Methanol dehydration distil

Azeotropic Distillation. The concept of azeotropic distillation is not new. The use of benzene to dehydrate ethyl alcohol and butyl acetate to dehydrate acetic acid has been in commercial operation for many years. However, it was only during World War II that entrainers other than steam were used by the petroleum industry. Two azeotropic processes for the segregation of toluene from refinery streams were developed and placed in operation. One used methyl ethyl ketone and water as the azeo-troping agent (81) the other employed methanol (1). 

Dehydration solutions specimens are transferred through graded solvents (50-60% in distilled water) up to 100% in the solvent. Solvents such as ethanol, methanol, or acetone can be used... 

Methanol containing no acetone is fractionally distilled through an efficient column, dehydrated with calcium hydride, and the distillation and drying are repeated three times. This process will yield about 50% of the starting material. One distillation of methanol over sodium reduces the water content to 0.003% after the second distillation it is 0.00005%. 

In the traditional "wood distillation industry" hardwood was preferred for production of chemicals. Hardwood distillation was formerly an important source for production of acetic acid, methanol, and acetone which were the primary products of this process. The heat required for pyrolysis was generated by burning gas, oil, or coal. In the thermal degradation of wood the volatile components are distillable and can be recovered as liquids after condensation (Fig. 10-2). The solid residue, charcoal, is mainly composed of carbon. At higher temperatures the carbon content is increased because of a more complete dehydration and removal of volatile degradation products. Charcoal is mainly used as combustible material for special purposes. A number of charcoal products are known, including activated carbon for adsorption purposes. 

DMA and TMA. Product ratios can be varied to maximize MMA, DMA, or TMA production. The correct selection of the N/C ratio and recycling of amines produces the desired product mix. Most of the exothermic reaction heat is recovered in feed preheating (3). The reactor products are sent to a separation system where firstly ammonia (4) is separated and recycled to the reaction system. Water from the dehydration column (6) is used in extractive distillation (5) to break the TMA azeotropes and produce pure anhydrous TMA. The product column (7) separates the water-free amines into pure anhydrous MMA and DMA. Methanol recovery (8) improves efficiency and extends catalyst life by allowing greater methanol slip exit from the converter. Addition of a methanol-recovery column to existing plants can help to increase production rates. 

Low boiling substances are removed from the chilled reactor product by distilling up to a cut point of 80 °C. These low boilers are gaseous dimethyl ether, methyl acetate, acetaldehyde, butyraldehyde, and ethyl acetate. The bottoms are flash-distilled to recover the rhodium catalyst. Flash distilled acid is azeotropically dehydrated. In the final distillation, glacial acid is obtained. Traces of iodine that may remain in the finished acid may be removed by fractional crystallization or by addition of a trace of methanol followed by distillation of the methyl iodide that forms. Somewhere in the carbonylation reaction, a minute amount of propionic acid seems to be made. It typically is found in the residues of the acetic acid finishing system and can be removed by purging the finishing column bottoms. 

Standard Alcohol Solutions. Add 100 p-1 of dehydrated alcohol or of methanol to 100 ml of distilled water. Add 50]al to 250 ]al of this solution, in increments of 50 p-1, to 1.0-ml aliquots of the internal standard solution in stoppered test-tubes. This gives standard alcohol solutions equivalent to... 

The catalytic activity of heteroion-exchanged TSM, Ti Zn -TSM, is different from the activities of Ti - and Zn -TSMs. The results of the methanol conversion over the catalysts 35, 36) are summarized in Table V, which includes the data for Ti -TSM from Table IV. The reaction conditions are the same as given in Table IV. The heteroion-exchange reaction was conducted using a mixed solution of Ti(IV) and Zn(II) chlorides (mole ratio = 9 1). The resultant precipitate was washed with distilled water repeatedly and quickly to obtain Ti" Zn -TSM and Ti Zn -TSM/Cl, respectively. Ti -TSM catalyzes the dehydration of methanol to give dimethyl ether and a small amount of hydrocarbons, mainly methane, as described in the preceding section. The catalytic activity of Ti Zn -TSM is less than one-sixth as low as that of Ti -TSM, although only one-tenth of the Ti" in Ti -TSM has been replaced with Zn, inactive for the... 

Water can be removed from methanol by a membrane of polyvinyl alcohol cross-linked with polyacrylic acid, with a separation factor of 465.204 A polymeric hydrazone of 2,6-pyridinedialdehyde has been used to dehydrate azeotropes of water with n- and /-propyl alcohol, s- and tort butyl alcohol, and tetrahydrofuran.205 The Clostridium acetobutylicum which is used to produce 1-butanol, is inhibited by it. Pervaporation through a poly(dimethyl-siloxane) membrane filled with cyclodextrins, zeolites, or oleyl alcohol kept the concentration in the broth lower than 1% and removed the inhibition.206 Acetic acid can be dehydrated with separation factors of 807 for poly(4-methyl-l-pentene) grafted with 4-vinylpyridine,207 150 for polyvinyl alcohol cross-linked with glutaraldehyde,208 more than 1300 for a doped polyaniline film (4.1 g/m2h),209 125 for a nylon-polyacrylic acid membrane (5400 g/m2h), and 72 for a polysulfone.210 Pyridine can be dehydrated with a membrane of a copolymer of acrylonitrile and 4-styrenesulfonic acid to give more than 99% pyridine.211 A hydrophobic silicone rubber membrane removes acetone selectively from water. A hydrophilic cross-linked polyvinyl alcohol membrane removes water selectively from acetone. Both are more selective than distillation.212... 

Purification. The effluent is sent to a series of distillations. The first (30 to 35 trays) separates a methanol/water mixture at the top, which is then sent to a dehydration tower (25 to 30 trays), while the bottom is sent to a column in winch the ester is fractionated under partial vacuum (40 to 45 trays). Methyl toluate and excess p-xylene leave at the top and are recycled to the oxidation reactor. The withdrawal, consisting of crude terephthalate, is redistilled under vacuum to remove heavy compounds (20 trays), and then sent to a vacuum crystallizer (40 to 50 kPa absolute) using methanol as solvent. This may be followed by a second crystallization, or a countercurrent washing with methanol to complete the purification. The dimethyl terephthalate is finally centrifuged, melted to remove residual methanol, and vacuum distilled (30 trays). The molar yield of the operation in relation to p-xylene is about 87 per cent... 

Syrup. Freely sol in water, slightly sol in methanol, ethanol, glacial acetic acid. Dehydration by distillation with diox an e yields iactobionic d-lac lone, C H On, non-deliquescent crystals, dec 195-196°. Shows mutarotation, (a)tf + 5.1.0 initial (c = 8,8) - [ajg1 +22.6 final (240 minutes). 

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