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Title:
Zn-Al复合氧化物负载的Ni基催化剂的制备及其在油酸加氢脱氧反应中的应用
Author: 张锋
Degree Level: 硕士
Issued Date: 2016-05
Degree Grantor: 中国科学院研究生院
Place of Degree Grantor: 青岛
Supervisor: 李学兵
Keyword: 生物柴油 ; 油酸 ; 加氢脱氧 ; 锌铝复合氧化物 ; 催化剂
Subject: 工业催化
Alternative Title:
Major: 化学工程
Abstract: 化石燃料消耗量的逐渐增加导致全球能源危机,同时,化石燃料燃烧后排放的温室气体引发的温室效应已经成为人类历史上环境问题的最大考验。因此,探索一种可替代非再生的化石燃料的能源就显得尤为重要。使用生物质燃料来代替传统能源燃料已经引起了研究者的广泛关注。其中,生物质通过加氢脱氧反应制备与传统石化能源相似组分的链烷烃是目前的研究热点。现阶段,加氢脱氧催化剂的载体有三种:负载型贵金属催化剂、负载型硫化态过渡金属催化剂和负载型还原态过渡金属催化剂。负载型硫化态催化剂中的硫会污染产物,贵金属催化剂价格较为昂贵,因此本课题选用负载型过渡金属催化剂作为研究对象。目前,相比于酸性或中性载体,如H-ZSM-5、SAPO-34,γ-Al2O3等,碱性载体很少受到人们的关注。考虑到碱性载体可以减少原料的裂解反应,增加液相产物的收率,而且抑制积碳。因此,本研究选用碱性复合氧化物作为催化剂载体。 本论文制备不同碱性复合氧化物作为催化剂载体MO-Al2O3( M = Mg, Ca, Ni, Cu, Zn)。然后采用等体积浸渍的方法制备Ni基催化剂Ni/ MO-Al2O3。以油酸作为模型化合物,在100 ml的高压反应釜中反应来测试不同催化剂的催化油酸加氢脱氧反应制备烷烃的催化性能。结果表明碱性催化剂载体对油酸加氢脱氧制备烷烃的反应有很好的促进作用。在反应温度为280 °C、H2压力为3.0 MPa下,碱性适中的Ni/ZnO-Al2O3 催化剂呈现出最佳的催化反应性能,可使油酸的转化率高达100 %,烷烃(C17+C18)的产率高达99%。相比之下,催化剂(Ni/CaO-Al2O3 和Ni/MgO-Al2O3)在反应过程中,由于催化剂载体碱性较强,易与反应物油酸或加氢后的硬脂酸生成脂肪酸盐,导致催化活性较低。另外,增加活性组分Ni的负载量、提高反应温度和H2压力均有助于烷烃的生成,且催化剂的活性对反应温度的变化更敏感。作为该反应的主要产物,C17主要来源于硬脂酸十八酯的氢解和随后生成的十八醛的脱羰反应,该反应为油酸加氢脱氧反应的主要路径。由不同中间产物的反应速率计算结果可知硬脂酸十八酯的氢解反应为整个反应的控速步骤。催化剂经过三次重复利用,仍然保持较高的催化活性,说明其具有较高的催化稳定性。 此外,催化剂载体中的Zn与Al的不同比例对催化剂的催化剂性能有着很大的影响。首先,制备了一系列不同锌铝比的催化剂载体,并通过等体积浸渍法制备相应催化剂。以油酸作为模型化合物,十氢萘作为溶剂,在100 ml的高压反应釜中反应来测试不同催化剂的油酸加氢脱氧反应制备烷烃的催化性能。结果发现具有适中碱性的催化剂Ni/ZnO-Al2O3(Zn/Al =2)具有最佳的催化活性。在反应温度为280 °C、H2压力为2.5 MPa条件下液相产物中烷烃的收率(C17+C18)高达95.8%。随着锌铝比的增加,载体的比表面积减小,其阻碍活性组分镍颗粒的分散。较低的分散度使得镍颗粒的尺寸较大,以及其内部的NiO无法被还原。油酸加氢脱氧反应的转化率及烷烃的选择性与暴露在催化剂表面的单质镍颗粒有密不可分的关系。
English Abstract: Progressive depletion of petroleum-based fuels has led to the global energy crisis. The greenhouse gas emission introduced by burning fossil fuels has made the global warming become one of the biggest environmental challenges in human history. Therefore, it is necessary to develop an alternative fuel source that can replace non-renewable fossil fuels. The use of biomass-derived fuels in place of conventional fuels is an emerging field of interest. Hydrodeoxygenation, which converts biomass to hydrocarbon fuels that have all the qualities of conventional fossil fuels, is one of the most interesting and promising techniques in this field. The commonly used hydrodeoxygenation catalysts are supported noble and sulfide or reduced metal catalysts. However, sulfide catalysts would contaminated products due to the formation of sulfur and noble catalysts are not favorable because of their high cost. Therefore, our study devoted to developing non-sulfided transition metal catalysts. Basic support can reduce the cracking of feedstock and increase the yield of liquid products. Moreover, they are more favorable to absorb acidic fatty acids, which may improve triglycerides deoxygenation. From this viewpoint, a series of Ni-based catalysts supported on basic composite oxides (MO-Al2O3, M = Mg, Ca, Ni, Cu, Zn) were prepared for the catalytic deoxygenation of oleic acid in the presence of H2. Oleic acid was selected as the model reactant for activity tests. Their catalytic activity for the hydrodeoxygenation (HDO) were studied in an autoclave reactor using decalin as solvent. The results indicated that t Ni supported on ZnO-Al2O3 composite exhibited the highest conversion of oleic acid (100%) and selectivity to n-alkanes (99%). A suitable amount of basicity on the support is favorable for oleic acid deoxygenation. Additionally, increasing Ni loading amount and reaction temperature or decreasing H2 pressure were beneficial for the formation of alkanes, especially n-heptadecane. The reaction temperature was more important than H2 pressure in the catalytic deoxygenation of oleic acid. As the predominant product, n-heptadecane was mainly derived from stearyl stearate hydrogenolysis and sequential octadecanal decarbonylation, which is the major route in the whole reaction pathway. The reaction rates of different intermediates confirm that the hydrogenlysis of stearyl stearate is the rate-determining step for the overall reaction of oleic acid. After reuse for three times, the catalyst still maintained a relatively high yield of alkanes (> 90%), showing a high activity stability. Furthermore, we prepared Ni supported on ZnO-Al2O3 with different Zn/Al atomic ratio by an incipient wetness impregnation method and compared their catalytic performance in HDO of oleic acid to diesel like fuel. The maxim diesel-like alkane (C17+C18) yield of 95.8 % was observed over 10wt %Ni/Zn2.0Al under mild reaction condition, showing its promising catalytic application in this reaction. The increase of Zn/Al ratio can remarkably decrease the specific surface area and weaken the interaction between Ni species and the supports, thereby hindering the dispersion of Ni species. Lower dispersion degree further led to the formation of Ni species particles with larger size, which prevented the Ni species inside of the particles from reducing even if the weak interaction was favorable to the reduction of Ni species. Conversion and deoxygenation of the reactants strongly depended on the hydrogenation performance of the catalysts which was controlled by the proportion of exposed metallic Ni atoms.
Language: 中文
Department: 多相催化转化团队
Available Date: 2020-07-01
DOC Type: 学位论文
Content Type: 学位论文
URI: http://ir.qibebt.ac.cn/handle/337004/9785
Appears in Collections:多相催化转化团队_学位论文

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description.institution: 中国科学院青岛生物能源与过程研究所

Recommended Citation:
张锋. Zn-Al复合氧化物负载的Ni基催化剂的制备及其在油酸加氢脱氧反应中的应用[D]. 青岛. 中国科学院研究生院. 2016.
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