Palladium sulfur poisoning

These results, coupled with the chemisorption titrations, provide evidence that a new phase of palladium is formed with tin under hydrogen that is more resistant to sulfur poisoning. ... 

The most selective and widely used catalyst is palladium, usually on an alumina support. A bimetallic palladium catalyst has also been developed.310 Palladium is more selective and less sensitive to sulfur poisoning than are nickel-based catalysts. Additionally, sulfides can also be employed. 

The nature of the unsaturated hydrocarbon has a very important role in the sulfur action Berenblyum et al. (83) have reactivated a palladium catalyst, poisoned with thiols, through the interaction with phenylacethyl-ene the presence of acetylenics together with low levels of sulfur even activate the nickel sites activity for acetylene hydrogenation (84, 85). 

Zeolite-based hydrogenation catalysts containing platinum and palladium have increased resistance toward sulfur poisoning (101-104), and a higher activity (95, 105) than many other supports. In recent years there has been some effort devoted to attempt to explain this phenomenon. Although there is general agreement that the catalytic surface of the zeolites most probably... 

Catalytic reduction in the presence of platinum or palladium is a very mild method for splitting trityl ethers. The products are an alcohol and tritane. The latter may be separated from the alcohol by taking advantage of its solubility in petroleum ether. If the trityl ether contains sulfur, poisoning of the platinum or palladium catalyst may occur. ... 

Similar deactivation is observed with bismuth and copper salts. A palladium catalyst poisoned with quinoline-sulfur and support on barium sulfate is used in the Rosenmund-Saytzeff reaction (p. 67). 

Potentially, the Claisen rearrangement is of greater synthetic utility merely because it is not confined to hydrocarbon substrates. However, no palladium-catalyzed thio-Claisen rearrangements have been observed, possibly owing to sulfur poisoning the catalysts. Nevertheless, thioimidates have been rearranged in the presence of catalytic quantities of [PdCl2 (PhCN)2]. 

The results of the sulfur poisoning, i.e. the difference in temperatures for achieving 10, 50 and 90 percent conversion of the different fuel components in the gas, H2, CO and CH4, are shown in fig 2. There are some clear trends that can be seen, the platinum catalysts (white bars) showed low deactivation (AT 0). This holds true for both the low temperature activity (i.e. H2 and CO combustion) and the high temperature activity (i.e. CH4 combustion). Palladium (stripy bars) showed a different behavior here the activity for CO and H2 remained more or less the same while the CH4 activity was greatly affected by the presence of SO2. For the Pd-YAG, the most affected catalyst, the temperature for 50 percent conversion for CH4 increased with as much as 250 °C, from 500 °C to 750 °C. For the metal oxides the picture is a little bit more complicated. For the MAS and LMA catalysts, the low temperature activities... 

As with all catalysts, palladium and its alloys are susceptible to poisoning [69]. Catalysts must be designed with resistance to poisoning, and proper precautions must be taken to minimize exposure of the membranes to catalyst poisons [69]. Typical poisons for palladium include H2S and other compounds of sulfur such as carbon disulfide (CS2), carbonyl sulfide (COS), aromatic thiophenes and mercap-tans (thiols, R-SH). Palladium is poisoned by the Group VA elements, P, As, Sb and Bi, the halides (Cl, Br, I), and Si, Pb and Hg. Alkenes and unsaturated organic compounds can poison palladium as can elemental carbon deposited from decomposition of carbonaceous materials. Carbon monoxide in high concentrations and at low temperatures can form a monolayer which blocks adsorption and dissociation of molecular hydrogen. Carbon monoxide can also decompose to produce car-... 

Other partially poisoned catalysts have long been used in the laboratory. Supported palladium catalysts, poisoned with lead (Lindlar catalysts), sulfur, or quinoline, are used for the hydrogenation of acetylenic compounds to cis-olefins. Another... 

Castro F J, Meyer G, Zampieri G (2002), Effects of sulfur poisoning on hydrogen desorption from palladium , / Alloys Compd.,330,612-616. 

A higher tolerance to sulfur poisoning was observed for autothermal reforming of synthetic diesel fuel over bimetallic platinum/palladium and platinum/nickel catalysts compared with monometallic samples [257]. 

Platinum combustion catalysts are probably more tolerant to sulfur poisoning than palladium catalysts [350,355]. Corro et al. reported that sulfur dioxide may even have a promoting effect on propane oxidation [356]. They claimed that aluminium sulfate needs to be present on the catalyst surface to promote the reaction in the low temperature range below 300 °C. The sulfate formation was assumed to start at temperatures exceeding 500 °C. Therefore, the catalyst must have previously been exposed to such a temperature in the presence of sulfur dioxide. Over a pre-sulfated platinum/alumina catalyst, 50% methane conversion was achieved by 530 °C, while 560 °C was required for the sulfur-free counterpart [357]. However, no promotion effect is to be expected over non-sulfating carrier materials, such as sflica, according to Gelin and Primet [351]. 

Deng, Y. and NeveU, T.G. (1993) Sulfur poisoning, recovery and related phenomena over supported palladium, rhodium and rridimn catalysts for methane oxidation. Appl. Catal. A, 101, 51-62. 

Palladium and promoted palladium catalysts are used for the hydrogenation of small amounts of acetylenic compounds from purified olefin streams. These catalysts are sensitive to sulfur poisoning and, therefore, the feed gas must be free of sulfur prior to hydrogenation. The noble metal catalysts are more active than the base metal types and can therefore operate at lower temperatures—as low as 80°F—and are capable of producing effluent purities below 1 ppmv acetylene under optimum conditions. An improved catalyst, consisting of promoted palladium on alumina, was introduced by United Catalysts, Inc., in 1988. The catalyst... 

Catalytic Oxidation. Catalytic oxidation is used only for gaseous streams because combustion reactions take place on the surface of the catalyst which otherwise would be covered by soHd material. Common catalysts are palladium [7440-05-3] and platinum [7440-06-4]. Because of the catalytic boost, operating temperatures and residence times are much lower which reduce operating costs. Catalysts in any treatment system are susceptible to poisoning (masking of or interference with the active sites). Catalysts can be poisoned or deactivated by sulfur, bismuth [7440-69-9] phosphoms [7723-14-0] arsenic, antimony, mercury, lead, zinc, tin [7440-31-5] or halogens (notably chlorine) platinum catalysts can tolerate sulfur compounds, but can be poisoned by chlorine. 

Figure 8 X-ray elemental imaging in a field-emission STEM (a) EDS data of Pd /Ce /alumina catalyst particle poisoned with SO2 and (b) 128 X 128 digital STEM images formed using X-ray counts collected at each image pixel for aluminum, palladium, cerium, and sulfur. (Courtesy of North-Holland Publishers) ...

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