Influence Of Asphaltenes On Coke Formation In Hydrotreating Of Residue/Coal Tar Blend System

With blend system of Merey atmospheric residue(MRAR)and Yulin middle/low temperature coal tar(CTAR)as material,reaction behavior and characteristics of coke of hydrotreating were investigated in the autoclave under different mixing ratio,reaction temperature and time.Then the influence of MR-Asp,CT-Asp and CT-TI on the hydrotreating reaction and coke was studied in the blend system.In order to better reveal the mechanism of influence on the coke of asphaltene,SEM,TG,~1H-NMR,FT-IR,SAXS and XRD characterization means were used to analyse the asphaltene and coke.The results showed that in the blend system of MRAR and CTAR,with the increase of CTAR content,the light oil yield of the system showed a trend of increasing first and then decreasing.When the content of CTAR was 30wt%,the light oil yield reached the maximum;The yield of coke also showed a trend of increasing first and then decreasing.When the content of CTAR was 30wt%,the ratio of deposited coke to total coke was about 81%.When the content of CTAR was 70wt%,the total coke yield reached maximum value and the ratio of deposited coke to total coke was about 12.6%.When the content of CTAR was 30wt%,with the increase of the reaction temperature and the reaction time,the yield of light oil and coke both increased.At the same time the suspended coke decreased gradually,while the deposited coke showed an increasing trend.The effects of different asphaltenes and their content on coke formation in blend system were investigated.When the blend system did not contain asphaltene or CT-TI,the coke yield was relatively small.The asphaltene was the main source of coke in the blend system.For this blend system,with the increase of MR-Asp or CT-Asp,the coke yield both gradually increased.The coke produced by MR-Asp mainly existed in the form of deposited coke while the coke produced by CT-Asp mainly existed in the form of suspended coke.In the CTAR system,CT-TI had a certain inhibition of coke formation,but in the blend system,CT-TI significantly increased the coke yield.In the blend system,due to the interaction between MR-Asp and CT-Asp,the aromatic average diameter the aromatic rings and the average number of aromatic rings/aromatic layer in the average molecular structure both increased,and the size of asphaltene association increased obviously which promoted the phase separation of the reaction system.So as the reaction severity increased,the amount of coke in the reaction system showed a trend of increase;Moreover,the decomposition temperature of coke produced by blend system was higher,which indicated that the degree of condensation of coke was greater.With the increase of CTAR content in the blend system,the particle size of coke produced in the reaction system became smaller.When the CTAR ratio was over 50wt%,the coke mainly existed in the form of suspended coke,while the deposited coke was little.