The synthesis of propylene oxide from propylene glycol, a derivative of bio-glycerol, was firstly realized in the presence of alkali-loaded silica catalysts to achieve 44% conversion and 70% selectivity.
The
adsorption and diffusion of adsorbates or reactants are the
most essential steps in zeolite-based processes for gas separation
and catalysis. An explicit description of the relationship between
adsorption and mass transport in confined environments of microporous
materials is a prerequisite to catalytic reaction and gas separation.
The dimensions, shapes, and types of pores are the most essential
properties that govern the adsorption and diffusion behaviors of guest
molecules. Here, a xenon atom was used as a sensitive probe to provide
information about the dynamic adsorption process between the lta cavity and double eight-membered rings (D8R) of DNL-6
molecular sieves with RHO topology by 129Xe NMR and pulsed
field gradient (PFG) NMR. Loading-dependent 129Xe NMR presents
the two types adsorption environments with different probabilities
of xenon distribution, and D8R is the preferential adsorption site.
Furthermore, 129Xe PFG NMR exhibits the mass-transport
limitations of the xenon atom in DNL-6 as the loading increases. On
the basis of molecular dynamics (MD) and Monte Carlo (MC) simulations,
the interaction energies between RHO framework and xenon were predicted
and the preferred adsorption character of D8R was displayed visually,
which further contribute to the understanding of adsorption and diffusion
behavior, especially for the loading dependence of intracrystalline
diffusion. The diffusion limitation caused by the preferential adsorption
of D8R can depress the mass transport in RHO-type molecular sieves.
A direct relationship between the adsorption preference and diffusion
was established at the molecular level.
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