高分散Ni基催化剂催化浆态床甲烷化性能研究

发布时间：2018-02-25 23:37

本文关键词： 浆态床反应器 CO甲烷化 Ni/SiO_2催化剂 Zr助剂 β-环糊精碳化　出处：《太原理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：甲烷化技术是煤制天然气的核心。采用浆态床反应器可避免固定床反应器中催化剂高温烧结和积炭问题,为甲烷化工艺提供一条新思路。但目前的工业甲烷化催化剂在浆态床中催化活性和稳定性不理想,因此亟需开发一种低温活性好、稳定性高的甲烷化催化剂。负载型甲烷化催化剂上的金属分散度、颗粒尺寸、金属与载体相互作用等均会影响其催化反应性能。本文采用二氧化硅为载体,通过改性浸渍法制备负载型Ni基催化剂,研究助剂ZrO_2、表面活性剂β-环糊精及沉积碳对催化剂结构及催化浆态床甲烷化性能的影响,以期获得高分散镍基催化剂。结合TEM、H_2-TPR、H_2脉冲化学吸附、N2-吸脱附、粉末XRD、in-situ XRD、TG-MS、XPS和CO-TPD等表征手段,深入分析了催化剂结构与浆态床甲烷化性能之间的关系,得出的结论如下:(1)与不含ZrO_2助剂的Ni/Si O_2催化剂相比,添加不同含量ZrO_2改性的NixZr/SiO_2催化剂的镍物种颗粒明显减小,镍物种与SiO_2载体相互作用增强且金属Ni表面积和分散度增大。ZrO_2含量为5 wt%和10 wt%的催化剂具有最优的催化剂结构与物化性质,在反应条件为300°C、1.0 MPa和空速为3000 mL·g-1·h-1下,这两者催化剂表现出相近且最佳的CO转化率,并显著提高了催化剂的稳定性。(2)在优选的ZrO_2含量为5 wt%基础上,添加不同含量的β-环糊精进一步改性催化剂。随着β-环糊精含量的增加,催化剂的比表面积、金属分散度逐渐增加,晶粒及颗粒尺寸逐渐减小。当β-环糊精与金属Ni摩尔比为1:5时制备的Ni5Zr/SiO_2-CD(1:5)催化剂镍物种晶粒及颗粒尺寸最小、金属Ni分散度最高、金属面积最大、活性Ni物种数最多。该催化剂在300°C、1.0 MPa和高空速6000 mL·g-1·h-1的反应条件下,表现出最优的CO转化率和CH4选择性。(3)采用丙三醇水溶液为溶剂,在惰性气氛中焙烧碳化制备Ni基催化剂。其与直接在空气中焙烧的Ni基催化剂相比,沉积碳制备的Ni基催化剂金属与载体相互作用强,活性Ni分散度从3.3%提高到7.1%,Ni颗粒尺寸从30.7 nm减小到14.2 nm且脱附的CO量最大。在300°C、1.0 MPa和高空速6000 mL·g-1·h-1反应条件下,CO转化率和CH4选择性分别达到~93%和91.4%,且反应40 h后催化剂未出现明显失活。
[Abstract]:The methanation technology is the core of the production of natural gas from coal. Slurry bed reactor can avoid the problems of high temperature sintering and coke deposition in the fixed bed reactor. This paper provides a new idea for methanation process, but the catalytic activity and stability of the industrial methanation catalyst in slurry bed is not ideal, so it is urgent to develop a kind of low temperature catalytic activity. High stability methanation catalyst. The dispersion of metal, particle size and the interaction between metal and support on the supported methanation catalyst will affect its catalytic reaction performance. In this paper, silicon dioxide is used as the carrier. Supported Ni based catalysts were prepared by modified impregnation method. The effects of additives ZrOW _ 2, surfactant 尾 -cyclodextrin and carbon deposition on the structure of catalyst and the methanation performance of slurry bed were studied. With a view to obtaining highly dispersed nickel-based catalysts, the relationship between the structure of the catalyst and the methanation properties of slurry bed was deeply analyzed by means of Tem H2-TPRH _ 2 pulse chemisorption and desorption, powder XRDin-in-situ XRDU TG-MSMSX XPS and CO-TPD, etc. The conclusion is as follows: (1) compared with Ni/Si O\ -2 catalyst without ZrO_2 promoter, the nickel species particles of NixZr/SiO_2 modified with different content of ZrO_2 decreased obviously. The interaction between nickel species and SiO_2 support was enhanced, and the surface area and dispersion of Ni were increased. The catalyst containing 5 and 10 wt% of ZrO2 had the best structure and physicochemical properties. The reaction conditions were 300 掳C ~ (-1) 1.0 MPa and 3 000 mL 路g ~ (-1) 路h ~ (-1) space velocity. These two catalysts showed similar and optimum CO conversion, and significantly improved the stability of the catalyst. 2) on the basis of the optimized ZrO_2 content of 5 wt%, With the increase of 尾 -cyclodextrin content, the specific surface area and metal dispersion of the catalyst increased. When the molar ratio of 尾 -cyclodextrin to metal Ni is 1: 5, the Ni _ 5Zr / Sio _ 2-CDO _ (1: 5) catalyst has the smallest grain size and particle size, the highest metal dispersion and the largest metal area. The catalyst showed the best CO conversion and CH4 selectivity under the reaction conditions of 300 掳C ~ (-1) 1.0 MPa and 6000 mL 路g ~ (-1) 路h ~ (-1). Ni-based catalysts were prepared by calcination and carbonization in inert atmosphere. Compared with Ni-based catalysts calcined directly in air, Ni based catalysts prepared by deposition of carbon interact strongly with the support. The particle size of active Ni decreased from 30.7 nm to 14.2 nm and the amount of CO desorbed was the largest. The CO conversion and CH4 selectivity reached 93% and 91.4% respectively under the reaction conditions of 300 掳C ~ (-1) 1.0 MPa and 6000 mL 路g ~ (-1) 路h ~ (-1) of high altitude velocity, and the catalytic activity was 40 h after the reaction. No obvious inactivation was found in the chemical agent.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE665.3;O643.36

【相似文献】