Vacuum distillation styrene

The dehydrogenation reaction produces crude styrene which consists of approximately 37.0% styrene, 61% ethylbenzene and about 2% of aromatic hydrocarbon such as benzene and toluene with some tarry matter. The purification of the styrene is made rather difficult by the fact that the boiling point of styrene (145.2°C) is only 9°C higher than that of ethylbenzene and because of the strong tendency of styrene to polymerise at elevated temperatures. To achieve a successful distillation it is therefore necessary to provide suitable inhibitors for the styrene, to distil under a partial vacuum and to make use of specially designed distillation columns. 

Superheated steam is used to bring the feed to reaction temperature. Reactor effluent is quenched, distilled to remove unreacted feed plus benzene and toluene made during the reaction, and the crude styrene finished by vacuum distillation. Inhibitors are added during the distillation steps to prevent polymerization of the styrene monomer. 

Styrene monomer was purified by vacuum distillation over CaHi. Inhibitor in styrene was removed using activated alumina. N-heptane was purified by distillation over sodium to remove tire trace of residual moisture. The purified slyreaie and n-heptane were stored over activated alumina under nitrogen blanket. Et[Ind]2ZrCl2 Strem Chem.), MAO (modified methylaluminoxane, type 3A, Akzo Novel) wee used without fiirtha" purification. 

Styrene (Fisher), p-methylstyrene (Mobil), and t-butylstyrene (DOW) were purified by passing through a column of activated alumina and then carefully degassed to remove all traces of 0. Further purification by vacuum distillation from dibutyl magnesium resulted in anionically pure monomers. 

Monomers. tetraethylsilicate (TES) and styrene were BDH AnalaR grade and hexamethylcyclotrisiloxane (HMCTS) was supplied by Aldrich. The styrene was distilled under reduced pressure from calcium hydrides prior to use and HMCTS sublimed under vacuum directly into the reaction vessel. 

Styrenes will give phenethylamines, 1-propenylbenzenes will give amphetamines. The tetrahydrofuran should be dried over KOH pellets and, if desired, distilled from sodium then from lithium aluminum hydride. The diglyme can be vacuum distilled from... 

Methylene dichloride [6] and perchloric acid [7] were purified and dosed as described. Silver perchlorate (BDH) was treated in vacuo for a few hours before use. 1-Phenylethyl bromide (Eastman-Kodak) was fractionally distilled under high vacuum and the middle fraction was collected into breakable phials since this compound undergoes a slow decomposition, yielding hydrogen bromide and styrene, when kept in bulk, solutions of it in methylene dichloride were prepared from the original phials by the tipping technique [7]. Styrene was purified [8], dried, and stored [9] as described. Shortly before use it was vacuum-distilled into breakable phials from a microburette. 

Monomeric styrene is destabilized as in Example 3-1 and pre-dried with calcium chlo-ride.The monomer is now allowed to stand over calcium hydride for 24 h and then distilled under reduced pressure of nitrogen into a previously flamed-out Schlenk tube. Pure 4-vinylpyridine is distilled twice over KOH pellets in vacuum.lt is then vacuum distilled under nitrogen through a column packed with Raschig rings into a previously flamed out Schlenk tube (bp 62 °C/12 torr).The closed Schlenk tubes containing the monomers are stored in a refrigerator until required.The preparation of the initiator solution (sodium naphthalene) is described in Example 3-19. 

Some liquids, e.g. styrene and nitrobenzene, have such low vapour pressures at ambient temperatures that vacuum distillation from ambient... 

The ability of PolyHIPE materials to absorb liquids has been exploited in experiments on their potential use as carrier materials for the safe transport of hazardous or flammable liquids [128]. A poly(styrene/DVB) sample was able to absorb twenty times its own weight of liquid paraffin, simply by immersing the material in the liquid. However, the problem in this application is the subsequent removal of the liquid from the polymer. This can only be achieved by vacuum distillation, which is very difficult with high boiling liquids. 

As noted in the introduction, the first successful studies of PCS near the glass transition in polymers employed thermally polymerized styrene. The monomer was dried over calcium hydride and vacuum distilled directly into the scattering cell. This procedure was also successfully employed to prepare poly(methyl methacrylate)(PMMA)28) and poly-(ethyl methacrylate)(PEMA)29). Although our own samples were all prepared without... 

The HDPE samples were compression-molded plaques (1.25 mm thick) prepared from Dow 04452N HDPE pellets. Styrene was vacuum distilled from calcium hydride, and ethylbenzene and tert-butyl perbenzoate (TBPB) were used as received (Aldrich). 

Materials. Styrene (BDH Chemicals Ltd.) was stabilized with 0.002 % t-butyl catechol. The stabilizer was removed by washing successively with 10 % potassium hydroxide solution and water, drying over calcium chloride for 24 hr, and vacuum distilling. The monomer was kept in a refrigerator until required. Effective removal of inhibitor was checked by gas chromatography and by dilatometric measurement of the rate of bulk thermal polymerization at 60 °C this was 0.080 % hr which compares with a literature value (17) of 0.089 % hr . ... 

Most dehydrogenations do not occur readily even at high temperatures. The driving force for this reaction is the extension in conjugation that results, since the double bond on the side chain is in conjugation with the ring. Conditions must be controlled to avoid polymerization of the styrene and sulfur may be added to prevent polymerization. The crude product is a mixture of styrene, and ethylbenzene that is separated by vacuum distillation, after which the ethylbenzene is recycled. Usually a styrene plant is combined with an ethylbenzene plant when designed. 

The monomers were vacuum distilled three times and dried with CaH2. THF was refluxed over CuCl2 (5 hr), refluxed five times over CaH2 (8 hr), distilled, and finally refluxed over LiAlH4. All treatments were carried out under nitrogen. Before the monomers were added, a drop of styrene was added to the solvent which was titrated with n-butyl lithium until the weakly red, styrylic anion color was stable. 

HydrogenadoB. The withdrawal stream from vacuum distillation is hydrogenated to remove the residual hydroperoxide and to convert the acetophenone. Fractionation removes the ethylbenzene and then the phenyl-1 ethanol from the hydrogenation effluent The separation of ethylbenzene must be carefiiUy effected to avoid subsequent superffactio-nation in the presence of styrene. 

C. styrene monomer was washed with 10 sodium hydroxide solution and vacuum distilled. All ingredients were oxygen-free and the system was co ntlnuously purged with nitrogen. The liquid additive and monomer were added to the aqueous surfactant solution prior to the addition of the initiation system. The formulation which consisted of a high surfactant concentration was as follows ... 

The styrene (Polysciences) was washed with 10 aqueous sodium hydroxide to remove the inhibitor and vacuum-distilled under dry nitrogen the 1-pentanol (Fisher Scientific) was dried over potassium carbonate and vacuum-distilled the potassium persulfate (Fisher Scientific) was recrystallized twice from water the 2,2 -azobls(2-methyl butyro-nltrlle) (E. I. du Pont de Nemours) was recrystallized twice from methanol the sodium dodecyl sulfate (Henkel) was used as received its critical micelle concentration measured by surface tension was 5.2 mM. Dlstllled-delonlzed water was used in all experiments. 

The styrene monomer (certified grade, Fisher Scientific Company) was cleaned before use. The inhibitor was removed by washing with 10% wt. aqueous sodium hydroxide solution. The monomer was then washed with distilled deionized water, dried overnight (at 5°C) with anhydrous sodium sulfate, vacuum distilled under dry nitrogen, and then stored at 5°C until use. 

Monomers were purchased from Polysciences, Inc. The liquid monomers (methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, methyl acrylate, n-butyl acrylate, methacrylic acid, acrylic acid, styrene and a-methylstyrene) were purified by vacuum distillation under nitrogen, poured into thin-walled ampules, degassed at 10 - 10 torr and subsequently frozen in liquid nitrogen. The partially filled ampules were then inserted between a pair of parallel plate electrodes connected to an International Plasma Corporation Model 3001 Radiofrequency Generator, which operates at 13.56 MHz and delivers up to 150 watts of power. In most of these experiments discussed in this work, the power input was limited to 40 - 80 watts. The ampules were allowed to warm up until droplets of liquids appeared. A glow discharge was then in-Current address Department of Chemistry, Ibaraki, University, Mito 310 Japan... 

Vacuum distil the reaction mixture to remove the excess styrene. 

Materials. Phillips polymerization grade cyclohexane and butadiene were used. Styrene was a commercial polymerization grade. Solvent was dried over activated Alcoa H151 alumina, and monomers were dried over activated Kaiser 201 alumina before they were transferred to the charge tanks. n-Butyllithium and sec-butyl lithium were purchased from Lithium Corporation of America. Chiorosilanes were vacuum distilled before use. 

Butadiene (B) sionomer vas flashed at 46 C from Its dimer and Inhibitor, then condensed by passing through activated alumina Into the container at -15 C under N2 pressure. Styrene (S), was either dried through activated alumina, or refluxed over CaH2 then vacuum distilled. e-Caprolactone (CL) was distilled from CaR2 at reduced pressure. Ethylene oxide (EO) was purchased from Eastman Chemical Co., diluted in dried cyclohexane before use and used without further purification. n-Butyllithlum (n-BuLi) In heptane was obtained from Alfa Products and dlethylalumlnum chloride (DEAC) was from Texas Alkyls. They were diluted In purified cyclohexane before... 

Anionic techniques were used to synthesize the block polymers which function as precursors to ion containing block polymers. Monomers were carefully dried by repeated vacuum distillation from CaH2. Distillation from dibutyl magnesium was also utilized for the final purification of the hydrocarbon monomers, styrene and diphenyl ethylene. The methacrylate monomers may also be finally purified... 

Chemicals. Reagent grade, thiophene free benzene (Baker), and vacuum distilled styrene (Matheson, Coleman and Bell) were used in the discharge experiments. The helium (Matheson) had a reported minimum purity of 99.995%. The acetylene (Matheson) was at least 99.6% pure. 

Photolysis of 1.00 g (3.90 mmol) of 9-diazothioxanthene-5,5-dioxidel l in 20 mL of p-methylstyrene, contained in 25 mL-size Vycor glass, using a Hanovia lamp (450 W), was continued until disappearance of the starting diazo-red color. After vacuum distillation of the unreacted styrene, column chromatographic separation of the residue (silica gel, methylene chloride/n-pentane (1 2)), solvent removal and recrystallization from ether afforded 1.10 g (81%) of 2.10b, mp 190 °C. 

After the radical polymerisation, there are around 0.3-0.5% unreacted monomers. ACN (bp = 77.3 °C) is very easy to eliminate by vacuum distillation, due to its low boiling point, but styrene (bp = 145.2 °C) is relatively difficult to eliminate and needs several... 

Example 4.7. Styrene is manufactured by catalytic dehydrogenation of ethylbenzene. The separation sequence includes vacuum distillation to separate styrene from unreacted ethylbenzene. Estimate the relative volatility between these two compounds based on Raoult s law AC-values at typical distillation operating conditions of 80°C (176°F) and lOOtorr (13.3 kPa) (the low temperature is employed to prevent styrene polymerization). Compare the computed relative volatility to the experimental value of Chaiyavech and Van Winkle. Also calculate the heat of vaporization of ethylbenzene at 80°C. 

This close agreement indicates that ethylbenzene and styrene obey Raoult s law quite closely at vacuum distillation conditions. 

Materials. VEC was prepared by the catalyzed addition of CO2 to 3,4-epoxy-l-butene using conditions typical of that used industrially [77], then purified by vacuum distillation. Other raw materials were used as received without any additional purification. Mixed xylenes, vinyl acetate (VA), butyl acrylate (BA), butyl methacrylate (BMA), methyl methacrylate (MMA), styrene (St), and t-butyl hydroperoxide were obtained from Aldrich Chemical Company. Lupersol 575 (t-amyl peroxy (2-ethylhexanoate)) was supplied by Elf Atochem. Vazo 67 (2,2 -azobis(2-methylbutyronitrile)) was obtained from DuPont Chemical Company. Vinyl pivalate (NE05), vinyl 2-ethylhexanoate (V2EH), Tergitol NP-40 (non-ionic surfactant) and QP-300 (hydroxy ethyl cellulose) were obtained from Union Carbide Coq)oration. Aerosol OT-75 (surfactant) was obtained from Cytec. Sodium formaldehyde sulfoxylate was obtained from Henkel Corporation. Ethyl 3-ethoxy propionate (EEP), propylene glycol monomethyl ether (PM) and PM acetate (PM Ac) are Eastman Chemical Company products. 

In contrast to alkylation of benzole, dehydration of ethyl benzole is endothermic. This process is carried out at high temperatures of 550-600 °C by means of heterocatalysis. The resulting styrene, to which a polymerization inhibitor has been added, is then vacuum-distilled before further processing. This complex purification procedure is made necessary by the close proximity of the boiling points of ethyl benzole and styrene. 

Olefinic hydrocarbons have a very strong tendency to polymerise, and commercially available materials are generally stabilised, e g. with hydroquinone. When distilling compounds such as vinylpyridine or styrene, the stabiliser remains behind and the purified olefinic material is mote prone to polymerisation. The most common impurities are higher-boiling dimeric or polymeric compounds. Vacuum distillation in a nitrogen... 

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