Chemistry of hydrocarbon compounds – Aromatic compound synthesis – Having alkenyl moiety – e.g. – styrene – etc.
Patent
1999-07-27
2000-12-05
Knode, Marian C.
Chemistry of hydrocarbon compounds
Aromatic compound synthesis
Having alkenyl moiety, e.g., styrene, etc.
585436, C07C 120, C07C 132, C07C 1207
Patent
active
061569488
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCES TO RELATED APPLICATIONS
This application was filed pursuant to 35 USC .sctn. 371 and was filed on Jan. 17, 1998 as International Patent Application PCT/EP/98 00244, which in term claims priority under 35 USC .sctn. 119 to German application 19 703 11 1.0, filed Jan. 29, 1997.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable. BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technically simple process for preparing substituted styrenes in the presence of oxide catalysts, in particular metal oxide catalysts.
2. Description of the Related Art
Owing to the great importance of substituted styrenes in industrial and preparative chemistry, e.g. use as monomers and as copolymers in the preparation of polystyrene (e.g. the preparation of p-hydroxystyrene (ACS Symp. Ser. 412(1989)), there are numerous methods for preparing them. However, the processes for the targetted preparation of pure, isomer-free, substituted styrenes are, if available, frequently not optimum.
Thus, for example, it is known that styrene can be prepared from methyl halides and substituted toluenes above 700.degree. C. in the gas phase (U.S. Pat. No. 3,636,182). The high temperatures, up to 1200.degree. C., necessary in the process described favor secondary reactions and also decomposition reactions. Furthermore, hydrochloric acid is formed during the reaction, so that the reactor has to be made of materials which are not attacked even under these extreme conditions. Particular disadvantages are the incomplete conversion and the low selectivity of the process disclosed here.
Furthermore, substituted styrenes can also be prepared from ethyl-benzenes by catalytic dehydrogenation (DE-A 2 317 525). Disadvantages of this process are the usually incomplete conversion of the starting material and the associated separation of the unreacted starting material from the product by distillation. Dehydrogenations of the type described here can only be carried out in special apparatuses and, in addition, ethyl-benzenes are not readily available in industrial amounts.
The preparation of p-substituted styrene derivatives by 1. reaction of para-substituted benzyl halides with triphenylphosphine in chloroform and 2. subsequent reaction with formaline solution and sodium hydroxide is described in Synth. Commun. 6(1976)53. Since the reaction is carried out in solution, this process too results in separation problems during the isolation of the final product after the reaction is complete.
The processes described in the prior art do not give satisfactory results in respect of the conversion of the starting materials or the selectivity of the reaction. Furthermore, the processes described are often associated with high temperatures and a relatively high cost for isolating the pure product.
It is therefore an object of the invention to find a simple and economical process for the selective preparation of styrenes which avoids the disadvantages known from the prior art.
BRIEF SUMMARY OF THE INVENTION
It has now been found that acetophenones can be converted into styrenes in one reaction step by means of hydrogen over an oxide catalyst.
The present invention accordingly provides a process for the selected preparation of a styrene of the formula (1) ##STR3## by reaction of an acetophenone of the formula (2) ##STR4## with hydrogen in the presence of a catalyst comprising one or more oxides, in particular metal oxides, where the oxide comprises an element of groups Ia, Ila, IIIa, IVa, Va, VIA, Ib, IIb, IIIb, IVb, Vb, VIb, VIIb and/or VIII or an element of the lanthanide series. The radicals R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 in the formulae (1) and (2) are identical or different and are each H, F, Cl, Br or I or a C.sub.1 -C.sub.30 -group which may contain heteroatoms, in particular a (C.sub.1 -C.sub.20)-alkyl, (C.sub.6 -C.sub.14)-aryl, (C.sub.1 -C.sub.10)-alkoxy, (C.sub.2 -C.sub.10)-alkenyl, (C.sub.7 -C.sub.20)-arylalkyl, (C.sub.7 -C.sub.20)-alkylaryl, (C.sub.6
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Abstract No. XP-002064376, pp. 881-882, 1985 ( No English ).
Periodic Table of the Elements (SArgent-Welch Scientic Company) 1979.
Borchert Holger
Dingerdissen Uwe
Roesky Rainer
Aventis Research & Technologies GmbH & Co. KG
Dang Thuan D.
Knode Marian C.
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