β-ジヒドロムコン酸複合リン酸八カルシウムの加熱変化

概要

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Apatitic layered octacalcium phosphate (Ca_8(HPO_4)_2 (PO_4)_4・5H_2O; OCP) was intercalated with β-dihydromuconate ions (-OOC(R)COO-, R; CH_2-CH=CH-CH_2). The basal spacing of the OCP structure was expanded to 23.7Å by the intercalation (OCP: 18.7Å). The spacing was contracted by heating (dehydration), and reverted by exposure to H_2O vapor (rehydration). Such zeolite-like behavior toward H_2O was observed below 350℃. A remarkable contraction in the basal spacing by dehydration suggested the bending of zig-zag R chains supporting the layer structure. Improvement of the thermal stability of the OCP layer structure was judged from increases in starting temperatures for the following processes: 2HPO_4^<2->→P_2O_7^<4->, formation of apatitic OH-, disappearance of OCP phase and appearance of apatitic phase. No significant differences were observed in thermal behavior between the intercalates of the doubly unsaturated R and saturated R,i.e., CH_2-CH_2-CH_2-CH_2, were a little. The intercalation decreased the catalytic activity for the dehydration of 2-propanol.
社団法人日本セラミックス協会の論文
1992-04-01