基于反气相色谱技术研究煤表面性质和热力学参数

Study on surface properties and thermodynamic parameters of coal by inverse gas chromatography

采用反气相色谱(IGC)技术测定煤的表面性质和热力学性质。在303.15~343.15 K温度范围内,以30种有机溶剂作为探针分子,测定探针溶剂的保留体积。用Schultz和Dorris-Gray两种方法计算了煤样的表面色散自由能,结果为20.26~36.56 mJ/m^(2),并且呈现随着温度的升高而递减的趋势。计算Lewis酸碱常数得出的能够表征煤样总酸碱能力的数值KB/KA值为6.66,说明表面偏碱性。另外,测定了无限稀释活度系数γ_(12)^(∞)、质量活度系数Ω_(1)^(∞)和Flory-Huggins相互作用参数χ_(12)^(∞)、溶解度参数δ_(2)等热力学参数。结果表明,γ_(12)^(∞)随着温度的升高而下降,表明探针溶剂与煤样之间的相互作用力随着温度的升高而增强;χ_(12)^(∞)随着温度的升高而递减,可知四氢呋喃和二氯甲烷的χ_(12)^(∞)值小于0.5,Ω_(1)^(∞)值小于5,说明探针溶剂四氢呋喃和二氯甲烷是良溶剂;煤的溶解度参数随着温度的升高呈下降的趋势。为加深了解煤性质和后续浮选提质技术提供了借鉴和理论支撑。

The surface properties and thermodynamic properties of coal are determined by means of inverse gas chromatography(IGC)technology.In the temperature range of 303.15-343.15 K,30 kinds of organic solvents are taken as probe molecules to determine the retention volume of probe solvents.The surface dispersion free energy of coal samples is calculated by means of Schultz and Dorris⁃Gray methods,respectively,and the result is in the range of 20.26-36.56 mJ·m^(-2),which shows a decreasing trend with the increasing temperature.Through calculating Lewis acid⁃base constant,total pH capacity of coal samples is 6.66,indicating that the surface of coal shows alkaline.In addition,thermodynamic parameters are determined,including infinite dilution activity coefficientγ_(12)^(∞),mass activity coefficientΩ_(1)^(∞)and Flory⁃Huggin's interaction parameter x_(12)^(∞),solubility parameterδ_(2).Results show thatγ_(12)^(∞)decreases with the increasing temperature,indicating that the interaction force between probe solvent and coal samples increases with the increasing temperature.x_(12)^(∞)declines with the increasing temperature,and the calculation results show that x_(12)^(∞)values of tetrahydrofuran and dichloromethane are less than 0.5,theΩ_(1)^(∞)values are less than 5,indicating that both tetrahydrofuran and dichloromethane are benign solvent.With the increase of temperature,the solubility parameter of coal samples decreases.The study deepens the understanding on coal properties,and provides reference and theoretical support for subsequent flotation and upgrading technologies.