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41.
42.
巯基活性炭分离富集发射光谱法同时测定金、铂、钯和铊 总被引:1,自引:0,他引:1
研究了巯基活性炭在盐酸介质中对金、铂、钯和铊的吸附能力。该法具有吸附速度快、吸附容量大、在一定条件下,普通金属不被吸附的特点,可用于分离富集各类矿物中微量贵金属。吸附后巯基活性炭低温灰化,与缓冲剂混合发射光谱法同时测定金、铂、钯和铊,选择锆作内标线,直接压样于杯形的石墨电极中,该方法简便、快速、准确。对测定条件、干扰因素进行了研究,从而建立测定金、铂、钯和铊的新方法。金、铂、钯和铊的分析线分别为312.3nm,306.5nm,311.4nm和313.1nm,内标线选择为310.7nm的锆,金、铂、钯和铊的线性范围(原子百分数)分别为0~0.20%,0~0.40%,0~0.20%和0~0.40%。金、铂、钯和铊的检测限分别0.01%,0.003%,0.003%和0.001%。用于样品的测定获得满意结果。 相似文献
43.
Tin electrodeposition in its initial stages in acid sulfate/gluconate baths was studied with varying tin and gluconate concentrations using potential-controlled electrochemical techniques. The deposit morphology was observed by scanning electron microscopy (SEM). A comparison with tin electrodeposition from acid sulfate baths in the absence of gluconate was also carried out. Use of a highly acidic bath leads to nonuniform deposits, even in the presence of gluconate; at pH 4 deposits are uniform, brilliant and suitable for finishing applications. Tin crystallites have a well defined morphology which depends on bath agitation conditions. In the absence of agitation, the crystallites have the same tetragonal shape as in a sulfate bath without gluconate. 相似文献
44.
45.
Gang Li Dan I. Enache Jennifer Edwards Albert F. Carley David W. Knight Graham J. Hutchings 《Catalysis Letters》2006,110(1-2):7-13
The oxidation of benzyl alcohol to benzaldehyde has been investigated in the absence of solvent using zeolite-supported Au
and Au–Pd catalysts. Three zeolites were investigated, ZSM-5, zeolite β and zeolite Y, and these were contrasted with the
titanoslicalite TS-1 and TiO2 as supports. For the Au catalysts the best results are obtained with zeolite β as the support and the conversions were comparable
or better than those observed with TiO2 in terms of turn over frequencies. However, the selectivities observed with the acidic zeolites were lower than the non-acidic
TS-1 and TiO2. This is due to the subsequent reaction of benzaldehyde via acid catalysed reactions to give benzyl benzoate and its dibenzyl
acetal, and, in some cases dibenzylether. Initial catalysts were evaluated with a gold loading of 2 wt% and increasing this
to 4 wt% showed the expected increase in activity, indicating that there is scope to improve the performance of these catalysts.
The most active catalysts were prepared by impregnation and catalysts prepared by deposition precipitation were considerably
less active. Introduction of Pd into the catalyst improved the activity without significantly affecting the selectivity. 相似文献
46.
Using a Debye function analysis, the presence of icosahedral and face centered cuboctahedral gold in a 1 1 ratio has been found in freshly prepared Au/Mg(OH)2 catalyst. The results support earlier studies which suggest the icosahedral form to be more stable at small nanometer sizes. Interactions between the gold and the Mg(OH)2 support appear to be weak, with the gold rapidly coagulating over a period of three months. Re-analysis of the aged sample shows the gold to be mainly in the form of truncated decahedra. 相似文献
47.
Saleh Al-Sayari Albert F. Carley Stuart H. Taylor Graham J. Hutchings 《Topics in Catalysis》2007,44(1-2):123-128
The preparation of Au/ZnO and Au/Fe2O3 catalysts using two coprecipitation methods is investigated to determine the important factors that control the synthesis
of high activity catalysts for the oxidation of carbon monoxide at ambient temperature. In particular, the factors involved
in the preparation of catalysts that are active without the need for a calcination step are evaluated. The two preparation
methods differ in the manner in which the pH is controlled during the precipitation, either constant pH throughout or variable
pH in which the pH is raised from an initial low value to a defined end point. Non-calcined Au/ZnO catalysts prepared using
both methods are very sensitive to pH and ageing time, and catalysts prepared at a maximum pH = 5 with a short ageing time
(ca. 0–3 h) exhibit high activity. Catalysts prepared at higher pH give lower activity. However, all catalysts require a short
operation period during which the oxidation activity increases. In contrast, the calcined catalysts are not particularly sensitive
to the preparation conditions. Non-calcined Au/Fe2O3 catalysts exhibit high activity when prepared at pH ≥ 5. Calcined Au/Fe2O3 prepared using the controlled pH method retain high activity, whereas calcined catalysts prepared using the variable pH method
are inactive. The study shows the immense sensitivity of the catalyst performance to the preparation methods. It is therefore
not surprising that marked differences in the performance of supported Au catalysts for CO oxidation that are apparent in
the extensive literature on this subject, particularly the effect of calcination, can be expected if the preparation parameters
are not carefully controlled and reported. 相似文献
48.
通过间歇式抗高温氧化实验,建立了纯镍电铸层和N i-ZrO2纳米复合电铸层高温氧化动力学模型,分析了电铸层表面和横截面的形貌,测定了电铸层的组织结构。结果表明,N i-ZrO2纳米复合电铸层抗高温氧化性能明显优于纯镍铸层,复合电铸层表面生成的氧化膜晶粒细小且致密,并且该氧化膜较薄,产生的内应力较小,与复合电铸层的黏附性较好。 相似文献
49.
Laura Prati Alberto Villa Francesca Porta Di Wang Dangsheng Su 《Catalysis Today》2007,122(3-4):386-390
The liquid phase oxidation of glycerol with oxygen has been studied using mono and bimetallic catalysts based on Au and Pd metals supported on activated carbon, in order to study the effect of the metal on the distribution of the products and on activity of catalysts. It was found that by using bimetallic catalysts (Au–Pd) a strong synergistic effect was shown. By using a preformed nucleating centre we were able to obtain a single alloyed phase, which allowed us to address the synergistic effect to the presence of alloyed Au/Pd. The advantage of using this latter catalyst lies not only in the high activity but also in a prolonged catalyst life. Although a partial leaching of palladium and assembling of the particles have been revealed by ICP and HRTEM respectively, activity after 10 re-cycles decreased less than expected (about 10%). 相似文献
50.