Characterization of Microscopic Properties of Molecular Sieve Catalysts

X-ray diffraction technology is an important test method to characterize molecular sieve catalysts, which can provide a lot of structural information.

In the catalytic conversion experiment of coal pyrolysis volatile gaseous products, 

the active metal components Mo and Ni were supported on HZSM-5 to form Mo/HZSM-5 and Ni/HZSM-5 catalysts, 

so as to investigate their effect on coal pyrolysis. Effects of gaseous products.

It can be seen that the crystal structures of Mo/HZSM-5 and Ni/HZSM-5 did not change significantly, 

and the diffraction peak intensity decreased significantly compared with the unsupported, 

indicating that the metal Mo and Ni have been supported on the HZSM-5 carrier, And may have a certain interaction with the carrier. 

After Mo is loaded, there is no related diffraction peak of Mo, indicating that Mo is highly dispersed on the carrier; 

while the diffraction peak of NiO begins to appear after loading of 5% Ni, 

and when the loading amount increases to 10%, the intensity of the diffraction peak becomes more obvious. .

This indicates that NiO is basically highly dispersed on the support at low loading, while NiO becomes larger due 

to sintering at high loading, so the diffraction peaks are enhanced. 

Supported oxides have a monolayer dispersion capacity.

Below the monolayer dispersion capacity, they cannot be detected by XRD due to their two-dimensional structure. 

With the gradual increase of the loading capacity, the supported oxides can turn from amorphous to crystalline state, the characteristic peaks gradually appeared, 

which also indicated that the supported oxide was not simply supported on the carrier, 

because the molecular sieve pores could hardly accommodate crystal grains that could produce diffraction effect. 

This may also be the reason why the catalytic effect of 10% Mo and 10% Ni is reduced, exceeding the monolayer dispersion threshold, 

which causes the pores to be blocked and the catalytic activity decreases.