无水苯甲酸锂的合成、结构表征及热化学研究

用分析纯苯甲酸和一水氢氧化锂作为反应物, 采用水热合成法制得苯甲酸锂. 利用X射线粉末衍射、FTIR、元素分析及化学分析等方法对样品进行组成和结构表征. 采用精密自动绝热热量计测量了其在80~400 K范围内的摩尔热容, 利用最小二乘法将此温区热容实验值对折合温度进行拟合, 得到热容随温度变化的多项式方程. 通过设计合理的热化学循环, 选用0.1 mol/L HCl溶液作为量热溶剂, 利用等温环境溶解-反应热量计分别测定合成反应的反应物和产物在所选溶剂中的溶解焓, 得到反应焓Δ_rH_m⁰=-(9.75±0.27) kJ/mol. 利用Hess定律计算出苯甲酸锂的标准摩尔生成焓Δ_fH_m⁰(C₆H₅COOLi, s)=-(307.82±0.57) kJ/mol.

Synthesis,Structure Characterization and Thermochemistry of Anhydrous Lithium Benzoinate

Benzoic acid and lithium hydroxide with the analytical grade were chosen as the reactants, and the lithium benzoinate was synthesized by means of hydrothermal synthesis. XRD,FTIR and elementary and chemical analyses were applied to characterize its composition and structure. Low-temperature heat capacities of the compound were measured via a precision automated adiabatic calorimeter over the temperature range from 80-400 K. A polynomial equation of the heat capacities as a function of the temperature was fitted by the least square method. A reasonable thermochemical cycle was designed on the basis of the preparation reaction of the substance, 0.1 mol/L of HC1 solution was chosen as the calorimetric solvent, and the standard molar enthalpies of dissolution for the reactants and products of the hydrothermal reaction in the selected solvents were measured by an isoperibol solution-reaction calorimeter, respectively. The enthalpy change of the preparation reaction was determined as △_rH_m~θ =-(9.75±0.27) kJ/mol from the standard molar enthalpies of dissolution. Eventually, the standard molar enthalpy of formation of anhydrous lithium benzoinate was derived to be △_rH_m~θ =-(307.82±0.57) kJ/mol by Hess's law.