中低温煤焦油沥青质的组成和结构调控及加氢定向转化机制研究

Pitch is the main precursor of coke formation during the hydrogenation process of low-medium temperature coal tar. It is easy to deposit on the surface of catalyst because of the condensation of aromatic hydrocarbons and relatively high content of heteroatom in the pitch.Therefore, it is a key step to control the composition and structure of pitch, and to study its change rule and coking mechanism in the process of coal tar hydrogenation. This project aims at selectively breaking the chemical bond during coal pyrolysis, such as Car-Cal, Cal-O and Car-Car and functional groups, to control the structure and composition of volatile matter, and then regulating the quality of pitch. At the same time, the influence mechanism of inherent minerals type in coal and their morphology changing with the varying temperature on the release behavior of volatile matter will be elucidated. After that, ball milling, ultrasonic and extraction method are used to change the composition and structure of coal tar pitch, and the relationship between pitch structure and coke formation are deeply analyzed. To achieve the goal of the orientation reaction of pitch in the hydrogenation process, the temperature and catalyst structure is to be controlled.. Based on that, the basic data and theoretical basis for enhancing the efficient conversion of coal tar pitch during hydrogenation process will be provided.

沥青质是中、低温煤焦油加氢热转化过程中的主要生焦前驱体，富含缩合芳烃和杂原子的结构使其易沉积在催化剂表面而导致催化剂失活，因此调控沥青质的组成和结构以及研究其在反应过程中的变化规律和生焦机理是煤焦油加氢利用过程中的关键环节。项目将从煤中固有矿物质对热解过程中芳香碳-脂肪碳键、脂肪碳-氧键、芳香碳-碳键和官能团C-H、C-O等化学键的选择性断裂入手，采用添加无机组分的方式改变煤热解中挥发分的组成和结构，调控沥青质的品质，同时阐明矿物质种类及形态对沥青质组成和结构的影响规律；通过球磨、超声、萃取等方式干预沥青质的组成和结构，揭示其与生焦行为的关联规律；通过控制温度和催化剂组成与结构干预沥青质的加氢裂解过程，揭示其定向转化的反应历程。这一研究将为煤焦油沥青质的高效转化提供基础数据和理论依据。

本项目通过改变煤热解过程调控沥青的品质和控制加氢条件干预沥青的加氢行为，抑制其在加氢过程中生焦。首先研究了金属离子对新疆中低阶煤热解特性的影响规律，浸渍K+、Ca2+、Fe3+和Ni2+的硝酸盐后，焦油产率不同程度降低，Fe3+对沥青质的抑制效果最明显；以Ni2+为阳离子研究了阴离子对和丰煤热解性能的影响，SO42-同时提高了焦油产率和品质，其它阴离子均抑制了焦油的生成。.通过焙烧、酸洗、负载Zr及活性金属对高岭土进行改性，探究其对低阶煤及其C-O桥键模型化合物苄基苯基醚（BPE）热解行为的影响。700oC焙烧并酸洗后的样品（K-A-700）作用下BPE的转化率最高，继续负载8wt.%Zr时，该值增至94.01%。进一步引入Ni后，二者分别提高了36%和40%。与和丰煤相比，Ni改性高岭土作用下焦油产率和沥青含量降低了29.7%和42.5%，轻油及酚油含量提高了75.0%与55.6%。.中温煤沥青经逐级分离后，各级可溶物中CH类化合物的含量高达60%。沥青及各级不溶物的平均芳环数约为5。与无催化剂时相比，添加NiWS/Al2O3后，环己烷可溶物CHS收率提高了23.32%，沥青质则下降16.21%，且CHS中环烷烃含量从4.88 wt.%到12.73 wt.%增加了1.6倍，沥青质的缩合度增大。反应时间为60 min时CHS收率达最大值55.27 wt.%。与NiWS/Al2O3相比，引入分子筛时，CHS中环烷烃含量不同程度降低。NiWS/Al2O3-USY促进了沥青加氢，当USY的加入量为5%时，残渣量降幅达44.4%。NiWS/Al2O3和NiWS/Al2O3-USY5催化剂作用下，二苯并噻吩的转化率分别达到87 wt.%和91.9 wt.%。当二苯并呋喃为研究对象时，该值分别为61.13 wt.%和70.10 wt.%。