Inorganic salt hydrates and zeolites composites studies for thermochemical heat storage

Salt hydrates (MgSO4 and ZnSO4) impregnated in zeolites, offer a variety of improvements, mostly providing a large surface area for salt hydrates and water molecules. A composite of 5 and 10% of salt contents were prepared as heat storage materials. The study’s finding showed that dehydration enthalpy of MgSO4 (1817 J g−1) and ZnSO4 (1586 J g−1) were 10 and 15% improved than pure salt hydrates by making composites. During the hydration process of composites, the water sorption is 30–37% improved and further the increasing of salt contents in composites enhances more 10% increase in the water resorption. The cyclicability of MgSO4/zeolite and ZnSO4/zeolite were 45 and 51% improved than their corresponding pure salt hydrates. The effect of humidity on the water sorption result reveals that composites of MgSO4/zeolite and ZnSO4/zeolite at 75% relative humidity (RH), the mass of water are 51 and 40% increase than 55% RH.

Acetonitrile Synthesis via Ammoxidation: Mo/zeolites Catalysts Screening

Mo/zeolites catalysts were investigated in ethane and ethylene ammoxidation into acetonitrile. The catalysts were prepared either in solid‒solid or liquid‒solid interface after varying different parameters. The stabilization of Mo species upon the exchange is dependent on the hydrophilic/hydrophobic character of the zeolite and the type of Mo precursor. In fact, zeolites with low Si/Al molar ratios should be avoided due to their higher dehydration enthalpy values (Δdehyd.H). On the other hand, the use of MoOCl4, Mo(CO)6 and MoCl3 precursors and zeolites with high Si/Al ratios led to inefficient [Mo7O24]6‒ species and amorphous MoO3 which catalyzes the combustion reaction. Nevertheless, the use of MoCl5, MoO3 and MoO2(C5H7O2)2 led to promising activities. In catalysis, [MoO4]2‒ species are required to activate C2H6 into C2H4, while [MoxO3x+1]2‒ (x =1, 2) species catalyze the ammoniation of C2H4 and the ethylamine dehydrogenation into CH3CN. Interestingly, active catalysts could be obtained by humid impregnation and a simultaneous oxidative treatment. Such a treatment improves the dispersion state of crystalline MoO3, which activate ethane molecules. It is judicious to perform C2H6 oxidative dehydrogenation before ammoxidation since the interference between the different investigated parameters could be noted.

Gas phase dissociation of protonated acetic acid to the acyl cation and water. Heat of formation of CH3CO+ and proton affinity of ketene

Pulsed electron beam high pressure mass spectrometry was used to measure the enthalpy and entropy of the dehydration of protonated acetic acid, and the proton affinity of ketene in the gas phase. The variation of the equilibrium constant with temperature from 515 to 615 K led to ΔH0 of 24.6 kcal/mol and a ΔS0 of 33.1 cal/deg for the dehydration of protonated acetic acid. Proton transfer equilibria measurements of reactions: BH+ + CH2CO = B + CH3CO+ at 600 K with reference bases of known proton affinity led to a proton affinity of 195 kcal/mol for ketene. The heat of formation of the acetyl cation (ΔHf0(CH3CO+) = 160) was obtained from both the proton affinity of ketene, and from the dehydration enthalpy of protonated acetic acid combined with the proton affinity of acetic acid. The energetics for the dehydration reaction in the gas phase and in solution are compared.