High Performing and Stable Cu/NiAlO_x Catalysts for the Continuous Catalytic Conversion of Ethanol into Butanol

Abstract

The catalytic conversion of ethanol into butanol is one of crucial reactions in biorefinery for the production of renewable fuels and chemicals. The development of highly durable non-noble metal-based catalysts is of great significance but poses big challenges. Herein, we prepared a series of NiAl-hydrotalcite derived Cu/NiAlO x catalysts via the hydrothermal precipitation method. Cu addition to the system shows an enhanced reactivity in the continuous catalytic conversion of ethanol into butanol. The 0.75 %Cu/NiAlO x catalyst afford a sustained ethanol conversion of ~35 % and butanol selectivity of ~45 % within 1000 h at 250 °C, 3 MPa N 2 . Complementary characterization studies reveal that Cu addition into the catalysts could not only provide redox sites for facilitating the dehydrogenation/hydrogenation processes, but also modulate the base/ acid property for suppressing the side reactions. The excellent stability might stem from the enhanced interaction between Cu and Ni species, as evidenced by EDX-mapping and H 2 -TPR. We believe this work will help to rational design and develop of high-performing and durable non-noble metal catalysts for ethanol coupling to higher alcohols.

Copper Supported on MgAlOx and ZnAlOx Porous Mixed-Oxides for Conversion of Bioethanol via Guerbet Coupling Reaction

“…8.0%). Such results are comparable or better than the previous results, in which a good compromise between ethanol conversion and butanol selectivity was pursued [23,31,34]. In contrast, the main product on the Cu/ZnAlOx was ethyl acetate, with the selectivity of 42.2%, which is widely used in paints, coatings, inks, and adhesives.…”

“…A couple of peaks located at 933.0 eV and 952.8 eV were ascribed to Cu 2p3/2 and Cu 2p1/2, respectively [27,39]. The Cu 2p3/2 at 933.0 eV and 934.8 eV should be assigned to Cu + /Cu 0 and Cu 2+ species [31,39]. Noteworthy, the Cu species of the Cu/MgAlOx are almost Cu + /Cu 0 , whereas for the Cu/ZnAlOx, except for Cu + /Cu 0 , Cu 2+ species also existed on the surface, as proved by the coexistence of satellite peaks at 940~945 eV [39,40].…”

“…Cu species in the form of Cu 0 /Cu + were proved to have a promotional effect on the rates of reaction steps that involve H-transfers [27,29]. Currently, our group also found that the addition of Cu to the NiAlOx could greatly enhance the activity and selectivity of ethanol coupling to butanol [31]. A small amount of Cu 0 /Cu + was suffi-…”

“…The presence of Cu species was supposed to create Lewis acid-base pairs and CuNi alloy sites, thus increasing H-transfer and condensation reactions, resulting in elevated ethanol conversion (30%) and butanol selectivity (64.2%). Recently, our group found that Cu supported on NiAlO x exhibited good performance and stability in the Guerbet coupling process [31]. An optimal compromise between the ethanol conversion (~35%) and butanol selectivity (~45%) has to be sustained for the 0.75%Cu/NiAlO x catalyst for 1000 h at 523 K [31].…”

“…Recently, our group found that Cu supported on NiAlO x exhibited good performance and stability in the Guerbet coupling process [31]. An optimal compromise between the ethanol conversion (~35%) and butanol selectivity (~45%) has to be sustained for the 0.75%Cu/NiAlO x catalyst for 1000 h at 523 K [31]. However, for the above catalysts, the effect of support was seldomly elaborated, which in most cases, influencing the property and performances of the catalysts [32][33][34][35].…”