Study On Atmospheric Pressyre Pyrolysis Of Several Substitute Components Of Gasoline

At present,about one-third of my country’s petroleum is used forautomobile fuel consumption.While automobiles bring us travel convenience,the exhaust gas produced brings harm to the environment and human health.In order to solve the energy shortage and reduce the pollution of automobile exhaust,it is necessary to develop clean and efficient engines and conduct in-depth research on the combustion reaction kinetics of gasoline.In order to simulate the combustion behavior of gasoline,the current mainstream method uses alternative fuel methods.This paper selects five typical gasoline substitute components n-heptane,isooctane,toluene,methylcyclohexane and 1-hexene for research.In terms of experiments,the atmospheric jet stirred reactor pyrolysis experimental platform was designed and built,and vacuum ultraviolet photoionization mass spectrometry technology combined with gas chromatography was applied to the experimental platform.This experimental platform has the advantages of high heating temperature（～1500 K）,uniform temperature zone,and high reliability.It can be used to carry out pyrolysis and oxidation experiments.There are two types of detection instruments:gas chromatograph and time-of-flight mass spectrometer.Compared with time-of-flight mass spectrometry,chromatograph can better distinguish some isomers,such as t-2-C₄H₈,n C₄H₈,i C₄H₈,c-2-C₄H₈ Four kinds of butene,propadiene and propyne.Nearly 20 species were detected in all five pyrolysis systems using this device.The temperature range of the experiment was750-1150 K,the pressure was 1 atm,and the initial mole fraction of fuel was about2500 ppm.In terms of the kinetic model,this paper builds a five-componentgasoline alternative fuel containing n-heptane,isooctane,toluene,1-hexene and methylcyclohexane based on the detailed mechanism of the predecessor’s second-grade cyclohexane.Chemical reaction kinetic model;and using Hy Chem modeling method,a simplified model containing 118 species and 831 reactions was obtained.The performance of the two models was verified by the experimental results of this paper,and the two models can make reasonable predictions on the experimental results.The kinetic simulation was carried out by Chemkin software,and the generation rate analysis and sensitivity analysis of the simulation results revealed the main reaction paths in the pyrolysis process of five fuels.The results of the kinetic analysis showed that isooctane and 1-hexene The initial decomposition temperature is close to about 850 K,n-heptane is about 900K,and methylcyclohexane starts to decompose at about 930 K.When the temperature is low,n-heptane,isooctane,and methylcyclohexane are mainly consumed by hydrogen abstraction reaction,and 1-hexene is mainly decomposed by C-C bond dissociation reaction due to the double bond.As the temperature increases,the contribution of consumption through the C-C bond dissociation reaction becomes greater,which is the main contribution to the pyrolysis process of isooctane and 1-hexene.In addition,the main products of the five groups of experiments（H₂,CH₄,C₂H₂,C₂H₄,a C₃H₄,p C₃H₄,C₃H₆,1,3-C₄H₆,1-C₄H₈,i C₄H₈ and C₆H₆）were also subjected to detailed path analysis and sensitivity analysis.The main reaction paths and carbon chain structure in the pyrolysis of the five components affect the formation of aromatic hydrocarbons.H₂ and CH₄ are mainly derived from the hydrogen abstraction reaction involving H/CH₃.The source of C₂H₂ is the decomposition of p C₃H₄ and C₂H₃.The production of C₂H₄ is mainly related to n C₃H₇,p C₄H₉,and C₂H₅.a C₃H₄ and p C₃H₄ are related to a C₃H₅.C₃H₆ comes from the recombination reaction of a C₃H₅ and hydrogen atoms,theβscission of the C-C bond of free radicals formed by fuel dehydrogenation,and the addition reaction of butene and H atoms.In 1-hexene,the single-molecule decomposition reaction of fuel directly generates C₃H₆,while in the pyrolysis of isooctane,propylene also comes from i C4H9 and i C₃H₇ generated by the decomposition of the parent body.1,3-C₄H₆ is generated through C₄H₇ It is produced by dehydrogenation,and in methylcyclohexane and 1-hexene,1,3-C₄H₆ can be obtained by the decomposition of generated olefin radicals.The formation of 1-C₄H₈ and i C₄H₈ is related to the fuel structure.Chain alkanes are easy to generate 1-C₄H₈,while branched alkanes are easy to generate i C₄H₈.C₆H₆ mainly comes from the reactions of C₁+C₅,C₂+C₄,C₃+C₃,cyclohexane dehydrogenation and C₅H₅CH₂ isomerization.