Selective catalytic oxidation of ammonia into nitrogen over PCH modified with copper and iron species

Porous heterostructured clays - recent advances and challenges - revisão

“…For uncalcined FCHs, the basal spacing is 3.74 nm, reducing 0.96 nm of the lamella thickness, 2.78 nm, indicates that the hexadecylamine molecules, the co-surfactant, are oriented perpendicularly to the clay lamellae, suggesting that they have cylindrical shape in the interlayer space (scheme c), since this value is twice the size of the hexadecylmanine molecule, which is approximately 1.44 nm (diagram b). In the same diffraction pattern, a peak of low intensity with basal spacing of 0.98 nm is detected, which can be attributed to lamellar pilingnot separated by the interlayer spacing, which is an effect than is possible when protons or other small dehydrated cations migrate from unoccupied octahedral positions, resulting in the neutralization of the negative charges of clay lamella [47]. When calcined (scheme d), the material does not change the position of the characteristic peak of the basal spacing; however, the refl ection intensity is relatively reduced, featuring a non-parallel arrangement of the clay lamella, as template decomposition occurs in the calcination, which is an exothermic process, and overheating of the sample can cause disturbances in the lamellae arrangement.…”

“…Chmielarz et al [21], before submitting PCHs to the calcination step, studied by thermogravimetry coupled with mass spectrometer, the thermal degradation of surfactant present in the pore system of PCHs and noted that several products are formed. At 184 °C, degradation of surfactant and co-surfactant molecules is observed.…”

Dehydrogenation of Cyclohexanol on Fe, Ti-MCM-41 Mesoporous Materials

“…3) of the modified materials exhibit a broad absorption peak in the 220-250 nm region attributable to isolated, tetrahedrally coordinated metal species [6,7,38,39]. The band at about 350 nm, characteristic for all iron containing samples most probably arise from the presence of oligomeric FeO x species in the silica matrix.…”

“…The intensity of this band is higher for samples with higher amount of iron and low amount of titanium (FeTiMCM-41 (3)). The low intensity band at about 500 nm in the spectra of bicomponent materials with high iron content indicate the presence of either extra-framework iron and/or iron oxide particles [6,39]. According to [39], this peak can be assigned to symmetrical and spin forbidden d-d transitions of Fe 3?…”

Study of the effects of lanthanum and the iron ion on the acidic properties of Al-pillared vermiculite

“…An efficient way to investigate this association is the use of organic bases such as pyridine, which second Chmielarz et al 22 , has frequently been used in the study of acidic sites.…”