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The development of methanation catalysts with a high catalytic activity at low temperatures and a long-term durability at high temperatures is still challenged by the conflicting constraint on the catalyst design. In this work, Ni(NO 3) 2 ·6H 2 O. and ordered mesoporous alumina (OMA) containing different amounts of the P123 template were co-ground to prepare Ni/OMA catalysts. Results indicate that NiO was embedded in the meso-channels of OMA via the solid-state grinding. Moreover, the metal particle size, dispersion and reducibility of the catalyst can be easily regulated by the amount of the residual P123 template in OMA, which can be simply controlled by changing the treatment temperature of the OMA precursor. The optimized 15Ni/OMA-120 with a high dispersion and small size of metallic Ni showed high low-temperature catalytic activity with TOF of 31.5 h−1 and STY of 319.1 mol CH4 g cat h−1 at 340 °C, but also demonstrated good anti-sintering and coke-resistance performance with a time-on-stream of 150 h long-term durability at 600 °C, which is comparable with the counterpart 15Ni-OMA prepared by traditional wet-process of one-pot evaporation induced self-assembly. [Display omitted] • High-performance Ni/OMA catalyst was prepared by solid-state grinding method. • The interaction between residual template and Ni precursor could be regulated. • Ni/OMA catalyst showed high dispersion and small size of metallic Ni. • 15Ni/OMA-120 showed both a high activity and good stability at high temperatures. [ABSTRACT FROM AUTHOR]

In this work, amorphous silica-alumina composite (ASA) with varied compositions was synthesized via the complex-decomposition method with different complex agents. The XRD characterization revealed the amorphous nature of ASA composites regardless of the synthesis conditions. However, the acidity and the textural properties of ASA composites characterized by BET, Py-FTIR and NH 3 -TPD were significantly affected by the specific complex agent and amount, Si/Al molar ratio and calcination temperature. Among the investigated complex agents, the optimal amount of ammonium carbonate was the most efficient in tailoring both the textural and acidic properties of ASA. The hybrid of the synthesized ASA and a commercial Cu/ZnO/Al 2 O 3 was studied for the steam reforming of dimethyl ether (SRD), and ASA synthesized by using ammonium carbonate as the complexing agent showed the optimal activity. Importantly, the synergetic effect between ASA and Cu/ZnO/Al 2 O 3 was found to play a crucial role in determining the activity and stability of the bifunctional catalyst, and the partial oxidation of Cu0 to Cu+ induced from the ASA acidity had a great contribution to the deactivation of the bifunctional catalyst. These understandings are favorable for developing a more efficient solid acid for SRD. [Display omitted] • ASA was prepared by complex-decomposition method with different complexing agents. • ASA obtained with ammonium carbonate as complexing agent was more effective for SRD. • Over 80% DME conversion and H 2 yield were achieved at 300 ℃ over optimal catalyst. • ASA-induced Oxidation of Cu0 to Cu+ was one reason for deactivating SRD catalyst. [ABSTRACT FROM AUTHOR]

• Various amorphous silica-alumina composites were synthesized by hydrolytic method. • Amorphous silica-alumina composite was revealed an efficient solid acid for SRD. • A stable bifunctional catalyst with >99% DME conversion and H 2 yield was obtained. • DME hydrolysis was revealed the rate-limiting step for two-step reactions of SRD. In this work, we demonstrate that the amorphous silica-alumina composite (ASA) is an efficient solid acid for the steam reforming of dimethyl ether (SRD). Thus, a series of ASA with different Si/Al molar ratios was synthesized via the modified hydrolytic method by using Al(NO 3) 3 ·9H 2 O and/or NaAlO 2 as Al precursor and tetraethoxysilane as Si precursor, respectively. Irrespective of the synthesis conditions, all of ASA composites were in an amorphous nature. However, both the acidity and the surface area were significantly affected by the synthesis conditions, the extent of which depends on the specific precursor and Si/Al molar ratios. The ASA physically mixed with a commercial Cu/ZnO/Al 2 O 3 was investigated as a bifunctional catalyst for SRD under the conditions of P=0.1 MPa and gas hourly space velocity of 4000 h−1. Results indicate that both the conversion of dimethyl ether (DME) and the hydrogen yield were strongly dependent on the acidic property of ASA and the ASA to Cu/ZnO/Al 2 O 3 ratios. Following the two-step consecutive mechanism of SRD, the catalytic results were well explained based on the acidic property of ASA, and the synergetic effect between the two catalytic functions was found to play a crucial role in determining the activity and stability of the bifunctional catalyst. Moreover, the DME hydrolysis was revealed to be the rate-limiting step for SRD reactions in the case of ASA as an acidic catalyst. By optimizing the synthesis conditions of ASA and the composition of the bifunctional catalyst, greater than 99% of DME conversion and hydrogen yield was achieved, and was kept for a time on stream of 66 h without an observable decrease. Thus, ASA is a very efficient solid acid for SRD. [ABSTRACT FROM AUTHOR]