Study On The Preparation And Decalcification Properties Of Phosphorus-free Grafted Polymer Decalcifying Agent

Crude oil is the most basic and important raw material in current industrial society.But with the increasing global oil consumption,the traditional high-quality crude oil resources are rapidly depleted in recent years.Additionally,the development of the tertiary recovery technology intensified the heavy and inferior of crude oil.These factors all increase the content of calcium ions in crude oil.And the calcium is complex and stable in crude oil,which brings many harms to the refining process of crude oil.At present,the chelate decalcification method is the most popular method for decalcification of crude oil,which is adding a suitable metal chelating agent in the existing electric desalination process to chelate with the calcium ion in the crude oil.And the chelated product is removed with the drainage of electric desalination to achieve the purpose of decalcification.However,there are still some disadvantages in the current chelating decalcifying agents,such as poor applicability,large dosage,low decalcification efficiency,high corrosivity and even containing phosphorus.So developing a chelating decalcifying agent with phosphorus-free environment,low corrosivity and high efficiency has far-reaching significance for petrochemical industry.In this paper,using carboxymethyl chitosan(CMCS),4-hydroxybutyl acrylate(HBA),hydroxypropyl acrylate(HPA),allyl thiourea(ATU),allyl glycidyl ether(AGE),iminodiacetic acid(IDA)as raw materials,the high-performance,phosphorus-free and environmentally-friendly grafted polymer crude oil decalcifying agents CMCS-g-ATUHPA and CMCS-g-AGI-HBA were prepared through the synthesis route design and reaction monomer selection.In this paper,the DPY-2C electric desalination performance test analyzer was used to simulate the industrial process.Meanwhile,the calcium content of pretreatment and desalination of Yichang pipeline crude oil were detected through the ICP-AES.The experimental contents are as follows:(1)For CMCS-g-ATU-HPA,its best synthesis conditions are as following: the molar ratio of ATU,HPA,CMCS was 2:1:1,the reaction temperature was 85°C,the polymerization time was 3.0 h,the initiator dosage was 5 wt%.Besides,the optimal electric desalination parameters are as following: the mass ratio of total agent to calcium was 4:1,the water injection amount was 7 wt%,the first-stage and second-stage electric desalting temperature were 135°C and 130°C respectively.Under these condition,calcium removal efficiency of Yichang pipeline crude oil could reach up to 75.6%.(2)For CMCS-g-AGI-HBA,its best synthesis conditions are as following: the molar ratio of AGI,HBA,CMCS was 3:1:1,the reaction temperature was 85°C,the polymerization time was 3.0 h,the initiator dosage was 7.5 wt%.Besides,the optimal electric desalination parameters are as following: the mass ratio of total agent to calcium was 5:1,the water injection amount was 5 wt%,the first-stage and second-stage electric desalting temperature were 135°C and 130°C respectively.Under these conditions,calcium removal efficiency of Yichang pipeline crude oil could reach up to 81.3%.(3)For composite decalcifying agent,when the mass fraction of CMCS-g-AGIHBA,hydrolytic polymaleic anhydride,hexamethylenetetramine,sulfamic acid,glycine and citric acid were 35%,15%,15%,10%,10% and 15%,respectively,Y18 sample possessed highest calcium removal efficiency for Yichang pipeline crude oil,reached up to 91.8%.In addition,the decalcification test was carried out using the simulated oil of CMCS-g-AGI-HBA decalcifying agent titration,and the chelation mechanism was roughly proposed.In addition,the decalcification mechanism was preliminarily proposed through the experimentation that CMCS-g-AGI-HBA was titrated by the prepared simulated oil.