Removal of peroxide contaminants from tertiary butyl alcohol

Abstract: Motor-fuel grade tertiary butyl alcohol contaminated with residual amounts of tertiary butyl hydroperoxide, ditertiary butyl peroxide and allyl tertiary butyl peroxide (which is prepared, for example, by reacting propylene with tertiary butyl hydroperoxide to form propylene oxide and a motor fuel grade tertiary butyl alcohol reaction product) can be effectively catalytically treated under mild conversion conditions including a temperature of about 160° to 200°C. with a catalyst consisting essentially of vitrified silica to substantially completely decompose the peroxide contaminants to thereby provide a treated tertiary butyl alcohol product substantially free from contaminating quantities of such peroxides.

Description: This invention relates to a method for the removal of residual contaminating quantities of tertiary butyl hydroperoxide, allyl tertiary butyl peroxide and ditertiary butyl peroxide from a tertiary butyl alcohol feedstock to provide a tert. butyl alcohol product which is useful as an octane-enhancing component for motor fuels. In accordance with the present invention the peroxide-contaminated feedstock is brought into contact with a catalyst consisting essentially of particulate vitrified silica (glass beads) in order to substantially selectively reduce the amount of tertiary butyl hydroperoxide, ditertiary butyl peroxide and allyl tertiary butyl peroxide in the tertiary butyl alcohol. A process for the manufacture of substituted epoxides from alpha olefins such as propylene is disclosed in Kollar U. S. - A - 3,351,653 which teaches that an organic epoxide compound can be made by reacting an olefinically unsaturated compound with an organic hydroperoxide in the presence of a molybdenum, tungsten, titanium, columbium, tantalum, rhenium, selenium, chromium, zirconium, tellurium or uranium catalyst. When the olefin is propylene and the hydroperoxide is tertiary butyl hydroperoxide, propylene oxide and tertiary butyl alcohol are coproducts. U. S. - A - 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 - A - 3,526,645 which teaches the slow addition of organic hydroperoxide to an excess of olefin as preferred. Stein, et al. in U. S. - A - 3,849,451 have improved upon the Kollar process of U. S. - A - 3,350,422 and 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. - A - 3,825,605 and Worrell U. S. - A - 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. - A - 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. ( 232°C.) and in that dehydration becomes rapid at temperatures above about 475°F. ( 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. ( 190° to 244°C.) for a time of from 1 to 10 minutes. The removal of trace quantities of tertiary butyl hydroperoxide and ditertiary butyl peroxide from motor grade tertiary butyl alcohol has received 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 US-A-4,547,598. In some instances, it is proposed to use silica as a support for the catalyst, e.g. Sanderson et al US-A-4,704,482. The silica when used as a support, is normally used in an un-vitrified high surface area form, such as Kieselguhr. The feedstocks of the present invention comprise tertiary butyl alcohol contaminated with tertiary butyl hydroperoxide, ditertiary butyl peroxide and allyl tertiary butyl 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 tertairy butyl hydroperoxide, ditertiary butyl peroxide, allyl tertiary butyl 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 US-A-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. The present invention provides a method for treating a tertiary butyl alcohol feedstock contaminated with residual quantities of tertiary butyl hydroperoxide, ditertiary butyl hydroperoxide and allyl tertiary butyl peroxide, comprising contacting said feedstock in a reaction zone with a catalyst at a temperature of 100°C to 200°C for a period of time sufficient to substantially decompose said tertiary butyl hydroperoxide, said ditertiary butyl peroxide and said allyl tertiary butyl peroxide and recovering from the products of said reaction a tertiary butyl alcohol product containing not more than 100 ppm of tertiary butyl hydroperoxide and not more than 100 ppm of ditertiary butyl peroxide, characterised in that said catalyst consists essentially of vitrified silica. The vitrified silica is preferably in the form of glass beads. The reaction is preferably carried out at a temperature of 160°C-200°C, preferably at a pressure of 0 to 420 MPa (0 to 2000 psig). It is preferred that the feedstock is passed through a tubular reactor containing said glass beads at the rate of about 1 to about 4 volumes of said feedstock per volume of said reactor per hour. The results obtained with the process of the present invention are surprising and unexpected in several respects. Silica is normally considered to be an inert material useful as a support for catalytically active metals, such as transition metals. It has been discovered in accordance with the present invention that vitrified silica has a slight catalytic activity in respect of the decomposition of peroxides such as tertiary butyl hydroperoxide, ditertiary butyl peroxide and allyl tertiary butyl peroxide, 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 principal decomposition product. 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. The motor-fuel grade tertiary butyl alcohol feedstock obtained by the reaction of propylene with tertiary butyl hydroperoxide to form propylene oxide and tertiary butyl alcohol will contain contaminating quantities of tertiary butyl hydroperoxide, ditertiary butyl peroxide, allyl tertiary butyl peroxide and acetone. The normal levels of contamination of such materials are such that the tertiary butyl alcohol will normally contain, prior to treatment, from about 0.0 to about 1 wt.% of tertiary butyl hydroperoxide, from about 0.1 to about 5 wt.% of ditertiary butyl peroxide and about 0.05 to about 2.5 wt.% of allyl tertiary butyl peroxide. Minor quantities of other peroxide contaminants may also be present. As indicated earlier, the reaction conditions used in the catalytic oxidation of isobutane will sometimes result in the formation of ditertiary butyl peroxide. Thus, the feedstock to be used for the practice of the present invention is an impure motor grade tertiary butyl alcohol containing from about 0.0 to about 1 wt.% of tertiary butyl hydroperoxide and from about 0.1 to about 5 wt.% of ditertiary butyl peroxide. The catalyst composition of the present invention consists essentially of vitrified silica, which is preferably used in the form of glass beads, such as beads having average diameters ranging from about 1 to about 10 mm. 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, methanol and isobutylene 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 160° to about 200°C. The reaction is most preferably conducted at 44 to 178 MPa (200 to 800 psig). The tertiary butyl alcohol should preferably be passed over the bed of catalyst at a liquid hourly space velocity of about 0.5 to about 4. 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, isobutylene and/or methanol, 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). EXAMPLES Reactors Reactor (300 cc) The reactor was a stainless steel tube 25 x 760 mm (1" x 30") which was electrically heated. The catalyst bed was 300 cc. Liquid feed was pumped into the bottom of the reactor. Pressure regulation was with a Skinner Uni-Flow® valve and a Foxboro® controller. The liquid feed was pumped with a Ruska® dual drive pump. Reactor (100 cc) The reactor was a stainless steel tube 13 x 736 mm (.51 x 29") which was electrically heated. The catalyst bed (if any) was 100 cc. Liquid was pumped into the bottom of the reactor. Pressure regulation was with a Skinner Uni-Flow valve and a Foxboro controller. The liquid feed was pumped with a Ruska dual drive pump. Feed The feed was a crude TBA stream from the PO pilot plant which was enriched with commercial DTBP. This feed then contained about 0.8% DTBP, 0.4% ATBP, 97% TBA and various other impurities. Thermal Decomposition Data on the thermal decomposition of dilute solutions of peroxides were generated at 160° to 200°C. and space velocities of 1.0 to 2.0. Data are shown in the following tables. Catalytic Decomposition of DTBP in a Continuous Reactor Run No. 1 2 3 4 Catalyst 1mm Glass Beads 1mm Glass Beads 1mm Glass Beads Reactor (300 cc) 150 150 150 Pressure (psig) 500 500 500 Feed Rate (cc/hr) 150 150 150 Temperature (°C) 160 180 200 Time on Stream (hr) 4 4 4 Space Vel. (cc/cc) 1.0 1.0 1.0 DTBP Conv. (%) 97.7 99.1 99.1 ATBP Conv. (%) 100.0 99.4 99.7 TBA Conversion (%) 0.0 0.0 0.0 Composition IC4 0.002 0.007 0.032 0.056 MEOH/MF 0.103 0.106 0.107 0.108 Acetone 1.214 1.780 1.828 1.841 TBA 96.600 97.274 97.231 97.083 DTBP 0.703 0.016 0.006 0.006 IPHP/ATBP 0.360 0.000 0.002 0.001 Catalytic Decomposition of DTBP in a Continuous Reactor Run No. 1 5 6 7 Catalyst 1mm Glass Beads 1mm Glass Beads 1mm Glass Beads Reactor (300 cc) 150 150 150 Pressure (psig) 500 500 500 Feed Rate (cc/hr) 300 300 300 Temperature (°C) 160 180 190 Time on Stream (hr) 4 4 4 Space Vel. (cc/cc) 2.0 2.0 2.0 DTBP Conv. (%) 80.5 99.1 99.1 ATBP Conv. (%) 99.7 100.0 99.7 TBA Conversion (%) 0.0 0.0 0.0 Composition IC4 0.002 0.005 0.012 0.012 MEOH/MF 0.103 0.110 0.108 0.108 Acetone 1.214 1.696 1.825 1.800 TBA 96.600 97.212 97.199 97.229 DTBP 0.703 0.137 0.006 0.006 IPHP/ATBP 0.360 0.001 0.000 0.001 Catalytic Decomposition of DTBP in a Continuous Reactor Run No. 1 8 9 10 Catalyst 3mm Glass Beads 3mm Glass Beads 3mm Glass Beads Reactor (300 cc) 125 125 125 Pressure (psig) 500 500 500 Feed Rate (cc/hr) 125 125 125 Temperature (°C) 160 180 200 Time on Stream (hr) 4 4 4 Space Vel. (cc/cc) 1.0 1.0 1.0 DTBP Conv. (%) 72.3 97.4 99.4 ATBP Conv. (%) 98.6 100.0 100.0 TBA Conversion (%) 0.0 0.0 0.0 Composition IC4 0.002 0.000 0.009 0.019 MEOH/MF 0.103 0.113 0.110 0.115 Acetone 1.214 1.545 1.713 1.768 TBA 96.600 97.166 97.160 97.083 DTBP 0.703 0.195 0.018 0.004 IPHP/ATBP 0.360 0.005 0.000 0.000 Catalytic Decomposition of DTBP in a Continuous Reactor Run No. 1 11 12 13 Catalyst 6mm Glass Beads 6mm Glass Beads 6mm Glass Beads Reactor (300 cc) 125 125 125 Pressure (psig) 500 500 500 Feed Rate (cc/hr) 125 125 125 Temperature (°C) 160 180 200 Time on Stream (hr) 4 4 4 Space Vel. (cc/cc) 1.0 1.0 1.0 DTBP Conv. (%) 55.9 91.7 99.4 ATBP Conv. (%) 96.9 99.7 100.0 TBA Conversion (%) 0.0 0.0 0.0 Composition IC4 0.002 0.004 0.006 0.017 MEOH/MF 0.103 0.113 0.113 0.115 Acetone 1.214 1.421 1.680 1.762 TBA 96.600 97.140 97.174 97.091 DTBP 0.703 0.310 0.058 0.004 IPHP/ATBP 0.360 0.011 0.001 0.000 Catalytic Decomposition of DTBP in a Continuous Reactor Run No. 1 14 15 16 Catalyst 6mm Glass Beads 6mm Glass Beads 6mm Glass Beads Reactor (300 cc) 125 125 125 Pressure (psig) 500 500 500 Feed Rate (cc/hr) 250 250 250 Temperature (°C) 160 180 190 Time on Stream (hr) 4 4 4 Space Vel. (cc/cc) 2.0 2.0 2.0 DTBP Conv. (%) 75.4 100.0 100.0 ATBP Conv. (%) 99.2 100.0 100.0 TBA Conversion (%) 0.0 0.0 0.0 Composition IC4 0.002 0.005 0.012 0.015 MeOH/MF 0.103 0.107 0.108 0.108 Acetone 1.214 1.595 1.775 1.777 TBA 96.600 97.268 97.248 97.246 DTBP 0.703 0.173 0.000 0.000 IPHP/ATBP 0.360 0.003 0.000 0.000 Catalytic Decomposition of DTBP in a Continuous Reactor Run No 1 17 18 19 Catalyst 10mm Glass Beads 10mm Glass Beads 10mm Glass Beads Reactor (300 cc) 150 150 150 Pressure (psig) 500 500 500 Feed Rate (cc/hr) 150 150 150 Temperature (°C) 160 180 190 Time on Stream (hr) 4 4 4 Space Vel. (cc/cc) 1.0 1.0 1.0 DTBP Conv. (%) 93.7 100.0 100.0 ATBP Conv. (%) 99.7 99.7 99.7 TBA Conversion (%) 0.0 0.0 0.0 Composition IC4 0.002 0.004 0.017 0.050 MEOH/MF 0.103 0.237 0.125 0.114 Acetone 1.214 1.729 1.767 1.797 TBA 96.600 97.200 97.313 97.250 DTBP 0.703 0.044 0.000 0.000 IPHP/ATBP 0.360 0.001 0.001 0.001 Catalytic Decomposition of DTBP in a Continuous Reactor Run No 1 20 21 22 Catalyst 10mm Glass Beads 10mm Glass Beads 10mm Glass Beads Reactor (300 cc) 150 150 150 Pressure (psig) 500 500 500 Feed Rate (cc/hr) 300 300 300 Temperature (°C) 160 180 190 Time on Stream (hr) 4 4 4 Space Vel. (cc/cc) 2.0 2.0 2.0 DTBP Conv. (%) 58.0 94.3 100.0 ATBP Conv. (%) 96.7 100.0 100.0 TBA Conversion (%) 0.0 0.0 0.0 Composition IC4 0.002 0.004 0.006 0.010 MEOH/MF 0.103 0.109 0.108 0.108 Acetone 1.214 1.538 1.762 1.785 TBA 96.600 97.226 97.269 97.239 DTBP 0.703 0.295 0.040 0.000 IPHP/ATBP 0.360 0.012 0.000 0.000 Catalytic Decomposition of DTBP in a Continuous Reactor Run No 1 23 24 25 Catalyst Empty Reactor Empty Reactor Empty Reactor Reactor (300 cc) 300 300 300 Pressure (psig) 500 500 500 Feed Rate (cc/hr) 300 300 300 Temperature (°C) 160 180 200 Time on Stream (hr) 4 4 4 Space Vel. (cc/cc) 1.0 1.0 1.0 DTBP Conv. (%) 38.0 92.3 98.7 ATBP Conv. (%) 87.5 99.4 99.7 TBA Conversion (%) 0.0 0.0 0.0 Composition IC4 0.002 0.003 0.006 0.010 MEOH/MF 0.103 0.114 0.116 0.116 Acetone 1.214 1.321 1.682 1.737 MTBE 0.207 0.175 0.142 0.146 TBA 96.600 97.088 97.179 97.144 DTBP 0.703 0.436 0.054 0.009 IPHP/ATBP 0.360 0.045 0.002 0.001 Catalytic Decomposition of DTBP in a Continuous Reactor (Empty Tube) Run No. 1 26 27 28 Catalyst None None None Reactor (cc) 300 300 300 Pressure (psig) 300 300 300 Feed Rate (cc/hr) 600 600 600 Temperature (°C) 170 180 190 Time on Stream (hr) 4 4 4 Space Vel. (cc/cc) 2.0 2.0 2.0 DTBP Conv. (%) 67.5 84.9 95.0 ATBP Conv. (%) 97.3 99.0 99.5 TBA Conversion (%) 0.0 0.0 0.0 Composition IC4 0.002 0.011 0.011 0.012 MEOH/MF 0.036 0.054 0.051 0.052 Acetone 0.216 0.926 1.067 1.166 TBA 96.864 97.173 97.214 97.212 DTBP 0.966 0.314 0.146 0.048 IPHP/ATBP 0.415 0.011 0.004 0.002 Appropriate data taken from Tables I through IX show clearly that glass beads have a weak-moderate effect-on the decomposition of peroxides (in particular DTBP). Glass Beads Diameter, mm Conv. DTBP (%) (Calculated) 1.0 97.7 3.0 72.3 6.0 55.9 10.0 93.7 None 38.0 The decomposition is faster in the presence of glass beads than in an empty reactor. This allows the decomposition to be conducted at lower temperatures. Since more TBA (and less acetone) is formed at lower temperatures, the process may be conducted at lower temperatures.

Claims: A method for treating a tertiary butyl alcohol feedstock contaminated with residual quantities of tertiary butyl hydroperoxide, ditertiary butyl peroxide and allyl tertiary butyl peroxide, comprising contacting said feedstock in a reaction zone with a catalyst at a temperature of 100°C to 200°C for a period of time sufficient to substantially decompose said tertiary butyl hydroperoxide, said ditertiary butyl peroxide and said allyl tertiary butyl peroxide and recovering from the products of said reaction a tertiary butyl alcohol product containing not more than 100 ppm of tertiary butyl hydroperoxide and not more than 100 ppm of ditertiary butyl peroxide, characterised in that said catalyst consists essentially of vitrified silica. A method as claimed in Claim 1 characterised in that the vitrified silica is in the form of glass beads. A method as claimed in Claim 1 or Claim 2 wherein the reaction zone is at a temperature of 160°C-200°C. A method as claimed in any one of Claims 1 to 3 wherein the reaction is carried out at a pressure of 0 to 420 MPa (0 to 2000 psig). A method as claimed in any one of Claims 1 to 4 wherein the feedstock is passed through a tubular reactor containing said glass beads at the rate of about 1 to about 4 volumes of said feedstock per volume of said reactor per hour.

Inventors: PETERS MICHAEL WARREN, SANDERSON JOHN RONALD, SHEU YU-HWA EDWARD, PETERS, MICHAEL WARREN, SANDERSON, JOHN RONALD, SHEU, YU-HWA EDWARD, Sheu, Yu-Hwa Edward, c/o Ind. Technology Res. Inst
Applicants: TEXACO CHEM INC, TEXACO CHEMICAL INC.
Application year: 1993
Main classification: C07C29
IPC codes: B01J21, C07C29, C07C31, C07B61