Ni晶粒粒径对Ni/SiO_2催化月桂酸甲酯脱氧制烃性能的影响  

Influence of Ni crystallite size on deoxygenation of methyl laurate to hydrocarbons over Ni /SiO_2 catalyst

作　　者：韩蒙蒙[1] 代吉才 陈吉祥[1] 

机构地区：[1]天津大学化工学院催化科学与工程系天津市应用催化科学与工程重点实验室,天津300072 [2]河北泊头职业学院,河北泊头062150

出　　处：《燃料化学学报》2014年第8期958-965,共8页Journal of Fuel Chemistry and Technology

基　　金：国家自然科学基金(21176177);天津市自然科学基金(12JCYBJC13200)

摘　　要：采用等体积浸渍-干燥-还原法及等体积浸渍-干燥-焙烧-还原法制备了3种具有不同Ni晶粒粒径的Ni/SiO2催化剂,利用H2-TPR、XRD、TEM、H2-TPR、NH3-TPD及TGA技术对其及前驱体进行了表征,并在固定床反应器上评价了其催化月桂酸甲酯脱氧制十一烷(C11)和十二烷(C12)的性能,分析了Ni晶粒粒径对其脱氧性能的影响。结果表明,采用等体积浸渍-干燥-还原法制备的催化剂中Ni晶粒粒径较小,提高还原温度可以促进Ni晶粒长大。随Ni晶粒粒径增大,月桂酸甲酯的转换频率提高,而C11和C12总选择性、C11/C12物质的量比及裂解产物选择性降低,Ni/SiO2催化剂上月桂酸甲酯脱氧为结构敏感反应。此外,还考察了重时空速对Ni/SiO2催化剂脱氧性能的影响,随重时空速提高,月桂酸甲酯转化率、C11和C12总选择性、C11/C12物质的量比及裂化产物选择性降低。月桂酸甲酯通过脱羰/脱羧反应路径生成的CO/CO2几乎全部加氢转化为CH4,表明Ni/SiO2催化剂具有很高的甲烷化活性。研究还发现,较小Ni晶粒烧结、有机物种吸附及积炭会导致催化剂失活。Three Ni / SiO2 catalysts with different Ni crystallite sizes were prepared by the incipient wetnessimpregnation-drying-reduction and incipient wetness impregnation-drying-calcination-reduction methods. Thecatalysts were characterized by H2-TPR, XRD, TEM, H2 chemisorption, NH3-TPD and TGA techniques. Theircatalytic performances in the deoxygenation of methyl laurate to undecane （C11 ） and dodecane （C12 ） wereevaluated in a fixed bed reactor. The effects of Ni crystallite size on the catalyst structure and performance wereinvestigated. It was found that the impregnation-drying-reduction method gave smaller Ni crystallite size, and thehigh reduction temperature promoted the growth of Ni crystallite. With the increase of the Ni crystallite size, theturnover frequency of methyl laurate increased, while the total selectivity to C11 and C12（sC11＋C12 ）, C11 / C12 molratio and the selectivity to cracking products decreased. We suggest that the deoxygenation of methyl laurate onNi / SiO2 is structurally sensitive. The effects of weight hourly space velocity （WHSV） on performance of Ni /SiO2 were also investigated. As WHSV increased, the methyl laruate conversion, sC11＋C12 , C11 / C12 mol ratio andthe selectivity to cracking products decreased. In addition, CO and CO2 generated from the decarbonylation /decarboxylation pathway were converted to CH4, indicating that Ni / SiO2 had high activity for methanation. Itwas also found that the sintering of small Ni crystallites, the adsorption of organic compounds and carbon depositled to catalyst deactivation.

关 键 词：Ni晶粒粒径 月桂酸甲酯 加氢脱氧 脱羰/脱羧 结构敏感 

分 类 号：O643[理学—物理化学]