| The environment problems have been received much more worldwide concern in the 21st century. As the development of the economy and the progress of science and technology, some environmental standards which were difficult to meet in the past have been realized today. In order to adapt to the trend of ultra-low diesel sulfide, the existing technology must be changed, it has become an urgent and important task. The existing hydrodesulfurization technology(HDS) is cost too much and needs a very rigorous reaction condition, so it is hard to achieve a further need. The oxidative desulfurization with its mild reaction condition, simple process, low cost and high desurfuriztion efficiency has been obtained a lot of attention as a prefer method. This paper uses a model diesel fuel as objects. The factors and the oxidatvie desulfurization performance of H2O2/HCOOH, H2O2/CH3COOH and H2O2/HCOOH/ultrasonic system are investigated respectively. The oxidative reaction kinetics of H2O2/HCOOH system are studied, the reagent costs of H2O2/HCOOH and H2O2/CH3COOH system are contrasted as well.The following are the main points of the paper: Six different kinds of acids are compared with their catalytic effect useing H2O2 as oxidant. The H2O2/HCOOH system show a better catalytic effect than others under the conditions of V(model diesel)/V(H2O2)/V(Acid) of 10/1/1. At the same reaction conditions, the desulphurization rate of H2O2/CH3COOH system is only 50%.The optimal condition of the oxidative desulfurization using H2O2/ CH3COOH system is:reaction temperature 40℃,V(model diesel)/V(H2O2)/ V(CH3COOH) from 10/1/3 to 10/1/4, reaction time 150min, no extraction. Under this conditon, the desulfurization rate is between 90% and 95%, S mass fraction of the model diesel fuel can decrease from 1142μg·g-1 to 60-114μg·g-1.Oxidation of model diesel fuel with H2O2/HCOOH system was investigated, and the organic sulfur compound DBT is removed efficiently from diesel fuel under condition of reaction temperature 40℃, V(model diesel)/V(H2O2)/V(HCOOH)=100/1/10, reaction time 1h, no need to extraction, S remvoal rate can reach 99%, S mass fraction of the model diesel fuel can decline to 10-20μg·g-1 that is conformity with the Euro IV Emission Standard.The reagent costs were estimated under the optimal conditions of oxidative desulfurization using H2O2/HCOOH system and H2O2/CH3COOH system. According with the market prices of hydrogen peroxide, formic acid and acetic acid, the reagent cost of H2O2/HCOOH system to deal with 1 ton of diesel is 835 RMB, and the H2O2/CH3COOH system requires 2086 RMB. The H2O2/HCOOH system is better than H2O2/CH3COOH system whether on the removal efficiency or the reagent cost. But the reagent cost of H2O2/HCOOH system is still high, a further study on recycleing of catalyst is necessary.Ultrasonic is used to enhance the mass transfer of aqueous phase and organic phase of H2O2/HCOOH system. The desulfurization rate can reach 80% in 10 min under the proper condition of V(model diesel)/V(H2O2)/V(HCOOH) =100/1/15, ultrasonic frequency 28kHz, ultrasonic power 400w. No need of external heat, the temperature of the system can rise to 56.6℃after reaction.The kinetics was also analysed. HPLC, IR and HPLC-MS were used to determine the molecular structure of reaction product. The results show that DBT is oxidated into DBTO and DBTO2 by H2O2, and the reaction process as follow:Some hypotheses have been drawn to simplify the real reaction:a. The mass transfer between two phases can be ignored as the strring rate is high enough to emulsify aqueous phase and oil phase; b. DBT is totally oxidated into DBTO2; c. The reaction can completely since the H2O and DBTO2 which are hydrophilic transfer into aqueous phase immediatly after generation; d. H2O2 is exceed.According with the hypotheses, the equation can be refined as follow: The results show that:a. The reaction is an endothermicreaction, the rate constants k will increase with the temperature rising. At 40℃,k=6.45×10-2 mM1-n·min-1; b. The reaction order n is close to 1, at 40℃, n=1.0462; c. Between 30-40℃, reaction activation energy Ea=42.14 kJ·mol-1, frequency factor A=6.94×105mM1-n·min-1.Through the reagent dosage proportioning changed, the LncDBT vs t also show a linear relation when n is 1 as setting value. This indicates that the kinetics factors can be applied in practice. |
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