One-pot Method For Aluminum Hydrideand Its Characterization

In this thesis, the synthesis and application research status of Al H3 were summarized. A new synthesis method of Al H3 was proposed.(1) The de-etherization and crystal transition procedure were completed by directly using the Li Cl mixed Al H3-etherate instead of the pre-procedure of Li Cl filtration.(2) The production in above step was washed for Li Cl removing and α-Al H3 stabilizing. This method was named as ―one-pot‖ method, which was subdivided into solid-vacuum method, solid-toluene method and slurry method based on the circumstances and status of Al H3-etherate and each method was investigated respectively. Finally, ―one-step‖ synthesis method of Al H3 was also investigated.The solid-vacuum method based on the crystal transition of solid Li Cl mixed Al H3-etherate in vacuum was employed for α-Al H3 production. The XRD and IR characterizations indicated the monocrystalline α-Al H3 was successfully synthesized by changing the reaction temperature, the reaction time and the amounts of Li BH4. When the ratio of raw materials Li Al H4 and Al Cl3 was 4:1, the reaction temperature and time were 77~80 ℃and 2~3 h, and when the Li Al H4:Li BH4:Al Cl3=4:1:0.5, the temperature and time were 80~85 ℃ and 1~2 h.The solid-toluene method based on the crystal transition of solid Li Cl mixed Al H3-etherate in toluene was employed for α-Al H3 production. The XRD and IR characterizations indicated the monocrystalline α-Al H3 could be also synthesized by changing the reaction temperature and the reaction time. When Li Al H4:Li BH4:Al Cl3=4:1:1, the reaction temperature and time were 80~85 ℃ and 1.5~2 h. The hydrogen content of monocrystalline α-Al H3 was 8.8~8.9 wt%.α-Al H3 was obtained by the crystal transition of Al H3-etherate enriched solution in toluene with slurry method. The preparation procedure of slurry method was optimized by changing reaction temperature and experiment steps. XRD characterization indicated the monocrystalline α-Al H3 has been successfully synthesized by this method, a weight loss in the TG trace of sample close to the theoretical hydrogen content(10.1wt%) was observed, and the initial decomposition temperature was 176 ℃. Similar to the slurry method, one-step method was used for non-solvent α-Al H3 synthesis by directly using the reaction of Li Al H4 and Al Cl3 in 80~90 ℃ toluene. The results indicated that the sample produced was 10~50 μm in diameter, its decomposition temperature was 170 ℃ and the hydrogen content was up to 10%.Compared comprehensively, the α-Al H3 produced by the slurry method was 10~50 μm in diameter. The formation enthalpy value of a-Al H3 was 11.9 k J/mol and the weight loss was 10wt%, which were similar to the theoretical values. The slurry method was more suitable for a-Al H3 synthesis.