Proton MAS Research Articles

The isomerization of 2‐methyl‐2‐pentene on stoichiometric and nonstoichiometric boron phosphate

The isomerization of 2‐methyl‐2‐pentene has been studied on boron phosphate (BP) catalysts with P/B ratios from 0.8 to 1.6 and at various reaction temperatures and contact times. Double‐bond shift occurs on the compositions with P/B of 1.0 and less, while methyl shifts occur on samples with P/B of 1.2–1.6, demonstrating the presence of strong acidity on the latter solids. Ammonia chemisorption and proton MAS NMR is employed to provide supplementary evidence of the variation in acidity with composition. Although BP of P/B 1.

Cation/proton interactions and acid strengths in salts of 12-tungstophosphoric acid prepared from 1A, 1B and 3B monovalent cations

The substitution of the protons in 12-tungstophosphoric acid by 1A, 1B and 3B monovalent cations leads to increases in surface area, the introduction of micropore structures and alterations in the interactions experienced by the protons, as well as the expected decreases in the concentration of protons. The resultant changes in the distribution of acidic strengths and the effect of changes in the preparative stoichiometry and the nature of the cation have been assessed from proton MAS NMR and NH3 TPD measurements and correlated with the catalytic activities in the dehydration of 1-, 2- and tert-butanol on stoichiometric and nonstoichiometric compositions of the aforementioned solids.

Interaction of H-rho zeolite with water and methanol studied by multinuclear NMR spectroscopy

A multinculear NMR study is preformed in the sorption of water and methanol onto zeolite H-rho. The effect of sorption on the MAS NMR of the framework nuclei is reflected in the progressive increase of the /sup 27/Al signal intensity (which is negligible in dry H-rho) and by the gradual improvement in the resolution of the /sup 28/Si spectrum (which is very poor in dry H-rho). The limiting spectra of these nuclei are reached at a sorbate:framework-Al ratio of 2:1. Proton MAS and /sup 2/H quadrupole-echo spectra are used to characterize the species formed upon sorbate addition. Depending on the loading level a variety of species are identified with dynamic features ranging from essentially solid (at low loading) to highly fluid (at high loading). Similar NMR results on the framework nuclei /sup 27/Al and /sup 28/Si are also reported for zeolite H-Y.