摘要
采用共沉淀法制备铜锰复合氧化物,运用XRD、TPR、BET和常压微反评价装置对所合成样品进行了物相结构和催化性能的研究。XRD分析表明,沉淀反应温度在25~90℃时所合成铜锰复合氧化物前驱体均由Cu2＋1O/Mn3O4组成,但随着温度的升高,其晶体组成Cu2＋1O/Mn3O4比逐渐提高,晶粒逐渐减小,这些前驱体经550℃焙烧后均转化为Cu1.5Mn1.5O4,且晶粒大小基本相同。TPR分析结果表明,所制备催化剂为单一组成的铜锰复合氧化物,当沉淀反应温度〈45℃时,随沉淀反应温度提高样品的还原温度升高,当沉淀反应温度从45℃提高到65℃,还原温度变化不大,只略有下降;而当沉淀反应温度〉65℃时,还原温度继续升高。BET结果表明,虽然室温下（25℃）所制催化剂前驱体的比表面积较大,但焙烧后却大幅度下降,反而小于45℃以上样品的比表面积;而当沉淀温度在45℃以上时,焙烧前后样品的比表面积相差不大,样品的比表面积均在36.5-39 m2/g,说明当沉淀温度提高到45℃以上时,焙烧后样品的比表面积与沉淀温度关系不大。沉淀温度45℃是Cu-Mn沉淀物织构发生明显变化的拐点,在此温度下,沉淀反应体系的反应、传递及沉淀物的转化达到最佳匹配,有利于变换反应活性中心和耐热性微、介观结构的形成。
The copper-manganese mixed oxides prepared by coprecipitation were characterized by XRD,TPR,BET and tested for water gas shift reaction on a Micro-reaction system with on-line GC.XRD analysis indicate that the precursor of copper-manganese mixed oxides is consistent of Cu2＋1O and Mn3O4 and with temperature raise of precipitation Cu2＋1O/Mn3O4 ratio increases and crystallite size decreases.Without any exception the as-prepared precursor of copper-manganese mixed oxides were transformed to single Cu1.5Mn1.5O4 with similar crystallite size.TPR shows that the as-prepared copper-manganese mixed oxides are isomorphic structure.When the precipitation temperature is less than 45℃ the reduction temperature raises with the precipitation temperature,Whereas the reduction temperature decrease slightly for the precipitation temperature from 45℃ to 65℃.In contrast,when the precipitation temperature higher than 65℃ the reduction temperature increases.By the BET,it is proved that despite of larger specific area for the precursor precipitation at 25℃ the specific area decrease significantly for the corresponding as-prepared copper-manganese mixed oxides by calcination,even less than that of the samples precipitation higher than 45℃.It should be noted that the specific area both precursor and calcined samples with precipitation temperature higher than 45℃ change with no significant discrepancy,and the specific area after calcination decreased relatively slightly,ranged from 36.5 to 39m2/g.It can be speculated that the precipitation temperature higher than 45℃ has slight impact on the specific area of calcined samples.It can be concluded that the 45℃ is the inflexion point for the texture of precipitate and the precursor,which favors the optimal condition for the cooperation of precipitation reaction,transportation and precipitate transformation to be benefit for the formation of activity site and the thermo resistant micro-and meso-structure for the water gas shift reaction.
出处
《内蒙古工业大学学报（自然科学版）》
2011年第1期38-42,共5页
Journal of Inner Mongolia University of Technology：Natural Science Edition
基金
教育部留学人员科研启动基金
教育部"春晖计划"
内蒙古自治区优秀学科带头人计划(20041001)
内蒙古人才基金
内蒙古高等学校科学研究(NJ06065)
内蒙古工业大学重点项目(ZD200612)资助
关键词
铜锰复合氧化物
沉淀反应温度
前驱体
变换反应
copper-manganese mixed oxide
precipitation temperature
precursor
water-gas-shift reaction
