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Records with Subject: Reaction Engineering
Showing records 1 to 25 of 77. [First] Page: 1 2 3 4 Last
Separating Electronic from Steric Effects in Ethene/α-Olefin Copolymerization: A Case Study on Octahedral [ONNO] Zr-Catalysts
Francesco Zaccaria, Roberta Cipullo, Andrea Correa, Peter H. M. Budzelaar, Vincenzo Busico, Christian Ehm
August 15, 2019 (v1)
Keywords: DFT, electronic effects, insertion kinetics, olefin capture, olefin copolymerization, post-metallocene, reactivity ratios, salan catalysts
Four Cl/Me substituted [ONNO] Zr-catalysts have been tested in ethene/α-olefin polymerization. Replacing electron-donating methyl with isosteric but electron-withdrawing chlorine substituents results in a significant increase of comonomer incorporation. Exploration of steric and electronic properties of the ancillary ligand by DFT confirm that relative reactivity ratios are mainly determined by the electrophilicity of the metal center. Furthermore, quantitative DFT modeling of propagation barriers that determine polymerization kinetics reveals that electronic effects observed in these catalysts affect relative barriers for insertion and a capture-like transition state (TS).
Dynamic Modelling of Phosphorolytic Cleavage Catalyzed by Pyrimidine-Nucleoside Phosphorylase
Robert T. Giessmann, Niels Krausch, Felix Kaspar, Mariano Nicolas Cruz Bournazou, Anke Wagner, Peter Neubauer, Matthias Gimpel
August 15, 2019 (v1)
Keywords: Dynamic Modelling, enzymatic reaction, ODE model, process kinetics, pyrimidine-nucleoside phosphorylase, reversible reaction, spectroscopic assay
Pyrimidine-nucleoside phosphorylases (Py-NPases) have a significant potential to contribute to the economic and ecological production of modified nucleosides. These can be produced via pentose-1-phosphates, an interesting but mostly labile and expensive precursor. Thus far, no dynamic model exists for the production process of pentose-1-phosphates, which involves the equilibrium state of the Py-NPase catalyzed reversible reaction. Previously developed enzymological models are based on the understanding of the structural principles of the enzyme and focus on the description of initial rates only. The model generation is further complicated, as Py-NPases accept two substrates which they convert to two products. To create a well-balanced model from accurate experimental data, we utilized an improved high-throughput spectroscopic assay to monitor reactions over the whole time course until equilibrium was reached. We examined the conversion of deoxythymidine and phosphate to deoxyribose-1-p... [more]
Catalytic Effect of NaCl on the Improvement of the Physicochemical Structure of Coal-Based Activated Carbons for SO2 Adsorption
Dongdong Liu, Rui Su, Zhengkai Hao, Xiaoman Zhao, Boyin Jia, Liangjie Dong
August 7, 2019 (v1)
Keywords: activated carbons, catalytic activation, physicochemical structure, SO2 adsorption
The utilization of coal-based activated carbons focuses on improving the physicochemical structure for achieving high-capacity. Herein, the catalytic effect of NaCl (1 and 3 wt%) in the presence of oxygen functional groups on the improvement of the physicochemical structure of coal-based activated carbons is studied in this work. A large quantity of Na can be retained in 1NaJXO and 3NaJXO with the presence of oxygen functional groups to promote further its catalytic characteristics during pyrolysis, resulting in the disordered transformation of the carbon structure. In addition, the development of micropores is mainly affected by the distribution and movement of Na catalyst, whereas the growth of mesopores is mainly influenced by the evolution of oxygen functional groups. Then, the active sites of 3NaJXO-800 can no longer be consumed preferentially in the presence of Na catalyst during subsequent CO2 activation to facilitate the sustained disordered conversion of the microstructure and... [more]
Experimental Study on Spent FCC Catalysts for the Catalytic Cracking Process of Waste Tires
Chuansheng Wang, Xiaolong Tian, Baishun Zhao, Lin Zhu, Shaoming Li
August 7, 2019 (v1)
Keywords: catalytic cracking, chemical raw materials, spent FCC catalysts, sulfur-containing material conversion, used tires
Research on the synergistic high-value reuse of waste tires and used catalysts in spent fluid catalytic cracking (FCC) catalysts was carried out in this study to address the serious ecological and environmental problems caused by waste tires and spent FCC catalysts. The experiment, in which a spent FCC catalyst was applied to the catalytic cracking of waste tires, fully utilized the residual activity of the spent FCC catalyst and was compared with a waste tire pyrolysis experiment. The comparative experimental results indicated that the spent FCC catalyst could improve the cracking efficiency of waste tires, increase the output of light oil in pyrolysis products, and improve the quality of pyrolysis oil. It could also be used for the conversion of sulfur compounds during cracking. The content of 2-methyl-1-propylene in catalytic cracking gas was found to be up to 65.59%, so a new method for producing high-value chemical raw materials by the catalytic cracking of waste tires with spent... [more]
Highly Porous Graphitic Activated Carbons from Lignite via Microwave Pretreatment and Iron-Catalyzed Graphitization at Low-Temperature for Supercapacitor Electrode Materials
Dongdong Liu, Xiaoman Zhao, Rui Su, Zhengkai Hao, Boyin Jia, Song Li, Liangjie Dong
July 31, 2019 (v1)
Keywords: activated carbons, graphitization, high porosity, supercapacitor material
At present, the preparation of highly porous graphitic activated carbons (HPGACs) using the usual physical and chemical activation methods has met a bottleneck. In this study, HPGACs are directly synthesized from lignite at 900 °C. The whole process is completed by a microwave pretreatment, a graphitization conversion of the carbon framework at a low temperature using a small amount of FeCl3 (10−30 wt%), and a subsequent physical activation using CO2. Consequently, the dispersed and mobile iron species, in the absence of oxygen functional groups (removed during the microwave pretreatment), can greatly promote catalytic graphitization during pyrolysis, and, as an activating catalyst, can further facilitate the porosity development during activation. The as-obtained AC-2FeHLH-5-41.4(H) presents a low defect density, high purity, and specific surface area of 1852.43 m2 g−1, which is far greater than the AC-HLH-5-55.6(H) obtained solely by physical activation. AC-2FeHLH-5-41.4(H) as a supe... [more]
Nitroxide-Mediated Copolymerization of Itaconate Esters with Styrene
Sepehr Kardan, Omar Garcia Valdez, Adrien Métafiot, Milan Maric
July 29, 2019 (v1)
Keywords: copolymerization, itaconate esters, nitroxide mediated polymerization
Replacing petro-based materials with renewably sourced ones has clearly been applied to polymers, such as those derived from itaconic acid (IA) and its derivatives. Di-n-butyl itaconate (DBI) was (co)polymerized via nitroxide mediated polymerization (NMP) to impart elastomeric (rubber) properties. Homopolymerization of DBI by NMP was not possible, due to a stable adduct being formed. However, DBI/styrene (S) copolymerization by NMP at various initial molar feed compositions fDBI,0 was polymerizable at different reaction temperatures (70−110 °C) in 1,4 dioxane solution. DBI/S copolymerizations largely obeyed first order kinetics for initial DBI compositions of 10% to 80%. Number-average molecular weight (Mn) versus conversion for various DBI/S copolymerizations however showed significant deviations from the theoretical Mn as a result of chain transfer reactions (that are more likely to occur at high temperatures) and/or the poor reactivity of DBI via an NMP mechanism. In order to suppre... [more]
High-Temperature Permittivity and Microwave Pretreatment Characteristics of Nickel-Containing Sludge from Battery Production
Zhanyong Guo, Ping Guo, Guang Su, Demei Zhai, Fang Cheng, Fachuang Li
July 29, 2019 (v1)
Keywords: dielectric properties, microwave, nickel-containing sludge
Permittivity is a vitally important parameter for the description of the absorption and heating characteristics of materials under microwave irradiation. In this paper, the permittivity of nickel-containing sludge (NCS), which is created during battery production as a cheap secondary resource, was measured at temperatures from 20 °C to 600 °C at 2.45 GHz using the cavity perturbation method. In addition, the loss tangent (tanδ) and penetration depth (Dp) of microwaves into the material were calculated. The results of the permittivity study show that the dielectric constant (ε′) and dielectric loss factor (ε″) of the NCS increase with increasing temperature. The variations of the loss tangent (tanδ) and penetration depth (Dp) with the temperature can be divided into two parts at 200 °C. The effect of the initial moisture content on the dielectric properties of the material is notably greater than that of the temperature, which was confirmed by the heating curve. After microwave pretreat... [more]
Mechanism and Modelling of Reactive Crystallization Process of Lithium Carbonate
Shaolei Zhao, Jie Gao, Siyang Ma, Chao Li, Yiming Ma, Yang He, Junbo Gong, Fu Zhou, Bingyuan Zhang, Weiwei Tang
July 28, 2019 (v1)
Keywords: crystallization mechanisms, lithium carbonate, multi-response optimization, reactive crystallization, response surface methodology
The reactive crystallization of lithium carbonate (Li2CO3) from lithium sulfate (Li2SO4) and sodium carbonate (Na2CO3) solutions is a key process in harvesting solid lithium, whether from ores, brines, or clays. However, the process kinetics and mechanism remain poorly understood and the modelling of the reactive crystallization of Li2CO3 is not available. Hence, this work aims to determine the kinetics and mechanisms of the nucleation and growth of Li2CO3 reactive crystallization by induction time measurements and to model and optimize the crystallization process using response surface methodology. Induction time measurements were carried out as functions of initial supersaturation and temperature using a laser method. It was found that the primary nucleation mechanism of Li2CO3 varies with solution supersaturations, in which, expectedly, the heterogenous nucleation mechanism dominates at low supersaturations while the homogeneous nucleation mode governs at high supersaturations. The... [more]
Study on the Adsorption, Diffusion and Permeation Selectivity of Shale Gas in Organics
Zhouhua Wang, Yun Li, Huang Liu, Fanhua Zeng, Ping Guo, Wei Jiang
July 26, 2019 (v1)
Keywords: adsorption diffusion, kerogen, molecular simulation, permeation selectivity, shale gas
As kerogen is the main organic component in shale, the adsorption capacity, diffusion and permeability of the gas in kerogen plays an important role in shale gas production. Based on the molecular model of type II kerogen, an organic nanoporous structure was established. The Grand Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) methods were used to study the adsorption and diffusion capacity of mixed gas systems with different mole ratios of CO₂ and CH₄ in the foregoing nanoporous structure, and gas adsorption, isosteric heats of adsorption and self-diffusion coefficient were obtained. The selective permeation of gas components in the organic pores was further studied. The results show that CO₂ and CH₄ present physical adsorption in the organic nanopores. The adsorption capacity of CO₂ is larger than that of CH₄ in organic pores, but the self-diffusion coefficient of CH₄ in mixed gas is larger than that of CO₂. Moreover, the self-diffusion coefficient in the horizontal directi... [more]
Nanostructure and Oxidation Reactivity of Nascent Soot Particles in Ethylene/Pentanol Flames
Yaoyao Ying, Chenxuan Xu, Dong Liu, Bo Jiang, Pengfei Wang, Wei Wang
July 26, 2019 (v1)
Keywords: ethylene/pentanol flame, nanostructure, nascent soot particles, oxidation reactivity
As byproducts of the combustion process of hydrocarbon fuels, soot particles are difficult to remove, and they can greatly harm human health and pollute the environment. Therefore, the formation and growth processes of the soot particles has become a study focus of researchers. In this paper, the nanostructure and oxidation reactivity of carbonaceous particles collected from ethylene inverse diffusion flames with or without the additions of three pentanol isomers (1-pentanol, 3-methyl-1-butanol, and 2-methyl-1-butanol) were investigated in detail. The nanostructure and oxidation characteristics of nascent soot particles were characterized using high resolution transmission electron microscopy (HRTEM), X-ray diffractometry (XRD) and thermogravimetric analysis (TGA). It was found that the nascent soot cluster of pure ethylene flame had a loose structure, while the additions of pentanol isomers made the soot agglomerates more compact and delayed the growth of graphitic structures. The pen... [more]
Desorption Kinetics and Mechanisms of CO₂ on Amine-Based Mesoporous Silica Materials
Yang Teng, Zhilin Liu, Gang Xu, Kai Zhang
July 26, 2019 (v1)
Keywords: amine modified MCM-41, Avrami’s fractional model, desorption kinetics, film diffusion, intraparticle diffusion, zero length column
Tetraethylenepentamine (TEPA)-based mesoporous MCM-41 is used as the adsorbent to determine the CO₂ desorption kinetics of amine-modified materials after adsorption. The experimental data of CO₂ desorption as a function of time are derived by zero-length column at different temperatures (35, 50, and 70 °C) and analyzed by Avrami’s fractional-order kinetic model. A new method is used to distinguish the physical desorption and chemical desorption performance of surface-modified mesoporous MCM-41. The activation energy Ea of CO₂ physical desorption and chemical desorption calculated from Arrhenius equation are 15.86 kJ/mol and 57.15 kJ/mol, respectively. Furthermore, intraparticle diffusion and Boyd’s film models are selected to investigate the mechanism of CO₂ desorption from MCM-41 and surface-modified MCM-41. For MCM-41, there are three rate-limiting steps during the desorption process. Film diffusion is more prominent for the CO₂ desorption rates at low temperatures, and pore diffusio... [more]
Assessment against Experiments of Devolatilization and Char Burnout Models for the Simulation of an Aerodynamically Staged Swirled Low-NOx Pulverized Coal Burner
Marco Torresi, Francesco Fornarelli, Bernardo Fortunato, Sergio Mario Camporeale, Alessandro Saponaro
July 26, 2019 (v1)
Keywords: char burnout, computational fluid dynamics (CFD), devolatilization, industrial burner, NOx formation, pollutant emissions, pulverized coal combustion
In the next few years, even though there will be a continuous growth of renewables and a loss of the share of fossil fuel, energy production will still be strongly dependent on fossil fuels. It is expected that coal will continue to play an important role as a primary energy source in the next few decades due to its lower cost and higher availability with respect to other fossil fuels. However, in order to improve the sustainability of energy production from fossil fuels, in terms of pollutant emissions and energy efficiency, the development of advanced investigation tools is crucial. In particular, computational fluid dynamics (CFD) simulations are needed in order to support the design process of low emission burners. Even if in the literature several combustion models can be found, the assessment of their performance against detailed experimental measurements on full-scale pulverized coal burners is lacking. In this paper, the numerical simulation of a full-scale low-NO x , ae... [more]
Highly Selective Syngas/H2 Production via Partial Oxidation of CH4 Using (Ni, Co and Ni−Co)/ZrO2−Al2O3 Catalysts: Influence of Calcination Temperature
Anis Hamza Fakeeha, Yasir Arafat, Ahmed Aidid Ibrahim, Hamid Shaikh, Hanan Atia, Ahmed Elhag Abasaeed, Udo Armbruster, Ahmed Sadeq Al-Fatesh
July 17, 2019 (v1)
Keywords: Al2O3, bimetallic catalyst, methane, partial oxidation, Syngas, ZrO2
In this study, Ni, Co and Ni−Co catalysts supported on binary oxide ZrO2−Al2O3 were synthesized by sol-gel method and characterized by means of various analytical techniques such as XRD, BET, TPR, TPD, TGA, SEM, and TEM. This catalytic system was then tested for syngas respective H2 production via partial oxidation of methane at 700 °C and 800 °C. The influence of calcination temperatures was studied and their impact on catalytic activity and stability was evaluated. It was observed that increasing the calcination temperature from 550 °C to 800 °C and addition of ZrO2 to Al2O3 enhances Ni metal-support interaction. This increases the catalytic activity and sintering resistance. Furthermore, ZrO2 provides higher oxygen storage capacity and stronger Lewis basicity which contributed to coke suppression, eventually leading to a more stable catalyst. It was also observed that, contrary to bimetallic catalysts, monometallic catalysts exhibit higher activity with higher calcination temperatur... [more]
An Experimental Approach on Industrial Pd-Ag Supported α-Al2O3 Catalyst Used in Acetylene Hydrogenation Process: Mechanism, Kinetic and Catalyst Decay
Ourmazd Dehghani, Mohammad Reza Rahimpour, Alireza Shariati
July 17, 2019 (v1)
Keywords: acetylene hydrogenation, catalyst decay, kinetic model, process modeling
The current research presents an experimental approach on the mechanism, kinetic and decay of industrial Pd-Ag supported α-Al2O3 catalyst used in the acetylene hydrogenation process. In the first step, the fresh and deactivated hydrogenation catalysts are characterized by XRD, BET (Brunauer−Emmett−Teller), SEM, TEM, and DTG analyses. The XRD results show that the dispersed palladium particles on the support surface experience an agglomeration during the reaction run time and mean particle size approaches from 6.2 nm to 11.5 nm. In the second step, the performance of Pd-Ag supported α-Al2O3 catalyst is investigated in a differential reactor in a wide range of hydrogen to acetylene ratio, temperature, gas hourly space velocity and pressure. The full factorial design method is used to determine the experiments. Based on the experimental results ethylene, ethane, butene, and 1,3-butadiene are produced through the acetylene hydrogenation. In the third step, a detailed reaction network is pr... [more]
Carbon Mineralization by Reaction with Steel-Making Waste: A Review
Mohamed H. Ibrahim, Muftah H. El-Naas, Abdelbaki Benamor, Saad S. Al-Sobhi, Zhien Zhang
June 18, 2019 (v1)
Keywords: Carbon Capture, CO2 sequestration, steel slag, steel-making waste
Carbon capture and sequestration (CCS) is taking the lead as a means for mitigating climate change. It is considered a crucial bridging technology, enabling carbon dioxide (CO₂) emissions from fossil fuels to be reduced while the energy transition to renewable sources is taking place. CCS includes a portfolio of technologies that can possibly capture vast amounts of CO₂ per year. Mineral carbonation is evolving as a possible candidate to sequester CO₂ from medium-sized emissions point sources. It is the only recognized form of permanent CO₂ storage with no concerns regarding CO₂ leakage. It is based on the principles of natural rock weathering, where the CO₂ dissolved in rainwater reacts with alkaline rocks to form carbonate minerals. The active alkaline elements (Ca/Mg) are the fundamental reactants for mineral carbonation reaction. Although the reaction is thermodynamically favored, it takes place over a large time scale. The challenge of mineral carbonation is to offset this limitat... [more]
Investigation of Nonthermal Plasma Assisted Charcoal Gasification for Production of Hydrogen-Rich Syngas
Yin Pang, Thomas Hammer, Dominik Müller, Jürgen Karl
June 18, 2019 (v1)
Keywords: carbon conversion, charcoal gasification, hydrogen release, nonthermal plasma, reaction kinetics, reaction mechanism
The motivation of this work is to investigate experimentally the influence of nonthermal plasma (NTP) application on the reaction kinetics of atmospheric pressure steam gasification of charcoal using a thermostatically controlled drop tube reactor. A gliding-arc generator provides about 1 kW electrical power NTP. For comparison thermal gasification is investigated under comparable flow and specific energy input conditions providing additional heat to the steam. Optical temperature measurement 20 cm flow down of the NTP zone is utilized to characterize the specific enthalpy of the reactive flow. The composition of produced syngas is measured by a gas analyzer and used for the calculation of gas flow rates. The results show a NTP-enhancement on the production of individual syngas components (H₂, CO, CH₄), especially on hydrogen production by around 39%. The syngas-based carbon conversion and hydrogen release are calculated from the carbon and hydrogen balance between the correspondent co... [more]
Reaction Kinetics of Carbon Dioxide in Aqueous Blends of N-Methyldiethanolamine and L-Arginine Using the Stopped-Flow Technique
Nafis Mahmud, Abdelbaki Benamor, Mustafa Nasser, Muftah H. El-Naas, Paitoon Tontiwachwuthikul
June 8, 2019 (v1)
Keywords: Carbon Dioxide, kinetics, L-Arginine, N-methyldiethanolamine, Reaction, stopped flow technique
Reduction of carbon dioxide emission from natural and industrial flue gases is paramount to help mitigate its effect on global warming. Efforts are continuously deployed worldwide to develop efficient technologies for CO₂ capture. The use of environment friendly amino acids as rate promoters in the present amine systems has attracted the attention of many researchers recently. In this work, the reaction kinetics of carbon dioxide with blends of N-methyldiethanolamine and L-Arginine was investigated using stopped flow technique. The experiments were performed over a temperature range of 293 to 313 K and solution concentration up to one molar of different amino acid/amine ratios. The overall reaction rate constant (kov) was found to increase with increasing temperature and amine concentration as well as with increased proportion of L-Arginine concentration in the mixture. The experimental data were fitted to the zwitterion and termolecular mechanisms using a nonlinear regression techniqu... [more]
Effect of Temperature and Microwave Power Levels on Microwave Drying Kinetics of Zhaotong Lignite
Pengfei Zhao, Chenhui Liu, Wenwen Qu, Zhixiu He, Jiyun Gao, Lijuan Jia, Siping Ji, Roger Ruan
May 16, 2019 (v1)
Keywords: apparent activation energy, effective diffusion coefficient, hot-air drying kinetics, lignite, microwave drying kinetics
Microwave drying is a promising and effective way to drying and upgrading lignite. The influence of temperature (100⁻140 °C) and microwave power levels (500⁻800 W) on thin-layer drying characteristics of Zhaotong lignite under microwave irradiation were investigated. Fourteen thin-layer drying models were used to analyze the microwave drying process while six thin-layer drying models were used to analyze the hot-air drying process. The microwave drying processes at all temperature (100⁻140 °C) or low microwave power levels (500⁻700 W) exhibited four periods: a warm-up period, a short constant period, the first and second falling rate period, while one falling rate period was found during hot-air drying. The effective diffusion coefficient of lignite were calculated and it increases with increasing temperature and microwave power levels. During microwave drying, the two-term exponential model is the most suitable model for all applied conditions, while the Modified Page model is the mos... [more]
Advances in Mathematical Modeling of Gas-Phase Olefin Polymerization
Mohd Farid Atan, Mohd Azlan Hussain, Mohammad Reza Abbasi, Mohammad Jakir Hossain Khan, Muhamad Fazly Abdul Patah
May 16, 2019 (v1)
Keywords: gas phase, kinetics, Modelling, olefin
Mathematical modeling of olefin polymerization processes has advanced significantly, driven by factors such as the need for higher-quality end products and more environmentally-friendly processes. The modeling studies have had a wide scope, from reactant and catalyst characterization and polymer synthesis to model validation with plant data. This article reviews mathematical models developed for olefin polymerization processes. Coordination and free-radical mechanisms occurring in different types of reactors, such as fluidized bed reactor (FBR), horizontal-stirred-bed reactor (HSBR), vertical-stirred-bed reactor (VSBR), and tubular reactor are reviewed. A guideline for the development of mathematical models of gas-phase olefin polymerization processes is presented.
Approaches to Suppress CO₂-Induced Plasticization of Polyimide Membranes in Gas Separation Applications
Moli Zhang, Liming Deng, Dongxiao Xiang, Bing Cao, Seyed Saeid Hosseini, Pei Li
April 15, 2019 (v1)
Keywords: Carbon Dioxide, gas separation, membrane, plasticization, polyimide
Polyimides with excellent physicochemical properties have aroused a great deal of interest as gas separation membranes; however, the severe performance decay due to CO₂-induced plasticization remains a challenge. Fortunately, in recent years, advanced plasticization-resistant membranes of great commercial and environmental relevance have been developed. In this review, we investigate the mechanism of plasticization due to CO₂ permeation, introduce effective methods to suppress CO₂-induced plasticization, propose evaluation criteria to assess the reduced plasticization performance, and clarify typical methods used for designing anti-plasticization membranes.
Adsorption of Organic Constituents from Reverse Osmosis Concentrate in Coal Chemical Industry by Coking Coal
Hongxiang Xu, Qizheng Qin, Changfeng Zhang, Kejia Ning, Rong Zhao, Penghui Wang, Jiushuai Deng, Gen Huang
April 15, 2019 (v1)
Keywords: Adsorption, adsorption mechanism, aromatic structure, kinetics
To solve the unwieldy problem of coal chemical wastewater reverse osmosis concentrate (ROC), a novel treatment method in which coking coal was used to adsorb the organic from ROC and the adsorption mechanism involved was investigated. The results showed that the organic components in the ROC of coal chemical industry can be effectively absorbed by the coking coal and the total organic carbon, UV254 and chromaticity of treated ROC reduced by 70.18%, 70.15% and 59.55%, respectively, at the coking coal dosage of 80 g/L. The isothermal adsorption data were fitted to the Langmuir model well. The kinetics were expressed well by the quasi-second-order kinetic model. The intragranular diffusion model and the BET (Acronym for three scientists: Brunauer⁻Emmett⁻Teller) test showed that the adsorption occurred mainly on the surface of the coking coal and its macropores and mesopores. When the pollutants further diffused to the mesopores and micropores, the adsorption rate decreased. The result of... [more]
Efficient Removal of Hexavalent Chromium from Wastewater with Electro-Reduction
Hao Peng, Yumeng Leng, Qinzhe Cheng, Qian Shang, Jiancheng Shu, Jing Guo
April 15, 2019 (v1)
Keywords: acidic medium, chromium, electro-reduction
Removal of hexavalent chromium had attracted much attention as it is a hazardous contaminant. An electrocoagulation-like technology electro-reduction was applied. The chromium (VI) in the wastewater was reduced to chromium (III) by the electron supplied by electricity power and Fe2+, formed from corrosion of steel electrodes in acidic conditions. The mechanism and parameters affecting the reaction were investigated. The results optimized by response surface methodology indicated that the influence of single factor on the reduction efficiency followed the order: A: dosage of H₂SO₄ > C: reaction time > D: reaction temperature > B: current intensity. The reduction efficiency was hardly affected by current intensity, while it was increased with the increasing of reaction time and acid concentration. The reducing agent, Fe2+ an and extra free electron, acted as a reducing agent and could easily reduce hexavalent chromium to trivalent chromium at high temperatures in an acidic medium.
Effective Dye Degradation by Graphene Oxide Supported Manganese Oxide
Hayarpi Saroyan, George Z. Kyzas, Eleni A. Deliyanni
April 15, 2019 (v1)
Keywords: characterization, degradation, dyes, graphene oxide, manganese oxide, reuse
Graphene oxide (GO) was used as a support for manganese oxide (MnO₂) for the preparation of a nanocomposite catalyst for the degradation of an azo dye, Reactive Black 5 (RB5). The nanocomposite was characterized for the structure by XRD, for the morphology with SEM, and for the surface chemistry with FTIR and potentiometric titration measurements. The GO-MnO₂ nanocomposite presented a high catalytic activity for the degradation/oxidation of RB5 at ambient conditions, which was higher than that of the pure MnO₂ and could be attributed to the beneficial contribution of the manganese oxide and the graphene oxide.
Multi-Tubular Reactor for Hydrogen Production: CFD Thermal Design and Experimental Testing
Elvira Tapia, Aurelio González-Pardo, Alfredo Iranzo, Manuel Romero, José González-Aguilar, Alfonso Vidal, Mariana Martín-Betancourt, Felipe Rosa
April 15, 2019 (v1)
Keywords: Computational Fluid Dynamics, Computational Fluid Dynamics, hydrogen production, model, solar reactor, solar receiver, thermal energy
This study presents the Computational Fluid Dynamics (CFD) thermal design and experimental tests results for a multi-tubular solar reactor for hydrogen production based on the ferrite thermochemical cycle in a pilot plant in the Plataforma Solar de Almería (PSA). The methodology followed for the solar reactor design is described, as well as the experimental tests carried out during the testing campaign and characterization of the reactor. The CFD model developed for the thermal design of the solar reactor has been validated against the experimental measurements, with a temperature error ranging from 1% to around 10% depending on the location within the reactor. The thermal balance in the reactor (cavity and tubes) has been also solved by the CFD model, showing a 7.9% thermal efficiency of the reactor. CFD results also show the percentage of reacting media inside the tubes which achieve the required temperature for the endothermic reaction process, with 90% of the ferrite pellets inside... [more]
Optimization of Reaction Selectivity Using CFD-Based Compartmental Modeling and Surrogate-Based Optimization
Shu Yang, San Kiang, Parham Farzan, Marianthi Ierapetritou
April 9, 2019 (v1)
Keywords: CFD-simulation, compartmental modeling, competing reaction system, Mixing, model order reduction, Optimization, surrogate-based optimization
Mixing is considered as a critical process parameter (CPP) during process development due to its significant influence on reaction selectivity and process safety. Nevertheless, mixing issues are difficult to identify and solve owing to their complexity and dependence on knowledge of kinetics and hydrodynamics. In this paper, we proposed an optimization methodology using Computational Fluid Dynamics (CFD) based compartmental modelling to improve mixing and reaction selectivity. More importantly, we have demonstrated that through the implementation of surrogate-based optimization, the proposed methodology can be used as a computationally non-intensive way for rapid process development of reaction unit operations. For illustration purpose, reaction selectivity of a process with Bourne competitive reaction network is discussed. Results demonstrate that we can improve reaction selectivity by dynamically controlling rates and locations of feeding in the reactor. The proposed methodology inco... [more]
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