Sulfur recovery catalyst
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Experts, low-temperature catalysts for filling hydrogenation reactors are gradually becoming the trend. What is the comparison in performance between low-temperature catalysts and high-temperature catalysts? The catalysts used in Claus reactors used to be unevenly distributed, with oxygen-resistant iron-based catalysts being employed; however, these are now hardly used. Instead, a combination of one-third alumina and two-thirds titanium dioxide is used at the first stage, while all catalysts at the second stage are alumina-based. Iron-based materials are also used as a substitute for ordinary alumina. What are the advantages and disadvantages of each of these options, and what factors determine their selection?
Low-temperature hydrogenation catalysts were originally designed for use in reactors fed with flue gas from S-Zorb units; they perform well, allowing for lower inlet and bed temperatures. Later, there was another type designed for the degassing of liquid sulfur. It makes sense to combine oxygen resistance with alumina; it is less meaningful to combine a titanium-based material with alumina, or else one should use solely titanium-based materials.
Since the main cause of reduced activity in Claus catalysts is sulfation, in addition to efforts to develop alumina-based catalysts resistant to sulfation, protective catalysts that remove SO3 and O2 from the process gas have also been developed.
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In addition to possessing the properties of conventional alumina catalysts, titanium-based catalysts can also increase the hydrolysis rate of organic sulfur, thereby reducing the hydrolysis burden on hydrogenation catalysts. There is not much difference in performance between low-temperature hydrogenation catalysts and conventional hydrogenation catalysts, and higher temperatures are more favorable for the hydrogenation reaction. By using a low-temperature hydrogenation catalyst, the temperature of the exhaust gas entering the hydrogenation reactor can be reduced. The heat exchange for the exhaust gas can be carried out using the medium-pressure steam generated within the facility, but there are limitations during the initial sulfidization process; as a result, many design schemes include a secondary heater or an electric heater.