Bis 2 catalysts

Bi promoted Pt catalysts were prepared using JM proprietary methods. Aqueous solutions of Pt and Bi salts were co-precipitated onto the catalyst support and reduced using chemical reducing agents. Thereafter the materials were washed, filtered and retained as pastes. Graphite supported materials were dried prior to use. Similar preparation methods were used for all Pt and Pt-Bi catalysts. 

Table 4 Chemisorption characterisation of fresh Pt and Pt-Bi catalysts supported on carbon and graphite. H2 chemisorption data calculated from the charge in the hydrogen under-potential deposition (H-UPD) region of the cyclic voltammetry profiles. Values given as m2/g (total catalyst).

Selective Oxidation with Molecular Oxygen on Pt/Bi Catalysts... 

Initially, the allylation reaction was studied with the /V-benzyloxycarbonylamino sulfone derived from benzaldehyde and benzoyloxycarbonyl (Cbz) carbamate (Scheme 1, R1 = Ph, R = Bn). Various catalysts were screened for the allylation of benzyl phenyl(phenylsulfonyl)methylcarbamate la with allyltrimethylsilane in dichloromethane (Table 1). Among the various Bi catalysts tested, Bi(OTf)3 4H20 was shown to be the most efficient (Table 1, entry 5). BiCl3, BiBr3, Bi(OAc)3, or Bi(OCOCF3)3 did not allow the reaction to proceed and starting material was... 

Scheme I Working hypothesis to activate allylic and propargylic alcohols using a Bi catalyst via cj-71 chelation...

The selective oxidation of a 50% aqueous solution of glycerol was performed at 50 °C with an oxygen/glycerol ratio of 2, in a continuous fixed bed process using a Pt-Bi catalyst supported on charcoal. Here, a DHA selectivity of 80% at a conversion of 80% was obtained. 

The oxidation of secondary hydroxyl functions to the carbonyl group is often an undesired side reaction. However, the oxidation of D-gluconic acid to 2-oxogluconic acid is a highly selective process (97% yield) when a Pt-Bi catalyst is employed.89 Such a procedure is of industrial interest. 

Thus, it was shown that gold on carbon was much better than the more complicated multi-metallic Pt/Pd/Bi catalysts evaluated previously [365,386-392] for the liquid-phase oxidation of D-glucose, giving 100% selectivity to gluconic acid [360,361], Claus and co-workers also studied a series of Au/C catalysts prepared by the sol-gel method and got conversions and selectivities... 

It is reported that a Pd/Bi catalyst gave excellent selectivity to the desired 1123, which is important since addition of HF readily provides HFC-134a [85] using Cr-based catalysts. Pd modified with Au, Te, Sb, and As [86], and Re catalysts modified with Group VIII metals [87] have also been reported. 

Promoting effects of bismuth in carbon-supported bimetallic Pd-Bi catalysts for the selective oxidation of glucose to gluconic acid... 

Scheme 7 Example of intermodular selectivity using Pd or Pt on charcoal promoted with Bi catalysts...

Bimetallic (Pt-Bi) or trimetallic (Pt-Pd-Bi) catalysts are available commercially from Degussa [85]. Metal promoters such as bismuth or lead, were added to platinum metals by co-impregnation, by impregnation of the supported noble metal catalyst with an aqueous promoter salt solution, or by redox surface reaction. A very simple and efficient way of loading Pt/C or Pd/C catalysts with bismuth is to add the required amount of aqueous Bi0N03 solution to a suspension... 

Good yields of ketones were obtained in the oxidation on Pt-Bi catalysts (Bi/ Pts = 0.5) of secondary alcohols insoluble in water under the same conditions as for cinnamyl alcohol oxidation (see Section 9.2.3.2). Table 2 shows that selectivity in excess of 95 % was obtained at 97-99% conversion [43]. 

Figure 3. Proposed mechanism of oxidation of o-glucose on Pd-Bi catalysts [44].

Liquid-phase oxidation of carbohydrates on supported metal catalysts results in high selectivity which occasionally, e. g. in glucose oxidation, can match or surpass that of enzymatic processes. Metal-catalyzed oxidation also affords high productivity, e. g. up to 8 mol h (gpd) for oxidation of glucose on Pd-Bi catalysts [39]. These processes have the important advantages of high simplicity of operation ( one-pot reaction) and environmental acceptability, because almost no harmful effluents are generated. 

The Reppe process is a method that was developed in the 1940s and typical manufacturers include BASF, Ashland, and Invista. Cu-Bi catalyst supported on silica is used to prepare the 1,4-butynediol by reacting formaldehyde and acetylene at 0.5 MPa and 90-110 C (Eq. (10.2)). The copper used in the reaction is converted to copper(I) acetylide, and the copper complex reacts with the additional acetylene to form the active catalyst. The role of bismuth is to inhibit the formation of water-soluble acetylene polymers (i.e., cuprenes) from the oligomeric acetylene complexes on the catalyst [5a]. The hydrogenation of 1,4-butynediol is accom-pUshed through the use of Raney Ni catalyst to produce 1,4-butanediol (Eq. (10.3)). The total yield of 1,4-butanediol production is 91% from acetylene [5b]. Since acetylene is a highly explosive compound, careful process control is necessary. 

The work on catalysts for C4 hydrocarbons has been relatively recent. Ai and Ikawa " have correlated acid-base properties of the catalyst with activities in a Mo-P-Bi catalyst with varying bismuth content. They suggest that increasing Bi content decreases the acidity. The formation of acid (anhydride) is favored over a low-Bi-containing catalyst, i.e., high-acidity catalyst. 

Li et al. also reported the colloidal synthesis of Co-doped CdSe nanowires by the SLS strategy using the same reactants, except (MnSt)2 was replaced by cobalt stearate (CoSt)2 and the injection temperature was increased to 280°C. As-grown Co Cdi. Se (x = 0.3%) NWs were of 17.7 1.9nm in diameter and 1.8 0.2 pm in length with Bi catalysts located on both NW ends which demonstrated the SLS growth mechanism. The admixture of zinc blende and wurtzite structures were observed from TEM images. The diameter of the NWs can be tailored between 8 to 30 nm and the Co concentration can be tuned from 0 to 2.1% by varying the concentration of the reactants and reaction temperature. The temperature-dependent emission spectra of the Co-doped CdSe NWs were blue-shifted with increase of... 

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