Role of manganese oxide in syngas conversion to light olefins

Transcription

1 Supporting information Role of manganese oxide in syngas conversion to light olefins Yifeng Zhu, Xiulian Pan,*, Feng Jiao,, Jian Li,, Junhao Yang,, Minzheng Ding, Yong Han,, Zhi Liu,, and Xinhe Bao*, State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian , People s Republic of China. University of Chinese Academy of Sciences, Beijing , People s Republic of China. State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai , People s Republic of China. School of Physical Science and Technology, ShanghaiTech University, Shanghai , People s Republic of China. To whom correspondence should be addressed. panxl@dicp.ac.cn; xhbao@dicp.ac.cn.

2 Experimental details Catalyst preparation MnCO 3 was prepared by a precipitation method at room temperature using aqueous solution of manganese nitrate as the precursor and ammonium bicarbonate as the precipitate. After precipitation, the suspension was aged for 30 min, followed by washing, filtering and then it was dried at 60 o C overnight. Thus MnCO 3 was obtained. Calcination of MnCO 3 at 400 o C for 6 h under 20 vol. % H 2 /Ar flow resulted in MnO while calcination of MnCO 3 at 520 o C for 6 h in air led to Mn 2 O 3. 1 MnO 2 was prepared by calcining MnCO 3 at 400 o C for 6 h in air. 2 Mesoporous SAPO-34 zeolite (MSAPO) was prepared following the same method as in our previous work. 3 Catalytic reaction The reaction tests were performed in a fixed-bed reactor. Typically, 300 mg catalyst with various MnO x /MSAPO mass ratios with a size of mesh was loaded into the reactor. The catalyst was heated in H 2 till 310 o C, and then a premixed syngas (H 2 /CO = 2.5) containing 5% Ar as the internal standard for the online gas chromatography (GC) analysis was introduced while the temperature was increased to 400 o C. The reaction was performed at the conditions: 400 o C, 2.5 MPa and 4800 ml h -1 g -1 cat unless otherwise stated. The effluents were analyzed by an online GC (Agilent 7890B) which was equipped with a TCD and FID detectors. Note that the hydrocarbon selectivities are reported excluding CO 2. Characterization The catalysts were characterized by a XRD (PANalytical Empyrean) using Cu Kα radiation. The crystal sizes were estimated by Scherrer equation. Temperature-programmed reduction (TPR) and temperature-programmed surface reaction (TPSR) were performed on a Micromeritics AutoChem instrument. 50 mg catalyst was loaded in a U-shape reactor. The TPR profiles were recorded in 10 vol.% H 2 /Ar at a heating rate of 10 o C/min. The H 2 consumption was quantitatively

3 calibrated by taking Ag 2 O (Micromeritics) as a reference. Before TPSR, the catalyst was reduced in situ at 400 o C in a flowing 10 vol.% H 2 /Ar, followed by sweeping in He till a stable baseline was obtained and then it was exposed to 5 vol.% CO/He at room temperature. Subsequently, the sample was purged for 30 min by 10 vol.% H 2 /Ar and then was heated at a rate of 10 o C/min with the effluents monitored by an online quadrupole MS. In situ AP-XPS and depth profile analysis were performed at Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences. The catalyst powder was pressed into a disc. Unfortunately, it was rather difficult to distinguish different Mn species due to broad peaks of Mn 2p, 3s, 3p and L 3 M 2,3 M 4,5 Auger spectra (Figure S7). 4-5 The depth profile analysis was performed by varying the electron emission angles with respect to the fresh sample. In situ IR was performed on a Bruker Tensor 27 at ambient pressure (1 bar). The sample was prepared as a thin wafer and placed inside an IR transmission cell. The effect of reduction temperature was studied at 300 and 400 o C in H 2, and 400 o C in syngas (H 2 /CO = 2.5) or heated at 110 o C in N 2, and then cooled down to room temperature. The corresponding samples were described in Table S2. For example, MnO-400Syn represents a sample reduced in syngas at 400 o C and then cooled down to room temperature in H 2. Afterwards the samples were allowed to adsorb CO for 25 min at room temperature, followed by sweeping in He. Subsequently, the sample was heated in H 2 or N 2 while the spectra were recorded in the range of cm -1.

4 Table S1 Catalyst performance of Mn 2 O 3 catalyst. a Oxide/Zeolite GHSV/ ml h -1 g cat -1 T/ o C CO Conv. (%) Hydrocarbon distribution (%) C = = 2 -C 4 C o o 2 -C 4 CH 4 Others Sel. Sel. Sel. Sel. O/P CO 2 Sel. (%) 2: : : a Reaction conditions: 400 o C, 2.5 MPa, H 2 /CO = 2.5, O/P represents the selectivity ratio of (C 2 = -C 4 = ) olefins to (C 2 o -C 4 o ) paraffins.

5 Table S2 Samples for in situ IR studies. Name Treatment conditions MnO MnO heated at 110 o C in N 2 MnO-300H 2 MnO reduced at 300 o C in H 2 MnO-400H 2 MnO reduced at 400 o C in H 2 MnO-400Syn. MnO reduced at 400 o C in syngas

6 Figure S1. XRD patterns of the MnCO 3 precursor.

7 Figure S2. XRD patterns of fresh manganese oxide catalysts.

8 Figure S3. XRD patterns of used manganese oxide catalysts.

9 Figure S4. Scheme for XPS depth profile analysis by varying the take-off angle.

10 Figure S5. IR spectra of MnO catalysts exposed to CO. The spectra were taken after the samples have been swept by N 2 or H 2 for 25 min at room temperature. From bottom to top, the spectra correspond to fresh MnO; MnO-300H 2 ; MnO-400H 2 ; MnO-400Syn.

11 Figure S6. The effluents detected by the online MS, during the experiments described in Figure 3C.

12 Figure S7. Mn 2p, Mn 3p, Mn 3s and L 3 M 2,3 M 4,5 Auger spectra of MnO catalysts treated under different conditions.

13 Reference 1. Lei, K.; Han, X.; Hu, Y.; Liu, X.; Cong, L.; Cheng, F.; Chen, J., Chem. Commun. 2015, 51, Zhao, J.; Tao, Z.; Liang, J.; Chen, J., Cryst. Growth Des. 2008, 8, Jiao, F.; Li, J.; Pan, X.; Xiao, J.; Li, H.; Ma, H.; Wei, M.; Pan, Y.; Zhou, Z.; Li, M.; Miao, S.; Li, J.; Zhu, Y.; Xiao, D.; He, T.; Yang, J.; Qi, F.; Fu, Q.; Bao, X., Science 2016, 351, Di Castro, V.; Polzonetti, G., J. Electron Spectrosc. Relat. Phenom. 1989, 48, Li, X.; Lunkenbein, T.; Pfeifer, V.; Jastak, M.; Nielsen, P. K.; Girgsdies, F.; Knop-Gericke, A.; Rosowski, F.; Schlögl, R.; Trunschke, A., Angew. Chem. Int. Ed. 2016, 55,