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Improvement of the catalytic activity of Ni/SiO2-C by the modification of the support and Zn addition: Bio-propylene glycol from glycerol
Applied Catalysis A: General ( IF 5.5 ) Pub Date : 2017-08-26 , DOI: 10.1016/j.apcata.2017.08.037
Martin N. Gatti , Martín D. Mizrahi , Jose M. Ramallo-Lopez , Francisco Pompeo , Gerardo F. Santori , Nora N. Nichio

In previous studies, we prepared Ni catalysts supported on a silica-carbon composite which is selective for obtaining 1,2-propylene glycol (1,2-PG). In order to improve the activity levels of this catalyst, in the present work we propose to modify the catalyst formulation by means of two strategies: on the one hand, to modify the acidity of the catalyst through the functionalization of the carbon support and, on the other hand, to modify the metallic phase by the addition of Zn from a controlled preparation technique (Surface Organometallic Chemistry on Metals), which allows the selective addition of small amounts of modifier on the metallic particles.

The functionalization of the SC support at 80 °C employing HNO3 at 60 wt% as oxidizing agent allowed increasing the number of surface acid sites that provide Lewis-type acidity without loss of specific surface area.

The addition of 1.1–1.8 wt% of Zn (which corresponds to catalysts NiZn0.2/SC and NiZn0.32/SC) generates the formation of an active site composed of an α-NiZn alloy responsible for the increase in activity. When the addition of Zn is 2.8 wt% (which corresponds to catalyst NiZn0.5/SC), the generation of a new tetragonal phase of β1-NiZn would cause the decrease of catalytic activity. These results indicate that the Zn addition has a more significant effect upon the activity and selectivity on the CO bond cleavage reactions than the effect of the support acidity upon the dehydration activity.



中文翻译:

通过改性载体和添加锌改善Ni / SiO 2 -C的催化活性:甘油中的生物丙二醇

在以前的研究中,我们制备了负载在二氧化硅-碳复合材料上的Ni催化剂,该催化剂对获得1,2-丙二醇(1,2-PG)具有选择性。为了提高这种催化剂的活性水平,在本工作中,我们提出通过两种策略来改变催化剂的配方:一方面,通过碳载体的官能化来改变催化剂的酸度;以及另一方面,通过控制制备技术(金属表面有机金属化学)中添加锌来修饰金属相,该方法允许在金属颗粒上选择性地添加少量改性剂。

使用60%(重量)的HNO 3作为氧化剂在80°C下对SC载体进行功能化,可以增加提供路易斯类型酸度的表面酸位点的数量,而不会损失比表面积。

添加1.1–1.8 wt%的Zn(对应于催化剂NiZn0.2 / SC和NiZn0.32 / SC)会形成由α-NiZn合金组成的活性位点,从而增加活性。当添加的Zn的是2.8重量%(其对应于催化剂NiZn0.5 / SC),一个新的四方晶相的生成β 1 -NiZn将导致催化活性的降低。这些结果表明,Zn的添加对活性和对CO键断裂反应的选择性的影响比支持酸度对脱水活性的影响更大。

更新日期:2017-08-26
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