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首页> 外文期刊>Catalysis science & technology >Controlling the redox properties of nickel in NiO/ZrO2 catalysts synthesized by sol-gel
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Controlling the redox properties of nickel in NiO/ZrO2 catalysts synthesized by sol-gel

机译：控制镍的氧化还原性质NiO /氧化锆催化剂合成了溶胶-凝胶法

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NiO-ZrO2 samples were prepared by the sol-gel method adjusting the nickel content to 3 and 10 wt% and varying the calcination temperature from 500 to 700 degrees C. The solids were characterized by X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), X-ray photoelectron spectroscopy, high resolution transmission electron microscopy (HRTEM) and scanning and transmission electron microscopy (STEM). For the sample with 3 wt% Ni, diffraction lines related to cubic zirconia were only detected when calcined from 500 to 650 degrees C, a NiO crystalline phase as well as the transition phase from cubic to tetragonal zirconia appeared when calcined at 700 degrees C. UV-vis DRS and HRTEM results indicated the presence of a highly dispersed NiO phase at the nanometric scale throughout the main zirconia crystalline phase. The NiO crystalline phase was already detected for the sample with 10 wt% nickel content calcined at 500 degrees C. The NiO-ZrO2 interaction was modified by reducing the hydrolysis rate during synthesis leading to a sample with a high dispersion of Ni throughout ZrO2, thus modifying the reducibility of NiO. The NiO-ZrO2 samples were catalytically tested for the oxidative dehydrogenation of ethane as a model reaction. Prior to reaction, the calcined catalysts were pre-treated in situ under reducing and oxidant atmospheres to study their redox properties. As the NiO-ZrO2 interaction modifies the electronic properties of both nickel oxide and zirconia, ethane conversion and ethylene selectivity were strongly influenced not only by the nickel content and calcination temperature but also by the in situ pre-treatment before reaction. This effect was particularly evident in the sample prepared with a modified hydrolysis rate, which changed the redox properties of the NiO species.
机译：NiO-ZrO2样本由溶胶-凝胶法方法调整镍含量3和10wt %和不同的煅烧温度500 - 700度c固体以x射线衍射、紫外可见漫反射率光谱(紫外可见DRS), x射线光电子光谱、高分辨率的传播电子显微镜和扫描透射电子显微镜(杆)。示例3 wt %倪,衍射线相关的立方氧化锆时才发现煅烧从500年到650摄氏度,NiO结晶相的过渡阶段从立方、四方氧化锆时出现煅烧在700度c .紫外可见DRS和介绍结果表明存在一个高度分散NiO nanometric规模阶段在主要的氧化锆结晶相。NiO结晶相已经检测到示例10 wt %镍含量煅烧在NiO-ZrO2 500度c相互作用是通过减少修改在合成导致水解率样本的高色散倪氧化锆、因此修改NiO的还原性。NiO-ZrO2样本催化地进行测试乙烷氧化脱氢的作为模型反应。催化剂预处理的原位在减少和氧化剂大气研究氧化还原属性。氧化镍的电子性质和氧化锆,乙烷转化率和乙烯选择性不仅严重影响了镍含量和煅烧温度之前还在原位预处理的反应。样品准备和修改后的水解率,这改变了氧化还原性能NiO起源。

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