Gujarat BoardEnglish MediumSTD 11 ScienceChemistryHydrogen5 Marks
Question
How can production of hydrogen from water gas be increased by using water gas shift reaction?
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Answer
Water gas is produced when super heated steam is passed over red hot coke or coal at 1270K in the presence of nickel as catalyst.
$\text{C(s)}+\text{H}_2\text{O(g)}\xrightarrow{\ \ \ \ \ \ \ \ \ \ }\underbrace{\text{CO(g)}+\text{H}_2\text{(g)}}-121.3\text{kj}\\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{Steam}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{Water gas}\ \ \ \ \ \ \ \ \ \ \ \ $
Pure $H_2$ from water gas cannot be obtained easily because it is difficult to remove CO. Therefore, to increase the production of $H_2$ from water gas, $CO$ is oxidized to $CO_2$ by mixing it with more steam and passing the mixture over heated $FeCrO_4$ catalyst at 673 K.
$\underbrace{\text{H}_2+\text{CO}}+\text{H}_2\text{O}\xrightarrow[\text{FeCrO}_4]{673\text{k}}\text{CO}_2+2\text{H}_2\\\text{Water gas}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ $
The $CO_2$ produced is removed by scrubbing with sodium arsenite solution.
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