Preparation And Application Of Carbon Fibers Derived From Hydrogenated Coal Tar Pitch

Coal tar,a by-product from coal thermal conversion,is an important chemical resource with high content of asphaltene component and various organic molecules.On average,the production capacity of coal tar in China is over 20 million tons every year.Up to now,how to efficiently make use of coal tar remains a big challenge.In this thesis,we have made efforts to develop a new process for converting high temperature coal tar to hydrogenated pitch(hydro-pitch,HP)and value-added liquid products by hydrogenation process.With HP as the starting material,high quality mesophase pitch(MP),pitch-based carbon fibers and heterojunction carbon nanofibers were fabricated,separately.Our results may help to pave a new way for the effective use of coal tar.The main results are summarized below.Based on the properties of raw material and the product requirements,a series of catalysts are designed.Then,full-fraction high temperature coal tar is successfully hydrogenated by fix-bed reactors,getting high yield of light oil and aliphatic hydrogen-enriched pitch component.The obtained liquid products could be used as aircraft oil or blend oil,while it could also be conducted to produce high quality gasoline or diesel oil after deep treatment.The as-made hydrogenated pitch features high content of alkyl side chain and large aromatic structure,therefore,it is considered as good precursor to produce carbon materials.Using the obtained HP,MP is synthesized,in which the content of mesophase is close or even reached to Japanese naphthalene-based MP.Then,pitch-based carbon fibers(the diameter,tensile strength and modulus are 10.3 ?m,1634 MPa and 120 GPa,separately)are faribricated by wet-spinning method,of which the parameters have exceeded domestic products,even close to Japanese naphthalene-based carbon fibers.A new kind of coaxial heterojunction carbon nanofiber(CNF)is produced from PAN/HP blend precursors by electrospinning method,and such CNFs are employed as electrodes in dye-sensitized solar cells(DSSCs),super capacitors(SCs)and SIBs.In DSSCs,a power conversion efficiency of 6.92%has been achieved,which is higher than that of Pt CE(6.34%).In SCs and SIBs,the CNFs are applied in form of free-standing membranes,without any binder and conductive agent,and excellent electrical-chemical performances both at high and low rates are achieved.In SCs,the specific capacitance reaches to 220.7 F g-1 at 1 A·g-1,and it maintains to 167.0 F·g-1 even at 10 A·g-1.In SIBs,the specific capacity at 0.1 and 1 A·g-1 are 408 and 236 mAh·g-1,respectively.PAN-based carbon shell provides abundant heteroatom,defects and large interlayer space,which benefit the catalytic reactions and ion storage process.At the same time,pitch-based carbon core effectively reduce the loss of electron,improve the charge transmission efficiency.Therefore,such CNFs deliver outstanding electrochemical performances in different cells.