Effect Of Reaction Medium Research Articles

Effect of reaction media on hydrogenolysis of polyethylene plastic waste: Polymer-surface interactions in small alkane/polymer blends

The polymer reaction media and its properties can be altered by recycling a fraction of liquid products or adding alkane solvents. Less clear is whether this strategy affects hydrogenolysis. Herein, we investigated the effect of short-chain alkanes Cn consisting of n carbons (n=8, 16, and 32) on the upcycling of high-density polyethylene (HDPE) plastic waste to lubricant-range products over Ru/TiO2 catalysts by multiscale simulations and experiments. First, we trained a force field for polymer/surface interactions on a Ru22 nanoparticle (NP) supported on TiO2. Using replica exchange molecular dynamics simulations, we studied the effect of small hydrocarbons on the adsorption of a surrogate polymer, C142, on the catalyst. We found segregation of long chains (C142) at the catalyst surface due to the enthalpy gained by adsorbing more C-C bonds of the long chains, compensating for entropic losses upon adsorption. Short-chain molecules decrease the adsorbed carbons of long chains on the Ru NP due to blocking Ru active sites. Compared to the bulk chains, competitive adsorption results in a broader, heavy-tailed distribution of end-to-end distance of adsorbed chains. Our experiments demonstrated that catalyst activity declines significantly beyond simple dilution due to changes in polymer adsorption, and tuning the reaction media by creating suitable blends impacts hydrogenolysis. Density distributions for a 50:50%wt mixture of PP and PE show that PE chains are segregated at the surface, so they are prone to C-C bond breaking much faster than PP chains. H/D exchange experiments show preferential deuteration of PE, while CH3 groups of PP remain undeuterated. This may be explained by the preferential sorption of PE over PP, leading to specific distribution in the polymer blend.

The fate of arsenic during the crystallization process of FeIII oxyhydroxides: Effect of reaction media, pH value, and Fe/As molar ratio under relatively low arsenic loading

Understanding the nature of arsenic (As) adsorbed on FeIII oxyhydroxides, and the subsequent behavior of As during the crystallization process, is critical to predicting its fate in a range of natural and engineered settings. In this work, As adsorbed on FeIII oxyhydroxides formed in the different reaction media at different pH values were characterized with X-ray diffraction (XRD), Raman spectra, transmission electron microscopy (TEM), and extended X-ray absorption fine structure spectroscopy (EXAFS) to determine how As is redistributed during the crystallization process. Results showed that at pH 12, a quarter of the added As was still left in the liquid phase with the formation of goethite and hematite as the major and minor product. The concentration of As was found to be the lowest at pH 4 which is independent of the reaction media, indicating the importance of pH value in the crystallization process of the As adsorbed FeIII oxyhydroxides. Under acidic conditions, sulfate and chloride media favored the formation of goethite and hematite, respectively. Arsenic can indeed be incorporated into the structure of the formed goethite at pH 4. The morphology of the formed products changed to rhombus-like particles if both goethite and hematite appeared as the later as the dominant product.

Effect of Reaction Media on Photoreduction of Co2 into Methanol Using Au- and Cu-Decorated Zeolitic Imidazolate Framework-8

Effect of Reaction Media on Photoreduction of Co2 into Methanol Using Au- and Cu-Decorated Zeolitic Imidazolate Framework-8

Synthesis and Characterization of Poly(methyl acrylate)-grafted-Sodium Salt of Partially Carboxymethylated Tamarind Kernel Powder

Ceric ammonium nitrate (CAN)-initiated graft copolymerization of methyl acrylate (MA) onto sodium salt of partially carboxymethylated tamarind kernel powder (Na-PCMTKP, DS = 0.15) was studied in an aqueous medium by solution polymerization technique. The growth of the graft reaction was monitored gravimetrically. The role of various synthesis variables on the grafting yields was examined to achieve the maximum graft yields (%G = 278.27, %GE = 94.38, %Hp = 5.62) and the influence of the synthesis variables in the graft copolymerization has been discussed. The reactivity of methyl acrylate (MA) towards graft copolymerization was compared with that of acrylonitrile (AN) on the basis of the results obtained from the earlier studies and plausible explanation was furnished for the observed reactivity of both the monomers towards grafting. The evaluated optimized reaction conditions were utilized to study the effect of reaction medium on grafting and it was found that reaction medium plays an important role in graft copolymerization. In order to ascertain the grafting, characterization of the samples made by FTIR, TGA and SEM was conducted. The synthesized novel graft copolymer may find potential application to be used as metal adsorbents.

Lipase-catalyzed selective esterification of catechin

Catechins show strong antioxidant, antitumoral, antiviral, and anti-inflammatory activities. The uses of catechins in food, cosmetic, and pharmaceutical formulations seem very attractive. Unfortunately, solubility and stability of catechins are poor in apolar media, which limits their efficient uses. In order to improve the solubility of catechins in the oil phase and maintain their oxidation resistance, a regioselective enzymatic acylation was investigated. The effects of reaction medium, water content, carbon chain length of acyl donor and other factors on the acylation reaction were studied, catechins were enzymatically esterified with an aliphatic acid (stearic acid) using an immobilized lipase Novozym 435 in n-butanol. The results show that when the ratio between catechins and stearic acid was 1:5, adding molecular sieves 4A after 11 h of reaction and the temperature of 60 °C led to the maximum conversion yield of 60.36%. Studies have shown that catechin stearate has a higher antioxidant activity than vitamin E and dibutyl hydroxytoluene (BHT).

Mesocellular silica foams supported size-controlled Pd nanoparticles for racemic and asymmetric iodomethyl dihydrobenzofuran synthesis

Supported metal nanoparticles (NPs) catalysts in constructing benzene-fused cyclic framework with chirality is very challenging. Dihydrobenzofuran and its derivatives are significant heterocyclic units in biologically molecules. Herein, size-controlled Pd NPs fixed on mesoporous silica (Pd/MS-xT) SBA-15, FDU-12 and mesocellular silica foams (MCFs) were utilized to synthesize racemic and asymmetric iodomethyl dihydrobenzofuran for the first time. The size of Pd NPs was regulated by increasing NaBH4 reduction treatments times (-xT) and enlarging supports pore. Based on large mesopore of MCF-3, supported catalyst 3%Pd/MCF-3-4T possessed larger Pd size gave the excellent performance at 92% racemic yield. Under chiral phosphine modifier N–Me-Xu3, we implemented more deserving asymmetric reaction over 3%Pd/MCF-3-1T with smaller Pd NPs. TGA for organic surface coverage demonstrated that the substrate preferred larger Pd NPs, N–Me-Xu3 capped more easily on smaller ones. Besides, effects of reaction medium and N–Me-Xu3 additive quantity further revealed the coordination of chiral modifier on Pd/MCF-3 was the determinant. For broader visions, the performance dependence based on surface properties of heterogeneous catalyst would play crucial contributions towards construction of complexed organic molecules.

Effect of reaction media on the scavenging reaction of water-solubilized 2,2-diphenyl-1-picrylhydrazy radical by ascorbic acid

Effect of reaction media on the scavenging reaction of water-solubilized 2,2-diphenyl-1-picrylhydrazy radical by ascorbic acid

Aromatic nucleophilic substitution (snar) reactions of halo‐substituted dinitrobenzene in liposome reaction media: Effect of reaction medium and role of halogen leaving group

AbstractSNAr reactions constitute an important pathway for the synthesis of many crucial organic derivatives from polyhaloaromatic compounds. The sluggish nature of the reaction in many cases makes it a challenging pathway and limits its potential applications. In the present report, liposomes have been used as model membrane systems to study nucleophilic substitution reactions of halo‐substituted dinitrobenzene with morpholine. The results show an interesting dependence of the reactivity on the size and composition of liposomes. The extent of rate acceleration in liposomes is strongly dependent on the identity of the halogen which undergoes the substitution—for example, chloro‐substituted aromatic compounds show the most sensitivity to the presence of lipsomal reaction media. The observed behavior correlates with the reported reactivity of halobenzenes while revealing interesting details which may be critical in harnessing the reactivity of less reactive substrates. The results explore the viability of employing liposomes as promising alternatives for synthetic protocols.

Bimetallic catalyzed decomposition of hydrogen peroxide – Kinetics, effect of support and reaction medium

Hydrogen peroxide is a versatile oxidant and has myriad industrial applications. The manuscript deals with the kinetic study for hydrogen peroxide decomposition using mono and bimetallic catalyst with different support and reaction mediums. Decomposition reaction has a major influence on three areas: (1) organic oxidations, where it is used as an oxidant to get intermediates and at times forming within the reaction as well; (2) polymer electrolyte fuel cells, where it acts as a degrading factor to cell stacks and (3) direct synthesis of peroxide through the gas-phase reaction of H2 and O2 to get H2O2. To enhance the hydrogen peroxide utility in the various processes, the decomposition activities of Au-Pd based bimetallic catalysts were tested. Bimetallic and monometallic supported catalysts were synthesized and evaluated to get the rate of decomposition. The catalysts were characterized using XRD, FTIR, TEM, and BET analysis. Hydrogen peroxide decomposition was studied in different mediums, namely, aqueous, acidic, and alkaline with/without halide to cater to the effect of change in the medium employed in different organic oxidations. First-order rate kinetics was assumed and the rate of decomposition was evaluated. Specific rate constants were evaluated and compared for all the catalysts for all the different mediums. The performance of the reaction in view of metal-support interaction and the effect of the reaction medium were studied.

Exploring Divergent Green Reaction Media for the Copolymerization of Biobased Monomers in the Teaching Laboratory

Polymerization reaction media can have a profound effect on the physical properties of the resultant polymer. This phenomenon is showcased in a new experiment for the organic chemistry and polymer science teaching laboratories wherein the radical copolymerization of biobased β-myrcene and dibutyl itaconate is performed using a nonhazardous aqueous emulsion solvent and compared to a bulk reaction. Both procedures demonstrate multiple green chemistry principles and application to sustainable polymer synthesis. The emulsion copolymerization produces a tacky, elastomeric cross-linked material, capable of swelling to many times its original volume in organic solvents, setting the stage for the exploration of the relationship between solvent polarity and swelling capacity. Conversely, the polymerization of β-myrcene and dibutyl itaconate in the bulk yields a viscous non-cross-linked polymer whose 1H NMR spectrum is suitable for student analysis and estimation of polymer number-average molar mass (Mn), monomer conversion, and copolymer composition. This inexpensive experiment models the use of renewable feedstocks, the effect of reaction medium on polymer architecture, the unique properties of cross-linked organogels, and the quantitative analysis of polymer structure using 1H NMR spectroscopy.

The effect of reaction medium and hydrothermal synthesis conditions on morphological parameters and thermal behavior of calcium phosphate nanoparticles

In this work, calcium phosphate nanoparticles were synthesized by a scalable hydrothermal method at significantly lower holding time, than was previously described in the literature.The morphological parameters of all the samples were characterized systematically by XRD, TEM, SSA, and FTIR. The lattice parameters and crystallite sizes are under discussion. It was shown that the surfactants and dopants greatly affect the nanoparticles formation process at all the stages – from the unit cell to crystallite size and nanoparticle sizes and shape.The possibility of NPs morphological parameters regulation via adding capping agents and dopants with different nature was demonstrated.Thermal properties of HAp and doped TCP nanoparticles are also reported. Results show that surfactant presence prevents sintering at high temperatures, in HAp case thermal stability depends on whether the nanoparticles are mono or polycrystalline, the presence of surfactant on the surface shifts the decomposition temperature to higher values.

Green hydrothermal synthesis of high aspect ratio wollastonite nanofibers: Effects of reaction medium, temperature and time

Wollastonite 1D nanostructures have attracted widespread concern for their wide applications in biomedical, constructions and many more, which however have been synthesized via high temperature solid state method or wet precipitation method which required organic template. Herein, a controllable green hydrothermal route is used to produce high aspect ratio wollastonite nanofibers. The effect of hydrothermal synthesis parameters on the aspect ratio of synthetic wollastonite nanofibers (SWN) were investigated and the hydrothermal formation mechanism was proposed. The formation of nanofiber starts from the nuclei formation in supersaturated solution then followed by the crystal growth. The synthesis reactions were conducted under different conditions with reaction medium containing different ethanol composition and temperature from 160 °C to 240 °C for 8 h to 32 h. The SWN produced was characterized using XRD, FTIR, TGA and FESEM analysis techniques. It is proven that all wollastonite produced were in nanofiber form with the average aspect ratio ranging from 10 to 20, except for those synthesized at 160 °C which mainly has irregular grain shape. The reaction medium consisting of 80% water and 20% ethanol, which was heated at 200 °C for 16 h, resulted in SWN with the highest aspect ratio of 20.15. The study demonstrated that the hydrothermal synthesis parameters can be manipulated to produce SWN with various aspect ratios to meet its demand in different applications.

Effect of Reaction Media on Photosensitized [2+2]‐Cycloaddition of Cinnamates

Effect of Reaction Media on Photosensitized [2+2]‐Cycloaddition of Cinnamates

Synthesis of substituted 2H-chromenes catalyzed by lipase immobilized on magnetic multiwalled carbon nanotubes.

Porcine pancreas lipase (PPL) was immobilized on magnetic multiwalled carbon nanotubes successfully for the synthesis of substituted 2H-chromenes. The catalytic activity of immobilized PPL was much higher than that of free PPL. Effects of reaction medium, temperature, and enzyme dosage were also investigated. Under optimum reaction conditions (acetylacetone (1 mmol), salicylaldehyde (1 equivalent), methanol (10 equivalent), and immobilized PPL (protein content: 30 mg; 65 °C; DMF 5 mL; 5 H), the immobilized PPL showed an excellent catalytic performance on the synthesis of substituted 2H-chromenes. Moreover, the immobilized PPL exhibited satisfactory thermostability, operational simplicity, and reusability in this reaction.

One-pot conversion of alginic acid into furfural using Amberlyst-15 as a solid acid catalyst in γ-butyrolactone/water co-solvent system

One-pot conversion of alginic acid, which was derived from brown algae, to furfural was investigated using various solid acid catalysts. Among the solid acid catalysts tested, Amberlyst-15 showed the highest activity in furfural production in aqueous media. When the effect of reaction media was examined by applying various organic solvent mixtures, it was found that γ-butyrolactone/water co-solvent system was selected as the most appropriate system for the reaction. Maximum furfural yield of 32.2% was obtained using Amberlyst-15 in the γ-butyrolactone/H2O at 210 °C for 20 min. Catalyst showed gradual deactivation behavior as the reaction proceeded, although the catalyst recovered its activity upon the simple treatment with sulfuric acid. N2 adsorption-desorption experiments, Fourier-transform infrared spectroscopy (FT-IR), back titration, and CHNS analysis were applied to investigate the physicochemical property of post-reaction samples, confirming that the leaching of the active sulfonic acid group and decrease in acid density was the major cause of deactivation.

Effect of Reaction Media on Photosensitized [2+2]-Cycloaddition of Cinnamates.

The outcome of photosensitized [2+2]‐cycloaddition reactions of various cinnamates has been compared in different reaction media, including homogeneous organic solutions under inert conditions, degassed water, and aerated physical gels. The reactions were performed under LED blue light (λmax=455 nm) irradiation and [Ir{dF(CF3)ppy}2(dtb‐bpy)]PF6 (1.0 mol%) as photocatalyst. The processes were optimized taking into consideration solvent, gelator, and substrate. Comparative kinetics analyses, as well as the effect of the reaction media on the diastereoselectivity of the process, were evaluated during this investigation. In a number of cases, carrying out the reaction in a less polar solvent, like toluene or highly polar solvent, like water had a tremendous impact on the diastereoselectivity of the process, pointing towards an effect on the stabilization of the putative diradical intermediate in this medium. Moreover, while for reactions run in homogeneous solution oxygen needs to be excluded, no erosion in yield is observed when the photoadditions were run in aerated gel media.

Cyclodehydration of 1,4-butanediol over Zr-Al Catalysts: Effect of Reaction Medium.

The conversion of 1,4-butanediol (BDO) to tetrahydrofuran (THF) in aqueous phase is desirable because BDO production technology is shifting to bio-based aqueous fermentation routes. In this study, liquid-phase cyclodehydration of BDO to THF was studied in two reaction media (pure BDO and aqueous BDO feeds) at 200–240 °C using ZrO2-Al2O3 (ZA) mixed oxides, which were made with a co-precipitation method and were characterized with XRD, BET, SEM/EDX, pyridine and n-butylamine adsorptions. The maximum acidity and the largest surface area occurred at Zr/Al atomic ratios of 1/1 (ZA11) and 1/3 (ZA13), respectively. The reaction exhibited pseudo-first-order; aqueous BDO feed had much greater rate constant than pure BDO feed, ascribed to the acidic properties of adsorbed water molecules (coordinated to surface metal cations) for the former case. For pure BDO feed, linear relation was observed between rate constant and catalyst acidity, and ZA11 reached a THF yield of 90.1% at 240 °C. With aqueous BDO feed, rate constant increased linearly with increasing surface area and ZA13 reached a THF yield of 97.1% at 220 °C. The change of optimum catalyst composition with reaction medium suggests that active sites for catalyzing BDO cyclodehydration changed with the reaction environment.

Biocatalytic upgrading of levulinic acid to methyl levulinate in green solvents

High value-added utilization of biomass-based platform chemicals has attracted increasing attention in recent years. The present study addresses the upgrading of levulinic acid (LA), an important biomass-based platform chemical, to methyl levulinate via a green and efficient enzymatic approach. Various lipases were assessed, with Novozym® 435 displaying the best results for the esterification of LA. Subsequently, the effect of reaction medium on Novozym® 435 catalyzed esterification was also studied. Compared with other reaction media, 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) showed the greatest enhancement in yield by suppressing hydrolysis activity. The catalysts reusability was also improved by protection from [bmim][PF6] with 43.2% activity remained after 5 cycles, compared to that of 19.1% in 2-Me THF. Reaction temperature exerted an unusual double-peak relationship over methyl levulinate yield because Novozym® 435 can simultaneously catalyze the esterification of LA and hydrolysis of methyl levulinate, each of which has a different optimal reaction temperature: ca. 30 °C and ca. 40 °C, respectively. When the molar ratio of LA/methanol, and the volume ratio of methanol/[bmim][PF6] were 1:5 and 1:3, respectively, methyl levulinate was obtained in 93% yield at 30 °C after 24 h with 10 mg/mL catalytic loading.

Solvent-free catalytic deoxygenation of oleic acid via nano-Ni/HZSM-5: Effect of reaction medium and coke characterization

Non-H2 and solvent-free catalytic conversion of waste lipids to liquid hydrocarbons is of great interest because of the associated low-cost, full-safety, and easy-operability. In this work, a solvent-free catalytic process for deoxygenating oleic acid was performed in H2 and non-H2 (N2, CH4, and CO2) media over nano-Ni/HZSM-5. 8-Heptadecene, a primary product obtained at 320 °C in four media, was derived from the straightforward decarboxylation of oleic acid. In non-H2 medium at 360 °C, the formation of C8–C15 alkanes was enhanced, with yields of ca. 65.05 mol%, 70.71 mol%, and 73.09 mol% for N2, CH4, and CO2, respectively. A low yield of 49.67 mol% C8–C15 alkanes in H2 medium suggested that the H2 medium reduced catalytic cracking. This was due to the preferential formation of stable heptadecane from 8-heptadecene in the presence of abundant H2. The absence of H2 favored the cracking of 8-heptadecene. These cracked products were further converted to C8–C15 alkanes, for which a mass supply of hydrogen was mandatory. Gas-phase reactions including methanation, Fisher-Tropsch (F-T) synthesis, and water-gas shift (WGS) reactions between deoxygenated gas products and reaction media provided significant pathways for the hydrogen required for the formation of alkanes. The CH4 medium also acted as a hydrogen source due to its decomposition, catalyzed by nano-Ni/HZSM-5. Coke was substantially formed in all the four media. It was highlighted that the medium of H2 favored the formation of aliphatic cokes, whereas the non-H2 media, particularly the CO2 medium, facilitated aromatic coke species on account of its weak oxidizability. Additionally, there was a severe loss of loaded Ni nanoparticles under H2 medium but a slight Ni loss in CO2 medium, which was proposed to the reason of aromatic cokes formation at the catalyst surface, acting as a trap for the loaded Ni nanoparticles.

Effect of Reaction Medium on the Yield and Composition of the Products of the Liquid-Phase Ozonization of Brown Coal

The effect of solvent polarity on the yield and composition of the ozonization products of brown coal from the Balakhtinskoe deposit was studied. The greatest yield of soluble oxygen-containing products was obtained upon ozonization in polar solvents—glacial acetic acid and acetone. The application of chlorinated solvents and lower alcohols, including their aqueous solutions, was less effective.