薄片状PtZn@Silicalite-1分子筛的合成及催化丙烷脱氢性能研究

doi:10.11949/0438-1157.20240318

摘要/Abstract

摘要：

采用水热晶化法，以四甲基胍（TMG）为形貌调控剂，一步合成封装PtZn纳米合金的薄片状Silicalite-1分子筛（PtZn@Silicalite-1）。采用X射线衍射（XRD）、透射电子显微镜（TEM）、X射线光电子能谱（XPS）等技术对样品进行表征分析，并考察了其丙烷脱氢催化性能。结果显示，加入TMG可有效调控Silicalite-1分子筛晶体的生长取向，晶体沿b轴的尺寸与TMG/SiO₂的比值呈反比。在550℃和纯丙烷气氛下，片状PtZn@Silicalite-1催化剂表现出优异的丙烷脱氢性能，经过20 h的连续反应，其失活常数仅为0.007 h^-1，而常规PtZn@Silicalite-1催化剂为0.013 h^-1。结合表征结果，薄片状分子筛催化剂具有更大的外比表面积和更短的b轴直通道，这提高了脱氢活性位的可接近性，缩短了气体分子在孔道中的扩散路径，从而提升了催化剂的活性和稳定性。

关键词: 薄片形貌, Silicalite-1分子筛, PtZn合金, 封装, 丙烷脱氢

Abstract:

The lamellar Silicalite-1 zeolite (PtZn@Silicalite-1) encapsulated PtZn nano-alloy was synthesized in one step by hydrothermal crystallization method with tetramethylguanidine (TMG) as morphology regulator. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), and their catalytic performance for propane dehydrogenation was investigated. The results show that the addition of TMG can effectively regulate the growth orientation of Silicalite-1 zeolite crystals, and the crystal size along the b-axis is inversely proportional to the ratio of TMG/SiO₂. At 550℃ and in pure propane atmosphere, the lamellar PtZn@Silicalite-1 catalyst showed excellent propane dehydrogenation performance. After 20 h of continuous reaction, its deactivation constant was only 0.007 h^-1, while that of the conventional PtZn@Silicalite-1 catalyst was 0.013 h^-1. Combined with the characterization data, the lamellar zeolite catalyst has larger external specific surface area and shorter b-axis through channel, which improves the accessibility of the dehydrogenation active site and shortens the diffusion path of gas molecules in the pore, thus improving the activity and stability of the catalyst.

Key words: lamellar shape, Silicalite-1 zeolite, PtZn alloy, encapsulation, propane dehydrogenation

中图分类号:

TQ 032.4

王靖宇, 刘佳, 徐继香, 王磊. 薄片状PtZn@Silicalite-1分子筛的合成及催化丙烷脱氢性能研究[J]. 化工学报, 2024, 75(9): 3188-3197.

Jingyu WANG, Jia LIU, Jixiang XU, Lei WANG. Synthesis of lamellar PtZn@Silicalite-1 zeolite and its catalytic properties for propane dehydrogenation[J]. CIESC Journal, 2024, 75(9): 3188-3197.

图/表 12

图1 不同TMG/SiO2摩尔比的PtZn@Silicalite-1分子筛扫描电镜图

Fig.1 SEM images of PtZn@Silicalite-1 zeolite with different TMG/SiO2 molar ratios

图2 不同TMG/SiO2摩尔比与分子筛晶体平均b轴厚度的关系曲线

Fig.2 The relationship between different TMG/SiO2 molarratios and average b-axis thickness of zeolite crystals

图3 不同TMG含量下合成PtZn@Silicalite-1催化剂的Pt含量、Zn含量和Zn/Pt比

Fig.3 Pt contents, Zn contents and Zn/Pt ratios of PtZn@Silicalite-1 catalysts synthesized with different TMG contents

图4 PtZn@S-1-0TMG和PtZn@S-1-0.5TMG催化剂的XRD谱图

Fig.4 XRD patterns of PtZn@S-1-0TMG and PtZn@S-1-0.5TMG catalysts

图5 PtZn@S-1-0TMG[(a)~(e)]和PtZn@S-1-0.5TMG[(f)~(j)]催化剂的透射电镜表征

Fig.5 Transmission electron microscopy characterization of PtZn@S-1-0TMG [(a)—(e)] and PtZn@S-1-0.5TMG [(f)—(j)] catalysts

图6 PtZn@S-1-0TMG和PtZn@S-1-0.5TMG催化剂的Pt 4f XPS光谱

Fig.6 Pt 4f XPS spectra of PtZn@S-1-0TMG and PtZn@S-1-0.5TMG catalysts

图7 PtZn@S-1-0TMG和PtZn@S-1-0.5TMG催化剂的N2吸附-脱附表征

Fig.7 N2 adsorption-desorption characterization of PtZn@S-1-0TMG and PtZn@S-1-0.5TMG catalysts

表1 PtZn@Silicalite-1催化剂的物理化学性质

Table 1 Physicochemical properties of as-prepared PtZn@Silicalite-1 catalysts

样品

S_micro/

(m²/g)

S_external/

(m²/g)

V_micro/

(cm³/g)

图8 不同温度下PtZn@S-1-0TMG和PtZn@S-1-0.5TMG催化剂的丙烷扩散动力学

Fig.8 Propane diffusion kinetics results of PtZn@S-1-0TMG and PtZn@S-1-0.5TMG catalysts at different temperatures

图9 PtZn@S-1-0TMG和PtZn@S-1-0.5TMG催化剂的丙烷脱氢性能（反应条件：550℃，101325 Pa，纯丙烷，WHSV=15.1 h-1）

Fig.9 Propane dehydrogenation performance of PtZn@S-1-0TMG and PtZn@S-1-0.5TMG catalysts （reaction conditions: 550℃, 101325 Pa, pure propane, WHSV=15.1 h-1）

图10 反应后PtZn@S-1-0TMG和PtZn@S-1-0.5TMG催化剂的热重分析曲线

Fig.10 TG analysis curves of spent PtZn@S-1-0TMG and PtZn@S-1-0.5TMG catalysts

图11 PtZn@S-1-0TMG和PtZn@S-1-0.5TMG催化剂的活化能表征

Fig.11 Activation energy characterization of PtZn@S-1-0TMG and PtZn@S-1-0.5TMG catalysts

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