Abstract: Effect of Water and Magnesium Stearate On the Strength of Ceramic Compacts (2012 Annual Meeting)

Sarang Oka, Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ, Alisar Tuncer, Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ, Alberto Cuitino, Mechanical Engineering, Rutgers University, Piscataway, NJ and Fernando Muzzio, Chemical & Biochemical Engineering, Rutgers University, Piscataway, NJ

Effect of Water and MgSt on the Strength of Ceramic Compacts

Sarang Oka, Alisar Tuncer, Alberto Cuitinio, Fernando Muzzio

Rutgers University

The strength of the catalyst support is critical in any process that employs the material since it more often than not is subject to intense process conditions as well physical stress. Alumina-Magnesia is a common catalyst support material compacted to various geometries. The penultimate step in its manufacturing process is the compaction of the milled and mixed granules. To maximize the strength of the compacts it is thus necessary to understand and quantify the effect of each material component as well as unit operation that leads up to the final formulation. The work focuses on the effect of quantity and timing of addition of water and MgSt to milled extrudates on the strength of the compacts. In addition, the PSD of the milled material also seems to play a dominant role on the final compact properties. The work explores the effect of the aforementioned parameters as well as their interplay on the strength of the compacts.

The addition of water to the milled ceramic material is an exothermic process and an immediate subsequent addition of the lubricant may compromise the strength of the compacts due to the fusing of the lubricant to the ceramic material. Thus, the effect of introducing a time delay in the addition of the lubricant is investigated.

Finally, past observations suggested that the strength of the compacts may be affected if the milled material is allowed to age after the addition of the water and hence the effect of material ageing is examined.

Water levels ranging from 0 to 25% at 5% intervals are explored. MgSt quantities ranging from 0% to 5% are studied while the effect of PSD ranging from a d90 of 700um to 1400um is quantified.

It is observed that the addition of water increases the bulk density of the material and this translates into a gain in strength of the compacts. An excess however may promote lumping and agglomeration and determining an optimum amount is thus the key. An increase in the amount of MgSt seems to have a detrimental effect on the strength of the compacts, with the compacts yielding at much lower stresses with higher amounts of lubricant. It is thus recommended to employ minimum amount of MgSt while ensuring homogeneity in mixing. The minimum amount of lubricant required for a formulation increases with an increase in water and decrease in particle size.

A decrease in particle size increases compact strength and decreases sensitivity to MgSt.

Neither ageing nor the introduction of a time delay seemed to have any effect on the compact strength. The tabletability profiles stayed intact in both the above cases.