Cumene phosphoric acid process

Propylation of benzene with propylene, catalyzed by supported phosphoric acid (or related catalysts such as AlCl ), gives cumene [98-82-8] in another important industrial process. Cumene (qv), through the intermediacy of cumene hydroperoxide, is used in the manufacture of phenol (qv). Resorcinol similarly can be made from y -diisopropylbenzene (6). 

Currently, almost all cumene is produced commercially by two processes ( /) a fixed-bed, kieselguhr-supported phosphoric acid catalyst system developed by UOP and (2) a homogeneous AlCl and hydrogen chloride catalyst system developed by Monsanto. 

SPA Catalyst. The sohd phosphoric acid (SPA) catalyst process has been the domiaant source of cumene siace the 1930s. This process accounts for more than 90% of cumene operating capacity (59). A simplified process flow diagram is given ia Figure 5. 

Catalysts. Nearly aU. of the industrially significant aromatic alkylation processes of the past have been carried out in the Hquid phase with unsupported acid catalysts. For example, AlCl HF have been used commercially for at least one of the benzene alkylation processes to produce ethylbenzene (104), cumene (105), and detergent alkylates (80). Exceptions to this historical trend have been the use of a supported boron trifluoride for the production of ethylbenzene and of a soHd phosphoric acid (SPA) catalyst for the production of cumene (59,106). 

Cumene as a pure chemical intermediate is produced in modified Friedel-Crafts reaction processes that use acidic catalysts to alkylate benzene with propylene (see Alkylation Friedel-CRAFTSreactions). The majority of cumene is manufactured with a soHd phosphoric acid catalyst (7). The remainder is made with aluminum chloride catalyst (8). 

During World War II, isopropyl benzene, more commonly and commercially known as cumene, was manufactured in large volumes for use in aviation gasoline. The combination of a benzene ring and an iso-paraffin structure made for a very high octane number at a relatively cheap cost. After the war, the primary interest in cumene was to manufacture cumene hydroperoxide. This compound was used in small amounts as a catalyst in an early process of polymerizing butadiene with styrene to make synthetic rubber. Only by accident did someone discover that mild treating of cumene hydroperoxide with phosphoric acid resulted in the formation of... 

The reachon of benzene with ethylene or propylene to form ethylbenzene or isopropylbenzene (cumene) is an industrially important transformahon, with ethylbenzene as the key building block for polystyrene and cumene as the feedstock for phenol produchon [55]. Fthylbenzene was originally produced with a Lewis acid catalyst consishng of AlCfi or a Bronsted acidic solid phosphoric acid (SPA) catalyst [56]. Both catalyst systems suffered from equipment corrosion so, in the 1980s the Mobil-Badger vapor phase alkylation process was introduced, which... 

The related manufacture of cumene (isopropylbenzene) through the alkylation of benzene with propylene is a further industrially important process, since cumene is used in the synthesis of phenol and acetone. Alkylation with propylene occurs more readily (at lower temperature) with catalysts (but also with hydrogen fluoride and acidic resins) similar to those used with ethylene, as well as with weaker acids, such as supported phosphoric acid (see further discussion in Section 5.5.3). 

Lewis and protic acids, usually AICI3 and H2SO4, are used in the liquid phase at temperatures of 40-70°C and at pressures of 5-15 atm. Phosphoric acid on kieselguhr promoted with BF3 (UOP process)309 319 is used in gas-phase alkylation (175-225°C, 30-40 atm). In addition to the large excess of benzene, propane as diluent is also used to ensure high (better than 94%) propylene conversion. This solid phosphoric acid technology accounts for 80-90% of the world s cumene production. 

Cumene is industrially produced by propylating benzene over supported acidic catalysts such as phosphoric acid. On the other hand, the largest-scale single industrial alkylation process—that is, ethylation of benzene with ethylene—is still carried out to a significant degree in the liquid phase using acid catalysts since ethylene is less polar than propylene, it requires more forcing conditions in the protolytic initiation step [Eq. (5.71)]. 

Cumene manufacture consumed about 10 percent (2.2 billion lb) of the propylene used for chemicals in the United States in 1998. It is prepared in near stoichiometric yield from propylene and benzene with acidic catalysts (scheme below). Many catalysts have been used commercially, but most cumene is made using a solid phosphoric acid catalyst. Recently, there has been a major industry shift to zeolite-based catalyst. The new process has better catalyst productivity and also eliminates the environmental waste from spent phosphoric acid catalyst. It significantly improves the product yield and lowers the production cost. Cumene is used almost exclusively as feed to the cumene oxidation process, which has phenol and acetone as its coproducts. 

In the reactor portion of this process, the olefin stock is mixed with benzene (for cumene) or recycle lights (for tetramer). The resulting charge is pumped to the reaction chamber. The catalyst, solid phosphoric acid, is maintained in separate beds in the reactor. Suitable propane quench is provided between beds for temperature control purposes because the reaction is exothermic. 

In the case of cumene, UOP introduced a liquid-phase process in the 1940s to compete with aluminum chloride technology. The catalyst is SPA, a solid phosphoric acid catalyst in which the phosphoric acid is supported on silica. Many improvements were made to the SPA catalyst and process over the years, leading to 70% of the world s cumene being produced with SPA by the 1990s. In 1996, UOP introduced the Q-Max process, featuring a zeolitic catalyst and operating in the liquid phase (21). A new Q-Max catalyst, QZ-2001 , was introduced in 2001. 

Cumene capacity topped 9.5 million metric tons in 1998 and is projected to reach 10.4 million metric tons by the end of 2003 (19). Like ethylbenzene, cumene is used almost exclusively as a chemical intermediate. Its primary use is in the coproduction of phenol and acetone through cumene peroxidation. Phenolic resins and bisphenol A are the main end uses for phenol. Bisphenol A, which is produced from phenol and acetone, has been the main driver behind increased phenol demand. Its end use applications are in polycarbonate and epoxy resins. The growth rate of cumene is closely related to that of phenol and is expected to be approximately 5.1% per year worldwide over the next five years. Process technologies for both chemicals have been moving away from conventional aluminum chloride and phosphoric acid catalyzed Friedel-Crafts alkylation of benzene, toward zeolite-based processes. 

In a new process for making phenol, cumene (isopropylbenzene) is oxidized with air to form cumene hydroperoxide, which is then changed to phenol and acetone. The cumene is made by the direct alkylation of gaseous benzene, using a phosphoric acid-kieselguhr catalyst and operating conditions of 500 K. 

However, from economic and environmental point of view both USA and Japan use the propylene alkylation route, as this method of manufacture is more amenable to continuous operations with recycle stream. The alkylation with propylene and isomerization are carried out upto 240° C with traditional solid phosphoric acid (SPA) catalyst and more recently with anhydrous AICI3 catalyst. Final catalytic oxidation at 90-110°C gives the hydroperoxide, as in cumene and cymene processes, which on cleavage with dilute sulfuric acid gives 2-naphthol in high overall yield. [53]... 

Cumene is an important intermediate in the industrial production of phenol, acetone and a-methylstyrene. The large-scale production of cumene is based on the alkylation of benzene with propene over Friedel-Crafts [1] or phosphoric acid on silica catalysts [2]. Zeolites, namely ZSM-5 and ZSM-11, have also been shown to be potential catalysts for this process [3, 4]. However, the formation of cumene (isopropylbenzene. IPB) on this catalysts is accompanied by its isomerization to n-propylbenzene (NPB). The latter is considered as an undesired by-product with respect to further processing of cumene to phenol and acetone. Therefore, preventing the formation of NPB would enable the substitution of the current catalysts used in the industrial process by ZSM-5 or ZSM-11 type solid acids which have major advantages in terms of environmental protection, safety, and avoidance of corrosion. 

Traditionally, the synthesis of cumene has involved the use of phosphoric acid (H3P04) as a catalyst. That process results in the release of harmful by-products into the environment, and a new process that uses... 

Isopropylbenzene (Cumene). Oxidation of isopropylbenzene, cumene, to cumene hydroperoxide and the subsequent decomposition to phenol and acetone have become of significant commercial importance in recent years and have, furthermore, pointed the way as a generally useful new route for potential commercial manufacture of other important chemicals. For use in the phenol-plus-acetone process, cumene is usually obtained by the phosphoric acid-catalyzed alkylation of benzene with propylene. 

---