Torrefaction reduction of coke formation on catalysts used in esterification and cracking of biofuels from pyrolysed lignocellulosic feedstocks
A bio-oil production process involving torrefaction pretreatment, catalytic esterification, pyrolysis, and secondary catalytic processing significantly reduces yields of reactor char, catalyst coke, and catalyst tar relative to the best-case conditions using non-torrefied feedstock. The reduction in coke as a result of torrefaction was 28.5% relative to the respective control for slow pyrolysis bio-oil upgrading. In fast pyrolysis bio-oil processing, the greatest reduction in coke was 34.9%. Torrefaction at 275° C. reduced levels of acid products including acetic acid and formic acid in the bio-oil, which reduced catalyst coking and increased catalyst effectiveness and aromatic hydrocarbon yields in the upgraded oils. The process of bio-oil generation further comprises a catalytic esterification of acids and aldehydes to generate such as ethyl levulinate from lignified biomass feedstock.
1. A method for reducing coke deposition on a catalyst used in cracking of a pyrolysis oil vapor, the method comprising:
(a) subjecting a biomass to torrefaction;
(b) pyrolyzing the torrefaction-treated biomass, thereby generating a heated pyrolysis oil vapor;
(c) catalytically esterifying the heated pyrolysis oil vapor or components thereof, thereby providing a heated pyrolysis oil vapor having a reduced acid and aldehyde content compared to a heated pyrolysis oil vapor not catalytically esterified; and
(d) cracking the catalytically esterified heated pyrolysis oil vapor, thereby generating a bio-oil, wherein said cracking step comprises contacting the heated pyrolysis oil vapor with a second catalyst, and wherein said catalyst accumulates a reduced coke deposition compared to when the heated pyrolysis oil vapor is generated from a biomass not treated with torrefaction.
2. The method of claim 1 , wherein in step (c) the heated pyrolysis oil vapor is contacted with an aqueous composition comprising at least one alcohol and a first catalyst selected to catalyze the esterification of at least one component of the heated pyrolysis oil vapor.
3. The method of claim 2 , wherein the at least one alcohol is a primary alcohol.
4. The method of claim 2 , wherein the at least one alcohol is methanol, ethanol, or a combination thereof.
5. The method of claim 1 , wherein the biomass comprises lignocellulose.
6. The method of claim 1 , wherein the first catalyst, the second catalyst, or the first and the second catalysts is a solid acid catalyst.
7. The method of claim 6 , wherein the catalyst is a zeolite-based catalyst.
8. The process according to claim 1 , wherein step (a) comprises heating the biomass at a temperature of between about 100° C. to about 300° C. in an inert gas.
9. The process according to claim 1 , wherein the pyrolysis of step (b) is fast pyrolysis.
10. The process according to claim 1 , wherein step (b) further comprises fractionating the heated pyrolysis oil vapor into an aqueous phase and a non-aqueous phase by condensing the heated pyrolysis oil vapor and providing the non-aqueous phase for the cracking step (c).
11. A method of generating a bio-oil from a biomass, the method comprising:
(a) subjecting a biomass to torrefaction, wherein the torrefaction comprises heating the biomass at a temperature of between about 100° C. to about 300° C. in an inert gas;
(b) pyrolyzing the torrefaction-treated biomass by fast pyrolysis, thereby generating a heated pyrolysis oil vapor;
(c) catalytically esterifying the heated pyrolysis oil vapor or components thereof, thereby providing a heated pyrolysis oil vapor having a reduced acid and aldehyde content compared to a heated pyrolysis oil vapor not catalytically esterified, wherein the heated pyrolysis oil vapor from step (b) is contacted with an aqueous composition comprising at least one alcohol and a first catalyst selected to catalyze the esterification of at least one component of the heated pyrolysis oil vapor; and
(d) cracking the catalytically esterified heated pyrolysis oil vapor, thereby generating a bio-oil, wherein said cracking step comprises contacting the heated pyrolysis oil vapor with a second catalyst, and wherein said catalyst accumulates a reduced coke deposition compared to when the heated pyrolysis oil vapor is generated from a biomass not treated with torrefaction.
12. The method of claim 11 , wherein the at least one alcohol is a primary alcohol.
13. The method of claim 12 , wherein the at least one alcohol is methanol, ethanol, or a combination thereof.
14. The method of claim 11 , wherein the biomass comprises lignocellulose.
15. The method of claim 11 , wherein the first catalyst, the second catalyst, or the first and the second catalysts is a solid acid catalyst.
16. The method of claim 3 , wherein the first catalyst, the second catalyst, or the first and the second catalysts is a zeolite-based catalyst.
17. The method according to claim 11 , wherein step (c) further comprises fractionating the heated pyrolysis oil vapor into an aqueous phase and a non-aqueous phase by condensing the heated pyrolysis oil vapor and providing the non-aqueous phase for the cracking step (d).
18. The method of claim 11 , wherein the product of the catalytic esterification comprises an ester selected from the group consisting of: ethyl acetate, ethyl formate, and ethyl levulinate.