Catalytic Solutions to Provide Relief From China’s Antimony Export Curbs
By Leonard Chan
China supplies approximately 50% of the global demand for antimony. Recently, China announced export curbs on antimony and gallium, set to be implemented on September 15, 2024. As a result, the price of antimony has doubled compared to a year ago. As seen below, together, China and Russia hold the majority of the world’s antimony reserves.
The primary industrial use of antimony is as a flame retardant in vehicles, electronics, and solar panels. Additionally, antimony is considered a strategic element for military applications, leading to stockpiling as part of defense strategies.
In a refinery setting, antimony is used in Fluid Catalytic Cracking (FCC) units to control dehydrogenation reactions that result in excessive hydrogen production catalyzed by nickel. FCC feed is injected through high-pressure nozzles into the riser, where the feed is atomized into small droplets. These droplets come into contact with a fast-moving stream of very hot fluidized catalyst. Contaminant nickel in the FCC feed deposits on the surface of the circulating catalyst in the riser. FCC catalysts have a large surface area, often 200-250 m² per gram, allowing nickel to distribute and remain an active catalyst for dehydrogenating feed hydrocarbons producing hydrogen. The resulting FCC dry gas is routed to the fuel gas system and is valued at the low price of natural gas. For FCC units with limited wet gas compressor capacity, an increase in hydrogen content can be problematic due to the disproportionate increase of gas volume it causes. To mitigate this, FCC units processing feeds high in nickel contamination often use antimony injection with the feed to suppress hydrogen production.
Antimony typically binds with nickel on a 1:1 basis to form a surface alloy, reducing hydrogen yield by approximately 40%. This binding blocks the nickel surface from hydrocarbons, suppressing its dehydrogenation activity. Antimony injection is controlled by monitoring the antimony content on the circulating equilibrium catalyst (Ecat). The optimal Sb/Ni ratio ranges from 0.2 to 0.4, depending on the effectiveness of the antimony injection and the presence of other contaminant metals like vanadium, copper, and iron.
FCC operators can decrease or eliminate the use of antimony in their unit by working with their catalyst suppliers to implement a nickel-trapping solution incorporated the FCC catalyst.
Ketjen’s MT-60 is a multifunctional matrix that encapsulates nickel, reducing coke and dry gas, especially hydrogen yield. MT-60 has the strongest nickel encapsulation power in the industry. Ketjen has developed the capability to incorporate a significant quantity of this component in their latest catalyst developments. MT-60 is incorporated into the catalyst particle and reacts with nickel to form nickel aluminate.
This offers an advantage over antimony injection, as it does not require perfect distribution of the Sb solution to contact the active nickel. MT-60 is evenly distributed within the catalyst particle during manufacturing and readily reacts with nickel deposited on the FCC catalyst, as seen in TEM analysis.
The effectiveness of MT-60 in reducing hydrogen yield is shown in the chart below
In addition to the benefits of nickel encapsulation, MT-60 combines with MT-20 synergistically to increase catalyst accessibility improving coke selectivity and bottoms cracking.
MT-60 features prominently in Ketjen’s newly developed DENALITM, ACTION®, ACTION+, and AFX catalyst families.
For more information, contact your Ketjen representative or reach us at ketjen.com today.
About the writer:
Leonard Chan
Country Manager (Singapore), Senior Business Director Asia/Pacific
Ketjen Singapore Pte Ltd