Study On The Synthesis And Property Of High Density Liquid Fuel Tetrahydrotricyclopentadiene

This dissertation is concerned with the approaches to a new high density liquid fuel, tetrahydrotricyclopentadiene (THTCPD), which can be synthesized with dicyclopentadiene (DCPD) as raw materials by three steps: Diels-Alder reaction, separation and hydrogenation. The main points of the paper are listed as follows.1. Synthesis of tricyclopentadiene (TCPD)Two methods of polymerization were analyzed in the synthesis of TCPD: thermal polymerization of DCPD, Diels-Alder reaction of DCPD and cyclopentadiene (CPD). The results show that the latter was much better then the former. By separating the cracking and addition procedure, the contradiction of two different reaction temperatures was successfully solved. The conversion of DCPD, yield of TCPD and reaction selectivity were much higher then the thermal polymerization. GC analysis results show that only two TCPD isomers were founded in the product. Temperature and pressure has considerable effect on the Diels-Alder reaction. Higher temperature and pressure can speed up the reaction, but excessively high temperature and pressure may lead to the formation of higher oligomers of CPD, such as tetracyclopentadiene (TeCPD), pentacyclopentadiene (PCPD). The higher oligomers were very difficult to be separated from TCPD and the properties of their hydrogenation products were not suitable for liquid fuels, so the reaction temperature and pressure were controlled to prevent the higher oligomers present in the product. The best reaction condition is high pressure and low temperature. Kinetics of the Diels-Alder reaction was measured by experiment with the power exponent equation as following.Solvent effect on the Diels-Alder reaction was analyzed with four different kinds of solvents: benzyl alcohol, cyclohexanone, toluent and decalin. The results show that the rate of the Diels-Alder reaction increased in more polar solvents and stereoselectivity of TCPD decreased. The polarity of DCPD, CPD and TCPD was calculated by Materials Studio 3.0 and the result was: exo-exo-endo-TCPD> endo-exo-endo-TCPD>DCPD>CPD. The effect of solvent on the rate of the Diels-Alder reaction and stereoselectivity can be commonly explained by assuming atransition-state model. They can be related to the free energy difference between the transition states with different solvent. Taking in isolation of dipole, the transition state leading to the greater polarity product will have lower activation energy in greater polarity solvent. Similarly, the polarity of both TCPD isomers is greater then the reagents, this implies an overall rate increase in polar solvents. From these results we know that the main product of TCPD is endo-exo-endo-TCPD. Reaction kinetics with different solvent were as follow.2. Pd-B/γ-Al₂O₃ amorphous alloy catalystThe Pd-B/γ-Al₂O₃ amorphous alloy catalyst was prepared by regular impregnation following the chemical reduction with KBH4 aqueous solution. Its amorphous structure was confirmed by X-ray diffraction. The activity of the as-prepared catalyst was measured by using TCPD hydrogenation as a probe and compared with those of corresponding Pd/γ-Al₂O₃ catalyst obtained by H2 reduction at 300°C. The effects of catalyst precursor calcination temperature, reductant amount, adding speedand and reducing temperature on the catalyst structure and its catalytic activity were also under investigation. Experiment results show that Pd-B/γ-Al₂O₃ amorphous alloy catalyst exhibited higher activity than the corresponding H2 reduced Pd/γ-Al₂O₃. The optimum preparation condition is: calcination temperature 300°C, KBH4 aqueous solution 0.2mol/L, KBH4:Pd2+=3:1(mol), adding speed 0.5mL/min and reducing temperature 0°C.When the as-prepared Pd-B/γ-Al₂O₃ amorphous alloy catalyst was pretreated at the temperature from 150°C to 600°C in N2 flow, the activity of the catalyst decreased with the increase of temperature. According to various characterizations, such as XRD, SEM, TEM, XPS, H2-chemisorption, H2-TPD, DSC and In-suit XRD, it was concluded that the effect of the pretreatment temperature on the activity should mainly attribute to the surface structure changes which was caused by the transformation from amorphous structure to crystalline structure. In-suit XRDanalysis of the catalyst show that its structure remained well after 150°C thermal treatment, the crystalline degree reaches 90% after 450°C thermal treatment and totally crystallized at 600°C.3. TCPD hydrogenation and product propertyHydrogenation material, intermediate product and product were characterized by ¹H-NMR. The results show that the two C=C double bond has different reactive behavior. Compared with the double bond of cyclopentene ring, the double bond of the norbornene ring has much more lower activation energy in the hydrogenation and the main intermediate product is 14,15-DHTCPD.The intrinsic kinetics of TCPD hydrogenation to THDCPD over Pd-B/γ-Al₂O₃ amorphous alloy catalyst was investigated using stirred kettle reactors in the absence of transport limitations over the ranges of temperature 110°C¹40°C and hydrogen pressure 2.0MPa³.5MPa. An Eley-Rideal equation model was proposed to describe the experimental data and its kinetic parameters were also regressed by comparing the calculated and experimental concentrations profiles of reactants and produces. It was found that the theoretical prediction on the concentration by the proposed model agreed well with the experimental data, the average relative error is less than 13%. The activation energy for the first and second reaction step is 11.1141kJ/mol and 34.7217kJ/mol.The characterization results show that THTCPD is liquid at room temperature with density 1.0283g/cm3 at 20°C. The mixture of THTCPD and JP-10 can be used as high density liquid fuel with good low temperature character especially for its low freezing point.