Researches On Accurate Methods And Related Certified Reference Materials For Nickel Vanadium Sulfur Elements In Crude Oil

Crude oil is the raw material of many chemical products.Some harmful substances,such as nickel,vanadium,sulfur elements,will have a negative impact on the refining process of crude oil,leading to an increase of refining costs and a decline of intermediate products and final products quality.Therefore,it is necessary to accurately determine the content of harmful elements in crude oil,developing certificated reference materials（CRMs）to support the implementation of national standards.This thesis mainly studies the accurate measurement methods of nickel,vanadium and sulfur in the crude oil,and develops crude oil certificated reference materials,which are of great significance to the quality monitoring and control of petroleum.In this paper,four kinds of crude oil samples with different origins and element contents were selected.Three different pretreatment methods（dry ashing,microwave-induced combustion,microwave digestion）were used to digest samples.The results of three pretreatment methods were compared,and the microwave digestion method was showed as the most effective pretreatment method of crude oil.By optimizing the pre-treatment conditions（sample quantity,acid system,microwave digestion procedure,etc.）of microwave digestion,four different crude oil samples were completely digested.The measurement repeatability of important harmful elements（Ni,V,S）in the four crude oils is less than 2.8%.Inductively coupled plasma spectroscopy（ICP-OES）was used to measure samples with different concentrations of elements.The accurate measurement of three different elements can be achieved.The ICP-OES results of two certified reference materials for fuel oil and crude oil showed that the recovery rates of three elements were between 97%and 104%,which shows that the method of microwave digestion combined with ICP-OES for the determination of Ni,V and S elements in crude oil is accurate and reliable,with less sample loss and high precision.The method can be used for the quality control of harmful elements in crude oil and other oil materials of a similar matrix,and the certified value of corresponding reference materials.Through a large number of studies,Russian crude oil with better quality was selected as the candidate of CRMs.The contents of S,Ni and V in the crude oil were certified by ICP-OES and AAS methods among NIM and other qualified collaborating laboratories.The results show that crude oil CRMS have good stability and stability.The certified values and expanded uncertainties of Ni,V and S are 4.05±0.14 mg·kg^-1,5.48±0.17mg·kg^-1,5.00±0.27 g·kg^-1,whose relative expansion uncertainty are 3.7%,2.9%,5%.The successful development of certified reference materials for important harmful elements in crude oil can be used for calibrating instruments and verificating analytical methods of crude oil elements content,which will facilitate the monitoring and control of domestic crude oil quality and meet the domestic market demand.