What are the common uses of Ammonium Molybdate Tetrahydrate in catalyst preparation and petroleum industry processes?

Introduction

Common Uses in Catalyst Preparation

1. Active Component in Hydrotreating Catalysts

Ammonium Molybdate Tetrahydrate is widely used as an active component in hydrotreating catalysts. In the petroleum industry, hydrotreating processes, such as hydrodesulfurization (HDS) and hydrodenitrogenation (HDN), are crucial for removing sulfur and nitrogen compounds from petroleum products. In HDS, the molybdenum species derived from Ammonium Molybdate Tetrahydrate can adsorb sulfur - containing molecules on its surface. For example, thiophene, a common sulfur - containing compound in petroleum, can interact with the molybdenum sites. The molybdenum - based active sites then facilitate the breaking of the carbon - sulfur bonds, allowing hydrogen to react with the sulfur atom to form hydrogen sulfide (H₂S), which can be easily removed. In HDN, it plays a similar role in breaking the carbon - nitrogen bonds of nitrogen - containing compounds like pyridine. By reducing the sulfur and nitrogen content in petroleum products, the quality of fuels is improved, and harmful emissions during combustion are reduced.

2. Promoting Catalytic Activity

It can be combined with other metals or promoters to enhance the catalytic activity. For instance, when combined with cobalt (Co) or nickel (Ni), the resulting Co - Mo or Ni - Mo catalysts show significantly improved performance. The addition of cobalt or nickel to the molybdenum - based catalyst can modify the electronic structure of the active sites. This modification increases the number of active sites available for the reaction and improves the catalyst's ability to adsorb reactant molecules. In addition, it can enhance the stability of the catalyst. During the hydrotreating process, the catalyst is exposed to high temperatures and harsh reaction conditions. The presence of molybdenum from Ammonium Molybdate Tetrahydrate helps to maintain the integrity of the catalyst structure, preventing sintering and deactivation of the catalyst over time. This results in a longer - lasting and more efficient catalyst for petroleum - processing reactions.

Applications in Petroleum Industry Processes

1. Desulfurization in Refining

In the refining process of petroleum, the desulfurization step is of great significance. Ammonium Molybdate Tetrahydrate - based catalysts play a crucial role here. The molybdenum in the compound acts as an active site for the adsorption and reaction of sulfur - containing compounds. For example, in the hydrodesulfurization process of diesel fuel, sulfur - containing thiophenic compounds are adsorbed onto the surface of the catalyst containing molybdenum species from Ammonium Molybdate Tetrahydrate. Then, hydrogen is introduced, and under the catalytic action of molybdenum, the sulfur - carbon bonds are broken. The sulfur atoms combine with hydrogen to form hydrogen sulfide, which can be removed from the system through subsequent separation processes. This not only improves the quality of diesel fuel by reducing its sulfur content but also helps to meet the strict environmental regulations regarding sulfur emissions from vehicle exhausts. If the sulfur content in diesel is too high, when it is burned in engines, it will produce sulfur dioxide (SO₂) emissions, which are major pollutants contributing to acid rain and air pollution. By using catalysts derived from Ammonium Molybdate Tetrahydrate for desulfurization, these negative environmental impacts can be effectively mitigated.

2. Cracking and Reforming Processes

In the cracking and reforming processes of petroleum, Ammonium Molybdate Tetrahydrate - based catalysts are also widely used. In catalytic cracking, which aims to break down large - molecular - weight hydrocarbons into smaller, more useful molecules such as gasoline, the catalyst promotes the cleavage of carbon - carbon bonds. The molybdenum - based active components can weaken the carbon - carbon bonds in heavy hydrocarbons, facilitating the cracking reaction. For instance, long - chain alkanes in heavy oil can be cracked into shorter - chain alkanes and alkenes, which are important components of gasoline. In reforming processes, such as catalytic reforming to produce high - octane gasoline and aromatics, the catalyst helps to rearrange the molecular structure of hydrocarbons. It can convert straight - chain alkanes into branched - chain alkanes and cycloalkanes, which have higher octane numbers. The presence of molybdenum in the catalyst enhances the reaction rate and selectivity. This results in an increase in the yield of high - quality gasoline components and valuable aromatics like benzene, toluene, and xylene. These aromatic hydrocarbons are not only important components of high - octane gasoline but also serve as essential raw materials for the chemical industry, such as in the production of plastics, synthetic fibers, and dyes.

Conclusion

Ammonium Molybdate Tetrahydrate is of great significance in the catalyst preparation and petroleum industry processes. As an active component in hydrotreating catalysts, it effectively promotes the removal of sulfur and nitrogen compounds in petroleum products. Its combination with other metals can enhance catalytic activity and stability. In the petroleum industry, it plays a crucial role in desulfurization, cracking, and reforming processes, improving product quality, and meeting environmental requirements. With the continuous development of the petroleum industry and the increasing emphasis on environmental protection, the demand for Ammonium Molybdate Tetrahydrate in these fields is expected to remain stable or even increase. Further research on its catalytic properties and applications may lead to more efficient and sustainable petroleum - processing technologies.