Vapor phase hydrogenation of furfural over nickel mixed metal oxide catalysts derived from layered double hydroxides

Abstract

The hydrogenation of furfural is investigated over various reduced nickel mixed metal oxides derived from layered double hydroxides (LDHs) containing Ni-Mg-Al and Ni-CoAl. Upon reduction, relatively large Ni(0) domains develop in the Ni-Mg-Al catalysts, whereas in the Ni-CoAl catalysts smaller metal particles of Ni(0) and Co(0), potentially as alloys, are formed, as evidenced by XAS, XPS, STEM and EELS. All the reduced Ni catalysts display similar selectivities towards major hydrogenation products (furfuryl alcohol and tetrahydrofurfuryl alcohol), though the side products varied with the catalyst composition. The 1.1Ni-0.8Co-Al catalyst showed the greatest activity per titrated site when compared to the other catalysts, with promising activity compared to related catalysts in the literature. The use of base metal catalysts for hydrogenation of furanic compounds may be a promising alternative to the well-studied precious metal catalysts for making biomass-derived chemicals if catalyst selectivity can be improved in future work by alloying or tuning metal-oxide support interactions.

Vapor Phase Hydrogenolysis of Furanics Utilizing Reduced Cobalt Mixed Metal Oxide Catalysts

“…Prior to reaction, the spectrum mimics Co 3 O 4 as ar esulto ft he lack of a2 p 3/2 satellite peak and the peak maximum of 2p 3/2 at approximately 780.5 eV. [26,[36][37][38] The emergence of as houlder after reduction at approximately at 778 eV,a nd the presence of as atellite peak, indicates the reduction of Co 3 O 4 to CoO and Co 0 . [36] With regards to the Fe species, very little change is indicated before and after reduction/passivation, with the peak maximum around7 12 eV.T his maximum is located at higher eV than standard Fe oxides( FeO, Fe 3 O 4 ,a nd Fe 2 O 3 ), which may furthers upport the strongi nteraction betweenF ea nd Co, causing the Fe spectra to shift as ac onsequence of the more electronegative Co oxide.…”

“…To that end, Co was chosen as the base metal in the system because of its uniques electivity properties previously determined in FUR reduction. [26] Along with Co, small amounts of Fe were added into the mixed metal oxide matrix to tune the activity and selectivity towards 2-MF.I n Ta ble 1, the physical properties are summarized for various Co/ Fe ratio.…”

“…The XRD patterns post calcination demonstrated that an on-crystalline structure was created, as evidenced by the lack of sharp peaks associated with the oxidespresent in Figure 1a.O ne broad peak is distinguishable between 35-408,w hich correlates with the Co 3 O 4 (3 11)p eak at 37.08.A dditionally,o ne nlarging that section in Figure 1b peaks, might suggest good dispersion of the oxide species, potentially forming as olids olution similar to Ni-Co-Al and Ni-Mg-Al mixed metal oxidesreportedi np rior literature. [26][27][28] The reduction profile of each catalyst was investigated through TPR to gatheri nformation about the catalystu nder an H 2 atmosphere with varyingt emperature. Figure 2s hows the reduction profile of each catalyst in 10 %H 2 /Ar using a58Cmin À1 ramp rate.…”

“…Co-Fe-Al mixed metal oxides with varying Co:Fe ratios of 12:1, 6:1, 4:1, 3:1, and no Fe addition (Co/(Fe + Al) always kept at 0.25) were prepared in the following manner,s imilar to prior LDH syntheses, with minor modifications. [26,47] A0 .6 m metal nitrate solution, Solution A, with corresponding metal cations ratios above, and a1 .0 m NaOH solution, Solution B, were created. A0 .3 m solution of Na 2 CO 3 ,S olution C, was placed in a3 -neck, 1L flask, and using ap eristaltic pump Solution Aa nd Solution Bw ere added dropwise into Solution Ca ta pproximately 5mLmin À1 under vigorous stirring, at room temperature, with N 2 bubbling.…”

“…Ap revious study involving Co-Al mixed metal oxidesd erived from layered double hydroxides (LDH) displayed elevated selectivities towards 2-MF in the vapor phase hydrogenation of FUR at 155 8C. [26] Use of LDH materials as precursors to synthesize mixed metal oxidesi sawell-known approacht oc reate well-dispersed and relativelyh igh porositym aterials. [27] The LDH materiala llows forh igh interaction between the various metals in the matrix, and can lead to smaller metal domains upon reduction.…”