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Records with Subject: Reaction Engineering
Showing records 93 to 117 of 281. [First] Page: 1 2 3 4 5 6 7 8 9 Last
Self-Humidifying Proton Exchange Membranes for Fuel Cell Applications: Advances and Challenges
Seyed Hesam Mirfarsi, Mohammad Javad Parnian, Soosan Rowshanzamir
February 22, 2021 (v1)
Keywords: gas cross-over, nanocomposite membranes, polymer electrolyte fuel cells, proton exchange membranes, self-humidifying membranes, ultra-thin membranes
Polymer electrolyte fuel cells (PEFCs) provide efficient and carbon-free power by converting the hydrogen chemical energy. The PEFCs can reach their greatest performance in humidified condition, as proton exchange membranes (PEMs) should be humidified for their proton transportation function. Thus, external humidifiers are commonly employed to increase the water content of reactants. However, being burdened with external humidifiers can make the control of PEFCs complicated and costly, in particular for transportation application. To overcome this issue, self-humidifying PEMs have been introduced, with which PEFC can be fed by dry reactants. In fact, internal humidification is accomplished by produced water from the recombination of permeated hydrogen and oxygen gases on the incorporated platinum catalysts within the PEM. While the water production agent remains constant, there is a broad range of additives that are utilized to retain the generated water and facilitate the proton condu... [more]
Process of Obtaining Chromium Nitride in the Combustion Mode under Conditions of Co-Flow Filtration
Nikolay Evseev, Mansur Ziatdinov, Vladimir Romandin, Alexander Zhukov, Aidos Tolynbekov, Yuliya Ryzhikh
February 22, 2021 (v1)
Keywords: chromium nitride, co-flow, filtration combustion, inverse combustion wave, nitrogen–argon mixture, self-propagating high-temperature synthesis, superadiabatic heating
In this work, the combustion process of chromium powder in the co-flow filtration mode was studied. The effect of nitrogen-containing gas flow rate on the nitridation of combustion products is shown. The effect of the amount of argon in the nitrogen−argon mixture on the burning rate and the burning temperature of the chromium powder is shown. It was found that an increase in the percentage of argon in the nitrogen−argon mixture can lead to the formation of an inverse combustion wave. The actual burning temperature is higher than adiabatic burning temperature in the co-flow filtration mode, thus the phenomenon of superadiabatic heating is observed. The phase composition of the obtained combustion products was studied. It was shown that the forced filtration mode allows for synthesizing non-stoichiometric Cr2N nitride.
Is Anoxic Operation Effective to Control Nitrate Build-Up and Sludge Loss for the Combined Partial Nitritation and Anammox (CPNA) Process?
Hongyan Wang, Yuanyue Wang, Junya Zhang, Qianwen Sui, Dazhou Hu, Fumin Zuo, Yuansong Wei
February 22, 2021 (v1)
Keywords: CPNA, nitrate build-up, sludge loss, start-up
There were three main issues of long start-up period, nitrate build-up and sludge loss during the operation of combined partial-nitritation anammox (CPNA). To fully start up the CPNA reactor, the fast achievement of partial-nitritation (PN) was the first step. Firstly, the PN process was successfully achieved within 22 days by 2 mg·L−1 hydroxylamine (NH2OH) addition and online intermittent aeration control at 0.2~0.3 mg·L−1 dissolved oxygen (DO). Then, a novel strategy of adding anoxic stirring phase between feeding and aeration period during CPNA operation was applied. It was shown effective to control nitrate build-up since the mole ratio of NO3−-N production and NH4+-N removed (MNRR) was mostly below 15%. Also, the procedure adjustment was proven useful to alleviate sludge loss by sustaining filamentous bacteria that could act as biomass framework and reduce nitrate substrate. The filamentous denitrifying bacteria could cause sludge bulking. The total nitrogen removal rate (TNRR) va... [more]
Effects in Band Gap for Photocatalysis in TiO2 Support by Adding Gold and Ruthenium
Omar Ricardo Fonseca-Cervantes, Alejandro Pérez-Larios, Víctor Hugo Romero Arellano, Belkis Sulbaran-Rangel, Carlos Alberto Guzmán González
February 22, 2021 (v1)
Keywords: oxidized and reduced oxidation states, photocatalysis, sol–gel method, supported on TiO2
One of the key features of a nano catalyst for photocatalysis is the band gap, because, through its analysis, the potential of the catalyst can be determined. In this investigation, the impact on the band gap of different catalysts made by the sol−gel method, compared with TiO2 P25 Sigma-Aldrich, showing the effect of using gold or ruthenium as a metal supported on TiO2, with two different dosage percentages of 1 and 3 percent, was analysed. Additionally, two oxidation states of the catalyst, the reduced form and the oxidized form of the metal, were used to see the effect on the band gap. The experiments show that the gold addition has a higher beneficial effect on the band gap for the UV region (ultra violet region), and the ruthenium addition has a higher beneficial effect for the UV/visible region. The preferred oxidation state for the band gap was the oxidized state. The characterisation of the catalyst provided an insight into the relation between the band gap and the catalyst its... [more]
Investigation of Itaconic Acid Separation by Operating a Commercialized Electrodialysis Unit with Bipolar Membranes
Tamás Rózsenberszki, Péter Komáromy, Enikő Kőrösi, Péter Bakonyi, Nándor Nemestóthy, Katalin Bélafi-Bakó
February 22, 2021 (v1)
Keywords: bipolar membrane, by-product, electrodialysis, integrated system, itaconic acid
Nowadays, the merging of membrane and fermentation technologies is receiving significant attention such as in the case of itaconic acid (IA) production, which is considered as a value-added chemical. Its biotechnological production is already industrially established; however, the improvements of its fermentative and recovery steps remain topics of significant interest due to sustainable development trends. With an adequate downstream process, the total price of IA production can be reduced. For the task of IA recovery, a contemporary electro-membrane separation processes, electrodialysis with bipolar membranes (EDBM), was proposed and employed in this work. In the experiments, the laboratory-scale, commercialized EDBM unit (P EDR-Z/4x) was operated to separate IA from various model solutions compromised of IA (5−33 g/L), glucose (varied in 15−33 g/L as a residual substrate during IA fermentation) and malic acid (varied in 0−1 g/L as a realistic by-product of IA fermentation) under dif... [more]
Study of H2S Removal Capability from Simulated Biogas by Using Waste-Derived Adsorbent Materials
Hua Lun Zhu, Davide Papurello, Marta Gandiglio, Andrea Lanzini, Isil Akpinar, Paul R. Shearing, George Manos, Dan J.L. Brett, Ye Shui Zhang
February 3, 2021 (v1)
Keywords: activated carbon, Adsorption, biochar, Catalysis, circular economy, H2S, waste
Three waste-derived adsorbent materials (wood-derived biochar, sludge-derived activated carbon and activated ash) were pre-activated at the laboratory scale to apply them for the removal of H2S from a biogas stream. The H2S removal capabilities of each material were measured by a mass spectrometer, to detect the H2S concentration after the adsorption in an ambient environment. The activated ash adsorbent has the highest removal capacity at 3.22 mgH2S g−1, while wood-derived biochar has slightly lower H2S removal capability (2.2 mgH2S g−1). The physicochemical properties of pristine and spent materials were characterized by the thermogravimetric analyzer, elemental analysis, X-ray fluorescence spectroscopy and N2 adsorption and desorption. Wood-derived biochar is a highly porous material that adsorbs H2S by physical adsorption of the mesoporous structure. Activated ash is a non-porous material which adsorbs H2S by the reaction between the alkaline compositions and H2S. This study shows... [more]
Glycerol Oxidation over Supported Gold Catalysts: The Combined Effect of Au Particle Size and Basicity of Support
Ekaterina Pakrieva, Ekaterina Kolobova, Dmitrii German, Marta Stucchi, Alberto Villa, Laura Prati, Sónia. A.C. Carabineiro, Nina Bogdanchikova, Vicente Cortés Corberán, Alexey Pestryakov
February 3, 2021 (v1)
Keywords: base additives, catalyst selectivity, glyceric acid, glycerol oxidation, glycolic acid, gold catalysts, tartronic acid
Gold nanoparticles supported on various oxides (CeO2, CeO2/TiO2, MgO, MgO/TiO2, La2O3, La2O3/TiO2) (with 4 wt.% Au loading) were investigated in the liquid (aqueous) phase oxidation of glycerol by molecular oxygen under mild conditions, in the presence of alkaline earth (CaO, SrO and MgO) or alkaline (NaOH) bases. Full conversion and selectivity between 38 and 68% to sodium glycerate were observed on different Au supported catalysts (Au/MgO/TiO2, Au/La2O3/TiO2, Au/CeO2 and Au/CeO2/TiO2). The combined effect of Au particle size and basicity of the support was suggested as the determining factor of the activity. Agglomeration of gold nanoparticles, found after the reaction, led to the deactivation of the catalysts, which prevents the further oxidation of sodium glycerate into sodium tartronate. Promising results were obtained with the use of alkaline earth bases (CaO, SrO, MgO), leading to the formation of free carboxylic acids instead of salts, which are formed in the presence of the mo... [more]
Synthesis of Calcium Orthophosphates by Chemical Precipitation in Aqueous Solutions: The Effect of the Acidity, Ca/P Molar Ratio, and Temperature on the Phase Composition and Solubility of Precipitates
Mykola V. Nikolenko, Kateryna V. Vasylenko, Victoria D. Myrhorodska, Andrii Kostyniuk, Blaž Likozar
December 28, 2020 (v1)
Keywords: Ca-deficient hydroxyapatite, hydroxyapatite, solubility isotherm, solubility product, wet chemical precipitation
Studies on chemical precipitation of the calcium orthophosphates have shown that their phase compositions do not vary depending on molar ratio Ca/P but are sensitive to solutions acidity and temperature. These are two key factors that determine the phase transformation progress of metastable phases into less soluble precipitates of the phosphates. It was proposed to compare calcium orthophosphates solubility products with calcium cations quantities in their formulas. It was found that there was a linear correlation between calcium orthophosphates specific solubility products and their molar ratios Ca/P if hydroxyapatite and its Ca-deficient forms were excluded from consideration. It was concluded that the relatively large deviations of their solubility products from the found correlation should be thought of as erroneous data. That is why solubility products were changed in accordance with correlation dependence: pKS for hydroxyapatite was 155, pKS for Ca-deficient hydroxyapatites was... [more]
N-Tosylcarboxamide in C−H Functionalization: More than a Simple Directing Group
Benjamin Large, Vincent Terrasson, Damien Prim
December 22, 2020 (v1)
Keywords: C–H functionalization, Catalysis, directing group, tosylbenzamide
C−H activation with transition metal catalysis has become an important tool in organic synthesis for the functionalization of low reactive bonds and the preparation of complex molecules. The choice of the directing group (DG) proves to be crucial for the selectivity in this type of reaction, and several different functional groups have been used efficiently. This review describes recent advances in C−H functionalization of aromatic rings directed by a N-tosylcarboxamide group. Results regarding alkenylation, alkoxylation, halogenation, and arylation of C−H in the ortho position to the tosylcarboxamide are presented. Moreover, the advantage of this particular directing group is that it can undergo further transformation and act as CO or CON fragment reservoir to produce, in sequential fashion or one-pot sequence, various interesting (hetero)cycles such as phenanthridinones, dihydroisoquinolinones, fluorenones, or isoindolinones.
Residue Char Derived from Microwave-Assisted Pyrolysis of Sludge as Adsorbent for the Removal of Methylene Blue from Aqueous Solutions
Gong Cheng, Yazhuo Li, Liming Sun, Siyi Luo, George Z. Kyzas, Jie Fu
December 22, 2020 (v1)
Keywords: Adsorption, methylene blue, microwave pyrolysis, residue char, sewage sludge
Residue char is the main by-product of the microwave-assisted pyrolysis of activated sludge and it has a high content of fixed carbon and porous structure, but little is known about its character as an absorbent. In this study, residue char of activated sludge with microwave-assisted pyrolysis was used as an adsorbent to absorb methylene blue. The effects of pyrolysis temperature, pyrolysis holding time, contact time, and adsorption temperature on the adsorption ability of residue char were investigated. Kinetics, isotherm, and thermodynamic models were also included to study the adsorption behavior. The results showed that the optimal pyrolysis condition was 15 min and 603 °C, and the adsorption capacity reached up to 80.01 mg/g. The kinetics analyses indicated the adsorption behavior followed the pseudo-second-order kinetics model and the adsorption process was mainly due to chemical interaction. The adsorption isotherm was described by Freundlich model and thus, its process was mult... [more]
Experimental Investigation of Primary De-NOx Methods Application Effects on NOx and CO Emissions from a Small-Scale Furnace
Ladislav Lukáč, Miroslav Rimár, Miroslav Variny, Ján Kizek, Peter Lukáč, Gustáv Jablonský, Ján Janošovský, Marcel Fedák
December 17, 2020 (v1)
Keywords: combustion, flue-gas recirculation, furnace, nitrogen oxides, reburning
Nitrogen oxides (NOx) from combustion contribute significantly to atmospheric pollution. An experimental setup was employed to investigate the application of three primary denitrification methods, i.e., reburning (staged combustion), overfiring air (OFA), and flue-gas recirculation (FGR), individually and in combination, combusting natural gas (NG) and propane−butane gas (PBG). Fuel heat inputs of 16 and 18 kW and air excess coefficients of 1.1 and 1.2, respectively, were tested. The highest individual denitrification efficiency of up to 74% was obtained for FGR, followed by reburning and OFA. A denitrification efficiency between 8.9% (reburning + OFA) and 72% (reburning + OFA + FGR) with NG combustion was observed. Using a 20% FGR rate yielded denitrification efficiency of 74% for NG and 65% for PBG and also led to a significant decrease in carbon monoxide (CO) emissions, so this can be recommended as the most efficient denitrification and de-CO method in small-scale furnaces. Reburni... [more]
Hydrogenation of Trans,Trans-Muconic Acid to Bio-Adipic Acid: Mechanism Identification and Kinetic Modelling
Alessandro Rosengart, Carlo Pirola, Sofia Capelli
December 17, 2020 (v1)
Keywords: adipic acid, hydrogenation, kinetics, LHHW model, muconic acid, slurry reactor
The hydrogenation of trans,trans-muconic acid was investigated on a Pt/C 5% (wt) catalyst in a batch slurry reactor at constant hydrogen pressure (4 bar) and temperature (323, 333 and 343 K), with the purpose of developing a kinetic model able to predict conversions and product distributions. A dual-site Langmuir−Hinshelwood−Hougen−Watson (LHHW) model with hydrogen dissociation provided good fitting of the experimental data. The model parameters were regressed by robust numerical methods to overcome the computational challenges of the model parameters’ collinearity. Different reaction mechanisms were tested; the best model involved two subsequent hydrogenation steps. The first step yielded from trans,trans-muconic acid a monounsaturated intermediate (trans-2-hexenedioic acid), which was further hydrogenated to adipic acid in the second step. The intermediate was subjected to an equilibrium isomerization with cis-2-hexenedioic acid. The activation energy values and the rate constants we... [more]
The Attractiveness of the Ternary Rh-Pd-Pt Alloys for CO Oxidation Process
Aleksey A. Vedyagin, Yury V. Shubin, Roman M. Kenzhin, Pavel E. Plyusnin, Vladimir O. Stoyanovskii
December 17, 2020 (v1)
Keywords: catalytic activity, phase diagram, single precursor, synthesis, ternary alloys, thermolysis
Ternary alloys of platinum group metals attract a growing interest due to their unique catalytic properties. The present research is aimed to synthesize a series of Rh-Pd-Pt alloys with varied ratios of metals using a single-source precursor approach. Rhodium and palladium are partly miscible metals, while each of these metals is unlimitedly miscible with platinum. Thermolysis of complex salts used as a precursor results in the formation of metastable systems. The 3D nanostructure alloys are being formed after the complete decomposition of the single-source precursor. High-resolution transmission electron microscopic studies have shown that the nanoalloys are composed of interconnected polycrystalline ligaments with a mean diameter of 50 nm. The single-phase composition is confirmed by an X-ray diffraction analysis. The ratio of metals plays an important role in determining the catalytic activity of alumina-supported alloys and their thermal stability. According to UV-vis spectroscopy... [more]
Kinetic Analysis of Algae Gasification by Distributed Activation Energy Model
Guozhao Ji, Abdul Raheem, Xin Wang, Weng Fu, Boyu Qu, Yuan Gao, Aimin Li, Ming Zhao, Weiguo Dong, Zhien Zhang
December 17, 2020 (v1)
Keywords: activation energy distribution, algal biomass, gasification, kinetics
Conversion of algal biomass into energy products via gasification has attracted increasing research interests. A basic understanding of the gasification kinetics of algal biomass is of fundamental importance. Distributed activation energy model (DAEM), which provides the information of energy barrier distribution during the gasification process, is a promising tool to study the kinetic process of algae gasification. In this study, DAEM model was used to investigate Chlorella vulgaris and Spirulina gasification. The activation energy of Chlorella vulgaris gasification was in the range from 370 to 650 kJ mol−1. The range of activation energy for Spirulina gasification was a bit wider, spanning from 330 to 670 kJ mol−1. The distribution of activation energy for both Chlorella vulgaris and Spirulina showed that 500 kJ mol−1 had the most components, and these components were gasified at around 300 °C. The DAEM algorithm was validated by the conversion and conversion rate from experimental m... [more]
Biomass-Derived Activated Carbon as a Catalyst for the Effective Degradation of Rhodamine B dye
Shamim Ahmed Hira, Mohammad Yusuf, Dicky Annas, Hu Shi Hui, Kang Hyun Park
December 17, 2020 (v1)
Keywords: Activated carbon, activation energy, degradation, reaction rate, Rhodamine B
Activated carbon (AC) was fabricated from carrot waste using ZnCl2 as the activating agent and calcined at 700 °C for 2 h in a tube furnace. The as-synthesized AC was characterized using Fourier-transform infrared spectroscopy, X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Brunauer−Emmett−Teller analysis; the results revealed that it exhibited a high specific surface area and high porosity. Moreover, this material displayed superior catalytic activity for the degradation of toxic Rhodamine B (RhB) dye. Rate constant for the degradation of RhB was ascertained at different experimental conditions. Lastly, we used the Arrhenius equation and determined that the activation energy for the decomposition of RhB using AC was approximately 35.9 kJ mol−1, which was very low. Hopefully it will create a great platform for the degradation of other toxic dye in near future.
Synthesis and Characterization of CoxOy−MnCO3 and CoxOy−Mn2O3 Catalysts: A Comparative Catalytic Assessment Towards the Aerial Oxidation of Various Kinds of Alcohols
Osamah Alduhaish, Syed Farooq Adil, Mohamed E. Assal, Mohammed Rafi Shaik, Mufsir Kuniyil, Khalid M. Manqari, Doumbia Sekou, Mujeeb Khan, Aslam Khan, Ahmed Z. Dewidar, Abdulrahman Al-Warthan, Mohammed Rafiq H. Siddiqui
December 17, 2020 (v1)
Keywords: alcohols, catalyst, cobalt oxide, manganese carbonate, oxidation, oxygen
CoxOy−manganese carbonate (X%)(CoxOy−MnCO3 catalysts (X = 1−7)) were synthesized via a straightforward co-precipitation strategy followed by calcination at 300 °C. Upon calcination at 500 °C, these were transformed to CoxOy−dimanganese trioxide i.e., (X%)CoxOy−Mn2O3. A relative catalytic evaluation was conducted to compare the catalytic efficiency of the two prepared catalysts for aerial oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) using O2 molecule as a clean oxidant without utilizing any additives or alkalis. Amongst the different percentages of doping with CoxOy (0−7% wt./wt.) on MnCO3 support, the (1%)CoxOy−MnCO3 catalyst exhibited the highest catalytic activity. The influence of catalyst loading, calcination temperature, reaction time, and temperature and catalyst dosage was thoroughly assessed to find the optimum conditions of oxidation of benzyl alcohol (BzOH) for getting the highest catalytic efficiency. The (1%)CoxOy−MnCO3 catalyst which calcined at 300 °C displaye... [more]
Design, Fundamental Principles of Fabrication and Applications of Microreactors
Adama A. Bojang, Ho-Shing Wu
November 24, 2020 (v1)
Keywords: construction, fabrication, laminar flow, microreactor, pharmaceutical
This study highlights the development of small-scale reactors, in the form of microstructures with microchannel networking. Microreactors have achieved an impressive reputation, regarding chemical synthesis ability and their applications in the engineering, pharmaceutical, and biological fields. This review elaborates on the fabrication, construction, and schematic fundamentals in the design of the microreactors and microchannels. The materials used in the fabrication or construction of the microreactors include silicon, polymer, and glass. A general review of the application of microreactors in medical, biological, and engineering fields is carried out and significant improvements in these areas are reported. Finally, we highlight the flow patterns, mixing, and scaling-up of multiphase microreactor developments, with emphasis on the more significant industrial applications.
A Simplified and Optimized Chemical Mechanism for Combustion of n-Pentane at Atmospheric Pressure
Zhiqun Meng, Jinggang Wang, Jiawen Qi, Chuchao Xiong, Liquan Hou, Jinghui Luo
November 11, 2020 (v1)
Keywords: atmospheric pressure, combustion, n-pentane, optimized mechanism, simplified mechanism
In the present study, the detailed mechanism of n-pentane combustion, including 697 species and 3214 reactions, is first simplified to a mechanism with only 26 species and 134 reactions, which is suitable for the pressure of 1 atm, temperatures of 1000−1600 K, and equivalent ratios of 0.5−1.6. However, when the equivalence ratio is 1.0, in the temperature range of 1000−1100 K, compared with the detailed mechanism, the maximum error of the ignition delay time predicted by the simplified mechanism exceeds 20%. Therefore, based on the method of temperature sensitivity analysis, the simplified mechanism is further utilized through reducing the A-factor of 2HO2 = H2O2 + O2 (−1) and 2HO2 = H2O2 + O2 (−2) by 10 times. By comparing with the detailed mechanism and predicting the ignition delay time, laminar flame speed, species profile, and extinction residence time, it is found that the optimized mechanism has good accuracy in the applicable range, and is fully capable of simulating the combus... [more]
Special Issue: Application of Advanced Oxidation Processes
Ciro Bustillo-Lecompte, Jose Colina-Marquez, Lars Rehmann
November 9, 2020 (v1)
Advanced oxidation processes (AOPs) are nowadays not only considered as a complementary treatment option but as an attractive alternative to conventional methods [...]
Influence of Humidity on Performance of Single Chamber Air-Cathode Microbial Fuel Cells with Different Separators
Mungyu Lee, Sanath Kondaveeti, Taeyeon Jeon, Inhae Kim, Booki Min
November 9, 2020 (v1)
Keywords: air-cathode, dissolved oxygen, microbial fuel cell, polypropylene, relative humidity
The maximum performance of microbial fuel cells (MFCs) is significantly affected by the reduction reactions in the cathode, but their optimum condition is not fully understood yet. The air-cathode MFC operations with different separators (Nafion 117 and polypropylene (PP80) were evaluated at various relative humidity (RH) at the cathode chamber. Air cathode MFCs with a Nafion 117 separator at RH of 90 ± 2% produced the highest cell voltage of 0.35 V (600 Ω) and power density of 116 mW/m2. With a PP80 separator, the maximum power generation of 381 mW/m2 was obtained at a relatively lower RH of 30 ± 2%. The cyclic voltammogram and Tafel analysis indicated that the best performance of cathodic oxygen reduction reactions could be observed at 90% RH for Nafion and 50% RH for the PP80 separator. Additionally, the RH conditions also affected the anodic reactions and oxygen mass transfer rates to the anode chamber through the cathode and separators. This study suggests that the optimum RH cond... [more]
Post-Polymerization Heat Effect in the Production of Polyamide 6 by Bulk Quasiliving Anionic Ring-Opening Polymerization of ε-Caprolactam with Industrial Components: A Green Processing Technique
Zsófia Osváth, Anita Szőke, Szabolcs Pásztor, Györgyi Szarka, László Balázs Závoczki, Béla Iván
November 9, 2020 (v1)
Keywords: anionic ring-opening polymerization (AROP), chain branching, chain-chain coupling, hexamethylene-1,6-dicarbamoylcaprolactam, Nylon 6, Polyamide 6, post-polymerization effect, quasiliving polymerization, sodium caprolactamate, thermoplastic reaction transfer molding (T-RTM), ε-caprolactam (CPL)
Bulk, solventless anionic ring-opening polymerization (AROP) of ε-caprolactam (CPL) with high yields, without side products and with short reaction times, initiated by caprolactamate-carbamoylcaprolactam initiating systems belong to green polymerization processes, leading to poly(ε-caprolactam) (Polyamide 6, PA6, Nylon 6). However, the effect of post-polymerization heat (i.e., slow, technically feasible cooling) on the fundamental characteristics of the resulting polymers such as yield and molecular weight distributions (MWDs) have not been revealed thus far. Significant post-polymerization effect was found by us in terms of both monomer conversions and MWDs by carrying out CPL polymerization with industrial components under conditions mimicking thermoplastic reaction transfer molding (T-RTM). Remarkably, higher monomer conversions and molecular weights (MWs) were obtained for Polyamide 6 samples prepared without quenching than that for the quenched polymers at the same reaction times.... [more]
Solution Polymerization of Acrylic Acid Initiated by Redox Couple Na-PS/Na-MBS: Kinetic Model and Transition to Continuous Process
Federico Florit, Paola Rodrigues Bassam, Alberto Cesana, Giuseppe Storti
November 9, 2020 (v1)
Keywords: free-radical polymerization, Poly(acrylic acid), Process Intensification, reaction model, semi-batch to continuous
This work aims at modeling in detail the polymerization of non-ionized acrylic acid in aqueous solution. The population balances required to evaluate the main average properties of molecular weight were solved by the method of moments. The polymerization process considered is initiated by a persulfate/metabisulfate redox couple and, in particular, the kinetic scheme considers the possible formation of mid-chain radicals and transfer reactions. The proposed model is validated using experimental data collected in a laboratory-scale discontinuous reactor. The developed kinetic model is then used to intensify the discontinuous process by shifting it to a continuous one based on a tubular reactor with intermediate feeds. One of the experimental runs is selected to show how the proposed model can be used to assess the transition from batch to continuous process and allow faster scale-up to industrial scale using a literature approach.
MCM-41 Supported Co-Based Bimetallic Catalysts for Aqueous Phase Transformation of Glucose to Biochemicals
Somayeh Taghavi, Elena Ghedini, Federica Menegazzo, Michela Signoretto, Delia Gazzoli, Daniela Pietrogiacomi, Aisha Matayeva, Andrea Fasolini, Angelo Vaccari, Francesco Basile, Giuseppe Fornasari
November 9, 2020 (v1)
Keywords: bimetallic, biochemicals, glucose, MCM-41, product selectivity, reactivity
The transformation of glucose into valuable biochemicals was carried out on different MCM-41-supported metallic and bimetallic (Co, Co-Fe, Co-Mn, Co-Mo) catalysts and under different reaction conditions (150 °C, 3 h; 200 °C, 0.5 h; 250 °C, 0.5 h). All catalysts were characterized using N2 physisorption, Temperature Programmed Reduction (TPR), Raman, X-ray Diffraction (XRD) and Temperature Programmed Desorption (TPD) techniques. According to the N2-physisorption results, a high surface area and mesoporous structure of the support were appropriate for metal dispersion, reactant diffusion and the formation of bioproducts. Reaction conditions, bimetals synergetic effects and the amount and strength of catalyst acid sites were the key factors affecting the catalytic activity and biochemical selectivity. Sever reaction conditions including high temperature and high catalyst acidity led to the formation mainly of solid humins. The NH3-TPD results demonstrated the alteration of acidity in diff... [more]
Characterization of Pyrolysis Products and Kinetic Analysis of Waste Jute Stick Biomass
Jayanto Kumar Sarkar, Qingyue Wang
November 9, 2020 (v1)
Keywords: fixed-bed, heating rate, jute stick, kinetics, pyrolysis, TGA
Thermochemical process of biomass is being considered as a latest technique for the restoration of energy source and biochemical products. In this study, the influence of the different heating rates on pyrolysis behaviors and kinetic of jute stick were investigated to justify the waste jute stick biomass as a potential source of bioenergy. Pyrolysis experiments were carried out at four several heating rates of 10, 20, 30 and 40 °C/min, by utilizing the thermogravimetric analyzer (TG-DTA) and a fixed-bed pyrolysis reactor. Two different kinetic methods, Kissinger−Akahira−Sunose (KAS) and Ozawa−Flynn−Wall (OFW) were used to determine the distinct kinetic parameters. The experimental results showed that, the heating rates influenced significantly on the position of TG curve and maximum Tm peaks and highest decomposition rate of the jute stick biomass. Both the highest point of TG and the lowest point of Derivative thermogravimetry (DTG) curves were shifted towards the maximum temperature.... [more]
Kinetic Parameter Determination for Depolymerization of Biomass by Inverse Modeling and Metaheuristics
Dalyndha Aztatzi-Pluma, Susana Figueroa-Gerstenmaier, Luis Carlos Padierna, Edgar Vázquez-Núñez, Carlos E. Molina-Guerrero
November 9, 2020 (v1)
Keywords: depolymerization, inverse modeling, kinetic parameters, metaheuristics, Michaelis–Menten
A computational methodology based on inverse modeling and metaheuristics is presented for determining the best parameters of kinetic models aimed to predict the behavior of biomass depolymerization processes during size scaling up. The Univariate Marginal Distribution algorithm, particle swarm optimization, and Interior-Point algorithm were applied to obtain the values of the kinetic parameters (KM and Vmax) of four mathematical models based on the Michaelis−Menten equation: (i) Traditional Michaelis−Menten, (ii) non-competitive inhibition, (iii) competitive inhibition, and (iv) substrate inhibition. The kinetic data were obtained from our own experimentation in micro-scale. The parameters obtained from an optimized micro-scale experiment were compared with a bench scale experiment (0.5 L). Regarding the metaheuristic optimizers, it is concluded that the Interior-Point algorithm is effective in solving inverse modeling problems and has the best prediction power. According to the result... [more]
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