Development of a Novel Time-Resolved Synchrotron-Radiation X-ray Diffraction Measurement System for In Situ Observation of Crystal Structure in Aqueous Solution during Chemical Reaction: Application to the Anion-Exchange Reaction of a Layered Double Hydroxide from Chloride to Nitrate

摘要

We successfully developed a novel time-resolved synchrotron-radiation X-ray diffraction (t-SXRD) measurement system with high temporal resolution (minimum time: 50 ms) at the BL02B2 facility at SPring-8 for the in situ observation of the crystal structure changes of inorganic compounds in aqueous solution during chemical reactions. For evaluating the performance of this novel system, we applied it to observe the crystal structure change of a layered double hydroxide consisting of Mg and Al (Mg/Al = 2) with chloride as the exchangeable anion species (Cl--MgAl(1/3)LDH) during the anion-exchange reaction from Cl- and NO3- in aqueous solution under various [NO3-] conditions. The t-SXRD patterns from the MgAl(1/3)LDH crystal particles dispersed in aqueous solution were recorded every 0.2 s using our measurement system; that is, we obtained t-SXRD data for kinetic analysis. Thus, we identified the features for the anion-exchange reaction of Cl- MgAl(1/3)LDH from Cl- and NO3- in aqueous solution under various [NO3-] conditions. All the present results revealed that the novel t-SXRD measurement system developed herein is very useful and effective for monitoring the in situ structural changes of crystalline compounds dispersed in solution during chemical reactions with a fast time constant.