Thermal transformations of Cu–Mg (Zn)–Al(Fe) hydrotalcite-like materials into metal oxide systems and their catalytic activity in selective oxidation of ammonia to dinitrogen

Layered double hydroxides (LDHs) containing $Mg^{2+}$, $Cu^{2+}$ or $Zn^{2+}$ cations in the $Me^{II}$ positions and $Al^{3+}$ and $Fe^{3+}$ in the $Me^{III}$ positions were synthesized by co- precipitation method. Detailed studies of thermal trans- formation of obtained LDHs into metal oxide systems were performed using high temperature X-ray diffraction in oxidising and reducing atmosphere, thermogravimetry coupled with mass spectrometry and temperature-pro- grammed reduction. The LDH samples calcined at 600 and 900 $^{o}\textrm{C}$ were tested in the role of catalysts for selective oxidation of ammonia into nitrogen and water vapour. It was shown that all copper congaing samples presented high catalytic activity and additionally, for the Cu–Mg–Al and Cu–Mg–Fe hydrotalcite samples calcined at 600 $^{o}\textrm{C}$ rela- tively high stability and selectivity to dinitrogen was obtained. An increase in calcination temperature to 900 $^{o}\textrm{C}$ resulted in a decrease of their catalytic activity, possibly due to formation of well-crystallised metal oxide phase which are less catalytically active in the process of selective oxidation of ammonia

Synthesis of Monoglycerides by Esterification of Oleic Acid with Glycerol in Heterogeneous Catalytic Process Using Tin–Organic Framework Catalyst

INGENIERIE+TLE:DFASelective synthesis of monoglycerides by esterification of glycerol with fatty acids is a difficult reaction because of immiscibility of reagents and the formation of di- and tri-glyceride by-products. In this work a heterogeneous catalytic process was conceived in which the reactant mixture was homogenized using tert-butanol solvent. Candidate catalysts were screened in the reaction of oleic acid with glycerol. While under such reaction conditions zeolites were rather inactive, metal-organic frameworks and, especially, tin-organic frameworks were found promising. A tin-organic framework (Sn-EOF) was most active and achieved a parts per thousand yen98 % monoglyceride selectivity at 40 % conversion in catalyzing esterification of oleic acid with glycerol at a low reaction temperature of 150 A degrees C. Leaching of tin from Sn-EOF catalyst was suppressed by limiting the amount of oleic acid in the starting mixture. Characterization of the acid sites of Sn-EOF by pyridine-chemisorption and FTIR revealed Lewis acidity to be responsible for the catalytic activity

Mesostructured Zeolites

Mesoporous materials constructed with microporous zeolitic frameworks (i.e., mesoporous zeolites) are of great interest owing to the very short diffusion path lengths across thin zeolite layers and the presence of large external surfaces containing strong Brønsted acid sites. These characteristics of mesoporous zeolites are highly advantageous for a wide range of applications, particularly in heterogeneous catalysis. The mesoporous materials show unprecedentedly high catalytic performances (e.g., high catalytic conversion and catalytic longevity) as zeolites in various petrochemical reactions and fine-chemical organic reactions and especially in reactions involving bulky molecules. In this chapter, we describe the various methods currently available for the synthesis of mesoporous zeolites