Catalytic pyrolysis of coffee grounds using NiCu-impregnated catalysts

NiCu/γ-Al₂O₃ catalysts with different Cu loadings were prepared using an ultrasonic-assisted impregnation method. The effect of the Cu content in the catalyst on the mass loss behavior of coffee grounds and the evolution of gaseous products during pyrolysis were investigated. The effect of two different heating rates of 10 and 60 C/min on the catalytic pyrolysis was also studied. The mass loss and evolution of the main pyrolytic volatiles were analyzed with a thermogravimetric (TG) analyzer connected to a Fourier transform infrared (FTIR) spectrometer. The bio-oils collected from non-catalytic and catalytic pyrolyses of coffee grounds were subjected to gas chromatography-mass spectrometry (GC-MS) analysis. Gram-Schmidt curves obtained by TG-FTIR indicated that the addition of NiCu/γ-Al ₂O₃ catalysts and the increase in the Cu content in the catalysts increased the concentrations of CO₂ and CO in the produced gas evolved during coffee grounds pyrolysis. In comparison to the slow heating rate of 10 C/min, the fast heating rate of 60 C/min resulted in the shift of the thermal events to higher temperatures. GC-MS analysis revealed that pyrolysis of coffee grounds in the presence of the catalyst produced lower amount of bio-oil and a more homogeneous distribution of organic compounds in the bio-oil than in the case without catalysts.