金属改性HZSM-5催化重整胜利褐煤热解挥发分研究

发布时间：2018-10-24 10:27

【摘要】：热解是褐煤等低阶煤提质利用的重要途径之一。但褐煤热解焦油中重质组分占比大且含氧量高,严重制约其储存和利用。褐煤焦油轻质化制备BTEXN等轻质芳烃是褐煤热解加工亟待解决的关键技术之一。本论文在下坠式管式反应器中对胜利褐煤热解挥发分进行原位催化重整,以在温和条件下裂解重质组分为目标研究焦油的轻质化,为褐煤热解定向制备轻质芳烃新工艺的开发提供理论依据。本论文首先通过热重手段采用非等温法模型获得了胜利褐煤热分解的动力学参数,考察了反应温度和停留时间对热解产物分布的影响,详细分析了热解焦油的化学族组分组成。等转化率KAS和FWO模型拟合得到热分解的活化能分别为292.7和277.6 kJ/mol。温度是影响褐煤热解的主要因素,当温度为600 oC,停留时间为1.0 s时,焦油达到最大产率21.4%(daf)。焦油中气相色谱/质谱联用仪可检测的族组分有含氮有机化合物(ONSs)、含氧有机化合物(OOSs)、含硫有机化合物(OSSs)、脂肪烃和芳烃,其中OOSs和芳烃分别占族组分的50.0%和28.9%。实验选用HZSM-5作为催化剂,通过浸渍法制备了Co、Mo和Ni改性的HZSM-5催化剂,考察了催化剂对褐煤热解挥发分的催化作用。用X射线衍射仪、物理吸附仪、化学吸附仪、傅立叶变换红外光谱仪和透射电子显微镜等对制备的催化剂进行了表征。当热解挥发分经HZSM-5催化裂解后,气体产率增加,焦油产率减少,重整焦油在600 oC达到最大产率11.9%。在600 oC下HZSM-5催化重整焦油中芳烃含量占族组分的87.3%,而OOSs含量只占8.1%;BTEXN的产率达到16.1 mmol/g,相比于非催化条件下BTEXN的含量增加了3.0倍,这是由于HZSM-5分子筛具有特殊孔道和酸性位,煤热解挥发分产物在经过HZSM-5作用后发生催化裂化、烯烃烷烃的芳构化以及酚脱羟基反应,从而生成了较多的BTEXN。由于活性金属位和酸位的共同作用,Co、Mo和Ni改性的HZSM-5具有更高的催化性能,在600 oC下催化重整焦油中芳烃分别占族组分的90.5%、88.8%和94.2%,焦油中BTEXN等轻质芳烃的产率分别达到33.0、26.6和39.7 wt.%,是HZSM-5重整焦油中产率的2.1、1.7和2.6倍。其中Ni/HZSM-5具有最好的催化性能,催化产生的轻质芳烃产率最高,且催化产生的H2占热解总气体量的62.7%,说明Ni/HZSM-5催化剂可作为褐煤催化热解挥发分重整制备轻质芳烃及富氢气体的潜在催化剂。
[Abstract]:Pyrolysis is one of the important ways to improve the quality of low rank coal such as lignite. However, the storage and utilization of lignite pyrolytic tar is restricted because of its large proportion of heavy components and high oxygen content. The production of light aromatic hydrocarbons such as BTEXN from brown coal tar is one of the key technologies to be solved in pyrolysis of lignite. In this paper, the pyrolysis volatilization of Shengli lignite was studied by in-situ catalytic reforming in a falling tubular reactor, and the light weight of tar was studied under mild conditions. It provides a theoretical basis for the development of a new process for the directional pyrolysis of lignite to produce light aromatics. In this paper, the kinetic parameters of pyrolysis of Shengli lignite were obtained by non-isothermal method by thermogravimetry. The effects of reaction temperature and residence time on the distribution of pyrolysis products were investigated, and the chemical composition of pyrolytic tar was analyzed in detail. The activation energies of thermal decomposition obtained by KAS and FWO models were 292.7 and 277.6 kJ/mol., respectively. Temperature is the main factor affecting pyrolysis of lignite. When the temperature is 600 oC, residence time is 1.0 s, the maximum yield of tar is 21.4% (daf). The group components that can be detected by gas chromatography-mass spectrometry in tar are nitrogen-containing organic compounds, (ONSs), oxygen-containing organic compounds, (OOSs), sulfur organic compounds, fatty hydrocarbons and aromatics, of which OOSs and aromatics account for 50.0% and 28.9% of the group components, respectively. Co,Mo and Ni modified HZSM-5 catalysts were prepared by impregnation method with HZSM-5 as catalyst. The catalytic effect of the catalyst on volatile matter of lignite pyrolysis was investigated. The catalysts were characterized by X-ray diffraction, physical adsorption, chemical adsorption, Fourier transform infrared spectroscopy and transmission electron microscope. When the pyrolysis volatiles were pyrolyzed by HZSM-5, the gas yield increased, the tar yield decreased, and the reforming tar reached the maximum yield of 11.9 at 600 oC. At 600 oC, the aromatics content in HZSM-5 catalytic reforming tar accounted for 87.3% of the group fraction, while the yield of OOSs content reached 16.1 mmol/g, which was 3.0-fold higher than that of BTEXN under non-catalytic conditions, which was due to the special pore and acidic potential of HZSM-5 molecular sieve. Catalytic cracking, aromatization of olefin alkanes and phenol dehydroxylation of the volatile products of coal pyrolysis take place after the action of HZSM-5, resulting in the formation of more BTEXN.. Because of the interaction of active metal site and acid site, Co,Mo and Ni modified HZSM-5 have higher catalytic performance. At 600 oC, the aromatics in the tar of catalytic reforming accounted for 90.588% and 94.2% of the group fraction, respectively. The yields of light aromatics such as BTEXN in tar reached 33.00.26.6 and 39.7 wt.%, respectively, which were 2.11.7,2.6 times higher than those in HZSM-5 reforming tar, respectively. Among them, Ni/HZSM-5 has the best catalytic performance and the highest yield of light aromatics. The hydrogen produced by the catalyst accounts for 62.7% of the total pyrolysis gas, which indicates that the Ni/HZSM-5 catalyst can be used as a potential catalyst for pyrolysis of lignite to prepare light aromatics and hydrogen rich body.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD849.2;TQ530.2

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