Industrial solvents tetrahydrofuran

The major use of this chemical is in the manufacture of polyesters. It is also used to make an industrial solvent, tetrahydrofuran (THE). 

Tetrahydrofuran, THF, is an important industrial solvent and forms an azeotropic mixture at 5.3 wt% with water (see Table 10.3). To separate water/THF, Li et al. [148] tested the pervaporation performance of different hydrophihc zeolite membranes, zeolite A, zeohte Y, MOR, and ZSM-5. The preliminary test showed that the separation factor increased as the Si/Al ratio of the zeohte decreased, except for the case of zeolite A. This fact is probably due to the lower quality of this membrane with respect to the others since in the permeation of triisopropylbenzene (TIPB), showed the highest flux, 3.1 g/m h, indicating the presence of nonselective defects. Therefore, the best results were obtained with zeolite Y, rendering a separation factor of 300 with a water flux of 2.24 kg/m h at 60°C. The water flux increased with water concentration in the feed, up to a value of 15 wt%, indicating that the zeolite was saturated, as was the same for the case of water/ethanol mixtures in zeolite A, previously described. At the same time, the separation factor decreases as water concentration decreased. The stabihty of the membrane was also studied, showing a stable performance after 35 h of operation. 

Tetrahydrofuran is an excellent solvent for high molecular weight polymers such as poly(vinyl chloride), rubbers, and many others it is also used as the solvent for the formation of Grignard reagents, an important industrial reactant. Tetrahydrofuran is also used as a plasticizer in thermoplastic elastomers, such as polyurethanes and polyesters [117]. 

Tetrahydrofuran (THF, tetramethylene oxide, diethylene oxide, 1,4-epoxybutane, tetrahydrofurane, oxoiane) is an industrial solvent widely recognized for its unique combination of useful properties. DuPont THF is better than 99.9% pure with a small (0.025-0.040 wt %) amount of butylated hydroxytoluene (BHT, 4-methyl-2,6-di-tert-butyl phenol) added as an antioxidant. Tetrahydrofuran is a cycloaliphatic ether and is not "photochemically reactive" as defined in Section k of Los Angeles County s Rule 66 (equivalent to Rule 442 of the Southern California Air Pollution Controi District). THF has an ethereal odor. 

Tetrahydrofuran is a widely used industrial solvent. It is aprotic, with a low dielectric constant (7.52), low viscosity, and a fairly wide liquid range. Many of the early measurements of acidities in THE were made by the research group of Robert Eraser at the University of Ottawa in Canada. These workers measured the pKj,s of weak carbon acids [515], monosubsti-tuted benzenes [516], secondary amines [517], pyridines [518], and heteroaromatic carbon acids [519] using nuclear magnetic resonance (NMR) measurements in the period 1983-1985. Additional pK values in THF were determined by Streitwieser et al. [520]. 

In the packaging printing industry solvents like ethyl acetate, ethanol, ketones, tetrahydrofuran (THF), hexane and toluene are used in printing. The solvent laden air generally contains between 2 and 15 g/m of solvent and, depending on the season, 5-18 g/m of water. 

Poly(vinyl chloride) is soluble in few solvents (tetrahydrofuran, cyclohexanone, etc.). An acetone-soluble polymerizate can be obtained by extensive post-chlorination of the PVC and this product contains 63-64% chlorine. Chlorinated PVC s are used as adhesives, lacquer bases, and industrial fibers. The chlorination occurs in solution at 60-100°C or in the gel state at 50°C. In the gel-state chlorination, PVC is swollen with chlorohydrocarbons and irradiated in aqueous suspension with UV light. Since CH2 groups are more easily chlorinated than CHCl groups, the polymer contains approximately equal proportions of- CHCl—CHCl and -f H2—CHCl groups. At an equal chlorine content, the PVC that was chlorinated as a gel possesses a higher glass-transition temperature, probably because of the stronger block copolymer character. 

Figure 3.1 identifies the major stages in a solvents life cycle production, transport, use, and disposal. Although there are many opportunities to recycle and reuse solvents they will eventually need to be disposed of as waste. As an example, consider a process which uses tetrahydrofuran (THF). A 1 kg reduction in the amount ofTHF would reduce the CO2 emissions from THF production by about 16kg [3], This reduction in CO2 emissions does not account for the savings in transportation or disposal of excess THF in a process. Therefore, reductions in solvent use by the pharmaceutical industry not only reduce the waste it produces as part of its processes but also the waste that would be generated from the manufacture of additional solvent. 

The industrial catalytic Reppe process is usually applied in the production of acrylic acid. The catalyst is NiBr2 promoted by copper halides used under forcing conditions. The BASF process, for example, is operated at 225°C and 100 atm in tetrahydrofuran solvent.188 Careful control of reaction conditions is required to avoid the formation of propionic acid, the main byproduct, which is difficult to separate. Small amounts of acetaldehyde are also formed. Acrylates can be produced by the stoichiometric process [Eq. (7.20)], which is run under milder conditions (30-50°C, 1-7 atm). The byproduct NiCl2 is recycled ... 

Furfural is obtained commercially by mealing pentosan-rich ugricullural residues (corncobs, oat hulls, cottonseed hulls, hagasse. rice hulls) with a dilute acid and removing the furfural by steam distillation. Major industrial uses of furfuraldehyde include (1) the production of t urnns and tetrahydrofurans where the compound is an intermediate (2) Ihc solvent refining of petroleum and rosin products (3) the solvent binding of bonded phenolic products and (4) the extractive distillation of butadiene from other C4 hydrocarbons. 

One of the major uses of activated carbon is in the recovery of solvents from industrial process effluents. Dry cleaning, paints, adhesives, polymer manufacturing, and printing are some examples. Since, as a result of the highly volatile character of many solvents, they cannot be emitted directly into the atmosphere. Typical solvents recovered by active carbon are acetone, benzene, ethanol, ethyl ether, pentane, methylene chloride, tetrahydrofuran, toluene, xylene, chlorinated hydrocarbons, and other aromatic compounds [78], Besides, automotive emissions make a large contribution to urban and global air pollution. Some VOCs and other air contaminants are emitted by automobiles through the exhaust system and also by the fuel system, and activated carbons are used to control these emissions [77,78],... 

An industrially spent hydrotreating catalyst from naphtha service was extracted with tetrahydrofuran, carbon dioxide, pyridine and sulfur dioxide under subcritical and supercritical conditions. After extraction, the catalyst activity, coke content, and pore characteristics were measured. Tetrahydrofuran was not effective in the removal of coke from catalyst, but the other three solvents could remove from 18% to 54% of the coke from catalyst. 

Fischer and co-workers undertook a LCA of the 26 organic solvents which they had already assessed in terms of EHS criteria (see above).They used the Eco-solvent software tool (http //www.sust-chem.ethz.ch/tools/ecosolvent/), which on the basis of industrial data considers the birth of the solvent (its petrochemical production) and its death by either a distillation process or treatment in a hazardous waste incineration plant. For both types of end-of-life treatment, environmental credits were granted where appropriate, e.g. solvent recovery and reuse upon distillation. The results of this assessment are shown in Figure 1.2. From an LCA perspective, tetrahydrofuran (THF), butyl acetate, cyclohexanone and 1-propanol are not good solvents. This is primarily due to the environmental... 

General-purpose organic solvents used in the chemical industry that are difficult to separate with conventional methods represent a potential area where pervaporation finds applications. The use of polymeric membranes in this case was not very successful due to the low chemical stability of the polymers in the organic solvent. The separations that have been accomplished up-to-date with zeolite membranes include tetrahydrofuran, dimethylformamide, and dioxane. 

Complex multiphase process waste streams are generated in the production of active substances in the chemical industry. A number of standard types of chemistry reactions currently carried out in the pharmaceutical industry would generate complex waste solvent mixtures containing tetrahydrofuran, hexane, alcohols and water. 

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