镁基储氢材料结构调控煤热解芳烃加氢选择性的研究

Learning from lattice oxygen in oxygen-storage materials being used for methane oxidation to produce syngas, lattice hydrogen in magnesium-based hydrogen-storage material is used for hydrorefining of coal pyrolysis arenes, such as crude benzene, naphthalene and anthracene. By adjusting the crystal plane direction of MgH2 crystallites and aggregation state (atomic dispersion or nanocluster) of doped transition metal (Ni, Cr, Co, Mo etc.), the adsorption state of arene molecules on material surface can be changed, and the reaction paths (direct hydrodesulfurization, aromatic ring hydrogenation, dealkylation, or olefin saturation) are controlled. Its reaction selectivity is high and operation conditions are mild, thus the coal-based arenes can be processed to superior chemical raw materials. The hydrogen-storage material is prepared by high-energy ball-milling reaction, and anthracite and coal tar pitch are used for nano-confinement to prevent magnesium crystallites from coalescing. 4,6-dimethyl-dibenzothiophen is used as probe molecule, and the analysis of molecular adsorption structure on material surface ( sulfur atom or π bond adsorption) and reaction path employ simulating calculation with software Materials Studio, reaction tracing with tritium, and analysis using combination of high-pressure temperature-programmed adsorption and differential scanning calorimetry, X-ray photoelectron spectroscopy and in-situ Fourier transform infrared spectroscopy. Crystal field theory of directional adsorption of thiophenic molecules and multiscale coupling theory of lattice hydrogen movement and hydrogenation reaction will be established. It will provide scientific basis for material controllable preparation and new process development of arene hydrorefining.

借鉴储氧材料中“晶格氧”用于甲烷氧化制合成气，将镁基储氢材料中“晶格氢”用于粗苯、粗萘、粗蒽等煤热解芳烃加氢精制，通过调整MgH2微晶的晶面择优取向、所掺杂过渡金属（Ni、Cr、Co、Mo等）的聚集态（原子分散态、纳米簇），可改变材料表面芳烃分子的化学吸附态、控制反应路径（直接氢解脱硫、芳环加氢、脱烷基、烯烃饱和），反应选择性高、操作条件温和，可把煤基芳烃加工成优质化工原料。储氢材料的制备用高能球磨反应法，以无烟煤和煤沥青进行纳米限域防止镁晶粒融并，用4,6-二甲基苯并噻吩作探针分子，借助Materials Studio软件模拟计算、氚示踪反应、高压吸附-量热联用、X射线光电子能谱、原位红外光谱，分析材料表面分子的吸附结构（S原子端连吸附、π键吸附）和反应路径，建立噻吩类分子的定向吸附晶体场理论、晶格氢转移与加氢反应的多尺度耦合理论，为芳烃加氢精制材料控制性制备、新工艺研发提供科学依据。

我国高温煤焦油、中低温煤焦油、粗苯的年产量达3千万吨，将煤热解芳烃加氢精制为高质量的化工原料，进而生产高性能的化工新产品，可为煤化工企业带来新的增长点。本项目借鉴储氧材料中“晶格氧”用于甲烷氧化制合成气，将镁基储氢材料中“晶格氢”用于粗苯、粗萘、粗蒽等煤热解芳烃的加氢精制，通过调整氢化镁微晶的晶面择优取向、所掺杂过渡金属（镍、铬、钴、钼等）的聚集态（原子分散态、纳米簇），以改变储氢材料表面芳烃分子的化学吸附态、控制反应路径（直接氢解脱硫、芳环加氢、脱烷基、烯烃饱和），加氢脱硫反应选择性高、操作条件温和，可把煤热解芳烃加工成为优质的化工原料。储氢材料的制备采用高能球磨反应法，以无烟煤和煤沥青进行纳米限域防止镁晶粒融并，用4,6-二甲基苯并噻吩等作探针分子，借助Materials Studio软件模拟计算、氚示踪反应、高压吸附-量热联用、X射线光电子能谱、原位红外光谱，分析了材料表面分子的吸附结构（硫原子端连吸附、π键吸附）和反应路径。.研究结果表明，氢化镁晶体表面噻吩类含硫化合物的吸附结构为硫原子端连吸附，而π键不发生化学吸附，该吸附结构有利于噻吩类含硫化合物选择直接氢解脱硫反应路径，脱硫氢耗低，脱硫效率高达99%以上；反应体系中氢化镁向煤热解芳烃加氢反应供氢，液-固相反应中氢传质高效高，氢化镁晶格氢用于加氢反应消耗氢的同时，通以少量低压氢气，当气相氢压高于氢化镁吸放氢平台压强（250℃时平台为0.3 MPa）时，气相中的分子态氢会不断溶入材料晶格，利用镁易结合氢而不易吸附有机物的特点使之吸氢维持饱和的氢化镁，从而维持动态平衡，材料无需另外加氢再生。建立了噻吩类分子的定向吸附晶体场理论、晶格氢转移与加氢反应的多尺度耦合理论，为芳烃加氢精制材料控制性制备、新工艺研发提供科学依据。