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On-line gas chromatographic analysis of higher alcohol synthesis products from syngas
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
2012 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1247, 134-145 p.Article in journal (Refereed) Published
Abstract [en]

An on-line gas chromatographic (GC) system has been developed for rapid and accurate product analysis in catalytic conversion of syngas (a mixture of H-2 and CO) to alcohols, so called "higher alcohol synthesis (HAS)". Conversion of syngas to higher alcohols is an interesting second step in the route of converting coal, natural gas and possibly biomass to liquid alcohol fuel and chemicals. The presented GC system and method are developed for analysis of the products formed from syngas using alkali promoted MoS2 catalysts, however it is not limited to these types of catalysts. During higher alcohol synthesis not only the wanted short alcohols (similar to C-2-C-5) are produced, but also a great number of other products in smaller or greater amounts, they are mainly short hydrocarbons (olefins, paraffins, branched, non-branched), aldehydes, esters and ketones as well as CO2, H2O. Trace amounts of sulfur-containing compounds can also be found in the product effluent when sulfur-containing catalysts are used and/or sulfur-containing syngas is feed. In the presented GC system, most of them can be separated and analyzed within 60 min without the use of cryogenic cooling. Previously, product analysis in "higher alcohol synthesis" has in most cases been carried out partly on-line and partly off-line, where the light gases (gases at room temp) are analyzed on-line and liquid products (liquid at room temp) are collected in a trap for later analysis off-line. This method suffers from many drawbacks compared to a complete on-line GC system. In this paper an on-line system using an Agilent 7890 gas chromatograph equipped with two flame ionization detectors (FID) and a thermal conductivity detector (TCD), together with an Agilent 6890 with sulfur chemiluminescence dual plasma detector (SCD) is presented. A two-dimensional GC system with Deans switch (heart-cut) and two capillary columns (HP-FFAP and HP-Al2O3) was used for analysis of the organic products on the FIDs. Light inorganic gases (H-2, CO, CO2, N-2) and methane were separated on packed columns and quantified with the TCD. The "sulfur GC" was optimized for on-line trace level sulfur analysis in hydrocarbon matrices and used to understand to which degree sulfur is released from the catalyst and incorporated into the liquid product, and if so in which form. The method provides excellent quantitative measurements with a carbon material balance near 99.5% (carbon in/carbon out) for individual measurement points.

Place, publisher, year, edition, pages
2012. Vol. 1247, 134-145 p.
Keyword [en]
On-line analysis, Higher alcohol synthesis, 2D heart-cut GC, Sulfur chemiluminescence detector, Oxygenates, Hydrocarbons
National Category
Biochemistry and Molecular Biology
Identifiers
URN: urn:nbn:se:kth:diva-100158DOI: 10.1016/j.chroma.2012.05.060ISI: 000306246100017Scopus ID: 2-s2.0-84862757525OAI: oai:DiVA.org:kth-100158DiVA: diva2:543048
Note
QC 20120806Available from: 2012-08-06 Created: 2012-08-06 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Catalytic conversion of syngas to higher alcohols over MoS2-based catalysts
Open this publication in new window or tab >>Catalytic conversion of syngas to higher alcohols over MoS2-based catalysts
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present thesis concerns catalytic conversion of syngas (H2+ CO) into a blend of methanol and higher alcohols, an attractive way of producing fuels and chemicals. This route has the potential to reduce the oil dependence in the transport sector and, with the use of biomass for the syngas generation, produce CO2-neutral fuels.

Alkali promoted MoS2-based catalysts show a high selectivity to higher alcohols, while at the same time being coke resistant, sulfur tolerant and displaying high water-gas shift activity. This makes this type of catalyst especially suitable for being used with syngas derived from biomass or coal which typically has a low H2/CO-ratio.

This thesis discusses various important aspects of higher alcohol synthesis using MoS2-based catalysts and is a summary of four scientific papers. The first part of the thesis gives an introduction to how syngas can be produced and converted into different fuels and chemicals. It is followed by an overview of higher alcohol synthesis and a description of MoS2-based catalysts. The topic alcohol for use in internal combustion engines ends the first part of the thesis.

In the second part, the experimental part, the preparation of the MoS2-based catalysts and the characterization of them are handled. After describing the high-pressure alcohol reactor setup, the development of an on-line gas chromatographic system for higher alcohol synthesis with MoS2 catalysts is covered (Paper I). This method makes activity and selectivity studies of higher alcohol synthesis catalysts more accurate and detailed but also faster and easier. Virtually all products are very well separated and the established carbon material balance over the reactor closed well under all tested conditions. The method of trace level sulfur analysis is additionally described.

Then the effect of operating conditions, space velocity and temperature on product distribution is highlighted (Paper II). It is shown that product selectivity is closely correlated with the CO conversion level and why it is difficult to combine both a high single pass conversion and high alcohol selectivity over this catalyst type. Correlations between formed products and formation pathways are additionally described and discussed. The CO2 pressure in the reactor increases as the CO conversion increases, however, CO2 influence on formation rates and product distribution is to a great extent unclear. By using a CO2-containing syngas feed the effect of CO2 was studied (Paper III).

An often emphasized asset of MoS2-based catalysts is their sulfur tolerance. However, the use of sulfur-containing feed and/or catalyst potentially can lead to incorporation of unwanted organic sulfur compounds in the product. The last topic in this thesis covers the sulfur compounds produced and how their quantity is changed when the feed syngas contains H2S (Paper IV). The effect on catalyst activity and selectivity in the presence of H2S in the feed is also covered.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. ix, 106 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:2
Keyword
conversion, higher alcohols, mixed alcohols, MoS2, syngas
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-158549 (URN)978-91-7595-392-2 (ISBN)
Public defence
2015-02-06, D2, Lindstedtsvägen 5, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20150115

Available from: 2015-01-15 Created: 2015-01-09 Last updated: 2015-01-15Bibliographically approved

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