Recycling Single Use Plastics to Useful Chemical Intermediates

Polymers are extremely stable and with rising landfill costs, forthcoming extended producer responsibility tax and the drive towards a circular economy, there is an increasing need to redirect polymer waste from landfill/energy recovery towards enhanced recovery of the raw materials/feedstocks. The COVID pandemic has introduced a significant amount of personal protective equipment (PPE) single use plastics in the form of facemasks into our global ecosystem, which is increasingly becoming an environmental issue due to their increasing non-biodegradability and with declining landfill capacity, this makes plastic recycling a necessity. Chemical recycling stands out as a viable method of converting plastic waste into valuable products, especially liquid fuels (naphtha) and liquefied petroleum gas (LPG). Chemical recycling of plastics can also serve as a route to introduce circularity into the plastic supply chain. This research study is focused on investigating the use of heterogeneous catalysts (zeolites Beta and USY) for the conversion of polypropylene (PP) and single use facemasks into chemical feedstock using hydrocracking. Catalytic hydrocracking reactions were carried out between 270-330 °C at 20 bar hydrogen pressure for 30-60 minutes. The results indicates that USY zeolite was more effective than zeolite beta due to its higher selectivity to liquid products. Moreover, the presence of highly acidic catalysts can be used to suitably recycle polymers into useful hydrocarbons with C3-C16 product distributions

The Effect of Binders on the Morphology and Performance of HZY/HZM-5 Zeolite Catalysts in Cracking n-heptane to Light Olefins

Light olefins (ethylene and propylene) are essential building blocks of the chemical industry. Fluid catalytic cracking and steam cracking are the key technologies to produce light olefins. However, these technologies can no longer satisfy the current demand for light olefins. Previous studies have found the catalyst formulation (ZY, ZSM-5, and binder) increased production with the most outstanding results using the catalytic cracking process. This study reports catalyst formulations with different loading of ZSM-5 (5%,10%, and 20%). The performance of catalysts were tested in the catalytic cracking of n-heptane as a model compound of light naphtha for the production of light olefins at 500 ºC and atmospherical pressure. The results of the tests showed high performance in terms of increased light olefins yield (24 - 64%) and improved C2 and C3 selectivity (35 %) over ZY/ZM/K/B(20:20:30:30) and ZY/ZM/K(20:20:60) with alkene/alkane= ~1.33 and reduction into the amount of undesired C1-C5 alkanes (3%). Therefore, adding ZSM-5 (20%) to catalyst formulation enhances the activity and shape selectivity of the catalytic cracking process onto the catalyst

Adsorption of Cd(II) and Pb(II) ions from aqueous solutions using mesoporous activated carbon adsorbent: Equilibrium, kinetics and characterisation studies

In this study, cadmium and lead ions removal from aqueous solutions using a commercial activated carbon adsorbent (CGAC) were investigated under batch conditions. The adsorbent was observed to have a coarse surface with crevices, high resistance to attrition, high surface area and pore volume with bimodal pore size distribution which indicates that the material was mesoporous. Sorption kinetics for Cd(II) and Pb(II) ions proceeded through a two-stage kinetic profile-initial quick uptake occurring within 30 min followed by a gradual removal of the two metal ions until 180 min with optimum uptake (qe,exp) of 17.23 mg g1 and 16.84 mg g1 for Cd(II) and Pb(II) ions respectively. Modelling of sorption kinetics indicates that the pseudo first order (PFO) model described the sorption of Pb(II) ion better than Cd(II), while the reverse was observed with respect to the pseudo second order (PSO) model. Intraparticle diffusion modelling showed that intraparticle diffusion may not be the only mechanism that influenced the rate of ions uptake. Isotherm modelling was carried out and the results indicated that the Langmuir and Freundlich models described the uptake of Pb(II) ion better than Cd(II) ion. A comparison of the two models indicated that the Langmuir isotherm is the better isotherm for the description of Cd(II) and Pb(II) ions sorption by the adsorbent. The maximum loading capacity (qmax) obtained from the Langmuir isotherm was 27.3 mg g1 and 20.3 mg g1 for Cd(II) and Pb(II) ions respectively

Kinetic modeling of metal ion transport for desorption of Pb(II) ion from oil palm fruit fibre (Elaeis guineensis) adsorbents

The kinetics of desorption of lead (II) ion from metal loaded adsorbent of mercaptoacetic acid modified and unmodified oil palm (Elaeis guineensis) fruit fiber was studied using different solutions, at different contact times. At the end of 25 minutes, 79.19%, 75.99%, 57.14%, 50.56% and 32.72% of Pb2+ were desorbed using 0.2 MHcl, 0.1 M H2S04, 0.1 MHNO3, 0.1 MNaOH and hot deionized H20 respectively for the 1.0 MOPF adsorbent. Desorption kinetic modeling of Pb2+ using the Elovich desorption and Pseudo-first Order Rate desorption equations showed that the latter described the kinetics of Pb2+ better. The desorption rate instant, β for 0.1 MHCl solution were: 7.27 x 10-1, 6.49 x 10-1 and 5.11 x 10-1, mg.g-1, .min-1, for UOPF, 0.5 MOPF and 1.0 MOPF adsorbents respectively. The surface residence time ح values for the 0.1 MHCl solutions were 24.83, 46.70 and 29.80 seconds for UOPF, 0.5 MOPF and 1.0 MOPF adsorbents respectively. br> International Journal of Natural and Applied Sciences Vol. 2 (4) 2006: pp. 288-29