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首页> 外文OA文献 >Effect of Na loading on the properties of catalysts and n-heptane isomerization over Pt/sulfate -ZrO2 catalystudud
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Effect of Na loading on the properties of catalysts and n-heptane isomerization over Pt/sulfate -ZrO2 catalystudud

机译：负载钠对Pt /硫酸盐-ZrO2催化剂上催化剂性能和正庚烷异构化的影响 ud ud

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摘要

The acidic properties of Pt/sulfate-ZrO2 (PSZ) have been characterized by a combined study using temperature-programmed desorption (TPD) of ammonia and infrared (IR) spectroscopy. PSZ samples were prepared by impregnation of Zr(OH)4 with 1.0N of sulfate ion and calcined at 873 K, followed by addition of 0.5wt% Pt. Then 0.1 and 0.5wt% of Na were loaded in order to change the acidity of PSZ. The ammonia TPD spectra confirmed the existence of peaks at 443 and 623 K corresponding to the weak and medium acid sites, respectively. The TPD plot did not change much by addition of 0.1wt% Na, but changed considerably by addition of 0.5wt% Na which the intensity of peak at 623 K decreased and the intensity of peak at 443 K increased. It is indicated the conversion of strong into weak acid sites by addition of Na. IR spectra of pyridine adsorbed on samples showed the presence of Na decreased the intensities of bands at 1450, 1490 and 1540 cm-1 which corresponding to pyridine adsorbed on Lewis, Lewis-Bronsted and Bronsted acid sites. The addition of Na caused a more extensive decrease in the number of strong Bronsted acid sites than in the number of strong Lewis acid sites. The activity of PSZ samples were examined by isotherm hydrogen adsorption and n-heptane isomerization. The presence of Na decreased the hydrogen uptake due to the reducing of the number and strong acid sites. The hydrogen uptakes in 8 h for the samples unmodified and modified with 0.1 wt% Na and 0.5 wt% Na were 6.19 x10(17), 3.62x10(17) and 2.66x10(17) atom/m2-cat, respectively. These numbers correspond to H/Pt ratios of 4.79, 2.75 and 2.01, respectively. The presence of Na decreased the conversion of n-heptane and increased the isomerization selectivity of n-heptane due to the weakening the acidity of catalyst.
机译：Pt /硫酸盐-ZrO2（PSZ）的酸性特性已通过使用氨的程序升温脱附（TPD）和红外（IR）光谱的组合研究进行了表征。通过用1.0N硫酸根离子浸渍Zr（OH）4制备PSZ样品，并在873 K下煅烧，然后添加0.5wt％的Pt。然后加入0.1和0.5wt％的Na以改变PSZ的酸度。氨气TPD光谱证实分别在443和623 K处存在弱酸和中酸位点的峰。通过添加0.1wt％的Na，TPD曲线变化不大，但通过添加0.5wt％的Na，TPD曲线变化不大，这导致623 K处的峰强度降低而443 K处的峰强度升高。表明通过添加Na将强酸位点转化为弱酸位点。吸附在样品上的吡啶的红外光谱表明，Na的存在降低了1450、1490和1540 cm-1处谱带的强度，这对应于吸附在Lewis，Lewis-Bronsted和Bronsted酸位上的吡啶。 Na的添加导致强布朗斯台德酸位点的数量比强路易斯酸位点的数量更广泛地减少。通过等温线氢吸附和正庚烷异构化检查了PSZ样品的活性。 Na的存在由于减少数量和强酸位而降低了氢吸收。未经改性和用0.1 wt％Na和0.5 wt％Na改性的样品在8小时内的氢吸收分别为6.19 x10（17），3.62x10（17）和2.66x10（17）原子/ m2-cat。这些数字分别对应于H / Pt比为4.79、2.75和2.01。 Na的存在降低了正庚烷的转化率并且由于削弱了催化剂的酸度而增加了正庚烷的异构化选择性。

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