Oxygenate reduction catalyst and process

Abstract

The invention provides a catalyst system and method for the deoxygenation of hydrocarbons, such as bio-oil, using a sulphide-sulfate or an oxide-carbonate (LDH) system. The invention extends to a pyrolysis process of a carbonaceous bio-mass wherein a first combustion zone is carried out in one or more combustion fluidised beds in which a particulate material including chemically looping deoxygenation catalyst particles is fluidised and heated, and a second pyrolysis zone carried out in one or more pyrolysis fluidised beds in which the hot particles, including the catalyst particles, heated in the combustion zone are used for pyrolysis of the bio-mass, said combustion zone being operated at a temperature of from 250 C. to 1100 C., typically around 900 C., and the pyrolysis zone being operated at a temperature of from 250 C. to 900 C., typically 450 C. to 600 C., said catalyst particles being oxygenated in the pyrolysis zone in the presence of oxygenates in the pyrolysis oil and regenerated in the combustion zone either by calcining to drive off the carbon oxides, such as CO.sub.2, or by reduction to its form which is active for deoxygenation of the pyrolysis oil.

Claims

1. A hydrocarbon deoxygenation catalyst system comprising: a chemical looping catalytically active substance that is oxidized in a presence of oxygenates in a fluid hydrocarbon product or a fluid hydrocarbon-containing product, thereby reducing an amount of the oxygenate therein, wherein the oxidized chemical looping catalytically active substance is at least partially regeneratable by either reducing under reducing conditions, or by calcining to release at least some of a captured oxygenate in a form of a carbonate, thereby returning the chemical looping catalytically active substance to an active state for deoxygenation of a pyrolysis oil, wherein the chemical looping catalytically active substance is on a solid catalyst support at a level of between 1% and 99% by mass in a form of a particulate material; a first combustion zone adapted to be operated at a temperature of from 250 C. to 1100 C. in one or more combustion fluidized beds, wherein the first combustion zone is adapted to fluidize and heat the particulate material, thereby regenerating the oxidized chemical looping catalytically active substance either by calcining to drive off carbon oxides or by reducing to the active state; and a second pyrolysis zone operated at a temperature of from 250 C. to 900 C. in a pyrolysis bed, wherein the pyrolysis bed is a fluidized bed, wherein the second pyrolysis zone is adapted to pyrolize a bio-mass to yield the pyrolysis oil containing the oxygenates, and wherein the chemical looping catalytically active substance is oxidized in a presence of the oxygenates.

2. The system of claim 1, wherein the chemical looping catalytically active substance is a compound or salt of a Group I substance with sulfur, a Group II substance with sulfur, a transition metal with sulfur, or a Group III substance with sulfur.

3. The system of claim 1, wherein the chemical looping catalytically active substance is a metal sulfide wherein the metal is selected from the group consisting of Na, K, Ca, Mg, a transition metal, Mn, Fe, Co, Ni, and Zn.

4. The system of claim 3, wherein the metal sulfide is Na.sub.2S.

5. The system of claim 1, wherein the chemical looping catalytically active substance is a metalloid sulfide or a post-transition metal sulfide.

6. The system of claim 1, wherein the chemical looping catalytically active substance is a layered double hydroxide clay.

7. The system of claim 6, wherein a metal lattice that makes up the layered double hydroxide clay comprises a metal selected from the group consisting of Al, Mg, Ca, Na, K, Li, Cr, Mn, Fe, Co, Ni, and combinations thereof.

8. The system of claim 7, wherein the chemical looping catalytically active substance is a MgAl layered double hydroxide clay.

9. The system of claim 6, wherein the layered double hydroxide clay is calcined, whereby interlayer ions are removed and hydroxides convert to oxides.

10. The system of claim 1, wherein the chemical looping catalytically active substance is on the solid catalyst support at a level of 10% by mass.

11. A process for pyrolysis of a carbonaceous bio-mass, comprising: fluidizing and heating a particulate material including chemically looping deoxygenation catalyst particles in a first combustion zone operated at a temperature of from 250 C. to 1100 C. in one or more combustion fluidized beds; introducing a bio-mass and the fluidized and heated particulate material into a second pyrolysis zone operated at a temperature of from 250 C. to 900 C. in a pyrolysis bed, wherein the pyrolysis bed is a fluidized bed, whereby the bio-mass is pyrolized to yield a pyrolysis oil, and whereby the chemically looping deoxygenation catalyst particles are oxygenated in a presence of oxygenates in the pyrolysis oil; and regenerating the oxygenated chemically looping deoxygenation catalyst particles in the first combustion zone either by calcining to drive off carbon oxides or by reducing to a form which is active for deoxygenation of the pyrolysis oil.

12. The process of claim 11, wherein the chemically looping deoxygenation catalyst particles are metal sulfide particles or layered double hydroxide clay catalyst particles.

13. The process of claim 11, wherein the chemically looping deoxygenation catalyst particles are circulated between the one or more combustion fluidized beds and the pyrolysis bed so that the chemically looping deoxygenation catalyst particles loop between an oxidized state and a reduced or deoxygenation active state.

14. The process of claim 11, wherein a fluidizing gas and/or non-condensed vapors in the second pyrolysis zone are recirculated and solid products and liquid products are removed as part of a recirculation loop and a portion of the recirculated fluidizing gas and/or the recirculated non-condensed vapors is introduced into the second pyrolysis zone through nozzles.

15. The process of claim 14, wherein where there is a net production of gas in the recirculation loop, it is removed as a purge stream.

16. The process of claim 11, wherein the chemically looping deoxygenation catalyst particles pass through an aperture divider from the first combustion zone into the second pyrolysis zone.

17. The process of claim 11, wherein the second pyrolysis zone is operated at or about atmospheric pressure.

Description

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(1) The invention will now be described, by way of non-limiting example only, with reference to the accompanying diagrammatic drawings. In the drawings,

(2) FIG. 1 shows the results of the pyrolysis oil deoxygenation for a MgAl LDH looping catalyst system;

(3) FIG. 2 shows the results of the pyrolysis oil deoxygenation for a CaAl LDH looping catalyst system;

(4) FIG. 3 shows the results of the pyrolysis oil deoxygenation for a zeolite catalyst system;

(5) FIG. 4 shows comparative data to FIGS. 1 to 3 for an uncatalysed pyrolysis production of pyrolysis oil;

(6) FIG. 5 shows the composition analysis results of the pyrolysis oil deoxygenation for a CaAl LDH looping catalyst system;

(7) FIG. 6 shows the composition results of the pyrolysis oil produced without a deoxygenation catalyst system of the invention;

(8) FIG. 7 shows the composition analysis results of the pyrolysis oil deoxygenation for a MgAl LDH looping catalyst system;

(9) FIG. 8 shows the composition results of a pyrolysis oil produced from eucalyptus without a deoxygenation catalyst system of the invention;

(10) FIG. 9 shows the composition results of a pyrolysis oil produced from eucalyptus with a deoxygenation catalyst system of the invention, Na.sub.2S on an alumina support; and

(11) FIG. 10 is a van Krevelen diagram relevant to the invention.

1. EXPERIMENTAL WORK ON METAL SULFIDE CATALYST SYSTEM

(12) An experiment was used to demonstrate Na.sub.2S as a suitable oxygen scavenger during the pyrolysis of wood. Eucalyptus grandis sawdust was mixed together with Na.sub.2S and placed in a muffle oven heated to 500 C. The char leftover was compared to the original sample using XRD analyses. The XRD analyses confirmed the presence of sodium sulfate (Na.sub.2SO.sub.4) in the char. It is believed that the oxygen used to convert the sulfide ion into the sulfate ion was derived from oxygen contained in the wood.

(13) A second experiment was completed, in which E. grandis mixed together with Na.sub.2S was pyrolysed in a nitrogen atmosphere using microwave radiation. The oil formed was found to be immiscible with water, and was remarkably different to uncatalysed pyrolysis oil produced on the same equipment.

(14) A third experiment made use of a pyro-GC-MS apparatus to pyrolyse 3 different woody biomass feedstocks with Na.sub.2S on an alumina support, namely E. grandis, bagasse, and lignin. GC-MS analysis of the products showed a notable difference when compared to uncatalysed pyrolysis oil produced using the same method.

(15) A third experiment used Na.sub.2S mixed with E. grandis sawdust to produce pyrolysis oil via microwave pyrolysis. For comparison, untreated E. grandis was pyrolysed using the same method to obtain uncatalysed oil. The Na.sub.2S-derived pyrolysis oil formed black immiscible oil with a strong bitumen like smell, which readily separated from pyrolytic water that also formed during the process. In contrast the uncatalysed oil was fully miscible with water and smelled of burnt sugar, similar to that of pre-hydrolysate. The oil produced using Na.sub.2S had a calorific value 38.0% higher than the uncatalysed oil.

(16) Based on these experiments, it has been suggested that Na.sub.2S may be a suitable chemical for use in a dual circulating fluidized bed (DCFB) system, an example of which is described in Applicants earlier PCT patent applications discussed above.

(17) This type of system is commonly used for pyrolysis oil production. In this system the bed material is transported cyclically from the pyrolysis fluidized bed to the combustion fluidized bed and back again, taking with it any other solid materials present in the system (such as char, wood biomass or catalysts). Oxidation of Na.sub.2S to Na.sub.2SO.sub.4 would be achieved during pyrolysis. The Na.sub.2SO.sub.4 could then be transported with the bed material and char to the combustion zone. The reduction of Na.sub.2SO.sub.4 to Na.sub.2S would then take place during combustion using residual carbon as char to reform Na.sub.2S. Na.sub.2S will then be transported back to the pyrolysis zone again.

(18) As can be seen from FIGS. 8 and 9, which are compositional analyses of pyrolysis oil produced from eucalyptus, by pyrolysis both without a deoxygenating catalyst and with a Na.sub.2S catalyst on an alumina support, the amount of acetic acid produced in the metal sulfide catalyst of the invention catalysed reaction is substantially less than that of the uncatalysed comparative analysis. As discussed below, the acetic acid is an indicator of the degree of deoxygenation of the bio-oil by the catalyst.

2. Experimental Work on LDH Catalyst System

(19) Biomass was pyrolysed to pyrolysis oil using the following experimental set up and the bio-oil thus produced was analysed to determine, amongst other things, its O/C ratio, H/C ratio, Higher Heating Value (HHV) and composition (including acetic acid).

(20) Biomass Used and Sample Preparation:

(21) E. grandis was milled using a particle size reduced using cutting mill to a particle size distribution between 150 m and 250 m at a moisture content measured as 8.88%.

(22) Various oxygen scavenging catalysts were used for the experiment including MgAl LDH and CaAl LDH on alumina support at a 10% m/m loading.

(23) For comparative purposes, an experiment was also conducted using zeolite as the catalyst and an uncatalysed experiment was conducted as well.

(24) The results of these experiments are shown in FIGS. 1 to 7 below.

(25) Equipment and Methods Used:

(26) pyrolysis-GC/MS (Py-GC/MS)Shimadzu multi-functional pyrolyser EGA/PY-3030D from Frontier Labs, Japan

(27) Evolved gas analysis (EGA-MS) was used to define the thermal desorption zone using a thermal programme of 100 C. to 600 C. at 20 C./min

(28) Sample sizes were in the range of 1.10 mg0.1 mg

(29) Samples reach pyrolytic temperatures in less than 20 ms

(30) As can be seen from the figures, where no deoxygenation catalyst was used, the O/C ratio for the pyrolysis oil produced was 0.48 with the H/C ratio being 1.74 while the HHV was 23.2 MJ/kg. Where Zeolite was used at a temperature of 500 C., the O/C ratio was 0.35, the H/C ratio was 1.58 and the HHV was 26.97 MJ/kg.

(31) With the use of LDH catalysts of the invention, the picture is quite different and the results obtained for MgAl LDH are O/C ratio of 0.02, H/C ratio of 1.69 and a HHV of over 40 MJ/kg. The results for CaAl LDH although slightly lower are still superior to that of the uncatalysed or zeoilte catalysed pyrolysis of biomass to bio-oil with an O/C ratio of 0.35, an H/C ratio of 1.65 and HHV of 28.8 MJ/kg.

(32) In FIG. 10 a van Krevelen diagram sets out the above ratios and the position of the bio-oil produced using the MgAl LDH catalyst as deoxygenating catalyst.

(33) Again, the advantages of using the LDH catalyst system for deoxygenation of the pyrolysis oil is clear from FIGS. 5 to 7 and it can be seen that less acetic acid is produced when the LDH catalyst was used then when it was not used. This also indicated a reduction in the yield of the pyrolysis oil from the biomass, however, the pyrolysis oil which is yielded is of a superior quality due to its reduced oxygenate levels.

(34) GC-MS chromatograms of uncatalysed pyrolysis oil in FIGS. 5 to 7 show that acetic acid which is typically formed from acetyl groups present in hemicellulose is present in pyrolysis oil as a result and the acetic acid peak clearly visible and can be seen to be reduced where the catalyst system of the invention was used.

(35) By using LDH as a chemical looping catalyst system in pyrolysis, it always decreases the product yield by stripping oxygen from the product. The same applies to the metal sulfide system.