The used auto catalytic converter is a valuable source of platinum group metals, so it is important to have it recycled in order to recover precious metals. World literature describes a number of pyro- or hydrometallurgical methods used for recovery of platinum from used automobile catalytic converters. However, all the methods, available in the literature, are used to recover platinum from ceramic carrier. Among automotive catalysts withdrawn from use, these with metallic carrier constitute quite a big group

A. Fornalczyk

J. Cebulski

J. Willner

M. Saternus

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609METALURGIJA 53 (2014) 4, 609-612A. FORNALCZYK, J. CEBULSKI, M. SATERNUS, J. WILLNERPOSSIBILITIES OF PLATINUM RECOVERY FROM METAL SUPPORTED SPENT AUTO CATALYSTSReceived – Prispjelo: 2013-10-10Accepted – Prihvaćeno: 2014-04-20Preliminary Note – Prethodno priopćenjeISSN 0543-5846METABK 53(4) 609-612 (2014)UDC – UDK 669.186:518.1:531.3=111A. Fornalczyk, J. Cebulski, M. Saternus, J. Willner: Silesian University of Technology, Institute of Metal Technology, Katowice, Poland The used auto catalytic converter is a valuable source of platinum group metals, so it is important to have it recycled in order to recover precious metals. World literature describes a number of pyro- or hydrometallurgical methods used for recovery of platinum from used automobile catalytic converters. However, all the methods, available in the literature, are used to recover platinum from ceramic carrier. Among automotive catalysts withdrawn from use, these with metallic carrier constitute quite a big group.Key words: Precious Metals Group (PGM) metals, metal recovery, spent auto catalysts, metallic carriers.INTRODUCTIONNowadays, ecological problems become a priority in many areas of science and industry. Also in the auto-motive industry, more strict standards for emission of harmful compounds in the form of exhaust gases into the atmosphere introduced. Thus, for several years, in-stallations reducing environmental pollution, common-ly referred to as automotive catalysts, are used in cars. In these devices, chemically active elements, especially Precious Metals Group (PGM) - having the ability to convert harmful substances - are used [1].Their main task is to limit the emission of dangerous substances such as: nitride oxide (NOx), hydrocarbons (CH) and carbon monoxide (CO). As a result, com-pounds neutral to the environment, such as carbon diox-ide, water and nitrogen are obtained at the outlet of catalytic converters [2]. Typical auto catalytic converter is built mainly from metallic or ceramic carrier with po-rous structure covered with the PGM metals (Figure 1). The most often used are: platinum, palladium and rho-dium. Catalytic carrier is wrapped by the ﬁ brous mate-rial (to prevent slipping) and closed in a shell made from stainless steel plate. The PGM layer is put on the ceramic carrier (Al2O3 with the addition of other oxides e.g. CeO2 - washcoat), which has the honeycomb struc-ture, that means a dense net of square holes. Such con-struction increases the active surface, which is the con-tact zone of catalytic substances (Pt, Pd, Rh) with the exhaust gases, that ﬂ ow through the channels [3]. For certain applications (reducing light-off, reduc-ing back-pressure, etc), a metallic carrier rather than ceramic one is chosen. It is a commonly known fact that converters with a ceramic substrate cover about 95 % of the total market [4].Considering the fact that the metal heats up much faster than ceramics, metal catalysts rapidly reach “working temperature” and quickly purify exhaust gas-es. At the same time, they are more resistant to damage caused by thermal shock and high temperature (deter-mined by their resistance to 1 300 °C). The advantage of metal supported catalysts is their better thermal conduc-tivity obtained due to high content of platinum [5].Catalytic converters with metallic carriers – MSC (Metal Substrate Converters) were originally designed for sport and racing cars where low back pressure and reliability under continuous high load is required. This is partially a cost issue. Ceramic carriers are inexpen-sive when manufactured in large quantities. Metallic cores are less expensive to build in small production runs. Either material is designed to provide a high sur-face area to support the catalyst washcoat, and therefore it is often called a “catalyst support” [6]. Metallic foil monoliths (Figure 2) are made of FeCrAl [7]. Analysis of chemical composition of this kind of catalytic con-verters is shown in Figures 3-7 and in Table 1. The surface of the sample catalysts was analyzed with the use of scanning electron microscope (SEM) equipped with a Hitachi S 4200 the X-ray detector. Ac-celerating voltage applied during the observation and X-ray microanalysis was 15kV. Microanalysis of the Figure 1 Scheme of auto catalyst610  METALURGIJA 53 (2014) 4, 609-612A. FORNALCZYK et al.: POSSIBILITIES OF PLATINUM RECOVERY FROM METAL SUPPORTED SPENT AUTO CATALYSTSchemical composition was performed by means of EDS method (Energy Dispersive Spectrum).Unfortunately, such a structure makes it difﬁ cult to recover the precious metal contained in these kind of catalyst [7].COMPARISON OF METALLIC OR CERAMIC CATALYTIC CARRIERConsequently, the most important element in the catalytic converter applied not only in automobile in-dustry, but generally in all industries is the material for the converters carrier (metallic or ceramic). The most commonly used are catalytic converters with ceramic carriers. Table 1 Chemical analysis for sample of catalytic converterElement Base(6)pt1Base(6)pt2Base(6)pt3Weight %Cr 6,1 11,8 1,8Fe 18,3 42,8 2,1Pt 4,5 2,1 5,0C 0,5 0,7 6,8O 42,3 24,4 44,2Al 28,0 18,0 22,4Si - 0,3 2,0S - - 1,7Ca - - 1,9Ti - - 1,0The advantages of ceramic carriers are: • very high speciﬁ c surface, • high corrosion resistance, • high adhesion of active substances, • high melting temperature, • easiness in shaping. The characteristic features of metallic catalytic car-riers are: •  easiness of heat transfer (they are resistant to local overheating), • small hydraulic resistances, • high mechanic strength, • all apparent powder density,• smaller susceptibility to mechanical damage [8]. Figure 2 Real view of catalytic carrier structureFigure 3  Structure of catalytic converter sample with marked selected areas for X-ray energy spectra (Magnifi cation x450)Figure 4 Structure of catalytic converterFigure 5  X-ray energy spectra (EDS) at point 1 for sample of catalytic convertersFigure 6  X-ray energy spectra (EDS) at point 2 for sample of catalytic convertersFigure 7  X-ray energy spectra (EDS) at point 3 for sample of catalytic converters611METALURGIJA 53 (2014) 4, 609-612A. FORNALCZYK et al.: POSSIBILITIES OF PLATINUM RECOVERY FROM METAL SUPPORTED SPENT AUTO CATALYSTSThe difference between both type of auto catalytic converters is shown in Table 2.Table 2  The diff erence between boths type of auto catalytic converters [7]Part of catalyst Ceramic carrier Metallic carrier (MSC)Steel shell 2,900 kg 1,300 kgIsolation 1,000 kg 0,800 kgCarrier 0,900 kg 1,300 kgWashcoat (with PGM) 0,160 kg 0,160 kgPGM 0,005 kg 0,005 kgSum 4,965 kg 3,555 kgMaterial for recycling 1,065 kg 0, 155 kgThe efﬁ ciency of the metallic and ceramic convert-ers measured by comparing how much gas is converted, is shown in Table 3.Table 3  Measured conversion at idle [9]Conversion effi  ciencyCeramicCarrier (TWC-C - Three Way Catalyst-ceramic)MetallicCarrier (TWC-M - Three Way Catalyst-metallic)HC 31,58 % 45,62 %CO 32,08 % 33,52 %NO 43,33 % 47,32 %RECYCLING OF USED AUTO CATALYTIC CONVERTERSIn Europe End-of life–vehicles (ELVs) are a particu-larly valuable waste source, amounting to more than 9 million tons per year thus they demand to be properly managed [10]. Derective 2000/53/EC gives basis for more sustainable approach and drives to a recovery im-provement, in order to reduce waste production from the sector of End-of-Life-Vehicles treatment. This regu-lation increases in the re-use and material recovery as shown in Table 4.Table 4  Targets of ELVs recycling and recovery (Directive 2000/53/EC) [10]Year 2006 2009 2015Re-use and recovery 85 % 80 % 95 %Re-use and recycling 80 % 80 % 85 %Catalytic converters are devices that should be peri-odically regenerated, and eventually replaced. Current-ly, this increasing number of catalysts (coming from exchanges and also from vehicles withdrawn from the market) should be recovered.The needs of waste management and high prices of precious metals contained within these wastes, makes the recovery of platinum group metals from used auto catalytic converters potentially proﬁ table. The main problem, in platinum recovery from catalysts, is how-ever its low content within a single catalyst.The ﬁ rst step to recover PGM metals and especially platinum from used auto catalytic converters (both with ceramic and metallic carrier) is to collect and then dis-mantle them. After these operations catalytic converter carriers are milled and homogenized. Then chemical analysis is necessary in order to check the level of plati-num and other precious metals. Thus, there are numer-ous pyro-, hydrometallurgical and mixed methods ap-plied in recovering of PGM metals from catalytic con-verters [11]. Both types of PGM metals recovery meth-ods are complex, multistage, in which the appropriate catalytic converter carrier grinding and primary homog-enizing is needed. Then many essential operations are applied and at the end a method, which allows to sepa-rate the obtained platinum or other PGM metals from the solution or alloy and reﬁ ne it/them to the desirable level.However, if recovery of PGM metals to be cost-effective, well over 90 % of these precious metals must be recovered [12-14]. As the precious metals are applied only to certain parts of the converter (washcoat), the ﬁ rst step of recy-cling process is a mechanically separate the washcoat and PGM from the substrate [15]. The next step is then to homogenize the PGM fraction. The metallic carrier is shredded by passing it through one or more different types of shredders, hammer mills. This step is preceded by separation of various fractions of steel scrap (such as can-fraction, foil-fraction) from the precious metal containing fraction. There is little in-formation on the recovery of precious metals from spent automotive catalysts with metal carriers in the world lit-erature. The Umicore Precious Metals Reﬁ ning - one of the world’s largest precious metals recycling facilities - has dedicated and highly fully automated shredding line for metallic carriers from spent automotive catalysts in Maxton (USA). This technology allow to achieve a high recovery yield for the washcoat [4].However, the crushing process can causes problem - a ﬁ ne dust (obtained after this process) is rich in pre-cious metals [15]. The authors Hensel, Konieczny and Brückhe [15] suggested that it allow to partly separated washcoat from the substrate! The wash coat can be seperated from the substrate by mechanical means in certain process parameters (dif-ference in form, size and weight mixture of). The end result is that different but homogeneous fractions of high purity are recovered.The main steps of PGM recovery process from spent automotive catalyst with metallic carrier suggested in paper [15] are:•  Mechanical Reduction - reduction to a deﬁ ned par-ticle size by means of a shredder. •  Magnetic Separation - metallic fraction is mag-netically separated. •  Mechanical After-treatment - the residue of pre-cious metals on the substrate foil is seperated from the steel parts by means of a mechanical separa-tion unit.All fractions of the wash coat are homogenized. The substrate foil and casing material can be reutilized in steel smelting [15].612  METALURGIJA 53 (2014) 4, 609-612A. FORNALCZYK et al.: POSSIBILITIES OF PLATINUM RECOVERY FROM METAL SUPPORTED SPENT AUTO CATALYSTSCONCLUSIONSThe automotive industry is facing signiﬁ cant chal-lenges as vehicles have considerably environmental im-pact on all stages of their life cycle [16]. The recovery of PGM metals and especially platinum in the last dec-ade has been growing but is not sufﬁ cient. The bigger and bigger demand for platinum causes the growth its price. Considering, however, the existing state of the technological development it is very unlikely that plati-num group metals shall be replaced (in automotive in-dustry) by other substitute in the nearest future. So, the recovery of PGM metals from used auto catalytic con-verters has become very important and catalytic con-verters very valuable sources of these metals. High pu-rity of recovered metals allows to use then again and does not cause any ﬁ nancial problems. AcknowledgementsFinancial support from Polish Ministry of Science and Higher Education is acknowledged (No N N508 6255 40).REFERENCES[1] A. Fornalczyk, M. Saternus: Metalurgija, 52 (2013) 2, 219-223. [2] M. Saternus, A. Fornalczyk: Metalurgija, 52 (2013) 2, 267-270.[3] A. Fornalczyk, M. Saternus: Acta Metall. Sin., 26 (2013) 3, 247-256.[4 www.preciousmetals.umicore/recyclables/SAC/Servi-ce/15.09.2013.[5] http://autokatalizatory.pl/inne-odpady,28.html 13.08.2013.[6]  http://en.wikipedia.org/wiki/Catalytic_converter 12.09.2013.[7] M. Kucharski: Recykling metali nieżelznych, Wydawnict-wo AGH, Kraków (2010).[8] http://ﬂ uid.wme.pwr.wroc.pl 22.06.2013.[9] H. Santos, M. Costa: Energy Conversion and Management, 49 (2008), 291-300.[10] L. Morselli, A. Santini, F. Passarini, I. Vassura: Waste Ma-nagement, 30 (2010), 2228-2234.[11] J. S. Yoo: Catalyst Today, 44 (1998), 27-46.[12] R. Przyłucki, A. Smalcerz: Metalurgija 52 (2013) 2, 235-238.[13] T. N. Angelidis: Topics in Catalysis, 16/17 (2001) 1-4, 419-423.[14] R. Rao: Resource recovery and recycling from metallurgi-cal wastes, Oxford University, Elsevier, (2006).[15] C. Hensel, R. Konieczny, R. Brück: Recycling Technology for Metallic Substrates: a Closed Cycle, Demet Recycling AG (2010).[16] I. Vermeulen, J. Van Caneghem, C. Block, J. Baeyens, V. Vandecasteele: Journal of Hazardous Materials, 190 (2011), 8-27.Note:  The responsible translator for English language is M. Kingsford, Katowice, Poland

Possibilities of platinum recovery from metal supported spent auto catalysts

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