物理化学学报 >> 2015, Vol. 31 >> Issue (5): 965-972.doi: 10.3866/PKU.WHXB201503024

催化和表面科学 上一篇    下一篇

甘油脱水合成丙烯醛ZSM-5催化剂的孔结构和酸性调控

潘文雅1, 黄亮1, 秦枫1, 庄岩2, 李雪梅2, 马建学2, 沈伟1, 徐华龙1   

  1. 1 复旦大学化学系, 上海市分子催化与功能材料重点实验室, 复旦大学先进材料实验室, 上海200433;
    2 上海华谊丙烯酸有限公司, 上海200137
  • 收稿日期:2014-12-09 修回日期:2015-02-11 发布日期:2015-05-08
  • 通讯作者: 沈伟, 徐华龙 E-mail:wshen@fudan.edu.cn;shuhl@fudan.edu.cn
  • 基金资助:

    上海市科学技术委员会资助国际合作项目(14120700700)和重点实验室基金(11JC1400400)资助

Regulation of Pore Structure and Acidity of a ZSM-5 Catalyst for Dehydration of Glycerol to Acrolein

PAN Wen-Ya1, HUANG Liang1, QIN Feng1, ZHUANG Yan2, LI Xue-Mei2, MA Jian-Xue2, SHEN Wei1, XU Hua-Long1   

  1. 1 Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Laboratory of Advanced Materials, Department of Chemistry, Fudan University, Shanghai 200433, P. R. China;
    2 Shanghai Huayi Acrylic Acid Ltd. Co., Shanghai 200137, P. R. China
  • Received:2014-12-09 Revised:2015-02-11 Published:2015-05-08
  • Contact: SHEN Wei, XU Hua-Long E-mail:wshen@fudan.edu.cn;shuhl@fudan.edu.cn
  • Supported by:

    The project was supported by the Science and Technology Commission of Shanghai Municipality for International Collaboration Project, China (14120700700) and Funding of Key Laboratory, China (11JC1400400).

摘要:

研究了ZSM-5 孔结构和表面酸性对甘油脱水合成丙烯醛反应性能的影响. 在碱浓度为0.2 mol·L-1的NaOH溶液中, 分别在65和85 ℃条件下对ZSM-5进行化学刻蚀, 成功地制备了含微介孔的ZSM-5催化剂, 提高了催化剂的表面强酸密度. 碱处理后的ZSM-5催化剂在甘油脱水反应中的稳定性得到显著提高, 在ZSM-5-at85 (经85 ℃碱处理的ZSM-5)催化剂上甘油转化率在反应10 h 后仍可保持95%以上, 丙烯醛选择性达到78%. 采用N2吸附-脱附等温线、X射线粉末衍射(XRD)、27Al 固体核磁共振(27Al MAS-NMR)和透射电子显微镜(TEM)等手段对ZSM-5 结构和表面性质进行了表征, 实验结果表明在碱处理过程中骨架中的硅发生了溶脱现象, 在分子筛表面上形成了大量介孔, 但是ZSM-5 的MFI 拓扑结构没有发生变化, 骨架中的大部分铝得到保持. X射线光电子能谱(XPS)、X射线荧光光谱(XRF)和氨气程序升温脱附(NH3-TPD)证实了在碱处理后ZSM-5分子筛外表面的Si/Al 摩尔比低于其骨架中的比例, 由此表明脱硅现象主要发生在ZSM-5 的外表面, 在新产生的介孔区域由于Si/Al 摩尔比的降低使得强酸密度得到提高. 具有微介孔结构和较高酸密度的ZSM-5催化剂增强了反应物扩散性能和容碳能力, 这对于提高甘油脱水合成丙烯醛催化剂的活性和稳定性起到了关键作用.

关键词: 微介孔ZSM-5, 表面酸性, 碱处理法, 甘油脱水, 丙烯醛

Abstract:

Pore structure and acidity of ZSM-5 catalysts were successfully regulated by alkali treatment. ZSM- 5 was etched in 0.2 mol·L- 1 NaOH solution at 65 and 85 ℃. Micro-mesoporous ZSM-5 catalysts were successfully prepared with a high density of acidic sites. The activity and stability were significantly enhanced with alkali-treated ZSM-5, giving a conversion of glycerol above 95%, with selectivity for acrolein of 78% after 10 h compared with a ZSM-5-at85 (alkali-treated at 85 ℃) catalyst. Characterization of N2 adsorption and desorption isotherms, X-ray diffraction (XRD), 27Al mass atomic spectroscopy-nuclear magnetic resonance (27Al MAS-NMR), and transmission electron microscopy (TEM) were performed to interpret the morphology and surface properties. The results reveal that the Si in the framework of ZSM-5 was leached out by alkali treatment, and many mesopores were formed on the ZSM-5 surface. However, the MFI topology did not change and Al was mainly integrated within the framework. X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), and NH3-temperature-programed desorption (NH3-TPD) experiments demonstrated that the molar ratio of Si/ Al on the external surface was lower than that in the framework, indicating that more Si on the external surface of ZSM-5 was leached by alkali treatment, while the acidic density increased because of the lower molar ratio of Si/Al near newly formed mesopores. ZSM-5 catalysts with mesopores and higher acidic density enhance reactant diffusion and coking tolerance, which improves the activity and stability during glycerol dehydration.

Key words: Micro-mesoporous ZSM-5, Surface acidity, Alkali treatment, Dehydration of glycerol, Acrolein

MSC2000: 

  • O643