Pyrolysis of scrap tires and conversion of chars to activated carbon

Abstract

The primary objective of this work was to demonstrate the conversion of scrap tires to activated carbon. We have been successful in this endeavor, producing carbons with surface areas greater than 500 m2/g and significant micropore volumes. Tire shreddings were pyrolyzed in batch reactors, and the pyrolysis chars activated by reaction with superheated steam. Solid products of pyrolysis and activation were studied with nitrogen adsorption techniques. We find that the porosity development during steam activation of tire pyrolysis char is similar to that reported for various other chars. A maximum in micropore volume is observed as a function of conversion, but the total surface area increases monotonically with conversion. We suggest that the activation process consists of micropore formation, followed by pore enlargement. The process conditions used in this study are a good starting point from which to optimize a process to convert tires to activated carbon. IntroductionScrap tires are a major environmental problem. An estimated 2.5 x lo9 kg of scrap tires are generated each year in North America (Williams et al., 1990). The conventional method of reusing waste rubber is to convert it into rubber reclaim, which is suitable for mixing with virgin rubber compounding materials. However, rubber reclaim generated from scrap tires does not have suitable properties for use in tire manufacture and must be used for low-value rubber goods (Makarov and Drozdovski, 1991). Moreover, production with rubber reclaim can be more costly than production with virgin raw materials (Crane and Kay, 1975). As a result, the majority of scrap tires accumulate in dumps, posing hazards such as disease and accidental fires.Tires contain carbon-black-reinforced rubber, and both inorganic and organic belt materials. The rubber component may be natural rubber, but styrene-butadiene (about 25% styrene) copolymer rubber (SBR) is more common. A typical tire compounding composition contains 62 wt. Vo SBR, 31 wt. % carbon black, and small amounts of other materials including extender oils, sulfur, zinc oxide, and stearic acid. Carbon black is used to reinforce the rubber. The rubber is cross-linked by vulcanization, which involves reactions with sulfur. Small amounts of zinc oxide and stearic acid are added to control Correspondence concerning this article should be addressed to M. A. Petrich. the vulcanization process and enhance the properties of the final products (Studebaker and Beatty, 1978).The potential value of reusing the polymeric base of old tires has received considerable attention. Alternatives include production of goods with reclaim, use of ground rubber as construction filler, and degradation to basic raw materials by pyrolysis (Makarov and Drozdovski, 1991). Filler and reclaim applications have relatively small economic potential. Incineration of tires may be an effective means of waste volume reduction, but incineration does not recover much of the intrinsic value of the materials in the tire (Williams et al., 1990). The hydrocarbon...

Cooperative Research Program in Coal-Waste Liquefaction

“…Finally, it is seen that increasing the value of the carbon product from a conservative price of $200 per ton (10¢ per pound) to a more optimistic price of $500 per ton (25¢ per pound) increases the ROI by nearly 20%. In view of the research results discussed earlier, (69)(70)(71) carbon priced at $500 per ton does not seem unrealistic.…”

“…Merchant and Petrich (69) produced carbons with surface areas greater than 500 m 2 /g by steam activation of tire pyrolysis char. They observe porosity development similar to that found for various other chars.…”

“…This assumes that the ash content of the carbon black has been reduced to about 1-2%. On the basis of results for carbon black activation, (69)(70)(71) about 40% of the carbon will be oxidized away in the activation process. Therefore, the plant should produce 12 tons/day of steel and 17 tons/day of activated carbon.…”

Surface Functional Characteristics (C, O, S) of Waste Tire-Derived Carbon Black before and after Steam Activation

“…Small amounts of zinc oxide and stearic acid were added to control the vulcanization process and to enhance the properties of the final products. 24 Electron microscopy with elemental X-ray analysis showed that the positions of zinc deposits within tire char particles coincide with the positions of sulfur deposits, suggesting that ZnO and sulfur in the tires can react with each other to form ZnS during the pyrolysis. 25 This study found that, after pyrolysis at 420°C, ZnS (58.9 wt%) was still retained on the surface of carbon black derived from the pyrolysis of waste tires.…”

Performance and Emission Studies of a SI Engine using Distilled Plastic Pyrolysis Oil-Petrol Blends

“…Vijaya Ku mar et al [18] had investigated the performance and emission characteristics of diesel engine with three hole injector by using tyre oil blends and their results shows that 20% tyre oil blend was given better performance compared with diesel and other blends at all injections pressures. [19][20][21][22] are conducted experiments on diesel engine fuelled with tyre pyrolysis oil blended at different proportions to evaluate the performance and emissions with and without ethanol. [23,24] are investigated the performance, emission and combustion studies using distilled tyre pyrolysis oil blends on diesel engine without any engine modificat ion.…”