Abstract
Tar is one of major products from biomass pyrolysis. Its formation mechanism in a catalytic pyrolysis system comprising pine sawdust and waste aluminum dross (AD) is investigated with the aid of analytical methods including thermogravimetric analysis (TG), Nuclear Magnetic Resonance (NMR), electron paramagnetic resonance (EPR), and gas chromatography coupling with mass spectrometry (GC-MS). The results show that AD plays a vital role in cleavage of C-O bonds to enhance selective formation of furans, ketones, and phenols. The catalytic pyrolysis is initiated by active C-O-M intermediate formation that accelerates C-O bond cleavage and generates great amounts of free radicals to 1020 spins/g at 300–500 °C. Compared with pure pine pyrolysis, the percentage of glucosidic bonds from cellulose decreases from 14.00% to 9.66% at 500 °C; the etherified guaiacyl is more actively ruptured and disappears at 700 °C. Furans and ketones increase from 17.45% to 22.23% and 6.71% to 10.80% at 500 °C, respectively. Phenols increase from 66.75% to 71.57%. The preferential production of higher value-added products via catalytic pyrolysis between biomass and industrial wastes may bring new insight to the simultaneous valorization of agricultural, municipal, and industrial waste.
Highlights
Biomass is the unique carbon-based renewable energy source and a potential supplement to fossil fuels in the worldwide energy system [1,2]
aluminum dross (AD) was produced from the secondary smelters during the dross recycling process of a factory in Changzhou, which is identified as the hazardous wastes to be disposed of that is rich in Al2 O3 as a catalyst for pyrolysis
AD accelerates the cleavage of C-O bonds to form a great amount of free radicals, which are confined in the aggregated structure of AD and biomass during pyrolysis
Summary
Biomass is the unique carbon-based renewable energy source and a potential supplement to fossil fuels in the worldwide energy system [1,2]. Biomass, composed of cellulose, hemicellulose, and lignin, can be converted into useful fuel gases or chemicals via gasification [3,4]. Pyrolysis is the first step during biomass gasification, which includes a set of complex reactions such as primary pyrolysis and secondary reactions of char forming, depolymerization, and fragmentation [5,6]. Tar is one of the primary products, taking part in the subsequent coking reaction and gasification reactions. The coking reaction forms tiny carbon particles, corroding the equipment and clogging the pipes during industrial applications [7,8]. Tar formation decreases the conversion rate of biomass to fuel gas, impacting negatively the energy efficiency of a gasification system [9]
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