Process for manufacturing cumene
United States Patent [1 1 Hiickele et al.  
 [451 Apr. 15, 1975 PROCESS FOR MANUFACTURING CUMENE [75] Inventors: Giinter Hiickele; Wilhelm Knepper,  
 both of Marl, Germany [73] Assignee: Chemische Werke Huls Aktiengesellschaft, Marl, Germany [22] Filed: Apr. 15, 1974 [21] Appl. No.: 460,679  
 [30 Foreign Application Priority Data Apr. 21, 1973 Germany 2320385 [52] U.S. Cl. 260/667; 260/683.9; 252/459; 208/143 [51] Int. Cl C07c 5/10; C07c 7/00 [58] Field of Search 260/667, 668 R, 683.9; 252/459 [56] References Cited UNITED STATES PATENTS 3,268,608 8/1966 Rosset 260/668 3,433,845 3/1969 Kovach et al 260/667 3,551,511 12/1970 Aglietti et al. 260/683.9 3,769,358 10/1973 Neta et al. 260/667 FOREIGN PATENTS OR APPLICATIONS 1,468,895 11/1967 France 260/667 2,284,261 11/1958 Australia 260/667 OTHER PUBLICATIONS Encyclopedia of Chem. Technology, 2nd Ed., Vol.  
 Encyclopedia of Chem. Technology, 2nd Ed., Vol. 11 (1966), pp. 426-428.  
 Encyclopedia of Chem. Technology, 2nd Ed., Vol. 19 (1969), pp. 80-83.  
 Primary Examiner-Delbert E. Gantz Assistant Examiner-Juanita M. Nelson Attorney, Agent, or F irm-Krafft &amp; Wells [57] ABSTRACT A process for the manufacture of cumene by hydrogenating alpha-methylstyrene with hydrogen in the presence of an alkalinated nickel aluminum oxide carrier catalyst, the improvement comprising, carrying out the hydrogenation at temperatures of about 60- 160C in the presence of a catalyst where the carrier material contains kappa and/or delta aluminum oxide having an alkali content of 0.1 5 percent by wweight of alkali oxide, wherein (if appropriate) molded aluminum hydroxide containing alkali is dried in a known manner, then it is heated in an air stream at about 400 500C and thereafter steam treated at about 700 800C. The calcined catalyst is then impregnated with a nickel salt in a conventional manner, the salt subsequently being completely decomposed into nickel oxide and volatile components, the nickel content of the catalyst (computed as nickel metal) being about 5 12 percent by weight referred to the calcined catalyst. The impregnated catalyst is thereupon reduced in a conventional manner.  
 9 Claims, No Drawings PROCESS FOR MANUFACTURING CUMENE BACKGROUND OF THE INVENTION The present .invention relates to a process for the manufacture of cumene by hydrogenating alphamethylstyrene with hydrogen in the presence of an alkalinated nickel-aluminum oxide carrier catalyst.  
 The state of the art may be ascertained by reference to Kirk-Othmer&#39; Encyclopedia of Chemical Technoldissociation of cumene hydroperoxide, alphamethylstyrene is obtained which is produced together with the non-converted cumene. This alphamethylstyrene, which is present in the crude cumene in proportions of about percent by weight, is appropriately hydrogenated back to cumene.  
  It is known to carry out this hydrogenation in the liquidphase. The catalysts used are sulfided nickel, platinum or palladium carrier catalysts, or cobaltmolybdenum carrier catalysts. Silicic acid, pure clay, aluminum silicates or activated carbon serve as catalyst carriers. These catalysts in general completely hydrogenate the alkenyl lateral chain without attacking the benzene nucleus. In the process described in US. Pat. No. 3,551,511, the crude cumene obtained in phenol production is hydrogenated in the presence of a cobaltmolybdenum catalyst or a nickel-cobalt-molybdenum catalyst on aluminum oxide at temperatures of 250 -300C and pressures of 0.5 70 atmospheres. The high temperature of hydrogenation is a drawback. In the process of US Pat. No. 3,268,608 a catalyst of which the active ingredient contains the metals of the platinum group or nickel is used on an alkalenated clay or activated carbon carrier is used for the hydrogenation of alpha-methylstyrene and this catalyst must be sulfided prior to use. The hydrogenation takes place at temperatures of -100 300C, generally at 175 225C, and at pressures of 2 100 atm., generally atm. This hydrogenation yields dimers and polymers as undesired side products. The example of US. Pat. No. 3,268,608 shows that the hydrogenation of a mixture of cumene and alpha-methylstyrene with an alkalinated clay carrier catalyst yields 10 percent by weight of high boiling point side products with respect to the alpha-methylstyrene input. Again, high boiling point products are obtained when a palladium activated carbon catalyst is used in conformity with the description of French Pat. No. 1,468,895. These high boiling point products are useless and bothersome side products which can no longer be converted into cumene and which lower the economic yield of the process.  
 SUMMARY OF THE INVENTION Having in mind the limitations of the prior art, it is an object of the present invention to use catalysts in the hydrogenation of alpha-methylstyrene to cumene inthe absence&#39;of the formation of bothersome side&#39;produ&#39;cts such as those having high boiling points or those wherein the aromatic nucleus is completely hydrogena&#39;ted, for instance isopropylcyclohexane, these catalysts also having good hydrogenation efficiency.  
  According to the present invention, a process for the manufacture of cumene by hydrogenating alphamethylstyrene with hydrogen in the presence of an alkalinated nickel-aluminum oxide carrier catalyst was found, which is characterized in that the hydrogenation is carried out at temperatures of about l60C in the presence of a catalyst containing kappa and/or delta aluminum oxide, with an alkali content of 0.1 5 percent by weight of alkali-oxide, as carrier material. The alkali containing aluminum hydroxide (which may be molded), is treated in known manner, that is, dried, then heated to 400 -500C in an air stream and then treated with steam at 700 -800C and impregnated in a manner known per so with nickel salt which thereupon is completely decomposed into nickel oxide and volatile components. The nickel content of the catalyst (computed as nickel metal) is 5 l2 percent by weight with respect to the calcined catalyst. The calcined catalyst is thereafter reduced in known manner prior to use. Precipitated aluminun hydroxide or aluminumm oxide gel are mixed. preferably with aqueous alkali solution, and corresponding to the desired alkali content, for the preparation of the carrier. Preferably aqueous solutions of sodium hydroxide are used, but also aqueous solutions of lithium hydroxide or potassium hydroxide are useful. Mixing of the aluminum hydroxide or aluminun oxide gel with the alkali solution is performed in such manner that the carrier material contains about 0.1 5 percent by weight of alkali (computed as alkali oxide) with respect to the calcined carrier. If one goes below the lower limit of 0.1 percent by weight. then the formation of the high boiling point products is no longer completely prevented. The upper limit of 5 percent by weight in alkali content is determined by the negative influence of high alkali contents on the physical properties of the catalyst carrier, the catalytic effect in such cases being visibly decreased. The alkali-containing aluminum hydroxide is generally moistened with diluted nitric oxide in order to improve the plastic properties, and then it is molded into strands or tablets and dried at about 100 -l50C. Graphite may also be added in order to improve the plastic properties. The internal surface area and the pore distribution of the carrier, also the structure of the aluminum oxide, is controlled by subsequent heating in an air stream at about 400 500C and an ensuing steam treatment at about 700 -800C. The carriers prepared in conformity with the present invention as a rule have internal specific surfaces of about 20 200 sq.m/gm, a pore volume of about 0.3 0.7 ml/gm and an average pore diameter of about 400 A. The operation of the present invention with carriers of internal specific surfaces of about 60 100 sq.m/gm, pore volumes of about 0.4 0.5 ml/gm and average pore diameters of about 200 300 A, was found to be particularly suitable. Such carriers are obtained by heating the dried, molded items to about 410 -440C and by treating them with steam at about 740 760C. Preparation of the catalyst is achieved by impregnating the carrier of the invention with nickel salt solutions, preferably with a nickel nitrate solution, by drying the molded items generally at 100 -l50C and by completely decomposing the nickel salt preferably at about 300 -400C. Impregnation is carried out in such manner that the calcined catalyst contains nickel to the extent of about 12 percent by weight (calculated as nickel metal). The lower limit is determined by the inadequate catalytic activity resulting from low nickel content catalysts. The higher nickel contents reduce selectivity.  
  Those nickel salts are used for impregnation. which are completely decomposed to nickel oxides and to volatile components at 300 400C. 1f nickel salts which are already completely decomposing below 300C are used, then one may easily obtain catalysts that are overactive. Vacuum impregnation is advantageous because the air already expelled from the pores and coating by means of the active catalyst component takes place more rapidly,  
  If desired, the properties of the catalyst may be modified by adding further metals. especially copper or copper and chromium. These metals are sprayed on the carrier in the form of aqueous nitrate solutions of copper and of chromic acid in the case of chromium.  
  Prior to use, the catalyst is reduced at about 250400C. The nickel in the reduced catalyst is hydrogenation effective and is predominantly in the elementary metallic form.  
  The nickel salts include but are not limited to Ni (N usefull are as well Ni-complex-salts as for example Ni(NH3) ;CO3 and )2 In the hydrogenation the feed rate of alphamethylstyrene is about 0.1 to 1 volumes of alphamethylstyrene per volume of carrier catalyst per hour and the feed rate of hydrogen is about 100 to 3,000 volumes of hydrogen per volume of carrier catalyst per hour.  
  In conformity with the process of the present invention, pure alpha-methylstyrene or mixtures of alphamethylstyrene and cumene as yielded in the production of phenol may be used. Fairly large amounts of contaminants may be present in the input mixture. Typical im purities in the mixture of alpha-methylstyrene/cumene are phenol: up to about 5 percent; butyl benzene: up to about 4 percent; ethyl benzene: less than 1 percent; cyclohexanol: less than 1 percent; acetone: less than 1 percent; isopropylcyclohexane: less than 0.1 percent; and sulfur and chlorine in ppm.  
  Generally the hydrogenation of the present invention takes place at pressures of about 1 atm. and at temperatures of about 60 -l60C. In contrast to the process of the known state of the art. the catalyst of the present invention is already fully active at 60C. The starting temperature in the freshly reduced or regenerated state in fact is only C. For good activity to be maintained over a long duration of operation, the temperature is raised. As a rule, the temperature is raised to 160C. Damage to the catalysts may occur above 160C, and they may lose their original properties, so that the aromatic nucleus of the alpha-methylstyrene is partly thoroughly hydrogenated. The catalysts are used for several years when they are regenerated following operation times of 4 8 months, the catalysts being heated to about 300400C in an atmosphere of molecular hydrogen.  
  The process of the present invention offers the advantage as contrasted with the state of the art that because of the selection of the process parameters in the preparation of the catalyst, application of the latter during hydrogenation completely suppresses the formation of useless side products such as those of higher boiling points and those in which the aromatic nucleus of alpha-methylstyrene is thoroughly hydrogenated, the  
 bothersome sulfiding step (such as required for instance by U.S. Pat. No. 3,268,608) becoming superfluous, and operation at low temperatures is feasible.  
  The following Examples are given to illustrate the process of the present invention.  
 EXAMPLE A Aluminum hydroxide is moistened by means of aqueous sodium hydroxide (0.6 kg of NaOH/lOO kg of Al- 0 and of dilute nitric acid, extruded, the strands being dried at C, calcined at 420C and treated with steam at 750C. The catalyst carrier so prepared is subjected to vacuum, impregnated by means ofa hot. concentrated nickel nitrate solution. then dried at C and calcined at 350 C. Prior to use. the catalyst is reduced at 350C in a nitrogen-hydrogen gas stream.  
 EXAMPLE B Aluminum hydroxide is moistened with dilute nitric acide. extruded, the strands are dreid, calcined and steam treated at 130, 420and 750C respectively. The catalyst carrier is impregnated under vacuum with hot. concetrated nickel nitrate solution, dried at 140 C. calcined at 350 C and reduced in situ with a nitrogenhydrogen gas at 350 C.  
 EXAMPLE C Nickel oxide prepared from precipitaed basic nickel carbonate at a temperature no more than 300C is mixed with graphite and alkalinated aluminum oxihydrate. compressed into tablets, dried at C, calcined at 350 C and reduced in situ with nitrogen-hydrogen gas at 350 C.  
 EXAMPLE 1 Alpha-methylstyrene (content: 98.74 percent by weight) was hydrogenated at standard pressure at 100C and at a ratio of one part by volume of alphamethylstyrene to one part by volume of catalyst per hour in a hydrogen stream of a rate of 2,000 parts by volume per hour, with respect to the standard conditions, on a reduced carrier catalyst (prepared per method A) containing 10.5 percent by weight of nickel, 85.5 percent by weight of aluminum oxide and 0.4 percent by weight of sodium oxide in the calcined state. 98.7 parts by weight were hydrogenated to cumene. Dimers and polymers did not arise even in traces. Nor was there any formation of isopropylcyclohexane.  
 EXAMPLE 2 A crude cumene such as is ordinarily obtained from the phenol-cumene process, and with a content of 10 parts by weight of alpha-methylstyrene, was hydrogenated at standard pressure at 100C at a loading of 3 parts by volume of liquid cumene to 1 part by volume of catalyst per hour in a hydrogen stream of 2,000 parts by volume per hour, with respect to standard conditions, on the same catalyst as in Example I. 9.6 parts by weight of alpha-methylstyrene were hydrogenated to cumene and 0.4 parts by weight remained unchanged. There was no dimer, not even in traces.  
 EXAMPLE 3 A catalyst prepared per Example A was used to hydrogenate crude cumene at a temperature of 70C and a pressure of 10 atm. gauge. The alpha-methylstyrene (IOpercent by weight) was completely hydrogenated to cumene. Dimers could not be found, not even in traces. The hydrogenation temperature was gradually raised to 160C over an operational period of 8 months. No dimer formation could be shown upon the increase of the non-hydrogenated alpha-methylstyrene to 0.6 percentby weight, whereupon the catalyst was regenerated and again used atabout 70C. The results obtained were repetitive over 7 cycles of operation and regeneration. The same results are obtained when the hydrogenation is carried out at atm.  
 COMPARISON EXAMPLE 1 Under the same conditions as described in Example 2, crude cumene is hydrogenated by means of a reduced nickel-aluminum-oxide carrier catalyst prepared per Example B and containing 10.7 percent by weight of nickel, 85.7 percent by weight aluminum oxide, and 0.008 percent by weight sodium oxide in the calcined state. 9.2 parts by weight of alpha-methylstyrene were hydrogenated to cumene, 0.6 percent by weight formed dimer products and 0.2 percent by weight remained unchanged.  
 COMPARISON EXAMPLE 2 Crude cumene at 100C and normal pressure was hydrogenated with a loading of 3 parts by volume of liquid cumene to one part by volume of catalyst per hour using a catalyst prepared per Example C but containing 21 percent by weight nickel, in a hydrogen stream of 2,000 parts by volume per hour. referred to standard conditions. The alpha-methylstyrene was completely hydrogenated. No dimers could be shown, but there were 0.4 percent by weight of isopropylcyclohexane from cumene nulear hydrogenation.  
 We claim:  
  1. In the process for manufacturing cumene by hydrogenating alpha-methylstyrene with molecular hydrogen in the presence of an alkalinated nickel aluminum-oxide carrier catalyst, the improvement comprising: said carrier containing calcined alkalinated aluminum oxide selected from the group consisting of kappa aluminum oxide, delta aluminum oxide and mixtures thereof and having an alkali content of about 0.1 5 percent by weight of alkali oxide, said calcined carrier is impregnated with nickel catalyst wherein the nickel content is about 5 12 percent by weight, calculated as nickel metal and based upon the total weight of said calcined carrier, and said hydrogenating is carried out at temperatures of about 60 160C.  
  2. The process of claim 1, wherein said aluminum oxide carrier has an internal specific surface of about 20 200 sq.m/gm and an average pore volume of about 0.3 0.7 ml/gm. and an average pore diameter of l00 400 A.  
  3. The process of claim 2, wherein said hydrogenating is carried out at pressures of about I to 30 atmospheres.  
  4. The process of claim 3, wherein said calcined carrier is prepared by molding aluminum hydroxide containing said alkali, drying, heating in an air stream at about 400-500C and steam treating at about 700800C.  
  5. The process of claim 4, wherein said nickel impregnated carrier catalyst is prepared by impregnating said calcined carrier with a nickel salt. decomposing said salt into nickel oxide and volatile components and reducing said nickel oxide to predominantly nickel metal.  
  6. The process of claim 5, wherein said impregnating is carried out under vacuum.  
  7. The process of claim 6, wherein said decomposing is conducted at a temperature of about 300400C.  
  8. The process of claim 7. wherein said nickel salt is nickel nitrate.  
  9. The process of claim 8, wherein the feed rate of alph-methylstyrene is about 0.1 to l volumes of alphamethylstyrene per volume of carrier catalyst per hour and the feed rate of hydrogen is about to 3.000 volumes of hydrogen per volume of carrier catalyst per