Catalytic removal of peroxide contaminants from tertiary butyl alcohol
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a method for removing residual quantities of peroxide contaminants including tertiary butyl hydroperoxide, ditertiary butyl peroxide, allyl tertiary butyl peroxide, etc., from a tertiary butyl alcohol feedstock to provide a tertiary butyl alcohol product that is useful as an octane-enhancing component of motor fuels and also useful as a recycle stream in a continuous process for the preparation of methyl tertiary butyl ether from tertiary butyl alcohol and methanol. In accordance with the present invention, the peroxide contaminated tertiary butyl alcohol feedstock is brought into contact with a catalyst comprising ferric oxide (rust) in order to substantially selectively reduce the quantity of peroxide contaminants- remaining in the tertiary butyl alcohol product. 
     2. Prior Art 
     A process for the manufacture of epoxides from olefins such as propylene is disclosed in Kollar U.S. Pat. No. 3,351,653 which teaches that the epoxide can be made by reacting an olefin with an organic hydroperoxide in the presence of an epoxidation catalyst, such as, for example, a molybdenum epoxidation catalyst. When the olefin is propylene and the hydroperoxide is tertiary butyl hydroperoxide, propylene oxide and tertiary butyl alcohol are coproducts. U.S. Pat. No. 3,350,422 teaches a similar process using a soluble vanadium catalyst. Molybdenum is the preferred catalyst. A substantial excess of olefin relative to the hydroperoxide is taught as the normal procedure for the reaction. See also U.S. Pat. No. 3,526,645 which teaches the slow addition of organic hydroperoxide to an excess of olefin as preferred. 
     Stein, et al. in U.S. Pat. No 3,849,451 have improved upon the Kollar process of U.S. Pat. Nos. 3,350,422 and U.S. Pat. No. 3,351,635 by requiring a close control of the reaction temperature, between 90°-200° C. and autogenous pressures, among other parameters. Stein et al. also suggests the use of several reaction vessels with a somewhat higher temperature in the last vessel to ensure more complete reaction. The primary benefits are stated to be improved yields and reduced side reactions. 
     It is known that isobutane can be oxidized with molecular oxygen to form a corresponding tertiary butyl hydroperoxide and that the oxidation reaction can be promoted, for example with an oxidation catalyst (see Johnston U.S. Pat. No. 3,825,605 and Worrell U.S. Pat. No. 4,296,263. 
     Thus, tertiary butyl alcohol can be prepared either by the direct thermal or catalytic reduction of tertiary butyl hydroperoxide to tertiary butyl alcohol or by the catalytic reaction of propylene with tertiary butyl hydroperoxide to provide propylene oxide and tertiary butyl alcohol. 
     It is also known that tertiary butyl alcohol can be used as an octane-enhancing component when added to a motor fuel, such as gasoline. Thus, it has heretofore been proposed, as shown, for example, by Grane U.S. Pat. No. 3,474,151 to thermally decompose tertiary butyl hydroperoxide to form tertiary butyl alcohol to be used as an octane-enhancing component of a motor fuel. Grane points out that the thermal decomposition must be conducted with care because tertiary butyl alcohol will start to dehydrate at a temperature of about 450° F. (about 232° C.) and in that dehydration becomes rapid at temperatures above about 475° F. (about 246° C.). Grane also points out that the tertiary butyl alcohol prepared in this manner will contain contaminating quantities of ditertiary butyl peroxide. Ditertiary butyl peroxide is more refractory than tertiary butyl hydroperoxide and adversely affects the octane-enhancing qualities of tertiary butyl alcohol. Grane discovered that the residual contaminating quantities of ditertiary butyl peroxide could be removed from the tertiary butyl alcohol by thermally treating the contaminated tertiary butyl alcohol at a temperature of 375° F. to 475° F. (about 190° to about 244° C.) for a time of from 1 to 10 minutes. 
     This concept was expanded upon by Grane et al. in U.S. Pat. Nos. 4,294,999 and 4,296,262 to provide integrated processes wherein, starting with isobutane, motor-fuel grade tertiary butyl alcohol was prepared by the oxidation of isobutane (e.g., in the presence of a solubilized molybdenum catalyst) to produce a mixture of tertiary butyl alcohol and tertiary butyl hydroperoxide from which a fraction rich in tertiary butyl hydroperoxide could be recovered by distillation. This stream, after being debutanized was subjected to thermal decomposition under pressure at a temperature of less than 300° F. (about 148.8° C.) for several hours to significantly reduce the concentration of the tertiary butyl hydroperoxide. However, the product of this thermal decomposition step still contained residual tertiary butyl hydroperoxide most of which was thereafter removed by a final thermal treatment of the contaminated tertiary butyl hydroperoxide in the manner taught by Grane U.S. Pat. No. 3,474,151. 
     Thus, the removal of trace quantities of tertiary butyl hydroperoxide and ditertiary butyl peroxide from motor grade tertiary butyl alcohol has received appreciable attention. Ditertiary butyl peroxide is the more refractory of the two peroxides. Another refractory peroxide that is frequently present as a contaminant is allyl tertiary butyl peroxide. Allyl tertiary butyl peroxide is more refractory than tertiary butyl hydroperoxide but less refractory than ditertiary butyl peroxide. 
     The problems encountered in attempting the thermal removal of contaminating quantities of peroxides such as allyl tertiary butyl peroxide and ditertiary butyl peroxide from tertiary butyl alcohol have led to the provision of a variety of catalytic processes for removing contaminating quantities of peroxides such as allyl tertiary butyl peroxide and ditertiary butyl peroxide from tertiary butyl alcohol as exemplified, for example, by Sanderson et al. U.S. Pat. No. 4,547,598, U.S. Pat. No. 4,704,482, U.S. Pat. No. 4,705,903, U.S. Pat. No. 4,742,179, U.S. Pat. No. 4,873,390, U.S. Pat. No. 4,910,349, U.S. Pat. No. 4,912,266, U.S. Pat. No. 4,912,267, U.S. Pat. No. 4,922,033, U.S. Pat. No. 4,922,034, U.S. Pat. No. 4,922,035, U.S. Pat. No. 4,922,036, etc. 
     In some instances, it is proposed to use silica as a support for the catalyst, e.g., Sanderson et al. U.S. Pat. No. 4,704,482, U.S. Pat. No. 4,705,903, U.S. Pat. No. 4,742,179, U.S. Pat. No. 4,873,380, etc. The silica when used as a support is normally used in an un-vitrified high surface area form, such as Kieselguhr. 
     SUMMARY OF THE INVENTION 
     The feedstocks of the present invention comprise tertiary butyl alcohol contaminated with tertiary butyl hydroperoxide, ditertiary butyl peroxide and, frequently, allyl tertiary peroxide. 
     When isobutane is treated to form tertiary butyl hydroperoxide, the reaction product will normally contain some tertiary butyl alcohol and other oxygenated by-products such as ditertiary butyl peroxide, allyl tertiary butyl peroxide, etc., as well as unreacted isobutane. After the unreacted isobutane is removed, a fraction composed mostly of tertiary butyl alcohol may be recovered as a distillate fraction. The tertiary butyl alcohol distillate, which will normally be contaminated with tertiary butyl hydroperoxide, ditertiary butyl peroxide, allyl tertiary peroxide, etc., may be used as a feedstock for the process of the present invention. 
     Tertiary butyl hydroperoxide is suitably reacted with propylene by a process of the type disclosed in Kollar U.S. Pat. No. 3,351,635 to provide an initial reaction product composed mostly of unreacted propylene, propylene oxide and tertiary butyl alcohol. However, residual quantities of tertiary butyl hydroperoxide and ditertiary butyl peroxide and other oxygenated impurities are normally present and remain dissolved in the tertiary butyl alcohol recovered from the reaction mixture. This tertiary butyl alcohol product can also be used as a feedstock for the process of the present invention. 
     It has been surprisingly discovered in accordance with the present invention that a feedstock comprising tertiary butyl alcohol contaminated with minor amounts of peroxide impurities such as tertiary butyl hydroperoxide, ditertiary butyl peroxide, allyl tertiary butyl peroxide, etc., can be effectively treated without significant dehydration of the tertiary butyl alcohol by bringing the peroxide-contaminated feedstock into contact with the ferric oxide catalyst in a continuous process conducted at a temperature of about 100° to about 300° C., more preferably about 160° to about 200° C., at a space velocity of about 100 to about 400 volumes of tertiary butyl alcohol feedstock per hour per volume of catalyst and a pressure of about 0 to about 2,000 psig, more preferably about 200 to about 800 psig. 
     Tertiary butyl alcohol obtained when propylene is reacted with tertiary butyl hydroperoxide will contain oxygenated impurities including ditertiary butyl peroxide, tertiary butyl hydroperoxide, allyl tertiary butyl peroxide, etc., and acetone. Normally, tertiary butyl alcohol prepared in this fashion will contain about 0.1 to about 5 wt. % of ditertiary butyl peroxide, about 0.0 to about 1 wt. % of tertiary butyl hydroperoxide and about 0.05 to about 2.5 wt. % of allyl tertiary butyl peroxide. Minor quantities of other peroxides and other oxygen-containing compounds such as methyl formate, etc., may also be present. 
     In accordance with the present invention, a tertiary butyl alcohol feedstock contaminated with peroxides such as a tertiary butyl alcohol feedstock contaminated with peroxides including about 0.1 to about 5 wt. % of ditertiary butyl peroxide, about 0.0 to about 1 wt. % of tertiary butyl hydroperoxide and about 0.05 to about 2.5 wt. % of allyl tertiary butyl peroxide, is brought into contact with a ferric oxide catalyst of the present invention under appropriate reaction conditions, such as those outlined above, to substantially selectively decompose the peroxide contaminants and thereby provide a tertiary butyl alcohol product substantially free of peroxide contaminants. 
     Manufacture of Methyl Tertiary Butyl Ether 
     Methyl tertiary butyl ether is finding increasing use as a blending component in high octane gasoline as the current gasoline additives based on lead and manganese are phased out. 
     Knifton U.S. Pat. No. 4,827,048 and Knifton et al. U.S. Pat. No. 4,822,921 disclose catalyst methods for the manufacture of methyl tertiary butyl ether from tertiary butyl alcohol and methanol. 
     The Process of the Present Invention 
     It has been discovered in accordance with the present invention that a peroxides-contaminated tertiary butyl alcohol recycle stream recovered from the reaction product obtained by the catalytic reaction of tertiary butyl alcohol with methanol is a suitable feedstock for use in the preparation of methyl tertiary butyl alcohol. 
     The results obtained with the process of the present invention are surprising and unexpected in several respects. Normally, ferric oxide, or rust, is not considered to be effective for use as a catalyst. It has been surprisingly discovered in accordance with the present invention that finely divided ferric oxide, in the form of rust, has a modest catalytic activity in respect of the decomposition of peroxides such as tertiary butyl hydroperoxide, ditertiary butyl peroxide, allyl tertiary butyl peroxide, etc., which permits effective decomposition of these impurities at temperatures below the temperature range specified in the prior art for effective thermal decomposition of the peroxide contaminants present in tertiary butyl alcohol. 
     The decomposition of the peroxide contaminants is substantially quantitative, conversion of the peroxides normally ranging from about 95 to about 100%. Also, there is good selectivity in that tertiary butyl alcohol is the principle decomposition product. 
     Thus, the provision of the process of the present invention wherein a motor-fuel grade tertiary butyl alcohol feedstock containing contaminating quantities of ditertiary butyl peroxide, tertiary butyl hydroperoxide, etc., is catalytically treated for the decomposition of the peroxides results in their substantially complete removal from the treated feedstock. 
     STARTING MATERIALS 
     The starting materials for the process of the present invention include a motor-fuel grade tertiary butyl alcohol feedstock obtained in the manner described above by the reaction of propylene with tertiary butyl hydroperoxide to form propylene oxide and tertiary butyl alcohol by the oxidation of isobutane to form tertiary butyl hydroperoxide, etc. 
     Tertiary butyl alcohol obtained when propylene is reacted with tertiary butyl hydroperoxide will contain oxygenated impurities including ditertiary butyl peroxide, tertiary butyl hydroperoxide, allyl tertiary butyl peroxide, etc., and acetone. Normally, tertiary butyl alcohol prepared in this fashion will contain about 0.1 to about 5 wt. % of ditertiary butyl peroxide, about 0.0 to about 1 wt. % of tertiary butyl hydroperoxide and about 0.05 to about 2.5 wt % of allyl tertiary butyl peroxide. Minor quantities of other peroxides and other oxygen-containing compounds such as methyl formate, etc., may also be present. 
     The catalyst compositions of the present invention comprise ferric oxide, or rust, and are easily and inexpensively prepared by using rusted iron particles such as iron filings, iron shavings, iron chips, etc. When metallic iron is exposed to air, it will react with oxygen to form ferric oxide, which will loosely adhere to the metallic iron substrate in the form of high surface area, finely divided particles. The reaction can be accelerated by immersing the particulate metallic iron in water. In accordance with one preferred embodiment of the present invention, a water-soluble transition metal compound, such as a hydroxide, acetate, acetyl acetone, etc., is dissolved in the water in which the particulate metallic iron is immersed. When this is done, the rust (i.e., ferric oxide) that is formed will also contain the corresponding transition metal oxides. 
     When metals, particularly iron, are exposed to air and water, they undergo corrosion. Pure iron corrodes (or rusts) slowly, while impure iron corrodes more rapidly. The reaction is slow in pure water, but rapid in solutions of electrolytes. 
     It has been shown that iron will not rust in dry air, nor in water which is free from dissolved oxygen. It follows that both air and water are involved in the corrosion process. The presence of an electrolyte in the water accelerates corrosion, particularly when the solution is acidic. Strained metals corrode more rapidly than unstrained ones because they are more active. Heated portions of a metal are more active than unheated ones, and corrode more rapidly. Finally, iron in contact with a less active metal such as tin, lead, or copper corrodes more rapidly than when alone, or when in contact with a more active metal such as zinc. 
     Corrosion can be explained by an electrochemical theory. It appears that minute primary electrochemical cells are set up when corrosion takes place. When iron is in contact with water containing an electrolyte, the half-reaction given below tends to occur. 
     
         (Anodic oxidation) Fe→Fe+2 e.sup.- 
    
     If one portion of the iron is more active than the rest, then its tendency to go into solution is greater. This means that the active portion of the iron has a higher potential than the rest, and this portion tends to dissolve in the electrolyte. On the less active portions of the iron (lower electrode potential), hydrogen tends to form according to the half-reaction 
     
         (Cathodic reduction) 2 H.sup.+ 2 e.sup.- →H.sub.2 
    
     The accumulation of hydrogen on the surface of iron tends to polarize the electrode and stop the cell action. However, dissolved oxygen tends to remove the hydrogen in the same manner that MnO 2  depolarizes the dry cell, and the electrochemical reaction proceeds, i.e., corrosion occurs. 
     
         4 H+O.sub.2 →2 H.sub.2 O 
    
     Iron (II) ions combine with hydroxide ions of the electrolytic solution, forming Fe(OH) 2 . Iron (II) hydroxide is then readily oxidized by air to Fe 2  O 3 .xH 2  O, which is iron rust. 
     Catalytic Treatment of Tertiary Butyl Alcohol 
     In accordance with the present invention, a tertiary butyl alcohol feedstock, as above described, is brought into contact with a catalyst of the present invention under reaction conditions correlated to substantially selectively catalytically convert the tertiary butyl hydroperoxide, the ditertiary butyl peroxide and the allyl tertiary butyl peroxide contaminants in the tertiary butyl alcohol feedstock to decomposition products, principally tertiary butyl alcohol with not more than a minor increase in the level of contamination of any acetone, etc., that may be present in the tertiary butyl alcohol as contaminants. 
     The reaction should be conducted on a continuous basis by passing the tertiary butyl alcohol through a reactor containing a bed of a catalyst of the present invention under reaction conditions including a temperature within the range of about 100° to about 300° and, more preferably, at a temperature of about 160° to about 200° C. The reaction is preferably conducted at 200 to 800 psig., although pressures of about 0 to about 2000 psig. may be used if desired. The tertiary butyl alcohol should be passed over the bed of catalyst at a liquid hourly space velocity of about 0.5 to about 10. 
     The reaction product, after being degassed, is suitable for use as an octane-enhancing component of motor fuel, such as gasoline. 
     Thus, for example, the effluent from the reactor may be passed through a phase separation zone in order to permit gaseous reaction components including hydrogen and isobutane to volatilize from the product to thereby provide the desired reaction product. 
     The specific correlation of conditions to be utilized with any specific catalyst of the present invention can be determined by one of ordinary skill in the art with comparative ease. Thus, for example, the tertiary butyl alcohol feedstock should be analyzed prior to catalytic treatment to determine the level of contamination by tertiary butyl hydroperoxide, ditertiary butyl peroxide, acetone, methanol and isobutylene. If there is an insufficient reduction of the peroxides such that a significant amount (e.g., more than about 0.1 wt. %) of tertiary butyl hydroperoxide and/or ditertiary butyl peroxide is still present, the reaction conditions are not sufficiently severe, and should be increased such as, for example, by increasing reaction temperature or contact time in order to obtain the desired reduction of the tertiary butyl hydroperoxide. 
     If, on the other hand, there is a significant increase in the level of contamination of acetone, etc., the reaction conditions are too severe for the particular catalyst and the reaction conditions should be ameliorated (e.g., by reducing contact time or temperature). 
    
    
     WORKING EXAMPLES 
     A. Reactor 
     The reactor was a stainless steel tube (0.51&#34;×29&#34;) 100 cc capacity which was electrically heated. Liquid feed was pumped into the bottom of the reactor. Pressure was regulated with a Skinner Uni-Flow valve and a Foxboro controller. The liquid feed was pumped with a Ruska dual drive pump. 
     B. Feed 
     The feed was a blend of 10 wt. % of water, 51 wt. % of methanol, 35 wt. % of tertiary butyl alcohol, 1.0 wt. % of methyl tertiary butyl ether and 2.5 wt. % of ditertiary butyl peroxide. 
     C. Catalyst Preparation (6773-78-1) 
     One kg Aldrich iron chips (Cat.#26,794-5) were placed in a beaker and covered with a 2 wt. % aqueous solution of sulfuric acid. Air was blown through the chips at about 200 cc/hr at ambient temperature overnight. The chips were then filtered and let stand at ambient temperature for several weeks. The chips were completely covered with a rusty-brown colored coating of ferric oxide. 
     D. Catalyst Preparation (6773-78-2) 
     About 500 g rusted iron chips from 6773-78-1 were placed in a reactor and heated to 250° C. under a nitrogen purge. Hydrogen was slowly added until the purge was 100% hydrogen. The reactor as kept at 250° C. for 4.0 hours under a flow of pure hydrogen. The reactor was then cooled to ambient temperature under nitrogen and placed in a stoppered bottle with a nitrogen pad until used. During reduction the catalyst changed from a rust brown color to black. 
     E. Catalyst Preparation (6773-92) 
     One kg Aldrich iron chips (Cat.#26,794-5) were placed in a beaker and covered with water containing 2 wt. % sulfuric acid, wt. % chromium acetylacetonate, and 1 wt. % copper acetylacetonate. Air was blown through the chips at about 200 cc/hr at ambient temperature overnight. The chips were then filtered and dried over the weekend at 100° C. The iron chips were completely covered with a rusty-brown coating of ferric oxide. Analysis by AA analysis showed more than 90 wt. % of iron, 0.05 wt. % of chromium and 0.037 wt. % of copper. 
     F. Thermal Decomposition 
     Data on the catalytic decomposition of the ditertiary butyl peroxide was generated in a plurality of runs conducted in the same reactor under reaction conditions including a pressure of 500 psig, feed rates of from 100 to 400 cc/hr, temperatures ranging from 120° to 180° C., run lengths of 4 hours and space velocities of from 1 to 4 cc of feed per hour per cc of catalyst. The data are shown in the following tables. 
     
                                           TABLE I                                 
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Catalytic Decomposition of DTBP in a Continuous Reactor                   
Notebook Number                                                           
           6773-16-O                                                      
                 6773-79-1                                                
                       6773-79-2                                          
                            6773-79-3                                     
                                  6773-79-4                               
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Catalyst         6773-78-1                                                
                       6773-78-1                                          
                            6773-78-1                                     
                                  6773-78-1                               
Reactor (cc)     100   100  100   100                                     
Pressure (psig)  500   500  500   500                                     
Feed Rate (cc/hr)                                                         
                 100   100  100   100                                     
Temperature (°C.)                                                  
                 120   140  160   180                                     
Time on Stream (hr)                                                       
                 4     4    4     4                                       
Space Vel. (cc/cc)                                                        
                 1.0   1.0  1.0   1.0                                     
DTBP Conv. (%)   12.8  38.4 97.8  99.9                                    
TBA Conversion (%)                                                        
                 0.0   0.o  0.0   0.0                                     
Composition                                                               
IC4         0.004                                                         
                 0.002 0.002                                              
                            0.003 0.009                                   
MEOH/MF    55.631                                                         
                 55.690                                                   
                       55.630                                             
                            55.398                                        
                                  55.111                                  
Acetone     0.000                                                         
                 0.078 0.343                                              
                            1.172 1.522                                   
MTBE        1.213                                                         
                 1.145 1.171                                              
                            1.165 1.170                                   
TBA        40.024                                                         
                 40.477                                                   
                       40.892                                             
                            41.820                                        
                                  41.573                                  
DTBP        2.765                                                         
                 2.411 1.702                                              
                            0.062 0.004                                   
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                                           TABLE II                                
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Catalytic Decomposition of DTBP in a Continuous Reactor                   
Notebook Number                                                           
           6773-16-O                                                      
                 6773-80-1                                                
                       6773-80-2                                          
                            6773-80-3                                     
                                  6773-80-4                               
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Catalyst         6773-78-1                                                
                       6773-78-1                                          
                            6773-78-1                                     
                                  6773-78-1                               
Reactor (cc)     100   100  100   100                                     
Pressure (psig)  500   500  500   500                                     
Feed Rate (cc/hr)                                                         
                 200   200  200   200                                     
Temperature (°C.)                                                  
                 120   140  160   180                                     
Time on Stream (hr)                                                       
                 4     4    4     4                                       
Space Vel. (cc/cc)                                                        
                 2.0   2.0  2.0   2.0                                     
DTBP Conv. (%)   6.3   28.9 95.8  100.0                                   
TBA Conversion (%)                                                        
                 0.0   0.0  0.0   0.0                                     
Composition                                                               
IC4         0.004                                                         
                 0.002 0.003                                              
                            0.003 0.009                                   
MEOH/MF    55.631                                                         
                 55.667                                                   
                       55.384                                             
                            55.182                                        
                                  55.053                                  
Acetone     0.000                                                         
                 0.057 0.592                                              
                            1.326 1.922                                   
MTBE        1.213                                                         
                 1.169 1.183                                              
                            1.157 1.186                                   
TBA        40.024                                                         
                 40.270                                                   
                       40.544                                             
                            41.629                                        
                                  41.200                                  
DTBP        2.765                                                         
                 2.591 1.966                                              
                            0.115 0.000                                   
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                       TABLE III                                                   
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Catalytic Decomposition of DTBP in a Continuous Reactor                   
Notebook Number                                                           
            6773-16-O 6773-81-1                                           
                               6773-81-2                                  
                                      6773-81-4                           
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Catalyst              6773-78-1                                           
                               6773-78-1                                  
                                      6773-78-1                           
Reactor (cc)          100      100    100                                 
Pressure (psig)       500      500    500                                 
Feed Rate (cc/hr)     400      400    400                                 
Temperature (°C.)                                                  
                      120      140    180                                 
Time on Stream        4        4      4                                   
(hr)                                                                      
Space Vel. (cc/cc)    4.0      4.0    4.0                                 
DTBP conv. (%)        2.7      13.3   99.9                                
TBA Conversion        0.0      0.0    32.0                                
(%)                                                                       
Composition                                                               
IC4          0.004    0.002    0.003  2.160                               
MEOH/MF     55.631    55.667   55.812 54.867                              
Acetone      0.000    0.052    0.117  1.252                               
MTBE         1.213    1.172    1.169  12.797                              
TBA         40.024    40.163   40.270 27.227                              
DTBP         2.765    2.690    2.396  0.004                               
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                                           TABLE IV                                
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Catalytic Decomposition of DTBP in a Continuous Reactor                   
Notebook Number                                                           
           6773-16-R                                                      
                 6773-93-1                                                
                       6773-93-2                                          
                            6773-93-3                                     
                                  6773-93-4                               
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Catalyst         6773-73-2                                                
                       6773-73-2                                          
                            6773-73-2                                     
                                  6773-73-2                               
Reactor (cc)     100   100  100   100                                     
Pressure (psig)  500   500  500   500                                     
Feed Rate (cc/hr)                                                         
                 100   100  100   100                                     
Temperature (°C.)                                                  
                 120   140  160   180                                     
Time on Stream (hr)                                                       
                 4     4    4     4                                       
Space Vel. (cc/cc)                                                        
                 1.0   1.0  1.0   1.0                                     
DTBP Conv. (%)   40.0  89.4 99.8  99.8                                    
TBA Conversion (%)                                                        
                 0.0   8.0  30.3  39.8                                    
Composition                                                               
IC4         0.004                                                         
                 0.070 0.652                                              
                            1.623 0.522                                   
MEOH/MF    55.922                                                         
                 56.177                                                   
                       54.991                                             
                            54.478                                        
                                  56.550                                  
Acetone     0.002                                                         
                 0.141 0.670                                              
                            0.909 0.915                                   
MTBE        1.218                                                         
                 1.672 5.782                                              
                            13.592                                        
                                  16.318                                  
TBA        39.901                                                         
                 40.071                                                   
                       36.692                                             
                            27.824                                        
                                  24.008                                  
DTBP        2.858                                                         
                 1.716 0.302                                              
                            0.007 0.006                                   
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                                           TABLE V                                 
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Catalytic Decomposition of DTBP in a Continuous Reactor                   
Notebook Number                                                           
           6773-16-R                                                      
                 6773-94-1                                                
                       6773-94-2                                          
                            6773-94-3                                     
                                  6773-94-4                               
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Catalyst         6773-78-2                                                
                       6773-78-2                                          
                            6773-78-2                                     
                                  6773-78-2                               
Reactor (cc)     100   100  100   100                                     
Pressure (psig)  500   500  500   500                                     
Feed Rate (cc/hr)                                                         
                 200   200  200   200                                     
Temperature (°C.)                                                  
                 120   140  160   180                                     
Time on Stream (hr)                                                       
                 4     4    4     4                                       
Space Vel. (cc/cc)                                                        
                 2.0   2.0  2.0   2.0                                     
DTBP Conv. (%)   17.6  62.8 96.8  99.8                                    
TBA Conversion (%)                                                        
                 0.1   5.9  24.5  39.7                                    
Composition                                                               
IC4         0.004                                                         
                 0.036 0.315                                              
                            1.231 1.417                                   
MEOH/MF    55.922                                                         
                 56.084                                                   
                       55.643                                             
                            54.849                                        
                                  56.028                                  
Acetone     0.002                                                         
                 0.078 0.384                                              
                            0.895 1.174                                   
MTBE        1.218                                                         
                 1.512 4.579                                              
                            11.222                                        
                                  14.997                                  
TBA        39.901                                                         
                 39.856                                                   
                       37.539                                             
                            30.112                                        
                                  24.073                                  
DTBP        2.858                                                         
                 2.355 1.064                                              
                            0.091 0.005                                   
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                                           TABLE VI                                
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Catalytic Decomposition of DTBP in a Continuous Reactor                   
Notebook Number                                                           
           6773-16-R                                                      
                 6773-95-1                                                
                       6773-95-2                                          
                            6773-95-3                                     
                                  6773-95-4                               
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Catalyst         6773-78-2                                                
                       6773-78-2                                          
                            6773-78-2                                     
                                  6773-78-2                               
Reactor (cc)     100   100  100   100                                     
Pressure (psig)  500   500  500   500                                     
Feed Rate (cc/hr)                                                         
                 400   400  400   400                                     
Temperature (°C.)                                                  
                 120   140  160   180                                     
Time on Stream (hr)                                                       
                 4     4    4     4                                       
Space Vel. (cc/cc)                                                        
                 4.0   4.0  4.0   4.0                                     
DTBP Conv. (%)   8.5   65.9 98.0  99.9                                    
TBA Conversion (%)                                                        
                 0.3   0.3  12.6  23.3                                    
Composition                                                               
IC4         0.004                                                         
                 0.015 0.211                                              
                            0.777 1.374                                   
MEOH/MF    55.922                                                         
                 56.283                                                   
                       55.845                                             
                            55.313                                        
                                  55.255                                  
Acetone     0.002                                                         
                 0.040 0.418                                              
                            0.806 1.176                                   
MTBE        1.218                                                         
                 1.212 2.524                                              
                            7.090 10.019                                  
TBA        39.901                                                         
                 39.782                                                   
                       39.764                                             
                            34.877                                        
                                  30.610                                  
DTBP        2.858                                                         
                 2.615 0.974                                              
                            0.058 0.004                                   
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                                           TABLE VII                               
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Catalytic Decomposition of DTBP in a Continuous Reactor                   
Notebook Number                                                           
           6773-16-O                                                      
                 6773-96-1                                                
                       6773-96-2                                          
                            6773-96-3                                     
                                  6773-96-4                               
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Catalyst         6773-92                                                  
                       6773-92                                            
                            6773-92                                       
                                  6773-92                                 
Reactor (cc)     100   100  100   100                                     
Pressure (psig)  500   500  500   500                                     
Feed Rate (cc/hr)                                                         
                 100   100  100   100                                     
Temperature (°C.)                                                  
                 120   140  160   180                                     
Time on Stream (hr)                                                       
                 4     4    4     4                                       
Space Vel. (cc/cc)                                                        
                 1.0   1.0  1.0   1.0                                     
DTBP Conv. (%)   15.9  42.1 69.5  99.6                                    
TBA Conversion (%)                                                        
                 0.0   4.5  6.5   29.4                                    
Composition                                                               
IC4         0.004                                                         
                 0.027 0.164                                              
                            0.343 1.172                                   
MEOH/MF    55.631                                                         
                 55.534                                                   
                       55.403                                             
                            55.102                                        
                                  55.344                                  
Acetone     0.000                                                         
                 0.046 0.307                                              
                            0.642 1.267                                   
MTBE        1.213                                                         
                 1.491 3.961                                              
                            4.902 12.041                                  
TBA        40.024                                                         
                 40.477                                                   
                       38.227                                             
                            37.442                                        
                                  28.263                                  
DTBP        2.765                                                         
                 2.324 1.600                                              
                            0.842 0.010                                   
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                                           TABLE VIII                              
__________________________________________________________________________
Catalytic Decomposition of DTBP in a Continuous Reactor                   
Notebook Number                                                           
           6773-16-O                                                      
                 6773-97-1                                                
                       6773-97-2                                          
                            6773-97-3                                     
                                  6773-97-4                               
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Catalyst         6773-92                                                  
                       6773-92                                            
                            6773-92                                       
                                  6773-92                                 
Reactor (cc)     100   100  100   100                                     
Pressure (psig)  500   500  500   500                                     
Feed Rate (cc/hr)                                                         
                 200   200  200   200                                     
Temperature (°C.)                                                  
                 120   140  160   180                                     
Time on Stream (hr)                                                       
                 4     4    4     4                                       
Space Vel. (cc/cc)                                                        
                 2.0   2.0  2.0   2.0                                     
DTBP Conv. (%)   11.9  54.4 95.7  99.6                                    
TBA Conversion (%)                                                        
                 0.0   0.0  13.5  22.8                                    
Composition                                                               
IC4         0.004                                                         
                 0.018 0.130                                              
                            0.626 0.991                                   
MEOH/MF    55.631                                                         
                 55.736                                                   
                       55.431                                             
                            54.634                                        
                                  54.834                                  
Acetone     0.000                                                         
                 0.050 0.339                                              
                            1.002 1.330                                   
MTBE        1.213                                                         
                 1.237 2.351                                              
                            7.479 9.834                                   
TBA        40.024                                                         
                 40.426                                                   
                       40.284                                             
                            34.624                                        
                                  30.896                                  
DTBP        2.765                                                         
                 2.436 1.262                                              
                            0.118 0.010                                   
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                                           TABLE IX                                
__________________________________________________________________________
Catalytic Decomposition of DTBP in a Continuous Reactor                   
Notebook Number                                                           
           6773-16-O                                                      
                 6773-98-1                                                
                       6773-98-2                                          
                            6773-98-3                                     
                                  6773-98-4                               
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Catalyst         6773-92                                                  
                       6773-92                                            
                            6773-92                                       
                                  6773-92                                 
Reactor (cc)     100   100  100   100                                     
Pressure (psig)  500   500  500   500                                     
Feed Rate (cc/hr)                                                         
                 400   400  400   400                                     
Temperature (°C.)                                                  
                 120   140  160   180                                     
Time on Stream (hr)                                                       
                 4     4    4     4                                       
Space Vel. (cc/cc)                                                        
                 4.0   4.0  4.0   4.0                                     
DTBP Conv. (%)   3.5   51.9 97.2  99.8                                    
TBA Conversion (%)                                                        
                 0.0   0.0  8.4   25.4                                    
Composition                                                               
IC4         0.004                                                         
                 0.004 0.111                                              
                            0.690 0.946                                   
MEOH/MF    55.631                                                         
                 55.844                                                   
                       55.256                                             
                            54.848                                        
                                  54.909                                  
Acetone     0.000                                                         
                 0.029 0.340                                              
                            0.839 1.468                                   
MTBE        1.213                                                         
                 1.177 1.801                                              
                            6.045 10.765                                  
TBA        40.024                                                         
                 40.194                                                   
                       40.932                                             
                            36.658                                        
                                  29.871                                  
DTBP        2.765                                                         
                 2.668 1.330                                              
                            0.077 0.006                                   
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                                           TABLE X                                 
__________________________________________________________________________
Catalytic Decomposition of DTBP in a Continuous Reactor                   
Notebook Number                                                           
           6844-32-A                                                      
                 6844-32-2                                                
                       6844-32-3                                          
                            6844-32-4                                     
                                  6844-32-5                               
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Catalyst         3 mm Glass                                               
                       3 mm Glass                                         
                            3 mm Glass                                    
                                  3 mm Glass                              
                 Beads Beads                                              
                            Beads Beads                                   
Reactor (cc)     100   100  100   100                                     
Pressure (psig)  500   500  500   500                                     
Feed Rate (cc/hr)                                                         
                 400   400  400   400                                     
Temperature (°C.)                                                  
                 120   140  160   180                                     
Time on Stream (hr)                                                       
                 4     4    4     4                                       
Space Vel. (cc/cc)                                                        
                 4.0   4.0  4.0   4.0                                     
DTBP Conv. (%)   0.1   4.4  24.6  79.9                                    
Composition                                                               
IC4         0.000                                                         
                 0.003 0.003                                              
                            0.006 0.009                                   
MEOH/MF     0.002                                                         
                 0.018 0.008                                              
                            0.010 0.010                                   
Acetone     0.017                                                         
                 0.091 0.087                                              
                            0.373 1.252                                   
MTBE        0.238                                                         
                 0.236 0.230                                              
                            0.206 0.167                                   
TBA        98.342                                                         
                 98.313                                                   
                       98.334                                             
                            98.428                                        
                                  97.989                                  
DTBP        0.895                                                         
                 0.894 0.856                                              
                            0.675 0.180                                   
__________________________________________________________________________
 
    
     Discussion 
     Tables I, II and III contain the DTBP decomposition data using the rusty iron catalyst (6773-78-1). 
     Tables IV, V and VI contain the DTBP decomposition data using the reduced rusty iron catalyst (6773-78-2). 
     Tables VII, VIII and IX contain the DTBP decomposition data using rusty iron catalyst which has chromium and copper introduced (6773-92). 
     Table X is a comparison example where the reactor is packed with glass beads. 
     The feed for Tables I through IX contains DTBP in a pseudo MTBE reactor recycle stream containing both TBA and methanol; whereas, Table X contains DIBP in almost pure TBA. A comparison of the data (rate of decomposition) is valid since solvents are not expected to have a large effect on the rate of decomposition of DTBP. 
     If one compares the same temperature (140° C.) and the same space velocity (4.0) for the three catalysts: 
     
         ______________________________________                                    
                          DTBP                                            
Table      Catalyst       Conversion                                      
______________________________________                                    
III        Rusty Iron     13.3                                            
VI         Partially Reduced                                              
                          65.9                                            
           Rusty Iron                                                     
IX         CR + Cu Rusty Iron                                             
                          51.9                                            
X          3 mm Glass Beads                                               
                           4.4                                            
______________________________________                                    
 
    
     Thus, rusty iron decomposes DTBP about three times faster than no catalyst (glass beads). Partially reduced iron is a very active catalyst decomposing DTBP about 15 times faster than no catalyst. Rusty iron treated with transition metal salts such as chromium and copper are also effective and catalyze the decomposition of DTBP about 12 times faster than no catalyst. 
     The foregoing examples are given by way of illustration only, and are not intended as limitations on the scope of this invention, as defined by the appended claims.