The primary objective of this research was to develop efficient solid catalysts that can directly convert the lactic acid (LA) obtained from lignocellulosic biomass into alanine (AL) through a reductive amination process. To achieve this, various catalysts based on ruthenium were synthesized using different carriers such as multi-walled carbon nanotubes (MWCNTs), beta-zeolite, and magnetic nanoparticles (MNPs). Among these catalysts, Ru/MNP demonstrated a remarkable yield of 74.0% for alanine at a temperature of 200 °C. This yield was found to be superior not only to the Ru/CNT (55.7%) and Ru/BEA (6.6%) catalysts but also to most of the previously reported catalysts. The characterization of the catalysts and their catalytic results revealed that metallic ruthenium nanoparticles, which were highly dispersed on the external surface of the magnetic carrier, significantly enhanced the catalyst’s ability for dehydrogenation. Additionally, the -NH2 basic sites on the catalyst further facilitated the formation of alanine by promoting the adsorption of acidic reactants. Furthermore, the catalyst could be easily separated using an external magnetic field and exhibited the potential for multiple reuses without any significant loss in its catalytic performance. These practical advantages further enhance its appeal for applications in the reductive amination of lactic acid to alanine.

The present study is integrated in a global effort to capitalize waste cooking oil (WCO) into versatile compounds by introducing an oxirane ring into the unsaturated carbon chain of fatty acid residues (the epoxidation of double bound). Therefore, an enzymatic method was set up for the epoxidation of artificially adulterated WCO (SFw) and WCO under real conditions (SFr) derived from sunflower biomass. Commercial lipase (Novozyme, NZ) was used as a biocatalyst for generating the peracid requested by the epoxidation pathway. Optimum experimental conditions (e.g., 1.5 wt% NZ, 1:1:0.5 = H2O2/double bonds/peracid precursor (molar ratio) and 12 h reaction time) allowed for the conversion of 90% of the SFw substrate into products with an oxirane ring. Octanoic acid was selected as the best peracid precursor. The versatility of the developed system was tested for olive, milk thistle, hemp and linseed oils as both fresh and WCO samples. The characterization of the oil samples before and after the enzymatic epoxidation allowed for the evaluation of the system performance. SFw/SFr exhibited a better susceptibility to enzymatic epoxidation. In addition, the reusability of the biocatalytic system was investigated. Furthermore, different strategies, such as biocatalyst coating and the addition of organic solvents/buffers were applied, limiting enzyme leaching, for the better recovery of the biocatalyst activity.

Cold-active lipase from the psychrophilic bacterial strain Psychrobacter SC65A.3 isolated from Scarisoara Ice Cave (Romania) was cloned and characterized as an extremophilic biocatalyst for silybin acylation. Structural analyses highlighted conserved motifs confirming a functional lipase and the presence of primary structure elements for catalysis at low temperatures. The recombinant enzyme (PSL2) heterologously expressed in Escherichia coli was purified in one step by affinity chromatography with a yield of 12.08 ± 1.72 µg L−1 of culture and a specific activity of 20.1 ± 3.2 U mg−1 at 25 °C. Functional characterization of PSL2 showed a neutral (7.2) optimal pH and a high thermal stability up to 90 °C. Also, this lipase was stable in the presence of different organic solvents, with 60% residual activity when using 20% DMSO. Kinetic measurements indicated performant catalytic efficiency of PSL2 for different short and long chain fatty acids, with Km in the mM range. The catalytic activity of PSL2 was assessed for silybin acylation with various fatty acids and fatty acid methyl esters, demonstrating a 90% silybin conversion when methyl decanoate ester was used. This result clearly highlights the biocatalytic capability of this new cold-active lipase.

Hydrogels are a viable option for biomedical applications due to their biocompatibility, biodegradability, and ability to incorporate various healing agents while maintaining their biological efficacy. This study focused on the preparation and characterization of novel hybrid hydrogels enriched with the natural algae compound Ulvan for potential use in wound dressings. The characterization of the hydrogel membranes involved multiple methods to assess their structural, mechanical, and chemical properties, such as pH measurements, swelling, moisture content and uptake, gel fraction, hydrolytic degradation, protein adsorption and denaturation tests, rheological measurements, SEM, biocompatibility testing, and scratch wound assay. The hydrogel obtained with a higher concentration of Ulvan (1 mg/mL) exhibited superior mechanical properties, a swelling index of 264%, a water content of 55%, and a lower degradation percentage. In terms of rheological properties, the inclusion of ULV in the hydrogel composition enhanced gel strength, and the Alginate + PVA + 1.0ULV sample demonstrated the greatest resistance to deformation. All hydrogels exhibited good biocompatibility, with cell viability above 70% and no obvious morphological modifications. The addition of Ulvan potentiates the regenerative effect of hydrogel membranes. Subsequent studies will focus on encapsulating bioactive compounds, investigating their release behavior, and evaluating their active biological effects.

Controlling the reaction selectivity by use of rationally designed catalysts provides high yields of desired products rendering the process more efficient and sustainable. In this study, we investigated a series of isoreticular zeolites (Al-IPC-n, n = 2, 4, 6, and 7), in the synthesis of lactide from L-Lactic acid as an intermediate for the polylactic acid production. Catalytic tests allowed a thorough understanding of the structure-acidity-activity relationship and the control of the shape selectivity. The lactide and the dimers of the lactic acid were obtained in one step with a high selectivity (>55% for lactide and >70% for the dimer of the lactic). The selectivity to L,L-lactide was comparable with that on more acidic commercial BEA. A balance between the acidity and the pore size afforded high yields of the dimer, avoiding the poisoning of the catalyst and the production of the larger oligomers.

Cationic transition metal (Cu and Co) based core-shell (core: magnetite, shell: SiO2, ZrO2 or CeO2) magnetic nanoparticles were investigated in the selective oxidation of D-glucose to gluconic (GLU) and glucuronic (GLUU) acids, working at low temperature, with H2O2 as oxidant and in the absence of any base in the liquid phase. The catalysts have been characterized by FTIR, XRD, NH3- and CO2-TPD and TGA-DTA analyses. Under the optimal reaction conditions (i.e., 40 degrees C and 10 h), the highest conversion of D-glucose was of 86.2 % and the selectivities to GLU and GLUU of 33.8 % and 14.6 %, respectively. These results corresponded to the MSA@Co (were: M - magnetite; S - silica shell, A -APTES) catalyst. This catalyst can be easily recovered by a simple external magnet and reused several consecutive runs, without any change in the catalytic efficiency.

The catalytic hydrotreatment of humins, the solid byproduct produced from the conversion of C6 sugars (glucose, fructose) to 5-hydroxymethylfurfural (HMF), using supported Pd@zeolite (Beta, Y, and USY) catalysts with different amounts of Pd (i.e., 0.5, 1.0 and 1.5 wt%) was investigated under molecular hydrogen pressure. The highest conversion of humins (52.0%) was obtained on 1.5Pd@USY catalyst while the highest amount of humins oil (27.3%) was obtained in the presence of the 1Pd@Beta zeolite sample, at PH2 = 30 bars and T = 250 °C. The major compounds in the humins oil evidenced by GC-MS are alcohols, organic acids, ethers, and alkyl-phenolics. However, although all these classes of compounds are obtained regardless of the nature of the catalyst used, the composition of the mixture differs from one catalyst to another. Furanic compounds were not identified in the reaction products. A possible explanation may be related to their high reactivity under the reaction conditions, in the presence of the Pd-based catalysts these compounds lead to alkyl phenolics, important intermediates in the petrochemical industry.

The green macroalga Ulva rigida represents a promising feedstock for biorefinary due to its fast growth and cosmopolitan distribution. The main component of the cell walls of U. rigida is a sulfated glucuronorhamnan polysaccharide known as ulvan. Herein it was found that due to the high (hydrogen)sulfate group content of ulvan, hydrothermal autohydrolysis at 130 degrees C renders a high percentage of rhamnose (78-79 % recovery from the initial content in the raw material), a rare sugar of high added value. In addition, acid catalysis by a triflate-based graphene oxide under oxygen-free conditions at 180 degrees C affords moderate amounts of tartaric acid (24-26 %). The same triflate-based graphene oxide catalyst under oxygen pressure yields remarkably high percentages of succinic acid (65 %). The catalyst preserves its activity for at least five consecutive reuses.

Weak acid centers of germanosilicate zeolites can serve as active sites in ketalization reactions.

Magnetic Fe@Y composites (carbon-coated magnetic iron nanoparticles incorporated in zeolite Y) with 5-8 wt % Fe were synthesized and characterized. Overall acidity of the samples ranged between 2.0 and 2.47 mmol/g and is mostly attributed to Lewis acid sites. The obtained materials were proven to catalyze the hydrolysis of the marine sulfated polysaccharide ulvan with high conversion rates. The distribution of the reaction products depended on the reaction conditions and the concentration of ulvan. The catalytic property catalytic performance correlations clearly showed that the acid zeolite Y is the active phase for the hydrolysis of ulvan, while the iron nanoparticles enable the catalyst separation in a magnetic field. Under oxygen pressure, the selectivity was completely changed to favor succinic acid production. All Fe@Y composites were recycled 10 times with no change in their catalytic performance after recovery via a simple magnetic separation and washing with water.

The cryptomelane form of manganese oxide, OMS-2, has been used a pure material as well as a 5 wt % Pt/OMS-2 catalyst for the oxidation of benzyl alcohol. In addition, these catalysts have been modified with ionic liquids via a thin layer of [Bmim][NTf2] or [Bmpyr][NTf2]. These catalysts were characterized using a series of techniques: NMR, XRD, DRIFT, Raman, BET, Dynamic Light Scattering, XPS, TEM, SEM. The Weisz-Prater criterion has also been considered to inform whether the reactions were under diffusional control. The presence of platinum on the OMS-2 surface results in the support transforming to form Mn3O4 during reaction. In contrast, in the presence of the ionic liquid, the catalysts exhibited an increased phase stability. Efficient oxidation of benzyl alcohol was observed with a conversion of 80% and 82% selectivity to aldehyde for 5 wt% Pt/OMS-2/[Bmim][NTf2] in air. As expected an increase of the oxygen pressure led to an increase in the conversion to the detriment of aldehyde selectivity. The catalytic tests also showed an important effect on the conversion and selectivity of benzyl alcohol as a function of the diluent gas comparing inert (N-2, He, Ar) or (CO2) reactive gases. This effect was influenced by the nature of the ionic liquid present.

Ru@MNP-MWCNT catalysts were obtained via functionalization of nanostructured carbon-based carriers (ie, MWCNT) with base molecules (ie, 2-aminophenol and ethylenediamine) followed by the complexation with RuCl3. These structures demonstrated a highly efficient behavior for the selective wet oxidation of levulinic acid and glucose to succinic acid. However, to ensure an easy recovery and high recyclability the MWCNTs nanotubes were modified by incorporation of super-paramagnetic Fe3O4 nanoparticles into porous structure. Besides the catalytic performances the resulted composites showed a good mechanical resistance.

Modification of GO by organic molecules changes its catalytic activity in the hydrogen transfer from i-propanol to enones, affecting the selectivity to allyl alcohol and diastereoselectivity to the resulting stereoisomers. It is noteworthy the system does not contain metals and is recyclable.

Impregnation of RuCl3 on N-doped graphenes results in the formation of well-dispersed, small ruthenium oxyhydroxide nanoparticles supported on N-doped graphene that may exhibit high selectivity (87%) for the conversion of glucose into succinic acid under wet oxidation conditions (160 degrees C, 18atm O-2 pressure). Ruthenium loading and N-atom distribution on graphene influence the catalytic activity, the best performing catalyst having 1wt.% Ru loading on a graphene having a large population of graphenic N atoms. The high catalytic selectivity to succinic acid was correlated with the presence of small ruthenium nanoparticles. The present catalyst improves the best one previously reported because it does not require the continuous addition of an excess of amine to reach high succinic acid selectivity and reusability.

This study reports the behaviour of SCILL based catalysts in the oxidative S-S coupling of aliphatic and aromatic thiols, namely 1-butanethiol and thiophenol, to dibutyl disulfide and diphenyl disulfide. A range of ionic liquids (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide) and metal supported catalysts (5% Pt/SiO2; 5% Ru/SiO2; 5% Ru/C; 5% Pt/OMS-2) were used to prepare the SCILL catalysts and all were found to be active for the reaction following the trend 5% Pt-OMS-2 > 5% Pt/SiO2 > 5% Ru/C > 5% Ru/SiO2. The presence of SCILL catalysts afforded high selectivity to the disulfide, and the activity of the SCILL catalyst was dependent on the ionic liquid used. A significant increase in the stability of all the supported metal catalysts was found in the presence of the ionic liquid, and there was no change in the selectivity towards disulfides. This demonstrated that the ionic liquids protect the active sites of the catalyst against sulfation, thus providing more stable and active catalysts.

A series of Nb (3 wt% or 60 wt% Nb2O5)-based magnetic nanocomposites (Nb-Si@MNP) was prepared by covering the magnetic cores with Nb2O5-SiO2 shells using either co-precipitation or sol-gel followed by precipitation methods. These materials were exhaustively characterized through XRD, Raman spectroscopy, CO2- and NH3-TPD, DRIFT spectroscopy, and TG-DTA, after which the catalytic one-pot conversion of cellulose to valuable α-hydroxy-acids (i.e. lactic and glycolic acids) was investigated. The catalytic performances, expressed in terms of lactic and glycolic acid yields, were directly correlated to the nature of the catalytic sites which, in turn, depended on the niobia content and the preparation route.

N-Containing graphenes have been found to act as catalysts for the selective wet oxidation of glucose to succinic acid.

A series of solid acid catalysts were prepared by functionalization of graphene-oxide (GO) and MWCNT-oxide (MWCNTO) with triflic and sulfonic acids affording a triflate-functionalized graphene oxide (GO@SO3CF3), and a sulfonated MWCNT (mu-CNT-SO3H). To facilitate the separation of the catalysts from the reaction mixture MWCNT5 were modified by incorporating magnetic nanoparticles. For comparison, the composites of MWCNTO with magnetic nanoparticles were further modified by deposition of niobia in two loadings, e.g. 30 and 60 wt.%. Depending of the functionality the catalysts exposed preponderantly either Bronsted (mu-CNT-SO3H) or Lewis (GO@SO3CF3) acid sites. Deposition of niobia also led to catalysts with acid properties, but as a function of the precursor nature and loading, they exposed niobia phases with either Bronsted (e.g., Nb-0 units) or Lewis acid sites (e.g., -Nb = O units) in excess. Catalytic performances, in terms of the yields in one of the platform molecule (ie, levulinic acid versus lactic acid) were directly correlated with the nature of these acid sites. Interestingly enough, the catalysts showing high efficiency for lactic acid led also to high efficiency for the synthesis of succinic acid under pressure of molecular oxygen. (C) 2016 Elsevier B.V. All rights reserved.

A new pathway for the catalytic wet oxidation (CWO) of glucose is described. Employing a cationic Ru@MNP catalyst, succinic acid is obtained in unprecedently high yield (87.5%) for a >99.9% conversion of glucose, most probably through a free radical mechanism combined with catalytic didehydroxylation of vicinal diols and hydrogenation of the resulted unsaturated intermediate.