Search

CO-selective methanation (CO-SMET) is an efficient hydrogen-rich (H2-rich) gas purification technology for proton exchange membrane fuel cells. It is vital to develop suitable catalysts with good low-temperature activity for CO-SMET reactions. In this study, RuNi/TiZrx-mixed metal oxide (RuNi/TiZrx-MMO) catalysts with different molar ratios of Zr/Ti, derived from a Zr-promoted NiTi-layered double hydroxide (NiTi-LDH) precursor were successfully prepared using the co-precipitation and wet impregnation methods. The RuNi/TiZr0.2-MMO catalyst possesses higher catalytic performance in a lower temperature window of 180–280 °C, which can reduce the CO concentration to be below 10 ppm. The characterization results obtained from XRD, BET, SEM, TEM, XPS, TPR, and TPD suggest that the addition of ZrO2 increases the surface area of the catalyst, improves the dispersion of metallic nanoparticles, increases the reducibility of Ni species on the RuNi/TiZr0.2-MMO catalyst's surface, and enhances the adsorption and activation ability of CO, resulting in remarkable catalytic performance at lower reaction temperatures. Moreover, the RuNi/TiZr0.2-MMO catalyst demonstrated long-term catalytic stability and carbon resistance. [ABSTRACT FROM AUTHOR]

CO selective methanation (CO-SMET) is a promising method for deep CO removal from H2-rich gases. In this study, a series of RuNi/MMO catalysts are prepared using the support MMO-N derived from NiAl-NO3-LDHs, which was prepared from NiAl-CO3-LDHs via an acid–alcohol ion-exchange reaction. The prepared catalysts were characterized by XRD, SEM, TEM, XPS, H2-TPR, CO-TPD, CO2-TPD, NH3-TPD, and TG. The RuNi/MMO-N catalyst demonstrated excellent CO-SMET performance, successfully reducing the CO to less than 10 ppm with a selectivity greater than 50% in a reaction temperature window ranging from 180 °C to 260 °C. Compared with similar catalysts derived from NiAl-CO3-LDHs, the exceptional CO-SMET capability of the RuNi/MMO-N catalyst is suggested to be associated with a more effective hydrogen spillover, a larger number of electron-rich Ni sites, and a higher density of acid sites on the surface of RuNi/MMO-N, which are conducive to CO adsorption and the inhibition of CO2 methanation. [ABSTRACT FROM AUTHOR]

Preharvest MeSA treatment enhanced the chilling tolerance of apricot by regulating the sugar metabolism under chilling stress. [Display omitted] • Preharvest spraying with MeSA can improve the postharvest quality of apricot. • MeSA treatment can alleviate CI of apricot by regulating sugar metabolism. • Increased sucrose content is responsible for enhanced chilling tolerance of apricot. • MeSA can increase SPS and SS-S activities and inhibit AI, NI and SS-C activities. Apricot is highly susceptible to chilling injury during low temperature storage, while methyl salicylate (MeSA) can alleviate chilling injury and enhance the postharvest quality of fruit. The apricots were preharvest sprayed twice with 0.05 mmol L−1, 0.1 mmol L−1 and 0.2 mmol L−1 of MeSA solution, and then were harvested and stored at 2 °C (humidity of 70 %). After cold storage for every 4 d, apricots were transferred to 20 °C for 2 d to determine the fruit quality. Our results indicated that 0.2 mmol L−1 MeSA treatment exhibited the best efficacy. Preharvest MeSA treatment could reduce decay rate and chilling injury (CI) index, and maintain firmness, soluble solid content (SSC), organic acids and antioxidant capacities at a relative higher level. Preharvest MeSA treatment inhibited the increase of electrolyte leakage, malondialdehyde (MDA) and H 2 O 2 content in apricot. The chilling temperature of 2 °C could lead to the degradation of sucrose to fructose and glucose in apricot. At the same time, preharvest MeSA treatment effectively alleviated CI symptoms of apricot by reducing the degradation rate. The enhanced chilling tolerance of apricot treated with MeSA could be affected by the increased sucrose content, which was regulated by the higher activities of sucrose phosphate synthase (SPS) and sucrose synthase-synthesis (SS-S), and the lower activities of acid invertase (AI), neutral invertase (NI) and sucrose synthase-cleavage (SS-C). We proposed that preharvest MeSA treatment could enhance the chilling tolerance by regulating sugar metabolism and further improve the postharvest quality of apricot during low temperature storage. [ABSTRACT FROM AUTHOR]