Catalytic Hydroconversion Of Xinghe Lignite Over Supported Iron Catalyst

In this paper, supported Fe/attapulgite powder(AP) was prepared by thermally decomposing iron pentacarbonyl onto AP in an autoclave. Multiple characterizations of Fe/AP reveal that high dispersive and low loaded metal Fe nano particles with diameter of 5-30 nm were successfully loaded on AP surface, and the supported Fe interacts with the skeleton structure of AP. The catalysis of Fe/AP for di(1-naphthyl)methane(DNM), a coal-related model compound, was investigated with sublimed sulfur as the additive under hydrogen atmosphere. The results show that Fe-S/AP exhibits high catalytic activity, selectivity, and stability for cleaving Car-Cal bond in DNM.Coals contain more or less solvent-soluble molecules, which not only disturb the identification of products from coal conversion, but also exercise negative influences on catalyst activity and coal reactivity. Xinghe lignite(XL) was sequentially extracted with petroleum ether, carbon disulfide, methanol, acetone, and isometric carbon disulfide/acetone mixed solvent at room temperature to isolate the soluble small molecules from XL as much as possible. The extraction residue(ER) was subjected to thermal dissolution in methanol at 300 oC to afford thermal dissolution residue(TDR). XL, ER, and TDR were directly characterized by solid-state 13 C nuclear magnetic resonance, X-ray photoelectron spectrometry, Fourier transform infrared(FTIR) spectrometry, and thermogravimetry. The results suggest that the macromolecular composition of XL differs hardly from that of ER, since extraction cannot destroy the skeleton structure of XL. However, the rupture of covalent bonds, such as Cal-Cal, Cal-O, Cal-N, and Cal-S in ER occurs during thermal dissolution in methanol, leading to large difference in organic structure between TDR and ER.XL, ER, and TDR were used as the reactants and subjected to noncatalytic hydroconversion(NCHC) and catalytic hydroconversion(CHC) in the presence of Fe/AP and sulfur at 300 °C. The molecular compositions of conversion products were analyzed using FTIR and gas chromatography/mass spectrometry(GC/MS). The results show that the yields of soluble portions(SPs) from CHC of XL, ER, and TDR are obviously higher than those from NCHC. In addition, the SPs from ER reach a biggest increase of 20% in yield before and after catalysis, suggesting that the catalytic effect of Fe-S/AP on ER is more significant after the separation of small molecules from XL through sequential extraction. According to GC/MS analysis, the group components in SPs from NCHC and CHC of XL, ER, and TDR consist of alkanes, alkenes, arenes, oxygen-containing species and small amounts of nitrogenand sulfur-containing species, most of which contain alkyl(methyl, ethyl, and isopropyl) moieties. Alkanes, arenes, and arenols are the main group components, the yields of which from CHC are remarkably higher than those from NCHC, especially arenols and arenes. Normal alkanes with C13-C33 are the main detected alkanes. The ring number of arenes is from 1 to 4 and 1- and 2-ring arenes are predominant. Arenols are the most important group components and dominated by phenols, naphthols, and indenols, among which phenols predominate. The addition of active hydrogen atoms catalytically generated over Fe-S/AP to the ipso-position of condensed aromatic rings(CARs) in XL, ER, and TDR could play a crucial role in cleaving-CH2- and-O- linkages connected to the CARs and thereby enhanced the yields of alkylarenes and alkylarenols through CHC. Meanwhile, the partial hydrogenation of some CARs during CHC could promote the sequential radical hydrogen transfer reactions catalyzed by Fe-S/AP along with thermal rupture of some relatively strong bonds to produce soluble molecules.