Howard Freund

Determination of Structural Building Blocks in Heavy Petroleum Systems by Collision-Induced Dissociation Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Collision-induced dissociation Fourier Transform ion cyclotron resonance mass spectrometry (CID-FTICR MS) was developed to determine structural building blocks in heavy petroleum systems. Model compounds with both single core and multicore configurations were synthesized to study the fragmentation pattern and response factors in the CID reactions. Dealkylation is found to be the most prevalent reaction pathway in the CID. Single core molecules exhibit primarily molecular weight reduction with no change in the total unsaturation of the molecule (or Z-number as in chemical formula C(c)H(2c+Z)N(n)S(s)O(o)VNi). On the other hand, molecules containing more than one aromatic core will decompose into the constituting single cores and consequently exhibit both molecular weight reduction and change in Z-numbers. Biaryl linkage, C(1) linkage, and aromatic sulfide linkage cannot be broken down by CID with lab collision energy up to 50 eV while C(2)+ alkyl linkages can be easily broken. Naphthenic ring-openings were observed in CID, leading to formation of olefinic structures. Heavy petroleum systems, such as vacuum resid (VR) fractions, were characterized by the CID technology. Both single-core and multicore structures were found in VR. The latter is more prevalent in higher aromatic ring classes.

O2 oxidation studies of the edge surface of graphite

We have studied the reactive adsorption of O2 on the edge surface of graphite. At 300°C the efficiency of oxygen uptake showed a strong coverage-dependent reactive adsorption coefficient. In general, the efficiencies were low (< 10−9) over the majority of the coverage range. In contrast, the uptake of oxygen from O2 and H2O on sputter-damaged graphite was far more rapid. Sputter-damaged carbon surfaces exhibit greatly enhanced reactivity and are poor models of edge carbon activity. Thermal stability studies on the resultant oxidized edge graphite surfaces provide information about the energetics of product formation in gasification reactions. CO was the dominant product. A fraction of the oxygen on the surface is very tightly bound with energies greater than 85 kcal/mole. The energy decreases to 70 kcal/mole over a wide coverage range. At the highest attainable coverages representing a small fractional population, the energy decreases further down to 58 kcal/mole. Our results show that increasing the amount of oxygen surface coverage decreases the energy barrier for gaseous CO formation but increases the barrier for O2 dissociation.

A comparison of O2 and CO2 oxidation of glassy carbon surfaces

We have separated and studied with surface spectroscopies the dissociative adsorption step from the CO formation step in the O2 and CO2 gasification of glassy carbon. The reactive adsorption probabilities decreased with increased coverage. Differences between O2 and CO2 were apparent at high oxygen coverages where the dissociative adsorption probability at 300°C for CO2 drops below 10−14, which is orders of magnitude less than that of O2. Estimates for the activation energy for dissociative adsorption at high coverage are 32 kcal/mol for O2 and 50–60 kcal/mol for CO2. We have examined the thermal stabilities of the resultant oxidized surfaces that yield desorption energies and provide quantitative information about the product formation step in gasification reactions. A substantial fraction of the oxygen on the carbon surface is very stable with CO formation energies of >80 kcal/mol. The energies decrease as a function of increasing oxygen coverage and at high coverages decrease below 70 kcal/mol. The energetics of CO formation from lattice carbon limit the rate of gasification by CO2. The increased gasification activity for O2 is associated with a more facile gaseous dissociation step causing higher oxygen coverages, which in turn generates lower energy CO formation sites.

The sulfur retention of calcium-containing coal during fuel-rich combustion

Abstract The fuel-rich combustion of coals containing calcium in various forms has been studied in a tubular downflow reactor to determine whether or not coal-bound sulfur can be efficiently retained as CaS in the recovered solids. Although physical mixtures of coal and limestone gave only limited sulfur retention, it was discovered that, under certain critical conditions, coals in which calcium had been atomically dispersed by ion exchange could be burned with the bulk of the sulfur remaining in the recovered ash/char mixture. The effect of various experimental parameters upon this new sulfur retention process are reported. Char characterization was done using scanning electron microscopy and x-ray diffraction. Analysis of the data indicated that under the conditions of these experiments, the extent of CaS formation was equilibrium limited when ion exchange Ca was used but less than equilibrium for bulk Ca.

The Science of Mineral Matter in Coal

Publisher Summary This chapter discusses the modes of occurrence of inorganic elements in coal, both as mineral phases and as organically bonded elements. The effects that highly dispersed elements may have on coal processing are also reviewed in the chapter. Mineral matter plays a variety of important roles in all coal utilization processes. Inorganically bound elements in present-day coals are the result of at least five mechanisms operating at or from the time of initial peat deposition: (1) incorporation of elements from the original plant material; (2) precipitation of elements from aqueous solution; (3) accumulation of airborne detritus; (4) accumulation of waterborne detritus; and (5) epigenetic mineralization, that is, minerals that have formed in cleats and fractures of the coal deposit. Accumulation of detrital mineral particles and the chemical precipitation of dissolved species from aqueous solution are the major processes by which inorganic elements are introduced into the peat deposit from external sources.

The Kinetics of Limestone/Dolomite with H2S Under Rich Combustion Conditions

Abstract The kinetics of the reaction of limestone/dolomite with H2S have been examined under fuel rich combustion conditions. The experiments were done in a tubular laminar flow reactor with co-current flow of gas and solids. In the temperature region, 1065-1310°C, the results were consistent with the absorption reaction of H2S first order with respect to calcium and half order with respect to H2S. Reactivity of the stones fell off substantially between 1065-1310°C because of severe desurfacing occurring at these temperatures to the limestone and dolomite. A diffusion controlled reaction is believed to be the dominant mechanism.