Deep Desulfurization Of Diesel Oil By Coupled Oxidation-adsorption Based On Low Titanium Loading Titania-silica Materials

Sulfur oxides will be produced during the combustion of sulfur-containing oil products,which will cause environmental pollution problems such as acid rain and haze,which seriously threaten human health.With the continuous improvement of quality standards for sulfur content in fuel oil,how to achieve high selective sulfur removal under mild conditions has become a research hotspot in this field.Coupled oxidation-adsorption desulfurization technology combines oxidation desulfurization and adsorption desulfurization properly,which can achieve high selective sulfur removal under mild conditions.In this paper,titanium silicon materials with low titanium loading were designed and synthesized,which showed excellent desulfurization performance in diesel system at room temperature.The reaction kinetics of sulfide catalytic oxidation process was further studied,and the mechanism of the process was revealed.In this paper,titanium silicon materials with low titanium loading were synthesized by excessive solution impregnation method and applied to coupled oxidation-adsorption desulfurization of diesel oil.Compared with the same type of transition metal catalysts reported in the literature,the materials in this paper have comparative advantages in the catalytic oxidation of DBT(TOF).The adsorption of DBTO₂ in real diesel conforms to the Langmuir adsorption isotherm model,and the adsorption saturated sulfur capacity at room temperature is 7.08 mg/g.Further tests show that the selectivity of DBT in coupled oxidation-adsorption process is much higher than(100 times)aromatics in diesel oil;the desulfurization performance of the material can be maintained by 97%after five desulfurization/regeneration cycles under real diesel oil conditions;the sulfur content of 10ppm in diesel oil can be reduced to 0.8 ppm.It is proved that the material has good desulfurization performance.In this paper,chemical titration based on hydrogen peroxide chemisorption and other characterization methods were used to characterize the amount and distribution of catalytic active sites on the surface of titanium silicon materials with low titanium loading.The results showed that the more dispersed active sites could be formed when the titanium loading was low,and the catalytic active sites(uncoordinated saturated titanium)accounted for about 22%of the total loading.Although the increase of the loading amount increased the number of active sites,the catalytic efficiency per unit Ti loading decreased due to the decrease of the proportion of active sites(reduced to 6%).The reaction kinetics of catalytic oxidation desulfurization process was explored by adjusting the temperature,oxidant concentration,sulfide concentration and type,catalyst consumption and other parameters.The results show that the oxidation rate of DBT in this system conforms to the pseudo-first-order kinetics model,and the oxidation rate increases with the increase of temperature,and increases exponentially with the increase of catalyst dosage,but is less affected by the changes of sulfide concentration and oxidant concentration.The kinetic constants of different sulfides in the catalytic oxidation process are as follows:DBT>4,6-dmdbt>BT>thiophene.Through the study on the kinetics of catalytic oxidation desulfurization process and other characterization,this paper innovatively proposed the process of titanium peroxide intermediate:the titanium with low coordination number in the catalyst first undergoes one-step fast reaction to form titanium peroxide coordination intermediate,and then reacts with sulfide,and the catalytic active center enters into the next catalytic oxidation process after the reduction product is desorbed.Based on the kinetic model of the coordination intermediate hypothesis,the apparent reaction order of the coordination intermediate is 1.7,so the rate equation of the total reaction is:r=k[A^*]^1.7[DBT].