8/9/2019 Prasert & Yamagami - Low Methanol Synthesis Low Grade Syngas

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8/9/2019 Prasert & Yamagami - Low Methanol Synthesis Low Grade Syngas

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0

10

20

30

40

50

60

0 2 4 6 8 10 12

Time (h)

Conv.orYield(%)

methanol

total carbon

ethyl formate

Figure 3.The effect of reaction time in batch reactor. Temperature =443 K; initial pressure = 30 bar; Cu/ZnO = 1.00 g; ethanol = 20 ml;stirring speed = 1260 rpm.

In Figure 4, it is shown the time-on-stream and conversion onCu/ZnO during 20 h. The conversions were very low at initial stagedue to the dead volume of the reactor and trap filled by the feed gas.The total carbon conversion was about 47%. Furthermore, at theinitial 10 h, the CO2conversion dropped to minimum 42% and thenincreased again to about 3%.

According to the time-on-stream of the conversions above, thatCO was converted to CO2, and then CO2 converted to methanol

through the designed routes, step (1) - (3). It should be noted that ifno alcohol was used as solvent, for example, in the case wherehexane was used instead as an inert solvent, no activity was observed.

-50-40-30-20-10

01020304050

0 5 10 15 20

Time on stream (h)

Conversion(%)

Figure 4. Variations of conversions with time on stream for themethanol synthesis from CO/CO2/H2. Temperature = 443 K; pressure= 50 bar; Cu/ZnO = 3.00 g; 2-butanol 20 ml; stirring speed = 1260rpm; 20 ml/min; () CO%; () CO2%; ( ) total carbon%.

In Figure 5, the relationship between conversion and reactionpressure is shown. It was found that the total carbon conversionincreased gradually with increasing reaction pressure.

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0

10

20

30

40

50

60

20 30 40 50

Pressure (bar)

C

onversion(%)

Figure 5. Variations of conversions with for the methanol synthesisfrom CO/CO2/H2. Temperature = 443 K; Cu/ZnO = 3.00 g; 2-butanol20 ml; stirring speed = 2000 rpm; 20 ml/min; () CO%; () CO2%;( ) total carbon%.

In Figure 6, it is shown the conversion and reaction temperature.It is interesting that the conversion continuously increased withincreasing in temperature of reaction without changing in themethanol selectivity (>98%). In contrary with high temperaturemethanol synthesis, high reaction temperature lowers the methanolselectivity.

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0

20

40

60

80

423 433 443 453 463

Temperature (K)

Conversion(%

)

Figure 6. Variations of conversions with temperature for themethanol synthesis from CO/CO2/H2. Pressure = 50 bar; Cu/ZnO =3.00 g; 2-butanol 20 ml; stirring speed = 2000 rpm; 20 ml/min; ()CO%; () CO2%; ( ) total carbon%.

In Table 1, the results on catalyst weight showed the conversion

can be improved by increasing the catalyst weight, in contrary tohigh-temperature gas phase reaction, the increased catalyst weightindeed improved the conversion due to relief of thermodynamiclimitation.

Table 1 Methanol synthesis with various weight of catalystConversion (%)Cat.

(g) CO CO2 Total C

CH3OHselectivity (%)

3.0 48.5 -5.8 41.4 98.5

6.0 63.8 -11.5 53.9 99.2

Temperature = 443K Pressure = 50 bar; 2-butanol 20 ml; stirringspeed = 2000 rpm; 20 ml/min.

ConclusionsThe low-temperature methanol synthesis from CO/CO2/H2using

2-butanol as

solvent has exhibited very high activity and selectivityfor methanol formation at temperature as low as 443 K and 50 bar.Since the reaction employed conventional

solid catalyst, very mildreaction conditions and syngas containing CO2and H2O, it might bea promising practical method for methanol synthesis at lowtemperature. The total carbon conversion increased with theincreasing of reaction temperature, pressure, and catalyst weight. The high conversion of methanol synthesis at low-temperature was

produced from CO and

H2containing small amount of CO2.

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Herman, R. G.; Simmons, G. W.; Klier, K. Studies in Surf. Sci.

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Graaf, G. H.; Sijtsema, P.; Stamhuis, E. J.; Oosten, G. Chem.Eng. Sci. 1986, 41,2883.

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Marchionna, M.; Lami, M.; Galleti, A. CHEMTECH, 1997,April, 27.

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