Reiji Aizawa

Decomposition of chlorofluorocarbons in the presence of water over zeolite catalyst

Abstract The decomposition of chlorofluorocarbons (CFCs) in the presence of water was examined over a variety of solid acid catalysts. More than 40% of the conversion of CFC was observed on HY zeolite, H-mordenite, H-ZSM-5, γ-Al2O3, and SiO2 TiO2 catalysts, and the selectivity to CO and CO2 was nearly 100% except on γ-Al2O3. Although the H-mordenite had the highest activity among the tested catalysts, it was gradually deactivated during the reaction due to the elimination of Al atoms from the zeolite framework. A good relationship was found between the reactivity on H-mordenite and the bond energy of C Cl in compounds of CCl4, CCl3F, CCl2F2, and CClF3, suggesting that the rate controlling step was the cleavage of the C Cl bond.

Decomposition of chlorofluorocarbons on TiO2ZrO2

The decomposition of chlorofluorocarbons (CFCs) in the presence of water was examined over a variety of solid acid catalysts. The TiO2ZrO2 catalyst was found to have the highest activity and longest life among the catalysts examined. The activity of the TiO2ZrO2 catalysts depended upon the content of TiO2. At the contents of TiO2 from 58 to 90 mole%, the TiO2ZrO2 catalysts exhibited high activity, and these catalysts were proven to contain TiZrO4 crystal. From the study of the XRD peak intensity of the TiZrO4 crystal, it was highest on the TZ-58 which contained 58 mole% of TiO2, and decreased with increasing the content of TiO2. Furthermore, the conversion of CFC113 measured at 673 K was highest at TZ-58, and decreased gradually with increasing TiO2 content. Therefore, the TiZrO4 crystal influences the activity of decomposition of CFC113. However, the TiO2ZrO2 catalyst was gradually deactivated during the reaction due to the elimination of titanium atoms. A good relationship was found between the activity on TiO2ZrO2 catalyst and bond energy of CCl in the compounds of chlorofluorocarbons and hydrochlorocarbons, suggesting that the rate controlling step was the cleavage of CCl bond.

Catalytic activity of oil-soluble molybdenum compounds for heavy oil hydrotreatment.

Catalytic activity of several oil-soluble molybdenum compounds was tested for upgrading low-quality heavy oil by high pressure thermalhydrotreatment.Reactions were performed by use of an autoclave of 300m1 capacity at temperature 470°C, reaction time 10min., initial hydrogen pressure 100kg/cm2 and stirring rate 1, 500ppm.Venezuela Morichal crude (S 4.19wt%, N 0.67wt%, V 463ppm, Ni 100ppm, C5-insoluble asphaltenes 17. 5wt%) was used as a feed.Molybdenumdithiophosphates, which are usually used as lubricant oil additives, were found to show high activity for sulfur and vanadium removal. Their activity was further enhanced by the addition of oil soluble cobalt compounds. The role of P and S in the activity enhancement for Mo catalysts was investigated with a variety of combinations of oil-soluble Mo, Co, P and S compounds. It was revealed that the addition of P compounds is essential for vanadium removal and the coexistence of P and S is effective for the removal both of sulfur and vanadium. Recycle use of the Mo-Co-P-S catalyst, which could be recovered as a solid matter, resulted in a gradual decline of activity. However, even after 3 to 4 recycle uses, its activity was still higher than the initial activity of conventional Co-Mo-Al2O3 catalyst.

Heavy Oil Hydrotreatment Using Dispersed Mo-based Catalyst. Effectiveness of Hydrogen Transfer Desulfurization with Tetralin.

The effectiveness of hydrogen transfer desulfurization (HTD) in heavy oil hydrotreatment was investigated using tetralin as a hydrogen donor solvent. Reactions were carried out at reaction temperatures 410 and 450& using a batch reactor with varying the initial hydrogen pressure.Three different catalysts, namely a highly active dispersed Mo-Co-P-S (I), another kind of dispersed Mo-Co-P-S which was severely poisoned by excess phosphorus (II) and CoMo/Al2O3, were utilized. Parallel experiments using decalin, a poor hydrogen donor, were also performed to compare with the results using tetralin.The results with the catalyst (I) revealed that at low hydrogen pressure the HTD did function effectively but at a higher pressure, i.e. at an initial hydrogen charge of 80kg/cm2 or higher, no advantageous effect of tetralin addition was observed. The effectiveness of HTD seemed to depend upon such catalyst functions as dissociative adsorption of molecular hydrogen and dehydrogenation of solvents.Both of the devanadization and the coke-forming reactions were largely affected by hydrogen pressure, and at 80kg/cm2 of initial charge the results of reactions with tetralin were almost the same as those with decalin, irrespective of the kind of catalyst used. This indicates the reaction sites for those reactions are different from the sites for desulfurization.

Kinetics of Catalytic Hydrodesulfurization of Fuel Oil in Trickling Packed Bed Reactor

灌液充填層方式による重油の水素化接触脱硫反応について, 水素の油への溶解, 細孔拡散, 真の化学反応などの過程を考慮して速度式を導いた。温度370～420℃。圧力51～131ataでカフジ残渣油の脱硫実験を行ない, 脱硫の化学反応は油中の硫黄濃度に関して2次であることをみとめ, 全圧の影響についても検討を行なった。