Martin L. Gorbaty

Direct determination and quantification of sulphur forms in heavy petroleum and coals: 1. The X-ray photoelectron spectroscopy (XPS) approach

X-ray photoelectron spectroscopy (XPS) was applied to the problem of speciating and quantifying organically bound forms of sulphur in non-volatile and solid hydrocarbons. XPS results from model compounds were used to interpret sulphur 2p signals from coals and heavy petroleum samples in terms of the amounts of alkyl sulphide and thiophen-like forms present. The determination of organic sulphur forms in Illinois No. 6 coal was accomplished by carefully monitoring the contributions due to iron sulphides and sulphates and application of the curve resolution method used with heavy petroleum samples. XPS data indicate that thiophenic sulphur forms the majority of the organic sulphur species in unoxidized Illinois No. 6 and Rasa coals.

Direct determination and quantification of sulphur forms in heavy petroleum and coals: 2. The sulphur K edge X-ray absorption spectroscopy approach

Abstract A sulphur K edge X-ray absorption spectroscopic method has been developed for the direct determination and quantification of the sulphidic and thiophenic forms of organically bound sulphur in non-volatile petroleum and coal samples. XANES spectra were taken of a number of model compounds, mixtures of model compounds, heavy petroleum and coal samples. A third-derivative analysis of these spectra allowed approximate quantification of the sulphidic and thiophenic components of the model mixtures and the heavy petroleum and coal samples.

Thermal reactivity of sulphur forms in coal

X-Ray absorption near edge structure spectroscopy (XANES), X-ray photoelectron spectroscopy (XPS) and temperature programmed decomposition (TPD) have been used to follow the chemical transformation of sulphur that takes place during the low temperature pyrolysis of coals of varying rank. This chemistry takes place under milder pyrolysis conditions than those required for the production of almost all of the other organic volatile matter of coal. The results provide evidence for the conversion of aliphatic sulphides to aromatic forms below 400 °C in addition to the elimination of some of the aliphatic sulphur forms as H2S. Results between temperatures of 400 and 750 °C indicate that a considerable amount of the aromatic sulphur forms identified by XPS and XANES in the chars made at 400 °C subsequently react (by 750 °C) to produce H2S. For some low rank coals, a direct relationship cannot be made between the initial aliphatic sulphur content and the total amount of H2S produced below 750 °C. A comparison of the TPD pattern of H2S evolution for high rank coal with those of chars made from lower rank coals at 400 °C shows that they are remarkably similar and suggests that the thermal reactions induced in sulphur species in laboratory pyrolysis experiments could be related to those that occur as a result of thermal reactions during coal metamorphism.

Chemistry of organically bound sulphur forms during the mild oxidation of coal

Abstract X-ray absorption near edge structure (XANES) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to study the chemistry of organically bound sulphur species in coal during mild coal oxidation. Spectra of preserved and oxidized samples were obtained and compared. Both techniques indicate that sulphide sulphur forms are converted to oxidized forms while the thiophenic forms remain largely untouched under these experimental conditions.

Characterization and reactivity of organically bound sulfur and nitrogen fossil fuels

Advances in X-ray instrumentation over the last decade have allowed the determination and quantification of organically bound sulfur and nitrogen forms in fossil fuels, which led to deeper understanding of their reactivities. This paper reviews recent technical advances in this area, highlights achievements of significant progress in chemical understanding and areas where further advances will likely occur.

Characterization and thermal reactivity of oxidized organic sulphur forms in coals

Abstract X-ray photoelectron spectroscopy (XPS) and sulphur K-edge X-ray absorption near edge structure spectroscopy (XANES) were used to define the transformations of organically bound sulphur forms during mild oxidation of three low pyrite coals, and the eight Argonne Premium coals. At the conditions studied (125°C, 5 days), both techniques indicate that aliphatic sulphides are selectively oxidized to sulphoxides and sulphones. In one case (Rasa) sulphonic acids were the major product of oxidation. Aromatic sulphur forms were relatively unreactive. The thermal reactivity of organically bound sulphur forms in oxidized coals was studied using a temperature programmed decomposition-mass spectrometry system coupled with XPS and XANES analysis of the solid reaction products. Hydrogen sulphide evolution from oxidized coals is suppressed relative to that evolved from unoxidized samples, sulphur dioxide evolves from oxidized samples and most oxidized sulphur forms are retained in the residues from thermal treatment.

Prominent frontiers of coal science: past, present and future

Abstract More fundamental knowledge of coal in terms of its structure and behaviour during various conversion processes is essential for generating the new technologies that will be required for the efficient and clean uses of coal as an energy source in the future. In this paper, the current state-of-the-science in each of several areas including coal characterization, combustion and liquefaction is discussed, along with suggested research opportunities in each area. These suggestions are coupled with an assessment of the impact such research programmes could have if successful.

Alkylation: a beneficial pretreatment for coal liquefaction

Abstract Several coals were alkylated employing isopropyl and methyl halides under Friedel-Crafts conditions. These alkylated coals, and corresponding untreated coals, were processed (liquefied) with tetralin in batch autoclaves (tubing bombs) at 700 K, 130 min residence time, and 10 MPa (1500 psi) hydrogen pressure. Conversion to cyclohexane-soluble liquids was found to be 10–21 percent higher (on an alkyl-group-free basis) for the alkylated coals than for untreated coals. These results are explained on the premise that alkylation beneficially disrupts the coal structure sufficiently to allow improved contacting between coal and tetralin.

Direct determination and quantification of organic sulfur forms by X-ray photoelectron spectroscopy (XPS) and sulfur k-edge absorption spectroscopy

Abstract The utility of X-ray Photoelectron Spectroscopy (XPS) and Sulfur X-ray Absorption Near Edge Structure (XANES) for the determination and quantification of sulfur forms in coal and petroleum asphaltenes has been demonstrated. XPS results showed differences in the Sulfur 2p signal which were interpreted in terms of the relative amounts of sulfur in sulfidic (163.3 eV) and thiophenic (164.1 eV) forms. Third derivatives of the XANES spectra from model compounds provided fingerprints for the discrimination of sulfur forms.

Stability of adamantane and its derivatives to coal-liquefaction conditions, and its implications toward the organic structure of coal☆

Abstract Adamantane, diamantane, 2-phenyladamantane, and adamantanone were shown to be stable to H-donor conditions, under which coals are converted to liquids (425 °C; 130 min; 2:1 tetralin to substrate). Both 1-adamantanol and 1-adamantane carboxylic acid were completely converted to adamantane. The data demonstrate the remarkable stability of this class of hydrocarbon, and argue against polyamantanes as models for major structural features of coals.