Zhongwei Fu, Yunyun Zhong, Yuehong Yu, Lizhen Long, Min Xiao, Dongmei Han, Shuanjin Wang *,

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1 Supporting Information TiO 2 Doped CeO 2 Nanorods Catalyst for Direct Conversion of CO 2 and CH 3 OH to Dimethyl Carbonate: Catalytic Performance and Kinetic Study Zhongwei Fu, Yunyun Zhong, Yuehong Yu, Lizhen Long, Min Xiao, Dongmei Han, Shuanjin Wang *, and Yuezhong Meng * The Key Laboratory of Low-carbon Chemistry & Energy Conservation of Guangdong Province / State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, No. 135, Xingang Xi Road, Guangzhou , PR China mengyzh@mail.sysu.edu.cn or wangshj@mail.sysu.edu.cn S1

2 Schedule S1. Diagram of apparatus for direct synthesis of DMC from CO2 and methanol. 1. CO2 cylinder 2. Pressure redactor value 3. Filter 4. Pressure regulator 5. Mass flow controller 6. Buffer 7. Methanol carrier 8. One-way value 9. Heater and reactor 10. Six-way value 11. Cooler 12. Cooling separator 13. Cut-off value 14. Back-pressure regulator 15. Gas chromatography Schedule S2. Diagram of modified apparatus for direct synthesis of DMC from CO2 and methanol. 1. CO2 cylinder 2. Pressure redactor value 3. Filter 4. Pressure regulator 5. Mass flow controller 6. Buffer 7. One-way value 8. Methanol carrier 9. HPLC syringe pump 10. Three-way inlet value 11. Blender 12. Heater 13. Reactor 14. Six-way value 15. Cooler 16. Cooling separator 17. Cut-off value 18. Back-pressure regulator 19. Gas chromatography S2

3 Figure S1.TEM images of CeO2 and TixCe1-xO2 nanorods: (a) CeO2; (b) Ti0.02Ce0.98O2; (c) Ti0.04Ce0.96O2; (d) Ti0.06Ce0.94O2; (e) Ti0.08Ce0.92O2; (f) Ti0.1Ce0.9O2. Figure S2.SEM images of Ti 0.04 Ce 0.96 O 2 nanorods. S3

4 Figure S3. Correlation between the surface Ce 3+ concentrations as derived from XPS analysis in nanorods S4

5 Figure S4. NH3-TPD profiles of CeO2 and TixCe1-xO2 nanorods: (a) CeO2; (b) Ti0.02Ce0.98O2; (c) Ti0.04Ce0.96O2; (d) Ti0.06Ce0.94O2; (e) Ti0.08Ce0.92O2; (f) Ti0.1Ce0.9O2. S5

6 Figure S5. CO2-TPD profiles of CeO2 and TixCe1-xO2 nanorods: (a) CeO2; (b) Ti0.02Ce0.98O2; (c) Ti0.04Ce0.96O2; (d) Ti0.06Ce0.94O2; (e) Ti0.08Ce0.92O2; (f) Ti0.1Ce0.9O2. S6

7 Figure S6. Relationships between catalytic activity and the amount of moderately acidic sites. Figure S7. Relationships between catalytic activity and the amount of moderately basic sites. S7

8 Table S1 Experimental conditions for kinetic experiments on Ti0.04Ce0.96O2 nanorods catalyst. S1-1 Initial rate with different CO2 feeding (ml min -1 ): Pressure 1.0 MPa; temperature 140 ; catalysts weight 1.0g; methanol liquid flow 40.5 ul min -1 (1.0 mmol min -1 ); time on stream 2 h. CO2 Feeding Run (ml min - 1 ) (mmol min - 1 ) a MeOH Conversion (%) DMC Selectivity (%) Yield (%) Initial Rate of DMC (mmol min - 1 ) a Molar flow rate of CO2 was calculated by gas volume flow rate through Van der Waals equation. S1-2 Initial rate with different methanol feeding (ul min -1 ): Pressure 1.0 MPa; temperature 140 ; catalysts weight 1.0g; CO2 gas flow 11.2 ml min -1 (3.23 mmol min -1 ); time on stream 2 h. MeOH Feeding Run MeOH Conversion (%) DMC Selectivity (%) Yield (%) Initial Rate of DMC (mmol min - 1 ) (ul min - 1 ) (mmol min - 1 ) b b Molar flow rate of MeOH was calculated by liquid volume flow rate. S1-3 Initial rate with different catalyst loading (g): Pressure 1.0 MPa; temperature 140 ; CO2 gas flow 11.2 ml min -1 (0.5 mmol min -1 ); methanol liquid flow 40.5 ul min -1 (1.0 mmol min -1 ); time on stream 2 h. Run Catalyst Loading (g) MeOH Conversion (%) DMC Selectivity (%) Yield (%) Initial Rate of DMC (mmol min - 1 ) S1-4 Initial rate with different reaction temperature ( ): Pressure 1.0 MPa; catalysts weight 1.0g; CO2 gas flow 11.2 ml min -1 (0.5 mmol min -1 ); methanol liquid flow 40.5 ul min -1 (1.0 mmol min -1 ); time on stream 2 h. Run Temperature ( )( MeOH Conversion (%) DMC Selectivity (%)( Yield (%) ( Initial Rate of DMC (mmol min - 1 ) * The Ti0.04Ce0.96O2 nanorods were calcined in air under 600 o C for 4h. S8

9 Table S2 S Experimental conditions for kinetic experiments on neat CeO2 nanorods catalyst. Initial rate with different reaction temperature ( ): Pressure 1.0 MPa; catalysts weight 1.0g; CO2 gas flow 11.2 ml min -1 (0.5 mmol min -1 ); methanol liquid flow 40.5 ul min -1 (1.0 mmol min -1 ); time on stream 2 h. Run Temperature ( )( MeOH Conversion (%) DMC Selectivity (%)( Yield (%) ( Initial Rate of DMC (mmol min - 1 ) * The neat CeO2 nanorods were calcined in air under 600 o C for 4h. S9

10 Figure S8. Kinetics study of the initial rate of DMC production with different CO2 and methanol feeding based on ER mechanism with the combination of MeOH* and CO2 rate controlling. Figure S9. Kinetics study of the initial rate of DMC production with different CO2 and methanol feeding based on LH mechanism with the formation of DMC* rate controlling. S10

11 Derivations of Apparent Rate Laws Shown in Table 7 (based on the method established by C. M. Marin et al. 1 ) Legend: DMC = dimethyl carbonate MeOH = methanol MC = methyl carbonate f = indicating forward reaction direction r = indicating reverse reaction direction k x = rate constant of elementary step x [*] = concentration of available catalyst sites A. Eley-Rideal Mechanism Elementary Steps from Table 7 1) MeOH + * MeOH * 2) MeOH * + CO 2 MC * 3) MC * + MeOH * DMC + H 2 O + * If step 2 is rate limiting and previous steps are fast: Rate f = k 2f [MeOH * ] 1 [CO 2 ] 1 -Rate = r f r r r f in initial rate region [MeOH * ] = [MeOH] [*] -From equilibrium condition in step 1 Rate f = [MeOH] 1 [*] 1 [CO 2 ] 1 -Substitution Rate = k [MeOH] [CO 2 ] [*] -Combine rate constants and QED S11

12 B. Langmuir-Hinshelwood Mechanism Elementary Steps from Figure 8 * 1) CO 2 + * CO 2 2) MeOH + * MeOH * 3) 2MeOH * + CO * 2 DMC * + H 2 O * + * 4) DMC * DMC + * 5) H 2 O * H 2 O + * If step 1 is rate limiting: Rate = k 1f [CO 2 ] [*] If step 3 is rate limiting and previous steps are fast: Rate = k 3f [CO 2 * ] [MeOH * ] [MeOH * ] -Rate = r f r r r f in initial rate region [CO 2 * ] = [CO 2 ] [*] -From equilibrium condition in step 1 [MeOH * ] = [MeOH] [*] -From equilibrium condition in step 2 Rate = [CO 2 ] [*] [MeOH] [*] [MeOH] [*] -Substitution Rate = k [CO 2 ] [MeOH] 2 [*] 3 - Combine rate constants and QED S12

13 Thermodynamic analysis of the direct synthesis of DMC from CO 2 and methanol is discussed under ideal conditions. Thermodynamics data of various substances involved is listed in the Table S3. Table S3 Thermodynamic data of various substances Substances (kj mol -1 ) (kj mol -1 ) (J K mol -1 ) for 273~400K DMC (l) CO 2 (g) H 2 O (l) CH 3 OH (l) Thus, it is easy to work out the change of enthalpy and Gibbs free energy with the following information. (Eq.1) (Eq.2) As shown above, it is an exothermic reaction under standard conditions ( rh298k = kj/mol < 0). Meanwhile, the change of Gibbs free energy ( rg298k = kj/mol > 0) suggests the reaction nonspontaneous at conditions of normal pressures and 298K. In addition, if we assume the Cp of all substances is constant within 273~400 K, we can calculate the value of rh and rg under a higher temperature based on the Kirchhoff's law (as shown in Eq.3). (Eq.3) It reveals that the heat effect decreases with the temperature rises. The changing of Gibbs free energy, a function of temperature, can be written in Gibbs-Helmholtz equation (as shown in Eq.4). (Eq.4) Eq.5, the integral of Eq.4, shows that rgt increases as temperature elevating. Thus, high temperature is thermodynamically unfavorable for direct synthesis of DMC. (Eq.5) The dependence of temperature on rg is shown in Figure S10. Assuming CO2 is ideal gas and the volume change ( V) of this reaction is approximates to -Vg, we can write the changing of Gibbs free energy in the equation shown in Eq.6 at a certain temperature (T). Then Eq.7 can be calculated by integrating Eq.6 at certain temperature. (Eq.6) (Eq. 7) When T > 298 K, rg(t) > 0. Then we can draw a conclusion that the raise of pressures is profitable when keep temperature constant. S13

14 Figure S10 The dependence of temperature on rg. 1 C. M. Marin, L. Li, A. Bhalkikar, J. E. Doyle, X. C. Zeng, C. L. Cheung, Journal of Catalysis 2016, 340, S14

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CSTR 1 CSTR 2 X A =? hemical Engineering HE 33 F Applied Reaction Kinetics Fall 014 Problem Set 3 Due at the dropbox located in the hallway outside of WB 5 by Monday, Nov 3 rd, 014 at 5 pm Problem 1. onsider the following