Conversion of V-porphyrin in asphaltenes into V2S3 as an active catalyst for slurry phase hydrocracking of vacuum residue

Abstract

The asphaltene hydrocracking (HCK) was carried out at 693 K and 11.0 MPa H2 to examine the phase transformation of V species contained in the asphaltene and the catalytic activity of the resulting V compounds in the HCK. The V K-edge X-ray absorption near edge structure spectroscopy (XANES) was employed to identify the V species dispersed in the asphaltene and the phase transformation with respect to the HCK conditions. The V in asphaltene was observed as a form of the vanadyl-porphyrins (VO-porphyrin) that was converted into V2S3 during the HCK in the presence of tetralin, whereas the VO-porphyrin was not converted fully into the V2S3 in the absence of tetralin due to its isolation within a coke. In addition, the catalytic activity of V2S3 formed from VO-porphyrins in the asphaltene was confirmed by an increase of H2 consumption and asphaltene conversion in the recycle tests of the vacuum residue (VR) HCK at 693 K and 11.0 MPa H2 in the presence of tetralin. The intrinsic catalytic activity of the dispersed V2S3 in the VR HCK was measured at 693 K and 11.0 MPa H2 in presence of the model V precursor of 0.113 mmol VO(acac)2, exhibiting a TOFT of 0.080 s−1 and the asphaltene conversion of 30%. The XANES and TEM analysis confirmed that the V precursor undergoes transformation into nano-scaled V2S3 particles in course of the VR HCK. Therefore, it was demonstrated that the VO-porphyrin in asphaltenes can be converted into the dispersed V2S3 catalysts during the VR HCK.