US2926191A

US2926191A - Chemical process

Info

Publication number: US2926191A
Application number: US657573A
Authority: US
Inventors: Lawson-Hall Griffiths; Millidge Alfred Frank
Original assignee: Distillers Co Yeast Ltd
Current assignee: Distillers Co Yeast Ltd; Distillers Co Ltd
Priority date: 1956-05-22
Filing date: 1957-05-07
Publication date: 1960-02-23
Anticipated expiration: 1977-02-23
Also published as: FR1175585A

Description

added catalysts.

, 51, 2,926,3 1 CHEMICALPROCESSW mas-Hm; stem, and Amara-'11; Manage, Coulsdon, England, assignors to The Distillers Coma l m ts? nb wfla l British .company Application Ma -7,1957;se rnNo.6s7,s73-

Claims priority, application Great Britain May 22, 1956 scl ims -rciszeo sss I 1 invention relates improvements in a processfor lthe production of C -C acids, .p'articularly iaceticzacid by theliquid-phase oxidationwith molecularoxyg'enof .substantially paraflinic hydrocarbons containing 4-8 car- ,bon. atoms.

The liquid. phaseoxidation-of low' molecular weight parafiins to produce lower aliphatic acids is well known,

Suitable feedstocks include .C to C paraifins, obtained for example .by the-distillation 'of crudespetroleum, and

theseare contacted with molecularzsoxygen at elevated temperatures and pressures in the presence or absence of The acids are suitably recovered from United States Patent the. oxidate by distillation. In one process, described in the British patent specification No. 743,990, theoxidate,

.or the aqueous phase from the'oxidate, is distilled to sep- ..larate the materials. boiling in'.'the-- presen'ce of water below 99 C.-, hereinafter-termed light ends)- before recovering the C we, acids from'the-oxidate,and the light ends..aresubmitted to further oxidation, preferably with fresh hydrocarbon feed.

In the oxidation process as usu'ally described, using air or oxygen-enriched air as oxidising agent, it is found I that, owing to the high volatility of the hydrocarbons, ap-

preciable quantities of hydrocarbons (accompanied by some low-,boilin'g partial oxidation products, e.g'. acetaldehyde) leave the apparatus in the stream'of nitrogenous waste-gas from the oxidation even if this is cooled in conventional water-cooled condensers -'to about 30 C.,

be recycled to the oxidation stage, where they are oxidised to give further yields of acids. Another method proposed for the recovery of these organic materials is to condense them-by cooling the waste-gas to a sufficiently low temperature (below 0 0.) and then to recycle the ;c ondens ate direct to theoxidation; It is found in' practice, however, that cooling in this way leads to theseparation of ice andlor other solid material which causes blockages in the cooling systemand renders.the.operation of such a system technically diflicult or impossible.

tic acid, comprises oxidising at an elevated temperature and this results 'in'a'lower yield of acids per unit weight ..;of.=hydrocarbon fed. It' has been proposed to remove thisorganic material fromthe waste-gas, for example by wscrubbing the waste-gas '(usually underpressure) with ahigh-boili ngoil atatmospheric temperature in a suitable absorber. Inorder'to recoverth is organic material, it mustbethenfstripped from mean 'with'steam or by distillation, usually at a pressure lower than' that used in the absorber; These recovered organic materialsican then and C. derived from petroleum,

2,926,191 Patented Feb. 23, 1 960 "ice with molecular oxygen a paraflin hydrocarbon of 4 to 8 carbon atoms or a mixture thereof in the liquid phase to produce lower aliphatic acids of 1 to 4 carbon atoms,

- distilling the primary oxidation product 'to separate as light ends the materials boiling in thepresence of water below 99 C., contacting at a low temperature the oxidation waste-gases with the light ends whereby organic materials from the waste gas are condensed, and thereafter oxidising the light ends together with the condensed material at an elevated temperature in the liquid phase l with molecular oxygen to produce additional quantities of lower aliphatic acids. In a preferred embodiment'of the invention, the oxidation waste gases are first cooled to about 30 C. to condense out part of the volatile organic materials which are recycled to the oxidation stage, and the waste gases are then contacted with the lightends at a low temperature whereby further organic materials are condensed, the light ends with the'condensed material then being subiected to further oxidation.

'It has been discovered that, in the presence of these vlight ends,*the degree of cooling required'to ensure that substantially all of the organic materials are condensed,

does not result in the deposition of ice or; other solid material. The recovery is aided by working at or near the reaction pressure of the oxidation. The recovered organic material soobtained admixed with or in solution in light ends may be recycled directly to the main oxidation, or

may be oxidised separately.

'In. order to'obtain optimum recovery of the organic materials, the oxidation waste-gases are contacted with the light ends at-a temperature between 1 and --50 C. It is preferred to use temperatures between .-10 and e-40. C. The cooling required may be produced by any known method, e.g. by heat exchanging with chilled brine or with a low-boiling refrigerant liquid, e.g. ammonia or methyl chloride. The light ends maybe precooled before contactingwith the waste-gas, or the cooling may beappliedto the contacting vessel, or both may be cooled. In our preferred method, the waste-gas, after removal of organic materials by they process of the invention, is expanded adiabatically,,for instance in a heat engine, thereby furnishing, by means of suitable heat ex- -changers at least part of the cooling necessary for the process.' p I The process may be varied by cooling the waste-gas .in the presence of light ends containing in solution filtered liquid residues (as defined below), the organic 'material so recovered being then recycled to the oxidation with the light ends and dissolved residues. These residues. are the materials formed in the oxidation having boiling points above about 140 C. which have been subjected to filtration. H a

As, starting material for this process it is, preferred to use a parafiinic hydrocarbon fraction of a boilingrange not exceeding about 100 C. As an example of a suitable starting material may be mentioned a C to C paraffinic hydrocarbon fraction boiling between about 15 The process of the invention is further illustrated by the following example:

Example The oxidation reactor and its ancillary equipment are shown diagrammatically in the accompanying drawing in which the reactor 1 has two air feed points 2 at the base and about the mid-point. Fresh hydrocarbon was introduced continuously by line 3 via pump 4. The reactor was run full, and a mixture of gaseous and liquid reaction products passed out from the reactor by line 5. The liquid products were separated in a separator 6 and returned directly to the bottom of the oxidation tower by line 7. The hot vapour/waste-gas mixture from the Separator 6 was cooled in a cooler 8, and the liquid condensate separated in the separator 9, and fed back into the main liquid recycle via preheater 10. Aqueous reaction product was continuously withdrawn from the system via the cooled separator 11, and reduced to atmospheric pressure through the valve 12. Any separated hydrocarbon layer from the separator 11, returned to the reactor with the rest of the liquid recycle via line 7. The aqueous product from 11 was fed to a continuous still '13 where the light ends were taken off at the head and passed to an intermediate storage vessel 14, the kettle product consisting of acids, water and residues. The kettle product from the still 13 was passed to a second continuous still 21, where the C -C acids and water were taken off at the head through line 22 to a storage vessel 23, and the residues were taken off from the kettle through line 24. The formic, acetic,

propionic and butyric acids were recovered from the product in 23 by fractional distillations. The residues were cooled to below 30 and filtered 25 from the separated solid (largely succinic acid). The liquid residues from 25 were then pumped back to the oxidation,

' but for part of the run this was done by feeding to the storage vessel 14 via line 26 and mixing with the light ends.

The waste-gas containing organic material, still under reaction pressure, passed from the separator. 9 through line 20 into the base of a jacketed packed tower 17 situated at a height several feet above the oxidation tower, and cooled to about +18 C. The light ends from storage 14 were transferred by pump 15 to a cooler 16 under the reaction pressure, where they were cooled to an average temperature of 18 C. and then passed to the top of tower 17. In the tower 17 the waste-gas was brought into intimate contact with the cooled light ends. The waste-gas from which most of the organics had been removed passed out of the top 17, and was vented to atmosphere through valve 18. The solution of recovered organic material in light ends returned by gravity to the reaction system by line 19,- and joining in with the major liquid recycle and hydrocarbon feed to the reactor. i

The feed to the oxidation was a cut from a Middle East petroleum, with a boiling range of approximately 30-70" C., and consisting mainly of parafiinic hydrocarbons. The oxidation was carried out in the liquid phase at a temperature of 175 C. and at 630 lbs./sq. inch, with air as the oxidising agent; no catalyst was added. The waste-gas from the oxidation contained 05% oxygen.

A continuous oxidation carried out in this way for a total period of 196 hours gave the following yields of acids, expressed as parts by weight per 100 parts by Weight of fresh hydrocarbon fed through line 3; formic acid 14.6, acetic acid 67.5, propionic acid 9.4, butyric acid 1.65; total 93.25 parts. 1

By way of comparison with the above example,"whcn .thecorresponding process was carried out, with recycle of both light ends and residues to the oxidation, but 0 with the waste-gas from separator 9 vented to atmosphere without treating in accordance with this invention, the yield of acids obtainedwas much reduced, being as follows: formic acid 11.3, acetic acid 48.1, propionic acid 2.8, butyric acid 0.7; total 62.9 parts per parts of hydrocarbon fed.

We claim:

1. The process for the production of lower aliphatic acids which comprises oxidising at an elevated temperature with molecular oxygen a paraffin hydrocarbon of 4 to 8 carbon atoms in the liquid phase to produce lower aliphatic acids of -1 to 4 carbon atoms and oxidation waste gases containing recoverable organic mater ial-separating the primary oxidation product from the oxidation waste gases, distilling the primary oxidation product to separate as light ends the material boiling inthe presence of water below 99 C.-, contacting at a temperature of 1 to 50 C. said oxidation waste gases with the light ends whereby organic materials from the waste gases are condensed, and thereafter oxidising the light ends. together with the condensed material at an elevated temperature in the liquid phase with molecular oxygen to produce additional quantities of lower aliphatic acids.

.2. The process as claimed in claim 1 wherein the oxidation waste gases are cooled to about 30 C. to condense out part of the volatile organic materials, said part being recycled to the oxidation stage, before being contacted with the light ends at a low temperature.

3. The process. as claimed in claim 1 wherein the oxidation waste gases are contacted with the light ends ata temperature between 10 and 40 C.

4. The process as claimed in claim 1 wherein the light ends containing condensed material from the oxidation waste gases are recycled to the oxidation stage.

5. The process as claimed in claim 1' wherein the oxidation Wastegases are contacted with the light ends at the pressure used in the oxidation reaction.

6. The process as claimed in claim 5 wherein the waste gas after being contacted with the light ends is expanded adiabatically to furnish at least part of the cooling necessary for the process.

7. Theprocess as claimed in claim 1 wherein the oxidationwaste gases are contacted with light ends containing dissolved, filtered, liquid oxidation residues.

8. A process which comprises continuously oxidizing with molecular oxygen a parafiin hydrocarbon boiling at not over 100 C., producing a mixture of aliphatic acids of 1 to 4 carbon atoms, light ends, and oxidation waste gases containing organic matter, said light ends boiling in the presence of water below 99 C., distilling the mixture and collecting acids, light ends and gaseous products separately, cooling such light ends to a temperature between about '-1 to --50.C., washing said gaseous products with such cooled light, ends to form a solution of substances other than waste gas and continuously recycling and oxidizing such solution with-fresh hydrocarbon to produce further amounts of acids, light ends and gaseous products.

FOREIGN PATENTS 743,990 Great Britain Ian. 25, 1956

Claims

1. THE PROCESS FOR THE PRODUCTION OF LOWER ALIPHATIC ACIDS WHICH COMPRISES OXIDISING AT AN ELEVATED TEMPERATURE WITH MOLECULAR OXYGEN A PARAFFIN HYDROCARBON OF 4 TO 8 CARBON ATOMS IN THE LIQUID PHASE TO PRODUCE LOWER ALIPHATIC ACIDS OF 1 TO 4 CARBON ATOMS AND OXIDATION WASTE GASES CONTAINING RECOVERABLE ORGANIC MATERIAL SEPARATING THE PRIMARY OXIDATION PRODUCT FROM THE OXIDATION WASTE GASES, DISTILLING OXIDATION PRODUCT TO SEPARATE AS LIGHT ENDS THE MATERIAL BOILING IN THE PRESENCE OF WATER BELOW 99*C., CONTACTING AT A TEMPERATURE OF -1 TO -50*C. SAID OXIDATION WASTE GASES ARE ENDS WHEREBY ORGANIC MATERIALS FROM THE WASTE GASES ARE CONDENSED, AND THEREAFTER OXIDISING THE LIGHT ENDS TOGETHER WITH THE CONDENSED MATERIAL AT AN ELEVATED TEMPERATURE IN THE LIQUID PHASE WITH MOLECULAR OXYGEN YO PRODUCE ADDITIONAL QUANTITIES OF LOWER ALIPHATIC ACIDS.