Precious metals can be green
Dr Hans Donkervoort , global marketing manager for precious metal powder catalysts at BASF , shares some results for some newly developed catalysts
Palladium Rhodium Platinum
Current price : $ 60,000 / kg 1kg of 5 % Pd catalyst : $ 3,000 Pd
Current price : $ 450,000 / kg 1kg of 5 % Rh catalyst : $ 23,000 Rh
Current price : $ 32,000 / kg 1kg of 5 % Pt catalyst : $ 1,600 Pt
Figure 1 ( slide 9 , chart only ) – Price development of precious metals , 2016-2021
Catalysts are widely used in the production of both basic and speciality chemicals . Indeed , the very act of using catalysts instead of a non-catalytic process in itself , delivers a very significant contribution to making that process more sustainable . At the same time , catalysts producers need to look constantly for sustainability improvements that the catalyst can deliver . In this context , BASF has been working intensively over the last few years to improve the performance of some of its precious metal-based catalysts and thus contribute to a more sustainable future . The work to date has focused on powder catalysts and carbon supports ; fixed bed catalysts and other supports will be the subject of future work . Developing these catalysts has been no easy task and there are many challenges to face : waste reduction , recyclability , reducing CO 2 emissions and , not least , improving the chemoselectivity of the catalysts in order to reduce the cost of using them . Since 2016 , there has been a steep increase in the price of the precious
metals used in catalysts ( Figure 1 ). Currently , the cost of palladium is around $ 60,000 / kg of metal while platinum , which has seen less price inflation , is about $ 32,000 / kg of metal . Rhodium currently costs about $ 450,000 / kg of metal , meaning that , if it is used for producing one kilogram of catalyst containing 5 % metal loading , the cost contribution of the metal alone is $ 23,000 / kg of catalyst . As well as the price impact , there is a sustainability impact on the use of precious metal catalysts . A full life-cycle assessment that was carried out recently indicated that for each kilogram of mined precious metal , 25-40 tonnes of CO 2 are emitted . There are also significant impacts in terms of acidification , eutrophication and photochemical ozone creation potential , among other things ( Figure 2 ). Precious metal powder catalysts are produced by taking a support and interacting it with the metal , which may or may not be reduced . The metal is typically carried on carbon , which has many functional groups to act as anchoring points for the metal . These variables provide opportunities
to control what type of catalyst is produced . It is possible to change the concentrations and oxidation state of the metals , the size of the metal crystallite or its location in the pores of the carrier . Broadly speaking , the higher the dispersion , the smaller the metal crystallites , the higher the metal surface , and the higher is the activity of the catalyst . That said , there are some reactions so sensitive that a lower metal surface area is required . It is thus essential that we can control what we are making by controlling the size of the crystallites . Also , the metal location on the carrier is important to control . In one example , a mixed metal location yields 94 % of the required product and 6 % by-product , while the selectivity is increased to more than 99 % by changing to an eggshell-style metal location catalyst . This shows the significant effect the location of the metal on the support has on the performance of the catalyst . With these background concepts , BASF set out to develop a toolbox of innovative catalyst production technologies that can deliver
36 SPECIALITY CHEMICALS MAGAZINE ESTABLISHED 1981