Vacuum Residue Thermal Cracking: Product Yield Determination and Characterization Using Thermogravimetry-Fourier Transform Infrared Spectrometry and a Fluidized Bed Reactor

To make full use of heavy oil by thermochemical conversion, the thermal behaviors of vacuum residue (VR) were investigated first by thermogravimetry Fourier transform infrared spectrometry (TG-FTIR) and then via a laboratory-scale fluidized bed reactor (FBR). The TG FTIR results showed that the changes in the absorbance of volatiles during thermal cracking were consistent with the weight loss in the derivative thermogravimetric curve. The dynamic information about the release profiles of the typical gaseous products such as CO, CO2, CH4, C2H4, light aromatics, and aliphatic olefins revealed the cleavage of varied structures and functional groups of VR at different temperatures. Moreover, the peaks for the maximum releasing rate on the evolving profiles of gaseous products became narrower and sharper, and the yield at maximum releasing rate for the gaseous species increased with increasing the heating rate. The pyrolysis experiments in a FBR with silica sand as a heat carrier showed that alkenes were the dominant gaseous products, with light olefin selectivity higher than 53%. The coke/Conradson carbon residue ratio was lower than that in the delay coking process. Furthermore, analysis of liquid oil using gas chromatography/time-of-flight mass spectrometry showed that 1-alkenes was the most abundant decomposition product and the selectivity of total olefins from C-6 to C-22 was 62.74%.