Monomer Recovery Research Articles

Chemical recycling of crosslinked poly(methyl methacrylate) and characterization of polymers produced with the recycled monomer

Abatract The chemical recycling of crosslinked poly(methyl methacrylate) wastes, PMMA, used as dental resins, was investigated for recovery and polymerization of the methyl methacrylate monomer, MMA. At temperatures of 400 °C in laboratory and pilot plant installations, PMMA could be depolymerized by pyrolysis to produce more than 90 wt% of liquid, containing more than 98 wt% of MMA. Gas chromatography (GC) and coupled gas chromatography – mass spectrometry (GC–MS) analyses were carried out to characterize the obtained liquid fraction. PMMA powders produced with different quantities of recycled MMA were prepared, after purification of the liquid through distillation, leading to polymer resins with properties that were similar to the ones obtained with virgin commercial MMA, as characterized by particle size, Fourier transform infrared (FT-IR), gel permeation chromatograph (GPC) and scanning electron microscopy (SEM) analyses.

Monomer recovery through advanced pyrolysis of waste high density polyethylene (HDPE)

Cold plasma increases the recovery of ethylene opening up a new route for plastic manufacture avoiding the use of fossil fuels.

Separation of aromatic monomers from oxidatively depolymerized products of lignin by combining Sephadex and silica gel column chromatography

Abstract The conversion of lignin into value-added aromatic monomers has attracted much attention as these monomers can be potentially used to prepare liquid fuel rather than heavy oil by further hydrodeoxygenation. A new process combining Sephadex and silica gel column chromatography was employed to obtain aromatic monomers with higher purity. It was found that pH and polarity of mobile phase were the most important factors affecting the separation effect for Sephadex G-10 and silica gel column chromatography, respectively. When the pH of mobile phase reached 10.5, the ionization of hydroxyl together with carboxyl groups resulted in electrostatic repulsion between the aromatic compounds and Sephadex G-10 gel, which counteracted the adsorption caused by hydrogen bond between aromatics and gel, causing the increase of the separation effect. Under the condition of pH above 10.5, Sephadex gel column chromatography gave 78.1% of purity of aromatic monomers (PAM) and 99.5% of recovery of aromatic monomers (RAM) due to the elimination of non-size exclusion effect. Silica gel column chromatography was further conducted to obtain 99.8% of PAM and 73.9% of RAM. The polar mobile phase was favorable for eluting aromatic monomers, while the non-polar mobile phase was beneficial to remove oligomers and increasing the PAM.

CFD simulations of polymer devolatilization in steam contactors

ABSTRACTRemoval of volatiles and other unwanted products in a polymer mix is a critical step in polymer manufacturing. This process serves many purposes, such as improvement in the physical and chemical properties of the polymer, elimination of odours, recovery of monomers and solvents, and fulfilment of environmental regulations. In this study, the mixture of polymer and solvent, or cement, is mixed with superheated steam which causes the unwanted solvent to evaporate. As the cement droplets lose solvent and dry out, they are ejected as cement ‘crumb’ from the mixing device. This process is modelled using computational fluid dynamics (CFD) to gain insight into the complex phenomena. The model simulates the heat transfer and phase changes associated with cement and steam, via 3D axisymmetric calculations. Using an Eulerian–Lagrangian approach, the superheated steam is modelled as the continuous phase and tracked in an Eulerian frame, while the cement droplets are treated using a Lagrangian tracking method, thus as a whole allowing us to track the particle sizes, temperatures, and solvent content. Furthermore, a parametric study is carried out to analyse the effect of initial polymer temperature on final polymer product. The simulation is carried out with three different initial polymer temperatures and the resulting solvent concentration, and the size of the cement particles between the three cases are compared. By increasing the cement operating temperature, the solvent concentration in the cement crumb is significantly lower, and the final cement crumb sizes shows a slight decrease, which indicates better production performance. Indeed, full 3D CFD calculations, presented to verify the axisymmetric assumption, show differences in the particle statistics, which could have implications for design considerations. Such studies can provide further insights into control parameters that can potentially enhance the efficiency of such a manufacturing process.

Ionic liquids/ZnO nanoparticles as recyclable catalyst for polycarbonate depolymerization

A useful protocol for waste bis-phenol A-polycarbonates (BPA-PC) chemical recycling is proposed based on a bifunctional acid/basic catalyst composed by nanostructured zinc oxide and tetrabutylammonium chloride (ZnO-NPs/NBu4Cl) in quality of Lewis acid and base, respectively. Retro-polymerization reaction proved to be of general application for several nucleophiles, including water, alcohols, amines, polyols, aminols and polyamines, leading to the complete recovery of BPA monomer and enabling the PC polymer to function as a green carbonylating agent (green phosgene alternative) for preparing carbonates, urethanes and ureas. A complete depolymerization can be obtained in seven hours at 100°C and ZnO nanocatalyst can be recycled several times without sensible loss of activity. Remarkably, when polycarbonate is reacted with glycerol, it is possible to realize in a single process the conversion of two industrial wastes (BPA-PC and glycerol) into two valuable chemicals like BPA monomer and glycerol carbonate (the latter being a useful industrial solvent and fuel additive).

Recovery and Utilization of Lignin Monomers as Part of the Biorefinery Approach

Lignin is a substantial component of lignocellulosic biomass but is under-utilized relative to the cellulose and hemicellulose components. Historically, lignin has been burned as a source of process heat, but this heat is usually in excess of the process energy demands. Current models indicate that development of an economically competitive biorefinery system requires adding value to lignin beyond process heat. This addition of value, also known as lignin valorization, requires economically viable processes for separating the lignin from the other biomass components, depolymerizing the lignin into monomeric subunits, and then upgrading these monomers to a value-added product. The fact that lignin’s biological role is to provide biomass with structural integrity means that this heteropolymer can be difficult to depolymerize. However, there are chemical and biological routes to upgrade lignin from its native form to compounds of industrial value. Here we review the historical background and current technology of (thermo) chemical depolymerization of lignin; the natural ability of microbial enzymes and pathways to utilize lignin, the current prospecting work to find novel microbial routes to lignin degradation, and some applications of these microbial enzymes and pathways; and the current chemical and biological technologies to upgrade lignin-derived monomers.

Depolymerization of Waste PET with Phosphoric Acid–Modified Silica Gel Under Microwave Irradiation

Chemical recycling of waste poly(ethylene terephthalate) (PET) using phosphoric acid–modified silica gel as a solid catalyst is reported. Advantageously, microwave irradiation was used to progress the depolymerization of PET. In this study, depolymerization of PET with a small amount of water is suggested as a suitable method. The depolymerized product, terephthalic acid was obtained and assigned by 1H NMR and FT-IR spectroscopy. Finally, over 90 % conversion to terephthalic acid was achieved when waste plastic bottles were treated with the method. This results confirm the importance of the microwave power technique as a promising recycling method for plastic bottles made from PET, resulting in monomer recovery in addition to substantial energy saving.

Pyrolysis and hydrolysis behaviors during steam pyrolysis of polyimide

Kapton film, which is a typical aromatic polyimide (PI) film, exhibits excellent thermal stability and flexibility. Therefore, it is used widely for flexible printed circuit boards in combination with other resins and metals. However, this makes it difficult to recycle it. In this work, we focused on the steam pyrolysis technique, which is a method of depolymerizing condensation polymers without solvents, catalysts, or high pressure, as a way of overcoming this issue. The steam pyrolysis of Kapton film was carried out using a thermogravimetric (TG) analyzer equipped with a steam generator. In addition, the TG results were evaluated further using model fitting techniques. It was found that steam enhanced the hydrolysis of the imide ring, which occurred on the surface of the PI film. The hydrolysis selectivity was as high as 89% at 528°C. However, steam did not significantly enhance the Kapton decomposition rate, owing to rapid carbonization, which took place because of the simultaneous occurrence of pyrolysis. Thus, the obtained results implied that high-yield monomer recovery can be achieved by lowering the temperature to prevent pyrolysis and by improving the steam contact efficiency to enhance hydrolysis within the material.

Polycarbonate Waste Management using Glycerol

Recycling method of polycarbonate (PC) plastic using glycerol is proposed as a novel green method. Glycerol was found as an efficient reagent for chemical recycling of PC and gives upto 98% monomer recovery, which is compatible with any of existing chemical recycling methods. Recycling involves digestion followed by glycerolysis reaction of PC. The various products thus obtained are Bisphenol A (BPA); mono glycerol ether of BPA and di glycerol ether of BPA. Addition of urea improves the yield toward more alkoxylated products, controls the dehydration of glycerol to acrolein at reaction temperature and improves the application of glycerol as a reagent. Temperature programmed FTIR spectra study provides a mechanistic picture of the proposed chemical recycling. Glycerol carbonate and glycerol urethane was found as the important reaction intermediates. The process works well with industrial grade glycerol to improve the economy in this process. Furthermore, a working model of the recycling of post-user optical disc is also proposes.

Near-Complete Recovery of Sugar Monomers from Cellulose and Lignocellulosic Biomass via a Two-Step Process Combining Mechanochemical Hydrolysis and Dilute Acid Hydrolysis

This study reports a two-step hydrolysis process for achieving near-complete recovery of sugar monomers from crystalline cellulose or lignocellulosic biomass. The first step is mechanochemical hydrolysis of the acid-impregnated sample in the solid state via ball milling at room temperature. It was found that mechanochemical hydrolysis not only effectively breaks the hydrogen-bonding network within the crystalline cellulose but also drives the acid-catalyzed hydrolysis reactions to form water-soluble products, mainly consisting of glucose and its oligomers, with a degree of polymerization up to 15. However, mechanochemical hydrolysis appears to be incapable of further hydrolyzing these oligomers into monomers and, hence, is not suitable for producing sugar monomers directly. Therefore, the second step is dilute acid hydrolysis of the mechanochemically hydrolyzed sample in the aqueous phase under low-severity conditions, i.e., at a low acid concentration of 0.25 wt % and a low temperature of 150 °C. The sec...

Styrene recovery from polystyrene by flash pyrolysis in a conical spouted bed reactor

Continuous pyrolysis of polystyrene has been studied in a conical spouted bed reactor with the main aim of enhancing styrene monomer recovery. Thermal degradation in a thermogravimetric analyser was conducted as a preliminary study in order to apply this information in the pyrolysis in the conical spouted bed reactor. The effects of temperature and gas flow rate in the conical spouted bed reactor on product yield and composition have been determined in the 450–600°C range by using a spouting velocity from 1.25 to 3.5 times the minimum one. Styrene yield is strongly influenced by both temperature and gas flow rate, with the maximum yield being 70.6wt% at 500°C and a gas velocity twice the minimum one.

Head to Head Comparison of the Formulation and Stability of Concentrated Solutions of HESylated versus PEGylated Anakinra

Although PEGylation of biologics is currently the gold standard for half-life extension, the technology has a number of limitations, most importantly the non-biodegradability of PEG and the extremely high viscosity at high concentrations. HESylation is a promising alternative based on coupling to the biodegradable polymer hydroxyethyl starch (HES). In this study, we are comparing HESylation with PEGylation regarding the effect on the protein's physicochemical properties, as well as on formulation at high concentrations, where protein stability and viscosity can be compromised. For this purpose, the model protein anakinra is coupled to HES or PEG by reductive amination. Results show that coupling of HES or PEG had practically no effect on the protein's secondary structure, and that it reduced protein affinity by one order of magnitude, with HESylated anakinra more affine than the PEGylated protein. The viscosity of HESylated anakinra at protein concentrations up to 75 mg/mL was approximately 40% lower than that of PEG-anakinra. Both conjugates increased the apparent melting temperature of anakinra in concentrated solutions. Finally, HESylated anakinra was superior to PEG-anakinra regarding monomer recovery after 8 weeks of storage at 40°C. These results show that HESylating anakinra offers formulation advantages compared with PEGylation, especially for concentrated protein solutions.

TG–FTIR study on thermal degradation mechanism of PTFE under nitrogen atmosphere and in air. Influence of the grain size

The influence of the formed polytetrafluoroethylene (PTFE) grain size on the thermal degradation mechanism under nitrogen atmosphere and in air was studied by the TG–FTIR technique. The possibility of the monomer recovering from the PTFE waste was followed since the fluorinated polymers are rather expensive if their obtaining and the monomer synthesis are taken into account. The characteristic amounts from TG–DTG–DTA afforded some information on the influence of the formed PTFE grain size on the degradation mechanism in air and in nitrogen that is similar to the PTFE from synthesis degradation mechanism. The TG–FTIR analysis of the gas species evolved by thermal degradation of the samples provides information on the monomer (C2F4) recovery from the waste resulting in the machining of the formed PTFE. Our results suggest optimal conditions for an advantageous recovery of monomer from the formed PTFE waste: heating rate of 10K/min, inert atmosphere, and a higher grain size of the formed PTFE.

Ethanol production from rice straw using thermotolerant Kluyveromyces sp. IIPE453

Present paper describes a process development for fractionation of holocellulose in rice straw into its monomeric sugars employing acid hydrolysis followed by enzymatic saccharification. Rice straw has been hydrolyzed at 140 °C and 0.6 % v/v dilute sulfuric acid with 90 min holding time for maximum recovery of pentose monomer (12.52 g xylose/100 g biomass). Pentose stream was used for yeast cell biomass generation. Commercial cellulase resulted in 79 ± 0.05 % saccharification efficiency with acid-hydrolyzed biomass. Fermentation of saccharified broth using thermophilic yeast Kluyveromyces sp. IIPE453 (MTCC 5314) with cell recycle produced ethanol with an overall yield and productivity of 93.5 ± 0.05 % and 0.90 ± 0.2 g/L/h, respectively, and with negligible residual sugar in fermentation broth. Lignin-rich residual biomass had a high gross calorific value and could be used as a source of clean gaseous fuel.

Melt Phase Polymerization of Racemic Lactide to High‐Performance Poly(Lactic Acid)

AbstractA process for the production of poly(lactic acid) with a melting point of > 150 °C from racemic lactide was developed. Only process steps that are usable in an industrial process were included to ensure an easy transfer to a commercial scale. A stereoselective catalyst system for lactide melt phase polymerization comprising of an Al‐salen initiator, a hydroxyl cocatalyst and an acidic quenching additive was developed. Monomer recovery aspects, temperature variation and different catalyst concentrations were evaluated to allow for a high yield process which can be transferred to a technical scale.

MICROBIAL AND ENZYMATIC DEGRADATION OF POLYMERS: A REVIEW

Polymer recycling has been one of the most important trend in the petrochemical area. Among different technologies, biotechnological (enzymatic and/or microbial) degradation of polymers for the recovery of monomers and oligomers is environmentally-friendly and meet some green chemistry principles. In this work, conditions for the biotechnological degradation of some industrially-relevant polymers (e.g. poly(ethylene terephthalate) and polyethylene) were revised, and the main biocatalysts were identified. In most cases, biodegradation mechanisms are still unclear, thus being necessary more studies to unravel these promising bioprocesses. Polymer biodegradation studies also present considerable importance for other fields, including biomedical and agricultural.

Influence of Hydroxypropyl‐Beta‐Cyclodextrin on the Stability of Dilute and Highly Concentrated Immunoglobulin G Formulations

Antibody solutions usually require the addition of suitable excipients-such as surfactants and polyols-to overcome stability problems under mechanical or thermal stress. Because cyclodextrins exhibit weak surface activity (similar to surfactants) and a sugar-based structure (like polyols), they can, in principle, stabilize proteins by a double mechanism. Accordingly, the stabilizing potential of increasing concentrations of hydroxypropyl-beta-cyclodextrin (HPβCD) was investigated for two antibodies in dilute (1.8 mg/mL) and highly concentrated (100 mg/mL) solutions and compared with standard polysorbate 80 or sucrose formulations as controls. Formulations were stressed by stirring or elevated temperature, and stability was evaluated by monomer recovery using size-exclusion chromatography, turbidity, and light obscuration measurements. Results show that increasing HPβCD concentrations up to 100 mM lead to a gradual protein stabilization during stirring-irrespective of the protein concentration and unaffected by an increased viscosity. Storage at 50°C induced a decrease of monomer recovery with increasing HPβCD concentrations, which was mirrored in differential scanning calorimetry measurements, where an increasing amount of HPβCD leads to a significant reduction of the protein melting temperature. In the light of previous results on protein stabilization by HPβCD, it is suggested that the stabilizing effects of HPβCD must be tested on a case-by-case basis.

Pyrolysis reactions of coniferyl alcohol as a model of the primary structure formed during lignin pyrolysis

It has been suggested that cinnamyl alcohol-type structures are formed during lignin primary pyrolysis using model dimers. In this article, the pyrolysis reactions of trans-coniferyl alcohol (CA) bearing a guaiacyl moiety were studied under N2 at temperatures in the range of 200–350̊C, with particular emphasis on the evaporation/degradation processes. Some (less than 15%) of the CA evaporated without undergoing any degradation reactions, whereas large portions of the CA were converted to polymerization products together with monomers (up to ∼15% in total) with various side-chains. The cis-isomer of CA and 4-vinylguaiacol with a C2 side-chain were also identified. Methylation of the phenolic OH group of CA substantially reduced the formation of polymerization products, whereas the influence of the methylation on the side-chain-converted monomers was limited. Since the methylated CA was not effective for quinine methide formation, quinine methide and radical pathways were indicated as more important reaction mechanisms for the polymerization and side-chain-conversion processes, respectively. These results suggest that CA, if it was formed through pyrolytic cleavage of lignin β-ether linkages, tended to be degraded before it could be recovered through evaporation. Furthermore, the recovery of different monomers suggested the process was greatly dependent on the relative evaporation/degradation efficiencies.

The effect of freeze-drying parameters and formulation composition on IgG stability during drying

The objective of this study was to explore the effects of freeze-drying parameters and formulation composition on polyclonal IgG stability during processing. Samples were freeze-dried with different primary drying pressures and secondary drying heating rates. After drying, changes in IgG in vitro binding activity, monomer recovery, average particle size, and polydispersity were studied from the rehydrated lyophilizates. Significant trends were not observed in binding activities or monomer recoveries, but increases in particle size and polydispersity were observed when using lower primary drying pressure. This effect could no longer be observed when sodium phosphate buffer was removed from the formulation. Altering the secondary drying heating rates did not result in any measurable changes in protein stability.

Solute recovery from ionic liquids: A conceptual design study for recovery of styrene monomer from [4-mebupy][BF4

Extractive distillation using ionic liquids (ILs) is a promising technology to separate the close-boiling mixture ethylbenzene/styrene. A proper solvent regeneration is crucial to obtain a technical and economic feasible process. In this work, several regeneration technologies were studied to recover styrene from the IL [4-mebupy][BF4] using Aspen Plus. Stripping with a hot gas (N2 or ethylbenzene), supercritical CO2 extraction, distillation by adding a co-solvent, and evaporation were investigated. It was found that the IL that was fed as solvent to the extractive distillation column should have a purity of at least 99.6wt% to maintain the purities of the top and bottom products from the extractive distillation column. This purity could not be obtained with an evaporator using mild conditions (T=130°C, Tcondenser≥20°C). From the process models and the economic evaluation for a typical production capacity of 500,000mta, the conclusion can be drawn that evaporation using very low pressures (P<10mbar) and stripping with ethylbenzene are the most promising technologies to recover styrene monomer from the IL [4-mebupy][BF4].