Conclusions
The proposed residue cracking gasification (RCG) process could
realize hierarchical utilization of petroleum residue via co-producing
liquid oil and H2-rich syngas. Fundamental study of residue
cracking and coke gasification was conducted using vacuum residue
(VR) in a fluidized bed reactor to provide technical support
of the RCG process. A self-made bifunctional catalyst (BFC) with
catalytic activity of both reside cracking and coke gasification
was specially designed and compared with commercial FCC catalysts.
The liquid yield was only about 50 wt.% over fresh FCC and
BFC catalysts due to their excessive cracking acidity. Hydrothermal
treatment of FCC and BFC could obtain moderate activity for VR
cracking. As a result, the liquid yield could reach 80 wt.%, with
the corresponding conversion ratio to be over 95% through properly
selected catalyst-to-oil ratio and reaction temperature. Gasifying
the formed coke (i.e., catalyst regeneration) via steam produced
high-quality syngas with a total H2 and CO concentration of above
80 vol.%. The corresponding gasoline fraction was up to 55 wt.%
and diesel of 30–40 wt.%, with no or a few percentage of heavy
oil fractions in the cracking liquid.
The BFC showed obviously better catalysis to the coke gasification
by steam, and the regeneration time of BFC shortened about
50% compared with that of FCC, justifying the bifunctional characteristics
of BFC. Considering the technical requirements of the RCG
process, VR cracking and in turn gasification of its deposited coke
(i.e., catalyst regeneration) was conducted in an alternative way.
For the hydrothermally treated catalysts, the cracking performance
was found to decrease at some extent in the first cycle of catalyst
regeneration, but after two times of regeneration both catalysts
tended to have stable activity for VR cracking. Thus, the hydrothermally
treated FCC and BFC would maintain their stable activity in
the RCG process. The self-made bifunctional catalyst had both catalytic
effects for petroleum residue cracking and coke gasification,
preliminarily demonstrating the feasibility of its utilization for the
RCG process