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Physicochemical properties of biomass
catalytic pyrolysis oils: A 13C NMR
spectroscopic investigation of the effects
of functional groups on oil properties.
Ofei D. Mante* and FA Agblevor
Biological Engineering, Utah State University, Logan UT;
*RTI International, Research Triangle, NC
Introduction
The production of infrastructure-ready biocrude oil from catalytic pyrolysis
offers an opportunity to co-process biomass derived intermediates alongside
petroleum feedstock.
One of the critical success factors for commercial scale biocrude co-
processing is the physicochemical properties of the upgraded bio-oil.
Fuel properties such as specific gravity, viscosity, acidity, storage stability,
carbon residue, and etc., are of interest to a Refiner.
The bulk oxygen content of the biocrude do not reflect the fuel properties and
may not per se be the yardstick in determining the suitability of upgraded
pyrolysis as a supplemental feedstock in a conventional petroleum refinery.
The chemical components responsible for the physical properties of biocrude
is still not well understood.
Objectives
• Develop advanced characterization methods to
understand the effect of functional groups on the physico-
chemical properties of catalytic pyrolysis oils(CPO).
• Develop catalysts that can completely eliminate the
functional groups that have adverse effect on the fuel
property of CPOs.
Materials and Methods
• Materials
• Corn stover, switchgrass, pinyon juniper, poplar, pine
wood and pine bark
• Catalysts: HZSM-5 (Clariant Inc)
• Methods
• Pilot scale bubbling fluidized bed catalytic pyrolysis
reactor
• Reactor capacity: 2 kg/h
Temperature = 475 oC, Fluidizing gas flow rate = (N2= 0.4 SCFM, NCG=2.0 SCFM)
Biomass feed rate = 1kg/h, Catalyst loading = 1 kg, Run time = 3 h
Pyrolysis System
Product Analysis
• Gas chromatography
• H2, CH4, CO, CO2 and C2-C5 hydrocarbons. (Varian 490 micro GC)
• Elemental analysis
• C, H, N, S and O (ThermoFisher Scientific organic elemental analyzer)
• Physical properties:
• Acidity, Viscosity, Density, Storage Stability, TGA residue, HHV, and Moisture
• 13C-NMR
• Solvent = dimethyl sulfoxide-d6, Number of scans = 3000, Temperature = 35 oC. (Varian 400 MHz, JOEL 300 MHz Spectrometer)
Elemental
Composition
(wt.%)d.b
Biomass Feedstock
Poplar Pine Pinyon-
Juniper
Switchgrass Corn
Stover
Pine
Bark
C 50.31 52.11 51.59 48.07 46.49 53.41
H 6.02 5.03 5.33 5.028 5.30 4.88
N 0.02 0.07 0.34 0.65 0.43 0.22
O* 43.18 42.36 42.34 40.93 38.81 40.47
Ash 0.46 0.43 0.40 5.32 8.97 1.02
Results: Elemental and ash analysis of the various
biomass feedstocks
([d.b]-dry basis, *by difference)
Pyrolysis Product
Yields (wt %)
Hybrid
PoplarPine
Pinyon-
JuniperSwitchgrass
Corn
Stover
Pine
bark
Total liquid
product
41.1±4.2 42.5±2.5 39.2±0.3 40.3±4.2 36.8± 34.8±
WESP Fraction8.4±2.8 9.3±1.5 10.2±1.1 10.0±2.6 5.3 6.4
Condenser
Fraction
32.7±1.4 32.2±4.0 29.2±1.1 30.2±1.6 31.5 37.6
Char/coke17.0±1.6 17.5±3.6 22.8±0.5 25.0±0.8 26.45 33.4
Gases
(by difference)
41.9±5.7 40.0±1.1 38.0±0.6 34.7±5.0 36.8 31.8
Results: Product Yields (wt% on biomass) from the
pilot-scale catalytic pyrolysis with ZSM-5 zeolite
Physical propertiesPine Hybrid
poplar
Corn
Stover
Switchgrass Pinyon
juniper
Pine
Bark
pH 3.71 3.66 4.58 4.99 4.51 4.03
Density (g/cm3) 1.10 1.12 1.08 1.10 1.06 1.14
Estimated gravity, oAPI -2.9 -5.2 -0.5 -2.9 2.0 -7.4
Kinematic Viscosity (at 40 oC, cSt) 30.0 43.3 23.7 87.5 15.3 90.9
Dynamic Viscosity (at 40 oC, cP) 33.2 48.6 25.6 95.9 16.2 103.5
Long term storage Stability
(Viscosity after 18 months of
storage, at 40 oC, cSt)
206.3 217.5 140.9 536.1 41.0 247.6
Average rate of viscosity change,
(cSt/day)0.43 0.46 0.31 1.18 0.07 0.41
TGA residue at 550 oC, wt.% 13.02 15.63 9.99 14.61 8.06 13.79
Results: Physical properties of CPOs
Results :13C-NMR Analysis
13C-NMR spectrum of biocrude oil produced from pinyon juniper
O-CH3
C-OH, C-OR
Aromatic C-O
Aromatic C-C
COOH, COOR, CONR2
COR & COH
Aliphatic
hydrocarbons
DMSO-d6
solvent
Aromatic C-H
Type of carbon Chemical
Shift, δ
(ppm)
Biocrude oils
Pine PoplarCorn
StoverSwitchgrass
Pinyon
Juniper
Pine
Bark
Aliphatic C-C 55-0 16.49 17.32 17.52 25.17 22.82 16.66
Methoxy C (-OCH3) 57-55 1.17 4.62 1.05 1.89 1.10 1.47
Aliphatic C-O (including
levoglucosan)103-60 3.57 6.20 1.25 2.53 1.28 7.95
Aromatic C-H 125-105 27.36 21.83 28.59 29.01 21.17 29.56
Aromatic C-C (carbons in
aromatic hydrocarbons
further from an O atom)
140-125 40.63 37.82 41.44 28.06 42.96 31.59
Aromatic C-O 160-140 10.11 10.62 8.67 10.88 9.97 12.07
Carbonyl (carboxylic acids
and derivatives)180-160 0.18 0.64 0.89 1.60 0.38 0.19
Carbonyl (aldehydes,
ketones)220-180 0.49 0.96 0.59 0.86 0.33 0.51
Results : 13C-NMR of CPOs (percentage total carbon)
Effect of Aromatic Hydrocarbon and Phenolics on Viscosity
Aromatic hydrocarbons decreases viscosity Phenolic compounds appear to increase viscosity
Effect of Sugars and Hydrocarbons on Density
Anhydrosugars increases the density Hydrocarbons decreases the density
Effect of Carbonyls and Hydrocarbons on Storage Instability
Carbonyl species appear to increase instability Aromatic hydrocarbons appear to decrease instability
Effect of Elemental Composition on Carbon Residue and Acidity
High carbon content results in less formation of residue Relatively high nitrogen contents reduces the acidity
Property
Carbons types determined by 13CNMR Elemental
Total C-C
carbons
Phenolic
Carbons
Levogluco
Carbons
Phenolic/
levoglucoCarbonyls
Oxyge
nates
Aroma
C-C
Aroma
C-OC N
pH 0.20 0.05 -0.64 -0.27 0.56 -0.20 -0.31 -0.22 0.70 0.90
Density (g/cm3) -0.93 0.76 0.94 0.95 0.02 0.94 -0.62 0.77 -0.87 -0.20
Gravity, oAPI 0.94 -0.76 -0.94 -0.95 -0.04 -0.94 0.63 -0.76 0.88 0.19
Kinematic
Viscosity (at 40
oC, cSt)
-0.88 0.86 0.59 0.85 0.38 0.88 -0.98 0.82 -0.47 0.43
Storage Stability-
Rate of change in
viscosity
(cSt/day)
-0.54 0.64 0.05 0.45 0.82 0.54 -0.83 0.33 -0.34 0.74
TGA residue at
550 oC, wt.%-0.81 0.66 0.70 0.77 0.43 0.81 -0.68 0.61 -0.91 0.04
Pearson Correlation Coefficients(Values in bold are different from 0 with a significance level alpha=0.05)
Summary
Conclusions
• Catalytic pyrolysis with product gas recycle was conducted on six different biomass feedstocks using HZSM-5 catalyst in a 2 kg/h fluidized bed reactor.
• Partially deoxygenated biocrudes oils with improved fuel properties was achieved with zeolite based-catalysts.
• 13C-NMR analysis revealed that the physicochemical property of the biocrudes is dependent on functional groups present.
• The aromatic carbon content of the the biocrude oils showed negative linear correlation with the viscosity of the oils. Phenolic carbons had a positive linear relationship with viscosity.
• Anhydrosugars and phenolics had a positive linear correlation with density, but the aromatic carbons decreases the density.
• Carbonyl species appear to have a positive linear effect on the storage stability of the oils; thus increases the rate of viscosity change.
• Bio-crude carbon content had a negative linear correlation with the formation of residue.
• Nitrogen content also showed a positive linear correlation with the pH of the oils and so could have a positive influence on corrosion of the oils.
Acknowledgements
• The authors acknowledge DOE BETO Program and the
USTAR Program for financial support.