| The hydrogenation process of used lubricating oil（ULO）has become the mainstream process for the recycling and resource utilization of ULO due to its economic,environmental and product advantages.However,the metal and chloride in the waste oil will lead to coking blockage of the regeneration equipment and poisoning of the hydrogenation catalyst,which cannot realize the continuous long-term operation of the equipment and seriously affect the production efficiency.Therefore,the core of the industrialization of the hydrogenation process of ULO is to remove the metal and chloride in the ULO by pretreatment,make its content meet the requirements of hydrogenation process,and reduce or avoid the problems of hydrogenation catalyst poisoning,equipment blockage and equipment corrosion caused by HCl in the hydrogenation process.Based on the mechanism of hot cracking metal release and nucleophilic substitution dechlorination,this paper focusing on the thermal stability,pyrolysis mechanism and chemical kinetic energy of organometallic and chlorine-containing additives in used lubricating oil,it combines experiment with simulation.The mechanism and process of efficient demetallization（calcium）and dechlorination of used lubricating oil pretreatment were studied.A continuous and efficient demetallization process of used lubricating oil regeneration pretreatment was proposed for the first time.The coking phenomenon was paid attention to in the pretreatment process,and the main influencing factors and coking mechanism of gas and liquid phase in the pretreatment process were determined by various analytical means.On the basis of this research,a used lubricating oil pretreatment process was developed,and a pilot plant with an annual output of 100 tons/year was established,which achieved continuous and stable operation for 624 hours.The waste lubricating oil treated by this process was verified by hydrogenation process.The main work and conclusions are as follows:（1）Due to the complex composition and many mutual influencing factors of used lubricating oil,the mechanism of thermal metal release cannot be accurately obtained.Calcium dodecyl benzene sulfonate（Ca-DDBS）was used as the model compound for the first time to study the thermal calcium release reaction of used lubricating oil.The intermediate and final products of the model compounds during pyrolysis in air and N2atmosphere were determined by various analytical methods.The pyrolysis mechanism of the model compounds was determined by initio quantum chemical combination method,density universal function theory and pyrolysis kinetics analysis.The results show that the fracture of C-S bond of the model compound leads to the pyrolysis reaction.Using NETZSCH Kinetics NEO software,four model-free analyses（FWO,KAS,FR and viyazovkin）and model-based methods were used to determine the kinetics parameters and transition functions of Ca-DDBS in air atmos.Compared with the four model-free methods,Friedman（FR）and Viyazovkin’s model-free method had a better fitting performance for the experimental data,among which FR had the best fitting performance.It can describe the whole pyrolysis process well.The model-based method shows that the thermal decomposition process of Ca-DDBS can be described by four successive reaction steps,where A→B→C→D follows the second-order reaction（Fn）model.For step D→E,the fitting effect of two-dimensional phase boundary（R2）model is better than that of Fn model.The final solid product of the reaction is the mixture of Ca SO4,Ca SO3 and Ca O,and the gas product is the short-chain alkane,olefin and benzene wash compound.Finally,the decomposition process of the model compound in the base oil was measured.The results showed that the pyrolysis process of the model compound in the base oil was similar to that in the air.（2）Organo-metallic calcium compounds generally exist in the form of colloid in waste oil.In order to get closer to the existence environment of metal calcium demineralization in waste oil and the mechanism of demineralization in waste oil,the pyrolysis characteristics of detergent colloid at different heating rates were studied by TG/DTA,and the kinetics of pyrolysis reaction were determined based on the isotransformation method and main graph method and the kinetic equation was established.The results show that the colloid is relatively stable at temperatures below 120°C.When the temperature rises,thermal decomposition of compounds occurs,and Ca CO3 is the main degradationproduct.Based on such as activation energy conversion method（KAS and FWO）obtainedvalues were 96.67and 100.78 k J/mol,colloid pyrolysis stage 1 and stage 2 kinetic model of pyrolysis reaction may be to Fn mechanism,including phase 1 n=1.39,phase 2 n=0.86.（3）In order to verify the accuracy of the model compound method and provide basic experimental data for the industrialization of demetallization of waste lubricating oil,a pyrolysis continuous demetallization process was proposed.The influence of process parameters such as reaction temperature and reaction time on the thermal release of metal was studied,and the optimum reaction conditions were obtained.After 90 min of continuous heat treatment at 380°C,the metal removal rate of used lubricating oil can reach 99.2%and the metal content is 44 ppm,which meets the metal content requirement of used lubricating oil hydrogenation.The first order kinetic model of thermal release of metal in used lubricating oil was established by tracking metal migration in pyrolysis products.The results of pyrolysis process and pyrolysis products of used lubricating oil are consistent with those of model compounds,which proves the feasibility of the model compound method.（4）To solve the adverse effects of chlorine compounds and coking on the industrialization of used lubricating oil pretreatment,we pay attention to the dechlorination process and coking mechanism of used lubricating oil pretreatment.The coking mechanism of used lubricating oil pretreatment process was deeply investigated by studying the composition characteristics and variation rules of used lubricating oil pyrolysis gas-liquid products.The liquid phase coking product of used lubricating oil is fibrous,which is mainly metal catalytic coking.The demetallization of pyrolysis is completed by the pyrolysis deposition of metal compounds into coke.Gas phase coke is amorphous carbon,which is mainly non-catalytic coke,and metal catalysis has less influence on gas phase coke.When HCl catalyzes coke,it can acidize coke,thus forming acidic sites,which can reduce the zero charge potential of activated carbon and promote the autocatalysis of coke to form new coke products.To avoid equipment corrosion and gas coking caused by chlorine-containing compounds,nucleophilic substitution method was used to remove a large amount of organic chlorides in used lubricating oil,which has significant advantages in dechlorination research.The nucleophilic substitution method,which has obvious advantages in dechlorination,was used to remove a large amount of organic chlorides in used lubricating oil.The effect of dechlorination of used lubricating oil under different conditions was investigated by changing the dosage,heating temperature and heating time.The optimal process conditions of dechlorination were determined as follows:potassium hydroxide was used as dechlorination agent,polyethylene glycol 400 was used as dechlorination agent,the addition amount was 2:2:100,the reaction temperature was 250°C,the reaction time was 4h,and the chlorine removal rate was 97.0%. |
