What exactly does precise desulfurization, sulfurization, and sulfur release mean?

This post was last edited by Zhenzhen Youci on 2010-11-30 00:18. Take nickel-molybdenum catalysts as an example: the main reactions that occur during the sulfidation process are as follows: CS2 + 4H2 = CH4 + 2H2S; MoO3 + 2H2S + MoS2 + 3H2O. Possible side reactions include: CS2 + 2H2 = C + 2H2S; CS2 + 2H2 = CH4 + S2. After the catalyst has been sulfidized, it is necessary to purge it with low-sulfur feed gas. At this time, the temperature of the catalyst bed can be gradually increased to 400°C, while the pressure should be reduced gradually, maintaining it at around 0.1 Mpa. Sufficient time must be allowed during this stage; once the outlet H2S level is ≤300 mg/m3, the purging can be stopped. The system pressure can then be gradually increased to 0.5 Mpa, and the equipment should be kept insulated and under pressure. This is done primarily to prevent the sulfur content in the catalyst from becoming too high after sulfidization, which could affect its performance once it is put into use.

What was mentioned upstairs refers to the sulfur release process. Since the active form of a catalyst is generally in a reduced state, but catalysts in this reduced state are not convenient to store and transport, catalyst manufacturers usually ship the catalysts in a deactivated state and must reduce them before use. As sulfur has a weaker oxidizing power than oxygen, it is displaced more easily than oxygen; therefore, whether sulfur has been completely displaced is used as an indicator of whether the catalyst has been fully reduced. This process is commonly referred to as \"sulfur removal\" in industrial practice.