The Application of Zeolites and Periodic Mesoporous Silicas in the Catalytic Conversion of Synthesis Gas

Abstract

In the recent years there has been a rising interest in the conversion of remote and abundant natural gas as well as renewable biomass sources into high quality fuels and valuable raw chemicals via synthesis gas (syngas, CO ? H 2 ) as a versatile intermediate. The metal catalysed CO hydrogenation can be selectively directed towards hydrocarbons as precursors of ultra clean liquid fuels (Fischer-Tropsch synthesis) or to added-value products such as light olefins and oxygenates (alcohols, carboxylic acids, ethers, etc.). By taking advantage of their unique and tunable structural and chemical properties, inorganic molecular sieves such as zeolites and periodic mesoporous silicas have been extensively explored as effective components of heterogeneous catalysts for the selective conversion of syngas. Thus, ordered mesoporous silicas (MCM-41, MCM-48, SBA-15) have shown interesting properties as catalytic supports for Co and Fe based Fischer-Tropsch catalysts. Besides, zeolite-entrapped mono and bimetallic clusters have been reported to selectively direct the synthesis towards oxygenates. In this work, the use of the original structural properties of these materials to tailor the dispersion, geometrical location and chemical state of metallic sites leading to heterogeneous catalysts with enhanced activity and selectivity in syngas catalytic routes is reviewed. The introduced peculiarities, benefits and drawbacks of these structured solids in comparison to conventional amorphous supports are also discussed.

Exploring Iron‐based Multifunctional Catalysts for Fischer–Tropsch Synthesis: A Review

“…The latest developments in multifunctional catalytic systems that combine hydrocarbon-forming reactions with in situ upgrading towards high-octane gasoline compounds or diesel-range products in a single material open new possibilities to increase the performance of the FT process. Multifunctional catalysts combining the one-step performance of acid or bifunctional metal/acid zeolites with a FT catalyst have not been explored to the same extent as cobalt, [53] but significant developments have been achieved and are reviewed in the following sections after a short introduction to the current state of the art of typical catalysts employed in FTS.…”

Mesoporous Zeolite‐Supported Ruthenium Nanoparticles as Highly Selective Fischer–Tropsch Catalysts for the Production of C5–C11 Isoparaffins

“…[2c, 4,9] In these catalytic systems, the primary hydrocarbon products formed on the active FT catalyst can migrate into the micropores of zeolites, where the hydrocracking occurs, and the products must diffuse out of the micropores. The slow transportation of products inside the long micropores of zeolites usually causes over-cracking, leading to high selectivity to undesirable light hydrocarbons (CH 4 and C 2 -C 4 alkanes).…”

Synthesis of Ethanol from Syngas over Rh/MCM-41 Catalyst: Effect of Water on Product Selectivity

“…The TPR profile of the Rh/MCM-41 catalyst suggests some metal-support interactions, which widen the reduction peak at higher temperatures. Metal-support interactions are observed in other mesoporous catalysts as well as in traditional catalysts [13,26]. Moreover, after the reduction treatment at 370 °C the surface of the …”

“…It has been suggested that a high concentration of water vapor can be formed in the pores of MCM-41 during catalyst reduction, which could promote metal-support interactions [13,27]. If so, water vapor can also be concentrated in the catalyst pores during catalytic testing, since most of the syngas reactions produce water as a main by-product (reactions 1-4) [7,8].…”

“…The rhodium-based catalysts are among the most selective catalysts reported in the literature [7,8]. However, few reports are found using mesoporous silica as catalyst support [9][10][11], although various mesoporous materials have been applied in other catalytic reactions showing interesting results [12,13]. MCM-41 is a mesoporous silica that has 1D-hexagonal porous arrangement with a pore diameter between 1.6-10 nm and a wall thickness of around 0.8 nm [14,15].…”