Why Use Alumina As A Carrier

Alumina carrier refers to white powder or shaped alumina solid, which is the most widely used catalyst carrier, accounting for about 70% of industrial supported catalysts, such as hydrofining, hydrocracking, catalytic reforming Aromatics production, catalytic combustion, steam reforming of methane to hydrogen production, ethylene epoxidation reaction and automobile exhaust control and other fields. The commonly used shapes of catalyst supports include: columnar, ring, spherical, pelletized, granular and extruded strips, etc. Generally, it is divided into the following categories: high-temperature alumina carrier; interactive carrier; synergistic or dual-functional carrier. The following are several application directions.

Good Catalyst Support Conditions

1.Suitable shape and size for specific reactions; 2.Sufficient mechanical strength; 3.Sufficient specific surface area and suitable pore structure for catalysts; 4.Sufficient chemical and thermal stability; 5.Wide sources of raw materials and low manufacturing costs ; 6. can be compatible with active components, so that the catalyst activity is good; 7. does not increase side reactions, low impurity content; 8. improve the heat resistance of the catalyst.

The reason why the alumina carrier is widely used is that the alumina carrier has a series of excellent characteristics, including: 1. high melting point of alumina and good thermal stability; 2. acidic centers and basic centers exist on the surface of the alumina carrier, making it It has a variety of catalyst properties; 3. there are a variety of transition phases in the alumina carrier, and its crystal phase and pore structure are diverse, and the selectivity is wide.

Among all hydrodesulfurization catalyst supports, alumina support is the commonly used one. Among the various transition phases of alumina carrier, γ-Al2O3 has larger porosity, specific surface area, better mechanical strength and more suitable surface acidity, making it the best choice for hydrodesulfurization catalyst carrier.

Application Of Alumina In Automobile Exhaust Catalyst Carrier

The main pollutants emitted by automobile exhaust are: CO, NOx, CxHy and Pb, etc. After NOx and hydrocarbons are irradiated by strong ultraviolet rays, they will also produce new secondary pollution—photochemical smog, which is directly or indirectly caused by photochemical smog. The indirect economic losses are huge. An important way to avoid photochemical smog is to carry out early treatment of vehicle exhaust. The best way at present is to install a catalytic device on the exhaust pipe of the automobile to convert unsaturated hydrocarbons and nitrogen oxides into saturated compounds, and alumina is an excellent carrier for the catalyst in this conversion process.

Application in Oxalate Synthesis Catalyst

The key technology of CO gas-phase coupling synthesis of oxalate is the development of high-efficiency catalysts, and alumina is one of the most widely used catalyst support materials in this reaction. The preparation of a suitable alumina support is the core performance of the catalyst for CO gas-phase coupling synthesis of dimethyl oxalate. Excellent alumina can improve the activity and selectivity of the catalyst.

Pore Expansion Method Of Alumina Carrier

As petroleum becomes more and more inferior, and there are more and more heavy/inferior macromolecular components, alumina needs to be modified to achieve high-efficiency catalytic performance. In the process of hydrogen catalysis, catalysts with different pore sizes are used to treat oils of different fractions. When dealing with heavy oil, it is a rate-controlling step for macromolecules to pass through the pores to reach the active sites, so it is necessary to expand the pores of the alumina carrier. Pore expansion can make it easier for macromolecules to pass through (reduce mass transfer resistance), make full use of the active sites of the carrier, and enhance the anti-coking ability. However, most of the alumina on the market has a small pore size (less than 10nm), and the pore size distribution is single and wide. During the reaction process, the small pores will limit the material transfer, easily cause coking, and reduce the life of the catalyst, which cannot meet the demand. Therefore, the preparation of suitable macroporous alumina supports has received more and more attention. The main methods to control the pore structure of alumina are self-assembly method, hydrothermal treatment method and pore expander method.

With the continuous expansion of the application of alumina carriers in the fields of chemical industry and environmental protection, the preparation process of alumina has been updated, and low-cost, green and environmentally friendly processes have been developed to control the pore size and pore size distribution of alumina and improve the thermal stability of alumina. The ability to prepare nano-alumina can make the alumina carrier better meet the actual production needs.