Records with Subject: Reaction Engineering
Showing records 1 to 25 of 281. [First] Page: 1 2 3 4 5 Last
The Kinetic Mechanism of the Thermal Decomposition Reaction of Small Particles of Limestone at Steelmaking Temperatures
Chenxiao Li, Yun Zhang, Yuekai Xue, Kaixuan Zhang, Shuhuan Wang, Huakang Sun, Huaqing Xie
February 10, 2024 (v1)
Keywords: carbon dioxide partial pressure, converter steelmaking, decomposition kinetics, low carbon, small-particle limestone
Converter blowing limestone powder making slag steelmaking process has the advantages of low carbon and high efficiency, and can realize the resource utilization of CO2 in the metallurgical process, which is in line with the development direction of green metallurgy. Based on a thermogravimetric-differential thermal analyzer, the kinetic mechanism of decomposition of small limestone at steelmaking temperatures was investigated by a modified double extrapolation method. The results showed that with a higher rate of heating, limestone decomposition lagged, and decomposition temperature increased. Furthermore, the smaller the limestone particle size, the lower the activation energy of decomposition. Compared with N2, air, and O2, small limestone powder used for converter blowing could complete more rapid decomposition, and the time required for decomposition shortened by about 1/3, although the decomposition temperature increased in the CO2. The limestone decomposition rate increased and... [more]
A New Approach to the Preparation of Stable Oxide-Composite Cobalt−Samarium Catalysts for the Production of Hydrogen by Dry Reforming of Methane
A. G. Dedov, A. S. Loktev, V. A. Arkhipova, M. A. Bykov, A. A. Sadovnikov, K. A. Cherednichenko, G. A. Shandryuk
September 20, 2023 (v1)
Keywords: cobalt–samarium oxide catalysts, dry reforming of methane, heterogeneous catalysis, Hydrogen, Syngas
A new approach to preparing a series of Co/Sm2O3 catalysts for hydrogen production by the dry reforming of methane has been developed. The catalyst precursors were synthesized with a simple method, including the evaporation of aqueous solutions of cobalt and samarium nitrates, followed by a short-term calcination of the resulting material. The as-prepared and spent catalysts were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, temperature-programmed reduction, and thermogravimetric analysis. The content of cobalt in the synthesized materials affects their phase composition and carbonization resistance in the dry reforming of the methane reaction. It has been shown that preheating in N2 atmosphere produces catalysts that provide a stable yield of hydrogen and CO of 94−98% for at least 50 h at 900 °C. These yields are among the highest currently available for the dry reforming of methane catalysts made from Co-Sm complex oxides. It h... [more]
Highly Dispersed and Stable Ni/SiO2 Catalysts Prepared by Urea-Assisted Impregnation Method for Reverse Water−Gas Shift Reaction
Ning Liu, Sha Cui, Zheyu Jin, Zhong Cao, Hui Liu, Shuqing Yang, Xianmin Zheng, Luhui Wang
July 4, 2023 (v1)
Keywords: Ni dispersion, Ni/SiO2 catalyst, reverse water-gas shift reaction, stability, urea
The nickel-based catalyst was more active in the reverse water-gas shift reaction, but it is easy to sinter and deactivate in high temperature reaction (≥600 °C). A urea-assisted impregnation method was utilized to create a Ni/SiO2-N catalyst to increase the catalytic stability of Ni-based catalysts. For at least 20 h, the Ni/SiO2-N catalyst in the reverse water-gas shift process at 700 °C remained stable, and in the high temperature RWGS reaction, the conversion rate of CO2 of the catalyst is close to the equilibrium conversion rate. The catalysts were characterized by BET, XRD, H2-TPR, and TEM, and the results demonstrate that the Ni particles had a small particle size and exhibited strong interaction with the SiO2 support in the Ni/SiO2-N catalyst, which led to the catalyst’s good activity and stability. Urea-assisted impregnation is a facile method to prepare stable Ni/SiO2 catalysts with high Ni dispersion.
Product Yields Dependency on the Carbide Phase Presence in Cobalt and Iron SBA-15 Catalysts Structure in the Fischer−Tropsch Synthesis
Nikita Sharkov, Zahra Gholami, Ivana Hradecká, Zdeněk Tišler, Josef Šimek
June 9, 2023 (v1)
Keywords: carbide catalyst, CoCx/SBA-15, FeCx/SBA-15, Fischer–Tropsch synthesis
The use of carbide catalysts in Fischer−Tropsch synthesis (FTS) is an active area of research, as carbide phases have been shown to improve the stability and performance of catalysts in this reaction. This study compared the catalytic activity and product selectivity of cobalt and iron catalysts supported on SBA-15, with and without a carbide phase and reduction treatment before the reaction. Results showed that the presence of the carbide phase had a noticeable influence on the catalytic behavior of the catalysts, and the reduction of the catalyst with hydrogen also affected the product selectivity. The presence of the carbide phase in non-reduced cobalt catalysts resulted in increased selectivity to liquid phase products, as evidenced by a CO conversion of 37% with 68% selectivity to the products in the liquid phase. The catalytic activity of the iron carbide catalyst for CO dissociation was found to be 38% after reducing the catalyst with hydrogen, leading to the formation of more a... [more]
In-Situ Generation of Nitrogen-Doped MoS2 Quantum Dots Using Laser Ablation in Cryogenic Medium for Hydrogen Evolution Reaction
Fatemeh Shahi, Parviz Parvin, Seyedeh Zahra Mortazavi, Ali Reyhani, Mohtada Sadrzadeh, Ali Moafi, Mahdi Ebrahimi, Mohammadreza Aghaei
May 2, 2023 (v1)
Keywords: hydrogen evolution reaction, liquid nitrogen, MoS2 quantum dots, nitrogen doping, pulsed laser ablation
Here, nitrogen doped molybdenum disulfide quantum dots (N-MoS2 QDs) are fabricated by making use of the pulsed laser ablation (PLA) process in liquid nitrogen (LN2) as a dopant agent. In fact, LN2 contributes the rapid condensation of the plasma plume to form MoS2 QDs, optimizing the conditions for the synthesis of N-doped MoS2 with p-type property. The structural/optical features of the synthesized products are studied using transmission electron microscopy (TEM), absorption spectroscopy, photoluminescence (PL) spectroscopy techniques, and X-ray photoelectron spectroscopy (XPS). The TEM image shows the creation of MoS2 QDs with 5.5 nm average size. UV-vis and PL spectroscopy confirm the formation of N-MoS2 QDs according to the dominant peaks. The Tuck plot gives a direct band-gap of 4.34 eV for MoS2 QDs. Furthermore, XPS spectroscopy reveals Mo-N bonding, indicating nitrogen doping as evidence of p-type MoS2 QDs. Thus, PLA provides a single-stage way to the clean and green synthesis o... [more]
Study of the NH3-SCR Mechanism on LaMnO3 Surfaces Based on the DFT Method
Dongdong Ren, Kai Wu, Siyi Luo, Yongjie Li, Keting Gui, Zongliang Zuo, Xianjun Guo
May 2, 2023 (v1)
Keywords: DFT, LaMnO3, NH3-SCR, NOx removal
LaMnO3 with perovskite structure is a SCR de-NOx catalyst with good performance at low temperatures. In this paper, the SCR reaction process on the 010 surface of LaMnO3 catalyst was studied by DFT method, to guide the development of catalysts and their effective application. The results obtained through research indicate that both E-R and L-H mechanisms exist on the catalyst surface. The NH3 molecule can be absorbed on L acid and then oxidized by lattice oxygen to form NH2. Then, NH2 can react with the NO molecule to form NH2NO and decompose to N2 and H2O. The NH3 can also be absorbed with hydroxyl to form NH4+, it can also react with NO to form NH2NO and then decompose. The NH4+ also can react with NO3− which is formed by NO oxidized when O2 is present, to participate in the rapid SCR process.
Effect of Mixing Section Acoustics on Combustion Instability in a Swirl-Stabilized Combustor
Donghyun Hwang, Cheolwoong Kang, Kyubok Ahn
May 2, 2023 (v1)
Keywords: combustion instability, inlet mixing section, swirl number, swirl-stabilized combustor, turbulent lean premixed flame
An experimental study was performed to investigate the characteristics of two different combustion instability modes in a swirl-stabilized combustor. The first is the eigenfrequency corresponding to the half-wave of the combustion chamber section, and the second is the quarter-wave eigenmode of the inlet mixing section. The purpose of this study is to understand the effects of the swirl number on each combustion instability mode and analyze their generalized characteristics. Premixed gases composed of hydrocarbon fuels (C2H4 and CH4) and air were burned by independently varying the experimental conditions. Three dynamic pressure transducers and a photomultiplier tube were installed to detect pressure oscillations and heat release fluctuations in the inlet and combustion chamber sections, respectively. A high-speed camera was used to capture the instantaneous flame structures. In the swirl-stabilized combustor, the bands of the dominant frequencies were strongly dependent on the swirl n... [more]
Stability of the Steady States in Multidimensional Reaction Diffusion Systems Arising in Combustion Theory
Qingxia Li, Xinyao Yang
May 2, 2023 (v1)
Keywords: exponential weights, nonlinear stability, planar front, steady state
We prove that the steady states of a class of multidimensional reaction−diffusion systems are asymptotically stable at the intersection of unweighted space and exponentially weighted Sobolev spaces, paying particular attention to a special case, namely, systems of equations that arise in combustion theory. The steady-state solutions considered here are the end states of the planar fronts associated with these systems. The present work can be seen as a complement to the previous results on the stability of multidimensional planar fronts.
The Influence Mechanism of Neutron Kinetics of the Accelerator-Driven Subcritical Reactor Based on the Fast/Thermal Neutron Spectra by Monte Carlo Homogenization Method
Nianbiao Deng, Chao Xie, Cheng Hou, Zhulun Li, Jinsen Xie, Tao Yu
April 28, 2023 (v1)
Keywords: ADS Subcritical Reactor, deep subcriticality, heterogeneity of neutron fluence rate in time–space, Monte Carlo homogenization method, neutron kinetics
For the sake of understanding the mechanism of deep subcriticality and high heterogeneity of neutron fluence rate in time−space on the neutron kinetics of the Accelerator-driven Subcritical Reactor Subcritical Reactor (ADSR) under varied beam transients and neutron spectra. A Monte Carlo homogenization approach for the neutron time−space kinetics of the ADSR is proposed in this study, and the influence mechanism on the kinetic parameters of the ADSR under varied neutron spectra, subcriticality, and beam transients is examined. The results show that the Monte Carlo homogenization for the α eigenvalue mode is more adaptable to the subcriticality characteristics under varied subcriticality; under beam transients, the relative differences in the kinetic parameters of the different modes of the ADSR with fast/thermal spectra increase with the depth of subcriticality, and the differences in neutron generation time for varied modes are larger than those of effective fraction of delayed neutro... [more]
Non-Coaxially Rotating Motion in Casson Martial along with Temperature and Concentration Gradients via First-Order Chemical Reaction
Noman Jabbar, Muhammad Bilal Hafeez, Sameh Askar, Umar Nazir
April 27, 2023 (v1)
Keywords: chemical reaction, non-coaxial rotation, Nusselt number, Sherwood number, transportation
The effect of non-coaxial rotation on the transport of mass subjected to first-order chemical reaction is studied analytically. The effects of thermal radiation, buoyancy, constructive and destructive chemical reactions along with Casson fluid in rotating frame are discussed. Time evolution of primary and secondary velocities, energy and solute particles are analyzed. The behavior of flow under the variation of intensity of magnetic field is also investigated. Evolutionary behavior of primary velocity is opposite to the evolutionary behavior of secondary velocity. The impact of buoyant force on primary velocity is opposite to the role of buoyant force on the secondary velocity. The evolutionary behavior of temperature is also examined and a remarkable enhancement in temperature is noticed. Thermal radiation causes the fluid to be cooled down as heat energy is escaped by thermal radiation. Evolutionary behavior of concentration is also analyzed and an increasing of concentration versus... [more]
Egalitarian Kinetic Models: Concepts and Results
Denis Constales, Gregory Yablonsky, Yiming Xi, Guy Marin
April 27, 2023 (v1)
Keywords: acyclic and cyclic mechanisms, egalitarian kinetics, hierarchical kinetics
In this paper, two main ideas of chemical kinetics are distinguished, i.e., a hierarchy and commensuration. A new class of chemical kinetic models is proposed and defined, i.e., egalitarian kinetic models (EKM). Contrary to hierarchical kinetic models (HKM), for the models of the EKM class, all kinetic coefficients are equal. Analysis of EKM models for some complex chemical reactions is performed for sequences of irreversible reactions. Analytic expressions for acyclic and cyclic mechanisms of egalitarian kinetics are obtained. Perspectives on the application of egalitarian models for reversible reactions are discussed. All analytical results are illustrated by examples.
The Thermodynamic and Kinetic Effects of Sodium Lignin Sulfonate on Ethylene Hydrate Formation
Yiwei Wang, Lin Wang, Zhen Hu, Youli Li, Qiang Sun, Aixian Liu, Lanying Yang, Jing Gong, Xuqiang Guo
April 27, 2023 (v1)
Keywords: hydrate, kinetics, model, sodium lignin sulfonate, thermodynamics
Hydrate-based technologies (HBTs) have high potential in many fields. The industrial application of HBTs is limited by the low conversion rate of the water into hydrate (RWH), and sodium lignin sulfonate (SLS) has the potential to solve the above problem. In order to make the HBTs in the presence of SLS applied in industry and promote the advances of commercial HBTs, the effect of SLS on the thermodynamic equilibrium hydrate formation pressure (Peq) was investigated for the first time, and a new model (which can predict the Peq) was proposed to quantitatively describe the thermodynamic effect of SLS on the hydrate formation. Then, the effects of pressure and initial SLS concentration on the hydrate formation rate (rR) at different stages in the process of hydrate formation were investigated for the first time to reveal the kinetic effect of SLS on hydrate formation. The experimental results show that SLS caused little negative thermodynamic effect on hydrate formation. The Peq of the e... [more]
Propane Pre-Reforming into Methane-Rich Gas over Ni Catalyst: Experiment and Kinetics Elucidation via Genetic Algorithm
Sergey I. Uskov, Dmitriy I. Potemkin, Leniza V. Enikeeva, Pavel V. Snytnikov, Irek M. Gubaydullin, Vladimir A. Sobyanin
April 27, 2023 (v1)
Keywords: Genetic Algorithm, kinetics, liquefied petroleum gas, nickel catalyst, pre-reforming, propane
Pre-reforming of propane was studied over an industrial nickel-chromium catalyst under pressures of 1 and 5 bar, at a low steam to carbon molar ratio of 1, in the temperature range of 220−380 °C and at flow rates of 4000 and 12,000 h−1. It was shown that propane conversion proceeded more efficiently at low pressure (1 atm) and temperatures above 350 °C. A genetic algorithm was applied to search for kinetic parameters better fitting experimental results in such a wide range of experimental conditions. Power law and Langmuir−Hinshelwood kinetics were considered. It was shown that only Langmuir−Hinshelwood type kinetics correctly described the experimental data and could be used to simulate the process of propane pre-reforming and predict propane conversion under the given reaction conditions. The significance of Langmuir−Hinshelwood kinetics increases under high pressure and temperatures below 350 °C.
Extension of Pin-Based Point-Wise Energy Slowing-Down Method for VHTR Fuel with Double Heterogeneity
Tae-Young Han, Jin-Young Cho, Chang-Keun Jo, Hyun-Chul Lee
April 26, 2023 (v1)
Keywords: double heterogeneity, PSM, resonance treatment, VHTR
For the resonance treatment of a very high temperature reactors (VHTR) fuel with the double heterogeneity, an extension of the pin-based pointwise energy slowing-down method (PSM) was developed and implemented into DeCART. The proposed method, PSM-double heterogeneity (DH), has an improved spherical unit cell model with an explicit tri-structural isotropic (TRISO) model, a matrix layer, and a moderator for reflecting the moderation effect. The moderator volume was analytically derived using the relation of the Dancoff factor and the mean chord length. In the first step, the pointwise homogenized cross-sections for the compact was obtained after solving the slowing down equation for the spherical unit cell. Then, the shielded cross-section for the homogenized fuel compact was generated using the original PSM. The verification calculations were performed for the fuel pins with various packing fractions, compact sizes, TRISO sizes, and fuel temperatures. Additionally, two fuel block probl... [more]
A Review on Production of Light Olefins via Fluid Catalytic Cracking
Zahra Gholami, Fatemeh Gholami, Zdeněk Tišler, Martin Tomas, Mohammadtaghi Vakili
April 26, 2023 (v1)
Keywords: catalyst types, FCC process, light olefin production, operating conditions
The fluid catalytic cracking (FCC) process is an alternative olefin production technology, with lower CO2 emission and higher energy-saving. This process is used for olefin production by almost 60% of the global feedstocks. Different parameters including the operating conditions, feedstock properties, and type of catalyst can strongly affect the catalytic activity and product distribution. FCC catalysts contain zeolite as an active component, and a matrix, a binder, and a filler to provide the physical strength of the catalyst. Along with the catalyst properties, the FCC unit’s performance also depends on the operating conditions, including the feed composition, hydrocarbon partial pressure, temperature, residence time, and the catalyst-to-oil ratio (CTO). This paper provides a summary of the light olefins production via the FCC process and reviews the influences of the catalyst composition and operating conditions on the yield of light olefins.
Influence of the Fuel/Oxidant Ratio on the Elaboration of Binary Oxide Catalyst by a Microwave-Assisted Solution Combustion Method
Kawthar Frikha, Simona Bennici, Jamel Bouaziz, Kamel Chaari, Lionel Limousy
April 26, 2023 (v1)
Keywords: CO oxidation, Cu, influence of the stoichiometry, microwave-assisted solution combustion, Ni, or Co oxides
Three series of binary metal oxide catalysts containing Ni, Cu, or Co oxides were prepared, fully characterized and tested in CO oxidation. The catalysts, with a constant transition metal loading of 10 wt%, were prepared from metal nitrates and urea mixtures by a microwave-assisted solution combustion method. The RV/OV ratio, corresponding to the stoichiometry of the reactants, calculated from their elemental oxidizing and reducing valences, was varied. In order to modify the redox character of the synthesis medium from the quantity of urea; an excess of urea was used for attaining reducing conditions, while a deficit of urea shifted the medium to oxidizing conditions. Three RV/OV ratios (0.9, 1.0, and 1.1) were selected to elaborate the different binary metal oxide catalysts, nine oxide catalysts were synthesized. Then, the influence of the stoichiometry (RV/OV ratio) on the bulk and surface properties of the binary metal oxide catalysts was investigated. Similarly, the influence of t... [more]
An Evaluation of the Effects of the Potato Starch on the Biogas Produced from the Anaerobic Digestion of Potato Wastes
R. Alrefai, A.M. Alrefai, K.Y. Benyounis, J. Stokes
April 25, 2023 (v1)
Keywords: anaerobic digestion, bioenergy, bioproducts, biorefinery, potato starch, response surface methodology, waste management
Anaerobic digestion (AD) has undergone many developments since its first appearance. Despite that, there are still some environmental and economical obstacles that are limiting its sustainability. On the other hand, different types of starch have proven their effectiveness in some different applications. Food processing industries are considered one of the largest generators of waste in the environment. With an aid of the response surface methodology (RSM), the proposed study aimed to find an optimised way to overcome the obstacles by studying the impacts of the starch isolated from the potato peels on the biogas produced from the AD of potato peels before and after starch separation. The study found that potato peels represented approximately 12.5% of the potato total weight. The starch has only a slight influence on the quantity of the biogas produced and much lower influences on its quality. This finding suggests further investigation is required on the production of starch bio-base... [more]
The Activity and Stability of Promoted Cu/ZnO/Al2O3 Catalyst for CO2 Hydrogenation to Methanol
Nor Hafizah Berahim, Noor Asmawati Mohd Zabidi, Raihan Mahirah Ramli, Nur Amirah Suhaimi
April 25, 2023 (v1)
Keywords: activity, Cu/ZnO/Al2O3 catalyst, methanol synthesis, stability
Cu/ZnO/Al2O3 catalyst with the addition of tri-promoters (Mn/Nb/Zr) was investigated with respect to their catalytic activity and stability in a prolonged reaction duration in methanol synthesis. Spent catalysts were characterized using N2 adsorption-desorption, FESEM/EDX, TEM, N2O chemisorption, and XPS for their physicochemical properties. The catalyst longevity study was evaluated at two days, seven days, and 14 days at 300 °C, 31.25 bar, 2160 mL/ GHSV, and H2:CO2 at 10:1. The CO2 conversion and methanol yield decreased by about 5.7% and 7.7%, respectively, when the reaction duration was prolonged to 14 days. A slight reduction in catalytic activity under prolonged reaction duration was found due to thermal degradation.
Extracellular Polymeric Substances (EPS) as Microalgal Bioproducts: A Review of Factors Affecting EPS Synthesis and Application in Flocculation Processes
Wioleta Babiak, Izabela Krzemińska
April 21, 2023 (v1)
Keywords: Biomass, extracellular polymeric substances, flocculation, harvesting, microalgae cultivation
Microalgae are natural resources of intracellular compounds with a wide spectrum of applications in, e.g., the food industry, pharmacy, and biofuel production. The extracellular polymeric substances (EPS) released by microalgal cells are a valuable bioproduct. Polysaccharides, protein, lipids, and DNA are the main constituents of EPS. This review presents the recent advances in the field of the determinants of the synthesis of extracellular polymeric substances by microalgal cells and the EPS structure. Physical and chemical culture conditions have been analyzed to achieve useful insights into the development of a strategy optimizing EPS production by microalgal cells. The application of microalgal EPS for flocculation and mechanisms involved in this process are also discussed in terms of biomass harvesting. Additionally, the ability of EPS to remove toxic heavy metals has been analyzed. With their flocculation and sorption properties, microalgal EPS are a promising bioproduct that can... [more]
The Prospects of Agricultural and Food Residue Hydrolysates for Sustainable Production of Algal Products
Ehab M. Ammar, Neha Arora, George P. Philippidis
April 11, 2023 (v1)
Keywords: agricultural residue, Biofuels, Biomass, bioproducts, food residue, hydrolysate, microalgae
The growing demand of microalgal biomass for biofuels, nutraceuticals, cosmetics, animal feed, and other bioproducts has created a strong interest in developing low-cost sustainable cultivation media and methods. Agricultural and food residues represent low-cost abundant and renewable sources of organic carbon that can be valorized for the cultivation of microalgae, while converting them from an environmental liability to an industrial asset. Biochemical treatment of such residues results in the release of various sugars, primarily glucose, sucrose, fructose, arabinose, and xylose along with other nutrients, such as trace elements. These sugars and nutrients can be metabolized in the absence of light (heterotrophic) or the presence of light (mixotrophic) by a variety of microalgae species for biomass and bioproduct production. The present review provides an up-to-date critical assessment of the prospects of various types of agricultural and food residues to serve as algae feedstocks an... [more]
Microalgal Consortia for Waste Treatment and Valuable Bioproducts
Shousong Zhu, Lauren Higa, Antonia Barela, Caitlyn Lee, Yinhua Chen, Zhi-Yan Du
March 20, 2023 (v1)
Keywords: biofuel, biomass production, microalgal consortia, resource recovery, symbiosis, wastewater treatment
Microalgae have been considered a promising and sustainable candidate for wastewater treatment and valuable bioproducts, such as feedstocks for food, nutrients, and energy. However, many challenging bottlenecks, such as low biomass productivity, expensive biomass harvesting techniques, and inefficient extraction of biofuels restrict its large-scale commercial production. Symbiotic relationships between microalgae and bacteria, also known as microalgal consortia, have proven to be effective solutions for mitigating technical and economic limitations. The natural and artificial symbiotic microalgal consortia combine microorganisms with various metabolic activities, which leads to valuable biomass production and the removal of nutrients, pharmaceuticals, and personal care products (PPCP) from wastewater. Many microalgal consortia have been applied for various wastewater treatments with reduced energy costs and higher efficiency in recovering valuable resources. In this study we review the... [more]
Py-GC-MS Study on Catalytic Pyrolysis of Biocrude Obtained via HTL of Fruit Pomace
Mariusz Wądrzyk, Marek Plata, Kamila Zaborowska, Rafał Janus, Marek Lewandowski
March 7, 2023 (v1)
Keywords: bio-oil, biocrude, Biomass, bioproducts, blackcurrant pomace, fruit pomace, hydrothermal liquefaction, pyrolysis, Renewable and Sustainable Energy, upgrading
Herein, we proposed new two-stage processing of blackcurrant pomace toward a value-added, hydrocarbon-rich biocrude fraction. The approach consisted of thermochemical liquefaction of a wet-type organic matter into liquid biocrude followed by its upgrade by thermal and catalytic pyrolysis. Particularly, we put effort into investigating the effect of selected catalysts (ZSM-5 and HY zeolite) on the composition of the volatiles released during the pyrolysis of the biocrude. The latter was obtained through liquefaction of the raw material in the binary solvent system of water and isopropanol. The biocrude yield accounted for ca. 45 wt.% of the initial dry biomass. It was a complex mixture of various component groups with an abundant share of oxygenates, especially carboxylic acids and esters. Thereafter, the biocrude was subjected to a pyrolysis study performed by means of the microscale coupled pyrolysis-gas chromatography-mass spectrometry technique (Py-GC-MS). The dominant components id... [more]
Recent Achievements in Microalgal Photobiological Hydrogen Production
Eleftherios Touloupakis, Cecilia Faraloni, Ana Margarita Silva Benavides, Giuseppe Torzillo
March 7, 2023 (v1)
Keywords: biohydrogen, Chlamydomonas reinhardtii, Chlorella sp., light conversion efficiency, microalgae, photobioreactors
It is well known that over the last 60 years the trend of long-lived greenhouse gas emissions have shown a strong acceleration. There is an increasing concern and a mounting opposition by public opinion to continue with the use of fossil energy. Western countries are presently involved in a so-called energy transition with the objective of abandoning fossil energy for renewable sources. In this connection, hydrogen can play a central role. One of the sustainable ways to produce hydrogen is the use of microalgae which possess two important natural catalysts: photosystem II and hydrogenase, used to split water and to combine protons and electrons to generate gaseous hydrogen, respectively. For about 20 years of study on photobiological hydrogen production, our scientific hopes were based on the application of the sulfur protocol, which indisputably represented a very important advancement in the field of hydrogen production biotechnology. However, as reported in this review, there is inc... [more]
Microalgal Systems for Wastewater Treatment: Technological Trends and Challenges towards Waste Recovery
Etiele G. Morais, Nathana L. Cristofoli, Inês B. Maia, Tânia Magina, Paulo R. Cerqueira, Margarida Ribau Teixeira, João Varela, Luísa Barreira, Luísa Gouveia
March 6, 2023 (v1)
Keywords: agroindustrial wastewater, industrial wastewater, microalgal bioproducts, strain isolation, urban wastewater
Wastewater (WW) treatment using microalgae has become a growing trend due the economic and environmental benefits of the process. As microalgae need CO2, nitrogen, and phosphorus to grow, they remove these potential pollutants from wastewaters, making them able to replace energetically expensive treatment steps in conventional WW treatment. Unlike traditional sludge, biomass can be used to produce biofuels, biofertilizers, high value chemicals, and even next-generation growth media for “organically” grown microalgal biomass targeting zero-waste policies and contributing to a more sustainable circular bioeconomy. The main challenge in this technology is the techno-economic feasibility of the system. Alternatives such as the isolation of novel strains, the use of native consortia, and the design of new bioreactors have been studied to overcome this and aid the scale-up of microalgal systems. This review focuses on the treatment of urban, industrial, and agricultural wastewaters by microa... [more]
Quantifying Environmental and Economic Impacts of Highly Porous Activated Carbon from Lignocellulosic Biomass for High-Performance Supercapacitors
Yuxi Wang, Jingxin Wang, Xufeng Zhang, Debangsu Bhattacharyya, Edward M. Sabolsky
March 3, 2023 (v1)
Keywords: activated carbon, bioproducts, economic feasibility, environmental impacts, lignocellulosic biomass, supercapacitor electrodes
Activated carbons (AC) from lignocellulosic biomass feedstocks are used in a broad range of applications, especially for electrochemical devices such as supercapacitor electrodes. Limited studies of environmental and economic impacts for AC supercapacitor production have been conducted. Thus, this paper evaluated the environmental and economic impacts of AC produced from lignocellulosic biomass for energy-storage purposes. The life cycle assessment (LCA) was employed to quantify the potential environmental impacts associated with AC production via the proposed processes including feedstock establishment, harvest, transport, storage, and in-plant production. A techno-economic model was constructed to analyze the economic feasibility of AC production, which included the processes in the proposed technology, as well as the required facility installation and management. A base case, together with two alternative scenarios of KOH-reuse and steam processes for carbon activation, were evaluat... [more]
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