| The Raney Fe and Raney Fe-Mn catalysts were prepared by leaching the aluminum from Al-Fe (50/50 weight percent, wt %) and Al-Fe-Mn (59/38/3 wt %) alloys with an aqueous solution of sodium hydroxide (2 to 20 wt %) in the temperature range of 298 to 363 K by two different leaching modes, caustic or alloy addition.;The optimum reduction temperature was found to be 648 K for the Raney catalysts (Fe and Fe-Mn) and 673 K for the precipitated catalysts (Fe and Fe-Mn) from thermogravimetric analyses. The Raney and precipitated catalysts, reduced in-situ in flowing hydrogen, were evaluated for the hydrogenation of carbon monoxide in a high-pressure fixed-bed reactor at the following standard reaction conditions: pressure = 1465 KPa, space velocity = 3.0 cm('3)g('-1)s('-1), H(,2)/CO = 2.0, and reaction temperature of 423 to 473 K.;The Raney Fe and Raney Fe-Mn catalysts were 2 to 4 times more active in terms of carbon monoxide conversion than the corresponding precipitated Fe and Fe-Mn catalysts, respectively, at the standard reaction conditions. The activation energy ranged from 96 to 139 KJ/mol depending on different catalysts. The C(,2)-C(,4) hydrocarbon yields for the Raney Fe and the Raney Fe-Mn catalysts were similar, ranging from 34 to 40 percent at 453 K. However, the Raney Fe-Mn catalysts showed higher C(,2)-C(,4) olefin selectivity than the Raney Fe catalysts. The same trend was found for the precipitated Fe and coprecipitated Fe-Mn catalysts. Less than 7 wt % Mn in the coprecipitated Fe-Mn and in the Raney Fe-Mn catalysts increased the olefin selectivity of the catalyst by a factor of about two.;The major phase in all the Raney Fe and Raney Fe-Mn catalysts was found to be (alpha)-Fe from X-ray diffraction study. The BET surface area of the Raney Fe catalyst ranged from 26 to 54 m('2)/g, while it ranged from 64 to 116 m('2)/g for Raney Fe-Mn catalysts depending on the preparation conditions. The crystallite size of the (alpha)-Fe in the Raney catalysts, estimated by X-ray line broadening, ranged from 70 to 250 (ANGSTROM) and it increased with increasing leaching temperature. |
