双金属镍基硅酸盐的制备、还原和催化性能研究

发布时间：2018-03-01 14:03

本文关键词： 双金属镍基硅酸盐制备还原催化性能　出处：《青岛科技大学》2017年博士论文　论文类型：学位论文

【摘要】：作为一类新型功能复合材料,核壳结构纳米材料不仅实现了内核材料和壳材料的结合与互补,而且具有结构和化学成分的多样性及可调性,所以该设计概念逐渐被引入到能量存储、催化和隔热等领域。但作为一种未来新能源和环境领域的重要候选材料,目前核壳纳米材料的制备调控程度有限,合成壳厚均一、单分散的颗粒具有一定挑战性。本研究以二氧化硅为牺牲模板,采用界面反应/牺牲模板法在水热条件下制备了一系列具有核壳结构和空心结构的双金属硅酸盐复合材料,并且通过反应时间或改变模板二氧化硅和金属离子的摩尔比,实现了对壳层厚度和微球尺寸的控制。在合成空心球的基础上进一步研究了空心球的形成机理,并讨论了它们的结构对硝基苯加氢反应催化性能的影响。以二氧化硅为牺牲模板,水热条件下制备了具有介孔结构的镍基双金属Ni-M(M=Cu/Fe/Co)硅酸盐复合材料。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)、氮气吸脱附(BET)和程序升温还原(TPR)等方法对样品进行了表征。探索了双金属Ni-M硅酸盐空心球在氢气气氛下的还原规律,并研究了不同金属摩尔比(Ni/M)的双金属催化剂Ni-M/SiO_2在硝基苯加氢中的催化性能。主要研究内容及结果如下:1.双金属Ni-Cu硅酸盐的制备、还原及催化性能考察了Ni-Cu元素摩尔比为2:1和1:2下复合硅酸盐的制备、还原及催化性能。在Ni-Cu元素摩尔比为2:1时,双金属Ni-Cu硅酸盐空心球的合成条件(120℃,6 h)均低于Ni3Si2O5(OH)4空心球(180℃,24 h)和CuSiO3?H2O空心球(140℃,10 h)的反应条件。在800℃下,反应5 h,双金属Ni-Cu硅酸盐被还原为Ni-Cu/SiO_2,还原后形貌基本不变,比表面积减小,孔径增大。在液相催化加氢反应中,以商用雷尼镍、Ni-Cu/SiO_2空心球和Ni/SiO_2核壳微球作催化剂,加氢反应1 h,硝基苯的转化率分别是39%、95%和77%。在Ni-Cu元素摩尔比为1:2时,在120℃、反应3 h合成出具有空心球结构的双金属Cu-Ni硅酸盐复合材料,反应条件温和。随着水热时间的延长,双金属Cu-Ni硅酸盐壳层表面的形貌越规则,越松散。500℃反应5 h,双金属Cu-Ni硅酸盐被还原为Cu-Ni/SiO_2。对还原前后及使用过的催化剂进行表征发现使用后的催化剂的组成不变,但比表面积大幅下降,孔径增大。催化性能随着温度的升高逐渐增大,但温度超过120℃,催化性能增幅较小;随着压力的增大,催化性能逐渐增大。2.双金属Ni-Fe硅酸盐的制备、还原及催化性能考察了Ni-Fe元素摩尔比为2:1和1:2下复合硅酸盐的制备、还原及催化性能。在Ni-Fe元素摩尔比为2:1时,双金属Ni-Fe硅酸盐空心球比单一金属Fe3Si2O5(OH)4空心球具有高的热稳定性、规则的形貌和好的分散性。双金属Ni-Fe硅酸盐复合材料在750℃下,反应5 h被完全还原,产物为合金FeNi3,其比表面积、孔容和介孔尺寸均有明显降低,形貌和结构基本未变。硝基苯加氢反应3h时,单一金属催化剂Ni/Si O2和Fe/SiO_2和双金属催化剂Ni-Fe/SiO_2的转化率分别是89%、17%和77%。在Ni-Fe元素摩尔比为1:2时,双金属Fe-Ni空心球在不同的温度连续反应可得空心球,反应条件为140℃-24 h+180℃-12 h。在650℃下,反应5 h,双金属Fe-Ni硅酸盐被完全还原为金属Fe单质和Fe0.64Ni0.36合金。还原产物比表面积和孔容大幅降低。双金属催化剂Fe-Ni-1/SiO_2核壳微球、Fe-Ni-2/SiO_2空心球和Fe/SiO_2核壳微球作催化剂催化硝基苯加氢反应2 h时,转化率分别是94%,96%和12%。3.双金属Ni-Co硅酸盐的制备、、还原及催化性能考察了Ni-Co元素摩尔比为2:1和1:2下复合硅酸盐的制备、还原及催化性能。在Ni-Co元素摩尔比为2:1时,双金属Ni-Co硅酸盐空心球相比较硅酸钴空心球,尺寸均匀,分散性好。在800℃下,反应5 h,复合材料被完全还原为Ni-Co/SiO_2,其比表面积仅为还原前硅酸盐的15%,孔容为50%,孔径增大了2倍,将其应用于催化加氢反应时,硝基苯转化率较低,催化性能较差,故未做深入研究。在Ni-Co元素摩尔比为1:2时,140℃下反应6 h时,产物为核壳结构,反应12 h时变为空心球结构。碱式硅酸镍钴在800℃下反应5 h,被完全还原为Ni-Co/SiO_2。还原前后形貌基本不变,比表面积有所减小,孔径增大。Ni-Co/SiO_2空心球催化剂硝基苯加氢1 h时,转化率为67%,比商用Raney Ni提高约28%。
[Abstract]:As a new kind of functional composite materials, core-shell structure nano materials not only to achieve the complementary combination of core material and shell material, but also has the structure and chemical composition of diversity and adjustability, so the design concept has gradually been introduced into energy storage, catalysis and insulation and other fields. But as a new energy future and in the field of the environment an important candidate materials, the core-shell nano material preparation control level is limited, the synthesis of uniform shell thickness, monodisperse particles have some challenges. The research on silicon dioxide as sacrificial templates, the interfacial reaction / sacrificial template method under hydrothermal conditions in the preparation of a series of core-shell structure and the hollow structure of double metal silicate composite material, and the molar ratio of reaction time or change the template silica and metal ions, realize the control of the shell thickness and particle size. The empty Based on the formation mechanism of ball hollow ball is further studied, and discussed the effect of their structure on the catalytic performance of hydrogenation of nitrobenzene. With silica as a sacrificial template under hydrothermal conditions, the preparation of Ni based mesoporous Ni-M (M=Cu/Fe/Co) double metal silicate composite material. By scanning electron microscope (SEM), transmission electron microscopy (TEM), X ray diffraction (XRD), nitrogen adsorption desorption (BET) and temperature programmed reduction (TPR) were used to characterize the samples. To explore the reduction law of double metal Ni-M silicate hollow spheres in hydrogen atmosphere under, and the effects of different molar ratio of metal (Ni/M) the double metal catalyst Ni-M/SiO_2 in nitrobenzene and catalytic performance in hydrogen. The main research contents and results are as follows: 1. Ni-Cu double metal silicate preparation, reduction and catalytic properties were investigated for 2:1 and Ni-Cu elements in molar ratio of 1:2 composite silicate Salt preparation, reduction and catalytic performance. The elements in a Ni-Cu molar ratio of 2:1, the synthesis conditions of double metal Ni-Cu silicate hollow spheres (120 C, 6 h) were lower than that of Ni3Si2O5 (OH) 4 hollow ball (180 DEG C, 24 h) and CuSiO3? H2O hollow spheres (140 C, 10 h). Reaction conditions. Under the temperature of 800 DEG C, the reaction 5 h, double metal silicate Ni-Cu was reduced to Ni-Cu/SiO_2 after reduction, morphology is basically unchanged, the specific surface area decreased, the pore diameter increases. The reaction in liquid phase catalytic hydrogenation, using commercial Raney nickel, Ni-Cu/SiO_2 hollow spheres and Ni/SiO_2 core-shell microspheres as catalyst for hydrogenation of 1 h, the conversion of nitrobenzene were 39%, 95% and 77%. elements in Ni-Cu molar ratio was 1:2, 120 degrees, 3 h reaction synthesis with double metal Cu-Ni silicate composite hollow ball structure, mild reaction conditions. With the increase of hydrothermal treatment time, the morphology of Cu-Ni double metal silicate shell surface more rules the more loose, .500 C 5 h reaction, Cu-Ni double metal silicate was reduced to Cu-Ni/SiO_2. were used to characterize the catalyst composition unchanged before and after reduction and catalyst used was found after use, but the specific surface area decreased significantly, the pore diameter increases. The catalytic performance increased gradually with the increase of temperature, but the temperature is above 120 degrees Celsius, the catalytic performance with a smaller increase; the increase of the pressure, the catalytic performance of.2. Ni-Fe gradually increased double metal silicate preparation, reduction and catalytic properties were investigated for Ni-Fe element molar ratio of 2:1 and 1:2 composite silicate under preparation, reduction and catalytic performance. The elements in a Ni-Fe molar ratio of 2:1, Ni-Fe double metal silicate hollow spheres than single metal Fe3Si2O5 (OH) 4 the hollow ball has high thermal stability, dispersibility and morphology rules. Ni-Fe double metal silicate composite material at 750 DEG C, the reaction is completely reduced to 5 h, is the product of alloy FeNi3, the ratio of The surface area, Kong Rong and the mesopore size decreased significantly, basically unchanged morphology and structure. The nitrobenzene hydrogenation reaction of 3H, O2 and Ni/Si into single metal catalyst Fe/SiO_2 and bimetallic catalyst Ni-Fe/SiO_2 rates were 89%, 17% and 77%. elements in Ni-Fe molar ratio was 1:2, the bimetallic Fe-Ni hollow spheres in different continuous reaction the temperature of the hollow ball, the reaction conditions of 140 DEG C -24 h+180 C -12 h. at 650 DEG C, the reaction 5 h, double metal silicate Fe-Ni was completely reduced to metal Fe element and Fe0.64Ni0.36 alloys. The reduction product specific surface area and pore volume decreased significantly. The double metal catalyst Fe-Ni-1/SiO_2 core-shell microspheres, catalyst and nitrobenzene hydrogenation of Fe-Ni-2/SiO_2 hollow spheres and Fe/SiO_2 core-shell microspheres for 2 h, the conversion rate is respectively 94%, 96% and 12%.3. Ni-Co double metal silicate, preparation, reduction and catalytic performance were investigated Ni-Co Moore Ratio of 2:1 and 1:2 composite silicate under preparation, reduction and catalytic performance. The elements in a Ni-Co molar ratio of 2:1, Ni-Co double metal silicate hollow spheres compared to cobalt silicate hollow spheres, uniform size, good dispersion. At 800 DEG C, the reaction is 5 h, the composite material is completely reduced to Ni-Co/ SiO_2, the the specific surface area is only 15% reduction before Portland, Kong Rong was 50%, size 2 times, its application in the catalytic hydrogenation of nitrobenzene, low conversion rate, the catalytic performance is poor, it did not do in-depth research. The elements in Ni-Co molar ratio was 1:2, 140 DEG C for 6 h, the product the core-shell structure and reaction of 12 h into the hollow spherical structure. Basic silicate nickel and cobalt in 800 DEG C for 5 h was completely reduced to Ni-Co/SiO_2. after reduction were basically unchanged, decreased surface area, pore size of.Ni-Co/SiO_2 hollow spherical catalyst hydrogenation of nitrobenzene with 1 h, the conversion rate was 67%, Increase about 28%. over commercial Raney Ni

【学位授予单位】：青岛科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.36;TB383.1

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