Abstract:
This invention relates to a method of making ethylbiphenyls by the reaction of biphenyl with polyethylbenzenes or with ethylene and polyethylbenzenes in the presence of a solid acid catalyst and offers advantages of industrial significance such as absence of acidic waste water, no need of costly materials for equipment, catalyst reuse, and adaptability to a fixed-bed flow reaction system suitable for large-scale production.

Description:
This application is a continuation of application Ser. No. 210,964, filed Jun. 24, 1988, now abandoned. 
    
    
     FIELD OF THE INVENTION AND RELATED ART STATEMENT 
     This invention relates to a method of making ethylbiphenyls which are useful as heat transfer fluids. 
     Ethylbiphenyls are made by the ethylation of biphenyl; for example, Japanese Patent Publication No. 15,945-1972(U.S. Pat. No. 3,636,179) discloses a method of making ethylbiphenyls by the catalytic transalkylation of biphenyl and ethylated benzenes containing ethylbenzenes, diethylbenzenes, triethylbenzenes, and tetraethylbenzenes in the presence of AlCl 3 . 
     The Friedel-Crafts reaction using AlCl 3 , however, generally possesses the following defects: 
     (1) The step for water washing and neutralization are required for the removal of AlCl 3  upon completion of the reaction, and acidic waste water is generated in large quantities; 
     (2) The reaction equipment must be made acid-resistant; 
     (3) The reaction is hard to carry out on a continuous basis; and 
     (4) The reuse of the spent AlCl 3  is difficult. The aforesaid method is no exception in this respect. 
     Another method in Japanese Kokai Document Nos. 156,222-1981 and 1,869-1972 (GB Patent No. 1,350,893) described the manufacture of ethylbiphenyls by the reaction of biphenyl with ethylene in the presence of a solid acid catalyst. It is, however, not readily applicable on an industrial scale because such solid acid catatlyst has a short life and the methods are difficult to practice in a fixed-bed flow reactor. 
     OBJECT AND SUMMARY OF THE INVENTION 
     The present inventors have conducted studies in search of remedies to the aforesaid defects, found that solid acid catalysts can be as reactive as AlCl 3  and yet free of the shortcomings of AlCl 3 , and completed this invention. 
     An object of this invention is to provide a method of making ethylbiphenyls which as effective as the Friedel-Crafts reaction using the conventional AlCl 3  catalyst, generates no acidic waste water, requires no costly materials for the reaction equipment, and uses reusable catalysts of long life. 
     Another object of this invention is to provide a method of making ethylbiphenyls which can be practiced on a continuous basis in a fixed-bed flow reactor. 
     Still another object of this invention is to provide a method of making ethylbiphenyls which prolongs the life of a solid acid catalyst to an industrially viable extent by the transethylation of biphenyl or by a combination of the ethylation and transethylation of biphenyl in the presence of such solid acid catalyst. 
     This invention thus relates to a method of making ethylbiphenyls which uses a solid acid as catalyst to the ethylation of biphenyl with polyethylbenzenes or with ethylene and polyethylbenzenes. 
     The solid acid catalysts useful for this invention include silica-alumina, zeolites such as mordenite and Y zeolite, sulfate ions on metal oxide carriers, heteropoly acids, and ion exchange resins, all generally known as exceedingly strong solid acids. Consideration of reactivity, commercial availability, and minimal production of thermally unstable byproducts favors silica-alumina and zeolites or their mixtures. The catalysts should preferably have from 0.1 mole to 3 moles of acid sites per kg, each mole of the acid sites showing heat of adsorption of ammonia of 85 kilojoules or more. Industrially sufficient conversion is difficult to obtain with acid sites of 0.1 kg or less while carbonaceous deposits form faster and the catalyst loses its activity faster with acid sites of 3 moles per kg or more. 
     The reaction temperature is set in the range of from 130° to 380° C., preferably from 150° to 350° C., and more preferbly from 200° to 320° C. Secondary reactions begin to accompany the ethylation above 380° C. while the conversion is not sufficiently high below 130° C. 
     The reaction pressure is from ambient to 30 kg/cm 2 .G, preferably from 2 to 20 kg/cm 2 .G. A pressure above 30 kg/cm 2 .G is allowable, but is not necessary. 
     The optimal reaction time or contact time varies with the reaction temperature chosen. A batch reaction should preferably run from 1 to 3 hours, and a continuous reaction should preferably run a weight hourly space velocity of from 0.5 to 3 kg/kg.hr. An unnecessarily long reaction time will cause the undesirable deethylation of the reaction products. 
     The quantity of feed polyethylbenzenes in the production of monoethylbiphenyls is chosen so that from 0.3 to 4 moles, preferably from 0.5 to 2 moles of the ethyl group or (ethyl group+ethylene) is present per each mole of (biphenyl ring+benzene ring). More biphenyl would remain unchanged if this mole ratio fell below 0.3 while less monoethylbiphenyls and more polyethylbiphenyls would form if the ratio exceeded 4. In the cases where the intended product is diethylbiphenyls or higher polyethyldiphenyls, from 1 to 4 moles, preferably from 1.5  to 3 moles of the ethyl group or (ethyl group+ethylene) should be present per each mole of (biphenyl ring+benzene ring). Moreover, when polyethylbiphenyls produced are returned to a reaction system, the ethyl groups and biphenyls thereof are taken into account as well. 
     It is desirable for the feed polyethylbenzenes to contain from 1.5 to 4 moles, preferably from 2 to 3 moles, of the ethyl group per mole of benzene ring. When a mixed feed of polyethylbenzenes and ethylene is used, it is desirable that 2 moles or less, preferably from 0.2 to 1 mole, of ethylene is present for each mole of the ethyl group in the polyethylbenzenes. A larger quantity of ethylene forms more carbonaceous deposits on the catalyst and shortens the catalyst life. 
     The method of this invention can be practiced in a flow or batch mode. A fixed-bed flow reactor is suitable for large-scale production and a batch reactor for small-scale one. In either case, the catalyst can be separated readily from the reaction products. The reaction equipment may be constructed of stainless steel equivalent to SUS 304 and requires no acid-resistant glass lining. 
     When the reaction is carried out batch-wise, the spent catalyst separated after the reaction is reused with or without regeneration in the usual manner by firing at 500° C. or so in a stream of air diluted with nitrogen. 
     On the other hand, in a continuous operation using a fixed-bed flow reactor, plural reactors are provided in parallel between the feed line and the product line; as soon as the catalyst in one of the reactors is deactivated, the process flow is switched to another reactor containing fresh catalyst, the spent catalyst is regenerated or replaced and used again when the fresh catalyst in turn loses its activity. The product line is connected to a distillation column, preferably several in series, and the products withdrawn from the reactor are continuously separated and purified into the product ethylbiphenyls. The biphenyl and polyethylbenzenes recovered unchanged and polyethylbiphenyls produced are returned to the reactors as recycle feed. 
     The method of this invention for making ethylbiphenyls with the use of solid acid catalysts differs markedly from the conventional method using the AlCl 3  catalyst and offers advantages of industrial significance in that it generates no acidic waste water, requires no costly construction material for the equipment, and permits reuse of the catalyst. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is the flowsheet for Example 7 in which ethylbiphenyls are manufactured continuously in a flow reactor embodying the method of this invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     This invention is explained with reference to the accompanying examples. 
     EXAMPLES 1˜4 
     Biphenyl (BP), polyethylbenzenes (PEB), and a silica-alumina catalyst (0.46 mole per kg of acid sites with heat of adsorption of ammonia of 8.5 kilojoules per mole or more) were introduced into a pressure reactor equipped with a stirrer and allowed to react under the conditions shown in Table 1. After completion of the reaction, the reaction mixture was filtered to separate the silica-alumina catalyst from the reaction products. The composition by weight of the compounds containing biphenyl ring in the reaction products is shown in Table 2. 
     The polyethylbenzenes used as feed were by-products in the manufacture of ethylbenzene. 
     
                                           TABLE 1__________________________________________________________________________BP         PEB  Catalyst                Et Group/                       Reaction                              Reaction                                   Reaction(Parts by  (Parts by           (Parts by                (BPR + BR)                       Temperature                              Time Pressureweight)    weight)           weight)                Mole Ratio                       (°C.)                              (h)  (kg/cm.sup.2 · G)__________________________________________________________________________Example 1 92.4 160.9           40   1.07   250    2     3Example 2 107.8      117.3           40   0.89   300    2    10Example 3 92.4 160.9           40   1.07   300    2    10Example 4 38.5 134.0           40   1.28   300    2    10__________________________________________________________________________ BP: Biphenyl PEB: Polyethylbenzene BPB: Biphenyl ring BR: Benzene ring. 
    
     
                                           TABLE 2__________________________________________________________________________BP        EBP (wt %) DiEBP                    TrEBP                        TeEBP                            9-MF                                Othersrts                                     Total(wt %)    meta        para           Subtotal                (wt %)                    (wt %)                        (wt %)                            (wt %)                                (wt %)                                     (wt %)__________________________________________________________________________Example 1 35.6     14.8        29.2           44.0 12.2                     4.1                        0.8 1.0 2.2  100Example 2 31.0     26.4        16.4           42.8 10.9                     6.4                        1.1 7.1 0.7  100Example 3 18.5     22.0        14.1           36.1 19.7                    11.9                        6.6 5.9 1.2  100Example 4 12.4     18.1        13.2           31.3 23.4                    15.5                        11.1                            4.0 2.3  100__________________________________________________________________________ EBP: Ethylbiphenyls DiEBP: Diethylbiphenyls TrEBP: Triethylbiphenyls TeEBP: Tetraethylbiphenyls 9MF: 9Methylfluorene. 
    
     COMPARATIVE EXAMPLE 1 
     The reaction was carried out as in Examples 1˜4 with the use of AlCl 3  as catalyst. The reaction conditions and the results are shown in Table 1 and 2 respectively. 
     EXAMPLE 5 
     A fixed-bed pressure flow reactor was filled with Y zeolite (acid sites, 1.19 mole per kg) and a mixture of biphenyl and diethylbenzenes at a mole ratio of 1:4 was fed at 250° C. and a liquid hourly space velocity of 1 l/l. hr. The effluents from the reactor accumulated over a period from the 24th to 32nd hour and those from 64th to 72nd hour after the start of the reaction were analyzed and the results are shown in Table 3. 
     
                                           TABLE 3__________________________________________________________________________(Example 5)Sampling Time       EBP(Hours from   BP  (wt %)         DiEBP                          TrEBP                              TeEBP                                  9-MF                                      Others                                          Totalstart)  (wt %)       ortho           meta              para                 Subtotal                      (wt %)                          (wt %)                              (wt %)                                  (wt %)                                      (wt %)                                          (wt %)__________________________________________________________________________24˜32 h   12.3       0.8 18.3              15.8                 34.9 35.7                          11.7                              1.2 3.0 1.2 10064˜72 h   12.6       0.8 18.1              17.5                 36.4 33.9                          11.4                              3.8 0.8 100__________________________________________________________________________ 
    
     EXAMPLE 6 
     Into a pressure reactor equipped with a stirrer were introduced 55 g (0.38 mole) of biphenyl (BP), 95 g (0.71 mole) of a mixture of diethylbenzene isomers (DiEB), and 45 g of the silica-alumina catalyst, the same as the one used in Example 1, and the transethylation reaction was carried out at an ethyl groups to aromatic groups mole ratio of 1.33 and at a catalyst to oil weight ratio of 0.30 by heating the mixture to 350° C. over a period of 105 minutes and maintaining the temperature at this level thereafter. Sampling was made periodically to analyze the reaction mixture. The results are shown in Table 4. 
     
                       TABLE 4______________________________________(Example 6)Reaction Time AfterTemperature Rise(min.)        0      60       120  180    240______________________________________BP Conversion (wt %)         43.3   78.0     81.5 82.0   82.3       Ratio of Monoethyl Isomers (%)o-EBP         5.79   5.76     5.55 5.58   5.37m-EBP         58.80  61.42    61.53                              61.15  61.21p-EBP         35.41  32.82    32.92                              33.27  33.42       Ratio of Diethyl Isomers (%)DiEBPrcle.    0.76   0.81     0.94 0.43   1.38DiEBPrcle.           0.19     0.35 0.31   0.80DiEBPrcle.    6.85   8.17     9.20 8.23   8.39DiEBPrcle.    5.63   6.14     5.58 5.59   5.163,5-DiEBP     14.11  13.50    12.81                              12.91  12.823,3&#39;-DiEBP    30.95  31.66    32.76                              32.70  32.303,4&#39;-DiEBP    33.23  31.81    30.63                              32.02  31.374,4&#39;-DiEBP    8.73   7.73     7.71 7.80   7.78______________________________________ 
    
     EXAMPLE 7 
     As illustrated in FIG. 1, fixed-bed pressure flow reactor 1 was filled with the silica-alumina catalyst, the same as the one used in Example 1, and the product line thereafter was connected to distillation columns 2a, 2b, 2c, and 2d in series. The feeds, biphenyl 3, ehtylene 4, and polyethylbenzene 5, were charged to reactor 1 together with recycle stream 6 which is a mixture of recycle stream 6a from the top of distillation column 2b and recycle stream 6b from the top of distillation column 2d. The reaction was carried out at 300° C. and a weight hourly space velocity of 2 kg/kg.hr. The mole ratio of (ethyl groups+ethylene) to (biphenyl rings+benzene rings) was 1.16 in reactor 1. 
     Reaction mixture 7 flowing through the reactor and emerging from the bottom thereof was charged to distillation column 2a, and top fraction 8 and bottom fraction 9 were taken out from the top and the bottom of distillation column 2a respectively. Top fraction 8 was sent to ethylbenzene plant 10 where it is a supply source of polyethylbenzene 5. 
     Bottom fraction 9 was charged to distillation column 2b and recycle stream 6a mainly containing biphenyls and diethylbenzenes was withdrawn from the top while fraction 11 was withdrawn from the bottom. 
     Bottom fraction 11 was charged to distillation column 2c where ethylbiphenyl 12 mainly consisting of ethylbiphenyls (EBP) and diethylbiphenyls (DiEBP) was withdrawn from the top and fraction 13 mainly consisting of triethylbiphenyls (TrEBP) and tetraethylbiphenyls (TeEBP) was withdrawn from the bottom. 
     Fraction 13 was then charged to distillation column 2d and recycle stream 6b was taken out from the top while residue 14 was taken out from the bottom. 
     When triethylbiphenyl is needed as product, recycle stream 6b is withdrawn from the side of distillation column 2d and the triethylbiphenyl is taken out from the top. 
     The material balance in the flowsheet of FIG. 1 is shown in Table 5. 
     
                                           TABLE 5__________________________________________________________________________(Example 7)     Sample No. (Corresponding to No. in FIG. 1)Compound  3  4 5  6  7   8  9   6a 11  12 13 6b 14__________________________________________________________________________E            38B                    118 118EB              6    268 268DiEB           507             122                126  4 122 122TrEB            39              16                 16     16  16TeEB               5  5      5   5Subtotal of Benzen          552             143                533 390                       143 143Ring CompoundsBP        817     290                294    294 290                               4   4EBP                3 573    573  3 570 5709-MF                  60     60     60  60DiEBP              11                313    313    313 302                                      11                                         11TrEBP             180                189    189    189  9 180                                        180TeEBP              83                105    105    105    105                                         83                                           22Others             5  53     53     53  45                                      8  5  3Subtotal of Biphenyl     817     572                1587   1587                           293                              1294                                  990                                     304                                        279                                           25Ring CompoundsTotal     817        38          552             715                2120                    390                       1730                           436                              1294                                  990                                     304                                        279                                           25__________________________________________________________________________