Method to obtain methylene malonate via bis(hydroxymethyl) malonate pathway
Method to obtain methylene malonate and related monomers following a bis(hydroxymethyl) malonate pathway. A bis(hydroxymethyl) malonate intermediary is subsequently reacted (i.e., subjected to thermolysis) to provide a methylene malonate monomer species. A source of formaldehyde (e.g., formalin) is provided in the presence of a basic catalyst (e.g., calcium hydroxide), to which a malonate (e.g., diethyl malonate) is added under suitable reaction conditions to obtain the desired intermediary (e.g., dialkyl bis(hydroxymethyl) malonate). The intermediary is reacted (i.e., subjected to thermolysis) under suitable conditions in the presence of a suitable catalyst (e.g., a zeolite) to obtain a methylene malonate monomer. In an exemplary embodiment, the thermolysis reaction includes the addition of the bis(hydroxymethyl) malonate intermediary onto a heated catalyst. The reaction product is collected and purified. The disclosed methods may be performed in a continuous operation. Discrete steps may be performed by using modular units within a plant.
1. A method of making a methylene malonate monomer comprising:
(a) reacting a dialkyl bis(hydroxymethyl) malonate composition in the presence of a catalyst which is a ZSM aluminosilicate molecular sieve to form a methylene malonate monomer; and
(b) isolating the methylene malonate monomer.
2. The method of making a methylene malonate monomer according to claim 1 , wherein each alkyl may be the same or different and is a straight or branched hydrocarbon group having between 1 and 16 carbon atoms.
3. The method of making a methylene malonate monomer according to claim 1 , wherein the dialkyl bis(hydroxymethyl) malonate composition is prepared by a method comprising: (i) reacting a source of formaldehyde with a dialkyl malonate ester in the presence of a catalyst to form a reaction product comprising the dialkyl bis(hydroxymethyl) malonate composition.
4. The method of making a methylene malonate monomer according to claim 3 , wherein the reacting step (i) to prepare the dialkyl bis(hydroxymethyl) malonate composition occurs without the addition of a solvent.
5. The method of making a methylene malonate monomer according to claim 3 , wherein the source of formaldehyde is formaldehyde, trioxane, formalin, or paraformaldehyde.
6. The method of making a methylene malonate monomer according to claim 3 , wherein the reaction product of step (i) is subjected to a diol purification step (ii) prior to the reaction step (a): wherein the diol purification step (ii) comprises subjecting the reaction product of step (i) to an ion-exchange process to exchange cations carried in the reaction product for another cation, to produce the dialkyl bis(hydroxymethyl) malonate composition, subjecting the dialkyl bis(hydroxymethyl) malonate composition to an evaporation step to remove volatile impurities, or a combination thereof.
7. The method of making a methylene malonate monomer according to claim 1 , further comprising the step of: c) purifying a thermolysis product obtained in step (a) to obtain the isolated methylene malonate monomer.
8. The method of making a methylene malonate monomer according to claim 1 , wherein the catalyst is in the form of a column through which the dialkyl bis(hydroxymethyl) malonate composition is passed.
9. The method of making a methylene malonate monomer according to claim 8 , wherein the catalyst column is heated to a wall temperature between about 180° C. and about 250° C.
10. The method of making a methylene malonate monomer according to claim 8 , wherein the dialkyl bis(hydroxymethyl) malonate composition is passed over the catalyst column at a rate of 0.01 to 65 kg/hr.
11. The method of making a methylene malonate monomer according to claim 1 , wherein the catalyst of step (i) is a basic catalyst.
12. The method of making a methylene malonate monomer according to claim 6 , wherein the diol purification step (ii) comprises subjecting the reaction product of step (i) to an ion-exchange process to exchange cations carried in the reaction product for another cation to produce the dialkyl bis(hydroxymethyl) malonate composition, and subjecting the dialkyl bis(hydroxymethyl) malonate composition to an evaporation step to remove volatile impurities.
13. The method of making a methylene malonate monomer according to claim 6 , wherein the the ion exchange process uses an ion-exchange column packed with an ion-exchange resin.
14. The method of making a methylene malonate monomer according to claim 13 , wherein the ion exchange column is a pressurized ion-exchange column.
15. The method of making a methylene malonate monomer according to claim 1 wherein the dialkyl bis(hydroxymethyl) malonate composition has less than 500 ppm cations.
16. The method of making a methylene malonate monomer according to claim 1 wherein the dialkyl bis(hydroxymethyl) malonate composition contains between 0 and 30% water.
17. The method of making a methylene malonate monomer according to claim 1 , wherein the catalyst is a ZSM-5 aluminosilicate molecular sieve.