Stabilizing Supported Ni Catalysts for Dry Reforming of Methane by Combined La Doping and Al Overcoating Using Atomic Layer Deposition

Abstract

Deposition of La 2 O 3 and Al 2 O 3 on Al 2 O 3 -supported Ni catalysts was performed to study their effects on heterogeneous catalysts for the dry reforming of methane (DRM) reaction. An alumina-supported Ni catalyst (Ni/Al 2 O 3 , 2 wt % of Ni), synthesized via incipient wetness impregnation, loses ∼87% of its initial activity within 45 h under DRM conditions. While overcoating of Al 2 O 3 on this catalyst via atomic layer deposition (ALD) helps stabilize the catalytic activity in long time-on-stream (TOS) tests, this overcoated catalyst is ca. 40 times less active than the uncoated catalyst at peak activity. This Al 2 O 3 -overcoated Ni/Al 2 O 3 catalyst also exhibits a long induction period (∼20 h) due to the slow reduction of Ni 2+ within the catalytically inactive nickel aluminate (NiAl 2 O 4 ) phase, formed by the interaction of metallic Ni with the Al 2 O 3 overcoat during pre-DRM treatment at the 700 °C reaction temperature. Here, we report that, while doping small amounts of La (∼0.03 wt %) into the Ni/Al 2 O 3 catalyst does not significantly affect the catalytic activity or stability by itself, the addition of ALD-Al 2 O 3 on top of the La 2 O 3 -promoted Ni catalysts significantly suppresses the long TOS deactivation, helps recover the peak activity of uncoated Ni/ Al 2 O 3 , and eliminates the DRM induction period. This strategy obtains the stabilization benefits of Al 2 O 3 overcoating on Ni/Al 2 O 3 while, at the same time, avoiding the formation of undesirable NiAl 2 O 4 species.

Review on supported metal catalysts with partial/porous overlayers for stabilization

“…42,79,80 Usually, oxides of SiO 2 , Al 2 O 3 ZrO 2 , and TiO 2 can be used as the overlayers, the thickness of oxide film is controlled by the number of deposition cycles, and the porosity of the oxide film is generally generated under high-temperature calcination. 81…”

“…42,79,80 Usually, oxides of SiO 2 , Al 2 O 3 ZrO 2 , and TiO 2 can be used as the overlayers, the thickness of oxide film is controlled by the number of deposition cycles, and the porosity of the oxide film is generally generated under high-temperature calcination. 81 This review focuses on several typical studies on SMCPO achieved by ALD. The catalyst of Al 2 O 3 @Pd/Al 2 O 3 is synthesized by 45 cycles of trimethylaluminum (TMA) and water at 200 °C onto Pd/Al 2 O 3 .…”

Ammonia-assisted reforming and dehydrogenation toward efficient light alkane conversion

“…Significant achievements were made during the past decade regarding the catalyst design and process innovation for efficient light alkane conversion, mainly for conventional steam-/dryreforming, [3][4][5][6][7][8] oxidative/non-oxidative dehydrogenation, [9][10][11][12][13][14][15][16][17] partial oxidation, [18][19][20][21][22][23][24][25] and dehydroaromatization. [26][27][28][29][30][31][32][33][34][35][36][37] For example, the McFarland group reported the simultaneous pyrolysis and dry reforming of methane in a bubble column reactor using a molten Ni/In alloy catalyst.…”

Engineering the TiOx Overlayer on Ni Catalyst to Balance Conversion and Stability for Methane Dry-CO2 Reforming

“…Nickel-based catalysts have a low price, high availability, and comparable activity. 6 Many methodologies have been applied to improve the coking and sintering resistance of the Ni-based catalyst, including the selection of the support 9−11 and promoters, 12−14 the application of bimetallic Ni catalyst, 15−20 strengthening the metal support interactions, 11,21,22 catalysts like core/yolk shell, 12,23 sandwiched catalyst, 24,25 perovskite, 20,26 and others. Among them, creating a strong metal support interaction (SMSI) between the Ni and the support has been reported to be an effective strategy to improve the thermal and the coke resistance by its unique geometric and electronic properties in DRM.…”