Contents lists available at ScienceDirectFueljournal homepage: www.elsevier.com/locate/fuelFull Length ArticleModif i ed ef f ect on properties of mesophase pitch prepared from various two-stage thermotreatments of FCC decant oilBin Lou a,1 , Dong Liu a, ? ,1 , Yu Qiu a , Yue Fu b , Shuhai Guo c , Ran Yu a , Xin Gong a , Zhichen Zhang a ,Xiaoyu He da State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao, Shandong 266580, People’s Republic of Chinab China National Of f shore Oil Corporation, Beijing 100010, People’s Republic of Chinac Institute of Applied Ecology, Chinese Academy of Sciences, People’s Republic of Chinad Sinopec Zhenhai Ref i ning & Chemical Company, Zhenhai 315200, People’s Republic of ChinaA R T I C L E I N F OKeywords:Vacuum treatmentExcessive condensationSub-fractions interactionStructural featureSpinnabilityA B S T R A C TThe comparative study of dif f erent two-stage heat treatments was conducted to illustrate the modif i ed ef f ects onimproving yield and spinnability of mesophase pitch. In such two-stage thermotreatments, a pressured con-densation is employed to involve low-molecular-weight species into the formation of mesogens, thereby in-creasing pitch yields. Subsequently, vacuum polymerization could contribute to rapid development of meso-phase and then reduce the residence time. The results indicate that the short duration could decrease occurrenceof the intramolecular aromatization and intermolecular polymerization reactions that are readily induced byelimination of α-methyl and dehyroaromatization of naphthenic rings during the later stage of heat treatment.Consequently, the formed semi-rigid molecules in QS sub-fraction (i.e., fusible component) are seldom trans-formed into rigid ones mainly constituting QI sub-fraction (i.e., infusible component). Ultimately, suf f i cient QSsub-fraction, with a higher average M w and a large amount of short alkyl and naphthenic substituents, is morelikely to completely dissolve QI sub-fraction. Thus, the resultant mesophase exhibits an excellent fusible de-formability. Besides, the structural feature of semi-rigid oligomer could somewhat loosen molecular associationof layered stacking and contribute to the slippage between stacked mesogens due to its steric ef f ects, therebydecreasing the softening points of mesophase pitch. Above modif i ed ef f ects are easily implementable during asuitable process of two-stage thermotreatment, such as the processes of preparing MP-4-0.01-1.0, MP-4-0.005-1.0 and MP-3-0.01-2.0 in this study. It is worthwhile to mention that the vacuum treatment is required to beconducted prior to large-scale coalescence of mesophase spheres in order to obtain spinnable mesophase pitch.1. IntroductionCarbon f i bers (CFs) and their composites have been attracting muchattentions in many f i elds. The immense interest stems from their out-standing properties of light weight, high strength, corruption resistanceand fatigue resistance et al. [1–3]. In comparison with the prevalentpolyacrylonitrile based carbon f i bers, enhanced features of mesophasepitch-based carbon f i bers (MPCFs) include low expansion coef f i cient,high stif f ness and excellent thermal conductivity. These features makethem irreplaceable in aerospace engineering, aviation, high-end in-dustrial equipment, et al. [4,5]. The extraordinary performances ofMPCFs are strongly dependent on its precursor, namely mesophasepitch. The properties of mesophase pitch don’t only determine the meltspinnability (fusibility or viscosity at spinning temperature) but alsosubsequent thermoset reactivity and carbonized behavior of spun f i ber[6–9]. Mesophase pitch is a liquid crystalline formed by parallelstacking of quasi-planar polyaromatic hydrocarbons (i.e., mesogen)with a polydisperse molecular-weight [10]. It demonstrates a potentialas an inexpensive and high-carbon-yielding precursor for structuralcarbon f i bers. Before such potential realizing, a simple preparativeprocedure for spinnable mesophase pitch with high pitch yield is cri-tical for the commercial production of mesophase pitch from somepetroleum or coal pitches.In the past decades, UCC company [11] f i rst patented the most ty-pical process to prepare mesophase pitch from A240 pitch, beingpolymerized at a relatively low temperature of 370–390 °C for 17–20 hhttps://doi.org/10.1016/j.fuel.2020.119034Received 22 June 2020; Received in revised form 5 August 2020; Accepted 18 August 2020? Corresponding authors.E-mail address: liudong@upc.edu.cn (D. Liu).1 These authors contributed equally to this workFuel 284 (2021) 119034Available online 26 August 20200016-2361/ © 2020 Elsevier Ltd. All rights reserved.T
