Support Induced Control of Surface Composition in Cu–Ni/TiO₂ Catalysts Enables High Yield Co-Conversion of HMF and Furfural to Methylated Furans

Abstract

5-(Hydroxymethyl)furfural (HMF) and furfural (FF) have been identified as valuable biomass-derived fuel precursors suitable for catalytic hydrodeoxygenation (HDO) to produce high octane fuel additives such dimethyl furan (DMF) and methyl furan (MF), respectively. In order to realize economically viable production of DMF and MF from biomass, catalytic processes with high yields, low catalyst costs, and process simplicity are needed. Here, we demonstrate simultaneous coprocessing of HMF and FF over Cu−Ni/ TiO 2 catalysts, achieving 87.5% yield of DMF from HMF and 88.5% yield of MF from FF in a one pot reaction. The Cu−Ni/TiO 2 catalyst exhibited improved stability and regeneration compared to Cu/TiO 2 and Cu/Al 2 O 3 catalysts for FF HDO, with a ∼7% loss in FF conversion over four sequential recycles, compared to a ∼50% loss in FF conversion for Cu/Al 2 O 3 and a ∼30% loss in conversion for Cu/TiO 2. Characterization of the Cu−Ni/TiO 2 catalyst by X-ray photoelectron spectroscopy, scanning transmission electron microscopy, and H 2 −temperature-programmed reduction and comparison to monometallic Cu and Ni on Al 2 O 3 and TiO 2 and bimetallic Cu−Ni/Al 2 O 3 catalysts suggest that the unique reactivity and stability of Cu−Ni/TiO 2 derives from support-induced metal segregation in which Cu is selectively enriched at the catalyst surface, while Ni is enriched at the TiO 2 interface. These results demonstrate that Cu−Ni/TiO 2 catalysts promise to be a system capable of integrating directly with a combined HMF and FF product stream from biomass processing to realize lower cost production of liquid fuels from biomass.

Effects of Cu–Ni Bimetallic Catalyst Composition and Support on Activity, Selectivity, and Stability for Furfural Conversion to 2-Methyfuran

“…Regeneration of the used catalysts was performed via calcination at 450°C for 5 h followed by reduction with pure H 2 at 450°C for 3 h. with TEMbased energy dispersive spectroscopy revealed that all observed metal particles contained both Cu and Ni, suggesting consistent formation of bimetallic particles. 39 The analysis was consistent with characterization using temperature-programmed reduction and X-ray diffraction, which both showed evidence of the formation of bimetallic particles. On the basis of this previous analysis, we focused here on analyzing the influence of Ni loading on the structure (both geometric and spatially varying composition) of the Cu−Ni bimetallic particles.…”

“…Given our previous conclusion that observed support effects on FF HDO reaction selectivity were not significantly influenced by differences in metal particle size of the same magnitude of variation observed here, we focused on analyzing the spatial distribution of Cu and Ni in bimetallic particles as a function of metal and support composition. 39 We note that differences in metal particle sizes as a function of support influenced the inherent reactivity of the catalysts.…”

“…Our previous study demonstrated that, apart from the difference in reactivity of Cu on Al 2 O 3 and TiO 2 , which can be explained by the differences in dispersion, differences in surface acidity of the support seemed to not contribute to differences in reactivity of the catalysts. 39 On the basis of this, any differences in FF HDO selectivity over Cu−Ni The influence of Ni addition to the supported Cu catalysts was observed to be different for the TiO 2 supported catalysts, as compared to the Al 2 O 3 supported catalysts. The addition of 0.5 and 1.5% Ni loadings, to form bimetallic Cu−Ni catalysts on TiO 2 , enhanced FF conversion and MF yields, as compared to the Cu(5%)/TiO 2 catalyst.…”

“…In our previous work for Cu(5%)−Ni(5%) catalysts, a significant Cu surface segregation within the bimetallic particles was observed when TiO 2 was used as a support, whereas a homogeneous distribution of the metals throughout the bimetallic particles was observed when Al 2 O 3 was used a support. 39 It was argued that this result was due to strong, specific interactions between Ni and TiO 2 that induced Ni segregation to the TiO 2 interface and Cu to the catalytic surface to minimize the energy of the supported particle. In contrast, the relatively similar interaction energy between Cu or Ni and Al 2 O 3 caused the formation of bimetallic particles with homogeneous Ni and Cu distributions to be energetically favorably.…”

Highly Active Mesoporous Cu−Al2O3 Catalyst for the Hydrodeoxygenation of Furfural to 2‐methylfuran

“…When compared to activity results reported in literature, the results reported herein are quite promising. First of all, binary Cu−Al 2 O 3 catalyst systems for FUR conversion to 2MF have mostly been tested in a batch reactor, indicating that our activity results obtained with a continuous reaction system will be useful in future reports. On the other hand, Jiménez‐Gómez et al reported selective production of 2MF over supported Cu on mesoporous silica (denoted as 10Cu‐MS).…”