The present work is an investigation of how the process conditions influence the synthesis of mixed alcohols from syngas over a K 2 CO 3 /Co/MoS 2 /C catalyst. The emphasis in the investigations is upon the effects of H 2 S in the syngas feed. However the effects of the temperature and of the partial pressures of H 2 and CO are also investigated. With or without H 2 S in the feed the pre-sulfided catalyst requires an initiation period to reach a stabilized behavior, but the duration of this period depends upon the H 2 S level. Operation with a feed containing more than 103 ppmv H 2 S leads to a fairly rapid stabilization of the product distribution and ensures that higher alcohols are the dominant reaction products. With less than 57 ppmv H 2 S in the feed the stabilization of the product distribution is much slower, and methanol is the dominant product. An investigation of the reaction kinetics indicates a high CO coverage and low hydrogen coverage. Hydrogen sulfide in the syngas feed generally promotes chain growth for both alcohols and hydrocarbons, but lowers the alcohol selectivity by enhancing the hydrocarbon formation. The highest alcohol productivity reached in these investigations was 0.276 g/g cat./h, and this was achieved at 350 °C, 100 bar, GHSV = 5244 h −1 , Feed: 49.9 vol% H 2 , 50.1 vol% CO. Finally it is found that sulfur fed to the reactor as H 2 S is incorporated into the condensed alcohol product, and the incorporation of sulfur species into the product continues for some time after H 2 S has been removed from the feed. When the catalyst is operated with an S-free syngas feed, the amount of sulfur in the condensed liquid product decreases over time, but after 35 h of operation with an S-free syngas the alcohol product still contains 340 ppmw of sulfur. Thiols appear to be the dominant sulfur compounds in the product.

Effects of H2S and process conditions in the synthesis of mixed alcohols from syngas over alkali promoted cobalt-molybdenum sulfide

The effects of Mo loading (0−12 wt %) on the properties of activated-carbon- (AC-) supported Fe−Cu−K catalysts and their performance for Fischer−Tropsch synthesis are studied. Physicochemical properties studied include particle size, reducibility, and dispersion, and catalytic properties include activity, selectivity, and stability. Catalysts were characterized by N2 adsorption, energy-dispersive spectroscopy, X-ray diffraction (XRD), H2 temperature-programmed reduction (TPR), and CO chemisorption. Catalyst performance was studied at 310−320 °C, 2.2 MPa, 3 Nl/g-cat/h, and H2/CO = 0.9. Reaction results in a fixed-bed reactor show that addition of 6% Mo into the Fe−Cu−K/AC catalyst improves catalyst stability without sacrificing activity, but activity is suppressed dramatically on a 12% Mo-loaded catalyst. Detectable hydrocarbons of C1 to C34 are produced on the Fe−Cu−K/AC catalysts with or without Mo. However, the addition of Mo results in the production of more CH4 and less C5+ hydrocarbons. The Mo promot...

Mo−Fe Catalysts Supported on Activated Carbon for Synthesis of Liquid Fuels by the Fischer−Tropsch Process: Effect of Mo Addition on Reducibility, Activity, and Hydrocarbon Selectivity

A series of silica-supported iron samples has been prepared by the microemulsion technology. The samples were characterized by temperature programmed reduction (TPR), UV–vis spectroscopy, N2 adsorption isotherms, X-ray photoelectron spectra (XPS), SEM and transmission electron microscopy (TEM) microscopy and tested in the carbon monoxide and carbon dioxide hydrogenation reactions. Although all samples have similar composition and metallic loading, the preparation route was crucial for the actual nature of the samples, tuning also their catalytic performance. The main result of the preparation route was the extension of the degree of the interaction between the active phase and the support. As a consequence, samples where a metal–support interaction was promoted showed a lower reducibility and therefore a lower catalytic activity. The addition of Mn, Cu and K promoters improves the catalytic performance in carbon monoxide hydrogenation. The low activity of the samples in carbon dioxide hydrogenation is due to their low reverse water–gas shift activity.

Carbon oxide hydrogenation over silica-supported iron-based catalysts influence of the preparation route

Tungsten catalysts supported on an activated carbon were prepared, with different metal loading, by using either ammonium tungstate or tungsten hexacarbonyl as metal precursor compounds. The catalysts so prepared were heat treated in H2 flow at 748 and 973 K or in He flow at 1223 K. The heat-treated catalysts were characterized by N2 adsorption at 77 K and mercury porosimetry, to determine their surface area and porosity, and by XPS and XRD, to evaluate the chemical state and dispersion of the active phase. These catalysts were tested in the hydrogenation reaction of ethene. The treatments in H2 yielded an active phase composed of metallic tungsten and tungsten trioxide, whereas the treatment in He generated a mixture of metallic tungsten, tungsten carbide, and tungsten trioxide. The catalysts containing tungsten carbide were the most active in the hydrogenation of ethene, even at a temperature as low as 273 K, although their rate of deactivation was dependent on reaction temperature; the lower the reacti...

R.D. Oades

Papers

Carbon supported molybdenum and molybdenum-potassium catalysts for the hydrogenation of carbon monoxide

Alumina-supported tungsten catalysts for the hydrogenation of carbon monoxide

Promoted iron catalysts for the production of C2–C4 hydrocarbon as enrichment gas for SNG