Synthesized Ni/MMO catalysts via ultrathin Ni-Al-LDH in a rotating packed bed for hydrogenation of maleic anhydride

Abstract

• Ni-Al-LDH with thicknesses of 1–19 nm were synthesized to prepare Ni/MMO catalysts. • The features of Ni/MMO can be tuned by regulating the thicknesses of Ni-Al-LDH. • Ni/MMO catalysts obtained from Ni-Al-LDH exhibit irregular core–shell structure. • The highest hydrogenation rate for Ni/MMO is 9.45 (10 -3 ·mol MA ·g cat −1 ·min −1 , 80 °C, 2 MPa). • Maleic anhydride hydrogenation to succinic anhydride exhibits structure-sensitive. Fabricating highly active supported Ni-based catalysts is a fundamental challenge in the industry. Herein, the Ni-Al-LDH with controllable thicknesses from 1 to 19 nm were first synthesized to fabricate Ni/MMO catalysts (MMO: Mixed Metal Oxides) using coprecipitation in a rotating packed bed (RPB), followed by hydrothermal aging. It was found that despite the collapse of the sheet-like structure of the ultrathin Ni-Al-LDH during the thermal treatment, the Ni/MMO (designated as 2-NiAl) catalyst obtained from ultrathin Ni-Al-LDH nanosheets (2 nm) possesses the smallest Ni particle size, highest amount of acid sites and surface ratios of Ni/Al among the prepared catalysts. Thus, 2-NiAl demonstrates the optimal activity for the hydrogenation of maleic anhydride (MA), of which the hydrogenation rate is 9.45 (10 -3 ·mol MA ·g Ni -1 ·min −1 , 80 °C, 2 MPa) with ∼100% selectivity to succinic anhydride, higher than most of previous reported values. Moreover, the turnover frequencies as a function of Ni particle sizes demonstrate a linear correlation, indicating that MA hydrogenation is a structure-sensitive reaction. These results provide a new route to optimize the catalytic performance of Ni-based catalysts and a guidance for designing catalysts derived from LDH for hydrogenation reactions. Furthermore, the prepared 2-NiAl catalyst is a potential catalyst for hydrogenation of MA into SA in the industry.