Study On The Application Direction Of Mixed C₄,C₅ Hydrocarbons In S-Zorb Unit Of Jinan Refinery

Chinese commercial gasoline standards are becoming more and more strict,gasoline desulfurization,olefins and aromatics reduction are overwhelming trend.Compared with the"World Wide Fuel Charte",there is a problem that the upper limit value of gasoline vapor pressure is high,if gasoline vapor pressure is too high,it will cause engine air resistance and environmental pollution of organic compounds.The key to reducing gasoline vapor pressure is to remove high vapor pressure components such as C₄,C₅ hydrocarbons from gasoline.Jinan Refinery is upgrading the processing equipment for the national six gasoline production,the processing scale of the catalytic cracking unit will increase from 0.8 million tons/year to 1.2 million tons/year,the processing scale of S-Zorb unit will increase from 0.9 million tons/year to 1.5 million tons/year.FCC gasoline is desulfurized by the S-Zorb process,C₄ and C₅ components are removed from gasoline to reduce gasoline vapor pressure.How to effectively utilize C₄ and C₅ components and increase their added value,it is an urgent problem to be solved in Jinan Refinery.In this paper,the detailed hydrocarbon compositions of mixed C₄,C₅ hydrocarbons were analyzed.Feed compositions are mainly C₄ alkane（50.59 wt%）,C₅ alkane（12.42wt%）,C₄ olefin（25.68 wt%）,C₅ olefin（4.30 wt%）;there are also some small molecule alkanes such as propane（4.72 wt%）and ethane（1.32 wt%）.The ratio of n-butane and isobutane is close to 1:1.The catalytic cracking reaction of mixed C₄,C₅ hydrocarbons was studied.Olefins are the main reactant,high severity benefits alkanes conversion.The pilot experiment on coprocessing of mixed C₄,C₅ hydrocarbons and heavy oil were carried out,compared with heavy oil catalytic cracking reaction,when mixed C₄,C₅ hydrocarbons feed below the heavy oil feed position,product distributions are improved,the yield of propylene and gasoline increases,coke yield becomes lower;the octane number of the gasoline fraction increases,and the initial boiling point decreases,it has less impact on diesel and slurry fraction.When mixed C₄,C₅ hydrocarbons feed above the heavy oil feed position,hydrogen transfer reaction of olefins increases,the olefin content in liquefied gas and gasoline decreases,the isoparaffin content increases.The feasibility of mixed C₄,C₅ hydrocarbons as ethylene cracking feedstock was studied.The hydrogenation reaction of mixed C₄,C₅ hydrocarbons was studied,the effects of reaction conditions on the hydrogenation reaction of olefins were investigated.The optimal reaction conditions are reaction temperature of 280°C,reaction pressure of2.5 MPa,hydrogen-oil ratio of 200 and space velocity of 6 h^-1.The olefins are almost completely saturated under this conditions.The evaluation indexes of ethylene cracking feedstock are olefin content,family composition,hydrogen content and BMCI.The olefin content in the hydrogenated products of mixed C₄,C₅ hydrocarbons is less than 1wt%,it can meet the olefin content requirements of ethylene cracking feedstock;n-alkanes content is 55.71 wt%,it is much larger than the n-alkanes content of high quality ethylene cracking feedstock;the hydrogen content of the hydrogenated products of mixed C₄,C₅ hydrocarbons is 17.25 wt%,which is greater than the hydrogen content in the naphtha;BMCI is-3.07,feedstock has good alkyl properties;the hydrogenated products of mixed C₄,C₅ hydrocarbons do not contain impurities such as sulfur,chlorine,arsenic and lead.Therefore,the hydrogenated products of the mixed C₄,C₅hydrocarbons can be used as high quality ethylene cracking feedstock.The preparation of high-octane gasoline components by mixed C₄,C₅hydrocarbons oligomerization reaction was studied.Firstly,isobutylene was used as model compound,and the effects of reaction conditions on olefin oligomerization reaction were investigated.The optimal reaction conditions are reaction temperature of200°C,reaction pressure of 5 MPa and the weight hourly space velocity of 1 h^-1.Isobutylene has good oligomerization effects.The conversion is 88.85%,the liquid yield is 83.92 wt%.Oligomerization reaction of mixed C₄,C₅ hydrocarbons were carried out under the conditions,C₄ olefins are the main reactants,the single pass conversion of C₄ olefins is 46.38%,and the gasoline yield is 9.50 wt%,the superimposed products of mixed C₄,C₅ hydrocarbons are mainly isomeric olefins with higher octane number,the hydrogenated products of the isomeric olefins have higher octane number.Therefore,mixed C₄,C₅ hydrocarbons can be used as feedstock for preparing high octane gasoline component.Three process schemes have different characteristics and advantages.For the catalytic cracking refining scheme of mixed C₄,C₅ hydrocarbons,when they undergo catalytic cracking reaction alone,they have wide product distributions.Coprocessing of mixed C₄,C₅ hydrocarbons and heavy oil can improve propylene and gasoline yield and product properties.For the steam cracking scheme of mixed C₄,C₅ hydrocarbons,the olefins can be sufficiently saturated,the hydrogenated products are high quality ethylene cracking feedstock,and the potential yield of ethylene is relatively high.For the oligomerization scheme of mixed C₄,C₅ hydrocarbons,the superimposed products are mainly isomeric olefins with higher octane number,mixed C₄,C₅ hydrocarbons can be used to prepare high octane gasoline components,however,the first-stage conversion needs further improvement.