How to Select Catalysts for Carbon Monoxide Shift Reaction?
How to Select Catalysts for Carbon Monoxide Shift Reaction?
In the ammonia synthesis and hydrogen production industries, the process conditions for carbon monoxide conversion mainly depend on the gas production process of the feedstock gas and the removal method of a small amount of carbon monoxide. The gas production processes of the feedstock gas mainly include: coal-based gas production process, coal-based gas production process Or oil as feedtock pressurized continuous gas production process, hydrocarbons (natural gas, naphtha) as feedstock steam reforming gas production process, etc . The main removal methods for a small amount of alkali monoxide include: copper liquid washing method, methanation method, liquid nitrogen washing method, etc. Sometimes the changing process conditions mainly depend on the gas production process; sometimes it depends on the removal method of a small amount of carbon monoxide. In addition, some factories co-produce methanol, which will also have an impact on the selection of shift catalysts.
Purification by copper liquid washing method for intermittent gas production using coal feedstock
The feedstock gas semi-water gas produced by intermittent gas production using coal as feedstock still contains a certain amount of sulfur although the semi-water gas is desulfurized; subsequent copper washing and purification generally requires a CO content of about 1.2%, which is more economical. These conditions are suitable for the use of iron-chromium medium-change catalysts and cobalt-molybdenum sulfur-resistant low-change catalysts. Therefore, it is announced to use iron-chromium medium-change catalysts (or sulfur-resistant iron-chromium medium-change catalysts) in tandem with cobalt-molybdenum sulfur-resistant low-change catalysts. Series low or medium-low conversion process: Or relax the requirements for semi-water gas desulfurization and select a full low-change shift process using cobalt-molybdenum sulfur-resistant low-change catalyst. However, an improved cobalt-molybdenum sulfur-resistant low-change catalyst should be selected and a protective agent should be used to prevent equipment corrosion. Desulfurization and post-system conversion gas desulfurization should be strengthened.
Intermittent gas production and co-production of methanol and copper liquid purification using coal as feedstock.
Due to the co-production of methanol, the CO% content of the shift gas is required to be increased accordingly. When the alcohol-to-ammonium ratio is high, the CO% content of the shift gas is even increased to greater than 6%: At this time, it is appropriate to use the medium-change process of iron-chromium medium-change catalyst or use low-gas Compared with the iron-chromium medium-change catalyst and the cobalt-molybdenum sulfur-resistant low-change catalyst, it is a mid-range and low-change process.
Purification by intermittent gas production and methanation using coal as feedstock.
Since the subsequent methanation method purification requires the CO% content of the shift gas to be less than 0.3%, it is appropriate to use an iron-chromium medium-change catalyst (or a sulfur-resistant iron-chromium medium-change catalyst) in series with a two-stage cobalt-molybdenum sulfur-resistant low-change catalyst. Deep shift process; or full low-change deep conversion process using cobalt-molybdenum sulfur-resistant low-change catalyst.
The liquid nitrogen scrubbing method purifies the feedstock gas produced by pressurized continuous gas production using coal or oil as raw material, which contains high sulfur and water vapor. The subsequent liquid nitrogen washing method purification is often matched with low-temperature methanol elution of carbon, and this method has a good removal effect on sulfur and other substances: therefore, cobalt-molybdenum sulfur-tolerant shift catalysts are directly selected to meet the requirements of the post-processing process.
The methanation method uses hydrocarbons (natural gas, naphtha) as feedstock for steam reforming to produce gas. The methanation method purifies the feed gas produced by using hydrocarbons (natural gas, naphtha) as feedstock for steam reforming. Since there is protective steam before entering the steam reforming The shift catalyst has been desulfurized, so the feedstock produced.
The feed gas is basically free of sulfur: In addition, the energy-saving hydrocarbon steam reforming process (water-to-carbon ratio is less than 2.75) has been widely used in subsequent methanation purification: Therefore, it is appropriate to use a low water vapor ratio iron-chromium medium change catalyst (or low-sulfur iron in the body) Transformation process of chromium medium change catalyst) string copper-zinc low change catalyst.
Each catalyst has the most suitable process conditions for it, and each process condition also has the most suitable catalyst for it. This article combines the performance and characteristics of the catalyst with the requirements of the process conditions, and puts forward the general selection principles for shift catalysis, giving everyone An intuitive understanding, so that you can be more specifically familiar with the essence of the transformation process.
