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Fischer–Tropsch synthesis over Co/montmorillonite—Insights into the role of interlayer exchangeable cations

Paper ID Volume ID Publish Year Pages File Format Full-Text
41357 45886 2011 10 PDF Available
Title
Fischer–Tropsch synthesis over Co/montmorillonite—Insights into the role of interlayer exchangeable cations
Abstract

To develop an efficient catalyst for controlling the product distribution of the Fischer–Tropsch (FT) synthesis, the natural Na-type montmorillonite (Na-MMT) was modified by ion-exchanging the interlayer Na+ with selected cations, NH4+, Co2+, and Al3+. The degree of the interlayer Na+ replaced by the selected cations was regulated by changing the ion-exchange conditions. A 20 wt.% Co/MMT catalyst was prepared by the incipient impregnation method. The materials were characterized by XRD, SEM/EDS, N2 adsorption–desorption at low temperature, H2-TPR, and NH3-TPD techniques, and the results indicate that the MMT interlayer structure was well reserved for all the ion-exchanged MMTs. Moreover, acidic sites, rich micropores and open mesopores were created after exchanging the Na-MMT with NH4+, Co2+, or Al3+. The Co-supported catalysts were investigated for the FT synthesis in a fixed-bed reactor under the conditions of 1.0 MPa, 235 °C, H2/CO = 2, and W/F = 5.02 g h mol−1. The results show that the Co/Na-MMT is an inefficient catalyst for the FT synthesis. In contrast, the Co/ion-exchanged MMT showed sharply increased CO conversion. The CO conversion was dependent on the ion-exchange conditions used, however. Moreover, the product selectivity over Co/MMT, i.e., 40–47% C4–C12 hydrocarbons and 13–20% C21+ hydrocarbons, significantly deviates from the Anderson–Schulz–Flory distribution in the FT synthesis over the typical Co/SiO2 catalyst. Based on the catalysts characterization, the difference of the FT activity as a result of interlayer cation can be explained as the different reduction behavior of the catalysts. Due to the cracking of the long-chain FT hydrocarbons, a narrow product distribution over the Co/MMT catalyst was observed, which correlates well with the NH3-TPD results.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (207 K)Download as PowerPoint slideHighlights► Acidic sites and rich pores are created after exchanging Na-montmorillonite with NH4+, Co2+, or Al3+. ► High selectivity of liquid FT hydrocarbons over Co-supported Na-montmorillonite exchanged with Al3+, Co2+, or NH4+. ► The content of Na+ is a key factor to control the CO conversion over Co/montmorillonite catalyst.

Keywords
Fischer–Tropsch; Cobalt; Montmorillonite; Ion exchange; Liquid fuel
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 405, Issues 1–2, 3 October 2011, Pages 45–54
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
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Any Questions? feel free to contact us