2278
Ind. Eng. Chem. Res. 1992, 31, 2278-2281
Westbrook, C. K.; Pitz, W. J. A Comprehensive Chemical Kinetic Reaction Mechanism for Oxidation and Pyrolysis of Propane and Propene. Combust. Sci. Technol. 1984,37, 117. Yarlagadda, P. S.; Morton, L. A.; Hunter, N. R.; Gesser, H. D. Direct Conversion of Methane to Methanol in a Flow Reactor. Ind. Eng.
Chem. Res. 1988,27, 252.
Received for review March 30, 1992 Revised manuscript received July 10, 1992 Accepted July 21, 1992
Cation-Exchange Resin (Amberlyst-15) Catalyzed Alkylation of Phenol with Unhydrogenated PA0 Decene Trimer. Rearrangement of tert -Alkylphenols to sec -Alkylphenols C u r t B. Campbell* and Anatoli Onopchenko Chevron Research and Technology Company, Richmond, California 94802
Alkylation of phenol with decene trimer, representative of poly-a-olefin (PAO) oligomers in general, catalyzed by Amberlyst-15, affords mostly 0-and p-tert-alkylphenols a t temperatures below 75 O C , but 0- and p-sec-alkylphenols above 100 O C , where tert-alkyl groups show great propensity to rearrange t o the more stable sec-alkyl groups. Introduction Synthetic hydrocarbon lubricants, such as hydrogenated PAOs, have been available in limited quantities in the past due to their moderate cost and the limited availability of noncommitted 1-decene. In recent years this has changed with the expansion of a-olefin plants giving rise to increased amounts of 1-decene. Thus the PA0 precursors-unhydrogenated dimers, trimers, and tetramers of decene-are now considered viable chemical feedstocks. Unfortunately, only limited information is available about products derived from PA0 precursors. Brennan (1980), for example, alkylated benzene with decene dimer and trimer olefins, while Buckley (1990) alkylated phenol with a mixture of CI4dimer, trimer, and tetramer olefins to give liquid alkylphenols which he then used in a subsequent step to prepare fuel additives. Horodysky and Gemmill (1988) prepared Mannich bases from decene dimer/trimer phenols for use as oil additives. Abramo et al. (1990) used decene trimer/tetramer phenols for the synthesis of Mannich bases to control deposits in gasoline engines. Finally, Farng et al. (1991) prepared phosphorodithioate derivatives of P A 0 oligomers for use as lubricant additives. Most of these references cited are patents which do not provide experimental details or any structural information. Structural information on alkylphenols is extremely valuable for elucidating structure/ property/performance relationship of lubricating oil additives. Alkylphenols based on propylene or isobutylene oligomers give a high proportion of the preferred para isomers (>90%)for the manufacture of metallic detergents (Liston, 1988). In some applications, all alkylphenol isomers perform satisfactorily (Anderson et al., 1971),but in others, ortho isomers are clearly preferred (Rosenwald et al., 1950). From the literature, it is apparent that the use of PA0 oligomers for the alkylation of phenol affords liquid products which have improved solubility and compatibility characteristics, especially in synthetic base oils where additives have poor solubility (Chen, 1989).
Results and Discussion As a starting point, decene oligomers from a commercial P A 0 plant were distilled into dimer (98% Czo),trimer (95% CW,5 % CN),and tetramer (14% CW,64%, CN, 22% C,) fractions, and their carbon numbers were determined by supercritical fluid chromatography (SFC). The use of bromine numbers (D1159) to determine the olefin content 0888-5885/92/2631-2278$03.00/0
of oligomers was totally ineffective, yet this method, because of its simplicity, is used routinely to measure the residual unsaturation (ppm) of many PAO-derived fluids (Galli et al., 1982). Catalytic hydrogenation (PhMe or i-PrOH, 5 % Pt/C, 50 "C,3 atm H2, 24 h) is tedious but more reliable than the D1159 procedure for determining the degree of unsaturation. The dimer olefin from the commercial process contained 16-35 % paraffins; the amount depends on whether or not it is recycled, the number of recycles, mixing efficiency in the storage tank, etc. For comparison, the dimer fraction from the PA0 pilot plant, where no recycling was used, contained 2% paraffins (Cupples et al., 1981). The hydrogenation results for the dimer were confirmed by HPLC, which also indicated the absence of any aromatics. The HPLC, however, would not separate small amounts of paraffins present in the trimer and tetramer fractions. The 'H NMR spectrum of the decene trimer (olefin region) is given in Figure 1. The trimer was highly branched: 83% trisubstituted olefins, 6 4.95-5.25; 11% vinylidine olefins, 6 4.6-4.95; and 6% linear internal olefins, 6 5.25-5.4 (Kalabin et al., 1986; Oswald et al., 1990). The NMR spectra of the dimer and tetramer oligomers were similar to that of the trimer, except that the dimer had a higher amount of the internal linear olefins (20%). No a-olefin structures were present in any of the oligomer fractions (-CH=, 6 5.75 (Kalabin et ai., 1986)). The composition of unhydrogenated PA0 oligomers is too complex for a more detailed analysis. Attempts to reduce the number of isomers by analyzing the saturated decene oligomers by I3C NMR had only limited success (Driscoll and Linkletter, 1985). Tsvetkov at al. (1985) carried out the oligomerization of 1-decene (neat) in the presence of AlC13, A1C13-water complex with toluene, AlEtCl,, or aluminosilicate and analyzed their product by mass spectrometry. Ignoring the aluminosilicate results which used an undefined catalyst, the producta contained 76-78% olefins (dimers to heptamers), 3-7% paraffins, 6-11 % cycloolefins, 1-2% cyclodienes, and 3 4 % alkylaromatics. The amount of cyclic products formed-cycloolefins, cyclodienes, and aromatics-increased with the following order of A1 catalyst: ALEtCl, < AlC13-water complex with toluene = AlC13 < aluminosilicate. As was mentioned earlier,we found only small amounts of paraffins in the decene oligomers from the pilot plant and have no evidence for the cyclic producta (BF3/n-C4H90Hcatalyst, no recycle). Similar conclusions 0 1992 American Chemical Society
Ind. Eng. Chem. Res., Vol. 31, NO. 10, 1992 2279
Para
Ortho
f -CH =CH
I
5.4
-
I
I
5.0
I
I
4.6
PPm
Figure 1. 'H NMR spectrum (olefin region) of PA0 decene trimer (C30Hm)
-
were made by Galli et al. (1982). It appears that the BF, system, operating at 25 "C and 3.4 atm (Cupples et al., 1981), is milder than the Friedel-Crafts catalysis used by Tsvetkov et al. (1985) at 100-120 "C. Since the major part of PA0 olefins consist of branched structures (hC=CH, and &C=CHR), which are capable of forming tert-alkyl carbonium ions (Karavaev et al., 1967; Schriesheim, 1964),it was anticipated that the alkylation of phenol with PA0 olefins would lead predominantly to the formation of p-tert-alkylphenols, in the same manner as previously reported for isobutylene and propylene oligomers (Rajadhyaksha and Chaudhari, 1988; Patwardhan and Sharma, 1990). Alkylations of phenol with PA0 decene trimer were carried out under conventional batch conditions with Amberlyst-15 catalyst (6 w t %, pheno1:PAO molar ratio = 3:l) at 75-140 "C (Sukhoverkhov et al., 1986). Since PA0 trimer olefins are hindered, long reaction times (48-52 h) were needed to obtain high conversions (95%). The 140 "C products were worked up by filtering and stripping at 140 "C (0.5 mmHg), while the lower temperature products were filtered, washed with aqueous 2propanol (75/25 v/v), and stripped at 65 "C (0.5 mmHg). If higher temperatures were used during the workup, the infrared spectra of products were indistinguishable from those obtained for the 140 "C products. This may be attributed to a thermal or acid-catalyzed rearrangement caused by traces of acids in the sample. The infrared analysis (Shrewsbury, 1960) showed the presence of significant amounts of ortho isomers in all runs: ortho:para 53:47 (140 "C), 4456 (100 "C), and 38:62 (75 "C). These results are contrary to the report that ortho substitution can be controlled by the use of more severe reaction conditions since ortho isomers were expected to
10.4
10.2
10.0
PPm
Figure 2. 'H NMR spectrum of C30alkylphenol in HMPA (dOH region).
isomerize to their para form (Rosenwald, 1978). In this respect, isobutylene and isoamylene, which form tertiary carbocations, give a high ratio of ortho:para alkylated product initially, but with an increase in temperature, the ratio drops substantially due to isomerization of the alkylated product to the para alkylated form (Chaudhuri and Sharma, 1991). Our data with PA0 oligomers do not support the above conclusion of Rosenwald (1978). The IR results for the 140 "C product were confirmed by lH NMR (HMPA), which gave two hydroxyl absorptions at bOH 10.25 (ortho) and 10.17 (para), respectively (Figure 2) (52:48 (Campbell et al., 1992)). The 'H NMR spectra of the benzylic region gave peaks for the sec-alkyl groups in the ortho, 6 2.72-3.12, and para, 6 2.25-2.68, regions, in a 67:33 ratio (Campbell et al., 1990). Assuming 6% dialkylation (SFC) to be negligible, the NMR integration showed the product to contain 52% o-sec-alkylphenols, 32% p-sec-alkylphenols, and 16% p-tert-alkylphenols (by difference). Surprisingly, alkylation of phenol at 100 "C (0rtho:para 4456) gave a product in which the ortho isomers had all rearranged to the o-sec-alkylphenols, and even at 75 "C (0rtho:para 38:62), analysis showed a 20% rearrangement of the tert-alkylphenols to o-sec-alkylphenols (perhaps due to prolonged reaction-48 h).
2280 Ind. Eng. Chem. Res., Vol. 31, No. 10, 1992
peratures. Furthermore, since sec-alkyl carbonium ions have less steric restrictions and are more reactive than tert-alkyl carbonium ions, they react with phenol to give both ortho and para isomers.
Scheme I ?-H
L
OrthoPara Mixture
Isomerization - H+
+ H+
\
O-H
Q H
w
+
+ H+
OrthoPara Mixture
g
Internal Olefins
Finally, with the homogeneous BF,*EhO (2%) catalyst at 75 "C, only tert-alkylphenols were formed in 6 h (ortho:para 3070), with no apparent rearrangement to secalkylphenols (82% conversion, no benzylic H's). As the phenol to PA0 molar ratio decreased from 3:l to 1:1, dialkylation increased from 6 to 25%. It was mentioned earlier that stripping at higher temperature promoted rearrangement of the PAO-derived alkylphenols. It follows that if these alkylphenols are to be used as intermediates in the synthesis of other additives, the reactions should be carried out under mild conditions to preserve the structural integrity of the PAO-derived phenols. The fact that identical stripping conditions have not been previously observed to degrade the para isomer content in alkylphenols prepared from 2-methyl-l-undecene indicates that the propensity for rearrangement of tert-alkyl-substituted phenols is greatly influenced by the nature of the alkyl groups on the benzylic position; i.e., it appears that tert-alkyl groups with long chains attached to the benzylic carbon are more prone to rearrangement than alkylphenols with short alkyl chains such as methyl groups. O-H
O-H
CH,-C-CH,
R,-C-R,
I
I
n-CeH19
R3
R1 Rz, R3 = C2H&1&1 I
R,
+ R, + R,
= c,
The simplest rearrangement mechanism is thought to involve dealkylation of the initially formed tertiary-substituted alkylphenol to form a tert-alkyl carbonium ion and phenol. The tert-alkyl carbonium ion isomerizes to an equilibrium mixture of olefins, which includes at least some internal olefins (see Scheme I). When an internal olefin alkylates phenol, an akylphenol is formed in which the alkyl groups is attached to the phenol through a secondary carbon atom. Secondary substituted alkylphenols are more thermally stable than the tertiary and show much less tendency to dealkylate relative to tertiary-substituted phenols at nominal tem-
Experimental Section Infrared spectra were recorded on a Nicolet 510 FT-IR spectrometer. Nuclear magnetic resonance (NMR) spectra were recorded as solutions in CDC1, on a Nicolet (300 MHz) or Varian Gemini (300 MHz) spectrometers. The chemical shifts are in 6 units (ppm) relative to Me4Si. Supercritical fluid chromatography (SFC) analyses were carried out using a Lee Scientificchromatograph, equipped with a 10-m X 1 0 0 - q i.d. SB-50 column, and frit restrictor at 100 "C;FID 325 "C; C02density ramp 0.20-0.75 g/mL. General Alkylation Procedure. A 200-mL, threenecked, round-bottomed flask, fitted with a Dean-Stark trap, a mechanical stirrer, a condenser connected to a dry nitrogen source, and a thermometer, was charged with phenol (34.0 g, 360 mmol), PA0 decene trimer (50.0 g, 120 mmol), and Amberlyst-15 (3.0 g) catalyst. The reaction mixture was heated at 75 "C, following the course of reaction by SFC. After 48 h and 79% olefin conversion, the mixture was filtered, washed with aqueous 2-propanol (75/25 v/v) four times, and stripped (65 "C, 0.5 mmHg) for 7 h to give a pale amber (52 g) product. IR (0rtho:para (762 cm-'/841 cm-') 3862); NMR (CDClJ (PhCH region) 6 2.7-3.1, ortho, 6 2.2-2.6, para. Integration showed, based on benzylic and aromatic regions, less than 20% sec-alkylphenols. About 80% of product still contained tertalkylphenol structure. Acknowledgment Appreciation is extended to C. Y. Chan for excellent technical assistance. Registry No. PhOH, 108-95-2; decene trimer, 72557-78-9; Amberlyst-15, 9037-24-5.
Literature Cited Abramo, G. P.; Trewell, J. C. Mannich Base Deposit Control Additives and Fuel Cornpositions Containing Same. European Patent Publication No. 0 376 563, 1990. Anderson, R. G.; Sharman, S. H. The Thermal Alkylation of Phenol with Olefins. J. Am. Oil Chem. SOC.1971,423,107-112. Brennan, J. A. Wide-Temperature Range Synthetic Hydrocarbon Fluids. Znd. Eng. Chem. Prod. Res. Dev. 1980,19, 2-6. Buckley, T. F. Substantially Straight Chain Alkylphenyl Poly(oxypropylene) Aminocarbamates and Fuel Compositions and Lubricating Oil Compositions Therewith. US.Patent Application Serial No. 581,345, 1990. Campbell, C. B.; Onopchenko, A.; Young, D. C. Amberlyst-15-Catalyzed Alkylation of Phenols with Branched Alkenes. Rearrangement of tert-Alkylphenols and Catechols to sec-Alkyl Isomers. Ind. Eng. Chem. Res. 1990,29,642-647. Campbell, C. B.; Lozier, R. W.; Onopchenko, A. A Study of Alkylphenol Mixtures by 'H NMR. A Reinvestigation. Anal. Chem. 1992, 64, 1502-1504. Chaudhuri, B.; Sharma, M. M. Alkylation of Phenol with a-Methylstyrene, Propylene, Butenes, Isoamylene, l-Octene, and Diisobutylene: Heterogeneous va Homogeneous Catalysts. Znd. Eng. Chem. Res. 1991,30,227-231. Chen, C. S.H. Synthetic Lubricants Containing Polar Groups. European Patent Publication No. WO89/ 12663, 1989. Cupples, B. L.; Kresge, A. N.; Onopchenko, A.; Pellegrini, J. P. Synthesis of Synthetic Hydrocarbons via Alpha Olefins. Report 1981, AFWAL-TR-81-4109. Driscoll, G. L.; Linkletter, S. J. G. Synthesis of Synthetic Hydrocarbons via Alpha Olefins. Report 1985, AFWAL-TR-85.4066. Farng, L. 0.;Horodysky, A. G.; Law, D. A. Phosphorodithioate Derivatives of Oligomers of PAO's of High VI for Use aa Lubricants or Additives. US. Patent 5,057,235, 1991. Galli, R. D.; Cupples, B. L.; Rutherford, R. E. A New Synthetic Food Grade White Oil. Lubr. Eng. 1 9 8 2 , s (6), 365-372.
I n d . Eng. Chem. Res. 1992,31, 2281-2286 Horodysky, A. G.; Gemmill, R. M. Mannich Base Oil Additives. U.S. Patent 4,187,996,1988. Kalabin, G. A.; Polonov, V. M.; Smirnov, M. B.; Kyshnarev, D. F.; Afonina, J. V.; Smirnov, B. A. Quantitative FT-NMR Spectroscopy in Petroleum Chemistry. Neftekhimya 1986,26(4),435-463. Karavaev, N. M.; Dmitriev, S. A.; Zimina, K. I.; Kazakov, E. I.; Korenev, K. D.; Kotova, G. G.; Tsvetkov, 0. N. Ortho Effect in the Alkylation of Phenol. Dokl. Akad. Nauk SSSR 1967,173(4), 832-833. Liston, T. V. Methods for Preparing Group I1 Metal Overbased Sulfurized Alkylphenols. U S . Patent 4,744,921,1988. Oswald, A. A.; Bhatia, R. N.; Mozeleski, E. J.; Brownawell, D. W.; Ashcraft, T. L. Alkylphenols and Derivatives thereof via Phenol Alkylation by Cracked Petroleum Distillates. U.S. Patent 4,914,246,1990. Patwardhan, A. A.; Sharma, M. M. Alkylation of Phenol with 1Dodecene and Diisobutylene in the Presence of a Cation Exchange as the Catalyst. Znd. Eng. Chem. Res. 1990,29,29-34. Rajadhyaksha, K. A.; Chaudhari, D. D. Alkylation of Phenol by C9 and C12Olefins. Bull. Chem. SOC.Jpn. 1988,61,1379-1381.
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Rosenwald, R. H. Alkylation of Phenols. In Kirk-Othmer Encyclopedia of Chemical Technology; Grayson, M., Ed.; Wiley: New York, 1978; Vol. 2. Rosenwald, R. H.; Hoatson, J. R.; Chenicek, J. A. Alkylphenols as Antioxidants. Znd. Eng. Chem. 1950,42,161-165. Schrewsbury, D. D. The Infra-Red Spectra of Alkyl Phenols. Spectrochim. Acta 1960,16,1294-1311. Schriesheim, A. Alkylation of Aromatics with Alcohols and Ethers. In Friedel-Crafts and Related Reactions; Olah, G. A., Ed.; Interscience: New York, 1964; Vol. 2. Sukhoverkhov, V. D.; Grechko, A. N.; Kravtsov, M. A.; Agakishieva, M. Ya. Preparation of Alkylaalicylate Additives from Propylene Oligomers. Khim. Tekhnol. (Kiev) 1986 (6),63-64. Tsvetkov, 0.N.;Muchinskii, Ya. D.; Toporitshsheva, R. I. MassSpectrometric Study of the Products of Oligomerization of 1Decene. Neftekhimiya 1985,25(6),786-790. Received for review March 9,1992 Revised manuscript received June 8,1992 Accepted July 7, 1992
Study of Coke Formation in Resid Catalytic Cracking Teh C . Ho Corporate Research Laboratories, Exxon Research and Engineering Co., Annandale, New Jersey 08801
This study is to shed some light on coke formation in resid catalytic cracking. The behaviors of thermal and catalytic cracking of resid components (asphaltenes and maltenes) and vacuum gas oil are compared and contrasted. Catalysts used include amorphous SiOz/Alz03,pure zeolite, and current commercial catalysts. The experiments, carried out in a fixed-bed reactor, were designed in such a way that the buildup of different kinds of coke could be followed. It is proposed that, from a kinetic standpoint, cokes be classified based on the time scales on which they are formed. Introduction There seems to be a general consensus that resid catalytic cracking (RCC) is certain to become more important in years to come, for at least two reasons: First, the supply of high-quality feeds is dwindling at an increasing pace. Second, catalytic crackers in today’s economic climate must be capable of responding to ever-changing feedstock cost and availability as well as to ever-changing market demands. The technical problems encountered in resid cracking have been reviewed by Maselli and Peters (1985), Otterstedt et al. (1986), and Stokes and Mott (1989). A major issue is that RCC produces far more coke than that required by existing catalytic crackers for heat integration. Due to the complexity of resids and the difficulty of executing experiments with tight material balances, fundamental understanding of RCC has lagged far behind that of vacuum gas oil (VGO) cracking. To date, most of the relatively few published studies have been aimed at gaining a better understanding of the effects of incremental resid addition on VGO cracking. Data of fundamental nature are scarce. In this study some controlled cracking experiments with “extreme”feeds over “extreme”catalysts were carried out. The objective was to shed some additional light on the evolution of coke buildup in catalytic cracking of vacuum resids. It is proposed that, from a kinetic standpoint, cokes be classified according to the time scales on which they are formed. The paper’s layout consists of a description of the experimental procedures, followed by data analysis and lastly a qualitative picture of the sequence of events leading to the buildup of different types of coke. Experimental Section Reactor and Procedures. The cracking experiments were carried out in a downflow MAT (microactivity test)
unit designed for handling heavy feeds. The unit consists of a fixed-bed reactor made of quartz, a syringe pump, a hot box, a chilled liquid product collector, a liquid (brine solution) displacement column, and a wet test meter. The desired liquid feed rate was checked by pumping the feed to a calibrated receiver. Catalyst charge was anywhere between 2 and 10 g. In most runs, the amount of oil injected at time zero was 3.6 g. The duration of a typical cracking experiment, the cracking time, was 40 s. The cracking time t is related to the catalyst-to-oil ratio (C/O) and weight hourly space velocity (WHSV, based on feed) by the expression t = (36OO/WHSV)/(C/O). The liquid products were characterized by high-temperature gas chromatograph distillation (GCD) (manufactured by Carlo Erba) and occasionally by thermogravimetric analysis (TGA) as needed. Gas compositions were analyzed by GC. The amounts of carbon (weight percent) on catalysts were measured by combustion. The stripping conditions used were much more severe than those used in typical pilot plant or commercial units. Therefore the coke formed from hydrocarbons trapped in pores and/or loosely adsorbed on catalyst surfaces was neglected. Since coke formation in RCC is much more complex than in VGO cracking, in the present study the conversion to
