Innovative and Sustainable Additives for the integrated energy industry

Calixarenes are cyclic oligomers obtained from the condensation of p-substituted phenols with formaldehyde. Their unique conformation, synthetic versatility, and high thermal and chemical stability make these macrocycles ideal candidates for developing novel derivatives for industrial applications. In this work, calixarenes and their analogues were designed, synthesized, and tested to create innovative lubricant additives with various properties and to develop ligands for the extraction of radionuclide, which may contaminate oil and gas extraction facilities. Additionally, an environmentally friendly synthetic approach was explored, starting from a renewable bio-feed. The first chapter introduces the field of lubricants and lubrication, covering essential parameters and characterization techniques. It also discusses the typical composition of lubricants, including the role of base oils and the main categories of additives. In the second chapter, the design and synthesis of star-shaped block-copolymers as viscosity index improvers are presented. Calixarenes serve as stable, versatile cores, with arms grown in two steps. The first step involves the synthesis of lactic acid as a biopolymer to enhance the product biocompatibility, while the second consists of a RAFT polymerization of methacrylic monomers to achieve precise control over molecular weight distribution. Various products were synthesized by adjusting both the core and arms chain lengths to evaluate how different morphologies impact the additive performance. Then, two other classes of additives were discussed in chapter three: detergents and friction reducers. Both types require amphiphilic structures, with polar heads to interact with polar insoluble particles or metal surfaces, and lipophilic sections to provide solubility in oil. The macrocyclic scaffolds offer a preorganized structure that aids the formation of detergent micelles (detergents) and protective films on metal surfaces (friction reducers). As reported in chapter four, the synthesis of macrocyclic additives was further explored using a renewable bio-feed to promote greener and more sustainable chemistry. Cashew nut shell liquid (CNSL) and model compound 3-pentadecylphenol were tested without success for the synthesis of calixarene-like macrocycles. However, multiple kinds of additives were synthesized, including detergents, antioxidants, and friction reducers, many of which demonstrated promising properties, suggesting the potential of this bio-feed for the development of innovative eco-friendly additives. Lastly, chapter five describes the functionalization and testing of calixarenes for the selective extraction of radionuclide. To optimize extraction rate and selectivity for Ra(II), macrocycles of different sizes and with various functional groups, such as amides, carboxylic acids, and crown ethers, were evaluated. A biphasic extraction protocol was first optimized with Ba(II) as a model ion, due to its similar ionic radius and charge to Ra(II). The most promising ligands were subsequently tested for radionuclide extraction at PoliMi laboratories.