2. Experimental
HZSM-5 (Si/Al=45), the catalyst used for MTG, was
supplied by Süd Chemie (Germany). Amounts of CuO/ZnO
7 wt.% each and 0.5 wt.% ZnO were doped on the HZSM-5.
In our previous work, the effect of copper oxide loading
on HZSM-5 was studied. It was found that on increasing
the CuO content, the yield and conversion increased [13].
All these catalysts were prepared by standard impregnation
technique[15,16].NH4OH solution was added to the slurry
of the catalyst wetted with copper nitrate solution to increase the pH to 5. The solution was stirred for 12 h. The
catalyst slurry was transferred to a rotary evaporator to remove excess water under vacuum. The pellets were dried at
120
◦
C for 12 h followed by calcination at 550
◦
C for 5 h.
Three different catalysts were prepared by impregnation over
HZSM-5 by CuO or ZnO and CuO/ZnO. The final weight
percent of the metal oxide as indicated inTable 1was determined by metal trace analyzer (Metrohm, Switzerland).
The total surface area and pore size of the catalysts were
determined with a Micromeretics ASAP-2010 by nitrogen
adsorption at 77 K. Prior to the analysis, the catalysts samples were pretreated for 4 h at 150
◦
C under vacuum.