Hydrogen (deuterium) donor effects and isotopic effect in substractions cracking in residue
供氢(氘)剂在减压渣油四组分裂化中的作用及其同位素效应

Four subfractions (saturates, aromatics, resin and asphaltene, SARA) from Liaohe vacuum residue (LHVR) were cracked in the thermal, hydrothermal and catalytic hydrocracking system without or with detuerated tetralin and tetralin in a high-pressure microreactor. The effects of D-donor, H-donor and molecular hydrogen on the cracking reaction of SARA were investigated. The results show that asphaltene is the major precursor of coke, and resin could produce some coke in thermal cracking. However, aromatics can hardly result in coking, and saturates is not precursor of coke compared with asphaltene and resin. In the hydrothermal cracking and catalytic hydrocracking systems, the trend of coking of SARA could be decreased by participation of molecular hydrogen, especially in the catalytic hydrocracking system. Three hydrogen sources including D-donor, H-donor and H_2 could decrease the formation of coke and asphaltene of SARA, especially the first two donors. D-donor and H-donor have the similar effect on the cracking and condensation of SARA. However, there is clear isotopic effect between H-donor and D-donor based on the difference of donation ability at same condition. The stable isotope study shows that C-H bond scission of tetralin or C-D bond scission of detuerated tetralin is incorporated into the race-controlling reaction pathway in the cracking systems of SARA. The degree of isotopic effect shows the race-controlling reaction pathway depended on the reaction system. The isotopic effect in thermal cracking system was clearest among the hydrothermal cracking and catalytic hydrocracking systems as a result of the change of race-controlling reaction pathway of thermal cracking of SARA by molecular hydrogen and dispersed catalysts.