Study On Surface Tension And Density Properties Of Alcohol+N,N-Dimethylcyclohexylamine+Water Systerm

As the global warming is becoming increasingly serious,controlling the emission of CO₂,one of the most important greenhouse gases,has gradually become a research hotspot.For CO₂ capture,chemical absorption method based on alcohol amine solution is one of the most widely used.Therefore,the study of the physicochemical properties of alcohol+amine binary systems and alcohol+amine+water ternary systems is important.The studies can provide fundamental datas for simulation of CO₂ capture,and provide theoretical guidelines for industrial applications.The main research in this work is as follows:Firstly,the surface tensions of the binary system containing N,N-dimethylcyclohexylamine（DMCA）and alcohols（ethanol,n-propanol,iso-propanol,n-butanol,iso-butanol）over the whole range of composition at atmospheric pressure and different temperatures ranging from（288.15 to 308.15）K were measured using the BZY-2 automatic surface tension meter.From the experimental datas,it can be also observed that the surface tension values decrease with the increasing temperature and increase with the increasing x DMCA for all compounds.According to the experimental surface tension values,the surface tension deviations（δγ）for the binary mixtures were calculated.The surface tension deviations are positive（0.07～1.89）m N·m^-1 for all the studied systems over the entire composition range.The surface tension deviations values for the binary mixtures decrease with increasing of the alkyl chain length of alcohol.For the branched-chain alcohol-based mixtures,the surface tension deviations values increase considerably compared with the isomers,straight-chain ones.According to the surface tension datas,the thermodynamic parameters,surface enthalpy（H^γ）and surface entropy（S^γ）were also estimated and further discussed.Secondly,the densities of the binary system containing N,N-dimethylcyclohexylamine（DMCA）and alcohols（ethanol,n-propanol,iso-propanol,n-butanol,iso-butanol,tert-butanol）over the whole range of composition at atmospheric pressure and different temperatures ranging from（288.15to 318.15）K were measured using the U-shaped vibrating tube densitometer.According to the experimental density values,molar volume（V_m）,thermal expansion coefficient（α_p）and excess molar volume（_mV^E）were calculated.And the excess molar volume values were correlated with Redlich-Kister polynomial equation.The results show that the thermal expansion coefficient of the alcohol component is related to the alkyl chain length of alcohol and the degree of branching of the alcohol.The thermal expansion coefficient decrease with increasing of the alkyl chain length of alcohol,and increase with increasing of the the degree of branching of the alcohol.Excess molar volume values were all negative（-1.169～-0.185）cm³·mol^-1 over the entire composition and the minimum values of the six systems were located at about x _DMCA=0.4.Finally,the densities of the two ternary systems of DMCA+water+ethanol/n-propanol at atmospheric pressure and different temperatures ranging from（288.15 to 318.15）K were measured using the U-shaped vibrating tube densitometer.,By measuring and drawing the ternary phase diagram,the homogeneous solution have been prepared in the completely miscible interval to measure the density.From the density datas,the excess molar volume for the ternary systems were calculated.The results show that the density values of the ternary systems decrease with increasing temperature,at the same temperature,when x _DMCA was constant,the density values of the ternary systems increase as x _H2O increase and decrease as x_alcohol increase,when x _H2O was constant,the density values of the ternary systems decrease as x_alcohol and x _DMCA increase,when x_alcohol was constant,the density values of the ternary systems increase as x _H2O and x _DMCA increase.Excess molar volume values of the ternary systems were all negative（-1.748～-0.608）cm³·mol^-1 over the entire composition and the minimum values of the the two systems were（-1.628,-1.571）cm³·mol^-1 at 298.15K,indicating that there was a strong interaction between different molecules.