CO + H20 CO2 + H2
If you are at equilibrium and you add more CO2 the CO2 (+H2) will shift to produce CO + H20 to restore equilibrium.
The Low Temperature Water Gas Shift (LT-WGS) reaction is a reaction between carbon monoxide (CO) and water vapor (H2O) to form carbon dioxide (CO2) and hydrogen (H2). According to Le Chatelier's principle, the presence of CO2 in the feed gas will affect the equilibrium of the LT-WGS reaction by shifting the equilibrium to the right. This means that the reaction will favor the formation of CO2 and hydrogen, and the conversion of CO to CO2 will increase.
The reason for this shift is that the addition of CO2 increases the concentration of a product, which shifts the equilibrium to the side with fewer moles of gas. Since the reaction produces CO2, the addition of CO2 to the feed gas will increase the concentration of CO2, which will shift the equilibrium towards the side with more CO2, thus increasing the conversion of CO to CO2.
Additionally, CO2 in the feed gas would also shift the equilibrium to the right by decreasing the partial pressure of H2O which is a reactant in the reaction.
It is worth mentioning that the addition of CO2 in the feed gas can also increase the reaction rate and improve the performance of the reactor. However, adding CO2 also increases the complexity of the process and the need for more sophisticated equipment and control systems.
The low-temperature water gas shift (LT-WGS) reaction is an important process for the production of hydrogen from syngas (a mixture of CO and H2) in various industrial applications. The reaction is typically catalyzed by metal oxide catalysts at temperatures below 300°C. The reaction is exothermic and can be represented by the following equation:
CO + H2O ⇌ CO2 + H2
According to Le Chatelier's principle, a system at equilibrium will respond to any stress by shifting the equilibrium position in a way that tends to counteract the stress. Therefore, the effect of adding CO2 to the feed gas for the LT-WGS reaction can be analyzed by considering how the equilibrium position of the reaction will shift in response to this stress.
Several studies have investigated the effect of CO2 on the LT-WGS reaction using different catalysts and reaction conditions. In general, the presence of CO2 in the feed gas can have a negative effect on the equilibrium conversion of CO and the selectivity for H2 production. This is because the presence of CO2 can shift the equilibrium position of the reaction to the left, thereby decreasing the concentration of H2 and increasing the concentration of CO and CO2 in the product gas.
For example, a study by Maiti et al. (2015) investigated the effect of CO2 on the LT-WGS reaction over a CuO-ZnO/Al2O3 catalyst. The results showed that the addition of CO2 to the feed gas led to a decrease in the CO conversion and H2 selectivity, due to the shift in the equilibrium position of the reaction to the left.
Similarly, a study by Cao et al. (2017) found that the presence of CO2 in the feed gas decreased the CO conversion and H2 selectivity during the LT-WGS reaction over a Fe-Cr mixed oxide catalyst.
Therefore, the presence of CO2 in the feed gas for the LT-WGS reaction can have a negative effect on the conversion and selectivity of the reaction. This effect should be taken into account when designing and operating LT-WGS reactors for hydrogen production.
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