Zeolite Fischer-Tropsch synthesis

Fischer-Tropsch synthesis could be "tailored by the use of iron, cobalt and ruthenium carbonyl complexes deposited on faujasite Y-type zeolite as starting materials for the preparation of catalysts. Short chain hydrocarbons, i.e. in the C-j-Cq range are obtained. It appears that the formation and the stabilization of small metallic aggregates into the zeolite supercage are the prerequisite to induce a chain length limitation in the hydrocondensation of carbon monoxide. However, the control of this selectivity through either a definite particle size of the metal or a shape selectivity of the zeolite is still a matter of speculation. Further work is needed to solve this dilemna. 

Carbenium ions, 42 115, 143 acid catalysis, 41 336 chemical shift tensors, 42 124-125 fragments in zeolites, 42 92-93 history, 42 116 superacids, 42 117 Carbide catalysts, 34 37 Carbidic carbon, 37 138, 146-147 Carbidic intermediates, 30 189-190, 194 Fischer-Tropsch synthesis, 30 196-197, 206-212... 

One shortcoming of the Fischer-Tropsch synthesis is its lack of selectivity in giving complex product mixtures. In an attempt to improve the selectivity of syngas-based hydrocarbon synthesis, Mobil researchers developed a process consisting of converting methyl alcohol (itself, however, produced from syngas) to gasoline (or other hydrocarbons) over a shape-selective intermediate-pore-size zeolite catalyst (H-ZSM-5) 22 78... 

Ruthenium is known to catalyze a number of reactions, including the Fischer-Tropsch synthesis of hydrocarbons (7) and the polymerization of ethylene (2). The higher metal dispersions and the shape selectivity that a zeolite provides has led to the study of ruthenium containing zeolites as catalytic materials (3). A number of factors affect the product distribution in Fischer-Tropsch chemistry when zeolites containing ruthenium are used as the catalyst, including the location of the metal (4) and the method of introducing ruthenium into the zeolite (3). 

The production of gasoline from methanol is a parallel process to the Fischer-Tropsch synthesis of hydrocarbons from syngas (Section 4.7.2). A shape-selective zeolite (ZSM-5) was the catalyst of choice in the process put on stream in 1987 by Mobil in New Zealand however the plant was later closed. The zeolite was used at ca. 400°C in a fluid catalyst reactor, which allows prompt removal of the heat of reaction. 

The activities of the cobalt supported catalyst for Fischer-Tropsch synthesis are summarised in Fig. 2 in terms of yields of Cj to C3 hydrocarbons. Only data at 250°C and 325°C are presented although other temperatures have been examined. The cobalt on IfeO, on the zeolite support, and on the blank supports alone, were inactive. The same groupings occurred with respect to CO consumption in the TPC runs. 250° C... 

P-ll - Zeolite-L as support of Fe microcrystals for the Fischer-Tropsch synthesis... 

For example, zeolites are used in different processes, but especially in the catalytic and thermal cracking to produce gasoline from petroleum. Another example is a well-known powdered catalyst of iron-silica (kieselguhr) promoted with K, applied in the Fischer-Tropsch synthesis to obtain hydrocarbons, in a wide range of light hydrocarbons, gasoline, and diesel. 

Ternary composites have also been used comprising a Fischer-Tropsch catalyst, a methanol synthesis catalyst, and a zeolite [100]. Two Fe-based catalysts (ie, one promoted by K and the other by Ru), two HY zeolites with different acidities, a commercial HZSM-5, and Cu/ZnO/AljOj (methanol synthesis catalyst) were tested in these composites. Dimethyl ether (DME), methanol, and hydrocarbons were formed. Addition of the Cu/ZnO/Al Oj catalyst to a binary mixture of a Fischer-Tropsch catalyst and HZSM-5 results in the increase of the CO conversion by more than 20 times. The DME selectivity decreases as the conversion increases. Y zeolites and the Fischer-Tropsch synthesis catalyst promoted by Ru generated the most active composites. The role of zeolites in the ternary composite is assumed with the DME synthesis. First, methanol is synthesized from syngas on Cu/ZnO/Al Oj then it is dehydrated by an acid catalyst to produce DME and finally, DME initiates FT synthesis, which is then propagated by CO. 

Co/lTQ-2 catalysts prepared by reverse micellar synthesis using a surface silylated lTQ-2 delaminated zeolite [103] is characterized by the uniform Co° particle size distribution (5-11 nm). The authors revealed the effect of the Co particle size on the catalyst performance. At the Fischer-Tropsch synthesis conditions (493 K, 2.0 MPa), TOF increases from 1.2 x 10 to 8.6x 10 s when /(Co°) increased from 5.6 to 10.4nm, and then it remains constant up to a particle size of 141 nm. The Co surface reconstruction occurs during the reaction, no matter what the metal particle size is. Interfacial Co + sites are likely the reason behind the decreased TOF observed for d Co°) < lOnm (Fig. 9). 

Fischer-Tropsch synthesis (see also carbon monoxide hydrogenation and synthesis gas ) 27, 33, 68, 83-85, 135, 168 fluorosilicate treatments, of zeolites 251, 252 formaldehyde... 

The Fischer-Tropsch synthesis (FTS) allows the synthesis of liquid hydrocarbons from various feedstocks, such as coal and natural gas, and has gained increasing interest in recent years. The removal of water, a reaction product, are threefold to reduce the deactivation of the catalysts to increase the reactor productivity and to enhance the conversion of CO2 to long-chain hydrocarbons by displacing the equilibrium of the water gas shift reaction on the reaction rate (Rohde et al, 2005). Different hydrophilic zeolite... 

The incorporation of a ZSM-5 class zeolite into a ruthenium Fischer-Tropsch catalyst promotes aromatics formation and reduces the molecular weight of the hydrocarbons produced. These composite catalysts can produce a high octane aromatic gasoline in good yield in a single step directly from synthesis gas. 

Fischer-Tropsch catalysis, 38 332 hydroformylation activity, 38 329-330 in NaY supercages, reversible formation and isomer transformation, 38 374 phosphino polystyrene support, 38 39 reactivity, 38 317-319, 323 ship-in-bottle synthesis in NaY zeolite supercages, 38 368-370... 

Modification of the zeolite appears to have affected the selectivity of Ru in these hydrogenation reactions. Exchange of K cations for Na cations in Y zeolite increases the basicity of the support (ref. 9). In Fischer-Tropsch reactions over similar catalysts, Ru/Y catalysts so modified yielded significant increases in the olefinic product fraction at the expense of paraffins. Olefins are believed to be primary products in F-T synthesis, with paraffins being produced from olefins in secondary hydrogenation reactions. In an analogous fashion, the Ru/KY catalyst used in the present study might also be expected to... 

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