metal ions with all tested activated carbons was endothermic where the oxygenated functional groups were involved in the adsorption mechanism. Isotherm data modeling with statistical physics indicated that Hg2+ and Pb2+ adsorption was mono-ionic, while the Zn2+ adsorption was multi-ionic. Antagonistic adsorption of these heavy metal ions occurred in multi-metallic solutions where Hg2+ affected significantly Zn2+ and Pb2+ removal. Regeneration of the best activated carbon was feasible with HNO3. These results contribute to valorize alternative agricultural and biomass wastes to satisfy the demand of activated carbons for water cleaning in Mexico applying a circular economy approach to reduce the production costs and to minimize the solid waste generation.

Combustion stages of waste-derived blends burned as pellets, layers, and droplets of slurry

This paper describes the results of an experimental investigation on the stages of thermochemical transformation of fuels prepared from waste. We studied the combustion of coal slime and its co-combustion with additives (waste turbine oil, sawdust, and rapeseed oil). The mass fraction of the additive was 5%. Fuels in the forms of a pellet, dry loose layer, and slurry were heated in a tubular muffle furnace. The reactivity of the fuels was evaluated, and the duration of the main process stages was recorded. Experiments have shown that it is more expedient to burn coal slime in combination with other components, which improved the ignition and burnout performance of the blends. The addition of turbine oil accelerated the flame combustion by 3–6 times. Rapeseed oil reduced the duration of the endothermic stage by 50–60%. The slurry droplets had the longest pre-flame stage. Their burnout was more intense than that of pellets or a layer and was less dependent on the temperature in the furnace. The longest burnout was typical of pellets. The data obtained are essential in planning and conducting industrial tests on the energy recovery of coal slime, biomass, and refined products.

The effect of radiolysis and thermally stimulated acid hydrolysis on tributyl phosphate and its solutions in ISOPAR-M

The radiolytic and post-radiation thermochemical (at 90–170 °C) transformations of tri-n-butyl phosphate (TBP) and its 30% solution into Isopar-M during pre-radiation and post-radiation acidification with nitric acid have been investigated. The assortment of nitrogen-containing products of TBP oxidation during gamma radiolysis, electron beam radiolysis, and thermally stimulated acid hydrolysis is similar. Specific products of radiolysis are TBP dimer and alkyl adducts of dibutyl phosphate, and specific products of thermolysis are ethylbenzene and xylenes. It was shown that, in contrast to 100% TBP, where radiolysis and hydrolysis have approximately the same additive effect on the degradation of TBP, hydrolysis in a 30% solution leads to the degradation of nitrogen-containing radiolysis products and additional formation of dibutyl phosphate and monobutyl phosphate. Temperatures above 110 °C during post-radiation thermolysis intensify the formation of highly volatile compounds from radiolysis products (up to 17 wt% at 170 °C), which increases the fire and explosion hazard of using extraction mixtures.

Gasification of fermentation residue in a fluidised-bed gasifier

Biogas production through anaerobic digestion in biogas stations is currently prevalent in the Czech Republic. Along with the increasing installed capacity of biogas stations and the amount of gas produced, the need for handling the solid residue of this process – digestate – is increasing. The digestate from pure input raw materials is most often used as a fertiliser; however, the regulations limit its use, hence creating a surplus of unused material. Moreover, digestate obtained from contaminated biomass or bio-waste is unsuitable for agricultural application. A natural demand for other means of utilisation is thus created, and since digestate cannot be directly recycled, the only feasible way is thermal disposal. To get a better understanding of its thermochemical transformation to synthetic gas, a series of experiments were carried out on an atmospheric fluidised-bed gasifier with a 100kWt output. Two digestate samples were chosen, one from wet and the other from dry fermentation, and are compared to results obtained from wood gasification. The lower heating value of the gas generated from digestate, with air as the gasifying agent, was found to be between 4 and 5,5 MJ/Nm3 with an efficiency of about 70%. The syngas quality and purity of both fermentation residues are comparable to the referential wood-gas. The results thus confirm the feasibility of digestate as a fuel for industrial-scale fluidised-bed gasification.

Efficient removal of Cd(II) by phosphate-modified biochars derived from apple tree branches: Processes, mechanisms, and application

Phosphate (P)-modified biochar is a good material for cadmium (Cd) immobilization, and the pore-forming effect of potassium ions (K+) can favor the P loading on biochar. However, few studies have been done specifically on Cd(II) removal by composites of potassium phosphates with biochar, and the removal potential and mechanisms are not clear. Herein, apple tree branches, a major agricultural waste suitable for the development of porous materials, were pyrolyzed individually or together with KH2PO4, K2HPO4·3H2O, or K3PO4·3H2O to obtain biochars to remove Cd(II), denoted as pristine BC, BC-1, BC-2, and BC-3, respectively. The results showed that the orthophosphates containing more K+ enlarged the specific surface area, total pore volume and phosphorus loading of biochar. Co-pyrolysis of apple tree branches and P promoted the thermochemical transformation of P species. Only weak signal of orthophosphate was observed in the pristine BC, while the presence of orthophosphate, pyrophosphate and metaphosphate were detected in BC-1, and BC-2 and BC-3 showed the presence of orthophosphate and pyrophosphate. The maximum Cd(II) adsorption capacities of pristine BC, BC-1, BC-2 and BC-3 were 10.4, 88.5, 95.8, and 116 mg·g−1, respectively. Orthophosphate modification enhanced the Cd(II) adsorption capacity due to the formation of Cd-P-precipitates, namely Cd5(PO4)3Cl, Cd5(PO4)3OH, Cd3(PO4)2, Cd2P2O7, and Cd(PO3)2. Furthermore, higher cation exchange efficiencies between Cd(II) and K+ in P-modified biochars also contributed to their high Cd(II) adsorption capacity. Cd(II) removal by BC-3 from artificially polluted water bodies showed more than 99.98% removal rates. Application of BC-3 also reduced the diethylene triamine pentaacetic acid-extracted Cd(II) in soil by 69.1%. The co-pyrolysis of apple tree branches and potassium phosphates shows great prospect in Cd(II) wastewater/soil treatment and provide a promising solution for agricultural waste utilization and carbon sequestration.

Using equilibrium thermodynamics to study thermochemical processes in arc discharges used in atomic emission spectral analysis (review)

Until the beginning of the 21st century, the arc discharge was the main source of excitation of the atomic spectra of elements during routine atomic emission spectral analysis. The wide application of this spectral source at the same time aroused great interest of analysts in the study of complex thermochemical processes occurring at its electrodes and in the discharge plasma. This was due to the need to improve the metrological and informational characteristics of the analysis. Equilibrium thermodynamics has often been used to carry out such studies. It is shown that three levels of the thermodynamic approach can be distinguished here, differing in the complexity of the applied apparatus of thermodynamics and the information content of the results obtained. Numerous examples of the application of these levels of approach to the study of thermochemical processes occurring in the electrode or in the discharge plasma are given. The main advantages and disadvantages of the approaches used, which provide only qualitative information about the ongoing processes, are noted. The main disadvantage is the impossibility of predicting the composition of the arc plasma from the initial composition of the condensed sample. The most informative is the generalized thermodynamic model of thermochemical processes in a DC arc discharge from the sample surface and from the electrode crater. The model is based on the division of a non-stationary non-equilibrium system of an arc discharge into successive quasi-stationary subsystems. They correspond to the stage of sample evaporation and thermochemical transformation of its components in the discharge plasma. According to the model, the total equilibrium composition of the evaporated sample is initially calculated. This determines the initial composition of the arc plasma. Then, the total equilibrium composition of the arc plasma is calculated and the transition to the intensities of the spectral lines of the analytes is performed. The correctness of the generalized model, which gives semi-quantitative results, is confirmed by comparison with experimental data.

Transformation of nitrogen during microalgae model compounds liquefaction in sub-/supercritical ethanol

Nitrogen migration significantly affects the quality of bio-oil and the emission characteristics of pollutants during microalgae thermochemical transformation. To investigate the nitrogen migration and transformation of the main components of microalgae during liquefaction in sub- or supercritical ethanol, three model compounds (soya protein, castor oil, and corn starch) were selected to explore the interaction among various biochemical components and organic solvent at 220 °C and 260 °C. The nitrogen contents in the products were accurately quantified and characterized by GC–MS, element analysis, XPS, and FTIR analysis. The results imply that the addition of castor oil has a negligible effect on the nitrogen transformation during liquefaction, while corn starch promotes more than 22.16 wt% of the nitrogen transfer into the solid residue. Pyrrolidinone is the main nitrogen-containing compound in the oil products; neither pyridine-N nor nitrile-N are detected. It indicates that the hydrogen supply of ethanol is also suitable for the addition of C-N unsaturated bonds in bio-oils. The model compounds containing corn starch generate pyrazines only at the higher temperature and pressure.

An appraisal on valorization of lignin: A byproduct from biorefineries and paper industries

Lignocellulose based processes consist of technology platforms for production of materials and products for developing a bio-based, sustainable economy. Production of sugar streams and ethanol from cellulose is a mature technology, and its deployment results in increased lignin availability. Although lignin is used for low-value applications, its high-value utilization needs to be explored and developed. The aromatic intermediates from lignin can be transformed into high-value products. The unique structural/chemical properties of lignin offer possibilities for valorization, which can be achieved through thermochemical or biological transformation platforms, each route having its pros and cons. Lignin degrading oragnisms hold promise for biovalorization. In this work, different categories of organisms (fungi and bacteria) capable of degrading lignin, possessing unique repertoires of enzymes have been discussed. Under natural niches consortium of organisms decay lignin as a single organism does not possess all the activities. The constraints in biological processing can be addressed by using a combination of processes for lignin depolymerization to aromatic intermediates, followed by their conversion to target products. The recent devised metabolic engineering strategies to tackle these challenges are reviewed. Ultimately, the success of biorefineries will be dictated by the technical feasibility of bioconversions, robustness of engineered organisms, and their ability to produce the desired products in high titers with relatively high purity, scalability, and overall economics.