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An efficient autocatalytic process for the production of 5-hydroxymethylfurfural (HMF) from fructose-based carbohydrates has been investigated without the addition of any external catalysts in a methyl isobutyl ketone/water biphasic system, leading to elevated HMF yield through continuous extraction of HMF from an aqueous solution. The results show that both the reaction temperature and time have significant effects on fructose conversion and HMF yield; 96.8% of fructose can be converted into 73.6% of HMF with a small amount of levulinic acid and formic acid formed at a point of compromise between the reaction temperature and time (160 °C for 2 h). In addition, this autocatalytic system is suitable for other fructose-based feedstocks, such as sucrose and inulin, to achieve acceptable HMF yield. Moreover, a simple and efficient purification strategy for as-prepared HMF, viz., the NaOH neutralization method, has also been tested, achieving more than 99% of HMF recovery with more than 98% of purity correspon...

Novel Mn–Zr mixed oxide catalysts have been prepared by the citric acid method for the low-temperature selective catalytic reduction (SCR) of NOx with ammonia in the presence of excess oxygen. They have been characterized by a series of techniques, specifically N2 adsorption–desorption, X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). It was found that an Mn(0.5)–ZrOx-450 (Mn/(Mn + Zr) mole ratio of 0.5) catalyst showed the highest activity, giving 100% NOx conversion at 100 °C with a space velocity of 30 000 h–1. XRD results suggested that an Mn–Zr solid solution was formed in the Mn(0.5)–ZrOx-450 catalyst, with highly dispersed MnOx. TPR data indicated a strong interaction between the zirconium oxide and manganese oxide, which improved the reduction ability of the MnOx. The TPD results indicated that an appropriate NH3 adsorption ability was beneficial for the low-temperature SCR. The catalyst showed a c...

Novel Fe–Mn mixed-oxide catalysts were prepared for the low-temperature selective catalytic reduction (SCR) of NOx with ammonia in the presence of excess oxygen. It was found that Fe(0.4)–MnOx catalyst showed the highest activity, yielding 98.8% NOx conversion and 100% selectivity of N2 at 120 °C at a space velocity of 30 000 h–1. XRD results suggested that a new crystal phase of Fe3Mn3O8 was formed in the Fe–MnOx catalysts. TPR and Raman data showed that there was a strong interaction between the iron oxide and manganese oxide, which is responsible for the formation of the active center―Fe3Mn3O8. Intensive analysis of fresh, used, and regenerated catalysts by XPS revealed that electron transfer between Fen+ and Mnn+ ions in Fe3Mn3O8 may account for the long lifetime of the Fe(0.4)–MnOx catalyst. In addition, the SCR activity was suppressed a little in the presence of SO2 and H2O, but it was reversible after their removal.