Palladium zeolite

Cheng Y.S. Performance of alumina, zeolite, palladium, Pd-Ag alloy membranes for hydrogen separation from Towngas mixture. J.Membr.Sci 2002 204 329-340. 

Surprisingly, palladium(II) salts supported on NaY zeolite produce DMC, even without halogens. The preferred support seems to be active carbon compared to zeolites because of higher DMC selectivities based on both MN and carbon monoxide, >95% in the case of active carbon and 80-90% in the case of zeolites. Palladium chloride/copper chloride on active carbon is likely used as a catalytic system in the industrial process. Because the carbonylation of MN to DMC occurs without water coproduction, the use of palladium salts as catalysts does not adversely affect selectivity. In the carbonylation reactor outlet some amount of methyl-chloroformate is present, as expected because it is known that palladium(II) chloride supported on alumina or silica catalyzes the reaction between MN, CO, and HCl to give methylchloroformate. " The presence of halide ions in the catalytic system and the methylchloroformate generation likely raise some corrosiveness issues. 

Hydrocracking is catalyzed by substances that promote cracking and hydrogenation together. In commercial use are Ni, Co, Cr, W, and V or their oxides, presulfided before use, on acid supports. Zeolites loaded with palladium also have been used. 

Direct hydroxylation of benzene to phenol could be achieved using zeolite catalysts containing rhodium, platinum, palladium, or irridium. The oxidizing agent is nitrous oxide, which is unavoidable a byproduct from the oxidation of KA oil (see KA oil, this chapter) to adipic acid using nitric acid as the oxidant. 

The separation factors are relatively low and consequently the MR is not able to approach full conversion. With a molecular sieve silica (MSS) or a supported palladium film membrane, an (almost) absolute separation can be obtained (Table 10.1). The MSS membranes however, suffer from a flux/selectivity trade-off meaning that a high separation factor is combined with a relative low flux. Pd membranes do not suffer from this trade-off and can combine an absolute separation factor with very high fluxes. A favorable aspect for zeoHte membranes is their thermal and chemical stability. Pd membranes can become unstable due to impurities like CO, H2S, and carbonaceous deposits, and for the MSS membrane, hydrothermal stability is a major concern [62]. But the performance of the currently used zeolite membranes is insufficient to compete with other inorganic membranes, as was also concluded by Caro et al. [63] for the use of zeolite membranes for hydrogen purification. 

Some companies are successfully integrating chemo- and biocatalytic transformations in multi-step syntheses. An elegant example is the Lonza nicotinamide process mentioned earlier (.see Fig. 2.34). The raw material, 2-methylpentane-1,5-diamine, is produced by hydrogenation of 2-methylglutaronitrile, a byproduct of the manufacture of nylon-6,6 intermediates by hydrocyanation of butadiene. The process involves a zeolite-catalysed cyciization in the vapour phase, followed by palladium-catalysed dehydrogenation, vapour-pha.se ammoxidation with NH3/O2 over an oxide catalyst, and, finally, enzymatic hydrolysis of a nitrile to an amide. 

The material being impregnated by the palladium precursor, once all the internal exchanged positions have been already occupied by Co2+, PdO is formed on the external surface of the zeolite grain, as observed by TEM (not shown, [12]). 

Okitsu K, Yue A, Tanabe S, Matsumoto H (2002) Formation of palladium nanoclusters on Y-zeolite via a sonochemical process and conventional methods. Bull Chem Soc Jpn 75 449 155... 

The investigated catalysts [9] were Pt-Pd/USY zeolite (SiO2/Al203 ratio 33.5, total- and mesopore surface areas 650 m2/g and 51 m2/g, total metal content 0,9%, Pd/Pt mass ratio 6 1 to 1 3, dispersion 0.41-0.55, acidity 0.20 mmol/g). Metal contents and Pd/Pt ratios are summarized in Table 1. As reference catalysts bimetallic Pt-Pd/Si02-Al203 (platinum-content 0.3%, palladium-content 0.6%, A1203 content 15%, surface area 292 m2/g, dispersion 0.41, acidity 0.18 mmol/g) and Pt-Pd/y-Al203 (platinum-content 0.3%, palladium-content 0.6%, surface area 182 m2/g, dispersion 0.35, acidity 0.12 mmol/g) were used. 

Supported palladium oxide is the most effective catalyst used in total methane oxidation and in catalytic oxidation of VOCs [1-5]. However, the activity of the conventional catalysts is not sufficient [5-6]. Recently, the Pd-zeolite catalysts have attracted considerable attention due to their high and stable CH4 conversion efficiency [4-8]. In this work, the effect of the preparation method, the nature of the charge-balancing cations, the palladium loading and the pre-treatment gas nature on the texture, structure and catalytic activity of the Pd-ZSM-5 solids are investigated. 

Ab initio methods, 147-49 Acetate ion, decomposition, 135 Acetylene, interaction with palladium, tunneling spectroscopy, 435,437f Acid-dealuminated Y zeolites catalytical properties, 183 sorption, 175-78 Acid sites, on zeolites, 254 acidification effects, 266 Acoustic ringing, in NMR, elimination, 386 Active sites, nature, 104 Activity measurements, Co-Mo catalysts, 74 Adsorbed molecules,... 

Y.Z. Zhang, T.T. Wong, and W.M.H. Sachtler, The effect of Ca + andMg + ions on the formation of electron-deficient palladium-proton adducts in zeolite, J. Catal. 128, 13-22 (1991). 

X. L. Bai and W. M. H. Sachtler, Methylcyclopentane conversion catalysis by zeolite encaged palladium clusters and palladium-proton adducts, J. Catal. 129, 121-129 (1991). 

When 1,2-dichlorobenzene in hydrogen-saturated deionized water was exposed to a slurry of palladium catalyst (1%) at room temperature, benzene formed via the intermediate chlorobenzene. The reaction rate decreased in the order of MCM-41 (mesoporous oxide having a silicon aluminum ratio of 35) > alumina > Y (dealuminated zeolite having a silicon aluminum ratio of 15). It appeared the reaction rate was directly proportional to the surface area of the support catalyst used (Schiith and Reinhard, 1997). 

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