Hydrocracking of Fischer-Tropsch Waxes with Acidic Tungstenvanadophosphoric Polyoxometalates as Catalysts

Titelangaben

Rausch, Peter ; Kern, Christoph ; Korth, Wolfgang ; Jess, Andreas:
Hydrocracking of Fischer-Tropsch Waxes with Acidic Tungstenvanadophosphoric Polyoxometalates as Catalysts.
2016
Veranstaltung: DGMK Conference "Catalysis - Novel Aspects in Petrochemistry and Refining" , 26.-28.09.2016 , Berlin, Deutschland.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung , Poster )

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Abstract

In the last decades, renewable energies have attracted great attention on a political and technical level due to the climate change caused by fossil fuel combustion and the limited resources of the fossil fuels in a long term perspective [1].
However, especially solar and wind power face fluctuating availability, which is a serious problem in developed and developing countries. Thus, surplus renewable energy has to be transformed into an energy form suitable for storage to avoid such fluctuations. Here, liquid hydrocarbons (LHC) can play an important part to store these huge amounts of energy chemically since LHCs possess the highest energy density available (about 40 MJ/l). The Fischer-Tropsch synthesis (FTS) is therefore of particular interest as FTS yields exactly these liquid fuels. However, the broad spectrum with regard to chain length of paraffinic hydrocarbons (liquids to waxes) leaving the FTS process are processed downstream in a cracking unit. The wax is converted into shorter liquid molecules, and the yield of gasoline, jet-fuel and diesel increases [2].
Within this work, the focus is on mild hydrocracking, which can be operated at low temperatures down to 350 °C [3]. Therefore, bifunctional acid catalysts like platinum-donated zeolites are commonly used, and saturated hydrocarbons are almost exclusively obtained as products. In addition, the very low presence of small hydrocarbons (C1-C3), high yields of diesel LHCs and operating flexibility offer further advantages of this process [4].
In this context, polyoxometalates (POMs) based on the phosphotungstic acid H3PW12O40 may offer a new alternative to the classical catalysts. These solid acids provide highly brønsted-acidic centres, where cracking reactions take place [5].
Based on H3PW12O40, POM catalysts were synthesized. Attention has been directed especially to vanadium substituted polyoxometalates as their specific acidity and therefore the selectivity towards gasoline, jet fuel and diesel fuel can be positively influenced. In this contribution, their properties and their activity and selectivity at a mild hydrocracking process conditions are presented.
[1] Das Erneuerbare-Energien-Gesetz (EEG) | EEG aktuell,
http://www.eeg-aktuell.de/das-eeg/.
[2] A. Jess, P. Wasserscheid, Chemical technology: An integral textbook, WILEY-VCH, Weinheim 2013.
[3] C. Marcilly, Calalyse acido-basique 2 volumes (French Edition), Technip
[4] J. Weitkamp, ChemCatChem 2012, 4 (3), 292.
[5] M. Pope, Heteropoly and Isopoly Oxometalates (Inorganic Chemistry Concepts) (Volume 8), 1st ed., Springer 2013.