ISSN 0965-5441, Petroleum Chemistry, 2007, Vol. 47, No. 4, pp. 273–284. © Pleiades Publishing, Ltd., 2007. Original Russian Text © V.M. Zakoshansky, 2007, published in Neftekhimiya, 2007, Vol. 47, No. 4, pp. 301–313.

The Cumene Process for Phenol–Acetone Production V. M. Zakoshansky ILLA International, LLC 4756 Doncaster Ct., Long Grove, IL 60047, USA e-mail: [email protected] Received January 11, 2007

Devoted to the memory of the inventors of this chemical process, Russian scientists R.Yu. Udris, M.S. Nemtsov, and B.D. Kruzhalov Abstract—The history of designing and the evolution of the process for the joint production of phenol and acetone, which is now the basic industrial method for the manufacture of these products, the state of the art and parameters of its key steps in industrial facilities among world manufacturers of phenol are presented. Special attention is given to the consideration of ways of improving the characteristics of the process and its environmental safety on the basis of the recent advances in science and to methods for the solution of scientific and practical questions of the reconstruction and renovation of out-of-date industrial phenol manufacturing facilities. DOI: 10.1134/S096554410704007X

HISTORICAL INFORMATION The purpose of this historical paper is to correct unintentionally introduced errors concerning the discovery of the reaction of acid-catalyzed decomposition of cumene hydroperoxide (CHP), whose authorship is attributed to respected scientist Hoch, who independently invented this process in 1944, i.e., two years later than R.Yu. Udris. In 1942, Rudolf Yur’evich Udris (Russia) was the first in the world to isolate cumene hydroperoxide (CPH) from cumene oxidation products. In 1942, Rudolf Yur’evich Udris (Russia) discovers the reaction of acid-catalyzed CHP conversion into phenol and acetone.1 In 1943, Mark Semyonovich Nemtsov, Rudolf Yur’evich Udris, and Boris Dmitrievich Kruzhalov with co-authors develop an industrial process for cumene oxidation into CHP (patent no. 106906, Russia, 1947) and acid CHP degradation into phenol and acetone (patent no. 106992, Russia, 1947). In 1944, Hoch independently discovers the reaction of acid-catalyzed CHP decomposition. In 1949, Two industrial units for phenol–acetone manufacturing plants for the production are commissioned for the first time (Dzerzhinsk, Russia, and Canada, British Petroleum.2 1 The

authorship of the discovery of the reaction is wrongly attributed to Hoch, who independently discovered, in 1944, the reaction of acid CHP decomposition. 2 The process was developed and implemented independently by these authors.

The cumene process for phenol–acetone (PA) manufacture is one of the unique high-volume petrochemical processes in which simultaneously two products (phenol and acetone) are obtained from one reactant (cumene), each of the products finding useful application; however, which is most important, their reaction with one another in the joint synthesis results in bisphenol, a chemical that forms the basis of the large-scale production of polycarbonate plastics, which are known for their unique consumer properties. The chemical beauty of the reactions proceeding in the cumene process and their tremendous practical importance have drawn the attention from researchers for decades, although the complexity and danger of the process for a long time did not allow any significant improvement in its characteristics over those reached by Th pioneers: the yield of the unutilizable byproduct, the so-called phenol tar, remained at the level of 150−200 kg/t of phenol, and the yield of useful α-methylstyrene (AMS) was 40–50% of theoretical values. Giving the authors and the first founders of the cumene process for PA manufacture their due, it should be noted that the design of the modern PA process has naturally required practically the complete abandonment of the strategy and philosophy of the process developed by the pioneers in all its parts without exclusion. Even the chemistry, let alone the production engineering of the key steps, underwent a radical change, a development which allowed the modern cumene process for phenol manufacturing to dominate over alternative methods; to attain a level of selectivity very close to the theoretical value, 97 mol %; and, accordingly, to reduce the yield of phenol tar to 25–35 kg/t of phenol,

273

274

ZAKOSHANSKY OFF-GAS CLEANUP WITH ZEOLITES BINARY ALKALINE AGENT

CUMENE OXIDATION

H2O

C U å E N COMMERCIAL ACETONE AMS HYDROGENATION E

ISOLATION OF COMMERCIAL ACETONE ALDEHYDE

NaOH INCLUDING CUMENE OBTAINED FROM COAL-TAR BENZENE

FRESH CUMENE NaOH

H2O

NH4OH

H2

air

DISTILLATION OF UNREACTED CUMENE

ISOLATION OF COMMERCIAL AMS

STEP OF NEUTRALIZATION AND REMOVAL OF HYDROXYACETONE

COMMERCIAL AMS

crude CHP

CHP DECOMPOSITION RECYCLING ACETONE

∆–

H2O H2SO4 H2O & NH4OH

ALKALINE AND OXIDATIVE AGENTS COMMERCIAL PHENOL

TO DEPHENOLIZATION PHENOL TAR

TWO-STEP CATALYTIC PURIFICATION OF PHENOL

Fig. 1. Simplified flow chart of the phenol process. Radical key engineering changes in the ILLA process relative to the conventional processes and those of other licensiates.

and to increase the yield of AMS to ~90 mol %. This breakdown was attained within the last 15–20 years owing to the close combination of profound experimental and theoretical studies of all steps of the phenol process in practice. PHENOL–ACETONE MARKET AND KEY PLAYERS ON THIS MARKET The rate of phenol production will remain at the same level (~5 rel. %/y) in the coming decade. Up to 2010, it is planned to build new facilities with a general total capacity of ~1.5 million t/year for phenol, a value that makes up ~20 % of the current capacity (7.5 million t/year). Some licensors of phenol manufacturing processes in the world are listed below: (1) Callog (United States), the base process of British Petroleum (BP); (2) Lammus (United States), ILLA International (United States) and the GE process (based on the BP process); (3) UOP (United States), the Allied process; (4) Mitsui (Japan) basically develops processes for its own plants; (5) ILLA International (United States–Russia) licenses its own the processes. It is easy to conclude that most of these companies do not license their own developments; thus, they upgrade the old technologies mainly at the engineering level, which does not change the nature of the process

and its parameters fundamentally. Designers of new phenol manufacturing processes are few in number globally. Note that only one research center (ILLA International) is engaged in extensive scientific research aimed at the radical improvement of the cumene process, the solution of the “painful” points of the traditional process, the design of systems for management, and the control, design, and licensing of their own phenol processes and their commissioning. TECHNOLOGY A simplified scheme of the ILLA phenol process used to discuss the current process is represented in Fig. 1. Practically all steps and components have experienced radical changes during the last 10–15 years, thus making it possible to develop an essentially new PA manufacturing process. The technical characteristics of the process are determined by its three key steps: cumene oxidation, CHP decomposition, and phenol cleaning of impurities to ensure the quality of phenol. The parameters of auxiliary steps of the process are practically identical in all types of licensed processes. Step of Cumene Oxidation to Cumene Hydroperoxide The cumene oxidation reaction follows the radical chain mechanism. Therefore, the general problem of this process is the absence of effective methods to overcome the inhibiting effect of impurities that are present in both initial cumene (sulfur compounds, such as merPETROLEUM CHEMISTRY

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Selectivity, mol %

(a)

96

with NH4OH

95

(b)

97

with NH4OH

96 95

94

without NH4OH

without NH4OH

93

94

92

93 5

10

15

20

25

30

5

10

15

20

25

30

CHP, wt %

Fig. 2. Change in total selectivity of processes: (a) “wet” oxidation with and without ammonia; (b) “dry” oxidation with and without ammonia.

captans, thiophene, etc.) and are formed during its oxidation. Despite almost 65 years of existence of the process, the problem of inhibition remained rather pressing. Researches at ILLA proved that the traditional approach to controlling the inhibition by means of NaOH—via its feeding to reactors or the pretreatment of the feedstock with alkali—was a mistake. On the one hand, this approach solved the problem of attaining a reasonable conversion of cumene, but, on the other hand, it simultaneously led to a significant decrease in the selectivity of the process. Other methods used to control inhibition (see below) also turned out to be practically ineffective: (a) Application of the so-called wet (emulsion) oxidation of cumene (Fig. 2a), in which the inhibiting role of formed phenol (BP process) is supposed to be reduced with the aid of water and Na2CO3 supplied to reactors, has not completely solved the problem and resulted (due to Na2CO3 recycling) in the formation of a new inhibitor (NaHCO3) whose inhibiting activity is equivalent to that of phenol. Moreover, the production engineering has become more complicated, leading to a marked increase in the reactor volume, i.e., an increase in capital costs. (b) Application of a physical method (significant decrease in the temperature of the process, UOP process) made it possible to increase the selectivity of the process, but simultaneously led to the necessity of using larger reactors; a larger volume will make the process extremely inflexible in response to a change in the loading and maintenance of the regime, as well as potentially dangerous owing to a huge amount of CHP present in reactors. (c) Abandonment of alkali supply to the reactors of the dry (water-free) oxidation of cumene simplified the process somewhat, but, did not solve the problem of the enhancement of selectivity, simultaneously leading to a PETROLEUM CHEMISTRY

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reduction in pH to 2–3, and, consequently, increased the danger of the cumene oxidation process and the CHP concentration step. (d) Alkali supply to dry (water-free) cumene oxidation reactors partly solved the problem of the neutralization of organic acids (safety issue), but has led to a marked loss of the selectivity both at the cumene oxidation and at the CHP concentration steps. Escape from this circle of problems that seem unresolvable simultaneously was found by ILLA [1] (Ammoxidation process, Figs. 2a, 2b) via the arrangement of the so-called chemical trap, the scavenging of formaldehyde by ammonia introduced for the purpose and its transformation into hexamethylenetetramine (HMTA). Owing to this arrangement, the route for the transformation of ëç2é into formic acid, which mediates the acid decomposition of CHP and the appearance of an inhibitor (phenol) in the cumene oxidation products, is barred: CH2O HCOOH CH3 Ar–CH(CH3)2

HCOOH

6CH2O + 4NH3

ArOH + CO(CH3)2 C6H12N4.

In this case, it is quite important that NH3 does not form salts with CHP, unlike NaOH, which gives the Na salt of CHP. The decomposition of the sodium salt of CHP when the alkali is used to control the inhibition in the conventional process is a source of the formation of dimethyl phenyl carbinol (DMPC) and acetophenone (ACP) as principal byproducts and leads to a decrease in the selectivity of the cumene oxidation process. The nonstandard “chemical trap” method made it possible to increase the selectivity of cumene oxidation to 94.5 mol %, to increase the productivity of reactors by 15–20 rel. % without a loss in selectivity, to reduce threefold the size of the reactors in comparison with the physical method of inhibition control, and to solve the

276

ZAKOSHANSKY [O2]/[O2–]av 0.9

S, rel. % 95

0.8 94

0.7 0.6

93

0.5 0.4

92

0.3 0.2 0.1 10 15 20 25 30 35 40 45 50 55 60

91 90

Specific CHP yield (kg/m3)/h

Fig. 3. Dependence of the ratio of the concentration of dissolved oxygen to its equilibrium value in the liquid phase on the specific yield of CHP.

safety problem by running the reaction in the pH range 7–8. The natural abandonment of the section reactors designed and realized by the pioneers, as well as the shift of the cumene oxidation process toward the cascade of in-series connected reactors, is no more than the requirement of the kinetics of consecutive and parallel side reactions. Accordingly, new plants that are under construction use a cascade of reactors and the old cumene oxidation facilities with a battery of parallel low-selectivity single plate reactors, as a rule, are modernized into the cascade. As applied to a cascade of reactors, the result of the optimally organized cumene oxidation process, considering the CHP yield from a unit volume, its selectivity, and minimal power consumption at the CHP concentration step, is represented in Fig. 3. As a result of the conducted studies and calculations, it was found that the ratio of the concentration of dissolved oxygen to its equilibrium value for various industrial conditions for the realization of an oxidation reaction is within the range 0.2–0.9. Industrial experience shows that the higher the ratio of the concentration of dissolved oxygen to its equilibrium concentration, the higher the selectivity of cumene oxidation. However, this is attained by a decrease in CHP removal from a unit volume of a reactor, i.e., by the reduction of the process temperature and, accordingly, by a strong increase in the reactor volume, leading to greater capital costs. For this reason, most industrial reactors operate at values of CHP yield from 30 to 50 kg/m3 per hour, obviously directing the reaction toward a decrease in selectivity. The only exception is the ammoxidation process for dry cumene oxidation, in which a selectivity of about 95 mol % is attained at a CHP yield of 35–40 kg/m3 per hour. This selectivity is not due to an increase in the oxygen concentration in the reaction medium and is owing to the application of the chemical trap, which

sharply reduces the formation of phenol, the inhibitor of the process [1]. In addition to the aforementioned, the combination of the “chemical trap” technique with a number of other chemical and engineering methods made it possible to solve the problem of the use of cumene contaminated with various sulfur-containing impurities. This combination allowed a selectivity of 94–94.5 mol % to be attained, a value that is very close to the selectivity of the aforementioned process, and the use of much cheaper coal-tar benzene. A further increase in the selectivity of the process is possible, in principle, but, is uneconomical because of both inadequately high power expenditures for the organization for the recycling of the returnable streams–while cumene conversion decreases—and a significant growth in capital costs for the construction of very large reactors. The industrial process of cumene oxidation to CHP has undergone significant changes from the time of its creation and practically attained a selectivity of 94.5−95 mol %, which is determined by the theory. Off-Gas Purification Step The sorption method for off-gas cleaning with carbon adsorbents has become morally obsolete. Serious defects of this method are the absence of an opportunity to remove methanol from offgases and a short lifetime of in adsorbent (1–1.5 years). In our opinion, the method of purification on zeolite adsorbents (ILLA process) is preferable; it has successfully solved the main problems: (a) total sorption capacity is comparable to that of carbons; (b) the degree of removal of cumene and acids is equal to that in carbons; PETROLEUM CHEMISTRY

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∆S, abs. % 1.2 1.0 0.8

Conventional process

0.6 0.4 ILLA process

0.2

0 20.0 20.5 21.0 21.5 22.0 22.5 23.0 23.5 24.0

CHP yield, (kg h)/m3

Fig. 4. Losses in CHP concentration depending on the CHP yield in both conventional and ILLA processes.

(c) the required sorption capacity for methanol, which is absent in carbons; (d) the lifetime is at least 3 years (presumably, 7); (e) the exclusion of yearly shutdowns and expenses for adsorbent recharging. Thus, the problem of environmentally hazardous gas emissions during the cumene process is successfully resolved. Cumene Hydroperoxide Concentration Step Loss in selectivity at this step is 0.1 to 1.2 abs. % and is predetermined by the chemical idea of the cumene oxidation process, rather than the engineering design of the concentration step. At low pH values in cumene oxidation reactors, the CHP concentration step becomes dangerous. When NaOH is used for the treatment of recycling cumene streams or for feeding cumene oxidation reactors, the loss of CHP (and, hence, cumene) increases to ~1.2 abs. %. However, the problems of chemical loss of CHP and safety problems have been successfully solved in the last decade owing to the use of NH3 at the cumene oxidation step. It is seen from Fig. 4 that losses significantly decrease in the CHP concentration step conducted according to the traditional and the improved (ILLA) process; i.e., in our opinion, the environmental protection problems pertaining to the CHP concentration step of the process are optimally solved. Crude CHP Degradation Step It is this step, not the cumene oxidation step, that determines the identity of the phenol process as a whole from the viewpoint of both its selectivity and safety, and the formation of trace impurities that complicate the manufacture of high-quality commercial products. The good parameters of the CHP decomposition step reasonably well compensate for the poor characteristics of the oxidation step and vice versa. As a result, the PETROLEUM CHEMISTRY

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overall process parameters in general become unsatisfactory. That is why numerous investigators of the phenol process and phenol manufacturers since the time of the design of the phenol process and the commissioning of the first facilities in 1949 in Russia (Dzerzhinsk) and Canada (by British Petroleum) have deliberately searched for ways of increasing the selectivity of the given process; the yield of the valuable byproduct (AMS), which is one of the criteria of selectivity, was 35 to 50% of the theoretical value. Correspondingly, the yield of nonutilizable byproducts, so-called phenol tar, varied from 300 to 150 kg/t of phenol. The chemical transformations proceeding during the decomposition of crude CHP (CCHP) are extremely diverse and complex. It is rather difficult to choose a way that will be useful for maximizing the yields of the three desired products (phenol, acetone and AMS). Since the CHP degradation reaction is accompanied by the evolution of a huge amount of heat (486 kcal/kg of CHP, which is equivalent to the adiabatic increase in temperature by ~700°C), the degradation reaction of CHP itself takes a few seconds and it is difficult to equilibrate heat release and heat withdrawal within this period of time. Therefore, the inventors of the homogeneous process of CCHP transformation (Fig. 5) were forced to increase the residence time of products in the reactor and in several series arranged water-cooled heat exchangers. As a result, the requirements on the conditions and regimes of the realization of the basic reaction have conflicted with conditions and requirements for the realization of side reactions. Moreover, the approach of development engineers to decompose CHP by 100% and very fast (3–5 s) in combination with a huge heat effect of this reaction have made the created process extremely dangerous in operation. In the process that suggests the withdrawal of the heat of the reaction by evaporating acetone (BP process, Fig. 6), heat release and heat withdrawal are

278

ZAKOSHANSKY Degradation products

CHP

cw

500 P-1

Heat released in the reactor

400 300

Heat removed in the heat exchanger

200 H2SO4

100 0

1

2

3

4

5

6

7 8 Time, Ò

Fig. 5. Heat release and heat withdrawal in the one-step process for homogeneous CHP decomposition.

Reflux acetone 2–2.5 t/t of phenol

T = 79 °C = const CHP

H2O H2SO4 Recycling acetone from the step of rectification of 10–12 rel. %/t of CHP

Products of CHP decomposition

Fig. 6. Schematic of the one-step CHP decomposition process using heat withdrawal by vaporized acetone.

almost automatically balanced by the vaporized acetone. To keep this balance, i.e., for the sake of the safety of the process, a very high concentration of the catalyst (H2SO4) was maintained, thus ruling out the possibility of attaining a high selectivity of the process. Unfortunately, this innovation [2, 3] not only solved the aforementioned problems of low selectivity, but also sharply reduced safety in comparison with the single-step process [4]. Over almost 50 years, the search for ways of increasing the selectivity of the process (lowering the catalyst (H2SO4) concentration, variation of the type of acid catalyst, change in the residence time of products in the reactor, the lowering or elevation of temperature, variation in the composition of the reaction medium by various additives, etc.) was actually unsuccessful: it was impossible in practice to increase the yield of AMS and, consequently, to decrease that of phenol tar. Neither the homogeneous CHP degradation technology (the version of the process first developed by Udris, Nemtsov, and Kruzhalov) nor another, radically different technology designed by British Petroleum (BP), the

so-called ebullating-acetone process, manages to achieve these goals. It seemed that the first designers of these two technologies for CHP decomposition have initially found optimum conditions of these two basically different processes and it is, in principle, impossible to improve the selectivity. To resolve these problems, ILLA abandoned the concept of the processes designed by the trailblazers. Within 20 years, since 1980, a fundamentally new process of CHP decomposition has been created and realized at many plants in the world: (1) On the basis on the detailed kinetic study, the one-step process was transformed (1980) to a two-step version. (2) The idea of the superfast and complete (100%) decomposition of CHP was rejected as erroneous and opposite approaches [5−7] were offered: —slow CHP decomposition; —incomplete CHP decomposition—the CHP conversion per pass of at most 65%; PETROLEUM CHEMISTRY

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THE CUMENE PROCESS FOR PHENOL–ACETONE PRODUCTION

—distribution of CHP conversion over three successive first-step reactors; —conversion of the residual amount of CHP in a second-step reactor. (3) A radical change in the composition of the reaction medium for CHP decomposition, i.e., the transfer of the process from the equimolar acetone/phenol ratio to the acetone : phenol : cumene = 1.2 : 1 : 0.2 reaction medium [6]. (4) Control of CHP conversion in the first step of the process and control of the safety and selectivity of the process with the aid of an additional reactor, a calorimeter [6, 7]. (5) The organization of the second steps of the process as an adiabatic reactor of replacement for the transformation of both: CHP nondecomposed in the first step; DMPC to AMS, and also dicumyl peroxide synthesized in the first step to the main products of the process [6, 7]. (6) The realization of transformations of products in a reactor of the second step: —in the reaction medium different from that of the first step [7]; —application of a “soft” acid catalyst (NH4HSO4) instead of “hard” H2SO4 [6, 7]. (7) The transfer of the process on computer start-up [7, 8]. (8) The creation and realization of a three-leveled protection of the process instead of a single-leveled one. (9) Computer (on-line) control and protection of the process against factors disturbing a regime and the optimizing the selectivity of the process [8]. Regarding the current process for CHP decomposition, it is interesting that a change in processing is caused by a change in the chemistry of the main and side reactions: H SO (1) The side reaction CHP 2 4 DMPC + AMS, which leads to a loss of the target products, is ruled out. (2) To protect DMPC from conversion to byproducts, practically quantitative synthesis of dicumyl peroxide (DCP) is realized in the first step, and the reversible reaction is shifted to DCP : CHP + DMPC DCP + H2O. (3) Reversible reaction DMPC AMS + H2O in the first step is shifted to DMPC. (4) Irreversible conversion of DMPC to byproducts of the process (AMS dimers and cumylphenols) 2DMPC DI,II,III + H2O DMPC + phenol o-, p-CP is practically completely stopped in the first step and minimized in the second step to the degree when the yields of the byproducts decrease by a factor of 7–10 compared to conventional processing. (5) The reaction of the formation of mesityl oxide (MOX) from acetone practically does not proceed, PETROLEUM CHEMISTRY

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despite a substantial growth in the acetone concentration in the reaction medium, and an amount of MOX decreases 10–20-fold in comparison with conventional processin. (6) The reactions of the irreversible formation of polycondensed phenols, which were ~20 rel. % of total phenol “tars” (waste products) in conventional processing, do not occur. The indicated changes made on the basis of the detailed study of the influence of the medium composition on the kinetics and mechanism of the principal [5] and side [9] reactions revealed the reasons behind the attempts of various researchers throughout the world to improve the parameters of the CHP decomposition process. As a result of these studies, it was found that: (1) The reaction medium (PA containing H2SO4) has a high acidity (Fig. 7), which is determined by the S Hammett acidity function H0 (more exactly, H 0 ), and this predetermines the extremely high rate of CHP decomposition; (2) The CHP decomposition reaction and most side reactions pertain to those of specific, not general, acid catalysis, i.e., they are determined by the acidity funcS tion H 0 , not by H2SO4 concentration. S

(3) The acidity value h 0 of the reaction medium, when the acetone/phenol ratio is varied [10], as well as when very small amounts of additives of protic (for example, ç2é [10], alcohols, etc.) and aprotic solvents (for example, cumene) can vary by dozen of times, leading to quite significant changes in the rate constants of the CHP decomposition reaction and other reactions of the process. (4) At a variable composition of the reaction medium (acetone/phenol/cumene/H2SO4concentration/ç2é conS

centration) based on the h 0 data and temperature effect S

on the h 0 data, the optimal composition and the regime have been selected to realize the first and second steps of a commercial run: —various (in weight) additives of acetone and water in the first and second steps; —the increased cumene content; —optimal H2SO4 concentration in the first step and replacement of H2SO4 by NH4HSO4 in the second step; —the decreased temperature in the first step providing a strictly certain and safety value of CHP conversion to DCP and PA, and increased temperature in the second step, providing together with “soft” acid catalyst NH4HSO4 increase in acetone and cumene contents and a high selectivity of DCP and DMPC conversion to the desired products. All this has allowed ILLA to implement a process having a high level of safety for today and the highest selectivity, 97.1 mol %.

280

ZAKOSHANSKY h0 9

(‡)

7 5 3 1 0

0 0.5 1.0 1.5 2.0 2.5 H2O, wt. %

21 18 15 12 9 6 3 0

(b)

100 200 300 400 500 600 H2SO4, wt. %

Fig. 7. Change in acidity h0 as a function of: (a) H2O in an equimolar phenol/acetone mixture ([H2SO4] = 100 ppm, T=25°C); [H2SO4] in phenol/acetone mixture at (1) H2O concentration 0.52 wt % and (2) 0.31 wt %.

The problem of designing a safe, computer-controlled, and highly selective process for CHP decomposition (table) has been effectively solved in the FAN-2000 technology successfully used in industrial practice. It is noteworthy that it is the first process of CHP decomposition designed in which the realized logic of the safety and protection of the process does not interfere with the purpose of achieving its maximal selectivity. Using the ILLA process, ~30 rel. % of the global amount of phenol–acetone—2.5 million t/year of phenol and 1.5 million t/year of acetone—is produced, and phenol production will increase by 1.5 million t/year in 2010.

phenol purification from HA even at extremely high (by ~5–10 times higher than usual) values of its concentration in raw phenol from the real commercial run. The term of the continuous operation of a catalyst without regeneration is not less than 1.5 years. The level of phenol purification from impurities on the catalyst of the second steps (acid zeolite catalyst) considerably exceeds the parameters characteristic of all known sulfonated cation-exchangers. The industrial term of the continuous operation of the catalyst of the second step without regeneration is 7 years. Parameters of the purity of the obtained phenol after the two-step purification correspond to a level of phenol used in the production of carbonate plastics.

Phenol Quality Problem This problem has been the Achilles’ heel of the phenol process for a long time, because only top-grade phenol having a total impurity level of no more than 0.01% and meeting the stringent color standards can be used for the manufacture of carbonate plastics. The color characteristics are directly related to the concentration of hydroxyacetone (HA) and 2-methylbenzofuran (2-MBF) that is formed from HA in the presence of an acid catalyst. This problem has not been completely solved by many phenol manufactureses. When performing detailed studies of all chemical reactions proceeding in the traditional single-step purification of phenol with the use of sulfonated cationexchangers and having revealed its principal drawbacks, ILLA completely rejected this method and developed a new two-step method for phenol purification [12]. Cardinal distinction of this method is that, at the first step, complete HA removal on special heterogeneous catalyst under conditions excluding the formation of 2-MBF is carried out; at the second step, purification is carried out with the use of traditional heterogeneous acid catalysts (preferably zeolite type). Results of the operation of a two-step purification ILLA unit on heterogeneous catalysts are presented in Figs. 8a and 8b. Based on these data, it can be concluded that the catalyst of the first step successfully solves the problem of

Feedstock and Steam Consumption for the Process as a Whole It is seen from the practical data on the selectivity of the basic steps of the phenol process and from the values of the physical and chemical losses at the auxiliary steps of the process, the overall selectivity (for phenol) of the phenol process on the fed cumene basis is 93.9 mol % and 97.1 mol % (1360 kg/t and 1315 kg/t, respectively). In our opinion, advertised values of the coefficient of materials consumption below 1315 kg/t are unrealistic. Depending on the type of the applied CHP decomposition technology, the level of steam consumption in optimal processes varies from ∼4.2 to 2.2 t/t of phenol. The optimal value was found to be ∼4,2 t/t, whereas the value of 2.2 t/t was attained owing to the practically complete integration of heat, leading to rather great difficulties for those who directly operate the process. The consumption of cooling water is ∼300–350 m3/t of phenol and is comparable for all types of licensed processes. In our opinion, there are approaches to improve the selectivity of the step of cumene oxidation of isopropyl toluene and the step of CHP decomposition, and, it is the most important factor is that they allow one to transform the process to practically wasteless and extremely economic, or the so-called “wasteless process for phenol–acetone production,” WEPP. The chemical and PETROLEUM CHEMISTRY

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Principal characteristics and parameters of the CHP decomposition process Processes “boiling” (Cellog, Mitsui, Shell, Sunoco/UOP)

homogeneous (Sunoco/UOP)

homogeneous, ILLA

First step, H2SO4, ppm

450–700

100–200

150–180

Second step, H2SO4, ppm

450–700

100–200

10–30

Reaction medium, acetone/phenol

1.05 : 1

1:1

1.5 : 1

Computer start-up

Cannot be realized in principle

None

Is realized in all plants

Computer control

Cannot be realized in principle

None, realization is difficult (*)

Is realized in all plants (**)

Number of protection levels of the process

1

1

3

Theoretically possible yield of AMS, mol %*

74

80

93

Actual yield of AMS, mol %*

∼65

67–74**

89–92.5**

Yield of phenol tar, kg/t of phenol*

90

70

45

1800–2000

1500–1700

1300

500

300–200

<50

[HA], ppm [MOX], ppm

Notes: * As borrowed by ILLA workers from published data, the inspection data obtained in active plants, the data of kinetic studies and modeling of the process on pilot units. ** The AMS yield of ~85 [11] has been reported in the advertising materials of Sunoco/UOP; however, it has not been reported in a concrete unit and its capacity where this result has been attained; all plants and their capacities are known (GE, ~350000 t/year, INEOS, two plants for 200000 t/year, FCFC, 200000 t/year, FQ, 42000 t of phenol/year), where the AMS yield has been ~89– 92.5% under industrial conditions according to the ILLA process of CHP decomposition.

technological essence of this process is presented in [13, 14]. If pilot tests will be successful, the expected cumene consumption will be 1283–1285 kg/t of phenol, i.e., selectivity for cumene will achieve 99.5 mol %. The second important difference and advantage of WEPP in comparison with traditional cumene processing is the safety and simplicity of the step of CHP decomposition, low power inputs to separate products of CHP decomposition, and the high quality of the products produced. The third important difference and advantage is the simple transfer from traditional cumene processing to WEPP. The simplified scheme (developed at ILLA) to transform the traditional cumene process (beginning PETROLEUM CHEMISTRY

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from the CHP decomposition step) to WEPP is shown in Fig. 9. However, until the pilot tests of a sorption–desorption step will be finished, it is premature to declare the creation of a new production technique. The represented data on this ILLA process have an especially informational character. RECONSTRUCTION OF OUT-OF-DATE PRODUCTION ENGINEERING AND PLANTS Economic expediency of the radical reconstruction of imperfect and obsolete production engineering does not require demonstrations—numbers of annual losses of such plants speak for themselves. In particular,

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ZAKOSHANSKY HA concentration at the inlet and outlet of a pilot unit for phenol purification

[HA], ppm 1000 (‡) 800 600 400 200 0 0 50 100 150 200 250 300 350 400 Test time, day

(b) [Total carbonyls], ppm

[Mesityl oxide],

Feedstock: 400 ppm

Feedstock: 100 ppm

150

30

100

1 year

50 0

new

7 year

20 10

new

Zeolite Cation exchanger Phenol purification of total carbonyls

0

1 year new 7 years

Zeolite

new

Cation exchanger

Phenol cleaning of mesityl oxide

[Total impurities], ppm Feedstock: 400 ppm

150 100

7 years

50 new

0

1 year

1 year year 7

new

Zeolite Cation exchanger Total impurities after purification

Zeolite Cation exchanger lifetime

Fig. 8. Treatment of crude phenol for hydroxyaxetone removal (a) on the ILLA heterogeneous catalyst (first step); (b) on the zeolitecontaining catalyst (second step).

plants with a low capacity (40000–60000 t/year of phenol), which continue to use old production engineering, lose from US $5 to $15 million annually. Plants of medium (70000–120000 t/year of phenol) and high capacity (150000–300000 t/year of phenol) lose, accordingly, much more, especially in proportion to capacity. However, note that many plants of medium and high capacity once every 10–20 years conduct modernization that leads to some decrease in their losses. Manufacturing applications of modern production engineering developed by the best licensors result in radical improvements of all production parameters, economy, safety, and ecology. As experience shows at ILLA, which has successfully conducted numerous reconstructions at various plants in the world, to achieve success in the modernization of obsolete plants and production engineering, a comprehensive approach is usually needed, including three steps: (1) Expenses to maintain a process under operable conditions.

(2) So-called “reanimation” is realized, owing to minimal possible changes in production engineering, which are carried out on the operative (or available) equipment, to vary regimes of the key steps of the process to improve it. But, this step does not exclude implementation of a part of the production engineering stipulated by the next, third stage of modernization. (3) Radical reconstruction, i. e., a total transfer of operations to modern production engineering. The first stage is in full measure a prerogative for the manufacturer of products and his responsibility; the second and third steps are based on the purchase of licenses, accordingly, the programs “reanimation” and “radical reconstruction” are developed by the licensor. The out-of-date plants really need the realization of the first step, owing to the depreciation of equipment, the use of obsolete measuring devices, and their insufficient amount, etc. Expenses at this step can be both greater and smaller and are predetermined by what measure fixed capital was renovated during long maintenance processes. But, in any case, these expenses are PETROLEUM CHEMISTRY

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THE CUMENE PROCESS FOR PHENOL–ACETONE PRODUCTION

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Commercial acetone

2 Products of CHP decomposition

1

3 Recycled cumene

Commercial phenol Fraction of ACP and cumene

Condensation products CATALYTIC PHENOL PURIFICATION

Recycled cumene

Acetophenone

Fig. 9. Simplified flow chart after the reconstruction of the conventional cumene production engineering and its transfer onto the WEPP technology (cumene oxidation and sorption-desorption steps are absent).

forcedly necessary if the producer intends to make products instead of closing the plant by virtue of its moral and physical obsolescence. There is one more objective reason why reconstruction of obsolete plants is the difficult problem. That is, only some of all licensors know one another’s production engineering. And, the use of local engineering and licensing companies, even if they have developed and designed in the past the plants to be reconstructed, appears to be completely senseless, because these companies do not possess either the rights to modern production engineering, or the knowledge of these production engineering. If the aforementioned difficulties are overcome and the customer begins reconstruction, the realization of the second stage of modernization is economically expedient because the volume of borrowed funds for the implementation of main stage—radical reconstruction—decreases owing to the partial increase in the selectivity of the key steps of the process. Moreover, the implementation of the second stage allows one to reduce markedly the payback time of expenses for overall modernization. In our opinion, it is possible in practice to choose three types of obsolete plants that are easily distinguished in terms of yields of byproducts, so-called phenol tar (without taking cracking into account): a) very obsolete, 170–250 kg/t of phenol; b) an average level of obsoleteness, 120–170 kg/t of phenol; c) obsolete, 100–120 kg/t of phenol. As shown by the experience of ILLA, all three types of obsolete plants can be successfully transformed by means of modern technology into those having a yield of phenol tar of 50–70 kg/t of phenol, a value that is equivalent to feedstock (cumene), saving from 50 to 200 kg/t of phenol. Note that the high yield of phenol tar (170–250 kg/t of phenol) at very old plants is not only a consequence PETROLEUM CHEMISTRY

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of the out-of-date technology or the absence of investments in production, but also a consequence of the technological level of their top managers and engineering staff. The evaluation is based on the facts that (1) a number of plants have the byproducts yields, which are lower by a factor of 1.5–2 even if the out-of-date technology is used and (2) modeling of the out-of-date technology based on the kinetics of the key steps of the process (cumene oxidation and CHP decomposition which mainly determine parameters of the process) unambiguously confirms that the yield of byproducts should not exceed 140–145 kg/t of phenol. Practice has convincingly proven that: (a) It is impossible to attain a high selectivity of cumene oxidation in reactors of old design. (b) The conversion of CHP decomposition reactors of old designs into modern production engineering is impossible unless the safety of the process and the loss in selectivity, higher than that in the original process of the licensor, are disregarded. In conclusion of the consideration of the stages of the improvement of the performance characteristics of the cumene method for phenol production, it is necessary to mention alternative methods for direct phenol preparation advertised recently. Analysis of the literature, patent, and promotional materials, nevertheless, shows that so-called “single-step” methods for benzene oxidation to phenol, even explicitly elegant from the chemical point of view, rank considerably below the ILLA cumene process in their technical-and-economic parameters. Accordingly, the prospects for industrial implementation of “single-step” processes in the near future seem doubtful. Most likely, the newly developed cumene process and its modifications will dominate the market of phenol production even in the remote perspective.

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REFERENCES 1. RU Patent No. 1455596 (1987); US Patent No. 5,908,962 (1998); RU Patent No. 2146670 (1998). 2. V. M. Zakoshansky, AICHE First International Aromatics Processing Conference (New Orleans, 2001), p. 166. 3. V. M. Zakoshansky, Katal. Khim. Neftekhim. Prom., No. 1, 29 (2002). 4. V. M. Zakoshansky, Second Asia Phenol/Acetone & Derivatives Market (2005). 5. V. M. Zakoshansky, Katal. Khim. Neftekhim. Prom., No. 5, 2 (2004). 6. SU Patent No. 1361937 (1985); SU Patent No. 1563181 (1990); US Patent No. 5,254,751 (1993). 7. RU Patent No. 2141938 (1999); RU Patent No. 2142 932 (1999); US Patent No. 6,057,483 (2000).

8. V. M. Zakoshansky, AICHE Second International Aromatics Processing Conference (New Orleans, 2003), p. 794. 9. V. M. Zakoshansky, AICHE Third International Aromatics Processing Conference (New Orleans, 2004), p. 504. 10. V. M. Zakoshansky, Yu. N. Yur’ev, G. S. Idlis, and A. S. Aleksandrov, Zh. Fiz. Khim. 58 (5), 1265 (1984). 11. UOP / R.J. Schmidt // 3rd Asia Phenol/Acetone & Derivatives Market. 2006. Peking. Febrary 23−24. 12. RU Patent No. 2111203 (1993); US Patent No. 5,502,259 (1996); RU Patent No. 2266275 (2004). 13. RU Patent No. 2125038 (1996); US Patent No. 6,252,124 (2000). 14. V. M. Zakoshansky et al., AICHE Second International Aromatics Processing Conference (New Orleans, 2003), p. 75.

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