Separation and determination of alkane and cycloparaffinic hydrocarbon in heavy oil by combining ultrasonic wave with the adductions of urea and thiourea

The separation and determination of alkane and cycloparaffinic hydrocarbon in heavy oil is the difficult problem in hydrocarbons analysis.The alkane and the cycloparaffinic hydrocarbon in Daqing VGO are separated by combining ultrasonic wave with the adductions of urea and thiourea.The obtained alkane and cycloparaffinic hydrocarbon are determined by GC/MS and NMR.When the mass ratio of isopropanol to oil sample is 7.5 and the temperature of reaction is 38～43 ℃,the average mass fractions of alkane and cycloparaffin in Daqing VGO are 46.56% and 41.88% and the RSD are 0.7% and 0.51% respectively according to 5 determination results.The carbon number distribution of normal paraffin in alkane is C_ 20 —C_ 38 .Cycloparaffinic hydrocarbon in alkane is less than the detection limit of NMR,and the total ion chromatogram of cycloparaffinic hydrocarbon shows that the content of alkane in cycloparaffinic hydrocarbon is very little.These indicate that ultrasonic wave can accelerate the adduction of urea and thiourea and improve the separation result of alkane and cycloparaffinic hydrocarbon in heavy oil.This method has high accuracy and good repeatability in the separation and analysis of alkane and cycloparaffin in heavy oil.