Controlled Precipitation Of Copper-Manganese Mixed Oxides For The Water Gas Shift Reaction

The copper manganese mixed oxides for the water gas shift reaction were prepared by co-precipitation.The synthesized catalysts samples were studied comprehensively by Micro-Reactor- Chromatography,XRD,TPR,TG/DTA,TEM and Special Surface Analysis.Emphasis was to study the effect of precipitation strategy on catalysts texture and performance for speculating the dependence of chemical composition,texture,performance of the catalyst on the preparation of synthesis techniques and process.For the normal precipitation strategy, appropriate concentration precipitator alkali solution makes for the formation and growth of the crystallization.It is proved that the increasing of the precipitator alkali solution can result in the enhancement of deoxidization temperature,more copper and manganese cation with low valence and less water in for the dried samples,less reduce dgree of specific surface caused by calcinations and improved crystallinity both for dried and calcined samples.The precipitation temperature is crucial for optimization of activity and thermostability and the optimized precipitation condition is 4mol/l precipitator and 45℃.For the reverse-strike precipitation strategy,Cu/Mn of the mother liquor is the pivotal factor to the texture and characteristics.Cu/Mn=1⁰.5 is prerequisite for the preparation of catalysts with higher activity and heat-resistanc and Cu_1.5Mn_1.5O₄ predominate the corresponding copper manganese mixed oxides.The crystallinity and thermostability enhance with the precipitation time.For Cu/Mn<1,the precursor consist of Cu₂₊₁ and Mn₃O₄,but Mn₃O₄ increases and Cu_2+1O decreases with the Cu/Mn.For Cu/Mn>1,There prsents Cu(OH)₂ other than Mn₃O₄ and Cu_2+1O and both Cu_2+1O and Mn₃O₄ decreases with the Cu/Mn till entirely substituted by Cu(OH)2 if Cu/Mn>2.Cu_1.5Mn_1.5O₄ with Mn₃O₄ is the primary crystallization and Cu_1.5Mn_1.5O₄ decrease with the increase of manganese content for Cu/Mn<1;there presents CuO and Cu0.451Mn0.549O2 besides Cu_1.5Mn_1.5O₄ but CuO decreases with Cu/Mn for Cu/Mn<1.For the parallel-current precipitation, the processes control is hardy than the above two methods.Parallel-current precipitation is impacted by the inner reaction precipitation and the input mother liquor and precipitator.So much factors result that precipitation processes is forced unsteady-state not conducive to the activity and thermostability of the catalyst.Wherever precipitation ways,Cu_2+1O and Mn₃O₄ predominates the dried precursors and Cu_1.5Mn_1.5O₄ is in the majority of the corresponding calcined samples.The composition and crystallinity is the predeterminate condition to prepare the copper manganese mixed oxide with composition and texture desired for the higher activity and heat-resistance.The more integrity of crystallinity the Cu_2+1O and Mn₃O₄,the superior performance of the catalysts are.The effect of synthesis condition on the catalyst texture and performance are depended on precipitation strategy.Normal precipitation strategy is influenced by synthesis condition significantly and reverse-strike precipitation strategy is influenced by synthesis condition slightly.