Search Results
Abstract
Samples with various amounts of tin oxide were prepared by impregnating γ-Al2O3, TiO2(anatase), SiO2, ZrO2 and MgO with tin tetrachloride or tributyltin acetate solutions. After drying and calcination, the samples were characterized by chemical analysis, XRD and BET measurements. Ammonia adsorption microcalorimetry was used in order to determine the number, strength and strength distribution of surface acid sites. The influence of the adsorption temperature, evacuation temperature, amount of SnO2 deposited and of the nature of the support on the adsorption properties were studied.
of SO 4 2− ions was already studied in several works [ 1 , 2 ]. Indeed, sulfatation produces a decrease in the amount of weak acid sites while new, very strong acid sites are formed on the molecular sieves. Particularly, dehydration of
oxides and zeolites have proved to be effective solid acid catalysts for a number of industrially important reactions [ 5 – 8 ]. The catalytic activity of solid acid catalysts is not only related to the surface concentration of acid sites, but
Abstract
The mechanism of surfactant adsorption on various forms of clinoptilolite was studied by DTA, TG and DTG analyses. The examined series of surfactant modified clinoptilolite (SMC) was previously prepared by the adsorption of the surface-active oleylamine on Ca2+, Na+, H+ and mechanochemically treated forms of clinoptilolite. The oleylamine was most strongly adsorbed on H+-forms of clinoptilolite due to the largest number and strength of adsorption sites. The surfactant adsorption mechanism on H+-form of clinoptilolite was studied by recording the series of variously surfactant-loaded samples. The products of sulphate, dihydrogenphosphate and hydrogenchromate adsorption on SMC were analyzed by DTA, TG and DTG in order to investigate the mechanism of anion adsorption.
represent an important model for the acid catalytic material in general [ 7 ]. The challenge to obtain solid acid catalysts with acid sites of comparable strength to those in sulfuric acid is still open in an attempt to eliminate environmental
, 29 , 38 ] think Si–Ti mixed oxides can provide the Lewis and Br⊘nsted acidic sites simultaneously, which are well known to adsorb pyridine to give rise to the adsorption bands appearing at 1,450 and 1,540 cm −1 . However, FT-IR spectra of adsorbed
attention [ 1 – 14 ], since not all the available (large deposits around the world) and produced natural gas is used. This reaction also produces hydrogen, which can be used on fuel cells. It is normally accepted that Br⊘nsted acid sites, molybdenum species
(471–533 °C) are assigned to the weak and strong acid sites, respectively [ 14 ]. Normally, the peak area can be used to estimate the amount of acidity of the samples [ 15 , 16 ]. The peak areas of the NH 3 -TPD profiles are listed in Table 2 . It was
cations [ 8 , 9 ]. The selectivity of a bifunctional catalyst for isomerization is expected to depend on the balance between the two catalytic functions, i.e. the density and the strength of the Brønsted acid sites (H + ) and the amount and the
behavior for C 2 + formation is directly related to the overall basicity of catalysts and methane oxidation to CO 2 on the acid sites. Experimental The MO–Sm 2 O 3 (M = Zn, Mg, Ca, Sr) mixed oxides were prepared starting from