Improvements to Quality-related Limitations to Market Growth of Biodiesel and Renewable Hydrocarbon Diesel Produced from Low-value Feedstocks

Final report for GNE19-203

Project Type: Graduate Student
Funds awarded in 2019: $15,000.00
Projected End Date: 05/31/2020
Grant Recipient: Delaware State University
Region: Northeast
State: Delaware
Graduate Student:
Faculty Advisor:
Dr. Gulnihal Ozbay
Delaware State University
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Project Information


Our findings on identification, characterization and quantification of sulfur impurities in biodiesel has been developed into a manuscript named

"Verification of Sulfonated Compounds Found in Biodiesel Produced from Brown Grease Lipids (BGL)".

It is currently being editted for publication at the American Society for Oil Chemists (AOCS).

Project Objectives:

1. Detection, Quantification, Identification and Removal of Sulfur-bearing impurities in biodiesel produced from brown grease lipids. This study is proposed to synthesize some sulfur-bearing compounds as surrogate species in order to fully understand the nature of the sulfur impurities present in biodiesel produced from BGL. Identifying individual sulfur-bearing compounds in brown grease lipid derived fatty acid methyl ester (BGL-FAME) should aid in developing more effective desulfurization technologies to reduce these sulfur-containing impurities in BGL-FAME and other BGL derived bio-lubricants as a potential strategy for market growth of biodiesel.

2. Synthesis and Analysis of Cold Flow Enhancers. Biodiesel produced from low-value feedstocks generally has poor cold flow properties: poor performance in cold weather such as North America and Europe and thereby limiting the biodiesel market growth. Biodiesel of bio-based oils are biodegradable, favorable environmental properties, low toxicity to aquatic life and safe to store and handle. As a consequence of their high molecular weights, they possess inherent properties such as low volatilities and high viscosity indices. The viscosity of oil usually increases with decreasing temperature. Thus, biodiesel is considered to have performance limitation with regards to cold flow properties. Most of the bio-based oil crystallize at low temperatures and thereby affecting biodiesel performance during cold weather. Biodiesel based on palm oil, peanut oil, sesame oil, soybean oil or rapeseed oil have start-up and operability problems when ambient temperatures fall below the cloud point (CP) of the fuel. The performance limitations can be overcome by chemical modification, genetic modification of plants, processing technology, blending with petrol diesel and treatment with cold flow improver additives.

3.Identify and develop new feedstocks and accompanying technologies to produce biodiesel and renewable hydrocarbon diesel (RHD) from fats and oils. Alternative lipids sources such as fats, oils and greases from brown grease lipids (BGL), poultry fat, tallow, distillers’ corn oil and other sources have not been proven as suitable feedstocks for either biodiesel or renewable hydrocarbon diesel. Elevated sulfur content in these feedstocks results in biodiesels that do not meet the ASTM specification for sulfur. Production of RHD from such feedstocks is also unproven. In order to overcome these challenges, in this work we will (1) take a combined approach to chemically and physical remove sulfur from biodiesel and provide structural identification of the sulfur-bearing compounds, and (2) evaluate the process of converting fatty acids derived BGL into RHD.


To provide alternative energy and biolubricants from Agricultural feedstocks than fossil fuels


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  • Dr. Victor Wyatt (Researcher)


Materials and methods:

Research is conducted at the Agricultural research services at USDA PA utilizing gas chromatography-mass spectroscopy (GC-MS) and gas chromatography-pulsed flame photometric detector (GC-PFPD) to characterize the sulfur bearing compounds found in biodiesel and synthesized in the laboratory for complete identification, quantification and developing desulfurization techniques.

The cold flow improvers and lubricants were synthesized and characterized using 13-carbon nuclear magnetic resonance (NMR) spectroscopy. The cold flow properties were conducted at the USDA facility in Chicago

Research results and discussion:

The GCMS/GC-PFPD retention times of synthesized products in comparison with literature values

Name of product

Product #


Molecular ion peak [M+]

Retention time (min)

Experiment Hughes et al(2017)

Methyl Hexythienyloctanoate


Unsaturated thiophene derivative


 13-14                    12- 13                           



Saturated thiophene derivative


14 – 15                  13 - 15

Crosslinked disulfide


Two fatty acid methyl ester crosslinked by a disulfide


31 - 33                 33 - 35

Crosslinked sulfide


Two FAME crosslinked by a sulfide


30 – 32                  32 - 33



Cyclic disulfide


20 -23                     19- 20

The GC chromatogram retention time (min) of methyl 8-(2’, 5’-hexylthienyl) octanoate (1) was between 13-14 minutes in good comparison with the isolated compound found in BGL-derived biodiesel of 13 – 13 minutes. Similarly, products 2, 3, 4, and 5 had retention times of 14 -15, 31-33, 30-32 and 20-23 respectively which compared favorably well with earlier isolated products in previous publication.

Dimer acid 2-EH esters 1 and 2 were synthesized from sulfuric acid catalyzed esterification reactions of C36-dimer acids obtained from two different types of zeolite catalysts (Ferrierite (dimer acid 1) and ZSM-5 (dimer acid 2)) as potential bio-lubricant base stock or cold flow improver additive (CFI).  Dimer acid 2-EH esters are of interest in this study because it had been previously shown that the 2-EH esters have superior cold temperature properties. It is also important to understand how the difference of the dimer acids will influence the properties of the corresponding esters.

Conversions as determined using quantitative 13CNMR spectroscopy were 96.7 % and 97 % for dimer acid esters 1 and 2 respectively. The proposed mechanistic pathway is the sulfuric acid catalyzed esterification of dimer acids by reacting with 2-EH at a molar ratio of 1:2.2 up to 1:10. The synthesized C52-dimer acid alkyl 2-EH ester products were characterized using attenuated total reflectance infrared (ATR-IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, liquid chromatography-mass spectroscopy (LC-MS). Due to the relatively high boiling point of 2-EH (~180 °C), rotary evaporation was not quite effective in its removal. Prior to characterization, the crude dimer acid 2-EH ester was isolated and purified using wiped film distillation (WFE). The distillate was primarily composed of dimer acid 2-EH ester (confirmed by MS, NMR and ATR-IR) and was obtained after the residues were reintroduced into the WFE to get rid of remaining fractions of 2-ethylhexanol and other volatile impurities. Two separate passes through the molecular distillation apparatus sufficiently fractionated the crude product for further characterization. As a result of its high point, it was not possible completely isolate 2-ethylhaxanol from the ester as traces (~1 %) as observed from GC analysis. Purified product was characterized by quantitative 13C NMR spectroscopy for molecular distillation yield of > 97%.

Research conclusions:

Synthesized organo-sulfur compounds include methyl 8-(2’5’-hexylthienyl) octanoate (yield, 23%), epithiostearate (yield, 27%), cross-linked disulfide (bis-methyl[12,12-dithiol] stearate (yield, 10% and 30%)), crosslinked sulfide (bis-methyl[9,12-thiol]stearate (yield, 7.5% and 93%)), and epidithiostearate (yield, 4.3%).The retention times of GC chromatograms and mass spectra of synthesized compounds in this project compared well with previously reported sulfur impurities in BGL-derived biodiesel. This novel approach of completely identifying, synthesizing and characterizing these sulfur impurities in biodiesel produced from BGL will result in developing more effective desulfurization technologies and secure the market potential of brown grease lipids as suitable feedstocks for biodiesel production.

Publication of manuscript with the Journal of American Oil Chemist Society is on hold pending NMR characterization of products. This was not concluded before shut down of research center arising from COVID-19

C36 dimer acids have been esterified (97± 0.2% conversion at 120°C for 72h) with 2-ethylhexanol (2-EH) to produce a new class of C52 dimer acid 2-Ethylhexyl (dimer acid 2-EH ester) that may be used in bio-lubricant base stock formulations and as cold flow improver (CFI) additives. Investigation of physical and lubricant properties showed good solubility in commercial base stocks such as poly alpha olefin (PAO-6) (> 20 w/w) and high oleic sunflower oil (HOSuO) (> 20 w/w). The addition of dimer acid 2-EH ester resulted in a 3 to 8-fold improvement in the kinematic viscosity of the base stocks and had comparable viscosity (134±0) with commercial base stock, PAO-6 (VI =137). Blends of dimer acid 2-EH esters showed improvement in the cold flow properties of high oleic sunflower oil (HOSuO) by lowering the pour point (PP) from -18°C to -22°C at 1% w/w admixture of dimer acid 2-EH ester 1 and lowering the cloud point (CP) from -6°C to -11 °C at 8 % w/w admixture. Similar trends were observed for dimer acid 2-EH ester 2. These dimer acid 2-EH esters, whose parent dimer acids were synthesized using two different zeolite catalyst, showed similar physicochemical and lubricant properties and are potential candidates for bio-lubricant base stocks formulation and CFI additives.

Participation Summary

Education & Outreach Activities and Participation Summary

2 Consultations
2 Curricula, factsheets or educational tools
2 Journal articles
2 Published press articles, newsletters
1 Webinars / talks / presentations
1 Workshop field days

Participation Summary:

2 Farmers participated
2 Number of agricultural educator or service providers reached through education and outreach activities
Education/outreach description:

Progress reports on synthetic methodologies and findings on sulfur bearing impurities was presented to the research team at USDA Wyndmoor on January 22, 2020 while the synthesis of C52 dimer acid 2-ethylhexyl esters and lubrication properties was presented to bio-lubricant research team on February 2020. See details on the powerpoint slides attached.Synthesis of Thiophene and Thiolane Derivatives USDA presentation July 23 edit Synthesis and Physicochemical properties of Dimer Acid 2-EthelhexylEsters

Workshop earlier scheduled with farmers in Dover DE. was not actualized due to shut down arising from COVID-19

Presentation to the American Chemical Society on March 2020 was conducted using online virtual presentation also due to the pandemic. See attached ACS presentation.ACS Philly 2020

Presentation to Chicago society of tribologist and bio-lubricant engineers (STLE) was cancelled. Attached is the accepted abstract which is rescheduled for September 2020.Abstract Dimer acid Ester

Dr. Ozbay presented this project focusing "Improving the Quality of Biodiesel for Heavy Machinery and Agricultural Equipment"during the Small Farm Meeting in November 2019. See attached flyerShehu Research Flyer

Project Outcomes

1 Grant applied for that built upon this project
1 Grant received that built upon this project
$16,000.00 Dollar amount of grant received that built upon this project
1 New working collaboration
Project outcomes:

We will be showcasing outcome to farmers either in January and February 2020

This meeting was called off due to COVID-19 pandemic.

Knowledge Gained:

We have developed renewable sources of energy and bio-lubricants from agricultural feedstocks such as soya bean oils (iso-oleic acid) methyl esters as potential replacement petrol diesel/lubricants. We devised alternative renewable feed stocks for fats, oils and greases from sewage scum grease and brown grease lipids (BGL) in order to minimize or reduce the food vs fuel debate. Inherent limitations on this alternative feedstocks were identified and improvements such as Sulfur reductions and cold flow properties provided in this project.

Further work is to investigate the viability of producing renewable hydrocarbon diesel (green diesel) by hydrocracking of brown grease lipids (BGL) derived from grease trap waste and sewage scum using sulfided bifunctional NiMo/ γ-Al2O3 catalyst. This is a similar catalyst used in refining operation for hydroprocessing of vacuum gas oil (VGO) which possesses an added advantage of high desulfurization activity.

Investigations of bio-based formulation derived from low-value feedstocks for start-up and operability problems when ambient temperatures fall below the cloud point (CP) of the fuel will continue.

Assessment of Project Approach and Areas of Further Study:

Work is in progress on the cold flow properties of biolubricant developed. Research will be presented to the American Chemican Society coming up on March 2020 in PA. Also the biolubricant developed will be presented to the society of tribologist and biolubricantengineers (STLE) sometime in May 2020 at Chicago IL.

The ACS presentation was accomplished via online virtual presentation. See attached media above. However, the STLE meeting in Chicago was cancelled totally which is tentatively rescheduled for September 2020. See attached abstract above

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.