Corrosion Inhibitors for Sour Oilfield Environment (H2S Corrosion)

Lower-grade steel materials are the most commonly used construction materials for oil and gas wells due to their low cost and high performance. However, they are susceptible to corrosion when they come in contact with corrosive environments that are highly acidic. In oil wells, particularly deep oil wells, hydrogen sulfide (H2S) is commonly found. The dissolution of H2S gas in produced water makes the fluid corrosive. The use of corrosion inhibitors is perhaps the most practical and costeffective means of controlling corrosion of low carbon steels in the sour environment. In this chapter, typical corrosion inhibitors used in oil and gas fields to control the internal corrosion of oilfield equipment caused by H2S are being examined. The inhibitors found to be effective are polar functional compounds, with many being based on nitrogen-containing compounds, such as amines, imidazolines, and quaternary ammonium salts. Drawbacks of these compounds in practical applications and potentials of future developments are discussed

Robust and durable superlubricity enabled by carboxylated graphene quantum dots in lubricated steel contacts

Achieving macroscale superlubricity on engineering steel by utilizing aqueous green lubricants has gained growing interest, given its substantial potential to reduce energy consumption and carbon footprint. However, maintaining superlubricity under diverse sliding conditions over a prolonged duration is a major obstacle for real-scale applications. Herein, we report that a robust and durable tribofilm enabled by a unique lubrication mechanism based on carboxylated graphene quantum dots (CGQDs) in aqueous glycerol triggers macroscale superlubricity in self-mated steel contacts. A dedicated intermittent test was designed to show the superlubricity's robustness and the ability of the tribofilm to adapt to a variety of relevant sliding conditions. Moreover, the boundary film provides an average coefficient of friction of around 0.007 and up to 69 % wear reduction (compared to the base lubricant), resulting in the maintenance of superlubricity at a real final contact pressure of 123 MPa, which increases the upper limit of the contact pressure compared to current aqueous-lubricated steel contacts. The new superlubricity mechanism was enabled by the chemical adsorption of the CGQDs onto the worn metal surface, coupled with the tribo-induced structural degradation and transformation of the CGQDs into layered graphitic structures that generate an adaptable low-shear interface. This work provides new insights into the role of chemical adsorption and structural transformation of CGQDs in achieving superlubricity and is an important step forward for implementing energy-efficient and green lubrication technologies for industrial applications

High–Entropy Oxides: A New Frontier in Photocatalytic CO2 Hydrogenation

This is the author accepted manuscript.Herein, we investigate the potential of nanostructured high–entropy oxides (HEOs) for photocatalytic CO2 hydrogenation, a process with significant implications for environmental sustainability and energy production. Several cerium–oxide–based rare–earth HEOs with fluorite structures were prepared for UV–light driven photocatalytic CO2 hydrogenation towards valuable fuels and petrochemical precursors. The cationic composition profoundly influences the selectivity and activity of the HEOs, where the Ce0.2Zr0.2La0.2Nd0.2Sm0.2O2–δ catalyst showed outstanding CO2 activation (14.4 molCO kgcat −1 h−1 and 1.27 molCH3OH kgcat −1h−1) and high methanol and CO selectivity (7.84 % CH3OH and 89.26% CO) at ambient conditions with 4–times better performance in comparison to pristine CeO2. Systematic tests showed the effect of a high–entropy system compared to mid–entropy oxides. XPS, in–situ DRIFTS as well as DFT calculation elucidate the synergistic impact of Ce, Zr, La, Nd, and Sm, resulting in an optimal Ce3+/Ce4+ ratio. The observed formate–routed mechanism and a surface with high affinity to CO2 reduction offer insights into the photocatalytic enhancement. While our findings lay a solid foundation, further research is needed to optimize these catalysts and expand their applications.Croatian Science FoundationSlovenian Research AgencyRepublic of SloveniaMinistry of Education, Science and SportEuropean UnionEuropean Regional Development FundNational Research, Development and Innovation FundMinistry of Human CapacitiesMinistry for Innovation and Technolog