Effect of catalyst dispersion on coal liquefaction with iron catalysts

Clean liquid fuels from direct coal liquefaction: chemistry, catalysis, technological status and challenges

“…The same trend was observed from the work reported by same researchers later (Table 10). 229 In the absence of a carbonaceous support, the transformation of FeOOH to iron sulfide results in a loss of surface area, possibly due to agglomeration. The presence of a carbonaceous support for FeOOH tends to mitigate particle size growth and favors the formation of smaller particle-sized iron sulfide catalysts that are likely to have high specific surface areas.…”

“…The presence of a carbonaceous support for FeOOH tends to mitigate particle size growth and favors the formation of smaller particle-sized iron sulfide catalysts that are likely to have high specific surface areas. 229 In the case of low rank coals, ion exchange procedures have been used to replace surface carboxyl-bound calcium or magnesium ions by iron ions, which under liquefaction conditions are converted to highly dispersed and catalytically active iron species. 230,231 Kaneko et al reported that a synthetic g-FeOOH catalyst (lepidcrocite) exhibited an excellent liquefaction activity because of its transformation into smaller crystallite size of pyrrhotites (Fe 1Àx S) under liquefaction conditions.…”

“…Effect of FeOOH mode of addition on coal conversion of DECS-6 blind canyon coal, Illinois No. 6, and Black Thunder coal229 …”

Catalysis in Direct Coal Liquefaction

“…Oxide and sulfide catalysts have been dispersed by physically mixing powders or suspensions of catalysts with coal. Under appropriate conditions, the high dispersion of the precursor is maintained during the in situ transformation to the active catalyst phase, whereas agglomeration can occur by using physical mixtures of precursor and coal [9,97,[99][100][101]107]. Impregnation/precipitation techniques were used to generate iron oxyhydroxide directly on the coal [101,106].…”

The relationship between the microstructures and catalytic behaviors of iron–oxygen precursors during direct coal liquefaction

“…Zhao et al [23,24] has suggested that it is also important for the catalyst to maintain its dispersion at high temperatures, based on a comparative study of an ultrafine catalyst (with an average particle diameter of 3 nm) and two binary iron oxide catalysts (Si/ferrihydrite and Al/ferrihydrite, with average particle diameters of 5 and 10 nm, respectively). Cugini [25] reported that liquefaction feed coal not only promoted the generation of ultrafine FeOOH but also assisted in dispersing the Fe1−xS that was generated in situ during DCL. It is worth noting that ultrafine γ-FeOOH catalysts supported on coal have been successfully applied in the first megaton DCL industrial demonstration plant, operated by the Shenhua Group [26][27][28].…”