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.

Thank you!!

• Questions?