HY沸石的碱处理改性及其催化α-蒎烯异构反应的性能

Modification of HY Zeolite by Alkali Treatment and its Catalytic Isomerization Performance of α-pinene

用不同浓度的NaOH溶液对HY沸石进行处理,考察不同浓度的碱处理对HY沸石的结构及其对蒎烯异构化催化性能的影响。采用XRD、SEM、Py-IR、N_(2)吸附-脱附等表征手段,揭示HY沸石经NaOH处理后的比表面积、孔容、酸强度、外观形态、结晶度等的变化情况。将经碱处理后的HY沸石用于催化α-蒎烯的异构化反应,考察其催化性能。实验结果表明,用于处理HY沸石的NaOH溶液,浓度应小于2mol·L^(-1),否则HY晶体结构会遭到严重破坏,呈无定形态。用NaOH溶液处理后,HY沸石含有的Br?nsted酸和Lewis酸中心的数量大幅减少,而改性HY沸石的催化活性增强,反应1h,α-蒎烯的转化率即达到98%以上。用适宜浓度的NaOH溶液处理HY沸石,可在保持晶体结构的前提下,有效调节HY沸石的比表面积、孔径、孔容等结构参数。在用碱处理后的HY沸石催化的α-蒎烯异构化反应中,苧烯的选择性由27.08%降至6.98%,小孔径改性的HY沸石对单一产物莰烯的选择性,优于大孔径改性的HY沸石。

HY zeolite was treated with different concentrations of NaOH solution.The effects of alkali treatment with different concentrations on the structure of HY zeolite and its catalytic performance for isomerization of pinene were investigated.By means of PY-IR,XRD,SEM,N_(2) adsorption-desorption characterization methods,the changes of zeolite acidity,crystallinity,specific surface area,pore volume and appearance morphology of HY zeolite treated by NaOH were revealed,the catalytic isomerism performance of HY zeolite by sodium hydroxide solution treatment was investigated by theα-pinene catalytic isomerization experiment.The results showed that the concentration of sodium hydroxide solution in the treatment of HY zeolite was less than 2mol/L,otherwise the crystal structure of HY was seriously damaged and presented amorphous shape.Sodium hydroxide solution treatment significantly reduced the number of Bronsted and Lewis acid centers in HY zeolite,but the catalytic activity of modified HY zeolite was enhanced,the conversion rate ofα-pinene was more than 98%after the reaction time of 1h.The structural parameters of HY zeolite such as specific surface area,pore size and pore volume could be effectively adjusted with sodium hydroxide solution of appropriate concentration on the condition of maintaining crystal structure.After HY zeolite by alkaline treatment,the selectivity of limonene in theα-pinene isomer reaction catalyzed by HY zeolite decreased from 27.08% to 6.98%.The selectivity of small pore modified HY zeolite to single product camphene was better than that of large pore modified HY zeolite.