No abstract

The high PET consume, mainly as bottles, associated with rapid disposal and high resistance to ambient conditions and biological degradation lead to accumulation in the enviromental, constituting a worrying scenario in world level. Chemical recycle PET by glycolysis is an important alternative, once bis(hydroxiethyl)terephthalate (BHET), high added value monomer, can be obtained. In this context, this study approaches the use of titanate nanotubes (i.e. sodium/protonated titanate nanotubes) as catalyst for PET glycolysis. Reactional conditions, the origin and granulometry of PET flakes were evaluated (at 196 °C). Best results (BHET yield > 80%) were obtained for both catalyst in 3 h of reaction. The protonated titanate nanotubes catalyst were more efficient than sodium titanate nanotubes due to greater concentration of Brönsted and Lewis acid sites, indicated by TPD analyzes.

No abstract

CO2 is the most important greenhouse gas in terms of emitted quantities and its emission has increased significantly due to the action of anthropogenic sources. Among the alternatives for mitigation of this gas is the direct synthesis of propylene carbonate (PC), which requires efficient and selective catalysts. In this scenario the titanate nanotubes (TNT) are promising catalysts because they can be modified to become selective for the PC synthesis. The present work has the objective to develop titanate nanotubes with different metals (Na, Sn and Zn) as well as protonated titanate nanotubes (HTNT) and to test their efficiency in the direct synthesis of PC. The synthesized nanostructures were characterized by TEM, EDS, XRD and N2 adsorption-desorption. The results showed that the synthesized TNT have a specific surface area of 155, 232, 56 and 140 m2/g (NaTNT, HTNT, SnTNT and ZnTNT, respectively). Besides, the ion exchange of [Na+] by [Sn+2] and [Zn+2] decreased the crystallinity of nanostructure. On the catalytic tests, the system NaTNT/ZnBr2 showed the best results with a yield of 61% and a selectivity of 81% in PC. The catalytic system SnTNT/DMF and ZnTNT/DMF are promising to this reaction showing interesting yields and catalytic activity (59 and 53%; 295 and 265 mmol/g) for PC synthesis.