LAUSR

Abstract This paper aims to propose a modified Joback method to predict the critical temperature, critical pressure, and critical specific volume of substances accurately based on their molecular structures. The Joback and the modified Joback methods have been applied to various environmentally friendly substances as R-1225ye(Z), R-1233zd(E), R-1234yf, R-1234ze(E), R-1234ze(Z), R-1243zf, and R-1336mzz(Z) to verify their accuracy. The average absolute percentage errors (AAPE) of the predicted critical temperatures from the Joback method using the predicted normal boiling temperatures for all the studied substances is 6.03%. If the experimental normal boiling temperature is used in the prediction of the critical temperature with the Joback method, the AAPE of the predicted critical temperatures is 1.73%. When the modified Joback method is applied, the AAPE of the predicted critical temperatures is 0.63%, smaller than half of that from the Joback method. In the prediction of the critical pressure, the AAPE of the predicted critical pressures with the Joback method and the modified Joback method are 8.01% and 3.10%, respectively. The AAPE of the predicted critical specific volumes with the Joback method and the modified Joback method are 1.93% and 1.49%, respectively. The study also shows the advantages of the modified Joback method, especially in the prediction of the critical temperature compared to some other available methods.