CATALYSTS
The Life Cycle Assessment of Platinum Group metals ( PGMs ); Reference year 2017 https :// ipa-news . de / assets / sustainability / 2021-08-02 _ IPA % 20LCA % 20Fact % 20Sheet . pdf
Figure 2 ( slide 10 , chart to right only ) – Environmental impact of precious metals
catalysts which bring together improved sustainability profiles with high cost-efficiency . This toolbox is used to produce catalysts called ‘ GREEn precious metal catalysts ’. GREEn stands for Green , Renewable , Efficient Enabler . This article will share several case studies showing the ‘ GREEn ’ benefits .
Lindlar catalyst replacement
Let ’ s begin with the Green aspect . In one case study , we developed a replacement for a Lindlar catalyst . These are used mainly for alkyne to cis-alkene hydrogenations . They are palladium catalysts that have been modified by the addition of a significant amount of lead ( 5 % Pd with 3 % Pb on CaCO 3
) to improve the selectivity of the reaction when compared to traditional palladiumcarbon catalysts . Lead brings major toxicity problems and the challenge was to find a leadfree replacement . BASF developed
GREEn LF 100 and LF 200 , which contain low levels of palladium ( 0.6 % and 0.5 %, respectively ) while having activity levels the same as that of the Lindlar catalyst , which contains 5 % palladium . Lead was entirely removed by controlling the size of the metal crystallite . The selectivity obtained was as high as with the Lindlar catalyst . The catalysts have a wide scope , with very good selectivity towards to the cis-alkenes . They work equally well with aromatic and aliphatic alkynes , despite the 90 % reduction in the amount of palladium needed in the catalyst from 2.5 mg to 0.25 mg ( Figure 3 ). This translates to a reduction of 90 % reduction in CO 2 emissions to 2 tonnes / kg of catalyst and a reduction of € 2,300 in the cost of the metal required .
Nitro group reduction
BASF also developed GREEn catalysts for nitro group reduction , a very
Figure 3 ( slide 19 , table and scheme above only ) – GREEn LF-100 v . Lindlar catalysts in alkyne hydrogenation
R 1 R 2
R 1 R 2
Catalyst mg Pd R 1 R 2 Olefin (%) Cis-olefin (%) Lindlar 2.5 CH 2 CH 3 CH 2 CH 2 OH 99 97 LF-100 0.25 99 97 Lindlar 2.5 H CMe 2 OH 99 NA LF-100 0.25 97 NA Lindlar 12.5 ( 48 % conv .) Me C 6 H 5 96 98 LF-100 1.25 90 97 common reaction in the production of speciality chemicals . Palladiumcarbon catalysts can be used in those reactions if no other functional groups are involved . However , in the presence of other functional groups , the chemoselectivity obtained with palladium-based catalysts is drastically reduced . Platinum catalysts offer better chemoselectivity in those situations but they also have a tendency to build up the intermediate hydroxylamine in the reactor , which is much more difficult to reduce . This hydroxylamine also tends to decompose explosively , bringing with it potential safety complications . To address these challenges , BASF developed four new catalysts : GREEn Pt-100 , Pt-200 , Pt-110 and Pt-210 . We reduced the levels of platinum in these catalysts from the 3-5 % typical in the standard catalysts and the 1 % platinum-vanadium catalyst seen more recently , to loadings of 0.8 % of Pt in the GREEn catalysts while still providing higher activity and maintaining good selectivity ( Figure 4 ). They also avoid hydroxylamine build-up . Users can employ the unpromoted catalyst , Pt-100 , and if for any reason the substrate is more difficult to hydrogenate and there is a tendency for hydroxylamine to build up , they can switch to Pt-200 or Pt-210 . These latter two contain molybdenum , which takes care of the hydroxylamine as soon as it is formed . These catalysts can also be applied to many different substrates . We have looked at substrates like orthochloronitrobenzene , 2,4-dichloronitrobenzene or 4-nitrobenzenonitrile compound , and found that they can all be converted to the primary aromatic amine in a selective way , all with up to 55 % reduction in the amount of platinum in the catalyst . At the same time , the reaction time to full conversion was close to half of what was required for the platinumvanadium-carbon catalyst . In summary , these catalysts help to reduce CO 2 emissions in the process
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