Process for the preparation of dialkyl carbonates
AssigneeBayer Aktiengesellschaft
InventorsHans-Josef Buysch, Alexander Klausener
Life of this patent
Estimating the term…
Abstract
A process for the preparation of dialkyl carbonates is described in which an alkylene carbonate is first formed from alkylene oxides and CO.sub.2 and this alkylene carbonate is then transesterified with alkanols. Both reaction steps are carried out in the presence of a bifunctional catalyst of the formula [A.sub.a -X.sub.b ].sub.m .multidot.[B.sub.c Y.sub.d ].sub.n (I) wherein A, B, X, Y and the indices a, b, c, d, m and n have the meaning indicated in the description.
Claims10
Process for the preparation of dialkyl carbonates from alkylene oxides, CO.sub.2 and alkanols in the presence of a catalyst, characterised in that, in a first step, an alkylene oxide having 2-8 C atoms is reacted with CO.sub.2 in the alkylene carbonate which is to be formed first as reaction medium, at 40.degree.-190.degree. C., preferably at 50.degree.-170.degree. C. and particularly preferentially at 60.degree.-160.degree. C. and a pressure below 10 bar, preferably below 8 bar, particularly preferentially below 5 bar and very particularly preferentially below 3 bar, and, in a second step, the alkylene carbonate thus formed is transesterified with a (cyclo)aliphatic C.sub.1 -C.sub.10 monohydroxy compound, which can be substituted by C.sub.3 -C.sub.6 cycloalkyl or phenyl, at 50.degree.-160.degree. C., preferably at 60.degree.-150.degree. C. and particularly preferentially at 70.degree.-140.degree. C., and under the autogenous pressure, both steps being carried out in the presence of a bifunctional catalyst of the formula
- [A.sub.a -X.sub.b ].sub.m .multidot.[B.sub.c Y.sub.d ].sub.n
- wherein
- A is the cation of a metal which belongs to the
- third period and Group IIa, the
- fourth period and Group IIa, IVa - VIIIa, Ib or IIb, the
- fifth period and Group IIa, IVa - VIIa, IIb or IVb, or the
- sixth period and Group IIa - VIa of the Periodic System of the elements in the short period form,
- X is the anion of an inorganic or organic acid,
- B represents a cation from the group comprising the alkali metal or alkaline earth metal cations, the quaternary ammonium, phosphonium, arsonium or stibonium ions and the ternary sulphonium cations,
- Y is a halide ion, preferably bromide or iodide, particularly preferentially iodide, it being possible for X and Y to change positions if at least one of the anions is bromide or iodide,
- a and b independently of one another represent integers from 1 to 5 and
- c and d independently of one another represent integers from 1 to 3, the requirements in respect of the valencies of the cations and anions for the formation of a neutral salt having to be met, and
- m and n independently of one another assume values of 0.001-1.
Dependencies are inferred from the claim text.