CAJ | 학술논문

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。
채용등체적침지-간조-환원법급등체적침지-간조-배소-환원법제비료3충구유불동Ni정립립경적Ni/SiO2최화제,이용H2-TPR、XRD、TEM、H2-TPR、NH3-TPD급TGA기술대기급전구체진행료표정,병재고정상반응기상평개료기최화월계산갑지탈양제십일완( C11)화십이완( C12)적성능,분석료Ni정립립경대기탈양성능적영향。결과표명,채용등체적침지-간조-환원법제비적최화제중Ni정립립경교소,제고환원온도가이촉진Ni정립장대。수Ni정립립경증대,월계산갑지적전환빈솔제고,이C11화C12총선택성、C11/C12물질적량비급렬해산물선택성강저, Ni/SiO2최화제상월계산갑지탈양위결구민감반응。차외,환고찰료중시공속대Ni/SiO2최화제탈양성능적영향,수중시공속제고,월계산갑지전화솔、C11화C12총선택성、C11/C12물질적량비급열화산물선택성강저。월계산갑지통과탈탄/탈최반응로경생성적CO/CO2궤호전부가경전화위CH4,표명Ni/SiO2최화제구유흔고적갑완화활성。연구환발현,교소Ni정립소결、유궤물충흡부급적탄회도치최화제실활。
Three Ni/SiO2 catalysts with different Ni crystallite sizes were prepared by the incipient wetness impregnation-drying-reduction and incipient wetness impregnation-drying-calcination-reduction methods. The catalysts were characterized by H2-TPR, XRD, TEM, H2 chemisorption, NH3-TPD and TGA techniques. Their catalytic performances in the deoxygenation of methyl laurate to undecane ( C11 ) and dodecane ( C12 ) were evaluated in a fixed bed reactor. The effects of Ni crystallite size on the catalyst structure and performance were investigated. It was found that the impregnation-drying-reduction method gave smaller Ni crystallite size, and the high reduction temperature promoted the growth of Ni crystallite. With the increase of the Ni crystallite size, the turnover frequency of methyl laurate increased, while the total selectivity to C11 and C12(sC11+C12), C11/C12 mol ratio and the selectivity to cracking products decreased. We suggest that the deoxygenation of methyl laurate on Ni/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 and the 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. It was also found that the sintering of small Ni crystallites, the adsorption of organic compounds and carbon deposit led to catalyst deactivation.