Extraction Separation Of Naphthenes From Naphtha

The efficient use of naphthenes in naphtha is an urgent requirement for molecular management and optimal utilization of naphtha resources.The solvent extraction process for separating naphthenes in naphtha has the advantages of simple process and low energy consumption.Based on the Hansen solubility parameter theory,three-dimensional solubility parameter models for n-paraffin and naphthene in naphtha were established.According to the solubility and selectivity of the solvent to naphthenes.2-pyrrolidone was selected as a single solvent for naphthene extraction.The reliability of the model was verified by experiments.The optimum operating conditions for single-stage extraction were as follows:a solvent to feed ratio of 5,an extraction temperature of 303K.Through the extraction process,the yield of extract oil was 34.1 wt%,and the yield of naphthenes was 38.3 wt%.On this basis,N-methyl pyrrolidone was selected as a cosolvent,and the investigation on complex extractant was carried out.Then the extraction conditions were optimized.Through the two-stage counter current extraction process,the optimal extraction conditions of complex extractant were as follows:2-pyrrolidone:N-methyl pyrrolidone(volume ratio)=0.4,a solvent to feed ratio of 1,and an extraction temperature of 308K.Through extraction process,the yields of extract oil and naphthene,were 38.7wt%and 45.5wt%.The complex extractant had both high naphthene separation selectivity and good naphthenes solubility.The complex extractant had the best extraction effect on C6 naphthenes.The yield of C6 naphthenes was 54.2wt%.which was 7.1wt%higher than 2-pyrrolidone.Among them,the yield of cyclohexane reaced 55.4wt%.Meanwhile,the selectivity parameters of naphthenes ?1,?2,?3 and ?4,were 17.8%.40.3%,36.8%and 43.2%,which increased by 5.5%.2.2%,0.9%and 1.0%compared with 2-pyrrolidone.Through the three-stage counter current extraction process,the yield of extract oilwas 68.8wt%,and the yield of naphthenewas 76.4 wt%.Compared with naphtha,the potential aromatics content of extract oil can be increased by 19.6wt%,indicating that extract oil was a good feed for catalytic reforming.The alkane content of raffinate oil increased by 16.5wt%,ethylene yield could increase by 2.4%.The raffinate oil was a high-quality steam cracking feed.Through the extraction separation of complex extractant,naphtha resources could be efficiently utilized by enriching naphthenes in naphtha.