United States Patent (19 11 Patent Number: 4,603,020 Kojima Et Al
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United States Patent (19 11 Patent Number: 4,603,020 Kojima et al. (45) Date of Patent: Jul. 29, 1986 54). PREPARATION OF ACETYL COMPOUNDS (56) References Cited U.S. PATENT DOCUMENTS 75 Inventors: Hidetaka Kojima; Masahiro 3,813,428 5/1974 Paulik et al. ........................ 562/519 Kagotani, both of Himeji, Japan 3,852,346 12/1974 Forster et al. ...... ... 260/408 4,252,741 2/1981 Porcelli et al. ...................... 260/549 4,374,070 2/1983 Larkins et al. ...................... 260/549 73 Assignee: Daicel Chemical Industries, Ltd., Sakai, Japan Primary Examiner-Natalie Trousof Assistant Examiner-L. Hendriksen Attorney, Agent, or Firm-Flynn, Thiel, Boutell & Tanis (21) Appl. No.: 624,635 57 ABSTRACT An O-acetyl compound, such as acetic anhydride, is 22 Filed: Jun, 26, 1984 prepared by carbonylating the corresponding O-methyl compound, such as methyl acetate, by heating the latter 30 Foreign Application Priority Data at 130 to 250° C. with carbon monoxide of a partial pressure of 1 to 100 kg/cm2 G in the presence of a Jul. 8, 1983 (JP) Japan ................................ 58-124342 rhodium catalyst and a iodine compound, whereby the reaction is caused to take place in a reaction solution 51) Int. Cl." .............................................. C07C 51/54 containing a carboxylic acid in the presence of an alumi 52 U.S. C. .................................... 260/549; 260/546; num accelerator and a rhodium catalyst treated with 502/174 hydrogen. 58) Field of Search ................... 260/549, 544A, 546; 560/232; 562/519 8 Claims, No Drawings 4,603,020 1. 2 examples, compounds containing nitrogen, phosphorus, PREPARATION OF ACETYL COMPOUNDS or arsenic are essential besides the carboxylic acids. Organic compounds such as organic phosphorus BACKGROUND OF THE INVENTION compounds or organic nitrogen compounds and metal 1. Field of the Invention compounds such as chromium hexacarbonyl, which are This invention relates to a process for the preparation more effective among the accelerators used in the prior of O-acetyl compounds such as acetic anhydride by the arts, are lacking in thermal and chemical stability as catalytic reaction of O-methyl compounds, such as well as being expensive, and hence special devices are methyl acetate, as starting material, with carbon mon required in the industrial application of these accelera oxide, using rhodium as a main catalyst. 10 tors to maintain the catalytic activity of them (see Japa Acetic anhydride is used in a large amount as a mate nese Patent Laid-open No. 51036/1980). rial for the production of cellulose acetate and further is SUMMARY OF THE INVENTION useful as a material for pharmaceuticals, perfumes, dye The present inventors have investigated the prepara stuffs and so on. 15 2. Description of Prior Art tion of O-acetyl compounds from O-methyl com Acetic anhydride has been conventionally produced pounds, such as methyl acetate, under mild, conditions on an industrial scale by the reaction of acetic acid with without using organic compounds which are expensive, ketene obtained by thermal cracking of acetic acid. poor in stability and contain elements of the nitrogen On the other hand, in research of so-called C1 chemis 20 group, or special compounds, such as chromium hex try, the production of acetic anhydride by the reaction acarbonyl. of carbon monoxide with methyl acetate or dimethyl This invention relates to a process for the preparation ether has been actively attempted. Particularly, in a of O-acetyl compounds by the carbonylation of O method in which rhodium is used as a main catalyst methyl compounds, with carbon monoxide, in which (Japanese Patent Laid-open No. 30820/1975), the reac 25 the reaction takes place in a reaction solution containing tion proceeds under milder conditions than those in carboxylic acids, in the presence of aluminum accelera which other transition metal catalysts are used, but this tor, an iodine compound and a rhodium catalyst treated method is still insufficient industrially in the reaction with hydrogen. rate, and hence improved methods in which various DETAILED DESCRIPTION OF THE reaction accelerators are added to the rhodium catalyst 30 PREFERRED EMBODIMENTS system have been proposed. The carbonylation of O-methyl compounds accord It is known that, in the carbonylation of methyl ace ing to the method of this invention is considered to tate to acetic anhydride, numerous kinds of metals act as proceed through the carbonylation of methyl iodide an accelerator effective for enhancing the catalytic present in the reaction system. When the method of this activity of the rhodium catalysts when added to rhodi 35 invention is applied to the reaction process comprising um-iodine compounds, typically, methyl iodide catalyst the carbonylation of methyl iodide and the conversion systems. According to Japanese Patent Laid-open No. with the resulting acetyl iodide of O-methyl compounds 52017/1975 (corresponding to British Pat. No. into the intended O-acetyl compounds under substan 1468940), elements having atomic weights of at least 5 tially water-free conditions, for example, to the prepara among those of Groups IA, IIA, IIIA, IVB, and VIB, tion of acetic anhydride from methyl acetate or to the non-noble metals of Group VIII, lanthanide elements, preparation of acetic anhydride and acetic acid from a and actinide elements are considered to be effective, and mixture of methyl acetate and methanol, one can obtain particularly lithium is given as a preferred metal. Japa a greatly improved reaction rate and conversion of nese Patent Laid-open No. 47922/1975 discloses a 45 methyl acetate and, further, the selectivity of acetic method wherein 14 kinds of metal salts such as lithium anhydride is of course good. salts are used. The method of this invention differs from that in Non-metallic compound accelerators are also known, which conventional rhodium catalysis is employed in and organic phosphorus compounds or organic nitro by virtue of the use of aluminum accelerators and rho gen compounds are typical. Further, combination of so dium catalysts treated with hydrogen in the reaction organic phosphorus compounds with metal compounds, liquid containing carboxylic acids, such as acetic acid. such as chromium hexacarbonyl, is known (Japanese These accelerator-catalyst systems are outstandingly Patent Laid open No. 15403/1976). special in that organic nitrogen group compounds, Since, in the preparation of acetic anhydride by car which have conventionally been considered to be sub bonylation, methyl acetate and acetic anhydride them 55 stantially indispensable for achieving an improvement selves act as a solvent, no other solvents are particularly of this kind of a reaction, are not required at all, and that added in most cases, as in the prior arts mentioned rather better yields are obtained in the absence of or above. Examples wherein solvents are used, however, ganic phosphorus compounds. are also known. For example, Japanese Patent Laid As mentioned above, numerous kinds of metals are open No. 47922/1975 discloses hydrocarbons, ethers, 60 known as accelerators, including aluminum compounds ketones, and fatty acids as inert solvents. such as aluminum iodide and aluminum oxide (Japanese Aliphatic carboxylic acids sometimes serve as more Patent Laid-open No. 52017/1975), aluminum chloride than mere inert solvents. For example, Japanese Patent (Japanese Patent Laid-open No. 47922/1975) and alumi Laid-open No. 28980/1980 discloses cocatalysts consist num isopropoxide (Japanese Patent Laid-open No. ing of a combination of picolinium salts with acids and, 65 142234/1981). However, it has not been reported at all further, Japanese Patent Laid open No. 57733/1981, that these aluminum accelerators exhibit a particular No. 99437/1981, and No. 99438/1981 disclose examples effect when used in the carbonylation in combination in which the presence of acids is essential. In all these with rhodium catalysts treated with hydrogen. 4,603,020 3 4 According to the method of this invention, rhodium hodium, and cluster complexes such as tetrarhodium catalysts treated with hydrogen to be combined with dodecacarbonyl. Although the amount of rhodium is aluminum accelerators may be either a catalyst pre not rigidly restricted, the rhodium is used in a concen treated with hydrogen before being supplied into a tration range from 0.1 to 50 mmol/l, preferably from 10 carbonylation reactor, a catalyst treated with hydrogen 5 to 30 mmol/l, in the reaction solution. present together with carbon monoxide in a carbonyla Halogen compounds commonly used in this field, tion reactor, or a catalyst treated with nascent hydrogen particularly iodine compounds, are used in the method generated in a catalyst solution, as in the case where the of this invention. Typically methyl iodide is the most accelerator is added in the form of metallic aluminum. commonly used. Although the amount of methyl iodide Although the carbonylation of methyl acetate in the O is not rigidly restricted, methyl iodide is used in a con presence of hydrogen is well known (Japanese Patent centration range from 0.5 to 10 mol/l, preferably from 1 Laid-open No. 65709/1976, No. 28980/1980, etc), no to 5 mol/l, in the reaction liquid. aluminum was used, and organic nitrogen compounds Aluminum accelerators may be added either as a or organic phosphorus compounds were used in these metallic aluminum or in the form of aluminum con patents. According to Japanese Patent Laid-open No. 15 pounds. The following aluminum compounds, for ex 52017/1975, accelerators can be used either in an ele ample, are used: aluminum salts of carboxylic acids such mental form such as a finely powdered or powdered as formic acid, acetic acid, propionic acid, lauric acid, metal or as a compound, and examples wherein a com and stearic acid, aluminum alcoholates having alkoxy bination of chromium metal powder with aluminum groups such as methoxy, ethoxy, and isopropoxy, alu iodide or aluminum oxide is used are disclosed.