Ethanol adsorption on Ni doped Mo2C(001): a theoretical study

Computational Insight into Methane-Methanol Coupling and Aromatization over Metal-Modified ZSM-5: From Mechanism to Catalyst Screening

ZSM-5 zeolite modified by molybdenum is one of the promising catalysts for methane dehydroaromatization (MDA). The introduction of methanol to couple with methane over metal-modified ZSM-5 can facilitate the MDA reaction, but the reaction mechanism, optimal energy pathways, and kinetic and selectivity controlling factors remain to be clarified. In this study, periodic density functional theory (DFT) calculations were performed to investigate the mechanism of methane-methanol coupling and aromatization over Mo/ZSM-5. The calculation results showed that the process of methane-methanol coupling to light olefins (mainly ethylene and propylene) was determined by the C-C coupling step, while further aromatization of the ethylene and propylene intermediate was kinetically controlled by the dehydrogenation step involved in the regeneration of the Brønsted acid site over Mo/ZSM-5. The co-adsorption of H2O produced from methanol dehydration had little effect on methane-methanol coupling to ethylene but increased the rate-limiting barrier for ethylene aromatization to benzene. To further improve the catalytic performance of Mo/ZSM-5, we found that introducing a second metal component such as Co, Ni, or Nb into Mo/ZSM-5 could promote the C-C coupling process and enable these bimetallic combinations to be promising candidates for methane-methanol coupling reactions.

Chemistry of Hydrogen Peroxide Formation and Elimination in Mammalian Cells, and Its Role in Various Pathologies

Hydrogen peroxide (H2O2) is a compound involved in some mammalian reactions and processes. It modulates and signals the redox metabolism of cells by acting as a messenger together with hydrogen sulfide (H2S) and the nitric oxide radical (•NO), activating specific oxidations that determine the metabolic response. The reaction triggered determines cell survival or apoptosis, depending on which downstream metabolic pathways are activated. There are several ways to produce H2O2 in cells, and cellular systems tightly control its concentration. At the cellular level, the accumulation of hydrogen peroxide can trigger inflammation and even apoptosis, and when its concentration in the blood reaches toxic levels, it can lead to bioenergetic failure. This review summarizes existing research from a chemical perspective on the role of H2O2 in various enzymatic pathways and how this biochemistry leads to physiological or pathological responses.