Journal Description

ChemEngineering

ChemEngineering is an international, peer-reviewed, open access journal on the science and technology of chemical engineering, published bimonthly online by MDPI.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, ESCI (Web of Science), Inspec, CAPlus / SciFinder, and other databases.
Journal Rank: CiteScore - Q1 (General Engineering)
Rapid Publication: manuscripts are peer-reviewed and a first decision provided to authors approximately 13.5 days after submission; acceptance to publication is undertaken in 4.6 days (median values for papers published in this journal in the first half of 2022).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.

Imprint Information Journal Flyer Open Access ISSN: 2305-7084

Latest Articles

Open AccessArticle

Effect of Artificial Freeze/Thaw and Thermal Shock Ageing, Combined or Not with Salt Crystallisation on the Colour of Zamora Building Stones (Spain)

Jacinta García-Talegón

Adolfo Carlos Iñigo

Rosa Sepúlveda

and

Eduardo Azofra

ChemEngineering 2022, 6(4), 61; https://doi.org/10.3390/chemengineering6040061 - 04 Aug 2022

Abstract

After subjecting Zamora building stones to accelerated ageing tests, colour changes were studied, namely: (a) freezing/thawing and thermal shock (gelifraction and thermoclasty), and (b) combination of freezing/thawing plus thermal shock and salt crystallisation (sulphates or phosphates) (gelifraction, thermoclasty and haloclasty). Zamora building stones are silicified conglomerates (silcretes) from the Cretaceous that show marked colour changes due to the remobilisation of iron oxyhydroxides. In this work, four varieties were: white stone; ochreous stone; white and red stone; and purple stone Their micromorphological characterization (skeleton, weathering plasma and porosity/cutan) is formed of grains and fragments of quartz and quartzite as well as by accesory minerals muscovite and feldspar (more or less altered), and some opaque. Quartz, feldspar and illite/mica were part of the skeleton; kaolinite, iron oxyhydroxides, and CT opal were part of the weathering plasma or cutans; their porosity were 11.7–8.7%. Their chromatic data have been statistically analysed (MANOVA-Biplot). They showed higher variations in ΔE*, ΔL*, Δa* and Δb*on combined freezing/thawing plus thermal shock and sulphates crystallisation leading to rapid alteration of the building stones. Chromatic differences between the other two artificial ageing tests were less evident and were not detected in all samples. The global effect of ageing on the Zamora building stones darkened them and reduced their yellowing. The ochreous stone suffered the least variation and the purple stone the most. This study of the colour by statistical analyse may be of interest for the evaluation and monitoring of stone decay, which is an inexpensive, simple, easy and non-destructive technique. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Prof. Dr. Vicente Rives)

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Open AccessFeature PaperArticle

30 Years of Vicente Rives’ Contribution to Hydrotalcites, Synthesis, Characterization, Applications, and Innovation

Raquel Trujillano

ChemEngineering 2022, 6(4), 60; https://doi.org/10.3390/chemengineering6040060 - 01 Aug 2022

Abstract

Hydrotalcite is the name of a mineral discovered in Sweden in 1842 whose formula is Mg₆Al₂(OH)₁₆CO₃·4H₂O and presents a layered crystal structure that consists of positively charged hydroxide layers neutralized by interlayer anions as carbonate, also containing water molecules. The ease of their synthesis and the possibility of incorporating other layer cations and interlayer anions have made this type of layered double hydroxides (LDH) a group of very interesting materials for industry. In addition to LDH and due to the name of the most representative mineral, this group of compounds is commonly called hydrotalcite-like materials, or simply hydrotalcites. Another way of referring to them is as anionic clays because of their layered structure but, unlike classical clays, their layers are positive and their interlayers are anionic. The main fields of application of these solids comprise catalysis, catalyst support, anion scavengers, polymer stabilizers, drug carriers, or adsorbents. This paper briefly summarizes some of the work carried out by Professor Rives over more than thirty years, focused, among other topics, on the study of the synthesis, characterization, and applications of hydrotalcites. This research has led him to train many researchers, to collaborate with research groups around the world and to publish reference papers and books in this field. This contribution, written to be included in the Special Issue “A Themed Issue in Honor of Prof. Dr. Vicente Rives”, edited on the occasion of his retirement, only shows a small part of his scientific research and intends to value and recognize his cleverness and his enormous scientific and human quality. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Prof. Dr. Vicente Rives)

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Open AccessArticle

Solubility of Rosmarinic Acid in Supercritical Carbon Dioxide Extraction from Orthosiphon stamineus Leaves

Ahmad Hazim Abdul Aziz

Nor Faadila Mohd Idrus

and

ChemEngineering 2022, 6(4), 59; https://doi.org/10.3390/chemengineering6040059 - 01 Aug 2022

Abstract

Rosmarinic acid (RA) is present in a broad variety of plants, including those in the Lamiaceae family, and has a wide range of pharmacological effects, particularly antioxidant activity. To extract RA from Orthosiphon stamineus (OS) leaves, a Lamiaceae plant, a suitable extraction process is necessary. The present study used a green extraction method of supercritical carbon dioxide (SCCO₂) extraction with the addition of ethanol as a modifier to objectively measure and correlate the solubility of RA from OS leaves. The solubility of RA in SCCO₂ was determined using a dynamic extraction approach, and the solubility data were correlated using three density-based semi-empirical models developed by Chrastil, del Valle-Aguilera, and Gonzalez. Temperatures of 40, 60, and 80 °C and pressures of 10, 20, and 30 MPa were used in the experiments. The maximum RA solubility was found at 80 °C and 10 MPa with 2.004 mg of rosmarinic acid/L solvent. The RA solubility data correlated strongly with the three semi-empirical models with less than 10% AARD. Furthermore, the fastest RA extraction rate of 0.0061 mg/g min⁻¹ was recorded at 80 °C and 10 MPa, and the correlation using the Patricelli model was in strong agreement with experimental results with less than 15% AARD. Full article

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Open AccessReview

Current Trends in the Utilization of Photolysis and Photocatalysis Treatment Processes for the Remediation of Dye Wastewater: A Short Review

Sitti Nurazida Maruja

and

Veena Vijayan

ChemEngineering 2022, 6(4), 58; https://doi.org/10.3390/chemengineering6040058 - 01 Aug 2022

Abstract

Development in the textile industry leads to an increased demand for the use of various dyes. Moreover, there is the use of some dyes in the food industry as well as medical diagnostics. Thereby, increased demand for dyes in various fields has resulted in dye-containing wastewater. Only a small portion of the generated wastewater is adequately treated. The rest is usually dumped or otherwise directly discharged into the sewage system, which ultimately enters rivers, lakes, and streams. The handling and disposal of such concentrated wastewater, especially the dye-containing wastewater, is considered to be a major environmental issue from the moment of its generation to its ultimate disposal. Conventional water treatment methods such as flotation, filtration, adsorption, etc., are non-destructive physical separation processes. They only transfer the pollutants to other phases, thereby generating concentrated deposits. The advanced oxidation process (AOP) is one of the most effective emerging methods for the treatment of wastewater containing chemical pollutants. The method involves the formation and interaction of highly reactive hydroxyl radicals under suitable activation conditions. These radicals are non-selective and efficient for the destruction and eventual mineralization of recalcitrant organic pollutants. This review aims at the pros and cons of using photocatalysis as an efficient AOP to degrade dye-containing wastewater. Full article

(This article belongs to the Special Issue Hybrid Materials and Their Uses in Water Treatment, Desalination and Reuse)

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Open AccessArticle

Acid-Modified Clays for the Catalytic Obtention of 5-Hydroxymethylfurfural from Glucose

Vladimir Sánchez

María Dolores González

Pilar Salagre

and

Yolanda Cesteros

ChemEngineering 2022, 6(4), 57; https://doi.org/10.3390/chemengineering6040057 - 26 Jul 2022

Abstract

5-hydroxymethylfurfural (5-HMF) is an important platform molecule for the synthesis of high-added value products. Several synthesized clay materials, such as mesoporous hectorite and fluorohectorite, in addition to commercial montmorillonite K-10, have been acid modified by different methodologies to be applied as catalysts for the obtention of 5-HMF from glucose. The effects of the Brønsted and/or Lewis acidity, the reaction temperature and time, and the catalyst/glucose ratio on the conversion but especially on the selectivity to 5-HMF have been studied. By comparing the synthesized clays, the best selectivity to 5-HMF (36%) was obtained at 140 °C for 4 h with H-fluorohectorite because of the presence of strong Brønsted acid sites, although its conversion was the lowest (33%) due to its low amounts of Lewis acid sites. Different strategies, such as physical mixtures of montmorillonite K10, which contains high amounts of Lewis acid centers, with Amberlyst-15, which has high amounts of Brønsted acid sites, or the incorporation of rhenium compounds, were carried out. The best selectivity to 5-HMF (62%) was achieved with a mixture of 44 wt % Amberlyst-15 and 56 wt % of montmorillonite K10 for a 56% of conversion at 140 °C for 4 h. This proportion optimized the amount of Brønsted and Lewis acid sites in the catalyst under these reaction conditions. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Prof. Dr. Vicente Rives)

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Open AccessArticle

A Hill Equation for Solid Specific Heat Capacity Calculation

Scott C. Rowe

Boris A. Chubukov

and

John C. Telotte

ChemEngineering 2022, 6(4), 56; https://doi.org/10.3390/chemengineering6040056 - 15 Jul 2022

Abstract

The Hill Equation and Hill Coefficient have been used extensively in biochemistry for the description of noncovalent binding. Previously, the Hill Coefficient was correlated with the Gibbs free energy, which suggests that the Hill Equation might be extensible to covalent binding phenomena. To evaluate this possibility, the Hill Equation was compared to the Debye Model and Einstein Solid in the calculation of heat capacity for 53 covalent solids, which included stainless steels and refractory ceramics. Hill Equation specific heat predictions showed a standard error of 0.37 J/(mole⋅Kelvin), whereas errors from the Debye Model and Einstein Solid were higher at 0.45 J/(mole⋅Kelvin) and 0.81 J/(mole⋅Kelvin), respectively. Furthermore, the Hill Equation is computationally efficient, a feature that can accelerate industrial chemical process simulation(s). Given its speed, simplicity, and accuracy, the Hill Equation likely offers an alternative means of specific heat calculation in chemical process models. Full article

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Open AccessArticle

Photodegradation of Fipronil by Zn-AlPO₄ Materials Synthesized by Non-Hydrolytic Sol–Gel Method

Omar José de Lima

Denis Talarico de Araújo

Liziane Marçal

Antonio Eduardo Miller Crotti

Guilherme Sippel Machado

Shirley Nakagaki

Emerson Henrique de Faria

and

Katia Jorge Ciuffi

ChemEngineering 2022, 6(4), 55; https://doi.org/10.3390/chemengineering6040055 - 13 Jul 2022

Abstract

In recent decades, the increasing use of pesticides to improve food productivity has led to the release of effluents that contaminate the environment. To prepare a material that may help to treat effluents generated during agricultural practice, we used a new method based on the non-hydrolytic sol-gel route to obtain zinc photocatalysts in aluminophosphate matrixes. IR spectroscopy, X-ray diffraction, thermal analysis, differential scanning electron microscopy, energy dispersion spectroscopy, and specific surface area and pore volume determined from the nitrogen adsorbed were used to characterize materials treated at different temperatures. X-ray analysis showed how heat-treatment affected the structure of the material: Zn-AlPO₄ in the trigonal and orthorhombic phase was obtained at 750 and 1000 °C, respectively. These phases directly influenced the ability of the material to generate OH radicals. The capacity of the materials to treat effluents was tested in the photodegradation of the pesticide Fipronil. The photocatalytic reactions were monitored by ultraviolet-visible spectroscopy and gas chromatography-mass spectrometry analyses. Zn-AlPO₄ treated at 750 °C showed better photodegradation results--it removed 80% of the pesticide in 2 h when higher mass (150 mg) was tested. Long-time treatment of the effluent with Zn-AlPO₄ treated at 750 °C completely photodegraded Fipronil. GC-MS analysis confirmed the photodegration profile, and only traces of Fipronil were observed after photocatalytic reaction for 120 min in the presence of Zn-AlPO₄ treated at 750 °C under UV radiation. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Prof. Dr. Vicente Rives)

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Open AccessArticle

Nanoparticle Black Ceramic Pigment Obtained by Hydrotalcite-like Compound Microwave Treatment

María Oset

Alejandro Moya

Guillermo Paulo-Redondo

and

Isaac Nebot-Díaz

ChemEngineering 2022, 6(4), 54; https://doi.org/10.3390/chemengineering6040054 - 11 Jul 2022

Abstract

Development of ceramic pigments with controlled particle sizes below 1 µm is essential for the preparation of ceramic inks used in inkjet digital decoration that is currently being applied in the ceramics sector. A black ceramic pigment based on NiCoCrFe composition has been prepared using thermal decomposition of hydrotalcite-like compounds. The stoichiometry ratio between different cations was studied to obtain the blackest pigment, giving Ni_0,5Co_0,5CrFeO₄ the better cation ratio, also the thermal treatment, comparing traditional firing in an electric furnace with microwave treatment. Samples have been characterized by X-ray diffraction, Scanning Electron Microscopy and Lab colour measurement. Microwave treatment showed the best way to obtain a pigment with spinel-type structure and a homogeneous size distribution near to 150 nm, with a high intensity and colorimetric data, reducing drastically the temperature and energy consumption to obtain a black ceramic pigment suitable to be utilized in digital ceramic inks. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Prof. Dr. Vicente Rives)

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Open AccessArticle

Use of Ethylamine, Diethylamine and Triethylamine in the Synthesis of Zn,Al Layered Double Hydroxides

Alexander Misol

Alejandro Jiménez

and

Francisco M. Labajos

ChemEngineering 2022, 6(4), 53; https://doi.org/10.3390/chemengineering6040053 - 06 Jul 2022

Abstract

Amines with two carbon atoms in the organic chain [ethylamine (EA), diethylamine (DEA), triethylamine (TEA)] have been used as precipitant agents to obtain a hydrotalcite-like compound with Zn (II) and Al (III) as layered cations and with nitrate anions in the interlayered region to balance the charge. This Layered Double Hydroxide was prepared following the coprecipitation method, and the effect on the crystal and particle sizes was studied. Also, the effect of submitting the obtained solids to hydrothermal post-synthesis treatment by conventional heating and microwave assisted heating were studied. The obtained solids were exhaustively characterized using several instrumental techniques, such as X-ray diffraction, Thermal Analysis (DTA and TG), Chemical Analysis, Infrared Spectroscopy (FT-IR), determination of Particle Size Distribution and BET-Surface area. Well crystallized solids were obtained showing two possible LDH phases, depending on the orientation of the interlayer anion with respect to the brucite-like layers. The results indicated that there is a certain influence of the amine, when used as a precipitating agent, and as a consequence of the degree of substitution, on the crystallinity and particle size of the final solid obtained. The LDHs obtained using TEA exhibited higher crystallinity, which was improved after a long hydrothermal treatment by conventional heating. Regarding the shape of the particles, the formation of aggregates in the former solid was detected, which could be easily disintegrated using ultrasound treatments, producing solid powder with high crystallinity and small particle size, with homogeneous size distribution. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Prof. Dr. Vicente Rives)

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Open AccessArticle

Evaluation of the Adsorptive Process on Adsorbent Surfaces as a Function of Pressure in an Isosteric System Compared with Adsorption Isotherm

Sindisiwe Ntsondwa

Velaphi Msomi

and

Moses Basitere

ChemEngineering 2022, 6(4), 52; https://doi.org/10.3390/chemengineering6040052 - 01 Jul 2022

Abstract

The developing significance of adsorption has brought about a steadily expanding quantity of logical and innovative writing on different adsorbents. This paper intends to propose experimental and computational methods for measuring the strength of adsorbate–solid interactions. It primarily focuses on the use of graphs to measure the effectiveness of an adsorbate’s bonds with the solid adsorbent by determining the isosteric heat. The Clausius–Clapeyron model equation is used to determine the isosteric enthalpy of adsorption from two adsorption isotherms at various but close temperatures, with ΔT of 10 °C. A full computational explanation of the Clausius–Clapeyron model equation for determining ΔH_ads is provided using experimental data. Logarithmic plots of uptakes vs. p in the low-pressure zone for the Freundlich–Langmuir graph are used to assess and confirm the quality of the crucial underlying isotherms. The isosteric heat was found to be between 13.5 kJ/mol and 16 kJ/mol. Full article

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Open AccessReview

An Overview on the Recent Advances in Alternative Solvents as Stabilizers of Proteins and Enzymes

and

ChemEngineering 2022, 6(4), 51; https://doi.org/10.3390/chemengineering6040051 - 01 Jul 2022

Abstract

Currently, the use of alternative solvents is increasing, namely ionic liquids (ILs) and deep eutectic solvents (DESs) in diverse fields of knowledge, such as biochemistry, chemistry, chemical engineering, biotechnology and biomedicine. Particularly, when compared to traditional solvents, these alternative solvents have great importance for biomolecules due to the enhanced solubility, structure stability and the biological activity of biomolecules, such as protein and enzymes. Thus, in this review article, the recent developments and efforts on the technological developments carried out with ILs and DESs for the stabilization and activation of proteins and enzymes are provided. The most studied IL- and DES-based formulations for proteins and enzymes are discussed and the molecular mechanisms and interactions related to the increased stability promoted by these alternative solvents are disclosed, while emphasizing their main advantages. Full article

(This article belongs to the Special Issue Ionic Liquids as New Alternative Engineering Solvents)

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Open AccessReview

Review of the Application of Hydrotalcite as CO₂ Sinks for Climate Change Mitigation

David Suescum-Morales

José Ramón Jiménez

and

José María Fernández-Rodríguez

ChemEngineering 2022, 6(4), 50; https://doi.org/10.3390/chemengineering6040050 - 01 Jul 2022

Abstract

In recent decades, the environmental impact caused by greenhouse gases, especially CO₂, has driven many countries to reduce the concentration of these gases. The study and development of new designs that maximise the efficiency of CO₂ capture continue to be topical. This paper presents a review of the application of hydrotalcites as CO₂ sinks. There are several parameters that can make hydrotalcites suitable for use as CO₂ sinks. The first question is the use of calcined or uncalcined hydrotalcite as well as the temperature at which it is calcined, since the calcination conditions (temperature, rate and duration) are important parameters determining structure recovery. Other aspects were also analysed: (i) the influence of the pH of the synthesis; (ii) the molar ratio of its main elements; (iii) ways to increase the specific area of hydrotalcites; (iv) pressure, temperature, humidity and time in CO₂ absorption; and (v) combined use of hydrotalcites and cement-based materials. A summary of the results obtained so far in terms of CO₂ capture with the parameters described above is presented. This work can be used as a guide to address CO₂ capture with hydrotalcites by showing where the information gaps are and where researchers should apply their efforts. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Prof. Dr. Vicente Rives)

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Open AccessArticle

Graphene-Wine Waste Derived Carbon Composites for Advanced Supercapacitors

Violeta Ureña-Torres

Gelines Moreno-Fernández

Juan Luis Gómez-Urbano

Miguel Granados-Moreno

and

Daniel Carriazo

ChemEngineering 2022, 6(4), 49; https://doi.org/10.3390/chemengineering6040049 - 29 Jun 2022

Abstract

In this work, we investigate the potential of a novel carbon composite as an electrode for high-voltage electrochemical double-layer capacitors. The carbon composite was prepared following a sustainable synthetic approach that first involved the pyrolysis and then the activation of a precursor formed by winery wastes and graphene oxide. The composite prepared in this way shows a very high specific surface area (2467 m²·g⁻¹) and an optimum pore size distribution for their use in supercapacitor electrodes. Graphene-biowaste-derived carbon composites are tested as active electrode materials in two different non-aqueous electrolytes, the ammonium salt-based conventional organic electrolyte and one imidazolium-based ionic liquid (1 M Et₄NBF₄/ACN and EMINTFSI). It was found that the presence of graphene oxide led to significant morphological and textural changes, which result in high-energy and power densities of ~27 W·h·kg⁻¹ at 13,026 W·kg⁻¹. Moreover, the devices assembled retain above 70% of the initial capacitance after 6000 cycles in the case of the organic electrolyte. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Prof. Dr. Vicente Rives)

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Open AccessArticle

Experimental Study and Numerical Simulation of Hydrodynamic Parameters of Tangential Swirlers

Nikolai A. Voinov

Alexander S. Frolov

Anastasiya V. Bogatkova

and

Denis A. Zemtsov

ChemEngineering 2022, 6(4), 48; https://doi.org/10.3390/chemengineering6040048 - 27 Jun 2022

Abstract

This paper presents and patents new profiled- and annular-channel tangential swirlers with 1.8–3 times less hydraulic drag coefficient compared to swirlers with straight channel walls at the same flow rate, respectively. The results of numerical simulation of the gas velocity and pressure profiles for tangential swirler channels of different structures are presented. The modelling was carried out with the help of OpenFOAM software using the k-ε turbulence model. It is found that the shape of the velocity profile at the channel inlet has a decisive influence on the swirler drag coefficient. The greatest contribution to the total drag coefficient of the tangential swirler is made by the pressure drop at the channel inlet compared to the pressure drop at the channel wall and the channel outlet. The experimental dependencies of the tangential swirlers’ drag coefficient on the Reynolds number with a gas criterion of 2000–20,000 and the following structural channel parameters: width 1, 2–9 mm, height 1, 5–10 mm, number 5–45 units, inclination angle 0–45° are presented. The experimental data were compared with the modelling calculations and the convergence of data was achieved. The generalized dependence for the measurement of the hydraulic drag coefficient of three types of tangential swirlers considering the effect made by the geometric parameters (flow rate, width and height of the channel, wall inclination angle) on the pressure drop has been determined; it can be useful at the unit design stage as it allows for reducing the calculation time of the swirler parameters. Full article

(This article belongs to the Special Issue Feature Papers in Chemical Engineering)

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Open AccessArticle

Hydrogen and CNT Production by Methane Cracking Using Ni–Cu and Co–Cu Catalysts Supported on Argan-Derived Carbon

Fernando Cazaña

Zainab Afailal

Miguel González-Martín

and

ChemEngineering 2022, 6(4), 47; https://doi.org/10.3390/chemengineering6040047 - 27 Jun 2022

Abstract

The 21st century arrived with global growth of energy demand caused by population and standard of living increases. In this context, a suitable alternative to produce COx-free H₂ is the catalytic decomposition of methane (CDM), which also allows for obtaining high-value-added carbonaceous nanomaterials (CNMs), such as carbon nanotubes (CNTs). This work presents the results obtained in the co-production of CO_x-free hydrogen and CNTs by CDM using Ni–Cu and Co–Cu catalysts supported on carbon derived from Argan (Argania spinosa) shell (ArDC). The results show that the operation at 900 °C and a feed-ratio CH₄:H₂ = 2 with the Ni–Cu/ArDC catalyst is the most active, producing 3.7 g_C/g_metal after 2 h of reaction (equivalent to average hydrogen productivity of 0.61 g H₂/g_metal∙h). The lower productivity of the Co–Cu/ArDC catalyst (1.4 g_C/g_metal) could be caused by the higher proportion of small metallic NPs (<5 nm) that remain confined inside the micropores of the carbonaceous support, hindering the formation and growth of the CNTs. The TEM and Raman results indicate that the Co–Cu catalyst is able to selectively produce CNTs of high quality at temperatures below 850 °C, attaining the best results at 800 °C. The results obtained in this work also show the elevated potential of Argan residues, as a representative of other lignocellulosic raw materials, in the development of carbonaceous materials and nanomaterials of high added-value. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Prof. Dr. Vicente Rives)

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Open AccessArticle

Computations of a Bluff-Body Stabilised Premixed Flames Using ERN Method

Shokri Amzin

ChemEngineering 2022, 6(4), 46; https://doi.org/10.3390/chemengineering6040046 - 24 Jun 2022

Abstract

Combustible carbon-based energy is still prevailing as the world’s leading energy due to its high energy density. However, the oxidation of these hydrocarbons disturbs the natural carbon cycle greatly by increasing greenhouse gases. As emission legislation becomes more rigorous, lean premixed combustion becomes promising because it can reduce nitrogen oxides (NO_x) and Carbon Monoxide (CO) emissions without compromising efficiency. However, utilising lean premixed flames in industrial combustors is not easy because of its thermo-acoustic instabilities associated with pressure fluctuations and the non-linearity in the mean reaction rate. Therefore, reliable predictive combustion models are required to predict emissions with sensible computational costs to use the mode efficiently in designing environmentally friendly combustion systems. Along with the promising methodologies capable of modelling turbulent premixed flames with low computational costs is the ERN-RANS framework. Thus, this study aims to compute a bluff-body stabilised premixed flames close to blow-Off using the ERN-RANS framework. As a result, a satisfactory agreement is reached between the predicted and measured values. Full article

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Open AccessReview

Layered Double Hydroxide/Nanocarbon Composites as Heterogeneous Catalysts: A Review

Didier Tichit

and

Mayra G. Álvarez

ChemEngineering 2022, 6(4), 45; https://doi.org/10.3390/chemengineering6040045 - 22 Jun 2022

Cited by 1

Abstract

The synthesis and applications of composites based on layered double hydroxides (LDHs) and nanocarbons have recently seen great development. On the one hand, LDHs are versatile 2D compounds that present a plethora of applications, from medicine to energy conversion, environmental remediation, and heterogeneous catalysis. On the other, nanocarbons present unique physical and chemical properties owing to their low-dimensional structure and sp² hybridization of carbon atoms, which endows them with excellent charge carrier mobility, outstanding mechanical strength, and high thermal conductivity. Many reviews described the applications of LDH/nanocarbon composites in the areas of energy and photo- and electro-catalysis, but there is still scarce literature on their latest applications as heterogeneous catalysts in chemical synthesis and conversion, which is the object of this review. First, the properties of the LDHs and of the different types of carbon materials involved as building blocks of the composites are summarized. Then, the synthesis methods of the composites are described, emphasizing the parameters allowing their properties to be controlled. This highlights their great adaptability and easier implementation. Afterwards, the application of LDH/carbon composites as catalysts for C–C bond formation, higher alcohol synthesis (HAS), oxidation, and hydrogenation reactions is reported and discussed in depth. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Prof. Dr. Vicente Rives)

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Open AccessReview

The Global Carbon Footprint and How New Carbon Mineralization Technologies Can Be Used to Reduce CO₂ Emissions

Abdulaziz Alturki

ChemEngineering 2022, 6(3), 44; https://doi.org/10.3390/chemengineering6030044 - 16 Jun 2022

Abstract

Carbon dioxide is a byproduct of our industrial society. It is released into the atmosphere, which has an adverse effect on the environment. Carbon dioxide management is necessary to limit the global average temperature increase to 1.5 degrees Celsius and mitigate the effects of climate change, as outlined in the Paris Agreement. To accomplish this objective realistically, the emissions gap must be closed by 2030. Additionally, 10–20 Gt of CO₂ per year must be removed from the atmosphere within the next century, necessitating large-scale carbon management strategies. The present procedures and technologies for CO₂ carbonation, including direct and indirect carbonation and certain industrial instances, have been explored in length. This paper highlights novel technologies to capture CO₂, convert it to other valuable products, and permanently remove it from the atmosphere. Additionally, the constraints and difficulties associated with carbon mineralization have been discussed. These techniques may permanently remove the CO₂ emitted due to industrial society, which has an unfavorable influence on the environment, from the atmosphere. These technologies create solutions for both climate change and economic development. Full article

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Open AccessArticle

Photocatalytic Hydrogen Production from Formic Acid Solution with Titanium Dioxide with the Aid of Simultaneous Rh Deposition

Mahmudul Hassan Suhag

and

ChemEngineering 2022, 6(3), 43; https://doi.org/10.3390/chemengineering6030043 - 10 Jun 2022

Abstract

Photocatalytic hydrogen production was studied with a formic acid solution with titanium dioxide (TiO₂) with the aid of simultaneous Rh deposition. The optimum conditions were as follows: Rh loading, 0.1 wt%; formic acid concentration, 1.0%; solution, pH 2.2; temperature, 50 °C. Under the optimum conditions, the photocatalytic hydrogen production with TiO₂ by the simultaneous deposition of Rh was 5.0 mmol g⁻¹, 12.2 mmol g⁻¹ and 16.0 mmol g⁻¹ after 1 h, 3 h and 5 h of irradiation time for black light, respectively. Rh/TiO₂ photocatalysts were characterized by XRD, SEM, photoluminescence spectra, diffuse reflectance spectra and the BET surface area. The reaction mechanism of photocatalytic hydrogen production from formic acid by Rh/TiO₂ was also proposed. Full article

(This article belongs to the Special Issue Novel Photocatalysts for Environmental and Energy Applications 2021)

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Open AccessArticle

Evaluation of VLEs for Binaries of Five Compounds Involved in the Production Processes of Cyclohexanone

and

ChemEngineering 2022, 6(3), 42; https://doi.org/10.3390/chemengineering6030042 - 27 May 2022

Abstract

In an attempt to evaluate the separation of certain impurities that arise in some stages of the production of cyclohexanone, this work analyzed the possibility of removing five of these substances via rectification. Due to the scarcity of experimental vapor–liquid equilibrium data for most of the solutions in the effluent of the global process, prior knowledge of their behavior is required. In this work, two predictive models, UNIFAC and COSMO-RS, were used to determine a priori the possibility of obtaining, by distillation, the individual components of seven of the binaries formed by the combination of these five compounds. Since both procedures described quasi-ideal behavior for all the chosen solutions, the results are considered as an approximation, owing to the special nature of the studied systems. The results and characteristics of each system are discussed separately. Full article

(This article belongs to the Special Issue Feature Papers in Chemical Engineering)

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MDPI’s 2021 Young Investigator Awards in “Engineering”—Winners Announced

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Travel Awards Sponsored by MDPI Journals: Presenting the Winners in "Engineering"

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Composites in Aerospace and Mechanical Engineering Topic Editors: Stelios K. Georgantzinos, Georgios I. Giannopoulos, Konstantinos Stamoulis, Stylianos Markolefas
Deadline: 31 December 2022

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Materials and Catalysts for Pollutants and CO₂ Capture and Transformation Topic Editors: Vicente Montes, Rafael Estevez, Manuel Checa
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Ionic Liquid and Deep Eutectic Solvent-Based Solutions Guest Editor: Mark P. Heitz
Deadline: 31 August 2022

Special Issue in ChemEngineering

Industrial Cultivation of Microalgae: Technologies, Applications and Challenges Guest Editor: Eleonora Sforza
Deadline: 30 September 2022

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Thermal Treatment of Biomass and Solid Municipal Waste Guest Editors: Corinna Netzer, Corinna Maria Grottola
Deadline: 31 October 2022

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Photocatalytic Degradation of Organic Wastes Guest Editor: Iuliana-Mihaela Deleanu
Deadline: 30 November 2022

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