Thermal Conversion Of Coal Tar Pitch And Molecular Composition Of Its Products

Coal tar pitch(CTP)is of poor properties and limited in application,which has seriously affected the development of the coal tar industry.In order to increase the added value of CTP,the medium and low temperature coal tar pitches from Shan Bei were used as raw material to produce fuel oil by thermal conversion reaction in this paper.The effect of raw material properties and reaction conditions on the composition,distribution and properties of thermal conversion products was investigated.The molecular composition of liquid product was analyzed by GC-MS & FT-ICR MS,and the thermal conversion rules of acidic oxygenates were detected,which can further deepen the understanding of thermal conversion process of CTP.The thermal conversion experiments of CTP were carried out in a stainless reactor capable of withstanding high temperature and high pressure.The effect of raw material properties and reaction conditions on product yield was investigated.The results show that the properties of CTP becomes heavier with the increase of cutting temperatures,the yield of liquid products decreases while the proportion of gasoline and diesel in liquid increases,and the total liquid products yield of separation-reaction operation increases The yield of liquid products,especially the CGO products,increase significantly with the raising of reaction temperature.The effect of prolonging reaction time on product yield is not obvious.The analysis of the composition and properties of the thermal conversion products of different CTPs shows that the methane is the most in the gas products,of which C1?C3 exceed 70%.Among the liquid products,the content of aromatics in diesel oil is higher than that of saturated hydrocarbons.The CGO products have the most resins content and the least saturation content.As the raw material becomes heavier,the content of high-boiling component in CGO increases.Meanwhile,the ash content of the solid products is higher than that of raw material CTP,and the enrichment of sulfur in solid products is higher than that of nitrogen under the same conditions.Nitrogen in the solid products increases and sulfur decreases as the CTP becomes heavier.The analysis of the thermal conversion products under different reaction temperatures and times shows that when raising the reaction temperature moderately,both the hydrogen and carbon compounds in the gas products increase.Along with the increase of reaction temperature,the performance of liquid product becomes worse,both the aromatic hydrocarbons in diesel fraction and the resins in CGO fraction increase.The higher reaction temperature helps to enhance the enrichment of sulfur in solid products and nitrogen in liquid products.The longer reaction time can reduce the volatile content of solid products.The last part is to explore the rule of thermal conversion of acid oxygen-containing compounds in CTP and liquid products by FT-ICR MS.15 types of acid oxygen-containing compounds were detected in CTP,which are O2,O3,O1 and O4 in order of relative abundance.In the process of thermal transformation,it is speculated that the O1 compounds(monophenols)in CTP may occur broken bridge bond and broken alkyl side chain reactions.Most O2 compounds are aryl-diphenols,and the O2compounds(fatty acid)with DBE=1 may occur the reactions of decarbonylation,decarboxylation and dealkylation side chains.In addition,O3 compounds tend to occur condensation coking reactions.Raising the reaction temperature can increase the relative abundance of O3 compounds with high degree of condensation,but it has no significant effect on O1 and O2 compounds.