Reductive pyrolysis of miocene-aged lignite lithotypes using MS and GC/MS detection systems for analysis of organic sulphur groups

Abstract

The atmospheric pressure temperature programmed reduction (AP-TPR) technique, an approach for organic sulphur speciation, was extended by mass spectral detection. The coupling gave ground for precise assignment of sulphur compounds in flue gases of lignite lithotypes pyrolyzed in H2 atmosphere. A broad range of sulphur compounds was determined, i.e. thiols, dimethylsulphide, dimethyldisulphide, CS2, thiophenes, benzothiophenes and their alkylated homologues. Certain peculiarities in organic sulphur distribution in lithotypes under study were noticed. Humovitrain was the lithotype with the highest organic sulphur content. A preponderance of aliphatic sulphur, thiols and dimethylsulfides were determined for both homogeneous lithotypes (xylain and humovitrain). In humovitrain, additionally thiophenes were also identified. For heterogeneous lithotypes, liptain and humoclarain, a dominance of disulphides and an almost lack of sulphides was observed. This is an indication that with coalification a gradual loss of aliphatic sulphur functions has proceeded, where more resistant disulphides sulphur bridges turned out to be present. Thiophenes are the most abundant aromatic structures, dominating in humoclarain. Some amounts of oxidised organic sulphur compounds (1% up to 4.1% of Sorg) were semi-quantitative determined in lithotypes using AP-TPR-MS.