A comparative study of different fluorine-containing compounds in the preparation of novel alumina binders with rich Brönsted acid sites
A comparative study of different fluorine-containing compounds in the preparation of novel alumina binders with rich Brönsted acid sites
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DOI：
10.1007/s13203-014-0088-4
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发表时间：
2015-06
影响因子：
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通讯作者：
P. Bai;Rui Feng;Songtao Liu;Peng Zhang;Zifeng Yan;Zhengguo Tan;Zhongdong Zhang;Xiong-hou Gao
中科院分区：
文献类型：
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作者：
P. Bai;Rui Feng;Songtao Liu;Peng Zhang;Zifeng Yan;Zhengguo Tan;Zhongdong Zhang;Xiong-hou Gao
氧化铝通常与铝溶胶一起用作现代流化床催化裂化 (FCC) 催化剂中的催化剂粘合剂。氧化铝的表面酸性特性强烈影响FCC催化剂的催化性能。路易斯酸位点由于其脱氢活性而倾向于产生焦炭，而布朗斯台德酸位点产生较少的焦炭。因此，将表面路易斯酸位转化为布朗斯台德型是有利的。含氟改性剂已被证明可有效在氧化铝表面产生布朗斯台德酸位。但不同类型的含氟化合物可能具有不同的改性效果。本工作测试并比较了氟硼酸铵(NH4BF4)、氟硅酸铵[(NH4)2SiF6]和氟化铵(NH4F)三种含氟化合物对氧化铝表面酸度的改性作用。结果表明，NH4BF4和(NH4)2SiF6在布朗斯台德酸位点的生成方面表现同样出色，而NH4BF4在路易斯酸位点的还原方面更有效。相比之下，NH4F 在生成布朗斯台德酸位点方面不如其他两种化合物那么有效。
Alumina is commonly used as a catalyst binder together with aluminum sol in modern fluid catalytic cracking (FCC) catalysts. The surface acidity properties of alumina strongly affect the catalytic performance of FCC catalysts. Lewis acid sites tend to produce coke because of their dehydrogenation activity, while Brönsted ones produce less coke. Thus, it is beneficial to convert the surface Lewis acid sites into Brönsted type. Fluorine-containing modifiers have been demonstrated to be effective to generate Brönsted acid sites on alumina surface. However, different types of fluorine-containing compounds may have different modification effects. In this work, three fluorine-containing compounds, ammonium fluoroborate (NH4BF4), ammonium fluorosilicate [(NH4)2SiF6], and ammonium fluoride (NH4F), were tested and compared in the modification of alumina surface acidity. Results show that NH4BF4and (NH4)2SiF6perform equally well in the generation of Brönsted acid sites, while NH4BF4is more effective in the reduction of Lewis acid sites. In comparison, NH4F is not so effective in the generation of Brönsted acid sites as the other two compounds.