Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1996-05-01
1998-06-09
Geist, Gary
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
568451, C07C 4550
Patent
active
057636788
DESCRIPTION:
BRIEF SUMMARY
This is the U.S. national stage application of PCT/EP 94/01936 filed Jun. 14, 1998 now WO 94/29018 published Dec. 22, 1994.
This invention relates to a chemical process, to apparatus for carrying out the process, and especially to a process carried out in a series of loop reactors, and more especially to hydroformylation carried out in such a series.
U.S. Pat. No. 4,239,930 (Allphin et al., assigned to Pearsall Chemical Company) describes the use of a series of liquid-filled pump-driven loop reactors for oligomerizing .alpha.-olefins in the presence of a promoted boron trifluoride catalyst. Fresh catalyst is pumped into each reactor in parallel, the entire olefin reactant feed being fed to the first reactor in the series.
U.S. Pat. No. 4,342,876 (Klingman, assigned to Bechtel International Corporation) describes the use of a loop reactor, in which circulation is gas-driven with excess gas being vented from the top of the reactor, in the oxidation of p-xylene and mentions the possibility of operating a number of such induced-flow reactors in series.
U.S. Pat. No. 4,312,837 (Papp et al., assigned to Produits Chimiques Ugine-Kuhlmann) describes an improved loop reactor for use in hydroformylation, the effect of the improvement being to retain some gas in the reaction mixture in the downward or return section of the loop. In the Example, the use of a series of three reactors is described.
It has been found, however, that at high throughputs temperature cycling of high amplitude takes place in the lead reactor in a series. These temperature instabilities could not be controlled by external cooling, and throughput reductions were necessary, resulting in a loss of efficiency.
The present invention provides a process for carrying out an exothermic chemical reaction in apparatus comprising a series of loop reactors, which comprises feeding reactants into the first reactor, transferring therefrom mixed reactants and reaction product to the second and any subsequent reactor in turn, and feeding a portion of at least one reactant directly to the second or a subsequent reactor.
More especially, the invention provides a process employing gaseous and liquid reactants, in which the material transferred from the first reactor is a mixture of reaction product and reactants, more particularly both gaseous and liquid reactants. In this case, it is advantageously a portion of a gaseous reactant that is fed directly to the second or subsequent reactor, optionally together with a portion of a liquid reactant.
More especially, the invention provides a process for hydroformylation of an olefin feedstock by syn gas in a series of loop reactors, which comprises feeding the olefin feedstock and syn gas to the first reactor, transferring therefrom mixed hydroformylation products and reactants to the second and any subsequent reactors in turn, and feeding a portion of syn gas directly to the second or a subsequent reactor.
Advantageously, a portion of both the syn gas and olefin feedstock is fed directly to the second or subsequent reactor.
It will be understood that by "directly" in the paragraphs above is meant that the reactant or feedstock is fed to the second or subsequent reactor without its having passed through a previous reactor.
The bypass of gaseous reactant enables the liquid reactant feed rate to be increased. However, at a certain feed rate, temperature oscillations recur, of a type known in the literature as "limit cycles". These are thermokinetic instabilities; at this point the capacity of the first reactor has been reached and liquid reactant is desirably also bypassed to the second or subsequent reactor.
The reader is referred to "Analysis of Limit Cycles in an Industrial Oxo Reactor", Vleeschhouwer, Carton, and Fortuin, Chem. Eng. Sci., 1992, 47, 2547, for a discussion of such temperature oscillations in loop reactors.
The present invention also provides apparatus comprising a series of loop reactors, each reactor being provided with reactant inlet means and product outlet means, the or each product outlet means of
REFERENCES:
patent: 4312837 (1982-01-01), Papp et al.
Beckers Hubertus Jozeph
De Rijke Jan Martin
Garton Ronald Dean
Exxon Chemical Patents Inc
Geist Gary
Hunt John F.
Padmanabhan Sreeni
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