Carbon-supported, Pt and PtCo nanocrystals (NCs) with controlled size and composition were synthesized and examined for hydrodeoxygenation (HDO) of 5-hydroxymethylfurfural (HMF). Experiments in a continuous flow reactor with 1-propanol solvent, at 120 to 160 °C and 33 bar H2, demonstrated that reaction is sequential on both Pt and PtCo alloys, with 2,5-dimethylfuran (DMF) formed as an intermediate product. However, the reaction of DMF is greatly suppressed on the alloys, such that a Pt3Co2 catalyst achieved DMF yields as high as 98%. XRD and XAS data indicate that the Pt3Co2 catalyst consists of a Pt-rich core and a Co oxide surface monolayer whose structure differs substantially from that of bulk Co oxide. Density functional theory (DFT) calculations reveal that the oxide monolayer interacts weakly with the furan ring to prevent side reactions, including overhydrogenation and ring opening, while providing sites for effective HDO to the desired product, DMF. We demonstrate that control over metal nanoparticle size and composition, along with operating conditions, is crucial to achieving good performance and stability. Implications of this mechanism for other reactions and catalysts are discussed

The liquid-phase (69 bar) reaction of 5-hydroxymethylfurfural (HMF) with 2-propanol for production of furanyl ethers was studied at 413 and 453 K over a series of oxide catalysts, including γ-Al 2 O 3 , ZrO 2 , TiO 2 , Al 2 O 3 /SBA-15, ZrO 2 /SBA-15, TiO 2 /SBA-15, H-BEA, and Sn-BEA. The acidity of each of the catalysts was first characterized for Brønsted sites using TPD-TGA of 2-propanamine and for Lewis sites using TPD-TGA of 1-propanol. Catalysts with strong Brønsted acidity (H-BEA and Al 2 O 3 /SBA-15) formed 5-[(1-methylethoxy) methyl]furfural with high selectivities, while materials with Lewis acidity (γ-Al 2 O 3 , ZrO 2 , TiO 2 , and Sn-BEA)or weak Brønsted acidity (ZrO 2 /SBA-15 and TiO 2 /SBA-15) were active for transfer hydrogenation from the alcohol to HMF to produce 2,5-bis(hydroxymethyl)furan, with subsequent reactions to the mono-or diethers. Each of the catalysts was stable under the flow-reactor conditions but the selectivities varied with the particular oxide being investigated.

The three-phase hydrodeoxygenation reaction of 5-hydroxymethylfurfural (HMF) with H 2 was studied over a 10 wt % Pt/C catalyst using both batch and flow reactors, with ethanol, 1-propanol, and toluene solvents. The reaction is shown to be sequential, with HMF reacting first to furfuryl ethers and other partially hydrogenated products. These intermediate products then form dimethyl furan (DMF), which in turn reacts further to undesired products. Furfuryl ethers were found to react to DMF much faster than HMF, explaining the higher reactivity of HMF when alcohol solvents were used. With the optimal residence time, it was possible to achieve yields approaching 70% in the flow reactor with the Pt/C catalyst. Much higher selectivities and yields were obtained in the flow reactor than in the batch reactor because side products are formed sequentially, rather than in parallel, demonstrating the importance of choosing the correct type of reactor in catalyst screening.

Hydrodeoxygenation (HDO) of 5-hydroxymethylfurfural (HMF) was examined over well-defined and uniform, Pt-Ni, Pt-Zn and Pt-Cu alloyed nanocrystals (NCs) supported on carbon, at 33 bar and between 160 and 200 °C. Pt-Ni alloy catalysts were prepared in three different Pt:Ni ratios, Pt6Ni, Pt3Ni, and PtNi. While all of the Pt-Ni alloys were more selective for producing 2,5-dimethylfuran (DMF) than were Pt or Ni monometallic catalysts, the Pt3Ni catalyst was superior to the other compositions, exhibiting a yield of 98% due to its optimum surface composition. Similarly high yields were obtained on catalysts prepared from Pt2Zn and PtCu NCs. Possible reasons are given for why each of the Pt-alloy catalysts is highly selective

The three-phase hydrodeoxygenation (HDO) of 5-hydroxymethylfurfural (HMF) and hydrogenation of 2,5-dimethylfuran (DMF) were studied over six carbon-supported metal catalysts (Pt, Pd, Ir, Ru, Ni, and Co) using a tubular flow reactor with 1-propanol solvent, at 180°C and 33 bar. By varying the space time in the reactor, the reaction of HMF is shown to be sequential, with HMF reacting first to furfuryl ethers and other partially hydrogenated products, which then form 2,5-dimethylfuran (DMF). Ring-opened products and 2,5dimethyltetrahydrofuran (DMTHF) were produced only from reaction of DMF. Rate constants for the pseudo-first-order sequential reactions were obtained for each of the metals. The selectivities for the reaction of DMF varied with the metal catalyst, with Pd forming primarily DMTHF, Ir forming a mixture of DMTHF and open-ring products, and the other metals forming primarily open-ring products. Catalyst stabilities followed the order Pt ~ Ir > Pd > Ni> Co > Ru. Since the stability order correlated with carbon balances in the product (>93% for Pt; <75% for Ru), deactivation appears to be caused by deposition of humins on the catalyst.

The selective hydrodeoxygenation (HDO) of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) is an important step in cellulosic biomass upgrading to biofuels, where bimetallic oxophilic catalysts have shown promising performance. Well controlled bimetallic NiCu and NiCu3 nanocrystals supported on carbon are shown to give high yields and selectivities to DMF. To shed light on the active phase, near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) was used to characterize the surface composition of these highly selective base-metal catalysts under reducing conditions relevant to the HDO reaction. Reactions were performed in a continuous flow reactor under reasonable conditions of 33 bar and 180 °C. The Ni alloys were significantly more selective for DMF compared to monometallic Ni or Cu catalysts. With a well-controlled surface composition, the nanocrystal NiCu3/C catalyst exhibited a maximum DMF yield of 98.7%. NAP-XPS characterization showed that the Ni–Cu nanocrystals were completely reduced below 250 °C in H2; this, together with bulk thermodynamic calculations, implies that the catalysts were completely reduced under the reaction conditions. NAP-XPS also indicated that the NiCu3 nanocrystal structure consisted of a Cu-rich core and a 1 : 1 molar Ni : Cu shell

Graphene nanoplatelet (GNP)–epoxy composites were fabricated for the investigation of the dielectric permittivity and microwave absorption in a frequency range from 8 to 20 GHz. The intrinsically conductive GNP particles and polarized interfacial centers in the composites contribute to the microwave absorption. A minimum reflection loss of −14.5 dB at 18.9 GHz is observed for the GNP–epoxy composites with 15 wt. % GNP loading, which is mainly attributed to electric conductivity and the charge multipoles at the polarized interfaces in the GNP–epoxy composites.

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