Records with Subject: Reaction Engineering
Showing records 1 to 25 of 250. [First] Page: 1 2 3 4 5 Last
Morphology and Structure Controls of Single-Atom Fe−N−C Catalysts Synthesized Using FePc Powders as the Precursor
Ning Yan, Fan Liu, Xu Meng, Meng Qin, Guangqi Zhu, Luxia Bu, Zigeng Liu, Wei Wang
January 24, 2022 (v1)
Keywords: Fe–N–C, morphology, ORR
Understanding the origin of the high electrocatalytic activity of Fe−N−C electrocatalysts for oxygen reduction reaction is critical but still challenging for developing efficient sustainable nonprecious metal catalysts used in fuel cells. Although there are plenty of papers concerning the morphology on the surface Fe−N−C catalysts, there is very little work discussing how temperature and pressure control the growth of nanoparticles. In our lab, a unique organic vapor deposition technology was developed to investigate the effect of the temperature and pressure on catalysts. The results indicated that synthesized catalysts exhibited three kinds of morphology—nanorods, nanofibers, and nanogranules—corresponding to different synthesis processes. The growth of the crystal is the root cause of the difference in the surface morphology of the catalyst, which can reasonably explain the effect of the temperature and pressure. The oxygen reduction reaction current densities of the different catal... [more]
Case Study of Anaerobic Digestion Process Stability Detected by Dissolved Hydrogen Concentration
Daniela Platošová, Jiří Rusín, Jan Platoš, Kateřina Smutná, Roman Buryjan
January 24, 2022 (v1)
Keywords: amperometric sensor, anaerobic digestion, dissolved hydrogen, Fermentation, rotary bioreactor
The paper presents the results of a laboratory experiment of mesophilic single-stage anaerobic digestion performed to verify the possibility of early detection of process instability and reactor overload by evaluating the course of dissolved hydrogen concentration of the main intermediate. The digestion process was run in a Terrafors IS rotary drum bioreactor for 230 days. The substrate dosed on weekdays was food leftovers from the university canteen. At an average temperature of 37 °C, an organic loading of volatiles of 0.858 kg m−3 day−1 and a theoretical retention time of 259 days, biogas production of 0.617 Nm3 kg VS−1 was achieved with a CH4 content of 51.7 vol. %. The values of the established FOS/TAC stability indicator ranged from 0.26 to 11.4. The highest value was reached when the reactor was overloaded. The dissolved hydrogen concentration measured by the amperometric microsensor ranged from 0.039−0.425 mg dm−3. Data were statistically processed using Pearson’s correlation c... [more]
Batch Mode Reactor for 3,5-Dinitrosalicylic Acid Degradation by Phanerochaete chrysosporium
Rafał Madaj, Witold Sroczyński, Michał Sójka, Tomasz P. Olejnik, Elżbieta Sobiecka
January 24, 2022 (v1)
Keywords: batch reactor, biodegradation, Phanerochaete chrysosporium, the 3,5-dinitrosalicylic acid
A new batch mode reactor was constructed to conduct continuous biodegradation of 3,5-dinitrosalicylic acid. Various types of matrices with immobilized Phanerochaete chrysosporium were immersed in a solution containing pollutant and mineral nutrients. Three parameters were chosen to optimize the process. The nitrate and nitrite ions concentrations and HPLC analysis were used to prove the biodegradation of 3,5-dinitrosalicylic acid, and the mixed effects model using one-factor ANOVA was used for statistical calculations. The results showed the correlation between the initial pH, a medium composition, and the process time. In pH = 6.5, the degradation effectiveness was estimated at 99% decrease in the substrate within 14 days, while an 80% decrease of acid concentration was indicated in pH = 3.5 after 28 days of the process duration.
Development of Carbonization and a Relatively High-Temperature Halogenation Process for the Removal of Radionuclides from Spent Ion Exchange Resins
Hee-Chul Yang, Hyeon-Oh Park, Kyu-Tae Park, Sung-Jun Kim, Hyung-Ju Kim, Hee-Chul Eun, Keunyoung Lee
January 24, 2022 (v1)
Keywords: carbonization, halogenation, kinetic analysis, numerical optimization, spent resin, thermodynamic analysis
This study investigated a two-step thermochemical treatment process consisting of carbonization and halogenation for the removal of radionuclides from spent cation-exchange resin (CER). Based on a thermal analysis of cation-exchange resins, we propose a two-step thermochemical treatment process involving the conversion of spent CER into pyrocarbon and then the removal of radioactive elements from the carbonized CER by converting them volatile halides at very high temperatures. The proposed process mainly consists of a carbonization and halogenation reactor, a UHC (unburned hydrocarbon) combustor, and wet scrubber. A step-by-step experimental and numerical optimization study was conducted with the carbonization and halogenation reactor and the UHC combustor. The optimum operating conditions could be established based on the results of a thermal analysis of the CER, a nonisothermal kinetic analysis, a numerical modeling study of a plug flow reactor (PFR)-type combustor, and a thermodynam... [more]
A Process for the Synthesis and Use of Highly Aromatic Organosilanes as Additives for Poly(Vinyl Chloride) Films
Safaa H. Mohamed, Ayad S. Hameed, Gamal A. El-Hiti, Dina S. Ahmed, Mohammed Kadhom, Mohammed A. Baashen, Muna Bufaroosha, Ahmed A. Ahmed, Emad Yousif
December 6, 2021 (v1)
Keywords: dehydrochlorination, organosilanes, photostability, Schiff’s bases, ultraviolet irradiation absorbers, weight and molecular weight loss
Three organosilanes were synthesized in good yields from the condensation of 4,4′,4″-((phenylsilanetriyl)tris(oxy))tribenzaldehyde and 4-substituted anilines under acidic conditions. The structure of the organosilanes was confirmed using a variety of techniques. Organosilanes were mixed with poly(vinyl chloride) (PVC) and homogenous films were produced. The effect of long-term irradiation on the films containing organosilanes was tested using various methods. Monitoring the infrared spectra of PVC films before, during and after irradiation processes showed the formation of side products comprising polyene, carbonyl and hydroxyl groups. The intensities of absorption bands due to these functional groups were much lower in the presence of organosilanes as compared to the blank film. Also, the decrease in the weight and molecular weight of PVC films after irradiation was lower in the presence of organosilanes. Additionally, there was a minimal surface change of irradiated PVC in the presen... [more]
Influence of the Ni-Co/Al-Mg Catalyst Loading in the Continuous Aqueous Phase Reforming of the Bio-Oil Aqueous Fraction
Pablo Lozano, Ana I. Simón, Lucía García, Joaquín Ruiz, Miriam Oliva, Jesús Arauzo
October 14, 2021 (v1)
Keywords: acetic acid, acetol, aqueous fraction, aqueous phase reforming, bio-oil, Butanol, Ni catalyst
The effect of catalyst loading in the Aqueous Phase Reforming (APR) of bio-oil aqueous fraction has been studied with a Ni-Co/Al-Mg coprecipitated catalyst. Because of the high content of water in the bio-oil aqueous fraction, APR could be a useful process to convert this fraction into valuable products. Experiments of APR with continuous feeding of aqueous solution of acetol, butanol and acetic acid as the only compound, together with a simulated and a real aqueous fraction of bio-oil, were carried out. Liquid products in the liquid effluent of the APR model compounds were quantified and the reaction pathways were revised. The increase of catalyst loading produced an increase of gas production and a gas with higher alkanes content. Acetol was the compound with the highest reactivity while the conversion of acetic acid was very low. The presence of acetic acid in the feed caused catalyst deactivation.
Microemulsion vs. Precipitation: Which Is the Best Synthesis of Nickel−Ceria Catalysts for Ethanol Steam Reforming?
Cristina Pizzolitto, Federica Menegazzo, Elena Ghedini, Arturo Martínez Arias, Vicente Cortés Corberán, Michela Signoretto
October 14, 2021 (v1)
Keywords: coke resistance, ethanol steam reforming, lanthanum doping, microemulsion, Ni/CeO2
Ethanol steam reforming is one of the most promising ways to produce hydrogen from biomass, and the goal of this research is to investigate robust, selective and active catalysts for this reaction. In particular, this work is focused on the effect of the different ceria support preparation methods on the Ni active phase stabilization. Two synthetic approaches were evaluated: precipitation (with urea) and microemulsion. The effects of lanthanum doping were investigated too. All catalysts were characterized using N2-physisorption, temperature programmed reduction (TPR), XRD and SEM, to understand the influence of the synthetic approach on the morphological and structural features and their relationship with catalytic properties. Two synthesis methods gave strongly different features. Catalysts prepared by precipitation showed higher reducibility (which involves higher oxygen mobility) and a more homogeneous Ni particle size distribution. Catalytic tests (at 500 °C for 5 h using severe Ga... [more]
Investigation of Ni−Fe−Cu-Layered Double Hydroxide Catalysts in Steam Reforming of Toluene as a Model Compound of Biomass Tar
David Díez, Ana Urueña, Gregorio Antolín
October 14, 2021 (v1)
Keywords: gasification, hydrogen production, hydrotalcite, layered double hydroxide, Ni-based catalyst, tar, toluene steam reforming
This work focused on the synthesis of a catalyst based on layered double hydroxides with a molar cation concentration Ni/Cu/Fe/Mg/Al of 30/5/5/40/20 and its performance in the steam reforming of toluene as a model compound of biomass tar. Its performance at different temperatures (500, 600, 700, 800, and 900 °C) and steam/carbon molar ratios (S/C ratios) (1, 2, 4, 6, 8) was studied. The contact time used was 0.32 g h mol−1. The catalyst obtained allowed us to reach 98−99.87% gas conversion of toluene with a low carbon deposition on catalyst surface (1.4 wt %) at 800 °C and S/C = 4. In addition, conversions in the range of 600−700 °C were higher than 80% and 90%, respectively, and the type of carbon deposited on the catalyst was found to be filamentous, which did not significantly reduce the performance of the catalyst.
Evaluation of Novel Bio-Based Amino Curing Agent Systems for Epoxy Resins: Effect of Tryptophan and Guanine
Stefano Merighi, Laura Mazzocchetti, Tiziana Benelli, Loris Giorgini
September 22, 2021 (v1)
Keywords: DSC, epoxy resin, guanine, hardener system, renewable material, tryptophan
In order to obtain an environmentally friendly epoxy system, L-tryptophan and guanine were investigated as novel green curing agents for the cross-link of diglycidyl ether of Bisphenol A (DGEBA) as a generic epoxy resin model of synthetic and analogous bio-based precursors. In particular, L-tryptophan, which displays high reaction temperature with DGEBA, was used in combination with various bio-based molecules such as urea, theobromine, theophylline, and melamine in order to increase the thermal properties of the epoxy resin and to reduce the crosslinking reaction temperature. Later, in order to obtain similar properties using a single product, guanine, a totally heterocyclic molecule displaying amine functional groups, was tested as hardener for DGEBA. The thermal behavior of the precursor mixtures was evaluated by dynamic differential scanning calorimetry (DSC) leading to a preliminary screening of different hardening systems which offered a number of interesting hints in terms of bi... [more]
Lumped Kinetic Modeling of Polypropylene and Polyethylene Co-Pyrolysis in Tubular Reactors
Andreas E. Lechleitner, Teresa Schubert, Wolfgang Hofer, Markus Lehner
September 22, 2021 (v1)
Keywords: feedstock recycling, kinetic modeling, lumped modeling, plastic pyrolysis, ReOil
The recycling rates, especially those from plastic packaging waste, have to be increased according to the European Union directive in the next years. Besides many other technologies, the pyrolysis of plastic wastes seems to be an efficient supplementary opportunity to treat mixed and unpurified plastic streams. For this reason, a pyrolysis process was developed for the chemical recycling of hydrocarbons from waste polyolefins. The obtained products can be further processed and upgraded in crude oil refineries, so that also monomers can be recovered, which are used for the plastic polymerization again. However, to achieve a scale up to a demo plant, a kinetic model for predicting the yields of the plastic pyrolysis in a tubular reactor is needed. For this reason, a pilot plant was built, in which different plastics and carrier fluids can be tested. Based on the data generated at the pilot plant, a very practical and suitable model was found to describe the plastic co-pyrolysis of the ca... [more]
Insights into Thermal Degradation Behaviors and Reaction Kinetics of Medical Waste Infusion Bag and Nasal Oxygen Cannula
Lifan Zhang, Jiajia Jiang, Tengkun Ma, Yong Pan, Yanjun Wang, Juncheng Jiang
September 21, 2021 (v1)
Keywords: activation energy, medical plastic waste, reaction mechanism, thermal degradation, thermogravimetric
The thermal degradation behaviors and reaction kinetics of medical waste infusion bag (IB) and nasal oxygen cannula (NOC) were investigated under inert atmosphere with the heating rates of 5, 10, 15, and 25 K·min−1. Ozawa−Flynn−Wall (OFW), Kissinger−Akahira−Sunose (KAS), and Friedman were employed to estimate the activation energy. Coats−Redfern and Kennedy−Clark methods were adopted to predict the possible reaction mechanism. The results suggested that the reaction mechanism of IB pyrolysis was zero-order, and that of NOC pyrolysis was concluded that zero-order for the first stage and three-dimensional diffusion Jander equation for the second stage. Based on the kinetic compensation effect, the reconstructed reaction models for IB and NOC pyrolysis were elaborated by introducing adjustment functions. The results indicated that the reconstructed model fitted well with the experimental data. The results are helpful as a reference and provide guidance for the determination of IB and NOC... [more]
Effect of Ni(NO3)2 Pretreatment on the Pyrolysis of Organsolv Lignin Derived from Corncob Residue
Wenli Wang, Yichen Liu, Yue Wang, Longfei Liu, Changwei Hu
September 21, 2021 (v1)
Keywords: bio-oil, lignin, Ni(NO3)26H2O, pretreatment, pyrolysis
The thermal degradation of lignin for value-added fuels and chemicals is important for environment improvement and sustainable development. The impact of pretreatment and catalysis of Ni(NO3)2 on the pyrolysis behavior of organsolv lignin were studied in the present work. Samples were pyrolyzed at 500 ∘C with an upward fixed bed, and the characteristics of bio-oil were determined. After pretreatment by Ni(NO3)2, the yield of monophenols increased from 23.3 wt.% to 30.2 wt.% in “Ni-washed” and decreased slightly from 23.3 wt.% to 20.3 wt.% in “Ni-unwashed”. Meanwhile, the selective formation of vinyl-monophenols was promoted in “Ni-unwashed”, which indicated that the existence of nickel species promoted the dehydration of C-OH and breakage of C-C in pyrolysis. In comparison with “Water”, HHV of bio-oil derived from “Ni-unwashed” slightly increased from 27.94 mJ/kg to 28.46 mJ/kg, suggesting that the lowering of oxygen content in bio-oil is associated with improved quality. Furthermore,... [more]
Iron-Based Catalytically Active Complexes in Preparation of Functional Materials
Katarzyna Rydel-Ciszek, Tomasz Pacześniak, Izabela Zaborniak, Paweł Błoniarz, Karolina Surmacz, Andrzej Sobkowiak, Paweł Chmielarz
July 29, 2021 (v1)
Keywords: “green” oxidants, controlled radical polymerization, heterogeneous catalysis, homogeneous catalysis, iron-based catalysts, oxidation processes
Iron complexes are particularly interesting as catalyst systems over the other transition metals (including noble metals) due to iron’s high natural abundance and mediation in important biological processes, therefore making them non-toxic, cost-effective, and biocompatible. Both homogeneous and heterogeneous catalysis mediated by iron as a transition metal have found applications in many industries, including oxidation, C-C bond formation, hydrocarboxylation and dehydration, hydrogenation and reduction reactions of low molecular weight molecules. These processes provided substrates for industrial-scale use, e.g., switchable materials, sustainable and scalable energy storage technologies, drugs for the treatment of cancer, and high molecular weight polymer materials with a predetermined structure through controlled radical polymerization techniques. This review provides a detailed statement of the utilization of homogeneous and heterogeneous iron-based catalysts for the synthesis of bo... [more]
Methanol Synthesis with Steel-Mill Gases: Simulation and Practical Testing of Selected Gas Utilization Scenarios
Kai Girod, Heiko Lohmann, Stefan Schlüter, Stefan Kaluza
July 29, 2021 (v1)
Keywords: Carbon2Chem®, gas recirculation, MegaMax®800, methanol synthesis, process simulation, steel-mill gases
The utilization of CO2-containing steel-mill gases for synthesis of methanol was investigated. Four different scenarios with syngas derived from steel-mill gases were considered. A process model for an industrial methanol production including gas recirculation was applied to provide realistic conditions for catalyst performance tests. A long-term test series was performed in a close-to-practice setup to demonstrate the stability of the catalyst. In addition, the experimental results were used to discuss the quality of the simulation results. Kinetic parameters of the reactor model were fitted. A comparison of two different kinetic approaches and the experimental results revealed which approach better fits CO-rich or CO2-rich steel-mill gases.
Study of Deactivation in Suzuki Reaction of Polymer-Stabilized Pd Nanocatalysts
Linda Nikoshvili, Elena S. Bakhvalova, Alexey V. Bykov, Alexander I. Sidorov, Alexander L. Vasiliev, Valentina G. Matveeva, Mikhail G. Sulman, Valentin N. Sapunov, Lioubov Kiwi-Minsker
July 29, 2021 (v1)
Keywords: catalyst stability, hyper-cross-linked polystyrene, palladium nanoparticles, Suzuki cross-coupling
This work is addressed to the phenomenon of catalyst deactivation taking place during the repeated uses in the reaction of Suzuki-Miyaura (S-M) cross-coupling, which is widely applied in industry for C-C bond formation. Ligandless catalysts based on Pd(0) NPs supported on hyper-cross-linked polystyrene (HPS) of two types (non-functionalized and bearing tertiary amino groups) were studied in a model S-M reaction between 4-bromoanisole and phenylboronic acid. Synthesized catalysts were shown to be highly active under mild reaction conditions. HPS allows stabilization of Pd(0) NPs and prevents their agglomeration and detectable Pd leaching. However, the loss of catalytic activity was observed during recycling. The deactivation issue was assigned to the hydrophobic nature of non-functionalized HPS, which allowed a strong adsorption of cross-coupling product during the catalyst separation procedure. A thorough washing of Pd/HPS catalyst by hydrophobic solvent was found to improve to the big... [more]
Promising Catalytic Systems for CO2 Hydrogenation into CH4: A Review of Recent Studies
M. Carmen Bacariza, Daniela Spataru, Leila Karam, José M. Lopes, Carlos Henriques
July 29, 2021 (v1)
Keywords: active metals, CO2 conversion, CO2 methanation, heterogeneous catalysts, Power-to-Gas, reaction mechanism, Sabatier reaction, supports
The increasing utilization of renewable sources for electricity production turns CO2 methanation into a key process in the future energy context, as this reaction allows storing the temporary renewable electricity surplus in the natural gas network (Power-to-Gas). This kind of chemical reaction requires the use of a catalyst and thus it has gained the attention of many researchers thriving to achieve active, selective and stable materials in a remarkable number of studies. The existing papers published in literature in the past few years about CO2 methanation tackled the catalysts composition and their related performances and mechanisms, which served as a basis for researchers to further extend their in-depth investigations in the reported systems. In summary, the focus was mainly in the enhancement of the synthesized materials that involved the active metal phase (i.e., boosting its dispersion), the different types of solid supports, and the frequent addition of a second metal oxide... [more]
Carbon Source Competition in Biological Selenate Reduction under Other Oxyanions Contamination
Hyun-Woo Kim, Seong Hwan Hong, Hyeoksun Choi
July 29, 2021 (v1)
Keywords: biological reduction, fixed-bed biofilm reactor, nitrate, perchlorate, selenate
Selenate removal in drinking water is being vigorously debated due to the various health issues concerned. As a viable treatment option, this study investigated a fixed-bed biofilm reactor (FBBR) with internal recycling. The experimental design tested how hydraulic loading rate and electron donor affect selenate reduction together with other oxyanions. The tested accompanying oxyanions were nitrate and perchlorate and experiments were designed to test how an FBBR responded to the limited electron donor condition. The results showed that the reactor achieved almost complete selenate reduction with the initial hydraulic loading rate of 12 m3/m2/day (influent concentration of 1416 µg SeO42−/L). Increasing the hydraulic loading rates to 16.24 and 48 m3/m2/day led to a gradual decline in selenate removal efficiency. A sufficient external carbon source (C:N of 3.3:1) achieved an almost complete reduction of nitrate as well as selenate. The FBBR acclimated to selenate instantaneously and redu... [more]
Mechanistic Approach to Thermal Production of New Materials from Asphaltenes of Castilla Crude Oil
Natalia Afanasjeva, Andrea González-Córdoba, Manuel Palencia
July 28, 2021 (v1)
Keywords: asphaltenes, chain reaction, pyrolysis, structural parameters
Asphaltenes are compounds present in crude oils that influence their rheology, raising problems related to the extraction, transport, and refining. This work centered on the chemical and structural changes of the asphaltenes from the heavy Colombian Castilla crude oil during pyrolysis between 330 and 450 °C. Also, the development of new strategies to apply these macromolecules, and the possible use of the cracking products as a source of new materials were analyzed. The obtained products (coke, liquid, and gas) were collected and evaluated through the techniques of proton and carbon-13 nuclear magnetic resonance (1H and 13C NMR), elemental composition, Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), saturates, aromatics, resins, and asphaltenes (SARA) analysis, and gas chromatography−mass spectrometry (GC-MS). A comparison of the applied methods showed that the asphaltene molecules increased the average size of their aromatic sheets, lost their aliphatic... [more]
Chemoenzymatic Synthesis of New Aromatic Esters of Mono- and Oligosaccharides
Alina Ramona Buzatu, August E. Frissen, Lambertus A. M. van den Broek, Anamaria Todea, Marilena Motoc, Carmen Gabriela Boeriu
July 28, 2021 (v1)
Keywords: aromatic oligosaccharides, lipases, sugar ester
An efficient and convenient chemoenzymatic route for the synthesis of novel phenolic mono-, di- and oligosaccharide esters is described. Acetal derivatives of glucose, sucrose, lactose and inulin were obtained by chemical synthesis. The fully characterized pure sugar acetals were subjected to enzymatic esterification with 3-(4-hydroxyphenyl) propionic acid (HPPA) in the presence of Novozyme 435 lipase as a biocatalyst. The aromatic esters of alkyl glycosides and glucose acetal were obtained with good esterification yields, characterized by mass spectrometry (MALDI-TOF MS), infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (1H NMR, 13C NMR). The synthesis of aromatic esters of disaccharide acetals was successful only for the enzymatic esterification of sucrose acetal. The new chemoenzymatic route allowed the synthesis of novel aromatic esters of inulin as the inulin monoacetal monoester and diester and the inulin diacetal monoester with a polymerization degree of... [more]
Effect of Temperature and Concentration of Zeolite Catalysts from Geothermal Solid Waste in Biodiesel Production from Used Cooking Oil by Esterification−Transesterification Process
Luqman Buchori, W. Widayat, Oki Muraza, Muhamad Iqbal Amali, Rahma Wulan Maulida, Jedy Prameswari
July 26, 2021 (v1)
Keywords: analcime zeolite catalyst, biodiesel, geothermal solid waste, used cooking oil, yield of biodiesel
The production of biodiesel using zeolite catalysts from geothermal solid waste has been studied. This study aims to make zeolite catalysts as catalysts in biodiesel production, assessing the effect of catalyst concentration, and temperature in the esterification−transesterification process on the biodiesel yield produced. The results showed that the synthesized zeolite catalyst was an analcime zeolite catalyst (Al1.9Na1.86O12Si4). The biodiesel yield of 98.299% with 100% fatty acid alkyl ester (FAAE) content was achieved at a catalyst concentration of 5%wt and a reaction temperature of 300 °C for one-hour reaction time. The yield of biodiesel decreased with repeated catalysts, which experienced morphological changes before and after three usage times. Consequently, in this case, the catalyst cannot be regenerated.
Synthesis of 2-(4-hydroxyphenyl)ethyl 3,4,5-Trihydroxybenzoate and Its Inhibitory Effect on Sucrase and Maltase
Wen-Tai Li, Yu-Hsuan Chuang, Jiahn-Haur Liao, Jung-Feng Hsieh
July 19, 2021 (v1)
Keywords: hyperglycemia, inhibitor, kinetics assay, maltase, sucrase
We report on the synthesis of an active component, 2-(4-hydroxyphenyl)ethyl 3,4,5-trihydroxybenzoate (HETB), from Rhodiola crenulata. Subsequent analysis revealed that HETB exhibits α-glucosidase inhibitory activities on maltase and sucrase, with potency exceeding that of the known α-glucosidase inhibitors (voglibose and acarbose). An inhibition kinetics study revealed that HETB, acarbose, and voglibose bind to maltase and sucrase, and HETB was shown to be a strong competitive inhibitor of maltase and sucrase. In a molecular docking study based on the crystal structure of α-glucosidase from Saccharomyces cerevisiae, we revealed the HETB binding in the active site of maltase via hydrogen-bond interactions with five amino acid residues: Ser 240, Asp 242, Glu 277, Arg 315, and Asn 350. For HETB docked to the sucrase active site, seven hydrogen bonds (with Asn 114, Glu 148, Gln 201, Asn 228, Gln 381, Ile 383, and Ser 412) were shown.
Comparative Technical Process and Product Assessment of Catalytic and Thermal Pyrolysis of Lignocellulosic Biomass
Akshay D. Patel, Masoud Zabeti, K. Seshan, Martin K. Patel
July 19, 2021 (v1)
Keywords: Biofuels, catalysts, lignocellulosic biomass, process and product simulation, pyrolysis
Availability of sustainable transportation fuels in future hinges on the use of lignocellulosic resources for production of biofuels. The process of biomass pyrolysis can be used to convert solid biomass resources into liquid fuels. In this study, laboratory experiments and process simulations were combined to gain insight into the technical performance of catalytic and thermal pyrolysis processes. Waste pinewood was used as a feedstock for the processes. The pyrolysis took place at 500 °C and employs three different catalysts, in the case of the catalytic processes. A process model was developed with Aspen Plus and a wide range of representative components of bio-oil were used to model the properties of the bio-oil blend. The results of the process model calculations show that catalytic pyrolysis process produces bio-oil of superior quality. Different technical process scenarios were explored based on the properties of the bio-oil after separation of water-soluble components, with the... [more]
Revisiting the Role of Mass and Heat Transfer in Gas−Solid Catalytic Reactions
Riccardo Tesser, Elio Santacesaria
July 13, 2021 (v1)
Keywords: chemical kinetics, gas–solid catalytic reactions, heat and mass transfer
The tremendous progress in the computing power of modern computers has in the last 20 years favored the use of numerical methods for solving complex problems in the field of chemical kinetics and of reactor simulations considering also the effect of mass and heat transfer. Many classical textbooks dealing with the topic have, therefore, become quite obsolete. The present work is a review of the role that heat and mass transfer have in the kinetic studies of gas−solid catalytic reactions. The scope was to collect in a relatively short document the necessary knowledge for a correct simulation of gas−solid catalytic reactors. The first part of the review deals with the most reliable approach to the description of the heat and mass transfer outside and inside a single catalytic particle. Some different examples of calculations allow for an easier understanding of the described methods. The second part of the review is related to the heat and mass transfer in packed bed reactors, considerin... [more]
Biosorption of Co2+ Ions from Aqueous Solution by K2HPO4-Pretreated Duckweed Lemna gibba
Jessica Lizeth Reyes-Ledezma, Eliseo Cristiani-Urbina, Liliana Morales-Barrera
June 21, 2021 (v1)
Keywords: biosorption, desorption, divalent cobalt, Lemna gibba, SEM-EDX
The wastewater of the many industries that use divalent cobalt (Co2+)-containing compounds has elevated levels of this metal. Thus, novel technology is needed to efficiently remove Co2+ ions from aqueous solutions. Biosorption is a low-cost technique capable of removing heavy metals from contaminated water. This study aims to evaluate the performance of KH2PO4-pretreated Lemna gibba (PLEM) as a biosorbent of Co2+ in aqueous solutions tested under different conditions of pH, particle size, and initial Co2+ concentration. Kinetic, equilibrium, and thermodynamic studies were conducted. The capacity of biosorption increased with a greater initial Co2+ concentration and was optimal at pH 7.0 and with small-sized biosorbent particles (0.3−0.8 mm). The pseudo-second-order sorption model best describes the experimental data on Co2+ biosorption kinetics. The Sips and Redlich-Peterson isotherm models best predict the biosorption capacity at equilibrium. According to the thermodynamic study, bios... [more]
Quantifying the Effect of COD to TN Ratio, DO Concentration and Temperature on Filamentous Microorganisms’ Population and Trans-Membrane Pressure (TMP) in Membrane Bio-Reactors (MBR)
Petros Gkotsis, Giannis Lemonidis, Manassis Mitrakas, Alexandros Pentedimos, Margaritis Kostoglou, Anastasios Zouboulis
June 10, 2021 (v1)
Keywords: filament index, filamentous bacteria, fouling control, fouling modeling, Membrane Bioreactors (MBR)
Using moderate populations of filaments in the biomass of Membrane Bio-Reactors (MBRs) is a biological anti-fouling method which has been increasingly applied over the last few years. This study aims to quantify the effect of COD to TN ratio, Dissolved Oxygen (DO) concentration and temperature on filaments’ population and Trans-Membrane Pressure (TMP) in a pilot-scale MBR, with a view to reducing membrane fouling. The novelty of the present work concerns the development of a mathematical equation that correlates fouling rate (dTMP/dt) with the population of filamentous microorganisms, assessed by the Filament Index (FI), and with the concentration of the carbohydrate fraction of Soluble Microbial Products (SMPc). Apart from TMP and SMPc, other fouling-related biomass characteristics, such as sludge filterability and settleability, were also examined. It was shown that at high COD to TN ratio (10:1), low DO concentration in the filaments’ tank (0.5 ± 0.3 mg/L) and high temperature (24−3... [more]
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