Hoechst method

Figure 98. Methane chlorination by the Hoechst method (production of dichloromethane and trichloromethane) a) Loop reactor b) Process gas cooler c) HCl absorption d) Neutralization system e) Compressor f) First condensation step (water) g) Gas drying system h) Second condensation system and crude product storage vessel (brine) i) Distillation columns for CHjCl, CH2CI2, and CHCI2... 

The reaction (Hoechst method) is conducted adiabatically at 350 - 450 C. The gas mixture is cooled in a heat exchanger, then the HCl is removed by washing the gas in three stages with dilute hydrochloric acid, with water and with sodium hydroxide solution or by adiabatic absorption, then dried with concentrated sulfuric acid, and finally condensed. Afterwards the products are separated by distillation. A typical output is 70% CH2CI2, 27% CHCI3 and 3% CCI4 (see Fig. 98). 

The ketene—crotonaldehyde route through polyester with various modifications and improvements is reportedly practiced by Hoechst Celanese, Cheminova, Daicel, Ueno, Chisso, Nippon Gohsei, and Eastman Chemical Company. Differences in thein processes consist mosdy in the methods of polyester splitting and first-stage purification. Production of the potassium salt can be from finished sorbic acid or from a stream in the sorbic acid production route before the final drying step. Several patents on the process for producing sorbic acid and potassium sorbate from this route are given in the hterature. 

Both continuous and batch methods may be used in methanolysis. The batch mediod requires an autoclave, crystallizer, and centrifuge and a system for the melting and distillation of the DMT obtained. In the two-stage Hoechst continuous process, waste PET is melted and fed to a reactor. Preheated methanol is added to the autoclave, which is equipped with a mixer. The conversion reaches 70-90% in the first reactor, after which the reaction stream is introduced into a second autoclave at a lower temperature near the bottom, where it rises slowly and die higher density impurities settle at the bottom. The reaction stream leaves the second autoclave and its pressure is reduced to 0.3 MPa. On further reduction of the pressure and cooling, DMT precipitates and is subsequently purified.12... 

NMR spectroscopy, 93. See also Proton NMR integrations Hoechst continuous process, 548 Homo-coupling reactions, aryl halide, 486-487 Homopolymers, 7 Hot-cast prepolymer method, 211 Hot phosgenation, 222 Houvink-Sakurada equation, 286 HTMAB. See Hexadecyltrimethylammonium bromide (HTMAB)... 

In 1958 Taylor demonstrated SCEs, using autoradiographic techniques to detect the disposition or labeled DNA following incorporation of [3H]-thymidine. 5-Bromo-2 -deoxyuridine (drdU) has now replaced [3H]-thymidine and various staining methods have been used to show the differential incorporation of BrdU between sister chromatids fluorescent Hoechst 33258 (Latt, 1973) combined fluorescent... 

Nelsen, S., Golder, M. and DeStio, P., Method and compositions for toughening polyester resins, US Patent 6020414 (to Hoechst Celanese Corporation, Somerville, NJ), 2000. 

Hoechst has developed a method moulding PP foam automobile air ducts that optimise air flow and also provide good sound and heat insulation. Machines are adapted to suck the parison onto the mould walls rather than to blow mould it. The process also uses a blowing pin operating in reverse mode to create a partial vacuum inside the moulding in order to roughen its inner surface. HOECHST AG... 

Other similar lipase/esterase resolution processes have been developed such as the use of Bacillus that esterase to produce the substituted propanoic acids that are precursors of non-steroidal anti-inflammatory drags, snch as naproxen and ibuprofen etc., and the formation of chiral amines by Celgene. Other methods start from prochiral precursors and have the advantage that enantioselective synthesis allows the production of particular isomers in yields approaching 100%, rather than the 50% yields characteristic of resolution processes. For instance Hoechst have patented the production of enantiomers using Pseudomonas fluorescens lipase to either acylate diols or hydrolyse diacetate esters. 

More important is the transformation of benzene to 1,3-benzenedisulfonic acid utilized in the manufacture of resorcinol.97 According to an older method benzene is sulfonated in two steps first by 100% sulfuric acid at 100°C, and then by 65% oleum at 80-85°C. The Hoechst new continuous one-step process applies sulfur trioxide at 140-160°C in molten 1,3-benzenedisulfonic acid. m-Diisopropylbenzene, via its dihydroperoxide is, however, displacing this process. 

Rinse with PBS and mount the coverslip as described above. This method, using unfixed preparations, is even more rapid than the one described above using Hoechst 33258. A kit based on DAPI is available from Bioassay Systems. 

A mixture of telomers which contain 4 to 20 carbon atoms with a high majority of C6 and C8 is obtained and exhibits a very narrow molecular distribution. These methods of oligomerization were mainly reviewed by Allied, Daikin, I.C.I., Hoechst, Dupont and Atochem. 

Following the technological breakthroughs which led to the discovery of (1) the liquid crystalline behavior ofpara-oriented aramids26 and (2) a novel method for spinning anisotropic liquid crystalline polymer solutions,27 Kevlar aramid fiber was produced and commercialized by the DuPont company in 1972. Other fibers based on aromatic polyamide compositions, which were produced and commercialized by other companies, were Technora (Teijin, Japan), Teijinconex (Teijin, Japan), andTwaron (Akzo, The Netherlands). Additionally, SVM is a fiber produced in the Former Soviet Union and it was announced in 1990 that a new aramid fiber had been introduced by Hoechst, in Germany. 

Other separation methods have also led to developments, without necessarily culmi Dating in plant construction. Thus, Hoechst has proposed esterification, or, more precisely, passage through t-butylacetate, and Union Carbide has proposed adsorption on molecular sieves. Butenes isomerization, isobutane dehydrogenation, and c-butyl alcohol dehydration (4i C0 Chemicat) offer complementary methods for synthesizing isobutene. 

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