From citrus waste to value: optimizing sulfonated carbons for limonene upcycling into value-added products

Author(s)

Reis, Gabrielle M. ; Nunes, Renan S. ; Xavier, Gabriela T. M. ; Kirillova, Marina V. ; Kirillov, Alexander M. ; Mandelli, Dalmo ; Carvalho, Wagner A.

• Document type: Journal article
• Source: RSC SUSTAINABILITY; v. N/A, p. 14-pg., 2024-12-12.

Abstract

Limonene extracted from orange essential oil represents one of the globally prevalent and low-cost terpenes. Through the isomerization of limonene, it is possible to obtain a variety of high-added-value terpenic compounds such as terpinolene, alpha-terpinene, and gamma-terpinene, as well as p-cymene. These products have diverse applications in the food, cosmetic, polymer, and chemical industries. The present study focused on developing a sustainable approach to producing valuable chemicals from renewable resources such as limonene, particularly via the isomerization of limonene over modified sulfonated carbons as bio-based catalysts. The synthesis of sulfonated carbons from glucose was optimized through a Central Composite Rotatable Design (CCRD), which enabled the identification of correlations between synthesis conditions and catalytic performance. Thus, sulfonated carbon catalysts with larger surface areas and smaller pore diameters lead to higher results in limonene isomerization. Various characterization techniques were employed to elucidate the physicochemical properties of the synthesized carbons, confirming the presence of acidic surface groups and showing the influence of textural characteristics on the limonene isomerization. After a 2 hour reaction at 150 degrees C, a 96% conversion of limonene was achieved, resulting in a good overall yield of the major products, ranging from 40% to 50%, namely alpha-terpinene, gamma-terpinene, and terpinolene. The obtained findings highlight that the use of sulfonated carbons has the potential to drive the sustainable transformation of limonene into valuable compounds. In particular, the sustainability approach of this work includes (i) using a minimal amount of concentrated H2SO4 acid in the catalyst synthesis, (ii) employing bio-based and metal-free carbon catalysts, (iii) exploring a renewable substrate, and (iv) conducting the reaction process without added solvents. (AU)

• FAPESP's process: 21/12342-0 - Production of bifunctional carbons for catalytic conversion of polyols and terpenes
• Grantee: Wagner Alves Carvalho
• Support Opportunities: Regular Research Grants
• FAPESP's process: 18/01258-5 - Novel chemical catalytic and photocatalytic processes for the direct conversion of methane and CO2 to products
• Grantee: José Maria Correa Bueno
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 23/01634-5 - Metal-Organic Frameworks (MOFs) as catalysts for sustainable oxidation of hydrocarbons derived from petroleum (methane and other alkanes) and natural (terpenes)
• Grantee: Dalmo Mandelli
• Support Opportunities: Regular Research Grants
• FAPESP's process: 23/13334-6 - Metal-organic frameworks (MOFs) as catalysts for sustainable oxidation of hydrocarbons derived from petroleum (methane and other alkanes) and natural (terpenes)
• Grantee: Gabriela Tuono Martins Xavier
• Support Opportunities: Scholarships in Brazil - Support Program for Fixating Young Doctors
• FAPESP's process: 21/06471-1 - Development of activated carbon and nanofunctionalized composites for the removal and passive monitoring of antineoplastic compounds in the aquatic environment
• Grantee: Taciana Guarnieri Soares Guimarães
• Support Opportunities: Scholarships in Brazil - Doctorate