Supporting information

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1 Supporting information Cu Sub-nanoparticles on Cu/CeO 2 as an Effective Catalyst for Methanol Synthesis from Organic Carbonate by Hydrogenation Masazumi Tamura* Takahisa Kitanaka, Yoshinao Nakagawa and Keiichi Tomishige* Graduate School of Engineering, Tohoku University, Aoba , Aramaki, Aoba-ku, Sendai, (Japan) mtamura@erec.che.tohoku.ac.jp, tomi@erec.che.tohoku.ac.jp Table of contents 1. General information 2. Catalyst 3. A typical procedure for hydrogenation of DMC to methanol 4. XAFS analyses 5. BET, XRD, TPR and FE-TEM analyses 6. Supporting Tables Table S1 Typical reported Cu-based catalysts for hydrogenation of CO 2 to methanol and Cu/CeO 2 catalyst for hydrogenation of DMC Table S2 Reported heterogeneous catalysts for hydrogenation of carbonates Table S3 Methanol synthesis by hydrogenation of dimethyl carbonate (DMC) over various catalysts Table S4 Detailed data for time-course of hydrogenation of DMC over Cu/CeO 2 catalyst Table S5 Effect of H 2 pressure on hydrogenation of DMC over Cu(1)/CeO 2 Table S6 Detailed data for curve-fitting results of Cu K-edge of Cu(1)/CeO 2 after reduction and after reaction Table S7 Consumption amount of H 2 from TPR analyses Table S8 Amount of each product in hydrogenation of DMC over Cu(1)/CeO 2 catalyst 7. Supporting Figures Figure S1 (I) XRD profiles of Cu(x)/CeO 2 (x=0-5) and Cu(1)/SiO 2 after the reaction and (II) the expanded XRD profiles at the range of o Figure S2 Time-courses of hydrogenation of DMC over Cu(1)/CeO 2 at (a) 8 MPa H 2 and (b) 2.5 MPa H 2 Figure S3 TEM images of Cu(1)/CeO 2 after the reaction (a) under focus image, (b) overfocus image (c) underfocus image Figure S4 TPR profiles of Cu(x)/CeO 2 (x=0-5) and Cu(1)/SiO 2 Figure S5 (I) k 3 -weighted EXAFS oscillations. (II) Fourier filtered EXAFS data (solid data) and 1

2 calculated data (dotted line). Figure S6 XRD profiles of Cu(1)/CeO 2 (a) before reduction, (b) after reduction (t=0 h) and (c) after reaction (t=4 h). Figure S7 Fourier transform of k 3 -weighted Cu K-edge EXAFS for Cu(1)/CeO 2 catalysts and Cu foil Figure S8 (a) Dependence of H 2 pressure on the reaction rate over Cu(1)/CeO 2, and (b) dependence of DMC concentration on the reaction rate over Cu(1)/CeO 2 Figure S9 GC chart of the reaction mixture after 20 h 8. References 2

3 1. General information The GC (Shimadzu GC-2014)) and GCMS (Shimazu QP5050) analyses were carried out with a TC-WAX capillary column (GL Sciences Inc.) using nitrogen as the carrier gas. All the chemicals for organic reactions were analytic reagents from chemical products corporation and were used without further purification: Dimethyl carbonate (DMC, anhydrous, Sigma-Aldrich Inc.), tetrahydrofuran (THF, anhydrous, Wako Pure Chemical Industries, Ltd.), dodecane (Tokyo Chemical Industry Co. Ltd.). 2. Catalyst Preparation of CeO 2 support was carried out by calcining cerium oxide HS (Daiichi Kigenso, Japan) for 3 hours under air at 873 K. The specific surface area (BET method) of pure CeO 2 was 84 m 2 /g. The purity of pure CeO 2 is 99.97%. Cu(x)/CeO 2 was prepared by impregnating the CeO 2 with an aqueous solution of Cu(NO 3 ) 2 3 H 2 O (Wako Pure Chemical Industries, Ltd.), where x means Cu amount (wt%). M(1)/CeO 2 catalysts (M=Pt, Ir, Au, Ni, Rh, Co, Pd, Ru and Ag) were prepared by the similar method using the corresponding precursors (Co(NO 3 ) 2 6H 2 O (Wako Pure Chemical Industries, Ltd.), HAuCl 4, Ni(NO 3 ) 2 6H 2 O (Wako Pure Chemical Industries, Ltd.), Pd(NH 3 ) 2 (NO 2 ) 2 aq (Wako Pure Chemical Industries, Ltd.), Ru(NO)(NO 3 ) X (OH) Y aq (Sigma-Aldrich Inc.), AgNO 3 (Wako Pure Chemical Industries, Ltd.), H 2 IrCl 6 nh 2 O (FURUYA METAL CO., LTD), Rh(NO 3 ) 3 aq (Wako Pure Chemical Industries, Ltd.), [Pt(NH 3 ) 4 ](NO 3 ) 2 (Sigma-Aldrich Inc.)). Cu(1)/support catalysts (support = ZrO 2, MgO, TiO 2, -Al 2 O 3, SiO 2, SiO 2 -Al 2 O 3 (SAL)) were prepared by impregnating each support with an aqueous solution of Cu(NO 3 ) 2 3 H 2 O: ZrO 2 (RC-100P, Daiichi Kigenso Kogyo Co. Ltd., calcined under air at 1273 K for 1 h.), MgO (Ube Industries, Ltd., MgO 500A), TiO 2 (Nippon Aerosil Co. Ltd., calcined under air at 973 K, P-25), γ-al 2 O 3 (Nippon Aerosil Co. Ltd.), SiO 2 (Fuji Silysia Chemical Ltd., G-6 was calcined under air at 973 K for 1 h.), SiO 2 -Al 2 O 3 (SAL, JRC-SAL-3). The specific surface areas of ZrO 2, MgO, TiO 2, -Al 2 O 3, SiO 2 and SiO 2 -Al 2 O 3 (SAL) are 31, 37, 25, 100, 530 and 560 m 2 /g, respectively. All catalysts were calcined at 773 K for 3 h. Carbon-supported 5 wt% metal catalysts (M(5)/C) were commercially available: Ru(5)/C (Wako Pure Chemical Industries, Ltd.), Rh(5)/C (Wako Pure Chemical Industries, Ltd.), Pd(5)/C (Wako Pure Chemical Industries, Ltd.), Pt(5)/C (Wako Pure Chemical Industries, Ltd.). 3. A typical procedure for hydrogenation of DMC to methanol Activity tests were performed in a 190 ml stainless-steel autoclave with an inserted glass vessel. DMC (30 mmol), THF (5 g) and dodecane (about 0.15 g, an internal standard) were poured into the glass vessel with a stirrer bar. Cu(1)/CeO 2 (100 mg), which was dried at 473 K for 10 min under 2% O 2 /N 2 flow just before the reaction, was quickly added to the mixture of DMC, THF and dodecane (an internal standard) under air. The reactor was sealed, and then the air content was quickly purged by flushing with 1 MPa H 2 (99.99%, Nippon Peroxide Co., Ltd.) three times. The autoclave was heated to 433 K and the temperature was monitored by using a thermocouple inserted in the autoclave. Once the temperature reached 433 K, 3

4 the H 2 pressure was increased to 8.0 MPa. Heating time to 433 K is about 15 min. During the experiment, the stirring rate was fixed at 400 rpm (magnetic stirring). After 4 h, the gases were collected in a gas bag. The reaction mixture was transferred to a vial. The details of the reaction conditions are described in each result. The products in the gas phase and liquid phase were analyzed by GC with TC-WAX (GL Sciences Inc.) and Porapak N (GL Science), respectively. A typical GC chart of liquid phase was shown in Figure S9. Conversion of the substrate, and yield and selectivity of the products were determined on the basis of the carbonyl of DMC by GC using dodecane as an internal standard. These values are calculated as follows. Methanol amount based on the carbonyl of DMC (mmol) [A] = (Produced methanol (mol) + 2 produced dimethyl ether (mmol) produced methyl formate (mol)) / 3. Total products and substrates on the carbonyl base of DMC (mmol) [B] = [A] + Methyl formate (mol) + Produced CO (mol) + Produced CH 4 (mol) [A] / (Produced methanol (mol)) + Produced CO 2 (mol) + residual DMC (mol). In this equation, CH 4 can be produced by hydrogenolysis of methanol or hydrogenation of CO or CO 2, but amount of CO and CO 2 is very small. Therefore, contribution of the carbonyl to CH 4 production was estimated using the ratio of [A]/(Produced methanol (mol)). CO 2 can be produced by H 2 O which is produced from hydrogenolysis of CH 3 OH with H 2 (CH 3 OH + H 2 CH 4 + H 2 O) and etherification of methanol (2 CH 3 OH CH 3 OCH 3 + H 2 O). Therefore, Produced CO 2 amount was calculated by sum of produced CH 4 (mol) and produced dimethyl ether (mol), although produced dimethyl ether amount was very small in the case of Cu(x)/CeO 2 catalysts ( 0.1 mmol). As above, conversion, selectivity and yield are as follows. The selectivity and yield are based on the carbonyl of DMC. Conversion (%) = Residual DMC (mol) / [B]. Selectivity (%) based on the carbonyl of DMC = Product (mmol) / [B] 100. Yield (%) based on the carbonyl of DMC = Conversion Selectivity / 100. Yield (%) based on the total produced methanol = Total produced methanol (mol) / 3 (Introduced DMC amount (mol)) 100. The carbon balance was essentially between 95 to 105 % in all catalysts. Moreover, H 2 O included in catalysts, substrates or solvents can be mixed in the reaction media, which causes hydration of DMC to two molar methanol and one molar CO 2. Therefore, influence of the external H 2 O was excluded in estimation of conversion, selectivity and yield by subtracting the external water amount from DMC amount. The external H 2 O amount can be estimated as follows; External H 2 O amount (mmol) = Produced CO 2 (mmol) produced CH 4 (mmol) produced dimethyl ether (mmol). The external H 2 O amount was very small and for example 0.45 mmol in entry 1 in Table 1, which is about 1.5 mol% with respect to DMC amount. The amount of each product in the case of Cu(1)/CeO 2 catalyst was shown in Table S8. 4

5 The reaction rates of methanol formation rate (mmol h -1 g -1 -cu ) was calculated from the methanol amount based on the carbonyl of DMC and based on total Cu metal. TOF (h -1 ) was calculated from the methanol amount based on the carbonyl of DMC and based on total Cu metal. TON was calculated from the methanol amount based on the carbonyl or total produced methanol and based on total Cu metal. TOF (h -1 ) and TON were calculated by the following equations. TOF (h -1 ) = (Methanol amount based on the carbonyl of DMC (mmol)) / (Total Cu amount (mmol)) / (Reaction time (h)) TON based on the carbonyl of DMC = (Methanol amount based on the carbonyl of DMC (mmol)) / (Total Cu amount (mmol)) TON based on the total produced methanol = (Total produced methanol (mmol)) / (Total Cu amount (mmol)) The reusability test of Cu(1)/CeO 2 catalyst was conducted as follows: After the reaction, the used catalyst was collected by decantation. The collected catalyst was dried under air. The recovered catalyst was treated at 473 K for 10 min under 2% O 2 /N 2 flow just before the next reaction test, and the obtained catalyst was applied to the next reaction test. 4. XAFS analyses The X-ray absorption spectroscopy (XAS) was measured at the BL01B1 station at SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI; Proposal No. 2014B1248). The storage ring was operated at 8 GeV, and a Si (111) single crystal were used to obtain a monochromatic X-ray beam. Ion chambers for I0 were filled with 100% N 2 for Cu K-edge measurement. Ion chambers for I were filled with 80% N 2 +20% Ar for Cu K-edge measurement. The sample of Cu(1)/CeO 2 catalyst for the XAFS measurement was prepared by pressing about 0.2 g Cu(1)/CeO 2 to disks for Cu K-edge measurement. The sample disk was transferred to the in situ cell. The sample was heated to 433 K in H 2 flow (30 ml/min) under atmospheric pressure. The XAFS data were collected in a fluorescence mode under in situ conditions using a 19-element Ge solid-state detector (19-SSD). In the case of the Cu(1)/CeO 2 catalyst after the reaction, the recovered powder was transferred to a plastic bag under N 2 gas, and the bag was sealed to avoid exposing the catalyst to air. The XAFS data were collected in a fluorescence mode measurement using a Lytle detector. For EXAFS analysis, the oscillation was first extracted from the EXAFS data using a spline smoothing method [1]. Fourier transformation of the k 3 -weighted EXAFS oscillation from the k space to the r space was performed to obtain a radial distribution function. The inversely Fourier filtered data were analyzed using a usual curve fitting method [2]. The empirical phase shift and amplitude functions for Cu-Cu and Cu-O bonds were extracted from the data of standard samples, Cu foil and Cu 2 O, respectively. Analyses of EXAFS and XANES (X-ray absorption near edge spectra) data were performed using a computer program (REX2000, ver ; Rigaku Corp.). 5

6 5. BET, XRD, TPR and FE-TEM analyses The surface area of Cu/CeO 2 was measured with BET method (N 2 adsorption) using Gemini (Micromeritics). X-ray diffraction (XRD) patterns were recorded by Rigaku Ultima IV with Cu Kα (40 kv, 40 ma) radiation. Temperature-programmed reduction (TPR) was carried out in a fixed-bed reactor equipped with a thermal conductivity detector using 5% H 2 diluted with Ar (30 ml/min). The amount of catalyst was 0.1 g, and the temperature was increased from room temperature to 1123 K at a heating rate of 10 K/min. Field emission transmission electron microscope (FE-TEM) images were obtained on a JEM-2100F instrument (JEOL Ltd.) operated at 200 kv. The catalyst after the reaction was used as a sample for the TEM observation. The sample was dispersed in ethanol. Once the sample was placed on Mo grids under air atmosphere, the sample was quickly transferred to the TEM chamber and degassed. 6

7 6. Supporting Tables Table S1 Typical reported Cu-based catalysts for hydrogenation of CO 2 to methanol and Cu/CeO 2 catalyst for hydrogenation of CO 2 and DMC a Catalyst Substrate Loading amount Cu particle size P H2 P CO2 P Total T Conv. Selec. Methanol formation rate of Cu (wt%) (nm) (MPa) (MPa) (MPa) (K) (%) (%) (mmol g -1 -Cu h -1 ) Ref. Cu/ZrO 2 CO [3] Cu/ZnO CO n.d Cu-Ga/ZnO CO n.d Cu-Ga/ZnO CO [4] Cu-ZnO/SiO 2 CO n.d Cu-Zn-Ga/SiO 2 CO n.d Cu-Zn-Ga/SiO 2 CO n.d Cu-Zn-Ga/SiO 2 CO [5] Cu/Zn/ZO 2 CO 2 63 n.d Cu/Zn/ZO 2 CO 2 63 n.d n.d. n.d 5.0 [6] Cu/Zn/ZO 2 CO 2 2 n.d Cu/Ga 2 O 3 /ZrO 2 Cu/B 2 O 3 /ZrO 2 CO 2 CO ~3 ~ n.d. n.d [7] 2 CO n.d. n.d. 5.1 Cu/ZnO/G 2 O 3 /ZrO 2 CO n.d Cu/ZnO/G 2 O 3 /ZrO 2 [8] Cu/ZnO/ZrO 2 CO 2 34 n.d CO 2 34 n.d [9] Cu/ZnO/ZrO 2 CO 2 38 n.d [10] CuO-ZnO-ZrO 2 (Glycine-nitrate) CO 2 38 n.d CuO-ZnO-ZrO 2 (Glycine-nitrate CO 2 38 n.d n.d. n.d. 8.0 [11] Cu/Zn/Al/ZrO 2 CO 2 46 n.d n.d. [12] Cu/ZnO CO < Cu/ZnO CO <5 n.d. 2.9 [13] Cu/ZnO CO <5 n.d. 0.6 Cu/ZnO/Al 2 O 3 CO 2 24 n.d Cu/ZnO/Al 2 O 3 CO 2 24 n.d n.d. [14] Cu/ZnO/Al 2 O 3 CO 2 58 n.d CO 2 1 < <1 - - Cu/CeO 1 < > DMC 1 < b This work 1 < b a Yellow bar represents the examples at comparatively low temperature (433 K and 453 K), and gray bar represents the examples with high reaction rate on total Cu amount basis (mmol g -Cu -1 h -1 ). b Reaction rate was calculated from the methanol amount based on the carbonyl of DMC. n.d. = no data. 7

8 Table S2 Reported heterogeneous catalysts for hydrogenation of carbonates Catalyst Cu loading amount (wt%) Cu particle size (nm) Substrate Reactor P H2 (MPa) T (K) t (h) Conv. (%) Selec. a (%) Yield (%) Methanol formation rate (mmol / g -Cu / h) CuCr 2 O EC Batch /0.2/3 (7.5) Cu/mesoporous-silica EC Cu-SiO 2 nanocomposite Fixed bed TOF b (h -1 ) TON c Active site Ref. Cu 0 and cubic spinel CuCr 2 O Cu 0 and Cu + 9b d 70 8 EC Batch > c d Cu 0 and Cu DMC Batch c d 9a d 1 <1 DMC Batch > Cu/CeO 2 1 <1 DMC Batch a Selectivity to methanol based on the carbonyl of carbonates. b TOF was calculated on the basis of total Cu amount using the data with the lowest conversion reported in each literature. c TON was calculated on the basis of total Cu amount. d These are the references in the manuscript. Cu 0 This work 8

9 Table S3 Methanol synthesis by hydrogenation of dimethyl carbonate (DMC) over various catalysts a Catalyst Conv. Yield Selectivity c (%) (%) (%) CH 3 OH HCOOCH 3 CH 4 CO CO 2 Cu(1)/CeO Pt(1)/CeO Ag(1)/CeO Au(1)/CeO Ir(1)/CeO Ni(1)/CeO Rh(1)/CeO Co(1)/CeO Pd(1)/CeO Ru(1)/CeO Ru(5)/C Rh(5)/C Pd(5)/C Pt(5)/C Cu(1)/ZrO Cu(1)/MgO Cu(1)/TiO Cu(1)/ -Al 2 O Cu(1)/SAL b Cu(1)/SiO 2 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 CeO c Cu(1)/CeO a Reaction conditions: DMC 30 mmol, catalyst 100 mg, THF 5 g, H 2 8 MPa, 433 K, 4 h. b SAL is SiO 2 -Al 2 O 3. c Selectivity based on the carbonyl amount of DMC. c 1st reuse. 9

10 Table S4 Detailed data for the time-course of hydrogenation of DMC over Cu(1)/CeO 2 catalyst Time (h) Conv. (%) Yield (%) Selectivity (%) CH 3 OH CH 3 OCOH CH 4 CO CO Reaction conditions: DMC 15 mmol, Cu(1)/CeO mg, THF 5 g, H 2 8 MPa, 433 K. 10

11 Table S5 Effect of H 2 pressure on hydrogenation of DMC over Cu(1)/CeO 2 H 2 pressure (MPa) Conv. (%) Yield (%) Selectivity (%) CH 3 OH CH 3 OCOH CH 4 CO CO Reaction conditions: DMC 30 mmol, Cu(1)/CeO mg, THF 5 g, 433 K, 4 h. 11

12 Table S6 Detailed data for the curve-fitting results of Cu K-edge of Cu(1)/CeO 2 after reduction and after reaction Catalyst Condition Shells CN a R b σ c d e ΔE 0 R f (10-1 nm) (10-1 nm) (ev) (%) Cu(1)/CeO 2 reduced by in-situ H 2 flow Cu-Cu Cu(1)/CeO 2 after reaction Cu-Cu Cu foil Cu-Cu a Coordination number. b Bond distance. c Debye Waller factor. d Difference in the origin of photoelectron energy between the reference and the sample. e Residual factor. Fourier filtering range: nm. 12

13 Table S7 Consumption amount of H 2 from TPR analyses Catalyst Cu amount (mmol g -1 ) H 2 consumption (mmol g -1 ) H 2 consumption - Cu amount (mmol g -1 ) Cu(1)/SiO Cu(0.5)/CeO Cu(1)/CeO Cu(2)/CeO Cu(3)/CeO Cu(5)/CeO

14 Table S8 Amount of each product in hydrogenation of DMC over Cu(1)/CeO 2 catalyst Experiment Table S1 Cu(1)/CeO 2 Figure 1 Cu(1)/CeO 2 DMC amount (mmol) Time (h) Conv. (%) Selectivity of CH 3 OH (%) a a Selectivity of CH 3 OH was calculated based on total produced methanol. Total amount (mmol) CH 3 OH CH 3 OCOH CH 4 CO CO 2 CH 3 OCH

15 Intensity (a.u.) Intensity (a.u.) 7. Supporting Figures (I) Cu 2 O CuO Cu CuO (II) CuO Cu 2 O CuO Cu (g) (f) (e) (d) (c) (b) (a) / o / o (g) (f) (e) (d) (c) (b) (a) Figure S1 (I) XRD profiles of Cu(x)/CeO 2 (x=0-5) and Cu(1)/SiO 2 after the reaction and (II) the expanded XRD profiles at the range of o. (a) CeO 2, (b) Cu(0.5)/CeO 2, (c) Cu(1)/CeO 2, (d) Cu(2)/CeO 2, (e) Cu(3)/CeO 2, (f) Cu(5)/CeO 2, (g) Cu(1)/SiO 2. 15

16 Yield of methanol / % Yield of methanol / % (a) 15 (b) Slope = 1.39 (R 2 = 0.997) 10 Slope = 1.07 (R 2 = 0.998) Time / h Time / h Figure S2 Time-courses of the hydrogenation of DMC over Cu(1)/CeO 2 at (a) 8 MPa H 2 and (b) 2.5 MPa H 2 Reaction conditions: DMC 30 mmol, Cu(1)/CeO mg, THF 5 g, 433 K. 16

17 (a) (b) (c) Figure S3 TEM images of Cu(1)/CeO 2 after the reaction (a) under focus image, (b) overfocus image (c) underfocus image. The TEM analyses were conducted ex-situ, and the sample was transformed from the liquid phase to the Mo grid as fast as possible to avoid exposing to the air. 17

18 H 2 consumption (a.u.) 5 (g) (f) (e) (d) (c) T / K Figure S4 TPR profiles of Cu(x)/CeO 2 (x=0-5) and Cu(1)/SiO 2. (a) CeO 2, (b) Cu(0.5)/CeO 2, (c) (b) (a) Cu(1)/CeO 2, (d) Cu(2)/CeO 2, (e) Cu(3)/CeO 2, (f) Cu(5)/CeO 2, (g) Cu(1)/SiO 2 18

19 k 3 x (k) k 3 (k) (I) (II) (e) (d) 10 (b) 5 (c) (b) (a) (a) k / 10 nm k / 10 nm -1 Figure S5 (I) k 3 -weighted EXAFS oscillations (a) Cu(1)/CeO 2 after reaction (t=4 h), (b) Cu(1)/CeO 2 after reaction by in situ H 2 flow, (c) Cu foil, (d) CuO, (e) Cu 2 O. (II) Fourier filtered EXAFS data (solid data) and calculated data (dotted line). (a) Cu(1)/CeO 2 after reaction (t=4 h) and (b) Cu(1)/CeO 2 after reduction by in situ H 2 flow. 19

20 Intensity (a.u.) Cu 2 O CuO Cu CuO (c) (b) (a) / o Figure S6 XRD profiles of Cu(1)/CeO 2 (a) before reduction, (b) after reduction (t=0 h) and (c) after reaction (t=4 h). 20

21 F(r) 5 Cu foil Cu(1)/CeO 2 a b Cu(1)/CeO Distance / 0.1 nm Figure S7 Fourier transform of k 3 -weighted Cu K-edge EXAFS for Cu(1)/CeO 2 catalysts and Cu foil, FT range nm -1. (a) after reduction by in situ H 2 flow; (b) after reaction (t=4 h) under the standard conditions. 21

22 Ln(TOF / h -1 ) Ln(TOF / h -1 ) (a) 4.5 (b) Slope = Slope = Ln(H 2 pressure / MPa) Ln(DMC concentration / M) Figure S8 (a) Dependence of H 2 pressure on the reaction rate over Cu(1)/CeO 2, and (b) dependence of DMC concentration on the reaction rate over Cu(1)/CeO 2. Reaction conditions of (a): DMC 30 mmol, Cu(1)/CeO mg, THF 5 g, H MPa, 433 K. Reaction conditions of (b): DMC mmol, Cu(1)/CeO mg, THF 5 g, H MPa, 433 K. 22

23 Dimethy ether Methyl formate THF (Solvent) DMC Methanol Impurity of n-dodecane n-dodecane (internal standard) Figure S9 GC chart of the reaction mixture after 20 h Reaction conditions: DMC 15 mmol, Cu(1)/CeO mg, THF 5 g, H 2 8 MPa, 433 K, 20 h. 23

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