Theory and Practice of Alkyl Phenol Synthesis. tert-Octylphenols

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Theory and Practice of Alkyl Phenol Synthesis. Tert-octylphenols Nikita Yu. Krymkin, Vladimir A. Shakun, Tatyana N. Nesterova, Pavel V. Naumkin, and Maxim V. Shuraev Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.6b02067 • Publication Date (Web): 24 Aug 2016 Downloaded from http://pubs.acs.org on September 8, 2016

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Industrial & Engineering Chemistry Research

Theory and Practice of Alkyl Phenol Synthesis. Tert-octylphenols Nikita Yu. Krymkin,a Vladimir A. Shakun,a Tatyana N. Nesterova,a Pavel V. Naumkin,*b Maxim V. Shuraeva a

Samara State Technical University, Molodogvardeyskaya, 244, Samara 443100, Russia

b

Saint Petersburg State University, Universitetsky Prospect 26, Petrodvoretz, Saint Petersburg 198504, Russia

* Corresponding author. Tel.: +7 911 2771781. E-mail: [email protected]

Abstract Liquid-phase alkylation of phenol with diisobutylenes was studied in the presence of ion-exchange resin Amberlyst 36 Dry. Thermodynamic characteristics were calculated for the reactions that occur in a reaction system. Kinetics of the alkylation process was studied. The conditions of selective synthesis were recommended for 4-tert-octylphenol. Recommendations on the use of obtained data were given. Introduction Para-tert-octylphenols (4-TOPhs) are widely used in productions of non-ionic surfactants, oil soluble resins, lubricant additives, antioxidants, calixarenes etc. Alkylation of phenol with alkenes does not belong to the unstudied processes. However, some problems of alkylphenols production have been left unsolved. On the one hand, those questions are concerned with competing reactions that proceed intensively in a reaction system. On the other hand, there are new catalysts that are offered by the world market regularly. Sulfonic ion-exchange resins satisfy the requirements for synthesis of branched alkylphenols and there is no equivalent to these catalysts at this moment. However, in order to implement novel and effective ionexchange resins in alkylation processes, advanced studies of alkylation should be conducted. The following information on the 4-TOPhs syntheses has been obtained at the present time. In 1938, the technology of 4-TOPhs synthesis was developed in the USA.1 The process is represented by phenol alkylation with diisobutylene (DIB) at 288–308 K in the presence of H2SO4 (7% mass.). A ratio of DIB to H2SO4 (7% mass) was 1:1. The yield of 4-TOPh was 90–95% of estimated. In 1957, it was claimed that the ion-exchange resins are excellent catalysts for phenol alkylation with olefins (isobutylene, DIB, nonene-1).2 In 1990, Patwardhan and Sharma discussed the results of phenol alkylation.3 Molar ratios of phenol to DIB were 1:1 and 4:1 at 323–373 K over the ion-exchange resins (2.5–10% mass). It was found that an increase in a catalyst amount leads to an increase in an alkylation rate. The reaction rate does not depend on the size of catalyst beads (0.3–0.6 mm), in other words, the diffusional resistance of reactants can be neglected. The authors also reported that it is difficult to develop the kinetic model that describes the whole process, but a model solution could be simplified by the following conditions: • The ratio of phenol to DIB ≥ 1. • The conversion of DIB < 80%. • The temperature of alkylation should be greater than 343 K that suppresses dimerization of DIB, but less than 373 K to prevent the formation of p-tert-butylphenol (4-TBPh). Dimerization of DIB cannot be completely suppressed at 323–373 K as the results of work3 showed. The ratio of 4-TOPh to 2-TOPh was discussed on a qualitative level, namely, this ratio is increased upon a temperature rise and a reaction time increase. In the presence of sulfonic ion-exchange resins, dimerization of DIB was separately studied, and tetraisobutylenes (TIB) were obtained as products.3 It was also suggested that the dimerization is a firstorder reaction that depends on the concentrations of phenol or DIB, and the presence of water in the catalyst suppresses the dimerization of DIB. 1 ACS Paragon Plus Environment


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Phenol alkylation with TIB leads to the formation of octylphenols instead of hexadecylphenol as it was expected. The yield of dioctylphenols was decreased from 6.8% to 1.8% upon the increase of the phenol to DIB ratio from 1:1 to 4:1 mol/mol. Nevertheless, the conversion of DIB was approximately 97% throughout the ratios phenol:DIB. Phenol alkylation was characterized by the following activation energies: 28.8 kJ·mol-1 over Amberlyst 15; 37.2 kJ·mol-1 over monodisperse K2661 (uncertainty was 10%). It was found that phenol alkylation is a more temperature-sensitive reaction than dimerization. Hence high temperatures promote the formation of 4-TOPh. On the other hand, DIB was depolymerized over the ion-exchange resins, and a depolymerizing product reacts with phenol to form 4-TBPh. This assumption was confirmed by several experiments that were carried out at 393 K (the upper region of the Amberlyst 15 workability range). As a result, 4-TOPh had better yield, while the yield of tetraisobutylene was decreased. However, 3–5% of 4-TBPh was also obtained. The next yields of 4-TBPh were observed in the presence of different catalysts: up to 20% over Filtrol 24 at 443 K; 95% over sulfuric acid (2% mass), 18% over p-toluenesulfonic acid, 85% over Nafion H. In 1991,4 Amberlyst 15, p-toluene sulfonic acid, and Ag+-exchanged Amberlyst 15 were used as alkylation catalysts. As a result, ratios of 2-TOPh to 4-TOPh were 5:95, 41:59, 20:80 respectively, while the phenol to olefin ratio was held at 4:1. The conversions of DIB attained 40, 40 and 8%, respectively. In 2000,5 4-TOPh was synthesized over KU-2 and toluene sulfonic acid at 383 K. The ratio of phenol to olefin was 1:1. The yields of 4-TOPh attain 93.1 and 98.1% mass over the selected catalysts for 2 h, respectively. The amount of 2-TOPh was 6.1 and 1.8% mass, respectively. The remaining compound was 2,4-diTOPh. In 2006,6 phenol was alkylated with DIB in the presence of metal triflates at 333 K. The phenol to olefin ratio was 2:1. The concentration of TOPhs reached 95% for 2 h over 1% mol of Bi(OTf)3 or 0.1% mol of triflic acid. The ratio of 4-TOPh to 2-TOPh was >100. The syntheses over 1% mol of Cu(OTf)2, Sc(OTf)3 and 0.1% mol of Bi(OTf)3 gives 93% and 77% yield of TOPhs. In this case, the ratios 4-TOPh:2-TOPh were decreased to 52, 37, 12 mol/mol, respectively. The effect of moisture on a products yield is studied throughout the usage period of ion-exchange resins. Moistened resins reduce their catalytic activity; it is a typical response for the reactions that are catalyzed by non-dissociated sulfonic acids. Also it was found that an increase in moisture unequally affects the deactivation of the following catalysts: Amberlyst 15, Amberlyst XN1010, monodisperse K2661 and Filtrol 24.3 Nevertheless, the selectivity of 4-TOPh was increased in the presence of some catalysts that contain 10–20% of moisture, while dry ion-exchange resins lead to the formation of 4-TBPh. The reason of catalyst deactivation was studied by Zundel7 by means of IR-spectroscopy. It was shown that every molecule of water is associated with 3 sulfonic groups, hence catalytic activity of the ionexchange resins are decreased unequally. The moisture effect on the formation of straight-chain nonylphenols was studied in work8 in the presence of nine ion-exchange resins. After water was injected into a reaction mixture, all of the studied resins were significantly deactivated. As an example, rate constants of reactions over Amberlyst 36 Dry (A-36) were 8–96 times decreased upon an increase in water contents from 0.5 to 3.1% mass. Therefore, we have shown all important information about phenol alkylation with DIB. Naturally, this information has limited volume, but it describes the complexity of the alkylation process. The following interrelated reactions occur during phenol alkylation: • The transformations of alkenes: isomerization, oligomerization, and decomposition. • The transformations of phenols and alkyl phenyl ethers: isomerization, decomposition. • C-alkylation and O-alkylation of phenol. • Dealkylation of alkylphenols. 2 ACS Paragon Plus Environment

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The effectiveness of a whole process depends on the realization of its potential, which requires reliable data on thermodynamics and kinetics for an entire set of reactions. These issues are considered in our work. Experimental section Alkylation. Industrial-grade phenol and A-36 were obtained from NZMP, Russia. According to gas chromatography (GC) analysis, the purity of phenol is more than 99% mass. The mixture (obtained from Sanors, Russia) of 2,2,4-trimethylpentene-1 (DIB-1, 86% mass) and 2,2,4-trimethylpentene-2 (DIB-2, 14%) was used as an alkylating agent. The properties of industrial-grade A-36 is given in Supporting Information (Table S1). Before the reaction, A-36 was dried to a constant weight in an air bath at 378 K. Thermogravimetric analysis (Mettler Toledo HR83 moisture analyzer) showed a residual moisture content in the dried catalyst of 1.2 ± 0.1% mass. The total static exchange capacity of A-36 was 5.2±0.2 eq/kg after a drying procedure. The results of our previous works8–10 recommend studying alkylation kinetics in the presence of ionexchange resin A-36. The alkylation kinetics conducted in a reactor with a stirrer, a jacket, and a reflux condenser. Temperature stability of the reaction was provided by boiling a heat carrier (acetone, benzene, water, toluene) in the reactor jacket. The molar ratios of phenol:DIB were 1.0, 2.4, 3.0, 6.3. The concentration of A-36 was varied from 8 to 26% mass (per a sum of reactants). Loading the reactor was carried out in the following order: phenol, catalyst, DIB. The catalyst was swollen in phenol under reaction temperature at constant stirring for 1 h. Then DIB was added into the reactor. The sampling was carried out at constant stirring and certain time. Collected samples were diluted with toluene and analyzed by GC. Study of diisobutylenes isomerization equilibrium. The equilibrium study was conducted in a liquid phase at 293–403 K in the presence of A-36 or Tulsion 66 MP. Isomerization was performed in a sealed batch reactor (molybdenum glass, 100 6 mm). The catalyst amount was varied from 5 to 50% mass per the sum of hydrocarbons. The solvent was cyclohexane with a molar ratio of cyclohexane:DIB from 5 to 70 mol/mol. The reaction was carried out at isothermal conditions (±1 K). The obtained reaction mixtures did not require special treatment before analysis. Throughout the study, the reaction mixture remains colorless and transparent. The samples were analyzed by GC without an additional treatment. Analysis and Identification. GC analyses of reaction mixtures were carried out with ChromatecCrystal 2000M gas chromatograph equipped with a flame ionization detector (FID) and a SE-30 (stationary phase is cross-linked 100% dimethylpolysiloxane) capillary column of 60 m × 250 µm × 0.25 µm (column length × internal diameter × film thickness). The carrier gas is helium. The temperature of injection is 543 K, and the temperature of the FID is 573 K. The temperature of a column oven was chosen separately. An efficiency of chromatographic separation and a temperature profile for the column oven are demonstrated in Figure 1. Identification of all components was performed by means of the chemical experiment and chromatography-mass spectrometry (MS). MS analyses were carried out with Agilent 6850 equipped with a mass-selective detector Agilent 5975C VL (MSD) and a HP-5MS capillary column of 30 m × 250 µm × 0.25 µm (column length × internal diameter × film thickness). The electron ionization (EI) is 70 eV. The structure of 4-TOPh (component 13 in Figure 1 in the manuscript) was confirmed by means of mass spectrometry. Obtained spectrum (Figure 2) shows 100% match of the NIST and AIST databases.11,12 The identification of TBPhs was carried out by pure components that were synthesized in this work. There are no available data on mass-spectra of tetramers of isobutylene. To identify these substances the main principles of bounds cleavage during electron ionization were used and possible fragmentation mechanisms that form fragment ions were compared. Substances 6–11 in Figure 1 were identified as TIBS according to these principles and the molecular ion at m/z 224. 3 ACS Paragon Plus Environment


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The detailed information on identification and obtained mass-spectra are given in Supporting Information.

Figure 1. Typical chromatogram for phenol alkylation with DIB: (1) 2,2,4-trimethylpentene-1; (2) 2,2,4trimethylpentene-2; (3) phenol; (4) 2-tert-butylphenol; (5) 4-tert-butylphenol; (6–11) tetramers of isobutylene; (12) 2-(1,1,3,3-tetramethylbutyl)phenol; (13) 4-(1,1,3,3-tetramethylbutyl)phenol; (14) 4-secoctylphenol; (15) 4-tert-octylphenol; (16) 2-tert-butyl-4-(1,1,3,3-tetramethylbutyl)phenol; (17) 2,4-di(1,1,3,3-tetramethylbutyl)phenol. Results and discussion. The alkylation process involves phenol and DIB, which are the substances with high reactivity. Hence, a variety of their reactions should be wide enough even at relatively low temperatures in the presence of ion-exchange resins. DIB intensively alkylates phenol (Figure 2) to form the next products: • Mono-TOPhs (2-TOPh and 4-TOPh): OH

OH k1

+

(1) OH

+

OH k2

(2) • Di-TOPhs (mainly 2,4-diTOPh):

4 ACS Paragon Plus Environment

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OH

OH k3

+

(3) OH

OH k4

+

(4) The interconversion of diisobutylene attains 100% for 60 min at 329 K (9.87% mass of A-36, phenol:DIB = 2.39 mol/mol). The same conversion level was also reached at 383 K for 10 min (12% mass of A-36, phenol:DIB = 5.58 mol/mol). The concentrations of DIB isomers are rapidly changed for 1 min, and then their amount is virtually remained steady throughout the reaction time (Figure 2). The amount of DIB-1 is kept at 80–81% (20–19% DIB-2) per the sum of DIBs. The following reasons can explain this case. First, the reaction quickly reaches an equilibrium state: K5

(5) Second, there is some kind of the balance between consumption of reactants that is preserved until the complete depletion of DIBs. The data on DIBs isomerization is gathered in Table 1 which includes results from this work and refs.13,14 We have analyzed this data and found that the constancy of consumption should not have thermodynamic nature. It is interesting that the mixture with 78% DIB-1 and 12% DIB-2 was obtained in paper15 during isobutylene dimerization at 393 K over Amberlyst 15 or Amberlyst 35. The equilibrium concentrations of DIB-1 (Figure 2) are significantly less than the values that were observed during phenol alkylation (in this work) or isobutylene isomerization (in work15). 100

%

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90

80

70 0

20 40 Reaction time, min

60



Figure 2. The interconversions of diisobutylene isomers at thermodynamic and kinetic conditions: (○) the conversion of DIB at 329 K (9.87% A-36); (□) the DIB-1 concentration at 329 K (9.87% A-36); () the conversion of DIB (12% A-36) at 383 K; () the DIB-1 concentration at 383 K (12% A-36). Dotted line shows the DIB-1 equilibrium concentration at 329 K. Dashed line shows the DIB-1 equilibrium concentration at 383 K. Along with reactions 1–4, DIB is oligomerized under the conditions of phenol alkylation over A-36 to form tetramers of isobutylene: k6

+

C 16H 32

(6) The concentration of TIBs rapidly passes through its maximum (Figure 3). A peak height and a rate of decrease in TIBs concentration depend on a reactants ratio and the reaction temperature. 2.5

Tetramers of isobutylene, %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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2.0 1.5 1.0 0.5 0.0 0

200 400 600 Reaction time, min

800

Figure 3. Conversion of isobutylene tetramers. () 329 K, A-36 9.8%, the phenol to DIB ratio is 2.4 mol/mol. (○) 383 K, A-36 12%, the phenol to DIB ratio is 6.0 mol/mol. () 329 K, A-36 19%, the phenol to DIB ratio is 6.0 mol/mol. The analysis of kinetics shows that destructive phenol alkylation with TIBs leads to the rapid decrease in TIBs concentration to form mono-TOPhs (mainly 4-TOPh): OH

OH

C16H32

+

k7

+

(7) Phenol is solely alkylated into an aromatic ring at selected conditions. In other words, alkylphenyl ethers are not formed, while their formation was observed in work.3 The ortho-substitution in the aromatic ring shows a high reactivity despite a steric hindrance. At the initial time, the amount of 2-TOPh attained 20–30% (per the sum of ortho- and para-isomers), these concentrations were determined throughout the studied temperatures and the catalyst amount. The intensity of isomerization of 2-TOPh into 4-TOPh


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depends upon the next conditions: the reaction temperature, the catalyst amount, and the position of 2-TOPh on kinetic correlation for the reversible reaction: OH

OH

OH

OH k8

+

+

k-8

(8) At this moment, it was agreed that the positional isomerization in the aromatic ring is carried out by a reversible intermolecular transfer of a tert-alkyl group. The equilibrium of reaction 8 was studied in this paper and work.16 These results are summarized in Table 1. The kinetics study shows that reaction 8 attains stable thermodynamic equilibrium in the presence of A-36 throughout temperature range (Figure 4). The equilibrium concentration of 4-TOPh reached 99% per the sum of 2- and 4-TOPhs. The temperature rise leads to a decrease in this concentration (Figure 4). 100

Concentration of 4-TOPh, %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


98 96 94 92 90 0

200 400 600 Reaction time, min

800

Figure 4. Concentrations of 4-TOPh per the sum of isomers: () 329 K, A-36 9.87%, the phenol to DIB ratio is 2.39 mol/mol; (○) 329 K, A-36 19.4%, the phenol to DIB ratio is 6.0 mol/mol; () 383 K, A-36 12.2%, the phenol to DIB ratio is 5.8 mol/mol. Dotted line shows the 4-TOPh equilibrium concentration at 329 K. Dashed line shows the 4-TOPh equilibrium concentration at 383 K. Under chosen conditions, the following reaction of transalkylation also reaches the equilibrium state:

OH

+

OH

OH

OH k9 k -9

+

(9) In order to describe chemical equilibrium in the phenol+2-TOPh+4-TOPh+2,4-diTOPh system, the results for reactions 8 and 9 were used (Table 1). Figure 5 shows that there is a convenient way to synthesize 4-TOPh under thermodynamic control. In this case, isomerization should be implemented under the middle7 ACS Paragon Plus Environment


temperature range of ion-exchange resins workability (353 K) and at the DIB:phenol molar ratio of 0–1.5 mol/mol. 1 0.8 mol. fr.

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0.6 0.4 0.2 0 0

0.25

0.5 0.75 1 1.25 1.5 Alk/Ar, mol/mol Figure 5. Dependence of equilibrium composition on a reactants ratio at 353 K in the phenol+TOPhs system: phenol; 4-TOPh; 2-TOPh; 2,4-diTOPh. Table 1. Isomerization equilibrium of DIB and TOPhs Kx ∆ d, kJ·mol-1 2,4,4-trimethylpentene-2 ⇋ 2,4,4- trimethylpentene-1 (5) ln 0.08571 0.3995 d

T, K

catalyst

293 323 323 373 413 423 453 473 473

A-36 (29.48%) Tulsion 66MP (40.59%) Amberlyst 35Wet A-36 (22.33%) Amberlyst 35Wet SPA, inert solvent SPA, inert solvent SPA, inert solvent SPA, without solvent

4.20±0.01 3.67±0.01 3.90a 3.13±0.07 2.94a

-3.3±0.5 (Tavg=394 K)

2.85b 2.67b 2.48b 2.49b 2-tert-octylphenol ⇋ 4-tert-octylphenol (8)

∆ d, J·mol-1·K-1

0.7±1.3 (Tavg=394 K)

329.3 353.1 373 382.8 403 423 443 463

329.3 353.1 373 382.8 403 423 443 453

ln 0.9838 1.8955 d A-36, 9,8–26,3 124.0±2.04 A-36, 7.4–26.6 79.2±0.45 H2SO4 59.5±1.80c A-36, (12.2–12.9% mass) 52.1±0.13 -15.8±0.8 (Tavg=396 K) -8.2±2.1 (Tavg=396 K) H2SO4; HCl 39.1±0.84c c H2SO4; HCl; KU-2-8 32.4±1.20 H2SO4; HCl 27.1±1.03c H2SO4; HCl 23.8±0.62c 2,4-di-tert-octylphenol + phenol ⇋ 2-tert-octylphenol + 4-tert-octylphenol (9) ln 0.5045 0.2845 d A-36, (9.8–26.3% mass) 1.38 A-36 (7.4–26.6% mass) 1.28±0.02 H2SO4 1.59±0.30c A-36, (12.2–12.9% mass) 1.24±0.01 -2.4±1.8 (Tavg=403 K) -4.2±4.6 (Tavg=403 K) H2SO4; HCl 1.18±0.31c H2SO4; HCl; KU-2-8 1.12±0.22c HCl; KU-2-8 1.13±0.27c HBr 1.07±1.65c 8 ACS Paragon Plus Environment

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1.20±0.66c

H2SO4; HCl

a

13 b

14 c

Data from work . Data from work . Data from work16. dThermodynamic characteristics and equations were obtained by processing the data from Table 1 To realize the potential that is demonstrated in Figure 5, it is necessary to exclude the other reactions from the reaction system. As the study results show, it is hard to completely exclude those reactions, but it is possible to keep them at minimal conversion. Indeed, along with the discussed reactions of isomerization and transakylation, phenol reacts with DIB to form tert-butylphenols. At low temperature, the role of TBPhs is insignificant; the yield (per phenol) of TBPhs is 1.5% at 329 K. The TBPhs amount is increased along with the temperature increase. It was found that the main source of TBPhs is the reaction of destructive transalkylation of TOPhs with phenol: OH

OH

OH

OH

k10

+

+

(10) OH

OH

OH

OH

k11

+

+

(11) The analysis of kinetics shows that the source of TBPhs formation is the destructive alkylation of phenol with DIB through the next reactions: OH

+

OH

OH

k12

2

+ (12) OH

OH

+

OH

k13 2

+

(13) According to our estimation, the share of destructive alkylation is no more than 10% per the sum of TBPhs. Moreover, the source of TBPhs formation acts at the high temperature and the initial time period when the concentration of DIB is relatively high in a reaction volume. Formed 2-TBPh and 4-TBPh interact with each other by the following interconversion:


Industrial & Engineering Chemistry Research OH

OH

OH

OH k14

+

+

k-14

(14) It has been shown that reaction 14 is carried out by intermolecular transfer of tert-butyl. That reaction quickly attains the equilibrium state during phenol alkylation with isobutylene using the ion-exchange resins.9,10 In our case, the amount of TBPhs is significantly less than it can be obtained during phenol alkylation with isobutylene. However, the system is equilibrated at relatively mild conditions (Figure 6). The equilibrium concentration of 4-TBPh, which is shown in Figure 6, was calculated by data from work9 and it almost equal to the equilibrium concentration of 4-TOPh (Figure 4). Reaction 14 reaches the equilibrium state for 2 h at 329 K and for 1 h at 383 K. The amount of A-36 was 26.3% and 12.2% mass, respectively. As in the case of 4-TOPh, the amount of 4-TBPh at the initial time is less than the same value at the equilibrium conditions. In other words, the concentrations of ortho-isomers (2-TOPh during alkylation and 2-TBPh during destructive transalkylation) are higher than the equilibrium conditions can provide. 100

4-TBPh, % mass

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90 80 70 60 50 0

200 400 Reaction time, min Figure 6. Dependence of the 4-tert-butylphenol concentration (per the sum of conditions: (○) 329 K, 9.87% A-36, phenol:DIB=2.4 mol/mol; () 383 K, 12.2% mol/mol; () 329 K, 26.3% A-36, phenol:DIB=6.0 mol/mol. Dashed line shows Dotted line shows equilibrium at 383 K.

600 isomers) on synthesis A-36, phenol:DIB=5.8 equilibrium at 329 K.

The discussed above reactions are the main processes that are carried out under the excess of phenol. Particular interest is usually drawn towards these reactions because they do not cause serious problems during a separation procedure. In addition, the discussed reactions do not require vast circulating streams and utilization of by-products, which are inevitably formed during alkylation at a high ratio of alkene to phenol. In order to describe the kinetics of the discussed reactions, the separate set of experiments were carried out varying temperature (329–383 K) at the phenol:DIB ratio of 5–6 mol/mol, over 12.6±0.4% mass of A36. At these conditions, the kinetic model of the process is relatively simple. A stoichiometry and a reactions matrix are given in Table 2. An equilibrium attainment specifies the maximum conversion of phenol and the maximum selectivity of 4-TOPh in the phenol+TOPhs system at given reactants ratio (DIB:phenol, mol/mol). At the same time, 10 ACS Paragon Plus Environment

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the alkylation under kinetic control shows less the phenol conversion and the 4-TOPh selectivity than the equilibrium state can provide (Figure 7). The phenol conversion of varies from zero to the value that corresponds the reactants ratio at the complete depletion of DIB. If we compare the maximum conversion at kinetic control and the conversion at the equilibrium state, these values are almost equal at low DIB:phenol ratios, while the kinetic control gives lower conversion at high DIB:phenol ratios (Figure 7). The 4-TOPh selectivity also depends on the reactants ratio. An increase in the DIB:phenol ratio leads to a gradual deviation of the 4-TOPh selectivity from the value that gives the equilibrium state. 100 80 % or % mass.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


60 40 20 0 0

0.2

0.4 0.6 0.8 1 1.2 1.4 1.6 a ratio of alkyl to aryl, mol/mol Figure 7.The conversion of phenol and the selectivity of 4-TOPh. The conversion at the kinetic control at the following DIB:phenol ratios: () and () at 0.179 mol/mol; () and () at 0.295 mol/mol; () and () at 0.375 mol/mol; (○) and (●) at 0.870 mol/mol. The selectivity at the kinetic control at the following DIB:phenol ratios: () and () at 0.179 mol/mol; () and () at 0.295 mol/mol; ( ) and ( ) at 0.375 mol/mol; ( ) and ( )at 0.870 mol/mol. The phenol conversion at equilibrium condition (%): (329 K); (373 K). The 4-TOPh selectivity at equilibrium condition: (329 K); (373 K). some points from experiment. the maximum conversions. It was found that the total concentration of tert-butyl-octylphenols does not exceed 0.1% mass under the high phenol:DIB ratio (5–6 mol/mol). Hence the kinetic model of alkylation does not involve 4-tertbutyl-2-tert-octyl-phenol and 2-tert-butyl-4-tert-octylphenol. A ratio of alkyl to aryl was monitored in each experiment. It has been found that alkylation products do not lose their alkyl groups during the study. Therefore the kinetic model also does not involve the destructive conversions that produce isobutylene. Adequacy of the considered kinetic model, which includes the rate constants from Table 3, is shown in Figures 8 and 9. It has been found that the reaction temperature provides a significant effect on the selectivity. On the one hand, 4-TOPh is mainly formed at low temperature (329 K) and this product is stable for 5 h of an experiment (Figure 8). On the other hand, all TOPhs are intensively decomposed at 383 K (Figure 9). Table 2. Stoichiometry and reactions matrix of phenol alkylation with DIBs reactants DIB+Ph DIB+Ph 4-TOPh+DIB 2-TOPh+DIB 2DIB TIB+Ph 2-TOPh+Ph 4-TOPh+Ph

products 4-TOPh 2-TOPh 2,4-diTOPh 2,4-diTOPh TIB 4-TOPh+DIB 4-TOPh+Ph 2-TOPh+Ph

ki k1 k2 k3 k4 k6 k7 k8 k-8

DIB -1 -1 -1 -1 -2 1

Ph -1 -1

2-TOPh

4-TOPh 1

2,4-diTOPh

-1

1 1

2-TBPh

4-TBPh

1 -1

-1 -1/1 -1/1

TIB

-1 1

1 1 -1

1 -1



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

2,4-diTOPh+Ph 2-TOPh+4-TOPh 4-TOPh+Ph 2-TOPh+Ph DIB+2Ph DIB+2Ph 2-TBPh+Ph 4-TBPh+Ph

2-TOPh+4-TOPh 2,4-diTOPh+Ph 24-TBPh 2-TBPh+4-TBPh 22-TBPh 24-TBPh 4-TBPh+Ph 2-TBPh+Ph

k9 k-9 k10 k11 k12 k13 k14 k-14

-1 -1

-1 1 -1 -1 -2 -2 -1/1 -1/1

1 -1

1 -1 -1

Page 12 of 19

-1 1

-1

1 2 -1 1

2 1 2 1 -1

The Runge-Kutta method was applied to process the obtained data. Calculated rate constants were given in Table 3. Table 3. The rate constants [kg·A-36·mol-1·min-1] at phenol to DIB ratio of 5.9 mol/mol over 12.6% A-36. rate constants (ki) a reactants

products

T, K

DIB+Ph

4-TOPh

k1

DIB+Ph

2-TOPh

k2

DIB+4-TOPh

2,4-diTOPh

k3

DIB+2-TOPh

2,4-diTOPh

k4

2DIB

TIB

k6

TIB+Ph

4-TOPh+DIB

k7

2-TOPh+Ph

4-TOPh+Ph

k8

4-TOPh+Ph

2-TOPh+Ph

k-8

2,4-diTOPh+Ph

2-TOPh+4TOPh

k9

2-TOPh+4TOPh

2,4-diTOPh+Ph

k-9

4-TOPh+Ph

24-TBPh

k10

2-TOPh+Ph

2-TBPh+4TBPh

k11

DIB+2Ph

22-TBPh

k12

DIB+2Ph

24-TBPh

k13

2-TBPh+Ph

4-TBPh+Ph

k14

4-TBPh+Ph

2-TBPh+Ph

k-14

a

329

329

353

353

353

353

383

4.61E03 3.41E04 1.20E03 1.81E03 4.82E03 5.08E04 1.62E04 1.36E06 2.00E04 1.39E04 1.20E07 7.28E07 1.92E07 7.90E07 1.64E04 1.38E06



7.00E03 8.99E04 2.43E03 3.80E03




5.16E06 9.59E06 3.89E07 1.19E06 3.80E04 4.73E06

383 4.15E-02 1.29E-03 4.01E-03 9.11E-03 1.31E-02 9.48E-03 2.07E-03 3.93E-05 3.49E-03 2.75E-03 4.74E-04 4.19E-04 9.92E-06 4.00E-05 1.99E-03 3.78E-05

383 3.80E02 1.59E03 4.11E03 9.36E03 1.11E02 3.91E03 2.12E03 4.03E05 4.59E03 3.61E03 3.02E04 3.10E04 9.08E06 3.36E05 1.84E03 3.50E05

Calculation uncertainty is no more than 10% rel.



4-TOPh, mol/kg of catalyst

0.6 0.5 0.4 0.3 0.2 0.1 0.0 100 200 reaction time, min

8 6 4 2 0

300

0.018 0.016 0.014 0.012 0.010 0.008 0.006 0.004 0.002 0.000

0

100 200 reaction time, min

300

0


300

0


300

0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00

0


300

2,4-TOPh, mol/kg of catalyst

0.6 0.5 0.4 0.3 0.2 0.1 0.0 0

10

4-TBPh, mol/kg of catalyst


0

TIB, mol/kg of catalyst

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Page 13 of 19


300

0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00

Figure 8. The comparison of experimental (□) and calculated (●) data on phenol alkylation with DIB at 329 K, the phenol to DIB ratio is 6.0, 12.8% A-36.





0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 100 200 reaction time, min

0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 0


2,4-TOPh, mol/kg of catalyst

0.30 0.25 0.20 0.15 0.10 0.05 0.00 50 reaction time, min

8 6 4 2 0 0

300

0.35

0

10

300



0

TIB, mol/kg of catalyst

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

100

Page 14 of 19


300

0


300

0


20 16 12 8 4 0

0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00 300

Figure 9. The comparison of experimental (□) and calculated (●) data on phenol alkylation with DIB at 383 K. The phenol to olefin molar ratio is 6.1, 12.9% A-36. It is interesting to compare the average values of rate constants for related reactions. So phenol alkylation demonstrates the following kinetic characteristics: • Rate constants dependencies on temperature run parallel to one another (Figure 10). 14 ACS Paragon Plus Environment

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• Positional isomerization in the aromatic ring has almost identical dependencies of ln on temperature for TOPhs and TBPhs (Figure 11). • Reactions of destructive alkylation have the parallel dependencies (Figure 12).

ln(ki)

-3 -4

Reaction (1)

-5

Reaction (2) Reaction (3)

-6

Reaction (4)

-7

y = -4.5706x + 8.4396 R² = 0.9924 y = -3.3818x + 2.4054 R² = 0.9962 y = -2.9343x + 2.2163 R² = 1 y = -3.9061x + 5.5176 R² = 0.9969

-8 2.5

2.6

2.7

2.8 1000/T

2.9

3

3.1

Figure 10. Dependence of alkylation rate constants on temperature -4 -6

Reaction (8)

y = -6.3276x + 10.231 R² = 0.9907

Reaction (-8)

y = -8.2231x + 11.215 R² = 0.9945

-12

Reaction (14)

y = -6.0817x + 9.6943 R² = 0.9775

-14

Reaction (-14)

y = -7.9772x + 10.678 R² = 0.9868

ln(ki)

-8 -10

-16 2.5

2.6

2.7

2.8

2.9

3

3.1

1000/T Figure 11. Dependence of isomerization rate constants on temperature -10 -11

ln(ki)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


-12

Reaction (12)

-13

y = -9.1306x + 13.126 R² = 0.9115

-14 Reaction (13)

-15

y = -8.9987x + 11.566 R² = 0.9836

-16 -17 2.5

2.6

2.7

2.8 1000/T

2.9

3

3.1

Figure 12. Rate constants dependence on temperature for reactions of destructive transalkylation 15 ACS Paragon Plus Environment


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Activation parameters of the studied reactions (Table 4) were calculated by Arrhenius equation ln ln !" ⁄#$ and the data from Table 3. Table 4. Activation parameters of the studied reactions ln , kg of reaction reactants products Ea, kJ·mol-1 catatalyst·mol-1·min-1 1 DIB+Ph 4-TOPh 37.1±8.2 8.07±2.77 2 DIB+Ph 2-TOPh 27.7±3.4 2.27±1.15 3 DIB+4-TOPh 2,4-diTOPh 24.3±1.4 2.19±0.46 4 DIB+2-TOPh 2,4-diTOPh 32.8±1.1 5.60±0.38 6 TIB 20.0±1.7 1.88±0.56 2DIB 7 TIB+Ph 4-TOPh + DIB 51.1±11.7 10.63±3.94 8 2-TOPh+Ph 4-TOPh + Ph 52.7±10.3 10.19±3.45 -8 4-TOPh+Ph 2-TOPh + Ph 68.5±10.3 11.17±3.45 9 2,4-diTOPh+Ph 2-TOPh+4-TOPh 63.2±10.5 14.24±3.53 -9 2-TOPh+4-TOPh 2,4-diTOPh+Ph 65.6±10.5 14.74±3.53 143.9±15.5 36.74±5.21 10 4-TOPh+Ph 24-TBPh 11 2-TOPh+Ph 2-TBPh+4-TBPh 112.8±6.6 27.17±2.23 12 75.3±10.7 11.60±3.60 DIB+2Ph 22-TBPh 13 80.0±15.8 14.31±5.34 DIB+2Ph 24-TBPh 14 2-TBPh+Ph 4-TBPh+Ph 49.9±6.8 9.48±2.28 -14 4-TBPh+Ph 2-TBPh+Ph 65.7±6.8 10.47±2.28 The analysis of the data from Table 4 shows that the studied reactions have the following activation parameters: • Alkylation that forms the products with para-substitution of an alkyl group (reactions 1, 4, 7, 13) has the higher activation energy than the reaction of ortho-substitution (reactions 2, 3, 12). • Isomerization of para-alkylphenols into ortho-alkylphenols (reactions -8, -14) has the higher activation energy than isomerization of ortho-alkylphenols into para-alkylphenols (reactions 8, 14). • Destructive transalkylation (reactions 10, 11) is characterized by the highest activation energy among the considered reactions. • The activation energy of transalkylation (reactions 9, -9) is comparable with positional isomerization of para-alkylphenols into ortho-alkylphenols (reactions -8, -14). • The dimerization of DIBs into TIBs (reaction 6) is characterized by the lowest activation energy among the considered reactions. Moreover, we can compare the obtained Ea=20.0±1.7 kJ·mol-1 (reaction 6) with the data on isobutylene isomerization from other works. The next values of Ea were obtained by Honkela and Krause:17 30±3 kJ·mol-1 and 2±15 kJ·mol-1, respectively for dimerization and trimerization of isobutylene. Arno de Klerk14 showed that DIBs (74.9% DIB-1 and 18.5% DIB-2) are quickly oligomerized even at 373 K in the presence of solid phosphoric acid. In work18 the following activation energies of consequent oligomerization into dimers, trimers and tetramers over Amberlyst 15 were obtained: 51.49, 60.45 and 16.01 kJ·mol-1 by kinetic model 1; 52.59, 63.67 and 17.27 kJ·mol-1 by kinetic model 2; 47.91, 63.08 and 14.83 kJ·mol-1 by kinetic model 3, respectively. In other words, TIB is formed at significantly lower Ea than the previous steppes. In the presence of Tulsion T-63, the Ea values are 89.34 for dimers, 26.70 for trimers and 31.0 for tetramers kJ·mol-1.19 In this case, trimers and tetramers of isobutylene are formed at significantly lower Ea then dimers. Therefore, an intensification of the oligomerization process should be expected when changing olefins from light to heavy. Conclusions Therefore, the study results can be generalized to the following conclusions: 16 ACS Paragon Plus Environment

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1) Phenol alkylation with DIB is solely carried out into the aromatic ring to form 2-TOPh and 4-TOPh at the selected reaction conditions. The formation of alkyl phenyl ethers was not observed during the reaction. 2) It is possible to reach the high selectivity of 4-TOPh, even though high-reactive substances (phenol, DIB) are used during a synthesis over acid catalysts. It has been found that the amount of para-isomer almost 120 times dominates over ortho-isomer at the equilibrium conditions and low temperature (329 K). The ratio of 4-TOPh to 2-TOPh is considerably decreased upon the isomerization temperature increase. 3) Low temperatures improve the overall selectivity of the phenol alkylation process with DIB. The kinetic study shows that the activation energy of destructive transalkylation is characterized by the highest value among considered reactions. Hence the TBPhs amount can be reduced by the decrease in reaction temperature. 4) Although the oligomerization of DIBs into TIBs has the lowest activation energy among the considered reactions, the temperature increase activates the exhaustion of TIBs through destructive phenol alkylation to form mono-TOPhs. Acknowledgements This work was financially supported by The Ministry of Education and Science of Russian Federation within the framework of the basic part of governmental tasks of Samara State Technical University (project code 1708). Pavel Naumkin is also grateful to SPbSU for financial support in the frame of the grant (12.50.1195.2014). Supporting Information Identification of all components was performed by means of the chemical experiment and chromatography-mass spectrometry. The issues of the octylphenyl ethers formation and isomerization (positional in the aromatic ring and structural of an aliphatic chain) of octylphenols were discussed. The mass spectra of alkylation products are summarized in Supporting Information. The mass-spectra for 9 compounds were presented for the first time. Figure S1. EI mass-spectra of 4-TOPh and 2-TOPh. Figure S2. EI mass-spectrum of silyl ethers of 2-TOPh and silyl ether of 4-TOPh. Figures S3 and S4. Chromatograms of TOPhs and silyl ether of TOPhs. Figures S5 and S6. Chromatograms of tert-butylphenols and silyl ether of tert-butylphenols. Figure S7. EI mass-spectrum of silyl ethers of tert-butylphenols. Figure S8. Typical chromatogram for phenol alkylation with DIB for 60 min at 409 K. Figures S9 A–T. EI mass-spectrum of alkylation products. Table S1. The properties of industrial-grade A-36.

References (1) Niederl, J. B. Disobutylphenol Synthesis-Structure-Properties-Derivatives. Ind. Eng. Chem. 1938, 30, 1269–1274. (2) Loev, B.; Massengale, J. Notes - Cation Exchange Resins as Catalysts in the Alkylation of Phenols. J. Org. Chem. 1957, 22, 988–989. (3) Patwardhan, A. A.; Sharma, M. M. Alkylation of phenol with 1-dodecene and diisobutylene in the presence of a cation exchanger as the catalyst. Ind. Eng. Chem. Res. 1990, 29, 29–34. (4) Chaudhuri, B.; Sharma, M. M. Alkylation of Phenol with a-Methylstyrene , Propylene , 17 ACS Paragon Plus Environment


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Butenes , Isoamylene , 1 -Octene , and Diisobutylene : Heterogeneous vs Homogeneous Catalysts. Ind. Eng. Chem. Res. 1991, 30, 227–231. (5) Korenev, K. D.; Zavorotnyi, V. A. Alkylphenol reagents for the oil and gas industry. Chem. Technol. Fuels Oils 2000, 36, 274–277. (6) Le Rouzo, G.; Morel-Grepet, M.; Simonato, J.-P. Synthesis of 4-tert-octylphenol and 4cumylphenol by metal triflate and metal triflimidate catalysts. J. Chem. Res. 2006, 2006, 521–522. (7) Zundel, G. Hydration and Intermolecular Interaction Infrared Inuestigations with Polyelectrolyte membranes; Academic Press: New York, 1968. (8) Nesterova, T. N.; Chernyshov, D. A.; Shakun, V. A.; Krymkin, N. Y.; Tarasov, A. V.; Voronin, I. O.; Bilenchenko, N. V. Sulfonic acid cation-exchange resins in the synthesis of straight-chain alkylphenols. Catal. Ind. 2016, 8, 16–22. (9) Voronin, I. O.; Nesterova, T. N.; Strelchik, B. S.; Zhuravskii, E. A. Efficiency of sulfonic cation-exchange resins used in para-tert-butylphenol production: A comparison based on the kinetics of transalkylation in the phenol-tert-butylphenols system. Kinet. Catal. 2014, 55, 705–711. (10) Voronin, I. O.; Nesterova, T. N.; Bilenchenko, N. V. The role of para–meta isomerization in the selective synthesis of para-tert-butylphenol in the presence of modern macroporous sulfonic cationexchange resins. Kinet. Catal. 2016, 57, 243–250. (11) Linstrom, P. J.; Mallard, W. G. NIST chemistry Webbook, NIST Standard Reference Database Number 69 http://webbook.nist.gov/chemistry/. (12) Spectral Database for Organic Compounds (SDBS); mass spectrum http://riodb01.ibase.aist.go.jp/sdbs/. (13) Karinen, R. S.; Lylykangas, M. S.; Krause, A. O. I. Reaction Equilibrium in the Isomerization of 2,4,4-Trimethyl Pentenes. Ind. Eng. Chem. Res. 2001, 40, 1011–1015. (14) De Klerk, A. Reactivity differences of octenes over solid phosphoric acid. Ind. Eng. Chem. Res. 2006, 45, 578–584. (15) Di Girolamo, M.; Lami, M.; Marchionna, M.; Pescarollo, E.; Tagliabue, L.; Ancillotti, F. Liquid-Phase Etherification/Dimerization of Isobutene over Sulfonic Acid Resins. Ind. Eng. Chem. Res. 1997, 36, 4452–4458. (16) Verevkin, S. P. Dependence study of thermodynamic properties of tertiary alkyl phenols on their structure. PhD. Dissertation [in Russian], Samara State Technical University, 1984. (17) Honkela, M. L.; Krause, A. O. I. Kinetic Modeling of the Dimerization of Isobutene. Ind. Eng. Chem. Res. 2004, 43, 3251–3260. (18) Talwalkar, S.; Chauhan, M.; Aghalayam, P.; Qi, Z.; Sundmacher, K.; Mahajani, S. Kinetic Studies on the Dimerization of Isobutene with Ion-Exchange Resin in the Presence of Water as a Selectivity Enhancer. Ind. Eng. Chem. Res. 2006, 45, 1312–1323. (19) Talwalkar, S.; Mankar, S.; Katariya, A.; Aghalayam, P.; Ivanova, M.; Sundmacher, K.; Mahajani, S. Selectivity Engineering with Reactive Distillation for Dimerization of C4 Olefins: Experimental and Theoretical Studies. Ind. Eng. Chem. Res. 2007, 46, 3024–3034.


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For Table of Contents Only OH

+

OH OH

OH OH OH

OH

OH

OH

OH

+

C16H32


Theory and Practice of Alkyl Phenol Synthesis. tert-Octylphenols

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