CO2 reforming of methane over coprecipitated Ni–Al catalysts modified with lanthanum

doi:10.1016/j.apcata.2004.06.017

Applied Catalysis A: General

Volume 274, Issues 1–2, 28 October 2004, Pages 139-149

https://doi.org/10.1016/j.apcata.2004.06.017 Get rights and content

Abstract

The influence of lanthanum oxide added to a Ni/Al₂O₃ catalyst has been studied in the carbon dioxide reforming of methane. The samples were prepared by variable pH coprecipitation, with different La₂O₃ contents: 0, 4, 8, and 12 wt.%. Although the NiO reducibility was not altered, the presence of La increased the metallic dispersion (XPS, XRD, TEM), slightly increased conversion levels, and also enhanced the catalyst stability due to a substantial decrease in coke formation during reaction. An increase in Ni dispersion in samples containing La leads to more metallic particles with diameters less than 10 nm that contribute to the catalytic conversion without producing large amounts of coke in filaments. However, there is a limit to the amount of lanthanum oxide (between 8 and 12 wt.%) above which metallic dispersion is not favored, and therefore coke filament formation and quick catalyst deactivation cannot be controlled. This is probably due to the poor La₂O₃ dispersion in these materials (XPS), leading to a loss in the improvement of Ni–Al–La catalyst properties. La atoms are included in the metallic nickel lattice after 4 h of reaction. After a long reaction time La is segregated and the Ni particle size increases, leading to greater coke production (in filaments).

Introduction

In recent years, the study of methane reforming with carbon dioxide (also called “dry reforming”) has been of great interest to the scientific world in general and catalysis specialists in particular. In this process, the H₂/CO ratio is significantly lower than with other reforming reactions (steam reforming). This is of great importance for some industrial processes such as oxo synthesis and Fischer–Tropsch synthesis. Also, the use of CH₄ and CO₂, both considered as contributors to the greenhouse effect, for conversion to added value products is attractive from an environmental point of view.

The main disadvantage of dry reforming is its high tendency towards coke formation. This can be solved by using noble metal based catalysts, such as Pt [1], Rh [2], and Ru [3]. However, these materials are expensive and the use of cheaper metals is preferred. An alternative is the use of nickel catalyst, a classic in steam reforming. In fact, Ni shows a high activity in the reforming of methane with CO₂, comparable in some studies to the noble metals [4]. Thus the objective is an efficient reduction of the coke production with these catalysts. In this context, the addition of various compounds such as MgO [5], [6] or other basic oxides (CaO, K₂O) has changed the properties of some catalysts (including commercial ones) for steam reforming. This has been particularly effective in reducing coke formation. Lanthanum oxide has been previously used in catalysts for dry reforming, mainly as the only support component [7], [8], [9]. Studies conducted by Zhang et al. [10] with Ni–Al₂O₃ and Ni–La₂O₃ catalysts in this reaction at 750 °C show the stability of the latter. While the former showed a high activity loss after 8 h, the reaction rate with the Ni–La₂O₃ increased during the 3 first hours and remained constant until the end of the experiment (ca. 100 h).

These results are interesting from the point of view of catalytic stability, because they attribute the higher stability to the lanthanum oxide. Nevertheless, alumina is probably a more suitable support (due to its high mechanical strength, high surface area, and low price) for use in catalysis, especially in the reforming of hydrocarbons. Thus the structural and thermal stability of Ni–B/γ-Al₂O₃ catalyst, as well as Ni dispersion, was reported to have been improved by La addition [11].

Interesting research was conducted in the 1980s relating to the use of Ni–Al catalysts prepared by coprecipitation in methanation of CO [12], [13], [14]. The authors found that samples obtained by coprecipitation were more or less active depending on the preparation conditions. They also conducted studies into the effects of the addition of various Group I and II compounds such as La and Ce [15], Ti [16], La [17], and Ce [18]. A slight increase in methanation activity was achieved by the presence of La in Ni–Al catalysts, either La-impregnated samples after coprecipitation, or La-containing coprecipitated catalysts. In the first case, this fact was attributed to a promotion of turnover number of nickel sites due to the lanthanum present at the metallic surface rather than stabilizing the Ni surface (dispersion) [15]. Coprecipitated Ni/Al₂O₃ samples showed slightly smaller Ni particle sizes with low La amounts (up to 3 mol% La) [17], increasing nickel dispersion.

In these studies, however, not much attention was paid to the carbon (coke) formation in both the methanation of CO and dry reforming of methane reactions, but especially in the latter. Only Olsbye et al. [19], [20] studied coke formation on 0.15 wt.% Ni/Al₂O₃ catalysts with and without 1.7 wt.% La in dry reforming, finding that the La promoter decreased coke formation (by half). Neither was much consideration given to catalyst stability during the reforming reaction.

Thus the aim of this work is to study the influence of an interesting additive such as lanthanum oxide with a Ni–Al₂O₃ catalyst prepared by coprecipitation for the reforming of methane with CO₂. The characterization of the catalysts prepared were evaluated by various techniques and their catalytic effects were studied. Carbon formation during reaction and the stability of different samples were evaluated.

Section snippets

Synthesis of catalysts

The Ni–Al–La catalysts were prepared in the laboratory by coprecipitation using a similar method to that described by Al-Ubaid and Wolf [21]. These authors concluded that Ni–Al catalyst prepared with a ratio of Ni:Al 1:2 (approx. 36 wt.% in Ni) resulted in the highest stability for the steam reforming of methane. The metallic nitrates Ni(NO₃)₂·6H₂O, Al(NO₃)₃·9H₂O, and La(NO₃)₃·6H₂O dissolved in deionized water were used as reagents, and a solution of NH₄OH as precipitating reagent. The

Catalyst characterization

The Ni/Al and La/Ni atomic ratios for the four calcined samples were obtained by chemical analysis (ICP) (Table 1). A comparison of these results with the theoretical ratios shows a good agreement. The difference is due to nickel losses during precipitation, as is demonstrated by the chemical analysis of the remaining solution.

The BET areas obtained were similar, ranging from 131 to 150 m²/g (Table 1).

Temperature-programmed reduction experiments (Fig. 1) showed a maximum at 712–730 °C. The

Conclusions

The benefit has been shown of adding lanthanum oxide to a Ni–Al catalyst prepared by coprecipitation (at variable pH) for methane reforming with carbon dioxide. This positive effect was expressed through better metallic dispersion, slightly higher conversion levels, and a significant decrease in coke formation during reaction. Temperature-programmed reduction experiments detected a narrower NiO particle size distribution in samples containing lanthanum. After reduction, Ni particles with

Acknowledgements

The authors thank the European Union (Project 2FD97-0890) and CICYT (Spain) for providing financial support for the study.

References (39)

J.H. Bitter et al.
J. Catal.
(1997)
A. Erdohelyi et al.
J. Catal.
(1993)
M.C.J. Bradford et al.
J. Catal.
(1999)
Z.L. Zhang et al.
Catal. Today
(1994)
Y. Hou et al.
Appl. Catal. A
(2004)
M.R. Gelsthorpe et al.
J. Mol. Catal.
(1984)
H.G.J. Lansink Rotgerink et al.
Appl. Catal.
(1988)
U. Olsbye et al.
Appl. Catal. A
(2002)
A. Al-Ubaid et al.
Appl. Catal.
(1988)
S.D. Robertson et al.
J. Catal.
(1975)

R. Blom et al.

Catal. Today

(1994)

E Ruckenstein et al.

J. Catal.

(1996)

K.S. Kim et al.

Surf. Sci.

(1974)

A. Slagtern et al.

Appl. Catal. A

(1997)

T. Horiuchi et al.

Appl. Catal. A

(1998)

J.H. Kim et al.

Appl. Catal. A

(2000)

T.Y. Chou et al.

Catal. Today

(1995)

A. Slagtern et al.

Appl. Catal. A

(1996)

J.R. Rostrup-Nielsen et al.

J. Catal.

(1992)

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CO2 reforming of methane over coprecipitated Ni–Al catalysts modified with lanthanum

Abstract

Introduction

Section snippets

Synthesis of catalysts

Catalyst characterization

Conclusions

Acknowledgements

J. Catal.

J. Catal.

J. Catal.

Catal. Today

Appl. Catal. A

J. Mol. Catal.

Appl. Catal.

Appl. Catal. A

Appl. Catal.

J. Catal.

Catal. Today

J. Catal.

Surf. Sci.

Appl. Catal. A

Appl. Catal. A

Appl. Catal. A

Catal. Today

Appl. Catal. A

J. Catal.

CO₂ reforming of methane over coprecipitated Ni–Al catalysts modified with lanthanum