1.756 registros encontrados - material ARTIGO E unidade Faculdade de Engenharia Química
(Epoxidized castor oil - citric acid) copolyester as a candidate polymer for biomedical applications
ARTIGO - Inglês
Assunto: Ácido cítrico
Vegetable oil-based polymers are attractive regarding environmental concerns to produce polymers through an environmentally friendly process to noble...
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Vegetable oil-based polymers are attractive regarding environmental concerns to produce polymers through an environmentally friendly process to noble applications, as the biomedical ones. Epoxidized vegetable oils can be used as a comonomer; however, its polymerization processes commonly use toxic raw materials which do not enable its use for biomedical application. In this paper is presented the synthesis procedure for a copolyester derived from epoxidized castor oil and citric acid, using a green route approach, with non-toxic solvents and reagents, without the use of catalysts or initiators, and no production of hazardous residues. Fourier transform infrared spectroscopy presented the infrared absorption bands of the copolyester. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) revealed good thermal stability (190 degrees C) and an elastomeric behavior (T-g<5 degrees C). Absorption capacity and gel fraction analysis indirectly showed the influence of the citric acid in the degree of reticulation. The cell colonization viability of the copolyester surface was evaluated by scanning electron microscopy (SEM), and the direct toxicity assessment investigated its non-toxic response. These results suggest the potential for biomedical application of the (epoxidized castor oil - citric acid) copolyester
3D Printed cartilage-like tissue constructs with spatially controlled mechanical properties
ARTIGO - Inglês
Assunto: Fibrina
Developing biomimetic cartilaginous tissues that support locomotion while maintaining chondrogenic behavior is a major challenge in the tissue...
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Developing biomimetic cartilaginous tissues that support locomotion while maintaining chondrogenic behavior is a major challenge in the tissue engineering field. Specifically, while locomotive forces demand tissues with strong mechanical properties, chondrogenesis requires a soft microenvironment. To address this challenge, 3D cartilage-like tissue is fabricated using two biomaterials with different mechanical properties: a hard biomaterial to reflect the macromechanical properties of native cartilage, and a soft biomaterial to create a chondrogenic microenvironment. To this end, a bath composed of an interpenetrating polymer network (IPN) of polyethylene glycol (PEG) and alginate hydrogel (MPa order compressive modulus) is developed as an extracellular matrix (ECM) with self-healing properties. Within this bath supplemented with thrombin, human mesenchymal stem cell (hMSC) spheroids embedded in fibrinogen are 3D bioprinted, creating a soft microenvironment composed of fibrin (kPa order compressive modulus) that simulate cartilage's pericellular matrix and allow a fast diffusion of nutrients. The bioprinted hMSC spheroids present high viability and chondrogenic-like behavior without adversely affecting the macromechanical properties of the tissue. Therefore, the ability to locally bioprint a soft and cell stimulating biomaterial inside of a mechanically robust hydrogel is demonstrated, thereby uncoupling the micro- and macromechanical properties of the 3D printed tissues such as cartilage
3D printed micro-chemical plant for biodiesel synthesis in millireactors
ARTIGO - Inglês
Assunto: Biodiesel
A micro-chemical plant implies the production increment of a determined product using micro/millireactor disposed in parallel. The flow distributor is...
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A micro-chemical plant implies the production increment of a determined product using micro/millireactor disposed in parallel. The flow distributor is responsible for the uniform distribution through these parallel mi-crodevices. A mal-distribution, resulted from inadequate flow distributors designs, decrease the micro-chemical plant performance. Hence, the main goal of this paper was to apply 3D printing in manufacturing micro-chemical plant parts and to obtain data on flow uniformity and reaction yield by experimental tests for the increase of biodiesel production. The methodology consisted of design, printing and assembly of the micro-chemical plant and experimental tests for flow rate and chemical reaction. The nonuniformity flow coefficient (Phi) values were obtained for ethanol, sunflower oil and ethanol-sunflower oil mixture. The conical distributor without obstacle with height of 26 mm (CD26) and the conical distributor with obstacle and height of 52 mm (CDO52) presented excellent performance (Phi < 1%) for ethanol and sunflower oil flow, respectively, being used in the biodiesel synthesis scale-up. In the microplant, the pipes used for oil and ethanol followed length/diameter ratios of 39 and 113, respectively, which offered low pressure drop. The flow uniformity deviation obtained in the micro-plant was 4.2%, and its global yield was 42%, close to a single millireactor operation (50.4%). Thereby, the biodiesel was produced at 126.4 mL min(-1). The developed microplant employed an efficient strategy for bio-diesel scale-up. Another advantage of the methodology described here is the sharing possibility of files or objects over the internet. A user anywhere around the world can access the microplant developed here and start producing the desired chemical using a 3D Printer
3D printed millireactors for process intensification
ARTIGO - Inglês
Assunto: Biodiesel
The scope of the present research aims at demonstrating the 3D printing use in the manufacturing of microchannels for chemical process applications. A...
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The scope of the present research aims at demonstrating the 3D printing use in the manufacturing of microchannels for chemical process applications. A comparison among digital model processing applications for 3D print (slicers) and a print layer thickness analysis were performed. The 3D print fidelity was verified in several devices, including the microchannels' printing with and without micromixer zones. In order to highlight the 3D print potential in Chemical Engineering, the biodiesel synthesis was also carried out in a millireactor manufactured by 3D printing. The millireactor operated under laminar flow regime with a total flow rate of 75.25 ml. min(-1) (increment of about 130 times over traditional microdevices used for biodiesel production). The printed millireactor provided a maximum yield of Ethyl Esters of 73.51% at 40 degrees C, ethanol:oil molar ratio of 7 and catalyst concentration of 125 wt% and residence time about 10 s. As a result of flow rate increment attained in the millireactor, the number of required units for scaling-up the chemical processes is reduced. Using the approach described in the present research, anyone could produce their own millireactor for chemical process in a simple way with the aid of a 3D printer
ARTIGO - Inglês
Assunto: Impressão tridimensional
Abstract: Aim: To produce valves to be used with full-face snorkeling masks for noninvasive ventilation (NIV) procedure during the coronavirus disease...
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Abstract: Aim: To produce valves to be used with full-face snorkeling masks for noninvasive ventilation (NIV) procedure during the coronavirus disease 2019 (COVID-19) pandemic. Materials & methods: ISINNOVA’s Charlotte valves for full-face snorkeling masks used for NIV procedures were redesigned, produced by selective laser sintering additive manufacturing, and submitted to air leakage tests. Results: The final model assembly did not present air leakage during the NIV procedure on human models, minimizing risks of air contamination. Conclusion: This study shows the feasibility of using additive manufactured valves with snorkel facial masks to support health systems during COVID-19 and possible future pandemics.
5-Hydroxymethylfurfural production in a lignocellulosic biorefinery : techno-economic analysis
ARTIGO - Inglês
Assunto: Biomassa
5-Hydroxymethylfurfural (HMF) is one of the leading versatile building blocks in the biorefinery context, and it is pointed as one of the top...
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5-Hydroxymethylfurfural (HMF) is one of the leading versatile building blocks in the biorefinery context, and it is pointed as one of the top value-added chemicals from biomass. Its derivatives are in the main segments of the chemical industry, especially in the polymer market. One example is 2,5-furan dicarboxylic acid (FDCA), one of the twelve most promising biobased chemicals according to the US Department of Energy. It can substitute terephthalic acid in the polyethylene terephthalate (PET) production, used in huge markets that include bottles, cans, foils, cosmetics, among others. HMF has been produced using fructose as raw material. However, this feedstock represents more than 80% of the final minimum selling price. In order to make the production process economically viable and competitive, it is essential to use cheaper raw material such as lignocellulosic biomass. The aim of this research, therefore, is to addresses a techno-economic analysis of the 5-hydroxymethylfurfural production in a lignocellulosic biorefinery, highlighting the main obstacles to reduce the product cost and the opportunities to make it more competitive. The analysis of raw materials cost indicated a minimum production cost of 0.21 US$/mol, and the cash flow analysis, considering the capital cost, indicated a minimum selling price of 3.18 US$/mol. The results indicate that the HMF production process analysed is not economically feasible. The results suggest the necessity to improve the biomass hydrolysis and to increase the glucose-HMF yield
A 3D-printed hybrid nasal cartilage with functional electronic olfaction
ARTIGO - Inglês
Assunto: Impressão tridimensional
Advances in biomanufacturing techniques have opened the doors to recapitulate human sensory organs such as the nose and ear in vitro with adequate...
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Advances in biomanufacturing techniques have opened the doors to recapitulate human sensory organs such as the nose and ear in vitro with adequate levels of functionality. Such advancements have enabled simultaneous targeting of two challenges in engineered sensory organs, especially the nose: i) mechanically robust reconstruction of the nasal cartilage with high precision and ii) replication of the nose functionality: odor perception. Hybrid nasal organs can be equipped with remarkable capabilities such as augmented olfactory perception. Herein, a proof-of-concept for an odor-perceptive nose-like hybrid, which is composed of a mechanically robust cartilage-like construct and a biocompatible biosensing platform, is proposed. Specifically, 3D cartilage-like tissue constructs are created by multi-material 3D bioprinting using mechanically tunable chondrocyte-laden bioinks. In addition, by optimizing the composition of stiff and soft bioinks in macro-scale printed constructs, the competence of this system in providing improved viability and recapitulation of chondrocyte cell behavior in mechanically robust 3D constructs is demonstrated. Furthermore, the engineered cartilage-like tissue construct is integrated with an electrochemical biosensing system to bring functional olfactory sensations toward multiple specific airway disease biomarkers, explosives, and toxins under biocompatible conditions. Proposed hybrid constructs can lay the groundwork for functional bionic interfaces and humanoid cyborgs
A cell model of hydrodynamics in a reactor with circulating fluidized bed
ARTIGO - Russo
Assunto: Reatores fluidizados
Состояние вопроса: Реакторы с циркуляционным кипящим слоем широко используются в энергетической, химической и других отраслях промышленности. Их...
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Состояние вопроса: Реакторы с циркуляционным кипящим слоем широко используются в энергетической, химической и других отраслях промышленности. Их применяют для сжигания угля, древесины и сланцев в топках энергетических котлов и утилизации твердых промышленных отходов, газификации углей и биомассы, проведения
разнообразных химических и тепломассообменных процессов. Благодаря циркуляции увеличивается время пребывания частиц в аппарате и интенсифицируются процессы взаимодействия частиц с газом. Однако для их надежного проектирования с полной реализацией имеющихся преимуществ необходима разработка адекватных математических моделей протекающих в них процессов. Несмотря на то, что моделированию отдельных процессов посвящено большое количество работ, работа реактора в целом с учетом имеющихся в нем обратных связей изучена
недостаточно. В связи с этим необходима разработка простых, но информативных моделей, учитывающих взаимодействие потоков частиц в различных зонах аппарата.
Материалы и методы: Используется метод математического моделирования, основанный на ячеечных моделях
процессов гидродинамики и теории цепей Маркова. Особенностью подхода является введение зависимости переходных вероятностей от текущего распределения содержания части в собственно реакторе и опускном канале.
Результаты: Построена нелинейная ячеечная модель процесса, позволяющая рассчитывать загрузку реактора
и опускного канала дисперсным материалом и распределение времени пребывания частиц в аппарате.
Выводы: Учет нелинейных явлений в процессе циркуляционного псевдоожижения позволяет адекватно выявлять взаимное влияние параметров псевдоожижения и циркуляции на распределение времени пребывания частиц в аппарате и загрузку его элементов материалом
разнообразных химических и тепломассообменных процессов. Благодаря циркуляции увеличивается время пребывания частиц в аппарате и интенсифицируются процессы взаимодействия частиц с газом. Однако для их надежного проектирования с полной реализацией имеющихся преимуществ необходима разработка адекватных математических моделей протекающих в них процессов. Несмотря на то, что моделированию отдельных процессов посвящено большое количество работ, работа реактора в целом с учетом имеющихся в нем обратных связей изучена
недостаточно. В связи с этим необходима разработка простых, но информативных моделей, учитывающих взаимодействие потоков частиц в различных зонах аппарата.
Материалы и методы: Используется метод математического моделирования, основанный на ячеечных моделях
процессов гидродинамики и теории цепей Маркова. Особенностью подхода является введение зависимости переходных вероятностей от текущего распределения содержания части в собственно реакторе и опускном канале.
Результаты: Построена нелинейная ячеечная модель процесса, позволяющая рассчитывать загрузку реактора
и опускного канала дисперсным материалом и распределение времени пребывания частиц в аппарате.
Выводы: Учет нелинейных явлений в процессе циркуляционного псевдоожижения позволяет адекватно выявлять взаимное влияние параметров псевдоожижения и циркуляции на распределение времени пребывания частиц в аппарате и загрузку его элементов материалом
A combined computational and experimental study on the polymerization of ϵ-caprolactone
ARTIGO - Inglês
Assunto: Catalisadores
Abstract: This paper reports the study on the synthesis of poly(?-caprolactone) - PCL by ring-opening polymerization (ROP) of ?-caprolactone (CL)...
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Abstract: This paper reports the study on the synthesis of poly(?-caprolactone) - PCL by ring-opening polymerization (ROP) of ?-caprolactone (CL) monomer with focus on mathematic developing of the growth mechanisms of polymer chain. Kinetics and mathematical modeling of ROP of CL was carried out to replicate the different experimental conditions. The computational results of conversion and molecular weight of the polymer were found to be comparable with the experimental results of nuclear magnetic resonance (NMR) spectroscopy and showed that the polymerization is highly dependent on the moisture (ROH). Moreover, parametric studies have shown how the concentrations of octanoic acid and catalyst affect the conversion and molecular weight of the polymer. The study here presented provides further understanding of synthesis of PCL, reporting mathematical models of PCL synthesis which can be used for predicting the characteristic of this biocompatible and biodegradable polymer. © 2018 American Chemical Society
ARTIGO - Inglês
Assunto: Óxidos de ferro
A solid-fuel combustion system based on chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU) has the potential to...
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A solid-fuel combustion system based on chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU) has the potential to assist in the capture of CO2 from coal-fired power plants. In both processes an air separation unit is not required, and the flue gas streams from CLC and CLOU contain primarily carbon dioxide and water, which facilitates CO2 capture. CLOU offers a potential advantage for solid fuels as it uses combustion reactions. The O-2 for the combustion reactions in CLOU is supplied from the reduction of a metal oxide (e.g. CuO). Iron-based materials are being considered for oxygen carriers in CLC, wherein the coal is gasified, and subsequently the product gas is oxidized to CO2 and H2O by reaction with the circulating oxygen carrier. CLOU affords faster coal char oxidation reaction rates, as compared to CLC coal gasification reactions, but CuO-based materials for CLOU will necessarily be more expensive. Furthermore, the stability of CuO-based oxygen carrier materials is also an important concern. In this paper, ASPEN PLUS process engineering models were developed for combustion of a Wyoming Powder River Basin coal using an iron-based oxygen carrier for CLC and a copper-based oxygen carrier for CLOU. The objective of these process models was to evaluate the material and energy requirements for a process development unit by incorporating insights from previously reported kinetic studies on laboratory scale units. A relative economic analysis has also been performed to address key technical challenges which will subsequently help in addressing the development of CLC and CLOU for solid fuels. Due to slower char gasification reaction times, CLC requires a larger reactor, which results in a relatively higher capital cost. It also manifests in a higher pressure drop and consequently higher energy costs for fluidizing the oxygen carrier
ARTIGO - Inglês
Assunto: Montmorilonita
The objective of this work was to use a statistical tool to study and evaluate the main parameters in the preparation of organo-montmorillonite (O-Mt)...
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The objective of this work was to use a statistical tool to study and evaluate the main parameters in the preparation of organo-montmorillonite (O-Mt) by using different compounds and reactional routes (aqueous, semi-solid and supercritical CO2 medium) aiming a better relationship between efficiency and environmental impact. For this, ammonium-modified montmorillonite (AmMt) and phosphonium-modified montmorillonite (PhMt) were prepared according to design of experiments. The samples were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) and contact angle. XRD and TGA analysis showed that the compounds were incorporated in the montmorillonite providing an efficient modification by all the reactional routes employed. The clay interlayer spacing was expanded and AmMt showed the largest d001 while PhMt showed better thermal stability. Statistical analysis indicated that the process parameters had low or no significance in the organo-montmorillonite characteristics. XRD, TGA and FTIR showed that the d001, yield and chemical environment of the O-Mt changed with the amount of organic compound and washing process. The contact angle test showed that the surface tension of montmorillonite was reduced with organophilization. It was concluded that semi-solid method could be a good, efficient and environmentally friendly alternative to prepare O-Mt
A competency-based chemical engineering curriculum at the University of Campinas in Brazil
ARTIGO - Inglês
Assunto: Currículos
Abstract: Engineering education is being called upon to move to a student-centered teaching. New challenges demand a curriculum that considers a set...
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Abstract: Engineering education is being called upon to move to a student-centered teaching. New challenges demand a curriculum that considers a set of competencies to enable engineers to learn autonomously and to develop solid technical and relevant soft skills. We present a top-down methodology for developing a competency-based curricula, which was employed to conceive a new chemical engineering curriculum at the University of Campinas. Our methodology is based on four main steps: i) definition of the desired profile of students with a bachelor’s degree in Chemical Engineering and their underlying competencies; ii) delineation of learning-experiences itineraries; iii) a macro conception of the curriculum entailing the logical-temporal arrangement of its learning-experiences itineraries; and the iv) establishment of each curricular component with its learning objectives. This new curriculum is integrated into the external society by experiences that engage students to practice social responsibility and develop technology based on the needs of society. Graduates’ profile and competencies were defined based on extensive surveys. We discuss how active learning methodologies can be an intrinsic part of the curriculum development process and how assessment strategies must fit the learning goals established for each curricular component. Finally, we discuss the current challenges of implementing and evaluating a competency-based curriculum
ARTIGO - Inglês
Assunto: Metais pesados
We present a feasibility study of different adsorbent materials, namely residual fish scales biosorbent (FS), mineral dolomite (DL) and commercial...
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We present a feasibility study of different adsorbent materials, namely residual fish scales biosorbent (FS), mineral dolomite (DL) and commercial resin (CR) in the heavy metals removal in multicomponent solution based on the properties of a real effluent from automotive battery recycling industry. Considering the effluent complex characteristics, the materials were assessed aiming to provide not only the heavy metals removal, but also the effluent neutralization and lower sludge generation. For this, all the studied materials were physicochemically and morphologically characterized with the aim of understanding the mechanisms involved in the process. Further, the elemental compositions of the solid and liquid phases generated from each treatment process were assessed by X-ray fluorescence spectrometry. The effluent presented highly acidic characteristics and heavy metals above the legislated limits for discharge (Fe, Zn and Pb). Each adsorbent material followed different mechanisms which led to dissimilar removal and neutralization capacities. The CR showed remarkable heavy metals removal capacity governed by an ion exchange mechanism; conversely, it did not show a neutralization effect. In contrast, FS and DL presented lower removal capacities by complex simultaneous phenomena (ion exchange, precipitation and/or complexation), but a great neutralization potential related to leaching of alkaline constituents. When sludge generation is considered as a key factor, mitigation and enhancement of treated effluent quality could alternatively be addressed by employing the materials in hybrid processes. Hence, the associated use of such materials could be viable yet very challenging for both neutralization and removal of heavy metals from the battery effluent
ARTIGO - Inglês
Assunto: Método dos volumes finitos
We investigate a novel technique to obtain the mesh porosity (volume and area) based on the Gilbert-Johnson-Keerthi (GJK) distance algorithm for flow...
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We investigate a novel technique to obtain the mesh porosity (volume and area) based on the Gilbert-Johnson-Keerthi (GJK) distance algorithm for flow modelling. The GJK algorithm is used to check collisions between two convex objects. This concept is applied to check the collision between an element of the computational mesh and the geometrical model where the element of the mesh is broken recursively to obtain refined values of the porosity. The approach has demonstrated that it can handle complex geometries within feasible computational time. The porosity values obtained using this methodology are coupled in the developed Navier-Stokes. Numerical findings are compared with selected benchmarking tests. Numerical findings agree with experimental data and the main features of the fluid flow are well captured
A critical assessment of the Flory-Huggins (FH) theory to predict aqueous two-phase behaviour
ARTIGO - Inglês
Assunto: Teoria de Flory-Huggins
This article provides an analysis on published models used to calculate phase separation in aqueous two-phase systems (ATPS) based on Flory-Huggins...
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This article provides an analysis on published models used to calculate phase separation in aqueous two-phase systems (ATPS) based on Flory-Huggins (FH) theory, in terms of problem formulation and mathematical solving algorithm. An integrated algorithm is presented, showing different mathematical approaches of using the FH theory. The algorithm involves the estimation of interchange energy, and the calculation of phase compositions. Based on experimental data, the thermodynamic model can provide a useful framework to perform a sensitivity analysis on parameters, in order to understand the influence of salt type, polymer molecular mass, and ionic strength on phase separation. However, this model, restricted to entropic and enthalpic terms, cannot quantitatively describe the data. This occurs mainly because of the strong influence of random experimental errors on the estimation of interchange energy and FH not being an exact description of phase separation in salt based ATPS. After providing a literature overview and mathematical analysis, we bring to the field the application of the FH theory for selecting ATPS and its limitations
ARTIGO - Inglês
Assunto: Redes neurais (Computação)
Abstract: The bubble flow is a flow regime present in various fields. A usual equipment that operates with the bubble flow is the bubble column. Many...
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Abstract: The bubble flow is a flow regime present in various fields. A usual equipment that operates with the bubble flow is the bubble column. Many papers deal with determining flow regime, hold up, and mass transfer coefficient in a bubble column. However, little attention has been given to the measurement of the gas flowrate. In this context, this work presents a technique to predict the gas flowrate in a bubble column from ultrasound signals using a new set of ultrasonic variables combined with process variables using a feedforward artificial neural network (ANN). Experiments were carried out in a 2-meters-long-bubble column, with inner diameter of 52.5 mm using a single 2.25 MHz ultrasound transducer. The gas flow rate varied in the range of 0 to 4 liters per minute. The best architecture obtained for ANN has one hidden layer with 36 neurons. The test mean absolute error was 0,1 LPM
A detailed design and construction of a supercritical antisolvent precipitation equipment
ARTIGO - Inglês
Assunto: Antissolvente supercrítico
This work consists of the steps for the assembly of a Supercritical Antisolvent Precipitation laboratory equipment and evaluation of the parts...
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This work consists of the steps for the assembly of a Supercritical Antisolvent Precipitation laboratory equipment and evaluation of the parts acquisition costs. A flow diagram with all components was developed, a complete list of all necessary components was presented, and an estimate of the acquisition of these parts in Brazil was reported. The stages of construction along with the importance of each component in the equipment were discussed. An equipment designs were presented as a result of the current work that serve as a basis for consulting future work on the development of new equipment.
ARTIGO - Inglês
Assunto: Xilose
An unstructured–unsegregated temperature-dependent kinetic model was developed and validated to describe ethanol fermentation in a mixture of xylose...
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An unstructured–unsegregated temperature-dependent kinetic model was developed and validated to describe ethanol fermentation in a mixture of xylose and glucose for the nonconventional yeast Spathaspora passalidarum NRRL Y-27907 under high cell density in the temperature range of 26–32 °C. The kinetic model consisted of 13 equations and 16 kinetic parameters, describing cell growth, individual xylose and glucose uptake and product formation. Global parametric estimation was executed through a differential evolution algorithm. Temperature-dependent parameters were identified and adjusted to Arrhenius-type equations as a function of temperature. The overall r2 of the process calibration and validation were 0.972 and 0.959, respectively, indicating that the model satisfactorily described the process in the temperature range investigated. Furthermore, using a 3D projection of the model to simulate ethanol production, it was concluded that temperatures between 30 and 32 °C resulted in the highest productivities
A foam-expansion and wall-evolution model for scaffold fabrication using supercritical CO2 foaming
ARTIGO - Inglês
Assunto: Artigo original
Abstract: Supercritical CO 2 foaming (SCF) is a green and highly controllable technique to fabricate polymer scaffolds. In the current work, SCF was...
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Abstract: Supercritical CO 2 foaming (SCF) is a green and highly controllable technique to fabricate polymer scaffolds. In the current work, SCF was modeled mathematically by combining a foam-expansion model (FEM) and a wall-evolution model (WEM). The model package is clearly presented, its solution strategy is precisely described, and its superiority over FEM is demonstrated. The model was validated by using experimental data of poly(e-caprolactone) scaffolds fabricated by the SCF technique at 300 bar and 50 °C with first and second pressure releases of 28.6 and 200 bar min -1 , respectively. It was revealed that coupling FEM and WEM enables the prediction of scaffold density, pore radius, pore geometry, and wall thickness at the same time
A general and robust approach for defining and solving microkinetic catalytic systems
ARTIGO - Inglês
Assunto: Catalisadores
Recent approaches for the rational design of heterogeneous catalysts have relied on first‐principles‐based microkinetic modeling to efficiently screen...
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Recent approaches for the rational design of heterogeneous catalysts have relied on first‐principles‐based microkinetic modeling to efficiently screen large phase spaces of catalytic materials for optimal activity and selectivity. Microkinetic modeling allows the calculation of catalytic rate and selectivity under a given set of conditions without a priori assumptions of rate or selectivity controlling steps by simultaneously solving nonlinear algebraic equations comprising species mass balances bound by the pseudo steady‐state approximation. We introduce a general approach to define and solve microkinetic systems that relies solely on its stoichiometric matrix and kinetic parameters of considered reaction steps. Our approach relies on linearization of the microkinetic system, enabling analytical calculation of system derivatives for use in quasi‐Newton solution schemes that exhibit excellent robustness and efficiency with minimal dependence on initial conditions
A green chemical production : obtaining levulinic acid from pretreated sugarcane bagasse
ARTIGO - Inglês
Assunto: Ácidos levulínicos
The Bio Based Press wrote “The production of levulinic acid is gaining momentum”. Today, researches are focusing efforts to convert biomass on new...
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The Bio Based Press wrote “The production of levulinic acid is gaining momentum”. Today, researches are focusing efforts to convert biomass on new chemicals platforms, including levulinic acid (LA), which has gained increased attention for being an attractive platform for products with high added value. LA can be obtained through the acid hydrolysis of some types of saccharides such as glucose and xylose, the constituent unit of cellulose and hemicelluloses.
In this work, three substantial steps to convert biomass, in this case sugarcane bagasse, in LA were investigated. Sugarcane bagasse was pretreated with acid (121 °C, 1.0 % w/v H2SO4, and 80 min) and alkali delignificated (80 °C, 0.5 % w/v NaOH, and 90 min reaction time) both with 20 % w/v of solids loading. Experiments were carried in a discontinuous reactor at different variations of temperature (160, 170 and 180 °C), acid concentration (3, 7 and 5 % w/v H2SO4), hydrolysis reaction time (55, 75 and 95 min) and substrate loadings (6, 8 and 12 % w/v).
This research has demonstrated that LA production at 170 °C, 5% w/v H2SO4, 75 min and 6 % w/v of solids loading conditions achieved a LA yield of 55.00 ± 0.36 % and selectivity about 45.65 ± 0.26 %
In this work, three substantial steps to convert biomass, in this case sugarcane bagasse, in LA were investigated. Sugarcane bagasse was pretreated with acid (121 °C, 1.0 % w/v H2SO4, and 80 min) and alkali delignificated (80 °C, 0.5 % w/v NaOH, and 90 min reaction time) both with 20 % w/v of solids loading. Experiments were carried in a discontinuous reactor at different variations of temperature (160, 170 and 180 °C), acid concentration (3, 7 and 5 % w/v H2SO4), hydrolysis reaction time (55, 75 and 95 min) and substrate loadings (6, 8 and 12 % w/v).
This research has demonstrated that LA production at 170 °C, 5% w/v H2SO4, 75 min and 6 % w/v of solids loading conditions achieved a LA yield of 55.00 ± 0.36 % and selectivity about 45.65 ± 0.26 %
A greener olefination process to produce alkenoic acids from levulinic acid
ARTIGO - Inglês
Assunto: Ácidos levulínicos
Levulinic acid (LA) is a bifunctional compound with high reactivity that can be produced by acid hydrolysis of biomass. Its ketone group can be...
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Resumo
Levulinic acid (LA) is a bifunctional compound with high reactivity that can be produced by acid hydrolysis of biomass. Its ketone group can be functionalized to an olefinic bond via Wittig reaction. However, this reactional system usually involves multiple steps and uses highly toxic raw materials. This study aims to produce alkenoic acids derived from LA via Wittig reaction using a greener process. For this, we evaluated the olefination of LA in the presence of different bases (NaHCO3, Na2CO3, and NaOH) and isopropanol as solvent (reduced toxicity). The products were identified by mass spectrometry, observing positive results for NaHCO3. The fragmentation mechanisms for the alkenoic acid ions (4-methyl-hex-4-enoic acid, m/z 127, and 4-methyl-hept-4-enoic acid, m/z 141) confirmed their production by the proposed process
A Markov chain model to describe fluidization of particles with time-varying properties
ARTIGO - Inglês
Assunto: Fluidização
A one-dimensional mathematical model of particulate solids thermal treatment in a fluidized bed based on the theory of Markov chains is proposed. A...
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A one-dimensional mathematical model of particulate solids thermal treatment in a fluidized bed based on the theory of Markov chains is proposed. A feature of the model takes into account the variation of particle properties that takes place during the fluidization. This variation occurs due to thermo-physical and chemical processes that take place during particulate solids treatment in the fluidized bed. These variations affect the particle settling velocity which is the main parameter that forms the bed expansion and local velocity of flow around the particles that strongly influences the thermo-physical and chemical processes in the bed. A generalized correlation for the drag force coefficient is proposed and tested for various materials. It was necessary to have more precise calculation of the particle settling velocity in the model. The model was developed to describe the drying process in the bed. A good correlation between computed and experimental data was achieved
A mathematical response curve for probabilistic explosion analysis
ARTIGO - Inglês
Assunto: Artigo original
Abstract: Accurate calculation of flammable cloud sizes is important for area classification and risk analysis. Numerical models, such as response...
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Abstract: Accurate calculation of flammable cloud sizes is important for area classification and risk analysis. Numerical models, such as response surfaces, are at the heart of Monte Carlo simulations for probabilistic explosion risk analysis. In the current work, we developed a mathematical model that can be used to calculate flammable cloud sizes in the context of probabilistic explosion analysis. The model considers the released fluid, the wind speed, the wind direction, the leak rate, the leak direction, and the geometry. The model is based on two non-dimensional groups that were developed using dimensional analysis. We applied the ? theorem of Buckingham, and we show that the two non-dimensional groups correlate in a unique way. Resorting the Kinetic Theory of Gases, the model shows that the flammable cloud volume in the process area increases up to a maximum value and then it decays exponentially. The two constants in the model that consider the gas dilution and the mixing are tuned using a minimum number of computational fluid dynamics (CFD) simulations. The model is then compared with numerical data (not used in the development), and good agreement is observed. Moreover, the model is straightforward to implement, and it can be used for risk analysis calculation and probabilistic explosion analysis