This application note from Micromeritics explains what aluminas are, their use as a vapor trap, and how a BET surface area measurement can be used as an indicator for their performance. Alumina is more correctly known as aluminum III oxide. Porous aluminas are produced from sintering the material at elevated temperatures;alumina in a pellet form is widely used inscience and industry to trap out unwanted water and other vapors. Common industrial applications for alumina vapor traps are compressors and vacuum pumps. Use of these traps allows air or gases at the required mass flow rates to pass through the trap to the device and, importantly,the air is supplied dry and free from vapor contamination. The alumina manufacturing process allows for some control of the porosity of these beads and their resultant surface area. It is the porosity and surface area characteristics of the alumina bead which makes it useful as a vapor trap. These materials typically have surface areas of hundreds of square meters per gram as measured by the BET surface area method. The large available surface area efficiently traps out vapors from the gas stream and adsorbs or “bonds” them within the alumina. With time and use, the alumina becomes less efficient as the surface area decreases and porosity is lost. Attrition between the pellets can also lead to their breakdown in the trap, resulting in restricted air flow and loss of efficiency. Alumina can be easily regenerated by heating in an oven; this renewal process, however, cannot be carried out indefinitely. Characterization of the regenerated material and a comparison of its surface area to virgin material are key to being able to assess on-going use and to choose the right time to start using a new batch of alumina. The surface area of the alumina can be easily determined using the Micromeritics TriStar gas adsorption analyzer and the application of the well-established BET method. Click here to see entire Application Note.
Michelle LongoAsst. Managing Editor
Striving Toward Secondary GoalsLate last month, Republican presidential candidate Newt Gingrich stunned most everyone when he declared his promise that "by the end of my second term, we will have the first permanent base on the moon." While I don’t fault Gingrich for dreaming and trying to set high standards and goals, I can’t help but think of the enormous amount of known and unknown variables that significantly deter this accomplishment...continue
