Robert L McCormick

• PhD Chemical Engineering
• Group Leader at National Renewable Energy Laboratory

The combustion kinetics of three symmetric diesel-boiling-range ether isomers were investigated experimentally using a plug flow reactor. The isomers were di-n-butyl ether (DNBE), diisobutyl ether (DIBE), and di-sec-butyl ether (DSBE). The flow reactor experiments employed oxygen as the oxidizer and helium as the diluent, with oxidation carried out...

The first isomerization reaction of an alkylperoxy (RO2) radical holds significant importance in low-temperature oxidation, as it governs the branching ratios of the hydroperoxyalkyl (QOOH) radicals, which influence the competition between the chain-propagation and chain-branching reactions. In this study, we systematically calculated high-pressure...

Computational predictions of vaporization properties aid the de novo design of green chemicals, including clean alternative fuels, working fluids for efficient thermal energy recovery, and polymers that are easily degradable and recyclable. Here, we developed chemically explainable graph attention networks to predict five physical properties pertin...

We develop a catalytic process comprising exclusively of flow reactions for conversion of wet waste-derived volatile fatty acids to sustainable aviation fuel (SAF) and key aromatic building blocks (benzene, toluene, ethylbenzene, and xylene; BTEX). Acids are upgraded via sequential ketonization and either cyclization of light (C3–7) ketones to BTEX...

While today’s biomass-based diesel fuels are used at relatively low blend levels in petroleum diesel, decarbonization of the heavy-duty trucking and off-road sectors is driving increasing use of higher level blends and the combination of hydroprocessing-derived renewable diesel (RD) with biodiesel (fatty acid methyl esters) to create a 100% renewab...

Sustainable aviation fuel (SAF) produced from lignocellulosic biomass is emerging as an ideal alternative to conventional jet fuel for aviation sector decarbonization. Catalytic fast pyrolysis (CFP) can convert lignocellulosic biomass...

div class="section abstract"> Cetane number (CN) is an important fuel property in designing high-performance fuels in recently diversifying compression ignition engines. We introduce graph neural networks (GNNs) that predict CNs of multicomponent surrogate mixtures when only 2D structures and mole fractions of molecules are given. It considers the...

Computational predictions of vaporization properties aid the de novo design of green chemicals, including clean alternative fuels and working fluids for efficient thermal energy recovery. Here, we developed chemically explainable graph attention networks to predict five physical properties pertinent to performance in utilizing renewable energy: hea...

A refinery modeling framework is developed to estimate the benefits of blending high-quality biofuels directly with refinery gasoline components to produce premium grade fuels. The results offer a change in paradigm - instead of biofuels being competitors to fossil fuels, biofuels can add value to refineries’ product slates, because of their favora...

Designing alternative fuels for advanced compression ignition engines necessitates a predictive model for cetane number (CN). In this study, the physics-informed graph neural networks are introduced for a reliable CN prediction by considering molecular features pertinent to the physical properties of molecules that affect CN. The reliability of mea...

Bioderived ethers have recently drawn attention as a response to increasing demands for clean alternative fuels. A theory-experiment combined approach was introduced for five ether molecules representing linear, branched, and cyclic ethers to derive rational design principles for low-emission and high-reactivity ethers. Flow reactor experiments and...

Developing economically viable, scalable, and sustainable technologies for the conversion of lignocellulosic polysaccharides to liquid fuels is widely seen as a centerpiece of the global bioeconomy, and a key part of a multi-pronged approach to achieve carbon neutrality. Here we identify technology challenges and opportunities to achieve this promi...

Utilizing kinetic simulations with the Co-Optimization of Fuels & Engines (Co-Optima) mechanism, the research octane number (RON) of various synergistic blendstocks at several blend levels in a four-component surrogate were predicted and compared against measured values. The blendstocks investigated include dimethylfuran (DMF), 2-methylfuran (2MF),...

Bioderived ethers have recently drawn attention as a response to increasing demands on clean alternative fuels. A theory-experiment combined approach was introduced for the five ether molecules representing linear, branched, and cyclic ethers to derive rational design principles for low-emission and high-reactivity ethers. Flow reactor experiments...

The Co-Optimization of Fuels and Engines (Co-Optima) initiative from the US Department of Energy aims to co-develop fuels and engines in an effort to maximize energy efficiency and the utilization of renewable fuels. Many of these renewable fuel options have fuel chemistries that are different from those of petroleum-derived fuels. Because practica...

Small aromatic molecules with oxygen-containing functional groups are a promising class of fuel additives, as they can be readily sourced from depolymerized lignin. These oxygenated aromatic compounds (OACs) show a lower sooting tendency than aromatic hydrocarbons, but OACs having alkyl groups such as ethylphenol show a higher sooting tendency than...

Yield Sooting Index (YSI) measurements have shown that oxygenated aromatic compounds (OACs) tend to have lower YSI than aromatic hydrocarbon (AHC) compounds. For example, typical AHCs such as toluene and ethyl benzene have a YSI of 170 and 216, respectively, in contrast, OACs such as phenol and anisole have a YSI of 81 and 111, respectively. Howeve...

The hazards to health and the environment associated with the transportation sector include smog, particulate matter, and greenhouse gas emissions. Conversion of lignocellulosic biomass into biofuels has the potential to provide significant amounts of infrastructure-compatible liquid transportation fuels that reduce those hazardous materials. Howev...

Several compression-ignition and low-temperature combustion strategies require a fuel where the ignition-delay-time (IDT) is highly sensitive to the fuel-to-air equivalence ratio (ϕ). Quantitative prediction of ϕ-sensitivity (i.e., the change in IDT with respect to ϕ) would enable rapid screening of the numerous possible (bio)fuel candidates for th...

Significance The development of market-ready biofuels requires advantaged performance, minimal environmental impact, infrastructure compatibility, and economic feasibility. Here, we leverage conventional and emerging fuel property prediction tools to evaluate a priori the merit of a biobased ether. Continuous ether production was achieved through d...

Several compression-ignition and low-temperature combustion strategies require a fuel where the ignition-delay-time (IDT) is highly sensitive to the fuel-to-air equivalence-ratio (φ). Quantitative prediction of φ-sensitivity (i.e., the change in IDT with respect to φ) would enable rapid screening of the numerous possible (bio)fuel candidates for th...

φ-sensitivity is the change in ignition delay time (IDT) with respect to the fuel-to-air equivalence ratio (φ). High φ-sensitivity is a desirable fuel property for applications in advanced compression ignition and multi-mode engine designs. Understanding how φ-sensitivity depends on chemical structure is essential for selecting promising biofuels f...

PM emissions from spark-ignited engines, particularly those with direct injection, now exceed those of diesel particle filter equipped light-duty diesel engines. Fuel chemistry is one of several interacting factors that determine the amount of particulate matter (PM) produced during combustion. Understanding the relationship between fuel chemistry...

This study examined the interactions of ethanol with aromatic compounds on aromatic species evolution during gasoline evaporation and the consequent impacts on particle emissions from a single-cylinder, gasoline direct injection engine. From a chemical kinetic standpoint, the dilution of the aromatic species in gasoline by ethanol blending should r...

Lignocellulosic biomass offers the potential to produce renewable fuels at a scale commensurate with petroleum consumption. Hybrid approaches that combine biological and chemocatalytic processes have garnered increasing attention due to...

The heat of vaporization (HOV) is a relatively poorly studied fuel property that can be related to a fuel’s evaporation characteristics and knock resistance and therefore the emissions and efficiency of direct-injection spark-ignition engines. Methods for measuring the HOV of complex gasoline mixtures and blends of gasoline with ethanol and other o...

Partially reacting candidate fuels under highly dilute conditions across a range of temperatures provides a means to classify the candidates based on traditional ignition characteristics using much lower quantities (sub-mL) than the full octante tests. Using a classifier based on a Gaussian Process model, synthetic species profiles obtained by plug...

Commercial biodiesel blends were aged at 43 °C while monitoring stability. The oxidation stability—or oxidation reserve expressed as Rancimat induction period (IP)—gradually decreased from its initial value. At a predetermined IP threshold, an antioxidant was used to restore IP to the ASTM D7467 specification minimum of 6 h, referred to as re-addit...

The formation of soot precursors during combustion of three positional isomers of methylcyclohexene was investigated in flow reactor experiments and through density functional theory simulations. As evidenced by a recently published structure-property model, the sooting tendencies of these compounds differ from those of structurally similar molecul...

Alkylated furans such as 2,5-dimethylfuran and 2-methylfuran can be produced from biomass and have very attractive properties for use as spark-ignition fuel blendstocks. Their high octane numbers, relatively high energy density, low water solubility, and minimal effect on gasoline blend volatility are potentially significant advantages over alcohol...

Blending cellulosic biofuels with traditional petroleum-derived fuels results in transportation fuels with reduced carbon footprints. Many cellulosic fuels rely on processing methods that produce mixtures of oxygenates which must be upgraded before blending with traditional fuels. Complete oxygenate removal is energy-intensive and it is likely that...

Algal lipids represent a promising feedstock for production of renewable diesel, but there is little information available regarding the integration of pretreatment, extraction, and catalytic upgrading steps. In this work, we examined oil bleaching by two methods and the effects of bleaching on oil deoxygenation over Pd/C and hydroisomerization ove...

The objective of this paper is to investigate the anti-knock quality of sugar-derived levulinic esters (methyl levulinate (ML) and ethyl levulinate (EL)) and cyclic ethers (furfuryl ethyl ether (FEE) and ethyl tetrahydrofurfuryl ether (ETE)). To this end, combustion experiments were carried out in both an engine and a constant volume autoignition d...

Particulate matter emissions negatively affect public health and global climate, yet newer fuel-efficient gasoline direct injection engines tend to produce more soot than their port-fuel injection counterparts. Fortunately, the search for sustainable biomass-based fuel blendstocks provides an opportunity to develop fuels that suppress soot formatio...

Oxygenated biofuels provide a renewable, domestic source of energy that can enable adoption of advanced, high efficiency internal combustion engines, such as those based on homogeneously charged compression ignition (HCCI). Of key importance to such engines is the cetane number (CN) of the fuel, which is determined by the autoignition of the fuel u...

We describe a study to identify potential biofuels that enable advanced spark ignition (SI) engine efficiency strategies to be pursued more aggressively. A list of potential biomass-derived blendstocks was developed. An online database of properties and characteristics of these bioblendstocks was created and populated. Fuel properties were determin...

Biodiesel is a renewable fuel with the potential to displace a portion of petroleum use. However, as with any alternative fuel, in order to be a viable choice it must be compatible with the emissions control devices. The finished biodiesel product can contain up to 5 ppm Na+K and 5 ppm Ca+Mg, and these metal impurities can lead to durability issues...

The performance of spark ignition engines is highly dependent on fuel anti-knock quality, which in turn is governed by autoignition chemistry. In this study, we explore this chemistry for various aromatic oxygenates (i.e., anisole, 4-methyl anisole, 4-propyl anisole, guaiacol, 4-methyl guaiacol, 4-ethyl guaiacol) that can be produced from lignin, a...

For renewable fuels to displace petroleum, they must be compatible with emissions control devices. Pure biodiesel contains up to 5 ppm Na + K and 5 ppm Ca + Mg metals, which have the potential to degrade diesel emissions control systems. This study aims to address these concerns, identify deactivation mechanisms, and determine if a lower limit is n...

Screening a large number of biologically-derived molecules for potential fuel compounds without recourse to experimental testing is important in identifying understudied, yet valuable molecules. Experimental testing, though a valuable standard for measuring fuel properties, has several major limitations, including: the requirement of testably high...

Fast pyrolysis is heating on the order of 1000 °C/s in the absence of oxygen to 40–600 °C, which causes decomposition of the biomass. Liquid product yield from biomass can be as much as 80% of starting dry weight and contains up to 75% of the biomass energy content. Other products are gases, primarily carbon monoxide, carbon dioxide, and methane, a...

The latent heat-of-vaporization (HoV) of blends of biofuel and hydrocarbon components into gasolines has recently experienced expanded interest because of the potential for increased HoV to increase fuel knock resistance in direct-injection (DI) engines. Several studies have been conducted, with some studies identifying an additional anti-knock ben...

Adoption of high-pressure common-rail (HPCR) fuel systems, which subject diesel fuels to higher temperatures and pressures, has brought into question the veracity of ASTM International specifications for biodiesel and biodiesel blend oxidation stability, as well as the lack of any stability parameter for diesel fuel. A controlled experiment was dev...

Several high octane number oxygenates that could be derived from biomass were blended with gasoline and examined for performance properties and their impact on knock resistance and fine particle emissions in a single cylinder direct-injection spark-ignition engine. The oxygenates included ethanol, isobutanol, anisole, 4-methylanisole, 2-phenylethan...

Spark-ignition engine fuel standards have been put in place to ensure acceptable hot and cold weather driveability (HWD and CWD). Vehicle manufacturers and fuel suppliers have developed systems that meet our driveability requirements so effectively that drivers overwhelmingly find that their vehicles reliably start up and operate smoothly and consi...

Processes such as fast pyrolysis of whole biomass or base-catalyzed depolymerization of lignin produce complex mixtures of oxygenated compounds that must be upgraded to be suitable for blending with petroleum and processing in a refinery. Complete removal of these oxygenated compounds is exceedingly energy intensive and it is likely that upgraded p...

This project looks at the potential of blending ethanol with natural gasoline to produce Flex-Fuels (ASTM D5798-13a) and high-octane, mid-level ethanol blends. Eight natural gasoline samples were collected from pipeline companies or ethanol producers around the United States. Analysis of the natural gasoline shows that the samples are 80–95% paraff...

Oxygenates present in partially hydroprocessed lignocellulosic-biomass pyrolysis oils were examined for their impact on the performance properties of gasoline and diesel. These included: methyltetrahydrofuran, 2,5-dimethylfuran (DMF), 2-hexanone, 4-methylanisole, phenol, p-cresol, 2,4-xylenol, guaiacol, 4-methylguaiacol, 4-methylacetophenone, 4-pro...

The objective of this work was to measure knock resistance metrics for ethanol-hydrocarbon blends with a primary focus on development of methods to measure the heat of vaporization (HOV). Blends of ethanol at 10 to 50 volume percent were prepared with three gasoline blendstocks and a natural gasoline. Performance properties and composition of the b...

Alkylphenolic antioxidants are commonly used as additives to stabilize gasoline, jet, and diesel fuels. The use of antioxidants in diesel, in particular, has become more common because of increased blending of cracked gas oils and blending of biodiesel. Combustion of these phenolic compounds may have unintended consequences. Nitroaromatic compounds...

Microalgae are one of the most promising sources of biomass for renewable fuels and chemicals due to their high growth rate and potentially favorable chemical composition. Although esterification and transesterification of fatty acids and triglycerides to biodiesel has traditionally been a strong driver of algae research and development, interest i...

Electrical conductivity and pH, are used in some parts of the world as fuel specification parameters for denatured fuel ethanol (DFE). Conductivity has been correlated with the presence of corrosive ions such as chloride, and high-conductivity fluids are more likely to cause electrochemical or galvanic corrosion. This study examined how electrical...

Longer-term storage stability of biodiesel and blends was studied in experiments simulating up to one year for 100% biodiesel (B100) and three years for blends. Aging was simulated by holding samples at 43 °C to accelerate oxidation (ASTM D4625). Biodiesels were treated with antioxidants before and after aging, with continued aging after antioxidan...

Small impurities in the fuel can have a significant impact on the emissions control system performance over the lifetime of the vehicle. Of particular interest in recent studies has been the impact of sodium, potassium, and calcium that can be introduced either through fuel constituents, such as biodiesel, or as lubricant additives. In a collaborat...

The effect of saturated monoglyceride (SMG) content of four B100s on the cloud point (CP) of blends with four diesel fuels was examined. Detecting CP with a more sensitive light-scattering method allowed observation of an early (higher temperature) CP in blends containing approximately 0.01 wt.% to 0.03 wt.% SMG. Blend samples with SMG content in t...

Pyrolysis offers a rapid and efficient means to depolymerize lignocellulosic biomass, resulting in gas, liquid, and solid products with varying yields and compositions depending on the process conditions. With respect to manufacture of “drop-in” liquid transportation fuels from biomass, a potential benefit from pyrolysis arises from the production...

This work presents a detailed analysis of the production design and economics of the cellulosic isobutanol conversion processes and compares cellulosic isobutanol with cellulosic ethanol and n-butanol in the areas of fuel properties and engine compatibility, fermentation technology, product purification process design and energy consumption, overal...

This study summarizes the best available public data on the production, capacity, cost, market demand, and feedstock availability for the production of biomass-based diesel and jet fuel. It includes an overview of the current conversion processes and current state-of-development for the production of biomass-based jet and diesel fuel, as well as th...

Combustion emissions from diesel engines emit particulate matter which deposits within the lungs. Alveolar macrophages (AMs) encounter the particles and attempt to engulf the particles. Emissions particles from diesel combustion engines have been found to contain diverse biologically active components including metals and polyaromatic hydrocarbons...

Certification gasoline was splash blended with alcohols to produce four blends: ethanol (16 vol%), n-butanol (17 vol%), i-butanol (21 vol%) and an i-butanol (12 vol%) / ethanol (7 vol%) mixture; these fuels were tested in a 2009 Honda Odyssey (a Tier 2 Bin 5 vehicle) over triplicate LA92 cycles. Emissions of oxides of nitrogen, carbon monoxide, non...

Recent studies suggest that by the year 2030 the U.S. will be capable of annually producing 1.3 billion tons of sustainable forest and agricultural waste as well as perennial crops that can be processed into biofuel. This vast quantity of biomass can potentially yield up to 45 billion gallons/year of liquid transportation fuels, which is far greate...

The objective of this study is to review and evaluate research conducted to date applicable to the effects of E15 on Model Year 2001 and newer cars, and to draw objective conclusions based on the entire available dataset. The project team reviewed 43 studies relevant to E15 usage in 2001 and newer model year on-highway automobiles. These included 3...

The distillation behavior of mixed alcohols was studied by use of the Advanced Distillation Curve (ADC) methodology. Crude mixed alcohols (oxygenates) were generated from syngas over a potassium-promoted cobalt–molybdenum-sulfide catalyst and assayed for major and minor products. Distillation (boiling) curves were generated for the crude mixed oxyg...

Alkali and alkaline earth metal impurities found in diesel fuels are potential poisons for diesel exhaust catalysts. Using an accelerated aging procedure, a set of production exhaust systems from a 2011 Ford F250 equipped with a 6.7L diesel engine have been aged to an equivalent of 150,000 miles of thermal aging and metal exposure. These exhaust sy...

Nine flex-fuel vehicles meeting Tier 1, light duty vehicle-low emission vehicle (LDV-LEV), light duty truck 2-LEV (LDT2-LEV), and Tier 2 emission standards were tested over hot-start and cold-start three-phase LA92 cycles for non-methane organic gases, ethanol, acetaldehyde, formaldehyde, acetone, nitrous oxide, nitrogen oxides (NOx), carbon monoxi...

We examined the chemical composition and properties of several diesel fuels and blendstocks derived from Fischer–Tropsch (FT) synthesis, hydroisomerization of lipids, and fermentation of sugar via the terpenoid metabolic pathway. Comprehensive two-dimensional gas chromatographic analysis with nonpolar and polar columns, 13C NMR, GC-MS, and elementa...

The objective of this research project was to compare the emissions of oxides of nitrogen (NOx) from transit buses on as many as five different fuels and three standard transit duty cycles to establish if there is a real-world biodiesel NOx increase for transit bus duty cycles and engine calibrations. Prior studies have shown that B20 can cause a s...

Biodiesel, a renewable fuel consisting of fatty acid methyl esters and made from lipid feedstocks, has presented persistent cold weather operability problems that are not predicted using the standards tests common in the petroleum refining industry. These problems have been referred to as “precipitate formation above cloud point” and are known to b...

Experiments were conducted with ultra low sulfur diesel (ULSD) and 20% biodiesel blends (B20) to compare lube oil dilution levels and lubricant properties for systems using late in-cylinder fuel injection for aftertreatment regeneration. Lube oil dilution was measured by gas chromatography (GC) following ASTM method D3524 to measure diesel content,...

Three hydrotreated bio-oils with different oxygen contents (8.2, 4.9, and 0.4 w/w) were distilled to produce Light, Naphtha, Jet, Diesel, and Gasoil boiling range fractions that were characterized for oxygen containing species by a variety of analytical methods. The bio-oils were originally generated from lignocellulosic biomass in an entrained-flo...

The properties of ethyl (EL) and n-butyl levulinate (BL), two potential cellulose-derived diesel blend components, were assessed as both neat oxygenates and blends with diesel fuel. The samples tested were produced commercially from cellulose and alcohols but were not reagent-grade samples. They were relatively free of impurities, although EL conta...

Trace components present in biodiesel have been shown to contribute to the precipitation of solids at temperatures above the cloud point. These precipitates represent an operability problem for use of biodiesel in cold climates. Separation methods for analysis of trace lipid impurities, such as gas and liquid chromatography, have been problematic,...

The oxygenates ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol (isobutanol), 1-pentanol, 3-methyl-1-butanol (isopentanol), methyl levulinate, ethyl levulinate, butyl levulinate, 2-methyltetrahydrofuran (MTHF), 2-methylfuran (MF), and 2,5-dimethylfuran (DMF) were blended in three gasoline blendstocks for oxygenate blending...

A survey of the quality of biodiesel blends in the United States was conducted in the winter of 2009–2010. Forty samples were collected in the study; two-thirds of the samples collected were from areas with a 10th percentile minimum ambient temperature below −12°C. Fuel properties were measured and compared to the relevant ASTM D7467-09 specificati...

An accelerated durability test method determined the potential impact of biodiesel ash impurities, including engine testing with multiple diesel particulate filter substrate types, as well as diesel oxidation catalyst and selective catalyst reduction catalysts. The results showed no significant degradation in the thermo-mechanical properties of a D...

This report reviews the use of higher alcohols and several cellulose-derived oxygenates as blend components in gasoline. Material compatibility issues are expected to be less severe for neat higher alcohols than for fuel-grade ethanol. Very little data exist on how blending higher alcohols or other oxygenates with gasoline affects ASTM Standard D48...

The purpose of this study was to measure the impact of various sources of petroleum-based and bio-based diesel fuels on regulated emissions and fuel economy in diesel particulate filter (DPF) equipped diesel engines. Two model year 2008 diesel engines were tested with nine fuels including a certification ultra-low sulfur diesel (ULSD), local ULSD,...

Introduction Levulinic acid (4-oxopentanoic acid) is one product of the acid-catalyzed hydrolysis of cellulose, a major component of ligno-cellulosic biomass. Levulinic acid is a gamma keto acid, and the presence of multiple functional groups make it a versatile intermediate chemical. 1 It has been suggested as a starting material for many compound...