Joseph F. Rovani

Molecular weight polarity map for residua pyrolysis

Abstract A new molecular weight/polarity map was developed for petroleum residua based on the Scatchard–Hildebrand solubility equation. A series of extractions is performed with solvents of increasing solubility parameter, and the fractions are analyzed by vapor pressure osmometry for number average molecular weight, and analytical scale size exclusion chromatography for molecular weight spread. The results are diagnostic of the layers of solvation by resin-type molecules around a central asphaltene core. As thermal treatment progresses, the solubility parameter of the components of residua fractions increases, and the apparent molecular weight decreases. Coking onset appears to coincide with the depletion of resin-type asphaltene solubilizing components of residua and the formation of a bimodal system.

EN CORE® Sampler Performance: Storing Soil for VOC Analysis

The En Core® sampler is designed to collect and store soil samples in a manner that minimizes loss of contaminants due to volatilization and/or biodegradation. Use of this device is described in American Society for Testing and Materials (ASTM) Practice D 6418, Standard Practice for Using the Disposable En Core Sampler for Sampling and Storing Soil for Volatile Organic Analysis. Two studies were performed to evaluate the performance of the En Core sampler to store VOC-contaminated soil for analysis. One study involved spiking soil samples with low concentrations of VOCs (less than 200 µg/kg) and storing them under various conditions prior to analysis. Results from this study show that the En Core sampler gives 80% or greater recoveries of low concentrations of VOCs from soil samples stored under a number of conditions. The second study was performed to generate data on the performance of the 25-g En Core sampler to store soil samples spiked with EPA Method 1311, Toxicity Characteristic Leaching Procedure (TCLP), volatile organic analytes. Results show that the En Core device gives 80% or greater recoveries of most of the Method 1311 volatile organic analytes from soil stored under various conditions for 14 days.

Petroleum Processing Efficiency Improvement

A series of volatile crude oils was characterized using the Asphaltene Determinator oncolumn precipitation and re-dissolution method developed at Western Research Institute (WRI). Gravimetric asphaltenes and polars fractions from silica gel chromatography separation of the oils were characterized also. A study to define the differences in composition of asphaltenes in refinery desalter rag layer emulsions and the corresponding feed and desalter oils was conducted. Results indicate that the most polar and pericondensed aromatic material in the asphaltenes is enriched in the emulsions. The wax types and carbon number distributions in the two heptaneeluting fractions from the Waxphaltene Determinator separation were characterized by repetitive collection of the fractions followed by high temperature gas chromatography (GC) and Fourier transform infrared spectroscopy (FTIR). High resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICRMS) was conducted by researchers at the Florida State University National High Magnetic Field laboratory in a no-cost collaboration with the study.

Enhanced Oil Recovery: Aqueous Flow Tracer Measurement

A low detection limit analytical method was developed to measure a suite of benzoic acid and fluorinated benzoic acid compounds intended for use as tracers for enhanced oil recovery operations. Although the new high performance liquid chromatography separation successfully measured the tracers in an aqueous matrix at low part per billion levels, the low detection limits could not be achieved in oil field water due to interference problems with the hydrocarbon-saturated water using the systems UV detector. Commercial instrument vendors were contacted in an effort to determine if mass spectrometry could be used as an alternate detection technique. The results of their work demonstrate that low part per billion analysis of the tracer compounds in oil field water could be achieved using ultra performance liquid chromatography mass spectrometry.

HEAVY OIL PROCESS MONITOR: AUTOMATED ON-COLUMN ASPHALTENE PRECIPITATION AND RE-DISSOLUTION

About 37-50% (w/w) of the heptane asphaltenes from unpyrolyzed residua dissolve in cyclohexane. As pyrolysis progresses, this number decrease to below 15% as coke and toluene insoluble pre-coke materials appear. This solubility measurement can be used after coke begins to form, unlike the flocculation titration, which cannot be applied to multi-phase systems. Currently, the procedure for the isolation of heptane asphaltenes and the determination of the amount of asphaltenes soluble in cyclohexane spans three days. A more rapid method to measure asphaltene solubility was explored using a novel on-column asphaltene precipitation and re-dissolution technique. This was automated using high performance liquid chromatography (HPLC) equipment with a step gradient sequence using the solvents: heptane, cyclohexane, toluene:methanol (98:2). Results for four series of original and pyrolyzed residua were compared with data from the gravimetric method. The measurement time was reduced from three days to forty minutes. The separation was expanded further with the use of four solvents: heptane, cyclohexane, toluene, and cyclohexanone or methylene chloride. This provides a fourth peak which represents the most polar components, in the oil.

RESIDUA UPGRADING EFFICIENCY IMPROVEMENT MODELS: WRI COKING INDEXES

Pyrolysis experiments were conducted with three residua at 400 C (752 F) at various residence times. The wt % coke and gaseous products were measured for the product oils. The Western Research Institute (WRI) Coking Indexes were determined for the product oils. Measurements were made using techniques that might correlate with the Coking Indexes. These included spin-echo proton nuclear magnetic resonance spectroscopy, heat capacity measurements at 280 C (536 F), and ultrasonic attenuation. The two immiscible liquid phases that form once coke formation begins were isolated and characterized for a Boscan residuum pyrolyzed at 400 C (752 F) for 55 minutes. These materials were analyzed for elemental composition (CHNS), porphyrins, and metals (Ni,V) content.

FUELS IN SOIL TEST KIT: FIELD USE OF DIESEL DOG SOIL TEST KITS

Western Research Institute (WRI) has developed a new commercial product ready for technology transfer, the Diesel Dog{reg_sign} Portable Soil Test Kit, for performing analysis of fuel-contaminated soils in the field. The technology consists of a method developed by WRI (U.S. Patents 5,561,065 and 5,976,883) and hardware developed by WRI that allows the method to be performed in the field (patent pending). The method is very simple and does not require the use of highly toxic reagents. The aromatic components in a soil extract are measured by absorption at 254 nm with a field-portable photometer. WRI added significant value to the technology by taking the method through the American Society for Testing and Materials (ASTM) approval and validation processes. The method is designated as ASTM Method D 5831-96, Standard Test Method for Screening Fuels in Soils. This ASTM designation allows the method to be used for federal compliance activities. In June 2001, the Diesel Dog technology won an American Chemical Society Regional Industrial Innovations Award. To gain field experience with the new technology, Diesel Dog kits have been used for a variety of site evaluation and cleanup activities. Information gained from these activities has led to improvements in hardware configurations and additional insight into correlating Diesel Dog results with results from laboratory methods. The Wyoming Department of Environmental Quality (DEQ) used Diesel Dog Soil Test Kits to guide cleanups at a variety of sites throughout the state. ENSR, of Acton, Massachusetts, used a Diesel Dog Portable Soil Test Kit to evaluate sites in the Virgin Islands and Georgia. ChemTrack and the U.S. Army Corps of Engineers successfully used a test kit to guide excavation at an abandoned FAA fuel-contaminated site near Fairbanks, Alaska. Barenco, Inc. is using a Diesel Dog Portable Soil Test Kit for site evaluations in Canada. A small spill of diesel fuel was cleaned up in Laramie, Wyoming using a Diesel Dog Soil Test Kit.

FIELD SCREENING FOR HALOGENATED VOLATILE ORGANIC COMPOUNDS

Western Research Institute (WRI) initiated exploratory work towards the development of new field screening methodology and a test kit to measure halogenated volatile organic compounds (VOCs) in the field. Heated diode and corona discharge sensors are commonly used to detect leaks of refrigerants from air conditioners, freezers, and refrigerators. They are both selective to the presence of carbon-halogen bonds. Commercially available heated diode and corona discharge leak detectors were procured and evaluated for halogenated VOC response. The units were modified to provide a digital readout of signal related to VOC concentration. Sensor response was evaluated with carbon tetrachloride and tetrachloroethylene (perchloroethylene, PCE), which represent halogenated VOCs with and without double bonds. The response characteristics were determined for the VOCs directly in headspace in Tedlar bag containers. Quantitation limits in air were estimated. Potential interferences from volatile hydrocarbons, such as toluene and heptane, were evaluated. The effect of humidity was studied also. The performance of the new devices was evaluated in the laboratory by spiking soil samples and monitoring headspace for halogenated VOCs. A draft concept of the steps for a new analytical method was outlined. The results of the first year effort show that both devices show potential utility for future analytical method development work towards the goal of developing a portable test kit for screening halogenated VOCs in the field.

Validation of a New Soil VOC Sampler: Precision of the Performance of the En Core Sampler to Store Low VOC Concentrations

Soil sampling and storage practices for volatile organic analysis must be designed to minimize loss of volatile organic compounds (VOCs) from samples. The En Core{reg_sign} sampler is designed to collect and store soil samples in a manner that minimizes loss of contaminants due to volatilization and/or biodegradation. An American Society for Testing and Materials (ASTM) standard practice, D 6418, Standard Practice for Using the Disposable En Core Sampler for Sampling and Storing Soil for Volatile Organic Analysis, describes use of the En Core sampler to collect and store a soil sample of approximately 5 grams or 25 grams for volatile organic analysis. To support the ASTM practice, four studies have been performed to evaluate the performance of the En Core sampler for storage of soil samples spiked with VOCs. The first study was conducted to evaluate the performance of the device to store soil samples spiked with VOCs at high-level concentrations of approximately 2,500 {micro}g/Kg under various conditions. This analyte concentration in the soil was selected to limit the influence of the analytical method on the data. A second study was conducted to answer questions on the performance of the En Core sampler for storage of soil samples containing low-level (<200 {micro}g/Kg) concentrations of VOCs. In this study, soil samples were spiked with concentrations of VOCs at approximately 100 {micro}g/Kg and stored under various conditions prior to analysis. The third study was performed to generate data on the performance of the 25-gram En Core sampler to store soil samples spiked with EPA Method 1311, Toxicity Characteristic Leaching Procedure (TCLP), volatile organic analytes under various conditions for 14 days. The low-level performance data and TCLP analyte storage data are included in appendices to the ASTM practice, and the ASTM research report describing the high-level study is referenced in the practice. The fourth study, which is described in this report, was performed to estimate the precision of the performance of the 5-gram and 25-gram En Core samplers to store soil samples spiked with low concentrations of VOCs. This was done so that information on the precision of the performance of the devices can be added to the ASTM practice. Data generated in the precision validation study show very good precision of the performance of the En Core samplers to store soil samples spiked with low concentrations of a variety of VOCs.