Elsayed G. Blall

Solar-driven CO₂ methanation is being investigated as a pathway for carbon utilization and renewable-energy storage, yet deployment at industrial point sources, including ammonia–urea complexes, remains constrained by heterogeneous reporting, uncertain feedstock availability, heat-management requirements, and boundary-dependent process economics. This structured critical narrative review evaluates thermocatalytic Power-to-Methane, H₂-fed photothermal and light-assisted methanation, and direct photocatalytic CO₂-to-CH₄ conversion across catalyst, reactor, and plant scales. A domain-specific evidence-grading framework is applied to distinguish comparatively well-supported mechanistic conclusions from studies with incomplete local thermometry, matched-temperature dark controls, photon-flux calibration, isotope tracing, or material and charge balances. The review further examines the stoichiometric and operational constraints governing residual process-CO₂ availability at ammonia–urea sites and assesses how renewable-H₂ supply, buffer storage, gas conditioning, heat recovery, and product specifications affect process integration. An illustrative industrial screening case for a 2000 t d⁻¹ NH₃/2000 t d⁻¹ urea complex yields a nominal residual of 472.4 t d⁻¹ CO₂ before operational deductions, corresponding to 86.5 t d⁻¹ H₂ demand and an approximately 198 MW electrolyzer load at 55 kWh kg⁻¹ H₂. Published techno-economic and life-cycle results are interpreted within their reported functional units and system boundaries rather than directly rank-ordered. The evidence base is strongest for conventional thermocatalytic methanation at pilot and industrial scale, whereas photothermal and direct photocatalytic routes retain substantial diagnostic, transport, durability, and scale-up uncertainties. Commercial feasibility depends not only on nominal CO₂ availability but also on the economically and environmentally justified conversion fraction, renewable-electricity cost, electrolyzer utilization, reactor durability, methane losses, product-conditioning requirements, and heat and co-product credits. Accordingly, complete methanation of a nominal residual CO₂ stream should not be adopted as a design objective without site-specific marginal techno-economic and life-cycle evaluation. A five-gate framework is proposed to guide progression from mechanistic credibility and reproducible performance to module qualification and site-specific deployment.

In this study, the author improved and modified g-C₃N₄ by doping it with the metals Ag and Cu, which changed the photochemical properties of g-C₃N₄, narrowed the band gap, and improved the photocatalytic performance regarding quantum efficiency. Organic hydrocarbons such as 1,2-dichloroethane (DCE) are very stable prepared materials produced as intermediates to obtain polyvinyl chloride, and the prepared photo-catalyst is an innovative method for extreme decomposition of chlorinated hydrocarbons. However, some significant results were obtained using different analysis techniques. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) showed that the addition of Ag and Cu-NPS partially altered the structure of pure graphitic carbon nitride (g-C₃N₄-Pure). Scanning electron microscopy (TEM) analysis revealed that the morphological features of Ag-Cu/g-C₃N₄ contain quantum dots of Ag and Cu nanoparticles in addition to 2d-g-C₃N₄. The better separation of the photo-generated charge carriers is attributed to better photoactivity in the case of 0.3 g Ag-Cu/g-C₃N₄ with a reaction time of less than 30 min. Furthermore, the Ag-Cu/g-C₃N₄ recycling experiment showed that the catalyst remained stable after three stages of the pyrolysis experimental cycle. Another clear indicator of DCE degradation is the measurement using the titration of the Cl ions released by the decomposition.

1,2-Dichloroethane(DCE) is one of the maximum critical chlorinated unstable natural pollution in waste liquid and has been indexed as a tough pollutant via way of means of numerous regulatory groups global. It is substantially used as a precursor with inside the petrochemical corporation to provide vinyl chloride monomers for the manufacturing of polyvinyl chloride (PVC). In this study, g-C₃N₄ photocatalysts synthesized by traditional thermal polycondensation methods have small specific surface areas and wide band gaps; these defects severely suppress the photocatalytic activity. Our research has focused on the optimization and modification of g-C₃N₄. by doping some bimetallic elements such as Ag and Cu Bimetals which alter the photochemical properties of g-C₃N₄, in particular, narrow the band gap and expand photoabsorption into the visible range, which improves the photocatalytic performance. quantum efficiencies, illumination area and increasing specific power irradiance. The tendencies of synthesized Ag-Cu/C₃N₄ have been showing the use of FTIR, XRD, EDX, and TEM strategies. This confirms the presence of enormous shapes with inside the shape of quantum dots and a 2-D Nanosheet. The degradation of DCE changed into showed through the dimension of UV-Visible spectra of degradable product and indicated the pseudo-first-order-kinetic response. Another sturdy indication of deterioration of DCE is the measuring of Cl ion liberated from degradation via titration.