Integrating experimental and computational approaches for deep eutectic solvent-catalyzed glycolysis of post-consumer polyethylene terephthalate

To achieve a sustainable and circular economy, developing effective plastic recycling methods is essential. Despite advances in the chemical recycling of plastic waste, modern industries require highly efficient and sustainable solutions to address environmental problems. In this study, we propose an efficient glycolysis strategy for post-consumer polyethylene terephthalate (PET) using deep eutectic solvents (DESs) to produce bis(2-hydroxyethyl) terephthalate (BHET) with high selectivity. Choline chloride (ChCl)- and urea-based DESs were synthesized using various metal salts and were tested for the glycolysis of PET waste; ChCl-Zn(OAc)2 exhibited the best performance. The DES-containing solvent system afforded a complete PET conversion, producing BHET at a high yield (91.6%) under optimal reaction conditions. The degradation mechanism of PET and its interaction with DESs were systematically investigated using density functional theory-based calculations. Furthermore, an intuitive machine learning model was developed to predict the PET conversion and BHET selectivity for different DES compositions. Our findings demonstrate that the DES-catalyzed glycolysis of post-consumer PET could enable the development of a sustainable chemical recycling process, providing insights to identify the new design of DESs for plastic decomposition.

Chemical upcycling of PVC-containing plastic wastes by thermal degradation and catalysis in a chlorine-rich environment

Chlorine (Cl)-containing chemicals, including hydrogen chloride, generated during thermal degradation of polyvinyl chloride (PVC) and corresponding mixture impede the chemical recycling of PVC-containing plastic wastes. While upgrading plastic-derived vapors, the presence of Cl-containing chemicals may deactivate the catalysts. Accordingly, herein, catalytic upgrading of pyrolysis vapor prepared from a mixture of PVC and polyolefins is performed using a fixed-bed reactor comprising zeolites. Among the H-forms of zeolites (namely, ZSM-5, Y, β, and chabazite) used in this study, a higher yield of gas products composed of hydrocarbons with lower carbon numbers is obtained using H-ZSM-5, thus indicating further decomposition of the pyrolysis vapor to C1-C4 hydrocarbons on it. Although the formation of aromatic compounds is better on H-ZSM-5, product distributions can be adjusted by further modifying the acidic properties via the alteration of the Si/Al molar ratio, and maximum yields of C1-C4 compounds (60.8%) and olefins (64.7%) are achieved using a Si/Al molar ratio of 50. Additionally, metal ion exchange on H-ZSM-5 is conducted, and upgrading of PVC-containing waste-derived vapor to aromatic chemicals and small hydrocarbon molecules was successfully performed using Co-substituted H-ZSM-5. It reveals that the highest yield of gas products on 1.74 wt% cobalt (Co)-substituted H-ZSM-5 is acquired via the selection of an appropriate metal and metal ion concentration adjustment. Nevertheless, introduction of excess Co into the H-ZSM-5 surface decreases the cracking activity, thereby implying that highly distributed Co is required to achieve excellent cracking activity. The addition of Co also adjusted the acid types of H-ZSM-5, and more Lewis acid sites compared to Brønsted acid sites selectively produced olefins and naphthenes over paraffins and aromatics. The proposed approach can be a feasible process to produce valuable petroleum-replacing chemicals from Cl-containing mixed plastic wastes, contributing to the closed loops for upcycling plastic wastes.

Enhancing polyethylene terephthalate conversion through efficient microwave-assisted deep eutectic solvent-catalyzed glycolysis

Chemical recycling of plastics is a promising approach for effectively depolymerizing plastic waste into its constituent monomers, thereby contributing to the realization of a sustainable circular economy. Glycolysis, which converts polyethylene terephthalate (PET) into the monomer bis(2-hydroxyethyl) terephthalate (BHET), has emerged as a cost-effective and commercially viable chemical recycling process. However, glycolysis requires long reaction times and high energy consumption, limiting its industrialization. In this study, we develop an energy-efficient microwave-assisted deep eutectic solvent-catalyzed glycolysis method to degrade PET effectively and rapidly, resulting in a high BHET yield. This combined approach enables the quantitative degradation of PET within 9 min, achieving a high BHET yield of approximately 99% under optimal reaction conditions. Furthermore, the proposed approach has a low specific energy consumption (45 kJ/g) and minimizes waste generation. The thermal behavior of PET and its degradation mechanism are systematically investigated using scanning electron microscopy and density functional theory-based calculations. The results obtained suggest that the proposed straightforward, swift, and energy-efficient strategy has the potential to offer a sustainable solution to plastic waste management challenges and expedite the industrialization of chemical recycling.

Catalytic conversion of waste corrugated cardboard into lactic acid using lanthanide triflates

The efficient strategy for waste conversion and resource recovery is of great interest in the sustainable bioeconomy context. This work reports on the catalytic upcycling of waste corrugated cardboard (WCC) into lactic acid using lanthanide triflates catalysts. WCC, a primary contributor to municipal solid wastes, has been viewed as a feedstock for producing a wide range of renewable products. Hydrothermal conversion of WCC was carried out in the presence of several lanthanide triflates. The reaction with erbium(III) triflate (Er(OTf)₃) and ytterbium(III) triflate (Yb(OTf)₃) resulted in high lactic acid yields, 65.5 and 64.3 mol%, respectively. In addition, various monomeric phenols were readily obtained as a co-product stream, opening up opportunities in waste management and resource recovery. Finally, technoeconomic analysis was conducted based on the experimental results, which suggests a significant economic benefit of chemocatalytic upcycling of WCC into lactic acid.

Optimized Immobilization Strategy for Dirhodium(II) Carboxylate Catalysts for C-H Functionalization and Their Implementation in a Packed Bed Flow Reactor

Herein we demonstrate a packed bed flow reactor capable of achieving highly regio- and stereoselective C-H functionalization reactions using a newly developed Rh₂ (S-2-Cl-5-CF₃ TPCP)₄ catalyst. To optimize the immobilized dirhodium catalyst employed in the flow reactor, we systematically study both (i) the effects of ligand immobilization position, demonstrating the critical factor that the catalyst-support attachment location can have on the catalyst performance, and (ii) silica support mesopore length, demonstrating that decreasing diffusional limitations leads to increased accessibility of the active site and higher catalyst turnover frequency. We employ the immobilized dirhodium catalyst in a simple packed bed flow reactor achieving comparable yields and levels of enantioselectivity to the homogeneous catalyst employed in batch and maintain this performance over ten catalyst recycles.

Silica-Supported Sterically Hindered Amines for CO2 Capture

Most studies exploring the capture of CO₂ on solid-supported amines have focused on unhindered amines or alkylimine polymers. It has been observed in extensive solution studies that another class of amines, namely sterically hindered amines, can exhibit enhanced CO₂ capacity when compared to their unhindered counterparts. In contrast to solution studies, there has been limited research conducted on sterically hindered amines on solid supports. In this work, one hindered primary amine and two hindered secondary amines are grafted onto mesoporous silica at similar amine coverages, and their adsorption performances are investigated through fixed bed breakthrough experiments and thermogravimetric analysis. Furthermore, chemisorbed CO₂ species formed on the sorbents under dry and humid conditions are elucidated using in situ Fourier-transform infrared spectroscopy. Ammonium bicarbonate formation and enhancement of CO₂ adsorption capacity is observed for all supported hindered amines under humid conditions. Our experiments in this study also suggest that chemisorbed CO₂ species formed on supported hindered amines are weakly bound, which may lead to reduced energy costs associated with regeneration if such materials were deployed in a practical separation process. However, overall CO₂ uptake capacities of the solid supported hindered amines are modest compared to their solution counterparts. The oxidative and thermal stabilities of the supported hindered amine sorbents are also assessed to give insight into their operational lifetimes.

Poly(ethylenimine)-Functionalized Monolithic Alumina Honeycomb Adsorbents for CO2 Capture from Air

The development of practical and effective gas-solid contactors is an important area in the development of CO2 capture technologies. Target CO2 capture applications, such as postcombustion carbon capture and sequestration (CCS) from power plant flue gases or CO2 extraction directly from ambient air (DAC), require high flow rates of gas to be processed at low cost. Extruded monolithic honeycomb structures, such as those employed in the catalytic converters of automobiles, have excellent potential as structured contactors for CO2 adsorption applications because of the low pressure drop imposed on fluid moving through the straight channels of such structures. Here, we report the impregnation of poly(ethylenimine) (PEI), an effective aminopolymer reported commonly for CO2 separation, into extruded monolithic alumina to form structured CO2 sorbents. These structured sorbents are first prepared on a small scale, characterized thoroughly, and compared with powder sorbents with a similar composition. Despite consistent differences observed in the filling of mesopores with PEI between the monolithic and powder sorbents, their performance in CO2 adsorption is similar across a range of PEI contents. A larger monolithic cylinder (1 inch diameter, 4 inch length) is evaluated under conditions closer to those that might be used in large-scale applications and shows a similar performance to the smaller monoliths and powders tested initially. This larger structure is evaluated over five cycles of CO2 adsorption and steam desorption and demonstrates a volumetric capacity of 350 molCO2  m-3monolith and an equilibration time of 350 min under a 0.4 m s(-1) linear flow velocity through the monolith channels using 400 ppm CO2 in N2 as the adsorption gas at 30 °C. This volumetric capacity surpasses that of a similar technology considered previously, which suggested that CO2 could be removed from air at an operating cost as low as $100 per ton.

Probing Intramolecular versus Intermolecular CO2 Adsorption on Amine-Grafted SBA-15

A mesoporous silica SBA-15 is modified with an array of amine-containing organosilanes including (i) propylamine, SiCH2CH2CH2NH2 (MONO), (ii) propylethylenediamine, SiCH2CH2CH2NHCH2CH2NH2 (DI), (iii) propyldiethylenetriamine, SiCH2CH2CH2NHCH2CH2NHCH2CH2NH2 (TRI), and (iv) propyltriethylenetetramine, SiCH2CH2CH2NHCH2CH2N(CH2CH2NH2)2 (TREN) and the low loading silane adsorbents (∼0.45 mmol silane/g) are evaluated for their CO2 adsorption properties, with a focus on gaining insight into the propensity for intramolecular vs intermolecular CO2 adsorption. Adsorption isotherms at low CO2 coverages are measured while simultaneously recording the heat evolved via a Tian-Calvet calorimeter. The results are compared on a silane molecule efficiency basis (mol CO2 adsorbed/mol silane) to assess the potential for intramolecular CO2 adsorption, employing two amine groups in a single silane molecule. As the number of amines in the silane molecule increases (MONO < DI < TREN ∼ TRI), the silane molecule efficiency is enhanced owing to the ability to intramolecularly capture CO2. Analysis of the CO2 uptake for samples with the surface silanols removed by capping demonstrates that cooperative uptake due to amine-CO2-silanol interactions is also possible over these adsorbents and is the primary mode of sorption for the MONO material at the studied low silane loading. As the propensity for intramolecular CO2 capture increases due to the presence of multiple amines in a single silane molecule (MONO < DI < TREN ∼ TRI), the measured heat of adsorption also increases. This study of various amine-containing silanes at low coverage is the first to provide significant, direct evidence for intramolecular CO2 capture in a single silane molecule. Furthermore, it provides evidence for the relative heats of adsorption for physisorption on a silanol laden surface (ca. 37 kJ/mol), a silanol-capped surface (ca. 25 kJ/mol), via amine-CO2-silanol interactions (ca. 46 kJ/mol), and via amine-CO2-amine interactions at low surface coverages (ca. 65 kJ/mol).

Probing the Role of Zr Addition versus Textural Properties in Enhancement of CO₂ Adsorption Performance in Silica/PEI Composite Sorbents

Polymeric amines such as poly(ethylenimine) (PEI) supported on mesoporous oxides are promising candidate adsorbents for CO2 capture processes. An important aspect to the design and optimization of these materials is a fundamental understanding of how the properties of the oxide support such as pore structure, particle morphology, and surface properties affect the efficiency of the guest polymer in its interactions with CO2. Previously, the efficiency of impregnated PEI to adsorb CO2 was shown to increase upon the addition of Zr as a surface modifier in SBA-15. However, the efficacy of this method to tune the adsorption performance has not been explored in materials of differing textural and morphological nature. Here, these issues are directly addressed via the preparation of an array of SBA-15 support materials with varying textural and morphological properties, as well as varying content of zirconium doped into the material. Zirconium is incorporated into the SBA-15 either during the synthesis of the SBA-15, or postsynthetically via deposition of Zr species onto pure-silica SBA-15. The method of Zr incorporation alters the textural and morphological properties of the parent SBA-15 in different ways. Importantly, the CO2 capacity of SBA-15 impregnated with PEI increases by a maximum of ∼60% with the quantity of doped Zr for a "standard" SBA-15 containing significant microporosity, while no increase in the CO2 capacity is observed upon Zr incorporation for an SBA-15 with reduced microporosity and a larger pore size, pore volume, and particle size. Finally, adsorbents supported on SBA-15 with controlled particle morphology show only modest increases in CO2 capacity upon inclusion of Zr to the silica framework. The data demonstrate that the textural and morphological properties of the support have a more significant impact on the ability of PEI to capture CO2 than the support surface composition.

Comparison between Transuncal Approach and Upper Vertebral Transcorporeal Approach for Unilateral Cervical Radiculopathy - A Preliminary Report

OBJECTIVE

The surgical treatments for unilateral cervical radiculopathy have been performed by either the anterior or posterior approach. The anterior approach has usually been used more than the posterior approach. The authors compared the results of newly advanced upper vertebral transcorporeal (UVTC) approach with those of the original transuncal (TU) approach in the anterior approach.

METHODS

The anterior cervical microforaminotomy was performed for 60 patients (male:female=40:20) from June, 2000 to October, 2003. 40 patients were treated by the TU approach while 20 patients were operated on by the new UVTC approach. The authors analyzed postoperative changes of disc height, the spinal instability, the average length of hospital stay, the degree of patients' satisfaction and complications from each approach. The mean follow-up period was 9.5 months.

RESULTS

In the TU approach, postoperative intervertebral disc height was decreased from 7.1+/-0.65 mm to 6.2+/-0.61 mm. In the UVTC approach, postoperative intervertebral disc height was decreased from 6.6+/-0.43 mm to 6.3+/-0.41 mm. The average length of hospital stay was 5.2 days for the TU approach and 3.4 days for the UVTC approach. In the TU approach, 28 patients experienced excellent results, 11 patients experienced good results, one patient who experienced a fair result was operated by anterior cervical fusion because of a recurrent herniated disc. In the UVTC approach, 16 patients had excellent results and four patients experienced good results.

CONCLUSIONS

This comparative study demonstrates that the UVTC approach is a better surgical technique than the TU approach considering the preservation of disc height, spinal stability, length of hospital stay, degree of satisfaction and complications.

U snRNP assembly in yeast involves the La protein

In all eukaryotic nuclei, the La autoantigen binds nascent RNA polymerase III transcripts, stabilizing these RNAs against exonucleases. Here we report that the La protein also functions in the assembly of certain RNA polymerase II-transcribed RNAs into RNPs. A mutation in a core protein of the spliceosomal snRNPs, Smd1p, causes yeast cells to require the La protein Lhp1p for growth at low temperatures. Precursors to U1, U2, U4 and U5 RNAs are bound by Lhp1p in both wild-type and mutant cells. At the permissive temperature, smd1-1 cells contain higher levels of stable U1 and U5 snRNPs when Lhp1p is present. At low temperatures, Lhp1p becomes essential for the accumulation of U4/U6 snRNPs and for cell viability. When U4 RNA is added to extracts, the pre-U4 RNA, but not the mature RNA, is bound by Smd1p. These results suggest that, by stabilizing a 3'-extended form of U4 RNA, Lhp1p facilitates efficient Sm protein binding, thus assisting formation of the U4/U6 snRNP.

The La protein in Schizosaccharomyces pombe: a conserved yet dispensable phosphoprotein that functions in tRNA maturation

Most RNA polymerase III transcripts are bound immediately after synthesis by an abundant nuclear phosphoprotein known as the La autoantigen. Experiments performed in the budding yeast Saccharomyces cerevisiae have revealed that binding of the La protein to tRNA precursors is required for the endonucleolytic maturation of the 3' terminus of many tRNAs. In the absence of this protein, the 3' ends of these tRNAs are trimmed by exonucleases (Yoo CJ, Wolin SL, 1997, Cell 89:393-402). Here we report the characterization of the La protein in the fission yeast Schizosaccharomyces pombe. As was described for budding yeast, S. pombe cells lacking the La protein are viable and exhibit alterations in the pathway of pre-tRNA maturation. Introduction of either the human, S. cerevisiae, or S. pombe La protein into these cells restores the detected pattern of tRNA processing intermediates to that of wild-type cells. By performing immunoprecipitations from cells that were metabolically labeled with 32P-orthophosphate, we demonstrate that the S. pombe and S. cerevisiae La proteins, like the human La protein, are phosphorylated in vivo. Thus, although the La protein is dispensable for growth in these yeasts, both the structure of the protein and its function in pre-tRNA maturation have been highly conserved throughout evolution.

The yeast La protein is required for the 3' endonucleolytic cleavage that matures tRNA precursors

Although the La autoantigen binds to the 3' ends of all nascent polymerase III transcripts, its function in vivo has long been unclear. Although S. cerevisiae cells lacking the La protein homolog Lhp1p are viable, cells containing a mutation that disrupts the anticodon stem of tRNA(Ser)CGA require Lhp1p for growth. We demonstrate that for the wild-type pre-tRNA(Ser)CGA and other pre-tRNAs, Lhp1p is required for the normal endonucleolytic removal of the 3' trailer sequence. In cells lacking Lhp1p, the 3' trailer is removed by exonuclease(s). Although maturation of the mutant pre-tRNA(Ser)CGA requires Lhp1p, introduction of a second mutation that restores base pairing eliminates the requirement. We propose that binding by Lhp1p stabilizes pre-tRNAs in conformations that allow the 3' endonucleolytic cleavage to occur.

La proteins from Drosophila melanogaster and Saccharomyces cerevisiae: a yeast homolog of the La autoantigen is dispensable for growth

The human autoantigen La is a 50-kDa protein which binds to the 3' termini of virtually all nascent polymerase III transcripts. Experiments with mammalian transcription extracts have led to the proposal that the La protein is required for multiple rounds of transcription by RNA polymerase III (E. Gottlieb and J. A. Steitz, EMBO J. 8:851-861, 1989; R. J. Maraia, D. J. Kenan, and J. D. Keene, Mol. Cell. Biol. 14:2147-2158, 1994). Although La protein homologs have been identified in a variety of vertebrate species, the protein has not been identified in invertebrates. In order to begin a genetic analysis of La protein function, we have characterized homologs of the La protein in the fruit fly Drosophila melanogaster and the yeast Saccharomyces cerevisiae. We show that both the Drosophila and yeast La proteins are bound to precursors of polymerase III RNAs in vivo. The Drosophila and yeast proteins resemble the human La protein in their biochemical properties, as both proteins can be partially purified from cells by a procedure previously devised to purify the human protein. Similarly to vertebrate La proteins, the Drosophila and yeast homologs preferentially bind RNAs that terminate with a 3' hydroxyl. Despite the fact that the La protein is conserved between humans and Saccharomyces cerevisiae, yeast cells containing a null allele of the gene encoding the La protein are viable, suggesting that another protein(s) plays a functionally redundant role.

The cytokines, interleukin-1 beta, interleukin-6 and interferon-gamma upregulate the expression of intercellular adhesion molecule-1(ICAM-1) in rat thyroid cell line, FRTL-5

OBJECTIVES

Recently, the role of adhesion molecules in the immune system has been recognized. ICAM-1 plays an important role in a variety of inflammatory and immune mediated mechanisms, including recruitment and targeting of lymphocytes. We observed the effects of cytokines on expression of rat homologue of human intercellular adhesion molecule-1 in rat thyroid cell line, FRTL-5.

METHODS

We have examined expression of rat intercellular adhesion molecule-1 (ICAM-1, CD54), a homologue of human intercellular adhesion molecule-1, by immunocytochemistry (immunoperoxidase staining) in the continuously growing rat thyroid cell line, FRTL-5.

RESULTS

Low level of ICAM-1 expression was noted at basal condition and this basal expression was not influenced by thyrotropin. Expression in rat homologue of ICAM-1 is increased by interferon-gamma, interleukin-1 beta and interleukin-6 with a dose dependent manner.

CONCLUSION

These results show that a pure line of rat thyroid cells can express an ICAM-1 homologue and this is directly enhanced by cytokines such as rat interferon-gamma, human interleukin-1 beta and interleukin-6. Expression of this homologue is partially responsible for lymphocyte adhesion to thyroid cells, which is likely to be a major event in T cell recognition of thyroid antigens in autoimmune thyroiditis.

Flow cytometric analysis of DNA ploidy in childhood rhabdomyosarcoma

Flow cytometric DNA analysis was performed on 17 rhabdomyosarcomas in conjunction with a histopathological review to determine the usefulness of this technique to predict the biologic behavior of the tumor and to establish the characteristic ploidy pattern of rhabdomyosarcoma compared to other small round cell tumors occurring in childhood. Aneuploidy including near-tetraploidy is the most common ploidy pattern encountered, followed by multiploidy and diploidy, and the presence of multiploidy in this tumor is useful for differentiating rhabdomyosarcoma from other kinds of small round cell tumors in which there are rare previous reports on occurrence of multiploidy. Even though there is no significant correlation between ploidy pattern and histologic type of rhabdomyosarcoma, patients with multiploid tumors or aneuploid tumors with a DNA index of 1.10-1.80 tend to have a high risk of treatment failure. Therefore, the ploidy pattern seems to be useful for predicting the patient's survival in concert with other variables.