RESEARCH Open Access Analysis of recycled poly (styrene-co-butadiene) sulfonation: a new approach in solid catalysts for biodiesel production

The disposal of solid waste is a serious problem worldwide that is made worse in developing countries due to inadequate planning and unsustainable solid waste management. In Mexico, only 2 % of total urban solid waste is recycled. One non-recyclable material is poly (styrene-co-butadiene), which is commonly used in consumer products (like components of appliances and toys), in the automotive industry (in instrument panels) and in food services (e.g. hot and cold drinking cups and glasses). In this paper, a lab-scale strategy is proposed for recycling poly (styrene-co-butadiene) waste by sulfonation with fuming sulfuric acid. Tests of the sulfonation strategy were carried out at various reaction conditions. The results show that 75°C and 2.5 h are the operating conditions that maximize the sulfonation level expressed as number of acid sites. The modified resin is tested as a heterogeneous catalyst in the first step (known as esterification) of biodiesel production from a mixture containing tallow fat and canola oil with 59 % of free fatty acids. The preliminary results show that esterification can reach 91 % conversion in the presence of the sulfonated polymeric catalyst compared with 67 % conversion when the reaction is performed without catalyst