Pyrolysis of heavy oil in the presence of supercritical water: The reaction kinetics in different phases

Electrokinetic Analyses Uncover the Rate-Determining Step of Biomass-Derived Monosaccharide Electroreduction on Copper

Electrochemical biomass conversion holds promise to upcycle carbon sources and produce valuable products while reducing greenhouse gas emissions. To this end, deep insight into the interfacial mechanism is essential for the rational design of an efficient electrocatalytic route, which is still an area of active research and development. Herein, we report the reduction of dihydroxyacetone (DHA)-the simplest monosaccharide derived from glycerol feedstock-to acetol, the vital chemical intermediate in industries, with faradaic efficiency of 85±5 % on a polycrystalline Cu electrode. DHA reduction follows preceding dehydration by coordination with the carbonyl and hydroxyl groups and the subsequent hydrogenation. The electrokinetic profile indicates that the rate-determining step (RDS) includes a proton-coupled electron transfer (PCET) to the dehydrated intermediate, revealed by coverage-dependent Tafel slope and isotopic labeling experiments. An approximate zero-order dependence of H+ suggests that water acts as the proton donor for the interfacial PCET process. Leveraging these insights, we formulate microkinetic models to illustrate its origin that Eley-Rideal (E-R) dominates over Langmuir-Hinshelwood (L-H) in governing Cu-mediated DHA reduction, offering rational guidance that increasing the concentration of the adsorbed reactant alone would be sufficient to promote the activity in designing practical catalysts.

Experimental Investigation on the Pyrolysis and Conversion Characteristics of Organic-Rich Shale by Supercritical Water

Organic-rich shale oil reservoirs with low-medium maturity have attracted increasing attention because of their enormous oil and gas potential. In this work, a series of experiments on pyrolysis of the particle and core samples were carried out in a self-made supercritical water pyrolysis apparatus to evaluate the feasibility and benefits of supercritical water in promoting the transformation efficiency and oil yield of the low-medium maturity organic-rich shale. Core samples had a mass loss of 8.4% under supercritical water pyrolysis, and many microcracks were generated, which increased the pyrolysis efficiency substantially. The oil yield of shale pyrolysis could reach 72.40% under supercritical water conditions at 23 MPa and 400 °C, which was 53.02% higher than that under anhydrous conditions. In supercritical water conditions, oxygen-containing compounds are less abundant than in anhydrous conditions, suggesting that supercritical water can inhibit their formation. Also, supercritical water conditions produced higher yields for light fraction, medium fraction, and heavy fraction shale oil than those under anhydrous conditions. These results indicate that supercritical water pyrolysis is feasible and has excellent advantages for low-medium maturity organic-rich shale.

Investigation of Potential Azeotrope Breakers Using DFT and COSMO Approach

Different combinations of cations (imidazolium, pyridinium, pyrrolidinium, phosphonium, and ammonium) and anions (basic anions, sulfate, phosphate, and borate) were studied based on the COSMO volume and quantum chemical parameters such as highest occupied molecular orbital/lowest unoccupied molecular orbital (HOMO/LUMO) energies, HOMO-LUMO energy gap, global hardness and softness, electronegativity, electrophilicity index, and chemical potential using the density functional theory (DFT) method. Further, the sigma profile and sigma potential for the selected cations and anions were generated using a COSMO-RS model. The activity coefficient at infinite dilution was also studied for the butanol-water system to find a greater degree of nonideality. A feasible entrainer for the azeotrope breaker for a butanol-water system is proposed.

Single-atom Pt in intermetallics as an ultrastable and selective catalyst for propane dehydrogenation

Propylene production via propane dehydrogenation (PDH) requires high reaction temperatures to obtain sufficient propylene yields, which results to prominent catalyst deactivation due to coke formation. Developing highly stable catalysts for PDH without deactivation even at high temperatures is of great interest and benefit for industry. Here, we report that single-atom Pt included in thermally stable intermetallic PtGa works as an ultrastable and selective catalyst for PDH at high temperatures. Intermetallic PtGa displays three-hold-Pt ensembles and single Pt atoms isolated by catalytically inert Ga at the surface, the former of which can be selectively blocked and disabled by Pb deposition. The PtGa-Pb/SiO₂ catalyst exhibits 30% conversion with 99.6% propylene selectivity at 600 °C for 96 h without lowering the performance. The single-atom Pt well catalyzes the first and second C–H activation, while effectively inhibits the third one, which minimizes the side reactions to coke and drastically improves the selectivity and stability.

Propylene production via propane dehydrogenation demands a highly stable catalyst that works without deactivation even at high temperatures. Here, the authors show that single-atom Pt included in thermally stable intermetallic PtGa works as an active and selective catalyst for propane dehydrogenation even at 600 °C for 96 h without deactivation.

Enhancement of the Generation and Transfer of Active Oxygen in Ni/CeO2 Catalysts for Soot Combustion by Controlling the Ni-Ceria Contact and the Three-Dimensional Structure

The effect of the three-dimensionally ordered macroporous (3DOM) structure and the Ni doping of CeO₂ on the physicochemical properties and catalytic activity for soot combustion was studied. Moreover, the way in which Ni is introduced to the ceria support was also investigated. For this, CeO₂ supports were synthesized with uncontrolled (Ref) and 3DOM-structured morphology, and their respective Ni/CeO₂ catalysts were prepared by impregnation of the previously synthesized supports or by successive impregnation of both precursors (Ni and Ce) on the 3DOM template. Conclusions reached in this study are: (1) the 3DOM structure increases the surface area of the catalysts and improves the catalyst-soot contact. (2) The doping of CeO₂ with Ni improves the catalytic activity because the NiO participates in the catalytic oxidation of NO to NO₂, and also favors the production of active oxygen and the catalyst oxygen storage capacity. (3) Ni incorporation method affects its physicochemical and catalytic properties. By introducing Ni by successive infiltration in the solid template, the CeO₂ crystal size is reduced, Ni dispersion is improved, and the catalyst reducibility is increased. All of these characteristics make the catalyst synthesized by successive infiltration to have higher catalytic activity for soot combustion than the Ni-impregnated CeO₂ catalyst.

Facile synthesis of laccase mimic Cu/H3BTC MOF for efficient dye degradation and detection of phenolic pollutants

Herein, we report an effectual method for designing a novel form of nanozyme laccase mimic namely Cu/H3BTC, using copper ions and 1,3,5-benzene tricarboxylic acid (1,3,5-H3BTC). This Cu-based metal-organic framework (MOF) was synthesized through a simple procedure of mixing of two usual reagents at room temperature. Amido Black 10B (AB-10B) was chosen as a model dye for degradation consequences. Results showed that Cu/H3BTC MOF revealed significantly higher catalytic efficacy under certain conditions like high pH, extreme temperature and high salt conditions and it has long-term storage stability, which can lead to a significant decline in catalytic activity of laccase. In addition, the degradation of AB-10B was up to 60% after ten cycles, showing good recyclability of Cu/H3BTC MOF. The UV-visible spectral changes clearly showed that Cu/H3BTC MOF is an effective laccase mimic for the degradation of azo dye AB-10B, which was degraded more easily within the time duration of 60 min. The Cu/H3BTC MOF also possessed fundamental activities like laccase with regard to oxidation of the phenolic compounds. Moreover, a technique for the quantitative detection of epinephrine by Cu/H3BTC MOF was established. These findings help to understand the laccase-like reactivity and provide a basis for the future design and application of metal-based catalysts.