Category Archives: Chemical Engineering & Technology

Physicochemical Properties and Applications of Deep Eutectic Solvents for CO2 Capture

Posted on 22 August 2023 by nRima Biswasn

CO₂ separation is critical for energy savings and CO₂ emission reduction. Deep eutectic solvents (DESs) as ionic liquids (ILs) analogues exhibit significant potential in CO₂ capture with favorable solvent properties and are considered economical alternatives to conventional ILs. The state-of-the-art of physicochemical properties of DESs related to their influence on CO₂ absorption mechanisms is discussed.

Abstract

Rising anthropogenic greenhouse gas concentrations, notably CO₂ emissions, have led to environmental issues that affect both humans and ecosystems. CO₂ separation makes it easier to reduce energy use and CO₂ emissions, both of which are essential for combating the concern of global warming. The use of ionic liquids (ILs) as CO₂ capture solvents is recommended. However, the high viscosity, toxicity, cost, and poor biodegradability of ILs limit their large-scale application. In recent years, deep eutectic solvents (DESs) have been created with improved CO₂ separation efficiency, lower preparation costs, and less negative environmental impact. The state-of-the-art of the physicochemical properties of DESs in connection to their influence on CO₂ capture processes and the studies of CO₂ solubility in DESs are discussed. The absorption mechanism of CO₂ in DESs and the effect of temperatures, pressures, and hydrogen bond donors (HBDs) on the solubility of CO₂ in DESs are overviewed and analyzed, and future research directions on this topic are suggested.

Removal of Organochlorine Compounds from Coal Tar by Nucleophilic Substitution and Coalescence

Posted on 16 August 2023 by nHengxing Du, nZhongyang Gao, nWangliang Lin

An integrated process of phase transfer nucleophilic substitution and coalescence separation is proposed to upgrade coal tar by removing organochlorine compounds (OOCs) and decreasing its moisture content. Different types of phase transfer catalysts and nucleophiles were selected to convert OOCs in coal tar. Glass fiber served as coalescence media to remove water and chloride compounds from coal tar simultaneously.

Abstract

An integrated process of phase transfer nucleophilic substitution and coalescence is proposed to upgrade coal tar by simultaneously removing organochlorine compounds (OOCs) and water. For the phase transfer catalysts (PTCs) and nucleophiles, polyethylene glycol 400 (PEG-400) and triethanolamine (TEOA) were the most effective to remove OOCs from coal tar. The optimal parameters of the dichlorination process in terms of molar ratio of PEG-400 and TEOA to OOCs, reaction temperature, reaction time, and stirring speed were determined. The chloride removal efficiency reached 80.66 % when glass fiber was used for oil-water coalescence separation. A promising method for simulllltaneously removing chloride and water from coal tar is provided.

Continuous Reactive Crystallization in a Mesoscale Oscillatory Baffled Reactor

Posted on 16 August 2023 by nSafaa M. R. Ahmed, nDavid Walton, nSaba A. Gheni, nAnh N. Phann

Continuous reactive crystallization of precipitated calcium carbonate (PCC) was performed in a mesoscale-oscillatory baffled reactor. Steady states were easily achieved due to a high degree of plug flow, with up to 95 % of solids suspended. The reactant concentration, the temperature, and the oscillation frequency have significant effects on the yield and particle size.

Abstract

Continuous reactive crystallization was carried out in a mesoscale oscillatory baffled reactor (meso-OBR), using calcium carbonate as a case study to demonstrate the ability of high solid loadings and to examine the fouling potential in continuous processes. Plug flow behavior was easily achieved in reactive solid-liquid phase reaction systems, as evidenced by the rapid establishment of a steady state. Effects of the operating conditions (reactant concentration, mixing conditions, and temperature) on the yield, particle size, and particle size distribution were studied. Increasing the reactant concentration and oscillation conditions reduced the particle size whereas increasing the operating temperature led to a large particle size. The meso-OBR produced uniformly shaped spherical crystals, with a 35 % reduction in average particle size and high purity compared to conventional stirred tanks. The meso-OBR could be used continuously for up to 6 h with less than 1 wt % of fouling (product loss).

Highly Effective B@g‐C3N4/Polyaniline Nanoblend for Photoelectrocatalytic Reduction of CO2 to Methanol

Posted on 15 August 2023 by

Photoelectrocatalytic (PEC) reduction can convert CO₂ and water to hydrocarbons and other value-added products. Herein, a B@g-C₃N₄/polyanaline nanostructured photoelectrocatalyst was synthesized, characterized, and used for PEC CO₂ reduction. Its enhanced photocurrent density when exposed to light in the presence of CO₂ suggests potential applications in the PEC reduction of CO₂ to methanol.

Abstract

Photoelectrocatalytic (PEC) conversion of CO₂ has been extensively investigated as it uses solar energy to combine CO₂ and water to produce hydrocarbons. In the present work, B@graphitic carbon nitride (g-C₃N₄)/polyaniline (PANI) nanoblend was synthesized by in situ polymerization of aniline in the presence of B@g-C₃N₄ for PEC CO₂ reduction. The catalyst was characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy, X-ray diffraction, UV-Vis absorption spectroscopy, photoluminescence, X-ray photoelectron spectroscopy (XPS), and Mott-Schottky analysis. The PEC activity was evaluated by linear sweep voltammetry (LSV) and chronoamperometry. XRD revealed the formation of g-C₃N₄, while B doping was confirmed by XPS. The presence of PANI was visualized by FESEM. A remarkable cathodic current associated with CO₂ reduction was observed during LSV from an onset potential of –0.01 V vs. normal hydrogen electrode (NHE), which is more positive than that of B@g-C₃N₄ (–0.82 V vs. NHE), and the positive shift is attributed to the slow charge recombination kinetics of B@g-C₃N₄/PANI as evidenced by PL results. The mechanism of PEC CO₂ reduction was investigated and discussed on the basis of the Mott-Schottky results. In conclusion, B@g-C₃N₄/PANI opens a new avenue to develop photoelectrocatalysts for PEC CO₂ reduction to methanol.

Optimizing the Disinfection Inactivation Efficiency in Wastewater Treatment: A Computational Fluid Dynamics Investigation of a Full‐Scale Ozonation Contactor

Posted on 15 August 2023 by

The disinfection efficiency of a full-scale ozonation contactor using a three-dimensional multiphase computational fluid dynamics model is investigated in order to improve the treatment performance for total coliforms and reduce energy costs. The proposed upgrading measures include design rehabilitation, ozone transfer improvements, inactivation kinetics improvements, and cost-benefit analysis.

Abstract

The inactivation kinetics of total coliforms to increase the pathogenic removal efficiency in a full-scale ozonation contactor in a wastewater treatment plant in Algeria is investigated. An enhanced ozone contactor design is proposed and 3D multiphase computational fluid dynamics simulations were conducted to optimize the operating parameters, including flow rates, ozone concentrations considering the treatment performance, and total operating cost. The existing design has several limitations, including poor mass-transfer efficiency and uneven distribution of dissolved ozone. To address these issues, the optimized design includes new injection-point settings and an increased number of diffusers. The optimized design achieved a significant improvement in mass transfer efficiency. The ozone treatment effectively reduced the total coliform counts in the wastewater samples compared to the existing design. The Chick-Watson model predicted inactivation kinetics, with a reduction of up to 99.997 %. The practical implications of this research can significantly improve the inactivation kinetics of ozone treatments.

Effect of Copper Oxide Nanoparticles on the Performance of Polyvinyl Chloride Membranes

Posted on 11 August 2023 by nHomayun Khezraqa, nArian Samiei, nHabib Etemadi, nMehdi Salami-Kalajahin

The strong trade-off between water flux and rejection is a challenge for polymeric membranes. The effect of CuO nanoparticles on the properties and performance of a polyvinyl chloride membrane for removal of bovine serum albumin (BSA) from contaminated surface water is evaluated. A positive impact in terms of surface porosity, permeation flux, antifouling performance, and BSA rejection could be stated.

Abstract

Polyvinyl chloride (PVC)/copper oxide (CuO) nanocomposite membranes were fabricated at different CuO nanoparticles loading levels using the phase inversion method. The fabricated membranes were tested through two filtration cycles in a submerged membrane system to remove bovine serum albumin (BSA) from water. Results showed that the hydrophilicity and porosity of the nanocomposite membranes were enhanced with an increase of CuO nanoparticles loading. The field emission electron microscopy images from the membrane surface demonstrated that the number and size of pores increased with addition of CuO nanoparticles. The atomic force microscopy test displayed that all nanocomposite membranes showed lower surface roughness in comparison to neat PVC membranes. The obtained results from membrane performance indicated that the irreversible fouling ratio for neat PVC membranes in the first and second cycles of filtration decreased for PVC/CuO-1.5 membranes. Compared with the neat PVC membrane, the membrane containing CuO exhibited better capabilities such as the enhanced permeation flux, higher BSA rejection rate, and better antifouling properties.

Comparative Life Cycle Assessment and Exergy Analysis of Coal‐ and Natural Gas‐Based Ammonia Production

Posted on 10 August 2023 by nAfşın Yusuf Çetinkaya, nLevent Bilgili, nS. Levent Kuzu, nFatih Yılmazn

Environmental and efficiency impacts of ammonia production based on coal and natural gas systems are compared in a comprehensive life cycle assessment analysis. Natural gas, also being a cleaner-burning fossil fuel, demonstrates higher energy and exergy efficiencies compared to anthracite coal, resulting in a superior net power generation rate. The advantages of natural gas over coal are highlighted.

Abstract

A comprehensive life cycle assessment (LCA) analysis of ammonia production is presented, focusing on the comparison between natural gas-based and coal-based processes. Ammonia production is associated with high energy consumption and significant carbon dioxide (CO₂) emissions. The objective of this research is to identify key processes and parameters within the ammonia synthesis industry and provide recommendations for cleaner and more sustainable development. Exergy analysis is performed to assess the efficiency of ammonia production technologies and determine optimal operating conditions. Natural gas-based ammonia production has lower environmental impacts compared to coal-based production in most categories, except for ionizing radiation. Natural gas, being a cleaner-burning fossil fuel, produces fewer greenhouse gas emissions and other air pollutants. However, it is essential to address the issue of ionizing radiation in natural gas-based processes. The potential for more efficient technologies and the importance of removing sulfur and other impurities during the production process to optimize catalyst performance are highlighted.

Cooling and Evaporative Crystallization of α‐D‐Galactose from a Highly Viscous Industrial Side Stream

Posted on 9 August 2023 by nAnna Zaykovskaya, nMarjatta Louhi-Kultanenn

An industrial side stream was used to crystallize α-D-galactose, applying various crystallization conditions and methods. The dynamic viscosity of galactose- and glucose-containing solution samples was measured, and the crystal size, shape, structure, and purity were analyzed. The crystallization time of α-D-galactose was shortened by cooling crystallization based on stepwise temperature decrease.

Abstract

An industrial side stream containing mainly glucose and galactose was used to crystallize α-D-galactose. The dynamic viscosity of samples containing galactose and glucose solutions was measured and compared with pure glucose and galactose solutions. Various crystallization conditions were investigated in terms of temperature range and batch times in cooling crystallization and their influence on the product crystal properties. The obtained results were compared with the results of evaporative crystallization. Several characterization methods were used for studying crystal size and shape, crystal structure, and purity. The overall crystallization time of α-D-galactose was shortened by cooling crystallization based on stepwise temperature decrease and the desired crystal properties were achieved.

Flow Pattern and Mixing Performance of a Dynamic Impinging Stream Reactor

Posted on 9 August 2023 by nJianwei Zhang, nZhongchuang Zhang, nRui Xu, nYing Feng, nXin Dongn

Impinging stream reactors generate a high-turbulence impingement region with enhanced mass and heat transfer and have potential applications in various industrial fields. The mixing process of a dynamic impinging stream reactor was investigated by planar laser induced fluorescence, and the fluid flow pattern and mixing characteristics were studied under different flow and structural conditions.

Abstract

The mixing process of a dynamic impinging stream reactor was measured by planar laser induced fluorescence. The fluid flow pattern and mixing characteristics were studied under different conditions. The flow field was divided into the following regions by flow pattern: free jet region, impingement region, radial jet region, and radial vortex region. The mixing characteristics were analyzed under different operational conditions. The mixing time first decreased and then increased with increasing nozzle spacing. The mixing time decreased with increasing outlet velocity difference and outlet average velocity, and the optimal working conditions were nozzle spacing L = 4d, where d is nozzle diameter, outlet velocity difference v _d = 1 m s⁻¹, and outlet average velocity v _p = 1.7 m s⁻¹.

The Aptness of Organic Diluents with Tri‐n‐Butyl Phosphate for Liquid‐Liquid Equilibria of Acrylic Acid

Posted on 9 August 2023 by nKanti Kumar Athankar, nKailas L. Wasewarn

Liquid-liquid extractions of acrylic acid with tri-n-butyl phosphate dissolved in conventional diluents (benzene, toluene, xylene, hexane, petroleum ether) are analyzed. The results are explained in terms of distribution coefficient, extraction efficacy, equilibrium complexation constant, loading ratio, and coextraction of water. These findings are used to design continuous extraction columns.

Abstract

Separation of carboxylic acids from downstream is a bottleneck in the chemical industry since it takes nearly 30–50 % of the overall production cost. In view of this, an attempt was made for the extraction of acrylic acid from aqueous solution with tri-n-butyl phosphate dissolved in organic diluents like benzene, toluene, xylene, hexane, and petroleum ether. The results are explained in terms of distribution coefficient (σ), extraction efficacy (η%), equilibrium complexation constant (K_ε ), loading ratio (ϕ), and coextraction of water. At lower concentration of acrylic acid and higher concentration of tri-n-butyl phosphate for the acrylic acid-tri-n-butyl phosphate system, maximum extraction efficacy and distribution coefficient for benzene was found as 88.60 % and 7.772, respectively. Coextraction of water in the extract phase and law of mass action were discussed, too. Diffusivity of acrylic acid to the interface of extract (organic) and raffinate (aqueous) phases was calculated using the Wilke-Chang equation and Reddy-Doraiswamy equation. In view of designing a continuous extraction column, the number of theoretical stages and minimum solvent-to-feed ratio were also determined.