Higher Reaction Time Research Articles

Systematic evaluation and optimization of crystallization conditions for an ethanol-templated ZSM-5 zeolite using response surface methodology

The present study aimed to systematically evaluate and optimize the crystallization conditions of ZSM-5 templated by ethanol in a 5-liter stirred autoclave. Response surface methodology was applied to investigate the effects of independent variables of temperature, time, and seed content on the responses of yield, crystallinity, and the specific surface area. A variety of characterization techniques, including XRD, FTIR, FESEM, EDX, and N2adsorption/desorption analyses,were performed to fully assess the effects of the parameters on the textural and structural properties of ZSM-5. The study of variance results showed that time played the most prominent role in the ethanol-templated synthesis of ZSM-5. The crystallization time and temperature had significant quadratic effects on the responses. It was also shown that the seed by itself exerted no noticeable influence on the responses and had only a slight interaction with time, suggesting that the surface integration reaction is mainly the rate-controlling step. Moreover, the findings revealed that seed addition led to increased surface roughness and particle agglomeration and could reduce the surface area at sufficiently high reaction times. Eventually, a highly pure and crystalline ZSM-5 with a surface area of over 430 m2/g was obtained at an optimum temperature of 169 °C within 34 h.

One pot three component synthesis of 2-amino-4H-chromene derivatives under microwave irradiation using Sr2As2O7 nanocatalyst

2-Amino-4H-chromene compounds are belonged to an important heterocyclic groups that have extensive important in organic chemistry and medicine. The compounds have anti-cancer, anti-bacterial, anti-coagulation and anti-tumor properties and have applications to produce dye, make up and hygienic materials. Until know, several methods have been reported for the synthesis of the compounds. Most of them, suffers defects such as poisoning and volatile solvents, low yield, high length reaction time, and no reusability of used catalyst. In the present work, Sr2As2O7 pyrochlore material was used as a catalyst for the synthesis of 2-amino-4H-cromens derivatives using a three component one-pot synthesis method under microwave irradiation. The raw materials were aromatic aldehydes, malononitrile and beta-naphtol. Sr2As2O7 was synthesized by an ultrasonic assisted solvothermal method using H2O and C2H5OH solvents mixtures at the 1:1 volumetric ratio. The materials were characterized by PXRD, FESEM and FTIR techniques. Then, the catalytic performance of the synthesized nanomaterial was used for the synthesis of 2-amino-4H-chromene derivatives. To do the process, the reaction parameters such as reaction time, solvent type and catalyst amount were optimized and the reactions were performed under the conditions. It was found that the optimum conditions were 15 mg catalyst, H2O as solvent and 6-9 min reaction time.

A Highly EfficientN‐Mesityl Thiazolylidene for the Aliphatic Stetter Reaction: Stereoelectronic Quantification for Comparison of N‐Heterocyclic Carbene Organocatalysts

AbstractThe NHC‐catalysed intermolecular Stetter reaction provides direct access to 1,4‐diketones, however current NHC catalysts for this specific transformation remain underdeveloped, significantly limiting the use of this reaction in target‐oriented synthesis. Here we report a novelN‐mesityl thiazolium NHC as a high‐performing catalyst for this reaction, enabling high yields and short reaction times for a range of sterically non‐trivial aliphatic aldehydes reacting with enone substrates. Quantification of the properties of novel and known NHC organocatalysts revealed that both steric and electronic properties play an important role in the success of the newN‐mesityl thiazolium NHC for this reaction. These developments will facilitate wider application of the Stetter reaction as a key carbon‐carbon bond forming reaction for coupling of complex fragments under mild conditions.

Tc(NO)Cl(Cp)(PPh3)] – A Technetium(I) Compound with an Unexpected Synthetic Potential

AbstractReactions of the chiral organometallic technetium(I) compound [Tc(NO)Cl(Cp)(PPh3)] (1 a) with phosphines and alkynes give unexpected products such as the dimeric cation [{Tc(NO)(Cp)(PPh3)}2Cl]+ (4) or the Fischer‐type carbene [Tc(NO)(Cp)(PPh3){C(OR)C2H4PPh3}]2+ (5). Both products could be isolated as PF6− salts and studied by spectroscopic methods and X‐ray diffraction. While [Tc(NO)(Cp)(PMe3)(PPh3)](PF6) (2PF6) can be obtained from 1 a, PMe3 and Ag(PF6) under ambient conditions, the synthesis of the corresponding bis‐triphenylphosphine complex [Tc(NO)(Cp)(PPh3)2](PF6) (3PF6) requires high temperatures and long reaction times. The products are stable in air.

Accelerated conversion of waste cooking oil into biodiesel by injecting 2-propanol and methanol under superheated conditions: A novel approach

Catalysed biodiesel production has issues such as high chemical costs, high reaction time and complex product separation which sometimes generate wastewater. However, superheated transesterification allows rapid conversion of reactants due to high operating temperatures with nearly uninterrupted operation. The present study discusses the semi-continuous production of biodiesel from waste cooking oil (WCO) through injection of (superheated) methanol and 2-propanol separately (for comparative assessment). Batch studies and central composite design (CCD) studies involved optimizing 4 parameters: initial oil mass, alcohol preheat temperature, reaction temperature and retention time. The optimization allowed for evaluation of the solitary and interactive influences of each reaction parameter on the biodiesel yield. From CCD experiments, the highest obtained biodiesel yields of 97.82% and 98.85% was obtained with methanol and 2-propanol at 235 °C and 250 °C reaction temperature, respectively, using 250 g of initial oil mass within 8 min retention time, when both alcohols were preheated to 130 °C. Obtained results show a higher biodiesel yield with 2-propanol compared to methanol. However, transesterification with methanol proceeds at a higher rate. Biodiesel from both methanol and 2-propanol have comparable physico-chemical properties, which are acceptable as per ASTM standards. Since product separation does not involve wet washing, wastewater is not a concern and the process can be scaled up with relative ease to obtain biodiesel of acceptable commercial purity.

Decreased preparatory activation and inattention to cues suggest lower activation of proactive cognitive control among high procrastinating students

Procrastination is a voluntary delay in completing an important task while being aware that this behavior may lead to negative outcomes. It has been shown that an increased tendency to procrastinate is associated with deficits in some aspects of cognitive control. However, none of the previous studies investigated these dysfunctions through the lenses of the Dual Mechanisms Framework, which differentiates proactive and reactive modes of control. The present study was designed to fill this gap, using behavioral and neurophysiological assessment during the completion of the AX-Continuous Performance Task (AX-CPT) by high (HP) and low (LP) procrastinating students (N = 139). Behavioral results indicated that HP (vs. LP) were characterized by increased attentional fluctuations (higher reaction time variability) and reduction in some indices of proactive cognitive control (lower d’-context and A-cue bias, but similar PBIs). Furthermore, the neurophysiological data showed that HP, compared with LP, allocated less attentional resources (lower P3b) to cues that help to predict the correct responses to upcoming probes. They also responded with reduced preparatory activity (smaller CNV) after cues presentation. The two groups did not differ in neural responses linked to conflict detection and inhibition (similar N2 and P3a). Obtained findings indicate that HP might present deficits in some cognitive functions that are essential for effective proactive control engagement, along with preserved levels of reactive cognitive control. In the present paper, we discuss the potential neural and cognitive mechanisms responsible for the observed effects.

Hydrogen-rich syngas production by gasification of Urea-formaldehyde plastics in supercritical water

Supercritical water is a promising medium to convert plastics into hydrogen and other recyclable products efficiently. In previous research, supercritical water gasification characteristics investigations focus on thermoplastics instead of thermoset plastics due to its chemical, thermal and mechanical stability. Urea-formaldehyde (UF) plastics were selected as a typical kind of thermoset plastics for investigation in this paper and quartz tubes were used as the reactor in order to avoid the potential catalytic effect of metal reactor wall. Conversion characteristic were studied and the influence of different operating parameters such as temperature, reaction time, feedstock mass fraction and pressure were investigated respectively. The molar fraction of hydrogen could reach about 70% in 700 °C. Products in gas phase and solid phase were analyzed, and properties, chemical structures and inhibition mechanism of thermoset plastics was analyzed after comparing with polystyrene (PS) plastics. The result showed that increase of high temperature and long reaction time could promote gasification process, meanwhile the increase in the feedstock mass fraction would result in suppression of the gasification process. Finally, kinetic study of UF was carried out and the activation energy and pre-exponential factor of the Arrhenius equation were calculated as 30.09 ± 1.62 kJ/mol and 0.1199 ± 0.0049 min−1, respectively.

Analysis of simultaneous visual and complex neural dynamics during cognitive learning to diagnose ASD.

The interactions between gaze processing and neural activities mediate cognition. The present paper aims to identify the involvement of visual and neural dynamics in shaping the cognitive behavior in Autism Spectrum Disorder (ASD). Electroencephalogram (EEG) and Eye-tracker signals of ASD and Typically Developing (TD) are recorded while performing two difficulty levels of a maze-based experimental task. During task, the performance metrics, complex neural measures extracted from EEG data using Visibility Graph (VG) algorithm and visual measures extracted from eye-tracker data are analyzed and compared. For both task levels, the cognition processing is examined via performance metrics (reaction-time and poor accuracy), gaze measures (saccade, fixation duration and blinkrate) and VG-based metrics (average weighted degree, clustering coefficient, path length, global efficiency, mutual information). An engagement in cognitive processing in ASD is revealed statistically by high reaction time, poor accuracy, increased fixation duration, raised saccadic amplitude, higher blink rate, reduced average weighted degree, global efficiency, mutual information as well as higher eigenvector centrality and path length. Over the course of repetitive trials, the cognitive improvement is although poor in ASD compared to TDs, the reconfigurations of visual and neural network dynamics revealed activation of Cognitive Learning (CL) in ASD. Furthermore, the correlation of gaze-EEG measures reveal that independent brain region functioning is not impaired but declined mutual interaction of brain regions causes cognitive deficit in ASD. And correlation of EEG-gaze measures with clinical severity measured by Autism Diagnostic Observation Schedule(ADOS) suggest that visual-neural activities reveals social behavior/cognition in ASD. Thus, visual and neural dynamics together support the revelation of the cognitive behavior in ASD.

Highly effective microwave plasma application for catalyst-free and low temperature hydrogenation of biodiesel

Partially hydrogenated biodiesel or partially hydrogenated fatty acid methyl ester (H-FAME) derived from palm oil has been successfully synthesized using a microwave plasma system equipped with negative high voltage at low temperature without the use of a catalyst. The impact of the process parameters such as hydrogen gas feed flow rate, microwave power, reaction temperature, negative high voltage and reaction time on FAME composition and product properties were studied. It was found that the optimal condition for the highest conversion of polyunsaturated FAMEs was 8.5 L/min hydrogen flow rate, 500 W microwave power, 30 °C reaction temperature, 60 kV negative high voltage and 3 h of reaction time. The oxidation stability increased from 12.5 to 21.6 h and no trans C18:1 formation was detected. Further we found that the microwave plasma system equipped with negative high voltage can also be applied to effectively hydrogenate other chemicals at low temperatures without using a catalyst.

Surface Hydrophobization of Block-Shaped Wood with Rapid Benzylation

With the aim of utilizing wood as a carbon cycle-oriented material, the improvement of hydrophobicity has been actively studied to solve manufacturing problems, such as dimensional stability and biodeterioration resistance. The introduction of benzyl group is a promising chemical modification for hydrophobizing wood. However, conventional benzylation methods are not suitable for industrial applications because they require high temperature and long reaction times. In this study, a novel method was developed for quickly benzylating the surface of block-shaped wood using an aqueous solution of tetra-n-butylphosphonium hydroxide as a pretreatment solvent and no heat. The color and shape of the benzylated wood was almost unchanged from that before the treatment. Analysis of the resulting chemical structure suggested that the developed method causes less damage to carbohydrates compared with the conventional method, which involves heating and stirring. The proposed method successfully imparted hydrophobicity and thermoplasticity to the benzylated wood surface. Furthermore, hydrophobicity of the benzylated wood was further improved by a simple heat treatment for only approximately 5 min. The water contact angle became ≥110° and remained almost unchanged even after 1 min after water dropping.

Current developments in esterification reaction: A review on process and parameters

Esters are among the highest volume of industrial organic compounds produced. They are frequently employed in various domestic and industrial processes. Fischer esterification regarded as the most common and widely practiced process of ester synthesis, faces serious limitations of low conversion and high reaction time attributed largely to establishment of equilibrium. Ester hydrolysis, reverse reaction to esterification, starts by supply of a byproduct- water. Several approaches have been developed to avoid equilibrium establishment and to improve overall conversion and rate of reaction, a significant difference exists between the current industrial practices and optimum esterification process/conditions. In the current review, a critical analysis of esterification techniques is conducted. Catalytic, non-catalytic thermal esterification, enzymatic esterification, along with factors affecting their productivity are discussed in detail. The current barriers, future challenges and potential of the esterification technologies are analyzed. Based on the comprehensive-data analysis, a novel technology-based solution is proposed.

A novel agent-based framework for evaluating pedestrian safety at unsignalized mid-block crosswalks

A critical safety problem in road networks is the conflicts on unsignalized crosswalks. Thus, a proactive approach to assess pedestrian safety performance is required. Simulating the microscopic road user behavior in a virtual platform is one of the typical approaches. However, current simulation tools are not flexible enough to properly reproduce various behaviors of pedestrians and drivers considering their interactions with the road environment and other road users. Therefore, the objective of this paper is to propose a novel agent-based framework for evaluating pedestrian safety at unsignalized crosswalks. Unsignalized mid-block crosswalks with refuge islands (UMCR) are considered as an example facility to implement the proposed framework, where relevant behavioral elements such as the reaction time, visual field with obstacles, and minimum safety margin time are addressed. Not only the pedestrian-vehicle interaction is modeled but also the vehicle-vehicle interaction is considered. Empirical validation on a UMCR shows that the proposed framework can reproduce reliable distributions of the post encroachment time compared to the observed distributions within an acceptable error range. The sensitivity analysis reveals that the high reaction time of drivers, small safety margin time, and visual obstacles near crosswalks increase the probability of serious conflicts. The results also show that the framework can reproduce traffic crashes under assumed extreme road conditions.

Nano cobalt ferrite encapsulated‐silica particles bearing melamine as an easily recyclable catalyst for the synthesis of dihydropyrano[2,3‐c]pyrazoles under green conditions

AbstractIn this research, it was displayed an efficient method for synthesis of 6‐amino‐2,4‐dihydropyrano[2,3‐c] pyrazol‐5‐carbonitrile derivatives by using CoFe2O4 silica supported bearing melamine as a magnetic nanocatalyst. This nanocomposite was prepared in several steps and characterized by XRD, FT‐IR, SEM, EDX, VSM, and TGA techniques. The catalyst has a large active site that has functionalized on the surface of nanostructure. The advantages of this magnetic nanocatalyst are simple achievable, effective heterogeneous nanocatalyst, non‐toxic, small amount of catalyst used, resulted products with high yields and short reaction times, easy work up, and reusability. The central core nanoparticles are excellent chemical and magnetic stability. Therefore, the magnetic moment of cobalt ferrite relaxes much slower than the magnetite with the similar particle size.

Three-Component Solvent-Free Synthesis of 3, 4-Dihydropyrimidones and Thiones by Iron-Phosphonate Nanoparticle

Organic-inorganic hybrid nanomaterials have been prepared through cooperative assembly of cetyltrimethylammonium bromide (CTAB), Iron(ΙΙΙ)nitrate, and (Nitrilotris(methylene)) triphosphonic acid (NMPA). Surfactant is used as a structure directing agent, while the other two chemicals are used as precursors for the formation of pore walls. The structure of the synthesized iron phosphonate nanomaterials was fully characterized by using different spectra such as FT-IR, VSM, thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), EDX and XRD. The SEM analyze confirmed a hollow spherical micromorphology with well-defined porosity. Obtained hybrid organic and inorganic Nano catalyst has high performance in the synthesis of heterocyclic compounds. Therefore, the reaction of aldehyde aromatic, urea and ethyl acetoacetate was performed in the presence of the catalytic amount of Fe- NMPA under solvent-free conditions. The 3, 4-dihydropyrimidin (1H)-ones/thiones derivatives were obtained in high yield and short reaction time. The products of the reaction were characterized by physical data and FT-IR spectrum. This method has several advantages such as a recyclable catalyst, easy workup, and not using a volatile organic solvent.

Anchoring Cu nanoparticles on functionalized multi‐walled carbon nanotube for regioselective synthesis of 1,2,3‐triazoles via click reaction

Unique properties of 1,2,3‐triazoles on the one hand and necessity of usage of an efficient catalyst with fidelity in principles of green chemistry on the other hand impelled us to design and synthesis of a novel heterogeneous nanocatalyst (Cu@Arg‐MWCNTs) with simple synthesis, immense power, high regioselectivity, and easy separation and recyclability. The Cu@Arg‐MWCNT structure is characterized by different analyses and used for the synthesis of various triazoles. Its high catalytic activity is confirmed by high yields and short reaction times under mild conditions in click reaction.

Synthesis and Characterization of a Novel Bio-Magnetically Recoverable Palladium Nanocomposite for the Photocatalytic applications

A novel immobilized sparteine palladium (II) complex on the bio α-Fe2O3 nanoparticles was synthesized (Pd-Sparteine- α -Fe2O3). XPS, FT-IR, and ICP were used to determine compositional information. High thermostability and magnetic properties of it were proved by TGA and VSM, respectively. The size and morphology of this heterogeneous catalyst were investigated using SEM and TEM. Photoluminescence spectrum, BET, DRS and EDAX of this novel nanocomposite were evaluated for further investigations. The synthesized magnetic nanohybrid was successfully exploited as a new recyclable heterogeneous photocatalyst in the degradation of 2,4- dichlorophenol under visible light irradiation. It exhibited better photocatalytic efficiency of Pd-Sparteine-α-Fe2O3 was much higher than that of pure iron oxide nanoparticles. High yield and low reaction time of this catalyst were indicated that Pd-Sparteine-α -Fe2O3 could be a promising catalyst for direct photocatalyst applications.

Biochar Grafted on CMC-Terpolymer by Green Microwave Route for Sustainable Agriculture

The deficiency of water sources and the environmental disposal of large amounts of biomass waste (orange peels) produces economic and environmental problems, though its conversion into biochar by a pyrolysis procedure might be used to improve soil productivity. In the current study, we investigated the performance of superabsorbent biochar composite grafted on CMC as a low-cost, alternative, and biodegradable terpolymer composite (IPNCB) for soil water retention capacity. The IPNCB composite was synthesized by both microwave and conventional routes. The optimal reaction parameters proved that the microwave route has a high grafting percentage (%G) and short reaction time compared to the conventional route. The superabsorbent composite was characterized using different methods: FTIR, TGA, and SEM. The results show that the equilibrium water swelling (EW) of the IPNCB composite was improved at a 2% biochar concentration. The incorporation of biochar (BC) into the polymer network improved the water holding capacity (WHC) to 57.6% and water retention (WR) to 9.1% after 30 days. The degradation test indicates the IPNCB composite has a good degradability rate. Mixing soil with the prepared IPNCB composite can improve plant growth and reduce water consumption through the irrigation of arid lands. The IPNCB composite is a candidate in sustainable agriculture applications.

Solvent-free coupling of aldehyde, alkyne, and amine over a versatile catalyst: Ag-functionalized mesoporous S, P-doped g-C3N4

In the present study, we introduce mesoporous g-C3N4/Ag co-doped with P and S which was designed and acquired by using mesoporous silica (SBA-15) as a hard templating agent and thiourea and chitosan phosphate as the dopants. The prepared catalyst was completely identified by FT-IR (Fourier-transform infrared spectroscopy), XRD (X-ray powder diffraction), FE-SEM (field-emission scanning electron microscopy), EDX (energy-dispersive spectroscopy), TEM (transmission electron microscopy), and Raman spectroscopy. The efficiency of the synthesized catalyst was evaluated toward the three-component coupling reaction, frequently named as A3 coupling. The higher activity of the prepared catalyst is because of the synergistic effects of phosphorus and sulfur co-doped together with Ag deposition. The desired products were achieved by an environmentally safe catalyst under the optimized conditions in high yields and short reaction time ranges.

Palladium Nanoparticles from Different Reducing Systems as Heck Catalysts

Palladium(0) nanoparticles have been widely used in cross coupling reactions, including Heck reactions. For this study, we synthesized palladium(0) nanoparticles in colloidal suspension using different combinations of solvents and reducing methods under aerobic conditions. The variation in systems used to synthesize palladium(0) nanoparticles resulted in different nanoparticle sizes. To investigate whether the particle size had an effect on catalysis, we first used common Heck C–C cross-coupling reaction conditions (200 °C and 18 h). In addition, we omitted the use of stabilizing agents, other than the solvent and/or the anions in the initial nanoparticle synthesis, since the use of stabilizing agents adds cost and processing time to catalysis. All of the catalysts investigated worked in the cross coupling C–C Heck reaction, but yields did not show appreciable differences, as high temperature and long reaction times promote a high reduction of palladium(II). Therefore, we decided to work with a temperature and reaction time in which conversion would start to be observed (minimum reaction conditions). The experiments to determine minimum reaction conditions showed that this would be 120 °C and 10 h, therefore we used these conditions in Heck C–C cross-coupling reactions and all the palladium nanoparticle systems. The best C–C catalysis conversion was observed when N,N-dimethylformamide was used as solvent in the absence of reducing agent. This catalyst system resulted in the largest possible nanoparticles, which were kept in dispersion (did not precipitate out), showing that size is important in obtaining good yields in C–C Heck catalysis (where cocktail-type catalysis could explain the conversion). Nanoparticles of this size also act as a reservoir of soluble palladium species that behave as the true catalyst. The second best conversion was observed in N,N-dimethylformamide with sodium citrate, where citrate may have added extra protection, and since the palladium(0) nanoparticles were small, cocktail-type catalysis was not involved in obtaining high yields.

New digital tools for assessing neuropsychological executive functioning in old and new addictions. an exploratory study

IntroductionNowadays new tools suitable for exploring executive functioning (EF) of behavioral addicted individuals are needed.ObjectivesThis study tests a novel digital assessment battery that can be easily and remotely adopted by neuropsychologists working in the field of addiction.MethodsTwenty-three participants were divided into two groups, balanced for age and education: an experimental (EXP) group of 13 patients with gambling behavior, and a control (CNT) group of 10 healthy subjects. A neuropsychological battery including 5 neuropsychological tests (measuring long- and short-term verbal memory, working memory, cognitive flexibility, verbal and non-verbal fluency, attention), and a behavioral task (modified Go/NoGo task with addiction-related stimuli) was digitally administered. Anxiety, depression, and impulsivity levels were collected before the evaluation.ResultsSignificantly higher scores were found for repetition errors in the short-term verbal memory test, in the EXP subjects compared to controls. Higher reaction times were found in the Go/No-Go task for the EXP compared to CNT, with significant differences for neutral and addiction-related (cocaine, THC) stimuli. Furthermore, EXP showed higher impulsivity scores.ConclusionsAlthough the study was only exploratory, the significant results could support the validity of this new digital tool. Besides, we could conclude that memory impairment and attentional bias in inhibitory control tasks could cover a significant role in new and old addiction and that impulsivity could represent a critical factor in explaining the relationship between EF impairment and addiction. Lastly, this study contributes not only to the understanding of EF impairment in addictions but also in the delivery of remote suitable digital neuropsychological testing.DisclosureNo significant relationships.