Mechanochemical Effects of Some Rare-Earth Ultraphosphates and Reforming of Their Surface for Catalytic Properties

Abstract

Rare-earth ultraphosphates, RP5O14, were synthesized, and their mechanochemical effects due to grinding were investigated by using TG-DTA, XRD, FT-IR and SEM. When the ultraphosphates were ground, their XRD peaks became smaller, their particles were flocculated to be paste, and their P-O-P bondings were cleaved to form P-O-H bondings. The P-O-H bondings formed by mechanical treatment were expected to raise catalytic activities of rare-earth ultraphosphates. The ultraphosphates reformed by grinding enlarged the surface areas, the acid strength, amount of acidic sites, and the conversion of 2-propanol to propylene.

Preparation of Aluminum Polyphosphate and Improvement on Its Physicochemical Properties by Mechanochemical Treatment

“…In IR spectra, the change due to O-H bonding by milling was less observed. In previous work, the ultraphosphate produced P-O-H bonding from P-O-P bonding and H 2 O in air by mechanochemical treatment 3) . Polyphosphate was thought to be much difficult to produce P-O-H bonding than ultraphosphate.…”

“…The mechanical treatment produced the acidic sites at pKa +1.5 on surface of aluminum polyphosphate powders. A small part of P-O-P bonding in polyphosphate was considered to cleavage to P-O-H bonding with H 2 O in air 3) . The amounts of acidic sites also improved to 360 min and then declined.…”

“…For these effects, mechanically treated materials are regarded as in an active state. In our previous work 3) , specific surface area, acid strength, and amount of acidic sites of ultraphosphate were improved by mechanical reforming. These properties are important for an acidic catalyst and an adsorbent of basic stinking gas.…”

“…Polyphosphate has a chain structure in which the PO 4 unit shares two oxygen atoms; cyclo-phosphate has a cyclic structure; and ultraphosphate has a network structure. Phosphates have been used for ceramic materials, catalysts, fluorescent materials, dielectric substances, pigments, adsorbent, etc [1][2][3] . The physical and chemical properties of solid materials are changed by crushing, pressing, milling, and other mechanical treatments.…”

“…However, CHF 3 also has a large global warming potential (GWP) 4) . Therefore, it is necessary to obtain the acid catalysts for decomposition of CHF 3 . Aluminum orthophosphate is a useful catalyst for many reactions.…”