Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
1999-09-15
2001-05-01
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S385000, C585S435000
Reexamination Certificate
active
06225513
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns an improved process for the production of phenol and acetone with oxidation of cumene with subsequent cleavage of cumene hydroperoxide in a reactor with an acidic catalyst and distillative separation of the reaction products.
All existing processes for the production of phenol and acetone from cumene consist of the following most important steps:
1. oxidation of cumene to cumene hydroperoxide (CHP),
2. distillation of the oxidation products and production of the technical CHP,
3. acidic cleavage of the CHP and of the dimethylphenylcarbinol (DMPC) contained therein to give the end products phenol, acetone and ∝-methylstyrene (AMS),
4. neutralisation of the acidic catalyst and separating off of the salts from the reaction products,
5. separation and purification of the reaction products.
As a rule, the research with regard to the process for the production of phenol was carried out with the object of the improvement of only one step of the process. One has thereby not attempted if possible simultaneously to improve the selectivity, energy characteristic value and certainty of the process. The most important characteristic value is the steam consumption.
Since the main amount of undesired by-products is formed in the step of the acidic cleavage of the CHP, most researchers observe, in the first place, precisely this step. In the course of the cleavage of the technical CHP, which contains the reactive DMPC, chemical reactions occur which lead to the loss of end products and to the formation of difficultly utilisable waste products, the so-called phenolic tars.
The most important criterion of the selectivity of the process is the yield of valuable by-products, especially of ∝-methylstyrene (AMS). As is known, AMS can be hydrogenated to cumene or isolated directly as product.
For the increasing of the yield of AMS, there are various possibilities:
a) selection of the composition of the reaction medium (chemical variants).
b) choice of the reactor type and nature of the heat removal (technological variants).
c) combination of the chemical and technological variants.
Our investigations have shown that the catalytic properties of sulphuric acid, which is used as catalyst, in the phenol-acetone reaction medium change by a multiple by the formation of strong bridge bonds between the phenol molecules, as well as between the phenol and acetone molecules, by the change of the ratio of phenol-acetone and by addition of an inert solvent, such as cumene. The change of the activity of the catalyst is also not less strongly influenced by water.
Combinations of varying ratios of phenol:acetone: water:cumene:sulphuric acid lead to qualitative changes of the catalytic properties of this multicomponent reaction medium, as the analysis of our experimental data show, which is illustrated in
FIGS. 1
,
2
,
3
.
These significant changes of the reaction constants of the CHP cleavage are connected in that great changes of the catalytic activity of the sulphuric acid take place in the multicomponent solution. These phenomena demonstrate the changeover from one to another type of catalyst. Actually, it is a question of the change over from a superstrong (magic acid) to a weak catalyst. Herefrom are understandable the great differences in the selectivity in the various patents and technologies in which the composition of the reaction medium is changed. Thus, the yields of AMS amount to about 40-45% of theory in the case of a reaction medium of an equimolar mixture of phenol and acetone (RU 1,361,937).
Description of the Prior Art
In the process according to U.S. Pat. No. 2,663,735, where a large excess of acetone is used and the mole ratio of acetone:phenol is 5:1, the yields of AMS do not exceed 55% of theory.
In the process according to RO 63,168, as reaction medium one also uses an equimolar mixture of phenol and acetone which contains up to 20 wt. % of cumene. In this case, the yield of AMS amounts to about 60% of theory.
In the process according to RO 1,563,181, the reaction medium contains an excess of acetone of 20% and only 1 to 2% of cumene. In this case, the yield of AMS already amounts to about 70% of theory.
In the processes according to the patents U.S. Pat. No. 5,254,751 and U.S. Pat. No. 5,530,166, the yields of AMS reach about 80% of theory. In these processes, one uses a reaction medium which contains up to 20 wt. % cumene and a mole ratio of acetone:phenol=1.5:1. At the same time, one uses for the process a mix reactor and a tubular reactor. It is stressed that the above-mentioned yield of AMS was achieved on the largest operating plant.
One obtains the success which is achieved in the U.S. Pat. No. 5,254,751 and U.S. Pat. No. 5,520,166 in the U.S. Pat. No. 4,358,618 in the case of a cumene content of up to 15 wt. % and equimolar ratio of phenol to acetone (mole ratio acetone:phenol:cumene=1:1:0.23). In this Patent, one uses a combination of a mix reactor and two tubular reactors. The composition of the reaction mixture in all reactors thereby remains constant but one uses a differing temperature range: in the mix reactor 50-90° C., in the tubular reactors 120-150° C.
REFERENCES:
patent: 1109297 (1914-09-01), Lötzsch
patent: 2663735 (1953-12-01), Filtar et al.
patent: 4358618 (1982-11-01), Sifniades et al.
patent: 5254751 (1993-10-01), Zakoshansky
patent: 5530166 (1996-06-01), Zakoshansky et al.
patent: 1915480 (1968-03-01), None
patent: 63168 (1978-04-01), None
patent: 1361937 (1985-11-01), None
patent: 1563181 (1988-07-01), None
Gerlich Otto
Griaznov Andrei Konstantinovitch
Kleine-Boymann Michael
Kleinloh Werner
Michalik Christian
Foley & Lardner
Illa International Ltd.
Padmanabhan Sreeni
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