C.V. Philip

Separation of coal-derived liquids by gel permeation chromatography

Abstract Coal-derived liquids, obtained from pilot plants and bench-scale reactors, have been separated by gel permeation chromatography into aromatic, phenolic, and asphaltenic fractions, where asphaltenes and long-chain hydrocarbons are in the same fraction. The Chromatographie system uses 10 nm μStyragel columns and solvents such as tetrahydrofuran (THF) and toluene. The separation is reasonably clean and almost devoid of overlapping. The saturated hydrocarbons are separated from the asphaltenes by vacuum distillation. Aromatic, phenolic and aliphatic fractions are characterized by high-resolution gas chromatography—mass spectrometry. The phenolic fraction contains alkylated phenols, indanols, and naphthols. The aromatic fraction is composed of alkylated benzenes, indans, naphthalenes and small amounts of multi-ring aromatics such as alkylated fluorenes and pyrenes. Most of the long-chain hydrocarbon fraction is of straight-chain alkanes ranging from tetradecane to tetratetracontane. Some branched alkanes, such as pristane and phytane, are also present. If olefins are present in the sample they also separate with the long-chain hydrocarbon fraction. Although various analytical data such as i.r., n.m.r., molecular size distribution and elemental composition of asphaltenes have been obtained, the chemical characterization is not complete. The gel permeation Chromatographie separation technique, as discussed in this paper, is very useful for fast analysis of any coal-derived liquid.

Chemistry of Texas lignite liquefaction in a hydrogen-donor solvent system

Abstract To study the nature of chemical cleavage and resultant product transfer from solid lignite phase to liquid phase, autoclave (300 cm 3 ) experiments have been carried out at pressures ranging up to 34 MPa and temperatures of 380–390 °C. The charge to the autoclave was freshly mined wet lignite, tetralin and hydrogen or helium. To obtain an indication of the reaction mechanisms underlying the liquefaction process, liquid and gas samples from the reactor at different time intervals were analysed. The gas samples were analysed by use of a multi-column, multi-valve automated gas Chromatograph, a system specially fabricated for coal-derived gas analysis. The liquid sample was filtered through Millipore filters and separate into three fractions by gel permeation chromatography. Fraction 1 is mostly colloidal carbon and high-molecular-weight species which cannot be separated on a g.c. Fractions 2 and 3 were analysed by gas chromatography — mass spectrometry (g.c.-m.s.). Fraction 2 represents the liquid products released from lignite and fraction 3 is mostly the tetralin and tetralin-derived products. Gel permeation chromatography (g.p.c.) followed by gas chromatography (g.c.) was used to devise a method for monitoring the extent of liquefaction. The production of carbon dioxide is at a maximum before the liquefaction reactions are at a significant rate. The source of carbon dioxide appears to be the carboxylic groups in lignite. The liquefaction reactions consume hydrogen from tetralin which undergoes dehydrogenation to form naphthalene. Once the lignite has undergone depolymerization, the tetralin to naphthalene conversion slows down. The continued heating of lignite conversion products in excess of tetralin does not appear to alter the molecular size distribution of the liquid product. The distillable fraction of lignite-derived liquid is composed of various alkylated phenols and aromatics and alkanes, and they are formed simultaneously.

GPC characterization for assessing compatibility problems with heavy fuel oils

Precipitation of solids is one of the major problems associated with the shipping and handling of heavy residual oils especially No. 6 heating oil. ASTM specifications which currently include viscosity, flash point and pouring point are not adequate to predict the handling problems. The residual oils are becoming more complex in composition due to modern refinery techniques for cracking the heavier residues into distillable fractions. In this study, several heating oil samples, including a sample which partially solidified during transport, were analyzed using various techniques including separation by gel permeation chromatography (GPC), vacuum distillation, separation of petroleum asphaltenes by ASTM method, elemental analysis and proton and 13C NMR spectroscopy. The distillable species in the fraction separated by GPC were characterized by high resolution gas chromatography-mass spectroscopy (GC-MS). The study showed that the GPC can be used as a reliable technique for the analysis of heavy residual oils. The GPC separation of No. 6 heating oil gave three fractions enriched with chemically distinct asphaltenes. The second fraction was mostly straight chain paraffins. The third fraction was composed of low molecular weight aromatics. Although occasional verification of GPC data by GC-MS and by NMR spectroscopy is desirable, the GPC alone is an efficient analytical tool for evaluating the composition as well as predicting the handling problems associated with shipping and storage of various residual oils.

Development and Properties of Cesium Selective Crystalline Silicotitanate (CST) Ion Exchangers for Radioactive Waste Applications

Crystalline silicotitanates (CSTs) are a new class of ion exchangers that were jointly invented and refined by researchers at Sandia National Laboratories and Texas A&M University. One particular CST, known as TAM-5, is remarkable for its ability to separate parts-per-million concentrations of cesium from highly alkaline solutions (pH>14) containing high sodium concentrations (>5M). It is also highly effective for removing cesium from neutral and acidic solutions, and for removing strontium from basic and neutral solutions. Cesium isotopes are fission products that account for a large portion of the radioactivity in waste streams generated during weapons material production. Tests performed at numerous locations with early lab-scale TAM-5 samples established the material as a leading candidate for treating radioactive waste volumes such as those found at the Hanford site in Washington. Thus Sandia developed a Cooperative Research and Development Agreement (CRADA) partnership with UOP, a world leader in developing, commercializing, and supplying adsorbents and associated process technology to commercialize and further develop the material. CSTs are now commercially available from UOP in a powder (UOP IONSIV® IE-910 ion exchanger) and granular form suitable for column ion exchange operations (UOP IONSIV® IE-911 ion exchanger). These materials exhibit a high capacity for cesium in a wide variety of solutions of interest to the Department of Energy, and they are chemically, thermally, and radiation stable. They have performed well in tests at numerous sites with actual radioactive waste solutions, and have been demonstrated in the Cesium Removal Demonstration at Oak Ridge National Laboratory with over 30,000 gallons of Melton Valley Storage Tank waste. It has been estimated that applying CSTs to the Hanford cleanup alone will result in a savings of more than

Liquid sulphur dioxide — a reagent for the separation of coal liquids

300 million over baseline technologies.

Dissolution of wet Texas lignite in tetralin

Abstract Liquid sulfur dioxide has been found to be an excellent solvent for coal derived liquids. The higher alkanes and mineral matter are insoluble in this solvent and they are effectively separated. The sulfur dioxide-soluble fraction is very low in ash content. However, no improvement is achieved with respect to sulfur content. The soluble fraction has been separated by gel permeation chromatography and a large number of components have been identified.

Dry process for recovering gallium from weapons plutonium using a rotary furnace equipped with a copper collector

Abstract Texas lignite with about 30% moisture is dissolved in tetralin with a gas overpressure of hydrogen or helium. Reaction temperature of about 375°C, which gave the maximum amount of liquid products, was used for most of the experiments. The effect of hydrogen versus helium on lignite dissolution in tetralin is observed as marginal. The products consisted of a tetralin-rich phase, a residue saturated with the tetralin-rich phase and lignite-conversion products, and a water-rich phase. The oily liquid phase is separated from the residues by injecting water saturated with CO 2 under high pressure. Ninety percent of the tetralin is recovered in the oily phase while 10% of the tetralin remained trapped in the pores of the solid residue.

Use of silicotitanates for removing cesium and strontium from defense waste

Currently the separation of gallium from weapons plutonium is achieved using complex aqueous processing involving solvent extraction and ion exchange; this process generates large quantities of wastewater containing radioactive materials. At Los Alamos National Laboratory, researchers have been developing a simpler alternative process referred to as the thermally induced gallium removal (TIGR) process; vaporized gallium suboxide is swept away by passing hydrogen/argon over gallium trioxide/plutonium oxide heated at 1100 °C or higher. During the TIGR process some of the gallium suboxide prematurely decomposes to gallium metal and gallium trioxide, which deposit on furnace and vent surfaces.