New Routes for Refinery of Biogenic Platform Chemicals Catalyzed by Cerium Oxide-supported Ruthenium Nanoparticles in Water

Highly selective hydrogenative carbon–carbon bond scission of biomass-derived platform oxygenates was achieved with a cerium oxide-supported ruthenium nanoparticle catalyst in water. The present catalyst enabled the selective cleavage of carbon–carbon σ bonds adjacent to carboxyl, ester, and hydroxymethyl groups, opening new eight synthetic routes to valuable chemicals from biomass derivatives. The high selectivity for such carbon-carbon bond scission over carbon-oxygen bonds was attributed to the multiple catalytic roles of the Ru nanoparticles assisted by the in situ formed Ce(OH)3.

 Table S7. Support effects on Ru dispersion and 2-BuOH yields in the reaction of LA and 1,4-PeD Figure S1. Time profiles of the hydrogenative decarboxylation of LA using Ru/CeO2. The reaction conditions were the same as those in Table 1, entry 1.

Captions of Figures 
 Figure S2. The gas chromatography analysis of the gaseous phase after the reaction of LA in Table 1, entry 1.  Figure S3. XRD patterns of (a) pristine CeO2, (b) fresh Ru/CeO2, (c) used Ru/CeO2 without exposure to air, (d) used Ce(OH)3 without exposure to air. Red triangle: Ce(OH)3.

1) General
Organic chemicals were purchased form Wako Pure Chemical Industries, Ltd, Tokyo Chemical Industry Co., Ltd and Sigma-Aldrich.
Hydrotalcite was obtained from Tomita Pharmaceuticals. The following materials were prepared according to literature procedures: 1,3,5-pentanetriol S1 and Ce(OH)3. S2 Ce(OH)3 was handled under the Ar atmosphere. Center for Ultra-High Voltage Electron Microscopy, Osaka University. Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) data were obtained using a SII Nano Technology SPS7800 instrument.

Preparation of metal oxide-supported noble metal catalysts
The Ru/CeO2 catalyst was prepared by the deposition-precipitation method. CeO2 (1 g) was added to 50 mL of an aqueous solution of RuCl3 (4 mM). After stirring for 1 h, 3 mL of an S4 aqueous NH3 solution (28%) was added to the reaction mixture, which was further stirred at 298 K for 12 h. The obtained slurry was filtered and washed with deionized water and dried at 383 K for 12 h, and finally calcined at 573 K for 3 h under static air atmosphere to obtain Ru/CeO2 as a blown powder. ICP-AES analysis determined the Ru content in Ru/CeO2 to be 2.0 wt%. Other metal oxide-supported Ru catalysts (Ru/ZrO2, Ru/TiO2, Ru/MgO, and Ru/Al2O3) were also prepared by the deposition-precipitation method. M/CeO2 (M = Pt, Pd, Rh, and Ir) catalysts were prepared in a similar way using H2PtCl6, Pd(NO3)2, RhCl3, and IrCl3 as the metal precursors.

Preparation of Ru/HAP and Ru/HT
Ru/HAP and Ru/HT were prepared according to reported procedures with slight modifications. S4.S5 HAP or HT (1 g) was added to 50 mL of an aqueous solution of RuCl3 (4 mM). After stirring for 12 h, the obtained slurry was filtered, washed with deionized water, and dried at 383 K for 12 h to obtain Ru/HAP or Ru/HT.

Preparation of Ru/SiO2
Ru/SiO2 was prepared by the impregnation method. SiO2 (1 g) was added to 50 mL of an aqueous solution of RuCl3 (4 mM) and the mixture was stirred magnetically for 4 h. Water was removed by rotary evaporation under reduced pressure to give a blown solid. The obtained powder was dried at 383 K for 12 h, then calcined at 573 K for 3 h under static air atmosphere to obtain Ru/SiO2 as a black powder.

3) Representative reaction procedures Typical reaction procedure under H2 pressure
The reactions with levulinic acid were carried out in a 50 mL stainless steel autoclave equipped with a Teflon® vessel. The vessel was charged with 1 mmol of levulinic acid, 0.1 g of catalyst, and 3 mL of water; a Teflon®-coated magnetic stir bar was also added. The reactor was sealed, purged three times with H2 at 1 MPa, then pressurized to 3 MPa, heated to 423 K, and stirred at 700 rpm for 12 h. After the reaction, the autoclave was cooled in an ice-water bath and the hydrogen gas was carefully released. The resulting reaction mixture was analyzed by GC-MS. (Tables 2 and S4, entries 3
Then, the vessel was charged with 1 mmol of substrate, 0.1 g of Ru/CeO2-reduced, and 3 mL of hexane; a Teflon®-coated magnetic stir bar was also added. The reactor was sealed, purged three times with H2 at 1 MPa, then pressurized to 3 MPa, heated to 453 K, and stirred at 700 rpm for 12 h. After the reaction, the autoclave was cooled in an ice-water bath and the hydrogen gas was carefully released. The resulting reaction mixture was analyzed by GC-MS.

Catalyst reuse experiments (Table S6)
Reuse experiments were carried out after each hydrodecarboxylation of LA, in which the catalyst was separated from the reaction mixture by centrifugation, washed with water, and dried at 383 K overnight. The recovered catalyst was subsequently calcined in air for 3 h at 573 K, after which it was reused for the next reaction.

Isolation of the products (Tables 2 and S4, entries 3, 4, 10, and 20)
After the reaction, the autoclave was cooled in an ice-water bath and the hydrogen gas was carefully released. The solid catalyst was removed by filtration and washed with ether. The obtained liquid phase was extracted with ether. The organic phase was dried with anhydrous Na2SO4 and then, concentrated by rotary evaporation. In the case of the reactions using hexane solvent, the catalyst was removed by filtration and evaporation of the solvent afforded the desired products.
[b] The data were also showed in Table 1.
[c] The reaction conditions were similar to those in Table 2, entry 17. S12 Figure S1. Time profiles of the hydrogenative decarboxylation of LA using Ru/CeO2. The reaction conditions were the same as those in Table 1, entry 1. Figure S2. The gas chromatography analysis of the gaseous phase after the reaction of LA in Table 1, entry 1.   Figure S5. Ce L3-edge XANES spectra of Ru/CeO2 (fresh and used), CeO2 and Ce2(CO3)3. Figure S6. FE-SEM images of (a) fresh Ru/CeO2, (b) used Ru/CeO2, and HR-TEM images of (c, d) used Ru/CeO2. Yellow circles showed the presence of Ru nanoparticles..