Magnetite nanoparticles catalyzed preparation of isatin ketals under solvent free conditions promoted by ultrasound irradiation

Fe₃O₄ magnetic nanoparticles (MNPs) were synthesized via chemical precipitation method and used as an efficient and recyclable catalyst in ketalization of isatins. It was found that a solvent free process, under irradiation of sonic waves provides good to excellent yields of the desired ketals.     

Reconsideration of solvent effects calculated by semiempirical quantum chemical methods

AM1 and PM3 semiempirical calculations are reported for the solvent effects on the tautomeric equilibria of 2-pyridone/2-hydroxypyridine and 4-pyridone/4-hydroxypyridine in the gas phase and solution. The solvent effects on the tautomeric equilibria were investigated by self-consistent reaction field (SCRF) theory implemented in the AMPAC and MOPAC program in two different ways: one in which all the solvent relaxation is included in the quantum mechanics and the total energy must be corrected for the solvent change in energy, method A; and a second in which the quantum mechanics directly includes this term, method B. The calculated (AM1, method A) tautomeric equilibrium constants (log K₁) for 2-pyridone in the gas phase, cyclohexane, chloroform, and acetonitrile are ?0.3, 0.3, 0.8, and 1.3, respectively, in good agreement with the experimental data (?0.4, 0.24, 0.78, and 2.17, respectively). For 4-pyridone/4-hydroxypyridine differences between calculated log K₁ for the gas phase, chloroform and acetonitrile (?6.0, ?2.6, and ?1.2, respectively) and experimental data (< ?1, 0.11, and 0.66, respectively) are larger but the experimental values are also less certain. The experimental acetonitrile data are disturbed by specific interactions. An extension of the SCRF for aqueous solutions is reviewed. © 1993 John Wiley & Sons, Inc.     

Improving chemical recycling rate by reclaiming polyurethane elastomer from polyurethane foam

Flexible polyurethane foam was decomposed into a polyol mixture by an extruder with diethanolamine (DEA) as a decomposing agent. The resulting decomposed product could be used as an alternative virgin polyol in reclaiming polyurethane. In the case of reclaiming elastomer by using the decomposed product without any purification, virgin polyol could be alternated by the decomposed product up to 80%. It is a great improvement compared with the reclamation to foam, whose percentage was maximum 5%. Furthermore, the percentage could be improved up to 100% by purifying the decomposed product. We have found that physical properties of reclaimed polyurethane elastomer, such as tensile strength, hardness, and elongation, can be regulated by the ratio of unrefined/refined polyol. Whereas the tensile strength and the hardness increased as the content increased, the elongation decreased.     

Evolution detection of phenol by pristine BN nanocone: chemical quantum study

Structural Chemistry - In order to evaluate the electrical response of boron nitride nanocones (BNNCs) to phenol gas, density functional theory (DFT) calculations are employed. The sensitivity and...     

Effect of binary solvent composition on phenol extraction from aqueous solutions

Partition factors D between an apolar solvent-ketone or ketone-ketone binary mixture and water have been determined for a series of p-alkylphenols. The effects of the composition of a binary solvent and phenol hydrophobicity on the partition factor have been studied. Empirical relationships adequately describing the partition factor isotherms versus the mole fraction of the active component of the binary organic solvent have been found and discussed.     

Deep eutectic solvent promoted hydrothiocyanation of alkynoates leading to Z-3-thiocyanatoacrylates

A mild and efficient protocol for the selective construction of Z-3-thiocyanatoacrylates is described. Various alkynoates reacted with KSCN and H₂O by using cheap and recyclable deep eutectic solvent as the catalyst and reaction media to produce the corresponding products in excellent yields with mild reaction conditions and wide substrate scope.     

Polyethylene glycol as a green chemical solvent

Polyethylene glycol (PEG) is an industrial commodity produced for applications foremost in the medial and personal care business. This review focuses on the much less explored application of using PEG as a chemical solvent. This review highlights some of the successful chemical synthesis strategies to illustrate the advantages of using PEG as an environmentally friendly reaction medium. These advantages include its ability to (a) dissolve a wide range of chemicals including mineral salts, (b) serve as a catalyst because of its acid/base functionalities, (c) complex metal cations, and (d) engage in redox chemistry. New developments of combining PEG with other green solvents and/or functionalizing PEGs are covered as well. The present state of physicochemical studies of PEG as a solvent is also provided and clearly shows the need for future research in this area to further promote the effective use of PEG as a medium for chemistry.     

Role of recycling in improving the performance of chromatographic solvent gradient purifications

With significant advancement in the upstream processing technology, downstream processing of large bio-molecules is becoming the bottle-neck in the production chain. To face this challenge, design and development of efficient separation processes has become crucial. As a step towards boosting the performance of a chromatographic separation process through improved design, we investigated the potential of recycling as a process option. The most important advantage of recycling is that it can be implemented in an existing batch system without any major investment and consultation. Although impure products are recycled in industries, it is done as additional batch, and only then, when the recoverable product is valuable enough to surpass the loss of productivity in running the additional batches. In our study, on the other hand, it was found that a well-designed recycle can not only improve the yield, but also the productivity of a multi-component purification. A series of multiobjective optimization studies were carried out on multi-component separation to comprehend the role of recycling with reference to an industrially relevant problem, i.e. the chromatographic purification step of the production process of calcitonin.     

萃取耦合化学转化法提质生物油油溶相的研究

采用萃取耦合化学转化技术对生物油油溶相进行了提质研究。将稻壳快速裂解油加入适宜水使其自然分为水溶相和油溶相。以正丁醇为萃取剂和转化剂,通过在线萃取将油溶相中的酸、醛、酮等可萃物不断萃取出来,再经酯化、缩醛化反应,转化为相应正丁醇的酯、缩醛和半缩醛等。与生物油直接酯化提质相比,萃取耦合化学转化法可以显著抑制提质过程中的结焦问题,降低了提质油相的含水量和酸值,提高了其热值和可挥发性。此外,还考察了油溶相预氧化和预还原对萃取耦合化学转化提质的影响。结果表明,预氧化后可将油溶相中的醛类转化为酸,再经酯化转化为稳定性好的酯类,提质后的油品水含量低于4%,热值高于30 MJ/kg,酸值低于2 KOH mg/g,并且结焦率为零。     

Advances and approaches for chemical recycling of plastic waste

The global production and consumption of plastics has increased at an alarming rate over the last few decades. The accumulation of pervasive and persistent waste plastic has concomitantly increased in landfills and the environment. The societal, ecological, and economic problems of plastic waste/pollution demand immediate and decisive action. In 2015, only 9% of plastic waste was successfully recycled in the United States. The major current recycling processes focus on the mechanical recycling of plastic waste; however, even this process is limited by the sorting/pretreatment of plastic waste and degradation of plastics during the process. An alternative to mechanical processes is chemical recycling of plastic waste. Efficient chemical recycling would allow for the production of feedstocks for various uses including fuels and chemical feedstocks to replace petrochemicals. This review focuses on the most recent advances for the chemical recycling of three major polymers found in plastic waste: PET, PE, and PP. Commercial processes for recycling hydrolysable polymers like polyesters or polyamides, polyolefins, or mixed waste streams are also discussed.     

Excited state electric dipole polarizabilities and moments by solvent spectral frequency shifts: Aniline,phenol and naphthalene

The solvent spectral frequency shift theory of Abe in its rigorous or unqualified form has been used to determine the electric dipole polarizabilities and moments of some of the excited electronic states of aniline, phenol and naphthalene. The results of the present analysis show the internal consistency of Abe's solvatochromic method and are largely in reasonable agreement with those determined by means of electro-optical measurements and/or molecular orbital calculations.     

Preferential solvation of phenol in binary solvent mixtures. A molecular dynamics study

Molecular dynamics computer simulations were carried out to study the preferential solvation of phenol in equimolar acetonitrile-water and ethanol-water binary mixtures. Two water models were used to investigate the model dependence of preferential solvation. The results are compared to recent intermolecular 1H NOESY experiments reported on the same systems. In the case of acetonitrile-water the local mole fraction obtained from simulations agrees quite well with experiments. In the case of ethanol-water there was a qualitative difference, which was observed for both water models. However, when comparing the degree of preferential solvation of the two cosolvents ethanol and acetonitrile with each of the two water models, the trend obtained from the simulations agrees with experimental data.     

Improvement in industrial re-chromatography (recycling) procedure in solvent gradient bio-separation processes

Re-chromatography or recycling impure products obtained from the batch runs of solvent gradient chromatography is commonly practiced in industry to improve product yield. However, as the re-chromatography steps are carried out at the expense of running fresh batches, any improvement in the yield comes as a trade-off with the production time, and hence productivity. In recent studies, on the other hand, it has been suggested that with a properly designed recycling process one can not only improve the yield, but the productivity as well. That study, however, considered a steady-state recycling process, a technology yet to be implemented with bio-chromatographic systems. In the present paper we are reporting a study made on non-steady-state recycling or re-chromatography, as it is typically done in industrial practice. The results point out an amendment to the standard way of designing solvent gradients, which is necessary to improve both the yield and the productivity of an industrial run with recycle. Although the test case used here was the separation of an industrial peptide, Calcitonin, in a reversed-phase column, the general methodology of gradient manipulation, needless to say, is also valid for other solvent gradient processes like ion-exchange, HIC, etc.     

Microwave promoted one-pot preparation of fluorinated propargylamines and their chemical transformation

A series of fluorinated propargylamines have been synthesized from the one-pot three-component reaction of fluorobenzaldehyde, aniline and phenylacetylene under solvent-free and microwave irradiation. The fluorinated propargylamines were then further transformed to chalcones or quinoline derivatives respectively depending on the different structures of propargylamines.     

Subcritical and supercritical water for chemical recycling of plastic waste

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Reheating decomposition process as chemical recycling for rigid polyurethane foam

We have found that a reheating process for the products in the chemical recycling of rigid polyurethane foam by an extruder with diethanolamine as a decomposing agent is effective for improving the product stability. The product with stable viscosity was obtained by the reheating process at 175-200 °C for 2 h, regardless of the extruding condition. An amine adduct, which is an intermediate, was found to be the cause of instability of the discharged product from the extruder. At the initial stage of reheating, the intermediate decomposed, releasing toluenediamine, which promoted further decomposition of the discharged products. We have succeeded in controlling the quality of the recycled products.     

Enzymatic synthesis and chemical recycling of poly(carbonate-urethane)

Novel enzymatically recyclable poly(carbonate-urethane) consisting of a diurethane moiety as a hard segment and a carbonate linkage as an enzymatically cleavable unit was prepared by the polycondensation of biodegradable diurethanediol and diethyl carbonate using lipase. The produced poly(carbonate-urethane) was readily transformed by lipase into the corresponding cyclic oligomers which were more easily repolymerized by lipase to produce a higher molecular weight poly(carbonate-urethane) than that of the parent poly(carbonate-urethane).     

环境温度对紫外辐照HDPE结构与性能的影响研究

采用元素、XPS、GPC分析，凝胶和力学性能测定，研究了空气中不同环境温度下紫外辐照官能化HDPE的结构、粘着性以及紫外辐照官能化HDPE对HDPE/聚乙烯醇(PVA)体系的增容作用。实验结果表明，提高环境温度可显著提高引入C-O、C(=O)O和C=O等含氧基团的速度。在相同辐照时间下，随环境温度提高，辐照HDPE的分子量下降、分子量分布变宽以及剥离强度提高的幅度增大，并在70℃时产生凝胶。较高环境温度下辐照的HDPE对HDPE/PVA共混体系有较好增容作用，在HDPE/PVA(83/17)体系中加入10%(质量分数)的70℃环境温度下辐照24h的HDPE，共混物的拉伸屈服强度和缺口冲击强度分别从30.8MPa和110J/m提高到34.9MPa和142J/m。     

Basic ionic liquids promoted chemical transformation of CO_2 to organic carbonates

Ionic liquids(ILs), especially basic ILs with unique physicochemical properties, have wide application in catalysis. Using basic ILs as catalysts for the conversion of cheap, abundant, nontoxic, and renewable CO_2 into value-added organic carbonates is highly significant in view of environmental and economic issues. This review aims at giving a detailed overview on the recent advances on basic ILs promoted chemical transformation of CO_2 to cyclic and linear carbonates. The structures of various basic ILs, as well as the basic ILs promoted reactions for the transformation of CO_2 to organic carbonates are discussed in detail,including the reaction conditions, the yields of target products, the catalytic activities of basic ILs and the reaction mechanism.