The measurement of mechanical strength for solid catalyst

As mentioned above in the beginning of Section 8.4, solid catalysts are subjected to many different mechanical stresses from the stage of manufacturing to usage. As it is not possible to design a single test to take into account all these factors, different tests should be taken to measure the catalyst particle s capability in bearing mechanical stress, abrasion and collision. 

In 1974, a scientific method of measurement for the mechanical strength of catalyst particles and the issues of its standardization were discussed in the first conference on the standardization for measurement methods in the U.S. Thereafter, some of the measurement methods for mechanical strength of catalysts were developed as standardsin many countries. At present, the characterization of mechanical strength of catalysts can be mainly divided into two kinds. 

The first is the strength of anti-fracture. This experimental method is divided into single particle crush strength (SPCS), the whole stack crush strength (WSCS) and the drop-shatter test. 

The nature of the area for dropping the catalyst must be prescribed. The ideal condition is that the area has the same hardness as that of the catalyst it can be harder than that of the catalyst and not softer. For tablets, the minimum drop height for particle fracture is related to the diameter/height ratio and the tablet s utmost tensile strength (UTS). A rough approximation of the relationship is as follows The drop height for particle fracture (m) = 0.075 x d/Lx(UTS), UTS is expressed in kg Cm .  

It can be seen from the above equation, the strength of tablets that are thin but long is poorer than that of tablets that are thick but short. The value of the d/L is usually one, and the design value of minimum drop height for the tablet is 3 m or the UTS is 40 kg-cm.  

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