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This is sometimes called the reverse water–gas shift reaction. [20] Water gas is defined as a fuel gas consisting mainly of carbon monoxide (CO) and hydrogen (H 2). The term 'shift' in water–gas shift means changing the water gas composition (CO:H 2) ratio. The ratio can be increased by adding CO 2 or reduced by adding steam to the reactor.
Most important is the water-gas shift reaction, which provides a source of hydrogen at the expense of carbon monoxide: [8] H 2 O + CO H 2 + CO 2 {\displaystyle {\ce {H2O + CO -> H2 + CO2}}} For FT plants that use methane as the feedstock , another important reaction is dry reforming , which converts the methane into CO and H 2 :
The first reaction, the reverse water gas shift reaction, is a fast one: CO 2 + H 2 → CO + H 2 O. The second reaction is the rate determining step: CO + H 2 → C + H 2 O. The overall reaction produces 2.3×10 3 joules for every gram of carbon dioxide reacted at 650 °C. Reaction temperatures are in the range of 450 to 600 °C.
A fourth solution to the stoichiometry problem would be to combine the Sabatier reaction with the reverse water-gas shift (RWGS) reaction in a single reactor as follows: [citation needed] 3 CO 2 + 6 H 2 CH 4 + 2 CO + 4 H 2 O {\displaystyle {\ce {3CO2 + 6H2 -> CH4 + 2CO + 4H2O}}}
The water gas shift reaction is the reaction between carbon monoxide and steam to form hydrogen and carbon dioxide: CO + H 2 O ⇌ CO 2 + H 2. This reaction was discovered by Felice Fontana and nowadays is adopted in a wide range of industrial applications, such as in the production process of ammonia, hydrocarbons, methanol, hydrogen and other chemicals.
The name-giving reaction is the steam reforming (SR) reaction and is expressed by the equation: [] + + = /Via the water-gas shift reaction (WGSR), additional hydrogen is released by reaction of water with the carbon monoxide generated according to equation [1]:
Changes in temperature can also reverse the direction tendency of a reaction. For example, the water gas shift reaction + () + is favored by low temperatures, but its reverse is favored by high temperatures.
The reaction is exothermic with ΔH= -41.1 kJ/mol and have an adiabatic temperature rise of 8–10 °C per percent CO converted to CO 2 and H 2. The most common catalysts used in the water-gas shift reaction are the high temperature shift (HTS) catalyst and the low temperature shift (LTS) catalyst.