The effect of copper loading on the acidity of Cu/HZSM-5 catalysts: IR of ammonia and methanol for methylamines synthesis

The Cu/HZSM-5 catalysts (1.2, 3.7 and 6.0%, p/p, in Cu) were tested in methanol amination showing that the 3.7% copper sample was fairly more selective to MMA than the other metallic catalysts. The results of textural and superficial analyses obtained in this work showed that the increase in copper content is associated with the procedure adopted in the samples preparation and accounts for the variations in Lewis surface acidity and metallic areas. The infrared spectra of 3.7% Cu/HZSM-5 and HZSM-5 after methanol and ammonia uptake in successive steps at 623 K presented mono-, di- and tri-methylamines that were influenced upon copper addition. The metal should facilitate amine desorption, probably, due to the decreasing Brönsted acidity.