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Katalytisk framställning av syntetisk naturgas (SNG)
KTH, School of Chemical Science and Engineering (CHE).
2015 (Swedish)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Catalytic Production of Substitute Natural Gas (English)
Abstract [en]

The aim of the  study  was to study  the  performance of nickel-based  catalysts  in the  production  of synthetic  natural  gas from synthesis gas (CO and H,). Nickel-based catalysts are preeminent catalysts in  this  reaction   due  to  their   high activity  and  selectivity  to  methane.  Nevertheless,   these   are threatened by severe  intrinsic deactivation  phenomena. In  more  detail, the goal of this work is to study   the   influence   of  different   catalyst   properties  on   the   three    most  severe   deactivation mechanisms  (nickel carbonyl formation,  carbon formation  and thermal  sintering). For that  purpose,  alumina-supported nickel catalysts containing  30 wt% Ni and promoted with Zr02, MgO, CaO and BaO were  prepared  and tested  in a high pressure  catalytic reactor.   The experimental work was divided in 3 parts according to specific study goals.

The first  part of the  work consisted  in the  study  of the  catalyst  pellet size on deactivation due  to nickel carbonyl  formation. For that  purpose,  the  non-promoted  alumina-supported  nickel catalyst

was tested  at 20 bar and 310 oc using three  different  pellet sizes. It was found  and  proved that  the

use of large catalyst  pellet sizes significantly suppresses this  kind of deactivation. The results  were scientifically explained  by the influence of internal mass transfer phenomena. In order  to support this conclusion,  COMSOL multihpysics computations were  performed  to estimate internal  temperature and concentration profiles for the different  pellet sizes.

The second  part of the  work was focused  on the effect of the selected  promoters on the  resistance towards  carbon  formation. For that  purpose, the different  catalysts  were tested  at 310 oc, 1 bar and

a H,/C0=3; conditions  at which the carbon formation  is favorable. The spent  samples  were analyzed by means  of temperature-programmed hydrogenation  analyses  in order  to quantify the  amount  of carbon  formed. It was found  that  the  use of Zr02,  in particular,  significantly reduces  the  rate  of carbon formation.

The third  part  of  the  work  consisted  in studying  the  effect  of these   promoters on  the  catalyst resistance  towards thermal  sintering.  For that  purpose,  the  different  catalysts  were  exposed  to an

accelerated aging  procedure (690 oc and  H20/H2=2). The intrinsic catalytic activity of the  catalysts

was  then  determined for  both  the  fresh  and  aged  samples   by testing  these  at  non-deactivating conditions  (300 oc, 1 bar and  H,jC0=9).  No clear  improvement neither  decline  in catalyst  stability

was observed for any of the promoted  catalyst samples.

Place, publisher, year, edition, pages
2015. , 54 p.
Keyword [en]
synthetic natural gas, nickel, carbon formation, nickel carbonyl, sintering
National Category
Other Chemical Engineering
URN: urn:nbn:se:kth:diva-172205OAI: diva2:846119
Available from: 2015-08-14 Created: 2015-08-14 Last updated: 2015-08-14Bibliographically approved

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