Study Of The Effect Of Petroleum Pitch On Mesophase And The Structure Of Coke Of Coal Tar Pitch In Carbonization Process

The structure of mesophase microspheres was a key factor for the formation of semicoke(SC). In order to acquire large number of mesophase microspheres, it is most important to explore the scientific laws and study on the proportion of petroleum pitch(PP) and coal tar pitch(CTP) and the effect of external conditions on the formation of mesophase. So as to improve the ordering of SC and needle coke which has widely application in many fields, such as the high and ultra high power electrode in high-temperature electric arc furnace steelmaking, due to its low thermal expansion coefficient, high density, good conductivity and higher mechanical strength. The widely application of needle coke in these aspects, not only significantly reduce the energy consumption and contribute to energy conservation and emissions reduction and other economic significance, but also more realistic significance for us, due to the coal is the main energy in our country. China is a power country of coal production and consumption. About 2-3 wt.% coal tar pitch will be in the deep processing of coal such as coking process. Furthermore, it can realize the use of science and effective allocation of resources via high efficient utilization of coal tar pitch. It has important significance for adding value of the coal, and extending industry chain of coal processing, promoting the sustainable development of coal chemical industry, optimizing the structure of the coal industry.In this paper, CTP and PP were selected as raw material for investigation. By means of co-carbonizing the mixture of PP and RCTP which was removed quinoline insolubles by electric field method in different condition. Effects of proportion of PP(mpp/(mpp+mRCTP)), temperature, pressure, heating rate, holding time and mechanical vibration on the structure and the formation of the mesophase were studied. Furthermore, the properties of modified pitch(MP) produced from different proportion of brominated petroleum pitch(BPP) and RCTP in the presence of benzoyl chloride(BC) were researched. On this basis, examines the influence of the modification conditions on the ordered structure of semicoke and coke and the properties of modified pitch(MP).The properties of BPP obtained from PP and Br2 with different reaction time, and RCTP, PP, TP( obtained from the optimal experimental conditions) and the structure of semicoke and coke were explored by FT-IR spectrometry elemental analysis, 1H NMR, thermogravimetry, viscometry, X ray diffraction(XRD) and Scanning electron microscope(SEM). The research results are as follow:1. On the basis of mechanical vibration, the size distribution and the quantity of MCMB were changed with the increasing of proportion(mpp/(mpp+mRCTP)). With the increase of ratio, this change is embodied in the size distribution concentrated in smaller size. According to the traditional statistical method, the MCMB was reached 100% when the proportion was 40%, and the particle size distribution was mainly in the range of 0.1 to 2.0 μm. It was indicated that we can control the size distribution of MCMB and raise its production through improve the carbonization process.2. Mesophase were perfect uniform under pressure 0.5 MPa, heating rate 2 ℃/min, temperature 410 ℃ for 4 h. The fiber structure and graphitization degree coke were also increased under the condition temperature 550 ℃, heating rate 2 ℃/min, holding for 3 h.3. Results demonstrated a distinct difference in the orientation structure of the typical synthesized pitch(TP), which produced from 10 wt % BPP in the mixture of BPP and RCTP and brominated for 6 h and reacted 10 h in the presence of 5 wt.% BC at 130 ℃. Moreover, the microstructure and the lattice parameters, such as d002 and Lc of SC from TP were better than those of the other SCs. The content of anisotropic group increased to 83%, and the d002 was the lowest, reached 0.3432 nm.4. Compared with the PP, new peak at 670 cm-1 assigning to C-Br stretching vibration appeared in BPP, suggesting Br was successfully introduced into PP. The mainly differences is that the intensity of the absorption peak at 670 cm-1, which is attributed to the stronger stretching vibration of C–Br in BPP-6 obtained from bromination time 6 h than 3 h and 9 h. The reasonable explanation is that the reaction time 6 h is more appropriate. Through elemental analysis and 1H NMR for TP, the results shown that the hydrogen content declined by 0.87%, the carbon content increased about 0.27% and the ratio of H/C increased to 0.7 after modification. Moreover, the proportion of aromatic hydrogen increased to 79.6%. These results indicated that appropriate amount of BPP(approximately 10 wt%(mBPP/(mBPP+mRCTP))) in the mixture of BPP and RCTP can promote the development of mesophase macromolecule. Fused ring structure and the degree of polymerization would increase after the modification. This would lead to form larger aromatic compounds. The heat behaviors of TP samples were characterized by thermogravimetry(TG). It was found that TP had a better thermal stability and its carbon yield was increased by 12% compared with RCTP and the viscosity of TP is slightly lower than that of RCTP. It will be more conducive to the formation and development of mesophase, which lay a foundation to form orderly structure of coke.