Cloverite, a microporous gallophosphate has attracted great attention as it possesses unusually large micropores. Cloverite possesses two types of structural hydroxyl groups (Ga-OH and P-OH groups), which exhibit high and moderate Br6nsted acid strength toward apolar hydrocarbon molecules. Sorption of polar base molecules on the Ga-OH groups, however, leads to a breaking of the Ga-O bond close to the Ga-OH adsorption site, resulting in a concerted Lewis and Br6nsted type interaction. For small molecules (like ammonia), multiple sorption at these sites causes a local rearrangement of the lattice leading to a collapse of the microporous structure upon thermal desorption of the probe molecules. Small alcohols are chemisorbed quite differently on the Ga-OH groups of cloverite compared to other acidic molecular sieves leading to the formation of dimethylether and formaldehyde upon desorption. The structural hydroxyl groups of cloverite exhibit high and moderate Bronsted acid strength toward apolar hydrocarbon molecules. With polar molecules, these hydroxyl groups show unique interactions leading to a local rearrangement of the lattice including a breaking of the Ga-O bond close to the Ga-OH sorption site. Consequently, a concerted Lewis and Br6nsted acid type interaction is concluded to exist between the basic molecules and the Ga-OH/Ga cation sorptionsites.
|Number of pages||7|
|Journal||Studies in surface science and catalysis|
|Publication status||Published - 1995|
|Event||International Zeolite Symposium 1995 - Québec, Canada|
Duration: 15 Oct 1995 → 20 Oct 1995