Controllable Synthesis of Highly Graphitizable Pitches from 1-Methylnaphthalene via Closed-System Dehydrobromination

Abstract

Novel graphitizable pitches with controllable softening points and methylene-bridged structures were successfully prepared through photobromination of 1-methylnaphthalene (1-MNa) followed by closed-system dehydrobromination (CSD). The structures of bromination products and dehydrobromination pitches were determined using gas chromatography–mass spectroscopy, NMR and laser desorption/ionization-time of flight/mass spectroscopy. It was found that the amount of bromine introduced greatly affected the composition of bromination products. 1-MNa brominated at a bromine/1-MNa molar ratio of 0.75 (BMNa-0.75) demonstrated the highest methyl bromination selectivity (S mb), which was selected as the dehydrobromination precursor. After a CSD/polymerization reaction under 200–250 °C, dehydrobromination pitches with softening points of 148–226 °C were acquired. Compared with open-system dehydrobromination (OSD), CSD endowed bromine radical longer life and boosted intramolecular and intermolecular linking, thereby substantially increasing softening points and coking values. The polymerization degree of CSD-derived pitches is highly regulable depending on dehydrobromination temperature and the amount of tetrahydronaphthalene (tetralin) introduced. Moreover, methyl migration products (naphthalene, 2-methylnaphthalene, dimethyl-naphthalene and trimethyl-naphthalene) together with hydrogenation products (mainly tetralin) were detected by analyzing the hexane-soluble components (HS). The structural features of CSD-derived pitches contributed to some unique properties such as high polymerization degree accompanied by low aromaticity, continuous molecular weight distribution and complex connection types among subunits including α–α′, α–β′, and β–β′. The semicoke with 94% anisotropy of coarse flow texture was synthesized at 420 °C under atmospheric pressure. Well-developed graphitic carbons with graphitization degree of 81.40% and I D/I G of 0.12 was obtained from graphitization of dehydrobromination pitches under 2600 °C.

One-Pot Synthesis of Methyl-Substituted Benzenes and Methyl-Substituted Naphthalenes from Acetone and Calcium Carbide

“…MS results shown in Table S1 indicate that, in addition to the five anticipated products, IP, mesityl oxide (MO), diacetone alcohol (DAA), mesitylene, and 3,5-xylenol, seven aromatic compounds are also identified: p -xylene (PX), 2-ethyl-1,4-dimethylbenzene (2-E-1,4-DMB), 2,3,5-trimethylphenol (2,3,5-TMP), 2-methylnaphthalene (2-MN), 2,6-dimethylnaphthalene (2,6-DMN), 2,3,6-trimethylnaphthalene (2,3,6-TMN), and 3,4-dihydro-3,3,6,8-tetramethylnaphthalen-1­(2 H )-one (3,3,6,8-TMNO). The formation of methyl-substituted naphthalenes is surprising and encouraging because they have never been reported in previous studies and are valuable platform chemicals for polymer synthesis. − For example, 2,6-DMN is an important precursor of 2,6-naphthalenedicarboxylic acid (a monomer for polyethylene naphthalate (PEN)). , Generation of methyl-substituted benzenes, methyl-substituted naphthalenes, and 3,5-xylenol confirm that coupling of acetone condensation and subsequent aromatization in one pot is realized in the presence of CaC 2 .…”

Constructing the Bridge from Isotropic to Anisotropic Pitches for Preparing Pitch-Based Carbon Fibers with Tunable Structures and Properties

“…The 1 H NMR spectra of the soluble fractions from the NP precursor and its derived SIP and SNPs with two levels of LC content are shown in Figure 3 . According to the well-established Brown–Ladner procedure 35 and previous similar work, 37 , 38 hydrogen located at a chemical shift of 6–10 or 4.5–6 ppm in the 1 H NMR spectrum is assigned to aromatic hydrogen or alkene hydrogen (i.e., hydrogen on a carbon–carbon double bond), hydrogen distributed at a chemical shift of 2–4.5, 1.1–2, and 0.3–1.1 ppm is ascribed to α, β, and γ aliphatic hydrogen, respectively, and the medium-strength peak at a chemical shift of ca. 1.35 ppm is attributed to the naphthenic −CH 2 –.…”