Hydrocarbons synthesis, from syngas

Hydrocarbon synthesis from syngas (Fischer-Tropsch reactions) can be carried out over the catalysts prepared from Co- and Cu-containing LDHs. The products include methane, higher paraffins, and olefins as well as methanol. The loading of Co and Cu determines the selectivity for each compound. For instance, Co-rich catalysts give more paraffins, while Co-poor ones lead to methanol (615). 

It is well admitted that the first step of the hydrocarbons synthesis from syngas is the CO dissociation on a metallic center (Co°, Fe°, or Co-Fe in the present case). CO dissociation into Cgurf and CO2 has been studied on the partially Lai j,Coo.4Feo,603 5 solids [43]. The results clearly show that the rate of CO dissociation increases almost linearly with the lanthanum deficiency. This is associated with the increased amount of reduced metal (2.1 wt% for y = 0-10.9 wt% for y=0A). The metal particles size has also an effect. For y = 0.4, CO dissociation is lower when catalysts were initially calcined at 900 °C (12% of CO conversion for 14.1 wt% of metal of average particle size of 28 nm) compared to those calcined at 750 °C (19% of CO conversion for 10.9 wt% of metal of average particle size of 10 nm). The larger size of particles led to a lower surface/volume ratio and to a decrease of CO dissociation. 

The higher hydrocarbon formation from syngas has long been industrialized as the Fischer-Tropsch synthesis [27]. Yet, syngas production from the C02 reforming of methane is an endothermic reaction, and requires a high temperature (ca. 1073 K) for a favorable equilibrium ... 

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... 

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 catalytic synthesis of hydrocarbons from syngas is also represented by the Fischer-Tropsch process (141). 

Recent study found that Pd sulfide prepared by sulfiding PdCU (structure detennined with XRD was Pd S ) yielded methanol with a selectivity above 95-mol% (70). This result is notable because, so far, only Mo and W sulfides have been known to show weak activities for the synthesis of gaseous hydrocarbons from syngas (77). This type of sulfides had some attentions because Mo sulfide modified with alkali metal additives showed a constant activity for alcohol synthesis even in die presence of H2S (77). This is in marked contrast with the... 

The synthesis of hydrocarbons from CO hydrogenation over transition metals is a major source of organic synthetic chemicals and fuels. The Fischer-Ttopsch (FT) reaction, which is directed to the production of hydrocarbons from syngas, implies the polymerisation of-CHx entities and carbon-carbon bond formation is required. The historical achievements have been revised on several occasions see for instance, the reviews by Vannice,2 Schulz3 and the special issue of Catalysis TodayA devoted to FT. Also, a synopsis of the main recent industrial developments has been presented by Adesina.5 Furthermore, the recent edition of Topics in Catalysis6 should be mentioned, where different aspects of the reaction mechanism, surface reconstruction of active surfaces, improved reactors and optimisation of catalyst preparations have been treated by various specialists, scientists and engineers. 

The synthesis of hydrocarbons from CO hydrogenation over transition metals is a m or source of organic synthetic chemicals and fuels. The Fischer-Tropsch (FT) reaction, which is directed to the production of hydrocarbons from syngas, implies the polymerisation of -CH, entities and carbon-carbon bond formation is required. 

A more detailed description of the GTL process is (1) the prodnction of synthesis gas (syngas) from carbon-based feedstocks, (2) the FT reaction for conversion of syngas to higher liqnid hydrocarbons and long-chain waxy paraffins, and (3) the conversion of the solid long-chain waxy paraffins through hydrocracking and hydroisomerization back to liquid fuels. 

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