Catalytic decomposition of formate impurities in tertiary butyl alcohol and methyl tertiary butyl ether streams

FIELD OF THE INVENTION
This invention relates to purification of tertiary butyl alcohol (TBA) and methyl tertiary butyl (MTBE) streams. More particularly it relates to a catalytic process for the purification of tertiary butyl alcohol and methyl tertiary butyl ether streams from organic formate esters and free acids. Still more particularly, this invention allows a high degree of removal of formates and peroxide impurities from TBA and MTBE streams by actual decomposition rather than neutralization.
BACKGROUND OF THE INVENTION
In the operation of a plant producing propylene oxide and methyl tertiary butyl ether one of the byproducts is formic acid. This formic acid may react in downstream operations with methanol or t-butanol to form methyl formate (MeF) or t-butyl formate (TBF). The tertiary butyl alcohol feed to the MTBE reactors may contain as much as 0.4-1.3 wt % of t-butyl formate. Tertiary butyl formate can be converted to methyl formate through the trans-esterification reaction with methanol in the MTBE reactor. In the acidic medium, methyl formate is hydrolyzed to form formic acid and methanol. Formic acid causes severe corrosion problems in the carbon steel vessels. Methyl formate is irreversibly converted to formate salt in a basic medium.
One method of addressing this problem is to neutralize methyl formate by the injection of a strong base such as, for example, KOH or NaOH. The problem with this method is that the potassium or sodium formate, thus formed, is disposed into a waste water stream and the residual caustic in the waste water stream can catalyze a number of undesirable side-reactions to generate C7-C11 ketones from acetone. In addition, the cost of injecting these caustics can be in the multiple millions of dollars.
Peroxide contaminants have been removed from motor-fuel grade tertiary butyl using catalysts. In U.S. Pat. No. 4,705,903, motor-fuel grade tertiary butyl alcohol which is prepared by reacting propylene with tertiary butyl hydroperoxide to form propylene oxide and a tertiary butyl alcohol (tBuOH) reaction product contaminated with residual amounts of tertiary butyl hydroperoxide and di-tertiary butyl peroxide was effectively treated under mild conversion conditions with a catalyst composed of iron, copper, chromia and cobalt in order to convert the two peroxide contaminants to tBuOH.
In U.S. Pat. No. 4,742,179 contaminated motor fuel grade tertiary butyl alcohol is treated with a base-treated hydrogenation catalyst from Groups VIB or VIIIB in order to selectively convert the two peroxide contaminates to tertiary butyl alcohol.
In U.S. Pat. No. 4,873,380, contaminated motor fuel grade tertiary butyl alcohol is treated with a catalyst consisting essentially of nickel, copper, chromium, and barium to substantially selectively convert the two peroxide contaminants to tertiary butyl alcohol.
In U.S. Pat. No. 5,457,243 there is disclosed a method for neutralizing organic acids in a crude methyl tertiary butyl ether stream over solid bases. Disadvantages are that the adsorption capacity of solid bases is generally low and therefor requires an excessively large bed or frequent regeneration of solid bases.
Methyl formate can be decomposed to give methanol and high purity CO by decarbonylation which is represented by HCOOCH.sub.3 .fwdarw.CH.sub.3 OH+CO. In the catalytic decarbonylation of methyl formate, CH.sub.3 OH and CO are desired products and methane and dimethylether are the main by-products. A number of methods are available for decarbonylation of methyl formate. Heterogeneous catalysts such as Al.sub.2 O.sub.3, SrO, BaO, ZnO, zeolite and MgO were reported to be effective. KCl and KOH supported on activated carbon were at one time considered for commercial application by Mitsubishi Gas Chemicals in Japan (T. Ikarashi, Chem Econ. Eng. Rev. 12 (1980) 31, nickel catalysts are also known to catalyze the decarbonylation.
Other researchers have investigated the catalytic decarboxylation of methyl formate over an alkaline metal salt supported on various supports. Active carbon and active carbon supported potassium carbonate showed the highest conversion levels of methyl formate (85.2-88.9%) at 300.degree. C. The selectivity to CH.sub.3 OH was about 86.6%, and to dimethyl ether about 11.2-4.3%. Magnesia-based catalysts were less active, but showed better selectivity toward CH.sub.3 OH with negligible side reactions such as decarboxylation and ether formation.
Hydrogenolysis of methyl formate in the presence of hydrogen gives methanol: HCOOCH.sub.3 +2H.sub.2 .fwdarw.CH.sub.3 OH. This reaction has been extensively studied in both the liquid-phase and/or gas phase. Copper chromite catalysts such as United Catalysts G-89 and Engelhard 1808 are known to provide a good system for the hydrogenolysis of methyl formate. Near equilibrium conversion values (for example <60%) can be obtained at moderate conditions (130.degree.-195.degree. C. and 1 atm). It is noteworthy that decomposition of formic acid to hydrogen and carbon dioxide catalyzed by supported metal catalysts can be achieved with 50% conversion at the same temperature range.
It would represent a distinct advance in the art if there were a method available for removing methyl formate and peroxide impurities from tertiary butanol and MTBE streams in a manner such that these chemicals would not be just neutralized, but would be completely broken down to noncondensible gas products, such as hydrogen, carbon monoxide, carbon dioxide, and methane as well as liquid products such as TBA, MeOH, and isobutylene.
A high degree of removal of formate would reduce consumption of caustic, reduce the potential for corrosion problems caused by formates, alleviate the problem of having high total organic content in the waste water stream and thereby permit a PO/MTBE plant to run at full design capacity.
SUMMARY OF THE INVENTION
In accordance with the foregoing this invention is directed to a method for decomposing the formate esters in tertiary butyl alcohol and methyl tertiary butyl alcohol streams to produce noncondensible gas products which comprises reacting a tertiary butyl alcohol stream or a methyl tertiary butyl alcohol stream containing formate esters over a catalyst comprising an alkali metal, a non-noble Group VIII metal and a metal of Group IB on a support comprising an inert composition mixed with a hydrotalcite-like composition.

DESCRIPTION OF THE DRAWINGS
FIG. 1 Decomposition of organic formates over 50% DHT-4A/alumina catalyst.
FIG. 2 Decomposition of organic formates over 6% Cu, 0.5% Ni catalyst on 25% DHT-4A/alumina support.
FIG. 3 Decomposition of organic formates over 6% Cu, 0.5% Ni catalyst on 50% DHT-4A/alumina support.
FIG. 4 Comparison of catalyst performance between CuNi catalyst and 50% DHT-4A/alumina support.
FIG. 5 Effect of tBA feed rate on formate and peroxide decomposition.

DESCRIPTION OF THE INVENTION
This invention provides a process for purification of TBA and MTBE streams. The formate esters (TBF and MEF) and formic acid as well as peroxides (di-tertiary butyl peroxide �DTBP!) and allyl butylperoxide (ATBP) can be removed by contacting the TBA feed with a hydrotalcite composition/alumina based catalyst containing Group IB and VIII metals. The reactor suitable for this process may be fixed-bed, ebullated-bed or catalytic distillation reactor. The desired process temperature and pressure are 250.degree.-500.degree. F. and 100-600 psi. The total metal content may be in the range of 0-40 wt % of the finished catalyst. The concentration of hydrotalcite composition in the support may range for 5-100%.
The charge stream which may be treated in the instant invention in order to decompose formate esters is a tertiary butyl alcohol or methyl tertiary butyl ether stream. An example is the tertiary butyl alcohol stream obtained from a t-butyl alcohol Day Tank from a PO/MTBE plant which would typically contain about 0.2-1.2 wt % tertiary butyl formate and about 0.1-1.0 wt % organic peroxides.
The catalyst comprises metals of Group IB and VIII on a support.
The catalyst is formed on a support which contains 2-75 parts, preferably 25-75 parts, say 50 parts of inert composition--typically metal oxide-type support such as alumina, silica, silica-alumina, magnesia, titania, etc. The preferred support is alumina, preferably gamma alumina.
There is mixed with the support, a hydrotalcite-like composition of the formula:
�X.sub.a Y.sub.b (OH).sub.c !.sub.n �A!.sub.d.e.H.sub.2 O
a=1-10
b=1-10
c=2 (a+b)=4-40
A is an anion of formal negative charge n
n=an integer 1-4
d is the formal positive charge of �X.sub.a Y.sub.b (OH).sub.c !
e=1-10
X is a divalent metal
Y is a trivalent metal of Group III or Group VI-B or non-noble Group VIII of the Periodic Table,
subject to the qualification that when one of d or n is an integral multiple of the other, they are both reduced to lowest integral terms. This is discussed in U.S. Pat. No. 5,340,466 and U.S. Pat. No. 5,459,118, incorporated herein by reference in its entirety.
The metal X may be a Group II-A metal such as beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), or radium (Ra). The preferred metal is magnesium (Mg). More than one metal X may be present.
The metal Y may be boron (B), aluminum (Al), gallium (Ga), indium (In), or thallium (Tl) of Group III, or iron Fe, cobalt Co, or nickel Ni of non-noble Group VIII, or chromium Cr, molybdenum, Mo, or tungsten W of Group VI-B. The preferred metal is aluminum (Al). More than one metal Y may be present.
a may be 1-10, preferably 3-6, say 4.5.
b may be 1-10, preferably 1-3, say 2.
c may be 4-40, preferably 10-16, say 13.
n may be an integer 1-4, preferably 1-2, say 2.
d may be 1-4, preferably 1.
e may be 1-10, preferably 3-4, say 3.5
A may be an anion such as CO.sub.3.sup.=, halogen eg. C1--, acetate C.sub.2 H.sub.3 O.sub.2 --, oxalate HC.sub.2 O.sub.4.sup.= or C.sub.2 O.sub.4.sup.=, NO.sub.3.sup.--, SO.sub.4.sup.=, or ClO.sub.4.sup.--. The preferred anion may be CO.sub.3.sup.=.
Illustrative hydrotalcite-like (HTlc) compositions may be those noted in the following table--the first listed (hydrotalcite (HT) itself), available under the designation DHT-4A is preferred: ##STR1##
Hydrotalcite �Mg.sub.6 Al.sub.2 (OH).sub.16 CO.sub.3.4H.sub.2 O! is a hydroxycarbonate of magnesium and aluminum and occurs naturally in the Urals of the Soviet Union and also in Snarum, Norway. In 1966 Kyowa Chemical Industry Co., Ltd. succeeded in the world's first industrial synthesis of hydrotalcite. (U.S. Pat. Nos. 3,539,306 and 3,650,704). DHT-4A �Mg.sub.4.5 Al.sub.2 (OH).sub.13 CO.sub.3.3.5H.sub.2 O! is a hydrotalcite-like compound. The first papers in the literature referring to hydrotalcite-like compounds appeared in 1971, written by Miyata et al., dealing with basic catalysts (S. Miyata et al., Nippon Kagaku Zasshi, 92 (1971) 514) and in 1977 by Miyata (S. Miyata, Kogaku Gijutsushi Mol, 15 (10) (1977) 32 and 15 (3) 1971 31).
The preparation, properties and applications of hydrotalcite-type anionic clays are reviewed by F. Cavani et al in CATALYSIS TODAY, Vol. 11, No. 2, 1991. The properties of the DHT-4A product are detailed in the data sheets provided by Kyowa Chemical. The natural product of calcination or activation in inert gas of a HTlc is believed to be a spinel. In the range between the temperature at which HTlc decomposition commences (between 572.degree. and 752.degree. F.) and that of spinel formation (1652.degree. F.), a series of metastable phases form, both crystalline and amorphous. Therefore, the surface area, pore volume, and structure depend on the temperature of calcination. Upon calcination, the crystal structure of DHT-4A is decomposed at about 660.degree. F. when water and carbon dioxide evolved from the structure, and a MgO--Al.sub.2 O.sub.3 solid solution of formula 4.5 MgO.Al.sub.2 O.sub.3 is formed. This solid solution is stable up to 1472.degree. F. MgO and MgAl.sub.2 O.sub.4 are formed at about 1652.degree. F. On the other hand, the solid solution calcined at less than 1472.degree. F. can be restored to the original structure by hydration.
The most interesting properties of the calcined hydrotalcite are 1) high surface area, 2) basic properties, and 3) formation of homogeneous mixtures of oxides with very small crystal size. Miyata et al., showed that there is a maximum in the number of basic sites when the hydrotalcite is calcined at 932.degree. F. Nakatsuka et al. examined the effect of the Mg/Al ratio in the hydrotalcite on the basic strength and the amount of basic sites. (Bull. Chem. Soc. Japan, 52 (1979) 2449). The number of basic sites increased with Mg/Al ratio, while the number of acid sites decreased; however the compound with ratio MgO/Al.sub.2 O.sub.3 of 5.23 exhibited the greatest number of basic sites per unit of surface area. The hydrotalcite and the calcined hydrotalcite have found applications in basic catalysis, hydrogenation of nitrobenzene, oxidation reaction, and support for Ziegler-Natta catalysts. U.S. Pat. No. 4,962,237 discloses a catalytic process for the preparation of polyols using the calcined DHT-4A.
The compositions are available commercially from Kyowa Chemical Industry Co. Ltd. of Kagawa, Japan. The preferred composition is marketed under the trademark DHT-4A having the formula:
Mg.sub.4.5 Al.sub.2 (OH).sub.13 CO.sub.3.3.5H.sub.2 O.
The catalyst support may be formed by mixing 10-840 parts, preferably 200-750 parts, say 300 parts of hydrotalcite-like composition with 360-1190 parts, preferably 500-1000 parts, say 900 parts of inert support, preferably 700-900 parts, say 800 parts of water and 5-40 parts, preferably 10-30 parts, say 24 parts of acid such as nitric acid. After mulling, the mixture is cast or extruded to form cylinders of diameter of about 0.8-1.6 mm, say 1.3 mm and length of 2.5-15 mm, say 3.8 mm. The cross-section of the particles is preferably a trilobar.
The particles are dried at 220.degree. F.-400.degree. F., preferably 220.degree. F.-300.degree. F., say 220.degree. F. for 10-30, preferably 12-24, say 16 hours and thereafter calcined at 1000.degree. F.-1200.degree. F., preferably 1050.degree. F.-1150.degree. F., say 1100.degree. F. for 0.2-3 hours, preferably 0.4-2 hours, say 0.5 hours.
The so-formed composition is typically characterized by the following properties:
TABLE______________________________________Property Broad Preferred Typical______________________________________Total Pore Vol. cc/g 0.5-1 0.7-0.9 0.7Pore Size Dist. cc/g>1500A 0.001-0.02 0.01-0.02 0.011>500A 0.01-0.5 0.01-0.4 0.014>250A 0.01-0.5 0.01-0.02 0.014>100A 0.15-0.6 0.2-0.6 0.22<100A 0.3-0.6 0.35-0.55 0.50Pore Mode Adv/dD Max 55-65 57-63 61BET 55-65 60-65 63Total Surface Area.sup.m2 /g 200-350 220-335 330______________________________________
Preparation of the catalyst of this invention is effected by contacting the support with preferably aqueous solutions of Group I-B and non-noble Group VIII metal. The non-noble Group VIII metal may be iron (Fe), cobalt (Co), or nickel (Ni), preferably cobalt; and the metal may be added, in solution in an amount sufficient to fill the pores of the support--preferably as an aqueous solution of a soluble nickel salt such as the acetate, nitrate, carbonate, etc. The Group I-B metal may be copper, silver or gold, preferably copper employed in an aqueous solution.
The metals may be added simultaneously or sequentially. After addition, the support bearing the metals is dried at 50.degree. F.-100.degree. F., preferably 60.degree. F.-90.degree. F., say 70.degree. F. for 0.5-24 hours, preferably 1-4 hours, say 2 hours, and then at a higher temperature of 220.degree. F.-400.degree. F., preferably 250.degree. F.-300.degree. F., say 250.degree. F. for 1-8 hours, preferably 2-6 hours, say 4 hours. Thereafter the catalyst is calcined at 600.degree. F.-1000.degree. F., preferably 700.degree. F.-900.degree. F., say 800.degree. F. for 1-8 hours, preferably 2-6 hours, say 4 hours, and thereafter at higher temperature of 800.degree. F.-1200.degree. F., preferably 900.degree. F.-1100.degree. F., say 1010.degree. F. for 0.5-5 hours, preferably 1-3 hours, say 2 hours.
The finished catalyst may be characterized as follows (parts by weight):
TABLE______________________________________Property Broad Preferred Typical______________________________________Inert Support 2-75 25-75 50Hydrotalcite-like 25-98 25-75 50CompositionGroup VIII 0.1-5 0.5-3 1Group I-B 1-30 5-25 12______________________________________
A preferred catalyst includes:
______________________________________(i) 25-98 wt %, say 43.5 wt %, of the DHT-4A (fromKyowa Chemical) synthetic hydrotalcite-like compositioncontaining:Mg.sub.4.5 A1.sub.2 (OH).sub.13 CO.sub.3.3.5H.sub.2 O(ii) 2-75 wt %, say 43.5 wt %, of gamma alumina(iii) 0.1-6 wt %, say 1 wt %, of Ni(iv) 1-30 wt %, say 12 wt %. of Cu______________________________________
The percentage figures for Cu, and Ni are % of metal in the finished catalyst wherein the metal is present either in the form of oxide or in the metallic state.
The process of catalytic removal of formates and peroxides was conducted using a fixed-bed downflow reactor made of 5/8" OD.times.17" long stainless steel tubing. 11 cc of catalyst granules having 20-30 mesh sizes was loaded into the center zone of catalyst bed in the reactor. The feedstock used in the catalyst screening is the tertiary butyl alcohol (TBA) obtained from TBA Day Tank of the PO/MTBE plant, which contains typically about 0.2-1.2 wt % tertiary butyl formate (TBF) and about 0.1-1.0 wt % organic peroxides.
The catalyst granules were dried at 200.degree.-600.degree. F. for 2 hours in a stream of nitrogen gas at a rate of 50 cc/min prior to contacting with the feed. The liquid feed rate was varied from 11 to 33 cc/hr (LHSV=1-3). The feed was pumped under 300 psi back pressure. The TBA feed and nitrogen were mixed and preheated at 120.degree.-180.degree. F. before entering the reactor. The reactor temperature was either maintained at constant level while LHSV was varied or raised from 200.degree. to 500.degree. F. when LHSV was fixed at one. The typical test conditions are: nitrogen feed rate 50 cc/hr; TBA feed rate 11 cc/min (LHSV=1; 300.degree. F.; and 300 psi). During the 48-hour test period samples of reactor effluent were withdrawn and the compositions were analyzed by gas chromatography.
Practice of the method of this invention will be apparent to those skilled in the art from the following examples. The examples are only for illustration and the invention is not intended to be limited thereby.
EXAMPLE 1
The catalyst support is prepared by mixing:
(i) Three pounds of DHT-4A powder (from the Kyowa Chemical Industry Co. Ltd. of Kagawa, Japan) having the formula:
Mg.sub.4.5 Al.sub.2 (OH).sub.13 CO.sub.3.3.5H.sub.2 O and
(ii) Nine pounds of alpha alumina monohydrate containing 2 wt % silica as a binder. The moisture content is adjusted by adding 8 pounds of deionized water and 108 ml of 70 wt % nitric acid.
The mixture is mulled to homogeneity and extruded into trilobe cylindrical pellets of maximum width of 1.3 mm and length of about 3.8 mm. The wet pellets are dried at 220.degree. F. for about 16 hours and calcined at 1100.degree. F. for 0.5 hours.
The Total Surface Area (TSA) of this support is 330 m.sup.2 /g and the Total Pore Volume (TPV) by mercury porosimetry is 0.72 cc/g. This support contains 16 wt % MgO and 84 wt % Al.sub.2 O.sub.3 /
Prior to impregnation, the support is dried again at 250.degree. F. overnight (18 hours). The impregnation solution is prepared by dissolving 18 parts of copper nitrate and 2 parts of nickel nitrate hexahydrate in 80 parts of deionized water at 140.degree. F.
The ratio of total volume of impregnating solution to Total Pore Volume (as measured by mercury porosimetry) is about 1.0-1.5:1. The support (30 g) is impregnated with 35 ml of solution. The wet support is permitted to stand at room temperature for 0.5 hours, dried at 250.degree. F. for 2 hours, calcined at 800.degree. F. for 3 hours, and finally calcined at 1000.degree. F. for 1 hours.
The composition and properties of the supports and the finished catalysts are set forth in the Tables infra.
EXAMPLE 2
Preparation of DHT-4A/Alumina with 6% Cu, 0.5% Ni
Support: 50% DHT-4A/Alumina
1. 59.00 grams of copper nitrate, Cu (NO.sub.3).sub.2.2.5H.sub.2 O and 6.50 grams of nickel nitrate, Ni (NO.sub.3).sub.2.6H.sub.2 O, were dissolved in distilled water--The total volume was 335 ml.
2. 251 grams of support was impregnated at room temperature dried at 250.degree. F. for two hours and calcined at 800.degree. F./3-Hrs., 1000.degree. F./1-Hr.
EXAMPLE 3
Support: 25% DHT-4A/Alumina
1. 33.80 grams of copper nitrate, Cu(NO.sub.3).sub.2.2.5H.sub.2 O and 3.75 grams of nickel nitrate, Ni(NO.sub.3).sub.2.6H.sub.2 O, were dissolved in distilled water--The total volume was 165 ml.
2. 144.16 grams of support was impregnated at room temperature, dried at 250.degree. F. for two hours and calcined at 800.degree. F./3-Hrs., 1000.degree. F./1-Hr.
EXAMPLE 4
Preparation of DHT-4A/Alumina with 12% Cu, 1% Ni
Support: 50% DHT-4A/Alumina, SN-7255
1. 15.15 grams of copper nitrate, Cu(NO.sub.3).sub.2.2.5H.sub.2 O and 1.71 grams of nickel nitrate, Ni (NO.sub.3).sub.2.6H.sub.2 O, were dissolved in distilled water--Total Volume 40 ml.
2. Thirty (30) grams of support was impregnated at room temperature, dried at 250.degree. F. for two hours and calcined at 800.degree. F./3-Hrs., 1000.degree. F./1-Hr.
EXAMPLE 5
Support: 25% DHT-4A/Alumina, SN-7097A
1. 15.15 grams of copper nitrate Cu(NO.sub.3).sub.2.2.5H.sub.2 O and 1.71 grams of nickel nitrate, Ni (NO.sub.3).sub.2.6H.sub.2 O, were dissolved in distilled water--The total volume was 35 ml.
2. Thirty (30) grams of support was impregnated at room temperature, dried at 250.degree. F. for two hours and calcined at 800.degree. F./3-Hrs., 1000.degree. F./1-Hr.
RESULTS
The data summary of formate decomposition over 50% DHT-4A/Alumina at various temperatures is presented in Table I. The TBA feed contains at least three kinds of formate esters, namely, 0.63% tertiary butyl formate (TBF) and 0.031% isopropyl formate (IPF) and 0.32% isobutyl formate (IBF). The feed also contains 0.53% di-tertiary butyl peroxide (DTBP) and 0.36% secondary butyl acetate (SBA). The conversions for all five components are shown in Table I. It is seen that TBF removal greater than 90% can be attained at temperature higher than 282.degree. F. Complete removal of di-tertiary butyl peroxide can be achieved at temperature higher than 421.degree. F. Over the temperature range of 200.degree.-500.degree. F., the TBA dehydration is below 30%.
Table II gives the data summary of formate decomposition over 6% Cu and 0.5% Ni on 50% DHT-4A/Alumina at various temperatures. TBF removal greater than 90% can be obtained at temperature as low as 188.degree. F. The catalyst also showed very significant improvement in the DTBP decomposition at lower reactor temperatures compared to the support. This CuNi catalyst exhibited a TBA conversion lower than 20% in the entire temperature range.
In Table III, the catalysts of this invention, Examples I-IV, are compared with the control examples, Examples V-IX for their TBF, DTBP and TBA conversions. The results clearly show that the catalysts of this invention are superior to the control catalysts in TBF and DTBP conversions. The catalytic performance of Example IV catalyst is presented in Table IV. It is seen that the catalyst gave very high activities (>90%) for TBF and DTBP removal at LHSV=1, and 2.
FIG. 1 shows the effect of reaction temperature on TBF and TDBP removal, TBA conversion, and weight percent recovery for 50% DHT-4A/Alumina catalyst (Example I). The decomposition of TBF and DTBP leads to the formation of noncondensible gas products including CO, CO.sub.2, H.sub.2, and CH.sub.4. The dehydration of TBA gives a gas product, isobutylene, and a liquid product, water. When the reaction temperature is increased, the conversions of TBA, TBF and DTBP are increased, and therefore the amount of gaseous products is increased. The weight percent recovery of total liquid product decreases with increasing temperature.
FIGS. 2 and 3 show similar plots for 6% Cu, 0.5% Ni on both 25% and 50% DHT-4A/Alumina, (Examples III and IV) respectively. It is noted that an increased percentage of DHT-4A, because of its basic nature, is less active for dehydration than alumina. Another advantage of DHT-4A is that the amount of undesired ether products such as dimethyl ether (DME), diisopropyl ether (DIPE) formed by dehydration reactions is also less than that for alumina.
In FIG. 4, Examples IV and I are compared for their relative performances to illustrate the advantage of metals in the catalyst. The incorporation of metals, Cu and Ni, significantly improves the activity for DTBE decomposition in the preferred range of process temperature of 250.degree.-400.degree. F. The effect of TBA feed rate (or liquid hourly space velocity) on TBF and DTBP conversions is shown in FIG. 5 for Examples IV and I. It appears that t-butyl formate conversion over CuNi/DHT-4A (Example IV) is almost independent of LHSV, whereas, over 50% DHT-4A (Example I) TBF conversion declines with increased LHSV. For di-tertiary butyl peroxide decomposition, there is no significant difference between the two catalysts in their dependency on LHSV.
TABLE I__________________________________________________________________________Data Summary of Formate Decomposition Over 50% DHT-4A/Aluminaat Various Temperatures WeightBed Percent TBA IPF TBF IBF DTBP SBATemperature Recovery Conversion Removal Removal Removal Removal Removal(.degree.F.) (%) (Wt %) (Wt %) (Wt %) (Wt %) (Wt %) (Wt %)__________________________________________________________________________188 91.5 10.3 37.6 88.4 97.0 61.6 50.5282 90.4 11.5 63.4 82.7 100.0 54.8 63.9373.5 90.7 10.7 100.0 100.0 100.0 88.7 100.0466.5 80.0 26.2 26.4 100.0 100.0 100.0 100.0421 100.3 0.0 67.8 100.0 100.0 100.0 100.0__________________________________________________________________________
TABLE II__________________________________________________________________________Data Summary of Formate Decomposition Over 6% Cu and 0.5% Nion 50% DHT-4A/Alumina at Various Temperatures WeightBed Percent TBA IPF TBF IBF DTBP SBATemperature Recovery Conversion Removal Removal Removal Removal Removal(.degree.F.) (%) (Wt %) (Wt %) (Wt %) (Wt %) (Wt %) (Wt %)__________________________________________________________________________188 105.5 0.0 0.0 92.2 100.0 31.8 100.0235 94.9 4.8 0.0 97.8 100.0 92.0 100.0379 91.9 8.7 100.0 100.0 100.0 100.0 100.0427 93.4 6.9 100.0 100.0 100.0 100.0 100.0475 87.5 15.4 100.0 100.0 100.0 100.0 100.0__________________________________________________________________________
TABLE III______________________________________RESULTS OF CATALYST EVALUATION FOR DECOMPOSITIONOF TBF AND DTBP IN TBA FEED SCREENING OF CATALYSTSUPPORTS TEMP. CONVERSION, WT. %CATALYST .degree.F. TBF DTBP TBA______________________________________50% DHT-4A/Alumina 374 100 89 12Example I 282 93 55 13 188 88 62 1125% DHT-4A/Alumina 370 96 100 13EXAMPLE II 282 96 99 7 189 92 27 10CuNi/25% DHT-4A 378 100 100 16Alumina 284 99 99 14EXAMPLE III 189 83 67 11CuNi/50% DHT-4A 379 100 100 9Alumina 285 98 92 5EXAMPLE IV 188 92 32 10UCI MgO 377 23 68 5Example V 283 18 25 5 188 26 28 11Calsicat MgO 377 90 83 11EXAMPLE VI 284 40 54 8 188 100 26 7Norton ZrO.sub.2 374 69 93 8EXAMPLE VII 285 55 50 15 188 100 38 13TK-753 .gamma./Al.sub.2 O.sub.3 379 65 92 14EXAMPLE VIII 283 51 31 6 188 59 13 8HTC-400 .theta./Al.sub.2 O.sub.3 374 67 98 4EXAMPLE IX 277 47 30 4 189 52 23 5______________________________________ Reaction Conditions: TBA DayTank Feed, LHSV 1.0, 300 psi
TABLE IV______________________________________SUMMARY FOR TBA DEHYDRATION AND CONTAMINANTSDECOMPOSITION OVER 12% Cu, 1% Ni ON SN-7255,50% DHT-4A ALUMINACatalyst ID: 052-95-6949-020, 12% Cu., 1% Ni on SN-7255, 50%DHT-4A AluminaRun No: 095-95-0056-0000 WeightBed TBA TBF DTBP PercentTemperature Conversion Removal Removal Recovery(F) (Wt. %) (Wt. %) (Wt. %) (%) LHSV______________________________________365 2.0 99.0 98.2 96.0 1368 0 93.7 94.6 93.2 2368 8.6 59.1 84.9 72.7 3______________________________________
The data in Tables V and VI indicate that alkalized activated carbons (prior art catalysts) give low TBF removal over a range of temperatures for 220.degree.-353.degree. F. The alkalized activated carbon catalysts are much less effective than the catalysts of the instant invention in the destruction of organic formates and free acids.
TABLE V______________________________________Summary for TBA Dehydration and ContaminantsDecomposition Over Alkalized, Activated CarbonCatalyst ID: Alkalized, Activated CarbonBed TBA TBF WeightTemper- Conver- Re- DTBP Percent SAP SAPature sion moval Removal Recovery No. No..degree.F. (Wt. %) (Wt %) (Wt %) (%) pH = 11 pH = 7______________________________________179 1.1 17.7 1.6 98.8220 5.5 23.6 9.3 95.1 7.87 5.84268 2.4 22.7 35.4 97.3 8.24 5.83284 39.2 52.8 68.0 69.7 8.76 6.23309 53.9 51.5 94.5 91.3 8.02 6.13327 19.2 40.7 98.2 84.5 8.42 5.88______________________________________
TABLE VI______________________________________Summary for TBA Dehydration and ContaminantsDecomposition Over Alkalized, Activated CarbonCatalyst ID: 052-95-2616-0000, Alkalized, Activated CarbonBed TBA TBF WeightTemper- Conver- Re- DTBP Percent SAP SAPature sion moval Removal Recovery No. No..degree.F. (Wt. %) (Wt %) (Wt %) (%) pH = 11 pH = 7______________________________________188 17.9 18.2 2.5 108.5234 46.9 61.7 54.0 64.1 6.31 5.43282 12.3 43.7 54.9 89.8 5.51 4.57308 8.7 46.5 84.6 92.3 5.16 4.37328 6.7 53.5 100.0 93.7 5.18 4.32353 7.6 72.8 100.0 93.2 4.49 3.97______________________________________
In summary, this invention provides a process for purification of TBA and MTBE streams. The formate esters (TBF and MeF) and formic acid as well as peroxides (DTBP and ATBP) can be removed by contacting the TBA feed with a DHT-4A/Alumina based catalyst containing Group IB and VIII metals. The reactor suitable for this process may be fixed-bed, ebullated-bed and catalytic distillation reactor. The desired process temperature and pressure are 250.degree.-500.degree. F. and 100-600 psi. The total metal content may be in the range of 0-40 wt % of the final catalyst. The concentration of DHT-4A in the support may range from 5-100%.

Number	Name	Date	Kind
4916104	Isogai	Apr 1990
5457243	Knifton	Oct 1995

Catalytic decomposition of formate impurities in tertiary butyl alcohol and methyl tertiary butyl ether streams

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