负载型双功能磁性催化剂的制备及性能研究
发布时间：2019-05-23 17:49
【摘要】：甲醇作为一种重要的碳一化工原料,近些年来出现了产量过剩的现象,以甲醇为原料制备下游产品受到广泛研究。其中甲酸甲酯(MF)是甲醇下游产品中一种非常重要的有机中间体,不仅可以直接用作干水果、谷物等的烟熏剂和杀菌剂,还可以用作有机溶剂和药物合成的原料,应用范围非常广泛。作为非均相反应体系中具有很大的发展前景的催化剂载体,介孔材料具有易调控的孔结构和高地吸附能力,在催化等方面含有广阔的发展前景。特别是将介孔材料和磁性Fe304相结合所制得的复合磁性催化剂载体。这种复合材料不仅具有便于回收分离的特性,而且还保持着介孔材料本身的特点。本文对甲醇液相一步催化转化制备甲酸甲酯反应体系的双功能催化剂进行了研究。本论文首先通过焙烧拟薄水铝石制备γ-A1203载体,并用浸渍-还原法把贵金属Au、Pd负载在了 γ-Al2O3载体上,制备了单金属纳米颗粒的Au/γ-Al2O3,Pd/γ-Al2O3和双金属Pd-Au/γ-Al203催化剂;另外还通过异丙醇铝水解在磁核Fe304外包覆了 γ-A1203,制备了磁性Pd/γ-Al2O3@ Fe3O4双功能催化剂,对催化剂进行了XRD、XPS、BET、NH3-TPD、H2-TPR、TEM等一系列表征,并测定了其在甲醇液相催化制备甲酸甲酯反应过程中的催化性能。实验结果如下:(1)将Au纳米颗粒负载在y-A1203载体上制备的一系列Au/γ-Al2O3催化剂,其比表面积和孔体积分别为353.5 m2·g-1和1.53cm3·g-1,Au纳米颗粒分布比较均匀,平均粒径约5.0 nm,但是该催化剂在甲醇液相催化反应中的催化效果不是很理想。在负载量为1.0wt%,5 mL无水甲醇、0.8 MPa氧气压力,130℃反应6 h时,甲醇转化率最高达到28.5%,甲酸甲酯选择性37.15%,收率10.59%。在Au催化剂中加入适宜比例的Pd制备的双金属Pd-Au/γ-Al2O3催化剂在甲醇液相催化转化生成甲酸甲酯反应体系中的催化活性和MF选择性明显比Au/γ-Al2O3催化剂高,该催化剂的比表面积和孔体积分别为332.7 m2·g-1和1.14 cm3·g-1,负载的贵金属纳米颗粒粒径在2～5 nm,而且该催化剂的酸性和氧化性与单金属Au/γ-Al2O3催化剂相比有明显提高。该催化剂在甲醇液相一步催化转化制备甲酸甲酯反应过程中的最佳反应条件为:反应温度160℃,氧气压力0.8 MPa,反应时间6 h时,甲醇转化率和甲酸甲酯选择性分别为53.47%和58.45%,收率31.25%。(2)用同样方法制备的Pd/γ-Al203催化剂与Au/γ-Al2O3催化剂相比催化活性有了明显的提高,氧化性与酸性都比Au/γ-Al2O3催化剂高,Pd纳米颗粒粒径平均约为5.0 nm。通过优化反应条件,甲醇转化率可以达到47.17%,甲酸甲酯选择性也可达到41.83%,收率19.73%。同时,还利用异丙醇铝水解制备了磁性双功能Pd/γ-Al2O3@Fe3O4催化剂,并对其进行了 XRD和VSM表征,结果表明,该催化剂具有良好的超顺磁性,且保持着γ-Al2O3和Fe3O4的特征衍射峰。其在最优反应条件下甲醇转化率和甲酸甲酯选择性分别为46.87%和40.79%,收率19.11%,催化性能与Pd/γ-Al2O3催化剂相比没有明显变化,但是其重复使用性能明显提高。
[Abstract]:As a kind of important carbon-chemical raw material, methanol has the phenomenon of excess production in recent years, and the preparation of the downstream products with methanol as the raw material is widely studied. The methyl formate (MF) is a very important organic intermediate in the downstream product of methanol, not only can be used as a fumigant and a bactericide for dry fruits, grains and the like, but also can be used as a raw material for organic solvent and drug synthesis, and the application range is very wide. As a catalyst carrier with great development prospect in the heterogeneous reaction system, the mesoporous material has an easily-regulated pore structure and high adsorption capacity, and has wide development prospect in the aspects of catalysis and the like. In particular to a composite magnetic catalyst carrier prepared by combining a mesoporous material and a magnetic Fe304. The composite material not only has the characteristics of convenient recovery and separation, but also maintains the characteristics of the mesoporous material itself. In this paper, a double-functional catalyst for preparing methyl formate reaction system by one-step catalytic conversion of methanol is studied. The Au/ Al-Al2O3, Pd/ Al-Al2O3 and the bimetallic Pd-Au/ Al-Al203 catalyst of the single-metal nanoparticles were prepared by roasting the pseudo-boehmite to prepare the Al-Al 203 carrier, and loading the noble metal Au and Pd on the Al-Al2O3 carrier by a dip-reduction method. A series of characteristics such as XRD, XPS, BET, NH3-TPD, H2-TPR, TEM and the like of the magnetic Pd/ Al-Al2O3 @ Fe3O4 double-functional catalyst are prepared by the hydrolysis of aluminum isopropoxide on the magnetic core Fe304, and the magnetic Pd/ Al-Al2O3 @ Fe3O4 double-functional catalyst is prepared. And the catalytic performance of the catalyst in the process of preparing the methyl formate by the liquid phase of the methanol is measured. The results of the experiment are as follows: (1) A series of Au/ I-Al2O3 catalysts prepared by loading Au nanoparticles on a y-A1203 carrier have a specific surface area and pore volume of 353.5 m2 路 g-1 and 1.53 cm3 路 g-1, and the distribution of Au nanoparticles is uniform, with an average particle size of about 5.0 nm. But the catalytic effect of the catalyst in the liquid-phase catalytic reaction of methanol is not ideal. The conversion of methanol was up to 28.5%, the selectivity of methyl formate was 37.15% and the yield was 10.59% when the loading was 1.0% by weight,5 mL of anhydrous methanol, 0.8 MPa of oxygen pressure and 130 鈩，
本文编号：2484096
[Abstract]:As a kind of important carbon-chemical raw material, methanol has the phenomenon of excess production in recent years, and the preparation of the downstream products with methanol as the raw material is widely studied. The methyl formate (MF) is a very important organic intermediate in the downstream product of methanol, not only can be used as a fumigant and a bactericide for dry fruits, grains and the like, but also can be used as a raw material for organic solvent and drug synthesis, and the application range is very wide. As a catalyst carrier with great development prospect in the heterogeneous reaction system, the mesoporous material has an easily-regulated pore structure and high adsorption capacity, and has wide development prospect in the aspects of catalysis and the like. In particular to a composite magnetic catalyst carrier prepared by combining a mesoporous material and a magnetic Fe304. The composite material not only has the characteristics of convenient recovery and separation, but also maintains the characteristics of the mesoporous material itself. In this paper, a double-functional catalyst for preparing methyl formate reaction system by one-step catalytic conversion of methanol is studied. The Au/ Al-Al2O3, Pd/ Al-Al2O3 and the bimetallic Pd-Au/ Al-Al203 catalyst of the single-metal nanoparticles were prepared by roasting the pseudo-boehmite to prepare the Al-Al 203 carrier, and loading the noble metal Au and Pd on the Al-Al2O3 carrier by a dip-reduction method. A series of characteristics such as XRD, XPS, BET, NH3-TPD, H2-TPR, TEM and the like of the magnetic Pd/ Al-Al2O3 @ Fe3O4 double-functional catalyst are prepared by the hydrolysis of aluminum isopropoxide on the magnetic core Fe304, and the magnetic Pd/ Al-Al2O3 @ Fe3O4 double-functional catalyst is prepared. And the catalytic performance of the catalyst in the process of preparing the methyl formate by the liquid phase of the methanol is measured. The results of the experiment are as follows: (1) A series of Au/ I-Al2O3 catalysts prepared by loading Au nanoparticles on a y-A1203 carrier have a specific surface area and pore volume of 353.5 m2 路 g-1 and 1.53 cm3 路 g-1, and the distribution of Au nanoparticles is uniform, with an average particle size of about 5.0 nm. But the catalytic effect of the catalyst in the liquid-phase catalytic reaction of methanol is not ideal. The conversion of methanol was up to 28.5%, the selectivity of methyl formate was 37.15% and the yield was 10.59% when the loading was 1.0% by weight,5 mL of anhydrous methanol, 0.8 MPa of oxygen pressure and 130 鈩，
本文编号：2484096
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