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    La, Mn and Zn promoted microporous iron catalysts with high productivity and stability for Fischer-Tropsch synthesis
    (Springer, 2016) Gul, Omer F.; Atac, Ozlem; Boz, Ismail; Ozkara-Aydinoglu, Seyma
    Fischer-Tropsch synthesis is studied over precipitated Fe catalysts promoted with Mn, Zn and La metals. The results showed that there was a large increase in surface area and pore volume, and a sharp decrease in average pore size upon the addition of promoters. Catalyst productivity and rate of syngas converted as well as hydrocarbon yield increased with addition of promoters to Fe structure during precipitation step. Addition of metal promoters led catalyst samples of microporous structures with relatively high surface areas. This effect probably yielded catalysts with enhanced long-term activity and stability. Samples containing 10 % Zn and 5 % Mn exhibited the highest catalytic activity and stability. Increasing the loading of Zn from 5 to 10 wt% led to a noteworthy increase on yield and productivity as well as rate of syngas converted. The highest productivity was obtained for the sample containing 10 % Zn, highest yield was attained over the sample containing 5 % Mn. The results indicate that the selectivity to C-12-C-18 range was more pronounced for the catalyst promoted with Mn metal whereas alpha-olefins and higher molecular weight products were increased with the addition of 5 % Zn over Fe based catalysts. The decrease in temperature from 523 to 493 K resulted in an increase in heavy hydrocarbons and a significant decrease in gaseous and light hydrocarbons for Fe4Si5Mn catalyst.
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    ?-olefin selectivity of Fe-Cu-K catalysts in Fischer-Tropsch synthesis: Effects of catalyst composition and process conditions
    (Elsevier Science Sa, 2012) Ozkara-Aydinoglu, Seyma; Atac, Ozlem; Gul, Omer F.; Kinayyigit, Solen; Sal, Sinan; Baranak, Murat; Boz, Ismail
    Fischer-Tropsch (FT) synthesis has been studied over a series of precipitated Fe catalysts promoted to investigate the effect of K and Cu promoters on the carbon number distribution of FT product. The main intention is to maximize the alpha-olefin selectivity by controlling the secondary reactions of alpha-olefin as a function of potassium and copper loadings. The results showed that impregnation of different loadings of Cu and K promoters to precipitated iron-based catalyst was found to have significant influences on the crystallographic structure, morphological and physical properties of iron-based catalysts, as well as catalytic activity, stability and selectivity performances during FT synthesis. 100Fe7Cu3K sample exhibited the highest catalytic activity and stability in TOS tests. The catalyst is capable of working under a variety of temperatures and space velocities at a same activity level with no significant activity loss. Proper control of Cu and K contents is essential to obtain maximum C-5+ yield since the changes in the relative loadings of both Cu and K promoters affect hydrocarbon product distribution. 100Fe7Cu3K sample has high secondary alpha-olefin hydrogenation activity as olefin/paraffin ratio decreases with increasing carbon number while C-19+ selectivity is relatively low compared to other samples. The effects of space velocity and temperature on alpha-olefin selectivity are strongly dependent on the amounts of Cu and K promoters and chain length. The maximum alpha-olefin/n-paraffin ratio has been obtained over 100Fe3Cu1K sample at 543 K with a space velocity of 3 NL/h/g-cat. (C) 2011 Elsevier B.V. All rights reserved.