Negative effect of Ni on PtHY in n-pentane isomerization evidenced by IR and ESR studies

• 作 者: Muhammad Afif Ab Aziz Nur Hida
• 机 构: Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia,
• 出 处: 天然气化学（英文版）
• 发表日期: 2012年1期
• 关键词: Ni Ni/PtHY n-pentane isomerization hydrogen protonic acid sites
• 基金项目: the Ministry of Higher Education,Malaysia through Fundamental Research;the UTM Short Term Research

Ni/PtHY with different Ni loadings was prepared by impregnating HY with hexachloroplatinic acid solution and Ni2+/N,N-dimethylformamide solution.An increase in the Ni loading decreased the crystallinity,specific surface area and meso-micropores of the catalysts.Ni interacted with hydroxyl groups to produce IR absorption bands at 3740-3500 cm-1.Increasing Ni loadings resulted in a decrease in the intensities of the broad bands at 3730-3500 cm-1 and the sharp band at 3740 cm-1 with simultaneous development of new absorbance band at 3700 cm-1 that was attributed to (-OH)Ni.The acidity of the samples did not significantly change with Ni loadings up to 1.0 wt％,which indicated that Ni mostly interacts with non-acidic silanol groups (terminal-and structural-defect OH groups).The presence of Ni decreased the activity of PtHY toward the isomerization of n-pentane because of a decrease in the number of active protonic-acid sites that formed from molecular hydrogen.IR and ESR studies confirmed that Pt facilitated the formation of protonic-acid sites from molecular hydrogen,whereas Ni,even when combined with Pt,didn’t exhibit such ability.The absence of protonic-acid sites from molecular hydrogen significantly decreased the yield of iso-pentane and markedly increased the cracking products.