Chemical characteristics of oil-like products from hydrous pyrolysis of scrap tires at temperatures from 150 to 400 °C

Abstract

Scrap tire waste consists of organic matter that is often commonly disposed in landfills, ultimately causing an environmental problem. Different pyrolysis techniques have been used to convert biomass into potential fuel products. Pyrolysis is considered a useful method for recycling scrap tires. These hydrous pyrolysis experiments were conducted to test the effects of water on product composition and yield from scrap tire rubber. The chemical compound compositions of the alteration products from two different pyrolysis conditions have been determined by gas chromatography–mass spectrometry. Two sets of experiments were conducted at temperatures ranging from 150 to 400°C with contact periods of 48h. The reaction mixtures of the first set included only shredded scrap tire rubber and water, whereas the second set also contained oxalic acid to provide excess hydrogen to enhance reduction of rubber pyrolysate. The yields of the total alteration products increased with temperature both in the presence and absence of oxalic acid, and were higher with oxalic acid. Hydrocarbon concentrations increased in the temperature range of 250–350°C for both experiment sets and decreased noticeably at 400°C due to cracking processes. The products confirm that alteration of scrap tire rubber in aqueous medium occurs rapidly and efficiently under reductive pyrolysis conditions above 150°C. At temperatures above 350°C cracking of organic products was the dominant reaction, and polycyclic aromatic hydrocarbons (PAHs) were the major products.