CATALYTIC PROCESS

Abstract

A catalytic process for the deoxygenation of an organic substrate, such as a biomass or bio-oil, is described. The catalytic process is conducted in the presence of a gaseous mixture containing both hydrogen and nitrogen. The presence of nitrogen in the gaseous mixture gives rise inter-aliato increased catalytic activity and/or increased selectivity for aromatic reaction products.

Claims

1. A catalytic process for reducing the oxygen content of an organic substrate, the process comprising the steps of: a) providing a mixture comprising: i. the organic substrate, and ii. a catalyst; b) contacting the mixture of step a) with a gaseous mixture comprising hydrogen gas and nitrogen gas, wherein the volume ratio of hydrogen gas to nitrogen gas in step b) is 1:0.5 to 1:20.

2. The process according to claim 1, wherein the volume ratio of hydrogen gas to nitrogen gas is 1:0.5 to 1:10.

3. The process according to claim 1, wherein the volume ratio of hydrogen gas to nitrogen gas is 1:2.75 to 1:8.4.

4. The process according to claim 1, wherein the volume ratio of hydrogen gas to nitrogen gas is 1:3.25 to 1:6.5.

5. The process according to claim 1, wherein greater than 60 vol. % of the gaseous mixture used in step b) is composed of hydrogen and nitrogen.

6. The process according to claim 1, wherein the catalyst comprises one or more metals selected from the group consisting of Ru, Pt and Pd supported on a support material selected from the group consisting of titania, alumina, silica, zirconia and carbon.

7. The process according to claim 6, wherein the catalyst is selected from the group consisting of Ru/TiO.sub.2, Pd/TiO.sub.2 and Ru/C.

8. The process according to claim 7, wherein the catalyst is Ru/TiO.sub.2.

9. The process according to claim 1, wherein the organic substrate is one or more organic compounds having a structure according to formula (I) or (II) shown below: ##STR00008## wherein ring A is unsaturated, partially saturated or fully saturated, optionally containing 1 or 2 oxygen atoms within the ring; n is a number selected from 0 and 1; each R.sub.1 is independently selected from (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)alkoxy, formyl, acyl, oxo, carboxy and hydroxyl; and m is a number selected from 1, 2, 3, 4, 5 and 6, providing that the compound contains at least one oxygen atom; ##STR00009## wherein R.sub.2 is oxo or hydroxyl; and R.sub.3 and R.sub.4 are independently selected from (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)alkoxy, carboxy, oxo and hydroxyl, wherein any of said (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl and (1-6C)alkoxy is optionally substituted with one or more groups selected from (1-6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1-6C)alkoxy, formyl, acyl, oxo, carboxy and hydroxyl.

10. The process according to claim 9, wherein ring A has a structure according to A1, A2, A3 or A4 shown below: ##STR00010##

11. The process according to claim 9, wherein m is a number selected from 1, 2, 3, 4 and 5.

12. The process according to claim 9, wherein each R.sub.1 is independently selected from (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy, formyl, acyl, oxo, carboxy and hydroxyl.

13. The process according to claim 9 wherein at least one R.sub.2 is selected from hydroxy and (1-2C)alkoxy.

14. The process according to claim 1, wherein the organic substrate is a mixture of oxygen-containing compounds derived from plant matter.

15. The process according to claim 14, wherein the mixture of oxygen-containing compounds derived from plant matter is: a biomass, a bio-oil, or liquid obtainable by the pyrolysis of a plant-derived material.

16. The process according to of claim 1, wherein the organic substrate is pyrolised lignocellulosic biomass, which may be liquid.

17. The process according to claim 1, wherein the mixture of step a) further comprises a solvent.

18. The process according to claim 17, wherein the solvent is an organic solvent.

19. The process according to claim 1, wherein step b) is carried out at a temperature of 40-500° C.

20. The process according to claim 1, wherein step b) is carried out at a temperature of 80-220° C.

Description

EXAMPLES

[0220] One or more examples of the invention will now be described, for the purpose of illustration only, with reference to the accompanying figures, in which:

[0221] FIG. 1 shows the effect of N.sub.2 on the catalytic activity of various catalysts in the catalytic deoxygenation of p-cresol to toluene. Reaction conditions: p-cresol (0.195 mmol), decalin (8 mL), 120° C., 1 bar H.sub.2 and 6 bar N.sub.2 or 1 bar H.sub.2 and 6 bar He, mixture stirred at 800 rpm. 10 mg of catalysts used. Ru/TiO.sub.2, m-Ru/TiO.sub.2 and Pd/TiO.sub.2 contained 1.25 wt % metal. Ru/C, containing 5 wt. % Ru, was commercially-obtained.

[0222] FIG. 2 shows the effect of N.sub.2 on the toluene selectively of various catalysts in the catalytic deoxygenation of p-cresol to toluene. Reaction conditions: p-cresol (0.195 mmol), decalin (8 mL), 120° C., 1 bar H.sub.2 and 6 bar N.sub.2 or 1 bar H.sub.2 and 6 bar He, mixture stirred at 800 rpm. 10 mg of catalysts used. Ru/TiO.sub.2, m-Ru/TiO.sub.2 and Pd/TiO.sub.2 contained 1.25 wt % metal. Ru/C, containing 5 wt. % Ru, was commercially-obtained.

[0223] FIG. 3 shows the N.sub.2 pressure effect on the catalytic deoxygenation activity of p-cresol to toluene. Reaction conditions: p-cresol (0.195 mmol), m-Ru/TiO.sub.2 (10 mg, including 1.25 wt % Ru), decalin (8 mL), 120° C., 6 bar He, 1 bar H.sub.2 and 1-5 bar N.sub.2, or 1 bar H.sub.2 and 6 bar N.sub.2, mixture stirred at 600 rpm.

[0224] FIG. 4 shows the N.sub.2 pressure effect on the catalytic deoxygenation selectivity of p-cresol to toluene. Reaction conditions: p-cresol (0.195 mmol), m-Ru/TiO.sub.2 (10 mg, including 1.25 wt % Ru), decalin (8 mL), 120° C., 6 bar He, 1 bar H.sub.2 and 1-5 bar N.sub.2, or 1 bar H.sub.2 and 6 bar N.sub.2, mixture stirred at 600 rpm.

[0225] FIG. 5 shows filtering gas effect (to avoid moisture and oxygen) on the catalytic deoxygenation activity of p-cresol to toluene. Reaction conditions: p-cresol (0.195 mmol), m-Ru/TiO.sub.2 (10 mg, including 1.25 wt % Ru), decalin (8 mL), 120° C., 6 bar He and 1 bar H.sub.2, or 6 bar N.sub.2 and 1 bar, mixture stirred at 600 rpm.

[0226] FIG. 6 shows filtering gas effect (to avoid moisture and oxygen) on the toluene selectivity of deoxygenation of p-cresol to toluene. Reaction conditions: p-cresol (0.195 mmol), m-Ru/TiO.sub.2 (10 mg, including 1.25 wt % Ru), decalin (8 mL), 120° C., 6 bar He and 1 bar H.sub.2, or 6 bar N.sub.2 and 1 bar, mixture stirred at 600 rpm.

[0227] FIG. 7 shows toluene selectivity using m-Ru/TiO.sub.2 and unmodified Ru/TiO.sub.2 in the catalytic deoxygenation of p-cresol with varying reaction temperature. Reaction conditions: p-cresol (0.195 mmol), decalin (8 mL), 120-240° C., 1 bar H.sub.2, 6 bar N.sub.2, catalysts (10 mg for 60-120° C., 2.5 mg for 150-240° C.), mixture stirred at 800 rpm.

[0228] FIG. 8 shows the effect of nitrogen on product yield and toluene selectivity using Ru/TiO.sub.2 in the deoxygenation of p-cresol in a fixed bed reaction.

[0229] FIG. 9 shows structure characterisations of the Ru/TiO.sub.2 catalyst. High-angle annular dark-field scanning transmission electron microscopy images of (a) a representative region and (b), an individual particle of the Ru/TiO.sub.2 catalyst corresponding to the arrow in panel (a). Scale bar equals 2 nm in (a), and equals 1 nm in (b). (c), Size distribution of the Ru particles. (d), STEM-EDS elemental mapping results for Ru/TiO.sub.2. Scale bars equal 10 nm. (e), X-ray diffraction patterns of Ru/TiO.sub.2 catalyst and TiO.sub.2. Inset highlights the reflection at around 2θ=44°.

[0230] FIG. 10 shows representative HAADF images of Ru/TiO.sub.2. Scale bars equal 5 nm.

[0231] FIG. 11 shows catalytic performance promoted by N.sub.2 in the hydrodeoxygenation of p-cresol using Ru/TiO.sub.2 catalyst. Comparison of conversion and selectivity with or without N.sub.2 in batch reaction. (a), Comparison at two different conversions, reaction conditions: (a), p-cresol (0.195 mmol), Ru/TiO.sub.2 catalyst (25, 10, 25, 25 mg from left to right column), decalin (8 mL), 160° C., reaction time (1, 1, 4, 1 hour from the left to right column), system pressure of 1 bar H.sub.2 and 6 bar He (or 1 bar H.sub.2 and 6 bar N.sub.2), mixture stirred at 600 rpm. (b), Comparison at varied H.sub.2 pressures, reaction conditions: p-cresol (0.195 mmol), Ru/TiO.sub.2 catalyst (25 mg), decalin (8 mL), 160° C., 1 hour, system pressure of 1-6 bar H.sub.2 and 6 bar He (or 1-6 bar H.sub.2 and 6 bar N.sub.2), mixture stirred at 600 rpm. (c), Comparison at varied N.sub.2 pressures, reaction conditions: p-cresol (0.195 mmol), Ru/TiO.sub.2 catalyst (25 mg), decalin (8 mL), 160° C., 1 hour, system pressure of 1 bar H.sub.2, 6 bar He and 0-6 bar N.sub.2, mixture stirred at 600 rpm. (d), Comparison of conversion and selectivity with or without N.sub.2 in fixed-bed reaction. Reaction conditions: p-cresol (concentration of 1.12 mg.Math.mL.sup.−1 with decalin as solvent, flow rate of 0.2 mL.Math.min.sup.−1), Ru/TiO.sub.2 (100 mg), 180° C., system pressure of 1 bar H.sub.2 and 6 bar He (or 1 bar H.sub.2 and 6 bar N.sub.2), H.sub.2 flow rate of 5 cm.sup.3(STP)min.sup.−1, N.sub.2 (or He) flow rate of 30 cm.sup.3(STP)min.sup.−1, weight hourly space velocity (WHSV, 0.134 h.sup.−1).

[0232] FIG. 12 shows time dependence of the p-cresol conversion and product yield. The reaction process by using Ru/TiO.sub.2 catalyst in the presence of N.sub.2 shows high toluene selectivity from the initial stage, and methylcyclohexanol or methylcyclohexene were not observed which are normally the reaction intermediates from the hydrodeoxygenation reaction following tandem reaction route.sup.11. Reaction conditions: batch reaction, p-cresol (0.195 mmol), Ru/TiO.sub.2 (65 mg), decalin (8 mL), 160° C., reaction time from 0.5 to 9 hours, system pressure of 1 bar H.sub.2 and 6 bar N.sub.2, reaction mixture stirred at 600 rpm.

[0233] FIG. 13 shows a comparison of toluene yield at varied H.sub.2 pressures. Reaction conditions: p-cresol (0.195 mmol), Ru/TiO.sub.2 (25 mg), decalin (8 mL), 160° C., 1 hour, system pressure of 1-6 bar H.sub.2 and 6 bar He (or 1 bar H.sub.2 and 6 bar N.sub.2), mixture stirred at 600 rpm.

[0234] FIG. 14 shows the dependence of HDO reaction rate on the partial pressure of H.sub.2 in the presence of N.sub.2. The data was derived from FIG. 11b. Insert “p” represents the reaction order for H.sub.2.

[0235] FIG. 15 shows the dependence of HDO reaction rate on the partial pressure of N.sub.2. The data was derived from FIG. 11c. Inset “a” represents the reaction order for N.sub.2. Error bars represent standard deviation from three independent measurements.

[0236] FIG. 16 shows representative HAADF images of Ru/TiO.sub.2 after HDO reaction under fixed-bed conditions for 7 h. Scale bars equal 5 nm.

[0237] FIG. 17 shows high-angle annular dark-field scanning transmission electron microscopy images of Ru catalysts with different support. Scale bar equals 5 nm in Ru/Al.sub.2O.sub.3 image and equals 20 nm in other images.

[0238] FIG. 18 shows a comparison of conversion and selectivity with/without N.sub.2 in batch reaction by using Ru catalysts with different support. Reaction conditions: p-cresol (0.195 mmol), catalysts with different supports (including 0.00183 mmol Ru, which is corresponding to 25 mg for Ru/TiO.sub.2, 25.5 mg for Ru/Al.sub.2O.sub.3, 57.4 mg for Ru/ZrO.sub.2 and 3.7 mg for Ru/C), decalin (8 mL), 160° C., 1 hour, system of 1 bar H.sub.2+6 bar He (or 1 bar H.sub.2+6 bar N.sub.2), mixture stirred at 600 rpm.

ANALYTICAL TECHNIQUES

High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy (HAADF-STEM)

[0239] An aberration-corrected JEOL ARM300 CF operated at 300 kV in STEM mode was used for microstructure characterisation. The convergence angle of the probe was 26 mrad [30 μm condenser aperture] with imaging performed at 9 cm camera length. This configuration was used to collect the scattered electrons between 77 to 210 mrad (annual dark-field—ADF-signal) and 13 to 28 mrad (annular bright field—ABF-signal). Energy-dispersive X-ray elemental maps and spectra were collected using a window-less Oxford Instruments XMAX 100 TLE silicon drift detector. For STEM imaging, the probe current used was around 25 pA. The probe current was increased to around 500 pA for EDX elemental mapping.

Powder X-ray Diffraction

[0240] Powder X-ray Diffraction (PXRD) data were obtained on a PANAnalytical X'Pert Pro diffractometer in reflection mode at 40 kV and 40 mA using Cu Kα radiation.

Gas Chromatograph-Mass Spectrometry Analysis

[0241] GC-MS and GC-FID analysis was conducted simultaneously by using an Agilent gas chromatograph equipped with an Agilent 19091 N-133 column of mode HP-INNOWax with high polarity, 30 m*250 μm*0.25 μm connected column splitter which connects to mass spectrometer and FID. The GC oven was programmed as: hold at initial temperature of 313 K for 5 minutes, ramp at 15 K minutes.sup.−1 to 523 K and hold at 523 K for 5 minutes. The peaks were analysed by comparing the corresponding spectra with those of the NIST 2011 MS library.

Part A

Example 1—Preparation of Catalysts

1.1. Preparation of M/TiO.SUB.2 .and M/SiO.SUB.2 .Catalysts (M=Ru, Pt or Pd)

[0242] M/TiO.sub.2 and M/SiO.sub.2 catalysts were prepared as follows: an appropriate amount of M precursor was dissolved in de-ionised water, the volume of which was determined by the water adsorption volume of metal oxides. The solution was stirred for 1 h and then dropwise added to an appropriate amount of TiO.sub.2 or SiO.sub.2. The obtained glue-like sample was stirred for another 2 h and dried in an oven at 397 K overnight and then reduced in H.sub.2, at a flow rate of 20 cm.sup.3/min and a heating rate of 2 K/min to the target temperature, with the target temperature held for several hours. The sample was subsequently cooled down to room temperature and protected with N.sub.2 for 1 h prior to removal from the tube reactor for catalytic testing.

1.2. Preparation of m-Ru/TiO.SUB.2

[0243] RuCl.sub.3 (0.0063 g, 0.03 mmol), 1-ethyl-3-methylimidazolium dicyanamide (0.0045 g) were dissolved in 3 mL de-ionised water. The mixture was stirred for 1 h and then dropwise added to TiO.sub.2 (0.24 g). The obtained glue-like sample was keeping stirred for another 2 h and then dried in an oven at 397 K overnight and then reduced in H.sub.2, at a flow rate of 20 cm.sup.3/min and a heating rate of 2 K/min to 673 K, with the target temperature held for 3 h. The sample was subsequently cooled down to room temperature and protected with N.sub.2 for 1 h prior to removal from the tube reactor for catalytic reaction.

Example 2—Catalytic Testing

2.1. General Procedure

[0244] An appropriate amount of catalytic substrate (e.g. p-cresol or bio-oil), catalyst and decalin were added to a Parr reactor (reactor volume, 50 mL) and sealed. After purging the reactor with H.sub.2, the reaction was carried out with an appropriate pressure of H.sub.2, N.sub.2 and/or He at 120° C. for 1 hour with a stirring speed of 600-800 rpm. After the reaction was completed and cooled down to room temperature, the organic mixture of the products was collected, qualitatively analyzed by GC-MS, and quantitively analysed by GC-FID.

2.2. Results and Discussion

[0245] The effect of nitrogen on the ability of various deoxygenation catalysts to catalyse the deoxygenation of p-cresol to toluene was investigated. The results are outlined in Table 1 below:

TABLE-US-00001 TABLE 1 Effect of nitrogen on the catalytic performance of various catalysts in the conversion of 4-methylphenol to toluene. Reactor: Parr 50 mL batch reactor. Temperature = 120° C. 8 mL decalin. Stirring speed = 600 rpm. Mass Mass catalyst p-cresol P(bar) P(bar) P(bar) Conv. Toluene TOF Run Cat (mg) (mg) of H.sub.2 of He of N.sub.2 t (h) (%) selec. (%) (h.sup.−1) 1 Ru/TiO.sub.2 10 21.1 1 6 0 1 1.8 54.7 1.6 2 Ru/TiO.sub.2 10 21.1 1 0 6 1 5.8 84.7 7.7 3 m-Ru/TiO.sub.2 10 21.1 1 6 0 1 3.4 55.5 3.0 4 m-Ru/TiO.sub.2 10 21.1 1 0 6 1 11.8 77.2 14.4 5 Ru/C* 10 21.1 1 6 0 1 38.9 4.3 0.7 6 Ru/C* 10 21.1 1 0 6 1 35.9 12.5 1.8 7 Ru/SiO.sub.2 10 21.1 1 6 0 1 0.9 45.4 0.6 8 Ru/SiO.sub.2 10 21.1 1 0 6 1 1.2 68.5 1.3 9 Pd/TiO.sub.2 10 21.1 1 6 0 1 37.7 6.1 3.6 10 Pd/TiO.sub.2 10 21.1 1 0 6 1 24.3 30.8 11.8 11 Pt/TiO.sub.2 10 21.1 1 6 0 1 28.8 24.5 11.1 12 Pt/TiO.sub.2 10 21.1 1 0 6 1 26.1 45.3 18.7 *commercially-obtained 5 wt. % Ru on carbon. All ofther catalysts contained 1.25 wt. % M relative to weight of TiO.sub.2/SiO.sub.2.

[0246] The results outlined in Table 1 illustrate that nitrogen had a beneficial effect on the activity and/or toluene selectivity of all of the catalysts tested. Similar trends are illustrated in FIGS. 1-2. It is also clear from the results that the use of nitrogen allows the catalytic process to be satisfactorily performed at a reduced temperature and/or pressure.

[0247] In order to investigate the effect of N.sub.2 in the conversion of p-cresol to toluene, the catalytic activity of m-Ru/TiO.sub.2 (Example 1.2) was tested at various N.sub.2 pressures (with H.sub.2 pressure and He pressure kept constant). The results are shown in Table 2 and FIGS. 3 to 6.

TABLE-US-00002 TABLE 2 catalytic performance in the conversion of 4-methylphenol to toluene by using m- Ru/TiO.sub.2 catalysts at different conditions. Reactor: Parr 50 mL batch reactor. Mass Mass En- catalyst p-cresol P(bar) P(bar) of P(bar) P(bar) t Conv. Toluene TOF try Catalyst (mg) (mg) T(° C.) of H.sub.2 He of N.sub.2 of CO (h) (%) selec.(%) (h.sup.−1) 1 m-Ru/TiO.sub.2 12.5 21.1 240 1 6 0 0 1 64.1 99.2 80.3 2 m-Ru/TiO.sub.2 12.5 21.1 240 1 0 6 0 1 97.6 99.9 123.2 3 m-Ru/TiO.sub.2 25 21.1 180 1 0 6 0 1 94.5 94.9 56.6 4 m-Ru/TiO.sub.2 50 21.1 120 1 0 6 0 9 90.1 81.1 3.3 5 m-Ru/TiO.sub.2 50 21.1 90 1 0 6 0 12 43.1 30.3 0.3 6 m-Ru/TiO.sub.2 50 21.1 60 1 0 6 0 24 40.1 11.2 0.06 7 m-Ru/TiO.sub.2 10 21.1 120 1 6 0 0 1 3.4 55.5 3.0 8 m-Ru/TiO.sub.2 10 21.1 120 1 6 0 0 1 4.1 58.6 3.8 9 m-Ru/TiO.sub.2 10 21.1 120 1 6 0 0 1 4.1 60.1 3.9 10 m-Ru/TiO.sub.2 10 21.1 120 1 6 0 0 1 5.8 55.7 5.1 11 m-Ru/TiO.sub.2 10 21.1 120 1 0 6 0 1 11.8 77.2 14.4 12 m-Ru/TiO.sub.2 10 21.1 120 1 0 6 0 1 10.1 80.4 12.8 13 m-Ru/TiO.sub.2 10 21.1 120 1 0 6 0 1 13.8 74.2 16.2 14 m-Ru/TiO.sub.2 10 21.1 120 1 0 6 0 1 12.7 76.4 15.3 15 m-Ru/TiO.sub.2 10 21.1 120 1 0 0 6 1 0.4 0 0 16 m-Ru/TiO.sub.2 10 21.1 120 1 6 0 1 1 0 0 0 17 m-Ru/TiO.sub.2 10 21.1 120 1 0 6 1 1 0 0 0 18 m-Ru/TiO.sub.2 10 21.1 120 5 0 0 0 1 36.6 14.2 8.2 19 m-Ru/TiO.sub.2 10 21.1 120 5 0 0 0 1 38.5 14.6 8.9 20 m-Ru/TiO.sub.2 10 21.1 120 5 6 0 0 1 32.0 18.3 9.3 21 m-Ru/TiO.sub.2 10 21.1 120 5 0 6 0 1 28.9 18.4 8.4 22 m-Ru/TiO.sub.2 10 21.1 120 5 6 0 0 1 38.0 20.2 12.1 23 m-Ru/TiO.sub.2 10 21.1 120 5 6 0 0 1 36.3 22.6 13.0 24 m-Ru/TiO.sub.2 10 21.1 120 1 6 0 0 1 3.4 55.5 3.0 25 m-Ru/TiO.sub.2 10 21.1 120 1 6 0 0 1 4.1 58.6 3.8 26 m-Ru/TiO.sub.2 10 21.1 120 1 6 1 0 1 6.7 76.0 8.0 27 m-Ru/TiO.sub.2 10 21.1 120 1 6 2 0 1 6.8 82.1 8.8 28 m-Ru/TiO.sub.2 10 21.1 120 1 6 3 0 1 13.7 88.5 19.1 29 m-Ru/TiO.sub.2 10 21.1 120 1 6 3 0 1 12.1 81.8 15.7 30 m-Ru/TiO.sub.2 10 21.1 120 1 6 4 0 1 9.5 82.9 12.4 31 m-Ru/TiO.sub.2 10 21.1 120 1 6 5 0 1 8.5 74.8 10.1 32 m-Ru/TiO.sub.2 10 21.1 120 1 6 6 0 1 4.6 69.3 5.1 33 m-Ru/TiO.sub.2 10 21.1 120 1 0 6 0 1 11.8 77.2 14.4 34 m-Ru/TiO.sub.2 10 21.1 120 3 0 6 0 1 26.3 49.4 20.5 35 m-Ru/TiO.sub.2 10 21.1 120 5 0 6 0 1 32.0 18.3 9.3 36 m-Ru/TiO.sub.2 10 21.1 120 7 0 6 0 1 51.7 13.1 10.7

[0248] As shown in FIG. 3, the activity was more than twice as high when 1 bar N.sub.2 was fed into the reaction (TOF=5.5 v.s. 2.3 h.sup.−1). It was further increased by a factor of greater than 6 when 3 bar N.sub.2 was fed (TOF=12.2 v.s. 2.3 h.sup.−1). Further increasing N.sub.2 led to higher activity compared to when no N.sub.2 was present. By using 1 bar H.sub.2 and 6 bar N.sub.2 in the absence He, the activity was also comparable with that of the highest obtained value (TOF=9.5 v.s. 12.2 h.sup.−1). These results clearly show that incorporating N.sub.2 gas boosts catalytic activity for deoxygenation reaction using m-Ru/TiO.sub.2. FIG. 4 shows that increasing the N.sub.2 pressure also has an effect on toluene selectivity. To verify the effect of N.sub.2, the gases (N.sub.2 and He) were filtered before purging, thereby removing any moisture and oxygen which may affect the catalytic performance. The results show only a minor difference in terms of TOF number (FIG. 5) and selectivity (FIG. 6) after the gases was filtered, suggesting that the increase of catalytic activity using m-Ru/TiO.sub.2 was indeed due to the presence of N.sub.2 gas.

[0249] The toluene selectivity increased with increasing temperature and reached >90% when the temperature was above 180° C. (FIG. 7).

2.3. Fixed Bed Reaction

[0250] A fixed bed reaction was carried out in a HEL made continuous trickle bed reactor (mode FlowCAT) with both the liquid feed and hydrogen gas (or hydrogen gas and nitrogen gas) passing in downward direction. The Ru/TiO.sub.2 catalyst (100 mg, 0.74 wt % Ru) was located in the middle of the tubular reactor with quartz wool plugs on both the sides. Liquid feed was prepared by dissolving p-cresol in decalin to form a solution of 1.12 mg/mL. The reaction was carried out at 180° C., 2 bar with H.sub.2 flow rate of 10 cm.sup.3(STP)minutes.sup.−1 (or 2 bar with H.sub.2 flow rate of 10 cm.sup.3(STP)minutes.sup.−1 and 6 bar with N.sub.2 flow rate of 30 cm.sup.3(STP)minutes.sup.−1), and liquid flow rate of 0.2 mL minutes.sup.−1. The liquid was preheated at the desired reaction temperature before being fed into the reactor. The products were periodically collected from the outlet stream throughout the reaction and were analysed by GC-FID. Weight hour space velocity (WHSV) was calculated by dividing the feed flow rate per hour by weight of catalyst.

[0251] The reaction conditions for the fixed bed reaction were as follows:

Catalyst: 100 mg Ru/TiO.SUB.2 .(Ru: 0.74 wt %)

Temperature: 180° C.

[0252] Gas pressure: 2 bar H.sub.2 or 2 bar H.sub.2+6 bar N.sub.2
Gas flow rate: v(H.sub.2)=10 cm.sup.3(STP)minutes.sup.−1
Or v(H.sub.2)=10 cm.sup.3(STP)minutes.sup.−1, v (N.sub.2)=30 cm.sup.3(STP)minutes.sup.−1
Liquid concentration (p-cresol in decalin)=1.12 mg.Math.min.sup.−1
Liquid flow rate: 0.2 ml.Math.min.sup.−1

WHSV=0.134 h.SUP.1

[0253] The results are outlined in Table 3 and FIG. 8.

TABLE-US-00003 TABLE 3 Effect of nitrogen on the catalytic performance of Ru/TiO.sub.2 in the conversion of 4- methylphenol to toluene in a fixed bed reaction Time Conversion Yield (%) (min) Gas (%) Toluene Methylcyclohexane Methylcyclohexanone Methylcyclohexanol 120 H.sub.2 + N.sub.2 25.8 15.6 3.3 0.9 6 150 H.sub.2 + N.sub.2 24.3 14.6 3.2 1.3 5.2 180 H.sub.2 20.0 12.4 2 0.8 4.8 210 H.sub.2 20.6 13.7 1.7 1.1 4.1 240 H.sub.2 + N.sub.2 24.5 16.2 2.4 1.2 4.7 270 H.sub.2 + N.sub.2 22.8 14.9 2.4 0.8 4.6 300 H.sub.2 18.9 12.8 1.3 0.7 4 330 H.sub.2 19.0 13.1 1.3 0.9 3.7 360 H.sub.2 + N.sub.2 23.2 15.3 2.5 1 4.4 390 H.sub.2 + N.sub.2 22.9 15 2.5 0.8 4.6 420 H.sub.2 20.2 13.1 1.8 1.1 4.2 450 H.sub.2 19.7 13.4 1.6 0.8 3.8

[0254] The results of the fixed bed reaction clearly illustrate the beneficial effect that nitrogen has on both total product yield and toluene selectivity.

Part B

Example 3—Preparation of Catalysts

3.1. Preparation of Ru/TiO.SUB.2

[0255] Ru/TiO.sub.2 catalyst was prepared using a wet-impregnation method. RuCl.sub.3 (0.03 mmol) was dissolved in 3 mL de-ionised water. The mixture was stirred for 1 h and then added dropwise to TiO.sub.2 (0.24 g). In the wet-impregnation method for preparing the catalyst, the water volume used was larger than that needed to saturate the TiO.sub.2 surface, so suspension liquid rather than glue-like sample was formed. The formation of the suspension liquid allows it to be stirred vigorously for 2 hours and then the sample was dried overnight in an oven at 120° C. and then reduced in H.sub.2, at a flow rate of 20 cm.sup.3/min and a heating rate of 2° C./min to 400° C., with the target temperature held for 3 hours. The sample was subsequently cooled down to room temperature and protected with N.sub.2 for 1 h prior to removal from the tube reactor for catalytic reactions or other tests.

3.2. Other Catalysts

[0256] Ru/Al.sub.2O.sub.3 and Ru/ZrO.sub.2 were prepared in an analogous manner to Ru/TiO.sub.2 (Example 3.1) except using the appropriate support in the place of TiO.sub.2. Ru/C was purchased from Sigma-Aldrich.

Example 4—Characterisation of Ru/TiO.SUB.2

[0257] HAADF-STEM images revealed that Ru particles were well-dispersed on TiO.sub.2 support (FIG. 9a,b and FIG. 10), with an average diameter of 1.2 nm (FIG. 9c). The composition of Ru/TiO.sub.2 was shown by energy dispersive X-ray spectroscopy (EDS) analysis in a STEM mode (FIG. 9d), and the loading amount of Ru was determined to be 0.74 wt % using inductively coupled plasma mass spectrometry (ICP-AES) analysis. Powder X-ray diffractogram (PXRD) data (FIG. 9e) revealed a mixed rutile and anatase phase of TiO.sub.2. There is no clear change in the reflection at 2θ=44° between TiO.sub.2 and Ru/TiO.sub.2 samples. The predicted Bragg reflection (201) of rutile TiO.sub.2 at 20=44.054° coincides with the Bragg reflection (201) for Ru at 20=44.005° for (101). Therefore, one can conclude that this reflection contains very little contribution from Ru due to the small size of the metal nanoparticles, which agrees with TEM results.

Example 5—Catalytic Performance in the Presence of N.SUB.2

5.1. Batch Reactor Using Ru/TiO.SUB.2

[0258] The catalytic performance of Ru/TiO.sub.2 was evaluated for the HDO of p-cresol in a batch reactor. p-cresol (0.195 mmol) was loaded into a stainless steel Parr autoclave (reactor volume, 50 mL) with decalin (8 mL) and Ru/TiO.sub.2 (2.5-50 mg). After the autoclave was sealed, it was cleaned with N.sub.2 for three times, purged 6 bar N.sub.2 and then 1 bar H.sub.2 at room temperature. The reaction was carried out at 60-240° C. for 1-24 h with a stirring speed of 600 rpm. After the reaction was completed and cooled down to room temperature, the products were collected and was qualitatively analysed by gas chromatograph-mass spectrometry (GC-MS) and quantitatively analysed by a flame ionisation detector (GC-FID) using external standard method. The gases composition and pressure maybe changed depending on the reaction.

[0259] Table 4 shows the comparison of catalytic performance of state-of-the-art HDO catalysts and Ru/TiO.sub.2 catalyst of Example 3.1 for the conversion of p-cresol or other phenols to aromatics. As comparison to HDO results from the literature.sup.11,12,15, most Ru-based catalysts were studied at temperature higher than 200° C. (entries 1-3 in Table 4). A higher activity was observed for isolated Co atoms doped onto MoS.sub.2 monolayers.sup.10 (Co-sMoS.sub.2, entry 4), but the H.sub.2 pressure required was 30 bar. Although extremely mild condition was used on Ru catalysts modified by C,N-matrix (entry 5), alicyclic compounds rather than aromatics were the main products.sup.16,17. As seen in entry 6, the Ru/TiO.sub.2 catalyst of Example 3.1 showed similar toluene selectivity under similar temperature range and lower H.sub.2 pressure. Remarkably, if 6 bar N.sub.2 is added to the gas mixture as the complementary gas, the conversion increased as well as toluene selectivity (entry 7).

[0260] As shown in the left columns in FIG. 11a, a 1.5-fold higher of toluene selectivity and 4.3-fold increase of HDO activity were observed in the presence of N.sub.2. The promoting effect of N.sub.2 in HDO reaction was also verified at another constant conversion of 21% (right two columns in FIG. 11a). Production of toluene follows a direct deoxygenation (DDO) pathway, with the formation of methylcyclohexane as over-hydrogenation product of toluene, and methylcyclohexanone and methylcyclohexanol as hydrogenation product of p-cresol (FIG. 12), which is in agreement with previous report.sup.10.

TABLE-US-00004 TABLE 4 Comparison of HDO activity for the conversion of 4-methylphenol to toluene by using Ru/TiO.sub.2 catalysts with/without N.sub.2 and state-of-the-art HDO catalysts from literature. [00007] P (bar) of Conversion Toluene selectivity Entry Catalyst T (° C.) P (bar) of H.sub.2 additional gas t (h) (%) (%) Ref. 1 Ru/Nb.sub.2O.sub.5 250 5 — 5 99.9 81.2 11 2 Ru/Zr(SO.sub.4).sub.2 240 2 6 (N.sub.2) 2 99 99.sup.a   12 3 Ru-WO.sub.x/Si—Al 220 10 — 1.5 100 83   15 4 Co-.sup.sMoS.sub.2 180 30 — 8 97.6 98.4 10 5 Ru/C,N-matrix  40 5 — 2 95 0.sup.d 16 6 Ru/TiO.sub.2 220 1 6 (He) 2 75.5 95.1 This work 7 Ru/TiO.sub.2 220 1 6 (N.sub.2) 2 97.4 98.4 This work T, temperature; P, pressure; t, time. Reaction conditions: batch reaction, p-cresol (0.915 mmol), Ru/TiO.sub.2 catalyst (25 mg), decalin (8 mL), reaction mixture stirred at 600 rpm. .sup.aAnisole as the substrate. Activity per mole of .sup.bMo and .sup.cCo, respectively. .sup.d99% selectivity to cyclohexanol.

[0261] The promoting effect of N.sub.2 for HDO was investigated under varied H.sub.2 and N.sub.2 pressures. With increased H.sub.2 pressure, the toluene selectivity (FIG. 11b) as well as its yield (FIG. 13) promoted by N.sub.2 became less pronounced. The reaction order for H.sub.2 of Ru/TiO.sub.2 catalyst was measured to be −0.57 in the presence of 1-3 bar H.sub.2 (FIG. 14). The negative value could be attributed to hydrogen adatoms on the Ru surface via hydrogenolysis suppressed the adsorption of N.sub.2 and thus inhibited the N.sub.2 promoting effect, which is consistent with hydrogen poisoning effect observed in ammonia synthesis.sup.18. The preferential adsorption of H.sub.2 was also confirmed by the observation of higher selectivity for hydrogenation products under higher H.sub.2 pressure. With increased N.sub.2 pressure from 0-4 bar, the conversion increased gradually and the toluene selectivity increased from 66.0 to 88.1% (FIG. 11c). It is known that the reaction order for N.sub.2 is between 0.8-1.0 for ammonia synthesis over conventional Ru-loaded catalysts and is smaller for catalyst with stronger N.sub.2 dissociation ability.sup.18. In this work, the HDO reaction order for N.sub.2 was estimated in the range of 0.38-0.98 (FIG. 15), although strictly it is inappropriate to call it ‘HDO reaction order’ because nitrogen is not incorporated in the reaction products. This result implies that N.sub.2 is activated on Ru/TiO.sub.2 with the formation of active species that provide a lower activation barrier for the overall HDO reaction. Interestingly, the conversion and toluene selectivity start to decrease when the N.sub.2 pressure was further increased.

5.2. Fixed-Bed Reactor Using Ru/TiO.SUB.2

[0262] Besides N.sub.2 promotion effect in batch reaction, the N.sub.2 promotion effect in a fixed-bed reaction was also investigated. The fixed bed reactions were performed on a reactor with mode of FlowCAT supplied by HEL (HEL is a company that specialises in research and pre-pilot scale chemical reactors and systems). The Ru/TiO.sub.2 catalyst (100 mg) was located in the middle of the tubular reactor with quartz wool plugs on both the sides. Liquid feed (p-cresol dissolved in decalin with concentration of 1.12 mg.Math.mL.sup.−1) was fed by using a HPLC pump with constant flow rate of 0.2 mL.Math.min.sup.−1. The N.sub.2 and H.sub.2 mixing gases or H.sub.2 gas were alternatively passed in downward direction with velocity controlled by mass-flow controllers, with the N.sub.2 and H.sub.2 flow rates of 10 and 30 cm.sup.3(STP)minutes.sup.−1, respectively, and total pressure of 8 bar mixing gas (2 bar H.sub.2+6 bar N.sub.2) or 2 bar H.sub.2, respectively. The flow rates are respectively calibrated by using a soap film bubble flowmeter. Weight hourly space velocity was maintained at 0.134 h.sup.−1. The reaction was carried out at 180° C. The products were collected and were qualitatively analysed by GC-MS and quantitatively analysed by GC-FID using external standard method.

[0263] The reaction was carried out at constant total pressure (7 bar) and constant H.sub.2 partial pressures (1 bar), while the complementary gas was changed between 6 bar N.sub.2 and 6 bar He for three successive cycles. As shown in FIG. 11d, a higher toluene selectivity (i.e. 1.2-fold higher for the 1.sup.st cycle) and conversion were observed in the presence of N.sub.2, while the selectivity of other products were not significantly changed. The fixed-bed reaction results showed the efficiency of N.sub.2 in promoting the HDO reaction. Although the catalytic results for batch and fixed-bed reactions are difficult to directly compare, both of the reaction systems show higher toluene selectivity in the HDO of p-cresol with N.sub.2. The Ru/TiO.sub.2 retained its particle size after reaction, as revealed by STEM imaging (FIG. 16).

5.3. Other Catalysts

[0264] It was investigated whether the N.sub.2 promotion effect is a generalised phenomenon for a variety of Ru-based catalysts with different supports (Ru/TiO.sub.2, Ru/Al.sub.2O.sub.3, Ru/ZrO.sub.2 and Ru/C).

[0265] The weight loading of Ru in the catalysts was determined by ICP-AES analysis (0.73% for Ru/Al.sub.2O.sub.3 and 0.32% for Ru/ZrO.sub.2). The weight loading of Ru in Ru/C is 5% according to the supplier. Ru particles were formed in nano-size regime (FIG. 17). Increase in HDO activity in the presence of N.sub.2 was observed over these catalysts with varied supports (FIG. 18), in which TiO.sub.2 exhibited a higher selectivity and conversion promoted by N.sub.2.

5.4. Conclusion

[0266] The results outlined herein suggest that associative N.sub.2 reduction through reaction with H-containing species provide N.sub.2H.sub.x species which help to promote the p-cresol to toluene conversion over a series of Ru supported on various metal oxides or carbon catalysts.

[0267] The processes outlined herein represent an efficient strategy for promoting HDO activity over Ru-based catalysts by introducing N.sub.2 into the HDO reaction. Experimental and theoretical calculations suggest that N.sub.2 may be converted to N.sub.2H.sub.x species, which provide protic hydrogen to assist hydrogenation of hydroxyl on p-cresol with lower activation energy than direct deoxygenation by H.sub.2. These data indicate that N.sub.2 should no longer be considered as a simple inert carrier gas.

[0268] While specific embodiments of the invention have been described herein for the purpose of reference and illustration, various modifications will be apparent to a person skilled in the art without departing from the scope of the invention as defined by the appended claims.

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