含氮合成气在三相淤浆床－固定床中直接合成二甲醚

在三相淤浆床－固定床反应装置中，研究含氮合成气直接合成二甲醚。使用双功能混合催化剂，粒度为0.15 mm～0.18 mm。在220 ℃～260 ℃、3.0 MPa～7.0 MPa、空速1 000 mL·g-1·h-1时考察了温度、压力及两种反应器中催化剂的装填比例对CO转化率及二甲醚选择性的影响。结果表明，一氧化碳转化率随反应压力的增加而提高，随着温度升高二甲醚的选择性变化不大，CO转化率的升高较明显，因此在催化剂活性适宜的温度范围内，该反应装置可以采用较高的反应温度。当260 ℃、7.0 MPa、三相床与固定床中催化剂比例为1∶1时，CO的转化率可达84.5％，二甲醚的选择性为78.7％。淤浆床－固定床反应装置具有操作稳定性好、CO转化率高的优点。催化剂在该装置中反应370 h活性没有明显下降。

Direct synthesis of dimethyl ether from syngas containing N2 in a slurry reactor in tandem with a fixed-bed reactor

The slurry reactor with inert liquid can transfer heat in time and avoid the catalysts sintering, CO rich synthesis gas can be used in this reactor. In order to maintain both effective heat transfer and higher CO conversion, a slurry reactor in tandem with a fixed-bed reactor was used for DME synthesis. The synthesis gas was pre-mixed in a pressurized gas cylinder. The high pressure syngas was regulated and its flow rate was controlled by a mass flowmeter and fed to the reactor. The reaction pressure was kept by a back pressure regulator. The reactor effluent was analyzed on-line by two gas chromatographs. The experiments were carried out in the range of 220 ℃～260 ℃, 3.0 MPa～7.0 MPa and 500 mL·g-1·h-1～2 000 mL·g-1·h-1. The catalyst was a physical mixture of commercial methanol synthesis catalyst and methanol dehydration catalyst, the granularity was 0.15 mm～0.18 mm. The experimental results showed that the conversion of CO increased with increasing reaction temperature and pressure, the selectivity of DME was insensitive to temperature and pressure. 7.0 MPa and 260 ℃ were the optimal reaction conditions, at which 84.5% of CO conversion and 78.7% of DME selectivity were obtained while the the weight ratio of the catalysts loaded in the two reactors was 1∶1. Then DME synthesis reactions carried out in a fixed-bed reactor, a slurry reactor and the slurry-fixed-bed equipment respectively were compared and the adiabatic temperature rise of syngas was calculated. The results demonstrated that higher CO conversion was obtained in the slurry-fixed-bed equipment and the high temperature of hotspot was avoided simultaneously. Moreover, the catalyst was stable in the reactor during the 370 h reaction.