Study On The Segmented Catalytic Pyrolysis Characteristics Of Waste Tire And The Comprehensive Application Of Pyrolysis Products

In recent years,due to the rapid development of the domestic automobile industry and the transportation industry,the domestic yield of tire had been ranked in the forefront of the world for ten consecutive years.Waste tires belong to the polymer elastic solid waste,which has the properties of solubility resistance,heat resistance,biodecomposition resistance,mechanical wear resistance,bacteria-carrying,and a large poison amount-carrying.And the massive accumulation of waste tire also lead to the occupation of land,as well as the pollution of enviroment.At present,pyrolysis was regared as one of the most efficient and environment-friendly means for recycling waste tires.In this paper,experimentally study had been done on the optimization of pyrolysis process of waste tire.As the most important content,the optimaloperation conditions in the process of segmented catalytic pyrolysis of tire rubber powders had been determined by studying the influences of reaction temperature,catalyst type and dosage on the yields distribution of high-value products generated via segmented catalytic pyrolysis process.The determination of optimal pyrolysis parameters provided favorable theoretical support for the large-scale and economical application of waste tire pyrolysis.The main research results were listed as follows:（1）The individual pyrolysis and catalytic pyrolysis characteristics of tire rubber powder were clarified,and the main weight loss stages were attributed to the thermal decompositions of NR and BR-SBR,respectively.The pyrolysis kinetic equation and pyrolysis activation energy under different catalysts and mixing ratios were analyzed using Coats-Redfern integration method.It was found that when the n values of Avrami-Erofeev equation were 2/3and 3/4,the pyrolysis reaction of WT was able to be more accurately described.,the correlation coefficient R²varied within 0.97～0.99,hence the fitting degree was high,and the average pyrolysis activation energy of tire was about 174.79 k J·mol^-1.When the Co Cl₂,Mg O,Ca CO₃and Ni Cl₂were employed as additions,the overall average pyrolysis reaction activation energy varied within 132.53～171.24 k J·mol^-1.Among the additions above,Co Cl₂was able to effectively reduce the pyrolysis reaction activation energy by up to 81.9 k J·mol^-1during the BR-SBR pyrolysis stage,Secondly,the precipitation characteristics of the pyrolysis products generated from WT with different catalysts,were analyzed based on FT-IR,and it was found that solid acid-base catalysts and transition metal chlorides such as Co Cl₂and Ni Cl₂had promoted the formation of benzene series.（2）The basic catalytic pyrolysis experiments had revealed that lower temperature was beneficial to generate pyrolysis carbon,the yield of liquid phase products achieved the largest value within medium temperature range（500℃～550℃）,and the yield of gas phase products always increased with the pyrolysis temperature.The distributions of the pyrolysis products at different temperature levels were compared,and it was found that the components of pyrolysis gas at both lower and higher temperature levels were mainly CH₄and H₂,and the gas yield increased with the pyrolysis temperature.The liquid component at lower temperature level were dominated by aliphatic hydrocarbons,the maximum proportion of which was up to 70%;at highertemperature level,the gas component was dominated by aromatic hydrocarbons,the yield of which increased with pyrolysis temperature,and the nitrogen and sulfur compounds of polluting products decreased with the increase of pyrolysis temperature.The study on the effects of different temperatures,catalysts and blending ratios on the distribution of liquid components had revealed that,transition metal chlorides at lower temperature was able to effectively improve the yield of aromatic compound in pyrolysis oil,and the yield increased with the mixed ratio of transition metal chlorides,while the pollution products yield did not change much.When the Ni Cl₂was blended with mass ratio of 30%,the amplification of aromatics yield achieved the maximum of 45.32%;the yield of D-limonene increased by 10.79%compared with the original condition when the Na OH was blended with mass ratio of 50%.Within the higher temperature range,the yield of high-value products such as toluene and xylene in the aromatic components achieved the maximum of 69.84%when Na OH was blended with mass ratio of 30%.When the transition metal chlorides were employed as addtions instead of Na OH,the generation of aromatic components was also promoted during the pyrolysis process,and the mass ratio of PAHs increased more significantly.The minimums of pollutants emission with different additions was compared as:30%COCl₂（27.31%）>10%Ni Cl₂（22.56%）>30%Na OH（7.38%）.Comprehensive analysis indicated that in the primary mixed pyrolysis stage,the best catalyst among the ones employed in the research was Na OH,the high-value products yield corresponding to the high-temperature and low-temperature stages were both relatively higher,and the yield of pollutants were relatively lower.（3）During the secondary stage of ectopic catalysis,the effects of temperature on the gas-liquid two-phase yield and liquid products distribution characteristics,had been investigated.It was found that the products distribution characteristics of ectopic catalysis and mixed catalytic pyrolysis were basically the same,and secondary cracking occurred in the high-temperature pyrolysis stage,more gas molecules were generated,and the gas-phase yield increased with temperature.;while the yield of aromatics via staged catalytic pyrolysis increased with pyrolysis temperature,and achieve the maximum yield of 85.84%at 600°C.It was found that ZSM-5 was able to catalyze and reform the volatiles in the primary stage,and improved the yield of light aromatics in the liquid phase.The effect of ZSM-5 addition ratioson the distribution characteristics of pyrolysis products was investigated,and it was found that the yield of aromatics increased with the addition ratio of ZSM-5;with higher catalysis temperature in the secondary stageand more ZSM-5 addition,the proportion of aromatic components in the liquid component was higher,and the yields of high-value products such as toluene and xylene were also increased.（4）The results of carbon black modification experiments showed that the quality of pyrolysis carbon black was the best and the specific surface area was the largest when the pyrolysis temperature was 550℃.The activation modification effect of hydrochloric acid was better than that of sulfuric acid.The optimal modification path was vibration frequency of190r/min,modification temperature of 40℃and addition of 1mol/L hydrochloric acid solution.After modification,the specific surface area was 9.0952E+01 m²/g and pore volume was 4.8281E-02 cm³/g,the aperture was 2.1234nm.