Factors Affecting the Activity and Selectivity of Alumina Catalysts in the Dehydration of 1-Butanol

Alumina catalysts A1, A2 and A3 calcined at 873 K, 973 K and 1073 K, respectively, were prepared. The textural properties (surface area and porosity) of these catalysts were determined from nitrogen adsorption studies at 77 K. The acidity (acid amount, acid strength and surface acid density) was determined from the thermal desorption of chemisorbed pyridine. The catalysts were employed in the conversion of 1-butanol at 473–548 K. The surface area and total pore volume decreased and the mean pore radius increased as the calcination temperature increased, while the amount of acid and the surface acid density also depended on the calcination temperature. The conversion of 1-butanol gave 1-butene and dibutyl ether as dehydration products and 2-butenes and isobutene as isomerization products. The acid sites on the alumina catalysts were of different strength, thereby explaining the bifunctionality of these catalysts. The reaction temperature and the flow rate of carrier gas contributed to the performance of alumina catalysts towards the conversion of 1-butanol, and possibly of other alcohols

Structural, textural and catalytic properties of pure and Li-doped NiO/Al2O3 and CuO/Al2O3 catalysts

Pure and Li-doped NiO/Al2O3 and CuO/Al2O3 catalysts were prepared to contain 2, 4 and 8 wt.% of Ni and Cu, respectively. The structural properties were determined using DTA, XRD and FTIR techniques, and the textural properties of the catalysts were determined from their adsorption–desorption isotherms of nitrogen at 77 K. The chemisorption of hydrogen at 473–823 K with the pre-reduced catalysts was measured. The data obtained allowed the determination of the metal surface area, S (m2/g); the percentage of metal distribution, R; and the diameter of metal crystallite, d (nm). The amount of surface acidity, measured in mmol/g, was determined from the amount of chemisorbed pyridine necessary to completely inhibit the catalytic dehydration (DHD) of isopropanol. The conversion of isopropanol at 533–623 K was investigated using the micro-catalytic pulse technique. DTA, XRD and FTIR indicated that NiO and CuO exist as separate phases with crystallite sizes too small to be detected. No evidence has been gathered to indicate the existence of an aluminate phase. With the increase of metal loading, the surface area decreased whereas the total pore volume and the mean pore radius increased. Conversion of iso-propanol to propene proceeded via (DHD) on surface acid sites, and conversion of isopropanol to acetone proceeded via dehydrogenation (DHG) on redox sites. DHD and DHG exhibited first-order kinetics, and the rates of both reactions increased with temperature, with the latter being more temperature-dependent

Kinetic and equilibrium adsorption of methylene blue and remazol dyes onto steam-activated carbons developed from date pits

AbstractSteam-activated carbons DS2 and DS5 were prepared by gasifying 600°C-date pits carbonization products with steam at 950°C to burn-off=20 and 50%, respectively. The textural properties of these carbons were determined from the nitrogen adsorption at −196°C. The chemistry of the carbon surface was determined from the surface pH and from neutralization of the surface carbon–oxygen groups of basic and acidic type. The kinetic and equilibrium adsorption of MB and RY on DS2 and DS5 was determined at 27 and 37°C and at initial sorption solution pH 3–7.DS2 and DS5 have expanded surface area, large total pore volume and contain both micro and mesoporosity. They have on their surface basic and acidic groups of different strength and functionality. This enhanced the sorption of the cationic dye (MB) and of the anionic dye (RY). The adsorption of MB and RY on DS2 and DS5 involves intraparticle diffusion and followed pseudo-second order kinetics. The adsorption isotherms were applicable to the Langmuir isotherm and high monolayer capacities for MB and RY dyes were evaluated indicating the high efficiencies of the carbons for dye adsorption