Fixed bed process for clay catalyzed alkylation of aromatic amines
Aromatic amines, for example, diarylamines such as diphenylamine, dinaphthylamine, N-phenyl-N-naphthyl amine etc., are alkylated by passing a mixture of the amine and an olefin, though a clay catalyst in a fixed bed reactor system. The process is conveniently run as a continued process, produces an alkylated aromatic amine in excellent purity and provides efficiencies in material and energy use.
1. A process for alkylating an aromatic amine comprising:
a) loading a tubular fixed bed reactor with an acidic bentonite clay,
b) heating or cooling the reactor at a temperature in a range of from about 140° C. to about 180° C.,
c) pumping through the acidic bentonite clay in the fixed bed reactor a liquid mixture of diphenylamine and a mixture of propylene oligomers comprising tri-propylene and/or tetra-propylene to yield a mixture of alkylated aromatic amines comprising
less than 1% by weight, based on all aromatic amines present, of diphenylamine,
about 15% to about 30%, of mono-alkyldiphenyl amine;
60% to about 80%, di-alkyldiphenyl amine; and
0.5 to about 10% of tri-alkyldiphenyl amine.
2. The process according to claim 1 wherein the mixture of propylene oligomers comprises tri-propylene and the product mixture of alkylated aromatic amines is liquid at room temperature.
3. The process according to claim 1 wherein the mixture of propylene oligomers and the diphenylamine are mixed together before being introduced to the fixed bed reactor through the same feed.
4. The process according to claim 1 wherein the mixture of propylene oligomers and the diphenylamine are introduced to the fixed bed reactor separately through different feeds.
5. The process according to claim 3 wherein the mixture of propylene oligomers and the diphenylamine are mixed together in a vessel and heated at temperatures of from about 40° C. up to the first selected reaction temperature before being introduced to the fixed bed reactor.
6. The process according to claim 1 wherein the mole ratio of propylene oligomers to diphenylamine of from about 2:1 to about 4:1.
7. The process according to claim 1 , wherein the mixture comprising diphenylamine and a mixture of propylene oligomers is pumped through the acidic bentonite clay in the fixed bed reactor, the product mixture is collected at elevated temperature while excess propylene oligomers are continuously stripped out.
8. The process according to claim 7 wherein the excess propylene oligomers are continuously stripped out and fed back into the reactor.
9. The process according to claim 7 wherein the fixed bed reactor is a tube of a shell and tube heat exchanger filled with the acidic bentonite clay where the shell is used to maintain temperature control of the reaction mixture.
10. The process according to claim 9 , wherein the reaction product is fed through heat exchanges as heat exchanger fluid.