US 2002O134662A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2002/0134662 A1 Parten (43) Pub. Date: Sep. 26, 2002 (54) DEWATERING PROCESS Publication Classification (75) Inventor: William David Parten, Stokesley (GB) (51) Int. Cl." ............................ B01D 3/34; CO7C 45/82; CO7C 51/44 Correspondence Address: (52) U.S. Cl. ................. 203/60; 203/61; 203/95; 203/99; Pillsbury Winthrop LLP 203/DIG. 3130824; 203/DIG. 3130824; Intellectual Property Group 203/DIG. 3130824; 562/600; 1600 Tysons Boulevard 568/449 McLean, VA 22102 (US) (73) Assignee: Ineos. Acrylics UK Ltd., (57) ABSTRACT A process for Separating a formaldehyde-containing product (21) Appl. No.: 10/152,819 from a formalin Solution comprising formaldehyde, water May 23, 2002 and methanol, wherein Said formaldehyde-containing prod (22) Filed: uct contains Substantially less water than Said formalin Solution, comprising distilling Said formalin Solution in the Related U.S. Application Data presence of a water entraining compound, especially methyl (62) Division of application No. 09/701,877, filed on Jan. propionate or methyl methacrylate. The formaldehyde-con 22, 2001. taining product is Suitable for use in a further proceSS which requires a Source of formaldehyde containing a relatively (30) Foreign Application Priority Data low level of water. One example of Such a proceSS is the reaction of methyl propionate with formaldehyde and Jun. 5, 1998 (GB)......................................... 98.12083.5 methanol over a catalyst to produce methyl methacrylate. Patent Application Publication Sep. 26, 2002 US 2002/0134662 A1 Figure 1 Product 30 Feed 21 Feed 22 Product 3 Product 32 US 2002/0134662 A1 Sep. 26, 2002 DEWATERING PROCESS 0007. It is therefore an object of the invention to provide a process for the preparation of a formaldehyde feed product 0001. The present invention relates to a process for the from a formaldehyde-containing Solution. removal of water from Solutions containing formaldehyde for the production of formaldehyde. 0008. It is a further object of the invention to provide a process for treatment of a formaldehyde-containing Solution 0002 Formaldehyde is a commodity chemical that is to yield a formaldehyde feed suitable for use in a methyl conveniently produced and transported in the form of for methacrylate production proceSS which contains a reduced malin Solutions. Formalin Solutions contain typically amount of water compared to the original formaldehyde between 30% and 60% formaldehyde, the balance of the containing Solution. Solution being mostly water, usually with Some methanol 0009. According to the invention, a process for separat present. The formaldehyde is predominantly present as ing a formaldehyde-containing product from a formalde complexes with water or methanol in the form of glycols or hyde Solution comprising formaldehyde, water and option hemiformals. There are a number of methods described in the patent literature for the dehydration of formaldehyde ally methanol, wherein Said formaldehyde-containing Solutions with the object of producing a dry monomeric product contains Substantially less water than Said formalin formaldehyde stream. For example U.S. Pat. No. 4,962,235 Solution, comprises distilling Said formalin Solution in the describes the purification of a formaldehydelwater/methanol presence of a water entraining compound. mixture by distilling in the presence of a polyalkylene oxide 0010. The water entraining compound is selected Such Such that formaldehyde vapour is produced at the top of the that it is capable of dissolving water, formaldehyde, metha column and polyalkylene oxide, water and methanol are nol and hemiformal compounds formed by the reaction of removed from the bottom of the column. formaldehyde with methanol. The water entraining com pound is preferably a Saturated or unsaturated carboxylic 0.003 NL-A-6814946 describes a process for recovering acid or ester or a carbonyl compound which is Substantially formaldehyde from aqueous formaldehyde Streams by con unreactive towards formaldehyde under the conditions of the tacting the Stream with a Co-Co aliphatic alcohol which distillation and also able to entrain the water, preferably by reacts with the formaldehyde to form a hemiformal which forming a minimum boiling azeotropic mixture with water can be separated from the water and Subsequently dissoci Preferably the water entraining compound forms a hetero ated back to the alcohol and formaldehyde components. geneous minimum boiling azeotrope with water. Suitable 0004 U.S. Pat. No. 3,174.912 describes a process for the compounds include C-C alkanoic acids and their lower removal of water and coloured organic impurities from a alkyl, e.g. C-C, esters, and ketones having at least 4 carbon dilute aqueous formaldehyde mixture by distillation in the atoms Such as diethyl ketone. Particularly preferred com presence of acetone. A mixed Stream containing acetone and pounds are esters and methyl propionate and methyl meth formaldehyde and a Small amount of water is removed from acrylate have been found to be especially useful in certain the top of the column and Separated by partial condensation processes. It is greatly preferred to use a compound which into a stream containing a relatively Small amount of form is intended to be introduced into a process in which the aldehyde in acetone and a stream containing a larger pro dewatered formaldehyde product is intended to be used. portion of formaldehyde in acetone. 0011. One particularly preferred compound for use in dewatering a formalin Solution to produce formaldehyde 0005. It is, however, desirable to avoid the introduction of Suitable for use in a process to react formaldehyde with additional chemical compounds into a process which methyl proprionate in the presence of methanol is methyl requires purified formaldehyde because the additional com propionate. In one preferred form of the invention we pound may need to be removed from the process at a therefore provide a process for Separating a formaldehyde Subsequent Stage. containing product from a formaldehyde Solution compris 0006. One process in which formaldehyde is used is that ing formaldehyde, water and optionally methanol, wherein for the production of methyl methacrylate by the reaction of Said formaldehyde-containing product contains Substantially methyl propionate with formaldehyde in the presence of less water than Said formalin Solution, comprises distilling methanol. The use of formaldehyde as a readily available Said formaldehyde Solution in the presence of methyl pro formalin Solution introduces water into the reaction which pionate. may have a deleterious effect on the catalyst used and is 0012. According to a second aspect of the invention we likely to promote the hydrolysis reactions of the methyl provide a process for the production of methyl methacrylate propionate reactant and of the methyl methacrylate product. by the reaction of formaldehyde with methyl proprionate in Water is produced as a by-product of the methacrylate the presence of methanol and of a Suitable catalyst, wherein Synthesis reaction and it is therefore desirable to reduce to a Said formaldehyde is produced from a formaldehyde Solu minimum the amount of water that is introduced into the tion by means of distilling Said formaldehyde Solution in the reaction Zone with the feeds so that the level of water in the presence of methyl proprionate. Suitable catalysts are reactor is maintained as low as possible. Processes for the production of methyl methacrylate, in which propionic acid known in the art and include Silica catalysts having alkali or its methyl ester is reacted with formaldehyde or methylal metal Sites. in the presence of methanol, are disclosed in U.S. Pat. No. 0013 The process of this aspect of the invention is 3,535,371, U.S. Pat. No. 4,336,403, GB-A-1 107234, JP-A- beneficial, in that formaldehyde feed is recovered as a 63.002951. However there is no disclosure in these refer complex with methanol in a methyl propionate rich Stream ences of how to prepare the feed materials, particularly the and water is removed from the process Substantially free of formaldehyde, for the required reaction. organics. Integration of the process for producing formal US 2002/0134662 A1 Sep. 26, 2002 dehyde of the present invention with a methyl methacrylate prises mainly methyl propionate may be refluxed into the producing process as described has the additional advantage distillation process. The aqueous phase produced from the that the overall energy requirement for the combined proceSS decanter may be further treated in a Second distillation unit, may be reduced compared with other formaldehyde dewa preferably at elevated preSSure, to give an aqueous Stream tering methods. which is largely free of methanol, formaldehyde and methyl 0.014. Although we have found that the process of the propionate. The overheads from the Second distillation unit present invention is particularly Suitable to provide a form can be recycled back to the main column or to the decanter aldehyde feedstock for Subsequent reaction for methyl meth or to the formaldehyde Solution pre-treatment, if present. acrylate production, the invention is not limited to the 0018 Most of the formaldehyde is taken as a bottom production of formaldehyde for Such a proceSS and may be product as a mixture with the water entraining compound. Suitable to produce dewatered formaldehyde for other appli This mixture may be used directly if required for a further cations. reaction in which both compounds are used together, e.g. in 0.015 The formaldehyde Solution is preferably standard the synthesis of methyl methacrylate. This formaldehyde formalin which usually contains water and formaldehyde in containing mixture contains Substantially less water than the approximately equal proportions, usually with a Small quan formaldehyde Solution fed to the process. For example, in a tity of methanol. At least some of the formaldehyde is typical process according to the invention using methyl normally present as various water-formaldehyde or metha propionate as the water entrainer, a formalin Solution con nol-formaldehyde adducts.