Green Industrial Processes Research Articles

Novel Bioplastic Based on PVA Functionalized with Anthocyanins: Synthesis, Biochemical Properties and Food Applications.

Over the last ten years, researchers' efforts have aimed to replace the classic linear economy model with the circular economy model, favoring green chemical and industrial processes. From this point of view, biologically active molecules, coming from plants, flowers and biomass, are gaining considerable value. In this study, firstly we focus on the development of a green protocol to obtain the purification of anthocyanins from the flower of Callistemon citrinus, based on simulation and on response surface optimization methodology. After that, we utilize them to manufacture and add new properties to bioplastics belonging to class 3, based on modified polyvinyl alcohol (PVA) with increasing amounts from 0.10 to 1.00%. The new polymers are analyzed to monitor morphological changes, optical properties, mechanical properties and antioxidant and antimicrobial activities. Fourier transform infrared spectroscopy (FTIR) spectra of the new materials show the characteristic bands of the PVA alone and a modification of the band at around 1138 cm-1 and 1083 cm-1, showing an influence of the anthocyanins' addition on the sequence with crystalline and amorphous structures of the starting materials, as also shown by the results of the mechanical tests. These last showed an increase in thickening (from 29.92 μm to approx. 37 μm) and hydrophobicity with the concomitant increase in the added anthocyanins (change in wettability with water from 14° to 31°), decreasing the poor water/moisture resistance of PVA that decreases its strength and limits its application in food packaging, which makes the new materials ideal candidates for biodegradable packaging to extend the shelf-life of food. The functionalization also determines an increase in the opacity, from 2.46 to 3.42 T%/mm, the acquisition of antioxidant activity against 2,2-diphenyl-1-picrylhdrazyl and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) radicals and, in the ferric reducing power assay, the antimicrobial (bactericidal) activity against different Staphylococcus aureus strains at the maximum tested concentration (1.00% of anthocyanins). On the whole, functionalization with anthocyanins results in the acquisition of new properties, making it suitable for food packaging purposes, as highlighted by a food fresh-keeping test.

Scaling-Up Microwave-Assisted Synthesis of Highly Defective Pd@UiO-66-NH2 Catalysts for Selective Olefin Hydrogenation under Ambient Conditions.

The need to develop green and cost-effective industrial catalytic processes has led to growing interest in preparing more robust, efficient, and selective heterogeneous catalysts at a large scale. In this regard, microwave-assisted synthesis is a fast method for fabricating heterogeneous catalysts (including metal oxides, zeolites, metal-organic frameworks, and supported metal nanoparticles) with enhanced catalytic properties, enabling synthesis scale-up. Herein, the synthesis of nanosized UiO-66-NH2 was optimized via a microwave-assisted hydrothermal method to obtain defective matrices essential for the stabilization of metal nanoparticles, promoting catalytically active sites for hydrogenation reactions (760 kg·m-3·day-1 space time yield, STY). Then, this protocol was scaled up in a multimodal microwave reactor, reaching 86% yield (ca. 1 g, 1450 kg·m-3·day-1 STY) in only 30 min. Afterward, Pd nanoparticles were formed in situ decorating the nanoMOF by an effective and fast microwave-assisted hydrothermal method, resulting in the formation of Pd@UiO-66-NH2 composites. Both the localization and oxidation states of Pd nanoparticles (NPs) in the MOF were achieved using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray photoelectron spectroscopy (XPS), respectively. The optimal composite, loaded with 1.7 wt % Pd, exhibited an extraordinary catalytic activity (>95% yield, 100% selectivity) under mild conditions (1 bar H2, 25 °C, 1 h reaction time), not only in the selective hydrogenation of a variety of single alkenes (1-hexene, 1-octene, 1-tridecene, cyclohexene, and tetraphenyl ethylene) but also in the conversion of a complex mixture of alkenes (i.e., 1-hexene, 1-tridecene, and anethole). The results showed a powerful interaction and synergy between the active phase (Pd NPs) and the catalytic porous scaffold (UiO-66-NH2), which are essential for the selectivity and recyclability.

Engineering RuBisCO-based shunt for improved cadaverine production in Escherichia coli

The process of biological fermentation is often accompanied by the release of CO2, resulting in low yield and environmental pollution. Refixing CO2 to the product synthesis pathway is an attractive approach to improve the product yield. Cadaverine is an important diamine used for the synthesis of bio-based polyurethane or polyamide. Here, aiming to increase its final production, a RuBisCO-based shunt consisting of the ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) and phosphoribulate kinase (PRK) was expressed in cadaverine-producing E. coli. This shunt was calculated capable of increasing the maximum theoretical cadaverine yield based on flux model analysis. When a functional RuBisCO-based shunt was established and optimized in E. coli, the cadaverine production and yield of the final engineered strain reached the highest level, which were 84.1 g/L and 0.37 g/g Glucose, respectively. Thus, the design of in situ CO2 fixation provides a green and efficient industrial production process.

N,O‐Codoped Onion‐like Carbon Catalyzed Selective Oxidation of Methanol to Dimethoxymethane: Structure‐Activity Relationship

AbstractOne‐step synthesis of dimethoxymethane (DMM) via methanol oxidation under the catalysis of nanocarbon is a green and sustainable chemical industrial process. In this work, nitrogen, oxygen codoped onion‐like carbon (NOLC) were prepared via a simple thermal treatment method, which was applied to one‐step synthesis of DMM. The physicochemical characterization results revealed that nitrogen and oxygen elements were successfully introduced into the onion‐like carbon (OLC) catalyst. The proposed NOLC catalysts exhibited DMM selectivity of 75 % at relatively low reaction temperature (150 °C) and long stability over 10 h. In‐situ titration experiments revealed that the carboxylic acid groups on NOLC surface were the main acidic active sites. The Clemmensen reduction control experiment revealed that the carbonyl groups were the active sites for the formation of formaldehyde. The basic reaction kinetics and mechanism such as reaction orders, apparent activation energy and rate determining step etc. for one‐step synthesis of DMM via methanol were studied systematically. The present work shows an important structure‐function relation for designing highly efficient nanocarbon catalyzed methanol conversion reaction system that the appropriate redox/acid intensity on catalyst surface through the modulation of N and O elements would effectively improve the selectivity of DMM.

Dimethyl carbonate as a green alternative to acetonitrile in reversed-phase liquid chromatography. Part I: Separation of small molecules

Nowadays, environmental problems are drawing the attention of governments and international organisations, which are therefore encouraging the transition to green industrial processes and approaches. In this context, chemists can help indicate a suitable direction. Beside the efforts focused on greening synthetic approaches, currently also analytical techniques and separations are under observation, especially those employing large volumes of organic solvents, such as reversed-phase liquid chromatography (RPLC). Acetonitrile has always been considered the best performing organic modifier for RPLC applications, due to its chemical features (complete miscibility in water, UV transparency, low viscosity etc); nevertheless, it suffers of severe shortcomings, and most importantly, it does not fully comply with Environmental, Health and Safety (EHS) requirements. For these reasons, alternative greener solvents are being investigated, especially easily available alcohols.In this work, chromatographic performance of the most common solvents used in reversed-phase chromatography, i.e., acetonitrile, ethanol and isopropanol, have been compared to a scarcely used solvent, dimethyl carbonate (DMC). The analytes of interest were two small molecules, caffeine and paracetamol, whose kinetics and retention behaviour obtained with the four solvents have been compared, and all contributions to band broadening have been assessed. Results about kinetic performance are very promising, indicating that a small amount (7 % v/v) of DMC is able to produce the same efficiency as a 2.5-times larger ACN volume (18 % v/v), and larger efficiency than alcohols.This paper reports, for the first time, fundamental studies concerning the mass transfer phenomena when DMC is used as an organic solvent in RPLC, and, together with the companion paper, represents the results of a research whose final aim was to discover whether DMC is suitable for chromatographic applications both in linear and preparative conditions.

Enhanced Laccase Activity and Stability as Crosslinked Enzyme Aggregates on Magnetic Copper Ferrite Nanoparticles for Biotechnological Processes

AbstractHighly stable and reusable magnetic crosslinked enzyme aggregates (m‐CLEAS) of laccase are synthesized with simultaneous improved enzymatic activity. Magnetic copper ferrite nanoparticles (CFNPs) were synthesized by solvothermal procedure with an average size of ~8 nm. The nanometric m‐CLEAS were formed by co‐aggregation of enzyme with CFNPs and crosslinked using glutaraldehyde. Different mass ratios of CFNPs:Laccase were assayed (1 : 2, 1 : 3, and 1 : 6), where 1 : 6 resulted in the highest activity recovery (97 %). The m‐CLEAS showed an average size of ~239 nm, ~24 % enzyme immobilization efficiency, and loading as high as 1.75 g of protein per g of support. As expected, m‐CLEAS oxidized the substrate with a higher transformation rate (kcat) and catalytic efficiency (kcat/Km) than the free enzyme. m‐CLEAS showed superior storage and thermostability compared to free enzyme and non‐magnetic CLEAS. In particular, the m‐CLEAS showed ~150 % and ~100 % residual activity after 30 days of storage at 4 °C and room temperature, respectively. Furthermore, m‐CLEAS showed good recyclability, retaining ~78 % and ~54 % laccase activity after 5 and 10 cycles of reuse, respectively. This work highlights the facile and cost‐effective synthesis of nanometric m‐CLEAS with exceptional storage stability and simultaneously improved laccase activity, making them suitable for a range of green industrial processes.

Evaluation of industrial green development based on set pair analysis

Industrial green development is an important part of the global sustainable development goals, and it is the only way for China to achieve the "dual carbon goals". This paper aims to explore the methods and indicators for the assessment of the level of industrial green development, and emphasizes its applicability in the "city area" scale. According to the characteristics of industrial green development, an evaluation system including 4 first-level indicators of economic benefits and structure, technological innovation and investment, environmental impact and governance, resource consumption and reuse, and a total of 16 s-level indicators were established, each indicator was determined using the entropy value theory The weight value is based on the conditions of 15 sub-provincial cities across the country to determine the standard value of each indicator. Through the set pair analysis of the five-element connection number and partial connection number, the comprehensive connection degree and the full partial connection number are obtained, so as to evaluate the level of industrial green development in Chengdu static evaluation and dynamic analysis. The results show that the constructed index system and evaluation method are applicable to the evaluation of industrial green development at the "city" scale. The current status of Chengdu's industrial green development is at a qualified level, and the industrial process will have a more active and green development trend in the future. The government management department should formulate appropriate management policies and strengthen comprehensive evaluation and research, so as to take the green industrial development process of Chengdu to a new level.

Carrier‐Free Enzyme Immobilizates for Flow Chemistry

AbstractFor the development of efficient and green industrial processes, the combination of biocatalysis and flow chemistry holds great promises. Flow chemical utilization of biocatalysts, essentially made possible by the immobilization (or retention) of enzymes in flow reactors, has attracted increased academic attention during recent years. In the present review we present an overview of immobilization strategies suitable for flow chemistry, particularly focusing on recently developed carrier‐free immobilization methods, highlighting advances in the field and presenting future trends.

A facile and efficient synthesis approach of salidroside esters by whole-cell biocatalysts in organic solvents.

Salidroside, the main bioactive compound isolated from the plant source of Rhodiola rosea L, possesses broad-spectrum pharmacological activities, but suffers from the low cell membranes permeability and alimentary absorption due to its high polarity. Therefore, a whole-cell catalytic strategy for the synthesis of salidroside esters was explored to improve its lipophilicity. The results showed that Aspergillus oryzae demonstrated the highest biocatalytic activity among the microbial strains tested. For the synthesis of salidroside caprylate, the optimum conditions of reaction medium, Aspergillus oryzae amount, molar ratio of vinyl caprylate to salidroside and reaction temperature were acetone, 30mg/ml, 10°C and 40°C, respectively. Under these conditions, the initial reaction rate was 15.36mM/h, and substrate conversion and regioselectivity all reached 99%. Moreover, the results indicated that although various 6'-monoesters derivatives of salidroside were exclusively obtained with excellent conversions (96%-99%), the reaction rate varied greatly with different chain-length acyl donors. This study details an efficient and cost-effective biocatalytic approach for the synthesis of salidroside esters by using Aspergillus oryzae as a catalyst for the first time. Considering the whole cell catalytic efficiency and operational stability, this strategy may provide a new opportunity to develop green industrial processes production for ester derivatives of salidroside and its analogues.

Characterization of Carboxylic Acid Reductase from Mycobacterium phlei Immobilized onto Seplite LX120.

A multi-domain oxidoreductase, carboxylic acid reductase (CAR), can catalyze the one-step reduction of carboxylic acid to aldehyde. This study aimed to immobilize bacterial CAR from a moderate thermophile Mycobacterium phlei (MpCAR). It was the first work reported on immobilizing bacterial CAR onto a polymeric support, Seplite LX120, via simple adsorption. Immobilization time and protein load were optimized for MpCAR immobilization. The immobilized MpCAR showed optimal activity at 60 °C and pH 9. It was stable over a wide range of temperatures (10 to 100 °C) and pHs (4–11), retaining more than 50% of its activity. The immobilized MpCAR also showed stability in polar solvents. The adsorption of MpCAR onto the support was confirmed by Scanning Electron Microscopy (SEM), Fourier-Transform Infrared (FTIR) spectroscopy, and Brunauer–Emmett–Teller (BET) analysis. The immobilized MpCAR could be stored for up to 6 weeks at 4 °C and 3 weeks at 25 °C. Immobilized MpCAR showed great operational stability, as 59.68% of its activity was preserved after 10 assay cycles. The immobilized MpCAR could also convert approximately 2.6 mM of benzoic acid to benzaldehyde at 60 °C. The successfully immobilized MpCAR on Seplite LX120 exhibited improved properties that benefit green industrial processes.

Data Analysis in Green Industrial Processes with Modified Chemical Efficiency and Environmental Impact: Smart Urea Production and CO2 Removal

Agriculture can benefit from urea fertilizer because it contains a lot of nitrogen at a reasonable cost. Urea fertilizer can be stored easily and does not pose a fire hazard over time. Due to its acidifying properties, urea fertilizer is an ideal fertilizer for many plants. Input and feed of the urea unit are taken from the output of the ammonia unit (CO2 and NH3). Hence, in this study, two methods of CO2 recovery from combustion gases and CO2 recycling in ammonia units will be used to increase urea production to realize low-carbon and industrial systems (including green agriculture). CO2 recovery also reduces environmental pollution, which is a very important factor in sustainable cities and societies. The results showed that CO reduction increases the overall efficiency compared to the data reported in the world for the same process, which is due to the reduction of CO input to methanize. Collecting information around the globe for constructing the same green system considering various conditions in each environment makes complicated situations in terms of how to design the process and the observed outcomes. However, we could find a new smart design to build the green system in our case study where it is completely acceptable compared to the same systems’ outputs. The obtained results indicate that the temperature of the shift reactor can be brought closer to 365°C without reducing the selectivity of the catalysts, which in turn would increase the CO conversion rate, the CO2 output, and the overall efficiency of the unit. Finally, it is shown that the rate of CO escape from shift reactors is decreased.

A Solvent-free/Effective Base Unsaturated Esters Synthesis using Novel Amine Functionalized Ionic Liquid

Abstract: 1-(2-aminoethyl)-3-methylimidazolium bromide [Aemim]Br ionic liquid acted as a catalyst as well as a solvent in the Knoevenagel condensation reaction. The extent of products formed with high yield and more flattering for the synthesis of aliphatic and aromatic esters. The [Aemim] Br can be recycled for 6 runs without great loss of activity. Background: The Knoevenagel condensation was one of the fundamental reactions in organic chemistry both at the laboratory and industrial levels. Objective: An effective method for the condensation of a variety of aliphatic and aromatic carbonyl compounds with ethyl acetoacetate and subsequent hydrolysis to corresponding α, β - unsaturated esters in [Aemim]Br was achieved. Method: The weighed quantity of [Aemim]Br, an aldehyde and ethyl acetoacetate were carried out at 25OC. The reaction commenced instantaneously making the reaction mixture highly viscous. The product was extracted with ether. The combined organic extracts were dried using anhydrous sodium sulphate, evaporated under reduced pressure and assayed on GC. Results: We could achieve to get Knoevenagel condensation with good yield. Conclusion: An effectual procedure for Knoevenagel condensation of a variety of aliphatic and aromatic aldehydes with active ethyl acetoacetate arises smoothly in the presence of [Aemim]Br without any additional solvents. This is the best method that proved an effective green industrial process.

Critical assessment of structure-based approaches to improve protein resistance in aqueous ionic liquids by enzyme-wide saturation mutagenesis

Ionic liquids (IL) and aqueous ionic liquids (aIL) are attractive (co-)solvents for green industrial processes involving biocatalysts, but often reduce enzyme activity. Experimental and computational methods are applied to predict favorable substitution sites and, most often, subsequent site-directed surface charge modifications are introduced to enhance enzyme resistance towards aIL. However, almost no studies evaluate the prediction precision with random mutagenesis or the application of simple data-driven filtering processes. Here, we systematically and rigorously evaluated the performance of 22 previously described structure-based approaches to increase enzyme resistance to aIL based on an experimental complete site-saturation mutagenesis library of Bacillus subtilis Lipase A (BsLipA) screened against four aIL. We show that, surprisingly, most of the approaches yield low gain-in-precision (GiP) values, particularly for predicting relevant positions: 14 approaches perform worse than random mutagenesis. Encouragingly, exploiting experimental information on the thermostability of BsLipA or structural weak spots of BsLipA predicted by rigidity theory yields GiP = 3.03 and 2.39 for relevant variants and GiP = 1.61 and 1.41 for relevant positions. Combining five simple-to-compute physicochemical and evolutionary properties substantially increases the precision of predicting relevant variants and positions, yielding GiP = 3.35 and 1.29. Finally, combining these properties with predictions of structural weak spots identified by rigidity theory additionally improves GiP for relevant variants up to 4-fold to ∼10 and sustains or increases GiP for relevant positions, resulting in a prediction precision of ∼90% compared to ∼9% in random mutagenesis. This combination should be applicable to other enzyme systems for guiding protein engineering approaches towards improved aIL resistance.

Examples of the Introduction of Sustainable Development and Green Industrial Processes for Secondary School Chemistry and Introductory Chemistry

Article Examples of the Introduction of Sustainable Development and Green Industrial Processes for Secondary School Chemistry and Introductory Chemistry was published on April 1, 2021 in the journal Chemistry International (volume 43, issue 2).

Oxidative dehydrogenation on nanocarbon: Polydopamine hollow nanospheres as novel highly efficient catalysts

Ethylbenzene oxidative dehydrogenation (EB ODH) reactions with nanocarbon as catalysts exhibit promising prospects as green and sustainable chemical industrial process. The present work reported the design and synthesis of polydopamine hollow nanospheres (PDA HNSs) carbon-based catalysts via a polymerization & carbonization method using silica as hard templates. The proposed PDA HNSs catalysts exhibit a high surface area of 641.6 m2 g−1 with the surface oxygen and nitrogen content up to 6.3% and 9.5%, respectively. It shows exceptional catalytic performance towards EB ODH reaction, which is even better than the commercial nanocarbon materials, such as carbon nanotubes, from the viewpoint of the apparent activity (EB conversion at 61.6%), the intrinsic activity (7.7 × 10−4 s−1) and the activation energy (42.5 kJ/mol), although they share the same catalytic active sites of ketonic carbonyl/quinone groups and reaction kinetics, such as rate determining step and reaction orders.

Catalytic and Photothermo-catalytic Applications of TiO2-CoOx Composites

Objective: The necessity to have green and sustainable industrial processes has promoted new technologies for air and water purification together with the research of new energy sources. In this contest, the TiO2-based photocatalysis can be considered a promising route for both environmental applications aIn this work, we have investigated the photocatalytic performance of TiO2-CoOx composites on both photooxidation and photoreduction reactions. Specifically, we have compared the performance of the composites in the thermo-catalytic, photo-catalytic and photothermal-catalytic oxidation of ethanol chosen as model volatile organic compound (VOC) and in the photocatalytic hydrogen production by simulated solar light from aqueous solution of ethanol.nd hydrogen production through water splitting. Background: The necessity to have green and sustainable industrial processes has promoted new technologies for air and water purification together with the research of new energy sources. In this contest, the TiO2-based photocatalysis can be considered a promising route for both environmental applications and hydrogen production through water splitting. Methods: The samples were prepared with a simple impregnation method, and were characterized by Scanning Electron (SEM) and Transmission Electron (TEM) microscopies, X-ray powder diffraction (XRD), N2 adsorption-desorption measurements, Temperature Programmed Reduction in hydrogen (H2- TPR) and X-ray Photoelectron (XPS), Raman, UV-Vis Diffuse Reflectance (UV-Vis DRS) and Photoluminescence (PL) spectroscopies. The catalytic and photocatalytic activity were carried out on pyrex reactors irradiated with a solar lamp and analyzing the reactions products through gas chromatography. Results: The presence and the amount of cobalt oxide were found crucial in determining the performance of the TiO2-based composites for both the catalytic and photocatalytic processes. In particular, the addition of 1 weight percent of CoOx led to the best performance in the photocatalytic processes, whereas a higher amount was beneficial in the thermo-catalytic tests. The multi-catalytic approach based on the synergistic effect of photocatalysis and thermocatalysis in the presence of the TiO2-1%CoOx sample allowed the temperature necessary to obtain 50% ethanol conversion and 50% yield in CO2 to be reduced by 40°C and 50°C, respectively. The same sample was also the best catalyst for photocatalytic solar H2 production. Conclusion: The presence of small amounts of cobalt oxide leads to an efficient composite with TiO2 facilitating the space charge separation and increasing the lifetime of the generated photoholes and electrons. The wide versatility of TiO2-CoOx catalysts both for photooxidation and photoreduction reactions motivates to further exploit the use of these systems in real solar-driven photocatalysis.

Improved hydrometallurgical extraction of valuable metals from spent lithium-ion batteries via a closed-loop process

The increasing market size of high-energy storage systems due to the booming of not only portable electronic devices but also electrical vehicles and renewable energy sources has promoted battery technologies, resulting in many spent lithium-ion batteries (LIBs). This study focuses on proposing a closed-loop process to recycle the full valuable metals from spent LiNi1/3Co1/3Mn1/3O2 material. Reduction roasting and hydrometallurgy were combined and used for de-agglomeration of cathode composites and enhanced recycling of valuable metals. Experimental results showed the cathode material was reduced to Ni, Co, Li2CO3, and MnO under microwave carbothermic reduction, and lithium carbonate was directly recovered after dissolved in water with a high yield of 99%. Afterward, transition metals (Ni, Co, Mn) enriched residues can be dissolved in fumaric acid with leaching efficiencies of more than 96% under optimized leaching conditions, and finally recovered as single compounds by step-wise addition of chemicals. The mechanism of the nonthermal effect of microwave on the leaching of metals was analyzed by kinetic studies, and the decreased Ea values for metals demonstrate that microwave treatment is beneficial for metals leaching through decreasing their apparent energies. Besides, the characterization results of X-ray diffraction and scanning electron microscope indicate the destruction of the layered crystal structure and an increased liberation degree after microwave treatment, which is also beneficial for the enhancement of metals leaching. Therefore, the microwave reductive-assisted process is found in a green and effective industrial process to recycle valuable metals from spent LIBs.

Wood processing industry by-products as a source of natural bioactive compounds

The chemical composition of several by-products, chips, screw waters, and concentrates from a fiberboards manufacture green industrial process, which only employs wood and water, was deeply evaluated. The three by-products analyzed represent different steps of the industrial process. In addition, different types of wood: pine, walnut, chestnut, oak and cherry tree, were evaluated. For all of them, total polyphenols content, and antioxidant activity have been assessed, showing significant differences. To characterize the volatile compounds, an environmentally friendly technique, solid-phase microextraction has been employed. Besides, aqueous and generally recognized as safe organic extracts obtained from the by-products have been prepared, and their chromatographic fingerprint was obtained by gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry to identify extractable organic wood components. Significant differences were observed between the studied by-products and wood types. More than 30 different compounds were successfully identified in the screw waters, and concentrates, including terpenes, sesquiterpenes, or polyphenols. Regarding the obtained extracts, up to 30 compounds were identified in the chips, screw waters, and concentrate extracts, highlighting the presence of 13 polyphenols in the cherry tree chips and more than 20 compounds with interesting properties in the concentrate extracts. This work contributes to improve the knowledge about the chemical composition of several wood industry by-products, which could be exploited to obtain natural extracts with added value for their reuse in the food, cosmetic, or pharmaceutical industry, reducing also the environmental impact of the industrial activity.

Moisture-induced crossover in the thermodynamic and mechanical response of hydrophilic biopolymer

The use of natural sustainable resources such as wood in green industrial processes is currently limited by our poor understanding of the impact of moisture on their thermodynamic and mechanical behaviors. Here, a molecular dynamics approach is used to investigate the physical response of a typical hydrophilic biopolymer in softwood hemicellulose—xylan—when subjected to moisture adsorption. A unique moisture-induced crossover is found in the thermodynamic and mechanical properties of this prototypical biopolymer with many quantities such as the heat of adsorption, heat capacity, thermal expansion and elastic moduli exhibiting a marked evolution change for a moisture content about 30 wt%. By investigating the microscopic structure of the confined water molecules and the polymer–water interfacial area, the molecular mechanism responsible for this crossover is shown to correspond to the formation of a double-layer adsorbed film along the amorphous polymeric chains. In addition to this moisture-induced crossover, many properties of the hydrated biopolymer are found to obey simple material models.

Chitosan–silica sulfate nanohybrid: a highly efficient and green heterogeneous nanocatalyst for the regioselective synthesis of N-alkyl purine, pyrimidine and related N-heterocycles via presilylated method

The presilylation of purine and pyrimidine nucleobases as well as other related N-heterocycles with HMDS utilizing chitosan–silica sulfate nanohybrid (CSSNH) is described. CSSNH is proved to be a useful, highly efficient and eco-friendly heterogeneous nanohybrid catalyst for silylation of nucleobases. The presilylated nucleobases then underwent the reaction with different sources of carbon electrophiles to afford the desired N-alkyl-substituted derivatives in good-to-excellent yields. CSSNH exhibits several advantageous involving ease of handling and preparation, low cost, reusability and environmental benignity. These unique properties render the CSSNH to be an ideal candidate for use in green industrial processes.