Ayoub Abdelkader Mekkaoui

Selective catalytic chlorination of renewable terpenic olefins provides versatile allylic and vinylic chlorides for sustainable synthesis. This review explores catalytic pathways, mechanisms and applications for biomass valorization.

Active pharmaceutical contaminants (APCs), i.e. antibiotics, cause significant environmental and health risks. A magnetically recoverable 2D g-C ₃ N ₄ /SrFe ₁₂ O ₁₉ heterojunction enables efficient photocatalytic degradation of tetracycline as a model APC.

Advanced characterizations of three magnetically recoverable MFe ₁₂ O ₁₉ (M = Cu, Sn and Sr) MNPs revealed that SnFe ₁₂ O ₁₉ and CuFe ₁₂ O ₁₉ are not isostructural with SrFe ₁₂ O ₁₉ M-type hexaferrite, due to confirmed coexistence of SnO ₂ –Fe ₂ O ₃ and CuFe ₂ O ₄ –Fe ₂ O ₃ .

Catalytic processing of biomass and its derivatives to produce graphitizable materials offers a transformative method for converting renewable resources into bio-energy and valuable carbon-based materials.

A simple, mild and efficient scope pathway for a selective catalytic chlorination of terpenic olefins is investigated in the presence of a highly efficient chlorination agent and a readily available Lewis acid catalyst. The sodium dichloroisocyanurate (NaDCC) used in the present work as an easy handling, sustainable and cost-effective chlorine donor due to its high free available chlorine (FAC), exhibits a high efficiency for selective catalytic chlorination. Herein, we report for the first-time the FeCl₂/NaDCC combination system for the selective catalytic chlorination towards new functionalized terpenic olefins. In order to examine the general features of this catalytic reaction, the effects of pH, solvent, dilution, chlorination agent nature, stoichiometry and reaction kinetics are optimized using carvone as a model substrate. Among the studied parameters, catalyst stoichiometry was found to be determinant for highly controllable chlorination selectivity towards new allylic and vinylic chlorides. Indeed, the oxidation state, ligand and metal effects of the catalyst are examined using various Lewis acids, where the chlorinated ones (MCl_x), such as FeCl₂, FeCl₃ and SnCl₂, exhibit a comprehensive approach for a controllable chlorination reaction. In addition, the homogeneous catalytic system shows good reusability with significant catalytic conversion depending on the FAC content in the reaction medium. The reaction proceeds under mild conditions with shorter reaction time and high selectivity towards new high added value allylic and vinylic chlorinated derivatives of naturally occurring terpenic olefins in good to excellent yields.

Biopolymer functionalization is perceived as an innovative approach to revolutionizing bio-catalyzed chemical transformations. Lignin, the chief natural source of polyphenols, has an aromatic structure with plenty of beneficial chemical groups. Accordingly, lignin can be functionalized, copolymerized, or recombined with different types of chemicals to produce highly efficient catalysts. Moreover, the stability and biodegradability of lignin make it an efficient bio-immobilizer for diverse metals (Pt, Pd, Ag, Cu, Co, Fe, etc.), which are known for their excellent catalytic performances. In addition, the solid nature of the lignin-derived catalysts has excellent advantages in terms of simple catalyst recovery and reuse over consecutive cycles with high stability. The present work compiles the newly adopted approaches to valorize lignin in the field of catalysis. Lignin-derived acid and base catalysts, lignin metal-free catalysts, and lignin-supported metal catalysts have demonstrated the full potential of lignin in hydrolysis, esterification, oxidation, condensation, hydration, and multicomponent reactions. The synthesis methods, properties, and catalytic capacity of lignin-based catalysts were assessed and contrasted with conventional catalysts. Attractively, the inclusion of lignin in catalysis appeared as a novel upgrading strategy that offers eco-friendly and profitable materials, leading to simple and green chemical synthesis, as well as a revolutionary shift in the industrialization of biomass-derived materials generally, and functionalized lignin-based catalysts specifically.

A facile wet‐chemical protocol for the synthesis of bimetallic CuPd alloy nanoparticles (NPs) anchored on mesoporous graphitic carbon nitride (m‐gCN), serving as both stabilizer and support material, was presented herein. The presented protocol allowed to synthesize nearly monodisperse CuPd alloy NPs with an average particle size of 3.9 ± 0.9 nm without use of any additional surfactants and to prepare CuPd/m‐gCN nanocatalysts with different Cu/Pd compositions (Cu₂₅Pd₇₅/m‐gCN, Cu₃₅Pd₆₅/m‐gCN, Cu₁₆Pd₇₄/m‐gCN, Cu₃₂Pd₆₈/m‐gCN, Cu₁₀Pd₉₀/m‐gCN, and Cu₅₀Pd₅₀/m‐gCN). After the detailed characterization of CuPd/m‐gCN nanocatalysts, they were utilized as catalysts in the dehydrogenation of terpenes. Among all tested nanocatalysts, Cu₅₀Pd₅₀/m‐gCN showed the highest activity in terms of the product yields within the same reaction time. Various parameters influencing the catalytic activity of Cu₅₀Pd₅₀/m‐gCN were studied using himachalene as a model substrate and the optimum conditions were determined. Under the optimized reaction conditions, the catalytic application of Cu₅₀Pd₅₀/m‐gCN nanocatalysts was extended to nine different terpenes and the corresponding products were obtained in high conversion yields (>90%) under mild conditions. A reusability test showed that Cu₅₀Pd₅₀/m‐gCN nanocatalysts can be re‐used up to four cycles without significant loss in their initial activity.

Herein, we report on the preparation of novel colloidal system based on carboxymethyl cellulose (CMC) and Pd nanoparticles (CMC@Pd NPs) via an ecofriendly auto-reduction process under mild conditions. In the first step, the follow-up of reduction and preparation of CMC anchored palladium nanoparticles (Pd NPs) in aqueous solution was carried out using UV–Vis spectroscopy. Thereafter, the monodispersed colloids were fully characterized by advanced analytical, structural, and morphological techniques. Based on Scherrer equation, the as-synthesized CMC@Pd NPs crystallite size was about 10.88 nm. Accordingly, the detailed microscopic study revealed CMC nanocolloids anchored uniform distribution of Pd NPs and the presence of CMC nanofilm as protective monolayer. To the best of our knowledge, the observed nanoscale properties are reported for the first time for CMC−M system. The performance of the as-synthesized CMC@Pd nanocolloids was first investigated in the reduction of 4-nitrophenol, as a model substrate, to 4-aminophenol using NaBH₄ as a hydrogen source. Moreover, the catalytic reduction of various nitroarenes bearing electron withdrawing or donating substituents was carried out and monitored by UV–Vis spectroscopy. The chemo- and regioselectivity of the catalytic reduction in presence of CMC@Pd NPs were also studied. Consequently, the prepared CMC@Pd nanocolloids exhibit remarkable activity, good heterogeneity, and higher reusability and stability for the catalytic reduction reaction under mild conditions.

Highly efficient magnetically separable hybrid GO/SrFe ₁₂ O ₁₉ nanocomposite was synthesized, as catalyst for epoxide ring-opening, via dispersing M-type strontium hexaferrite (SrFe ₁₂ O ₁₉ ) on graphene oxide (GO) sheets.