Zeolites syngas conversion

SYNGAS CONVERSION OVER RUTHENIUM/ZEOLITE CATALYSTS AT 51 atm,... 

Syngas conversion to methanol has been shown to take place on supported palladium catalyst [1]. Methanol can in turn be converted to gasoline over ZSM-5 via the MTG process developed by Mobil [2]. In recent work we have reported syngas (CO/H2) conversion to hydrocarbon products on bifunctional catalysts consisting of a methanol synthesis function, Pd, supported on ZSM-5 zeolites [3]. Work on syngas conversion to hydrocarbon products on Pd/SAPO molecular sieves has been published elsewhere [Thomson et. al., J. CataL. in press].Therefore, this paper will concentrate on propylene conversion. 

Syngas conversion has also been studied with physically mixed Pd/SiOi and acidic zeolites, including HY, HZSM-5, and HMor. The mixture of Pd/SiOi with HY was found to produce mainly aliphatic higher hydrocar-... 

Balliveit-Tkatchenko et al. (140) also reported the similar observation that Fe3(CO)i2 incorporated in NaY decomposed to give highly dispersed Fe particles which chemisorbed CO to form carbonyl species characterized by IR. In the pressurized syngas conversion reaction, this catalyst provided higher selectivity toward lower olefins with an upper limit of C9-C10, owing to the shape selectivity of the zeolite framework. No further aggregation of Fe particles was seen under syngas reaction conditions. 

It has been demonstrated by means of IR, XPS, and Mossbauer methods that the deposition of Fe3(CO),2 on NaY or NaX zeolites, followed by cluster decomposition and extraction of residual carbonyl species, gives highly dispersed Fe particles consisting of i -Fe203 with a small amount of Fe . These particles exhibit high activity for syngas conversion to lower olefins, with unusually high ethane and low methane contents in the product (243). 

Rabo has shown that ALPO s and SAPO s may be used in many chemical and petrochemical processes. They give unique opportunities to be tailored to specific requirements. On the other hand, they have only mild acidity (which could be an Advantage in some cases), they are difficult to synthetize, and they may be more expensive than present commercial zeolites. Therefore they rely on their superior performance to compete with their aluminosilicate cousins. Applications include the removal of nitrogen oxides, cracking of heavy petroleum fractions, octane increase in hydrocracking, various reactions of olefins and aromatics such as oligomerization and xylene isomerization, syngas conversions, and methane activations. Co- and Co-Si-aluminophosphates have been active for this last reaction. 

Syngas conversion offers a potential alternative to flaring or reinjection for monetization of associated gas. The Chevron s Gas Conversion Catalysis (GCC ) technology, a commercially viable hybrid syngas conversion catalyst comprising both a Fischer-Tropsch active metal and a zeolite component that provides the proper product distribution in favor of liquid hydrocarbons without the need for downstream hydroprocessing at high pressures is described in [99]. 

Chain-Length Control in the Conversion of Syngas over Carbonyl Compounds Anchored into a Zeolite Matrix... 

Erena, J., Arandes, J.M., Bilbao, J., Ga5mbo, A.G., and de Lasa, H. Conversion of syngas to hquid hydrocarbons over a two-component (Cr203-Zn0 and ZSM-5 zeolite) catalyst kinetic modeling and catalyst deactivation. Chem. Eng. Set 2000, 55, 1845-1855. 

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. 

The capsule catalyst Co/SiO -Z with zeolite HZSM-5 as the shell and the Co/SiO -Z-Pd capsule catalysts were used for isoparaffin synthesis from syngas at H2/CO=2/l, 1.0 MPa and 533 K [107]. The isoparaffin and olefin selectivity increased for the HZSM-5-based capsule catalysts compared to the conventional Co/SiO catalyst. Supporting Pd by sputtering caused the selectivity to isoparaffins to increase, and the selectivity to olefins to decrease compared to the samples prepared by incipient wetness, because metallic Pd supported by sputtering on the zeolite shell could hydrogenate olefins efficiently. The CO conversion, CH and CO selectivity on the catalyst Co/SiO -Z-Pd prepared by sputtering increased with a temperature rise from 513 to 553 K. At elevated temperatures, the isoparaffin selectivity also increased, whereas the olefin selectivity diminished. 

Surprinsingly, the hydrocarbon distribution obtained with mixed pillared laponites does not follow a Schulz-Flory law. This selectivity deviation is comparable to the shape selectivity observed with zeolite encapsulated metal clusters in the conversion of syngas or methanol into light olefins as shown by Nazar et al, 1983 (Ref. 4). 

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