Performance of Catalysts of Different Nature in Model Tar Component Decomposition

Abstract

Municipal solid waste constitutes one of the major challenges and concerns of our society. Disposal of waste material is potentially dangerous, harming both environment and mankind. In order to diminish negative effects of municipal solid waste, its thermal decomposition to valuable chemicals has been studied. The principal draw-back of thermal processes used for solid waste utilization as raw material is tar formation. In this study, low-cost catalysts of different origin were tested in the decomposition of a model component of tar originating from waste material pyrolysis/gasification. p-Xylene was selected as the model compound found in biomass decomposition products. Its decomposition was carried out in the presence of either tire pyrolysis char- or clay minerals-based catalysts. Tar-cracking activities of both catalyst types at varying experimental conditions were compared and related to the catalysts physical-chemical properties. In experiments, either empty reactor or reactor filled with 10 g of the catalyst was used; p-xylene mass flow was set to 2.58 g h−1 (50 μL min−1, room temperature), and decomposition temperature ranging from 750 °C to 850 °C was applied. Moreover, evolution of the output variables, p-xylene conversion and hydrogen content in the gas phase, with the reaction time was investigated. Catalysts’ properties were assessed based on nitrogen adsorption isotherms, thermogravimetric and elemental composition analyses. Amounts and composition of p-xylene catalytic decomposition products were evaluated using GC analysis of both gaseous phase and condensable products. Results showed the superiority of tire pyrolysis char catalyst over that based on clay minerals.

Gasification of RDF and Its Components with Tire Pyrolysis Char as Tar-Cracking Catalyst

“…The catalytic activity of the studied pyrolysis char was confirmed on model tar compounds in our previous studies [13,14]. P-xylene conversion as a model tar component at 800 • C increased from 71.5% in a process without any catalyst to 99.1% in a process with the char catalyst.…”

“…Then, the compacted pyrolysis char was dried at 105 • C for h. The preparation of catalyst was finished by its carbonization, which was carried out at 800 • C in a continuous flow of CO 2 . This procedure took 4 h. The surface properties of carbonized and raw pyrolysis char were determined by the nitrogen adsorption and BET (Brunauer-Emmett-Teller) isotherm from our previous studies [13,14] and they are presented in Table 4. The studied catalyst in this work had the same origin as the catalyst described in [14].…”

“…The preparation of char-based catalysts usually includes their activation at temperatures above 700 • C in the presence of CO 2 or steam [12]. In our previous works, the tar-cracking potential of tire pyrolysis char in cracking model tar components, such as toluene and para-xylene, was investigated [13,14]. The results showed high tar cracking activity of tire pyrolysis char, especially when char impregnated with Ni and char pellets carbonized at 900 • C were used.…”

Semi-Batch Gasification of Refuse-Derived Fuel (RDF)

“…This catalyst was characterized in the framework of a previous work [22] by pore structure and specific surface measurements at different stages of preparation, thermogravimetric analysis, elemental analysis, and X-ray diffraction analysis, X-ray fluorescence (XRF) analysis, and scanning electron microscopy (SEM). In addition, in the previous work [23], catalytic activity of the used catalyst was confirmed by cracking of model tar components.…”

“…Further reduction of tar can be achieved by physical or chemical ex-situ methods such as scrubbing or secondary catalytic cracking. A detailed discussion of the secondary catalytic cracking of tars is presented in previous works [22][23][24].…”