Supporting Information. acrolein hydrogenation

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1 Electronic Supplementary Material (ESI) for Catalysis Science & Technology. This journal is The Royal Society of Chemistry 216 Supporting Information x /SiO 2 catalyst for enhanced selectivity to allyl alcohol in acrolein hydrogenation Xiaocheng Lan, Tiefeng Wang *, Xiaodan Li, Ning Huang, Jinfu Wang Beijing Key Laboratory of Green Reaction Engineering and Technology Department of Chemical Engineering, Tsinghua University, Beijing 184, China *Corresponding author: Tiefeng Wang, wangtf@tsinghua.edu.cn, Tel: Experimental 1.1 Catalyst preparation The Pt@SnO x /SiO 2 catalysts were prepared from Pt@Sn nanoparticles (NPs) with a twostep method developed in this work. The Pt@Sn NPs were prepared with colloidal method following Wang et al. 1. For the synthesis of Pt NPs, 2.5 ml of NaOH/ethylene glycol (EG) solution (.3 M) was mixed with 2.5 ml of H 2 PtCl 6 6H 2 O/EG (.2 M) at room temperature, then heated to 16 o C and kept at this temperature with vigorous stirring for 3 h to form a homogeneous black Pt/EG solution. To prepare Pt@Sn NPs with a nominal Sn:Pt molar ratio of 6:1, toluene (4 ml) and oleic acid (1 ml) were first heated to 1 o C and then 47.2 mg DDAB and 5 mg TBAB in 1 ml toluene were added. The prepared 2.5 ml Pt/EG solution containing 34. mg SnCl 2 2H 2 O was added dropwise into the above toluene-based solution. The obtained Pt@Sn NPs were washed with methanol for three times and then the methanol solution of Pt@Sn NPs was mixed with SiO 2 support and evaporated with stirring at room temperature. Finally, the Pt@Sn deposited on SiO 2 (Alfa Aesar, 147 m 2 /g) support was kept at

2 12 o C in air for 12 h to convert to Pt@SnO x /SiO 2. The Pt@SnO x /SiO 2 was kept at 2 o C with a 5 ml/min flow of 4% H 2 /N 2 for 2 h before reaction. The PtSn/SiO 2 catalysts with a Sn:Pt molar ratio of 1:1, 2:1 and 6:1 were prepared by coimpregnation using H 2 PtCl 6 6H 2 O and SnCl 2 2H 2 O as precursors. After impregnation, the dried catalysts were calcined at 4 o C for 4 h and reduced with a 5 ml/min flow of 4% H 2 /N 2 at 4 o C for 4 h before use. The Pt/SiO 2 catalyst with a metal loading of.1% was prepared by impregnation using H 2 PtCl 6 6H 2 O as precursors. After impregnation, the dried catalysts were calcined at 4 o C for 4 h and reduced with a 5 ml/min flow of 4% H 2 /N 2 at 4 o C for 4 h before use. The Ag/SiO 2 catalyst with a metal loading of 8. wt% was prepared by impregnation of AgNO 3 using the conditions described in the literature [2]. The dried catalysts without calcination were reduced with a 5 ml/min flow of 4.% H 2 /N 2 for 2 h before use. The.1% SnO x /SiO 2 sample was prepared with the impregnation method according to the previous literature [3]. SnCl 2 2H 2 O ethanol solution was used as the precursor. After impregnation, the sample was kept at 12 o C overnight. 1.2 Catalyst characterization The X-ray diffraction (XRD) powder patterns of the Pt and Pt@Sn nanoparticles were characterized by a Bruker Advance D8 X-ray diffractometer with Cu Kα (λ = Å) monochromatic radiation, where the samples were prepared by dropping the Pt or Pt@Sn methanol solution on a single crystal Si substrate followed by evaporation of the solvent. The actual loadings of Pt, Sn and Ag on the catalysts were estimated by inductively coupled plasma (ICP) analysis, where the metals were dissolved by boiling the catalyst powders in aquaregia. The chemistry of the Pt@SnO x /SiO 2 catalysts was investigated by XPS measurements (Thermal

3 Scientific ESCALAB 25Xi) with a CAE: pass energy 1. ev analyser mode and an Al Kα X-ray source. The nanoparticle size of the catalysts was estimated by transmission electron microscopy (TEM, JEOL Ltd., Tokyo, Japan), where the samples were ultrasonically dispersed in ethanol for 3 min and the solution was dropped on a carbon film supported on a copper grid. More than 1 particles were collected to analyze the particle size distribution. The reducibility of the catalysts was investigated by H 2 -TPR on a Quantachrome ChemBET Pulsar instrument equipped with a TCD detector, where the samples were heated from room temperature to 8 o C at a ramp of 1 o C/min with a 1 ml/min flow of 5% H 2 /He. The CO uptake of the catalysts was determined by CO chemisorption. For each test, 2 mg of catalyst was placed in a sample tube and reduced in 1% H 2 /He at 2 o C (Pt@SnO x -X/SiO 2 ) or 4 o C (Pt /SiO 2 ). After the reduction, the sample was purged with He for 3 min to remove absorbed H 2 on the catalyst surface and then cooled to room temperature. The titration was carried out by the pulse adsorption of 5% CO/He. The adsorption model of CO on Pt metals has been investigated via FTIR subtraction spectra [4]. The percentage of bridge adsorbed CO on Pt was very low so that a 1. stoichiometric ratio of CO/metal was widely used for the Pt or PtSn catalysts in the literature 4. Therefore, the stoichiometry ratio of CO/Pt was assumed to be 1:1 in this work. 1.3 Acrolein hydrogenation The hydrogenation of acrolein was carried out in a fixed-bed reactor of 5 mm i.d. and 6 mm long. The catalyst was mixed with quartz particles in a ratio of 1:29 (.1 g catalyst and 2.9 g quartz particles). The reaction temperature was measured by a K-type thermocouple inserted in the catalyst bed. For each experiment,.13 g/h acrolein was pumped into the evaporator with a temperature of 1 o C by a digital HPLC pump (Series III) and the evaporated acrolein was

4 carried into the system by reaction feed gas. The molar ratio of H 2 to acrolein was 2:1, and the total flow rate of the steam was 114 ml/min balanced with N 2. The outlet steam was analyzed online by a gas chromatograph (GC 79, Techcomp Ltd.) equipped with a super-wax capillary column (3 m.25 mm.5 μm) and an FID detector. The acrolein conversion and selectivity were calculated as: Conversion (%) = (N A,in N A,out ) / N A,in (1) Selectivity (%) = N i,in / (N A,in N A,out ) (2) where N A,in and N A,out are moles of acrolein in the inlet and outlet of the reactor, and N i,in is the moles of the products. The hydrogenation rate of acrolein was calculated as: r = (F A X) / (m cat W metal ) (mmol min -1 g metal -1 ) (3) where F A is the feeding rate of acrolein, X is the conversion, m cat is the catalyst loading on the fixed bed reactor and W metal is Ag or Pt loading of the catalyst. The TOFs were calculated as: TOF total = (F A X) / n active sites (s -1 ) (4) TOF C-C = (F A X S C2 ) / n active sites (s -1 ) (5) TOF C=C = (F A X (S PA +S n-proh )) / n active sites (s -1 ) (6) TOF C=O = (F A X (S AyOH +S n-proh )) / n active sites (s -1 ) (7) where n active sites is the total active sites of the catalyst measured by CO-uptake, S C2, S PA, S n-proh and S AyOH are the selectivity to hydrocarbon, propanal, propanol and allyl alcohol, respectively. 2. Figures

5 Pt degree Fig S1. XRD patterns of as-prepared Pt and Pt@Sn core-shell nanoparticles. Pt 2+ Pt Sn 2+ Sn 4+ Sn (a) Sn 4+ Sn 2+ Pt 2+ Pt Sn (b)

6 Sn 4+ Sn 2+ Sn Pt 2+ Pt (c) (d) Pt 2+ Pt Sn 4+ Sn 2+ Sn Fig S2. XPS results of (a) Pt@SnO x -1.2/SiO 2, (b) Pt@SnO x -2.1/SiO 2, (c) Pt@SnO x -6.2/SiO 2 and (d) PtSn-1.1/SiO 2. According to literature 5, the Sn 3d peaks were deconvoluted into features assigned to Sn, Sn 2+, and Sn 4+ species, the Pt 4f peaks were deconvoluted into features assigned to Pt and Pt 2+, and the results were listed in Table S3

7 Pt Sn x -6.2/SiO 2 Intensity, a.u. PtSn-6.7/SiO 2 SnO x /SiO 2 Pt/SiO T, o C Fig S3. H 2 -TPR profiles of supported Pt@SnO x -6.2/SiO 2, PtSn-6.7/SiO 2, SnO x /SiO 2 and Pt/SiO 2 Pt NPs 1.9 nm Pt@SnO x -1.2/SiO nm Pt@SnO x -2.1/SiO nm Pt@SnO x -6.2/SiO nm Fig S4. TEM images and particle size distribution of Pt NPs, Pt@SnO x -1.2/SiO 2, Pt@SnO x - 2.1/SiO 2 and Pt@SnO x -6.2/SiO 2.

8 7 Frequency, % Pt/SiO nm Ag/SiO nm Frequency, % Frequency, % PtSn-1.1/SiO 2 5. nm Frequency, % PtSn-2.3/SiO nm PtSn-6.7/SiO nm Frequency, % Fig. S5. TEM images of Pt/SiO 2, Ag/SiO 2 and PtSn alloy catalysts prepared by impregnation.

9 8 5 Conversion, % Conversion Selectivity Selectivity to allyl alcohol, % Pt@SnO x -6.2 pre-reduced Pt@SnO x -6.2 Fig. S6. Conversion and selectivity of acrolein hydrogenation over Pt@SnO x -6.2/SiO 2 and prereduced Pt@SnO x -6.2/SiO 2. (a) (b) (c) (d) (e)

10 Fig S7. TEM images of (a) x -1.2/SiO 2 (after reaction), (b) Pt@SnO x -2.1/SiO 2 (after reaction), (c) Pt@SnO x -6.2/SiO 2 (after reaction), (d) Pt@SnO x -6.2/SiO 2 with reduction treatment (after reaction) and (e) Pt@SnO x -6.2/SiO 2 with reduction treatment (before reaction). The images showed that the nanoparticles of Pt@SnO x -1.2/SiO 2, Pt@SnO x -2.1/SiO 2 and Pt@SnO x - 6.2/SiO 2 did not aggregate after reaction. This was consistent with the stable conversion and selectivity during the reaction. On the contrast, the nanoparticles of the Pt@SnO x -6.2/SiO 2 catalyst with reduction treatment greatly grew after the pre-reduction in 4 o C for 2 h. Fig. S8. HRTEM image of PtSn-1.1/SiO 2. The lattice space of the nanoparticle was 2.99 Å, which was larger than any orientation of the metallic Pt. This lattice space could be indexed to the orientation of PtSn alloy 6.

11 3. Tables Table S1. Metal loading of the supported catalysts ICP-analysis Catalyst Pt/% Sn/% Sn/Pt(mol) x -1.2/SiO x -2.1/SiO x -6.2/SiO Pt/SiO PtSn-1.1/SiO PtSn-2.3/SiO PtSn-6.7/SiO Ag/SiO Table S2. CO-uptake of Pt/SiO 2, Pt@SnO x -X/SiO 2, PtSn/SiO 2 and Sn/SiO 2. Catalyst CO-uptake, mol/g Pt@SnO x -1.2/SiO 2.78 Pt@SnO x -2.1/SiO 2.66 Pt@SnO x -6.2/SiO 2.23 PtSn-1.1/SiO 2.54 PtSn-2.3/SiO 2.38 PtSn-6.7/SiO 2.21 Pt/SiO 2.85 Sn/SiO 2 <.1 Table S3. XPS results of the Pt@SnO x -X/SiO 2 and PtSn-1.1/SiO 2 Catalyst Species Pt 2+ /Pt or Sn /(Sn 2+ + Sn 4+ ) Pt Pt 4f 7/ Pt Pt@SnO x Sn Sn 3d 5/ Sn Sn Pt Pt 4f 7/ Pt Pt@SnO x Sn Sn 3d 5/ Sn Sn Pt Pt@SnO x -6.2 Pt 4f 7/ Pt 2+.9

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