A C/MoS2 mixed-layer phase (MoSC) occurring in metalliferous black shales from southern China, and new data on jordisite

A new phase composed mainly of Mo, S, and C and referred to herein as MoSC occurs widely in organic-rich, metalliferous Cambrian black shales in south China. MoSC, which has previously been referred to as jordisite, has been studied by scanning electron microscopy (SEM), electron microprobe analysis (EMPA), transmission electron microscopy (TEM), powder X-ray diffraction, (XRD), extended X-ray absorption fine structure (EXAFS), and catalytic acti vity. TEM data show MoSC to have a layered structure, with packets resembli ng molybdenite and graphite-like carbon that average five layers in thickne ss. Analytical data are consistent with an idealized formula of Mo3S6C10 to but it commonly contains 1-3 wt% each of Fe, Ni, and As so that its compos ition may be better approximated by the formula (Mo,Fe,Ni)(3)(S,As)(6)C-10. Selected area electron diffraction (SAED) patterns show a small number of broad, inhomogeneous rings corresponding to randomly oriented layers arrang ed in subspherical cells. A single broad, weak peak corresponds to a 10-11 W layer spacing in powder XRD diffraction patterns. Pseudomorphism after fo ssil bacteria implies an origin by replacement of sedimentary organic mater ial. In its chemical properties and structure, MoSC resembles synthetic com pounds used as catalysts for hydrodesulfurization (HDS) in the petrochemica l industry. The large surface-to-volume ratio for MoSC may be an important factor in its relatively strong HDS catalytic activity. Cotype samples of jordisite from Germany, previously thought to be amorphou s MoS2, were also studied by SEM and TEM. Jordisite occurs as sequences of a few curved layers that form subspherical units, with an appearance remark ably like that of MoSC. However, the layer spacing is similar to6 W, like t hat of molybdenite. The ratio of Mo:S is similar to1:2, and no carbon was d etected, although it coexists with kerogen. Jordisite is thus confirmed to be a form of MoS2, but because powder diffraction-like SAED patterns were o btained, it is not amorphous.