Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6453543 | Applied Catalysis B: Environmental | 2018 | 10 Pages |
â¢Pd(0), In2O3 and PdIn intermetallic nanoparticles prepared and assessed.â¢PdIn intermetallic compound is highly active and selective for the liquid phase methanol synthesis from CO2.â¢70% higher methanol production rate than the reference Cu/ZnO/Al2O3 catalyst.â¢Surface In-enriched intermetallic PdIn nanoparticles (ca. 8 nm) identified.â¢PdIn intermetallic compound shows improved stability.
Direct hydrogenation of CO2 to methanol could offer significant environmental benefits, if efficient catalysts can be developed. Here, bimetallic Pd-In nanoparticles show good performance as catalysts for this reaction. Unsupported nanoparticles are synthesised by the thermal decomposition of Pd(acetate)2 and In(acetate)3 precursors in a high boiling point solvent (squalane), followed by reduction using dilute H2 gas (210 °C). Adjusting the ratio of the two metallic precursors allow access to 5-10 nm nanoparticles with different phase compositions, including metallic Pd(0), In2O3 and intermetallic PdIn. Liquid phase methanol synthesis experiments (50 bar, 210 °C, H2:CO2 = 3:1) identify the intermetallic PdIn nanoparticles as the most efficient. The catalysts exhibit around 70% higher methanol rates (normalised to the overall molar metal content) compared to the conventional heterogeneous Cu/ZnO/Al2O3 catalyst (900 and 540 μmol mmolPdInorCuZnAlâ1 hâ1, respectively). In addition, the optimum Pd/In catalyst shows an improved methanol selectivity over the whole temperature range studied (190-270 °C), reaching >80% selectivity at 270 °C, compared to only 45% for the reference Cu/ZnO/Al2O3 catalyst. Experiments showed an improvement in stability; the methanol production rate declined by 20% after 120 h run for the optimum PdIn-based compared with 30% for the Cu/ZnO/Al2O3 catalyst (after 25 h). The optimum catalyst consists of â¼8 nm nanoparticles comprising a surface In-enriched PdIn intermetallic phase as characterised by XRD, HR-TEM, STEM-EDX and XPS. Post-catalysis analysis of the optimum catalyst shows that the same PdIn bimetallic phase is retained with only a slight increase in the nanoparticle size.
Graphical abstractDownload high-res image (96KB)Download full-size image