Cellulosic materials as biopolymers and supercritical CO2as a green process: chemistry and applications

In this review, we describe the use of supercritical CO2 (scCO2) in several cellulose applications. The focus is on different technologies that either exist or are expected to emerge in the near future. The applications are wide from the extraction of hazardous wastes to the cleaning and reuse of paper or production of glucose. To put this topic in context, cellulose chemistry and its interactions with scCO2 are described. The aim of this study was to discuss the new emerging technologies and trends concerning cellulosic materials processed in scCO2 such as cellulose drying to obtain aerogels, foams and other microporous materials, impregnation of cellulose, extraction of highly valuable compounds from plants and metallic residues from treated wood. Especially, in the bio-fuel production field, we address the pre-treatment of cellulose in scCO2 to improve fermentation to ethanol by cellulase enzymes. Other reactions of cellulosic materials such as organic inorganic composites fabrication and de-polymerisation have been considered. Cellulose treatment by scCO2 has been discussed as well. Finally, other applications like deacidification of paper and cellulosic membranes fabrication in scCO2 have been reviewed. Examples of the discussed technologies are included as well

Green ultrafiltration membranes

Green ultrafiltration membrane

Phase equilibrium of the CO2/glycerol system: Experimental data by in situ FT-IR spectroscopy and thermodynamic modeling

Phase equilibrium experimental data for the CO2/glycerol system are reported in this paper. The measurements were performed using an in situ FT-IR method for temperatures ranging from 40 ◦C to 200 ◦C and pressures up to 35.0 MPa, allowing determination of the mutual solubility of both compounds. Concerning the CO2 rich phase, it was observed that the glycerol solubility in CO2 was extremely low (in the range of 10−5 in mole fraction) in the pressure and temperature domains investigated here. Conversely, the glycerol rich phase dissolved CO2 at mole fractions up to 0.13. Negligible swelling of the glycerol rich phase has been observed. Modeling of the phase equilibrium has been performed using the Peng–Robinson equation of state (PR EoS) with classical van der Waals one fluid and EoS/GE based mixing rules (PSRK and MHV2). Satisfactory agreement was observed between modeling results and experimental measurements when PSRK mixing rules are used in combination with UNIQUAC model, although UNIFAC predictive approach gives unsatisfactory representation of experimental behavior

ScCO2/Green Solvents: Biphasic Promising Systems for Cleaner Chemicals Manufacturing

Solvents play a key role in the chemical industry; novel classes ofsolvents such as gas expanded liquids and switchable solvents have attracted greatinterest in recent years as their emergence and utilization in chemical processeshold many promises to develop benign environmental technologies. Thisperspective paper aims at reflecting on the state of the art concerning biphasicscCO2/green solvent systems. Rather than discussing the reactions that have beenperformed in each major type of scCO2/green solvent biphasic system, this paper isstructured instead in terms of the problems or difficulties that these innovativesystems help to solve in processes engineering by taking advantage of the uniqueadvantages of these systems such as greenness, solubility enhancement, andpressure-tunable properties, allowing for overcoming issues concerning mono-phasic systems that the chemical engineer is confronted with when scCO2or agreen solvent are used separately and that have limited their utilization at industrialscales. Among such issues, one can cite (1) difficulties in the solubilization of these compounds, (2) difficult separation ofreactants, products, and catalysts, and (3) loss of the catalyst. These problems arise on one hand from the poor solvent power ofscCO2when used in homogeneous phase and on another hand from the need for a decrease in the usage of distillation as aseparation technique. However, their association in biphasic systems allows for overcoming these problems and provides uniqueopportunities and perspectives to develop future versatile,flexible, and atom economical chemical processes in full accordancewith the principles of green sustainable engineering. The green solvents considered in this perspective paper are water, ionicliquids, biobased ionic liquids, and other green solvents such as glycerol and liquid polymers. Ionic liquids have been consideredin this paper as they have been claimed as“green”because they allow the prevention of volatile emissions; however, some ofthem present toxic issues together with a high environmental impact because of their nonbiodegradability and highmanufacturing costs.1We have then tried to attract special attention to biosourced ionic liquids that may have better toxicologicaland environmental properties and that may hold promise for their future use in chemical processes. This paper presents also thestudies concerning phase equilibrium between scCO2and green solvents where biphasic systems can be obtained, as phasebehavior control is an interesting tool for designing effective catalytic reactions and catalyst-product separation processes. Theunique properties of green solvents that have been proposed as a homogeneous phase in previous studies have prompted us toinclude them in this perspective paper with the aim of interesting the scientific community in testing them in biphasic systemsincluding scCO2. Finally, some reflections about the next steps toward greener processes using scCO2/green solvent biphasicsystems are presented and concern technical and scientific requirements to take full advantage of the capabilities of thesesystems.This perspective paper does not intend to be comprehensive but instead tries to attract attention on recent usages ofthese systems in order to stimulate future advances in the study and development of such systems

Resolution of 2-bromo-arylacetic acid ester by Yarrowia lipolytica lipase in water/supercritical CO2 two-phase systems

A mutated lipase from Yarrowia lipolytica was used in aqueous phase/scCO2 two-phase systems to perform the enzymatic resolution of (R, S) 2-bromophenyl acetic octyl ester. A solution of phosphate salt (1000 mmol/L) was added to buffer the aqueous phase in contact with CO2 and resulting pH values around 6 were measured in a high pressure cell using a solvatochromic probe. Thus, an acceptable conversion rate and good enantioselectivity could be obtained but kinetics were shown to remain slower compared to an aqueous phase/decane two-phase system. Moreover, increasing pressure was shown to further slowdown the kinetics. This was hypothesized to be related to the mechanism of opening of the active site of the lipase which requires interfacial contact with a hydrophobic solvent phase. This condition is suspected not to be met in the case of scCO2 in contact with an aqueous phase because the amount of water dissolved in the supercritical phase diminishes its hydrophobicity

Innovate contactor for CO2 recovery

Innovate contactor for CO2 recover

Modulating biocatalytic activity towards sterically bulky substrates in CO2-expanded bio-based liquids by tuning physicochemical properties

The study of CO2-expanded liquids using a green component such as a bio-based solvent has been recently raised as a new concept for an alternative solvent, and yet been largely unexplored in literature for neither fundamental nor application studies. On the other hand, structural bulkiness of substrates remains one of the main limitations to promote enzymes as an efficient versatile catalytic tool for organic synthesis, especially biocatalysis in non-conventional solvents. Herein, we report a detailed investigation of CO2-expanded bio-based liquids as reaction media for improved biocatalysis of sterically hindered compounds. We have found that CO2 acts as a crucial trigger for various lipases to catalyse transesterification of challenging bulky alcohols in CO2-expanded 2-methyltetrahydrofuran (MeTHF). Furthermore, this study determines physicochemical and transport properties of CO2-expanded MeTHF for the first time, which were then utilized for modulating biocatalytic activity. It was found that lipase activity increased with the accordingly decrease of the dipolarity of CO2-expanded MeTHF, which is tunable by altering the concentration of CO2 in the solvent system

CO2-Expanded alkyl lactates : A physicochemical and molecular modeling study

With the perspective of finding alternative benign media for various applications, this paper presents a study of the physicochemical behavior of some members of the alkyl lactate family when expanded by CO2. Experimental and molecular modeling techniques have been used to determine and/or predict relevant physicochemical properties of these systems such as swelling, Kamlet–Taft parameters {polarity/polarizability (p*) and proticity or hydrogen-bond donator ability (a), dielectric constants and solubility parameters}. To complete the study of these properties, sigma profiles of the three lactates molecules have been obtained by performing quantum mechanical and phase equilibria calculations of CO2/alkyl lactate systems by using the Peng–Robinson equation of stat

Palladium nanoparticles stabilized by novel choline-based ionic liquids in glycerol applied in hydrogenation reactions

Palladium nanoparticles stabilized by choline-based ionic liquids in glycerol were prepared from Pd(II) precursors by simply heating at 80 °C under argon; in this process, the water present in the ionic liquid was found to be responsible for the reduction of Pd(II) into zero-valent palladium species. Palladium nanoparticles were fully characterized in both liquid phase and solid state. The as-prepared metal nanoparticles exhibited remarkable catalytic activity in hydrogenation processes for a significant variety of functional groups (alkenes, alkynes, nitro derivatives, benzaldehydes, aromatic ketones)

Experimental study and modeling of phase equilibrium of the methanol–tripalmitin system: application to palm oil transesterification with supercritical methanol

The phase behavior of the methanol–palm oil system was first experimentally assessed in the temperature range of 363–393 K and pressure range of 1–4 MPa. Second, comparative modeling of the phase equilibrium of the methanol–tripalmitin system was performed using the Peng–Robinson equation of state (PR EoS) with second-order modified Huron–Vidal (MHV2) mixing rules, in combination with the universal functional activity coefficient model (UNIFAC) and the universal quasi-chemical (UNIQUAC) excess Gibbs free-energy model. The agreement between experimental and modeling results was found to be satisfactory when MHV2 mixing rules are used in combination with the UNIQUAC model. Finally, the thermodynamic model was applied to predict fluid phase equilibria of palm oil transesterification with supercritical methanol. From the isochoric method in the temperature range of 373–693 K and the pressure range of 1–16 MPa, the model was found to predict global mixture behavior