Enthalpies of formation of microporous titanosilicates ETS-4 and ETS-10

✍ Scribed by Hongwu Xu; Yiping Zhang; Alexandra Navrotsky

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 102 KB
• Volume: 47
• Category: Article
• ISSN: 1387-1811
• DOI: 10.1016/s1387-1811(01)00388-2

✦ Synopsis

Á 2:89H 2 O) has been investigated by high-temperature drop solution calorimetry using lead borate as the solvent at 974 K. Combining the measured heats of drop solution with the published enthalpies of drop solution and formation for the constituent oxides, the standard enthalpies of formation from the oxides (DH 0 f;ox ) and from the elements (DH 0 f;el ) for both phases were derived for the ®rst time. The obtained values (in kJ/mol) are as follows: DH 0 f;ox ETS-4 À818:5 AE 13:1, DH 0 f;el ETS-4 À14, 642:8 AE 15:9, DH 0 f;ox ETS-10 À262:2 AE 3:1, and DH 0 f;el ETS-10 À6995:2 AE 6:1. Comparison between the DH 0 f;ox (or DH 0 f;el ) values of the two phases suggests that ETS-4 is thermodynamically more stable than ETS-10 with respect to the oxides (or the elements) at 298 K and 1 atm. This behavior can largely be attributed to the higher degree of hydration of ETS-4 than that of ETS-10.