Propylene from cumene

Production of a-methylstyrene (AMS) from cumene by dehydrogenation was practiced commercially by Dow until 1977. It is now produced as a by-product in the production of phenol and acetone from cumene. Cumene is manufactured by alkylation of benzene with propylene. In the phenol—acetone process, cumene is oxidized in the Hquid phase thermally to cumene hydroperoxide. The hydroperoxide is spHt into phenol and acetone by a cleavage reaction catalyzed by sulfur dioxide. Up to 2% of the cumene is converted to a-methylstyrene. Phenol and acetone are large-volume chemicals and the supply of the by-product a-methylstyrene is weU in excess of its demand. Producers are forced to hydrogenate it back to cumene for recycle to the phenol—acetone plant. Estimated plant capacities of the U.S. producers of a-methylstyrene are Hsted in Table 13 (80). 

AH commercial processes for the manufacture of caprolactam ate based on either toluene or benzene, each of which occurs in refinery BTX-extract streams (see BTX processing). Alkylation of benzene with propylene yields cumene (qv), which is a source of phenol and acetone ca 10% of U.S. phenol is converted to caprolactam. Purified benzene can be hydrogenated over platinum catalyst to cyclohexane nearly aH of the latter is used in the manufacture of nylon-6 and nylon-6,6 chemical intermediates. A block diagram of the five main process routes to caprolactam from basic taw materials, eg, hydrogen (which is usuaHy prepared from natural gas) and sulfur, is given in Eigute 2. 

The reaction of benzene with propylene produces cumene see Figure 7-1), but a catalyst must be present to make the reaction go. The chemistry is such that the benzene-propylene bond will be at the middle carbon of the propylene molecule, hence, the name isopropylbenzene. Note that there is also a transferal of hydrogen from benzene to the propylene. 

Two vessels are used for the reaction, and for two reasons. First, the reaction is exothermic and in a fixed catalyst bed, and one way to control the temperature is to take out the streams being processed and cool them down. The second reason is that the second reactor also is used as a fractionator, venting the unreacted propylene and the propane part of the chemical grade propylene from the benzene/cumene mix. 

Cumene made in this manner is about 99.9% pure. The cumene yield, ie., the percent of benzene that ends up as cumene, is about 95%- About 5% of the benzene ends up as part of the heavies. Conversion of propylene is a little lower, about 90%, particularly if there s no depropanizer up front to which the unreacted propane/propylene from the second reactor can be recycled. 

Both the cumene and the PIPB will continue down the column. The hot propylene and cumene vapors and the column trays will strip any remaining, unreacted benzene from the falling cumene/PIPB liquids, pushing it up the column, back to the catalyst bed where it will react with the propylene. 

There are nine chemicals in the top 50 that are manufactured from benzene. These are listed in Table 11.1. Two of these, ethylbenzene and styrene, have already been discussed in Chapter 9, Sections 5 and 6, since they are also derivatives of ethylene. Three others—cumene, acetone, and bisphenol A— were covered in Chapter 10, Sections 3-5, when propylene derivatives were studied. Although the three carbons of acetone do not formally come from benzene, its primary manufacturing method is from cumene, which is made by reaction of benzene and propylene. These compounds need not be discussed further at this point. That leaves phenol, cyclohexane, adipic acid, and nitrobenzene. Figure 11.1 summarizes the synthesis of important chemicals made from benzene. Caprolactam is the monomer for nylon 6 and is included because of it importance. 

Desorption of similar products from cumene- and propylene-deactivated parent H-mordenite is a result analogous to that of Venuto and Hamilton (3). They found that deactivation of rare earth X (REX) faujasite by alkylation of benzene with ethylene to ethylbenzene resulted in trapped products similar to those for deactivation with ethylene alone. 

Liquid phase oxidation of hydrocarbons by molecular oxygen forms the basis for a wide variety of petrochemical processes,3 "16 including the manufacture of phenol and acetone from cumene, adipic acid from cyclohexane, terephthalic acid from p-xylene, acetaldehyde and vinyl acetate from ethylene, propylene oxide from propylene, and many others. The majority of these processes employ catalysis by transition metal complexes to attain maximum selectivity and efficiency. 

Figure 1.7 Propylene oxide formation from propylene with cumene hydroperoxide (CHP) as a recyclable oxidizing agent. After hydrogenolysis of the alcohol (which is the reduction product) to cumene, cumene hydroperoxide is generated again through oxidation of the cumene in air. Adapted from Ref. (197a), with permission from the Royal Society of Chemistry.

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.

Acetone now is made from propylene by two processes. In the first, propylene is hydrated to isopropyl alcohol, which is then oxidized to acetone. In practice, 1.1 lb propylene yields 1.2 lb isopropyl alcohol, which in turn gives 1 lb acetone. Most new facilities use a second process, namely coproduction of acetone and phenol from cumene, which is made from propylene plus benzene. 

Saponites were synthesised at 90°C and 1 atmosphere from a Si/Al-gel and a solution containing urea and M2+-nitrate (M2+= Zn, Mg, Ni and Co) in only a few hours. The products were characterised by XRD, TEM, BET, 27a1- and 29si-MASNMR. Furthermore, the catalytic properties of the synthetic saponites in the Friedel-Crafts alkylation of benzene with propylene to cumene were tested. Incorporation of Zn, Mg, Ni, Co, or a combination of Zn and Mg, in the octahedral layer, as well as controlling the Si/Al-ratio in the tetrahedral layer between 7.9 and 39 could easily be established. The specific surface areas and the pore volumes of the saponites are extremely high, viz., 100-750 m /g and 0.03-0.32 ml/g, respectively. Zn-saponite with A]3+ in the interlayer exhibited a higher catalytic activity as compared to a commercial SPA-catalyst (Solid Phosphoric Acid). 

Friedel-Crafts alkylation of benzene with propylene to cumene on synthetic Zn-saponite(Al3+) is successful. At 160°C for 0.25 hours, the 0.2 wt.% Zn-saponite(Al3+) exhibits a comparable conversion as 1.5 wt.% SPA-catalyst at 190°C after 2 hours. Removing the saponite from the autoclave after the reaction provides no problems. 

For the cumene problem in Section 22.4. it has been determined that the feed is off specification. Until we can contract with a new propylene supplier we will have to use the propylene from the current supplier. Tests have shown that we can expect this propylene to have between 5 wt% and 10 wt% propane impurity. It has been decided to try to maintain the design cumene production rate by increasing the propylene feed rate so that a constant, design amount of propylene enters the reactor. Identify the botdenecks to the proposed process change. Debotdeneck this situation. 

Production of acetone by dehydrogenation of isopropyl alcohol began in the early 1920s and remained the dominant production method through the 1960s. In the mid-1960s virtually all United States acetone was produced from propylene. A process for direct oxidation of propylene to acetone was developed by Wacker Chemie (12), but is not beheved to have been used in the United States. However, by the mid-1970s 60% of United States acetone capacity was based on cumene hydroperoxide [80-15-9], which accounted for about 65% of the acetone produced. 

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). 

Diisopropjibenzenes (DIPB) are readily obtained via Eriedel-Crafts alkylation of benzene or cumene by propylene. This reaction inhquid phase has not evolved drastically since 1980 with the exception of the large variety of heterogeneous acid catalysts that are now being used, mainly zeoHtes, type HZSM-12, giving a para/meta ratio = 0.7 (4). In fact, propylene can also be replaced by isopropyl alcohol coming from the hydrogenation of acetone that... 

Worldwide propylene production and capacity utilization for 1992 are given in Table 6 (74). The world capacity to produce propylene reached 41.5 X 10 t in 1992 the demand for propylene amounted to 32.3 x 10 t. About 80% of propylene produced worldwide was derived from steam crackers the balance came from refinery operations and propylene dehydrogenation. The manufacture of polypropylene, a thermoplastic resin, accounted for about 45% of the total demand. Demand for other uses included manufacture of acrylonitrile (qv), oxochemicals, propylene oxide (qv), cumene (qv), isopropyl alcohol (see Propyl alcohols), and polygas chemicals. Each of these markets accounted for about 5—15% of the propylene demand in 1992 (Table 7). 

Cresols can be made from propylene by reaction with toluene to produce cumene (111). 

The oxidation step is similar to the oxidation of cumene to cumene hydroperoxide that was developed earlier and is widely used in the production of phenol and acetone. It is carried out with air bubbling through the Hquid reaction mixture in a series of reactors with decreasing temperatures from 150 to 130°C, approximately. The epoxidation of ethylbenzene hydroperoxide to a-phenylethanol and propylene oxide is the key development in the process. 

Other Derivatives and Reactions. The vapor-phase condensation of ethanol to give acetone has been well documented in the Hterature (376—385) however, acetone is usually obtained as a by-product from the cumene (qv) process, by the direct oxidation of propylene, or from 2-propanol. 

By far the preponderance of the 3400 kt of current worldwide phenolic resin production is in the form of phenol-formaldehyde (PF) reaction products. Phenol and formaldehyde are currently two of the most available monomers on earth. About 6000 kt of phenol and 10,000 kt of formaldehyde (100% basis) were produced in 1998 [55,56]. The organic raw materials for synthesis of phenol and formaldehyde are cumene (derived from benzene and propylene) and methanol, respectively. These materials are, in turn, obtained from petroleum and natural gas at relatively low cost ([57], pp. 10-26 [58], pp. 1-30). Cost is one of the most important advantages of phenolics in most applications. It is critical to the acceptance of phenolics for wood panel manufacture. With the exception of urea-formaldehyde resins, PF resins are the lowest cost thermosetting resins available. In addition to its synthesis from low cost monomers, phenolic resin costs are often further reduced by extension with fillers such as clays, chalk, rags, wood flours, nutshell flours, grain flours, starches, lignins, tannins, and various other low eost materials. Often these fillers and extenders improve the performance of the phenolic for a particular use while reducing cost. 

The most common precursor to phenolic resins is phenol. More than 95% of phenol is produced via the cumene process developed by Hock and Lang (Fig. 7.1). Cumene is obtained from the reaction of propylene and benzene through acid-catalyzed alkylation. Oxidation of cumene in air gives rise to cumene hydroperoxide, which decomposes rapidly at elevated temperatures under acidic conditions to form phenol and acetone. A small amount of phenol is also derived from coal. 

Q-Max A process for making cumene from benzene and propylene by catalytic alkylation using a proprietary legenerable zeolite catalyst. Developed by UOP and first installed in 1996 by JLM Chemicals in Illinois. 

In more recent vintages of the cumene manufacture processes, zeolyte catalysts permit going directly to cumene from the same two feeds, benzene and propylene. The introduction of catalytic distillation has even further improved the process economics, a thing that delights the manufacturers. 

---