JPS58189136A - Manufacture of acetic anhydride and acetic acid - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

The present invention provides a net co-producer of acetic acid.
It also relates to a method for producing acetic anhydride with and without Fi. Acetic acid and acetic anhydride have long been known as industrial chemicals. Acetic anhydride constitutes the 24th largest end use of acetic acid and is widely used in the production of cellulose acetate and other cellulose esters. Smaller amounts are used in the production of 1% special esters, aspirin and pesticides. Acetic acid is used as a preservative and as an intermediate in the production of eg acetate esters. Until recently, acetic acid has been produced on an industrial scale almost exclusively by the oxidation of petroleum-derived components. However, production by rhodium-catalyzed carbinylation of methanol is currently gaining increasing importance. Currently, acetic anhydride is produced on an industrial scale either by the reaction of ketene with acetic acid obtained by dehydration of the 18rl acid or by decomposition of acetone (or by the oxidation of acetoldehyde P) (
Vinegar also produces gold). The known shortcomings of these connoisseur routes, coupled with the increasing attention being paid to the chemical synthesis of -carbon oxides and -carbon/hydrogen oxide mixtures. As a result, research into the production of acetic anhydride using these substances has become active. 4 National Special Law No. 1468940 discloses that caldic acid esters satisfying the formula RCOOR or ethers satisfying the formula ROR to within 1 can be prepared in situ or in a separate process using R
COX (In each of the above formulas,
is a hydrocarbon group of 11111i or a hydrocarbon group with 11 curves, and the If substituent is anhydrous in real life. A method for producing monocarboxylic acid/acid anhydride, which consists of inverting ↓δ under the following conditions, is published and wait i? We are looking for f, +11. The acyl halide has the formula FIX (wherein R and
is as determined previously -)'t tn plus... is produced by carbinylation of lornoide, carbinylation is
■ Group metals as catalysts, i.e., ilinium, osmium, platinum, tuyaradium, rhozoum, ruthenium; optionally, an element with an atomic ring greater than 5 from Group 1^, Group IlA, Group IlA, Group VB, ■ Group 8; Non-noble metals of the group and metals of the lanthanides and actinides of the periodic table (among which are suitable gold i!li dilithium, magnesium, calcium. titanium, chromium, iron, nickel, aluminium)
The process is carried out in the presence of an accelerator selected from the following. British Patent No. 1468940 discloses a carmenylation reaction ft
It is stated that it is important that the reaction must be carried out in a substantially anhydrous state, ie that the reaction components must be substantially transferred. British patent no.
By treating methyl acetate with carbon monoxide in the presence of a metal selected from iridium and platinum (hereinafter referred to as a fugitive product) and a free, bonded or bound... The method for using acetic anhydride has been fully described. This specification describes that the reaction is carried out in the absence of water. However, the starting material i may also contain, for example, up to 25 ts of methanol or a small amount of water, up to 5 ts, relative to the total amount of methyl acetate plus methanol. !
In the case of , the method of the patent uses not only acetic anhydride but also
The amount is approximately equivalent to the electricity of methanol or water used once! IO: Also produces acid. (Acetic acid can be separated from the main product, aqueous acetic acid, for example by distillation. A process for producing practically anhydrous methyl acetate from wet methyl acetate containing a significant amount of water by 6-piS
! has been done. This process is particularly suitable for the production of acetic anhydride as described above and in Tomo 4M patent no. It is described as being particularly effective and suitable for the dehydration of methyl acetate to be treated as Pr4. This specification 4 also provides, in claim 6, that methyl acetate is produced by esterification of acetic acid with methanol in an esterification zone, and that the obtained wet methyl acetate is dehydrated and then carbonated. A method for producing acetic anhydride by cardanylation in a dehydration zone/
reacting the tII wet methyl acetate with acetic anhydride in an amount at least substantially stoichiometrically equivalent to the water present in the wet methyl acetate to produce substantially anhydrous methyl acetate and acetic acid. and the step of making the 'jl! a step of sending qualitatively anhydrous methyl acetate and acetic acid to a cargonylation zone;
A step of recovering acetic anhydride and acetic acid from the carmenylation zone, a step of separating acetic anhydride and acetic acid, and a step of recovering acetic anhydride from acetic anhydride. from acetic anhydride to a dehydration zone, said portion being at least substantially chemically equivalent to the water present in the ay methyl acetate sent to said dehydration seam 7; and sending the separated acetic acid to the esterification zone for reaction with methanol to produce the wet column methyl acetate. The object of the present invention is to provide an integrated single esterification step;
In the carmenylation step and separation step. Co-production of acetic acid from methanol and carbon monoxide as essential feedstocks fp
fh Tsutema-ku is an improved production method for producing acetic anhydride without halving, in which the esterification reaction product containing methyl acetate and water is subjected to extensive nit production or oxidation before being sent to the carzanylation step. An object of the present invention is to provide an improved manufacturing method that does not require dehydration. ＋The method of the invention includes methanol and −

[Co-product of normal bed of acetic acid from enriched carbon]
A method for producing acetic anhydride that is not crushed or halved using 1) In the esterification step, methanol gold recycling = *v
2) removing a portion of the water from the esterification product; 3) removing a portion of the water from the esterification product; 3) removing a portion of the water from the esterification product; In a chemical process, the esterification product still containing water is converted to carbon monoxide in the presence of a free or bound metal carnonylation catalyst as a catalyst and free or bound/% Rodan as a promoter. 4) reacting the carbonylated product with acetic acid and acetic anhydride to form a car-nylated product comprising acetic acid and acetic anhydride; a low boiling point fraction containing an accelerator component, tIi acid and anhydrous vinegar elR
5) separation into a low-boiling fraction containing a car-nylation product and a carbonylation accelerator component, and a car-nylation catalyst component, and a car-nylation catalyst component; 6) recycling at least a portion of the acetic acid fraction to the esterification step; and 6) recycling at least a portion of the acetic acid fraction to the esterification step. As for the individual steps, in esterification process 5(1), methanol is reacted with recycled acetic acid to form an esterification product containing methyl acetate, water, and unreacted methanol. In a preferred embodiment, recycled acetic acid forms substantially all of the acetic acid in the feed to the esterification step. It is an advantage of the present invention that the methanol (recycled acetic acid also does not have to be essentially pure). Thus, the methanol can be contaminated with water, for example, and the recycled acetic acid can be contaminated with water, e.g. may include car-nylation catalyst components such as methyl acetate, acetic anhydride, and alkyl halides (e.g., methyl iodide), although if desired, the esterification step can be carried out without a catalyst. It is preferred to use a catalyst, and the catalyst used can be any commonly used Il!II catalyst.Suitable esterification catalysts include acid buffing acids such as sulfuric acid and sulfuric acids such as p-toluenesulfonic acid. Alternatively, other esterification catalysts can be used if desired, such as ionic fathers. The esterification medium suitably contains 0.1 ~10 stacks, preferably ri
It can be present in an amount of 2-6% by weight. The esterification step can be performed in various ways. Thus, a feed mixture containing excess methanol and recycled acetic acid can be fed continuously under reflux conditions to an esterifier containing a tFi dense aqueous acid catalyst. A mixture of methyl acetate, water and excess methanol can then be taken overhead as the distillate product. 2:1 molar ratio of methanol: 6! l! A typical ester trade product obtained from the feed contains 57.5 parts by weight of methyl acetate, 27.931 parts by weight of methanol, and 13.8 parts by weight of water. A portion of the water can be removed from the product by azeotropic drying and, if desired, methanol can be taken off for recycling by hydro*electron K. For recycling, additional distillers can be used for recovery of methanol from the hydroselection bottom product and recovery of methyl acetate from the decanter aqueous phase/entrainer. Alternatively, the method described in JP-A-57-181036@IIC can be used as appropriate. In this method, methanol is reacted with acetic acid at elevated temperature in the presence of an entraining agent and an esterification catalyst that is soluble in water and forms a minimum s, a azeotrope with water. A product containing water, water, and an entraining agent is produced, and an overhead fraction containing methyl acetate, an entraining agent, and water is distilled from the product mixture in a first column, and water is removed from the methyl acetate and entraining agent. After separation, the methyl acetate is recovered from the entraining agent in a second column by distillation V. Preferably 4? The method described in JP-A-57-181037 is used. In this method, methanol is reacted with acetic acid at high temperature in the presence of water [an entraining agent that elutes and forms a lowest boiling azeotrope with water and an esterification catalyst] to form methyl acetate and water. is produced, and in a distillation column, methyl acetate is recovered as an overhead fraction, and a liquid containing water and entraining agent is taken off from the middle of the column. JP-A-57-181036 mentioned above and 4! 1977-
The entraining agent VC that can be used in the method described in JP 1131037 includes hydrocarbons, ethers, esters, and ketones, but butyl acetate is preferred. These methods are described in detail in the above-mentioned British patent specification, which description is incorporated herein by reference. Another method for carrying out the esterification process is ICE
By esterification. This mode of operation uses a single distillation column. Acetic acid is fed near the top of this distillation column, methanol is fed near the bottom, and if necessary, a small stream of water is added to augment the methanol/methyl acetate separation tube, with methyl acetate as the overhead product. , and water is removed as a bottom product. The distillation column may be packed with an acid ion exchange resin catalyst or a liquid acid catalyst such as sulfuric acid may be fed to the column. In step (2), a portion of the water is removed from the esterification product. In one preferred embodiment, the removal of water from the esterification step is carried out by removing water from the reactor over which the esterification occurs.The reactions that are believed to occur are as follows. 2CH30H+2CH'3COOH→2C)45CQO
CH3+ 2H20(2) Car-nylated 2CH3COOCH3+ 2CO→2(CH3CO)2
0 (31 water use (CH, Co), 20 + H20 → 2CH3Coot
−1 So the overall equation is 27C830H+ 2CO → (CH3CO)20 +
It is H2O. As can be seen from the formula after iIk, if some water is removed, 6-acid anhydride will be obtained. The yield of acetic anhydride is higher than that of acetic acid, which has a larger proportion of water removed. Since the aim of the invention is to co-produce acetic acid and acetic anhydride (C0prOduC), the important thing is to remove part of the water, but not all of it. Preferably, the water content is reduced to less than 14 gw relative to the weight of the ester + water alcohol (if present), or less than the equivalent of water and methanol, such as less than 12 g. 1, but preferably there is at least 6 weights of water, more preferably at least 7 weights, relative to the amount of ester+water alcohol. In step (3), the esterification product, which mainly contains ethyl acetate and optionally unreacted methanol, and still contains water, is used as a catalyst in a cal/nylation process. or react with carbon oxide in the presence of a bound metal cal/nylation catalyst and free or bound carbon as promoter to form cargenylation products including acetic acid and acetic anhydride, as known Any metal carnonylation catalyst can be used. Suitable gold 114Vc includes gold IA of group 1 of the periodic table of elements, among which the noble metals iridium, osmium, platinum, radium, rhodium, and ruthenium are preferred. Rhodium is particularly preferred. Preference is given to using the metal in the form of a soluble salt, such as a ronium halide, or in the form of a maple complex, such as a carbonyl complex. As a promoter, free form 19 and bound form 710rn are used. In a suitable form, elemental 7
10rn, 10denated water bulk, inorganic 4 (such as) sodium rhodanide or potassium halodide or cobalt halides) and quaternary ammonium or phosphonium halides (?11e or tetrahalodide) (such as methylammonium). Preferred promoters for t# are organic halodides such as alkyl halides (eg methyl iodide) or aryl halides. Particularly preferred is methyl iodide. Suitable reaction components and operating conditions are described in British Patent No. 14, supra.
Details V in No. 68940 and No. 1.523.546
c is described. It is particularly preferred to use a co-promoter (ω-p "tars").A suitable co-promoter (co-p)
promoters) VCn, metals such as norconium in free or bonded form and the above UK%
468941:1, such as lithium, magnesium, calcium, titanium, chromium, iron, nickel, aluminium, alkyl or arylphosphines and the above mentioned British Patent No. 152554.
6 and heteroaromatic compounds in which at least one heteroatom is a quaternary nitrogen atom, as described in European Patent No. 8396-q, or e.g. Included are precursors of heteroaromatic compounds in which at least one heteroatom is a quaternary nitrogen atom, such as N-methylimidazole. Other suitable accelerator systems are for example British Patent No. 4,153,8783 and published nine British Patent Applications Nos. 2,059,794, 2,047,557 and European Patent Application Nos.
s 2628Q. In one embodiment, the carnonylation product from the process is separated by fractional distillation into an overhead fraction of the carbonylation feed and the carnonylation-biased component 4j in the first separation step. , an intermediate fraction containing ha and black water acetic acid, and a cal/
The lower fraction containing the nylation catalyst component is separated by VC, and the column top 1
The fraction and bottom fraction are recycled to the carnonylation step:
The intermediate fraction is separated into a naI product fraction and an acetic anhydride product fraction by fractional distillation rC in the #IJ2 separation step.
All of the residue and a portion of the acetic acid product fraction are recycled to the esterification step. In step (4), the carnonylation product is subjected to fractional distillation to separate a low-boiling point compound containing a carbonylation co-supplate and a carnonylation-promoting cutting component, acetic acid and anhydride, and a carsenylation catalyst component. It is separated into a high boiling point fraction containing In one preferred embodiment of the process, ffl +41, (5), (6), the carnonylation product, comprising the carnonylation process product and the carnonylation promoter component, is separated by fractional distillation in the m1 separation step. Separate into an overhead fraction, an intermediate fraction containing acetic acid and acetic anhydride, and a lower fraction containing a carnonylation catalyst component, and recycle the overhead fraction and the lower fraction to the carnonylation step. , and the intermediate fraction is divided by fractional distillation into an acetate product fraction and an anhydrous encIR fraction, and at least a portion of the acetate product fraction is recycled to the esterification step (41 is suitably sends the carnonylation product to a flash zone from which it extracts mainly acetic acid and acetic anhydride, but also the metal catalyst components present in the product and some co-promoters. a liquid product comprising acetic acid and anhydrous I!r! acid and a volatile carnonylation promoter and a volatile product comprising a powder component (e.g. an alkyl halide such as methyl iodide) and methyl acetate. and, optionally,
- Applying a partial pressure of carbon oxide and/or hydrogen within the flash zone to help maintain catalyst activity. Further details are given in GB 2037276A, which describes , hereby incorporated by reference. The volatile fraction is suitably sent to a distillation column where the volatile calcining promoter and feed components are combined with a small amount of acetic acid. 61) and acetic anhydride are removed from the top of the column together with acetic anhydride and recycled to the carnonylation zone. The liquid residue containing the carbenylation catalyst components can be discharged from the bottom of the column for recycling to the carbenylation zone along with the liquid product from the flash zone. If the catalyst carryover from the fluoridation stage is acceptable, it contains less low-boiling impurities. y, acid/acetic anhydride can be taken from the bottom of the distillation column. 41Af containing acetic acid and black water acetic acid
lt and the bottoms stream are then sent to a second distillation column from which pure acetic anhydride is removed as a bottom product and 111 tl of impure acetic acid as an overhead product. This impure
The acetic acid column overhead is acid +1! /Depending on whether the acetic anhydride is taken as a side stream from the distillation column or as a bottom product, it may contain some black water acetic acid and small amounts of methyl acetate and methyl iodide. ,next,
P+ is added directly to the esterification process. If desired, a portion of this vinegar elf can be withdrawn and made into TfI in another distillation column to produce pure acetic acid. In the following, the process of the present invention will be described as a simplified method for the production of acetic acid and acetic anhydride from methanol and carbon monoxide in a series of integrated esterification, carnonylation and separation steps. Further reprints are made with reference to the accompanying drawings showing flow sheets. In this process, the esterification step is carried out entirely continuously in a single distillation column xoI& with rhodityl acetate as internal entrainment agent, and water is removed from line 4 by side decantation. The internal entrainment agent is recycled to the distillation column. Recycled tri-acid is fed to the kettle from line 2, along with at least equimolar amounts of methanol from line 3, and a mixture of methyl acetate and some water and unreacted methanol is fed to the line as an overhead product. 5 and sent directly to the carnonylation reactor 6. In the carnonylation reactor 6, the esterification product is mixed with the rhodium hydrogenylation catalyst recycled from line 13, the methyl chloride promoter recycled from line 2, and the methyl chloride promoter recycled from line 13. It reacts with the carbon monoxide fed to the reactor from line 7 in the presence of the N-methylimidazole co-promoter (co-promot@r) which is recycled as a quaternary ammonium salt. Initial catalyst components are charged through line 8, but line 8 is also used for subsequent replenishment. The cargenylation reaction product, consisting mainly of acetic anhydride, acetic acid, unreacted methyl acetate, and a small amount of methyl iodide, is produced in line 10.
into a separation zone 11 in which the low-boiling overhead self, containing the carzanylation feed and the intermittent promoter component, is recycled by line 12 to the carbonylation reaction tI6, and the carboxyl. contains the calgenylation catalyst component and is recycled to the calgenylation reaction 'a6 by line 13, and the high-boiling bottom product containing the calgenylation catalyst component is withdrawn as a liquid stream by line 14 and It is separated into a vinegar d/acetic anhydride heated fraction which is sent to a separation zone 15. In the reactor 15, the acetic acid/acetic anhydride product is recycled to the esterification reactor 1 in line 6 by fractional distillation.
The impure acetic acid 4 overhead fraction is collected and the bottom raw ti
i, the acetic anhydride product fraction, which is collected as a proboscis. The net rn# product from line 16 can be further selected if desired. Examples are given below. In each example, parts are parts by weight or parts by weight per hour. Example 1 In this example, the esterification product was carried out continuously in the reaction kettle of a 31-stage Oldershaw column. Tray 16 was a chimney tray with side stream liquid withdrawal. Next, 3130 parts of methanol was fed into a reaction kettle containing a reflux mixture consisting of 520 parts of #1, 235 parts of n-butyl acetate as an internal entrainment agent, 10 parts of water, and 40 parts of methanesulfonic acid catalyst. The temperature was maintained at t-80-90°C in tray 15. Cool 1iIflL from the chimney tray and r
Separate the two phases Vζ with a canter. The lower oil phase containing the entrainment agent was returned to tray 415. 1925 parts of aqueous phase were discharged via line 4. Recirculated acetic acid (5450f
R1) was supplied to the reaction kettle via line 2. After maintaining the reflux to the column at 5=2, methyl acetate 650Qi
A mixture of S, 200 s of water and 150 parts of methanol was removed as an overhead product via line 5. To this product in line 5 is added 220 parts of methyl acetate and 70 parts of methanol, corresponding to the material that can be recovered in a single stripping step from the wastewater stream of line 4, and 550 parts of water to the carnonylation reactor 6. The total amount of water in the feed is 9.8-
I made it. The reactor 6 is a stirred autoclave made of corrosion-resistant material, in which methyl acetate reacts with carbon monoxide dispersed by line 7. This reactor contained 14 parts of rhodium, designated as diacetate rhodicum, and 40 parts of norconyl diacetate and N, N/- iodide.
Tsumethylimida! Mixture 4 containing 215 parts of Limium
It held 290 copies. The remainder was methyl acetate, acetic acid, acetic anhydride and acetophuninone as a high boiling solvent. The carnonylation reactor was maintained at a temperature of 1830° C. and a total pressure of 50° C.
It was also used for any supplementation after i. fn acid anhydride as king,
Acetic acid, methyl iodide, solvents and hydrogen! 9. The cargenylation reaction product consisting of 5-methyl acetate is sent via line 10 to separation zone 11. The separator was maintained at a pressure of 3) Cool absolute. Contains all of the above ronium catalyst, zirconium promoter and quaternary ammonium salt promoter. % fluoropolymer bottom product with the above acetophenone and some I
! r1: Recirculated to carnonylation reactor 6 via line 13 together with acid and acetic anhydride. The low-boiling overhead fraction containing unreacted erF, the majority of the carbinylation feed being methyl acid, and a significant amount of unquaternized methyl iodide promoted series is passed through line 12 to carnonylation reactor 6.
Recirculate to the next. Minjl! Flash stage i'4 of band 11
The mixture IC1.49G of cy acid and acetic anhydride vaporized at a temperature of about 1350° C. was recovered as a middle distillate by a fluid side stream and sent to separation zone 15 via line 14vc. ''! It was a 40-stage Orgusho column with a feed point in tray 15 maintained at a temperature of 126°C to give a temperature of 146°C and a top temperature of 118°C. 5050 parts of product were recovered via line 17. The column reflux was adjusted to 2:1 and 5460 parts of Vinegar #I overhead relative containing traces of methyl acetate and methyl iodide was recovered via line 1.
Obtained by 6. All of the acetic acid was recycled 4 to the esterification column 1 via line 2. Example 1 was repeated except that the water in line 5 going to the carnonylation step was brought to 955 mVc to correspond to part 12.1 of the carnonylation feed. In this case, 10,640 parts of a mixture of acetic acid and acetic anhydride were added to the separation zone 1.
1 and supplied to the separation zone 15 via line 14. 5,845 parts of acetic anhydride was added as product to line 17.
and 1360 parts of net acetic acid product were recovered via line 16 for use or for splitting from the required VC. The above method has the following nine advantages. Esterification, r: The rounded acetic acid (or at least a significant portion of it) sent to Sugi is directly removed from the separation process (separated from acetic anhydride in the separation process) without any further treatment. ! Sent to i&c esterification process. This means that the esterification feed is not dependent on recovered acetic acid from subsequent operations involving the use of acetic anhydride. This method provides flexibility in the ratio of #1/acetic anhydride and does not require a separate facility to hydrolyze the anhydrous non-acid to acetic acid. The esterification product is sent directly from the esterification reactor (from which water is removed) to the calization reactor without any treatment such as purification or drying.

[Brief explanation of drawings]

Attached are nine simplified flow sheets for the production of acetic acid and acetic anhydride from methanol and carbon monoxide in a series of integrated esterification, carnonylation and separation steps. be. Diagram [Explanation of fi number 1... Distillation column, 6... Carnonylation reactor, 1]
...Separation band, 15...Minute m band procedural amendment (method) familiarization (18 Showa year) Director General of the Japan Patent Office! Display of the case Showa 3J year Patent application No. 226
B ≠ No. 2, Title of the invention: Acetic anhydride and method for producing acetic acid 3, Relationship with the case of the person making the amendment: Name of the applicant: BP Chemicals Limited 4.
Agent 5, Date of amendment order: Showa, 37th day of J month, 5f 6, Subject of amendment: All drawings

Claims (1)

[Claims] (Net co-production of acetic acid from methanol and carbon monoxide in the esterification step, gal-Inylation step, and separation step of 11-4)
- A method for producing acetic anhydride in half or half a batch, comprising: 1) In the esterification step, methanol is reacted with recycled acetic acid to produce mainly methyl acetate, water and unreacted methanol. 2) removing a portion of the water from the esterification product of -f. 3) The still water-containing esterification product is treated in the carbonylation process with a female or bound metal carmenylation catalyst as catalyst and free or bound halodane free F as promoter, - reacting with carbon oxide to produce a carbonylated bioacid containing acetic acid, acetic acid and gold; 4) separating the carbonylated product by fractional distillation;
separating into a low point fraction comprising the carmenylation feed and the recalcitrant carzanylation promoting components, an acetic acid and acetic anhydride fraction, and a high point fraction comprising the carbonylation catalyst components;
5) recycling the low-boiling fraction containing the carbonylation conjugate and the carbinylation promoting +11 component and the high-boiling fraction containing the carmenylation catalyst component to the carmenylation step;
and 6) at least a portion of 1 minute of acetic acid P to the sonic esterification step.
+To be able to vomit. How to make it a percentage value. (2) By fractional distillation, 1 min 4 [at about 1 min.
Separated into four fractions containing the product gold, cargenylation feed and carbonylation promoting cutting components, an intermediate fraction containing acetic acid and acetic anhydride, and a lower fraction containing carbonylation catalyst components, and 4 min and 1 min and recirculated to the total carnylation step. In the second separation step, the pickling product fraction and the acetic anhydride product fraction are separated by fractional distillation, and a portion of the acetic acid product fraction is completely removed from the entire esterification step. % pestle. (3) The recycled acetic acid forms at least 5Ot- of acetic acid in the feed to the esterification step.
1) Section 9 is the method described in section (2). (4) 1 of the water in the powder is used for the carzanylation process. The ester and methyl alcohol, if present, are at least 4 w/w '14 to ensure that sufficient precipitate is produced so that the recycled acetic acid is the feed to the esterification step. at least 5 of acetic acid in
Claim No.
3) Method described in section 3). (5) the amounts of water and alcohol (if present) are such that the carbinylation step produces more non-acid than the required amount of acetic acid in the feed to the esterification step; The method of claim 1MA paragraph (4), wherein the method is adapted to produce a net amount of acetic acid. (6) A process according to any one of the preceding claims, wherein the esterification product is sent directly to the carbinylation step (3) after removal of water in step C21. 7. A process as claimed in any one of the preceding claims, in which recycled acetic acid is sent directly to the esterification step from the cargenylation product separation step in which acetic acid and C-acetic anhydride are separated from each other.