Preparation of MgAl LDH with Various Morphologies and Catalytic Hydrogenation Performance of Pt/LDH Catalysts

doi:10.15541/jim20210100

Abstract

Abstract:

How to design and fabricate highly efficient and stable Pt nano-catalyst is of important practical value and scientific significance for improving the C=O hydrogenation selectivity of cinnamaldehyde. In present study, a series of MgAl hydrotalcite (LDH) supports with various morphologies were synthesized by co-precipitation and hydrothermal methods. The supported Pt/LDH catalysts were prepared by incipient wet impregnation (IMP) method with LDH supports, and used for cinnamaldehyde selective hydrogenation reaction, and influences of LDH with different morphology for the catalyst activity were studied. The structure, morphology, surface physicochemical properties of these catalysts were characterized. The results show that the morphology of different supports exerts a significant influence on the structure and properties of Pt/LDH catalysts. Interaction between lamellae LDH nanosheet and active component Pt facilitates dispersing and stabilizing of Pt nanoparticles. Meanwhile, there are abundant alkaline sites and surface hydroxyl groups in the LDH support, which are beneficial to improve the catalytic hydrogenation activity and stability. Results of catalytic performance show that selectivity of cinnamon alcohol (CMO) and conversion of cinnamon aldehyde (CMA) at reaction temperature of 40 ℃, reaction pressure of 1 MPa, and reaction time of 120 min were 82.1% and 79.8%, respectively. After 5 rounds of cycle tests, the Pt/LDH catalyst still has excellent stability.

Key words: MgAl hydrotalcite, nanosheet, Pt catalyst, cinnamaldehyde hydrogenation, catalytic performance

CLC Number:

TQ174

LIU Wenwen, MIAO Yuxin, ZHANG Yifei, WANG Xinyu, LAN Yuting, ZHAO Zhen. Preparation of MgAl LDH with Various Morphologies and Catalytic Hydrogenation Performance of Pt/LDH Catalysts[J]. Journal of Inorganic Materials, 2021, 36(12): 1283-1289.

Figures/Tables 9

Fig. 1 XRD patterns of different morphologies LDH (a), SEM images of LDH-1 (b) and LDH-AS (c, d), TEM images of Pt/LDH-1 (e) and Pt/LDH-AS (f)

Table 1 Effects of Pt catalysts with various morphologies on the hydrogenation properties of cinnamaldehyde

Catalyst	Conversion/%	Selectivity/%
Catalyst	Conversion/%	CMO	HCMA	HCMO
Pt/LDH-1	79.8	82.1	12.6	5.3
Pt/LDH-AS	42.3	89.4	8.5	2.1

Table 2 Surface elemental compositions of Pt/LDH-1 and Pt/LDH-AS catalysts determined by XPS

Catalyst	Pt content/ at%	Pt^δ⁺/Pt⁰	O_ads/(O_ads+O_lat)	Mg/Al atomic ratio
Pt/LDH-1	0.35	2.51	0.35	1.19
Pt/LDH-AS	0.28	2.30	0.21	0.98

Fig. 2 XPS spectra of the as-prepared catalysts (a) Full spectrum; (b) C1s; (c) O1s; (d) Pt4f

Fig. 3 Effect of temperature (a), pressure (b), reaction time (c), and recycling stability (d) on catalytic performances of Pt/LDH-1 catalysts Curves represent the conversion rate, while bar charts represent the selectivity

Fig. S1 FT-IR spectra of LDH-1 and LDH-AS samples

Fig. S2 CO2-TPD profiles of the as-prepared catalysts LDH-1 and LDH-AS supports (a), Pt/LDH-1 and Pt/LDH-AS catalysts (b)

Fig. S3 TEM images of the used Pt/LDH-1 (a, b) catalyst

Fig. S4 Summary of the selective hydrogenation mechanism of Pt/LDH-1 catalyst represents Mg2+, represents Al3+, represents Pt

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