The photo is sourced from catalysis.ru
Every year, municipal wastewater treatment produces 100 million tons of sludge worldwide, which is a big problem for municipalities: waste disposal requires huge areas that must remain intact for 100–150 years. Moreover, sludge often contains pathogenic microorganisms and toxic materials, including lead and cadmium, which, when buried, are washed away into groundwater and released into the air along with dust.
One of the chief methods of sludge disposal is incineration, which causes emissions of pollutants, the capture of which requires expensive equipment. An alternative method is pyrolysis – high-temperature treatment with a lack of oxygen under low pressure producing a pyrolysis liquid, from which organic solvents and reagents can be synthesised.
However, before being used in the chemical industry, the pyrolysis liquid needs to undergo hydroprocessing, including in order to extract oxygen and nitrogen, which prevent it from being used as fuel for direct combustion. For that purpose, the scientists from the Institute of Catalysis SB RAS tested a number of nickel-molybdenum (NiMo) catalysts that are used for hydrotreatment at refineries.
“We have shown that catalysts, which are sulphide in nature, such as NiMo, are best suited for this type of process, especially at a temperature of 400 degrees Celsius. Overall, one can say that the use of such catalysts significantly reduces the content of undesirable elements: it reduces oxygen by almost seven times and nitrogen by two times, and it removes sulfur almost completely. Treatment with hydrogen using a catalyst based on nickel and molybdenum makes it possible to increase the yield of the fraction with a boiling point of 200–360 degrees Celsius, which is important for the production of fuels,” Maria Alekseeva, one of the authors of the study and candidate of chemical sciences, is quoted as saying by the Institute of Catalysis SB RAS.
The scientists from the Institute of Catalysis SB RAS plan to modify the conditions for the hydroprocessing of pyrolysis liquid, including with intermediate separation of fractions, in order to make further processing of raw materials more efficient.
