Synthesis of Ethyl Isoamyl Ketone from sec-butyl Alcohol over Platinum Metals-Metal Oxides Catalysts*

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Synthesis of Ethyl Isoamyl Ketone from sec-butyl Alcohol over Platinum Metals-Metal Oxides Catalysts* by Hiroshi Miyake**, Fujio Suganuma**, Tadashi Matsumoto** and Hiroki Kamiyama** Summary: The

1 Synthesis of Ethyl Isoamyl Ketone from sec-butyl Alcohol over Platinum Metals-Metal Oxides Catalysts* by Hiroshi Miyake**, Fujio Suganuma**, Tadashi Matsumoto** and Hiroki Kamiyama** Summary: The synthesis of ethyl isoamyl ketone from sec-butyl alcohol was studied over various catalysts composed of noble metals and metal oxides. The reaction was carried out by a flow method in vapour phase under atmospheric pressure. Weak solid acids or bases such as ZnO, ThO2, TiO2 and ZrO2 were effective as metal oxide components of the catalysts, but strong acids or bases were not. Pt-ZrO2 was found to be the most active and selective for the reaction. Moreover, the activity of Pt-ZrO2 did not decline during 110 hours run. Experimental results on Pt-ZrO2 were elucidated by the following mechanism. Two molecules of methyl ethyl ketone formed from sec-butyl alcohol react to form 5-hydroxy-5-methylhepta-3-one which is dehydrated and then hydrogenated to form ethyl isoamyl ketone. The rate determining step seemed to be the condensation reaction of methyl ethyl ketone. The acid-base concerted mechanism was proposed for the condensation reaction over Pt-ZrO2, on the basis of the fact that the introduction of acidic and basic materials to the reaction system caused marked decrease of the activity. 1 Introduction It is well known that higher ketones can be synthesized from secondary alcohols with a vapour phase catalytic reaction. Although many in- thyl isobutyl ketone (MIBK) from isopropyl al- about that of ethyl isoamyl ketone*) (EAK) from sec-butyl alcohol (SBA). An old patent2) claimed a process for the production of EAK over a catalyst composed of a mixture of the chromites of zinc, copper and cadmium. Another patent12) described the use of an alumina-copper catalyst. Kawamoto13) reported that EAK is obtained over a precipitated copper. However, all of the catalysts reported for the synthesis of MIBK and EAK seem to exhibit either the low catalytic activity for the formation of EAK or the rapid decline of the activity with reaction time. The present work was carried out in order to find an excellent catalyst for the synthesis of EAK. EAK is known as an useful solvent of high boiling point. 2 Experimental 2.1 Catalysts Pt-ZrO2 was prepared as follows. ZrO2, Na2CO3 and formalin were added to aqueous solution of K2PtCl6. After the mixture had been * Received December 21, 1973 ** Research & Development Center, Maruzen Oil Co., Ltd. (Gongendo, Satte-machi, Saitama ) heated for 1 hour, the black powder formed was talysts were prepared in the similar way. 2.2 Apparatus and Procedure The reactions were carried out in an ordinary continuous flow type reactor under atmospheric pressure. The reactor was a quartz tube of 9 mm inside diameter. Several ml of a catalyst reactor and reduced with hydrogen while the reactor was gradually heated to a reaction temperature. Liquid feed materials were introduced to the reaction tube by a microfeeder, accompanied with hydrogen. Reaction temperature was measured by a thermocouple placed in the center of the catalyst zone. Reaction product was quenched by passing through a trap cooled with dry-ice acetone and was analyzed by gas chromatography. 3 Results and Discussion 3.1 Reaction over Various Catalysts Table 1 shows the results of the reaction of EAK formation over various catalysts composed of metal oxides and platinum metals. Noble metal- ZnO catalysts exhibited stable activities. The activity of Pd-ZnO did not change practically over 160 hours15). Addition of Cr2O 3 to Pd- *) EAK is a mixture of 5 -methylhepta-3-one and 3, 4- dimethylhexa-2-one. The content of the latter in EAK described in this paper is usually a few percents. Bulletin of The Japan Petroleum Institute

2 Miyake, Suganuma, Matsumoto and Kamiyama: Synthesis of Ethyl Isoamyl Ketone from sec-butyl Alcohol Table 1 EAK Formation over Various Catalysts ZnO increased the initial activity but made it unstable. Pd-Al2O3 gave only olefins and no EAK as the reaction product. This may be dehydration of alcohols. Davis et al.11) have been reported that olefins were obtained and that no EAK could be obtained as the reaction product from SBA by the use of noble metal catalysts on alumina having no acidic sites, although MIBK could be obtained from IPA. As shown Al2O3 inhibited the intramolecular dehydration activity and increased the condensation activity. Pt-TiO2 exhibited moderate activity and high stability. Anatase type of TiO2 was active but rutile type was not. Noble metal-zro2 catalysts were found to be the best. As a noble metal component, Pt is likely preferable to Ir, Rh and Pd. Therefore, in the next section, detailed study on Pt-ZrO2 catalyst will be described. 3.2 Reaction over Pt-ZrO Reaction Products Fig. 1 is a gas chromatogram of the reaction products of SBA over Pt-ZrO2. In addition to EAK, several by-products were observed. These are methyl ethyl ketone (MEK), butenes, octenes, 5-methylhepte-3-one, 5-methylhepta-3-ol and Volume 16, No. 1, May 1974 Fig. 2 Effect of Pt Content on Activity higher condensates Effect of Pt Content Fig. 2 shows the effect of Pt content on the yield of EAK. The yield was kept nearly constant over the 0.1% content Selectivity Fig. 3 shows the selectivity for EAK formation over Pt-ZrO2 and Cu-ZnO-Cr2O3 which is a typical catalyst for the condensation of secondary alcohols. Pt-ZrO2 has the selectivity superior to that of Cu-ZnO-Cr2O Change of Catalytic Activity with Reaction Time Fig. 4 shows the change of catalytic activity of Pt-ZrO2 with reaction time, in comparison with that of Cu-ZnO-Cr2O3. In the case of Cu-ZnO-Cr2O3, the yield of EAK decreased gradually with reaction time, that is a typical pattern observed in most catalysts for the condensation of secondary alcohols. On the other hand, in the case of Pt-ZrO2, the yield was almost con-

3 Miyake, Suganuma, Matsumoto and Kamiyama: Synthesis of Ethyl Isoamyl Fig. 5 Order of Reaction over Pt-ZrO2 Fig. 3 Selectivity of EAK Formation Fig. 4 Change of Activity with Reaction Time Fig. 6 Order of Reaction over Pt-ZrO2 Table 2 Comparison of Reactant stant during 110 hours run Feed Materials As shown in Table 2, three kinds of feed, that is, SBA, MEK and their equimolar mixture, yielded practically same amounts of EAK. Accordingly, EAK can be produced from SBA as well as MEK in the presence of hydrogen Order of Reaction As shown in Fig. 5, partial pressure of SBA has no effect on the initial rate of EAK formation. From this figure, the order of the reactoin seems to be zero with respect to SBA partial pressure. Fig. 6 shows a linear relation between conversion to EAK and contact time. This result also indicates that the order of the reaction is zero Effect of Hydrogen The reactions have been carried out in the Feed: SBA-H2-N2, Partial pressure of SBA: 0.18atm, Fig. 7 Effect of Hydrogen on Activity of Pt-ZrO2 presence of hydrogen, because it serves to minimize the decline of the activity. Fig. 7 indicates that the rate of EAK formation is substantially independent of the presence of hydrogen Reaction Mechanism Though there are no reports about the reaction mechanism of EAK formation from SBA, several investigators have discussed that of MIBK formation from IPA or mixture of IPA and acetone. Kudo et al.,4) Kawamoto13) and Davis et al.11) stated that MIBK is produced by the direct condensation between IPA and acetone. However, Murakami et al.10) and Echigoya et Bulletin of The Japan Petroleum Institute

4 Ketone from sec-butyl Alcohol over Platinum Metals-Metal Oxides Catalysts Table 3 Effect of Additive on Rate of EAK Formation al.16) have recently proposed the mechanism that two molecules of acetone formed from IPA react to form diacetone alcohol which is dehydrated and then hydrogenated to form MIBK. Such an aldol condensation mechanism is considered to be applicable to EAK formation over Pt-ZrO2. This is schematically shown as follows. In order to confirm the above scheme, 5- hydroxy-5-methylhepta-3-one or 5-methylhepte-3- one was passed through the catalyst with SBA. Table 3 shows the results. No 5-hydroxy-5- methylhepta-3-one was found, and very small amount of 5-methylhepte-3-one was present in the reaction products. Accordingly, the products were composed of SBA, MEK, EAK, and very small amount of 5-methylhepte-3-one. Substantially, no other component was observed. Therefore, 5-hydroxy-5-methylhepta-3-one and 5-methylhepte-3-one may be considered to be converted almost completely to EAK. These results support the assumption that both the compounds are the reaction intermediates and indicate that steps 3 and 4 proceed faster than step 2. Table 3 also shows that the addition of 5- hydroxy-5-methylhepta-3-one and 5-methylhepte- 3-one have no effect on the rate of EAK formation. These facts can be elucidated by the following assumptions. The active sites for the condensation reaction (step 2) on the catalyst are fully covered with adsorbed MEK molecules. This explains the zero order of the reaction. All the molecules of 5-hydroxy-5-methyl-hapta-3-one and 5-methylhepte-3-one occupy a part of the condensation sites by replacing the MEK molecules until both the compounds change to EAK. This explains the fact that both the compounds were scarcely found in the reaction product. Thus, only the remainder of the sites is available for the condensation of MEK. On the assumption that the rate of EAK formation is proportional to the total number of the sites, the presence of the intermediates in the feed has no effect on the rate. From the above discussion, the rate determining step may be step 2 or the desorption of EAK. If the desorption of EAK is the rate determining step, the addition of EAK in the reaction system must decrease the rate of EAK formation from MEK as a result of the increase of adsorbed EAK molecules and the decrease of adsorbed MEK molecules. As shown in Table 3, that is not the case. Accordingly, step 2 is considered to be the rate determining step. In order to clarify the role of Pt and ZrO2 in Pt-ZrO catalyst, the reactions of MEK and SBA over Pt and ZrO2 were carried out. As shown in Table 4, ZrO2 catalyzed the dehydrogenation of SBA (step 1) and the condensation of MEK to 5-methylhepte-3-one (setp 2 and 3), but did not the hydrogenation of 5-methylhepte- 3-one. Platinum (on aal2o3) catalyzed the dehydrogenation of SBA and the hydrogenation of 5-methylhepte-3-one (step 4), but did not the condensation of MEK. These findings indicate the role of ZrO2 and Pt in the Pt-ZrO2 catalyst. Moreover, the difference of overall rate of condensation between ZrO2 and Pt-ZrO2 can be elucidated as follows. In the case of ZrO2, 5- methylhepte-3-one formed is strongly absorbed on the active site, and the rate determining step is considered to be the desorption of 5-methylhepte-3-one. On the other hand, in the case of Pt-ZrO2, 5-methylhepte-3-one absorbed on the active site is rapidly hydrogenated to form EAK by Pt, and EAK formed on the active site is rapidly desorbed. Accordingly, the rate deter- Volume 16, No. 1, May 1974

5 Miyake, Suganuma, Matsumoto and Kamiyama Table 4 Reaction over ZrO2 and Pt-Metal Oxides Table 5 Effect of Addition of Acid and Base ming step is considered to be changed to step Active Sites for Condensation Generally, solid acids17) and bases18) have been considered to be active for the condensation of ketones. In fact, cation exchange resins19) having strong acid group and some other solid acids are known to be active for the reaction in liquid phase. The authors had found that the order of catalytic activities of various solid bases for the condensation reaction of MEK in liquid phase is consistent with that of their basicities. On the other hand, ZnO, ThO2 and ZrO2 which exhibited high condensation activities in vapour phase reaction, as shown in Table 1, have neither strong acid sites nor strong base ones. They have been reported that ZnO20) and TiO221) have weak acid sites and that ThO222) has both weak acid and base sites. Yamaguchi et al.23) have recently argued that ZrO2 also has both sites, while these had not been detected24) with indicator method. It is shown that Pt-ZrO2 have neither strong acid sites nor strong base ones, because no color changes on Pt-ZrO2 were observed with dimethyl yellow (pka=3.3) and 2, 4-dinitroaniline (pka=15.0). In order to clarify the role of the acidic and basic sites of Pt-ZrO2 on the reaction, acidic and basic materials were introduced into the reaction system. Table 5 shows the results. From the fact that both the acidic and basic materials reduced markedly the activity, it can be deduced that both acidic and basic sites catalyze the reaction. Such acid-base concerted mechanism for aldol condensation of ketone has also been proposed by Sukeno et al.25) References 1) Lassiuer, M. A., Compt. rend., 156, 101 (1913). 2) E. I. dupont de Nemours and Co., U. S. 1,895,516 (1933); 1,999,196 (1935). 3) Ipatieff, V. N., Hansel, V., J. Org. Chem., 7, 189 (1942). 4) Kudo, S., Kogyo Kagaku Zasshi, 58, 785 (1955); Kyowa Ferment. Ind. Co., Japan 32-7,766 (1957). 5) Knapsack-Griesheim A. -G., Brit. 777,508 (1957). 6) Kanemori, T., Kogyo Kagaku Zasshi, 61, 1576 (1958); Kanemori, T., Toosaka, N., Seki, T., Hirai, S., Fujii, R., Matsuda, I., ibid., 61, 1578 (1958); Kyowa Ferment. Ind. Co., Japan (1959). 7) Bolotov, B. A., Dolgov, D. N., Katokova, K. P., Ivanova, L. S., Zhur. Priklad. Khim., 31, 903 (1958). 8) British Hydrocarbon Chemicals, Japan 36-10,963; 36-21,169 (1961). 9) Kawamoto, K., Bull. Chem. Soc. Japan, 34, 161 (1961). 10) Murakami, Y., Onda, Y., Kogyo Kagaku Zasshi, 72, 1033 (1969). 11) Davis, B. H., Venuto, P. B., J. Catalysis, 13, 100 (1969). 12) Shell Development Co., U.S. 2,725,400 (1955). 13) Kawamoto, K., Bull. Chem. Soc. Japan, 34, 799 (1961). 14) N. V. de Battaafsche Petrol. Maatschappij, Dutch 83,028 (1956). 15) Miyake, H., Suganuma, F., Matsumoto, T., Kamiyama, H., Maruzen Oil Tech. Rep., 16, 60 (1971). 16) Echigoya, Y., Hasumi, S., Ann. Meeting Chem. Soc. Japan Preprint, 26th (Spring), 3A42 (1972). 17) Young, R. P., Sheppard, N. J., J. Catalysis, 7, 223 (1967). 18) Tanabe, K., Takeshita, T., Shokubai, 7, 467 (1965). 19) Les Jugis de Mers, Japan (1966). 20) Tanabe, K., "Solid Acids and Bases", 7, (1970) Kodansha. 21) Shibata, K., Yamaguchi, T., J. Res. Inst. Catalysis Hokkaido Univ., 11, 179 (1964). 22) Tomatsu, T., Yoneda, N., Ootsuka, H., Yukagaku, 17, 236 (1968). 23) Yamaguchi, T., Sasaki, H., Tanabe, K., Chemistry Letters, 1973, ) Take, J., Kikuchi, S., Yoneda, Y., Shokubai, 10, 127 p (1968). 25) Sukeno, T., Shirasaki, T., Ann. Meeting Cheṃ Soc. Japan Preprint, 26th (Spring), 2A05 (1972). Bulletin of The Japan Petroleum Institute

The Oxidation Activity and Acid-base Properties of. V2O5-K2SO4-H2SO4 Catalysts* by Mamoru Ai**

The Oxidation Activity and Acid-base Properties of V2O5-K2SO4-H2SO4 Catalysts* by Mamoru Ai** Summary: The vapor-phase oxidation of 1-butene, butadiene, and acetic acid were carried out in the presence