Oxidation of propylene with

Propylene Process. The oxidation of propylene with nitric acid is a two-step process (22—29). Propylene reacts with Hquid NO2 to produce an... 

Ammonia is used in the fibers and plastic industry as the source of nitrogen for the production of caprolactam, the monomer for nylon 6. Oxidation of propylene with ammonia gives acrylonitrile (qv), used for the manufacture of acryHc fibers, resins, and elastomers. Hexamethylenetetramine (HMTA), produced from ammonia and formaldehyde, is used in the manufacture of phenoHc thermosetting resins (see Phenolic resins). Toluene 2,4-cHisocyanate (TDI), employed in the production of polyurethane foam, indirectly consumes ammonia because nitric acid is a raw material in the TDI manufacturing process (see Amines Isocyanates). Urea, which is produced from ammonia, is used in the manufacture of urea—formaldehyde synthetic resins (see Amino resins). Melamine is produced by polymerization of dicyanodiamine and high pressure, high temperature pyrolysis of urea, both in the presence of ammonia (see Cyanamides). 

Noncatalytic oxidation of propylene to propylene oxide is also possible. Use of a small amount of aldehyde in the gas-phase oxidation of propylene at 200—350°C and up to 6900 kPa (1000 psi) results in about 44% selectivity to propylene oxide. About 10% conversion of propylene results (214—215). Photochemical oxidation of propylene with oxygen to propylene oxide has been demonstrated in the presence of a-diketone sensitizers and an aprotic solvent (216). 

The direct oxidation of propylene with oxygen is a noncatalytic reaction occurring at approximately 90-140°C and 15-20 atmospheres. In this reaction hydrogen peroxide is coproduced with acetone. At 15% isopropanol conversion, the approximate yield of acetone is 93% and that for H2O2 is 87% ... 

Since approximately 2.2 lb of /-butyl alcohol would be produced per 1 lb of propylene oxide, an alternative reactant in this method is ethylbenzene hydroperoxide. This eventually forms phenylmethylcarbinol along with the propylene oxide. The alcohol is dehydrated to styrene. This chemistry was covered in Chapter 9, Section 6 as one of the syntheses of styrene. Thus the side product can be varied depending on the demand for substances such as /-butyl alcohol or styrene. Research is being done on a direct oxidation of propylene with oxygen, analogous to that used in the manufacture of ethylene oxide from ethylene and oxygen (Chapter 9, Section 7). But the proper catalyst and conditions have not yet been found. The methyl group is very sensitive to oxidation conditions. 

Fic. 10. lsO concentration in acrolein as a function of consumed oxygen in the oxidation of propylene with IS02 and l60 catalyst. The arrows show the point where consumption of loxide ions as the Bi2(Mo04)3 phase in the catalyst system (40). 

The mobility of lattice oxide ion under the working conditions was examined in the oxidation of propylene with 1802 for a series of... 

Propylene thermal oxidation with hydrogen peroxide is implemented with formation of propylene oxide, acrolein and allene, and C3H6 present in the system plays the role of the active oxygen acceptor from 0—OH. To put it another way, the conjugated oxidation of propylene with hydrogen peroxide is also a H02-dependent reaction [31]. 

Most important is the cumene process with an 80-85% share worldwide cumene (isopropylbenzene obtained from alkylation of benzene with propylene) is oxidized to the corresponding hydroperoxide which is decomposed to a mixture of phenol and acetone. In Japan the second most important process for acetone production is the direct oxidation of propylene with a 12% share. 

Kambing [7] has quantified the comparative mass transfer in OCFS and monoliths for the oxidation of propylene. With equal residence times, virtually 100% conversion was achieved in the OCFS at a throughput for which only 79% conversion was achieved in the monolith, although the temperature in the latter was higher and the surface area 1.4 times that of the OCFS. The mass transfer data, in the form of the Sherwood number, Sh, can be correlated with the Reynolds and Schmidt numbers. Re and Sc, respectively, in the form... 

Two process routes to propylene oxide are commercially practiced hydroperoxide formation and then use of this to oxidize propylene, and formation of propylene chlorohydrin followed by treatment with a base to form propylene oxide [22, 23]. It has not been possible to produce adequate yields of propylene oxide via the direct oxidation of propylene with air in the manner in which ethylene oxide is now produced, although attempts to come close to this continue [24]. 

Citric acid derived from sugars by fermentation can be converted to methacrylic acid with hot water (as mentioned in Chap. 8). Acrylonitrile (a carcinogenic monomer) is made by the oxidation of propylene with a mixture of ammonia and oxygen.21... 

The discovery ofmesoporous MCM-41 has opened up new avenues for the oxidation of larger substrates and the use of bulkier oxidants. The cumene hydroperoxide-based chemistry is characterized by a high selectivity and, consequently, very low by-product formation. The principal steps of the selective oxidation of propylene with cumene hydroperoxide are shown in Figure 1.7. When using mesoporous silicates with isomorphous titanium substitution, alkylaromatic hydroperoxides such as CFIP become the more attractive oxidants than TBFIP because of the ease of reuse. 

Sumitomo developed a recirculation process for manufacture of PO using CHP as oxidant (196). The company developed both a new catalyst and a new process for PO production. The production method is fundamentally similar to known methods involving organic peroxides as oxidants the major difference is that cumene is used as the reaction medium and hence the process is referred to as the cumene PO-only process. Laboratory tests started in 2000 and pilot plant testing in 2001. A plant was completed in 2002 and started up in 2003. This commercial plant was the first PO-only plant in Japan, producing PO by oxidation of propylene with cumene hydroperoxide without a significant formation of coproducts. The plant is located in the Chiba prefecture, operated by a joint venture between Nihon Oxirane Co. and Lyondell, and produces aroimd 200,000 t of PO/year. A second plant was started in May 2009 in Saudi Arabia, as a joint project of Sumitomo with Saudi Arabian Oil Co. 

Figure 1.15 Process flow diagram for the oxidation of propylene with cumene hydroperoxide as the oxidizing agent and titanium-containing mesoporous material as the heterogeneous catalyst (Sumitomo process). The process involves the following steps (1) A process for oxidation of cumene with air to obtain CMHP, (2) a process for epox-idation of propylene in the presence of a catalyst whereby o,a-dimethyl benzyl-alcohol CMA) is concomitantly obtained from CMHP, (3) a process for the hydrogenation of CMA with H2 i n the presence of a catalyst to obtain cumene, (4) a process for purification of the cumene, followed by recycle of cumene to the oxidation process, and (5) a process for the purification of PO. Adapted from Ref. (271), with permission from Wiley-VCH.

The TS-1 catalyst has also been found effective in the epoxidation of olefinic compounds. It is of particular interest in the preparation of propylene oxide by oxidation of propylene with hydrogen peroxide (Hoelderich, 1988). Ethylene has also been epoxidized to ethylene oxide with 30% H2O2 in aqueous /-butanol to obtain 96% selectivity at 97% H2O2 conversion (Sheldon, 1991). 

Fig. 60. Kinetics of pressure variation in the slow oxidation of propylene with oxygen. Initial pressure of the CgHg/Og mixture 320 torr at 300 °C, (For further explanations see...

Direct oxidation of propylene with air or pure oxygen (equivalent to ethylene oxide manufacturing) is not efficient, since the silver catalysts used in the direct ethylene oxidation are not suitable for the reaction of alkenes with allylic hydrogen atoms (like propylene). Direct oxidation of propylene results mainly in acrolein formation and total oxidation. Some 3% of the world capacity of PO is produced by very recently developed processes, for example, hydroperoxidation of cumene and propylene and catalytic epoxidation of propylene using H2O2. 

Indirect oxidation of propylene is an important route for propylene oxide production that proceeds in two reaction steps. The first step is the formation of a peroxide from alkanes, aldehydes, or adds by oxidation with air or oxygen. The second reaction step is the epoxidation of propylene to PO by oxygen transfer from the peroxide with formation of water, alcohol, or acid. The catalytic oxidation of propylene with organic hydroperoxides is nowadays a successful commercial production route (51% of world capacity). Two organic hydroperoxides dominate the processes (i) a process using isobutane (peroxide tert-butyl hydroperoxide, co-product tert-butyl alcohol), which accounts for 15% of the world capacity and (ii) a process using ethylbenzene (peroxide ethylbenzene hydroperoxide, co-product styrene) that accounts for 33% of the world capacity. The process via isobutane is presented by ... 

Compared to EO, propylene oxide (PO) is less reactive and less hazardous. PO is mainly used for the production of polyether, polyols, polyurethane, glycols, and ethers. Direct oxidation of propylene with air or pure oxygen is not efficient, and PO is produced either by the chlorohydrin process (46% share) or by indirect oxidation. Indirect oxidation of propylene proceeds in two steps. The first step is the formation of a peroxide from iso-butane or ethylbenzene by oxidation with air/oxy-gen (peroxides tert-butyl hydroperoxide and ethylbenzene hydroperoxide, respectively). The second step is the catalytic epoxidation of propylene to propylene oxide by oxygen transfer from the peroxide. In future, oxidation processes based on H2O2 will probably also play an important role. In 2008, the first commercial plant of this kind went on stream. 

The continuous flow oxidation of propylene with O2 to propylene glycol in SCCO2 at 138 bar on a Cu/Cu20/Mn02 catalyst showed strong pressure dependence with a maximum selectivity of 95%. Catalyst dissolution and deactivation did not occur over a run time of 50 hours. However, the space-time yields were still one order of magnitude too low for scale-up. ... 

In the oxidation of propylene with the same experimental setup, fronts propagating back and forth were obtained [43]. The latter were associated with macroscopic oscillations. The motion of the front could even become irregular (Figure 4) [43], at the same time the integral oscillations became chaotic (Figure 5) [48,49]. 

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