Adventures in maceral separation

Progress has been made in recent years in the science of maceral separation. However, there are many areas that can be improved and new areas investigated. Power of density gradient centrifugation to physically resolve macerals and submaceral species coupled with other instrumental techniques is attractive for defining the limits of coal heterogeneity as well as investigating the ability of other separation methods

Chemically modified coal macerals. Separation, density and surface area variations

Two Argonne Premium Coals were O-alkylated and O-acylated using a variety of different reagents, and then separated using density gradient centrifugation (ADGC). The separation data suggested that the hydroxyl groups are fairly evenly distributed in the maceral particles. However, several reagents produced results counter to this generalization, and exhibited enhanced maceral separation. Comparison of ADGC densities and He densities of the modified coals showed several reactivity families that appear to be based on wettability differences. Surface areas were also measured; areas as high as 200 m{sup 2}/g were obtained for some modified coals. The data suggest that there is an optimum molecular size for the added group that leads to the large areas

Determination of sulfur compounds in coal by mass spectrometry, correlated with XANES and XPS

The objective of this study is to identify important organic sulfur-containing compounds in the Argonne Premium Coals and in selected, separated coal macerals. In-source, desorption/pyrolysis high resolution mass spectrometry is being used to characterize the volatile species of whole coals, macerals, and their extracts. To examine the possibility of secondary reactions and undesirable selectivity, the MS data is compared to data from direct techniques, XANES and XPS. The MS results con-elate very well which supports the suggestion that the species seen are indigenous to the original sample. Therefore, specific structural assignments to the sulfur species can be made. Quantitative speciation of organic sulfur in coals has been accomplished by both XANES and XPS with what appears to be good reliability. Mass spectrometry approaches provide more detailed molecular information, but suffer from problems with sampling. In the past we have found it difficult to isolate aliphatic sulfur compounds by thermal desorption or pyrolysis due to their thermal transformation to aromatic species. However, recently we have found that with in-source pyrolysis the occurrence of secondary reactions is reduced significantly. Results from both a selected setof the Argonne Premium Coal Samples and a set of three macerals from the Listen-Stockton coal (APCS 7) are discussed