Research On Hydrogenation And Diffusion Of Vanadium-enriched Components In Heavy Oil

With the depletion of conventional petroleum and increasing stringent environmental regulations,residue hydrotreating is becoming one of the most important processes for effective conversion of residuum oils..Residues contain many vanadium compounds,which can deposit and deactivate catalysts for resid hydroprocessing and catalytic cracking..Removal of vanadium is crucial to the processes mentioned above.At present,the research on hydrodevanadication is mostly based on vacuum residue and the results obtained are quite different due to the complicated composition of residue.Furthermore,the vanadium compounds are easily associated with other substances,which leads to a significant effect on their diffusion in the catalyst.In this study,Venezuela vacuum residue was separated into vanadium porphyrin and nonporphyrin enriched components by solvent extraction-column chromatography separation method.The residue and separated fractions are subjected to diffusivity and hydrogenation experiments.Therefore,preliminary understanding of the hydrogenation properties of the two types of vanadium compounds in the oil and the hindered diffusion behavior of the vanadium porphyrin-enrich component of the reduced residue under the reaction conditions are obtained by comparison.In the study of vanadium separation,Acetonitrile is found to be superior to methanol in the extraction of vanadium porphyrins.Vanadium porphyrin-enriched components with polarity of 1.75-2.84 were separated by column chromatography using acetonitrile extracts as raw material.The metal vanadium concentration of vanadium porphyrin-enriched component is up to 6215.91?g/g,which is 21.2 times of the raw material.Both vanadium porphyrin-enriched and nonporphyrin-enriched components followed a first-order kinetic law for HDV reaction,while their mixture vacuum residuum followed a second-order law.The results are consistent with the kinetic lumped theory.By comparison,it reveals that the activation energy of vanadium porphyrin-enriched HDV is much smaller than that of that of nonporphyrin-enriched components,but the reaction rate of the former is larger than that of the later.It indicates that the main resistance of the hydrodevanadic reaction of the vacuum residue is attributed to the nonporphyrin components instead of vanadium porphyrin components.However,the reaction activation energy of vacuum residue is greater than vanadium and nonporphyrin-enriched components,so its hydrogenation performance is worse.By changing the particle size of the catalyst,the intrinsic and apparent kinetic reaction data of the vanadium porphyrin-enriched components are obtained,and the effective diffusion coefficients under the reaction conditions were calculated.The effectiveness factors of HDV for porphyrin-enriched components range from 0.74 to 0.87 and decreases with the increase of reaction temperature.It indicate that a large restrictive diffusion effect is significant under reactive conditions.Furthermore,pore diffusion resistance becomes more important at higher temperatures since a larger increase in the chemical reaction rate due to temperature rise occurs in comparison with that of pore diffusion phenomena.The diameter of the membrane pores was changed and the diffusion behavior of vanadium-enriched porphyrin-enriched components was investigated by membrane pool method.The results showed that the smaller the membrane pore size,the smaller the hindered diffusion factor,and the more serious the hindered diffusion.