Continuous Production of Dimethyl Ether from Methane and Carbon Dioxide.

The dry reforming of CH4 (with CO2) at 800 °C under 1 MPa to synthesis gas and the synthesis of dimethyl ether (DME) from synthesis gas were combined. A Ni/(MgO)3·Al2O3 catalyst derived from Mg3Ni3Al2(OH)16CO3·xH2O hydrotalcite precursor showed a CH4 conversion of 85.4% after 5 min on stream for the dry reforming. The CH4 conversion decreased to 70.1% after 15 h on stream because the carbonaceous deposit formed during the reaction covered the active sites of Ni/(MgO)3·Al2O3 catalyst. The deactivated Ni/(MgO)3·Al2O3 catalyst was refreshed by calcining in air at 800 °C and subsequently reducing in H2. A mechanical mixed catalyst containing Cu/(ZnO)3·Al2O3 and Cs2.5H0.5PW12O40 (denoted as Cu/(ZnO)3·Al2O3 + Cs2.5) was used for the DME synthesis from syngas. Cu/(ZnO)3·Al2O3 + Cs2.5 showed a CO conversion of 38.5% and a DME selectivity of 63.8% at 260 °C under 1 MPa. A stable activity of Cu/(ZnO)3·Al2O3 + Cs2.5 had been maintained over 30 h in the DME synthesis. A two-stage process was designed for the DME synthesis from CH4 and CO2. Two fixed-bed reactors filled with Ni/(MgO)3·Al2O3 were connected in parallel (switching between reaction and refresh) for the CH4 dry reforming. A fixed-bed reactor filled with Cu/(ZnO)3·Al2O3 + Cs2.5 was connected in series with the two reactors filled with Ni/(MgO)3·Al2O3 to produce DME. The conversion of CH4 was kept at above 80% and the yield of DME was kept at above 20% after 30 h on stream for the DME synthesis from CH4 and CO2.A two-step process combining CH4 dry reforming to syngas and DME synthesis from syngas was designed for the DME synthesis from CH4 and CO2. The conversion of CH4 was kept at above 80% and the yield of DME was kept at above 20% after 30 h on stream in the two-stage processGraphic Abstract: The dry reforming of CH4 (with CO2) at 800 °C under 1 MPa to synthesis gas and the synthesis of dimethyl ether (DME) from synthesis gas were combined. A Ni/(MgO)3·Al2O3 catalyst derived from Mg3Ni3Al2(OH)16CO3·xH2O hydrotalcite precursor showed a CH4 conversion of 85.4% after 5 min on stream for the dry reforming. The CH4 conversion decreased to 70.1% after 15 h on stream because the carbonaceous deposit formed during the reaction covered the active sites of Ni/(MgO)3·Al2O3 catalyst. The deactivated Ni/(MgO)3·Al2O3 catalyst was refreshed by calcining in air at 800 °C and subsequently reducing in H2. A mechanical mixed catalyst containing Cu/(ZnO)3·Al2O3 and Cs2.5H0.5PW12O40 (denoted as Cu/(ZnO)3·Al2O3 + Cs2.5) was used for the DME synthesis from syngas. Cu/(ZnO)3·Al2O3 + Cs2.5 showed a CO conversion of 38.5% and a DME selectivity of 63.8% at 260 °C under 1 MPa. A stable activity of Cu/(ZnO)3·Al2O3 + Cs2.5 had been maintained over 30 h in the DME synthesis. A two-stage process was designed for the DME synthesis from CH4 and CO2. Two fixed-bed reactors filled with Ni/(MgO)3·Al2O3 were connected in parallel (switching between reaction and refresh) for the CH4 dry reforming. A fixed-bed reactor filled with Cu/(ZnO)3·Al2O3 + Cs2.5 was connected in series with the two reactors filled with Ni/(MgO)3·Al2O3 to produce DME. The conversion of CH4 was kept at above 80% and the yield of DME was kept at above 20% after 30 h on stream for the DME synthesis from CH4 and CO2.A two-step process combining CH4 dry reforming to syngas and DME synthesis from syngas was designed for the DME synthesis from CH4 and CO2. The conversion of CH4 was kept at above 80% and the yield of DME was kept at above 20% after 30 h on stream in the two-stage process [ABSTRACT FROM AUTHOR]