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Records with Subject: Reaction Engineering
Showing records 1 to 25 of 287. [First] Page: 1 2 3 4 5 Last
Investigation of the Mixing Time Distribution and Connected Flow Fields in Two-Stage Stirred Vessels
Marian Matzke, Mathias Ulbricht, Heyko Jürgen Schultz
June 24, 2024 (v1)
Keywords: flow fields, laser-induced fluorescence (LIF), mixing time, stirred vessels, two-stage impellers
In this study, laser-induced fluorescence is used to investigate the homogenization in stirred vessels equipped with single- and two-stage stirrers. The acquired local mixing times across the reactor cross-section are plotted as mixing time distribution (MTD) and then compared with the previously measured flow fields of the identical systems. With the help of a novel evaluation method, the mixing times are characterized with a normal distribution fit. With mean value and standard deviation as determined parameters, the mixing results of different installation heights and stirrer combinations are quantitatively evaluated and lead to clear recommendations for installations that enable efficient mixing.
Aza-Michael Additions of Benzylamine to Acrylates Promoted by Microwaves and Conventional Heating Using DBU as Catalyst via Solvent-Free Protocol
Leticia Chavelas-Hernández, Luis G. Hernández-Vázquez, José D. Bahena-Martínez, Alexa B. Arroyo-Colín, Sinuhe G. Flores-Osorio, Gabriel Navarrete-Vázquez, Jaime Escalante
June 24, 2024 (v1)
Keywords: aza-Michael addition, DBU, microwaves, solvent free, β-amino esters
In recent years, the use of solvent-free reactions represents a challenge for organic chemists, since it would help to optimize methodologies and contribute to the development of sustainable chemistry. In this regard, our research group has intensified efforts in the search for reactions that can be carried out in the absence of a solvent. In this paper, we present a protocol for the aza-Michael addition of benzylamine to α,β-unsaturated esters to prepare N-benzylated β-amino esters in the presence of catalytic amounts of DBU (0.2 eq) via solvent-free reaction. Depending on the α,β-unsaturated esters, we observed a reduction in reaction times, with good to excellent yields for aza-Michael addition.
Synthesis of 2,6-Dihydroxybenzoic Acid by Decarboxylase-Catalyzed Carboxylation Using CO2 and In Situ Product Removal
Daniel Ohde, Benjamin Thomas, Paul Bubenheim, Andreas Liese
June 24, 2024 (v1)
Keywords: Carbon Dioxide, carboxylation, decarboxylase, in situ product removal, process development
For the enzymatic carboxylation of resorcinol to 2,6-dihydroxybenzoic acid (2,6-DHBA) using gaseous CO2 in an aqueous triethanolamine phase, an adsorption-based in situ product removal was demonstrated. The aim is to improve the reaction yield, which is limited by an unfavourable thermodynamic equilibrium. First, a screening for a high-affinity adsorber was carried out. Then, the application of a suitable adsorber was successfully demonstrated. This enabled achieving reaction yields above 80% using the adsorber for in situ product removal. The applied biotransformation was scaled up to 1.5 L at lab-scale. Furthermore, a downstream process based on the elution and purification of the product bound to the adsorber was developed to obtain 2,6-DHBA in high purity. Recycling is one of the key factors in this system, making it possible to recycle the reaction medium, the adsorber and the solvents in additional batches.
Catalytic Acetone Oxidation over MnOx Catalysts: Regulating Their Crystal Structures and Surface Properties
Bohang Cai, Fawei Lin, Xuan Guo, Yongtao Li
June 7, 2024 (v1)
Keywords: calcination conditions, microwave hydrothermal, MnOx catalysts, VOC oxidation
This study investigates the catalytic oxidation of acetone by different crystal phases of MnO2 prepared via different methods. Compared with β-MnO2 and γ-MnO2, α-MnO2 exhibited superior catalytic activity. Moreover, as replacements for traditional hydrothermal methods and air calcination, the use of microwave hydrothermal methods and N2 calcination significantly enhanced the catalytic performance of the MnO2 catalyst. The optimal catalyst, MnO2-WN (α-MnO2 synthesized via microwave hydrothermal method and N2 calcination), converted 100% of 100 ppm acetone below 150 °C, with the CO2 yields reaching 100%. Further, the stability of the catalyst and its potential for other volatile organic compounds (VOCs) were also determined. The experimental data demonstrated that its outstanding activity primarily stemmed from the improved preparation method, enhancing the specific surface area of the catalyst, optimizing the pore structure, improving the redox performance, and generating more acidic si... [more]
MYB Transcriptional Factors Affects Upstream and Downstream MEP Pathway and Triterpenoid Biosynthesis in Chlamydomonas reinhardtii
Muhammad Anwar, Jingkai Wang, Jiancheng Li, Muhammad Mohsin Altaf, Zhangli Hu
June 6, 2024 (v1)
Keywords: C. reinhardtii, heterologous overexpression, MEP pathway, MYB transcriptional factor, squalene, synthetic biology, triterpenoids
Terpenoids are enormous and different types of naturally occurring metabolites playing an important role in industrial applications. Cost-effective and sustainable production of terpenoids at commercial scale is the big challenge because of its low abundance from their natural sources. Metabolic and genetic engineering in microorganisms provide the ideal platform for heterologous overexpression protein systems. The photosynthetic green alga Chlamydomonas reinhardtii is considered as a model host for the production of economic and sustainable terpenoids, but the regulation mechanism of their metabolisms is still unclear. In this study, we have investigated the genetic and metabolic synthetic engineering strategy of MYB transcriptional factors (MYB TFs) in terpenoids’ synthesis from C. reinhardtii for the first time. We heterologous overexpressed MYB TFs, specifically SmMYB36 from Salvia miltiorrhiza in C. reinhardtii. MYB upregulated the key genes involved in the 2-C-methyl-D-erythritol... [more]
Synergistic Effects of Plastid Terminal Oxidases 1 and 2 in Astaxanthin Regulation under Stress Conditions
Jun Chen, Jiangxin Wang, Hui Li, Ming Xiao, Yihong Zheng, Jiancheng Li, Jinxia Wu, Guanqin Huang
June 6, 2024 (v1)
Keywords: Chlamydomonas reinhardtii CC849, plastid terminal oxidases, ptox1, ptox2, RNAi
Plastid terminal oxidases (PTOXs) are essential for maintaining photosynthetic efficiency and cellular redox homeostasis. Astaxanthin, a carotenoid pigment with antioxidant properties, is synthesized and accumulates in response to oxidative stress induced by high-light intensity or nutrient limitation. It suggests that PTOX may impact astaxanthin biosynthesis under environmental stress conditions due to its involvement in ROS regulation. The ptox1 gene is thought to have a conserved role in safeguarding the photosynthetic apparatus from over-reduction and participating in energy dissipation. On the other hand, the ptox2 gene seems to be involved in the evolution of astaxanthin synthesis and adaptive responses to diverse environmental stressors. Efficient gene silencing strains were developed in Chlamydomonas reinhardtii CC849 for ptox1 and ptox2. The study found that the ptox2 gene correlates highly with resistance to intense light stress. Furthermore, the ptox2 gene showed increased a... [more]
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/g.hr 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]
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