Gold catalysts experiment

The accumulation of carbonates is another reason for gold catalyst deactivation [9]. The in-situ FTIR experiments in Fig. 6 show that the carbonate build-up is slower in the 03/02-treated gold catalyst (Fig. 6a) compared to the air-treated sample (Fig. 6b). Also, the air-treated catalyst displays a strong band at 1435 cm" corresponding to the non-coordinated carbonate. Although our understanding of the process is incomplete, it is clear from the results that O3 pretreatment inhibits the deactivation of gold catalyst. 

Thus, several experiments have shown that the aldehyde reacts faster than the alcohols, and primary alcohols are more reactive than the secondary ones with gold catalysts [4]. Moreover, it has emerged that mild conditions, allowed... 

Looking back at the literature published in the last 11 years, there are numerous reactions which without any doubt work with gold catalysts - but are not dependent on gold catalysts. Other Lewis or Bronsted acids might catalyze these reactions too, maybe even with similar reactimi rates and selectivities. Under the impression of a specific type of reaction being published as gold catalyzed, we finally published our own findings and control experiments [104]. As the control experiments clearly had shown that the reaction is catalyzed by protons, we previously had never intended to publish these results (which we had in our drawer for about 5 years). 

Studied the activation of B2pin2 and the catalytic diboration of terminal alkynes, they found a remarkably increased activity with completed diborated reactions in 1.5 h, giving the corresponding ds-adduct as the major isomer with a small amount of trans-zdduct. It is worth noting that AuNPore was active only in toluene as solvent. The leaching experiments and ICP-MS analysis indicated that no gold catalyst was leached. 

Fig. 9.46 Consequent experiments adding the fresh catalyst. (From 0. SImakova, E.V. Murzina, A.-R. Leino, P. Maki-Arvela, S. Willfor, D.Yu. Murzin, Gold catalysts for selective aerobic oxidation of the lignan hydroxymatairesinol to oxomatairesinol catalyst deactivation and regeneration, Catal. Lett. 142 (2012) 1011. Copyright 2012 Springer).

The actiyities of the gold catalysts were measured in the oxidation of CO or H2. Experiments were carried out in a small fixed bed reactor with O.lOg of catalysts that had passed through 70 and 120 mesh sieves. A standard gas of 1.0 vol.% H2 or CO balanced with air to 1 atm was passed through the catalyst bed at a flow rate of 33ml/min. The conversion of CO and H2 was determined through gas chromatographic analyses (G-2800, Yanagimoto Co. Ltd.) of effluent from the reactor. 

The initial rates of CO oxidation were determined on the samples treated in different ways. The reactivity of the samples investigated in the preliminary experiments decreases in the sequence of Au/FeO c/SiO (/Si(l 0 0) > FeO / SiO,/Si(10 0)>Au/Si02/Si(100)>Si(100). The Au/ Fe0 c/Si02/Si(l 0 0) catalyst has the highest initial activity. The results along with XPS and TEM data demonstrate that the interaction of gold nanoparticles and iron oxide tends to stabilize the metal character of gold and due to this stabilization, the Au/FeO catalyst has enhanced activity in the CO oxidation. 

According to the procedure of sol deposition described in Section 2.3, more than 10% Au can be deposited on XC72R, thus allowing the use of the catalysts in fuel cells and other electrochemical applications [36]. In all the experiments the common mother gold solution 1 (Section 2.3) was used containing a low PVA amount (PVA Au = 0.05) in order to facilitate the adsorption step. Table 8 shows the results. According to ICP analysis, an almost total gold adsorption was obtained. 

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