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Records with Subject: Reaction Engineering
Showing records 1 to 25 of 105. [First] Page: 1 2 3 4 5 Last
Quality Properties and Pyrolysis Characteristics of Cassava Rhizome Pellets Produced by Alternating between Pelletizing and Torrefaction
Nitipong Soponpongpipat, Paisan Comsawang, Suwat Nanetoe
January 7, 2020 (v1)
Keywords: cassava rhizome, pellets, pyrolysis characteristics, TGA, torrefaction
This work investigated quality properties of pellets of raw cassava rhizome (P-RC), pellets of pelletized cassava rhizome followed by torrefaction (T-CP), and pellets of torrefied cassava rhizome followed by pelletizing (P-TC). Torrefaction was conducted at temperatures of 230, 250, and 280 °C for 30 min. Pyrolysis characteristics of T-CP and P-TC at torrefied temperatures of 230 and 250 °C were studied using thermogravimetric analysis. It was found that at the similar torrefied temperature, P-TC had a higher bulk density, energy density, and pellet durability than that of T-CP and P-RC while T-CP had a higher HHV and moisture absorption than P-TC and P-RC. The bulk density of P-TC was 1.13−1.19 and 1.33−1.52 times higher than that of P-RC and T-CP, respectively. The HHV of T-CP was 1.07 and 1.29 times higher than P-TC and P-RC, respectively. The energy density of P-TC was 1.24−1.56 and 1.20−1.41 times higher than that of P-RC and T-CP. In terms of Pellet Fuel Institute (PFI) standard,... [more]
Evaluation of Nano Zero-Valent Iron (nZVI) Activity in Solution and Immobilized in Hydrophilic PVDF Membrane for Drimaren Red X-6BN and Bisphenol-a Removal in Water
Larissa L. S. Silva, Júlio A. Caldara, Ana Maria Rocco, Cristiano P. Borges, Fabiana V. Fonseca
January 7, 2020 (v1)
Keywords: Bisphenol-a, Drimaren red X-6BN, nZVI, polyacrylic acid, PVDF membranes
Fenton reactions that involve nano zero-valent iron (nZVI) have shown high promise in the removal of organic pollutants. In this work, nZVI stabilized with carboxymethyl cellulose (CMC) was evaluated for drimaren red X-6BN (DRX-6BN, 10 mg/L) and bisphenol-a (BPA, 800 mg/L) removal. Oxidation reactions were conducted for removal of both compounds by varying nZVI/CMC concentration (0.01−5 g/L), hydrogen peroxide (H2O2, 0.01−0.1 g/L), and pH (3−9). DRX-6BN degradation rate was the highest (kinetic constant (kobs) = 4.622 h−1) when working at pH 3 and 3 g/L of nZVI/CMC. Increasing H2O2 concentration could not improve the reaction. For BPA, all the conditions tested showed removals of more than 96% with 0.02 g/L of H2O2. This result was compared with the activity of nZVI loaded in hydrophilic PVDF (Polyvinylidene fluoride) membranes by polyacrylic acid (PAA) to entrap nanoparticles to the membrane surface. As expected, the attachment of nZVI onto the membranes diminished nanoparticles’ acti... [more]
New Aspects on the Modeling of Dithiolactone-Mediated Radical Polymerization of Vinyl Monomers
Anete Joceline Benitez-Carreón, Jesús Guillermo Soriano-Moro, Eduardo Vivaldo-Lima, Ramiro Guerrero-Santos, Alexander Penlidis
December 16, 2019 (v1)
Keywords: dithiolactones, kinetic modeling, methyl methacrylate, RAFT polymerization, vinyl monomers
A kinetic model for the dithiolactone-mediated radical polymerization of vinyl monomers based on the persistent radical effect and reversible addition (negligible fragmentation) was used to calculate the polymerization rate and describe molar mass development in the polymerization of methyl methacrylate at 60 °C, using 2,2-azobisisobutyronitrile (AIBN) as an initiator, as well as dihydro-5-phenyl-2(3H)-thiophenethione (DTL1) and dihydro-2(3H)-thiophenethione (DTL2) as controllers. The model was implemented in the PREDICI commercial software. A good agreement between experimental data and model predictions was obtained.
Esterification of Free Fatty Acids with Glycerol within the Biodiesel Production Framework
Juan Francisco García Martín, Javier Carrión Ruiz, Miguel Torres García, Chao-Hui Feng, Paloma Álvarez Mateos
December 16, 2019 (v1)
Keywords: biodiesel, esterification, free fatty acids, glycerol, waste cooking oil
Companies in the field of the collection and treatment of waste cooking oils (WCO) for subsequent biodiesel production usually have to cope with high acidity oils, which cannot be directly transformed into fatty acid methyl esters due to soap production. Since glycerine is the main byproduct of biodiesel production, these high acidity oils could be esterified with the glycerine surplus to transform the free fatty acids (FFA) into triglycerides before performing the transesterification. In this work, commercial glycerol was esterified with commercial fatty acids and commercial fatty acid/lampante olive oil mixtures over tin (II) chloride. In the first set of experiments, the esterification of linoleic acid with glycerol excess from 20 to 80% molar over the stoichiometric was performed. From 20% glycerol excess, there was no improvement in FFA reduction. Using 20% glycerol excess, the performance of a biochar obtained from heavy metal-contaminated plant roots was compared to that of SnCl... [more]
Simulation of Batch Slow Pyrolysis of Biomass Materials Using the Process-Flow-Diagram COCO Simulator
Chaiyot Tangsathitkulchai, Natthaya Punsuwan, Piyarat Weerachanchai
December 11, 2019 (v1)
Keywords: biomass pyrolysis, cassava pulp residue, coconut shell, longan fruit seed, palm kernel cake, palm shell, process simulation model
The commercial COCO simulation program was used to mimic the experimental slow pyrolysis process of five different biomasses based on thermodynamic consideration. The program generated the optimum set of reaction kinetic parameters and reaction stoichiometric numbers that best described the experimental yields of solid, liquid and gas products. It was found that the simulation scheme could predict the product yields over the temperature range from 300 to 800 °C with reasonable accuracy of less than 10% average error. An attempt was made to generalize the biomass pyrolysis behavior by dividing the five biomasses into two groups based on the single-peak and two-peak characteristics of the DTG (derivative thermogravimetry) curves. It was found that this approximate approach was able to predict the product yields reasonably well. The proposed simulation method was extended to the analysis of slow pyrolysis results derived from previous investigations. The results obtained showed that the p... [more]
The Production of Engineered Biochars in a Vertical Auger Pyrolysis Reactor for Carbon Sequestration
Patrick Brassard, Stéphane Godbout, Vijaya Raghavan, Joahnn H. Palacios, Michèle Grenier, Dan Zegan
December 10, 2019 (v1)
Keywords: agricultural biomass, auger reactor, engineered biochar, forest residues, pyrolysis, response surface methodology
Biomass pyrolysis and the valorization of co-products (biochar, bio-oil, syngas) could be a sustainable management solution for agricultural and forest residues. Depending on its properties, biochar amended to soil could improve fertility. Moreover, biochar is expected to mitigate climate change by reducing soil greenhouse gas emissions, if its C/N ratio is lower than 30, and sequestrating carbon if its O/Corg and H/Corg ratios are lower than 0.2 and 0.7, respectively. However, the yield and properties of biochar are influenced by biomass feedstock and pyrolysis operating parameters. The objective of this research study was to validate an approach based on the response surface methodology, to identify the optimal pyrolysis operating parameters (temperature, solid residence time, and carrier gas flowrate), in order to produce engineered biochars for carbon sequestration. The pyrolysis of forest residues, switchgrass, and the solid fraction of pig manure, was carried out in a vertical au... [more]
Reduction of Furfural to Furfuryl Alcohol in Liquid Phase over a Biochar-Supported Platinum Catalyst
Ariadna Fuente-Hernández, Roland Lee, Nicolas Béland, Ingrid Zamboni, Jean-Michel Lavoie
December 10, 2019 (v1)
Keywords: biochar, furfural, furfuryl alcohol (FA), hydrogenation, maple, platinum catalyst
In this work, the liquid phase hydrogenation of furfural has been studied using a biochar-supported platinum catalyst in a batch reactor. Reactions were performed between 170 °C and 320 °C, using 3 wt % and 5 wt % of Pt supported on a maple-based biochar under hydrogen pressure varying from 500 psi to 1500 psi for reaction times between 1 h and 6 h in various solvents. Under all reactive conditions, furfural conversion was significant, whilst under specific conditions furfuryl alcohol (FA) was obtained in most cases as the main product showing a selectivity around 80%. Other products as methylfuran (MF), furan, and trace of tetrahydrofuran (THF) were detected. Results showed that the most efficient reaction conditions involved a 3% Pt load on biochar and operations for 2 h at 210 °C and 1500 psi using toluene as solvent. When used repetitively, the catalyst showed deactivation although only a slight variation in selectivity toward FA at the optimal experimental conditions was observed.
Qualitative Analysis of Transesterification of Waste Pig Fat in Supercritical Alcohols
Jeeban Poudel, Malesh Shah, Sujeeta Karki, Sea Cheon Oh
December 10, 2019 (v1)
Keywords: biodiesel, supercritical ethanol, supercritical methanol, transesterification, waste pig fat
In this work, the characteristics of waste pig fat degradation using supercritical alcohols have been studied. Comparative analysis of the influence of supercritical methanol and supercritical ethanol as solvents on the transesterification was the primary focus of this research. The experiments were carried out with waste pig fat to alcohol weight ratios of 1:1.5 (molar ratio: 1:40.5 for methanol and 1:28 for ethanol), 1:2.0 (molar ratio: 1:54 for methanol and 1:37.5 for ethanol) and 1:2.5 (molar ratio: 1:67.5 for methanol and 1:47 for ethanol) at transesterification temperatures 250, 270 and 290 °C for holding time 0, 15, 30, 45 and 60 min. Increase in the transesterification and holding time increased the conversion while increase in alcohol amount from 1:1.5 to 1:2.0 and 1:2.5 had minimal effect on the conversion. Further, majority of the ester composition in using SCM as solvent falls in the carbon range of C17:0, C19:1 and C19:2 while that for SCE falls in the carbon range of C18:... [more]
Kinetic Studies and Moisture Diffusivity During Cocoa Bean Roasting
Leydy Ariana Domínguez-Pérez, Ignacio Concepción-Brindis, Laura Mercedes Lagunes-Gálvez, Juan Barajas-Fernández, Facundo Joaquín Márquez-Rocha, Pedro García-Alamilla
December 10, 2019 (v1)
Keywords: activation energy, cocoa bean roasting, diffusivity coefficients, kinetic models
Cocoa bean roasting allows for reactions to occur between the characteristic aroma and taste precursors that are involved in the sensory perception of chocolate and cocoa by-products. This work evaluates the moisture kinetics of cocoa beans during the roasting process by applying empirical and semi-empirical exponential models. Four roasting temperatures (100, 140, 180, and 220 °C) were used in a cylindrically designed toaster. Three reaction kinetics were tested (pseudo zero order, pseudo first order, and second order), along with 10 exponential models (Newton, Page, Henderson and Pabis, Logarithmic, Two-Term, Midilli, Verma, Diffusion Approximation, Silva, and Peleg). The Fick equation was applied to estimate the diffusion coefficients. The dependence on the activation energy for the moisture diffusion process was described by the Arrhenius equation. The kinetic parameters and exponential models were estimated by non-linear regression. The models with better reproducibility were the... [more]
Modeling and Observer-Based Monitoring of RAFT Homopolymerization Reactions
Patrick M. Lathrop, Zhaoyang Duan, Chen Ling, Yossef A. Elabd, Costas Kravaris
December 10, 2019 (v1)
Keywords: measurements with delay, multi-rate observer, nonlinear sampled-data system, parameter fitting, RAFT polymerization
Reversible addition−fragmentation chain−transfer (RAFT) polymerization of methyl methacrylate (MMA) is modeled and monitored using a multi-rate multi-delay observer in this work. First, to fit the RAFT reaction rate coefficients and the initiator efficiency in the model, in situ 1 H nuclear magnetic resonance (NMR) experimental data from small-scale (400 mL) reflux reactions is then used to validate the fitted model. The fitted model accurately predicts the polymer properties of the large-scale reactions with slight discordance at late reaction times. Based on the fitted model, a multi-rate multi-delay observer coupled with an inter-sample predictor and dead time compensator is designed, to account for the asynchronous multi-rate measurements with non-constant delays. The multi-rate multi-delay observer shows perfect convergence after a few sampling times when tested against the fitted model, and is in fair agreement with the real data at late reaction times when implemented ba... [more]
Equilibrium and Kinetic Studies of Biosorptive Removal of 2,4,6-Trichlorophenol from Aqueous Solutions Using Untreated Agro-Waste Pine Cone Biomass
Nadavala Siva Kumar, Mohammad Asif, Anesh Manjaly Poulose, Madala Suguna, Mansour I. Al-Hazza
December 10, 2019 (v1)
Keywords: 2,4,6-trichlorophenol, biosorption, kinetics and isotherm models, pine cone powder
The present work discusses the adsorptive removal of a phenolic pollutant, i.e., 2,4,6-trichlorophenol (TCP), using low cost untreated agricultural waste pine cone powder (PCP). The present biosorbent was thoroughly characterized with the help of FTIR, SEM, XRD, and CHN analysis. The presence of amine (-NH2), hydroxyl (-OH) and carbonyl (C=O) functional groups was detected by the FTIR analysis. The important biosorption factors like agitation time, biomass dosage, initial adsorbate concentration, and the initial pH were examined by batch studies. The biosorption kinetic process was fast, reaching equilibrium in 75 min. The experimental kinetic data revealed an excellent agreement with the pseudo second order (PSO) model. On the other hand, the Langmuir isotherm model best described the equilibrium data with the maximum biosorption capacity (qmax) of 243.90 mg/g. These values are better than the adsorption capacities of most agro-based untreated adsorbents previously reported in the lit... [more]
Effect of Assisted Ultrasonication and Ozone Pretreatments on Sludge Characteristics and Yield of Biogas Production
Tuan Minh Le, Phong Thanh Vo, Tuan Anh Do, Lien Thi Tran, Hoa Thi Truong, Thanh Thao Xuan Le, Yi-Hung Chen, Chia-Chi Chang, Ching-Yuan Chang, Quoc Toan Tran, Tran Thanh, Manh Van Do
December 10, 2019 (v1)
Keywords: biogas, ozonation, sludge pretreatment, solubilization, ultrasonic
The effects of ultrasonic and ozonation pretreatments on organic solubilization, anaerobic biodegradability, and biogas production were elucidated in this study. Two pretreatment methods for batch anaerobic digestion for biogas recovery with the same material and experimental conditions were the focus for comparison. Anaerobic digestion experiments were conducted at ambient temperature with the solid retention time set to 25 days. The obtained results indicated that the soluble chemical oxygen demand increased from 0.344 without pretreatment to 1.023 and 1.228 g/L with ultrasound and ozone pretreatments, respectively, whereas the yields of biogas production in the 25 days increased by 32.3 and 52.9% via ultrasonic irradiation and ozonation relative to the control case, respectively. The biodegradability of the organic compounds of the samples for the cases of ultrasound, ozone pretreatments, and control achieved 55.9, 64.31, and 39.18%, respectively, in terms of chemical oxygen demand... [more]
Siderite Formation by Mechanochemical and High Pressure−High Temperature Processes for CO2 Capture Using Iron Ore as the Initial Sorbent
Eduin Yesid Mora Mendoza, Armando Sarmiento Santos, Enrique Vera López, Vadym Drozd, Andriy Durygin, Jiuhua Chen, Surendra K. Saxena
December 10, 2019 (v1)
Keywords: calcination, Carbon Dioxide Capture, carbonation, carbonation kinetics, iron ore, mechanochemical reactions, recyclability
Iron ore was studied as a CO2 absorbent. Carbonation was carried out by mechanochemical and high temperature−high pressure (HTHP) reactions. Kinetics of the carbonation reactions was studied for the two methods. In the mechanochemical process, it was analyzed as a function of the CO2 pressure and the rotation speed of the planetary ball mill, while in the HTHP process, the kinetics was studied as a function of pressure and temperature. The highest CO2 capture capacities achieved were 3.7341 mmol of CO2/g of sorbent in ball milling (30 bar of CO2 pressure, 400 rpm, 20 h) and 5.4392 mmol of CO2/g of absorbent in HTHP (50 bar of CO2 pressure, 100 °C and 4 h). To overcome the kinetics limitations, water was introduced to all carbonation experiments. The calcination reactions were studied in Argon atmosphere using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis. Siderite can be decomposed at the same temperature range (100 °C to 420 °C) for the samples... [more]
Modelling and Kinetic Study of Novel and Sustainable Microwave-Assisted Dehydration of Sugarcane Juice
Tayyaba Alvi, Muhammad Kashif Iqbal Khan, Abid Aslam Maan, Akmal Nazir, Muhammad Haseeb Ahmad, Muhammad Issa Khan, Muhammad Sharif, Azmat Ullah Khan, Muhammad Inam Afzal, Muhammad Umer, Shabbar Abbas, Shahnah Qureshi
December 10, 2019 (v1)
Keywords: brix, dehydration, kinetics, microwave, Modelling, Renewable and Sustainable Energy, sugarcane
Sugarcane juice is a perishable food with a good nutritional profile. Thus, there is a need to increase its shelf life by reducing water content which facilitates storage and transportation. In this study, process conditions were optimized to concentrate the sugarcane juice at various microwave powers (30, 50, 80, 100 W). A central composite design was applied to optimize the process conditions (power and time). The overall evaporation time depends on microwave powers; increase in power reduced the processing time. The results showed that at 100 W sugarcane juice was concentrated to 75° brix for 15 min which reduced the energy consumption to 1.3 times compared to other powers. Moreover, microwave processing better retained the sensory properties of concentrate and preserved its antioxidant activity. Thus, 100 W was most energy efficient in concentrating sugarcane juice. In general, microwave processing reduced the processing time and cost making it a sustainable approach to concentrate... [more]
Thermochemical Conversion of Napier Grass for Production of Renewable Syngas
Mohamad Syazarudin Md Said, Wan Azlina Wan Abdul Karim Ghani, Tan Hong Boon, Siti Aslina Hussain, Denny Kok Sum Ng
December 9, 2019 (v1)
Keywords: energy crop, gasification, Napier grass, Renewable and Sustainable Energy, solid biofuel
Fuel resource diversification is a global effort to deviate from non-renewable fossil fuels. Biomass has been identified as an alternative solid biofuel source due to its desirable properties and carbon neutrality. As reported in the literature, biomass can positively contribute towards combating climate change while providing alleviation for energy security issue. As part of efforts to diversify biomass resources, this work intends to explore the potential of Napier grass, one type of energy crop, for the production of renewable syngas via gasification. This energy crop is originally from Africa, which is highly productive with low cost (40 tonnes per year per hectare). Limited studies were conducted to analyze the potential of such an energy crop as a fuel source, which is the subject of this work. In order to analyze the full potential of such energy crop, the physical and chemical characteristics of this biomass was first analyzed. To determine the productivity of syngas from this... [more]
A Theoretical and Experimental Study for Screening Inhibitors for Styrene Polymerization
Ali Darvishi, Mohammad Reza Rahimpour, Sona Raeissi
December 9, 2019 (v1)
Keywords: density functional theory, inhibitors, phenolic, polymerization, stable nitroxide radicals, styrene
Styrene is one of the most important monomers utilized in the synthesis of various polymers. Nevertheless, during distillation, storage, and transportation of ST, undesired polymer (i.e., UP) formation can take place. Thus, the control of undesired polymerization of styrene is a challenging issue facing industry. To tackle the mentioned issue, the antipolymer and antioxidant activity of stable nitroxide radicals (i.e., SNRs) and phenolics in styrene polymerization were studied by density functional theory (DFT) calculation and experimental approach. The electrophilicity index and growth percentage have been determined by DFT calculation and experimental approach, respectively. It is depicted that 2,6-di-tert-butyl-4-methoxyphenol (DTBMP) and 2,6-di-tert-butyl-4-methylphenol (BHT) from phenolics, and 4-hydroxy-2,2,6,6-tetramethyl piperidine 1-Oxyl (4-hydroxy-TEMPO) and 4-oxo-2,2,6,6-tetramethylpiperidine 1-Oxyl (4-oxo-TEMPO) from stable nitroxide radicals were the most effective inhibit... [more]
An Overview of Temperature Issues in Microwave-Assisted Pyrolysis
Mattia Bartoli, Marco Frediani, Cedric Briens, Franco Berruti, Luca Rosi
December 3, 2019 (v1)
Keywords: microwave, pyrolysis, temperature control
Microwave-assisted pyrolysis is a promising thermochemical technique to convert waste polymers and biomass into raw chemicals and fuels. However, this process involves several issues related to the interactions between materials and microwaves. Consequently, the control of temperature during microwave-assisted pyrolysis is a hard task both for measurement and uniformity during the overall pyrolytic run. In this review, we introduce some of the main theoretical aspects of the microwaves−materials interactions alongside the issues related to microwave pyrolytic processability of materials.
Numerical Investigation of Solid-Fueled Chemical Looping Combustion Process Utilizing Char for Carbon Capture
Xiaojia Wang, Xianli Liu, Yong Zhang, Bo Zhang, Baosheng Jin
November 24, 2019 (v1)
Keywords: bubbling fluidized bed, char, chemical looping combustion, fuel reactor, numerical simulation
The in-depth understanding of the gas−solid flow and reaction behaviors, and their coupling characteristics during the chemical looping combustion (CLC) process has the guiding significance for the operation and optimization of a chemical looping combustor. A three-dimensional numerical model is applied to investigate the char-fueled CLC characteristics in a fuel reactor for efficient CO2 separation and capture. Simulations are carried out in a bubbling fluidized bed fuel reactor with a height of 2.0 m and a diameter of 0.22 m. The initial bed height is 1.1 m, and hence the height−diameter ratio of the slumped bed is five. The oxygen carrier is prepared with 14 wt% of CuO on 86 wt% of inert Al2O3. In the process of mathematical modeling, a Eulerian-Eulerian two-fluid model is adopted for both of the gas and solid phases. Gas turbulence is modeled on the basis of a k−ε turbulent model. The reaction kinetics parameters are addressed based upon previous experimental investigations from li... [more]
Insights into Kinetics of Methane Hydrate Formation in the Presence of Surfactants
Jyoti Shanker Pandey, Yousef Jouljamal Daas, Nicolas von Solms
November 24, 2019 (v1)
Keywords: gas uptake, induction time, methane hydrate, rocking cell, sodium dodecyl sulfate
Sodium dodecyl sulfate (SDS) is a well-known surfactant, which can accelerate methane hydrate formation. In this work, methane hydrate formation kinetics were studied in the presence of SDS using a rocking cell apparatus in both temperature-ramping and isothermal modes. Ramping and isothermal experiments together suggest that SDS concentration plays a vital role in the formation kinetics of methane hydrate, both in terms of induction time and of final gas uptake. There is a trade-off between growth rate and gas uptake for the optimum SDS concentration, such that an increase in SDS concentration decreases the induction time but also decreases the gas storage capacity for a given volume. The experiments also confirm the potential use of the rocking cell for investigating hydrate promoters. It allows multiple systems to run in parallel at similar experimental temperature and pressure conditions, thus shortening the total experimentation time. Understanding methane hydrate formation and st... [more]
Improvement of Catalytic Activity of Platinum Nanoparticles Decorated Carbon Graphene Composite on Oxygen Electroreduction for Fuel Cells
Halima Begum, Young-Bae Kim
November 24, 2019 (v1)
Keywords: composite, Fuel Cells, graphene, oxygen reduction reaction, platinum carbon
High-performance platinum (Pt)-based catalyst development is crucially important for reducing high overpotential of sluggish oxygen reduction reaction (ORR) at Pt-based electrocatalysts, although the high cost and scarcity in nature of Pt are profoundly hampering the practical use of it in fuel cells. Thus, the enhancing activity of Pt-based electrocatalysts with minimal Pt-loading through alloy, core−shell or composite making has been implemented. This article deals with enhancing electrocatalytic activity on ORR of commercially available platinum/carbon (Pt/C) with graphene sheets through a simple composite making. The Pt/C with graphene sheets composite materials (denoted as Pt/Cx:G10−x) have been characterized by several instrumental measurements. It shows that the Pt nanoparticles (NPs) from the Pt/C have been transferred towards the π-conjugated systems of the graphene sheets with better monolayer dispersion. The optimized Pt/C8:G2 composite has higher specific surface area and b... [more]
Understanding the Lack of Reactivity of 2,4-Dihydroxybenzaldehyde Towards the Biginelli Adduct Using Density Functional Theory Molecular Modeling
Virginia Flores-Morales, Eduardo D. Ayala-Medrano, José García-Elías, Margarita L. Martínez-Fierro, Edgar Marquez, José Mora
October 26, 2019 (v1)
Keywords: density functional theory, dihydropyrimidinthione derivatives, intermediaries, mechanism reaction, one-pot reaction
The Biginelli reaction is a multicomponent reaction for obtaining dihydropyrimidinthiones quickly, with multiple substitution patterns. The reaction mechanism remains unclear. Three possible pathways proposed for the reaction are the iminium route, an enamine intermediate, and the Knoevenagel pathway. However, when thiourea was used, no theoretical calculations were reported. Thus, based on the literature, the iminium pathway was used to obtain evidence explaining the lack of reactivity of 2,4-dihydroxybenzaldehyde towards the Biginelli adduct, compared with 4-hydroxybenzaldehyde. This computational study, carried out using the B3LYP/6-31++G(d,p) level of theory, showed an increment of 150 kJ/mol in the activation energy of the slowest pathway, due to the presence of a hydroxyl group in position 2 (ortho) of the aromatic aldehyde, decreasing its reactivity. Natural bond orbital (NBO) calculations suggest that the determinant steps are simultaneous, i.e., the polarization of the carbony... [more]
On the Recovery of PLP-Molar Mass Distribution at High Laser Frequencies: A Simulation Study
Shaghayegh Hamzehlou, M. Ali Aboudzadeh, Yuri Reyes
October 26, 2019 (v1)
Keywords: degree of branching, n-butyl acrylate, PLP-SEC
Due to the inherent difficulties in determination of the degree of branching for polymers produced in pulsed laser polymerization (PLP) experiments, the behavior of the degree of branching and backbiting reaction in high laser frequency and relatively high reaction temperatures have not been well-established. Herein, through a simulation study, the validity of different explanations on the recovery of PLP-molar mass distribution at high laser frequencies is discussed. It is shown that the reduction of the backbiting reaction rate at high laser frequency, and consequent decrease in the degree of branching, is not a necessary condition for recovering the PLP-molar mass distribution. The findings of this work provide simulation support to a previous explanation about the possibility of using high laser frequency for reliable determination of the propagation rate coefficient for acrylic monomers.
Aqueous and Enzymatic Extraction of Oil and Protein from Almond Cake: A Comparative Study
Thaiza S. P. Souza, Fernanda F. G. Dias, Maria G. B. Koblitz, Juliana M. L. N. de M. Bell
September 23, 2019 (v1)
Keywords: almond cake, aqueous extraction, oil extraction, protein extraction, solubility
The almond cake is a protein- and oil-rich by-product of the mechanical expression of almond oil that has the potential to be used as a source of valuable proteins and lipids for food applications. The objectives of this study were to evaluate the individual and combined effects of solids-to-liquid ratio (SLR), reaction time, and enzyme use on oil and protein extraction yields from almond cake. A central composite rotatable design was employed to maximize the overall extractability and distribution of extracted components among the fractions generated by the aqueous (AEP) and enzyme-assisted aqueous extraction process (EAEP). Simultaneous extraction of oil and protein by the AEP was favored by the use of low SLR (1:12.82) and longer reaction times (2 h), where extraction yields of 48.2% and 70% were achieved, respectively. Increased use of enzyme (0.85%) in the EAEP resulted in higher oil (50%) and protein (75%) extraction yields in a shorter reaction time (1 h), compared with the AEP... [more]
Lanthanum Effect on Ni/Al2O3 as a Catalyst Applied in Steam Reforming of Glycerol for Hydrogen Production
Nuria Sánchez, José María Encinar, Sergio Nogales, Juan Félix González
September 23, 2019 (v1)
Keywords: biodiesel, Hydrogen, non-noble transition metals, Syngas, X-ray photoelectron spectroscopy
Nowadays, the massive production of biodiesel leads to a surplus of glycerol. Thus, new applications of this by-product are being developed. In this study, glycerol steam reforming was carried out with Ni catalysts supported on Al2O3 rings and La-modified Al2O3. The catalysts were characterized by N2 physical adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and thermogravimetry. Both catalysts were effective in glycerol steam reforming. However, Ni/Al2O3 activity decreased over reaction time. Ni/La2O3/Al2O3 showed the best stability during the reaction. In addition, the activity of the modified support, La2O3/Al2O3, was evaluated. The modification of the support lent catalytic properties to the solid. Some conditions such as catalyst arrangement (catalyst in the first or second reactor), space velocity, and reaction temperature were studied. The highest hydrogen production was obtained when half the amount of the catalyst was located in bot... [more]
Recent Novel Hybrid Pd−Fe3O4 Nanoparticles as Catalysts for Various C−C Coupling Reactions
Sanha Jang, Shamim Ahmed Hira, Dicky Annas, Sehwan Song, Mohammad Yusuf, Ji Chan Park, Sungkyun Park, Kang Hyun Park
September 13, 2019 (v1)
Keywords: C–C coupling reaction, heterogeneous catalyst, hybrid catalyst, Pd–Fe3O4 nanoparticles
The use of nanostructure materials as heterogeneous catalysts in the synthesis of organic compounds have been receiving more attention in the rapid developing area of nanotechnology. In this review, we mainly focused on our own work on the synthesis of hybrid palladium−iron oxide nanoparticles. We discuss the synthesis of Pd−Fe3O4—both morphology-controlled synthesis of Pd−Fe3O4 and transition metal-loaded Pd−Fe3O4—as well as its application in various C−C coupling reactions. In the case of rose-like Pd−Fe3O4 hybrid nanoparticles, thermal decomposition can be used instead of oxidants or reductants, and morphology can be easily controlled. We have developed a method for the synthesis of nanoparticles that is facile and eco-friendly. The catalyst was recyclable for up to five continual cycles without significant loss of catalytic activity and may provide a great platform as a catalyst for other organic reactions in the near future.
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