Reaction parameters influence on the catalytic performance of copper-silica aerogel in the methanol steam reforming
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Abstract: Steam reforming of methanol was carried out on the copper-silica aerogel catalyst. The effects of reaction temperature, feed rate, water to methanol molar ratio and carrier gas flow rate on the H2 production rate and CO selectivity were investigated. Methanol conversion was increased considerably in the range of about 240-300, after which it increased at a slightly lower rate. The used feed flow rate, steam to methanol molar ratio and carrier gas flow were 1.2-9.0 mL/h, 1.2-5.0 and 20-80 mL/min, respectively. Reducing the feed flow rate increased the H2 production rate. It was found that an increase in the water to methanol ratio and decreasing the carrier gas flow rate slightly increases the H2 production rate. Increasing the water to methanol ratio causes the lowest temperature in which CO formation was observed to rise, so that for the ratio of 5.0 no CO formation was detected in temperatures lower than 375 ℃. In all conditions, by approaching the complete conversion, increasing the main product concentration, increasing the temperature and contact time, and decreasing the steam to methanol ratio, the CO selectivity was increased. These results suggested that CO was formed as a secondary product through reverse water-gas shift reaction and did not participate in the methanol steam reforming reaction mechanism.
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Key words:
- copper-silica aerogel /
- activity /
- CO selectivity /
- reaction parameters /
- methanol steam reforming
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Figure 1 Catalytic activity of copper silica aerogel in methanol steam reforming.
(t=300 ℃, H2O/CH3OH (molar ratio)=2, Ar flow=30 mL/min, MeOH Feed=23.5 mmol·h-1·gcat-1)
Figure 2 Effect of the feed flow rate on the methanol conversion, H2 production and CO selectivity at different temperatures (H2O/CH3OH (molar ratio)=2)
■: 240 ℃; ▲: 300 ℃◇: 325 ℃; ●: 350 ℃
Figure 3 Hydrogen production rate using different molar ratio (R) of steam to methanol
Figure 4 Effect of reaction temperature on the methanol conversion using H2O/CH3OH molar ratio of 5.0 at different liquid feed rates
Figure 5 Effect of reaction temperature on the methanol conversion and CO selectivity using H2O/CH3OH molar ratio of 2.0 at different liquid feed rates
Figure 6 Effect of carrier gas flow rate on the methanol conversion at different conditions
(R: H2O/CH3OH molar ratio, F: liquid feed flow: (mL/h), t: reaction temperature (℃))
Figure 7 Effect of carrier gas flow rate on CO selectivity at different conditions (R: H2O/CH3OH molar ratio, F: liquid feed flow: (mL/h), t: reaction temperature (℃))
Table 1 Stability comparison of various methanol steam reforming catalysts
Catalyst Reaction temp. t/℃ Time on stream t/h Decrease in MeOH conversion w/% CuO/Cr2O3/F2O3/Graphite[2] 220 100 about 30%-40% of its initial activity CuO/ZrO2/CeO2[2] CuO/ZnO/Al2O3/Graphite[2] Cu/La2O3/ZrO2 [5] 300 10 about 18%-24% of its initial activity Cu/Y2O3/ZrO2 30/20/50[5] 300 10 stable at about 70% Cu/Y2O3/ZrO2[5] 300 10 about 11%-32% of its initial activity Cu/CeO2/ZrO2[5] 300 10 about 30% of its initial activity Cu/Al2O3/ZrO2[5] 300 10 about 21%-32% of its initial activity CuO/CeO2[14] 300 40 from 98% to 90% in the first 10 h, then stable at 90% Cu/ZnO/Al2O3[15] 400 8 from 82% to 52% Cu/ZrO2[15] 400 8 from 64% to 22% Cu/ZnO/25%ZrO2[15] 400 24 from 93% to 70% 40-Cu/SiO2[17] 300 6 from 95% to 84% Mo2C/ZrO2[24] 400 10 stable at about 90% Cu/ZnO/Al2O3[25] 250 8 from 39% to 33% 50%Cu/ZnO[25] 250 8 stable at 22%-23% 40%Cu/ZnO/ZrO2[25] 250 8 stable at 31%-32% 50%Cu/ZnO[25] 400 7 from 89% to 69% 40%Cu/ZnO/ZrO2[25] 400 28 from 100% to 80% Cu/ZnO/ZrO2/Al2O3[26] 260 5 from 98% to 92% ZnO/Cu/SiO2[27] 300 6 stable at 87%-88% CuO/ZnO/ZrO2/Al2O3[28] 250 110 about 18%-31% of its initial activity CuO/ZnO/Al2O3[29] 250 320 from 60% to 52% CuO/ZnO/Al2O3[30] 250 24 stable at about 92%-94% This work 300 60 stable at about 88%-92% 
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Table 2 Lowest temperature of the CO formation and corresponding CO selectivity at different steam to methanol molar ratios
Steam to methanol molar ration Lowest temperature of CO formation t/℃ Liquid feed flow q/(mL·h-1) CO selectivity s/% 1.2 325 1.2 8.8 2.4 6.9 4.8 5.2 6.0 4.5 2 325 1.2 8.2 1.8 4.4 3.0 0 4.8 0 3 350 3.0 3.4 6.0 2.8 9.0 2.0 5 375 8.4 2.5
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