Aromatics alkylation process

Long chain alkyl substituted aromatic compounds, particularly alkylated naphthalenes, are produced by the alkylation of aromatics, e.g. naphthalene, with an olefin or other alkylating agent possessing at least 6 carbon atoms, usually 12 to 20 carbon atoms, in the presence of a zeolite alkylation catalyst, preferably a large pore size zeolite such as zeolite Y and in the presence of from about 0.5 to 3.0 weight percent water, preferably 1.0 to 3.0 weight percent. The use of the water co-feed increases the selectivity of the alkylation for the production of long chain mono-alkyl substituted naphthalenes in preference to more highly substituted products and also increases activity and catalyst stability.

CROSS-REFERENCE TO RELATED APPLICATIONS 
U.S. application Ser. No. 07/505,392, now U.S. Pat. No. 5,034,563 filed 
Apr. 6, 1990, relates to the production of alkylated naphthalenes with 
improved selectivity for the mono-alkylated product. 
FIELD OF THE INVENTION 
This invention relates to the production of alkylated aromatics, especially 
of alkylated naphthalenes and substituted naphthalenes. 
BACKGROUND OF THE INVENTION 
Alkylaromatic fluids have been proposed for use as certain types of 
functional fluids where good thermal and oxidative stability are required. 
For example, U.S. Pat. No. 4,714,794 (Yoshida) describes the monoalkylated 
naphthalenes as having excellent thermal and oxidative stability, low 
vapor pressure and flash point, good fluidity and high heat transfer 
capacity and other properties which render them suitable for use as 
thermal medium oils. The use of a mixture of monoalkylated and 
polyalkylated naphthalenes as a base for synthetic functional fluids is 
described in U.S. Pat. No. 4,604,491 (Dressler) and Pellegrini U.S. 
4,211,665 and 4,238,343 describe the use of alkylaromatics as transformer 
oils. 
The alkylated naphthalenes are usually produced by the alkylation of 
naphthalene or a substituted naphthalene in the presence of an acidic 
alkylation catalyst such as a Friedel-Krafts catalyst, for example, an 
acidic clay as described in Yoshida U.S. Pat. No. 4,714,794 or Dressler 
U.S. Pat. No. 4,604,491 or a Lewis acid such as aluminum trichloride as 
described in Pellegrini U.S. Pat. No. 4,211,665 and U.S. Pat. No. 
4,238,343. The use of a catalyst described as a collapsed silica-alumina 
zeolite as the catalyst for the alkylation of aromatics such as 
naphthalene is disclosed in Boucher U.S. Pat. No. 4,570,027. The use of 
various zeolites including intermediate pore size zeolites such as ZSM-5 
and large pore size zeolites such as zeolite L and ZSM-4 for the 
alkylation of various monocyclic aromatics such as benzene is disclosed in 
Young U.S. Pat. No. 4,301,316. 
In the formulation of functional fluids based on the alkyl naphthalenes, it 
has been found that the preferred alkyl naphthalenes are the 
mono-substituted naphthalene since they provide the best combination of 
properties in the finished product: because the mono-alkylated 
naphthalenes posses fewer benzylic hydrogens than the corresponding 
di-substituted or polysubstituted versions, they have better oxidative 
stability and therefore form better functional fluids and additives. In 
addition, the mono-substituted naphthalenes have a kinematic viscosity in 
the desirable range of about 5-8 cSt (at 100.degree. C.) when working with 
alkyl substituents of about 14 to 18 carbon atoms chain length. Although 
the mono-alkylated naphthalenes may be obtained in admixture with more 
highly alkylated naphthalenes using conventional Friedel-Krafts catalysts 
such as those mentioned above or by the use of zeolites such as USY, the 
selectivity to the desired mono-alkylated naphthalenes is not obtained. 
Zeolite catalysts have been found to be effective for the production of 
mono-alkylated naphthalenes, as disclosed in U.S. Pat. No. 4,301,316 and, 
more recently, U.S. Pat. No. 4,962,256. Good selectivity for the preferred 
mono-substituted naphthalenes may be obtained by the incorporation of 
cations having a radius of at least 2.5 A in large pore size zeolites such 
as zeolite Y, as described in Ser. No. 07/505,392 now U.S. Pat. No. 
5,034,563. 
SUMMARY OF THE INVENTION 
It has now been found that co-feeding of water during zeolite-catalyzed 
aromatic alkylation is very effective in controlling the product 
selectivity, i.e. the degree of alkyl substitution on the aromatic ring. 
When the alkylation reaction is carried out in the presence of zeolite 
catalysts as USY and MCM-22, the addition of water to the feed provides 
improved alkylation activity and selectivity for the production of the 
preferred mono-alkylated naphthalene synthetic lube base stocks and 
additives. 
According to the present invention there is therefore provided a process 
for controlling the product selectivity of an aromatics alkylation process 
by co-feeding water during the reaction. The presence of water during the 
reaction not only alters the product selectivity toward mono-alkylated 
aromatic production but also enhances catalyst activity and stability by 
suppressing undesirable side reactions such as olefin oligomerization and 
coke formation. The option of water co-feeding to control product 
selectivity and viscosity provides greater process flexibility for the 
production of multiple-viscosity grade alkylaromatic lubes.

DETAILED DESCRIPTION 
The starting materials for the production of the alkylaromatic products 
include various aromatic compounds such as the low and high molecular 
weight alkylbenzenes, including low molecular weight alkylbenzenes such as 
toluene and the isomeric xylenes and mixtures of such materials. Higher 
molecular weight alkylbenzenes typically with a molecular weight of from 
about 300 to 3,000, may be alkylated in this way as well as other 
aromatics including anthracene, phenanthrene and aromatics with other 
fused ring systems. The process is, however, of primary applicability with 
the production of alkylated naphthalenes since these products have been 
found to provide lubricant materials of very good stability which may be 
blended with other lubricant components such as the poly-alphaolefins. For 
convenience and brevity, the process is described below primarily with 
reference to the production of alkylated naphthalenes but it may also be 
used in a similar manner for the production of other alkylated aromatics. 
The starting materials for the production of alkylated naphthalenes include 
naphthalene itself as well the substituted naphthalenes which may contain 
one or more short chain alkyl groups containing up to about eight carbon 
atoms, such as methyl, ethyl or propyl. Suitable alkyl-substituted 
naphthalenes include alpha-methylnaphthalene, dimethylnaphthalene and 
ethylnaphthalene. Naphthalene itself is preferred since the resulting 
mono-alkylated products have better thermal and oxidative stability than 
the more highly alkylated materials for the reasons set out above. 
The alkylating agents which are used to alkylate the naphthalene include 
any aliphatic or aromatic organic compound having one or more available 
alkylating aliphatic groups capable of alkylating the naphthalene The 
alkylatable group itself should have at least about 6 carbon atoms, 
preferably at least about 8, and still more preferably at least about 12 
carbon atoms. For the production of functional fluids and additives, the 
alkyl groups on the alkyl-naphthalene preferably have from about 12 to 30 
usually 12 to 20, carbon atoms, with particular preference to about 14 to 
18 carbon atoms. A preferred class of alkylating agents are the olefins 
with the requisite number of carbon atoms, for example, the hexenes, 
heptenes, octenes, nonenes, decenes, undecenes, dodecenes. Mixtures of the 
olefins, e.g. mixtures of C.sub.12l -C.sub.20 or C.sub.14 -C.sub.18 
olefins, are useful. Branched alkylating agents, especially oligomerized 
olefins such as the trimers, tetramers, pentamers, etc., of light olefins 
such as ethylene, propylene, the butylenes, etc., are also useful. Other 
useful alkylating agents which may be used, although less easily, include 
alcohols (inclusive of monoalcohols, dialcohols, trialcohols, etc.) such 
as hexanols, heptanols, octanols, nonanols, decanols, undecanols and 
dodecanols; and alkyl halides such as hexyl chlorides, octyl chlorides, 
dodecyl chlorides; and higher homologs. 
The alkylation reaction between the naphthalene and the alkylating agent is 
carried out in the presence of a zeolite catalyst which contains a cation 
of certain specified radius. The molecular size of the alkylation products 
will require a relatively large pore size in the zeolite in order for the 
products to leave the zeolite, indicating the need for a relatively large 
pore size in the zeolite, which will also tent to reduce diffusion 
limitations with the long chain alkylating agents. The large pore size 
zeolites are the most useful zeolite catalysts for this purpose although 
the less highly constrained intermediate pore size zeolites may also be 
used, as discussed below. The large pore size zeolites are zeolites such 
as faujasite, the synthetic faujasites (zeolites X and Y), zeolite L, 
ZSM-4, ZSM-18, ZSM-20, mordenite and offretite which are generally useful 
for this purpose are characterized by the presence of a 12-membered oxygen 
ring system in the molecular structure and by the existence of pores with 
a minimum dimension of at least 7.4 .ANG., as described by Frilette et. 
al., in J. Catalysis 67,218-222 (1981). See also Chen et. al., 
Shape-selective Catalysis in Industrial Applications, (Chemical 
industries; Vol. 36) Marcel Dekker Inc., New York 1989, ISBN 0-8247-7856-1 
and Hoelderich et. al., Agnew. Chem. Int. Ed. Engl. 27 226-246 (1988), 
especially pp.226-229. The large pore size zeolites may also be 
characterized by a "Constraint Index" of not more than 2, in most cases 
not more than 1. Zeolite beta, a zeolite having a structure characterized 
by twelve-membered pore openings, is included in this class of zeolites 
although under certain circumstances it has a Constraint Index approaching 
the upper limit of 2 which is usually characteristic of this class of 
zeolites. The method for determining Constraint Index is described in U. 
S. Pat. No. 4,016,218, together with values for typical zeolites and of 
the significance of the Index in U.S. Pat. No.4,861,932, to which 
reference is made for a description of the test procedure and its 
interpretation. 
Zeolites whose structure is that of a ten membered oxygen ring, generally 
regarded as the intermediate pore size zeolites may also be effective 
catalysts for this alkylation reaction if their structure is not too 
highly constrained. Thus, zeolites such as ZSM-12 (Constraint Index 2) may 
be effective catalysts for this reaction. The zeolite identified as MCM-22 
is a particularly useful catalyst for this reaction because it gives a 
highly linear product with attachment to the alkyl chain at the 
2-position. MCM-22 is described in U.S. Pat. No. 4,954,325, to which 
reference is made for a description of this zeolite. Thus, zeolites having 
a Constraint Index up to about 3 will generally be found to be useful 
catalysts, although the activity may be found to be dependent on the 
choice of alkylating agent, especially its chain length, a factor which 
imposes diffusion limitations upon the choice of zeolite. 
The selectivity of the zeolite for the production of the preferred 
mono-alkylated alkylnaphthalene products is improved by the incorporation 
into the zeolite of cations of a certain minimum radius, at least 2.5 
.ANG., as described in U.S. Ser. No. 07/505,392, to which reference is 
made for a description of the manner in which this improvement in 
selectivity can be made. The selected cations have a radius of least 2.5 
.ANG., and preferably at least 3 0 .ANG.. A number of cations conform to 
this requirement, including the hydrated cations of a number of metals, 
including monovalent, divalent and polyvalent, transitional and 
non-transitional metals. Even though the non-hydrated cations may not 
themselves conform to the ionic size requirement, the hydrated forms of 
the cations may do so. In particular, the relatively small radius cations 
of the alkali metals such as sodium and lithium (ionic radii of 0.95 and 
0.60 .ANG., respectively) do not conform to the requirement, but the 
hydrated forms of these cations readily meet the requirement (radii of 
3.58 and 3.82 .ANG.). Cations of the required radius may also be provided 
by various organic species, especially the organic nitrogenous bases. A 
preferred class of cations of this type are the substituted ammonium 
cations, for example, alkylammonium cations, especially the short chain 
alkylammonium cations e.g. tetramethylammonium (TMA), tetraethylammonium 
(TEA) or tetrapropylammonium (TPA). The hydrated ammonium cation is also a 
suitable cationic form of the zeolite and is often preferred for zeolite Y 
or USY since these zeolites may be commercially available in the ammonium 
form as a precursor of the decationised or hydrogen form of the zeolite. 
The hydrated protonic form of the zeolite i.e. where the cation is the 
hydronium ion H.sub.3 O, is also effective as a catalyst. 
The preferred zeolites for use in the present process are treated in this 
way to effect further improvements in the selectivity to the desired 
products. 
A highly useful zeolite for the production of the mono-alkylated 
naphthalenes is zeolite Y in the ultrastable form, usually referred to as 
USY. When this material contains hydrated cations of the preferred minimum 
size, it catalyses the alkylation in good yields with excellent 
selectivity, as described in Ser. No. 07/505,392. 
The zeolite may be composited with a matrix material or binder which is 
resistant to the temperatures and other conditions employed in the 
alkylation process. Such materials include active and inactive materials 
and synthetic or naturally occurring zeolites as well as inorganic 
materials such as clays, silica and/or metal oxides such as alumina, 
silica or silica-alumina. The latter may be either naturally occurring or 
in the form of gelatinous precipitates or gels including mixtures of 
silica and metal oxides. Use of an active material in conjunction with the 
zeolite may change the conversion and/or selectivity of the catalyst. 
Inactive materials suitably serve as diluents to control the amount of 
conversion so that alkylation products can be obtained economically and 
orderly without employing other means for controlling the rate of 
reaction. Binders which may be incorporated to improve the crush strength 
and other physically properties of the catalyst under commercial 
alkylation operating conditions include naturally occurring clays, e.g., 
bentonite and kaolin as well as the oxides referred to above. 
The relative proportions of zeolite, present in finely divided crystalline 
form oxide matrix may vary widely, with the crystalline zeolite content 
ranging from about 1 to about 90 percent by weight and more usually, 
particularly when the composite is prepared in the form of beads, in the 
range of about 2 to about 80 weight percent of the composite. 
The stability of the alkylation catalyst of the invention may be increased 
by steaming, as described in Ser. No. 07/505,932. 
The alkylation is conducted such that the organic reactants, i.e., the 
alkylatable aromatic compound and the alkylating agent, are brought into 
contact with the zeolite catalyst in a suitable reaction zone such as, for 
example, in a batch type reactor or flow reactor containing a fixed bed of 
the catalyst composition, under effective alkylation conditions. Such 
conditions typically include a temperature of from 100.degree. to 
400.degree. C., usually from 100.degree. to 300.degree. C., a pressure of 
from about 0.2 to 25, preferably 1 to 5, atmospheres, a feed weight hourly 
space velocity (WHSV) of from about 0.1 hr.sup.-1 to about 10 hr.sup.-1 
aromatic compound to alkylating agent mole ratio of from about 0.1:1 to 
about 50:1, preferably from about 4:1 to about 1:4 e.g. from about 2:1 to 
about 1:2. 
In a continuous, fixed bed type operation, the temperature will normally be 
in the range 200.degree. to 600.degree. F. (about 93.degree. to 
315.degree. C.), preferably 300.degree. to 400.degree. F. (about 
150.degree. to about 205.degree. C.), with pressures in the range of 50 to 
1000 psig (about 450 to about 7,000 kPa abs). The WHSV is based upon the 
weight of the catalyst composition employed, i.e., the total weight of 
active catalyst (and binder if present) and is normally in the range of 
0.1 to 5.0, preferably 0.5 to 5.0, with most cases in the range 0.25 to 
1.50. Preferred reaction conditions include a temperature within the 
approximate range of from about 100.degree. to about 350 C., a pressure 
of from about 1 to about 25 atmospheres, a WHSV of from about 0.5 hr.sup.1 
to about 5 hr.sup.-1 and an alkylatable aromatic compound to alkylating 
agent mole ratio of from about 0.5:1 to about 5:1. 
When using naphthalene as the aromatic compound, the pressure should 
preferably be maintained at a value of at least about 50 psig in order to 
prevent the naphthalene from subliming into the overhead of the alkylation 
reactor; the required pressure may be maintained by inert gas 
pressurization, preferably with nitrogen. The reactants can be in either 
the vapor phase or the liquid phase and can be neat, i.e., free from 
intentional admixture or dilution with other material, or they can be 
brought into contact with the zeolite catalyst composition with the aid of 
carrier gases or diluents such as, for example, hydrogen or nitrogen. The 
alkylation can be carried out as a batch-type reaction typically employing 
a closed, pressurized, stirred reactor with an inert gas blanketing system 
or in a semi-continuous or continuous operation utilizing a fixed or 
moving bed catalyst system. 
The addition of water to the feed to the alkylation reaction suppresses the 
formation of poly-alkylated naphthalene product and shifts the product 
selectivity toward mono-alkylated naphthalene production. The 
mono-alkylated naphthalene selectivity typically increases from about 40 
to 75% with 1 wt % water co-feed and the addition of additional water up 
to 2 wt % may be effective to increase the naphthalene conversion, 
typically from about 70 or 75 to about 90 or 95 weight percent. The water 
also suppresses olefin oligomerization reactions as evidenced by a 
significant reduction in the formation of the dimer, typically from about 
10 to 6 weight, percent. The amount of water added to the feed is 
preferably at least about 0.1 weight percent in to produce a significant 
improvement and in most cases, at least 0.5 weight percent, based on the 
total hydrocarbon feed will be preferably employed, but will normally not 
exceed 5.0 weight percent of the feed, preferably not more than 3.0 weight 
percent of the feed, both for fixed bed, continuous and batch type 
operations. The amount of water is preferably from about 10 to 60 weight 
percent of the catalyst (including binder), and in most cases, from about 
10 to about 40 weight percent of the catalyst, especially in batch type 
processes. The maximum amount of water should, however, be determined for 
each system since excessive amounts of water co-feed will cause a decrease 
in catalyst activity. With large excesses of water, the activity of the 
catalyst may be entirely suppressed. In most cases, the optimum amount of 
water should normally be in the range of about 1-3, preferably about 1-2 
weight percent. Above these water levels, the excess water may block the 
zeolite acid sites either partly or completely, with a suppression of 
catalytic activity. 
The products comprising alkylated aromatics are characterized by 
exceptional oxidative and thermal stability. They may be separated from 
the reaction mixture by stripping off unreacted alkylating agent and 
naphthalene compound in the conventional manner. It has also been found 
that the stability of the alkylated product may be improved by filtration 
over activated charcoal and by alkali treatment to remove impurities, 
especially acidic by-products formed by oxidation during the course of the 
reaction. The alkali treatment is preferably carried out by filtration 
over a solid alkali material, preferably calcium carbonate (lime). In a 
typical product work-up, it has been found, for example, that the RBOT 
(Rotating Bomb Oxidation Test) stability can be increased from a value of 
184 minutes for an unstripped product (C.sub.14 -alkylnaphthalene) to 290 
minutes if the unreacted materials are removed by stripping and to 350 
minutes if the stripped product is filtered over lime (CaCO.sub.3). 
EXAMPLE 1 
This example demonstrates the catalytic activity of a conventional, 
calcined USY zeolite for alkylating naphthalene with a long chain alpha 
olefin to produce alkylated naphthalene lube base stocks. 
The catalyst used in this example was a USY catalyst containing about 40 
weight percent USY component with an unit cell size of 24.55 .ANG.. The 
catalyst was calcined at 1000 F for 24 hours prior to use. The alkylation 
experiment was carried out in an 1 liter autoclave using a C.sub.14 olefin 
as the alkylating agent at a 2:1 molar ratio of C.sub.14 =:naphthalene, 5 
weight percent catalyst at 400.degree. F. for 6 hours under a nitrogen 
pressure of 1 atmosphere. After decanting and filtering the catalyst, the 
total liquid product was vacuum distilled at 600.degree. F. to obtain 68 
wt % lube base stock comprising of 31%, 23% and 5 weight percent mono-, 
di- and tri-alkylated naphthalene product, respectively. The lube also 
contains about 9 weight percent of C14 dimers due to olefin 
oligomerization reaction. This corresponds to the conversion of 79 weight 
percent naphthalene and 65 weight percent alpha C14 olefin. Table 1 shows 
the product properties of this alkylated naphthalene lube base stock. 
TABLE 1 
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Product Yield, wt % 
Mono-alkylated 31 
Di-Alkylated 23 
Tri-Alkylated 5 
C14 Dimer 9 
Lube Properties 
Pour Point, .degree.F. 
-50 
KV @ 40.degree. C., cSt 
35.54 
KV @ 100.degree. C., cSt 
5.68 
Viscosity Index 97 
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This alkylated naphthalene synthetic lube base stock has excellent 
low-temperature characteristic as indicated by a very low pour point 
product (-50.degree. F.). 
EXAMPLE 2 
In this example, the alkylation reactions were carried out under identical 
process conditions as in Example 1 except that water in the range of 1-4 
weight percent based on the feed was added to the reactant mixture prior 
to the alkylation. Table 2 shows the affect of water addition on the 
performance of the USY catalyst. 
TABLE 2 
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Example No 1 2A 2B 2C 
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H2O, wt % on feed 0 1.0 2.0 4.0 
Conversion, wt % 
Naphthalene 79 96 96 0 
Alpha C14 Olefin 65 59 62 0 
Product Distribution, wt % 
Mono-Alkylated 46 75 77 0 
Di-Alkylated 34 19 16 0 
Tri-Alkylated 7 -- -- 0 
C14 Dimer 13 6 7 0 
Total Alkylated Lube, wt % 
59 64 64 0 
______________________________________ 
The results indicate that the addition of water suppresses the formation of 
poly-alkylated naphthalene product and shifts the product selectivity 
toward mono-alkylated naphthalene production. The mono-alkylated 
naphthalene selectivity increases from 46 to 75% with 1 weight percent 
water co-feeding. Furthermore, the addition of additional water up to 2 
weight percent increases the naphthalene conversion from 79 to 96 weight 
percent and suppresses the olefin oligomerization reaction as evidenced by 
a significant reduction of dimer formation (from 13 to 6-7 weight 
percent). For this particular USY catalyst the optimum water concentration 
is in the range of 1-2 weight percent. Above this water level, the excess 
water may completely block the zeolite acid sites and consequently totally 
suppresses catalyst alkylation activity as seen in Example 2C. 
EXAMPLE 3 
This example illustrates the effectiveness of water addition on the 
naphthalene alkylation performance of MCM-22 zeolite catalyst. The 
autoclave experiment was carried out in a similar as in Example 1. The 
process conditions and the alkylation performance of MCM-22 with and 
without water co-feeding as shown in Table 2/ 
TABLE 3 
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Example No. 3A 3B 3C 
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Water, wt % on feed 
0 1.5 3.0 
Temp, .degree.F. 
350 300 300 
MCM-22, wt % 0.5 1.8 1.8 
Conversion, wt % 
Naphthalene 75 79 4 
Alpha C14 Olefin 
46 45 7 
Product Dist., wt % 
Mono-Alkylated 76 87 100 
Di-Alkylated 17 8 -- 
Tri-Alkylated 3 -- -- 
C14 Dimer 4 5 -- 
______________________________________ 
The results indicate MCM-22 has very high naphthalene alkylation activity 
and very good product selectivity toward mono-alkylated naphthalene 
products (Example 3A). The presence of 1.5 weight percent water enhances 
further catalyst mono-alkylated naphthalene products (Example 3A). The 
presence of 1.5 weight percent water enhances further catalyst 
mono-alkylated selectivity from 76 to 87% (Example 3B). Similar to USY 
zeolite shown in Example 2, the excess water co-feeding (3 weight percent 
completely deactivates the catalyst activity as shown by Example 3C.