Why must hydrogen sulfide reach 1000 ppm before 230°C during catalyst presulfurization?

This is because during the catalyst pre-sulfidization process, before hydrogen sulfide penetrates the catalyst, if the temperature is above 230°C, the catalyst in its oxidized state will be reduced to metallic form by hydrogen, thereby reducing the catalyst’s activity and affecting the sulfidization process.

Isn’t it also because of the fear that the catalyst will be reduced by hydrogen? The same principle applies to hydrogen release at a constant temperature

This value is necessary to ensure that vulcanization is complete at this temperature, as the vulcanization reaction releases a significant amount of heat. If vulcanization is not complete, continuing the vulcanization process once the temperature rises can pose a risk of excessive temperature elevation.

This is necessary, mainly to prevent the sulfided catalyst from being reduced by hydrogen :):):):):)

Previously, when operations started in Guangxi, hydrogen sulfide would penetrate through all the layers of the reactor; that is, before 230°C, the hydrogen sulfide concentration had to be below 3000 ppm. Below is the sampling and analysis table from the sulfidation process: Sampling and analysis of circulating hydrogen on September 25: Time: 1:00, 2:00, 3:00, 4:00, 5:00, 6:00; H2S concentration in ppm: 0, 0, 20, 30, 180, 450. Time: 7:00, 8:00, 9:00, 10:00, 11:00, 12:00; H2S concentration in ppm: 1000, 2000, 2000, 2100, 2100, 3000. Time: 13:00, 14:00, 15:00, 16:00, 17:30, 18:00; H2S concentration in ppm: 3800, 4000, 5900, 7200, 8200, 8100. Time: 19:00, 20:00, 21:00, 22:00, 23:00, 24:00; H2S concentration in ppm: 9600, 11000, 10300, 10000, 9800, —— Sampling and analysis of circulating hydrogen on September 26: Time: 1:00, 2:00, 3:00, 4:00, 5:00, 6:00; H2S concentration in ppm: 10900, 10000, 7100, 5000, 5800, 9400. Time: 7:00, 8:00, 9:00, 10:00, 11:00, 12:00; H2S concentration in ppm: 10800, ——, 13600, 12000, 14000, 14000. Time: 13:00, 14:00, 15:00, 16:00, 17:00, 18:00; H2S concentration in ppm: 13800, 12000, 12400, 7100, 5000, 4000. Time: 19:00, 20:00, 21:00, 22:00, 23:00, 24:00; H2S concentration in ppm: 3700, 2100, 2000, 4000, 5800, 6000

In fact, 1000 ppm is a relatively safe concentration; oxidation-state catalysts will be reduced to their metallic form in a hydrogen atmosphere at temperatures above 230°C, and this change is irreversible, affecting the catalyst’s activity. To prevent this phenomenon from occurring, it is necessary to keep the hydrogen sulfide concentration in the circulating hydrogen above a certain limit.