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Depletion of oil and gas resources is a major concern for researchers and the global community. Researchers are trying to develop a way to overcome these issues using the Fischer-Tropsch synthesis (FTS) process. The FTS reaction converts a mixture of hydrogen and carbon monoxide gases into a liquid fuel. The reactions are performed in the reactor and in the presence of a catalyst. A series of catalysts, such as iron, cobalt, nickel, and ruthenium, have been used for the FTS process. In iron-based catalysts, the Fe5C phase is the active phase that produces C5+ hydrocarbons. At higher conversion rates, the presence of water in the products is a problem for cobalt catalysts because it can trigger catalyst deactivation mechanisms. Ni-based catalysts play key roles as base catalysts, promoters, and photothermal catalysts in FTS reactions to produce different useful hydrocarbons. Ruthenium catalysts offer not only high activity but also selectivity toward long-chain hydrocarbons. Moreover, depending on the Ru particle size and interaction with the oxide support, the catalyst properties can be tuned to enhance the catalytic activity during FTS. The detailed reaction pathways based on catalyst properties are explained in this article. This review article describes the issues and challenges associated with catalysts used for the FTS process. [ABSTRACT FROM AUTHOR]

The goal of this study was to evaluate the biodegradation of 1,4–dioxane using a mixed biological culture grown in textile wastewater sludge with 1,4–dioxane as the sole carbon source. The conditions for the long-term evaluation of 1,4–dioxane degradation were determined and optimized by batch scale analysis. Moreover, Monod's model was used to determine the biomass decay rate and unknown parameters. The soluble chemical oxygen demand (sCOD) was used to determine the concentration of 1,4–dioxane in the batch test, and gas chromatography/mass spectrometry (GC/MS) was used to measure the concentrations via long-term wastewater analysis. Two types of reactors (continuous stirred reactor (CSTR) and plug flow reactor (PFR)) for the treatment of 1,4–dioxane from textile wastewater were operated for more than 120 days under optimized conditions. These used the mixed microbial culture grown in textile wastewater sludge and 1,4–dioxane as the sole carbon source. The results indicated efficient degradation of 1,4–dioxane by the mixed culture in the presence of a competitive inhibitor, with an increase in degradation time from 13.37 h to 55 h. A specific substrate utilization rate of 0.0096 mg 1,4–dioxane/mg MLVSS/h was observed at a hydraulic retention time of 20 h for 20 days of operation in a biomass concentration of 3000 mg/L produced by the mixed microbial culturing process. In the long-term analysis, effluent concentrations of 3 mg/L and <1 mg/L of 1,4–dioxane were observed for CSTR and PFR, respectively. The higher removal efficacy of PFR was due to the production of more MLVSS at 4000 mg/L compared to the outcome of 3000 mg/L in CSTR in a competitive environment. [ABSTRACT FROM AUTHOR]

Hydrogen production via chemical looping steam methane reforming (CL-SMR) is among the most promising current technologies. This work presents the development in gPROMS Model Builder 4.1.0 ® of a 1D model of an adiabatic packed bed reactor used for chemical looping reforming (CLR). The catalyst used for this process was 18 wt. % NiO with the support of Al 2 O 3 . A brief thermodynamic analysis using Chemical Equilibrium Application (CEA) was carried out to identify the optimum operating conditions. The model was simulated for 10 complete CL-SMR cycles. The effects of variations in temperature, pressure, gas mass velocity, nickel oxide concentration, reactor length, and particle diameter were studied to investigate the performance of the CL-SMR process under these variations. A parametric analysis was carried out for different ranges of conditions: temperatures from 600 to 1,000 K, pressure from 1 to 5 bar, gas mass velocity between 0.5 and 0.9 kg·m -2 s -1 , nickel oxide concentration values between 0.1 and 1 mol·m -3 , particle diameters between 0.7 and 1 mm, and fuel reactor (FR) lengths between 0.5 and 1.5 m. At the optimum temperature (950 K), pressure (1 bar), and steam-to-carbon molar ratio (3/1), with an increase in particle diameter from 0.7 to 1 mm, an 18% decrease in methane conversion and a 9.5% increase in hydrogen yield were observed. Similarly, with an increase in FR length from 0.5 m to 1.5 m, a delay in the temperature drop was observed., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Qayyum, Cheema, Abdullah, Amin, Khan, Lee and Lee.)

Heterogeneous growth of photocatalysts on different porous substrates is a solution to avoid secondary pollution caused by composite photocatalysts themselves. However, the heterogeneous growth of composite photocatalysts with nitrogen-doped carbon quantum dots (NCQDs) inclusions-introduced during synthesis-impedes the direct growth on the substrate. To overcome this problem, NCQDs were grown on a Co 9 S 8 (NCQDs-G@Co 9 S 8 ) layer, decorated on cotton fabric. This optimal coupling mode of NCQDs and Co 9 S 8 showed 54% degradation, compared to 33% dye degradation via NCQDs-doped Co 9 S 8 (NCQDs-D@Co 9 S 8 ). The change in the crystal structure and its lower loading on fabric results in significantly lower performance of NCQDs-D@Co 9 S 8 . Even with the combination of both surface growth and doping (NCQDs-DG@Co 9 S 8 ), the performance was still limited to 42%. In addition, the optimum growth concentration of NCQDs on Co 9 S 8 was observed for 7.5 w/w %, resulting in 92% photocatalytic activity (PCA) in 80 min. Comparing different surface states formed in NCQDs using different solvents, water-based surface states (oxygen-rich surface) are most suitable for the dye degradation. NCQDs-G@Co 9 S 8 also offers 67% Cr-VI reduction to Cr-III, showing its suitability for both inorganic and organic compounds. Better electrode performance was related to suitable charge separation of the composite, where -OH groups mainly contribute in the photocatalytic dye degradation.., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)