August 30, 2018
Nickel-containing catalysts are widely used in the refining and petrochemical industries worldwide. At end-of-life, catalysts are either sent to landfill or sent for recycling to recover the valuable metals they contain. Refineries in Kuwait are changing the way they handle spent catalysts.
A catalyst is a substance which speeds up chemical reactions or causes the reaction to take place under conditions it would not normally occur. The catalyst material generally has a very high surface-to-weight ratio, and is sometimes attached to an inert material such as alumina or silica. Many nickel catalysts are so reactive they will auto-ignite, that is, catch fire when exposed to air. The nickel content is often proprietary but can range from as low as 1.5% to as much as 98% of the total catalyst weight.
In oil refineries, nickel catalysts play a key role in several processes – hydrotreating, hydrocracking and steam reforming. In those first two processes, nickel acts as a promoter, that is, it increases the efficiency of the process. Steam reforming is a high temperature process which breaks down a fuel such as natural gas into hydrogen, carbon monoxide or other useful products. Here nickel is the main catalyst metal.
After a period of use, the catalyst becomes “spent” and no longer efficient. It is estimated that refineries worldwide generate roughly 150,000 tonnes/year of spent catalysts of all metals. Kuwaiti refineries alone generate about 6,000-7,000 tonnes/year. In the past most of this was sent to special landfills as hazardous waste, as there were no sites in the Middle East for recycling of such materials. Increasingly, the Kuwaiti refineries have become aware that this is not a sound environmental solution. Specialised metal recyclers are willing to take the spent catalysts and send them to a proper recycling centre where the valuable metals can be recovered. Dr. Ashish Pathak of the Kuwait Institute for Scientific Research (KISR) clarifies that “Due to the environmental concerns and company sustainability policies, the preferred option these days in Kuwaiti refineries seems to sell the spent catalyst to metal recyclers.”