Influence of acid–base properties of cobalt–molybdenum catalysts supported on magnesium orthophosphates in isomerization of 3,3-dimethylbut-1-ene

AbstractSynthesis and physico-chemical characterization of a pure magnesium phosphate (MgP) prepared by coprecipitation, and MgP modified by introduction of cobalt–molybdenum (4–12wt.% of MoO3 with the Co/Mo ratio fixed at 0.5) have been carried out. The structural properties of these catalysts were characterized by X-ray diffraction, their textural properties were determined by N2 adsorption–desorption isotherms and the dispersion of cobalt–molybdenum was studied by XPS spectroscopy. Their acid properties have been investigated by in situ FT-IR spectroscopy of adsorbed molecules, often, 2,6-dimethylpyridine (pKa=6.7), pyridine (pKa=5.3). Co–Mo incorporation leads to a modification in the MgP acid–base properties, especially on the acid sites type and number. Thus, lower loading of cobalt–molybdenum species decreased the number of strong Lewis acid sites whereas higher loading increased it. It was found that Lewis acid sites on magnesium phosphates play an important role in the isomerization of 3,3-dimethylbut-1-ene.The 3,3-dimethylbut-1-ene (33DMB1) conversion increases with the reaction temperature from 493 to 653K for MgP, but decreases after 573K for MgP supported by Co–Mo. A linear relationship between both types of acid sites and conversion values was found. The deactivation of the catalysts appears at high reaction temperature (>573K)

Synthesis and characterization of a catalyst containing vanadium supported on alumina

This work describes the preparation, the characterization of the hysico chemical properties of catalyst containing vanadium supported on Al$_{2}$O$_{3}$, and study of its catalytic activity in the reaction of conversion of SO$_{2}$ to SO$_{3}$, the synthesis of the alumine was carried out by hydrolysis of isopropoxyde aluminium in solution of isopropanol. Vanadium is introduced by impregnation with porous volume in several stages. The same technique is used for the SO$_{4}{}^{2-}$, K$_{2}$O.followed of calcination under-air with 450$^{\circ}$C. This solid is characterized by DRX, IR and analyzes elementary. IR highlighted the presence of the surface sulphated species, adsorption of the molecule probes 2,6-dimethylpyridine on V$_{2}$O$_{5}$/Al$_{2}$O$_{3}$ followed by infra-red shows the presence of coordinated species (Lewis acidity) about 1580, 1470 and 1452 cm$^{-1}$and protonic species (Brönsted acidity) characterized by vibrations infra-red about 1650 and 1620 cm$^{-1}$

Sulfate species in MgO-supported LaMn0.5Mg0.5O3 perovskites: an insigh into the chemistry of MgO

The structure, thermal stability, and reducibility in H2 of sulfate species formed in MgO-promoted perovskites, LaMn0.5Mg0.5O3·17 MgO, have been studied by infrared spectroscopy, temperature-programmed desorption, and temperature-programmed reduction−mass spectrometry. Sulfation at 1073 K generates on the MgO phase both bulk and subsurface sulfates, whereas the latter species are the major product of sulfation at room temperature. In contrast with high-surface MgO samples (where sulfate species of covalent nature are found), the surface species closely resemble those in the bulk. Bulk sulfates are more resistant to thermal treatments than surface sulfates. A transformation of bulk sulfates at higher temperature into sulfides is suggested by IR spectroscopy and proved by chemical analysis. SO2, SO, and H2S are the products of sulfate reduction

Characterization of a flying ash stemming from the combustion of the coal

In this study, we were interested in the physic - chemical characterization (SEM, BET, X-ray, DTA-TG, and IR) of the flying ashes stemming of the combustion of the coal in the thermal power station of JORF-LASFAR in EL Jadida (Morocco). On the one hand, we deduce from this study that these flying ashes are belonging to the class F Fly ash (according to ASTM standards). The X-ray diffraction shows that the ashes are mainly constituted by the aluminosilicate and the quartz. The thermal analysis (DTA-TG), the IR, and SEM proves the presence of the carbonates of the calcium. On the other hand, after washing the ashes, with the distilled water, an equilibrium of adsorption - desorption of the carbonates was reached after 30 minutes

Oxygen Storage Capacity of Pt-CeO2 and Pt-Ce0.5Zr0.5O2 Catalysts

International audienc

Influence of acid-base properties of the support on the catalytic performances of Pt-based catalysts in a gas-phase hydrogenation of acetonitrile

International audienc