Particle size effect metal loading

As already pointed out, the first particle size effect in skeletal rearrangement was found for the hydrogenolysis of methylcyclopentane (55). Nonselective hydrogenolysis takes place on highly dispersed catalysts, with a metal loading smaller than 0.6%, while selective rupture of bisecondary C-C bonds occurs on heavily loaded catalysts (more than 6% platinum on alumina). 

The same authors reported the effect of different reduction methods on Pt dispersion and particle size distribution [60]. The metal particle size and Pt loading ranges were 1 to 6 mn and 10 to 73 wt%, respectively. Differences in the mechanism of particle formation and growth during chemical and thermal reduction were found, attributable to the varying chemistry of these processes. 

This filler is mined, ground and sieved to a particle size less than 100 mesh and used as an inert diluent and cheapening filler for rubber compounds. It is usually off-white to cream in colour. Depending upon source, the filler can be contaminated with metal ions, e.g., iron, copper, manganese, which can catalyse oxidation. It can be used in very high loadings with great effect on compound hardness. 

The second factor to consider is the catalyst conditions and the catalyst-particles, environment. From the point of view of the effectiveness factor, the size, shape, porosity, metal-loading, and other internal characteristics, must be the same. Otherwise, the intrinsic reaction rate and selectivity will be compromised. In practice there will be a trend to reduce costs by using less metal. This will change the process markedly, and other adjustments will be required. 

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