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1 DOI: /NCHEM.2345 Efficient green methanol synthesis from glycerol Muhammad H. Haider*, Nicholas F. Dummer 1, David W. Knight, Robert L. Jenkins, Stuart H. Taylor and Graham J. Hutchings* Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff, CF10 3AT UK *Corresponding authors: Contents (Supplementary material) Page Section Title Figure/Tables 2 Fig. S Experimental methods and Fig. S2 4 Confirmation of product formation Fig. S Reaction of aqueous glycerol over MgO prepared by different methods Fig. S Studies on the source of Fig. S5 8 oxygen in MeOH Fig. S Effect of feed concentration and reaction time Fig. S7 10 Table S Catalytic results Table S2 12 Table S3 Fig. S Crude glycerol analysis and Fig. S9 treatment 14 Fig. S10 NATURE CHEMISTRY 1

2 1. Experimental methods and Confirmation of product formation Reactor description Figure S1 Schematic diagram of the catalytic reactor. Glycerol/water was injected using the syringe pumpp into the pre-heater (8 mm i.d.) through a long needle extended into the centre of the pre-heater. This ensured complete vaporization of the feed. The vaporized feed entered intoo the main reactor (8 mmm i.d.) after passing through the middle connector (4 mm i.d.). The catalyst was loaded intoo a stainless steel reactor tube and held in place between plugs of quartz wool. The catalyst bed temperature was monitored by a thermocouplee placed in the catalyst bed. The catalyst bed was heated by an external electric furnace. Products were collected in a series of cold traps. The first trap was ice/water, and escaping volatile productss were condensed in a subsequent trap cooledd by liquid nitrogen. NATURE CHEMISTRY 2 2

3 The temperature profile of the reactor was: preheater 563 K, middle m connector 563 K and the catalystt bed temperature was varied between 448 K and 673 K.. Initially catalysts were tested using a glycerol/h 2 2O feed (0.5-30wt%, 1 ml min -1 in 100 ml minm -1 inert carrier) with g catalyst. For analysis the liquid l products of the first and second traps were combined. Gaseous products were collected after thee third trap in a gas bagg for furtherr analysis. Figure S2 Photograph of laboratory reactor setup. Typical GC analysis Reaction products, collected in the cold traps, were combined for analysis, which was performed offline using a Varian CP 3800 gas chromatograph equipped with capillary column (ZBWAX plus: i.d x 30 m) ). Gas samples were also collectedd and analyzed offbalances were calculated to be 99 % + 5 % for all reactions. Typical product analysis by gas chromatography is shown in Figure line by means of a Varian CP 3800 GC with a Porapack Q: 1/8 x 2 m column. Mass S3. NATURE CHEMISTRY 3 3

4 Figure S3 Labelled GCMS trace for confirming different reaction products. NATURE CHEMISTRY 4 4

5 2. Reaction of aqueous glycerol over MgO prepared by different methods Product Selectivity (mol%) a b Conversion (mol%) c A B C D Catalysts d a b c Feed 0 30 Product Selectivity (mol%) Conversion (mol%) / STY* Feed (wt %) Temperature (K) MeOH EtOH Acetol Ethanal Acrolein EG Conversion STY g MeOH Kg -1 h -1 Figure S4 (a) The conversion of glycerol and methanol selectivity over different MgO catalysts with varying surface areas (m 2 g -1 ); A: 144, B: 107, C: 20, D: 14 (for detail see methods). Experimental conditions: 1 ml h -1 glycerol feed (0.5 wt %) at 523 K temperature for 3 h over MgO (0.25 g) catalyst. (b) The effect on conversion of glycerol upon using different isotopic feeds of glycerol (a: 12 C-glycerol/H 2 O, b: 13 C-glycerol/H 2 O, c: 13 C- glycerol/d 2 O, conditions: 1 ml h -1 glycerol feed (0.5 wt %) at 523 K temperature for 3 h over 0.25 g of MgO-A catalyst). (c) Effect of feed concentration on the conversion and product selectivity. Experimental conditions: 1 ml h -1 glycerol feed (0.5 & 10 wt %) at 523 K temperature for 3 h over 0.25 (for 0.5 wt% feed) & 0.5 g (for 10 wt% feed) of MgO-A catalyst. (d) Effect of temperature on the feed conversion and product selectivity Experimental conditions: 1 ml h -1 glycerol feed (10 wt %) for 3 h over 0.5 g of MgO-A catalyst at different temperatures. 0 A low feed concentration of pure glycerol was investigated (Figure S4) using a range of various MgO catalysts. MgO (A) was prepared by calcining high purity magnesium hydroxide (Sigma Aldrich) first at 723 K with a ramp of 283 K min -1 for 24 h, followed by NATURE CHEMISTRY 5 5

6 refluxing with water for 3 h to obtain a slurry. The slurry was dried at 383 K for 24 h and then calcined again at 875 K at 283 K min -1 ramp for 3 h under flowing N 2. The BET surface area of MgO (A) catalyst was determined to be 144 m 2 g -1. MgO (B) catalyst was prepared by calcining magnesium hydroxide first at 723 K at 283 K min -1 ramp for 24 h. The powder was then refluxed with water for 3 h until a slurry was formed, followed by drying at 383 K for 24 h. The resulting material is then calcined at 873 K at 283 K min -1 ramp for 3 h under flowing nitrogen. The BET surface area of this catalyst was determined to be 107 m 2 g -1. MgO (C) catalyst was prepared by calcining magnesium hydroxide first at 723 K at 283 K min -1 ramp rate for 24 h in air then at 973 K at 283 K min -1 ramp rate for 24 h. The BET surface area of this catalyst was determined to be 20 m 2 g -1. MgO (D) catalyst was prepared by calcining magnesium hydroxide first at 723 K at 283 K min -1 ramp for 24 h and used directly. The BET surface area was determined to be 14 m 2 g -1. NATURE CHEMISTRY 6 6

7 3. Studies on the source of oxygen in MeOH Figure S5 GC-MS analysis confirming the source of oxygen inn the product MeOH. Figure shows the minor mass fragments of 18 O-MeOH and major 16 O-MeOH. Experimental conditions: 0.5 g MgO-A catalyst, 10 wt % 12 C-glycerol/H 18 2 O feed (1 ml h -1 ), 100 mll min -1 inert carrier at 573 K for 3 h. Experiments using 18 O labelled water were carried out to confirm the source of oxygen in the methanol product. It was found that (as shown in Figure S5) that glycerol was the source of oxygen in the methanol, and not water, as only minor fragments of labelled oxygen methanol were obtained, and methanol containing unlabelled oxygen wass the major fragment. NATURE CHEMISTRY 7 7

8 Figure S6 GC-MS analysis for f the stability of MeOH on the catalyst surface. Experimental conditions: 0.5 g MgO-A catalyst, 10 wt % 12 C-MeOH/H 18 2 O feed (1 ml h -1 ), 100 ml min -1 inert carrier at 573 K for 3 h. The stability of the methanol product was investigated by feeding methanol over the catalyst. Methanol was found to be stable over the catalyst and did not undergo any further reaction. r To see if there was a transfer of oxygen from water to the methanol m product, water with labelled oxygen was fed with methanol and the effluent analysed for the presence of labelled methanol. Again this experiment confirmed that glycerol was w the source of oxygen in methanol formation as the methanol feed remained unchanged apart from very minor quantities of labelled oxygen methanol ass seen in Figure S6. NATURE CHEMISTRY 8 8

9 4. Effect of feed concentration and reaction time Figure S7 (a) Effect of feed concentration on the conversion (mol. %) of glycerol and MeOH selectivity (mol. %) over MgO (A) catalyst after 3 h at 573 K. Experimental conditions: 0.5 g, 0.75 g, 1 g for 10, 20, 30 wt% feed respectively, 100 ml min -1 inert carrier, 1 ml h -1 feed flow. (b) Time online analysis of glycerol conversion (mol. %) and methanol selectivity (mol. %) over MgO (A) catalyst at 573 K. Experimental conditions: catalyst 1 g, 100 ml min -1 inert carrier, 1 ml h -1 feed flow (10 wt% glycerol/h 2 O). NATURE CHEMISTRY 9

10 5. Catalytic results Table S1 Experimental data for catalytic conversion of glycerol to methanol using basic oxides. Temperature (K) Catalysts a e a b c d e a b c d e f g a b c d e f g c e f g Conversion (mol. %) Selectivities (mol. %) MeOH EtOH Acetol Ethanal Acrolein Ethylene glycol Propanal propanol propanol Allyl alcohol ,3-butanedione hexanone Acetone CO unknowns g MeOH kg -1 cat. h a: MgO (A:144 m 2 g -1 ), b: Mg 3 CaO x (25 m 2 g -1 ), c: MgCaO x (17 m 2 g -1 ), d: MgCa 3 O x (11 m 2 g -1 ), e: CaO (13 m 2 g -1 ), f: MgSr 3 O X (3 m 2 g -1 ), g: SrO (3 m 2 g -1 ). The experiments were carried out in the stainless steel fixed bed flow reactor housed in the furnace for temperature maintenance. Experiments were performed under the following conditions: catalyst (0.5 g)., feed flow (1 ml h -1, 10 wt% glycerol/h 2 O), inert carrier (100 ml min -1 ), 3 h. 10 NATURE CHEMISTRY 10

11 Table S2 Experimental data for catalytic conversion of glycerol to methanol using oxide catalysts. Temperature (K) Catalysts a* b* c * d* e* f* a b c d e f a b c d e f Conversion (mol. %) Selectivities (mol. %) MeOH EtOH Acetol Ethanal Acrolein Ethylene glycol Propanal Allyl alcohol ,3-butanedione hexanone hexanone Acetone CO unknown g MeOH kg -1 cat. h * a: lanthanum oxide-nitrate source, b: lanthanum oxide-hydroxide source, c: ceria, d: Ce 2 Mg 3 O x, e: praseodymium oxide-cal. method, f: praseodymium oxide-ppt. method. The experiments were carried out in the stainless steel fixed bed flow reactor housed in the furnace for temperature maintenance. Experiments were performed under the following conditions: 0.5 g cat., 1 ml h -1 feed flow (10 wt. % glycerol/h 2 O), 100 ml min -1 inert carrier, 3 h duration. 11 NATURE CHEMISTRY 11

12 Table S3 Comparison of the catalytic conversion of pure and crude glycerol to methanol over CeO 2. Feed wt. % Starting feed Pure Crude Pure Crude Pure Crude Conversion (mol. %) Selectivities (mol. %) MeOH EtOH Acetol Ethanal Acrolein Ethylene glycol Propanal Allyl alcohol ,3-butanedione hexanone hexanone Acetone CO unknowns g MeOH kg -1 cat. h The experiments were carried out in the stainless steel fixed bed flow reactor housed in the furnace for temperature maintenance. Experiments were performed under the following conditions: 1.0 g ceria, 1 ml h -1 feed flow, 100 ml min -1 inert carrier, 3 h duration at 613K. NATURE CHEMISTRY 12

13 6. Crude glycerol analysis and treatment Figure S8 Analysis of crude glycerol sample utilised in this work. Crude glycerol After decantation After charcoal treatment Figure S9 Different forms of crude glycerol NATURE CHEMISTRY

14 Figure S10 Analysis of treated crude glycerol. The crude glycerol sample obtained from industry contained impurities,, such as unreacted triglycerides, nitrogenous compounds of plant origin, long chain esters, long chain acids and long chain alkanes. The crude sample consisted a non-polarr layer in addition to a polar aqueous layer containing glycerol (Figure S9). The sample was simply allowed to stand s for 2h so that the aqueous layer separated andd the distinct upper organic layer was decanted using a separating funnel. After decanting, the sample was gravity filtered through charcoal, which removee the coloured impurities to produce a clear solution. This solution was used directly in the catalytic reaction to produce methanol. NATURE CHEMISTRY