The release of certain gases to the atmosphere is controlled in many countries owing to their negative impact on the environment and human health. These gases include carbon dioxide (CO₂), sulfur oxides (SOx), nitrogen oxides (NOx), hydrogen sulfide (H₂S) and ammonia (NH₃). Considering the major contribution of greenhouse gases to global warming and climate change, mitigation of these gases is one of the world’s primary challenges. Nevertheless, the commercial processes used to capture these gases suffer from several drawbacks, including the use of volatile solvents, generation of hazardous byproducts, and high-energy demand. Research in green chemistry has resulted in the synthesis of potentially green solvents that are non-toxic, efficient, and environmentally friendly. Deep eutectic solvents (DESs) are novel solvents that upon wise choice of their constituents can be green and tunable with high biocompatibility, high degradability, and low cost. Consequently, the capture of toxic gases by DESs is promising and environmentally friendly and has attracted much attention during the last decade. Here, we review recent results on capture of these gases using different types of DESs. The effect of different parameters, such as chemical structure, molar ratio, temperature, and pressure, on capture efficiency is discussed.

Green Deep Eutectic Solvents (DESs) are considered here as an alternative to conventional organic solvents and ionic liquids (IL) for the extraction of phenolic compounds from pyrolysis oil. Although ionic liquids have shown a promising future in extraction processes, DESs possess not only most of their remarkable physico-chemical properties, but are also cheaper, easier to prepare and non-toxic, increasing the infatuation with these new moieties to the detriment of ionic liquids. In this work, phenol was selected as a representative of phenolic compounds, and toluene and heptane were used to model the pyrolysis oil. COSMO-RS was used to investigate the interaction between the considered Dess, phenol, n-heptane, and toluene. Two DESs (one ammonium and one phosphonium based) were subsequently used for experimental liquid–liquid extraction. A ternary liquid–liquid equilibrium (LLE) experiment was conducted with different feed concentrations of phenol ranging from 5 to 25 wt% in model oil at 25 °C and at atmospheric pressure. Although both DESs were able to extract phenol from model pyrolysis oil with high distribution ratios, the results showed that ammonium-based DES was more efficient than the phosphonium-based one. The composition of phenol in the raffinate and extract phases was determined using gas chromatography. A similar trend was observed by the COSMO-RS screening for the two DESs.

In this study, we discussed the main recent studies on PV systems worldwide and specifically in the Gulf Cooperation Council (GCC) region. We focused on different PV cells and their characteristics in terms of efficiency, importance, and negative impacts, and examined the classification of PV systems and their comparison. In addition, the adoption of PV technologies in GCC countries is considered, focusing on the future aspects. In addition, technical and economic evaluations were carried out for a 600-kW commercial PV solar project at one of the selected sites in the Riyadh region, and the PV energy generation performance was assessed. The monthly energy production, module orientation and tracking system, peak voltage, net power consumption, rated output power, cash flow and capacity factor were calculated. In addition, the direct, normal and diffuse solar radiation are calculated to determine the cost-effective and efficient PV system. Two simulation programs, namely system advisor model (SAM) and RETScreen, are used in this study. In addition, a comparison between annual energy production, cash flow, and electricity loads was performed to evaluate the accuracy of the simulation results. The study suggests that a low-cost PV system could be developed in the Riyadh region.

Rising greenhouse gas concentrations are causing climatic change that threatens ecosystem sustainability. This study investigated the impact of silica incorporation into alumina-supported nickel catalysts for the partial oxidation of methane (POM), a crucial process for syngas production. The investigation also focuses on the impact of using different calcination temperatures. The catalysts were synthesized using the impregnation method and structurally characterized with BET, TPR, FTIR, UV, XRD, TGA, Raman, and TEM analysis techniques. These characterization techniques revealed that increasing the silica content reduced the surface area and weakened the interaction between nickel and the support. The calcination temperature significantly influenced catalyst properties, affecting pore structure, nickel reducibility, and the formation of nickel aluminates and silicates. Activity tests of synthesized catalysts were performed in a packed-bed reactor at 600 °C with a 24 mL/min gas flow rate. The catalyst composition of 5Ni/10Si + 90Al demonstrated the highest activity, achieving optimal performance at lower calcination temperatures. This catalyst generates a greater concentration of active sites, primarily due to nickel oxide (NiO), which creates these sites through both mild and strong interactions. The degree of graphitization is notably lowest for the 5Ni/10Si + 90Al composition. This catalyst achieved an impressive hydrogen yield of approximately 54%, with an H₂/CO ratio of 3.4 over a streaming period of up to 240 min. When the silica loading exceeds 10 wt.%, the interaction between the metal and the support weakens, resulting in a significant decrease in surface area and, subsequently, lower catalytic activity. The 5Ni/10Si + 90Al catalyst, which was prepared with calcination temperatures above 500 °C, has very few active sites during the Partial Oxidation of Methane (POM) reaction at a reaction temperature of 600 °C. This catalyst also exhibits a high degree of crystallinity, which leads to reduced exposure of the active sites. As a result, incorporating higher weight percentages of silica into the 5Ni/xSi + (100 − x) Al catalysts results in decreased activity. When the silica loading exceeds 10 wt.%, the interaction between the metal and the support weakens, resulting in a significant decrease in surface area and, subsequently, lower catalytic activity. The 5Ni/10Si + 90Al catalyst, which was prepared with calcination temperatures above 500 °C, has very few active sites during the POM reaction at a reaction temperature of 600 °C. This catalyst also exhibits a high degree of crystallinity, which leads to reduced exposure of the active sites. As a result, incorporating higher wt.% of silica into the 5Ni/xSi + (100 − x) Al catalysts results in decreased activity. These findings highlight the complex interplay between silica content, calcination temperature, and catalyst properties, significantly influencing catalytic performance in POM.

The separation of aromatic/olefin mixtures is a difficult task in the petrochemical industry, since the boiling points of these hydrocarbons are very similar. This work aims to use deep eutectic solvents (DESs) for the extraction of toluene from 1-hexene by liquid–liquid extraction. A total of 53 DESs were studied qualitatively and quantitatively using the COSMO-RS approach to separate the binary mixture of toluene and 1-hexene. The selectivity, capacity, and performance index of all DESs were evaluated by calculating the activity coefficient at infinite dilution. The σ-profile and σ-potential of each component were interpreted to evaluate the interactions between the different species. We then selected three DESs for experimental validation, namely benzyltriphenylphosphonium chloride:triethylene glycol BzTPPCl:TEG (1:8), tetrabutylammonium bromide:triethylene glycol TBABr:TEG (1:3), and tetrabutylammonium bromide:ethylene glycol TBABr: EG (1:4). Experimental liquid–liquid equilibrium data were obtained for the ternary mixtures {1-hexene (1) + toluene (2) + DES (3)} at T = 298.15 K and atmospheric pressure. Based on the selectivity data and the solute distribution ratio, the feasibility of different DESs as extractive solvents was tested. Finally, ¹H NMR was performed to elucidate the extraction mechanism. No DES was found in the raffinate phase, indicating minimal cross-contamination.

The separation of benzene and cyclohexane is a challenging process in the petrochemical industry, mainly because of their close boiling points. Extractive separation of the benzene-cyclohexane mixture has been shown to be feasible, but it is important to find solvents with good extractive performance. In this work, 23 eutectic solvents (ESs) containing aromatic components were screened using the predictive COSMO-RS and their respective performance was compared with other solvents. The screening results were validated with experimental work in which the liquid–liquid equilibria of the three preselected ESs were studied with benzene and cyclohexane at 298.5 K and 101.325 kPa, with benzene concentrations in the feed ranging from 10 to 60 wt%. The performance of the ESs studied was compared with organic solvents, ionic liquids, and other ESs reported in the literature. This work demonstrates the potential for improved extractive separation of the benzene-cyclohexane mixture by using ESs with aromatic moieties.