Effect of Torrefaction on Biomass Chemistry and Hydrocarbons Production from Fast Pyrolysis

Transcription

1 Effect of Torrefaction on Biomass Chemistry and Hydrocarbons Production from Fast Pyrolysis Sushil Adhikari, Ph.D., P.E. Biosystems Engineering Department Auburn University February 03, 2015

2 Lignocellulosic Biomass O, 43.92% N, 0.36% H, 5.96% C, 49.76% o o o o Cellulose Hemicellulose Lignin Others (extractives and ash) Photo courtesy:

3 Biomass to Biofuels Biomass Intermediates Products q Thermochemical v Pyrolysis v GasificaFon v HTL v Aqueous phase reforming q Biochemical v Hydrolysis & FermentaFon

4 Challenges with Pyrolysis Oil and Upgrading v High acidity (ph~2-3) v High viscosity and ageing v High water content (~20%) v High oxygen content (~40%) v Low heating value (~18 MJ/kg) Cataly7c cracking of bio- oil Biomass derived bio- oil compounds Hydrocarbons Schema7c representa7on of HDO process Photo Courtesy : ChemSusChem May 2008, Vol. 1(5) Carlson et al.

5 Biomass Pretreatment: Torrefaction " Thermal treatment: 200 C-300 C and 15 min-3 h " Performed under inert conditions Coarse biomass Energy needed : ~ 100 KWh/t Torrefied coarse biomass Energy needed : ~ 237 KWh/t Energy needed : ~23 KWh/t Fine biomass Fine torrefied biomass Comparison of energy required for grinding and torrefaction of biomass

6 Results: Solids & Energy Retained HHV (MJ/kg) dry basis Pine Sweetgum Untreated Coal 27.0 Source: Carter et al., Trans. Of ASABE, Vol.56 (3):

7 Untreated Elemental Analysis: Sweetgum O, 43.92% C, C, 49.76% O, 52.16% 41.86% N, 0.36% O, 33.81% H, 5.96% C, 60.61% N, 0.41% H, 5.57% O, 27.61% Coal C, 66.74% N, 0.66% H, 4.92% N, 1.89% H, 3.76% " Elemental values of treated biomass approaches those of coal with increasing treatment conditions. Source: Carter et al., Trans. Of ASABE, Vol.56 (3):

8 Proximate Analysis 100% Biomass Type: Switchgrass 80% 60% Fixed Carbon % 40% VolaFle % Ash % 20% 0% Raw 225 C 250 C 275 C Coal " Torrefaction increases the fixed carbon of biomass to values similar to coal, while maintaining lower ash content. Source: Carter et al., Trans. Of ASABE, Vol.56 (3):

9 Fast Pyrolysis of Torrefied Biomass Ø Torrefaction pretreatment is reported to improve the quality of bio-oil by Reduction in acidity and O/C ratio 1 Increase in heating value 1,2 and aromaticity 2,3 Increase in aromatic HC yield 1,3 and improvement in BTX selectivity 3,4 during catalytic pyrolysis using H + ZSM-5 Ø Changes in structure/chemistry of biomass during torrefaction can alter the reaction pathways during pyrolysis favoring the production of certain bio-oil compounds Ø Due to differences in process conditions and biomass types used in different studies, no clear conclusion can be drawn on the relationship between biomass structural changes and hydrocarbon yield 1. J. Meng, J. Park, D. Tilo[a and S. Park, Bioresource Technology, 2012, 111, A. Zheng, Z. Zhao, S. Chang, Z. Huang, F. He and H. Li, Energy & Fuels, 2012, 26, V. Srinivasan, S. Adhikari, S. A. Cha[anathan and S. Park, Energy & Fuels, 2012, 26, A. Zheng, Z. Zhao, Z. Huang, K. Zhao, G. Wei, X. Wang, F. He and H. Li, Energy & Fuels, 2014, 28,

10 Ø Overall objective Research Objectives To understand biomass torrefaction chemistry and its impact on noncatalytic and catalytic pyrolysis for hydrocarbons production Ø Specific objectives 1. Investigate the effect of torrefaction on biomass structure 2. Understand the effect of biomass structural changes on product distribution from fast pyrolysis Source: Neupane et al., Green Chemistry, DOI: /c4gc02383h

11 Results: Biomass Component Analysis Cellulose Hemicellulose Lignin Normalized wt.% Control 225 C- 15min 225 C- 30min 225 C- 45min 250 C- 15min 250 C- 30min 250 C- 45min 275 C- 15min 275 C- 30min 275 C- 45min Samples Figure: Cellulose, hemicellulose and Klason lignin: normalized wt.% in extrac7ve free and dry basis v Hemicellulose degrada7on started from sample 225 o C- 30min where it was reduced by 30% v Significant reduc7on in cellulose for samples 225 o C- 45min, 250 o C - 30 and 45min, 275 o C 15, 30 and 45min. v Ini7al reduc7on of 23% in lignin for sample 225 o C- 30min. Higher lignin% in samples 225 o C- 45min, 250 o C- 45min, 275 o C- 15, 30 and 45 min

12 Results: 13 C NMR spectra Lignin: etherified (151 ppm) Lignin methoxyl (56 ppm) Lignin: non- etherified (148 ppm) 10 # Untreated Pine Hemicellulose: Acetyl carboxyl (173 ppm) Alipha7c C (32ppm) Hemicellulose: Acetyl methyl (21ppm) Aroma7c C- C and C- H ( ppm) Cellulose: C1- C6 Hemicellulose: Xylan C1- C5 (62-105ppm) Figure: CP- MAS 13 C spectra of non- torrefied (control) sample

13 Results: 13 C NMR spectra 225 o C-15min 225 o C-30min 225 o C-45min 250 o C-15min 250 o C-30min 250 o C-45min 275 o C-15min 275 o C-30min 275 o C-45min Figure: CP- MAS 13 C spectra of torrefied samples

14 Results: 13 C NMR spectra v De-acetylation of hemicellulose started at 225 o C-15min and almost all acetyl carboxyl and acetyl methyl peaks were absent in samples treated at 275 o C-30min and 275 o C-45min v Glycosidic components decreased markedly with increase in torrefaction severity v 50% reduction in ether linkage when torrefaction severity was increased from 225 o C-15min to 225 o C-30min, and non-etherified components increased v Decrease in ether linkage of lignin was more prominent when torrefaction time was increased from 15 to 30 min in all three temperatures v Increase of aromatic and aliphatic signals at higher severity can be due to polymerization and recondensation reactions of cellulose degradation products

15 Results: XRD Table: CrI of control and torrefied samples (%) Sample CrI Control o C- 15min o C- 30min o C- 45min o C- 15min o C- 30min o C- 45min o C- 15min o C- 30min o C- 45min - Figure: XRD spectra (from bo[om to top): Control, 225 o C- 15min, 225 o C- 30min, 225 o C- 45min, 225 o C- 15min, 250 o C- 30min, 250 o C- 45min, 275 o C- 15min, 275 o C- 30min, 275 o C- 45min v CrI of sample 225 o C- 15 min was slightly higher (75.4%) than control pine (75.03%) v Further increase in torrefac7on 7me and temperature resulted in decrease in CrI 15

16 Results: Non-catalytic Pyrolysis Table: Carbon yield from non- cataly7c pyrolysis Sample Carbon yield % AromaFc (BTX) Furan Phenolic Guaiacol Ketone Total Control 0.13 c 3.07 a 0.99 b 2.34 a,b,c 0.24 a,b,c 6.78 a,b,c 225 o C- 15min 0.13 c 2.88 a 1.44 b 1.95 a,b.c 0.45 a,b 6.85 a,b,c 225 o C- 30min 0.15 c 2.36 a,b,c 2.64 a 2.43 a,b,c 0.33 a,b 7.91 a,b 225 o C- 45min 0.18 c 1.59 b,c,d 2.57 a 1.47 b.c 0.17 b,c 5.99 b,c 250 o C- 15min 0.18 c 2.73 a,b 2.67 a 2.74 a,b 0.34 a,b 8.66 a,b 250 o C- 30min 0.20 a,b,c 2.00 a,b,c,d 3.26 a 2.66 a,b,c 0.21 a,b,c 8.32 a,b 250 o C- 45min 0.20 a,b,c 1.47 c,d 3.16 a 2.03 a,b,c 0.21 a,b,c 7.08 a,b,c 275 o C- 15min 0.19 b,c 2.83 a 3.22 a 3.46 a 0.09 b,c 9.79 a 275 o C- 30min 0.32 a 1.16 d,e 3.45 a 2.25 a,b,c 0.05 c 7.24 a,b,c 275 o C- 45min 0.32 a,b 0.14 e 2.94 a 0.72 c 0.04 c 4.16 c Any two means in the same column with no le[er in common are significantly different (p<0.05) by the Tukey s HSD test v Significantly higher aroma7c HC yield for samples 275 o C- 30min compared to control and 275 o C- 45min as v Significantly higher phenolic yield for samples torrefied at 225 o C- 30min and higher 16

17 Results: Non-catalytic Pyrolysis Aromatic Selectivity 225 C 250 C 275 C Control Furan Selectivity 225 C 250 C 275 C SelecFvity % Control SelecFvity % Residence Fme (min) Residence Fme (min) Figure 24: Selec7vity of phenolic and guaiacol compounds v Aroma7c selec7vity increased dras7cally with torrefac7on residence 7me at 275 o C v Furan selec7vity decreased with torrefac7on temperature and residence 7me 17

18 Non-catalytic Pyrolysis: Biomass Structure and HC yield R² = AromaFc yield (C%) Furan Yield (C%) 2 1 R² = ,000 10,000 15, C NMR area of aromafc component in biomass Hemicellulose wt.% Figure: Aroma7c HC yield vs aroma7c components Figure: Furan yield vs hemicellulose wt.% v Aroma7c HC yield was directly propor7onal to aroma7c components in biomass v Yield of furan compounds, which are mainly derived from hemicellulose was directly propor7onal to its wt.% 18

19 Results: Non-catalytic Pyrolysis SelecFvity % Control Phenolic Selectivity 225 C 250 C 275 C SelecFvity % Control Guaiacol Selectivity 225 C 250 C 275 C Residence Fme (min) Residence Fme (min) Figure: Selec7vity of phenolic and guaiacol compounds v Phenolic selec7vity increased with increase in torrefac7on severity reaching maximum of 70% at 275 o C- 45min v Selec7vity of guaiacols can either increase - due to increase in lignin wt.%; or decrease - due to demethoxyla7on of lignin which favor produc7on of phenolics to guaiacols 19

20 Non-catalytic Pyrolysis: Biomass Structure and HC yield 4 Phenolic compounds Predicted yield (C%) R² = Actual yield (C%) Figure: Predicted phenolic yield vs actual phenolic yield v Cleavage of ether linkages and methoxyl components of lignin led to increased phenolic yield 20

21 Results: Catalytic Fast Pyrolysis Sample BTX Benzene derivafves Table: Carbon yield from CFP AromaFcs Naphthalene Anthracene, phenanthrene and fluorene Total aromafc HC Oxygenates (benzofurans and guaiacol) Phenolic Control b,c 0.13 a,b 0.08 a 225 o C- 15min a,b,c 0.16 a,b 0.17 a 225 o C- 30 min a 0.22 a 0.26 a 225 o C- 45min a,b,c 0.14 a,b 0.28 a 250 o C- 15min a 0.3 a 0.43 a 250 o C- 30min a,b 0.26 a,b 0.61 a 250 o C- 45min c 0.05 a,b 0.14 a 275 o C- 15min a,b,c 0.14 a,b 0.3 a 275 o C- 30min c,d 0.05 a,b 0.21 a 275 o C- 45min d 0.00 b 0.04 a Any two means in the same column with no le[er in common are significantly different (p<0.05) by the Tukey s HSD test v Samples torrefied at 225 o C- 30min and 250 o C- 15min yielded approx. 38% aroma7c HC 1.6 7mes higher than control pine v Carbon yield from oxygenates (benzofuran, guaiacols and phenolics) was very less and varied from 0.02% (in 275 o C- 45min) to 0.8% (in 225 o C- 30min) 21

22 Catalytic Pyrolysis: Biomass Structure and HC Yield Ø Significantly high aromatic yield from 225 o C-30min and 250 o C-15min can be attributed to: Higher wt.% of cellulose in the sample (14% higher than control) In presence of zeolite catalyst, furan and other small oxygenates from decomposition of cellulose undergo dehydration, decarboxylation and decarbonylation reactions to form aromatic HC. Previous studies have also confirmed that among three biomass components, cellulose yields the highest aromatic compounds from CFP 1, 2 Changes in lignin structure Increased production of phenolic compounds due to de-etherification and demethoxylation of lignin, which in presence of catalyst undergo dehydration reaction to form aromatic HC 1. A. Zheng, Z. Zhao, S. Chang, Z. Huang, H. Wu, X. Wang, F. He and H. Li, Journal of Molecular Catalysis A: Chemical, 2014, , K. Wang, K. H. Kim and R. C. Brown, Green Chemistry, 2014, 16,

23 Catalytic Pyrolysis: Biomass Structure and HC yield AromaFc HC yield (C%) a) Cellulose wt.% R² = AromaFc HC yield (C%) b) AromaFc components R² = Cellulose wt.% CNMR area of aromafc components/105 Figure: Aroma7c HC yield vs a) cellulose wt.% and b)aroma7c components v v Wt.% of cellulose in biomass is directly proportional to aromatic HC yield Aromatic components in biomass was inversely related to aromatic HC yield from CFP, implying that secondary pyrolysis of cellulose degradation products do not favor aromatic production during CFP 23

24 Overall Carbon Yield Ø Overall carbon yield accounting for mass loss of carbon during torrefaction was calculated using equation: Sample Table: Overall carbon yield accoun7ng for mass loss of carbon AromaFc yield Non- catalyfc pyrolysis (C%) Phenolic yield Total carbon yield CatalyFc pyrolysis (C%) Total carbon AromaFc yield yield Control 0.13 b 0.99 c 6.78 a,b c,d,e b,c,d 225 o C- 15min 0.13 b 1.41 b,c 6.71 a,b a,b,c,d a,b,c 225 o C- 30min 0.14 a,b 2.45 a 7.36 a,b a,b a 225 o C- 45min 0.16 a,b 2.29 a,b 5.33 a,b b,c,d,e a,b,c,d 250 o C- 15min 0.17 a,b 2.59 a 8.38 a a a 250 o C- 30min 0.16 a,b 2.54 a 6.50 a,b a,b,c a,b 250 o C- 45min 0.15 a,b 2.43 a 5.44 a,b,c d,e,f c,d,e 275 o C- 15min 0.16 a,b 2.72 a 8.25 a,b a,b,c,d,e a,b,c,d 275 o C- 30min 0.24 a 2.58 a 5.41 a,b,c e,f d,e 275 o C- 45min 0.21 b 1.94 a,b 2.76 c 5.47 f 5.50 e 24

25 Conclusions Ø Changes in biomass composition and structure due to torrefaction was studied using component analysis, 13 C NMR and XRD spectra. Non-catalytic and H + ZSM-5 catalyzed fast pyrolysis experiments were carried out using py-gc/ MS to study the product distribution from biomass torrefied at different severity Ø Non-catalytic pyrolysis of torrefied biomass favored the production of phenolic and aromatic compounds while decreased the furan compounds. This can be used to control the end product distribution in the bio-oil Ø For CFP, torrefaction can be an important pretreatment step to increase the aromatic HC yield. However, torrefaction parameters i.e. temperature and time should be properly adjusted. The results from this study can be useful in determining the optimum torrefaction condition to be used to maximize aromatic hydrocarbon yield from CFP 25

26 Acknowledgements Ø Funding Agency: National Science Foundation (NSF-CBET ) Ø Sneha Neupane, M.S. Student Ø Prof. Arthur J. Ragauskas, Georgia Institute of Technology (currently at University of Tennessee Knoxville) for carrying out NMR experiments Ø Southeastern Sun Grant Center Ø Torrefaction and pyrolysis of torrefied biomass BIOSYSTEMS ENGINEERING 26