The long term effect of up to 10 ppm H2S was studied for Fischer–Tropsch conversion of syngas by catalytic testing at 240 °C, 5 bar, H2/CO = 2.1 and GHSV = 2400 Nml/gcat h. Sulphur was dosed after ~ 300 or ~ 1000 h time on stream and the effect was monitored using on-line GC. The activity declined, and the effect correlated to the concentration of H2S in the feed. However, dosing after ~ 1000 h caused a stronger effect than dosing after ~ 300 h. The effects of sulphur are significant with respect to operational risks and mitigation but are substantially less severe than for a standard Co-based catalyst operated at 20 bar for wax production. The spent catalyst consisted of a mixture of cubic (Co, Mn)O, hexagonal Co, Co2C and sulphurous deposits; mainly MnSO4. It could not be concluded that sulphur had a direct effect on product selectivity, but it may have impacted water-gas-shift activity, and sudden changes in shift activity was found to correlate to changes in hydrocarbon selectivity.

A series of CoMnOx catalysts with lanthanum and phosphorus promoters were prepared by wet impregnation and investigated for syngas conversion to hydrocarbons activity via Fischer Tropsch Synthesis. The effects of the promoters on the catalyst structure were examined by ICP, XRD, TPR and XPS measurements. The results of the catalytic tests showed that the addition of promoters altered the product selectivities when compared to the unpromoted catalyst. (C) 2016 Elsevier B.V. All rights reserved.

Catalyst comprising elements relative molar ratios represented by the formula CoaMobScMdOf, wherein a is 1; wherein b is from 0.8 to 1.2; wherein c is from 1 to 2; wherein M comprises Zn, Ti, Zr, or Ni, or a mixture thereof, wherein d is from 0.000001 to 0.2; and wherein f is a number determined by the valence requirements of the other elements present in the catalyst.

Catalysts comprising zeolite ZSM-5 impregnated with precious metals including Ag, Cu, Ni, Pd, Ir and Ru, have been tested for the methanol to hydrocarbons reaction in a continuous flow fixed bed reactor. Comparison with the activity of unmodified ZSM-5 showed that Ag, Cu and Ni enhanced the selectivity to C6–C11 aromatic products by a factor of two or higher. Moreover, Ag/ZSM-5 showed improved selectivity for the C6–C7 fraction of aromatic products. Ni/ZSM-5 was found to be selective to naphthalene, while Cu/ZSM-5 was selective for C9–C11 aromatic products. It was ascertained that all the impregnated metals were present as metal oxides in the starting materials. It is therefore proposed that the enhanced selectivity to aromatic products is due to the interaction of the acid sites of the zeolite with the basic sites of the metal oxide at the edge of the zeolite crystals, as well as the possible coordination of propene molecules formed during the reaction, that are likely to be the building blocks for the formation of aromatics.

Composites of Ga2O3 clusters and zeolite ZSM-5 were evaluated for the transformation of methanol to hydrocarbons. Comparison of the activity with ZSM-5 showed that the Ga2O3 clusters are responsible for the enhanced selectivity to aromatics via contact synergy, thus showing the importance of non framework gallium species for this reaction. TEM analysis of fresh and spent catalysts allowed the identification of the formation of carbonaceous products at the Ga2O3/zeolite interface region, and this interface is also the probable location of the catalyst active sites.

A kinetics study for the partial oxidation of ethane to ethylene and acetic acid is performed over MoV type catalysts. It is established that ethylene is the primary product and acetic acid and carbon oxides are secondary products. Formation of acetic acid product increases significantly with the co-feeding of water into the reactor. The elementary steps of the reaction network are formulated using a two-site Eley-Rideal-Redox (ERR) model, which includes the participation of water in the reaction scheme through surface OH− groups. The derived ERR model predicts the experimental data satisfactorily.

The formation of acetic acid and/or ethylene by oxidation of ethane is strongly dependent on X additives or Y promotor added to MoVO-based catalysts. MoV0.4X0.12YɛOz (X=Nb; Y=Pd; ɛ=10−4) catalysts were prepared by the slurry method and their structural properties were studied by in situ (redox conditions) XRD, Raman and XPS techniques. The reactivity during reduction and reoxidation was analysed by thermal analysis (TGA/DSC). The oxidation of ethane was carried out in a conventional fixed bed microreactor with on line analysis by gas chromatography. Results show that Nb exerts mainly a structural effect as it is responsible for the stabilisation of molybdenum (VI) by formation of solid solutions with V, and that Pd modifies the rate of reduction of the solid catalysts. The increase of selectivity to acetic acid observed by Pd promotion is likely due to the transformation of ethylene to acetic acid occurring on neighboring Pd–V active sites.