Dimerization Of Α-methylstyrene Research Articles

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 < 10 MJ/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.

Cationic β-Scission of C-H and C--C Bonds for Selective Dimerization and Subsequent Sulfur-Free RAFT Polymerization of α-Methylstyrene and Isobutylene.

A series of exo-olefin compounds ((CH3)2C(PhY)-CH2C(=CH2)PhY) were prepared by selective cationic dimerization of α-methylstyrene (αMS) derivatives (CH2=C(CH3)PhY) with p-toluenesulfonic acid (TsOH) via β-C-H scision. They were subsequently used as reversible chain transfer agents for sulfur-free cationic RAFT polymerization of αMS via β-C-C scission in the presence of Lewis acid catalysts such as SnCl4. In particular, exo-olefin compounds with electron-donating substituents, such as a 4-MeO group (Y) on the aromatic ring, worked as efficient cationic RAFT agents for αMS to produce poly(αMS) with controlled molecular weights and exo-olefin terminals. Other exo-olefin compounds (R-CH2C(=CH2)(4-MeOPh)) with various R groups were prepared by different methods to examine the effects of R groups on the cationic RAFT polymerization. A sulfur-free cationic RAFT polymerization also proceeded for isobutylene (IB) with the exo-olefin αMS dimer ((CH3)2C(Ph)-CH2C(=CH2)Ph). Furthermore, telechelic poly(IB) with exo-olefins at both terminals was obtained with a bifunctional RAFT agent containing two exo-olefins. Finally, block copolymers of αMS and MMA were prepared via mechanistic transformation from cationic to radical RAFT polymerization using exo-olefin terminals containing 4-MeOPh groups as common sulfur-free RAFT groups for both cationic and radical polymerizations.

Crystallization of SAPO-11 Molecular Sieves Prepared from Silicoaluminophosphate Gels Using Boehmites with Different Properties

In this article, we report the results of research the formation of silicoaluminophosphate gels under changing gel aging conditions and the influence of an aluminum source (boehmite), characterized by different properties. The samples of initial gels were characterized by XRF, X-ray diffraction, MAS NMR 27Al and 31P, and scanning electron microscopy (SEM). Products of crystallization were characterized by XRF, X-ray diffraction, MAS NMR 27Al and 31P, scanning electron microscopy (SEM), N2-physical adsorption, and IR spectroscopy with pyridine adsorption. It has been established that the chemical and phase composition of aging gels and the products of further crystallization is conditioned by the size of the crystals and the porous structure of boehmite. Methods of management the morphology and secondary porous structure of SAPO-11, including the hierarchical porous structure, are proposed based on the use of boehmits characterized by different properties and changing the aging conditions of the initial gels. SAPO-based catalyst with a hierarchical porous structure showed excellent catalytic performance in dimerization of α-methylstyrene with a high degree of conversion and selectivity for linear isomers.

Selective dimerization of α-methylstyrene by tunable bis(catecholato)germane Lewis acid catalysts.

The synthesis of a variety of bis(catecholato)germanes is reported. The Lewis acidity of the bis(catecholato)germanes was assessed using the experimental Gutmann-Beckett method and computational FIA and GEI methods. The oligomerization of alkenes using bis(catecholato)germanes demonstrates the use of these complexes in catalysis. The use of donor additives in the dimerization of α-methylstyrene resulted in selectivity control comparable to transition metal catalyst systems.

Effect of the Aging Temperature of Gel on the Synthesis and Properties of the Silicoaluminophosphate Molecular Sieve SAPO-11

The effect of the aging temperature of the starting silicoaluminophosphate gel on the crystallization of the SAPO-11 molecular sieve was studied. When pseudoboehmite was used as an aluminum source, a gel containing di-n-propylamine phosphate, undissolved pseudoboehmite, and amorphous silicoaluminophosphate were formed. An increase in the aging temperature of the gel from 25 to 90°C led to an increase in the fraction of the amorphous phase in the latter. Crystallization of the silicoaluminophosphate gel aged at 90°C allows crystallization of SAPO-11 of high phase purity and nearly 98% crystallinity. High activity and selectivity for linear dimers (86%) of SAPO-11 in the dimerization of α-methylstyrene was shown.

Natural Nanofibrous Cellulose-Derived Solid Acid Catalysts.

Solid acid catalysts (SACs) have attracted continuous research interest in past years as they play a pivotal role in establishing environmentally friendly and sustainable catalytic processes for various chemical industries. Development of low-cost and efficient SACs applicable to different catalysis processes are of immense significance but still very challenging so far. Here, we report a new kind of SACs consisting of sulfonated carbon nanofibers that are prepared via incomplete carbonization of low-cost natural nanofibrous cellulose followed by sulphonation with sulfuric acid. The prepared SACs feature nanofibrous network structures, high specific surface area, and abundant sulfonate as well as hydroxyl and carboxyl groups. Remarkably, the nanofibrous SACs exhibit superior performance to the state-of-the-art SACs for a wide range of acid-catalyzed reactions, including dimerization of α-methylstyrene, esterification of oleic acid, and pinacol rearrangement. The present approach holds great promise for developing new families of economic but efficient SACs based on natural precursors via scalable and sustainable protocols in the future.

Catalytic Activity of Mordenite from Natural Source in the Dimerization of α-methylstyrene

Studying the activity of any catalyst and selectivity toward special products is easy by selecting a module reaction, and choosing appropriatecondition. In our case the reaction of α- methylstyrene dimerization was a choice to study the activity of mordenite type zeolite crystallized from natural clay mineral (kaolin P-2), and also the selectivity toward dimers.The prepared catalyst in the form of hydrogen showed that the acceptable activity and selectivity to linear dimers were (72.5%), at 80 °C, and atmospheric pressure. Different products from the dimerization of α- methylstyrene over prepared catalyst was investigated, and the conversion rate reached to 73%wt.

Computational Design of 2D Covalent-Organic Framework Membranes for Organic Solvent Nanofiltration

Covalent-organic frameworks (COFs) are ordered crystalline materials covalently formed by building blocks of light elements. There has been increasing interest in the development of COF membranes for chemical separation. In this study, seven two-dimensional (2D) COF membranes are computationally designed with different functional groups and aperture sizes. By 245 sets of molecular simulations, the seven ultrathin COF membranes are investigated for organic solvent nanofiltration (OSN) of seven solvents (acetonitrile, acetone, methanol, ethanol, isopropyl alcohol, methyl ethyl ketone, and n-hexane) and four solutes (2,5-furandiamine, paracetamol, α-methylstyrene dimer, and Nile red). The solvent fluxes through the COF membranes are revealed to be governed by the aperture size and membrane functionality, as well as solvent properties. In general, the larger the aperture size, the higher is the flux. For membranes with comparable aperture size, the hydrophobic one exhibits higher fluxes than the hydrophilic c...

One-Pot Chlorine-Free Synthesis of Chiral Organophosphorus Compounds from Elemental Phosphorus and α-Methylstyrene Dimer

Direct phosphorylation of α-methylstyrene dimer with red phosphorus in KOH/DMSO superbasic system has provided the preparation of 4-methyl-2,4-diphenylpentylphosphonous acid (heating at 105°C for 3 h) or tris(4-methyl-2,4-diphenylpentyl)phosphine oxide (microwave irradiation, 15 min) in 21 and 38% yield, respectively.

Influence of synthesis conditions on the adsorption and catalytic properties of mordenite zeolite

The effect of the preliminary holding of the BS-100 “white soot” at 150–155°C for 6 to 7 h and the crystallization conditions on both the characteristics of powdered MOR zeolite samples (degree of crystallinity, composition, particle size composition, and adsorption of C6H6 molecules) and their catalytic properties in the α-methylstyrene dimerization reaction has been studied.

Revelation of the Photoactive Species in the Photocatalytic Dimerization of α-Methylstyrene by a Dinuclear Ruthenium–Palladium Complex

A quantum chemical study of the photocatalytic dimerization of α-methylstyrene catalyzed by a dinuclear ruthenium-palladium complex was performed at the DFT/TD-DFT level in order to find the key steps of the catalytic reaction. This study reveals that the second insertion of α-methylstyrene is the rate-determining step and that it proceeds via triplet excited states of an intermediate complex. These excited states have geometries significantly different from that of the reactant, especially within the coordination sphere of the Pd unit. Indeed, one Pd-carbon bond is considerably lengthened, favoring the insertion process. These results open up the possibilities to optimize the process by fine modulation of the catalyst structure.

One-pot synthesis of a novel catalyst with strong acid sites based on carbon/silica composite

A novel catalyst with strong acid sites based on carbon/silica composite has been synthesized through one-pot hydrothermal carbonization of hydroxyethylsulfonic acid, glucose and tetraethyl orthosilicate (TEOS). The novel solid acid showed an acidity of 2.1 mmol/g, much higher than that of traditional solid acids such as Nafion and Amberlyst-15 (0.8 mmol/g). The catalytic activity of the solid acid was investigated in the acetalization and dimerization of α-methylstyrene. The results showed that the novel solid acid was very efficient for both hydrophilic and hydrophobic acid-catalyzed reactions. Because of the high acidity and catalytic activity the novel solid acid based on carbon/silica composite is a promising catalyst for the processes in green chemistry.

A kinetic model of the dimerization of α-methylstyrene in the presence of high-silica zeolite Y

The kinetics of the dimerization of α-methylstyrene in the presence of high-silica zeolite HNaY has been studied, and a nine-stage scheme of the monomer conversion has been developed. Analysis of the kinetic models developed in the form of the Langmuir-Hinshelwood relationships and in terms of the mass action law has shown that the first model more adequately describes the experimental data. The numerical values of kinetic and adsorption parameters are represented.

Recycling of valuable chemicals through the catalytic decomposition of phenol tar in cumene process

The base catalyst LZ-2, which was the mixture of CaO and Na–NaOH/Al2O3·3H2O, was chosen for the decomposition of phenol tar to generate valuable chemicals. The selectivity of LZ-2 for dimethyl phenyl carbinol, α-methyl styrene dimer and cumenyl phenol was 100%, 100% and 98%, respectively. Under the optimum operating conditions of catalyst 2.5wt%, operating temperature 603.15K and decomposition time 3.5h, decomposition ratios of cumenyl phenol and dimethyl phenyl carbinol were 98.7% and 99.97%, respectively. In addition, the experimental repeatability demonstrated that the total yield of valuable chemicals still reached 90.1% after the catalyst being used five times. Mass and energy balance indicated that the catalytic decomposition was a high potential for the recycling of chemicals from phenol tar.

Heteropolyacid-catalyzed dimerization of α-methylstyrene; on the efficiency and selectivity dependence

In the presence of catalytic amounts of a Keggin (H3PW12O40), Wells–Dawson (H6P2W18O62) or Preyssler (H14NaP5W30O110) heteropolyacid, α-methylstyrene (1) leads to dimers. The efficiency and the selectivity toward 2,4-diphenyl-4-methyl-1-pentene (2), 2,4-diphenyl-4-methyl-2-pentene (3) and 1,1,3-trimethyl-3-phenylindan (4) depend on the reaction temperature and the nature of both the catalyst and the solvent. Thus, 2, 3 and 4 can be produced in 45%, 50% and 97% yields, respectively.

SO 3H-bearing mesoporous carbon with highly selective catalysis

A SO 3H-bearing mesoporous carbon material was investigated as a new type of heterogeneous catalyst. Carbonization of resorcinol–formaldehyde resin at 773 K, followed by sulfonation results in amorphous carbon consisting of graphene with high densities of SO 3H (0.9 mmol g −1) and phenolic OH (2.0 mmol g −1) groups. The mesoporous carbon that has a large surface area (433 m 2 g −1) due to uniform mesopores (ca. 10 nm) exhibits remarkable catalytic performance for the selective dimerization of α-methylstyrene (AMS); the selectivity for unsaturated AMS dimers exceeds 99%. This catalysis is attributed to not only the large surface area based on large mesoporosity, but also to preventing intramolecular Friedel–Crafts alkylation.

Cyclodimerization of α-methylstyrene under homogeneous and heterogeneous acid catalysis conditions

The cyclodimerization of α-methylstyrene in the presence of Bronsted and Lewis acids was realized. The dependence of the cyclic α-methylstyrene dimer yield on the catalyst nature and structure was established. It was shown that the activity of the catalysts is determined by the strength of their acid sites, and the selectivity for the cyclic α-methylstyrene dimer depends on the nature of the anion (homogeneous acids) or the porous structure (heterogeneous catalysts). Sulfuric acid and silicophosphate exhibit the highest selectivity in the cyclodimerization of α-methylstyrene into 1,1,3-trimethyl-3-phenylindane.

Synthesis and Polymerization of Bismaleimide Derived from 5(6)-amino-1(4′-aminophenyl)-1,3,3′-trimethyl indane

The acid-catalyzed dimerization of α-methyl styrene led to the formation of trimethyl phenyl indane, which on nitration followed by reduction using hydrazine hydrate gave 5(6)-amino-1(4′-aminophenyl)-1,3,3′-trimethyl indane. This aromatic diamine was used to synthesize bismaleamic acid and imidized to yield bismaleimide. The bismaleamic acid was converted to prepolymer directly by imidizing it in refluxing toluene. All the materials synthesized were characterized using FTIR, 1H and 13C NMR. The direct inlet mass spectral characterizations were carried out for bismaleamic acid, bismaleimide and bismaleimide prepolymer. The fragmentation pattern was discussed in detail and the structure proposed was confirmed. The thermogravimetric studies were done for all the materials and kinetic parameters (energy of activation and frequency factor) were calculated using Dharwadkar and Kharkhanavala method. The structural changes occurring in the thermally polymerized bismaleimide and bismaleimide prepolymer were discussed.

Dimerization of α-methylstyrene in the presence of mordenite, aimed at preparation of transformer oils

Dimerization of α-methylstyrene in the presence of natural mordenite and its modified form was studied. The dependence of the yield and composition of the products on the process parameters was found. Conditions were determined for preparing linear dimers with a high selectivity.

Dimerization of vinylarenes on zeolite catalysts

The main features of dimerization of vinylarenes, such as styrene, α-methylstyrene, β-methylstyrene, p-methylstyrene, p-methoxystyrene, p-methoxy-β-methylstyrene, m-chlorostyrene, and m-nitrostyrene used as an example, over zeolite catalysts were studied, and the high activity and selectivity of these catalysts in the reaction was shown. For styrene and α-methylstyrene, the vinylarenes having the largest production volume, catalysts that hold promise for industrial application were developed. Conditions for the selective linear dimerization (85–93%) and cyclodimerization (85–98%) of styrene and α-methylstyrene at a high conversion (100%) were determined.