Browse
Subjects
Records with Subject: Reaction Engineering
Showing records 51 to 75 of 281. [First] Page: 1 2 3 4 5 6 7 Last
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]
Catalytic Performance of Lanthanum Promoted Ni/ZrO2 for Carbon Dioxide Reforming of Methane
Mahmud S. Lanre, Ahmed S. Al-Fatesh, Anis H. Fakeeha, Samsudeen O. Kasim, Ahmed A. Ibrahim, Abdulrahman S. Al-Awadi, Attiyah A. Al-Zahrani, Ahmed E. Abasaeed
June 10, 2021 (v1)
Keywords: catalyst stability, lanthanum promoters, methane dry reforming, nickel catalyst, zirconium oxide
Nickel catalysts supported on zirconium oxide and modified by various amounts of lanthanum with 10, 15, and 20 wt.% were synthesized for CO2 reforming of methane. The effect of La2O3 as a promoter on the stability of the catalyst, the amount of carbon formed, and the ratio of H2 to CO were investigated. In this study, we observed that promoting the catalyst with La2O3 enhanced catalyst activities. The conversions of the feed, i.e., methane and carbon dioxide, were in the order 10La2O3 > 15La2O3 > 20La2O3 > 0La2O3, with the highest conversions being about 60% and 70% for both CH4 and CO2 respectively. Brunauer−Emmett−Teller (BET) analysis showed that the surface area of the catalysts decreased slightly with increasing La2O3 doping. We observed that 10% La2O3 doping had the highest specific surface area (21.6 m2/g) and the least for the un-promoted sample. The higher surface areas of the promoted samples relative to the reference catalyst is an indication of the concentration of the meta... [more]
Influence of Gasoline Addition on Biodiesel Combustion in a Compression-Ignition Engine with Constant Settings
Wojciech Tutak, Arkadiusz Jamrozik
June 10, 2021 (v1)
Keywords: biodiesel, combustion, dual fuel, Gasoline, ignition delay
This paper presents results of investigation of co-combustion process of biodiesel with gasoline, in form of mixture and using dual fuel technology. The main objective of this work was to show differences in both combustion systems of the engine powered by fuels of different reactivity. This paper presents parameters of the engine and the assessment of combustion stability. It turns out that combustion process of biodiesel was characterized by lower ignition delay compared to diesel fuel combustion. For 0.54 of gasoline energetic fraction, the ignition delay increased by 25% compared to the combustion of the pure biodiesel, but for dual fuel technology for 0.95 of gasoline fraction it was decreased by 85%. For dual fuel technology with the increase in gasoline fraction, the specific fuel consumption (SFC) was decreased for all analyzed fractions of gasoline. In the case of blend combustion, the SFC was increased in comparison to dual fuel technology. An analysis of spread of ignition d... [more]
Laser-Induced Ignition and Combustion Behavior of Individual Graphite Microparticles in a Micro-Combustor
Yue Wang, Minqi Zhang, Shuhang Chang, Shengji Li, Xuefeng Huang
June 10, 2021 (v1)
Keywords: graphite, laser ignition, microscale combustion, photophoresis, repetitive extinction
Microscale combustion has potential application in a micro power generator. This paper studied the ignition and combustion behavior of individual graphite microparticles in a micro-combustor to explore the utilization of carbon-based fuels at the microscale system. The individual graphite microparticles inside the micro-combustor were ignited by a highly focused laser in an air flow with natural convection at atmospheric temperature and pressure. The results show that the ignition of graphite microparticles was heterogeneous. The particle diameter had a small weak effect on ignition delay time and threshold ignition energy. The micro-combustor wall heat losses had significant effects on the ignition and combustion. During combustion, flame instability, photophoresis, repetitive extinction and reignition were identified. The flame structure was asymmetric, and the fluctuation of flame front and radiation intensity showed combustion instability. Photophoretic force pushed the graphite aw... [more]
Carbonaceous Adsorbent Derived from Sulfur-Impregnated Heavy Oil Ash and Its Lead Removal Ability from Aqueous Solution
Takaaki Wajima
May 28, 2021 (v1)
Keywords: heavy oil ash, K2S immerse, lead removal, pyrolysis, selectivity
A novel carbonaceous adsorbent was prepared from sulfur-impregnated heavy oil ash via pyrolysis using potassium sulfide (K2S) solution, and its ability to remove lead (Pb2+) from aqueous solutions was examined. It was compared with an adsorbent synthesized by conventional pyrolysis using potassium hydroxide (KOH) solution. Specifically, the raw ash was immersed in 1 M K2S solution or 1 M KOH solution for 1 day and subsequently heated at 100−1000 °C in a nitrogen (N2) atmosphere. After heating for 1 h, the solid was naturally cooled in N2 atmosphere, and subsequently washed and dried to yield the product. Regardless of the pyrolysis temperature, the product generated using K2S (Product-K2S) has a higher sulfur content than that obtained using KOH (Product-KOH). Moreover, Product-K2S has a higher lead removal ability than Product-KOH, whereas the specific surface area of the former is smaller than that of the latter. Product-K2S obtained at 300 °C (Product-K2S-300) achieves the highest l... [more]
NOx Emission Reduction by Advanced Reburning in Grate-Rotary Kiln for the Iron Ore Pelletizing Production
Bing Hu, Peiwei Hu, Biao Lu, Zhicheng Xie, Liu Liu, Gangli Cheng, Jiaoyang Wei
May 27, 2021 (v1)
Keywords: advanced reburning, denitrification, grate-rotary kiln, NOx reduction
The NOx reduction in the iron ore pelletizing process becomes an important environmental concern owing to its role in the formation of photochemical smog and acid rain. Thus, it is essential to develop new technologies for reducing NOx emissions in order to contribute to the cleaner production of pellets. In this paper, NOx reduction by advanced reburning ingrate-rotary kiln for oxidized pellet production was performed on a laboratory-scale gas kiln. Temperature and NH3/NOx molar ratio (NSR) were the key factors affecting the reduction of NOx. A better denitrification effect can be obtained on flus gas with higher initial NOx concentration, at temperature = 900 °C, NSR = 1.2, and reaction time exceeds one second. NOx reduction rate had reached 55−65% when the initial NOx concentration was above 400 ppm, and exceeds 70% when the initial NOx concentration was around 680 ppm. Urea solution has the best denitrification effect compared with NH3·H2O and NH4HCO3 solution. As for additives, th... [more]
Alcohol Dehydration by Extractive Distillation with Use of Aminoethers of Boric Acid
Alexander V. Klinov, Alexander V. Malygin, Alina R. Khairullina, Sergey E. Dulmaev, Ilsiya M. Davletbaeva
May 27, 2021 (v1)
Keywords: aqueous solution, Extraction, UNIFAC model, vapor–liquid equilibrium
Aminoethers of boric acid (AEBA) were studied as potential extractants for the separation of aqueous−alcoholic azeotropic mixtures by extractive distillation. The conditions of vapor−liquid equilibrium in aqueous solutions of ethanol and isopropanol in the presence of AEBA were studied. The division of AEBA molecules into group components was proposed, and previously unknown geometric parameters of the boron group and the energetic pair parameters of the boron group with the alkane group, ether group, amine-3d group, and alcohol group were determined within the framework of the Universal Functional Group Activity Coefficient (UNIFAC) model. The modeling of the extractive rectification process of an ethanol−water mixture with AEBA as extractant has been carried out. The dependences of the cost function on the extractant flow rate, the residual water content in it and the number of theoretical trays were obtained. A technological scheme for ethanol dehydration has been proposed, and its... [more]
Controlled Degradation of Lubricating Media by Means of an Accelerated Electron Beam
Jiří Stodola, Petr Stodola
May 26, 2021 (v1)
Keywords: accelerated electron beam, changes in the properties of the lubricating medium, engines, ionizing radiation
The article deals with the possibilities of using electron accelerator for controlled aging of lubricating media used in special vehicles. During use, e.g., in combustion engines, the lubricants get contaminated and thermo-oxidative degradation also occurs. The pilot project confirms the hypothesis that ionizing radiation makes it possible to simulate the operating load of lubricating media, which was repeatedly confirmed by long-term monitoring of changes in viscosity of statistically significant samples of motor oils used in special equipment. Preliminary test results also show that there are likely to be possibilities to influence other selected properties, such as the coefficient of friction depending on the radiation dose. The authors describe physicochemical processes during irradiation and, in the example of kinematic viscosity, present summary results for selected lubricating media.
Charcoal as an Alternative Reductant in Ferroalloy Production: A Review
Gerrit Ralf Surup, Anna Trubetskaya, Merete Tangstad
May 26, 2021 (v1)
Keywords: bio-based reductant, charcoal, ferroalloy industry, kiln, pyrolysis
This paper provides a fundamental and critical review of biomass application as renewable reductant in integrated ferroalloy reduction process. The basis for the review is based on the current process and product quality requirement that bio-based reductants must fulfill. The characteristics of different feedstocks and suitable pre-treatment and post-treatment technologies for their upgrading are evaluated. The existing literature concerning biomass application in ferroalloy industries is reviewed to fill out the research gaps related to charcoal properties provided by current production technologies and the integration of renewable reductants in the existing industrial infrastructure. This review also provides insights and recommendations to the unresolved challenges related to the charcoal process economics. Several possibilities to integrate the production of bio-based reductants with bio-refineries to lower the cost and increase the total efficiency are given. A comparison of chall... [more]
Study of a Method to Effectively Remove Char Byproduct Generated from Fast Pyrolysis of Lignocellulosic Biomass in a Bubbling Fluidized Bed Reactor
Jong Hyeon Ha, In-Gu Lee
May 25, 2021 (v1)
Keywords: BFB reactor, bio-oil, biochar, fast pyrolysis, inner and outer tubes, wood sawdust
A critical issue in the design of bubbling fluidized bed reactors for biomass fast pyrolysis is to maintain the bed at a constant level to ensure stable operation. In this work, a bubbling fluidized bed reactor was investigated to deal with this issue. The reactor consists of inner and outer tubes and enables in situ control of the fluidized-bed level in the inner-tube reactor with a mechanical method during biomass fast pyrolysis. The significant fraction of biochar produced from the fast pyrolysis in the inner-tube reactor was automatically removed through the annulus between the inner and outer tubes. The effect of pyrolysis temperature (426−528 °C) and feeding rate (0.8−1.8 kg/h) on the yield and characteristics of bio-oil, biochar, and gaseous products were examined at a 15 L/min nitrogen carrier gas flow rate for wood sawdust with a 0.5−1.0 mm particle size range as a feed. The bio-oil reached a maximum yield of 62.4 wt% on a dry basis at 440 °C, and then slowly decreased with in... [more]
Equilibrium, Kinetic and Thermodynamic Studies for Sorption of Phosphate from Aqueous Solutions Using ZnO Nanoparticles
Tra Huong Do, Van Tu Nguyen, Quoc Dung Nguyen, Manh Nhuong Chu, Thi Cam Quyen Ngo, Lam Van Tan
May 25, 2021 (v1)
Keywords: aqueous solution, equilibrium, kinetic, nanoparticles, phosphate, thermodynamic, ZnO
In this study, ZnO nanoparticles were fabricated by using the hydrothermal method for adsorption of phosphate from wastewater. The obtained ZnO nanorods were characterized by powder X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), specific surface area (BET) and energy dispersive X-ray spectroscopy (EDS). The ZnO materials were applied for adsorption of phosphate from water using batch experiments. The effects of pH (4−10), adsorption time (30−240 min), the amount of adsorbent (0.1−0.7 g/L) and initial concentration of phosphate (147.637−466.209 mg/L) on the adsorption efficiency were investigated. The optimum condition was found at pH = 5 and at an adsorption time of 150 min. The adsorption was fitted well with the Langmuir isotherm and the maximum adsorption capacity was calculated to be 769.23 mg/g. These results show that ZnO nanomaterial would highly promising for adsorbing phosphate from water. The adsorption of phosphate on ZnO nanomaterials follows the... [more]
Direct Solid Oxide Electrolysis of Carbon Dioxide: Analysis of Performance and Processes
Severin Foit, Lucy Dittrich, Tobias Duyster, Izaak Vinke, Rüdiger-A. Eichel, L. G. J. (Bert) de Haart
May 24, 2021 (v1)
Keywords: Carbon Dioxide, carbon dioxide reduction, carbon dioxide utilization, CO2-electrolysis, high-temperature electrolysis, solid oxide electrolysis
Chemical industries rely heavily on fossil resources for the production of carbon-based chemicals. A possible transformation towards sustainability is the usage of carbon dioxide as a source of carbon. Carbon dioxide is activated for follow-up reactions by its conversion to carbon monoxide. This can be accomplished by electrochemical reduction in solid oxide cells. In this work, we investigate the process performance of the direct high-temperature CO2 electrolysis by current-voltage characteristics (iV) and Electrochemical Impedance Spectroscopy (EIS) experiments. Variations of the operation parameters temperature, load, fuel utilization, feed gas ratio and flow rate show the versatility of the procedure with maintaining high current densities of 0.75 up to 1.5 A·cm−2, therefore resulting in high conversion rates. The potential of the high-temperature carbon dioxide electrolysis as a suitable enabler for the activation of CO2 as a chemical feedstock is therefore appointed and shown.
Gasification Applicability of Korean Municipal Waste Derived Solid Fuel: A Comparative Study
Sang Yeop Lee, Md Tanvir Alam, Gun Ho Han, Dong Hyuk Choi, Se Won Park
May 17, 2021 (v1)
Keywords: Biomass, Coal, gasification, municipal solid waste, solid recovered fuel, Syngas
Gaining energy independence by utilizing new and renewable energy resources has become imperative for Korea. Energy recovery from Korean municipal solid waste (MSW) could be a promising option to resolve the issue, as Korean MSW is highly recyclable due to its systematic separation, collection and volume-based waste disposal system. In this study, gasification experiments were conducted on Korean municipal waste-derived solid fuel (SRF) using a fixed bed reactor by varying the equivalence ratio (ER) to assess the viability of syngas production. Experiments were also conducted on coal and biomass under similar conditions to compare the experimental results, as the gasification applicability of coal and biomass are long-established. Experimental results showed that Korean SRF could be used to recover energy in form of syngas. In particular, 50.94% cold gas efficiency and 54.66% carbon conversion ratio with a lower heating value of 12.57 MJ/Nm3 can be achieved by gasifying the SRF at 0.4... [more]
Influences of Ash-Existing Environments and Coal Structures on CO2 Gasification Characteristics of Tri-High Coal
Lang Liu, Qingrui Jiao, Jian Yang, Bowen Kong, Shan Ren, Qingcai Liu
May 17, 2021 (v1)
Keywords: ash-free coal, CO2 gasification, coal structure, tri-high coal
Two kinds of tri-high coals were selected to determine the influences of ash-existing environments and coal structures on CO2 gasification characteristics. The TGA results showed that the gasification of ash-free coal (AFC) chars was more efficient than that of corresponding raw coal (RC) chars. To uncover the reasons, the structures of RCs and AFCs, and their char samples prepared at elevated temperatures were investigated with SEM, BET, XRD, Raman and FTIR. The BET, SEM and XRD results showed that the Ash/mineral matter is associated with coal, carbon forms the main structural framework and mineral matters are found embedded in the coal structure in the low-rank tri-high coal. The Raman and FTIR results show that the ash can hinder volatile matters from exposing to the coal particles. Those results indicate that the surface of AFC chars has more free active carbon sites than raw coal chars, which are favorable for mass transfer between C and CO2, thereby improving reactivity of the A... [more]
Thermo-Acoustic Catalytic Effect on Oxidizing Woody Torrefaction
Edgar A. Silveira, Luiz Gustavo Oliveira Galvão, Lucélia Alves de Macedo, Isabella A. Sá, Bruno S. Chaves, Marcus Vinícius Girão de Morais, Patrick Rousset, Armando Caldeira-Pires
May 17, 2021 (v1)
Keywords: catalytic effect, numerical modeling, severity factors, thermoacoustic, woody biomass torrefaction
The torrefaction (mild pyrolysis) process modifies biomass chemical and physical properties and is applied as a thermochemical route to upgrade solid fuel. In this work, the catalytic effect of thermo-acoustic on oxidizing woody torrefaction is assessed. The combined effect of two acoustic frequencies (1411, 2696 Hz) and three temperatures (230, 250, and 290 °C) was evaluated through weight loss and its deviation curves, calculated torrefaction severity index (TSI), as well as proximate, calorific, and compression strength analysis of Eucalyptus grandis. A new index to account for the catalytic effects on torrefaction (TCEI) was introduced, providing the quantitative analysis of acoustic frequencies influence. A two-step consecutive reaction numerical model allowed the thermo-acoustic experiment evaluation. For instance, the thermogravimetric profiles revealed that the acoustic field has a catalytic effect on wood torrefaction and enhances the biomass oxidation process for severe treat... [more]
Thermal Decontamination of Spent Activated Carbon Contaminated with Radiocarbon and Tritium
Hee-Chul Yang, Min-Woo Lee, Hee-Chul Eun, Hyung-Ju Kim, Keunyoung Lee, Bum-Kyung Seo
May 17, 2021 (v1)
Keywords: radiocarbon, reactivation, spent activated carbon, thermal desorption, tritium
The thermal desorption of tritium (3H, T) and radiocarbon (14C) from spent activated carbon was investigated and three thermal desorption steps were established: the vaporization of homogeneously condensed molecules, the desorption of molecules physically binding with the carbon surface, and the decomposition of chemisorbed molecules. A model-free kinetic analysis was conducted to establish the optimum condition of vacuum thermal desorption. Physisorbed species, including tritiated water (HTO) and 14CO2, were effectively removed by vacuum thermal desorption. However, a fraction of 14C, which may take the form of carbon molecules in pyrocarbon form during the heating process, was not removed, even at a high temperature of 1000 °C under a vacuum of 0.3−0.5 Pa. Oxidative peeling of the pore surfaces by filling the evacuated pores with pure oxygen via vacuum thermal desorption and heating to 700 °C was found to be effective for reducing the level of 14C to a level below the established fre... [more]
Kinetics and Modeling of Aqueous Phase Radical Homopolymerization of 3-(Methacryloylaminopropyl)trimethylammonium Chloride and its Copolymerization with Acrylic Acid
Ikenna H. Ezenwajiaku, Emmanuel Samuel, Robin A. Hutchinson
May 11, 2021 (v1)
Keywords: aqueous phase polymerization, modeling and simulation, polyelectrolytes, radical polymerization
The radical homopolymerization kinetics of 3-(methacryloylaminopropyl) trimethylammonium chloride (MAPTAC) and its batch copolymerization with nonionized acrylic acid (AA) in aqueous solution are investigated and modeled. The drift in monomer composition is measured during copolymerization by in situ NMR over a range of initial AA molar fractions and monomer weight fractions up to 0.35 at 50 °C. The copolymer becomes enriched in MAPTAC for monomer mixtures containing up to 60 mol% MAPTAC, but is enriched in AA for MAPTAC-rich mixtures; this azeotropic behavior is dependent on initial monomer content, as electrostatic interactions from the cationic charges influence the system reactivity ratios. Models for MAPTAC homopolymerization and AA-MAPTAC copolymerization are developed to represent the rates of monomer conversion and comonomer composition drifts over the complete range of experimental conditions.
Suzuki−Miyaura Reactions of (4-bromophenyl)-4,6-dichloropyrimidine through Commercially Available Palladium Catalyst: Synthesis, Optimization and Their Structural Aspects Identification through Computational Studies
Ayesha Malik, Nasir Rasool, Iram Kanwal, Muhammad Ali Hashmi, Ameer Fawad Zahoor, Gulraiz Ahmad, Ataf Ali Altaf, Syed Adnan Ali Shah, Sadia Sultan, Zainul Amiruddin Zakaria
May 4, 2021 (v1)
Keywords: DFT, FMO, Pd catalyst, reactivity descriptors, Suzuki–Miyaura
5-(4-bromophenyl)-4,6-dichloropyrimidine was arylated with several aryl/heteroaryl boronic acids via the Suzuki cross-coupling reaction by using Pd(0) catalyst to yield novel pyrimidine analogs (3a-h). It was optimized so that good yields were obtained when 5 mol % Pd(PPh3)4 was used along with K3PO4 and 1,4-Dioxane. Electron-rich boronic acids were succeeded to produce good yields of products. Density functional theory (DFT) calculations were also applied on these new compounds to analyze their reactivity descriptors and electronic and structural relationship. According to DFT studies, compound 3f is the most reactive one, while 3g is the most stable one. As per DFT studies, the hyperpolarizability (β) values of these compounds do not show them as very good non-linear optical (NLO) materials. Compound 3f has the highest β value among all the compounds under study but still it is not high enough to render it a potent NLO material.
Initiator Feeding Policies in Semi-Batch Free Radical Polymerization: A Monte Carlo Study
Ali Seyedi, Mohammad Najafi, Gregory T. Russell, Yousef Mohammadi, Eduardo Vivaldo-Lima, Alexander Penlidis
April 29, 2021 (v1)
Keywords: initiator feeding policies, methyl methacrylate, Monte Carlo simulation, polymer microstructure, styrene
A Monte Carlo simulation algorithm is developed to visualize the impact of various initiator feeding policies on the kinetics of free radical polymerization. Three cases are studied: (1) general free radical polymerization using typical rate constants; (2) diffusion-controlled styrene free radical polymerization in a relatively small amount of solvent; and (3) methyl methacrylate free radical polymerization in solution. The number- and weight-average chain lengths, molecular weight distribution (MWD), and polymerization time were computed for each initiator feeding policy. The results show that a higher number of initiator shots throughout polymerization at a fixed amount of initiator significantly increases average molecular weight and broadens MWD. Similar results are also observed when most of the initiator is added at higher conversions. It is demonstrated that one can double the molecular weight of polystyrene and increase its dispersity by 50% through a four-shot instead of a sin... [more]
Photochemical Oxidation Process of Copper from Electroplating Wastewater: Process Performance and Kinetic Study
Aji Prasetyaningrum, Teguh Riyanto, Mohamad Djaeni, Widayat Widayat
April 29, 2021 (v1)
Keywords: advanced oxidation process, Cu, kinetics, ozone, photochemical oxidation, ultraviolet irradiation
An investigation of the process of ozone combined with ultraviolet radiation has been carried out in order to establish the kinetics for photochemical oxidation of copper (Cu) from electroplating wastewater. The effects of operating parameters, including initial Cu concentration, ozone dosage, UV irradiation intensity, and pH value on the photochemical oxidation of Cu have been studied comprehensively. The Cu concentration during the reaction was identified using atomic absorption spectroscopy (AAS) method. The solid product was analyzed using X-ray diffraction (XRD) and scanning electron microscope−energy-dispersive X-ray (SEM−EDX) methods. It was found that the UV-Ozone process has high performance on Cu removal compared to UV and Ozone processes due to the high production rate of HO• radicals. It was also found that the solid product from the UV-Ozone process was CuO monoclinic crystal phase. The initial Cu concentration, ozone dosage, and pH value were significantly affected the Cu... [more]
Showing records 51 to 75 of 281. [First] Page: 1 2 3 4 5 6 7 Last
[Show All Subjects]