A process for producing hydroxyacetone (acetol)

Abstract

The disclosure relates to a process for producing hydroxyacetone, by catalytic dehydration of glycerol in the presence of a copper catalyst slurry comprising a copper catalyst and a polymeric material or an ionic liquid.

Description

[0001] A PROCESS FOR PRODUCING HYDROXYACETONE (ACETOL)

[0002] FIELD OF THE INVENTION

[0003] The present disclosure relates to a process for producing hydroxyacetone. In particular, the disclosure relates to a process for producing hydroxy acetone from glycerol.

[0004] BACKGROUND

[0005] Hydroxyacetone or acetol is a vital value-added product derived from glycerol. It finds application in food, textiles, cosmetics, and pharmaceutical industries. Moreover, hydroxyacetone is extremely reactive as it contains both hydroxyl and carbonyl functional groups and is therefore used as a raw material to produce various value-added chemicals via, dehydration, hydrogenation, oxidation, and polymerization. For example, industry-important chemicals such as 1,2- propane diol and acrolein are synthesized from hydroxyacetone. It is also used to synthesize compounds such as propionaldehyde, acetone and furan derivatives.

[0006] Various methods have been reported in literature to produce hydroxyacetone from glycerol. These methods include batch, semi -batch, and continuous processes using transition metal (Cu, Co, Ni) catalysts. PCT published document W02005095536A2 discloses the preparation of hydroxyacetone and propylene glycol from glycerol using catalyst based on copper, nickel, alumina, and others with a focus on getting the 1,2-propane diol and acetol as by-product up to 65%. Indian patent No. 261918 describe a batch process with low selectivity of hydroxyacetone (60-65%) with incomplete conversion of glycerol using copper catalysts. US 8809593B2 discloses a batch process for the synthesis of hydroxyacetone employing high pressure autoclave with poor to moderate conversion of glycerol. The process disclosed requires a very dilute solution of ~20 wt% aqueous or alcoholic glycerol. The highest yield of 85% acetol was reported by C. Chiu (AIChE J. 52, 2006, 3543-3548) in a semi-batch process involving solid-liquid-gas phases. The reaction is performed by taking a solid catalyst directly at a higher temperature (-240 °C) and adding glycerol to get the hydroxyacetone in a reactive distillation method. This process has a severe limitation in terms of the reaction foaming, cock deposition on the catalyst, difficulty in catalyst isolation and re-use and thus, is not a scalable process.

[0007] FIGURES

[0008] FIG 1 depicts a schematic illustration of a hydroxyacetone production system in accordance with an embodiment.

[0009] SUMMARY

[0010] The present disclosure provides a process for producing hydroxyacetone, by catalytic dehydration of glycerol in the presence of a copper catalyst slurry comprising a copper catalyst and a polymeric material or an ionic liquid.

[0011] DETAILED DESCRIPTION

[0012] To promote an understanding of the principles of the disclosure, reference will now be made to embodiments, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended, such alterations and further modifications in the disclosed composition and process, and such further applications of the principles of the disclosure therein being contemplated as would normally occur to one skilled in the art to which the disclosure relates. It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the disclosure and are not intended to be restrictive thereof.

[0013] Reference throughout this specification to “one embodiment” “an embodiment” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, appearances of the phrase “in one embodiment”, “in an embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0014] As used herein, the term “glycerol’ may refer to any of crude, treated, or refined glycerol as described herein, unless the glycerol is specifically designated as being crude, treated, or refined.

[0015] All percentages are by weight unless otherwise specified.

[0016] The present disclosure provides a process for producing hydroxyacetone (also referred to as acetol) from glycerol. In its broadest scope the present disclosure provides a process for producing hydroxyacetone by catalytic dehydration of glycerol in the presence of a copper catalyst slurry, comprising a solid copper catalyst and a polymeric material (PM) or an ionic liquid (IL)

[0017] The polymeric material or the ionic liquid acts as a stable liquid support for the copper catalyst, which helps to disperse the catalyst powder well in the reaction medium and provides uniform heat transfer, resulting in increasing the catalyst activity, maximum conversion of glycerol and excellent selectivity of hydroxyacetone.

[0018] The process for producing hydroxy acetone from glycerol comprises: charging glycerol into heated copper catalyst slurry in a reactor and allowing catalytic dehydration of glycerol to obtain a mixture of hydroxyacetone, 1-2-propane diol, water and other by-products in a gas phase; condensing the gas phase to collect a liquid mixture of hydroxyacetone, 1-2-propane diol, water and other by-products; and separating the hydroxyacetone from the liquid mixture of hydroxy acetone, 1-2-propane diol, water and other by-products.

[0019] The glycol that may be used in the process may be pure glycerol (100% glycerol) or crude glycerol that includes impurities, such as water, inorganic salts (e.g., chlorides, sulfates), and organic compounds (e.g., fatty acids, fatty ester, mono-glycerides, di-glycerides, phospholipids, protein residues). In some embodiments, the impurities may account for less than 10% of the crude glycerol. In some preferred embodiments, the impurities may account for less than 5% of the crude glycerol.

[0020] The crude glycerol may be obtained during the production of biodiesel or from the conversion of plant or animal fats / oils via saponification, transesterification or hydrolysis reactions. In some embodiments, the glycerol may be purified to remove impurities.

[0021] In the first step of the process, the copper catalyst and the polymeric material or the ionic liquids are mixed and heated to form the copper catalyst slurry. In some embodiments, the copper catalyst and the polymeric material or the ionic liquids are mixed and heated under a nitrogen atmosphere.

[0022] In accordance with an aspect, the copper catalyst is selected from a group consisting of copper powder, copper oxide, copper oxide nanoparticles, copper oxide supported on SiC , copper oxide supported on AI2O3, copper chromite with acidic promoters consisting of Ba, SiCh, and Mn. In some embodiments, the copper catalyst is copper chromite. In alternative embodiments, the copper catalyst is copper oxide nanoparticle having a size in the range of lOnm to 50nm.

[0023] In accordance with an aspect, the polymeric material is selected from a group consisting of Polyethylene glycol (PEG), Polypropylene glycol (PPG) and their ether derivatives and a combination thereof. Examples of ether derivatives of Polyethylene glycol include but are not limited to polyethylene glycol monomethyl ether, and polyethylene glycol dimethyl ether. Examples of ether derivative of Polypropylene glycol (PPG) include polypropylene glycol dimethyl ether.

[0024] In some embodiments, the polymeric material is polyethylene glycol (PEG). In some embodiments, the polyethylene glycol (PEG) has an average molecular weight in the range from 400 to 8000. In some preferred embodiments, the polyethylene glycol has an average molecular weight in a range of 800 to 4000. In yet other preferred embodiments, the polyethylene glycol (PEG) has a molecular weight of 1000.

[0025] In some embodiments, the ionic liquid is derived from imidazolium, pyridinium, and isoquinolium. Examples of imidazolium-derived ionic liquids include l-ethyl-3-methylimidazolium tetrafluoroborate. Examples of pyridiniumderived ionic liquids include Pyridinium tetrafluoroborate. Examples of isoquinolium-derived ionic liquids include 2-methylisoquinolin-2-ium tetrafluoroborate .

[0026] In accordance with an aspect, the ratio of copper catalyst to the polymeric material or the ionic liquid in the range from 1:0.5 to 1: 100. In some preferred embodiments, the ratio of copper catalyst to the polymeric material or the ionic liquid is in the range from 1 : 1 to 1 : 10. In yet other preferred embodiments, the ratio of copper catalyst to the polymeric material or the ionic liquid is in the range from 1: 1 to 1:5. In some embodiments, the ratio of copper catalyst to glycerol is in a range from 0.5: 100 to 5: 100. In some preferred embodiments, the ratio of copper catalyst to glycerol is in a range from 0.5: 100 to 1: 100.

[0027] In an embodiment, the copper catalyst and the polymeric material or the ionic liquids are heated to a temperature in the range from 150°C to 290 °C. In some preferred embodiment, the copper catalyst and the polymeric material or the ionic liquids are hearted to a temperature in the range from 200 °C to 260 °C. In yet other embodiments, the copper catalyst and the polymeric material or the ionic liquids are heated to a temperature in the range from 230 °C to 260 °C.

[0028] Once the copper catalyst slurry is obtained, in some embodiments the copper catalyst slurry is maintained at a reaction temperature. In some embodiments, the copper catalyst slurry is maintained at a temperature in the range from 150°C to 290°C. In some preferred embodiment, the slurry of the copper catalyst is maintained at a temperature in the range from 200°C to 260°C. In yet other embodiments, the slurry of the copper catalyst is maintained at a temperature in the range from 230°C to 260 °C.

[0029] In the next step, glycerol is charged into the copper catalyst slurry, maintained at the reaction temperature. The glycerol undergoes catalytic dehydration in the presence of the copper catalyst, resulting in a mixture of hydroxyacetone, 1-2- propane diol, water and other by-products in a gas phase.

[0030] In some embodiments, the glycerol is pre-heated to a temperature in the range from 50 °C to 290 °C before it is charged into the copper catalyst slurry. In some other embodiments, the glycerol is pre-heated to a temperature in the range from 100°C to 220°C before it is charged into the copper catalyst slurry. In yet other embodiments, the glycerol is pre-heated to a temperature in the range from 100°C to 150 °C before it is charged into the copper catalyst slurry. In some embodiments, glycerol is charged into the copper catalyst slurry under vacuum. In some other embodiments, glycerol is charged under nitrogen or argon gas atmosphere. In some embodiments, the glycerol is charged into the slurry of the copper catalyst under stirring.

[0031] In some embodiment, the catalytic dehydration is carried out under vacuum. In some embodiments, the vacuum applied is in the range from 500mbar to 950mbar. In some preferred embodiments, the vacuum applied is in the range from 600mbar to 950mbar. In yet other preferred embodiments, the vacuum applied is in the range from 800mbar to 950mbar. In other embodiments, the catalytic dehydration is carried out under purging with an inert gas, such as nitrogen or argon, into the reactor

[0032] In some embodiments, the reaction is carried out in a batch manner / operation. In such embodiments, where the reaction is carried out in the batch manner / operation, a predetermined amount of glycerol is added to the copper catalyst slurry allowing it to undergo catalytic dehydration in the presence of the copper catalyst. The mixture of hydroxyacetone, 1-2-propane diol, water and other by-products in a gas phase are collected and condensed for further processing. The copper catalyst slurry is then removed from the reactor and the copper catalyst is recycled. In some embodiments, the ratio of copper catalyst to glycerol is in a range from 0.5: 100 to 5: 100. In some preferred embodiments, the ratio of copper catalyst to glycerol is in a range from 0.5: 100 to 1: 100.

[0033] In some embodiments, the reaction is carried out in a continuous operation / manner. In such embodiments, where the reaction is carried out in a continuous operation / manner, the glycerol is charged into the heated copper catalyst slurry at a predetermined rate. Simultaneously, the gas phase that includes the mixture of hydroxyacetone, 1-2-propane diol, water and other by-products is removed. In such embodiments, the glycerol is added to the heated copper catalyst slurry and the gas phase is removed till the catalytic activity of the copper catalyst maintains, after which the copper catalyst is removed and recycled. In some embodiments, the glycerol is charged into the heated copper catalyst slurry at the Weight Hourly Space velocity rate (WHSV) in the range from 1 to 20. In some preferred embodiments, the glycerol is charged into the heated copper catalyst slurry at the WHSV in the range from 1 to 6. In yet other preferred embodiments, the glycerol is charged into the heated copper catalyst slurry at the WHSV in the range from 2 to 4.

[0034] In some embodiments, the reaction is allowed to proceed in a continuous manner until the copper catalyst slurry can no longer effectively catalyse the catalytic dehydration of glycerol, after which the reaction is stopped.

[0035] In some other embodiments, spent copper catalyst slurry i.e., the copper catalyst slurry that has already catalysed the catalytic dehydration of glycerol is removed at a predetermined rate and fresh copper catalyst slurry is added at a predetermined rate. In some embodiments, the fresh copper catalyst slurry is heated to the reaction temperature before adding it to the reactor. In some embodiments, the fresh copper catalyst slurry is heated to a temperature in the range from 150 °C to 290 °C. In some preferred embodiments, the fresh copper catalyst slurry is heated to a temperature in the range from 200°C to 260°C. In yet other preferred embodiments, the fresh copper catalyst slurry is heated to a temperature in the range from 230 °C to 260 °C.

[0036] In the next step of the process, the gas phase of mixture of hydroxyacetone, 1-2-propane diol, water and other by-products are condensed to collect the liquid mixture of hydroxyacetone, 1-2-propane diol, water and other by-products.

[0037] The hydroxyacetone is then separated from the liquid mixture of hydroxy acetone, 1-2-propane diol, water and other by-products. In some embodiments, the purity of hydroxyacetone obtained is in a range of 90 % to 95%. In some embodiments, the purity of the purity of hydroxy acetone obtained is greater than 95%. In accordance with an aspect, the hydroxy acetone is separated from the mixture of hydroxyacetone, 1-2-propane diol, water and other by-products by distillation under vacuum.

[0038] In some embodiments, the process further comprises of recycling the copper catalyst from the copper catalyst slurry. To recycle the copper catalyst from the copper catalyst slurry, water is added to the spent copper catalyst slurry. From the resultant solution, the copper catalyst is separated followed by drying. In some embodiments, the dried copper catalyst may be used again to catalyse the dehydrogenation of glycerol, without reactivation.

[0039] The copper catalyst is dried at a temperature in the range of 110 °C to 130 °C. In some embodiments, the copper catalyst is dried at 120 °C.

[0040] In an embodiment, the copper catalyst is recycled between 6 to 11 times and more preferably between 9 to 11 times without compromising the selectivity of the desired product. In order words, the copper catalyst is recycled between 6 to 11 times and more preferably between 9 to 11 times, before it is required to be reactivated.

[0041] A hydroxyacetone production system is also provided. In some embodiments, the system for a continuous operation can comprise of the configuration as depicted in FIG 1. By way of example, FIG 1 depicts a schematic illustration of a hydroxyacetone production system 100 that comprises of a continuous stirred tank reactor 2 equipped with a stirrer, heating system, a glycerol feed 1, thermal sensor connected to the products receiver tank 4 via a condenser 3. The glycerol is fed into the reactor 2 containing a slurry of catalyst at a constant flow rate. The mixture of products including hydroxyacetone, 1-2-propane diol, water and other by-products that evaporated out from reactor 2 is condensed by the condenser 3 and collected at receiver tank 4. The system 100 is further equipped with a vacuum distillation unit 5 connected to the products receiver tank 4 and a residue tank 7. The pure hydroxy acetone is distilled out from the mixture of products contained in the receiver tank 4 by factional distillation in the fractional distillation unit 5 under vacuum, to be collected in the tank 6 that holds the product. The remaining fractions obtained from the factional distillation unit 5 are collected in the residue tank 7.

[0042] In some embodiments, the system 100 is further equipped with a tank 8 connected to a stirred tank reactor 2 which is equipped to receive the spent copper catalyst slurry. The tank 8 is equipped with water supply and connected to a filter 10. The slurry of copper catalyst is washed with water from water supply. The copper catalyst is separated via filtration at filter 10 and dried at 120 °C in the dryer 12. The catalyst can be re-used without any further activation. The spent aqueous polymeric material or the ionic liquid is collected in a spent wash liquid tank 11.

[0043] The following examples illustrate certain embodiments and aspects of the present invention and are not to be construed as limiting the scope thereof. All parts and percentages are on a weight basis unless otherwise stated.

[0044] Example: 1:

[0045] In a round bottom flask fitted with the glycerol feed line, mechanical stirrer, heating mantle, condenser, and thermal sensor, 0.5-1 wt% of the copper chromite catalyst along with 5-10 wt% of polyethylene glycol-1000 slurry was taken with respect to glycerol. The mixture was heated to a temperature of 220 °C while stirring under nitrogen atm. Once the temperature reached the desired level, glycerol (Purity-95-100 wt%) was fed into flask at an appropriate flow rate under a vacuum (800-940 mbar). The low boiling product hydroxy acetone along with water and by-products evaporated which then cooled and collected in the receiver. The product mixture was analysed by Gas Chromatography. The selectivity of the hydroxyacetone is 70-75% with 98-100% conversion of glycerol. 1-4% selectivity of byproduct 1,2-propane diol was observed. The hydroxy acetone was isolated from the mixture of products by distillation under vacuum. The purity of hydroxy acetone is 90-95%. The residue containing copper catalyst and polyethylene glycol was washed with water and the settled copper catalyst was filtered through filter cloth under vacuum, dried in oven at 120 °C for 3 h and reused without further activation.

[0046] Example: 2:

[0047] In a round bottom flask fitted with the glycerol feed line, mechanical stirrer, heating mantle, condenser, and thermal sensor, 0.5-1 wt% of the copper chromite catalyst along with 5-10 wt% of polyethylene glycol-1500 slurry was taken with respect to glycerol. The mixture was heated to a temperature of 245 °C while stirring under nitrogen atm. Once the temperature reached the desired level, Glycerol (Purity: 95-100 wt%) was fed into flask at an appropriate flow rate under a vacuum (800-940 mbar). The low boiling product hydroxy acetone along with water and by-products evaporated which then cooled and collected in the receiver. The product mixture was analysed by Gas Chromatography. The selectivity of hydroxyacetone is 80-85% with 98-100% conversion of glycerol. 1-4% selectivity of byproduct, 1,2-propane diol was observed. The hydroxy acetone was isolated from the mixture of products by distillation under vacuum. The purity of hydroxy acetone is 90-95%. The residue containing copper catalyst and polyethylene glycol was washed with water and the settled copper catalyst was filtered through filter cloth under vacuum, dried in oven at 120 °C for 3 h and reused without further activation.

[0048] Example: 3:

[0049] In a round bottom flask fitted with the glycerol feed line, mechanical stirrer, heating mantle, condenser, and thermal sensor, 0.05-0.2 wt% of the copper oxide nanoparticle (10-50 nm) catalyst along with 5-10 wt% of polyethylene glycol-1500 slurry taken. The mixture was heated to a temperature of 260 °C while stirring under nitrogen atm. Once the temperature reached the desired level, Glycerol (Purity: 95- 100 wt%) was fed into flask at an appropriate flow rate under a vacuum (800-940 mbar). The low boiling product hydroxy acetone along with water and by-products evaporated which then cooled and collected in the receiver. The product mixture was analysed by Gas Chromatography. The selectivity of hydroxyacetone is 60- 70% with 93-98% conversion of glycerol. 2-5% selectivity of byproduct, 1,2- propane diol was observed. The hydroxy acetone was isolated from the mixture of products by distillation under vacuum. The purity of hydroxy acetone is 90-95%. The residue containing copper catalyst and polyethylene glycol was washed with water and the catalyst was separated either by nano-filtration or centrifugation method.

[0050] Example: 4:

[0051] In a round bottom flask fitted with the glycerol feed line, mechanical stirrer, heating mantle, condenser, and thermal sensor, 5 wt% of the copper chromite catalyst along with 20 wt% of polyethylene glycol- 1500 slurry was taken with respect to glycerol. The mixture was heated while stirring under nitrogen atm. to a temperature of 245 °C. Once the temperature reached the desired level, Glycerol (Purity: 95-100 wt%) was fed into flask at an appropriate flow rate under a vacuum (800-940 mbar). The low boiling product hydroxy acetone along with water and by-products evaporated which then cooled and collected in the receiver. Glycerol was continuously fed 7 -9 times of that Example 2 condition without isolating the catalyst and polyethylene glycol- 1500. The product mixture was analysed by Gas Chromatography. The selectivity of the hydroxyacetone is 76-85% with 95-100% conversion of glycerol. 1-4% selectivity of byproduct, 1,2-propane diol was observed. The hydroxy acetone was isolated from the mixture of products by distillation under vacuum. The purity of hydroxyacetone is 90-95%. Example: 5

[0052] In a round bottom flask fitted with the glycerol feed line, mechanical stirrer, heating mantle, condenser, and thermal sensor, 0.5-1 wt% of the copper chromite catalyst along with 5-10 wt% of polyethylene glycol mono-methyl ether-5000 slurry was taken with respect to glycerol. The mixture was heated to a temperature of 245 °C while stirring under nitrogen atm. Once the temperature reached the desired level, Glycerol (Purity: 95-100 wt%) was fed into flask at an appropriate flow rate under a vacuum (800-940 mbar). The low boiling product hydroxy acetone along with water and by-products evaporated which then cooled and collected in the receiver. The product mixture was analysed by Gas Chromatography. The selectivity of hydroxyacetone is 80-83% with 98-100% conversion of glycerol. 1-3% selectivity of byproduct, 1,2-propane diol was observed. The hydroxy acetone was isolated from the mixture of products by distillation under vacuum. The purity of hydroxy acetone is 90-95%. The residue containing copper catalyst and polyethylene glycol was washed with water and the settled copper catalyst was filtered through filter cloth under vacuum, dried in a vacuum oven at 120 °C for 3 h and re-used without further activation.

[0053] Example: 6

[0054] In a round bottom flask fitted with the glycerol feed line, mechanical stirrer, heating mantle, condenser, and thermal sensor, 0.5-1 wt% of the copper chromite catalyst along with 5-10 wt% of polyethylene glycol di-methyl ether-2000 slurry was taken with respect to glycerol. The mixture was heated to a temperature of 245 °C while stirring under nitrogen atm. Once the temperature reached the desired level, Glycerol (Purity: 95-100 wt%) was fed into flask at an appropriate flow rate under a vacuum (800-940 mbar). The low boiling product hydroxy acetone along with water and by-products evaporated which then cooled and collected in the receiver. The product mixture was analysed by Gas Chromatography. The selectivity of hydroxyacetone is 75-88% with 98-100% conversion of glycerol. 1- 4% selectivity of byproduct, 1,2-propane diol was observed. The hydroxy acetone was isolated from the mixture of products by distillation under vacuum. The purity of hydroxyacetone is 90-95%. The residue containing copper catalyst and polyethylene glycol was washed with water and the settled copper catalyst was filtered through filter cloth under vacuum, dried in a vacuum oven at 120 °C for 3 h and re-used without further activation.

[0055] Example: 7

[0056] In a round bottom flask fitted with the glycerol feed line, mechanical stirrer, heating mantle, condenser, and thermal sensor, 0.5-1 Wt% of the copper chromite catalyst along with 5-10 wt% of polypropylene glycol-2000 slurry was taken with respect to glycerol. The mixture was heated to a temperature of 245 °C while stirring under nitrogen atm. Once the temperature reached the desired level, Glycerol (Purity: 95-100 wt%) was fed into flask at an appropriate flow rate under a vacuum (800-940 mbar). The low boiling product hydroxy acetone along with water and by-products evaporated which then cooled and collected in the receiver. The product mixture was analysed by Gas Chromatography. The selectivity of hydroxyacetone is 80-83% with 98-100% conversion of glycerol. 1-3% selectivity of byproduct, 1,2-propane diol was observed. The hydroxy acetone was isolated from the mixture of products by distillation under vacuum. The purity of hydroxy acetone is 90-95%. The residue containing copper catalyst and polyethylene glycol was washed with water and the settled copper catalyst was filtered through filter cloth under vacuum, dried in a vacuum oven at 120 °C for 3 h and re-used without further activation.

[0057] Example: 8

[0058] In a round bottom flask fitted with the glycerol feed line, mechanical stirrer, heating mantle, condenser, and thermal sensor, 0.5-1 wt% of the copper chromite catalyst along with 5-10 wt% of an Ionic liquid (l-ethyl-3-methylimidazolium tetrafluoroborate) slurry was taken with respect to glycerol. The mixture was heated to a temperature of 240 °C while stirring under nitrogen atm. Once the temperature reached the desired level, Glycerol (Purity: 95-100 wt%) was fed into flask at an appropriate flow rate under a vacuum (800-940 mbar). The low boiling product hydroxy acetone along with water and by-products evaporated which then cooled and collected in the receiver. The product mixture was analysed by Gas Chromatography. The selectivity of hydroxyacetone is 70-75% with 95-98% conversion of glycerol. 1-4% selectivity of byproduct, 1,2-propane diol was observed. The hydroxy acetone was isolated from the mixture of products by distillation under vacuum. The purity of hydroxy acetone is 90-95%. The residue containing copper catalyst and ionic liquid was washed with water and the settled copper catalyst was filtered through filter cloth under vacuum, dried in a vacuum oven at 120 °C for 3 h and re-used without further activation.

[0059] Example: 9

[0060] In a jacketed SS reactor equipped with a mechanical stirrer, heating oil circulation, condenser, and thermal sensor, 5 wt% of the copper chromite catalyst along with 20 wt% of polyethylene glycol-3350 were taken with respect to glycerol. The mixture was heated while stirring under nitrogen atm. to a temperature of 240- 245 °C. Once the temperature reached the desired level, a pre-heated Glycerol (Purity: 95-100 wt%) having a temperature of 110-130 °C was fed to the reactor at a Weight Hourly Space velocity rate (WHSV) of 3-4 under a vacuum (900-940 mbar). Glycerol has been fed continuously for 40-45 hours by maintaining above stated process conditions. The low boiling product hydroxy acetone along with water and by-products evaporated which then cooled and collected in the receiver. The product mixture was analysed by Gas Chromatography. The selectivity of the hydroxyacetone is 76-85% with 98-100% conversion of glycerol. 1-3% selectivity of byproduct, 1,2-propane diol was observed. The hydroxy acetone was isolated from the mixture of products by distillation under vacuum. The purity of hydroxy acetone is 90-95%. Example: 10

[0061] In a jacketed SS reactor equipped with a mechanical stirrer, heating oil circulation, condenser, and thermal sensor, 5 wt% of the copper chromite catalyst along with 20 wt% of polyethylene glycol-3350 were taken with respect to glycerol. The mixture was heated while stirring under nitrogen atm. to a temperature of 240- 245 °C. Once the temperature reached the desired level, a pre-heated Glycerol (Purity: 95-100 wt%) having a temperature of 110-130 °C was fed continuously to the reactor at a Weight Hourly Space velocity rate (WHSV) of 3-4 under a vacuum (800-940 mbar). 10%-25% of the spent slurry was removed and introduced mixture of a fresh slurry of catalyst and PEG to the reactor continuously at the desired rate. The low boiling product hydroxy acetone along with water and by-products evaporated continuously which then cooled and collected in the receiver. The product mixture was analysed by Gas Chromatography. The selectivity of the hydroxyacetone is 76-85% with 98-100% conversion of glycerol. 1-3% selectivity of byproduct, 1,2-propane diol was observed. The hydroxy acetone was isolated from the mixture of products by distillation under vacuum. The purity of hydroxy acetone is 90-95%.

[0062] INDUSTRIAL APPLICABILITY

[0063] The disclosed process wherein a copper catalyst slurry comprising of a copper catalyst dispersed in a polymeric material or an ionic liquid is used for the catalytic dehydration of glycerol allows production of hydroxyacetone from glycerol in an efficient sustainable, and scalable manner. The polymeric material and the ionic liquid acts as a stable liquid support for the copper catalyst, which helps to disperse the catalyst powder evenly in the reaction medium and provides uniform heat transfer, resulting in increasing the catalyst activity, maximum conversion of glycerol and excellent selectivity of hydroxyacetone. Thus, the process disclosed allows for 95-100% conversion of glycerol with 80-90% selectivity for hydroxyacetone, and about 1-4% for the by-product 1,2-propane diol. Moreover, there is no foaming of reaction mixture.

[0064] The process requires 80-90% less amount of the catalyst (0.5-1%) to glycerol compared to the prior art reported (5% minimum). Moreover, the copper catalyst slurry is prepared by simply mixing and heating the copper catalyst with polymeric material or the ionic liquid without any further processing. Furthermore, the process allows for the recycling of the copper catalyst in a simple and efficient matter, that does not require the use of any organic solvents, thus making the entire recycling process a green process. The copper catalyst may be recycled between 6 to 11 time without compromising the selectivity of the desired product.

Claims

We Claim:

1. A process for producing hydroxy acetone, by catalytic dehydration of glycerol in the presence of a copper catalyst slurry comprising a copper catalyst and a polymeric material or an ionic liquid.

2. The process as claimed in claim 1 , wherein the catalytic dehydration is carried out by a process comprising: charging the copper catalyst and the polymeric material or the ionic liquid in a reactor; preparing the copper catalyst slurry by heating the mixture of copper catalyst and polymeric material or ionic liquid to a reaction temperature; charging glycerol into the heated copper catalyst slurry; and allowing the glycerol to undergo catalytic dehydration to obtain a mixture of hydroxy acetone, 1-2-propane diol, water and other by-products in a gas phase.

3. The process as claimed in claim 2, further comprising condensing the gas phase to collect a liquid mixture of hydroxyacetone, 1-2-propane diol, water and other by-products; and separating the hydroxyacetone from the liquid mixture of hydroxy acetone, 1-2-propane diol, water and other by-products.

4. The process as claimed in claim 1, wherein the ratio of copper catalyst to the polymeric material or the ionic liquid is in the range from 1:0.5 to 1: 100.

5. The process as claimed in claim 1, wherein the copper catalyst is selected from a group consisting of copper powder, copper oxide, copper oxide nanoparticles, copper oxide supported on SiC , copper oxide supported on AI2O3, copper chromite with acidic promoters consisting of Ba, SiCh, and Mn and combinations thereof.

6. The process as claimed in claim 1 , wherein the copper catalyst is copper oxide nanoparticle having a size in the range of lOnm to 50nm.

7. The process as claimed in claim 1, wherein the polymeric material is selected from a group consisting of Polyethylene glycol (PEG), Polypropylene glycol (PPG), their ether derivatives and combinations thereof.

8. The process as claimed in claim 1, wherein the ionic liquid derived from a group comprising imidazolium, pyridinium and isoquinolium.

9. The process as claimed in claim 1, wherein the ratio of copper catalyst to glycerol is in a range from 0.5: 100 to 5: 100.

10. The process as claimed in claim 2, wherein the copper catalyst slurry is prepared by heating the mixture of the copper catalyst and the polymeric material or the ionic liquid to a temperature in the range of 150 °C to 290°C.

11. The process as claimed in claim 2, wherein the glycerol is pre-heated to a temperature in the range of 50 °C to 290 °C before charging it into the copper catalyst slurry.

12. The process as claimed in claim 2, wherein the catalytic dehydration of glycerol is carried out under vacuum in the range from 500 mbar to 950 mbar.

13. The process as claimed in claim 2, wherein the catalytic dehydration of glycerol is carried out under nitrogen or argon gas purging.

14. The process as claimed in claim 2 wherein the glycerol is charged into the copper catalyst slurry under nitrogen or argon gas atmosphere.

15. The process as claimed in claim 2, wherein the process is a continuous process comprising charging glycerol into the copper catalyst slurry at a weight hourly space velocity rate (WHSV) in the range from 1 to 20; and removing the gas phase containing the mixture of hydroxy acetone, 1-2-propane diol, water and other by-products.

16. The process as claimed in claim 15, wherein the process is a continuous process comprising removing a portion of the copper catalyst slurry after glycerol undergoes catalytic dehydration and introducing fresh copper catalyst slurry.

17. The process as claimed in claim 2, wherein the hydroxyacetone is separated from the mixture of hydroxyacetone, 1-2-propane diol, water and other byproducts by distillation under vacuum.

18. The process as claimed in claim 1, further comprising recycling the copper catalyst from the copper catalyst slurry, by:- adding water into the copper catalyst slurry;- separating the copper catalyst from the water and the polymeric material or the ionic liquid; and- drying the separated copper catalyst.

19. The process as claimed in claim 2, wherein the copper catalyst is recycled between 6 to 11 times.