Catalytic Cracking of Toluene as a Tar Model Compound Using Sewage-Sludge-Derived Char

The catalytic cracking of model tar species (toluene) using sewage sludge char (SSC) was investigated. The effects of typical syngas components from municipal solid waste (MSW) gasification on toluene conversion ratio, cracking product distribution, and characteristics of the SSC catalyst were studied. Deposited coke significantly decreased the Brunauer Emmett Teller (BET) surface area from 74.213 to 51.782 m(2)/g in a N-2 atmosphere. CO2 and steam slowed the decrease of the BET surface area. Hydrogen chloride (HC1) showed a negative effect on the pore structure by the formation of low-melting-point chlorides, which melted above 750 degrees C and blocked the pores. The cracking efficiency in different reaction atmospheres was ordered as CO2/H2O/N-2 > H-2/CO/H2O/N-2 > H-2/CO/H2O/HCl/N-2 > N-2. The conversion ratios were all above 65% at 750 degrees C, which reached more than 93% at 950 degrees C. The highest conversion ratio of 97.1% was achieved at 950 degrees C when CO2 and steam were presented. CO2 and steam significantly increased the tar conversion ratio and enhanced the resistance of deactivation. CO and H-2 increased the tar conversion ratio and changed the cracking product distribution mainly by gas-phase reactions. Besides, when 300 ppm of HCl was presented, the toluene conversion ratio decreased from 86 to 81.2% at 850 degrees C.