| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | July 15, 2003 |
| PATENT TITLE |
Process for the preparation of polyols |
| PATENT ABSTRACT | The invention relates to a process for the preparation of polyols having 3 or 4 hydroxyl groups, from an aldehyde and formaldehyde in the presence of water, followed by hydrogenation of the aldolisation product in the presence of a hydrogenation catalyst at an elevated temperature. The aledhyde is obtained by an aldolisation reaction of an aldehyde having at least two .alpha.-hydrogen atoms and a formula according to R.sub.1 CH.sub.2 CHO, wherein R.sub.1 is selected from a group comprising hydrogen, alkyl groups having 1-7 carbon atoms which can have cycloalkyl substituents, cycloalkyl groups, aryl groups and aralkyl groups with 1-7 carbon atoms is the alkyl chain, with formaldehyde in the presence of water in an amount of 20-70 wt %, preferably 40-60 wt % and in the presence of an anion exchange resin. The hydrogenation is preferably carried out in the presence of water |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | January 2, 2002 |
| PATENT PARENT CASE TEXT | This data is not available for free |
| PATENT CLAIMS |
What is claimed is: 1. A process of preparing triols and tetrols by aldolization of an aldehyde having at least two .alpha.-hydrogen atoms and having a formula of R.sup.1 CH.sup.2 CHO, where R.sup.1 is hydrogen, an alkyl having 1 to 7 carbon atoms, an alkyl having 1 to 7 carbon atoms having at least one cycloalkyl substituent, cycloalkyl, aryl or an aralkyl having 1 to 7 carbon atoms in its alkyl chain, with formaldehyde in the presence of anion exchange resin followed by hydrogenation of the aldol product in the presence of a hydrogenation catalyst, the improvement comprising conducting said aldolization at a temperature of 50.degree. C. to 100.degree. C. in the presence of 48% to 65% by weight of water; and conducting said hydrogenation at a temperature of 50.degree. C. to 200.degree. C. in the presence of 20% to 90% by weight of water as the sole solvent. 2. A process in accordance with claim 1 wherein said hydrogenation is performed at a temperature of 60.degree. C. to 90.degree. C. 3. A process in accordance with claim 1 wherein said aldehyde is n-butanal, propanal or acetaldehyde. 4. A process in accordance with claim 1 wherein said ion exchange resin is a weak basic anion exchange resin which includes at least one --NH.sub.2, --NHR or --NR.sub.2 functional group, where each R is independently alkyl or aryl. 5. A process in accordance with claim 1 wherein said hydrogenation catalyst includes Ni, Cu, Cr, Zn, Pt, Pd, Ru, Co or Mn. 6. A process in accordance with claim 5 wherein said hydrogenation catalyst is a Ni catalyst. 7. A process in accordance with claim 5 wherein said hydrogenation catalyst is supported on a carrier. 8. A process in accordance with claim 6 wherein said nickel hydrogenation catalyst is supported on a carrier. 9. A process in accordance with claim 7 wherein said carrier is carbon or an inorganic oxide. 10. A process in accordance with claim 8 wherein said carrier is carbon or an inorganic oxide. 11. A process in accordance with claim 1 wherein said aldehyde, obtained in said aldolization, is steamed distilled before said hydrogenation. 12. A process in accordance with claim 11 wherein said steam distillation is conducted at a pressure below atmospheric. 13. A process in accordance with claim 12 wherein said steam distillation is performed in vacuo. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
The invention relates to a process for the preparation of polyols having 3 or 4 hydroxyl groups, from an aldehyde and formaldehyde in the presence of water, followed by hydrogenation of the aldolisation product in the presence of a hydrogenation catalyst at an elevated temperature. Polyols and especially 1,1,1-trimethylolpropane (TMP) are important starting materials and intermediates in the production of synthetic resins, such as polyester resins and the like. They may also be used in the manufacture of plasticizers, synthetic lubricants, surfactants etc. Polyols like 1,1,1-trimethylolpropane are prepared by allowing formaldehyde and another aldehyde to react in the presence of a strongly alkaline catalyst, such as sodium hydroxide, potassium hydroxide or calcium hydroxide to form a desired alcohol. However, large amounts of formate salts are formed as by-products thus making the process not very attractive for commercial purposes. In another, alternative process the aldolisation reaction of formaldehyde and another aldehyde is carried out in the presence of an amine catalyst, such as triethylamine, followed by hydrogenation. The aldolisation reaction may also be performed with an anion exchange resin acting as a catalyst. A method for the manufacture of polyalcohols is presented in DE 19542036, wherein an alkanal or ketone is allowed to react with formaldehyde in an aqueous solution in the presence of an amine, then water, excess of amine, excess of formaldehyde and methanol formed from Cannizzarro-reaction with formaldehyde are separated. The remaining reaction mixture is heated and polyalcohol formate is formed. The obtained polyalcohol formate is subjected to trans-esterification with an alcohol in order to obtain the desired polyalcohol, which is isolated from the reaction mixture. In U.S. Pat. No. 5,144,088 is disclosed a process for the manufacture of a polyol, and especially neopentyl glycol wherein isobutyraldehyde is reacted with paraformaldehyde in the presence of a tertiary amine, preferably triethylamine and of one or more oxides of elements of groups IB, IVA, IVB, VA, VB, VIB and VII of the periodic table and then hydrogenating the obtained monomeric and dimeric hydroxypivaldehyde. In U.S. Pat. No. 5,146,012 is described a method of making neopentyl glycol by reacting isobutyraldehyde with paraformaldehyde to obtain a reaction product comprising hydroxypivaldehyde, forming a mixture of the reaction product with about 40-90% of an alcohol, preferably methanol and then contacting the mixture with hydrogen in the presence of a hydrogenation catalysts. A process for the manufacture of polyols is disclosed in FI 965268 wherein an aldolisation reaction is performed with formaldehyde and another aldehyde comprising at least 2 carbon atoms, in the presence of a weakly basic anion exchange resin, followed by hydrogenation which is performed in the presence of a solvent and a hydrogenation catalyst. A process is disclosed in FI 974638 for the preparation of neopentyl glycol by hydrogenation of hydroxypivaldehyde in the presence of hydrogen and a hydrogenation catalyst containing nickel, at a temperature below 100.degree. C. in a liquid phase comprising a solvent in an amount of 1-70 wt %, preferably an aliphatic alcohol or ether or a mixture thereof and water in an amount of less than 15 wt %. A method is disclosed in JP 10287606 for the purification of dimethylol alkanal. Unreacted formaldehyde is separated from a reaction product containing dimethylol alkanal, obtained by carrying out a condensation reaction of an aliphatic aldehyde with formaldehyde in the presence of a hydroxide, a carbonate or a bicarbonate of an alkali metal or an alkaline earth metal, or other basic catalyst, such as an anion exchange resin and water. Water is added to the reaction product solution so that the water amount is about 4 times by weight, based on the formaldehyde content in the reaction product solution, then the mixture is fed to a thin-film type vaporizer to concentrate the solution and the thus generated formaldehyde vapour and steam are distilled away from one end of the thin-film type vaporizer to purify the dimethylol alkanal. It has been observed that several problems are related to the methods according to the state of the art. For example, in the first step of the manufacturing process of 1,1,1-trimethylolpropane (TMP), the aldolisation step of the aldehydes, undesired side reactions may occur. When the starting material, such as n-butanal, reacts with formaldehyde, 2-ethyl-3-hydroxypropanal is formed but also as a result of dehydration 2-ethylpropenal (ethyl acrolein) is obtained. 2-Ethyl-3-hydroxypropanal further reacts with formaldehyde to yield the desired intermediate 2-ethyl-3-hydroxy-2-(hydroxymethyl)propanal (TMPA). Because of the side reactions, the yield of the aldol in the aldolisation step and further the yield and purity of the final product are lower. The aldol product 2-ethyl-3-hydroxy-2-(hydroxymethyl)propanal contains varying amounts of unreacted formaldehyde which is a catalyst inhibitor affecting the subsequent catalytic hydrogenation step. To compensate the inhibiting effect of formaldehyde on the hydrogenation reaction, large amounts of the hydrogenation catalyst must be used thus increasing the reactor size and investment costs. Usually, the number of phases of a component depends on the temperature and concentration. If formaldehyde concentration increases, especially at low temperatures below 50.degree. C., solid paraformaldehyde is formed, which can cause severe blocking problems in the process. Based on the above it can be seen that there clearly exists a need for an improved process for the manufacture of polyols with improved yields, purity, conversion and selectivity. The invention relates to a process for the preparation of polyols by aldolisation of an aldehyde with formaldehyde over an anion exhange resin catalyst, followed by hydrogenation of the aldol product over a supported metal catalyst. Characteristic features of the process for the preparation of polyols are stated in the claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph illustrating the effect of methanol on the TMP-aldol yield (Y). FIG. 2 is a graph illustrating the effect of water on the TMP-aldol yield (Y) in a methanol-free environment. FIG. 3 is a graph illustrating the effect of formaldehyde concentration on the hydrogenation of aldol. FIG. 4 is a graph illustrating the hydrogenation of TMP-aldol with high FH-content FIG. 5 is a graph illustrating the hydrogenation of TMP-aldol with low initial FH-content. It has been observed that above mentioned objectives can be achieved and the disadvantages of the methods according to the state of the art can be avoided by the method according to the invention. Polyols may conveniently be produced by performing an aldolisation reaction followed by hydrogenating the aldol product. The aldolisation reaction is preferably carried out in the presence of water and in the presence of an anion exchange resin and in a substantially alcohol-free environment and the subsequent hydrogenation of the aldol product is performed preferably in the presence of water. In the process according to the invention for the preparation of polyols having 3 or 4 hydroxyl groups, an aldehyde is obtained by aldolisation reaction of an aldehyde having at least two .alpha.-hydrogen atoms and a formula according to R.sub.1 CH.sub.2 CHO wherein R.sub.1 is selected from a group comprising hydrogen, alkyl groups having 1-7 carbon atoms which can have cycloalkyl substituents, cycloalkyl groups, aryl groups and aralkyl groups with 1-7 carbon atoms in the alkyl chain, with formaldehyde in the presence of water in an amount of 20-70 wt %, preferably 40-60 wt %, and the obtained aldehyde is hydrogenated. The substantially alcohol-free environment means that the aldolisation reaction is carried out in the presence of methanol in an amount of 0-20 wt %, preferably 0-12 wt %. In the aldolisation reaction an aldehyde having at least two .alpha.-hydrogen atoms and formaldehyde are reacted in the presence of an anion exchange resin with a molar ratio of formaldehyde to the aldehyde of 2:1-6:1 and at a temperature of 15-100.degree. C., preferably 50-70.degree. C. Any suitable anion exchange resin catalyst may be applied, preferably weakly basic anion exchange resins, and the upper limit for the reaction temperature is limited by the thermal resistance of the anion exchange resin used. Preferable the anion exchange resins comprise functional groups which are selected from primary amines (--NH.sub.2), secondary amines (--NHR where R is an alkyl or an aryl group), tertiary amines (--NR.sub.2, where R is as above and R can be same or different alkyl group), and combinations thereof The resin matrix used may suitably be a condensation product of epichloro-hydrine with an amine or ammonia, a phenolic resin, an acrylic resin or a styrene copolymer, such as chloromethylated styrene-divinyl benzene copolymer. Suitable weakly basic anion exhange resins are disclosed in FI 965268. The aldolisation reaction is carried out preferably under an inert atmosphere, such as nitrogen atmosphere, and it can be carried out as a batch process, as a semibatch process or preferably as a continuous process. The effect of methanol on the TMP-aldol yield (Y) is presented in FIG. 1. Three different experiments were carried out with 0, 6, and 18 wt % of methanol. The experiment in the absence of methanol was carried out with paraformaldehyde. The graph of FIG. 1 illustrates TMP-aldol yield (Y) in the presence of 18 wt % of methanol (.diamond-solid.), 6 wt % of methanol (.box-solid.), 0 wt % of methanol (.tangle-solidup.) and with a formaldehyde-to-aldehyde molar ratio of 4:1, T=70.degree. C., 55 wt % of water. The effect of water content on the TMP-aldol yield (Y) in a methanol-free environment is presented in FIG. 2. It can be seen that the yield of the aldol CV) after 5 hours at 70.degree. C. with a formaldehyde-to-aldehyde molar ratio of 4:1 for three different water concentration values reaches a maximum value with 55 wt % of water in the reaction mixture. After the aldolisation step the aldol product is hydrogenated. The hydrogenation is carried out at a temperature of 50-200.degree. C., preferably at 60-90.degree. C. and under a pressure of 1-200 bar, preferably 10-80 bar. Solvents may optionally be used in the hydrogenation and suitable solvents are aliphatic alcohols, such as methanol, ethanol and propanol in an amount of 0-70 wt %, preferably 30-50 wt %. However, in the case the aldolisation mixture, after the aldolisation step, contains formaldehyde, it was found that with using Ni-catalyst as the hydrogenation catalyst it is advantageous to use only water as a solvent instead of alcohols in the hydrogenation of the aldol product. Normally formaldehyde retards the hydrogenation of the aldol product but when using only water as a solvent, the hydrogenation rate of the aldol product increases noticeably. A suitable water concentration is 0-90 wt %, preferably 20-90 wt %. The aldol product may also optionally be purified before hydrogenation by steam distillation, wherein the obtained aldolisation reaction mixture and water are mixed and distillation is carried out. Water, formaldehyde and impurities are co-distilled. Alternatively, steam may also be directly passed into the liquid to be distilled. The separation of formaldehyde and impurities, such as ethylacrolein, from the aldol product by steam distallation is preferably performed in vacuum or under atmospheric pressure and typically at a temperature of 50-110.degree. C. The unreacted formaldehyde separated from the aldol product can be recycled back to the aldolisation reactor thus dereasing the formaldehyde consumption and increasing the efficiency of the overall process. As a hydrogenation catalyst a commercial catalyst such as a supported metal catalyst may be used comprising Cu, Cr, Ni, Zn, Pt, Pd, Ru, Mn or Co. Suitable catalysts are Cu--Zn/Al.sub.2 O.sub.3, Cu--Cr/Al.sub.2 O.sub.3, Ni/SiO.sub.2, Ni--Cr/SiO.sub.2, Pt/C, Pt--Pd/C, Ru/C and Ru--Pd/C, and preferable ones are Cu--Cr/Al.sub.2 O.sub.3 and Ni--Cr/SiO.sub.2. The amount of nickel in the catalyst may be 60-99 wt % and the amount of chromium may be 1-40 wt %. When the reaction mixture from the aldolisation step contains formaldehyde and the hydrogenation step is performed in water, Ni-catalyst is a preferable choice. The catalyst may be combined with a suitable carrier which can be an inorganic oxide such as silica or carbon. The catalyst may optionally be activated before the hydrogenation, preferably at a temperature of about 400.degree. C. in hydrogen flow. The hydrogenation step may be carried out as a batch process, as a semi-batch process or preferably as a continuous process. After the hydrogenation step, the desired polyol is separated from the reaction mixture by any suitable method, such as distillation, and the solvents used may be recycled to the hydrogenation step. The method according to the invention has several advantages. The aldolisation reaction is performed using a solid catalyst, and thus no separation of the catalyst after the reaction and no recycling of the catalyst are required. The process for the manufacture of polyols exhibits improved selectivity and good conversion due to the optimum amount of water in the aldolization step. In the case of 1,1,1-trimethylolpropane, the formation of ethylacrolein can be reduced by optimizing the amount of water in the reaction mixture. By using water as solvent in the hydrogenation step, the performance of the hydrogenation step is improved because surprisingly no catalyst inhibiting effect of formaldehyde occurs and thus less hydrogenation catalyst is needed. The process is very effective and economic because complete removal of formaldehyde is not required after the aldolisation step, and the hydrogenation process in water works with smaller and larger amounts of formaldehyde equally well. The improved selectivity of the aldolisation step in the presence of a weakly basic anion exchange resin, the improved performance of the hydrogenation step and the improved overall yield of the crude product make the process economically advantageous, because as a result the raw material consumption is decreased and also the purification costs of the final product will decrease |
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| PATENT PHOTOCOPY | Available on request |
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