Analytical and Characterization Studies of Organic and Inorganic Species in Brown Coal

Abstract

Detailed studies have been carried out on the distribution of organic functional groups and inorganic species in as-received (ar) and acid-washed (aw) brown coals using elemental analysis, energy dispersive X-ray analysis (SEM-EDX), X-ray photoelectron spectroscopy (XPS), and Time-of-flight−secondary ion mass spectrometry (TOF−SIMS). Surface concentrations of the various carbon groups, organic oxygen, and inorganic hydroxide were obtained using XPS, but oxygen from clay and quartz, if present, interfered with organic oxygen determinations for the coals. A comparison of ar and aw coals using XPS and SEM-EDX is provided in terms of inorganic and organic sulfur groups. Chloride in these coals is present mainly as acid extractable forms, but small amounts of chloride in the organic matrix were indicated by the elemental analysis of ultra low-ash coals. TOF−SIMS fragments from brown coals were indicative of polymers consisting mainly of single aromatic groups linked by hydrocarbons with carboxyl and phenol functional groups. Sulfur fragments were from inorganic sulfur, thiols, organo-sulfates, and S−N−organic species. Numerous fragments containing organically bound chloride were observed. Fragments of the inorganic species Na, Mg, Al, Si, K, Ca, Ti, Cr, Fe, Mn, Ni, Cu, and Ga were also observed. Environmentally undesirable species, particularly from organo-sulfur and organo-chloride groups in brown coal, are likely to emerge from processes that heat coal−water mixture.

The role of activated carbons functionalized with thiol and sulfonic acid groups in catalytic wet peroxide oxidation

“…Phenol Quinone Anhydride Lactone Carboxylic Thiol Sulfonic AC 320 820 80 20 220 60 40 ACSA1 380 820 100 40 260 400 40 ACSA2 440 820 120 40 260 520 80 ACSA3 500 940 120 20 240 540 140 ACSA4 380 740 100 20 260 340 100 ACSA5 500 840 120 40 220 380 100 ACSA6 740 1100 160 60 420 [ [26][27][28][29]. Accordingly, XPS of S 2p core level were recorded for samples AC, ACSA3 and ACSA6 in order to confirm the presence of thiol and sulfonic acid groups on the carbon samples, as evidenced by TPD analysis.…”

Identification of basic nitrogen compounds in ethanol-soluble portion from Zhaotong lignite ethanolysis by positive-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

“…(neutral), pyridine (basic), and amide groups (basic) using X-ray photoelectron spectroscopy and 15 N nuclear magnetic resonance spectroscopy analyses [6][7][8][9][10][11]. Nevertheless, previous nondestructive analyses cannot afford detailed information on ONCs in coals at the molecular level.…”

A comparison of acid treatment in the dewatering of Chinese and Australian lignites by mechanical thermal expression at high temperatures

“…They reported an increased level of inorganic cation (Na, K, Mg and Ca) in the product water and their concentrations are dependent on the concentration of HCl solutions used. The reduction in the ash content was found to be more apparent in higher temperature treatments using acid washed coal [9,[11][12][13].…”