Spent palladium

Dry reduced nickel catalyst protected by fat is the most common catalyst for the hydrogenation of fatty acids. The composition of this type of catalyst is about 25% nickel, 25% inert carrier, and 50% soHd fat. Manufacturers of this catalyst include Calsicat (Mallinckrodt), Harshaw (Engelhard), United Catalysts (Sud Chemie), and Unichema. Other catalysts that stiH have some place in fatty acid hydrogenation are so-called wet reduced nickel catalysts (formate catalysts), Raney nickel catalysts, and precious metal catalysts, primarily palladium on carbon. The spent nickel catalysts are usually sent to a broker who seUs them for recovery of nickel value. Spent palladium catalysts are usually returned to the catalyst suppHer for credit of palladium value. 

The use of palladium as a catalyst is common in the development and synthesis of active pharmaceutical ingredients (APIs). Palladium is an expensive metal and has no known biological function. Therefore, there is a need to recover spent palladium, which is driven both by cost and by government regulations requiring residual palladium in APIs to be <5 ppm (1). Thus, much research has been conducted with the aim of heterogenizing active palladium that can then be removed via simple filtration and hopefully reused without significant loss of activity. 

The Larock synthesis was used by Chen and co-workers to synthesize the 5-(triazolyl-methyl)tryptamme MK-0462, a potent 5-HTjn receptor agonist, as well as a metabohte [366], Larock employed his methodology to prepare tetrahydroindoles [367], and Maassarani used this method for the synthesis of /V-(2-pyridyl)indoles [368]. The latter study features the isolation of cyclopalladated Y-phenyl-2-pyridylammes. Rosso and coworkers have employed this method for the industrial-scale synthesis of an antimigraine drug candidate 331. In this paper removal of spent palladium was best effected by trimer-captotriazine (332) although many techniques were explored [369]. 

Rosso and co-workers have employed this method for the industrial-scale synthesis of an anti-migraine drug candidate. The triethylsilyl masked protective group was removed under strong acidic conditions to reveal the C2-H. The removal of spent palladium was best effected by trimercapto-triazine (TMT) although many techniques were explored. ... 

The palladium may be recovered by heating the spent catalyst to redness in order to remove organic impurities this treatment may reduce some of the barium sulphate to barium sulphide, which acts as a catalytic poison. The palladium is then dissolved out with aqua regia and the solution evaporated the residue is dissolved in hot water and hydrochloric acid to form palladium chloride. 

Several processes are available for the recovery of platinum and palladium from spent automotive or petroleum industry catalysts. These include the following. (/) Selective dissolution of the PGM from the ceramic support in aqua regia. Soluble chloro complexes of Pt, Pd, and Rh are formed, and reduction of these gives cmde PGM for further refining. (2) Dissolution of the catalyst support in sulfuric acid, in which platinum is insoluble. This... 

Catalysts reduced with formaldehyde carry no adsorbed hydrogen and are less pyrophoric. Barium carbonate as a support may sometimes be advantageous in that the neutrality of the h3 drogenation mixture may be maintained. Barium sulfate or barium carbonate may be a better support than carbon, which may, in some instances, so strongly adsorb the derived product that recovery is difficult or incomplete. Palladium may be more completely and easily recovered from a spent catalyst where carbon rather than barium sulfate is the support. In general, the submitter prefers a catalyst prepared according to procedure C. 

For the noble metals used in oxidation, the loading is about 0.1 oz per car, with calls for a million ounces per year. The current world production rates of platinum, palladium, and rhodium are 1.9, 1.6, and 0.076 million ounces respectively the current U,S. demand for platinum, palladium, rhodium, and ruthenium are 0.52, 0.72, 0.045, and 0.017 million ounces respectively (72, 73). The supply problem would double if NO reduction requires an equal amount of noble metal. Pollution conscious Japan has adopted a set of automobile emission rules that are the same as the U.S., and Western Europe may follow this creates a demand for new car catalysts approaching the U.S. total. The bulk of world production and potential new mines are in the Soviet Union and South Africa. The importation of these metals, assuming the current price of platinum at 155/oz and palladium at 78/oz, would pose a balance of payment problem. The recovery of platinum contained in spent catalysts delivered to the door of precious metal refiners should be above 95% the value of platinum in spent catalysts is greater than the value of lead in old batteries, and should provide a sufficient incentive for scavengers. 

The widespread use of platinum, palladium and other metals in automotive catalytic converters has been driven by environmental considerations and the increasing costs of the metals. This has not been matched by the development of clean reprocessing technologies for the catalysts themselves. The spent catalyst metals are oxidized to their cations via leaching into concentrated acids. 

After ARCO patents issued, Stille and coworkers published on butadiene oxycarbonylation(14-16). Palladium was utilized as the oxidative carbonylation catalyst and copper(II) chloride was employed as a stoichiometric reoxidation agent for palladium. Although the desired hex-3 -enedioate is the exclusive product, commercial technology which uses stoichiometric copper is not practical. Once the copper(Il) is consumed, the monoatomic palladium spent catalyst agglomerates affording polymeric palladium which is not easily reoxidized to an active form. 

Platinum, palladium and rhodium catalysts are non-pyrophoric as normally manufactured. Iridium and, more particularly, ruthenium catalysts may exhibit pyrophoricity in their fully reduced form, and for this reason are usually manufactured in the unreduced form and reduced in situ. Spent catalysts should be purged from hydrogen and washed free from organics with water before storage in the water-wet... 

Fig. 4 shows the TPR profiles of the fresh and spent catalyst. Curve C shows the desorption of hydrocarbons during reduction of the spent catalyst, formed by reduction of carbonaceous deposits on the catalyst surface. The hydrogen consumption profiles of the catalyst (see Curve A and B) show the two peaks, characteristic of palladium sulfate-based catalysts, with a vanadium oxide reduction peak at approximately 400 K and a sulfate reduction peak at 600 K [11,13,16]. The peak position of the sulfate reduction peak is comparable for both catalysts. For the spent catalyst, however, an additional small hydrogen consumption is observed at 700 K, which coincides with the large peak in the FID signal,... 

This is equivalent to 1.2 kg of palladium/metric ton of spent fuel burned to 32,000 MWd. One megawatt-day of thermal energy from fission is approximately equivalent to one gram of fission products. 

ON BARIUM SULFATE, 26, 77 ON CARBON, 26, 31,45, 78 recovery from spent catalyst, 26, 80 Palladium catalysts, 26, 77... 

Fig. 8. Comparison of the IINS spectra (TOSCA, ISIS) of palladium catalysts (a) IINS spectrum of the spent catalyst as taken directly from the hydrogenation process and sealed under argon, (b) same sample as in (a) after solvent extraction, (c) same sample as in (a) and (b) after hydrogenation at hydrogen equilibrium partial pressures up to 1.5 bar, and (d) a used but still active catalyst as characterized after cleaning by solvent extraction under the same conditions as the deactivated sample. The spectra are normalized to the same total sample mass.

The price of adsorbents and catalysts varies very widely depending on the nature of the material. The cheapest catalysts and adsorbents cost less than l/lb, while more expensive catalysts containing noble metals such as platinum and palladium have costs that are mainly determined by the amount of precious metal on the catalyst. In some cases, the value of the noble metal on a load of catalyst is so high that the chemical plant rents the catalyst rather than buying it, and when the catalyst is spent, it is returned to the manufacturer for precious metal recovery. 

The reaction of phosgene with spent platinum-containing or palladium-containing catalysts on aluminium(IIl) oxide, silicon(IV) oxide, or carbon supports at 140-450 C has been used as part of a recovery process [20,231,1864a,1864c], and car exhaust oxidation catalysts can be reactivated by heating in phosgene at 260 "C [1251],... 

Spent technical palladium catalysts used in the hydrogenation of polyaromatic ketones were studied by INS to determine the surface... 

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