Impact Of Reaction Conditions Research Articles

Elaborate structural design of polypyrrole-based microwave absorbers: Synthesis, enhanced dielectric characteristics, and superior absorption capability

Intrinsically conductive polymers are expected as an advanced microwave absorption material due to their adjustable dielectric characteristics and low density. In this investigation, polypyrrole (PPy) with spherical aggregation and nanofiber structures were successfully synthesized by chemical oxidation polymerization strategy. The impact of reaction conditions on the structure, morphology, size, and chemical constituents has been investigated. The results indicate that the strong interfacial interaction between dopamine and pyrrole monomer leads to the formation of nanofibers. Because of the synergistic effect of favorable impedance matching, improved dielectric loss, and conductive loss, the PPy aggregations with nanosized particles exhibit outstanding absorption capability. At 6.32 GHz, the minimum reflection loss even reaches -46.73 dB. The effective absorption bandwidth (EAB) covers a broad frequency range of 6.51 GHz. Our work provides a versatile strategy for PPy-based materials with elaborately structural design to achieve excellent and modulated microwave absorption capability.

Mechanism of Plasmon-Induced Catalysis of Thiolates and the Impact of Reaction Conditions.

The conversion of the thiols 4-aminothiophenol (ATP) and 4-nitrothiophenol (NTP) can be considered as one of the standard reactions of plasmon-induced catalysis and thus has already been the subject of numerous studies. Currently, two reaction pathways are discussed: one describes a dimerization of the starting material yielding 4,4'-dimercaptoazobenzene (DMAB), while in the second pathway, it is proposed that NTP is reduced to ATP in HCl solution. In this combined experimental and theoretical study, we disentangled the involved plasmon-mediated reaction mechanisms by carefully controlling the reaction conditions in acidic solutions and vapor. Motivated by the different surface-enhanced Raman scattering (SERS) spectra of NTP/ATP samples and band shifts in acidic solution, which are generally attributed to water, additional experiments under pure gaseous conditions were performed. Under such acidic vapor conditions, the Raman data strongly suggest the formation of a hitherto not experimentally identified stable compound. Computational modeling of the plasmonic hybrid systems, i.e., regarding the wavelength-dependent character of the involved electronic transitions of the detected key intermediates in both reaction pathways, confirmed the experimental finding of the new compound, namely, 4-nitrosothiophenol (TP*). Tracking the reaction dynamics via time-dependent SERS measurements allowed us to establish the link between the dimer- and monomer-based pathways and to suggest possible reaction routes under different environmental conditions. Thereby, insight at the molecular level was provided with respect to the thermodynamics of the underlying reaction mechanism, complementing the spectroscopic results.

Solid- and aqueous-phase approaches on zinc oxide-based photocatalytic system for degradation of plastics and microplastics: A review

The accumulation of plastics and microplastics in the environment is a major global concern because of their negative impact on ecosystems and human health. The use of zinc oxide (ZnO)-based systems for photocatalytic degradation of these pollutants has shown promise. This review presents an overview of the solid- and aqueous-phase approaches employed for the degradation of plastics and microplastics using ZnO-based photocatalytic systems. The preparation of microplastic samples is discussed, highlighting various techniques used to generate representative samples for testing. The experimental setup or reactor design is explored, encompassing different configurations employed in both the solid- and aqueous-phases. Next, the impact of reaction conditions on degradation efficiency is investigated, including catalyst concentration, pH, temperature, and irradiation source. Sampling techniques for post-reaction analysis are explored, discussing methods for collecting and analyzing degraded products and byproducts in solid- and aqueous-phases. The comparative discussion was meant to assess the effectiveness and suitability of solid- and aqueous-phase methods, revealing their potential for practical use. This review paper presents an extensive analysis of the methods used in ZnO-based photocatalytic systems for plastic and microplastics degradation which the output will aid researchers and practitioners in developing effective strategies to mitigate plastic pollution.

Kinetic studies on the radical ring‐opening polymerization of 2‐methylene‐1,3,6‐trioxocane

AbstractRadical ring‐opening polymerization (RROP) of cyclic ketene acetals allows for the synthesis of functional and biodegradable polyesters. To gain a better understanding of RROP, kinetic studies of this reaction method are thus essential but still rare. In here we conducted kinetic experiments on RROP of 2‐methylene‐1,3,6‐trioxocan (MTC) for the first time. In line with earlier findings, the kinetic behavior could be distributed into a chain growth, stationary and step growth behavior probably caused by dominating branching and recombination reactions impacting the polymerization with increasing conversion. The impact of reaction conditions, such as monomer concentration, reaction temperature and source of energy input (Oil bath, microwave, UV light) were varied systematically. All of these factors were studied towards their influence on polymerization rate constant, density of branches (DB), polymer dispersity and molar mass. While each of these factors were impacted by the reaction conditions, the DB was only depending on monomer conversion. Elution fractionation of PMTC samples with high conversion proved decreasing DB with increasing molar mass. Altogether, this study gives a holistic insight into the kinetics of MTC under various means of free RROP, paving the way for developing a more hydrophilic polyester with adjustable DB and molecular weight.

Plant-Mediated Synthesis of Mono- and Bimetallic (Au–Ag) Nanoparticles: Future Prospects for Food Quality and Safety

The environmental, economic, and operational limits associated with the physical, chemical, and microbiological techniques for the production of nanoparticles (NPs) are the principal obstructions to their rapid commercial applications in various fields including food packaging and sensing to ensure food quality and safety. Over the years, many reports revealed that the nanotechnological (metal-based NPs) application facilitates an alternate, interactive, reliable, as well as simple technology in the food industries and packaging sector. In this review, we summarized the usage of plant extract for the biosynthesis of bimetallic (Au–Ag) and monometallic counterpart NPs. Further, the impact of reaction conditions and identification of reactive phytochemicals with the reaction mechanism of these nanoparticles was reviewed. The recent progress on the applications of Ag, Au, or Au–Ag NPs in food quality analysis and food packaging was comprehensively discussed. The safety aspect of the nanoparticles for food sector use was also briefly stated.

Highly efficient removal of Pb2+ from wastewater by a maleic anhydride modified organic porous adsorbent

Sorption is prominent in low price, high efficiency, availability, and eco-friendliness. Organic porous materials have the characteristics of easy functionalization, diverse structure and stability, and show great potential in adsorption, energy storage, catalysis, and other fields. A mesoporous phenolic resin-type polymer (PRP) was successfully synthesized and modified by solid state reaction with maleic anhydride to prepare adsorbent (called as PRP-MAH) for sorption of Pb2+. The impact of reaction conditions (the pH value, reaction temperature, fresh concentration of solution, ionic strength and reaction time, etc.) was systematically studied. Characterization methods such as SEM, FTIR, and XPS indicated that the synthesized adsorbent PRP-MAH had regular morphology and good stability. The fitting of isothermal adsorption experiment data conforms to Langmuir sorption isotherm, and the sorption capacity reached 366.40mg·g-1 at 308K. The kinetic data were consistent with the quasi-second-order model, which indicated that the chemisorption might play the main role in the sorption process. Thermodynamic research manifested that the sorption of Pb2+ by PRP-MAH was carried out by a spontaneous process at the study temperature. The studies show that PRP-MAH can remove Pb2+ from water solution through ion exchange, electrostatic attraction, and surface complexation.

Conformational Variations for Surface-Initiated Reversible Deactivation Radical Polymerization: From Flat to Curved Nanoparticle Surfaces

Although progress in surface-initiated reversible deactivation radical polymerization (SI-RDRP) has already enabled the production of increasingly novel and advanced polymer structures on solid surfaces, fundamental kinetic questions remain regarding the impact of reaction conditions on the molecular properties of synthesized tethered chains. In the current work, we put forward a matrix-based kinetic Monte Carlo (kMC) model, which is based on an implicit SI-RDRP reaction scheme and continuous three-dimensional (3D) representations, capable of following the temporal evolution of the molecular properties of individual free and surface-tethered polymer chains. This is uniquely possible for variable surface curvature (nanoparticle radii from 4.5 to 32 nm; 353 K; monomer: methyl methacrylate), also including the comparison with the limiting case of a flat surface and addressing various (average) RDRP initiator surface coverages. For the tethered chains, we emphasize the prediction of the variation of the molecular height, monomer occupancy, and radius of gyration and also focus on the simulation of the chain length distribution (CLD) to enable a comparison with solution RDRP results. It is shown that confinement effects on the surface lead to the formation of heterogeneous polymer layers with a marked bimodality in the number CLD. This bimodality is, however, wiped out in experimental analysis based on log-molar mass distributions. It is also shown that an increase in the size of the spherical particles and, hence, a decrease in their curvature results in a deterioration of the control over molecular properties, leading to behavior more similar to that of flat surfaces. Average molecular heights and monomer occupancies can vary with a factor of 2. The impact of the targeted chain length is shown to be of lower importance.

Bibliometric analysis of phosphogypsum research from 1990 to 2020 based on literatures and patents.

The demand together with the urgency of phosphogypsum (PG) treatment will pose significant challenges for many countries. This research aims to explore the research progress of PG, including basic status, cooperation situation, research fields, and development trends, based on the Web of Science database through bibliometric analysis of publications (articles and patents) from 1990 to 2020. The results show that academic research on PG originated early, but the number of patents grew quickly. China is a global leader in terms of the number of publications and plays a significant role in international cooperation. The knowledge of PG has remained concentrated in the fields of natural radioactivity, cement paste backfilling, soil, crystal morphology, and synthetic gas. However, academic hotspots focus on the microstructure of chemical processes and various environmental impacts; patents and hot technologies are based on the production of refractory materials, ceramics, surface materials, cement mortar, and composite materials. The academic frontiers of PG will be centered on exploiting the methods of recovering rare earth elements from PG, the conditions of ion solidification/stabilization in PG, the impact of reaction conditions on product quality, and the reaction mechanism at the micro-level. The frontiers of patents need to focus on the improvement of manufacturing equipment, new wall materials, and chemically modified polymer materials. Envisaging the number of articles and patents to be published in the future, architectural research has a large room for improvement. This paper conducts an in-depth analysis of PG and provides information on the technological development prospects and opportunities, which is helpful for researchers engaged in PG management.

Synthesis – properties correlation and the unexpected role of the titania support on the Grignard surface modification

While the impact of reaction conditions on surface modification with Grignard reactants has been studied for silica supports, such information is absent for metal oxides like titania. Differences between modified titania and silica are observed, making it paramount to explore the reaction mechanism. A detailed study on the impact of the reaction conditions is reported, with a focus on the chain length of the alkyl Grignard reactant, its concentration, the reaction time and temperature, and the type of titania support. While the increase in the chain length reduces the amount of organic groups on the surface, the concentration, time and temperature show little/no influence on the modification degree. However, the type of titania support used and the percentage of amorphous phase present has a significant impact on the amount of grafted groups. Even though the temperature and concentration show no clear impact on the modification degree, they can cause changes in the surface hydroxyl population, which are thus not linked to the modification degree. Furthermore, the titania support is reduced during functionalization. This reduction dependents on the reaction temperature, the titania support and the chain length of the Grignard reactant. Similarly, this reduction is not linked to the modification degree.

CO2 Hydrogenation to Methanol over Ce and Zr Containing UiO-66 and Cu/UiO-66

Direct hydrogenation of CO2 to methanol is an interesting method to recycle CO2 emitted e.g., during combustion of fossil fuels. However, it is a challenging process because both the selectivity to methanol and its production are low. The metal-organic frameworks are relatively new class of materials with a potential to be used as catalysts or catalysts supports, also in the reaction of MeOH production. Among many interesting structures, the UiO-66 draws significant attention owing to its chemical and thermal stability, developed surface area, and the possibility of tuning its properties e.g., by exchanging the zirconium in the nodes to other metal cations. In this work we discuss—for the first time—the performance of Cu supported on UiO-66(Ce/Zr) in CO2 hydrogenation to MeOH. We show the impact of the composition of UiO-66-based catalysts, and the character of Cu-Zr and Cu-Ce interactions on MeOH production and MeOH selectivity during test carried out for 25 h at T = 200 °C and p = 1.8 MPa. Significant increase of selectivity to MeOH was noticed after exchanging half of Zr4+ cations with Ce4+; however, no change in MeOH production occurred. It was found that the Cu-Ce coexistence in the UiO-66-based catalytic system reduced the selectivity to MeOH when compared to Cu/UiO-66(Zr), which was ascribed to lower concentration of Cu0 active sites in Cu/UiO-66(Ce/Zr), and this was caused by oxygen spill-over between Cu0 and Ce4+, and thus, the oxidation of the former. The impact of reaction conditions on the structure stability of tested catalyst was also determined.

The impact of reaction conditions and material composition on the stepwise methane to methanol conversion over Cu-MOR: An operando XAS study

The direct methane to methanol (DMTM) conversion is often referred to as a ‘dream reaction’ with enormous potential to alter energy sector and chemical industry. After O2-activation, Cu-exchanged zeolites form CuxOy species that activate CH4 and release it in the form of CH3OH upon interaction with H2O. Despite extensive research efforts in the last years, several questions concerning the influence of materials composition and process parameters on the reaction mechanism remain open. Herein, we characterize Cu-MOR zeolites with different composition by operando X-ray absorption spectroscopy (XAS), monitoring their spectroscopic response under two characteristic DMTM reaction protocols varied in the duration of the key reaction steps. Linear Combination Fit (LCF) analysis of the time-resolved X-ray absorption near edge structure (XANES) spectra collected during CH4-loading and steam-assisted CH3OH extraction enabled to quantify the abundance of different Cu species during these two steps. Data analysis revealed a positive linear correlation between the methanol yield generated per incorporated copper and the Cu(I) component formed during the CH4-loading step. Cu(I) development during CH4-loading is accompanied by modifications in the extended X-ray absorption fine structure (EXAFS) spectra suggesting substantial rearrangement in the active site structure. The obtained results provide new mechanistic insights for the DMTM over Cu-MOR.

Dechlorination of carbon tetrachloride by Nanoscale Nickeled Zero‐Valent Iron @ Multi‐Walled Carbon Nanotubes: Impact of reaction conditions, kinetics and mechanism

The nanoscale nickeled zero‐valent iron @ multi‐walled carbon nanotubes (NF@MWCNTs) were synthesized, characterized and used to dispose carbon tetrachloride (CT) in aqueous solution. Scanning electron microscopy (SEM), X‐ray energy dispersive spectroscopy (EDS), X‐ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) gas sorptometry measurements were conducted to characterize the microstructure of the NF@MWCNTs. And batch experiments under different operation parameters were conducted to investigated the activity of NF@MWCNTs on degrading CT, including the content of NF@MWCNTs composites, temperature, catalyst dosage, initial pH and different anions. The experimental results showed that 4% nickel content of Ni/Fe bimetal and 2:1 doping ratio of Fe/MWCNTs were the wise choices in this study, which provided excellent degradation efficiency of CT when compared with nanoscale zero‐valent iron (nZVI) (97.44% and 55.28%, respectively). That was benefited from the fact that MWCNTs as an excellent support material could reduce the activation energy of 7.952 kJ/mol, and the nickel metal further reduced the reaction activation energy of 11.022 kJ/mol as presented in the conceptual model. Beyond that, NF@MWCNTs showed good reusability after five times consecutive reaction. Based on these, the reaction mechanism and degradation pathway also had been discussed.

Analysis of biomass hydrothermal liquefaction and biocrude-oil upgrading for renewable jet fuel production: The impact of reaction conditions on production costs and GHG emissions performance

This paper shows a detailed analysis of a biomass HTL process by considering changes in three main reaction variables (i.e. catalysts (water, Na2CO3(aq.), and Fe(aq.)), temperature (280–340 °C), and catalysts/biomass mass ratio (0–0.33 kg catalysts/kg biomass)), and by assessing their influence on the techno-economic and GHG emissions performance. This analysis is based on Aspen Plus® simulations, process economics and life-cycle GHG assessment on SimaPro (using Ecoinvent 2.2). Results showed that the lowest production cost for biocrude oil is achieved when HTL is performed at 340 °C with Fe as catalyst (450 €/tbiocrude-oil or 13.6 €/GJbiocrude-oil). At these conditions, the biocrude oil produced has an oxygen content of 16.6 wt% and a LHV of 33.1 MJ/kgbiocrude-oil. When the hydrotreatment and hydrogen generation units are included, the total production costs was 1040 €/tupgraded-oil or 0.8 €/Lupgraded-oil. After fractionation, the estimated production cost was 1086 €/tbiojet-fuel or 25.1 €/GJbiojet-fuel. This value is twice the commercial price of fossil jet fuel. However, the allocated life cycle GHG emissions for renewable jet fuel were estimated at 13.1 kgCO2-eq./GJbiojet-fuel, representing only 15% the GHG emission of fossil jet fuel and therefore, indicating a significant potential on GHG emission reduction.

BIGINELLI REACTION – AN EFFECTIVE METHOD FOR THE SYNTHESIS OF DIHYDROPYRIMIDINE DERIVATIVES

A brief review of the publications over the past 5 years devoted to the synthesis of 3,4-dihydropyrimidin-2(1 H )-one or -thione derivatives using Biginelli reaction is presented. The impact of reaction conditions (solvents, catalysts, energy input) on the yield is discussed. New combinations of reagents enabling the synthesis of a wide range of 3,4-dihydropyrimidin-2(1 H )-one derivatives with various functional groups are considered.

The effect of polyacrylic acid and reaction conditions on nanocluster formation of precipitated calcium carbonate on microcellulose

The precipitation of micro- and nanoparticles of calcium carbonate onto lignocellulosic microfibers was investigated at different microfiber concentrations with and without polyacrylic acid (PAA), i.e. a polymer commonly used to form polymer-induced liquid precursors of CaCO3. Concentrations of PAA, Ca(OH)2, CO2 and microfiber were varied in order to study the impact of reaction conditions on PCC formation in a batch reactor operated at ambient temperature. High resolution scanning electron micrographs of the samples show that both microfiber concentration and PAA dosage affected the nucleation and crystal growth of PCC filler on cellulosic fiber. Interestingly, at higher microfiber concentrations, larger amount of nano-sized spherical crystals were formed on the microfibers. A higher dosage of PAA, on the other hand, resulted in less nucleation on the microfiber, suggesting a preferential bulk nucleation mechanism. A higher concentration of PAA during the precipitation also led to the formation and stabilization of amorphous CaCO3, which was supported by SEM images and XRD analysis (lack of characteristic crystal structure).

Biginelli reaction – an effective method for the synthesis of dihydropyrimidine derivatives (microreview)

A brief review of the publications over the past 5 years devoted to the synthesis of 3,4-dihydropyrimidin-2(1H)-one or -thione derivatives using Biginelli reaction is presented. The impact of reaction conditions (solvents, catalysts, energy input) on the yield is discussed. New combinations of reagents enabling the synthesis of a wide range of 3,4-dihydropyrimidin-2(1H)-one derivatives with various functional groups are considered.

Preparation of Copper Selenide Platelets

Preparation of Copper Selenide Platelets Copper selenide (CuxSe) particles were prepared by heating copper carbonate and selenous acid in diethylene glycol in the presence of various dispersing agents. The impact of reaction conditions on the structural and morphological properties of the precipitated particles were assessed by X-ray diffraction (XRD) and electron microscopy. Although all additives promoted anisotropic growth, it was found that polyvinyl alcohol (PVA) was particularly effective in generating dispersed high aspect ratio CuxSe platelets. The optimum reaction conditions for the formation of hexagonal copper selenide were 190°C and a Cu: Se molar ratio of 1 to 1.2.

Research on Catalytic Degradation of Organic Wastewater Using CoFeMgO Non Homogeneous Fenton

Methyl orange stimulated wastewater was treated using non-homogeneous Fenton reaction. First the effect of catalyst composition on the treatment was investigated and then further investigation of the impact of reaction conditions on the degradation effect in the catalytic process was carried out. It showed the optimal conditions of treating methyl orange wastewater(100ml) of 10mg/L, The optimal conditions for catalyst preparation through experiments above were: proportion of the elements in the catalyst was Co0.5Fel.0(MgO)2.5, this article examined the impact of reaction conditions on the catalytic properties of the catalytic process. It turned out that on the condition that the amount of catalyst was 0.9g/L hydrogen peroxide concentration was 2.5ml/L, within the scope of application in a wide pH (4~14), catalyst degradation efficiency was significantly superior to conventional homogeneous Fenton system and methyl orange removal efficiency was above 95%.

Impact of Reaction Conditions on the Structures of Nickel(II) Complexes Based on 3‐(4‐Carboxyphenyl)propionic Acid

AbstractTwo new nickel(II) complexes, [Ni(4, 4′‐bpy)(H2O)4]n·n(cpp)·0.5nH2O (1) and [Ni(cpp)(4, 4′‐bpy)(H2O)2]n (2) [4, 4′‐bpy = 4, 4′‐bipyridine, H2cpp = 3‐(4‐carboxyphenyl)propionic acid] were synthesized and characterized by single‐crystal X‐ray diffraction, elemental analysis, IR spectroscopy, and thermal analysis. In complex 1, NiII ions are bridged by 4, 4′‐bpy into 1D chains, and cpp ligands are not involved in the coordination, whereas in complex 2, cpp ligands adopt a bis(monodentate) mode and link NiII ions into 2D (4, 4) grids with the help of 4, 4′‐bpy ligands. Triple interpenetration occurs, which results in the formation of a complicated 3D network. The difference in the structures of the two complexes can be attributed to the different reaction temperatures and bases.

Impact of reaction conditions on the simultaneous production of polysaccharides and bio-oil from heterotrophically grown Chlorella sorokiniana by a unique sequential hydrothermal liquefaction process

A two-step sequential hydrothermal liquefaction (SEQHTL) model for simultaneous extraction of polysaccharide at the first step followed by bio-oil in the second was established. The effects of reaction temperature, residence time, and biomass/water ratio on the product distribution of each SEQHTL step were evaluated. Maximum yield (32wt.%) of polysaccharides was obtained at 160°C, 20min and 1:9 biomass/water ratio. Considering the operation cost and bio-oil yield (>30%); 240°C, 20min and 1:9 biomass/water ratio was preferred as ideal SEQHTL condition for bio-oil extraction. SEQHTL always produced ∼5% more bio-oil and ∼50% less bio-char than direct hydrothermal liquefaction (DHTL). Free fatty acid content of the bio-oils exhibited a sharp decrease with increase in temperature. Comparative analysis of the energy input and net energy balance showed that SEQHTL requires ∼15% less MJ/kg bio-oil than DHTL. Energy recovery rate for SEQHTL is nearly 4% higher than the DHTL.