06.07.2017 / D3_1_PHYSICO_CHEMICAL_PROPERTIES_OF_FPBO_2.2_VTT_20170706 1/14 Project title: Renewable residential heating with fast pyrolysis bio-oil Grant Agreement: 654650 Start of the project: 01.01.2016 (48 months) Deliverable number: D3.1 Deliverable title: Physico-chemical properties of FPBO Work package: WP3 Delivery due date: 31/03/2016 Actual submission date: 06/07/2017 Responsible organisation: VTT Authors: Anja Oasmaa Version: 2 Revision: 2 (06/07/2017) Dissemination (Please cross-tick the correct type and level) Type: R R - Report DEM - Demonstrator, pilot, prototype DEC - Websites, patent fillings, videos etc. Level: PU PU - Public CO - Confidential, only for members of the Consortium*) Cl - Classified*) DISCLAIMER This document contains information which is the proprietary to the Residue2Heat Consortium. Neither this document nor the information contained herein shall be used, duplicated or communicated by any means to any third party, in whole or in parts, except with prior written consent of the Residue2Heat Coordinator. Contents of this document are not intended to replace consultation of any applicable legal sources or the necessary advice of a legal expert, where appropriate. All information in this document is provided "as is" and no guarantee or warranty is given that the information is fit for any particular purpose. The user, therefore, uses the information at its sole risk and liability. For the avoidance of all doubts, the European Commission has no liability in respect of this document, which is merely representing the authors' view. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 654650
Project title: Renewable residential heating with fast pyrolysis bio-oil
Grant Agreement: 654650
Start of the project: 01.01.2016 (48 months)
Deliverable number: D3.1
Deliverable title: Physico-chemical properties of FPBO
Work package: WP3
Delivery due date: 31/03/2016
Actual submission date: 06/07/2017
Responsible organisation: VTT
Authors: Anja Oasmaa
Version: 2
Revision: 2 (06/07/2017)
Dissemination (Please cross-tick the correct type and level)
Type: R R - Report
DEM - Demonstrator, pilot, prototype
DEC - Websites, patent fillings, videos etc.
Level: PU PU - Public
CO - Confidential, only for members of the Consortium*)
Cl - Classified*)
DISCLAIMER
This document contains information which is the proprietary to the Residue2Heat Consortium. Neither this document nor the information contained herein shall be used, duplicated or communicated by any means to any third party, in whole or in parts, except with prior written consent of the Residue2Heat Coordinator. Contents of this document are not intended to replace consultation of any applicable legal sources or the necessary advice of a legal expert, where appropriate. All information in this document is provided "as is" and no guarantee or warranty is given that the information is fit for any particular purpose. The user, therefore, uses the information at its sole risk and liability. For the avoidance of all doubts, the European Commission has no liability in respect of this document, which is merely representing the authors' view.
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 654650
Executive summary This deliverable is the first one in a series of deliverables describing the physico-chemical properties of fast pyrolysis bio-oil (FPBO) produced in the project. The first bio-oil batch (D2.2) was provided by BTG and the feedstock was pine. This pine bio-oil (R2H.BTG.2016.001b, as defined in D2.2) will be used as a reference during the project.
Numerous FPBO samples will be sent around between the partners over the course of the four-year Residue2Heat project. Sample delivery is a joint task, partners VTT and BTG will supply the consortium with conditioned FPBO samples. The sample delivery will be described throughout the project in seven deliverables (D2.2 – D2.8) and is connected to Task 2.1. To have a full overview, each deliverable report will be an updated version of the previous one, rather than a new report describing only the delivery in the relevant reporting period. A detailed analysis on the production of FPBO from different biomass and processing conditions will be documented in D2.1 (due in M26). Details on the analysis results of the various samples send to the project partners will be performed in T3.1 and its related deliverables (D3.1-D3.8) which will provide feedback for WP2, and will be employed in WP4 and WP5 in modelling and utilization.
Both D2.2 and D3.1 are primarily used for Residue2Heat internal documentation although they are marked as public. For the project partners it was essential to receive a documented fast pyrolysis bio-oil sample as soon as possible. The follow up deliverables will include more details and analysis concerning benchmarking of processes, comparison of data between VTT and BTG, the performance of measures to lower the water content (related to T2.1) and improve the phase stability.
Table of Contents .............................................................................................................................................. 3
1 Introduction Fast pyrolysis bio-oils are completely different than mineral oils or other bio-oils in the market. They are highly polar liquids containing hundreds of various compounds (Table 1). Major part of FPBO is water-soluble. The chemical composition of FPBO determines its physical properties and behaviour. FPBOs are not as stable as light and heavy fuels. The instability is observed as an increase in viscosity and is caused by various polymerisation and condensation reactions taking place in the liquid during storage and especially when heated. This phenomena is called as aging. The high amount of oxygen-containing reactive functional groups present in almost each compound in the bio-oil is the main reason for the instability of FPBOs. Acids present provide a catalytic environment for the aging reactions. The aging of FPBOs from woody biomass is an exothermic process with notable heat generation under adiabatic conditions.9 Aging reactions may finally lead to so called phase-separation8 where the lignin-derived fraction of FPBO separates out from the aqueous phase containing most of the water-soluble compounds. This phenomena typically requires more than one year of aging at room temperature or several weeks at higher temperatures. A high ash content of agrobiomass leads to bio-oils with a higher water content and lower oil yield. Figure 1 shows the effect of the feedstock ash content on the yield of organics and phase separation tendency of FPBOs.
Table 1: Chemical Composition of a Fresh Pine1 and Forest Residue FPBOs Produced at VTT’s 20 kg/h Unit.8
Quantitative gas chromatography−mass spectrometry (GC−MS) analyses were made at Thunen Insitute (TI, Germany). WIS = LMM +
HMM + extractives. Extractives contains triglycerides, resin and fatty acids, fatty alcohols, and sterols.
Figure 1: Effect of feedstock ash on phase separation tendency of fresh bio-oil. The curve is based on numerous experimental
data points with wood and agrobiomass obtained by VTT’s 20 kg/h pyrolyzer.8
Table 2 presents typical properties for FPBOs and applicable test methods. More background information on production and general properties of fast pyrolysis bio-oil (FPBO) it has been developed under Task 3.2 in
WP 3, and also covered relevant open-access publications.1,2 This draft report has been delivered to partners in February 2016. It has been developed under Task 3.2 in WP3, and also covered in relevant open-access publications.
Table 2: Typical properties of FPBO7
Property Unit Typical range Applicable test methods
HHV MJ/kg 14 - 19 DIN51900, ASTM D240
LHV MJ/kg 13 - 18 DIN51900, ASTM D5291 for H
Water wt% 20 - 30 ASTM E203
pH - 2 - 3 ASTM E70
TAN mg KOH/g 70 - 100 ASTM D664, ASTM D3339
Kinematic viscosity at 40 °C mm2/s 15 - 40 EN ISO 3104, ASTM D445
Density at 15 °C kg/dm3 1.11 – 1.30 EN ISO 12185, ASTM D4052
Pour point °C -9 -
-36 EN ISO 3016, ASTM D97
Carbon wt% on d.b. 50 - 60 ASTM D5291
Hydrogen wt% on d.b. 7 - 8 ASTM D5291
Nitrogen wt% on d.b. < 0.5 ASTM D5291
Sulfur wt% on d.b. < 0.05 EN ISO 20846, ASTM D 5453-09
Oxygen wt% on d.b. 35 - 40 as difference
Solids wt% < 1 ASTM D7579
MCR, CCR wt% 17 - 23 ASTM D4530, ASTM D189
Ash wt% < 0.3 EN ISO 6245
Flash point °C 40 - 110 EN ISO 2719, ASTM D93B
Sustained combustibility - does not sustain EN ISO 9038, UN Guidance on TDG
Na, K, Ca, Mg wt% on d.b. < 0.06 AAS, ICP, ICP-AES, ICP-OES, NA
2 Experimental Samples: A 28 liter batch of pine fast pyrolysis bio-oil (R2H.BTG.2016.001b, VTT’s identification number 16.98.1) was obtained from BTG on 2nd March 2016 (D2.1). The bio-oil batch was divided into smaller samples, and stored in a freezer at – 16 °C.
Analytical methods: Bio-oil was analysed for fuel oil properties and chemical composition. Main analytical methods are described here and other methods can be found in open-access publications.1,2
Ash: Present ash standard EN ISO 6245 is time-consuming and needs large sample volumes. A faster method for smaller sample sizes was developed at VTT. Micro Carbon Residue (MCR) from bio-oil sample continued with ashing of the residue was carried out according to ASTM D4530. In the method the sample (1 g) is weighed in a quartz sample tube, sample is heated to 500 °C under inert atmosphere (N2), kept at 500 °C for 15 minutes, and cooled. The tube with carbon residue is transferred into a muffle furnace at 775 °C until no weight loss takes place. Comparison with ashing standard EN7 was made. Reproducible results using various samples (bottom, top phases and whole oil of forest residue fast pyrolysis oil) on ash content of 0.04 – 0.55 wt% were obtained (Table 3).
Table 3: Determination of ash content (wt% of liquid) and reproducibility (VTT results from a national project).
Sample Method Amount Number of Average Min Max Stdev g duplicates wt% wt% wt%
PDU*11/12 bottom MCR + oven 775 °C 1 12 0.038 0.02 0.05 0.011 EN ISO 6245 100 2 0.043
PDU11/12 top MCR + oven 775 °C 1 22 0.54 0.46 0.59 0.03 EN ISO 6245 100 2 0.547
PDU5/07 whole oil MCR + oven 775 °C 1 2 0.12 0.12 0.13 EN ISO 6245 30 3 0.11 0.11 0.11
* VTT FPBOs from experiments PDU11/12 and PDU5/07. Top = extractive-rich top phase, Bottom = Whole –Top, MCR = Micro
Carbon Residue
Acidity: Acid numbers are determined as the consumed amount of potassium hydroxide (mg KOH / g bio-oil) in acid-base titration. The difference of the various numbers is the end point of titration or the amount of sample. The end point is the electrochemical potential that corresponds to pH value 4 or 11 buffer solutions or more commonly an equivalence point that is detected in those potential regions.
Detection of the equivalence points of titration is sometimes difficult. FPBOs contain various acids with different pKa values, which give smooth titration curves instead of clear sharp ones. Compared to the standard method ASTM D664 novel base – solvent combinations have been published which make detection of equivalence point easier and more reproducible, and determination of both CAN (Carboxylic Acid Number) and PN (Phenolic Number) possible (Table 4). Based on the available results, method B10-11 is the best choice for determination of both CAN and PN of bio-oils. Figure 2 shows the titration curve for a fast pyrolysis bio-oil (VTT FPBO PDU35/06 pine). Areas and pH ranges for CAN, and PN, are marked to the Figure. In addition, the value for TAN (Total Acid Number) according to the standard ASTM D664 is indicated. It is seen that the titration end-point in the standard should be changed to include also FPBO containing also acidic phenolic groups (PN). For FPBO the TAN indicated in the standard is CAN and the real TAN is CAN + PN. Several laboratories are already reporting the TAN as CAN + PN. Discussions on changing the standard are going on under on-going standardisation work in CEN TC19/WG41.
Table 4: Base-solvent combinations for determination of acid numbers of bio-oil.
Method Base Solvent Publisher
Method A potassiumhydroxide toluene-isopropanol-water ASTM D664 Method B tetrabutylammoniumhydroxide isopropanol NREL-PNNL 2011 Method C tetramethylammoniumhydroxide tert-butanol-acetone CUT-WSU 2014 Method D potassiumhydroxide isopropanol -
NREL = National Renewable Energy Laboratory, PNNL = Pacific Northwest National Laboratory,
CUT = Curtin University of Technology, WSU = Washington State University
Figure 2: Titration curve of pine bio-oil. TAN, CAN, PN and ASTM TAN areas and pH values of equivalence points are shown in
Figure.
Stability: There is no standardized method for measuring the stability of bio-oil. The main changes in aging, increase in viscosity, in amount of water-insolubles (WIS), and in average molecular weight (Mw), and in reduction in carbonyl compounds can be used as stability indicators. The viscosity increase-based stability test (80 °C for 24 h) is typically used. The viscosity increase in the test at 80 °C for 24 hours correlates approximately to one year’s storage at room temperature. Several round robins3-5 have been carried out to validate the viscosity increase based stability test (24 h at 80 °C). The stability of FPBO correlates with the total content of “diluents” like water (Figure 9).
Homogeneity: A homogeneous fresh FPBO consists typically of 55 wt% polar compounds (water and “sugars”), 20 wt% WIS compounds (lignin-derived material, extractives, and solids), and 25 wt% “co-solvent” compounds (light aliphatic and aromatic acids, aldehydes, ketones, alcohols, and mono phenols). An increase in the relative amount of the polar fraction above 60 wt% or a WIS fraction above 35 wt% (increase in polymerization products) or a decrease in the amount of co-solvents to below 15 wt% (reactions of carbonyl compounds leading to WIS material) may lead to phase separation. An oversized polar fraction may result from moist feedstock or high ash content of feedstock that decreases the organic yield and increases the amount of pyrolysis water.8 Preliminary specification for FPBO homogeneity are visual/microscopic homogeneity1 and the ratio of (polar compounds) : WIS : ”co-solvents” is (55 - 60) : (20 - 35) : (15 - 25).
Chemical composition based on solvent fractionation:1 In the method, bio-oil is divided into a water-soluble (WS) and water-insoluble (WIS) fractions by water extraction. The water-insoluble fraction can further extracted with dichloromethane to obtain low molecular mass lignin (LMM, Dichloromethane-solubles) and high molecular mass lignin (HMM, DCM-insolubles). The “sugars” are obtained from the WS fraction, with extraction of diethyl ether as an ether-insoluble (EIS) fraction. The water content is analysed with Karl Fischer titration according to ASTM E203. Water-soluble compounds: The water-soluble fraction was also analysed with gas chromatography. An Agilent Technologies 7890 A gas chromatography equipped
with an Agilent 19091 N-136 HP-Innowax column was used. The length of the column was 60 m, inner diameter was 250 μm, and thickness of the liquid phase 0.25 μm. Helium was used as carrier gas. A flame ionization detector was used at a temperature of 280 °C. The column oven was first heated to 60 °C using a temperature ramp of 3 °C/min and then 230 °C for 30 min. Calibration was carried out using 40 water-soluble model compounds, and n-butanol was used as the internal standard.
3 Results and Discussion Fuel oil properties of BTG pine FPBO (R2H.BTG.2016.001b) are presented in Table 5. The viscosity curve as a function of temperature is seen in the Figure 4. The titration curve for total acid number (TAN) is shown in Figure 3. The TAN value according to the standard ASTM 664 is the same than the CAN value in the Figure 3. As mentioned earlier the present standard ASTM D664 should be change to include also FPBO.
The microscopic image of the bio-oil is seen in Figure 5. The chemical composition based on solvent fractionation scheme is seen in Figure 6 and the water-soluble compounds in the Table 6. As a reference a good quality VTT pine FPBO used as a reference bio-oil in EU BIOCOUP project (Contract Number: 518312) is included in Figure 6. The ratio of “polar compounds” : WIS : ”co-solvents” is 55.5 (55 - 60) : 26.2 (20 - 35) : 18.3 (15 - 25). The allowed variation range is shown in parentheses. The removal of some water after bio-oil condensation as described in D2.2 has lowered slightly the relative amount of “co-solvents” and increased the relative amount of WIS in BTG bio-oil.
Figure 3: TAN curve for pine FPBO (R2H.BTG.2016.001b).
Figure 9: Stability (viscosity change at 80 °C over 24 h) of VTT PDU (20 kg/h) pyrolysis liquids from various softwoods (pine,
spruce, forest residues) as a function of water.6
4 Conclusion When compared the BTG pine FPBO (R2H.BTG.2016.001b) with other FPBOs (Figures 7 - 9) and based on the visual and microscopic observations (Figure 5) as well as the chemical composition it can be concluded that BTG pine FPBO is a typical good quality pine bio-oil.
Bibliography 1. Oasmaa, A.; Peacocke, C. A Guide to Physical Property Characterisation of Biomass-Derived Fast
2. Lehto, Jani, Oasmaa, Anja, Solantausta, Yrjö, Kytö, Matti, Chiaramonti, David. 2013. Fuel oil quality and combustion of fast pyrolysis bio-oils. VTT Technology: 87, Espoo, VTT, 79 p. ISBN 978-951-38-7929-7 (Soft back ed.), 978-951-38-7930-3. http://www.vtt.fi/inf/pdf/technology/2013/T87.pdf
3. Oasmaa, Anja, Meier, Dietrich. 2005. Norms and standards for fast pyrolysis liquids 1. Round robin test. Journal of Analytical and Applied Pyrolysis, Vol. 73, No. 2, pp. 323 - 334
4. Elliott, D.C., Oasmaa, Anja, Meier, D., Preto, F, Bridgewater, A.V.. 2012. Results of the IEA round robin on viscosity and aging of fast pyrolysis bio-oils: Long-term tests and repeatability. Energy and Fuels, Vol. 26, No. 12, pp. 7362 – 7366
5. Elliott, D.C., Oasmaa, Anja, Preto, F., Meier, D., Bridgwater, A.V.. 2012. Results of the IEA round robin on viscosity and aging of fast pyrolysis bio-oils. Energy and Fuels, Vol. 26, No. 6, pp. 3769 – 3776
6. Oasmaa, Anja, Korhonen, Jaana, Kuoppala, Eeva. 2011. An approach for stability measurement of wood-based fast pyrolysis bio-oils: ACS Publications. Energy and Fuels, Vol. 25, No. 7, pp. 3307-3313
7. Oasmaa, A., Van De Beld, B., Saari, P., Elliott, D.C., Solantausta, Y.. 2015. Norms, standards, and legislation for fast pyrolysis bio-oils from lignocellulosic biomass: American Chemical Society. Energy and Fuels, Vol. 29, No. 4, pp. 2471-2484
8. Oasmaa, Anja, Sundqvist, Tom, Kuoppala, Eeva, Garcia-Perez, Manuel, Solantausta, Yrjö, Lindfors, Christian, Paasikallio, Ville. 2015. Controlling the phase stability of biomass fast pyrolysis bio-oils: American Chemical Society. Energy and Fuels, Vol. 29, No. 7, pp. 4373-4381
9. Sundqvist, Tom, Solantausta, Yrjö, Oasmaa, Anja, Kokko, Lauri, Paasikallio, Ville. 2016. Heat generation during the aging of wood-derived fast-pyrolysis bio-oils: ACS Publications. Energy and Fuels, Vol. 30, No. 1, pp. 465-472
10. Christensen E, Ferrell J, Olarte MV, Padmaperuma AB and Lemmon T, Acid number determination of pyrolysis bio-oils using potentiometric titration. Technical Report No.: NREL/TP-5100-65890, NREL, Golden, CO, USA (2016).
11. Christensen ED, Chupka GM, Luecke J, Smurthwaite T, Alleman TL, Iisa K et al., Analysis of oxygenated compounds in hydrotreated biomass fast pyrolysis oil distillate fractions. Energy Fuel 25:5462–5471 (2011).
