The Plasma Treatment of Spent FCC Catalysts by Dr Tim Johnson
It is an extraordinary fact: during my own lifetime the global population has more than doubled from around three billion to more than seven billion. Equally sobering is that this growth will continue unabated well into the future and by the time I reach retirement (assuming it hasn’t been banned by the time I get there), there will be around three times as many people on the planet as when I was born. In case you’re wondering, most of this growth has been and will continue to be in the cities of the developing world and this is a huge force for global technological and economic change. In particular, experienced watchers of such things expect this general population growth to be accompanied by especially strong increases in the size of the middle classes of these expanding economies, which of course will result in a sharp increase in demand for all kinds of materials and chemicals as new generations strive for improvements in living standards and material goods.
The potential environmental, political and economic implications raised by these mind-boggling trends are almost limitless but let us focus for a moment on one area where these forces are already having an impact: the rapid growth of passenger and goods transport in Asia. As readers of this blog will be familiar, this has already led to big increases in the demand (and the cost) of many scarce and strategic metals, such as rare earth elements for use in electronics or platinum, palladium and rhodium for use in catalytic converters in vehicles. And I am sure it will come as no surprise to hear the demand for petrol and diesel is also rising in Asia in tandem with the growth of transport as a direct result of the self-same forces.
Now, as I am sure you know, when petrol fulfils its destiny by being burnt to create the power to drive our vehicles forward, the last thing the resulting gases see before they reach the outside world is a catalyst, i.e. the catalytic converter in the car’s exhaust pipe. Perhaps you are less aware that, not only are catalysts present at the end of petrol’s life but, like some technological priest or physician, they are also there at its birth. This is because catalysts are used to produce a large proportion of the petrol we consume, especially through a very important process known as Fluid Catalytic Cracking (FCC).
Around one third of all crude oil is processed by a FCC unit. Crude oil is actually a complex mixture of different types of oils but rather inconveniently it does not contain enough of the lighter oils we need for petrol and diesel production. FCC technology is so widespread because of its very valuable ability to break down heavier oils into lighter oils more suitable for petrol and diesel. At the heart of this process is a catalyst.
Many catalysts rely on the properties of precious or valuable metals to accelerate a particular chemical reaction, whilst the physical structure of the catalyst is provided by a ceramic (or less frequently a metal) substrate onto which the metal particles are attached. By contrast, the catalysts employed in the FCC process do not use a metal but instead rely on a highly porous clay-based mineral (zeolite) to provide both the chemical and physical properties required. However, they are not free from the influence of metals because crude oil contains small amounts of various metals, including nickel and vanadium, which gradually build up on the catalyst and eventually prevent the catalyst from functioning properly. At this point the catalyst must be discarded and fresh catalyst added.
The increasing demand for motor fuels is leading to the generation of more spent FCC catalyst. Meanwhile, increasing levels of trace metals in crude oils and improvements in catalyst design are leading to an increase in the levels of nickel (which is both hazardous and valuable) in those spent catalysts. Taken together, these things provide an ideal opportunity for Tetronics’ plasma technology. For many years our plasma systems have been recovering precious metals and an inert construction material from a wide range of spent catalysts. The plasma treatment of spent FCC catalysts is now also receiving considerable attention as this same metal recovery process can be used to destroy the hazardous nature of the spent catalyst whilst recovering the nickel for re-use in the metals industry.
It is all too easy in a Western country with a dismal economic forecast to lose sight of the enormous growth of demand for materials and chemicals that will surely come in the decades ahead in Asia and other parts of the developing world as their urban populations expand. Such demands create great opportunities for recycling technologies which can meet these economic and environmental challenges and we believe Tetronics’ plasma arc technology is ideally suited to make its own valuable contribution.