Study On Catalytic Conversion Of Naphthenic Acids

The crude oil with high-neutralization number has the advantage of abundant reserve and low price; however, it hasn't been processed widely because of its serious corrosivity to the refinery equipments during the conventional process. The direct catalytic cracking method seems to be a feasible route which could avoid the corrosion and simultaneously shorten the processing procedures. The two-stage riser fluid catalytic cracking (TSRFCC) process offers flexible controllability through which reaction depth could be controlled effectively, therefore shows advantages in processing high acid crude oil. This research would verify the feasibility of high acid crude oil TSRFCC industrial test.In this work, the thermal and catalytic conversion of naphthenic acids was carried out in fixed bed flow reactor, and the effect of different catalysts(acid catalysts and alkaline catalysts), temperatures, catalyst weights and weight hourly space velocity(WHSV) on deacidification was investigated. The experimental results showed that, reaction temperature is the primary factor affecting thermal treatment deacidification but the thermal treatment has slight effect on deacidification, the acid removal rate only reached 40% even at 560°C. The solid acid catalysts showed better effect on deacidification than base catalysts, the industrial solid catalysts CORH and LTB-2 both exhibited 100% of the acid removal rate. In the context of experiments, temperatures, catalyst weight and WHSV have little effect on deacidification, even at the low temperature of 400°C or the catalyst weight of 3 or WHSV of 12h-1 naphthenic acids can also be effectively removed, the acid removal rate is 99.42%, 99.42%, 99.55% respectively. Moreover, decresing reaction temperature or increasing catalyst weight favored the H2O formation during the deacidification process, while the WHSV has little effect.The deacidification reaction of mixtures with different diesel-naphthenic acids proportions over CORH catalyst was also investigated. The results demonstrated that the existence of diesel oil did not affect the conversion of naphthenic acids on solid acid catalyst. Therefore, the direct catalytic cracking of crude oil with high-neutralization number is a feasible route for dealing with the corrosion problem. Moreover, the results of micro-reactor and in-situ FT-IR analysis indicated that decarboxylation and decarbonylation reactions of naphthenic acids took place readily before -C-C bond cleavage of the resulting hydrocarbon radicals. Furthermore, with solid acid catalysts and MgO, naphthenic acids removal proceeded mainly via catalytic deacidification, but with CaO neutralization was also responsible for naphthenic acids removal.XTL-5 pilot plant results showed that lower reaction temperature, modest ratio of catalyst to oil, shorter residence time are the suitable 1st operation conditions aim at keeping virgin diesel fraction of the Sudanese crude oil as much as possible. 1st reaction at 480oC, catalyst to oil ratio of 6, residence time of 1.1s; 2nd at 520oC, catalyst to oil ratio of 7.5, residence time of 1.8s, the yields of gasoline and diesel are 35.39% and 19.52%, meanwhile the yields of propylene and butylene can also achieve 9.28% and 9.90%.