Chemical Valorization Research Articles

Crucial parameters determining efficient use of fly ashes from energy sector as raw materials for dedicated advanced applications

This paper describes the physicochemical properties of three types of samples: fly ashes received directly from the coal power plant (FA_PP), fly ashes coming from commercial warehouses (FA_Mix) and the commercial cenospheres (FA_Cen). The main goal of our studies was to identify crucial parameters of fly ashes decisive to use these materials for such advanced applications as synthesis of zeolites or structured catalysts as well as to choose optimal ways of their effective chemical valorization. The chemical composition of the studied samples was determined by XRF, the phase composition - by both XRD and Raman spectroscopy. Textural properties - by using jointly SEM-EDS and low-temperature nitrogen adsorption. The grain size distribution was determined by laser diffraction analysis. DRIFT spectroscopy was used to examine the functional features of the analyzed samples. Physicochemical properties of the functional materials obtained from ash samples (containing i.a. NaX zeolites) were determined by the XRF, XRD and DRIFT. The obtained results confirmed a decrease of the Si/Al ratio from 1.94 to 1.34, accompanying NaX zeolite synthesis starting from FA_Cen ashes and from 2.27 to 2.13 starting from FA_Mix. XRD measurements performed for the obtained preparations showed intense reflections characteristic of NaX zeolite only in the case of FA_Mix ashes used as a starting material. The differences in synthesis progress were mainly influenced by the content ratio of the glassy to crystalline phases and by such textural properties as: specific surface area and particle size distribution. The reported results clearly confirm the complex nature of the tested materials and their evident potential to be used for synthesis of such functional materials as e.g. zeolites.

Recent advances in the chemical valorization of cellulose and its derivatives into ester compounds

This review highlights recent advances in the conversion of cellulose and its derivatives (monosaccharides and platform molecules) into ester chemicals.

Recent Advances in the Brønsted/Lewis Acid Catalyzed Conversion of Glucose to HMF and Lactic Acid: Pathways toward Bio-Based Plastics

One of the most trending topics in catalysis recently is the use of renewable sources and/or non-waste technologies to generate products with high added value. That is why, the present review resumes the advances in catalyst design for biomass chemical valorization. The variety of involved reactions and functionality of obtained molecules requires the use of multifunctional catalyst able to increase the efficiency and selectivity of the selected process. The use of glucose as platform molecule is proposed here and its use as starting point for biobased plastics production is revised with special attention paid to the proposed tandem Bronsted/Lewis acid catalysts.

Mixed-​ligand-devised anionic MOF with divergent open Co(II)-nodes as chemo-resistant, bi-functional material for electrochemical water oxidation and mild-condition tandem CO2 fixation

Metal-organic frameworks (MOFs) combine unique merits of heterogeneous and molecular catalysts, where purposeful implantation of task-specific functionalities along the pore structure can promise electrocatalytic oxygen evolution reaction (OER) and cascade chemical valorization of CO2. Although, both these attributes are crucial for renewable energy and environmental remediation, their effective amalgamation over a single platform is hitherto unexplored, yet extremely demanding. The chemically robust, and non-penetrated charged framework CSMCRI-10 (CSMCRI = Central Salt & Marine Chemicals Research Institute) exemplifies activation induced generation of high density Co(II) nodes with diverse open coordination positions along the unidirectional porous channels, and act as unique bi-functional material. Building on the presence of redox-active [Co2(µ2-OH)(COO)4] secondary building units, the activated framework (10a) demonstrates efficient water oxidation in alkaline medium (1 M KOH). The MOF requires only 396 mV overpotential to reach 10 mA/cm2 anodic current density, and possesses a Tafel slope of 102 mV/decade with admirable 95.1% Faradaic efficiency, signifying high rate of oxygen evolution reaction. The OER turn-over frequency is found to be within the range of best reported values (0.03s−1), and the framework stability is preserved in both potentiodynamic and potentiostatic conditions over 500 consecutive cycles. Further, the Lewis acid functionalized 10a benefits solvent-free CO2 conversion to cyclic carbonate in highly synergistic manner with adequate reusability and broad substrate scope. To the best of tandem catalysis, rarest oxidative carboxylation of CO2 and styrene is realized via single-step styrene carbonate synthesis with exceptional conversion under relatively mild reaction condition.

Chemical Recycling of Polyhydroxybutyrate (PHB) into Bio-Based Solvents and Their Use in a Circular PHB Extraction

Two novel protocols for the chemical valorization of polyhydroxybutyrate (PHB) were developed, aiming at the production of two bio-based molecules: methyl 3-hydroxybutyrate (MHB) and methyl 3-methoxybutyrate (MMB). Optimized reaction conditions were applied to pure PHB and PHB inclusions inside bacterial cells as starting materials. MHB was synthesized through a single-step catalytic methanolysis, while MMB was synthesized through a three-step process: thermolytic distillation to give crotonic acid (CA), esterification to give methyl crotonate (MC), and oxa-Michael addition of MeOH. The obtained MHB and MMB were tested as solvents for the recovery of PHB itself both from freeze-dried single strain cultures (SSC) and mixed microbial cultures (MMC) with low to medium contents of PHB (22–57 wt %). High PHB recovery was achieved: up to 96 ± 1% through MHB and up to 98 ± 1% through MMB. Extraction from MMC slurry (with a PHB content of 39% on dry weight) was also performed, recovering 77 ± 2% using MHB and 92 ± 2% using MMB. High purities and excellent molecular weights and polydispersity indexes of extracted PHB were obtained with both MHB and MMB. Solubility in water, octanol/water partition coefficients (log Kow), and aerobic ready biodegradability of both solvents were also evaluated.

Manganese‐Catalyzed Hydroborations with Broad Scope

AbstractReductive transformations of easily available oxidized matter are at the heart of synthetic manipulation and chemical valorization. The applications of catalytic hydrofunctionalization benefit from the use of liquid reducing agents and operationally facile setups. Metal‐catalyzed hydroborations provide a highly prolific platform for reductive valorizations of stable C=X electrophiles. Here, we report an especially facile, broad‐scope reduction of various functions including carbonyls, carboxylates, pyridines, carbodiimides, and carbonates under very mild conditions with the inexpensive pre‐catalyst Mn(hmds)2. The reaction could be successfully applied to depolymerizations.

Selective Production of Linear Aldehydes and Alcohols from Alkenes using Formic Acid as Syngas Surrogate.

Performing carbonylation without the use of carbon monoxide for high-value-added products is an attractive yet challenging topic in sustainable chemistry. Herein, effective methods for producing linear aldehydes or alcohols selectively with formic acid as both carbon monoxide and hydrogen source have been described. Linear-selective hydroformylation of alkenes proceeds smoothly with up to 88 % yield and >30 regioselectivity in the presence of single Rh catalyst. Strikingly, introducing Ru into the system, the dual Rh/Ru catalysts accomplish efficient and regioselective hydroxymethylation in one pot. The present processes utilizing formic acid as syngas surrogate operate simply under mild condition, which opens a sustainable way for production of linear aldehydes and alcohols without the need for gas cylinders and autoclaves. As formic acid can be readily produced via CO2 hydrogenation, the protocols represent indirect approaches for chemical valorization of CO2 .

Using a natural chlorite as catalyst in chemical recycling of waste plastics: Hydrolytic depolymerization of poly-[bisphenol A carbonate] promoted by clinochlore

The present study describes the first example of utilization of a natural clay mineral as catalyst in a process addressed to chemical valorization of poly-[bisphenol A carbonate] (PC; (1)) wastes. A natural clinochlore was investigated for the first time as the catalyst of the hydrolysis reaction of 1, a potential route to chemical recycling of wastes of this polymeric material. At 473 K, in tetrahydrofuran (THF) as the solvent, the mineral promoted effectively the depolymerization (up to 99%, after 6 h) of 1 by H2O and the selective (~99%) regeneration of the monomer bisphenol A (BPA, (2)). Temperature, catalyst loading, reaction time, H2O/PC weight ratio affected markedly the productivity of the process. The role of the catalyst was also focused: the experimental data showed that the exposed brucite-like sheets of clinochlore are involved in the hydrolysis reaction and take active part in promoting the depolymerization process.

Cover Feature: The Use of Heterogeneous Catalysis in the Chemical Valorization of Plastic Waste (ChemSusChem 22/2020)

Cover Feature: The Use of Heterogeneous Catalysis in the Chemical Valorization of Plastic Waste (ChemSusChem 22/2020)

The Use of Heterogeneous Catalysis in the Chemical Valorization of Plastic Waste

Plastic solid waste (PSW) is an ever-growing environmental challenge for our society, as it not only ends up in landfills but also in waterways and oceans and is consequently entering the food chain. A key strategy to overcome this problem while also preserving carbon resources is to use PSW as a feedstock, evolving towards a circular economy. To implement this, mechanical as well as chemical recycling technologies must be developed. Indeed, owing to the high volume of PSW generated each year, mechanical recycling alone is not adequate for addressing this global challenge. Because of this, chemical recycling via thermal and heterogeneous catalytic conversion has received growing attention. This process has the potential to take PSW and convert it into usable monomers, fuels, synthesis gas, and adsorbents under more sustainable conditions than thermal degradation. This Review highlights the recent research advances in catalytic technologies for PSW conversion and valorization.

Chemical Investigation and Biological Valorization of Two Essential Oils Newly Extracted from Different Parts of Drimia maritima

For the first time, the chemical constituents of two essential oils extracted by hydrodistillation from Drimia maritima flowers and bulbs were identified using analytical GC-MS analysis. Eugenol (41.23 %) and carvacrol (27.29 %) were the most abundant compounds in bulbs while the major components in flowers were p-vinylguaicol (14.33 %), eugenol (8.49 %) and carvacrol (7.51 %). The antioxidant activity of both essential oils was evaluated using three methods DPPH, ABTS+. and total antioxidant capacity. The results showed that essential oils from bulbs and flowers exhibited a strong antioxidant capacity compared to Trolox and Vitamine E. Additionally; the samples were evaluated for their nitric oxide chelation activity and showed an important scavenging effect with IC50 5.05 and 5.12 μg/mL for bulbs and flowers respectively. Furthermore, both essential oils were endowed with effective antimicrobial properties. It was noticed that the extents of antioxidant and antibacterial activities of Drimia maritima essential oils are in accordance with their high amount of eugenol and carvacrol.

The unique interplay between copper and zinc during catalytic carbon dioxide hydrogenation to methanol

In spite of numerous works in the field of chemical valorization of carbon dioxide into methanol, the nature of high activity of Cu/ZnO catalysts, including the reaction mechanism and the structure of the catalyst active site, remains the subject of intensive debate. By using high-pressure operando techniques: steady-state isotope transient kinetic analysis coupled with infrared spectroscopy, together with time-resolved X-ray absorption spectroscopy and X-ray powder diffraction, and supported by electron microscopy and theoretical modeling, we present direct evidence that zinc formate is the principal observable reactive intermediate, which in the presence of hydrogen converts into methanol. Our results indicate that the copper–zinc alloy undergoes oxidation under reaction conditions into zinc formate, zinc oxide and metallic copper. The intimate contact between zinc and copper phases facilitates zinc formate formation and its hydrogenation by hydrogen to methanol.

Catalytic production of 5-hydroxymethylfurfural from sucrose and molasses by aluminum chloride in green aqueous γ-valerolactone system

5-Hydroxymethylfurfural (HMF) is a promising platform chemical for production of value-added chemicals and fuels. Conversion of abundantly available and cheap sucrose for HMF synthesis was systematically investigated in the present study. Results showed that Lewis acid AlCl3 is effective in catalytic transformation of sucrose. Combining AlCl3 with different Bronsted acids, no matter whether they were inorganic acids (HCl, H2SO4, and H3PO4) or organic acids (malic acid, succinic acid, and oxalic acid), or variation of ratio of Lewis acid/Bronsted acid represented by AlCl3/HCl, did not change the obtained maximum HMF yields compared with AlCl3 alone, but shortened the time required to reach the maximum HMF yield. Sucrose conversion in a green reaction media of aqueous γ-valerolactone (GVL) solvent resulted into comparable HMF yields with dimethyl sulfoxide (DSMO)-water system. Addition of monovalent salt NaCl and divalent salt Na2SO4 produced opposite effect with Cl− promoting while SO42− inhibiting HMF production. Furthermore, HMF synthesis from constituent monosaccharides of sucrose and molasses, a by-product from sugar manufacturing process, was also carried out and it was found that an equivmole mixture of glucose and fructose gave rise to almost identical HMF yield to the same mole of sucrose. Molasses, even after chemical pretreatment for removal of certain amount of inorganic salts and color substances, was significantly inferior to synthetic molasses in terms of HMF formation, indicating the complexity and difficulty in chemical valorization of molasses for production of platform molecules.

Recovery of Rare Earth Oxide from Waste NiMH Batteries by Simple Wet Chemical Valorization Process

Nickel metal hydride (NiMH) batteries contain a significant amount of rare earth metals (REMs) such as Ce, La, and Nd, which are critical to the supply chain. Recovery of these metals from waste NiMH batteries can be a potential secondary resource for REMs. In our current REM recovery process, REM oxide from waste NiMH batteries was recovered by a simple wet chemical valorization process. The process followed the chemical metallurgy process to recover REM oxides and included the following stages: (1) H2SO4 leaching; (2) selective separation of REM as sulfate salt from Ni/Co sulfate solution; (3) metathesis purification reaction process for the conversion REM sulfate to REM carbonate; and (4) recovery of REM oxide from REM carbonate by heat treatment. Through H2SO4 leaching optimization, almost all the metal from the electrode active material of waste NiMH batteries was leached out. From the filtered leach liquor managing pH (at pH 1.8) with 10 M NaOH, REM was precipitated as hydrated NaREE(SO4)2·H2O, which was then further valorized through the metathesis reaction process. From NaREE(SO4)2·H2O through carbocation, REM was purified as hydrated (REM)2CO3·H2O precipitate. From (REM)2CO3·H2O through calcination at 800 °C, (REM)2O3 could be recovered.

Radical Redox Mediator Free Photoelectrochemical Biomass Valorization

Over the past decade, researchers have begun to re-explore the idea of replacing water oxidation with more kinetically facile oxidation reactions for photoelectrochemical solar H2 production.1–3 Alternate photo-oxidation reactions can be employed as a means of chemical valorization, in addition to providing electrons for H2 production from water while reducing the losses associated with water oxidation. In particular, the oxidation of 5-hydroxymethylfurfural (HMF)—which is a key intermediate derived from the acid catalyzed poly-dehydration of 6 carbon monosaccharides—has gained significant attention. This is because a number of its oxidation products, such as 2,5-Furandicarboxylic acid (FDCA), may be employed as monomers in the synthesis of renewable polyesters, and FDCA in particular, has also been identified by the US Department of Energy as one of 12 priority chemicals for establishing the green chemistry industry of the future.4 As a result, solar powered chemical transformations of HMF have recently gained attention. However, to date, the selective oxidation of HMF using either photo-, or electrochemical means, has been limited by the need to employ the radical redox mediator (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO). This additional redox-mediating reagent poses a problem by increasing system complexity, and by behaving as a competitive light absorber in photoelectrochemical (PEC) systems —which reduces the solar conversion efficiency. Recently, our group has investigated TEMPO free, direct PEC oxidation of HMF using metal oxide photoelectrodes. In this presentation, we show that the direct oxidation of HMF can be carried out on sol-gel processed WO3 electrodes without the need to use an additional redox shuttle such as TEMPO. Figure 1 depicts a linear sweep voltammogram under 1 sun illumination of a sol-gel processed WO3 electrode in the presence and absence of HMF. We observe that the addition of HMF to an aqueous buffered solution improves photocurrent densities by 33%, and the onset potential is favorably shifted by -50 mV. These properties highlight this reaction’s promise as a replacement for water oxidation in an H2 producing PEC cell. In addition, we report the oxidation product distribution as well as efforts to control product selectivity via solution processed heterogeneous catalysts and the optimization of the electrolyte solution. Figure 1: Linear sweep voltammograms of a WO3 electrode in a pH 4 0.1M KPi buffered solution with (red), and without (black), 5mM HMF in solution. The illumination intensity was 1 sun AM1.5G. Dotted lines represent the linear sweep voltammograms in the absence of illumination.

Effect of Bi modification on Pt single crystals towards the glycerol electrooxidation in alkaline media

The high demand for the biodiesel has increased the glycerol (GlOH) generation, since it is a co-product of biodiesel production, surpassing the industrial demand. In this context, the glycerol electrooxidation reaction (GER) is an interesting option for its chemical valorization, generating high value-added products. In the present work, we studied the GER on different surfaces of Pt single crystals modified with bismuth to understand the effect of the catalyst structure on the activity and reaction pathways.

Alternative Oxidation Reactions for Solar-Driven Fuel Production

For nearly half a century, water oxidation has been extensively investigated as the electron source for solar-powered H2 fuel production from water. However, despite a thermodynamic potential of only 1.23 V required at standard conditions, driving the oxygen evolution reaction (OER) typically requires 1.5–1.8 V resulting in a significant loss. Over the past decade, numerous researchers have begun to re-explore the idea of replacing water oxidation with more kinetically facile oxidation reactions in photoelectrochemical and photocatalytic solar H2 production systems. Alternate photo-oxidation reactions can be employed as a means of chemical valorization, in addition to providing electrons for H2 production from water while reducing the losses associated with the OER. In this Perspective, we discuss other possible oxidation reactions, and in particular, we highlight recent progress in the investigation of organic-based photo-oxidation reactions. We focus on oxidation reactions that have potential applicatio...

Recent progress in homogeneous Lewis acid catalysts for the transformation of hemicellulose and cellulose into valuable chemicals, fuels, and nanocellulose

AbstractThe evolution from petroleum-based products to the bio-based era by using renewable resources is one of the main research challenges in the coming years. Lignocellulosic biomass, consisting of inedible plant material, has emerged as a potential alternative for the production of biofuels, biochemicals, and nanocellulose-based advanced materials. The lignocellulosic biomass, which consists mainly of carbohydrate-based polysaccharides (hemicellulose and cellulose), is a green intermediate for the synthesis of bio-based products. In recent years, the re-engineering of biomass into a variety of commodity chemicals and liquid fuels by using Lewis acid catalysts has attracted much attention. Much research has been focused on developing new chemical strategies for the valorization of different biomass components. Homogeneous Lewis acid catalysts seem to be one of the most promising catalysts due to their astonishing features such as being less corrosive to equipment and being friendlier to the environment, as well as having the ability to disrupt the bonding system effectively and having high selectivity. Thus, these catalysts have emerged as important tools for the highly selective transformation of biomass components into valuable chemicals and fuels. This review provides an insightful overview of the most important recent developments in homogeneous Lewis acid catalysis toward the production and upgrading of biomass. The chemical valorization of the main components of lignocellulosic biomass (hemicellulose and cellulose), the reaction conditions, and process mechanisms are reviewed.

Thermodynamic insights on the viscometric and volumetric properties of binary mixtures of ketals and polyols

Recently, solketal (Sk) and glycerol formal (GF) have appeared as alternatives for the chemical valorization of glycerol (Gly), a by-product derived from the biodiesel industry. Sk and GF are versatile products with increasing interest in several industries due to their attractive properties, particularly in foods, pharmaceuticals and products of the fast moving consumer goods industry. In addition, glycols like 1,2-propanediol (1,2-PD), ethylene glycol (EG) are also valuable chemicals whose production can also derive from the valorization of Gly.Information on the viscometric and volumetric properties of these compounds is very scarce, yet simultaneously critical to assess potential industrial applications. Here the density and viscosity of the binary mixtures of {GF + 1,2-PD}, {GF + EG}, {GF + Gly}, {Sk + 1,2-PD}, {Sk + EG} and {Sk + Gly} are experimentally measured over the entire range of compositions at 298.15, 308.15 and 313.15 K and atmospheric pressure. Correlation of these properties to the Jouyban-Acree equation was made to explain their variation with composition and temperature. Furthermore, molar excess volumes and viscosity deviations are herein calculated and Redlich-Kister equations are employed to model the behaviour with composition. Finally, the experimental results are supported with quantum chemical calculations based on COSMO-RS method in order to shed light on the interaction between the compounds, and further understand the thermodynamic behaviour of the corresponding binary mixtures.

Biosourced Polymetallic Catalysis: A Surprising and Efficient Means to Promote the Knoevenagel Condensation.

Zn hyperaccumulator (Arabidobsis halleri) and Zn accumulator Salix “Tordis” (Salix schwerinii × Salix viminalis) have shown their interest in the phytoextraction of polluted brownfields. Herein, we explore a novel methodology based on the chemical valorization of Zn-rich biomass produced by these metallophyte plants. The approach is based on the use of polymetallic salts derived from plants as bio-based catalysts in organic chemistry. The formed ecocatalysts were characterized via ICP-MS, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) in order to precise the chemical composition, structure, and behavior of the formed materials. The Doebner-Knoevenagel reaction was chosen as model reaction to study their synthetic potential. Significant differences to usual catalysts such as zinc (II) chloride are observed. They can principally be related to a mixture of unusual mineral species. DFT calculations were carried out on these salts in the context of the Gutmann theory. They allow the rationalization of experimental results. Finally, these new bio-based polymetallic catalysts illustrated the interest of this concept for green and sustainable catalysis.