Abstract
A mesh-type structured anodic alumina supported Cu/Ni bi-functional catalyst was developed for steam reforming of dimethyl ether (SRD). It was found that the Cu/Ni/γ-Al2O3/Al catalyst had remarkable catalytic activity and stability, but a high CO selectivity. Therefore, a multi-functional catalyst was proposed by metals (Fe, Zn, or La) addition to inhibit CO formation during the SRD process. The results show that promoter Fe can improve the Cu dispersion and decrease the reduction temperature of catalyst, and CO selectivity was minimized from 27% to around 3%. However, the addition of Zn and La only can decrease the CO selectivity to 12%. Furthermore, there was an excellent synergetic effect between Cu/Ni/γ-Al2O3 and Fe over the Cu/Ni/Fe/γ-Al2O3/Al catalyst by evaluating catalytic performance of catalysts with different packing structures. And the synergetic mechanism of the active components (γ-Al2O3, Cu or Cu2O, and Fe3O4) for SRD and CO in suit removal was proposed. Finally, a 400-h durability test was carried out and the results show that the Cu/Ni/Fe/γ-Al2O3/Al catalyst had an excellent stability with a 100% DME conversion and low CO selectivity.
Highlights
The overall steam reforming of dimethyl ether (SRD) proceeds via two successive steps: hydration of dimethyl ether (DME) to methanol (MeOH) (Equation (1)), and methanol steam reforming to hydrogen (SRM)
The Cu dispersion of different catalysts decreased in the order of: Cu/Ni/Fe/γ-Al2O3/Al > Cu/Ni/γ-Al2O3/Al > Cu/Ni/Zn/γ-Al2O3/Al > Cu/Ni/La/γ-Al2O3/Al, indicating that the Cu dispersion was improved by the incorporation of Fe promoter, while decreased by the addition of Zn or La
The multifunctional Cu/Ni/γ-Al2O3/Al catalysts loaded with different metals were prepared to inhibit CO formation in SRD system
Summary
The sintering of metallic Cu will lead to a poor thermal stability above 300 ̊C, which is a shortcoming for combining metallic Cu and γ-Al2O3 as the bi-functional catalysts for SRD To solve this problem, copper-based spinel type of catalysts have been investigated as alternative metallic components, since they have a high thermal stability in SRD above 325 ̊C, but a very high temperature (up to 1000 ̊C) was required to prepare the spinel [9] [10] [11]. Copper-based spinel type of catalysts have been investigated as alternative metallic components, since they have a high thermal stability in SRD above 325 ̊C, but a very high temperature (up to 1000 ̊C) was required to prepare the spinel [9] [10] [11] Another promising method is to improve the dispersion of metal Cu on the support by adding an extra metal. A 400-h stability evaluation was carried out over the optimized Cu/Ni/Fe/γ-Al2O3/Al catalyst
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