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velocities (GHSV) of 43,000 h−1. The first set of results of

catalytic tests is presented in Fig. 1.

Moreover, the stability of the catalysts was evaluated, after a 10h

reaction at 400°C.

As a general observation, some of these firstly prepared catalysts

revealed interesting properties towards the selective CO

2

hydrogenation into methane, when compared to the best cases

previously studied and published reporting the use of potentially

more expensive rare earth oxides bulk supports.

Optimised methanation CATHPRO catalysts

After the first results, the effects of several catalyst preparation

details and methods, such as the drying method after

impregnation, the calcination temperature, as well as of the pre-

reduction conditions of the samples, were evaluated towards the

carbon dioxide methanation. Thus, it was proved that CO

2

conversion and CH

4

selectivity can be maximised through the

proper choice of both preparation and pre-reduction conditions.

The impact of doping these catalysts with Ce was also

investigated. The Ce addition was responsible for a further

enhancement of the catalytic properties, concerning the activity

and selectivity (Fig. 2).

On the other hand, the recent installation of an operando infrared

spectroscopy (FTIR) facility at the CATHPRO Laboratory, allowed a

specific characterisation of the reaction process, thus revealing

some interesting insights concerning the reaction mechanism,

namely pointing out the possibility that the support could

promote the CO

2

activation.

Under methanation conditions, it was observed that dissociated

hydrogen reacts with carbonates and/or physisorbed CO

2

, leading

firstly to monodentate formates, then carbonyls (both adsorbed

onto Ni

o

particles), and finally to methane.

Furthermore, the formation of inactive ‘free’ carbonates is

observed from T = 350°C, on all Ni/USY catalysts, probably

resulting from interaction with nickel oxide species.

The simultaneous measurements of both adsorbed and gaseous

species seems to confirm previous conclusions in the literature

indicating that the CO dissociation/hydrogenation is the rate-

determining step for the CO

2

methanation.

Ongoing studies

Taking into account the general features of zeolites, and the

possibilities to finely regulate its properties, inducing relevant

changes on the properties of adsorbed metal species and in the

CO

2

activation ability of the final catalyst, a wide window of future

research was opened.

In fact, further recent improvements have already been reached

after preparing another set of zeolite Y samples, with different

framework aluminium contents, and by exchanging the sodium

cations of the initially tested zeolite forms.

Carlos Henriques

Associated Professor/DEQ

tel :

+351 218419288

carlos.henriques@tecnico.ulisboa.pt

José Manuel Lopes

Associated Professor/DEQ

tel :

+351218419286

jmlopes@tecnico.ulisboa.pt

CATHPRO webpage:

http://groups.ist.utl.pt/~cqe.daemon/members- contacts/research-groups-2/149-2/ www.horizon2020projects.com

H O R I Z O N 2 0 2 0 P R O J E C T S : P O R TA L

I S S U E S E V E N

31

P R O F I L E

S P E C I A L F E AT U R E : M AT E R I A L S

Thermodynamic CH

4

selectivity (%)

CH

4

selectivity (%)

Temperature (°C)

200

0

20

40

60

80

100

250300350400450500

15%Ce - 15% Ni/USHY

15% Ni/USHY

Thermodynamic CH

4

selectivity (%)

CH

4

selectivity (%)

Temperature (°C)

200

0

20

40

60

80

100

250300350400450500

15%Ce - 15% Ni/USHY

15% Ni/USHY

Fig. 2 CO

2

conversion and CH

4

selectivity, at GHSV = 43000 h-1, for 14% Ni/USNaHY (

) and 15%Ce - 14% Ni/USNaHY (

) catalysts. Dashed line:

thermodynamic equilibrium values