Study On Copper Catalysts For Methanol Synthesis By Hydrogenation Of CO In The Slurry Reactor

Methanol is well known as one of the major chemicals as well as animportant fundamental material in C₁ industries, and it can be also used as acleaning fuel. The basic theory and industrial technology of methanol synthesishave been significantly developed since 1960s'. In spite of industrialized processfrom syngas in fixed bed reactors, methanol synthesis in a slurry reactor havebeen studied in recent years. It is noticeable, due to the influence of liquid fluxon mass transfer in the reactor, the system become more complicated. In thispresent study, C302-2 catalysts were selected for methanol synthesis in theslurry reactor to optimized processing conditions. A series of Cu/ZnO/Al₂O₃catalysts were prepared by changing preparation conditions and methods withadding Zr promoter. These catalysts were characterized by means of BET, XRD,XPS, TPR, and the key factors on catalytic activity were investigated.Through above studies, the main conclusions in this work can be drawn asfollows:(1) The highest CO conversion and STY of methanol were acquired in the slurryreactor reached points when the system was conducted at the reactionconditions: T=250℃, P=4.5 MPa, r=900 r.min^-1, CO/H₂=1/3. Besidesthe increase of mass space velocity led to a decrease in CO conversion andan increase in STY of methanol.(2) It was found that trace CO₂ in the synthesis gas may accelerate the rate ofmethanol synthesis and the activity of catalysts increased first then decreased with increasing CO₂ content. The optimal concentration of CO₂ was4.0mol%, and methanol content in coarse alcohols rised with the CO₂content increased.(3) The characterization results of Cu/ZnO/Al₂O₃ catalysts showed that copperwas highly dispersed on the support when the catalysts containing a lowcopper loading, appropriate aging time, as well as temperature and time. Thehighly dispersed copper has different reduction behavior from bulk copper,and interacted with zinc, which was critical to the high activity for methanolsynthesis. Subsequently, the performance of Cu/ZnO/Al₂O₃ catalysts wassignificantly enhanced by optimizing Cu/Zn ratio(1:1), aging time(2h),calcined temperature (350℃) and time (9h).(4) The active sequence of catalysts prepared by different methods was:Fractional step 1＞Co-precipitation＞Fractional step 2＞Two-stage＞Reverse＞Normal. The high performance of catalysts prepared by theFractional step 1 and co-precipitation method was similar to that ofindustrial C302-2 catalysts.(5) ZrO₂ in the catalyst can increase the specific surface area and improve theadsorbed amounts of H₂ on the surface of catalyst with an optimumconcentration 4 mol%.