Synthesis of dimethyl ether from syngas using a hierarchically porous composite zeolite as the methanol dehydration catalyst
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摘要: 以Beta分子筛为核、Y型分子筛为壳层的多级孔复合分子筛(BFZ)作为甲醇脱水催化剂用于固定床中合成气一步法制备二甲醚,并与纯Y型分子筛进行了比较,研究了二甲醚合成催化反应活性与甲醇脱水催化剂孔道结构和酸性之间的关系.结果表明,复合分子筛HBFZ具有中等强度的酸性和中孔孔道结构,有利于提高合成气制备二甲醚的催化反应活性.二甲醚直接合成催化剂由工业CuO/ZnO/Al2O3催化剂(CZA)与分子筛(HBFZ、HY)采用机械混合方法制备;催化评价结果显示,CZA/HBFZ比CZA/HY具有更优的催化活性和稳定性.在250 ℃, 5.0 MPa 和 1 500 h-1的反应条件下,CZA/HBFZ催化剂上CO的转化率和DME的选择性分别达到94.2%和67.9%.Abstract: Hierarchically porous composite zeolite (BFZ, with Beta zeolite cores and Y zeolite polycrystalline shells) was employed as the methanol dehydration catalyst in the direct synthesis of dimethyl ether (DME) from syngas in a fixed-bed reactor. The correlation between the catalytic activity and the textural and acid properties of the dehydration catalyst was investigated. The results indicate that the composite zeolite of H-form (HBFZ) exhibits moderate acid strength and meso-porosity, which is responsible for the high activity of CO hydrogenation. For the direct synthesis of DME from CO hydrogenation over the physical mixture of commercial CuO/ZnO/Al2O3 catalyst (CZA) and the H-form zeolites (HBFZ or HY), CZA/HBFZ exhibits higher activity and stability than CZA/HY. Under 250 ℃, 5.0 MPa and 1 500 h-1, the conversion of CO and the selectivity to DME over CZA/HBFZ achieve 94.2% and 67.9%, respectively.
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Key words:
- composite zeolite /
- dimethyl ether /
- hybrid catalysts /
- hierarchical pore structure /
- syngas /
- methanol dehydration
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