Preparation and Fuel Properties of Field Pennycress (Thlaspi

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Preparation and Fuel Properties of Field Pennycress (Thlaspi arvense) Seed Oil Ethyl Esters and Blends with Ultra-Low Sulfur Diesel Fuel Bryan R. Moser, Roque L. Evangelista, and Terry A. Isbell Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.5b02591 • Publication Date (Web): 04 Dec 2015 Downloaded from http://pubs.acs.org on December 4, 2015

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Energy & Fuels

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Preparation and Fuel Properties of Field Pennycress

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(Thlaspi arvense) Seed Oil Ethyl Esters and Blends

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with Ultra-Low Sulfur Diesel Fuel

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Bryan R. Moser,* Roque L. Evangelista and Terry A. Isbell

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United States Department of Agriculture

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Agricultural Research Service

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National Center for Agricultural Utilization Research

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Bio-Oils Research Unit

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1815 N. University St., Peoria, Illinois 61604, USA

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* Tel.: +1-309-681-6511; fax: +1-309-681-6524. E-mail address: [email protected].

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ACS Paragon Plus Environment

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ABSTRACT: Field pennycress (Thlaspi arvense L.) is a widely distributed winter annual with

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high seed oil content (36%) and is suitable as an off-season rotational crop in the Midwestern

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United States. Erucic [(13Z)-docosenoic] acid (36.2%) is the most abundant constituent in the

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oil, with unsaturated and very long chain (20+ carbons) fatty acids comprising most of the

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remaining content. In a previous study we described field pennycress seed oil methyl esters

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(FPME). Here we report field pennycress seed oil ethyl esters (FPEE) along with the properties

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of blends of FPME and FPEE (B2-B20) in petrodiesel. These results are compared to American

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and European biodiesel and petrodiesel fuel standards. FPEE were characterized by excellent

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low temperature properties (cloud point -15 oC), high cetane number (61.4), high kinematic

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viscosity (5.65 mm2/s), and low oxidative stability (induction period of 4.6 h). Both kinematic

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viscosity and oxidative stability did not meet EN 14214 limits, but were within the ranges

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prescribed in ASTM D6751. With regard to blends, highly linear correlations (R2 0.99) were

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noted between blend ratio and density, energy content, kinematic viscosity, moisture content, and

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specific gravity. Acid value, sulfur content and surface tension were essentially unaffected by

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blend ratio. Oxidative stability was negatively affected by higher biodiesel content, which is

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typical for blends. Cold flow properties were minimally impacted by blend ratio, thus

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representing a significant advantage of FPME and FPEE over other biodiesel fuels. Both FPME

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and FPEE were excellent lubricity enhancers, as even small amounts (B2) markedly improved

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the lubricity of petrodiesel. Where applicable, fuel properties of the blends were within the

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limits prescribed in the petrodiesel standards.

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Energy & Fuels

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INTRODUCTION We recently reported fatty acid methyl esters (FAMEs) from field pennycress (Thlaspi

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arvense L.) seed oil (FPO).1 Here we describe the preparation and fuel properties of the

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corresponding fatty acid ethyl esters (FAEEs) along with blends of field pennycress seed oil

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methyl (FPME) and ethyl (FPEE) esters in ultra-low sulfur (< 15 ppm S) diesel (ULSD) fuel.

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These results are compared to American and European biodiesel (ASTM D6751 and EN 14214)

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and petrodiesel (ASTM D7467, D975 and EN 590) fuel standards. Ethyl esters were of interest

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because ethanol is obtained from fermentation of sugars as opposed to petrochemically-derived

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methanol, thus yielding a biodiesel fuel in the case of FPEE that is composed entirely of

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renewable carbon.2 Such a study is important due to the limited availability, high cost, and

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competing food-related applications of commodity lipids typically used for biodiesel

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production.3 For example, feedstock acquisition represents 80% or more of the production costs

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of biodiesel.4 Therefore, low-cost, non-food alternatives that do not displace existing food

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production are attractive options for reducing the cost of biodiesel while simultaneously

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enhancing the supply of commodity lipids for food use. Recent examples that have gained

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considerable attention are oils derived from Jatropha (Jatropha curcas L.) and various

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microalgae.5,6

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Field pennycress is a winter annual belonging to the Brassicaceae family with a broad

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distribution throughout temperate North America. With a seed oil content of approximately

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36%, field pennycress is adapted to a wide variety of climatic conditions and is compatible with

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existing farm practices and infrastructure. In much of the Midwestern United States it can be

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planted in the fall after a corn harvest and harvested during spring in time for a full soybean

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growing season using conventional farming equipment. Field pennycress is tolerant of marginal


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lands not otherwise suited for traditional agriculture, is not part of the food chain, and requires

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minimal agricultural inputs such as fertilizer, pesticides and water.7-9 The Brassicaceae family is

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a prolific source of oilseed crops for production of biodiesel, as evidenced by canola/rapeseed

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(Brassica napus L.), camelina (Camelina sativa L.) and wild mustard (B. juncea L.), among

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numerous others.3,10,11

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Typical seed yields of 1680 kg/ha were reported from T. arvense, which equates to an

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average of 540 pounds/acre of oil at a seed oil content of 36%.8 For comparison, yields of canola,

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corn and soybean oils are 647-728, 215-390 and 456-506 pounds/acre, respectively.12 Lipids are

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readily expelled from the seeds using a conventional heavy duty screw press to yield both liquid

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(oil) and solid (press cake) fractions.13 Extraction of proteins from T. arvense seeds and press

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cake was reported, as well as the influence of cold-pressing on composition and functional

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properties of protein in the press cake.14,15 The press cake also inhibits seedling germination and

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emergence of agricultural pests, thus suggesting biofumigation properties.16

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FPO contains a diverse set of fatty acids (FAs) that range in size from palmitic

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(hexadecanoic) to nervonic [(15Z)-tetracosenoic] acids, with erucic [(13Z)-docosenoic] acid

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(36%) representing the largest individual component. Most of the remaining FA profile is

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composed of unsaturated constituents such as linoleic [(9Z), (12Z)-octadecadienoic; 19.5%] and

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linolenic [(9Z), (12Z), (15Z)-octadecatrienoic; 9%] acids.17 We recently reported enrichment of

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erucic acid from FPO for potential use in non-fuel industrial applications.18 One such example is

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as an industrial lubricant, both in the neat form and chemically modified as estolides.19,20

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Because of the comparatively high content of erucic acid and polyunsaturated FAs relative to

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commodity lipids such as soybean or canola oils, FPO and the corresponding biodiesel have

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superior cold flow properties but comparatively high kinematic viscosity (KV) and low oxidative


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stability.1,17,19 As a consequence, complementary blends of FPME with other biodiesel fuels

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ameliorated technical deficiencies associated with individual fuels in a previous study.21 For

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example, soybean oil methyl esters (SME) exhibit poor cold flow properties but satisfactory

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KV.22 Blends of FPME with SME yielded cold flow and KV values that were within the ranges

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specified in ASTM D6751 and EN 14214.21 In addition, the combustion and emissions of FPO,

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FPME, and renewable diesel (RD) resulting from hydrotreatment of FPO were evaluated in a

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John Deere 4.5 L compression-ignition engine and found to behave similarly to analogous fuels

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derived from other lipids.23 Lastly, a life cycle assessment of FPO-derived jet fuel and RD

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revealed that fossil energy consumptions were considerably lower than the corresponding

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petroleum fuels. Those results indicated that field pennycress-based biofuels should qualify as

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advanced biofuels and as biomass-based diesel fuels as defined by the Renewable Fuels Standard

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(RFS2).24

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2.

EXPERIMENTAL 2.1.

Materials. Field pennycress seeds were collected from wild populations in

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Peoria County, IL. Certification-grade ULSD that was free of performance-enhancing additives

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was donated by a major petroleum company that wishes to remain anonymous. FAME standards

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(>99%) were purchased from Nu-Chek Prep, Inc. (Elysian, MN). Single element calibration

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standards for ICP-AES were obtained from SCP Science (Champlain, NY). All other reagents

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were obtained from Sigma-Aldrich Corp (St. Louis, MO). All materials were used as received.

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2.2.

Extraction of Field Pennycress Seed Oil. Seeds were cold pressed using a

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model L250 laboratory screw press from the French Oil Mill Machinery Company (Piqua, OH).

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Details of this expeller and the extraction are available elsewhere.13,25 Once extracted, crude


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FPO was filtered to remove solid material. Quantification of oil content by exhaustive hexane

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extraction of seeds as well as determination of FA profile by GC is described previously.1,17

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2.3.

Field Pennycress Seed Oil Ethyl Esters. Crude FPO with an acid value (AV) of

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0.61 mg KOH/g was pretreated with catalytic sulfuric acid (1.0 vol %) and ethanol (40 vol %) as

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described previously to lower the AV of FPO to 0.09 mg KOH/g.1 Acid-pretreated FPO was

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then subjected to ethanolysis in a 500 mL three-necked round bottom flask connected to a reflux

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condenser and a magnetic stirrer set to 1200 rpm. Initially, FPO (180 g; 200 mL; 0.20 mol) and

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ethanol (110 mL, 1.82 mol) were combined and heated to 70 °C, followed by addition of 1.0 wt

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% KOH (1.8 g). After 2.0 h the mixture was equilibrated to room temperature and ethanol was

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removed by rotary evaporation, followed by removal of glycerol via gravity separation. Crude

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FAEEs were treated with 2.5 wt % Magnesol® at 65 °C for 25 min with continuous stirring (500

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rpm), followed by vacuum filtration using #54 Whatman (VWR; Radnor, PA) filter paper to

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remove the adsorbent to provide purified FPEE (160 g, 89%).

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2.4.

Preparation of Blends. Precisely measured volumes of FPME and FPEE were

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splash blended with ULSD with continuous stirring (22-24 oC) to ensure homogeneity. FPME

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and FPEE were blended with ULSD at 2 (B2), 5 (B5), 10 (B10), and 20 (B20) vol %. Samples

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were stored in amber jars under argon at 4 oC prior to use. Before the samples were analyzed

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they were equilibrated to room temperature, vigorously stirred to ensure homogeneity, and

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smaller samples were removed from the middle of the stock solution using a glass pipette.

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2.5.

Fuel Properties. Properties were measured in triplicate with mean values

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reported following AOCS, ASTM, and CEN standard test methods using instrumentation

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described previously:1,10,11,26 acid value (AV, mg KOH/g), AOCS Cd 3d-63; cloud point (CP,

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o

C), ASTM D5773; cold filter plugging point (CFPP, oC), ASTM D6371; density (kg/m3),


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AOCS Cc 10c-95; flash point (FP, oC), ASTM D93; free and total glycerol (mass %), ASTM

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D6584; higher heating value (HHV, MJ kg-1), ASTM D4809; induction period (IP, h), EN

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15751; iodine value (IV, g I2 100 g-1), AOCS Cd 1c-85; kinematic viscosity (KV, mm2/s), ASTM

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D445; lubricity (µm), ASTM D6079; moisture content (ppm), ASTM D6304; phosphorous (P,

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mass %), ASTM D4951; pour point (PP, oC), ASTM D5949; specific gravity (SG), AOCS Cc

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10c-95; sulfur (S, ppm), ASTM D5453; surface tension (ST, mN/m), ASTM D3825. For greater

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precision, PP was measured with a resolution of 1 °C instead of the specified 3 °C increment.

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Elemental analyses (S, P) were performed using inductively coupled plasma optical emission

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spectroscopy (ICP-OES) using a model 7000DV Optima instrument from PerkinElmer Inc.

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Waltham, MA). Derived CN (DCN) was determined (n=32) by Southwest Research Institute

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(San Antonio, TX) following ASTM D6890.

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Data for each biodiesel/ULSD blend set was analyzed by least-squares statistical

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regression to yield R2 values for plots of fuel property (y-axis) versus blend ratio (x-axis).

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Properties modeled in this fashion included density, IP, KV, lubricity, and moisture content of

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blends (B0-B20) of FPME and FPEE in ULSD. Plots are not shown herein, but R2 values

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obtained from statistical regression are discussed in the next section. Modeling and statistical

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analyses were performed using Microsoft (Redmond, WA) Office Excel® 2007 spreadsheets.

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3.

RESULTS AND DISCUSSION 3.1.

Preparation of Field Pennycress Seed Oil Ethyl Esters. FPO was subjected to

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homogenous base-catalyzed ethanolysis employing classic conditions elucidated previously to

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afford FPEE in 89% yield.27 Prior to ethanolysis, crude FPO was pretreated with ethanol and

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catalytic sulfuric acid to render the oil more amenable to subsequent KOH-catalyzed


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transesterification. Pretreatment lowered the AV of FPO from 0.61 to 0.09 mg KOH/g. Such a

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treatment was necessary because free FAs react with alkaline catalysts such as KOH to form

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soap (potassium salt of FA) and water, thus irreversibly quenching the catalyst and reducing

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product yield.27 FPME used for comparison in this study was prepared as described previously.1

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3.2.

Composition and Quality of Field Pennycress Seed Oil Ethyl Esters. Depicted

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in Table 1 is the FA composition of FPO. As mentioned previously, the most abundant FA was

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erucic acid (C22:1) at 36.2%, with linoleic (C18:2; 19.5%), oleic (C18:1 9c; 11.0%), gondoic

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[C20:1; (11Z)-eicosenoic; 10.2%], and linolenic (C18:3; 8.9%) acids also present in significant

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amounts. Overall, FAs containing 20+ carbons collectively constituted 54.4% of the

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composition of FPO, with the greatest contributions from erucic and gondoic acids.

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Monounsaturated FAs, such as erucic, oleic and gondoic acids, comprised 64.6%, while

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polyunsaturated and saturated FAs were 30.4% and 5.0%, respectively, of the overall content.

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Quality of FPEE was assessed by determination of free and total glycerol, AV, FP, and

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moisture content. These results are shown in Table 2. Data for FPME is also depicted for

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comparison, but its significance is discussed elsewhere.1 Both ASTM D6751 and EN 14214

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specify maximum limits for free and total glycerol in biodiesel. As seen in Table 2, the values

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obtained for FPEE were significantly below the prescribed maximum thresholds, thus indicating

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that ethanolysis proceeded nearly to completion. Furthermore, the AV of FPEE was 0.38 mg

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KOH/g, which was below the maximum limit specified (0.50 mg KOH/g) in the biodiesel

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standards. Minimum FPs prescribed in the standards are 130 and 101 oC for ASTM D6751 and

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EN 14214, respectively. The FP of FPEE (189 oC) was significantly above the minimum limits,

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thereby indicating it was free of residual ethanol. Lastly, the moisture content of FPEE was 323


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ppm, which was below the maximum limit of 500 ppm prescribed in EN 14214. ASTM D6751

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does not contain a dissolved water specification.

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3.3.

Fuel Properties of Field Pennycress Seed Oil Ethyl Esters. Depicted in Table

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2 are fuel properties of FPEE along with those of FPME. Also shown are the limits specified in

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ASTM D6751 and EN 14214, where applicable. Fuel properties measured included cold flow,

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DCN, density, energy content, heteroatom (S and P) content, IV, KV, lubricity, oxidative

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stability, SG, and ST.

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The cold flow properties of FPEE were determined by CP, CFPP and PP, which provided

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values of -15, -17 and -19 oC, respectively. Such results were significantly lower (better) than

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the corresponding values obtained for biodiesel prepared from commodity lipids such as

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soybean, canola, sunflower, and especially palm oils.22 The low level of saturated FAEEs

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identified in FPEE (5.0%) was in part attributed to its low temperature behavior, as saturated

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esters have considerably higher melting points than the corresponding unsaturated analogues.29

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In addition, FAEEs generally have lower melting points than FAMEs, as evidenced by

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comparison of the CPs of FPME and FPEE.

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The IP of FPEE was 4.6 h. Addition of antioxidants or blending with more oxidatively

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stable fuels would be necessary to satisfy the oxidative stability requirement (IP > 6 h) specified

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in EN 14214.21,22,26 FPEE was within the limit (IP > 3 h) prescribed in ASTM D6751. The

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failure of FPEE to meet the EN 14214 specification was attributed to its high percentage (30.4%)

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of polyunsaturated FAEEs, such as ethyl linoleate and linolenate. Polyunsaturated esters are

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more susceptible to oxidation than monounsaturated and especially saturated esters.30 IV is

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indirectly related to oxidative stability, as it gives an indication of overall double bond content.

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In general, biodiesel fuels with high IVs will yield poor IPs and vice versa.22 ASTM D6751 does


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not contain an IV specification, but IV is limited in EN 14214 to a maximum of 120 g I2/100 g.

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The IV of FPEE (104 g I2/100g) was within the limit prescribed in EN 14214. FPEE yielded a

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lower IV than FPME, as seen in Table 2. This is because IV is affected by molecular weight.31

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The KV of FPEE (5.65 mm2/s) was within the range specified in ASTM D6751 but

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exceeded limit prescribed in EN 14214. The high KV of FPEE was due to the presence of

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longer-chain (C20+) FAEE. For example, the KVs of methyl erucate and gondoate are 7.33 and

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5.77 mm2/s, respectively.32 These constituents as ethyl esters, together with smaller amounts of

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other C20+ FAEEs, comprised 54.4% of the FA profile of FPEE. As expected, FPEE exhibited

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a higher KV than FPME. Blending with less viscous fuels represents a viable strategy to satisfy

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the EN 14214 KV specification.21,22,26

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Minimum limits for CN (ASTM D613) of 47 and 51 are prescribed in ASTM D6751 and

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EN 14214, respectively. DCN (ASTM D6890) was measured in this study, as it requires a

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smaller sample size and is approved as an alternative to CN in ASTM D6751.33 The DCN of

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FPEE was 61.4, which was considerably higher than the minimum limits specified in the

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biodiesel standards. DCN is influenced by chain length, degree of unsaturation and branching,

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with higher DCNs observed for linear saturated chains of longer lengths.3 FPEE yielded a high

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DCN because it contained a high percentages of ethyl erucate and ethyl gondoate, which we

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determined in a previous study to have DCNs of 74.2 and 73.2, respectively, as methyl esters.1

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Lubricity is not specified in the biodiesel standards but is included in the petrodiesel

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standards ASTM D975, D7467 and EN 590 with maximum wear scars (60 oC) of 520, 520 and

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460 µm prescribed, respectively. The wear scar generated by FPEE (113 µm) was significantly

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below the maximum limits listed in the petrodiesel standards, which was in agreement with prior

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studies indicating that biodiesel possessed inherently good lubricity.1,10,11,34-36 The shorter wear


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scar observed for FPEE relative to FPME was attributed to the presence of FAs in FPEE (see AV

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data), as FAs have even better lubricity than alkyl esters.36

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The concentration of sulfur is limited in ASTM D6751 and EN 14214 to maximum

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values of 15 and 10 ppm, respectively. The sulfur content of FPEE (7 ppm) was below these

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maximum limits. The concentration of phosphorous is also limited to a maximum value of 0.001

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mass %. However, no phosphorous was detected in FPEE.

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ASTM D6751 does not contain a density specification, but EN 14214 prescribes a range

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of 860-900 kg/m3 at 15 oC. FPEE provided a density (884 kg/m3) within the range specified in

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EN 14214. Also measured was SG at 15 oC, for which FPEE yielded a value of 0.885.

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However, neither ASTM D6751 nor EN 14214 contain limits on SG. The density and SG of

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FPEE were similar to those reported for several biodiesel fuels and higher than that of ULSD.37,38

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The HHV of FPEE was 39.44 MJ/kg, which due to its content of C20+ FAEEs provided

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greater energy content than biodiesel fuels comprised almost exclusively of C16-C18 FAMEs.39

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FPEE also yielded higher energy content than FPME due to the presence of additional energetic

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C-H bonds in the ethyl ester moiety. The STs of FPEE at 25 and 40 oC were 31.0 and 29.6

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mN/m, respectively. Such values agreed closely with previously reported STs of biodiesel fuels

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prepared from a variety of feedstocks at similar temperatures.1,10,39,40 Neither ASTM D6751 nor

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EN 14214 contain limits on energy content or ST.

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3.4.

Fuel Properties of Blends with Ultra-Low Sulfur Diesel Fuel. Depicted in

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Tables 3 and 4 are the fuel properties of FPME and FPEE blended with ULSD at B0, B2, B5,

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B10, and B20 levels along with a comparison to the petrodiesel standards ASTM D975, D7467

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and EN 590. Each standard permits a different range of blend levels: biodiesel up to the B5 and

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B7 levels are allowed by ASTM D975 and EN 590, respectively, whereas ASTM D7467 covers


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blends from 6-20 vol%. Properties of interest included AV, cold flow, density, HHV, KV,

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lubricity, moisture, oxidative stability, SG, ST, and sulfur content.

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The biodiesel-petrodiesel blend standard, ASTM D7467, limits AV to a maximum value

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of 0.30 mg KOH/g. ASTM D975 and EN 590 do not contain AV specifications. Neither the

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FPME nor the FPEE blends contained a detectable level of acids, thereby satisfying the ASTM

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D7467, where applicable. Another parameter that was minimally affected by blend ratio was

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sulfur content. This was because ULSD (9 ppm), FPME (7 ppm) and FPEE (7 ppm) contained

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similar concentrations of sulfur. All blends yielded sulfur concentrations that were within the

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limits specified in the petrodiesel standards.

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Density is limited in EN 590 to a range of 820-845 kg/m3 (15 oC) but no such limits are

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specified by ASTM D975 or D7467. As the percentages of FPME and FPEE in ULSD increased

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from B0 to B20, density increased linearly (R2 0.99) as a result of the higher densities of FPME

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and FPEE relative to ULSD. The values obtained for the B0-B5 blends were below the

264

maximum threshold listed in EN 590. However, The B20 samples were above the limit but

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contained too much biodiesel to be covered by EN 590. Analogous to density were the results

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obtained for SG in which highly linear (R2 = 0.99) increases were noted as the blend ratio

267

increased. These results were in agreement with a previous study that elucidated a linear

268

correlation between blend ratio and SG.37 The petrodiesel standards do not specify limits for SG.

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Also yielding highly linear correlations (R2 = 0.99) were moisture content and KV. Both

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FPME and FPEE yielded higher moisture levels and KVs than ULSD, so the corresponding

271

blends afforded progressively higher values with increasing blend ratio. All of the blends were

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within the ranges prescribed in the standards for moisture content and KV, where applicable. A

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strongly linear negative correlation (R2 = 0.99) was noted for energy content. Both FPME and


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274

FPEE had lower HHVs than ULSD, so the corresponding blends provided progressively lower

275

values with increasing blend ratio. Energy content is not specified in the petrodiesel standards.

276

FPME and FPEE were considerably less stable to oxidation than ULSD, as seen by an IP

277

of 40.1 h for ULSD. Such a result is typical of biodiesel, as biodiesel contains oxidatively

278

susceptible olefinic moieties whereas ULSD does not. As a result, lower IPs were observed as

279

the content of biodiesel increased from B0-20. In agreement with previous studies, the response

280

of IP to ester content was non-linear.34 ASTM D7467 specifies a minimum IP of 6.0 h. The B10

281

and B20 blends met this requirement. A minimum IP of 20 h is specified in EN 590, whereas

282

ASTM D975 does not contain an oxidative stability specification. The B2 blends along with the

283

B5 FPEE blend met the requirement, but the FPME B5 blend did not satisfy the EN 590 limit.

284

The cold flow properties of biodiesel are generally inferior to ULSD, as evidenced by

285

numerous studies on the influence of biodiesel on the low temperature behavior of

286

ULSD.10,34,35,38,39,41 However, FPME and especially FPEE exhibited CP, CFPP and PP values

287

much closer to ULSD than traditional biodiesel fuels. As a result, the deleterious effect of

288

increasing blend ratio on cold flow behavior of ULSD was mitigated. Although CP, CFPP and

289

PP trended toward higher temperatures with increasing content of biodiesel, the changes were

290

minimal compared to other biodiesel fuels. For instance, the CP, CFPP and PP of the B20 FPEE

291

blend increased by only 3 oC relative to ULSD. For comparison, increases of 6-7 oC were

292

reported for the corresponding B20 blends of SME in ULSD.10 The petrodiesel standards do not

293

contain limits on low temperature operability. Instead, ASTM D975 and D7467 offer guidance.

294

As already mentioned, ULSD is inferior to biodiesel with regard to lubricity, as seen by a

295

comparison of the wear scar generated by ULSD (571 µm) to FPME and FPEE and the

296

petrodiesel standards. Accordingly, the blends exhibited significantly shorter wear scars with


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

297

increasing content of biodiesel. The response of lubricity to blend ratio was non-linear, as small

298

increases in biodiesel content resulted in substantial reductions in wear scar length. Even at the

299

B2 blend level, the blends were well within the limits listed in the petrodiesel standards. As was

300

the case in prior studies, biodiesel was an excellent lubricity enhancer for ULSD.10,11,34,38,39,42

301

Although ST is not among the specifications listed in the petrodiesel standards, it affects

302

fuel atomization in combustion chambers in diesel engines.43 The STs of ULSD at 25 and 40 °C

303

(27.3 and 25.9 mN/m) were lower than both FPME and FPEE. Hence, blends of FPME and

304

FPEE in ULSD displayed progressively higher STs with increasing content of biodiesel, which

305

was in agreement with previous studies.10,11,39,40 The minimal increase in ST among the blends

306

relative to ULSD was not considered significant enough to negatively impact fuel atomization.

307 308

4.

309

FPEE was prepared in 89% yield from pretreated FPO using potassium hydroxide as catalyst.

310

The dominant FA in FPO was erucic acid (36.2%), with linoleic (19.5%), oleic (11.0%), gondoic

311

(10.2%), and linolenic (8.9%) acids also present in significant amounts. FPEE was within

312

ASTM D675and EN 14214 limits, where applicable, for AV, FP, free and total glycerol, and

313

moisture content, thus indicating that high quality esters were prepared. The cold flow properties

314

of FPEE were significantly better than biodiesel from commodity lipids such as soybean, canola,

315

sunflower, and especially palm oils. The low level of saturated FAs identified in FPEE (5.0%)

316

was in part attributed to its excellent low temperature behavior. The failure of FPEE (4.6 h) to

317

meet the EN 14214 oxidative stability specification (> 6 h) was attributed to its high percentage

318

(30.4%) of polyunsaturated FAEEs, such as ethyl linoleate and linolenate. As is the case with

319

most biodiesel fuels, antioxidant additives are recommended. The KV of FPEE (5.65 mm2/s)

CONCLUSIONS


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Energy & Fuels

320

was within the range specified in ASTM D6751 but exceeded the maximum limit prescribed in

321

EN 14214. The high KV was caused by the presence of longer-chain (C20+) FAEE. The

322

presence of longer-chain FAEE also resulted in a DCN of 61.4, which was significantly higher

323

than biodiesel prepared from typical commodity lipids and well above the minimum

324

requirements specified by the biodiesel standards. Density, energy content, heteroatom content,

325

IV, lubricity, specific gravity, and surface tension were within the limits of ASTM D6751 and

326

EN 14214, where applicable.

327

Blends (B2, B5, B10, and B20) of FPME and FPEE in ULSD were also prepared and the

328

resulting fuel properties were compared to the petrodiesel standards ASTM D975, D7467 and

329

EN 590. Highly linear correlations (R2 = 0.99) were noted between blend ratio and density,

330

HHV, KV, moisture content, and SG. AV, sulfur content and ST were essentially unaffected by

331

blend ratio. Oxidative stability was negatively affected by blend ratio, which is typical for

332

biodiesel. In contrast to other biodiesel fuels, cold flow properties were minimally impacted by

333

blend ratio, thus representing a significant advantage for FPME and FPEE. Both FPME and

334

FPEE proved to be excellent lubricity enhancers for petrodiesel, as even small amounts (B2)

335

markedly improved lubricity. Where applicable, fuel properties of the blends were within the

336

limits prescribed in the petrodiesel standards.

337 338

AUTHOR INFORMATION

339

Corresponding Author

340

(B.R.M.) E-mail: [email protected]; Tel.: +1-309-681-6511; fax: +1-309-681-6524.

341 342

Disclaimer


Energy & Fuels

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343

Mention of trade names or commercial products in this publication is solely for the purpose of

344

providing specific information and does not imply recommendation or endorsement by the U.S.

345

Department of Agriculture. USDA is an equal opportunity provider and employer.

346 347

Notes

348

The authors declare no competing financial interest.

349 350

ACKNOWLEDGEMENTS

351 352

Kim Ascherl, Benetria Banks, Billy Deadmond, and Jeff Forrester are acknowledged for

353

technical assistance.

354 355

REFERENCES

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Moser, B. R.; Knothe, G.; Vaughn, S. F.; Isbell, T. A. Energy Fuels 2009, 23, 4149-4155.

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Kim, S.; Dale, B. E. Biomass Bioenergy 2005, 29, 426-439.

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Moser, B. R. In vitro Cell. Dev. Biol.-Plant 2009, 45, 229-266.

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Haas, M. J.; McAloon, A. J.; Yee, W. C.; Foglia, T. A. Bioresour. Technol. 2006, 97,

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671-678.

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Berchmans, H. J.; Hirata, S. Bioresour. Technol. 2008, 99, 1716-1721.

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Chisti, Y. Biotechnol. Adv. 2007, 25, 294-306.

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Moser B. R. Biofuels 2012, 3, 193-209.

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Isbell, T. A. Ol. Crops Gras. Lipides 2009, 16, 205-210.


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Royo-Esnal, A.; Necajeva, J.; Torra, J.; Recasens J.; Gesch, R. W. Ind. Crops Prod. 2015, 66, 161-169.

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Moser, B. R.; Vaughn, S. F. Bioresour. Technol. 2010, 101, 646-653.

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Moser, B. R.; Evangelista, R. L.; Jham, G. Renewable Energy 2015, 78, 82-88.

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O,Brien, R. D. Fats and Oils. Formulating and Processing Applications. 3rd Ed; CRC

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Press: Boca Raton, 2009; p 3.

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Evangelista, R. L.; Isbell, T. A.; Cermak, S. C. Ind. Crops Prod. 2012, 37, 76-81.

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Selling, G. W.; Hojilla-Evangelista, M. P.; Evangelista, R. L.; Isbell, T.; Price, N.; Doll,

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Moser, B. R.; Shah, S. N.; Winkler-Moser, J. K.; Vaughn, S. F.; Evangelista, R. L. Ind. Crops Prod. 2009, 30, 199-205.

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Vaughn, S. F.; Isbell, T. A.; Weisleder, D.; Berhow, M. A. J. Chem. Ecol. 2005, 31, 167177.

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Hojilla-Evangelista, M. P.; Evangelista, R. L.; Isbell, T. A.; Selling, G. W. Ind. Crops

Cermak, S. C.; Biresaw, G.; Isbell, T. A.; Evangelista, R. L.; Vaughn, S. F.; Murray, R. Ind. Crops Prod. 2013, 44, 232-239.

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Cermak, S. C.; Durham, A. L.; Isbell, T. A.; Evangelista, R. L., Murray, R. E. Ind. Crops. Prod. 2015, 67, 179-184.

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Moser, B. R. Renewable Energy 2016, 85, 819-825.

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Moser, B. R. Energy Fuels 2008, 22, 4301-4306.


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Drenth, A. C.; Olsen, D. B.; Cabot, P. E.; Johnson, J. J. Fuel 2014, 136, 143-155.

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of Standards; American Society for Testing and Materials: West Conshohocken, PA,

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Ejim, C. E.; Fleck, B. A.; Amirfazli, A. Fuel 2007, 86, 1534-1544.


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Table 1. Fatty Acid Composition (area %) of Field Pennycress Seed Oil FPO Fatty Acida C16:0 2.4 C18:0 0.2 C18:1 9c 11.0 C18:1 11c 1.2 C18:2 9c, 12c 19.5 (0.1) C18:3 9c, 12c, 15c 8.9 (0.1) C20:0 2.2 C20:1 11c 10.2 C20:2 11c, 14c 1.6 C20:3 11c, 14c, 17c 0.4 (0.1) C22:0 0.2 C22:1 13c 36.2 (0.2) C24:1 15c 3.6 (0.1) b 5.0 Σ saturated c 64.6 Σ monounsaturated 30.4 Σ polyunsaturatedd e 54.4 Σ C20+ a For example, C18:1 9c signifies an 18 carbon fatty acid chain with one cis (c) double bond located at carbon 9 (methyl 9Z-octadecenoate; methyl oleate). Numbers in parenthesis represent standard deviations (n=3). When none is given standard deviation was zero. b

Σ saturated = C16:0 + C18:0 + C20:0 + C22:0.

c

Σ monounsaturated = C18:1 + C20:1 + C22:1 + C24:1.

d

Σ polyunsaturated = C18:2 + C18:3 + C20:2 + C20:3.

e

Σ C20+ = C20:0 + C20:1 + C20:2 + C20:3+ C22:0 + C22:1 + C24:1.


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Energy & Fuels

Table 2. Fuel Properties of Field Pennycress Seed Oil Methyl (FPME) and Ethyl Esters (FPEE) with a Comparison to the Biodiesel Standards ASTM D6751 and EN 14214a ASTM D6751 0.50 max

Acid value, mg KOH/g Glycerol content: Free, mass % 0.020 max Total, mass % 0.240 max Flash point, oC 130 min Cold flow properties: CP, oC Report o CFPP, C PP, oC Oxidative stability: 3 min IP, 110 oC, h Iodine value, g I2/100 g Kinematic viscosity, 40 oC, mm2/s 1.9-6.0 Cetane number 47 min Sulfur, ppm 15 max Phosphorous, mass % 0.001 max Moisture content, ppm Wear scar, 60 oC, µm Density, 15 oC, kg/m3 Specific gravity, 15 oC HHV, MJ/kg Surface tension, mN/m 25 oC o 40 C a min = minimum; max = maximum.

EN 14214 0.50 max

FPME N/Db

FPEE 0.38 (0.04)c

0.020 max 0.250 max 101 min

0.005 0.041 186

0.010 0.069 189

-d Variablee -

-10 (1) -17 -18 (1)

-15 (1) -17 -19

6 min 120 max

4.4 (0.1) 104

4.6 (0.2) 109

3.5-5.0 51 min 10 max 0.001 max 500 max 860-900 -

5.24 (0.01) 59.8 (1.3)f 7 N/D 296 (1) 145 (3) 889 0.890 38.92 (0.03)

5.65 (0.01) 61.4 (2.1)f 7 N/D 323 (3) 113 (2) 884 0.885 39.44 (0.06)

-

31.5 29.8

31.0 29.6

b

None detected.

c

Values in parentheses are standard deviations from the reported means. Where none is given standard deviation was zero.

d

Not specified.

e

Variable by location and time of year.

f

Derived cetane number.


Energy & Fuels

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Page 22 of 23

Table 3. Fuel Properties of Blends of FPME in ULSD along with a Comparison to the Petrodiesel Standards ASTM D975, D7467 and EN 590a Petrodiesel Standards ASTM D975 ASTM D7467 EN 590 0-5 6-20 0-7 0.30 max 200 max

Biodiesel content, vol % Acid value, mg KOH/g Moisture content, ppm Cold flow properties: -b CP, oC o CFPP, C -b o PP, C Oxidative stability: IP, 110 oC, h Kinematic viscosity: 40 oC, mm2/s 1.9-4.1 Sulfur, ppm 15 max 520 max Wear scar, 60 oC, µm Density, 15 oC, kg/m3 Specific gravity HHV, MJ/kg Surface tension, mN/m 25 oC o 40 C a Refer to footnotes in Table 2. b

B0 0 N/D 17 (1)

Blends of FPME in ULSD B2 B5 B10 2.0 5.0 10.0 N/D N/D N/D 23 (2) 31 (1) 45 (2)

B20 20.0 N/D 73 (1)

-b -b -

-

-18 -19 -24

-18 (1) -19 -23

-16 -17 -20

-16 -17 -20

-15 -15 -20

6 min

20 min

40.1 (1.2)

22.9 (0.7)

19.0 (0.5)

14.3 (0.9)

9.7 (0.1)

1.9-4.1 15 max 520 max -

2.0-4.0 10 max 460 max 820-845 -

2.30 (0.01) 9 571 (4) 837 (1) 0.838 46.23 (0.10)

2.31 9 345 (2) 838 0.839 46.08 (0.09)

2.38 9 237 (3) 840 0.841 45.86 (0.11)

2.47 9 164 (3) 842 0.843 45.50 (0.06)

2.69 8 158 (2) 847 0.848 44.77 (0.08)

-

-

27.3 25.9

27.4 26.0

27.5 26.1

27.6 26.2

27.8 26.6

No limits are specified, but guidance is provided.


Page 23 of 23

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Energy & Fuels

Table 4. Fuel Properties of Blends of FPEE in ULSD along with a Comparison to the Petrodiesel Standards ASTM D975, D7467 and EN 590a Petrodiesel Standards ASTM D975 ASTM D7467 EN 590 0-5 6-20 0-7 0.30 max 200 max

Biodiesel content, vol % Acid value, mg KOH/g Moisture content, ppm Cold flow properties: -b CP, oC o CFPP, C -b o PP, C Oxidative stability: IP, 110 oC, h Kinematic viscosity: 40 oC, mm2/s 1.9-4.1 Sulfur, ppm 15 max 520 max Wear scar, 60 oC, µm Density, 15 oC, kg/m3 Specific gravity HHV, MJ/kg Surface tension, mN/m 25 oC o 40 C a Refer to footnotes in Tables 2 and 3.

B0 0 N/D 17 (1)

Blends of FPEE in ULSD B2 B5 B10 2.0 5.0 10.0 N/D N/D N/D 23 (1) 32 (1) 48 (2)

B20 20.0 N/D 79 (2)

-b -b -

-

-18 -19 -24

-17 -18 -24

-16 -17 -23

-16 -16 -23

-15 -16 -21

6 min

20 min

40.1 (1.2)

> 24

20.1 (0.9)

15.8 (0.7)

9.9 (0.4)

1.9-4.1 15 max 520 max -

2.0-4.0 10 max 460 max 820-845 -

2.30 (0.01) 9 571 (4) 837 (1) 0.838 46.23 (0.10)

2.32 (0.01) 9 167 (1) 838 0.839 46.09 (0.07)

2.38 9 143 (1) 839 0.840 45.89 (0.10)

2.49 9 135 (1) 842 0.843 45.55 (0.08)

2.73 8 132 (3) 847 0.848 44.87 (0.10)

-

-

27.3 25.9

27.3 26.0

27.5 26.0

27.6 26.1

27.9 26.4


Preparation and Fuel Properties of Field Pennycress (Thlaspi

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