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The synthesis, structure, and acid function of solid phosphoric acid (SPA) catalyst were studied in detail. 31P and 29Si MAS NMR and X-ray powder diffraction identified the following crystalline silicon phosphate phases in SPA:  Si5O(PO4)6, hexagonal-SiP2O7, Si(HPO4)2·H2O, and SiHP3O10. The acidity of SPA is due to a liquid or glassy solution of phosphoric acid oligomers supported on the silicon phosphate phases. 15N MAS NMR of adsorbed pyridine-15 N and 13C MAS NMR of adsorbed acetone-2-13 C showed Brønsted acid sites and no Lewis acid sites. 1H→15N→31P and 1H→13C→31P double cross polarization MAS NMR of the probe molecules provided a rare opportunity to use NMR to unambiguously localize chemisorption sites; the probe molecules are complexed to phosphoric acid and pyrophosphoric acid but not to the silicon phosphate phases. In situ NMR of the oligomerization of propene on SPA suggests that propene quantitatively reacts with phosphoric acid and its oligomers to form isopropyl phosphate, and formation of this very stable intermediate accounts for the lower olefin oligomerization activity of SPA relative to acidic zeolites. Theoretical calculations including geometries at B3LYP/6-311+G(d,p) and chemical shifts at GIAO-MP2/tzp/dz were used to model complexation of acetone or propene to SPA, and these support our conclusions.

Barium titanium sulfide (BaTiS3) and calcium, strontium and barium zirconium sulfides (CaZrS3, SrZrS 3 and BaZrS3) have been synthesized by the reaction of CS 2 with the respective ternary oxides at elevated temperatures. Barium titanium sulfide is hexagonal but its sulfur content decreases with increasing temperature of preparation. This results in a variation of unit cell dimensions from a=6.752, c=5.810 Jk when prepared at 700 °C. to a=6"77, c=5.74 A when prepared at 1100 °C. BaTiS a containing a stoichiometric or near stoichiometric equivalence of sulfur has the barium nickelate structure. As the sulfur content decreases the structure becomes increasingly disordered. BaZrS 3 is orthorhombic with a = 7.037, b = 9-983, c = 7.050 A and has a distorted perovskite structure. SrZrS 3 and CaZrS 3 have even more highly distorted perovskite structures and require orthorhombic unit cells with a = 13.49, b =9"79, c = 14.23 A for SrZrS 3 and a = 13.07, b =9"58, c = 14.05 A for CaZrS 3.

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