Residue upgrading using dispersed catalysts prepared in reverse micelles

• Main Author: Duangchan, Apinya
• Format: Others
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/8481

Previous studies of slurry phase reactors for residue oil upgrading used dispersed metal sulfide catalysts, prepared by in situ decomposition of either FeSO4 or the naphthenate salts of Co, Mo and Ni, that were mixed with the residue oil. However, the size of the catalyst particles was not well established and a high dispersion of the catalysts in the oil was not always achieved. Recent studies have shown that catalysts prepared in reverse micelles can be well characterized and have particle sizes in the nm range. In the present study, catalysts prepared in reverse micelles were investigated as model catalysts for residue oil upgrading, to study the effects of metal type, particle size and dispersion on residue oil upgrading. Fe, Co and Mo catalysts were prepared in n-hexane/PE4LE (polyoxyethylene-4- lauryl ether), decalin/PE4LE, toluene/DDAB (didodecyldimethylarnmonium bromide), and tetrahydrofuran/DDAB microemulsions, using nitrate salts of Fe and Co, and MoCI5. The metal catalysts were prepared by reduction of the metal ions with N2H4.XH2O or LiBH4. The size of metal particles prepared in the n-hexane/PE4LE microemulsions was measured using transmission electron microscopy (TEM). The size of the catalysts was in the range 5-8 nm and decreased in the order: Mo > Fe > Co. The size of Co particles prepared from Co/PE4LE/n-hexane with various water/PE4LE ratios was in the range 5.1-5.9 nm, but no trend of increased particle size with increased water/PE4LE ratio was apparent from these measurements. The catalysts prepared in microemulsions using different solvents were sulfided in situ in the reactor. The performance of the colloidal catalysts for residue oil upgrading was determined in a batch reactor operated at 430°C, in 5%H2S/95%H2, at an initial pressure of 500 psig and a reaction time of 1 h. The dispersion of the metal catalysts in the residue oil was studied by mixing the residue oil with the metal catalysts prepared in reverse micelles. The amount of metal catalyst recovered in the asphaltene fraction of the residue oil was measured. A high catalyst content of the asphaltenes was taken as a measure of good dispersion of the catalysts in the asphaltenes. There was no significant difference in dispersion of metal catalysts prepared in hexane, decalin, toluene or tetrahydrofuran based microemulsions. Hence, any effect of microemulsion solvent on hydroconversion activity could be ascribed to the chemical properties of the solvents rather than catalyst dispersion effects. Residue oil hydroconversion using different metal catalysts prepared from different microemulsions using different solvents, showed a significant effect of metal type and solvent. Mo was superior to Fe and Co for suppression of coke and gas formation. Coke yield from decalin/PE4LE microemulsions was 5.8%, 6.2%, and 7.1% for Mo, Co and Fe, respectively. Mo provided the highest MCR and S conversions but lowest asphaltene conversion. Hence, it was concluded that Mo was a better hydrogenolysis catalyst whereas Fe and Co were better hydrogenation catalysts at the conditions of the present study. Hydrogen donor ability was important for residue upgrading and the choice of microemulsion solvent had a detectable effect on catalyst performance. Mixed CoMo and NiMo catalysts showed lower coke yield than the Co catalyst (5.0% for CoMo and NiMo compared to 6.2% for Co) and lower than that of Mo (5.8%). A synergistic effect of the CoMo and NiMo catalysts was observed for MCR conversion and coke yield. Cobalt naphthenate catalyst precursor gave higher conversions of MCR and S, and a comparable >525°C fraction conversion but gave lower asphaltene conversion than the Fe, Co, and Mo catalysts prepared in microemulsions. === Applied Science, Faculty of === Chemical and Biological Engineering, Department of === Graduate