CO hydrogenation over K‐Co‐MoSₓ catalyst to mixed alcohols: A kinetic analysis

Higher alcohol synthesis (HAS) from syngas is one of the most promising approaches to produce fuels and chemicals. Our recent investigation on HAS showed that potassium‐promoted cobalt‐molybdenum sulfide is an effective catalyst system. In this study, the intrinsic kinetics of the reaction were studied using this catalyst system under realistic conditions. The study revealed the major oxygenated products are linear alcohols up to butanol and methane is the main hydrocarbon. The higher alcohol products (C3+) followed an Anderson‐Schultz‐Flory distribution while the catalyst suppressed methanol and ethanol formation. The optimum reaction conditions were estimated to be at temperature of 340°C, pressure of 117 bar, gas hourly space velocity of 27 000 mL g–1 h–1 and H2/CO molar feed ratio of 1. A kinetic network has been considered and kinetic parameters were estimated by nonlinear regression of the experimental data. The results indicated an increasing apparent activation energy of alcohols with the length of alcohols except for ethanol. The lower apparent activation energy of alcohols compared with hydrocarbon evidenced the efficiency of this catalyst system to facilitate the formation of higher alcohols

Potential biological role of poly (ADP-ribose) polymerase (PARP) in male gametes

Maintaining the integrity of sperm DNA is vital to reproduction and male fertility. Sperm contain a number of molecules and pathways for the repair of base excision, base mismatches and DNA strand breaks. The presence of Poly (ADP-ribose) polymerase (PARP), a DNA repair enzyme, and its homologues has recently been shown in male germ cells, specifically during stage VII of spermatogenesis. High PARP expression has been reported in mature spermatozoa and in proven fertile men. Whenever there are strand breaks in sperm DNA due to oxidative stress, chromatin remodeling or cell death, PARP is activated. However, the cleavage of PARP by caspase-3 inactivates it and inhibits PARP's DNA-repairing abilities. Therefore, cleaved PARP (cPARP) may be considered a marker of apoptosis. The presence of higher levels of cPARP in sperm of infertile men adds a new proof for the correlation between apoptosis and male infertility. This review describes the possible biological significance of PARP in mammalian cells with the focus on male reproduction. The review elaborates on the role played by PARP during spermatogenesis, sperm maturation in ejaculated spermatozoa and the potential role of PARP as new marker of sperm damage. PARP could provide new strategies to preserve fertility in cancer patients subjected to genotoxic stresses and may be a key to better male reproductive health

A kinetic study on the conversion of glucose to levulinic acid

Levulinic acid has been identified as a promising green. biomass derived platform chemical. A kinetic study oil one of the key steps in the conversion of biomass to levulinic acid, i.e., the acid catalysed decomposition of glucose to levulinic acid has been performed. The experiments were Performed in a broad temperature window (140-200 degrees C), using sulphuric acid as the catalyst (0.05-1 M) and a initial glucose concentration between 0.1 and 1 M. A kinetic model of the reaction sequence was developed including the kinetics for the intermediate 5-hydroxymethyl-2-furaldehyde (HMF) and humins byproducts using a power-law approach. The yield of levulinic acid is favoured in dilute glucose solution at high acid concentration. On the basis of the kinetic results, continuous reactor configurations with a high extent of back-mixing are preferred to achieve high levulinic acid yields