Abstract:
A process for converting anisoles to ortho-methylated phenolic products in high selectivity is disclosed. The process comprises passing methoxybenzene, o-methylmethoxybenzene, 2,6-dimethylmethoxybenzene, or mixtures thereof, over gamma-alumina in the presence of an effective amount of water at a temperature in the range of about 225° to about 295° C.

Description:
FIELD OF THE INVENTION 
     The invention is in the general field of preparing ortho-methylated phenolic products from anisoles (e.g. methoxybenzene). 
     GENERAL BACKGROUND 
     Methylated phenolic products have many uses. For example, 2,6-xylenol is useful in polymer synthesis. It is the primary monomer for producing polyphenylene oxide, which is an important engineering plastic. 
     o-Cresol is a valuable intermediate in herbicide synthesis, especially for making 2-methyl-4-chlorophenoxyacetic acid and 2-methyl-4-chlorophenoxypropionic acid. Both of these compounds are widely used as herbicides in Europe. 
     Blends of such cresylics as o-cresol and 2,6-xylenol are useful for a variety of applications, including use as disinfectants, use as solvents for the magnet wire industry, and use as metal cleaners (degreasers, paint strippers, et cetera). 
     The conversion of anisoles to methylated phenolic products over solid catalysts such as gamma-alumina is known. The vapor phase conversion of anisoles, such as methoxybenzene, o-methylmethoxybenzene, and 2,6-dimethylmethoxybenzene, in general yields a wide variety of isomeric cresols and xylenols. It would be highly desirable to have a process which provides a high selectivity of o-cresol and/or 2,6-xylenol in the product mixture. I have developed a process which provides the desired high selectivity of o-cresol and/or 2,6-xylenol in the product mixture. 
     BRIEF SUMMARY OF THE INVENTION 
     Briefly stated, the present invention is directed to a process for converting a feedstock comprising methoxybenzene, o-methylmethoxybenzene, 2,6-dimethylmethoxybenzene, or mixtures thereof, to ortho-methylated phenolic products, such as o-cresol and 2,6-xylenol, in high selectivity wherein the process comprises passing the feedstock in vapor phase over an effective amount of gamma-alumina in the presence of an effective amount of water at a temperature in the range of about 225° to 295° C. 
     DETAILED DESCRIPTION 
     The feedstock used in my process comprises methoxybenzene (anisole), o-methylmethoxybenzene, and 2,6-dimethylmethoxybenzene. The materials can be used individually or in any combination of mixtures. 
     My process uses gamma-alumina. Generally any alumina which has been calcined at about 470° to about 870° C. for at least one hour, to provide gamma-alumina, is suitable. The preferred alumina is one that has been calcined at 500° to 650° C. for about 1 to about 3 hours. 
     Suitable alumina has a surface area in the range of about 75 to about 350 m 2  /g. Preferably, the surface area is in the range of about 150 to about 200 m 2  /g. 
     The alumina can be in a variety of shapes and sizes, e.g. spheres, pellets, tablets. 
     As implied in the foregoing the feedstock and water are passed in the vapor phase over the gamma-alumina catalyst in a suitable reaction vessel (e.g. a tube or cylinder). 
     The amount of water used, based on the feedstock, as weight percent is as follows: 
     
         ______________________________________            Suitable                   Preferred______________________________________Water (based on feedstock),about              0.5-10   1-4______________________________________ 
    
     The amount of gamma-alumina catalyst used can be expressed as follows: ##EQU1## 
     On this basis the suitable and preferred amounts of catalyst are: 
     
         ______________________________________      Suitable Preferred______________________________________about        0.5-2.5 hr.sup.-1                   0.8-1.5 hr.sup.-1______________________________________ 
    
     While the process can be conducted at a temperature as high as 325° C. the selectivity of desired products is such that a temperature in this range is not considered suitable. In order to have the desired selectivity the process suitably is conducted at a temperature of about 200° to about 295° C., preferably about 240° to about 280° C. 
     Usually the process is conducted at ambient pressure. However, a pressure as high as 100 psig can be used, if desired. 
     My process provides a high selectivity of orthomethylated phenolic products (i.e. o-cresol and 2,6-xylenol) in the product mixture. One selectivity parameter is the &#34;R&#34; value wherein R is defined as follows: 
     R=2,6-xylenol/m,p-cresol ratio (weight ratio) 
     A means of expressing ortho-selectivity is the value &#34;Sel(o+26)&#34; wherein &#34;Sel(o+26)&#34; is defined as follows: 
     Sel(o+26)=combined selectivity of o-cresol+2,6-xylenol 
     Using the foregoing definition my process will usually produce an &#34;R&#34; value of at least 18 and a &#34;Sel(o+26)&#34; value of at least 89. Preferably my process produces an &#34;R&#34; value of at least 30 and a &#34;Sel(o+26)&#34; value of at least 91. 
    
    
     In order to illustrate the nature of the present invention still more clearly the following examples will be given. It is to be understood, however, that the invention is not to be limited to the specific conditions or details set forth in these examples except insofar as such limitations are specified in the appended claims. 
     EXAMPLE 1 
     This example is comparative and shows the conversion of a feedstock over gamma-alumina in the absence of water. The feedstock had the following composition: 
     
                       TABLE 1______________________________________Feedstock - Example 1Component       Weight (g)  w/o    Moles______________________________________Methoxybenzene  108         21.70  1.0o-Methylmethoxybenzene           61          12.26  0.52,6-Dimethylmethoxybenzene           13.6        2.73   0.1Phenol          207         41.60  2.2o-Cresol        108         21.70  1.0Total           497.6       99.99  4.8______________________________________ 
    
     The gamma-alumina was prepared by calcining *CATAPAL® alumina spheres at 650° C. for 2 hours. The alumina had a surface area of 193 m 2  /g and a crystallite size of 60 A°. 
    
     Process was conducted at 0 psig. 
     Runs were made at 300°, 325°, 350° and 375° C. 
     The results are shown in Table 2. 
     
                       TABLE 2______________________________________Results Obtained - Example 1                        % A   % OMA  % DMARun  Temp           Sel(o + 26).sup.b                        Conv..sup.c                              Conv.  Conv..sup.CNo.  (°C.)        R.sup.a               (m/o)    (w/o) (w/o)  (w/o)______________________________________A    300     33.1   92.9     91.5  70.6   68.2B    325     22.2   95.8     99.6  95.7   92.7C    350     3.90   81.9     100   100    100D    375     1.94   75.3     100   100    100______________________________________ .sup.a R = 2,6xylenol/m,p-cresol .sup.b Sel(o + 26) = selectivity (ocresol + 2,6xylenol) (mole .sup.c % A Conv. = percent anisole conversion. % OMA Conv. = percent omethylanisole conversion. % DMA Conv. = percent 2,6dimethylanisole conversion. 
    
     EXAMPLE 2 
     This example is illustrative and shows the results obtained when converting a feedstock, containing water, over gamma-alumina. The feedstock had the following composition: 
     
                       TABLE 3______________________________________Feedstock - Example 2Component       weight (g)  (w/o)   Moles______________________________________Methoxybenzene  108         21.34   1.0o-Methylmethoxybenzene           61          12.05   0.52,6-Dimethylmethoxybenzene           13.6        2.69    0.1Phenol          207         40.91   2.2o-Cresol        108         21.34   1.0Water           8.45*       1.67     0.47Total           506.05      100      5.27______________________________________ *1.67 weight percent of total 
    
     The gamma-alumina and amount used were the same as in Example 1. 
     Process was conducted at 0 psig. 
     Runs were made at 250°, 275°, 300° and 325° C. 
     The results are shown in Table 4. 
     
                       TABLE 4______________________________________Results Obtained - Example 2                 Sel    % A   % OMA   % DMA  Temp           (o + 26).sup.b                        Conv..sup.c                              Conv..sup.c                                      Conv..sup.CRun No.  (°C.)          R.sup.a                 (m/o)  (w/o) (w/o)   (w/o)______________________________________E      250     56.9   91.5   75.7  68.6    89.1F      275     34.5   92.5   98.6  97.7    99.4G      300     16.1   87.9   99.9  99.8    100H      325     10.0   86.1   100   100     100______________________________________ .sup.a R = 2,6xylenol/m,p-cresol ratio. .sup.b Sel(o + 26) = selectivity for ocresol + 2,6xylenol. .sup.c See footnote c of Table 2 for definitions of these terms. 
    
     Thus, having described the invention in detail, it will be understood by those skilled in the art that certain variations and modifications may be made without departing from the spirit and scope of the invention as defined herein and in the appended claims.