Development of efficient thermocatalysts for Guerbet alcohol reactions

Abstract

Biofuels have gained recognition as a promising sustainable and renewable energy alternative. Among them, butanol has emerged as a particularly attractive product due to its higher energy density compared to bioethanol. The conversion of ethanol to butanol, known as the Guerbet alcohol mechanism, plays a crucial role in this context. However, the application of this mechanism relies on the performance, selectivity, stability, and cost of the Guerbet alcohol catalyst in batch reactors. The second-generation biofuel, butanol, has garnered significant attention, and Ni and Cu-based catalysts are commonly employed in batch reactions. Despite their low cost, their performance and poor selectivity have hindered commercial utilization of butanol. Therefore, the exploration of alternative metals or metal alloys is crucial to advance the commercialization of biofuel.

The synthesized NiCuSn/MgAlO catalyst demonstrates a 62% yield and 92% selectivity for butanol. This catalyst exhibits a yield three times higher than Raney copper, a commercial catalyst. The stability of the NiCuSn/MgAlO catalyst remains consistent for two cycles, with a subsequent yield decrease rate of 9% compared to a rate of 33% for the commercial catalyst. Removing the Cu element from NiCuSn/MgAlO results in a 20% decrease in yield. On the other hand, the NiCuSn/C catalyst achieves a yield of 47% with 91% selectivity for butanol, which is twice as high as Raney copper. As the copper content decreases, the yield also diminishes by 8%.

The high yield of NiCuSn/MgAlO is attributed to the significant content of Ni and Cu, as confirmed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Additionally, the presence of Cu⁰ and Cu⁺ species enhances the transfer hydrogen reaction. The NiCuSn/C catalyst attains a yield of 47% due to the elevation of Ni²⁺ content, , which prevents C-C bond cleavage, and the substantial Ni⁰ species present.

Date of Award	2024
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Minhua SHAO (Supervisor)