Catalyst Reclamation

Even though noble-metal hydrocracking catalysts contain only small amounts of Pd or Pt, these metals are so expensive that recovering the metals is more cost-effective than throwing them away. Other hydroprocessing catalysts contain Mo or W, Ni, and/or Co. Spent hydrotreating catalysts -especially those used to hydrotreat residue - can be very rich in vanadium, richer than many ores. 

Reclamation companies convert these materials into salable products using different combinations of oxidation, pyrolysis, dissolution in acid or alkali, precipitation, extraction or ion exchange. Depending on the process used, the salable products may include several of the materials shown in Table 11. 

The book by Scherzer and Gruia provides a well-written description of catalyst reclamation processes used by four major companies - CRI-MET, Eurecat, Gulf Chemical, and TNO/Metrex. 

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Table 11. Some of the Materials Sold by Catalyst Reclamation Companies...

Commercially, a small amount of the 4,4 -MDA is isolated by distillation from PMDA. Depending on the process employed, the removal of MDA can be partial (as is done with the isocyanates) or total. Partial removal of MDA gives some processiag latitude but yields of 4,4 -MDA are reduced. Distillation residues from PMDA manufacture that contain less than 1% MDA pose a disposal problem. Processes for the regeneration of MDA by heating these residues ia the presence of aniline and an acid catalyst have been patented (33—35). Waste disposal of PMDA is expensive and reclamation processes could become commercially viable. The versatility of the isocyanate process, however, can be used to avoid the formation of low MDA content distillation residues. 

In the United States, the largest concentration of atmospheric vanadium occurs over Eastern seaboard cities where residual fuels of high vanadium content from Venezuela are burned ia utility boilers. Coal ash ia the atmosphere also coataias vanadium (36). Ambient air samples from New York and Boston contain as much as 600—1300 ng V/m, whereas air samples from Los Angeles and Honolulu contained 1—12 ng V/m. Adverse pubHc health effects attributable to vanadium ia the ambieat air have aot beea deteroiiaed. lacreased emphasis by iadustry oa controlling all plant emissions may have resulted ia more internal reclamation and recycle of vanadium catalysts. An apparent drop ia consumption of vanadium chemicals ia the United States since 1974 may be attributed, in part, to such reclamation activities. 

Reclamation, Disposal, and Toxicity. Removal of poisons and inorganic deposits from used catalysts is typically difficult and usually uneconomical. Thus some catalysts are used without regeneration, although they may be processed to reclaim expensive metal components. Used precious metal catalysts, including automobile exhaust conversion catalysts, are treated (often by the suppHers) to extract the metals, and recovery efficiencies are high. Some spent hydroprocessing catalysts may be used as sources of molybdenum and other valuable metals. 

Major areas of application are in the field of aqueous electrochemistry. The most important application for perfluorinated ionomers is as a membrane separator in chloralkali cells.86 They are also used in reclamation of heavy metals from plant effluents and in regeneration of the streams in the plating and metals industry.85 The resins containing sulfonic acid groups have been used as powerful acid catalysts.87 Perfluorinated ionomers are widely used in worldwide development efforts in the held of fuel cells mainly for automotive applications as PEFC (polymer electrolyte fuel cells).88-93 The subject of fluorinated ionomers is discussed in much more detail in Reference 85. 

Reclamation Renewal or restoration of a catalyst to initial chemical and physical properties. 

Without length grading, the refiner was planning to ship all of the material to reclamation. Application of LDG provided an economical way to recover a high quality product as well as reduce the amount of waste catalyst. 

This type of separation is very economically attractive to the refiner since it enables regeneration and reuse of the high value material and facilitates reclamation of the spent catalyst. 

Landfills have been the most popular depositories of spent nickel catalyst. Environmental concerns regarding the impact of nickel and conservation elforts to preserve nickel supplies have stimulated recycling and reclamation of the nickel component. Solvent extraction of organic material from the nickel is most effective with polar solvents such as isopropanol and methyl ethyl ketone (108). 

Reclamation of cobalt as described is not complete as some formation of Co " by oxidation cannot be avoided, leading to deterioration of the wastewater stream. For the recovery of cobalt from this stream, the usual techniques of precipitation may be applied, leading to carbonate or hydroxide [177], The overall losses are compensated by fresh cobalt, introduced via the carbonyl generator. In order to convert cobalt formate into HCo(CO)4, the presence of palladium on a support as catalyst is recommended [174],... 

OTHER COMMENTS Platinum metal is used in the manufacture of apparatus used in laboratories and industries, including thermocouples, acid-proof containers, chemical reaction vessels, platinum resistance thermometers, electrodes, etc. has found applications in dentistry, electroplating industry, and in the jewelry industry soluble platinum salts have been used as catalysts in the production of high octane gasoline, vinylesters, petrochemicals, and pharmaceuticals platinum metals, as well as soluble platinum salts, have been employed as oxidation catalysts in the manufacture of sulfuric acid, nitric acid from ammonia, and acetic acid soluble platinum salts have been used and reused in the reclamation of platinum ore. 

M. Marafi, S. Anthony and E. Furimsky, Handbook of Spent Hydroprocessing Catalysts Regeneration, Rejuvination, Reclamation, Environment and Safety, Elsevier, 2010. ISBN 9780444535566. 

Several alternative methods such as disposal in land fills, reclamation of metals, regeneration/ rejuvenation and reuse, and utilization as raw materials to produce other useful products are available to the refiners to deal with the sp>ent catalyst problem. The choice between these options depends on technical feasibility and economic consideration. 

Today, RCE cells find continuing use in controlled metal reclamation in a recent study, attention was focused on the recovery of precious metals from spent automobile exhaust catalysts [67]. 

An additional resource is industrially used silver that is recycled. Most important are scrapped photographic film and paper as well as used photographic baths. Reclamation of scrap from the electronics industry and catalysts from chemical industry contribute to modern silver manufacturing and dental scrap, silver amalgam, is also important. 

The Fenton oxidation, particularly using solid catalysts, is especially suitable for (a) domestic wastewater treatment, (b) wastewater reclamation and reuse (destruction and removal of harmful substances from the water streams to substantially promote the reuse of safe, treated water in industry or in agriculture), (c) sludge production reduction, and (d) water disinfection. The use of solid catalysts allows some of the drawbacks of homogeneous Fenton catalysts to be overcome, including ... 

The reclamation company makes money on both ends of the plant - from the refiner who must dispose of the catalyst, and from the customer who buys reclaimed products. 

Hardeners in these processes are strong sulphonic acids, such as paratoluensulphonic (PTS), xylenosulphonic (XSA) or benzensulphonic (BSA), sometimes with additions of sulphuric or phosphoric acids, usually in a diluted form, as catalysts. The XSA and BSA are strong acids, which are used when a short hardening time is required. However such catalysts create problems due to a corrosion effect. Sands with UF-FA resins can be catalysed by means of phosphoric acid, which virtue is a lack of unpleasant smells and none sulphur content but a reclamation of such sands is difficult [4]. 

Reclamation. Metals in the spent catalyst, such as vanadium, tungsten, and titanium, nuy be reclaimed for use in other products. 

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