Porous palladium

Similar studies were carried out with benzoic acid on porous palladium electrodes [150]. The objective of this work was to investigate the adsorption processes and the reactivity of benzoic acid on different noble metals, in order to compare these results with those obtained for related aromatic compounds. On-line mass spectroscopy analysis of volatile products revealed that the adsorption of benzoic acid is irreversible at platinum while it is mainly reversible on palladium. Accordingly, different catalytic activity of platinum and palladium was found in the electrooxidation. 

Tetrammino-palladous Chloro-palladate, [Pd(NH3)4]PdCl3, is produced by the action of chlorine on cold aqueous diehloro-diammino-palladium, or by the action of aqua-regia on tetrammino-palladous chloride. The substance is a brownish-black crystalline body. It is precipitated and decomposed by hydrochloric acid, with liberation of nitrogen, the formation of ammonium chloride and porous palladium. Boiling water decomposes it into ammonium chloro-palladite. The corresponding bromo-palladite, [Pd(NH3)4]PdBr4, and nitrito-palladite, [Pd(NH3)4]Pd(N02)4, are also known. ... 

One of the earliest applications of membrane to shift equilibrium was developed by Wood(5) (1960). He showed that by imposing a nonequilibrium condition on a hydrogen-porous palladium silver alloy membrane, an otherwise stable cyclohexane vapor is rapidly dehydrogenated to cyclohexene. 

Electroplating. Basically in electroplating, a substrate is coated with a metal or its alloy in a plating bath where the substrate is the cathode and the temperature is maintained constant Membranes from a few microns to a few millimeters thick can be deposited by carefully controlling the plating time, temperature, current density and the bath composition. Dense membranes made of palladium and its various alloys such as Pd-Cu have been prepared. Porous palladium-based membranes have also been made by deposition on porous support materials such as glass, ceramics, etc. 

A bench-scale steam electrolyser was fabricated and pure hydrogen gas extracted at the rate of a few litres per hour . Fig. 34.6 represents the cross section of the cell which contains a one-end-closed ceramic tube made of SeCeo.95Ybo.05O3-a (inside diameter 12-14 mm, thickness 1-1.5 mm, length 35-150 mm). As a cathode, porous platinum was baked on the inner side of the tube, and, as an anode, porous palladium was attached to the outer side of the tube. Four cells could be accommodated in a cell furnace and connected electrically either in series or in parallel. Steam... 

Lee SM, Dyer DC, Gardner JW (2003) Design and optimisation of a high-temperature silicon micro-hotplate for nano-porous palladium pellistors. Microelectron J 43 115-126... 

Ionic liquids have already been demonstrated to be effective membrane materials for gas separation when supported within a porous polymer support. However, supported ionic liquid membranes offer another versatile approach by which to perform two-phase catalysis. This technology combines some of the advantages of the ionic liquid as a catalyst solvent with the ruggedness of the ionic liquid-polymer gels. Transition metal complexes based on palladium or rhodium have been incorporated into gas-permeable polymer gels composed of [BMIM][PFg] and poly(vinyli-dene fluoride)-hexafluoropropylene copolymer and have been used to investigate the hydrogenation of propene [21]. 

Palladium Advantages have been claimed for new baths (e.g. using chelated complexes ). Antler summarised the use of palladium as coatings, inlays and weldments in electronic connectors . Crosby noted that palladium deposits are of two kinds (1) soft but continuous or (2) hard but porous or cracked. To resist wear and substrate corrosion on contacts, he proposed the application of type 1 (from a bath with tetranitropalladium(ii) anion) over type 2 (from solution containing tetramminepalladium(ii) cation) . 

In order to probe the influence of Au and KOAc on the vinyl acetate synthesis chemistry, four different catalysts were synthesized. All of these catalysts were prepared in a manner exemplified in prior patent technology [Bissot, 1977], and each contained the same palladium loading in an egg-shell layer on the surface of a spherical silica support. The palladium content in the catalyst was easily controlled by adjusting the solution strength of palladium chloride (PdClj) added to the porous silica beads prior to its precipitation onto the support by reaction with sodium metasilicate (Na SiOj). The other two catalyst components (Au and KOAc) were either present or absent in order to complete the independent evaluation of their effect on the process chemistry, e.g., (1) Pd-i-Au-hKOAc, (2) Pd-i-KOAc, (3) Pd-hAu, and (4) Pd only. 

Selective gas permeation has been known for generations, and the early use of palladium silver-alloy membranes achieved sporadic industrial use. Gas separation on a massive scale was used to separate U from U using porous (Knudsen flow) membranes. An upgrade of the membranes at Oak Ridge cost 1.5 billion. Polymeric membranes became economically viable about 1980, introducing the modern era of gas-separation membranes. H2 recovery was the first major application, followed quickly by acid gas separation (CO2/CH4) and the production of N2 from air. 

Scheme 7.122 Heck couplings utilizing palladium on porous glass.

In the same report, the Strauss group furthermore presented the effective use of palladium on porous glass to achieve quantitative conversions in couplings of phe-nylacetylene with iodobenzene and 4-bromobenzaldehyde. Additionally, satisfactory results were obtained for couplings of phenylacetylene with 4-bromoacetophenone and 2-bromopyridine [146]. 

Heck C-C coupling reactions were also facilitated by the presence of a palladium catalyst when Pd was deposited on a tubular membrane of porous glass. Thus, the coupling of iodobenzene with allyl alcohol affording 3-phenylpropionaldehyde in the presence of this Pd catalyst had several advantages - the ease of catalyst manufacture, mechanical strength, thermal stability, and resistance to organic solvents [46],... 

The cost of Pd-alloy membranes used for hydrogen separation may be reduced by depositing a thin Pd-alloy film on a suitable porous substrate to form a composite membrane. Almost all of the Pd-alloy membrane development efforts are, thus, focused on preparing thin yet defect-free Pd-alloy composite membranes (e.g., Hopkins, 2007 Coulter, 2007 Delft et al., 2005 Damle et al., 2005 Mardilovich et al., 2002). A detailed review of the Pd-alloy membrane research has been prepared by Paglieri and Way (2002) with an extensive bibliography of the palladium membrane research to date. An updated review has been recently prepared by Collot (2003) and Paglieri (2006). 

An integrated proof-of-concept (POC) size fluidized-bed methane reformer with embedded palladium membrane modules for simultaneous hydrogen separation is being developed for demonstration (Tamhankar et al., 2007). The membrane modules will use two 6 in. X 11 in. Pd-alloy membrane foils, 25-pm thick, supported on a porous support. The developmental fluidized-bed reactor will house a total of five (5) membrane modules with a total membrane area of about 0.43 m2 and is scheduled for demonstration by September 2007. 

Buxbaum, R.E. and T.L. Marker, Hydrogen transport through non-porous membranes of palladium-coated niobium, tantalum and vanadium. /. Membr. Sci., 85, 29-38,1993. 

Uemiya, S., Y. Kude, K. Sugino, N. Sato, T. Matsuda, and E. Kikuchi, A palladium/porous glass composite membrane for hydrogen separation, Chem. Lett., 10,1687-1690,1988. 

Uemiya, S. et al., Separation of hydrogen through palladium thin film supported on a porous glass tube, /. Membr. Sci., 56, 303,1991a. 

Crotonaldehyde is hydrogenated at 1 atm and 51 C in a trickle bed reactor using palladium on porous alumina as catalyst (Kenney Sedricks, Chem Eng Sci 27 2029, 1972). The reaction is first order. These data are known,... 

ENCAPSULATION OF PALLADIUM IN POROUS WALL HOLLOW GLASS MICROSPHERES... 

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