Study On Solubility Of Polyacrylamide In Supercritical Or Subcritical Fluids

Supercritical or subcritical fluid technology as a green chemical technology has been applicated in polymer flooding,polymer material preparation,polymer modified,polymer processing and so on.However,the study on the solubility and phase equilibrium data of polymers which are basis for the application of the polymer in(sub)supercritical fluid technology is deficient and need more attentions.To promote the application of polyacrylamide(PAM)in supercritical carbon dioxide(SCCO2)flooding and in subcritical 1,1,1,2-tetrafluoroethane(R134a)technology.In this article,CO2 and R134a were chosen as the solvents for study and the solubility of PAM with three different molecular weights in SCCO2 and subcritical R134a at different pressures and temperatures were measured.The specific study contents are follows:The solubility of PAM with different molecular weights(5000000,7000000 and 14000000 g·mol-1)in SCCO2 and subcritical R134a was determined.The solubility experiments were performed at the pressures ranging from 9.0 to 18.0 MPa and temperatures between 313-333 K by dynamic method in SCCO2,and at pressures ranging from 7.0 to 18.0 MPa and temperatures between 313-343 K by static method in subcritical R134a.The effects of experiment conditions(pressure,temperature),solvents and molecular weights of PAM on the solubility of PAM in SCCO2 and subcritical R134a were analyzed using molecular motion theory and the enhancement factor(?)of solvents was given.Five commonly used semi-empirical models which were Chrastil model,Adachi and Lu(A-L)model,Sung and Shim(S-S)model,Mendez-Santiago and Teja(M-T)model and Bartle model were used to correlate the solubility data of PAM with three different molecular weights in SCCO2 and subcritical R134a,and the average absolute relative deviation(AARD)was applied to evaluate the accuracy of different models.The total heat,solvation heat and vaporization heat of PAM were given by calculating parameters of models.In addition,statistical association fluid theory(SAFT)as a purely theoretical approach was applied to predict the solubility of PAM in SCCO2 and subcritical R134a.Solubility prediction results were compared with experiment results,and SAFT had a satisfactory accury.