Fischer-Tropsch synthesis activity, catalyst

Mochizuki T., Hara T., Koizumi N., and Yamada M. 2007. Surface structure and Fischer-Tropsch synthesis activity of highly active Co/Si02 catalysts prepared from the impregnating solution modified with some chelating agents. Appl. Catal. A Gen. 317 97-104. 

Summary of Catalyst Composition and Reaction Conditions Selected for Comparing Fischer-Tropsch Synthesis Activity in CSTR... 

Note Prior to Fischer-Tropsch synthesis, all catalysts were activated with CO at 270°C and atmospheric pressure for 24 h with a CO SV of 3.0 sl/h/g Fe. 

Ngantsoue-Hoc, W., Zhang, Y., O Brien, R.J., Luo, M., and Davis, B.H. 2002. Fischer-Tropsch synthesis Activity and selectivity for Group I alkali promoted iron-based catalysts. Appl. Catal. 236 77-89. 

The most difficult problem to solve in the design of a Fischer-Tropsch reactor is its very high exothermicity combined with a high sensitivity of product selectivity to temperature. On an industrial scale, multitubular and bubble column reactors have been widely accepted for this highly exothermic reaction.6 In case of a fixed bed reactor, it is desirable that the catalyst particles are in the millimeter size range to avoid excessive pressure drops. During Fischer-Tropsch synthesis the catalyst pores are filled with liquid FT products (mainly waxes) that may result in a fundamental decrease of the reaction rate caused by pore diffusion processes. Post et al. showed that for catalyst particle diameters in excess of only about 1 mm, the catalyst activity is seriously limited by intraparticle diffusion in both iron and cobalt catalysts.1... 

Iron-based Fischer-Tropsch synthesis (FTS) catalysts are preferred for synthesis gas with a low H2/CO ratio (e.g., 0.7) because of their excellent activity for the water-gas shift reaction, lower cost, lower methane selectivity, high olefin... 

Fig. 23. The effect of catalyst structural parameter ix) on Fischer-Tropsch synthesis activation energy and kinetics (473 K, 2000 kPa, H2/CO = 2.1 55-65% CO conversion, > 24 h onstream).

To verify the influence this monolayer silica had on catalyst activity and selectivity, the intrinsic Fischer-Tropsch synthesis activity as well as the selectivity of the supported cobalt catalysts studied in this paper (i.e. catalyst A and B), were determined at realistic Fischer-Tropsch synthesis conditions (refer Table 1). 

From Table 1, it can be concluded that silicon modification of alumina did not have any substantial effect on the Fischer-Tropsch synthesis activity nor did it substantially influence the selectivity of the silica modified catalyst B. 

A considerable interest has been expressed in using the SBCR to carry out FTS particularly for the conversion of stranded natural gas into liquids. Currently, the Center for Applied Energy Research (CAER) is utilizing a Prototype Integrated Process Unit (PIPU) system for scale-up research of the FTS. The purpose of this study was to compare the performance and activity decline of a precipitated Fe/K Fischer Tropsch Synthesis (FTS) catalyst in a revamped slurry bubble colurtm reactor (SBCR) to that of previous CSTR and SBCR rans using the same catalyst and operating conditions. The activity decline measured in the revamped SBCR system was shown to be similar to that of the CSTR experiments. The apparent activity decline in a previous SBCR run was due a transient startup effect from the slurry filtration system. 

Fischer-Tropsch synthesis activity and selectivity data for the different catalysts have been presented elsewhere, for the catalysts containing 12 wt.% cobalt by Storsaeter et al. [5], and for the alumina supported catalysts containing 20 wt.% cobalt by Borg et al. [11], A summary of the results are presented in Table 2. 

Based on the development of both catalysts and reactors [4, 5], the Fischer-Tropsch synthesis activity and selectivity of cobalt catalyst have increased as illustrated in Figure 1.1. The volume-based activity has increased by a factor of 10 going from 1940 at space time yield (STY) = 10 to 1990 at STY = 100, and another factor of 3 is expected to lead to STY = 300 by 2010. Most importantly, with increasing activity the catalysts displayed improved selectivities to higher hydrocarbons. 

Fischer Tropsch synthesis is catalyzed by a variety of transition metals such as iron, nickel, and cobalt. Iron is the preferred catalyst due to its higher activity and lower cost. Nickel produces large amounts of methane, while cobalt has a lower reaction rate and lower selectivity than iron. By comparing cobalt and iron catalysts, it was found that cobalt promotes more middle-distillate products. In FTS, cobalt produces... 

Ruthenium is a known active catalyst for the hydrogenation of carbon monoxide to hydrocarbons (the Fischer-Tropsch synthesis). It was shown that on rathenized electrodes, methane can form in the electroreduction of carbon dioxide as weU. At temperatures of 45 to 80°C in acidihed solutions of Na2S04 (pH 3 to 4), faradaic yields for methane formation up to 40% were reported. On a molybdenium electrode in a similar solution, a yield of 50% for methanol formation was observed, but the yield dropped sharply during electrolysis, due to progressive poisoning of the electrode. 

The potential of carbon nanomaterials for the Fischer-Tropsch synthesis was investigated by employing three different nanomaterials as catalyst supports. Herringbone (HB) and platelet (PL) type nanofibers as well as multiwalled (MW) nanotubes were examined in terms of stability, activity, and selectivity for Fischer-Tropsch synthesis (FTS). 

Recently, the Fischer-Tropsch synthesis regained much attention mainly due to the (political) desire for cleaner fuels and the potential shortage of crude oil. Therefore, research activity is focusing on the development of improved reactor concepts as well as on novel and promising catalysts for an economic production of clean fuels via FTS. 

Yu, Z., Borg, 0., Chen, D., Enger, B. C., Frpseth, V., Rytter, E., Wigum, H., and Holmen, A. 2006. Carbon nanofiber supported cobalt catalysts for Fischer-Tropsch synthesis with high activity and selectivity. Catalysis Letters 109 43 -7. 

Nurunnabi, M., Murata, K., Okabe, K., Inaba, M., and Takahara, I. 2007. Effect of Mn addition on activity and resistance to catalyst deactivation for Fischer-Tropsch synthesis over Ru/A1203 and Ru/Si02 catalysts. Catal. Commun. 8 1531-37. 

Preparation of Highly Active Co/Si02 Catalyst with Chelating Agents for Fischer-Tropsch Synthesis Role of Chelating Agents... 

Bian, G., Mochizuki, T., Fujishita, N., Nomoto, H., and Yamada, M. 2003. Activation and catalytic behavior of several Co/Si02 catalysts for Fischer-Tropsch synthesis. Energy Fuels 17 799-803. 

Mochizuki, T., Hara, T., Koizumi, N., and Yamada, M. 2007. Novel preparation method of highly active Co/Si02 catalyst for Fischer-Tropsch synthesis with chelating agents. Catal. Lett. 113 165-69. 

The aim of this work was to apply combined temperature-programmed reduction (TPR)/x-ray absorption fine-structure (XAFS) spectroscopy to provide clear evidence regarding the manner in which common promoters (e.g., Cu and alkali, like K) operate during the activation of iron-based Fischer-Tropsch synthesis catalysts. In addition, it was of interest to compare results obtained by EXAFS with earlier ones obtained by Mossbauer spectroscopy to shed light on the possible types of iron carbides formed. To that end, model spectra were generated based on the existing crystallography literature for four carbide compounds of... 

At this point, the system was tested with catalyst for activation and FTS, in the hopes that the seal leak rates would be impeded by the presence of small catalyst particles. The FTFE 20-B catalyst (L-3950) (Fe, 50.2% Cu, 4.2% K, 1.5% and Si, 2.4%) was utilized. This is part of the batch used for LaPorte FTS run II.20 The catalyst was activated at 543 K with CO at a space velocity (SV) of 9 sl/h/g catalyst for 48 h. A total of 1,100 g of catalyst was taken and 7.9 L of C30 oil was used as the start-up solvent. At the end of the activation period, an attempt was made for Fischer-Tropsch synthesis at 503 K, 175 psig, syngas SV = 9 sl/h/g catalyst, and H2/CO = 0.7. However, the catalyst was found to be completely inactive for Fischer-Tropsch synthesis. Potential reasons for catalyst poisoning under present experimental conditions were investigated. Sulfur and fluorine are known to poison iron-based Fischer-Tropsch catalysts.21,22 Since the stator of the pump is... 

In this work, a detailed kinetic model for the Fischer-Tropsch synthesis (FTS) has been developed. Based on the analysis of the literature data concerning the FT reaction mechanism and on the results we obtained from chemical enrichment experiments, we have first defined a detailed FT mechanism for a cobalt-based catalyst, explaining the synthesis of each product through the evolution of adsorbed reaction intermediates. Moreover, appropriate rate laws have been attributed to each reaction step and the resulting kinetic scheme fitted to a comprehensive set of FT data describing the effect of process conditions on catalyst activity and selectivity in the range of process conditions typical of industrial operations. 

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