BET theory

About: BET theory is a research topic. Over the lifetime, 9046 publications have been published within this topic receiving 286142 citations.

XPS and TPD characterization of manganese-substituted iron–potassium oxide catalysts which are selective for dehydrogenation of ethylbenzene into styrene

Abstract: Manganese-substituted (0–100%) iron–potassium oxide (Mn–Fe–K) catalysts which are selective for dehydrogenation of ethylbenzene to styrene were prepared by the alcoxide sol–gel method. They have been characterized by XPS, BET surface area measurement and TPD studies. The differences of surface properties between the Mn–Fe–K catalysts and unsubstituted iron–potassium oxide (Fe–K) catalyst were reasonably reflected in the XPS spectrum of oxygen (O 1s) and potassium (K 2p). The XPS spectra of Mn–Fe–K catalysts based on the binding energy shifts of O 1s and K 2p bands resembled those of KFeO2 as an active phase for the dehydrogenation of ethylbenzene. On the contrary, the unsubstituted Fe–K catalyst showed the XPS spectra including KOH and Fe3O4 as inactive phases. The presence of Mn ions in the catalyst matrix (γ-Fe2O3, MnFe2O4) results in stabilization of the KFeO2 active phase, and did not affect catalytic behavior of the K-promoted iron based oxide. The maximum enhancement of catalytic activity at the optimum 20% Mn-substitution is owing to the large surface area, the minimization of carbonaceous deposition, and the retardation of pyrolysis of KFeO2 to KOH and Fe3O4.

Pd nanoparticles supported mesoporous γ-Al2O3 film as a reusable catalyst for reduction of toxic CrVI to CrIII in aqueous solution

Abstract: Pd nanoparticles (NPs) were generated inside the nanocrystalline mesoporous γ-Al2O3 films of thickness ∼2 μm. The support γ-Al2O3 films were prepared from boehmite sols derived from Al-alkoxide in presence of CTAB. The BET surface area (171 m2g−1) and pore size (4.3 nm) of the undoped γ-Al2O3 films were found to be decreased to 139 m2g−1 and 3.5 nm respectively after incorporation of Pd NPs. The films were characterized by GIXRD, cross-sectional FESEM, and TEM. TEM/GIXRD confirmed the existence of uniformly dispersed Pd NPs inside the γ-Al2O3 films. The Pd NPs (average size ∼4.1 nm)-incorporating mesoporous γ-Al2O3 films were used as catalyst to reduce toxic CrVI compounds to non-toxic CrIII in presence of formic acid as reducing agent at different temperatures (30, 40, 50 and 60 °C). This catalytic reduction process was monitored by UV–visible spectrometer. The rate constant value for the reduction was estimated to be 0.085 min−1 at 50 °C. The same catalytic film can be used for three consecutive cycles by simple washing with water. The catalytic property started to deteriorate after the third cycle. The original catalytic property can be restored fully after heat-treatment of the used films at 300 °C in nitrogen atmosphere.