(439f) Toluene Reforming Using Nickel Based Catalysts Made from Mining Residues

The formation of aromatic compounds is one of the problems facing the processes of gasification and pyrolysis. The usage of nickel-based catalysts is a prospective method for converting tar. These catalysts deactivate quickly due to sintering when carbon is formed. The patent-pending catalyst Ni-UGSO made from mining residues is used in this study for tar reforming. Ni-UGSO showed high activity and high resistance to carbon deposition in methane and bio-oil reforming.

Toluene, which forms approximately 24% of tar is used as tar model compound. The catalyst is prepared by the incipient wetness method through mixing the mining residues with nickel nitrates, then drying and calcining the mixture for 12 hours at 900°C. The reforming runs were conducted in a fixed bed reactor. Toluene and water were emulsified with H₂O/C ratio equal to one.

The tested parameters are:

• Temperature from 650 to 850°C, to determine the activation temperature of the catalyst.
• Variation of Nickel mass fraction, to test its influence on the total conversion, yields of H₂ and CO and carbon formation.

GC analysis of the product gases showed that the main products were H₂ and CO, with 60% and 75% yields, respectively, while the overall conversion was between 85 and 98%. At the locally optimal conditions, a 24h long test was performed. During this period the fraction of carbon deposited on its surface was about 2% of the total carbon injected in the reactor, without signs of deactivation.

The activity of the catalyst was then tested by adding naphthalene to the emulsion; the reforming results revealed high decomposition of the mixture with a total conversion of 73%.

The same reforming experiment was repeated using another catalyst made from olivine and activated with nickel to compare its efficiency with that using Ni-UGSO.

All tested catalysts were analysed before and after the reforming experiments through XRD, BET and FEG/SEM microscopy. These analyses provided useful information on the involved crystalline phases, the specific surface area changes as well as the changes of the catalyst’s particles morphology.