Abstract:
There is disclosed a process for producing an alkylphenol comprising reacting a phenol with an aldehyde and hydrogen in the presence of (a) an alkaline or alkaline earth metal catalyst selected from a hydroxide of an alkaline metal, hydroxide of an alkaline earth metal, a carbonate of an alkaline metal, and a hydrogencarbonate of an alkaline metal and (b) a hydrogenation catalyst. By the use of the process, the alkylphenols can be produced in good yield in one stage method.

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention relates to a process for producing alkylphenols and, more particularly, it relates to a process for producing alkylphenols in good yield using one stage method. 
     (2) Description of the Prior Art 
     A two stage method for producing alkylphenols which are useful as antioxidants and materials of other chemical products is disclosed in U.S. Pat. No. 2,909,568. The method comprises reacting a phenol with formaldehyde in the presence of a basic catalyst to form a (hydroxymethyl)phenol followed by reduction with hydrogen to form a methylphenol. 
     However, the above described method is complicated in practice since it needs acid precipitation of the (hydroxymethyl)phenol which is recovered as a salt thereof in first stage. Further, at relatively low temperature, the first stage should be carried out for very long time and, in such a condition, the yield of the (hydroxymethyl)phenol is low, resulting in a low yield of the methylphenol. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to produce alkylphenols by a one stage method in good yield. 
     It has been found, as the result of diligent study, that alkylphenols can be produced in good yield in one stage by reacting a phenol with an aldehyde and hydrogen in the presence of certain catalysts, and the knowledge led them to complete the invention. 
     The present invention is a process for producing an alkylphenol comprising reacting a phenol with an aldehyde and hydrogen in the presence of (a) an alkaline or alkaline earth metal catalyst selected from an hydroxide of an alkaline metal, an hydroxide of an alkaline earth metal, carbonate of an alkaline metal, and a hydrogencarbonate of an alkaline metal and (b) a hydrogenation catalyst. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The phenols which may be used in the process of the present invention are those represented by the general formula ##STR1## wherein each R 1  and R 2  is independently selected from alkyl radicals and alkoxy radicals. The illustrative examples of such phenol include phenol, o-cresol, m-cresol, p-cresol, xylenol, ethylphenol, propylphenol, p-tert-butylphenol, p-tert-amylphenol, o-sec-amylphenol, octylphenol, nonylphenol, 2,6-dimethylphenol, 2,6-diethylphenol, 2,6-diisopropylphenol, 2,6-di-tert-butylphenol, 2,6-di-tert-amylphenol, 2,6-di-sec-amylphenol. Among these, 2,6-di-tert-butylphenol is preferably used. 
     The aldehydes which may be used in the process of the present invention are those represented by the general formula R 2  CHO wherein R 3  is selected from hydrogen and alkyl radicals. 
     The illustrative examples of such aldehyde include formaldehyde, acetaldehyde, propionaldehyde, enanthaldehyde, acrolein, crotonaldehyde, hydroxy-aldehyde, salicylaldehyde, anisaldehyde, vanillin. Among these, formaldehyde is preferably used. Formaldehyde may be used in the form of monomer, and may also be used in the form of trioxane, paraformaldehyde, or the like, which liberates formaldehyde under the reaction condition. Alternatively, it may be used as an aqueous solution (formalin). 
     The above described hydrogen may includes impurities in some quantity so long as the forming of the alkylphenols is not to be disturbed, and for example, those obtained by conversion of water gas, gasification of petroleum, complete gasification of coal, conversion of natural gas may be used. 
     The above described phenols and aldehydes react as shown, for example, in the following equation to form the corresponding alkylphenols. ##STR2## 
     The reaction in the process of the present invention is conducted in the presence of an alkaline or alkaline earth metal catalyst selected from a hydroxide of an alkaline metal, a hydroxide of an alkaline earth metal, a carbonate of an alkaline metal, and a hydrogencarbonate of an alkaline metal. The illustrative examples of the hydroxide of alkaline or alkaline earth metal include sodium hydroxide, potassium hydroxide, lithium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide. The illustrative examples of the carbonate or hydrogencarbonate of alkaline metal include lithium carbonate, lithium hydrogencarbonate, sodium carbonate, sodium hydrogencarbonate, potassium carbonate, potassium hydrogencarbonate, rubidium carbonate, rubidium hydrogencarbonate, cesium carbonate, cesium hydrogencarbonate, francium carbonate, francium hydrogencarbonate, sodium-potassium carbonate. These may be used individually or in a combination of two or more of them, and the amount to be used of these, which is not to be particularly limited, is usually 1/300 to 1/10 mol, preferably 1/200 to 1/50 mol per 1 mol of the phenol. 
     The reaction in the process of the present invention which is carried out by contacting a phenol, an aldehyde, and hydrogen in the presence of the above described catalyst also needs the presence of a hydrogenation catalyst. The illustrative examples of the hydrogenation catalyst to be used in the process of the present invention include nickel or cobalt catalysts such as nickel sulfide catalyst, nickel sulfide catalyst, nickel peroxide catalyst, nickel-pumice catalyst, nickel-thioria-diatomaceous earth catalyst, nickel-copper-alumina catalyst, nickel-diatomaceous earth catalyst, nickel-alumina catalyst, nickel-berillia catalyst, nickel-chromia catalyst, nickel chromite catalyst, nickel-calcium phosphate catalyst, Raney nickel catalyst, Urushibar nickel catalyst, nickel formate catalyst, cobalt-diacetomaceous earth catalyst, cobalt-copper catalyst, cobalt-barium oxide-alumina catalyst, cobalt-molybdenum catalyst, cobalt-thoria-magnesia-ciatomaceous earth catalyst, cobalt-thoria-magnesia-diacetomaceous earth catalyst, Raney-cobalt-catalyst, Urushibara-cobalt catalyst, and cobalt formate catalyst; chromium catalysts such as chromium oxide catalyst and chromium oxide catalyst supported on a carrier; molybdenum or tungsten catalysts such as Raney tungsten catalyst, molybdenum oxide catalyst, molybdenum oxide catalyst supported on a carrier, tungsten disulfide catalyst, molybdenum trisulfide catalyst, tungsten disulfide catalyst, molybdenum chloride catalyst, molybdenum pentachloride catalyst, and tungsten chloride catalyst; platinum group catalysts such as ruthenium chloride catalyst, ammonium chlororuthenate catalyst, ruthenium hydroxide catalyst, ruthenium dioxide catalyst, potassium ruthenate catalyst, ruthenium-carbon catalyst, ruthenium catalysts supported on a carrier, colloidal rhodium catalyst, rhodium oxide catalyst, rhodium hydroxide catalyst, rhodium chloride catalyst, sodium chlororhodate catalyst, ammonium chlororhodate catalyst, rhodium catalysts supported on a carrier, palladium chloride catalyst, chlorotetraammine palladium catalyst, ammonium tetrachloropalladate catalyst, palladium oxide catalyst, palladium hydroxide catalyst, palladium black catalyst, colloidal palladium catalyst, palladium-carbon catalyst, palladium hydroxide-carbon catalyst, palladium-barium sulfate catalyst, palladium-calcium carbonate catalyst, other palladium catalysts supported on a carrier, osmium black catalyst, colloidal osmium catalyst, osmium-carbon catalyst, osmium-alumina catalyst, iridium black catalyst, colloidal iridium catalyst, iridium oxide catalyst, iridium oxide-platinum oxide catalyst, iridium asbestos catalyst, iridium-carbon catalyst, platinum black catalyst, colloidal platinum catalyst, platinum-carbon catalyst, platinum-asbestos catalyst, platinum-silica gel catalyst, and platinum-alumina catalyst. Among these, the preferred are platinum group catalysts, and particularly preferred are palladium-carbon catalyst and platinum-carbon catalyst. The amount to be used, which is not to be particularly limited, is usually 1 to 80 g, preferably 5 to 50 g for 1 mol of phenol. 
     In conducting the reaction, a solvent, for example alcohols such as methanol, ethanol, isopropanol, tert-butanol, etc. and ethers such as diethyl ether, methyl ethyl ether, tetrahydrofuran, 1,4-dioxane, etc., may be optionally used. 
     The ratio of the phenol and the aldehyde, which is not to be particularly limited, is usually 1 to 6 mol, preferably 2 to 4 mol of aldehyde to 1 mol of phenol. 
     The reaction pressure, which is not to be particularly limited, is usually 0 to 10 kg/cm 2  -G, preferably 0 to 70 kg/cm 2  -G, and it is desirable to control the conditions so that the partial pressure of hydrogen is in the range of from 1 to 95 kg/cm 2  -G, preferably from 1 to 90 kg/cm 2  -G. 
     The reaction temperature, which is not to be particularly limited, is usually 50° to 150° C., preferably 70° to 130° C., and the reaction time is usually 1 to 20 hours, preferably 2 to 10 hours. 
     The reaction in the process of the present invention may either be carried out in a batch type reaction or be carried out using the catalyst in a continuous-flow system such as fixed bed, fluidized bed, or the like. 
     According to the present invention, alkylphenols can be produced from a phenol and an aldehyde by one stage reaction in good yield and therefore, the industrial value of the present invention is extremely large. 
     The alkylphenols produced according to the present invention are useful as antioxidants, raw materials of other chemical products, and the like. 
    
    
     EXAMPLES AND COMPARATIVE EXAMPLES 
     The present invention will now be described in details with reference to the following Examples that by no means limit the scope of the invention. 
     EXAMPLES 1 TO 4 
     Into a 50-ml autoclave were charged a phenol, an aldehyde, an alkaline or alkaline earth metal catalyst, hydrogenation catalyst, and a solvent listed in the Table in the quantities listed in the Table. Hydrogen was introduced into the autoclave and reaction was carried out under the conditions shown in Table. After the conclusion of the reaction, the content was cooled to 25° C., the reaction product was filtered, and the filtrate was analyzed by gas chromatography. The yield of the alkylphenol was calculated on the basis of the amount of the phenol. 
     EXAMPLES 5 TO 12 
     The procedure of Examples 1 to 4 was repeated with the exception that a 250-ml autoclave was used in place of the 50-ml autoclave. 
     COMPARATIVE EXAMPLE 1 
     310 g of 2,6-dimethoxyphenol, 300 g of 38 wt% formalin, and 810 g of 10% wt% aqueous sodium hydroxide were reacted for 60 hours at 25° C. under a pressure of 0 kg/cm 2  -G, the reaction mixture was and then neutralized with sulfuric acid, to obtain 80 g of 2,6-dimethoxy-4-(hydroxymethyl)phenol. (Yield: 22 mol%) 25 g of the obtained 2,6-dimethoxy-4-(hydroxymethyl)phenol was reacted in 320 ml of methanol in the presence of 0.375 wt% of platinum-alumina catalyst and hydrogen for 4 hours at 200° C. at 199 kg/cm 2  -G, and 15 g of 2,6-dimethoxy-4-methylphenol was obtained. (Yield: 66 mol%) The yield on the basis of the amount of the raw material was 15 mol%. 
     COMPARATIVE EXAMPLE 2 
     108 g of o-cresol, 215 g of 38 wt% formalin, 50 g of sodium hydroxide, and 200 g of water were reacted for 96 hours at 25° C., and the reaction mixture was then neutralized with acetic acid, to obtain 126 g of 2,6-bis(hydroxymethyl)-4-methylphenol. (Yield: 75 mol%) The obtained 2,6-bis(hydroxymethyl)-4-methylphenol was reacted in 250 ml of methanol in the presence of 0.375 wt% of platinum-alumina catalyst and hydrogen for 4 hours at 180° C. at 179 kg/cm 2  -G, and 15 g of 2,4,6-trimethylphenol was obtained. (Yield: 45 mol%) The yield on the basis of the raw material was 34 mol%. 
     
                                           TABLE__________________________________________________________________________                      Example                      1  2  3  4  5  6  7  8  9  10 11 12__________________________________________________________________________Phenolic compound       2,6-di-tert-butylphenol                      8  8  8  8  120                                     120                                        120                                           120                                              120                                                 120                                                    120                                                       120(mmol)Aldehyde (mmol)       35 wt % formalin                      20 20 -- 20 200                                     -- -- -- 200                                                 -- -- --       92 wt % paraformaldehyde                      -- -- 20 -- -- 200                                        200                                           200                                              -- 200                                                    200                                                       200Alkline/alkaline       sodium hydroxide                      -- 0.05                            -- --earth metal lithium hydroxide                      0.05                         -- 0.05                               0.05catalyst    sodium carbonate           1  1  -- -- -- -- -- --EX. 1-4(mmol)       sodium hydrogencarbonate   -- -- 0.5                                           -- -- -- -- --EX. 5-12(g) patassium carbonate        -- -- -- 0.5                                              0.5                                                 0.5                                                    0.5                                                       0.5Hydrogenation       5 wt % palladium supported                      200                         200                            -- 200                                  500                                     500                                        500                                           500                                              500                                                 -- 500                                                       500catalyst (mg)       on carbon       5 wt % palladium supported                      -- -- 400                               -- -- -- -- -- -- -- -- --       on alumina       5 wt % platinum supported                      -- -- -- -- -- -- -- -- -- 500                                                    -- --       on carbonSolvent (ml)       methanol       20 20 20 20 100                                     100                                        100                                           100                                              110                                                 100                                                    100                                                       100Temperature (°C.)   90 90 90 90 130                                     130                                        130                                           110                                              120                                                 120                                                    110                                                       110Pressure (kg/cm-G)         7  7  7  7  20 20 20 20 20 20 20 20Time (hour)                5  5  5  5  5  5  5  4  5  6  4  4Yield of    2,6-di-tert-butyl-4                      84.0                         63.5                            78.0                               59.2                                  80 85 83 94 82 65 93 91alkylphenol (mol %)methylphenol                                          *1 *2__________________________________________________________________________ *1 The hydrogenation catalyst employed in Ex. 4 was reused. (the second time) *2 The hydrogenation catalyst employed in Ex. 4 was reused. (the third time)