共查询到17条相似文献,搜索用时 109 毫秒
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采用浸渍法制备钴基催化剂,考察了催化剂焙烧温度对其F-T合成反应性能和产物分布的影响。制备催化剂时,不对催化剂进行焙烧,Co物种容易还原,并可较好分散,催化剂具有较高的催化活性和重质烃选择性。较高温度下焙烧,Co物种和载体间的相互作用增强,形成难还原的铝酸钴化合物,同时氧化钴晶粒聚集或烧结,Co物种的还原程度下降,催化剂CO加氢活性降低,重质烃选择性下降。在原料气n(H2)∶n(CO)=2.0、483 K、1.5 MPa和800 h-1条件下,未焙烧、673 K和923 K焙烧的催化剂上进行F-T合成反应,CO的转化率分别为80.27%、78.41%和61.14%,重质烃的选择性C5+分别为88.54%、88.57%和77.95%。较低焙烧温度有利于反应速率的提高和重质烃的合成,较高焙烧温度使CO加氢活性下降,有利于低碳烃的生成。 相似文献
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草酸二甲酯加氢制乙二醇Cu/SiO2催化剂的制备与改性 总被引:6,自引:0,他引:6
采用均匀沉淀沉积法制备Cu/SiO2催化剂。考察了Cu2+浓度、洗涤条件及铜与硅物质的量比等的影响,并通过BET和XRD等表征手段研究分析,结果表明,前驱体制备过程及条件对催化剂结构和活性有较大影响。低Cu2+浓度、醇洗干燥均有利于形成大孔径高活性的催化剂。铜与硅物质的量比对反应活性的影响较大,存在一个最佳值,在0.4时活性最高。最优条件下制得的催化剂用于草酸二甲酯加氢制乙二醇,在反应温度205 ℃、压力2 MPa、n(H2) ∶n(DMO)=80和空速1.0 h-1条件下,草酸二甲酯的转化率为100%,乙二醇选择性为99.1%,乙醇酸甲酯选择性为0.9%,无其他副产物生成。 相似文献
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用L 9(34) 正交配置实验对2%Mo/SiO2 催化剂进行了改性研究, 发现Cr、Cu、Sn 和P 可改变催化剂的活性和选择性, 在Cr 为0.5% 时有较高的甲醇收率, 在450℃、常压下反应可使甲醇收率为2176%。XPS、FT -IR、TPR 和TPD 研究表明催化剂表面上的Mo 为+ 6 价, 且存在Mo-Si 作用键, 催化剂表面有大量的酸性中心和多种相互作用相。 相似文献
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负载型TiO2/SiO2光催化降解苯酚的研究 总被引:4,自引:0,他引:4
以白炭黑为载体、聚乙烯醇 (PVA) 和 Ti(SO4)2 为原料, 在分散剂存在下直接焙烧制备超细负载型 TiO2/SiO2 光催化剂, 结果表明, 在450 ℃焙烧2 h所制 SO42-/TiO2-SiO2(SO42-质量分数3.4%,TiO2∶SiO2=1∶6,比表面积54 m2/g)具有最佳光催化效果。光催化苯酚结果显示,在紫外灯下光降解苯酚(<100 mg/L)符合零级动力学方程,催化活性随pH值的增加而增加,pH=10时表观速率常数[WTBX]k[WTBZ]=0.33 mg/L·min,为苯酚废水处理提供了一条简便易行、成本低廉的方法。同时考察了光催化剂制备因素对催化剂活性的影响。 相似文献
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采用溶胶-凝胶法首先制备出Zr(OH)4凝胶,再将凝胶用乙醇进行醇化处理,经烘干和焙烧制得ZrO2纳米载体。载体颗粒粒径均匀,大小为20 nm左右。以ZrO2为载体,采用浸渍法分别负载Fe2O3、CuO、NiO和Mo2O3等不同金属氧化物,制得负载型催化剂。通过XRD、TEM、SEM和IR等对催化剂进行表征。以乙醇氧化脱氢合成乙醛为探针反应,考察了催化剂的催化性能。实验结果表明,催化剂Fe2O3/ZrO2在反应温度为573 K时,乙醇转化率为75.8%,乙醛选择性为97.3%。 相似文献
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Takehisa Mochizuki Takeshi Hara Naoto Koizumi Muneyoshi Yamada 《Catalysis Letters》2007,113(3-4):165-169
Co/SiO2 catalysts were prepared by the incipient wetness method using the aqueous Co nitrate solution modified with various organic
acids and/or chelating agents followed by drying and calcination. After H2 reduction at 773 K, the catalyst prepared with nitrilotriacetic acid (NTA) showed Fischer-Tropsch synthesis (FTS) activity
ca. 3 times higher than the catalyst without additives under mild reaction conditions (503 K, 1.1 MPa). 相似文献
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以不同孔道结构Al_2O_3作载体,甲醇、乙醇和柠檬酸作分散剂,通过等体积浸渍法制备系列Co/Al_2O_3费托合成催化剂。采用XRD、TG-DSC和H2-TPR等考察制备方法对催化剂结构的影响,并在固定床反应器中对催化剂进行性能评价。结果表明,采用具有适宜孔道结构Al_2O_3作载体才能获得综合性能较好的催化剂,3种分散剂的加入,促进了钴物种在载体上的分散,增强了钴与载体间的相互作用,改善了催化剂费托合成反应活性,显著提高了重质烃时空收率。 相似文献
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Wenping Ma Dennis E. Sparks Venkat Ramana Rao Pendyala Jennifer L.S. Klettlinger Burtron H. Davis 《Fuel》2011,90(2):756-765
The influence of support type and cobalt cluster size (i.e., with average diameters falling within the range of 8-40 nm) on the kinetics of Fischer-Tropsch synthesis (FT) were investigated by kinetic tests employing a CSTR and two Co/γ-Al2O3 catalysts having different average pore sizes, and two Co/SiO2 catalysts prepared on the same support but having different loadings. A kinetic model that contains a water effect constant “m” was used to fit the experimental data obtained with all four catalysts. Kinetic parameters suggest that both support type and average Co particle size impact FT behavior. Cobalt cluster size influenced kinetic parameters such as reaction order, rate constant, and the water effect parameter. In the cluster size range studied, decreasing the average Co cluster diameter by about 30% led to an increase in the intrinsic reaction rate constant k, defined on a per g of catalyst basis, by 62-102% for the γ-Al2O3 and SiO2-supported cobalt catalysts. This increase was due to the higher active Co0 surface site density as measured by hydrogen chemisorption. Moreover, less inhibition by adsorbed CO and greater H2 dissociation on catalysts having smaller Co particles was suggested by the higher a and lower b values obtained for the measured reaction orders. Interestingly, irrespective of support type, the catalysts having smaller average Co particles were more sensitive to water. Comparing the catalysts having strong interactions between cobalt and support (Co/Al2O3) to the ones with weak interactions (Co/SiO2), the water effect parameters were found to be positive (indicating a negative influence on CO conversion) and negative (denoting a positive effect on CO conversion), respectively. No clear trend was observed for b values among the different supports, but greater a and a/b values were observed for both Al2O3-supported Co catalysts, implying greater inhibition of the FT rate by strongly adsorbed CO on Co/Al2O3 relative to Co/SiO2. For both supports, the order on PCO was always found to be negative (i.e., suggesting an inhibiting effect) and positive for PH2 for all four catalysts. The order of the reaction on PH2 was close to 0.5, suggesting that dissociated H2 is likely involved in the catalytic cycle. Finally, in the limited range of average pore diameters studied (13.5 and 18.2 nm), the average pore size of the Al2O3-supported Co catalysts displayed no observable impact on the reaction rate or water effect, suggesting either that the reaction is kinetically controlled, or that the pore size difference was not significant enough to elicit a measurable response. 相似文献