Monitoring of structural changes accompanying ultrastabilization of faujasitic zeolite catalysts

Conversion of methanol to olefins: Stabilization of nanosized SAPO-34 by hydrothermal treatment

“…Deconvolution of 29 Si NMR bands corresponding to different Si environments was performed with Origin Pro 9.0 software with Gaussian shapes of constant width. 27 Al MAS NMR spectra were recorded at 104.218 MHz with a spinning rate of 10 kHz at a 90º pulse length of 0.5 µs with 1 s repetition time.…”

“…In the present work we started from the hypothesis that it could be possible to increase the stability of SAPO-34 samples by performing a controlled hydrolysis of a part of the silicon, in an analogous way as it occurs with high aluminum zeolites that can be stabilized by controlled partial dealumination [27]. Therefore, we will present here the effect of the hydrothermal treatment at different temperatures on the long-term stability of nano and standard SAPO-34 materials.…”

“…29 Si, 27 Al and 31 P chemical shifts are reported relative to tetramethylsilane, Al(H2O)6, and H3PO4 respectively.…”

Density Functional Theory Calculations of the Effects of Local Composition and Defect Structure on the Proton Affinity of H−ZSM-5

“…6 No enhancement in the specific activity of Brønsted acid sties is observed for severe steaming (high temperature and water partial pressure), and such pretreatment results in significant delaumination of the zeolite framework and the deposition of extraframework alumina species in the pores. [4][5][6][7][8][9][10][11][12][13][14] Several authors have suggested that both dehydroxylation and dealumination of the zeolite results in the formation of Lewis acid centers via the following processes: 5,[15][16][17][18] In other studies, it has been proposed that dehydroxylation can occur as well via the reaction of acidic bridging hydroxyl groups with silanol hydroxyl groups present at defects in the lattice. 17 This process is illustrated by reaction 3.…”

Synthesis of high quality alkyl naphthenic kerosene by reacting an oil refinery with a biomass refinery stream

“…As can be observed there crystallinity and micropore volume are decreased during the generation of mesopores in good agreement with previous results. 35 However, in spite of the decrease in crystallinity, the USY-MY sample is not significantly dealuminated according to the unit cell size values determined by XRD and the 27 Al MAS-NMR spectra (not showed) which exhibits a single peak centered at a chemical shift of around 60 ppm, and assigned to tetrahedrally coordinated Al 36 . Additionally, the Bronsted acidity of USY-MY sample is increased possibly as a consequence of the decrease of the sodium content during the post-synthetic treatment.…”