Insights on Active Sites of CaAl-Hydrotalcite as a High-Performance Solid Base Catalyst toward Aldol Condensation

doi:10.1021/acscatal.7b03022

	Insights on Active Sites of CaAl-Hydrotalcite as a High-Performance Solid Base Catalyst toward Aldol Condensation
	Rao, DM; Xu, M; Zheng, LR; Wang, B; Wang, YD; Wei, M; Zheng L(郑雷); Zheng LR(郑黎荣); Bing, WH; Zheng, L
刊名	ACS CATALYSIS
	2018
卷号	8 期号:1 页码:656-664
关键词	CaAl-hydrotalcite solid basic catalysts aldol condensation hydroxypivaldehyde structure-activity correlation
ISSN号	2155-5435
DOI	10.1021/acscatal.7b03022
文献子类	Article
英文摘要	Solid base catalysts are highly demanded in many heterogeneous catalysis processes, but insights on active sites and structure-property correlation have rarely been revealed and remain a challenge. Herein, activated MxAl-layered double hydroxides (denoted as re-MxAl-LDH, M = Ca, Mg), as solid base catalysts toward the aldol condensation reaction, were prepared via a two-step procedure: calcination of the MxAl-LDH precursor to produce MxAl-mixed metal oxide (MxAl-MMO), followed by a further rehydration treatment. Structural characterizations confirm that re-CaxAl-LDH and re-MgxAl-LDH show similar morphology, particle size, specific surface area, and pore size distribution. However, a combination study including XPS, EXAFS, CDCl3-FTIR, and DFT calculations verifies that the host layer of re-CaxAl-LDH contains a distorted Ca(OH)(6) octahedron with an additional Ca-OH coordination that provides weak Bronsted basic site; in contrast, re-MgxAl-LDH consists of a Mg(OH)(6) octahedron structure accompanied by surface adsorbed hydroxyl group via noncovalent interaction, resulting in a medium Bronsted basic site. For the re-CaxAl-LDH samples, the concentration of weak Bronsted basic sites can be enhanced by tuning the Ca/Al molar ratio in the LDH precursor. The optimized re-CaxAl-LDH catalyst (re-Ca4Al-LDH) exhibits prominent catalytic performance toward the condensation of isobutyraldehyde (IBD) and formaldehyde (FA) to produce hydroxypivaldehyde (HPA), with a HPA yield of 61.5%. This is much higher than that of re-MgxAl-LDH (12.2%) and conventional solid base catalysts (4-33%), and even comparable to the level of liquid alkali (55-72%). Studies on the structure-property correlation reveal that the weak Bronsted basic site serves as active center to catalyze the aldol condensation, which accelerates the product desorption and largely promotes the HPA selectivity.
WOS关键词	LAYERED DOUBLE HYDROXIDES ; ACETONE SELF-CONDENSATION ; FRIEDELS SALT ; MIXED-OXIDES ; WATER ; HYDROGENATION ; OXIDATION ; PHOSPHATE ; ALCOHOLS ; ALKANES
WOS研究方向	Chemistry
语种	英语
WOS记录号	WOS:000419751100067
内容类型	期刊论文
源URL	[http://ir.ihep.ac.cn/handle/311005/285548]
专题	高能物理研究所_多学科研究中心
通讯作者	Zheng LR(郑黎荣)
作者单位	中国科学院高能物理研究所
推荐引用方式 GB/T 7714	Rao, DM,Xu, M,Zheng, LR,et al. Insights on Active Sites of CaAl-Hydrotalcite as a High-Performance Solid Base Catalyst toward Aldol Condensation[J]. ACS CATALYSIS,2018,8(1):656-664.
APA	Rao, DM.,Xu, M.,Zheng, LR.,Wang, B.,Wang, YD.,...&He, S.(2018).Insights on Active Sites of CaAl-Hydrotalcite as a High-Performance Solid Base Catalyst toward Aldol Condensation.ACS CATALYSIS,8(1),656-664.
MLA	Rao, DM,et al."Insights on Active Sites of CaAl-Hydrotalcite as a High-Performance Solid Base Catalyst toward Aldol Condensation".ACS CATALYSIS 8.1(2018):656-664.