Thermal desulfurization of pyrite: An in situ high-T neutron diffraction and DTA–TGA study

Abstract

Abstract

Thermal Evolutions and Resulting Microstructural Changes in Kerogen-Rich Marcellus Shale

“…35−37 Further, during stage II, pyrite (FeS 2 ) decomposes to pyrrhotite (Fe 1−x S) completely by 600 °C and finally to troilite (FeS) at 800 °C. 38 Finally, stage III (−5.88 wt %), 750−1000 °C, contains the decarbonation of carbonate phases, including hydrated carbonate phases; see the DTG and DSC (endothermic) peaks at ∼727 and ∼737 °C, respectively, as well as the m/z = 18 peak at 784 °C and m/z = 44 peaks at ∼734 and ∼784 °C. 39 The higher temperatures of carbonate decomposition are likely due to mass transfer limitations within the tight void space of the shale structure.…”

“…The mass loss is higher than in the pyrolysis (N 2 ) environment, expected to be due to coking of kerogen and incomplete desulfurization of pyrite, as pyrite decomposes to pyrrhotite and then troilite (FeS). 38 Multi-stage Inert Oxidative Thermal Analysis. To further investigate the decomposition of kerogen and the influence of oxygen, we conduct a multi-stage thermal treatment analysis, whereby we (1) dynamically heat from 40 to 600 °C at 5 °C/min in N 2 , (2) isothermally heat at 600 °C for 30 min in N 2 , (3) introduce air and continue isothermally heating for 30 min, and (4) dynamically heat from 600 to 1000 °C at 5 °C/min in air.…”

“…Of our highlight phases, those present in high amounts and relevant in gaseous evolutions from shale, pyrite has the lowest thermal stability, decomposing at about 400 °C, but reacts "quickly" compared to the decomposition of kerogen products, which occurs over a large range of temperatures (400−600 °C). 38 Kerogen cannot be treated as one simple compound as a result of its extremely complex carbon networks and structures formed under geochemical environments. The decomposition of kerogen is a kinetically complex phenomenon with intercompeting reactions: faster heating rates lead to higher coking, and slower heating rates lead to more evolved hydrocarbons.…”

“…Stage II (−7.48 wt %) sees the decomposition of kerogen into light and heavy organics, inorganic gases, and coke from 450 to 750 °C, shown by the DTG and DSC (endothermic) peaks at 534 and 524 °C, respectively. − , The DSC peak occurring before the DTG peak points to mass transport limitations as a result of the inaccessible closed and open pores within rock and kerogen networks. Water and CO 2 are evolved from the decomposition of carbonates, suggested by m / z = 18 peaks at 534 and 654 °C and m / z = 44 peaks at 569 and 654 °C. − Further, during stage II, pyrite (FeS 2 ) decomposes to pyrrhotite (Fe 1– x S) completely by 600 °C and finally to troilite (FeS) at 800 °C . Finally, stage III (−5.88 wt %), 750–1000 °C, contains the decarbonation of carbonate phases, including hydrated carbonate phases; see the DTG and DSC (endothermic) peaks at ∼727 and ∼737 °C, respectively, as well as the m / z = 18 peak at 784 °C and m / z = 44 peaks at ∼734 and ∼784 °C .…”

Bulk synthesis of stoichiometric/meteoritic troilite (FeS) by high‐temperature pyrite decomposition and pyrrhotite melting

“…In previous studies, the synthesis of pyrrhotite (Fe 1− x S) or troilite (FeS) was achieved using chemical (Akhtar et al., 2013; Pedoussaut & Lind, 2008; Roberts et al., 2018) or thermal treatment (Boyabat et al., 2003; Coats & Bright, 1965; de Oliveira et al., 2018; Onufrienok et al., 2020; Selivanov et al., 2008; Xu et al., 2019). For example, the synthesis of pyrrhotite by heating pyrite at high temperature (<1100 K) in CO 2 or N 2 atmosphere (Boyabat et al., 2003; de Oliveira et al., 2018) or the synthesis of troilite from pyrite at higher temperature under vacuum (1200 K; Onufrienok et al., 2020) was successfully achieved.…”