Separation And Characterization Of Inferior Heavy Oil-derived N-Heptane And N-pentane Asphaltenes And Study On Pyrolysis Kinetics

The asphaltenes have the strongest relative average molecular,associating properties and polarity.Well,it also has the highest components of hetero atom.In the production and processing of heavy oil,using the asphaltenes to solve the problems such as blockage from the deposit.According to the definition of the asphaltenes,asphaltenes are insoluble in low relative molecular mass's n-alkanes?n-heptane and n-pentane?and soluble in toluene.This paper contrasts n-heptane and n-pentane for comparing with related components.At first,this paper uses n-heptane and n-pentane as precipitant and the method of column separation.Then,separates vacuum residuum into saturates,aromatics,colloid and asphaltenes.After that,they has CHONS main elements characterization.The results show that n-pentane asphaltenes are 13%higher than n-heptane asphaltenes,and this part of the substance which enter the saturation is soluble in paraffin.These two kinds of precipitant of colloid and aromatics content are basically the same.And FTIR and XRD testing-pictures for these asphaltenes show that they do not have obvious differences in functional group structure.Then n-heptane asphaltenes and n-pentane asphaltenes are soluble in toluene and their density are measured under different temperature.By the test,the asphaltenes had good linear relationship between solution concentration and density.Through linear regression extrapolation,the intrinsic density of the asphaltenes can be gotten.They both have the same dependence on temperature.It means that the chemical structure are the same.And n-heptane asphaltenes have the lower density than n-pentane asphaltenes,this indicates its space packing is closer and the rejection of asphaltenes and n-heptane is stronger in the process of precipitation.Under nitrogen atmosphere protection,using thermogravimetric analyzer for SARA four components under 10,15,20,25 k/min^-1 heating rate,respectively.TGA study the thermal decomposition behavior of n-heptane and n-pentane SARA four components.The results turn out that the TG and DTG curves can be found that initial weightlessness temperature of four components are about at 500k,the maximum weight loss rate of the four components are at about 750k.Thermal stability of the asphaltenes is significantly higher than the other three components.Corresponding transformation temperature of components from low to high:saturation<aromatics<colloid<asphaltenes,which indicates that saturates,aromatics just need relatively low temperatures reaching to certain cracking conversion,so,the heat transfer reaction activity of saturates and aromatics is greater than the colloid and asphaltenes.Using the Distributed Activation Energy Model?DAEM?and the same conversion of Fiynn-wall-Ozawa?FWO?Model to calculate the pyrolysis dynamics,the results show that the activation energy of FWO analysis method and the DAEM method is calculated in almost same way.Decomposition of each composition line fit with the first kinetics,the Activation Energy of the four components is between 50kJ/mol to 250kJ/mol,and the relative activation energy of the four components is asphaltenes<aromatics<saturation<colloid.The lowest temperature to achieve the same conversion is saturation,the others are aromatics,colloid and asphaltenes,respectively.