Samples
Data provided:
Fischer-Tropsch Synthesis of samples AW1-AW5, a series of Co on Mg-modified gamme

Aw1-AW5 relate to catalyst samples in table:
	Nominal Mg loading (wt%)	Calcination T after Mg addition (°C)			XRF		XRD		TPR		H2 Chemisorption
Sample			Wash		Mg (wt%)	Al (wt%)	Co (wt%)		Co3O4 lattice parameter (Å)	x in Mgx Co3-xO4	Mg in MgxCo3-xO4 (%)	Other Mg (%)	Co3O4 PS (nm)		Peak pos. (°C)	Peak pos. (°C)		CoSA (m2/gCo)
AW1	0	N/A	N/A		0.00	36.57	17.08		8.0796 (3)	0.00	0	0	13.9		259	439		57.4
AW2	3	550	N/A		2.64	34.89	17.37		8.0889 (4)	0.21	0.54	2.10	13.3		283	501		63.9
AW3	3	550	Buff		1.94	35.08	17.08		8.0834 (3)	0.09	0.22	1.72	11.5		291	501		61.5
AW4	3	800	N/A		2.64	35.11	17.21		8.0801 (3)	0.01	0.02	2.62	11.9		275	466		57.5
AW5	6	550	Buff		2.56	34.84	16.95		8.0859 (4)	0.15	0.37	2.19	11.3		303	545		62.5
AW6	6	800	N/A		5.18	33.09	17.25		8.0833 (3)	0.09	0.22	4.96	13.0		281	510		58.6



Catalysts were synthesised by an incipient wetness impregnation process. The support, ?-Al2O3 (Sasol, Puralox TH100/150, 145 m2g-1) was dried at 120 °C overnight. The impregnation was carried out in plastic bags (zipper seal sandwich bags, 18 x 18 cm, Tesco). The impregnation was a multi-step process, the first step being the impregnation of magnesium nitrate hexahydrate (Fluka, ?99%) followed by heat treatment at either 550 °C or 800 °C, then the impregnation of the cobalt nitrate hexahydrate (99%, Acros) and ruthenium (III) nitrosyl nitrate (Alfa Aesar, min 31.3% Ru), followed by a final heat treatment at 250 °C or 400 °C. To the ?-Al2O3 was added the appropriate amount of hot aqueous nitrate solution (ca 60 °C) to achieve the desired loading. The impregnated solid was then kneaded in the plastic bag until homogenous. For thermal treatments, the damp solid was spread out on a stainless steel tray and treated in static air in a muffle furnace. After thermal treatment, subsequent impregnations were carried out using the same procedure. The volume used for the initial impregnation was 1 mL g-1 for unmodified Puralox TH100/150 and the volume required was recalculated after each impregnation.

Some of the Mg modified supports were subjected to an acid wash. Two different solutions with different pH were used to wash the Mg/?-Al2O3 materials – acetic acid (1 mol dm-3, pH 2.4) and an acetic acid – ammonium acetate buffer (0.5 mol dm-3, pH 4.7). Acetic acid was chosen as it has a similar pH to Co(NO3)2 (ranges from ~3 at 1 M concentration to ~2 at 4 M) and the buffer solution was chosen to determine if a milder treatment could produce the same results. Additionally, residual species left after the washes could be removed by appropriate heat treatments, unlike for instance acetic acid-sodium acetate buffers. The washing procedure was thus:
To each Mg/?-Al2O3 sample (1 g) contained in a centrifuge tube (50 mL) was added the weak acid solution (40 mL) followed by shaking for 30 s. Tubes were then centrifuged for 30 min at 4000 rpm before removing the supernatant with a pipette. In some cases the Mg and Al content of the supernatant was analysed by ICP. The wet solid was washed with water (40 mL) via shaking by hand for 30 s before returning to the centrifuge for 30 min at 4000 rpm. The supernatant was removed by pipette before drying the wet solid for 18 h at 80 °C. The dry solid was calcined at 550 °C for 2 h in static air to remove residual acetate or ammonium ions.

XRD data on samples from Boldrin et al. Chemical Science, 6 (2), 935-944 (doi:10.1039/C4SC02116A) (supports and catalysts) and on the catalysts in the acid washing study described above were collected on a Panalytical X-Pert diffractometer fitted with a X-Celerator detector and a spinner stage set up in Bragg-Bentano geometry. X-rays were produced with a Co anode filtered by Ge giving monochromatic K?1 radiation (1.7890 Å). Variable divergence slits were used with an illuminated length of 15 mm. The measuring time for XRD scans in the 2? range 18°-82° was 1 h. Samples were spiked with KCl in order to more accurately calculate the lattice parameters of the Co3O4 phase. Two methods were used to extract quantitative information from XRD patterns; empirical peak fitting and Le Bail whole pattern fitting. Empirical peak fitting was used to calculate particle size from the Scherrer equation while Le Bail fitting was used to calculate the lattice parameters of Co3O4 phases. TOPAS 4.2 was used to refine the patterns of the Co3O4/?-Al2O3 samples. In addition to the background polynomial, the lattice parameters and effective particle size parameters were refined although determination of instrumental broadening was not performed so these particle size measurements are not discussed as they would lead to a false impression of their accuracy. Where particle size measurements are quoted, these are calculated from single peaks using the Scherrer equation.

In addition to this, the acid washed supports were characterised using the high throughput XRD technique described in Boldrin et al.Chemical Science, 6 (2), 935-944 (doi:10.1039/C4SC02116A). Samples were placed in well-plates, adhesive tape was stuck over the tops of all wells and the plates were upturned to stick the sample to the tape to ensure the sample height was the same across all wells. HT XRD was performed in reflection mode on a Panalytical X-pert Pro diffractometer fitted with a XYZ stage using Co K?1/K?2 (ratio = 2) radiation, Fe filter, 5 mm mask and automatic divergence slits with an illuminated length of 3 mm. The Soller slits used were 0.02° on the incident side and 0.04° on the reflection side. The measuring time for a XRD scan in the 2? range 38°-57° was 13 min.

Fourier transform infrared (FTIR) spectra were recorded for Mg modified ?-Al2O3. Spectra were collected from 600-4000 cm-1 with a resolution of 4 cm-1 using a Perkin Elmer Spectrum 100 spectrometer fitted with the Spectrum 100 Universal Diamond/ZnSe ATR.

Temperature-programmed reduction (TPR) was carried out on an Altamira AMI-200 unit. Samples (70 mg) were purged with flowing argon at 30 mL min-1 before the gas was switched to 10 % H2/Ar at 30 mL min-1. Samples were ramped from room temperature to 1100 °C at 10 °C min-1, holding at 1100 °C for 10 min. Five injections were performed at the end of the experiment which allowed the peak area to be related to H2 consumption.

TGA scans were carried out on a TA Q5000IR thermal analyser using 5 % H2/N2 as the sample gas flowing at 25 mL min-1. Samples (ca 5 mg) were placed in aluminium pans. The dynamic high resolution mode was used with a ramp rate of 50 °C min-1, sensitivity of 1.0 and a resolution of 4.0. Samples were heated from room temperature to 600 °C where the temperature was held for 5 min. The maximum temperature was limited to 600 °C by the use of aluminium pans.

CO2 temperature-programmed desorption (TPD) was carried out on an Altamira AMI-200 unit. Samples (250 mg) were first heated to 250 °C at 10 °C min-1 and purged with flowing He at 30 mL min-1 for 10 min before being cooled to 35 °C at 10 °C min-1. Subsequently the gas was switched to 10 % CO2/He at 30 mL min-1 for 1 h at 35 °C followed by 30 mL min-1 He for 30 min. Finally the sample was heated to 800 °C at 10 °C min-1 in He flowing at 10 mL min-1, holding at 800 °C for 10 min. Five injections were performed at the end of the experiment which allowed the peak area to be related to CO2 desorption.

Co surface areas were determined by H2 chemisorption at 150 °C in a Micromeritics ASAP 2020C by extrapolating the total gas uptakes in the H2 adsorption isotherms at zero pressure. Prior to adsorption, the samples (ca. 0.5 g) were pre-treated in flowing He at 120 °C for 1 h. Afterward, the samples were reduced in situ by flowing pure H2 and raising the temperature to 425 °C and maintaining this temperature for 6 h. After reduction, the samples were degassed, the temperature lowered to 150 °C and H2 dosed over the sample in the pressure range of 100-760 mmHg.

Transmission electron microscopy (TEM) was performed to calculate Co particle size distributions and to produce elemental maps. Samples were first reduced and passivated. Powder samples were embedded in resin, cured, microtomed and placed on holey carbon coated Cu grids. The samples were examined in the Birmingham University probe corrected JEOL-2100F transmission electron microscope using the scanning transmission mode with high angle annular dark field (HAADF) and bright-field detectors and a voltage of 200 kV. Parallel electron energy loss spectroscopy (EELS) using a GATAN Enfina spectrometer was used to investigate the composition.

Inductively coupled plasma (ICP) analysis was performed to determine the compositions of solid samples. Following complete dissolution of the samples using microwave digestion in HCl, analysis was performed on a Perkin Elmer Optima ICP-OES

ICP analysis was performed to determine the amount of Mg and Al ions removed from Mg modified ?-Al2O3 solids by washing with acetic acid or ammonium acetate on a Ciros CCD optical emission spectrometer.

The FTS testing was carried out in a stainless-steel isothermal fixed bed six-way micro-reactor connected to an on-line VARIAN CP-3800 gas chromatograph with three detectors. A Valco-valve was used to select between the gas streams for on-line analysis. Catalysts were reduced at 425 °C for 9 h in pure H2 prior to testing. After reduction the reactor was cooled to 160 °C and H2 was replaced with syngas (H2:CO:Ar = 2:1:0.1) and pressure was raised to 20 bar. Conversion was measured by the consumption of the syngas mix (CO + H2) relative to Ar. Wax and water were collected from the gas-liquid separators and analysed using an off-line GC with a FID on a SimDist column in order to calculate the chain growth probability, ? from the C22-C40 fraction.