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.

中文翻译：

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1-甲基萘通过闭环系统脱氢溴化可控制地合成高度可石墨化的沥青

通过1-溴萘（1-MNa）的光溴化，然后进行闭环系统脱氢溴化（CSD），成功制备了具有可控软化点和亚甲基桥结构的新型可石墨化沥青。使用气相色谱-质谱，NMR和激光解吸/电离-飞行时间/质谱来确定溴化产物的结构和脱氢溴化沥青。发现引入的溴的量极大地影响了溴化产物的组成。以0.75的溴/ 1-MNa摩尔比（BMNa-0.75）溴化的1-MNa表现出最高的甲基溴选择性（S _mb），它被选作脱氢溴化前体。在200–250°C下进行CSD /聚合反应后，获得了软化点为148–226°C的脱氢溴化沥青。与开放系统脱氢溴化（OSD）相比，CSD赋予了溴自由基更长的寿命，并增强了分子内和分子间的连接，从而显着提高了软化点和焦化值。取决于脱氢溴化温度和引入的四氢萘（四氢化萘）的量，源自CSD的沥青的聚合度是高度可调节的。此外，通过分析己烷可溶成分（HS），检测到甲基迁移产物（萘，2-甲基萘，二甲基萘和三甲基萘）以及氢化产物（主要是四氢化萘）。CSD衍生的沥青的结构特征有助于一些独特的特性，例如高聚合度，低芳香性，连续分子量分布以及亚基（包括α–α'，α–β'和β–β'）之间复杂的连接类型。在大气压下于420°C合成了具有94％各向异性的粗流织构的半焦。发达的石墨碳，石墨化度为81.40％，在2600°C下通过脱氢溴化沥青的石墨化获得的I _D / I _G为0.12。