Α-methyl Styrene Research Articles

Free Alcohol-Mediated Radical Alkynylation and Allylation of Unactivated C(sp3)-H Bonds.

The daunting challenges in converting alcoholic O-H bonds with high bond-dissociation energy (BDE) to alkoxy radicals and harnessing those unruly reaction species largely limit exploiting free alcohols in C(sp3)-H functionalization. Herein we describe a novel radical alkynylation and allylation of unactivated C(sp3)-H bonds with unmodified aliphatic alcohols. The use of phenyliodine bis(trifluoroacetate) (PIFA) enables the formation of alkoxy radicals under mild photochemical conditions. α-Methyl styrene serves as a sacrificial-reagent that significantly improves the reaction outcomes. This transition-metal free protocol further features broad substrate scope, exclusive site-selectivity, high product diversity, and simple operation, supplying a robust manifold for C(sp3)-H functionalization using easily available aliphatic alcohols as feedstock.

Characterization and kinetics study of poly(α-methyl styrene) synthesized by living anionic polymerization

Characterization and kinetics study of poly(α-methyl styrene) synthesized by living anionic polymerization

Synthesis and Characterization of Graft Copolymers with Poly(ε-caprolactone) Side Chain Using Hydroxylated Poly(β-myrcene-co-α-methyl styrene).

Graft copolymers have unique application scenarios in the field of high-performance thermoplastic elastomers, resins and rubbers. β-myrcene (My) is a biomass monomer derived from renewable plant resources, and its homopolymer has a low glass transition temperature and high elasticity. In this work, a series of tapered copolymers P(My-co-AMS)k (k = 1, 2, 3) were first synthesized in cyclohexane by one-pot anionic polymerization of My and α-methyl styrene (AMS) using sec-BuLi as the initiator. PAMS chain would fracture when heated at high temperature and could endow the copolymer with thermal degradation property. The effect of the incorporation of AMS unit on the thermal stability and glass transition temperature of polymyrcene main chain was studied. Subsequently, the double bonds in the linear copolymers were partially epoxidized and hydroxylated into hydroxyl groups to obtain hydroxylated copolymer, which was finally used to initiate the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) to synthesize the graft copolymer with PCL as the side chain. All these copolymers before and after modifications were characterized by proton nuclear magnetic resonance (1H NMR), gel permeation chromatography (GPC), thermogravimetry analysis (TGA), and differential scanning calorimeter (DSC).

Thermodynamic and economic analysis of a deployable and scalable process to recover Monomer-Grade styrene from waste polystyrene

Less than 5% of polystyrene is recycled, motivating a search for energy efficient and economical methods for polystyrene recycling that can be deployed at scale. One option is chemical recycling, consisting of thermal depolymerization and purification to produce monomer-grade styrene (>99%) and other co-products. Thermal depolymerization and distillation are readily scalable, well-established technologies; however, to be considered practical, they must be thermodynamically efficient, economically feasible, and environmentally responsible. Accordingly, mass and energy balances of a pyrolysis reactor for thermal depolymerization and two distillation columns to separate styrene from α-methyl styrene, styrene dimer, toluene, and ethyl benzene co-products, were simulated using ASPEN to evaluate thermodynamic and economic feasibility. These simulations indicate that monomer-grade styrene can be recovered with energy inputs <10MJ/kg, comparable to the energy content of pyrolysis co-products. Thermodynamic sensitivity analysis indicates the scope to reduce these values and enhance the robustness of the predictions. A probabilistic economic analysis of multiple scenarios combined with detailed sensitivity analysis indicates that the cost for recycled styrene is approximately twice the historical market value of fossil-derived styrene when styrene costs are fixed at 15% of the total product cost or less than the historical value when feedstock costs are assumed to be zero. A Monte Carlo and Net Present Value-based economic performance analysis indicates that chemical recycling is economically viable for scenarios assuming realistic feedstock costs. Furthermore, the CO2 abatement cost is roughly $1.5 per ton of averted CO2, relative to a pyrolysis process system to produce fuels. As much as 60% of all polystyrene used today could be replaced by chemically recycled styrene, thus quantifying the potential benefits of this readily scalable approach.

Catalytic pyrolysis characteristics of polystyrene by biomass char-supported nanocatalysts

Plastics originate from the synthesis of chemical products, and the regeneration of chemical products from waste plastics through catalytic pyrolysis helps to reduce the dependence on fossil resources and improve the treatment of waste, which is an important aspect of current sustainable social development. In this study, metasequoia was used as a biomass precursor and three porous char-supported nanocatalysts (Fe-MEC, Ni-MEC, and Co-MEC) were synthesized via a simple and feasible microwave heating method, which were then used as catalysts for the preparation of high-quality liquid oil from polystyrene powder via an ex-situ catalytic pyrolysis method. The results indicate that Fe-MEC, Ni-MEC, and Co-MEC possessed good pore structures due to the microwave-heating and catalytic effect of these metals, and metal nanoparticles are generated and uniformly anchored on the matrix of the char support. Using these catalysts, the yield of liquid product from polystyrene pyrolysis decreased slightly, while the gas yield increased slightly. Fe-MEC catalysis reached the highest liquid yield of 91% among the three catalysts. The catalysts can improve the yield of a series of high-value liquid products such as toluene, ethylbenzene, and α-methyl styrene. The catalysts also exhibited excellent cycle stability, and carbon nanotubes were formed which are less prone to deactivation.

Catalytic pyrolysis of polystyrene in different reactors: Effects of operating conditions on distribution and composition of products

The effects of temperature and pressure on product distribution were investigated by catalytic slow pyrolysis of polystyrene in a fixed bed. Simultaneously, the catalytic fast pyrolysis of polystyrene was carried out in a fixed-fluidized bed to study the effects of temperature and reaction time on the product distribution. The slow and fast pyrolysis experiments of polystyrene were conducted using γ- Al2O3 (basic) as catalyst and silica sand as control group. The compositions of oil and gas products were analyzed by GC-FID, GC-MS and GC to investigate the catalytic activity of basic catalyst. The results showed that catalytic slow pyrolysis and catalytic fast pyrolysis achieved maximum oil yields of 94.6 wt% and 92.19 wt%, respectively. In slow pyrolysis, toluene, ethylbenzene, and styrene were the main products, and the introduction of catalyst led to reduced yields of toluene, ethylbenzene, cumene, and α-methyl styrene. However, the main product of fast pyrolysis was only styrene, with a recycling rate nearly 80% under catalytic conditions. The presence of the catalyst increased the yield of styrene, with slow pyrolysis rising from 27.15% to 32.58%, and fast pyrolysis increasing from 82.28% to 86.56%. Longer residence time strengthened secondary reactions to generate more aromatics such as toluene and ethylbenzene. Both catalytic slow and fast pyrolysis yielded higher styrene contents than thermal pyrolysis because the basic catalyst reduced the occurrence of secondary reactions.

Cu(II) and Mo(VI) Schiff base complexes immobilized on magnetic multiwalled carbon nanotubes: Oxidation of olefins and theoretical study

In this study, magnetic multiwalled carbon nanotubes (MMWCNT@SiO2) were anchored with phenylene diamine and subsequently prepared as Schiff base through mono condensation with salicylaldehyde, resulting in MMWCNT@SiO2/Schiff base. This was then complexed with either copper acetate monohydrate or molybdenum oxide to form MMWCNT@SiO2/Schiff base/M (M=Cu, MoO2). The prepared samples were characterized with FTIR, EDS, SEM and XRD. The catalytic behavior of the prepared samples was studied in the oxidation reaction. The results revealed that MMWCNT@SiO2/Schiff base/M (M=Cu, MoO2) effectively catalyzed the oxidation reaction of α-methyl styrene leading to more than 99% conversion and selectivity of acetophenone. In addition to the experimental investigations, theoretical calculations were conducted using DFT calculations to provide further insights into the results.

Synthesis and characterization of N4-donor Schiff base copper(II) immobilized on superparamagnetic Fe3O4@SiO2 and its use as a recyclable catalyst for oxidation of alkenes, alcohols, and determination of antibacterial activity

N4-donor Schiff base copper(II) nanoparticles were easily prepared through surface modification of silica-coated magnetite nanoparticles (Fe3O4@SiO2) with pyrrole 2-carbaldehyde Schiff base and a subsequent reaction with Cu(CH3COO)2.H2O in ethanolic solution. This nanocatalyst was characterized using thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and magnetization. Efficient oxidation of alkenes and alcohols was carried out over the Schiff base copper(II) nanoparticles. Catalytic tests showed that the catalyst was particularly effective for the oxidation of α-methyl styrene, norbornene, benzyl alcohol, and benzohydrol. The results showed that acetophenone, 2-norbornanone, benzoic acid, and benzophenone with selectivity values of 88, 100, 100, and 100, respectively, were obtained. The heterogeneous catalyst of N4-donor Schiff base copper(II) offers advantages such as ease of product separation, catalyst recycling, and ease of preparation. Antibacterial tests against two gram-positive and two gram-negative bacterial species found that the bacteria stopped growing in the catalyst medium.

Fuel oil production from thermal decomposition of the model and waste polystyrene: Comparative kinetics and product distribution

The thermal degradation of model polystyrene (MPS) and waste polystyrene (WPS) was performed in a thermobalance system at four heating rates (β) i.e., 5, 10, 15 and 20 °C/min in an inert atmosphere. The apparent activation energy (Ea) and frequency factor (A) for the MPS and the WPS were calculated using Ozawa-Flynn-Wall (OFW), Kissinger-Akahira-Sunose (KAS), and Augis-Bennetis (AB) methods. It has been determined that Ea and A vary according to fraction conversion, heating rates, and applied models. The activation energy determined for MPS was found to be in the range of 91-106, 90-105, and 114-133 kJ/mol, while, for WPS, Ea was determined in the range of 82-160, 79-159 and 102-202 kJ/mol by applying OFW, KAS, and AB models, respectively. From the results obtained, it was concluded that the Ea determined by all of these methods increases with fraction conversion, indicating that the decomposition of polystyrene follows a complex mechanism of the solid-state reaction. Hence, the kinetic parameters, i.e., Ea and A, seem to play a key role in investigating the mechanism of solid-state reactions and will provide an opportunity to develop the mechanism of the industrial decomposition reactions. The results show that the MPS has a lower activation energy compared to WPS. This high Ea of WPS may be due to the additives used in the manufacturing of different polystyrene products. Pyrolysis GC/MS of WPS indicates that the main components of pyrolysis oil are 1-hydroxy-2-propanone, styrene, α-methyl styrene, toluene, and 1,2-dimethyl benzene. The presence of some oxygenated compounds in the fuel oil of WPS may be due to contamination or additives used during polystyrene processing, as the WPS samples were collected from a garbage dump near a local market. WPS can be utilized as fuel if the fuel oil collected from the pyrolysis of WPS is properly upgraded to make it equivalent to commercial fuel oil.

Rh(II)-Catalyzed Enynal Cycloisomerization for the Generation of Vinyl Carbene: Divergent Access to Polycyclic Heterocycles

Described herein is an unprecedented example of generating the endocyclic donor–donor vinyl carbene achieved by the dirhodium(II)-catalyzed enynal cycloisomerization. The endocyclic vinyl carbene intermediate could be trapped by a diversity of alkenes, including 1,1-disubstituted alkenes, dienes, and α-methyl styrenes, which could undergo [2 + 1], [4 + 3] cycloaddition and an unexpected formal allylation, respectively, giving spiro and fused polycyclic heterocycles. In these cascade transformations, up to three rings and three stereocenters were constructed in one step with good selectivities. The enantioselective versions were also achieved with up to 84% ee. Mechanistic studies revealed that a concerted intramolecular [2 + 3] cycloaddition was the key step for the generation of vinyl Rh(II) carbene. Detailed studies were conducted to elucidate the intriguing mechanism of the formal allylation.

Effects of Heating Rate and Temperature on the Thermal Pyrolysis of Expanded Polystyrene Post-Industrial Waste.

The use of plastic as material in various applications has been essential in the evolution of the technology industry and human society since 1950. Therefore, their production and waste generation are high due to population growth. Pyrolysis is an effective recycling method for treating plastic waste because it can recover valuable products for the chemical and petrochemical industry. This work addresses the thermal pyrolysis of expanded polystyrene (EPS) post-industrial waste in a semi-batch reactor. The influence of reaction temperature (350-500 °C) and heating rate (4-40 °C min-1) on the liquid conversion yields and physicochemical properties was studied based on a multilevel factorial statistical analysis. In addition, the analysis of the obtaining of mono-aromatics such as styrene, toluene, benzene, ethylbenzene, and α-methyl styrene was performed. Hydrocarbon liquid yields of 76.5-93% were achieved at reaction temperatures between 350 and 450 °C, respectively. Styrene yields reached up to 72% at 450 °C and a heating rate of 25 °C min-1. Finally, the potential application of the products obtained is discussed by proposing the minimization of EPS waste via pyrolysis.

Homo- and copolymerization of 2-benzothiazoylacrylamide with α-methyl styrene and methyl acrylate: synthesis, characterization and reactivity

2-benzothiazolyl acrylamide (BTA) monomer was synthesized by reacting of 2-aminobenzothiazole with acryloyl chloride. Homo- and copolymerization of this monomer with α-methylstyrene (MSt) and methyl acrylate (MA) was carried out in dimethylsulfoxide (DMSO) solution. The prepared homo-and copolymers were characterized by Fourier Transform Infrared (FTIR) and their thermal stability was studied by thermogravimetric analysis (TGA). The composition of copolymers and the reactivity coefficients (r1, r2) were determined on the basis of sulfur analysis using linearization methods proposed by Fineman-Ross and Kelen-Tudos and the Mayo-Lewis intersection method. The derived (r1, r2) for BTA-co-MSt and BTA-co-MA are: (0.197, 0.230) and (0.294, 4.314), respectively. The microstructure of the copolymers and the distribution of the monomer sequences in the copolymers were calculated statistically, the results obtained are consistent with the values (r1, r2). BTA with MSt form alternative copolymer whilst BTA-co-MA tends to be block with MA.

Influence of Carbon Dioxide on the Glass Transition of Styrenic and Vinyl Pyridine Polymers: Comparison of Calorimetric, Creep, and Rheological Experiments

The glass transition of amorphous polymers determines the mobility of polymer chains and the time scale of relaxation processes. The glass transition temperature is reduced by the presence of low molecular weight molecules, e.g., dissolved gases or organic solvents. The quantitative knowledge of reduction of the glass transition temperature caused by the addition of carbon dioxide in a polymer melt is highly relevant for foam extrusion. However, measurement of the reduction of glass transition temperature caused by gas loading has to be performed under elevated pressure which implies high experimental efforts. In this work, we discuss and compare three methods for determination of the influence of carbon dioxide on thermal properties of amorphous polymers, i.e., calorimetric measurements, creep tests, and rheological experiments. The advantages and disadvantages of these methods are elucidated. Furthermore, the influence of molecular structure of the styrenic and vinylpyridine polymers on the glass transition temperature is discussed. Polystyrene generally shows the highest reduction of glass transition temperature. Poly(2-vinylpyridine) and poly(4-vinylpyridine) show a slightly less pronounced behaviour in comparison to polystyrene because of the lower polarity of polystyrene. Poly(α-methyl styrene) is associated with a different dependence of glass transition temperature on gas loading in calorimetric and rheological experiments.

Alkali-Grafting Proton Exchange Membranes Based on Co-Grafting of α-Methylstyrene and Acrylonitrile into PVDF.

A novel alkali-induced grafting polymerization was designed to synthesize a PFGPA proton exchange membrane based on the co-grafting of α-methyl styrene (AMS) and acrylonitrile (AN) into the poly(vinylidenedifluoride) (PVDF) membrane. Three kinds of alkali treatments were used: by immersing the PVDF membranes into a 1 M NaOH solution and mixing the PVDF powders with 16% or 20% Na4SiO4. Then, AMS with AN could be co-grafted into the PVDF backbones in two grafting solvents, THF or IPA/water. Finally, the grafted membranes were sulfonated to provide the PFGPA membranes. In the experiments, the Na4SiO4 treatments showed a greater grafting degree than the NaOH treatment. The grafting degree increased with the increasing amount of Na4SiO4. The grafting solvent also influenced the grafting degree. A 40–50 percent grafting degree was obtained in either the THF or IPA/water solvent after the Na4SiO4 treatment and the THF resulted in a greater grafting degree. FTIR and XPS testified that the PFGPA membranes had been prepared and a partial hydrolysis of the cyano group from AN occurred. The PFGPA membranes with the grafting degree of about 40–50 percent showed a better dimensional stability in methanol, greater water uptake capabilities, and lower ion exchange capacities and conductivities than the Nafion 117 membranes. The PFGPA membrane with the 16% Na4SiO4 treatment and THF as the grafting solvent exhibited a better chemical stability. The obtained experimental results will provide a guide for the synthesis of alkali-grafted PFGPA membranes in practical use.

PREPARATION OF OPTICAL TRANSPARENT COMPOSITES ON THE BASIS OF BUTYL METHACRYLATE WITH -METHYL STYRENE

The process of radical binary copolymerization of butyl methacrylate and α-methyl styrene in a solvent has been carried out and optically transparent copolymers at various molar ratios have been synthesized. The copolymers synthesized based on butyl methacrylate and α-methyl styrene have relatively high refraction coefficient ( =1.5880) and transmission values (about 86%). The copolymerization constants values (r1 and r2) of the above-mentioned monomer pairs have been found and Q-e parameters have been calculated. The microstructure of the obtained copolymer samples of the butyl methacrylate with α-methyl styrene has been determined

Catalytic cracking of polystyrene pyrolysis oil: Effect of Nb2O5 and NiO/Nb2O5 catalyst on the liquid product composition

The catalytic cracking of polystyrene pyrolysis oil was investigated over a Nb2O5 and a NiO/Nb2O5 catalyst in a fixed bed reactor. First, the pyrolysis of two different polystyrene feedstock (polystyrene foam and polystyrene pellet) was carried out in a semi-batch reactor, and the resulting polystyrene pellets pyrolysis oil was selected for catalytic cracking reaction because of its high liquid yield (85%). Catalytic cracking experiments were then performed at different temperatures (350–500 °C) using Nb2O5 or NiO/Nb2O5 catalyst. Gas chromatography–mass spectrometry analysis of liquid product obtained from the catalytic cracking process showed that the dimers in the pyrolysis oil were converted to monomers during the catalytic cracking process. The catalytic cracking results also showed that the NiO/Nb2O5 catalyst (having slightly higher acidic sites) had slightly higher activity for monomer conversion than the Nb2O5 catalyst (having less acidic sites). X-ray diffraction, transmission electron microscopy, pyridine Fourier transform infrared spectroscopy, NH3 Temperature Programmed Desorption and X-ray photoelectron spectroscopy were used to characterize the catalyst. The highest catalytic cracking activity was observed at 400 °C with the Nb2O5 catalyst with 4% toluene, 6% ethylbenzene, approximately 50% styrene, 13% α-methyl styrene, and only 6% of dimers in the liquid oil. The increase in temperature positively affected the yield of gases during catalytic cracking process.

Poly(α-methyl styrene) polymer additive for organic thin film transistors

Poly(α-methyl styrene) polymer additive for organic thin film transistors

Chemical Recycling of WEEE Plastics—Production of High Purity Monocyclic Aromatic Chemicals

More than 200 kg real waste electrical and electronic equipment (WEEE) shredder residues from a German dismantling plant were treated at 650 °C in a demonstration scale thermochemical conversion plant. The focus within this work was the generation, purification, and analysis of pyrolysis oil. Subsequent filtration and fractional distillation were combined to yield basic chemicals in high purity. By means of fractional distillation, pure monocyclic aromatic fractions containing benzene, toluene, ethylbenzene, and xylene (BTEX aromatics) as well as styrene and α-methyl styrene were isolated for chemical recycling. Mass balances were determined, and gas chromatography–mass spectrometry (GC-MS) as well as energy dispersive X-ray fluorescence (EDXRF) measurements provided data on the purity and halogen content of each fraction. This work shows that thermochemical conversion and the subsequent refining by fractional distillation is capable of recycling WEEE shredder residues, producing pure BTEX and other monocyclic aromatic fractions. A significant decrease of halogen content (up to 99%) was achieved with the applied methods.

New Cu(II), Co(II) and Ni(II) azo-Schiff base complexes: Synthesis, characterization, catalytic oxidation of alkenes and DFT study

Three new complexes with general formula of ML (M = Cu (1), Co (2), Ni (3)) containing an azo-Schiff base ligand (H2L) derived from 2,3-butanediamine and 4-(benzeneazo) salicylaldehyde were synthesized by template method. Characterization of the ligand and complexes were accomplished with FT-IR, UV–Vis, and 1H NMR. The catalytic activity of the complexes (1–3) were tested for the oxidation of various alkenes (cyclooctene, cyclohexene, styrene, α-methyl styrene, and norbornene) applying tert-butyl hydroperoxide (TBHP) as an oxidizing agent, and it was found that they were acceptable catalysts. Under the optimized reaction conditions, CuL complex displayed 94% conversion for the oxidation of cyclooctene, and CoL and NiL complexes exhibited 90 and 85% conversions for oxidizing α-methyl styrene, respectively. Based on our density functional computations, diffuse functions are compulsory in the basis set for geometry optimization of these systems. Therefore, the most stable structures and the vibrational frequencies were calculated at the M06-2X/6–311++G(d,p) level. By establishing the correlation between observed and calculated frequencies, the assignment of the vibrational modes was performed. Based on natural charge analysis (NAO), the back electron transfer from ML to the TBHP breaks the OO bond and facilitates the formation of tert-butoxyl radicals.

N-Arylbenzo[b]phenothiazines as Reducing Photoredox Catalysts for Nucleophilic Additions of Alcohols to Styrenes: Shift towards Visible Light

Abstract N-Phenylphenothiazines are an important class of photoredox catalysts because they are synthetically well accessible, they allow the tuning of the optoelectronic properties by different substituents, and they have strong reduction properties for activation of alkenes. One of the major disadvantages of N-phenylphenothiazines, however, is the excitation at 365 nm in the UV-A light range. We synthesized three differently dialkylamino-substituted N-phenylbenzo[b]phenothiazines as alternative photoredox catalysts and applied them for the nucleo­philic addition of alkohols to α-methyl styrene. The additional benzene ring shift the absorbance bathochromically and allows performing the photocatalyses by excitation at 385 nm and 405 nm. This type of photoredox catalysis tolerates other functional groups, as representatively shown for alcohols as substrates with C–C and C–N triple bonds.