The Changing Fortunes of Rhodium – Can Chemical Catalysis Secure its Future?
Dr Michelle K. Lynch CChem FRSC, CEO, Enabled Future Limited
The Changing Fortunes of Rhodium – Can Chemical Catalysis Secure its Future?
Rhodium metal is seeing some recent price stability at around $12,000 per troy oz compared with the all-time highs of over $30,000 per troy oz in early 2021. According to Johnson Matthey’s latest PGM Report, total net demand of rhodium for 2022 was predicted to reach 731,000 troy oz (22.8 tons).
Rhodium is used almost entirely in automotive engine emission control catalysts and in particular for controlling nitrogen oxide (NOx) emissions in gasoline vehicles. Internal combustion engine (ICE) sales therefore have a fundamental impact on rhodium demand and its price trends.
The total car market globally currently sits at around 80 million vehicles of which around 10 million were EV’s in 2022 – approximately 2 million PHEV’s and 8 million BEV’s according to analysts at RhoMotion. By 2035 this is expected to have grown to 60 million BEV’s and around 7 million PHEVs. (Ruid & Lucas, 2023). ICE numbers peaked in 2018 according to RhoMotion and the rapidly increasing proportion of EV’s is continuing to erode ICE numbers, although it should also be noted that plug in hybrid electric vehicles (PHEV), which can switch between hydrocarbon fuel and electricity modes, still also require an automotive catalyst. The growth in PHEV is nearer term before it plateaus. Technavio for instance predicts that the PHEV market will grow from around two to seven million sales per annum by 2027. (Technavio, 2022). This growth will require more rhodium for this sector.
In the near term ICE’s will dominate the market. For instance, in the EU as of Q3, 2022, BEV’s made up just 12% of new passenger car sales and therefore most new vehicles are still to be dependent upon an autocatalyst. (ACEA, 2022) Clearly, the EU has a long way to go to enact its proposed ban on all new ICE car sales by 2035 and it will be necessary for the price differential between new ICE’s and EVs (currently around €20,000) to be much reduced in order for typical ICE buyers to be able to afford them. In the USA, BEV’s are even further behind making up just 5% of the market and the majority of passenger car sales are gasoline, rather than diesel.
Set against solid demand fundamentals, rhodium supply is predicted to suffer large deficits until at least 2028. (Edison Group, 2021) The difficulty with this is that any outages/unplanned shutdowns in rhodium mines could cause the price to spike again. When this happens, industries tend to thrift or remove metals from their products. This has already been seen with the bushings used in the glass industry to make glass fibres. Traditionally bushings have been made with up to a 20% Rh-containing platinum/rhodium alloy with a technical lower limit of 10% rhodium, however high Rh prices have led Chinese glass producers to start using bushings with even lower loadings of rhodium. (Johnson Matthey, 2022). Thrifting is normally a positive especially from the point of view of the environment. However, this change in rhodium loadings for glassmaking could be counterproductive because lower rhodium loadings can reduce the total campaign length, decrease productivity, and an increase the cost of recycling and refabrication of bushings. (Johnson Matthey, 2022)
Rhodium is a tricky market to smooth and the extreme swing in demand for manufactured goods due to the Covid-19 pandemic in 2020-2022 certainly won’t have helped. Added to this speculators can drive up the price in a thin market. PGM miners can respond by increasing production, however in the face of the inevitable increase in the EV market, it would be potentially difficult to build a business case for the life of the mining operation.
The above picture is somewhat gloomy, and it is tricky to see how the situation can be improved at least in the next few years. Longer-term, when it could be expected that rhodium prices would decrease considerably, this may open up the opportunities for new uses. Chemicals applications are a good area to consider as new plants use significant amounts of metal and then offer a steady market for top ups over subsequent decades. Currently it is mainly hydroformylation catalysts which use rhodium for making oxo-chemicals e.g., n- and iso-butyraldehyde. Acetic acid can be made with a homogeneous rhodium catalyst although mainly the processes now use an iridium + ruthenium promoter homogeneous catalyst. Even so, Chiyoda Corp received a granted patent in the USA, Japan, China and Europe in 2021 for a vinylpyridine resin catalyst support, used for a rhodium-based methanol carbonylation catalyst which it claims has improved heat and abrasion resistance. (Chikako, Ryuichi, Zhixiong, Tetsuro, & Yoichi, 2021).
A quick look more broadly at chemical process patent filings from January 2015 to date show where the research interest is for rhodium catalysts. Some key interesting areas that show up are as follows:
- Syngas to alcohols (Rh hydroformylation catalyst)
- Adipic acid synthesis (Pt/Rh on zirconia)
- Hydrogenations for fine chemicals (Homogeneous Rh catalysts)
- Synthesis of durene feedstock for specialty polymers, medicines & dyes (Rh-containing ZSM-5/MOR eutectic zeolite)
- Hydroformylation of allyl alcohol to make 4-Hydroxybutanal (HBA) which is the precursor to 1, 4-Butanediol (BDO). (Homogeneous Rh with novel ligand)
In order to improve the chances of one or more of these opportunities to reach commercialisation, it is important for industry stakeholders to be aware of the patented science and to collaborate on scale-up. Tracking of PGM catalyst patents and process developments are available from Enabled Future Limited on request.
ACEA. (2022). New Car Registrations by Fuel Type. Retrieved from ACEA: https://www.acea.auto/files/20221103_PRPC-fuel_Q3-2022_FINAL.pdf
Chikako, H., Ryuichi, K., Zhixiong, Y., Tetsuro, M., & Yoichi, U. (2021, July 20). US11065607B2. Vinylpyridine resin for catalyst supports, production method therefor, and catalyst for methanol carbonylation reaction.
Edison Group. (2021). The PGM markets – Outlook and price forecasts. Retrieved from Edison Group: https://www.edisongroup.com/thematic/the-pgm-markets-outlook-and-price-forecasts/
Johnson Matthey. (2022, May). PGM Reports. Retrieved from Johnson Matthey: https://matthey.com/documents/161599/509428/PGM-market-report-May-2022.pdf/542bcada-f4ac-a673-5f95-ad1bbfca5106?t=1655877358676
Ruid, M., & Lucas, A. (2023, January 9). Q&A with Adam Panayi on Electric Vehicles. Retrieved from GlobalXETFs: https://www.globalxetfs.com/qa-with-adam-panayi-on-electric-vehicles/
Technavio. (2022, December). Mild Hybrid Vehicles Market by Type, Capacity, and Geography – Forecast and Analysis 2023-2027. Retrieved from Technavio: https://www.technavio.com/report/mild-hybrid-vehicles-market-analysis
Trading Economics. (2023, January 19). Rhodium. Retrieved from Trading Economics: https://tradingeconomics.com/commodity/rhodium#:~:text=Rhodium%20is%20expected%20to%20trade,11234.98%20in%2012%20months%20time.&text=Rhodium%20is%20a%20silver%2Dwhite,to%20corrosion%20and%20highly%20reflective.