Phosgene, from oxidation

FIG. 23-3 Temperature and composition profiles, a) Oxidation of SOp with intercooling and two cold shots, (h) Phosgene from GO and Gfi, activated carbon in 2-in tubes, water cooled, (c) Gumene from benzene and propylene, phosphoric acid on < uartz, with four quench zones, 260°G. (d) Mild thermal cracking of a heavy oil in a tubular furnace, hack pressure of 250 psig and sever heat fluxes, Btu/(fr-h), T in °F. (e) Vertical ammonia svi,ithesizer at 300 atm, with five cold shots and an internal exchanger. (/) Vertical methanol svi,ithesizer at 300 atm, Gr O -ZnO catalyst, with six cold shots totaling 10 to 20 percent of the fresh feed. To convert psi to kPa, multiply by 6.895 atm to kPa, multiply by 101.3. 

A possible exception to the foregoing statement is the so-called "disproportionation" of phosgene (see Chapter 8). This process. Equation (4.15), has been proposed as an efficient method for the manufacture of tetrachloromethane, although in the present feedstock situation this process would not be economical. Indeed, at the current prices commanded for phosgene, and with the perceived availability of carbon tetrachloride, it would be more beneficial to be able to derive phosgene from CC1 , for example by oxidation or hydrolysis. 

The formation of phosgene by the aerial oxidation of chlorinated organic compounds is of considerable industrial interest and has been considered, in its proper context, in some detail in Section 3.3, whilst the in vivo and in vitro formation of phosgene from organochlorine compounds has been discussed in Section 2.5.4. Only those reactions which might constitute a synthetic procedure will be considered here. 

Bromine compounds are much more expensive than chlorine compounds and, since the atomic weight of bromine is about twice that of chlorine, the halogen cost incurred in the use of bromine compounds as intermediates is likely to be at least an order of magnitude greater than the cost of the corresponding chlorine compound. Not least for this reason, the synthesis of phosgene from bromine-containing compounds is unlikely to be economically practical and are probably not worthy of development on a purely commercial basis. However, C-Br bonds are more readily cleaved than C-CI bonds, and bromide is readily oxidized back to bromine. 

Desulfurization of petroleum feedstock (FBR), catalytic cracking (MBR or FI BR), hydrodewaxing (FBR), steam reforming of methane or naphtha (FBR), water-gas shift (CO conversion) reaction (FBR-A), ammonia synthesis (FBR-A), methanol from synthesis gas (FBR), oxidation of sulfur dioxide (FBR-A), isomerization of xylenes (FBR-A), catalytic reforming of naphtha (FBR-A), reduction of nitrobenzene to aniline (FBR), butadiene from n-butanes (FBR-A), ethylbenzene by alkylation of benzene (FBR), dehydrogenation of ethylbenzene to styrene (FBR), methyl ethyl ketone from sec-butyl alcohol (by dehydrogenation) (FBR), formaldehyde from methanol (FBR), disproportionation of toluene (FBR-A), dehydration of ethanol (FBR-A), dimethylaniline from aniline and methanol (FBR), vinyl chloride from acetone (FBR), vinyl acetate from acetylene and acetic acid (FBR), phosgene from carbon monoxide (FBR), dichloroethane by oxichlorination of ethylene (FBR), oxidation of ethylene to ethylene oxide (FBR), oxidation of benzene to maleic anhydride (FBR), oxidation of toluene to benzaldehyde (FBR), phthalic anhydride from o-xylene (FBR), furane from butadiene (FBR), acrylonitrile by ammoxidation of propylene (FI BR)... 

Cyclic ureas have many applications as intermediates in the preparation of biologically active molecules. The conventional methods involve cyclization of 1,2-diamines with phosgene or oxidative carbonylation of diamines. Varma and coworkers developed a direct synthesis of cyclic ureas from urea and diamines in the presence of ZnO using microwaves. The major advantage of the method is that the reaction is accelerated by exposure to microwave irradiation the byproducts were, moreover, easily eliminated compared with traditional methods [32]. 

To do this, a highly active, nonselective catalyst is required. This is in direct contrast to almost all industrial oxidation reactions where selectivity for partially oxidized products is essential. Another consideration for removal of trace contaminants is that, if the oxidation is incomplete, compounds more toxic than the trace contaminant may be formed (e.g., formation of phosgene from incomplete oxidation of vinyl chloride vapors). 

Hazardous Decomp. Prods. Heated to decomp., emits highly toxic fumes of hydrogen chloride gas, chlorine, phosgene, CO NFPA Health 4, Flammability 2, Reactivity 0 Storage Sensitive to moisture, heat store refrigerated, away from oxidizing materials protect from moisture storage under inert atm. rec. 

Crystalline solid m.p. 35-36 "C, b.p. 154--156 C, prepared by oxidizing A,A -dicycIo-hexylthiourea with HgO in carbon disulphide solution, also obtained from cyclohexylamine and phosgene at elevated temperatures. Used as a mild dehydrating agent, especially in the synthesis of p>eptides from amino-acids. Potent skin irritant. 

In the ketone method, the central carbon atom is derived from phosgene (qv). A diarylketone is prepared from phosgene and a tertiary arylamine and then condenses with another mole of a tertiary arylamine (same or different) in the presence of phosphoms oxychloride or zinc chloride. The dye is produced directly without an oxidation step. Thus, ethyl violet [2390-59-2] Cl Basic Violet 4 (15), is prepared from 4,4 -bis(diethylamino)benzophenone with diethylaruline in the presence of phosphoms oxychloride. This reaction is very useful for the preparation of unsymmetrical dyes. Condensation of 4,4 -bis(dimethylamino)benzophenone [90-94-8] (Michler s ketone) with AJ-phenjl-l-naphthylamine gives the Victoria Blue B [2580-56-5] Cl Basic Blue 26, which is used for coloring paper and producing ballpoint pen pastes and inks. 

Liquid aliphatic halides are obtained alcohol-free by distillation from phosphorus pentoxide. They are stored in dark bottles to prevent oxidation and, in some cases, the formation of phosgene. 

A new route to ethylene glycol from ethylene oxide via the intermediate formation of ethylene carbonate has recently been developed by Texaco. Ethylene carbonate may be formed by the reaction of carbon monoxide, ethylene oxide, and oxygen. Alternatively, it could be obtained by the reaction of phosgene and methanol. 

A series of reactions with gases have been selected for the rapid quantification of many of the major products from the oxidation of polyolefins. Infrared spectroscopy is used to measure absorptions after gas treatments. The gases used and the groups quantified include phosgene to convert alcohols and hydroperoxides to chloroformates, diazomethane to convert acids and peracids to their respective methyl esters, sulfur tetrafluoride to convert acids to acid fluorides and nitric oxide to convert alcohols and hydroperoxides to nitrites and nitrates respectively. 

Aromatic polycarbonates are currently manufactured either by the interfacial polycondensation of the sodium salt of diphenols such as bisphenol A with phosgene (Reaction 1, Scheme 22) or by transesterification of diphenyl carbonate (DPC) with diphenols in the presence of homogeneous catalysts (Reaction 2, Scheme 22). DPC is made by the oxidative carbonylation of dimethyl carbonate. If DPC can be made from cyclic carbonates by transesterification with solid catalysts, then an environmentally friendlier route to polycarbonates using C02 (instead of COCl2/CO) can be established. Transesterifications are catalyzed by a variety of materials K2C03, KOH, Mg-containing smectites, and oxides supported on silica (250). Recently, Ma et al. (251) reported the transesterification of dimethyl oxalate with phenol catalyzed by Sn-TS-1 samples calcined at various temperatures. The activity was related to the weak Lewis acidity of Sn-TS-1 (251). 

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