Catalyst for preparing lactide from alkyllactate and method for preparing same

Abstract

The present invention relates to a catalyst for preparing lactide from alkyl lactate and a method for preparing same and, more specifically, to a catalyst for preparing lactide from alkyl lactate and a method for preparing same, the catalyst being capable of preparing lactide, which is used as a monomer of polylactide, from alkyl lactate at a high conversion rate and a high yield.

Description

Catalyst for producing lactide from alkyl lactate and method for producing the same

[0001] The present invention relates to a catalyst for producing lactide from alkyl lactate and a method for producing the same, and more specifically, to a catalyst and a method for producing the same that can produce lactide used as a monomer for polylactide from alkyl lactate with a high conversion rate and high yield.

[0002] Lactide is a dimeric cyclic ester of lactic acid and is useful as a raw material for polylactide (or polylactic acid; PLA), which is widely used as a biodegradable polymer. Recently, it has been attracting attention as a food additive used as a preservative, pH regulating agent, coagulating agent for tofu and dairy products, acidulant, and auxiliary expanding agent.

[0003] Traditionally, such lactide is produced by primary polymerizing lactic acid to obtain a prepolymer with a molecular weight of about 100 to 5,000, and then depolymerizing the prepolymer under a catalyst such as a tin-based catalyst, with an inert gas flow and reduced pressure conditions.

[0004] However, lactic acid, which serves as the raw material for lactide, is generally produced by anaerobic bacteria through the fermentation of carbohydrates such as glucose. At this time, the lactic acid produced from the fermentation process generally exists in the form of ammonium, sodium, calcium, or potassium lactate, because the corresponding cation hydrates are added to maintain the neutral conditions required by the bacteria during the fermentation process. Therefore, in order to convert the lactate obtained from the fermentation process into lactic acid, a step of acidifying the lactate using an inorganic acid such as sulfuric acid after the fermentation process is typically required. However, there is a problem in that ammonium, sodium, calcium, or potassium sulfates are inevitably generated as byproducts during this lactic acid conversion process.

[0005] Accordingly, as a method for producing lactic acid that does not generate such acidification byproducts, a method is proposed in which lactic acid fermentation is carried out in the form of ammonium lactate, and the aqueous solution is subjected to high-pressure decomposition (U.S. Patent No. 6,291,708) or electrodialysis and membrane technology (U.S. Patent No. 5,723,639). However, lactic acid produced by the above method is still unsuitable for producing PLA polymer-grade lactide because it contains a large amount of impurities such as metals, polysaccharides, and proteins resulting from the fermentation process.

[0006] Meanwhile, to obtain a polymer-grade lactide monomer, high-purity lactic acid must be used as a raw material; however, since lactic acid easily forms oligomers during the concentration process, it is difficult to purify it by distillation. Therefore, to obtain high-purity lactic acid from the lactic acid brine obtained by the fermentation method, it is common practice to pre-treat the brine, convert it into alkyl lactate, purify the alkyl lactate, and then hydrolyze it to obtain high-purity lactic acid. Consequently, rather than obtaining lactide by pre-polymerizing the high-purity lactic acid obtained by the above method and then depolymerizing it, obtaining lactide directly from alkyl lactate can be considered an efficient method that simplifies the process and significantly reduces energy costs.

[0007] As a known technique for directly obtaining lactide from alkyl lactate, Japanese Patent Publication No. 1993-286966 describes a method of condensing a lactic acid ester containing an alkyl group having 1 to 8 carbon atoms under heating and reduced pressure conditions using a catalyst such as zinc chloride (ZnCl2) or tin chloride (SnCl2); and Japanese Patent Publication No. 1994-031175 describes a method of obtaining lactide by performing a two-molecular condensation cyclization reaction of a lactic acid ester containing a lower alkyl group having 1 to 6 carbon atoms under a catalyst combining a dibutyl tin chloride catalyst or a catalyst combining phosphorus pentoxide or phosphorus trioxide with dibutyl dichlorotin. Additionally, Chinese Patent Publication No. 112266376 describes a method of producing lactide by cyclizing lactate under titanium-containing molecular sieve catalyst conditions.

[0008] However, the technology using the above-mentioned organotin catalyst has the disadvantage that the fraction of meso-optical isomer lactide produced is large and the yield of lactide is low, and the technology using a titanium-containing molecular sieve catalyst through post-treatment has the problem that the selectivity of lactide and the conversion rate of alkyl lactate drop significantly depending on the manufacturing method of the molecular sieve and catalyst.

[0009] Accordingly, the inventors made diligent efforts to solve the aforementioned problems while simultaneously producing lactide with high yield and conversion rates. As a result, they confirmed that when a titanium-containing zeolite-based catalyst produced by a specific manufacturing method is used in the cyclization reaction of gaseous alkyl lactate, lactide can be directly produced with high yield and conversion rates while maintaining optical properties, and thus completed the present invention.

[0010] [Prior Art Literature]

[0011] [Patent Literature]

[0012] (Patent Document 1) Japanese Published Patent No. 1993-286966 (Date of publication: Nov. 02, 1993)

[0013] (Patent Document 2) Japanese Published Patent No. 1994-031175 (Date of publication: Feb. 8, 1994)

[0014] (Patent Document 3) Chinese Published Patent No. 112266376 (Publication Date: Jan. 26, 2021)

[0015] The objective of the present invention is to provide a catalyst for producing lactide and a method for producing the same, which can produce lactide from alkyl lactate with high yield and conversion rate while maintaining optical properties.

[0016] Another objective of the present invention is to provide a method for producing lactide from alkyl lactate with high selectivity in a simple and economical manner using the above-mentioned catalyst for lactide production.

[0017] To solve the above problem, one embodiment of the present invention provides a catalyst for producing lactide from alkyl lactate, wherein the catalyst for producing lactide from alkyl lactate is a titanium-containing zeolite having an MWW-type framework formed by mixing a titanium source, a silica source, and a template compound, followed by hydrothermal synthesis.

[0018] In one embodiment of the present invention, the titanium-containing zeolite may be characterized by containing titanium in an amount of 0.1 wt% to 20 wt% relative to the total weight of the zeolite.

[0019] Another embodiment of the present invention provides a catalyst for producing lactide from alkyl lactate, characterized in that the catalyst is a titanium-substituted exfoliated MWW zeolite.

[0020] In another embodiment of the present invention, the titanium-substituted exfoliated MWW zeolite may be characterized in that titanium is substituted in an amount of 0.1 wt% to 10 wt% relative to the total weight of the catalyst.

[0021] In another embodiment of the present invention, the titanium-substituted exfoliated MWW zeolite may be characterized as having an interlayer exfoliated plate-like structure.

[0022] Another embodiment of the present invention provides a method for producing a catalyst for producing lactide from alkyl lactate, characterized by comprising the step of mixing a titanium source, a silica source, and a template compound, and then hydrothermally synthesizing to produce a titanium-containing zeolite having an MWW-type framework.

[0023] In another embodiment of the present invention, the titanium source may be characterized as being selected from the group consisting of titanium alkoxide, titanium halide, titanium organometallic compound, titanium oxide precursor, titanium composite, and mixtures thereof.

[0024] In another embodiment of the present invention, the silica source may be characterized as being one or more selected from the group consisting of silicic acid, tetraethyl orthosilicate, tetrapropyl orthosilicate, sodium silicate, colloidal silica, silica sol, silica gel, natural silica, fumed silica, and synthetic silica.

[0025] In another embodiment of the present invention, the template compound may be characterized as being one or more selected from the group consisting of hexamethyleneimine (HMI), piperidine, TMAdaOH (N,N,N-trimethyl-1-adamantylammonium hydroxide), TMAdaBr (N,N,N-trimethyl-1-adamantylammonium bromide), TMAdaF (N,N,N-trimethyl-1-adamantylammonium fluoride), TMAdaCl (N,N,N-trimethyl-1-adamantylammonium chloride), and TMAdaI (N,N,N-trimethyl-1-adamantylammonium iodide).

[0026] In another embodiment of the present invention, the hydrothermal synthesis may be characterized by being performed at 50 ℃ to 250 ℃.

[0027] In another embodiment of the present invention, the titanium-containing zeolite having a MWW-type framework synthesized after hydrothermal synthesis may be further characterized by the addition of a step of recovering, drying, and calcining at a temperature of 200°C to 600°C.

[0028] Another embodiment of the present invention provides a method for producing a catalyst for producing lactide from alkyl lactate, comprising: (a) a step of preparing a boron-substituted MWW zeolite; (b) a step of swelling and exfoliating the boron-substituted MWW zeolite prepared in step (a) to obtain a boron-substituted exfoliated MWW zeolite; (c) a step of deboration from the boron-substituted exfoliated MWW zeolite obtained in step (b); and (d) a step of producing a titanium-substituted exfoliated MWW zeolite by substituting titanium into the deborationd exfoliated MWW zeolite.

[0029] In another embodiment of the present invention, the swelling and peeling of step (b) may be characterized by using one or more methods selected from the group consisting of a surfactant treatment method, an alkali treatment method, an ultrasonic treatment method, and an acid treatment method.

[0030] Another embodiment of the present invention provides a method for producing lactide from alkyl lactate, characterized by cyclizing gaseous alkyl lactate in the presence of the catalyst for producing lactide or the catalyst produced by the above method of production.

[0031] In another embodiment of the present invention, the content of the catalyst for producing lactide may be characterized as being 0.1 to 90 parts by weight per 100 parts by weight of alkyl lactate.

[0032] In another embodiment of the present invention, the cyclization reaction of the alkyl lactate may be characterized by being carried out at 150 ℃ to 300 ℃.

[0033] In another embodiment of the present invention, the cyclization reaction of the alkyl lactate may be characterized by being carried out at a pressure of 1 bar to 5 bar.

[0034] In another embodiment of the present invention, the alkyl lactate is 0.1 h -1 ~ 50 h -1 Supply at the spatial velocity of It can be characterized by performing a cyclization reaction.

[0035] The catalyst for producing lactide according to the present invention can produce lactide with high selectivity and conversion rate while maintaining optical properties by directly using gaseous alkyl lactate.

[0036] In addition, the method for producing lactide according to the present invention applies a titanium-containing MWW-type zeolite catalyst produced by a specific method as a catalyst for producing lactide from alkyl lactate, thereby enabling the production of lactide with high selectivity and conversion rate while maintaining optical properties by directly using gaseous alkyl lactate, thus simplifying the manufacturing process and economically providing high-purity lactide.

[0037] Figure 1 is a Power XRD measurement graph of the catalysts prepared in Example 1 and Comparative Examples 2 and 3 of the present invention.

[0038] FIG. 2 is a graph of the DR UV-Vis measurements of the catalysts prepared in Example 1 and Comparative Examples 2 to 5 of the present invention.

[0039] Figure 3 is a graph showing the results of measuring the methyl lactate conversion rate and lactide selectivity of the catalysts prepared in Example 1 and Comparative Examples 2 and 5 of the present invention.

[0040] Figure 4 is a graph showing the results of measuring the productivity of the catalysts prepared in Example 1 and Comparative Examples 2 and 5 of the present invention regarding the turnover frequency (TOF).

[0041] Figure 5(a) is a graph showing the results of measuring the methyl lactate conversion rate and lactide selectivity of the catalyst prepared in Example 1 of the present invention, and (b) is a graph showing the results of measuring the methyl lactate conversion rate and lactide selectivity of the catalyst prepared in Comparative Example 1.

[0042] FIG. 6 is a conceptual model of a titanium-substituted plate-like structured exfoliated MWW zeolite catalyst according to another embodiment of the present invention.

[0043] Figure 7 is a graph showing the results of measuring the lactide productivity of the catalysts prepared in Example 2 and Comparative Examples 6 to 10 of the present invention.

[0044] Figure 8 is a graph showing the results of measuring the lactide productivity under harsh reaction conditions for the catalysts prepared in Example 2 and Comparative Example 9 of the present invention.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by a skilled expert in the art to which this invention pertains. In general, the nomenclature used herein is well known and commonly used in the art.

[0046] The singular expressions used in the present invention include the plural expressions unless the context clearly indicates otherwise, and terms such as "comprising," "having," or "having" described below should be interpreted as indicating the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0047] Additionally, in this specification, where each layer or element is described as being formed "on" or "above" each layer or element, it means that each layer or element is formed directly on each layer or element, or that another layer or element may be additionally formed between each layer, on an object, or on a substrate.

[0048] In one aspect, the present invention relates to a catalyst for producing lactide from alkyl lactate, wherein the catalyst for producing lactide from alkyl lactate is a titanium-containing zeolite having an MWW-type framework formed by simultaneously mixing a titanium source, a silica source, and a template compound, followed by hydrothermal synthesis.

[0049] The catalyst for producing lactide according to the present invention is a titanium-containing zeolite catalyst having an MWW-type framework that is applied to produce lactide of Formula 2 by the cyclization reaction of a gaseous alkyl lactate represented by Formula 1 as shown in Reaction Scheme 1 below, and is a zeolite catalyst in which titanium atoms are substituted for some silicon atoms within the lattice framework of a molecular sieve.

[0050] [Reaction Equation 1]

[0051]

[0052] In the above reaction scheme 1, R may be an alkyl group having 1 to 20 carbon atoms.

[0053] A catalyst for producing lactide according to one embodiment of the present invention is produced by direct hydrothermal synthesis of a titanium source, a silica source, and a template compound, so that a larger amount of titanium (Ti) is stably positioned at the tetrahedral position, thereby increasing the selectivity of lactide and the conversion rate of alkyl lactate.

[0054] Hereinafter, the characteristics of each constituent component will be specifically explained along with the method for manufacturing a catalyst for lactide according to one embodiment of the present invention described above.

[0055] A method for producing a catalyst for producing lactide according to one embodiment of the present invention relates to a method for producing a catalyst for producing lactide from alkyl lactate, characterized by comprising the step of mixing a titanium source, a silica source, and a template compound, and then hydrothermally synthesizing to produce a titanium-containing zeolite having a MWW-type framework.

[0056] A method for manufacturing a catalyst for lactide according to one embodiment of the present invention can be manufactured by mixing a titanium source, a silica source, and a template compound, and then hydrothermally synthesizing them.

[0057] In one embodiment of the present invention, the silica source is a silicon precursor that is the main component of the zeolite, and any silicon or silicon-containing compound can be used without limitation. Specifically, silicic acid, tetraethyl orthosilicate, tetrapropyl orthosilicate, sodium silicate, colloidal silica, silica sol, silica gel, natural silica, fumed silica, synthetic silica, etc., can be used, and in terms of high-purity crystalline synthesis, it may preferably be tetraethyl orthosilicate or fumed silica.

[0058] Additionally, the titanium source is a source capable of providing titanium to the zeolite, and any compound containing titanium can be used without limitation and may include titanium alkoxide, titanium halide, titanium and mixtures thereof. Specifically, the titanium alkoxide may be titanium tetraisopropoxide, titanium tetraethoxide, titanium tetrabutoxide, etc., and the titanium halide may be titanium trichloride, titanium tetrachloride, etc.

[0059] Meanwhile, the template compound is a structure directing agent, and any compound containing imine, amine, or ammonium can be applied without limitation. Specifically, it may be hexamethyleneimine (HMI), piperidine, TMAdaOH (N,N,N-trimethyl-1-adamantylammonium hydroxide), TMAdaBr (N,N,N-trimethyl-1-adamantylammonium bromide), TMAdaF (N,N,N-trimethyl-1-adamantylammonium fluoride), TMAdaCl (N,N,N-trimethyl-1-adamantylammonium chloride), and TMAdaI (N,N,N-trimethyl-1-adamantylammonium iodide), and in terms of MWW structure synthesis, it may preferably be hexamethyleneimine or piperidine.

[0060] At this time, the silica source, titanium source, and template compound can be mixed in such a ratio of 0.002 moles to 0.2 moles of titanium source and 1.0 moles to 5.0 moles of template compound for every 1 mole of silica source to obtain a reaction mixture.

[0061] The reaction mixture mixed within the above content range can produce a high-content Ti-MWW type zeolite in which a large amount of Ti is contained in the zeolite framework structure, as titanium and silica share a tetrahedral structure with oxygen.

[0062] In addition, the reaction mixture may include a solvent such as water, and may also include other solvents such as alcohol in addition to water, and specifically, the alcohol may be isopropyl, ethyl alcohol, methyl alcohol, etc.

[0063] At this time, the solvent may be included in an amount of 1 mole to 50 moles per 1 mole of silica source so that titanium atoms can be uniformly substituted within the lattice framework of the molecular sieve. When the content ratio of the solvent satisfies the above range, the structure of the catalyst synthesized by the hydrothermal reaction can be uniformly formed.

[0064] In the above reaction mixture, the mixing order of the aforementioned silica source, titanium source, template compound, and solvent can be prepared by mixing in any order without special restrictions to form a gel state without precipitates. The above gel state reaction mixture has a pH of 9 to 13, and an alkaline aqueous solution in which a small amount of NaOH, etc. is dissolved can be used to adjust the pH.

[0065] Subsequently, the obtained reaction mixture can be used to produce a titanium-containing zeolite (Ti-MWW zeolite) having a MWW-type framework through a hydrothermal reaction.

[0066] The above hydrothermal reaction can be carried out at 50°C to 250°C, preferably 100°C to 200°C, for 10 hours to 14 days. When the above reaction conditions are satisfied, deformation of the zeolite structure due to prolonged heating can be prevented, and at the same time, the solubility of Si in the gel phase of the reaction mixture can be lowered, thereby enabling the production of an MWW-type zeolite containing a large amount of Ti in the zeolite framework structure.

[0067] The above hydrothermal reaction can be carried out under static or stirred conditions in a reactor vessel, such as an autoclave.

[0068] The titanium-containing zeolite having an MWW-type framework produced after the above hydrothermal reaction can be recovered by known methods such as filtration and washing, rotary evaporation, and centrifugation, and can be dried at a temperature of 20°C or higher, preferably 30°C to 90°C.

[0069] The titanium-containing zeolite having a recovered MWW-type framework may be calcined at a temperature of 200°C to 600°C, preferably 400°C to 600°C, to remove any residual template compounds. The calcination can typically be preferably carried out in an oxygen-containing atmosphere, such as air or a mixture of inert gases such as oxygen and nitrogen.

[0070] The titanium-containing zeolite having an MWW-type framework manufactured in this way may contain titanium, silicon, and oxygen within the lattice framework, and the Si:Ti molar ratio within the lattice framework of the zeolite may be 1:0.005 to 0.1, preferably 1:0.01 to 0.1.

[0071] A method for manufacturing a titanium-containing zeolite having a MWW-type framework according to one embodiment of the present invention has the advantage of being able to stably place a larger amount of titanium (Ti) in the zeolite active sites (tetrahedral positions) in a short time with a simple manufacturing process compared to a conventional method for manufacturing a titanium-containing zeolite that involves ion exchange of a boron-containing zeolite (B-MWW zeolite) with a titanium source, and the titanium-containing zeolite having a MWW-type framework manufactured by the method of the present invention has the advantage of being able to increase lactide selectivity and the conversion rate of alkyl lactate.

[0072] Meanwhile, from another perspective, the present invention relates to a catalyst for producing lactide from alkyl lactate, characterized in that it is a titanium-substituted plate-like exfoliated MWW zeolite.

[0073] The catalyst for producing lactide according to the present invention is a plate-like exfoliated MWW zeolite that is applied to produce lactide of Formula 2 by the cyclization reaction of gaseous alkyl lactate represented by Formula 1 as shown in the aforementioned reaction scheme 1, and is an exfoliated MWW zeolite catalyst in which titanium atoms are substituted within the lattice framework of a molecular sieve as shown in FIG. 6.

[0074] In another embodiment of the present invention, the zeolite catalyst may be characterized by being substituted with titanium in an amount of 0.5% to 10 wt% relative to the total weight of the catalyst. If the titanium is substituted in an amount of less than 0.5 wt% relative to the total weight of the catalyst, a problem with alkyl lactate activity may occur due to the distribution of a small amount of active sites, and if it exceeds 10 wt%, TiO2 in the form of anatase and rutile may be formed due to excessive aggregation of Ti, which may severely inhibit catalyst activity.

[0075] Hereinafter, the characteristics of each constituent component will be specifically described along with a method for manufacturing a zeolite catalyst according to another embodiment of the present invention.

[0076] According to another embodiment of the present invention, a method for producing a catalyst for producing lactide from alkyl lactate comprises: (a) preparing a boron-substituted MWW zeolite (B-MWW); (b) delaminating the prepared boron-substituted MWW zeolite (B-MWW) to obtain a boron-substituted delaminating MWW zeolite (B-MWW-del); (c) deborating the obtained boron-substituted delaminating MWW zeolite (B-MWW-del); and (d) substituting titanium into the deborated delaminating MWW zeolite to produce a titanium-substituted delaminating MWW zeolite (Ti-MWW-del).

[0077] Step (a) above is a step of preparing a boron-substituted MWW zeolite (B-MWW). The boron-substituted MWW zeolite (B-MWW) can be prepared without limitation using any method capable of producing a conventional boron-substituted MWW zeolite, and can be prepared as a commercially available boron-substituted MWW zeolite (B-MWW).

[0078] Specifically, the boron-substituted MWW zeolite (B-MWW) can be manufactured by hydrothermally synthesizing a starting mixture comprising a seed compound, a silica source, a boron source, a template compound, etc. At this time, the seed compound can be any MWW-type zeolite seed compound capable of manufacturing the boron-substituted MWW zeolite without limitation, and specifically, MWW-type fuming silica, colloidal silica, etc. can be used.

[0079] In addition, the boron source is a source capable of providing boron to the zeolite, and is a compound containing boron that can be used without limitation. Specifically, examples include boric acid, B2O3, borates, boric acid, boric anhydride, boron oxides (BxOy), boric acid esters, alkoxyborates, organic borate salts, boron halides, etc.

[0080] The silica source can be a silicon precursor, which is the main component of the zeolite, and any silicon or silicon-containing compound can be used without limitation. Examples include silicic acid, tetraethyl orthosilicate, tetrapropyl orthosilicate, sodium silicate, colloidal silica, silica sol, silica gel, natural silica, fumed silica, synthetic silica, etc., and in terms of minimizing impurities, it can preferably be fumed silica.

[0081] Meanwhile, the template compound is a structure directing agent, and any compound containing imine, amine, or ammonium can be applied without limitation. Specifically, it may be hexamethyleneimine (HMI), piperidine, TMAdaOH (N,N,N-trimethyl-1-adamantylammonium hydroxide), TMAdaBr (N,N,N-trimethyl-1-adamantylammonium bromide), TMAdaF (N,N,N-trimethyl-1-adamantylammonium fluoride), TMAdaCl (N,N,N-trimethyl-1-adamantylammonium chloride), and TMAdaI (N,N,N-trimethyl-1-adamantylammonium iodide), and preferably piperidine or hexamethyleneimine in terms of stable supply.

[0082] These starting materials are mixed to obtain a starting mixture, and the obtained starting mixture can be used to produce a boron-substituted MWW zeolite by hydrothermal synthesis. At this time, hydrothermal synthesis can be carried out for 6 to 7 days at, for example, 160 °C to 190 °C, preferably 170 °C to 180 °C, but is not limited thereto.

[0083] The boron-substituted MWW type zeolite (B-MWW) obtained after the reaction can be recovered by known methods such as filtration and washing, spray drying, centrifugation, etc., and can be dried at a temperature of 100°C to 150°C, preferably 100°C to 120°C.

[0084] Subsequently, the boron-substituted MWW zeolite (B-MWW) obtained above is delaminated to obtain a boron-substituted delaminated MWW zeolite (B-MWW-del) [Step (b)].

[0085] Step (b) above is a step of delaminating the boron-substituted MWW type zeolite (B-MWW), and any method that can be generally performed in the industry can be applied without limitation. Specifically, delamination can be performed after swelling using a surfactant and an alkali.

[0086] For example, the above surfactant treatment method can be performed using surfactants such as quaternary ammonium series such as hexadecyltrimethylammonium bromide, tetrapropylammonium hydroxide, cetyltrimethylammonium chloride, dodecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, etc., the acid treatment method can be performed using acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, propionic acid, oxalic acid, tartaric acid, etc., and the alkali treatment method can be performed using alkalis such as tetrapropylammonium hydroxide (TPAOH), tetramethylammonium hydroxide (TMAOH), tetraethylammonium hydroxide (TEAOH), and tetrabutylammonium hydroxide (TBAOH).

[0087] In the above swelling process, the mixture containing the boron-substituted MWW type zeolite is typically in the pH range of 12 or lower, preferably 10 to 12, and in order for sufficient exfoliation of the boron-substituted MWW type zeolite to occur, the process may be carried out at 40 ℃ to 80 ℃, more preferably 50 ℃ to 70 ℃ for 1 hour to 12 hours, but is not limited thereto.

[0088] After the above exfoliation, the exfoliated boron-substituted exfoliated MWW zeolite (B-MWW-del) can be recovered by known methods such as centrifugation and can be dried at a temperature of 80°C to 120°C.

[0089] Subsequently, the boron-substituted exfoliated MWW zeolite (B-MWW-del) obtained above can be deborided to obtain an exfoliated MWW zeolite. [(c) Step]

[0090] Step (c) above is a step of deboronizing the boron-exfoliated MWW zeolite (B-MWW-del) obtained in step (b). Any method that can be generally performed in the industry can be applied without limitation, and specifically, deboronization from the boron-substituted MWW-del type zeolite can be performed using acid treatment or a solvent.

[0091] At this time, the acid that can be used for the acid treatment may be one or more inorganic and / or organic acids, examples of which include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, propionic acid, oxalic acid, and tartaric acid, and preferably, in terms of the deboronization rate, it may be nitric acid, etc. In addition, any solvent capable of deboronizing the boron-substituted exfoliated MWW zeolite may be applied without limitation, examples of which include monohydric alcohols such as water, methanol, ethanol, propanol, and butanol, and preferably, in terms of solubility and safety, it may be water, methanol, or ethanol.

[0092] The deboration of the boron-exfoliated MWW zeolite can be carried out using conditions such as maintaining a constant temperature or starting the reaction at a low temperature and gradually increasing the temperature. Specifically, the deboration can be performed at 20°C to 200°C, preferably at 40°C to 120°C. At this time, if the deboration temperature is below 20°C, the deboration reaction may not proceed sufficiently, and if it exceeds 200°C, there is a risk that the zeolite structure may be damaged.

[0093] In addition, it is preferable to determine the above deboration time by adjusting it according to conditions such as the zeolite content and temperature, but if the reaction time is to be limited, it can be performed for 10 to 40 hours.

[0094] Subsequently, the deboride exfoliated MWW zeolite can be recovered by known methods such as washing and spray drying, and the drying can be performed at a temperature of 50°C to 300°C, preferably 100°C to 150°C.

[0095] The above-mentioned deboride exfoliated MWW zeolite can be substituted with titanium to produce a plate-like titanium-substituted exfoliated MWW zeolite (Ti-MWW-del) [Step (d)].

[0096] Step (d) above is a step of substituting titanium into the deboride exfoliated MWW zeolite, and any method capable of substituting titanium can be applied without limitation. Specifically, it can be manufactured by synthesizing the obtained deboride exfoliated MWW zeolite with a titanium source.

[0097] The above titanium source may be used without limitation as long as it is a compound containing titanium, and may include, for example, titanium alkoxide, titanium halide, titanium inorganic salt and mixtures thereof, wherein the titanium alkoxide may be titanium tetraisopropoxide, titanium tetraethoxide, titanium tetrabutoxide, etc., the titanium halide may be titanium trichloride, titanium tetrachloride, etc., and the titanium inorganic salt may be titanium nitrate, titanium sulfate, titanium oxide sulfate, etc.

[0098] At this time, the substitution reaction can be carried out for 0.5 hours to 48 hours, more preferably 1 hour to 5 hours at a temperature in the range of 50 ℃ to 250 ℃, more preferably 80 ℃ to 120 ℃.

[0099] The titanium-substituted exfoliated MWW zeolite produced after the above reaction can be recovered by known methods such as filtration and washing, spray drying, and centrifugation, and the drying can be performed at 50 ℃ to 250 ℃, preferably 80 ℃ to 120 ℃.

[0100] The titanium-substituted exfoliated MWW zeolite prepared in this manner may contain titanium, silicon, and oxygen within its lattice framework and may generally have a composition corresponding to the empirical formula xTiO2·(1-x)SiO2 (where x is 0.005 to 0.1), and more preferably, the x value may be 0.01 to 0.05. At this time, the Si : Ti molar ratio within the lattice framework of the zeolite may be 10 : 1 to 200 : 1, preferably 20 : 1 to 100 : 1.

[0101] A catalyst for producing lactide according to another embodiment of the present invention is prepared by substituting titanium into a zeolite with an expanded surface area due to interlayer exfoliation, thereby allowing a larger amount of titanium (Ti) to be stably positioned at the tetrahedral position and having an interlayer exfoliated plate-like structure that expands the reaction surface area, while simultaneously increasing the conversion rate of alkyl lactate and the selectivity of lactide according to the porous structural characteristics of the MWW framework.

[0102] Meanwhile, in another aspect, the present invention relates to a method for producing lactide from alkyl lactate, characterized by cyclizing gaseous alkyl lactate in the presence of the aforementioned catalyst for producing lactide.

[0103] In the method for producing lactide from an alkyl lactate according to the present invention, the alkyl lactate may be represented by Formula 1 as a starting material and may be one or more of the alkyl lactates having 1 to 20 carbon atoms in the alkyl group in Formula 1. In order to obtain lactide in a short time with high yield, the number of carbon atoms in the alkyl group may preferably be 1 to 14, more preferably 1 to 10, even more preferably 1 to 7, and most preferably 1 to 4.

[0104] The above alkyl lactate may be a commercially available product or may be obtained using a process known in the art. For example, it may be obtained by esterifying a lactic acid fermentation liquid with an alcohol, and may have a moisture content of 40 wt% or less, preferably 5 wt% or less.

[0105] The cyclization reaction of the above alkyl lactate may be characterized by using a catalyst for lactide production according to the present invention.

[0106] The catalyst for producing lactide according to the present invention may be a titanium-containing zeolite catalyst having an MWW-type framework produced by hydrothermal synthesis of a titanium source, a silica source, and a template compound, and the catalyst for producing lactide according to the present invention may also be a titanium-substituted exfoliated MWW-type zeolite catalyst with a plate-like structure.

[0107] The above catalyst can be used in an amount of 0.1 to 100 parts by weight, preferably 5 to 30 parts by weight, relative to 100 parts by weight of alkyl lactate. If the above catalyst is used in an amount exceeding 100 parts by weight relative to 100 parts by weight of alkyl lactate, the space velocity may increase while the selectivity of lactide may decrease; if it is used in an amount less than 0.1 parts by weight, it may be difficult to control the reaction rate and problems may arise such as a decrease in the optical purity of the lactide produced at the end.

[0108] The cyclization reaction of the alkyl lactate described above can be carried out using conditions such as maintaining a constant temperature or starting the reaction at a low temperature and gradually increasing the temperature. Specifically, it can be performed at 150°C to 300°C, preferably 180°C to 250°C. If the reaction temperature is below 150°C, the reaction rate may be slowed down, and if it exceeds 300°C, problems may arise where the reaction does not proceed smoothly due to excessive boiling of the alkyl lactate reactant.

[0109] In addition, it is preferable to determine the reaction time of the above cyclization reaction by adjusting it according to conditions such as the type or content of alkyl lactate and the reaction temperature, but if the reaction time is to be limited, it can be performed for 1 hour to 100 hours.

[0110] Furthermore, the above cyclization reaction can be carried out under constant pressure conditions to remove alcohol produced as a byproduct from the reaction system, or by gradually reducing the pressure over the reaction time. At this time, the reaction pressure may be 1 bar to 5 bar, preferably 1 bar to 3 bar. If the pressure is less than 1 bar, energy costs are high to maintain the vacuum, and if it exceeds 5 bar, it is difficult to separate the alcohol produced within the reaction system, which can lead to a reverse reaction and significantly lower the selectivity of lactide.

[0111] At this time, the space velocity (WHSV) of the starting material, alkyl lactate, is 0.1 h -1 ~ 50.0 h -1 , preferably 1.0 h -1 ~ 10.0 h -1 It could be. If, the above space velocity is 0.1 h -1 In cases below 50.0 h, additional continuous reactions other than lactide may occur due to the small influx of reactants, and 50.0 h -1If it exceeds [amount], the problem of inactivation due to a decrease in the alkyl lactate conversion rate caused by an excessive supply of reactants may occur quickly.

[0112] In addition, the method for producing lactide according to the present invention may proceed with the reaction in a solvent-free state, or may use a solvent if necessary. When using a solvent, it is preferable to use a solvent with a solubility similar to that of alkyl lactate in order to prevent the reaction from being inhibited by the generated lactide and to increase the efficiency of the reaction. Specifically, lower alcohols and polyalcohols such as ethanol, methanol, 2-propanol, and isopropyl alcohol (IPA) can be utilized as suitable solvents.

[0113] The present invention will be explained in more detail below through specific embodiments. The following embodiments are merely examples to aid in understanding the present invention and do not limit the scope of the present invention.

[0114] <Preparation Example 1: Preparation of Boron-Substituted MWW Zeolite (B-MWW)>

[0115] 9.2 g of boric acid, 6.7 g of fumed silica, 1.8 g of sodium hydroxide (NaOH), 7.4 g of hexamethyleneimine (HMI), and 32.5 g of water were added to a plastic beaker and stirred for a sufficient amount of time to form a reaction mixture. Subsequently, the reaction mixture was transferred to an autoclave, mounted in a stainless steel container, and hydrothermal synthesis was performed for 7 days at a temperature of 175 °C under stirring. The solid product obtained from the hydrothermal synthesis was filtered and washed with deionized water repeatedly, and then dried at room temperature to produce B-MWW zeolite.

[0116] <Example 1: Preparation of Ti-MWW Zeolite Catalyst According to One Embodiment of the Present Invention>

[0117] 5 g (1 mol) of silica sol (silica 99 wt%), 2 g (0.006 mol) of titanium tetrabutoxide, 6 g (1.0 mol) of HMI, 1.0 g of butanol, 0.5 g (0.2 mol) of boric acid, and 25 g (20 mol) of water were added to a plastic beaker and stirred for 24 hours to form a reaction mixture. Subsequently, the formed reaction mixture was transferred to a Teflon reactor and placed in a stainless steel container to hydrothermally synthesize at 170 °C for 120 hours. The solid product produced by the hydrothermal synthesis was repeatedly washed with water and then dried at room temperature for 12 hours. Subsequently, the dried solid product was calcined at 550 °C for 8 hours in an air atmosphere to produce a titanium-containing zeolite (Ti-MWW zeolite) having a MWW-type framework.

[0118] <Example 2: Preparation of Titanium Substituted Exfoliated MWW Zeolite (Ti-MWW-del) Catalyst According to Another Embodiment of the Present Invention>

[0119] 1 g of the boron-substituted MWW-type zeolite (B-MWW) prepared in Preparation Example 1 was mixed with 1.4 g of hexadecyltrimethylammonium bromide (CTMABr), 6 g of tetrapropylammonium hydroxide (TPAOH), and 22.6 g of water, and swollen at 80 °C for 10 hours, after which interlayer exfoliation was performed by ultrasonic treatment. Subsequently, the pH was adjusted to 2 or lower using hydrochloric acid, and the boron-substituted exfoliated MWW-type zeolite (B-MWW-del) was obtained by repeatedly washing with water using a centrifuge. 1 g of the boron-substituted exfoliated MWW zeolite (B-MWW-del) obtained above was added to 20 ml of 6 M nitric acid and deboronized at 60 °C for about 20 hours, and then stirred at 100 °C for 1 hour in a 20 ml mixed solution containing 0.7 g of titanium tetrachloride (TiCl4) and 6 M hydrochloric acid. Afterward, the product from the above synthesis was repeatedly washed with water and then dried at 120 °C for 10 hours. The dried solid product was calcined at 550 °C for 10 hours in an air atmosphere to prepare a plate-like exfoliated MWW zeolite (Ti-MWW-del) catalyst in which titanium was substituted at 0.4 wt% relative to the total weight of the catalyst.

[0120] <Comparative Example 1: Preparation of Ti-MWW Zeolite Catalyst According to Conventional Method>

[0121] 5 g (0.08 mol) of boric acid, 38 g (0.2 mol) of silica sol (silica 30 wt%), 3.2 g (0.04 mol) of piperidine, and 40 g (2.2 mol) of water were added to a plastic beaker and stirred for 12 hours to form a reaction mixture. Subsequently, the formed reaction mixture was transferred to a Teflon reactor and then placed in a stainless steel container for hydrothermal synthesis at 100 °C for 30 hours. The solid product produced by the hydrothermal synthesis was repeatedly washed with water and then dried at room temperature for 12 hours to obtain B-MWW zeolite. The obtained B-MWW zeolite was deboronized with nitric acid at a mass fraction of 33% at 120 °C, and then 1.5 g (0.004 mol) of titanium tetrabutoxide was added and hydrothermal synthesis was performed at 160 °C for 60 hours. Subsequently, the solid product produced by the above hydrothermal synthesis was repeatedly washed with water and then dried at room temperature for 12 hours. The dried solid product was calcined at 500°C for 10 hours in an air atmosphere to produce a titanium-containing zeolite (Ti-MWW zeolite) having a MWW-type framework.

[0122] <Comparative Example 2: Preparation of TiO2 / ITQ-2 Catalyst>

[0123] 10 g of ITQ-2 support was prepared and immersed in 50 g of a 5 wt% titanium isopropoxide [Ti(OiPr)4] solution. The solution was prepared by dissolving isopropoxide [Ti(OiPr)4] in isopropanol, and the concentration of the Ti precursor was adjusted through experimental optimization. With the support immersed in the solution, the mixture was stirred at room temperature for 1 hour to ensure that the TiO2 precursor was uniformly adsorbed onto the surface of the ITQ-2 within the solution. After immersion, the solvent was removed by vacuum evaporation at 80 °C, and the mixture was dried at 120 °C for 12 hours. Subsequently, the dried support was calcined in air at 500 °C for 3 hours to produce a TiO2 / ITQ-2 catalyst evenly impregnated with TiO2.

[0124] <Comparative Example 3: Preparation of TiO2 / MCM-22 Catalyst>

[0125] A TiO2 / MCM-22 catalyst was prepared in the same manner as Comparative Example 2 above, except that MCM-22 was used instead of the ITQ-2 support.

[0126] <Comparative Example 4: Preparation of TiO2 / MCM-41 Catalyst>

[0127] A TiO2 / MCM-41 catalyst was prepared in the same manner as Comparative Example 2 above, except that MCM-41 was used instead of the ITQ-2 support.

[0128] <Comparative Example 5: Preparation of TS-1 Catalyst>

[0129] TS-1 zeolite was prepared using sodium silicate and titanium isopropoxide [Ti(OiPr)4] as major precursors. First, 100 g of a 0.5 M sodium silicate solution was prepared to supply a silica source, and an isopropanol solution containing 10 g of titanium isopropoxide was slowly added while stirring. The pH of the stirred solution was adjusted to 10, and then 5 g of tetrapropylammonium bromide (TPABr) was added as a template agent and mixed. Subsequently, the reaction solution was hydrothermally synthesized at 170 °C for 48 hours to form TS-1 crystals. The resulting solid was filtered, washed, and dried, then calcined at 550 °C to remove the organic template, which acts as a structure-directing agent, thereby preparing the TS-1 catalyst.

[0130] <Comparative Example 6: Preparation of Exfoliated MWW Zeolite (TiO2 / MWW-del) Catalyst Supported on TiO2>

[0131] 1 g of the boron-substituted MWW-type zeolite (B-MWW) prepared in Preparation Example 1 was mixed with 1.4 g of hexadecyltrimethylammonium bromide (CTMABr), 6 g of tetrapropylammonium hydroxide (TPAOH), and 22.6 g of water, and swollen at 80 °C for 10 hours, after which interlayer exfoliation was performed by ultrasonic treatment. Subsequently, the pH was adjusted to 2 or lower using hydrochloric acid, and the boron-substituted exfoliated MWW-type zeolite (B-MWW-del) was obtained by repeatedly washing with water using a centrifuge. 1 g of the obtained boron-substituted exfoliated MWW zeolite (B-MWW-del) was supported with a supporting solution consisting of 0.19 g of titanium isopropoxide (Ti(OiPr)4) and 0.79 mL of 2-propanol under a nitrogen atmosphere for a sufficient amount of time. Subsequently, the supported solid product was dried at 120 °C for 8 hours, and then calcined at 550 °C for 4 hours under an air atmosphere to prepare an exfoliated MWW zeolite (TiO2 / MWW-del) catalyst in which TiO2 was supported at 4.7 wt% relative to the total weight of the catalyst.

[0132] <Comparative Example 7: Preparation of TiO2-supported MCM-41 mesoporous silica zeolite (TiO2 / MCM-41) catalyst>

[0133] 1 g of pure silicon-based MCM-41 was used and dehydrated under a nitrogen atmosphere, and then a supporting solution consisting of 0.19 g of titanium isopropoxide (Ti(OiPr)4) and 0.79 ml of 2-propanol was supported under a nitrogen atmosphere. The supported solid product was dried at 120 °C for 8 hours and then calcined at 550 °C for 4 hours under an air atmosphere to prepare an MCM-41 mesoporous silica zeolite (TiO2 / MCM-41) catalyst in which TiO2 was supported at 4.7 wt% relative to the total weight of the catalyst.

[0134] <Comparative Example 8: Preparation of TiO2-supported MWW zeolite (TiO2 / MWW) catalyst>

[0135] 1 g of the boron-substituted MWW type zeolite (B-MWW) prepared in Preparation Example 1 was used, and after dehydrating it under a nitrogen atmosphere, a supporting solution composed of 0.19 g of titanium isopropoxide (Ti(OiPr)4) and 0.79 g of 2-propanol was supported under a nitrogen atmosphere. The supported solid product was dried at 120 °C for 8 hours, and then calcined at 550 °C for 4 hours under an air atmosphere to prepare a MWW zeolite (TiO2 / MWW) catalyst in which TiO2 was supported at 4.7 wt% relative to the total weight of the catalyst.

[0136] <Comparative Example 9: Preparation of Titanium-Substituted MWW Zeolite (Ti-MWW) Zeolite Catalyst>

[0137] 1 g of the boron-substituted MWW type zeolite (B-MWW) prepared in Preparation Example 1 was added to 20 ml of 6 M nitric acid and deboronized at 60 °C for about 20 hours, and then stirred at 100 °C for 1 hour with 20 ml of a mixed solution containing 0.32 g of titanium tetrachloride (TiCl4) and 6 M hydrochloric acid. Afterward, the product from the above synthesis was repeatedly washed with water and then dried at 120 °C for 10 hours. The dried solid product was calcined at 550 °C for 10 hours under an air atmosphere to prepare a MWW zeolite (Ti-MWW) catalyst in which titanium was substituted at 0.4 wt% relative to the total weight of the catalyst.

[0138] <Comparative Example 10: Preparation of Titanium Silicate Zeolite (TS-1) Catalyst>

[0139] A reaction solution was prepared by mixing 18 g of tetraethyl orthosilicate (TEOS) and 0.36 g of tetraethyl orthotitanate (TEOT). 37 g of tetrapropylammonium hydroxide (TPAOH) was added to the solution and mixed, after which ethanol was removed. Subsequently, water was added to form a reaction mixture, which was transferred to an autoclave and hydrothermally synthesized at 175 °C for 2 days under rotary stirring. After the reaction was completed, the obtained solid product was recovered by filtration and washing, dried at 120 °C for 10 hours, and then calcined at 550 °C for 8 hours to produce titanium silicate zeolite (TS-1).

[0140] <Experimental Example 1>

[0141] To evaluate the characteristics of the catalysts prepared in Example 1 and Comparative Examples 1 to 5, the surface area and pore size of the catalysts were measured using Brunauer-Emmett-Teller (BET) measurement (Autochem II, Micromeritics) and are shown in Table 1. The pore size was calculated using the Hgoorvath-Kawazoe (HK) method, and the titanium content in the zeolite was measured using ICP-AES (iCAP PRO XP Duo.). Additionally, the catalyst morphology and crystal structure were measured using X-ray diffraction (XRD; Rigaku Ultima IV, Cu Kα radiation) and are shown in Fig. 1. Meanwhile, the oxidation state and coordination state of titanium within the catalyst were measured using Diffuse Reflectance UV-vis Spectrum (DR UV-vis, Agilent) and are shown in Fig. 2. Since the Ti-MWW in Fig. 1 and Fig. 2 appears identical for Example 1 and Comparative Example 1, the Ti-MWW of Example 1 is shown as a representative example.

[0142] [Table 1]

[0143]

[0144] As shown in Table 1, the titanium content in the examples and comparative examples was within 5 wt%, so there was no significant difference between them; thus, it was confirmed that no change in catalyst performance was caused by significant differences in titanium content between the samples. As indicated by the BET surface area, it was confirmed that the porous surface was maintained despite substitution or impregnation of titanium within the framework.

[0145] In addition, as shown in Figure 1, it was confirmed that each manufactured catalyst is a crystalline porous material and has the characteristics of an MWW or MFI structure.

[0146] In the case of Example 1, Comparative Example 1, and Comparative Example 5 above, Ti is substituted into the framework, and in the case of Comparative Examples 2 to 4, TiO2 is supported on the support. As shown in FIG. 2, it was confirmed that compared to the titanium-impregnated catalyst, the proportion of independent tetrahedral titanium tetroxide with activated oxidation-coordination states of titanium in the Ti-MWW and TS-1 catalysts substituted into the framework is higher.

[0147] <Experimental Example 2>

[0148] The catalytic reaction required for the conversion of methyl lactate (Aldrich, 98%) to lactide was carried out in a continuous-flow fixed-bed microreactor under atmospheric pressure conditions. Two thermocouples for temperature control were installed directly above and on the side of the catalyst layer inside the reactor, and 0.3 g of catalyst (30 / 40 mesh size) was fixed between two quartz wools in the center of the reactor. Prior to the reaction, the MCM-41 catalyst and the zeolite catalyst were pretreated at 300 °C and 500 °C, respectively, for 2 hours under nitrogen (N2) gas (heating rate 7 °C / min, N2 flow rate 20 mL / min).

[0149] Subsequently, the catalyst was cooled and maintained at the reaction temperature. The methyl lactate feed was transferred to the reactor at a rate of 0.01 mL / min, mixed with N2 (40 mL / min) heated to 220 °C in a preheater to be completely vaporized, and then injected into the reaction chamber under WHSV conditions set at 220 °C to carry out the reaction and produce lactide. The selectivity, productivity, and methyl lactate conversion rates of the produced lactide were calculated using Equations 1 to 3 and are shown in Figures 3 to 5.

[0150] Selectivity (%) = Moles of lactide produced / Moles of converted methyl lactate × 100.....(1)

[0151] Conversion rate (%) = moles of consumed methyl lactate / moles of initial input methyl lactate × 100.....(2)

[0152] Productivity (%) = Moles of produced lactide / (Amount of catalyst × Time) × 100.....(3)

[0153] As shown in Fig. 3, it was confirmed that the lactide selectivity of impregnated TiO2 / ITQ-2 (Comparative Example 2) and Ti-MWW (Example 1) was superior to that of TS-1 zeolite (Comparative Example 5). Through this, it was found that the skeletal structure of MWW is superior to other zeolite skeletal structures for lactide production. However, when considering the concept of productivity taking into account the amount of catalyst and the TOF calculated by the frequency per active site of Ti, it was found that the Ti-MWW (Example 1) of the present invention exhibited significantly higher TOF and productivity, as shown in Fig. 4.

[0154] In addition, as shown in Fig. 5, it was confirmed that even within the same MWW structure, the Ti-MWW produced by the impregnation method of (a) (Example 1) had superior productivity compared to the Ti-MWW produced by the post-processing method of (b) (Comparative Example 1).

[0155] <Experimental Example 3>

[0156] 0.3 g of the catalyst prepared in Example 2 and Comparative Examples 6 to 10 was loaded into a fixed-bed reactor and pretreated under a nitrogen atmosphere, after which 0.01 mL / min of methyl lactate (ML) was supplied. At this time, the reactor temperature was maintained at 220 °C and the pressure at atmospheric pressure, and nitrogen at a flow rate of 40 mL / min was mixed, vaporized, and introduced into the reactor. The reaction was carried out at a WHSV of 2.16 h -1 or 4.33 h -1 The procedure was performed under WHSV conditions, and the products were analyzed using online gas chromatography (GC). The results are shown in Figures 7 and 8 below.

[0157] As shown in Figure 7, it was confirmed that titanium-substituted MWW-series zeolites (Ti-MWW, Ti-MWW-del) exhibited significantly higher lactide productivity compared to the catalysts prepared in other comparative examples.

[0158] Also, as shown in Fig. 8, under harsher reaction conditions (4.33 h -1 The difference in catalyst performance is more clearly revealed in WHSV, and it can be confirmed that the titanium-substituted exfoliated MWW zeolite (Ti-MWW-del) prepared in Example 2 exhibits superior lactide productivity compared to the Ti-MWW prepared in Comparative Example 9.

[0159] Although the present invention has been described with reference to the embodiments described above, different embodiments may be constructed within the concept and scope of the invention. Accordingly, the scope of the invention is defined by the appended claims and their equivalents, and is not limited by the specific embodiments described in this specification.

Claims

1. As a catalyst for the production of lactide from alkyl lactate, The catalyst for producing lactide from the above alkyl lactate is characterized by being a titanium-containing zeolite having an MWW-type framework formed by mixing a titanium source, a silica source, and a template compound, followed by hydrothermal synthesis.

2. In Paragraph 1, The above titanium-containing zeolite is a catalyst for producing lactide from alkyl lactate, characterized in that titanium is contained in an amount of 0.1 wt% to 20 wt% relative to the total weight of the zeolite.

3. As a catalyst for the production of lactide from alkyl lactate, A catalyst for producing lactide from alkyl lactate, characterized in that the catalyst is a titanium-substituted exfoliated MWW zeolite.

4. In Paragraph 3, A catalyst for producing lactide from alkyl lactate, characterized in that the titanium-substituted exfoliated MWW zeolite is substituted with titanium in an amount of 0.1 wt% to 10 wt% relative to the total weight of the catalyst.

5. In Paragraph 3, A catalyst for producing lactide from alkyl lactate, characterized in that the titanium-substituted exfoliated MWW zeolite has an interlayer exfoliated plate-like structure.

6. A method for producing a catalyst for producing lactide from alkyl lactate, wherein A method for producing a catalyst for producing lactide from alkyl lactate, characterized by including the step of producing a titanium-containing zeolite having an MWW-type framework by hydrothermal synthesis after mixing a titanium source, a silica source, and a template compound.

7. In Paragraph 6, A method for producing a catalyst for lactide from alkyl lactate, characterized in that the titanium source is selected from the group consisting of titanium alkoxide, titanium halide, titanium organometallic compound, titanium oxide precursor, titanium complex, and mixtures thereof.

8. In Paragraph 6, A method for producing a catalyst for producing lactide from alkyl lactate, characterized in that the above silica source is one or more selected from the group consisting of silicic acid, tetraethyl orthosilicate, tetrapropyl orthosilicate, sodium silicate, colloidal silica, silica sol, silica gel, natural silica, fumed silica, and synthetic silica.

9. In Paragraph 6, A method for producing a catalyst for producing lactide from an alkyl lactate, characterized in that the above template compound is one or more selected from the group consisting of hexamethyleneimine (HMI), piperidine, TMAdaOH (N,N,N-trimethyl-1-adamantylammonium hydroxide), TMAdaBr (N,N,N-trimethyl-1-adamantylammonium bromide), TMAdaF (N,N,N-trimethyl-1-adamantylammonium fluoride), TMAdaCl (N,N,N-trimethyl-1-adamantylammonium chloride), and TMAdaI (N,N,N-trimethyl-1-adamantylammonium iodide).

10. In Paragraph 6, A method for producing a catalyst for producing lactide from alkyl lactate, characterized in that the above hydrothermal synthesis is performed at 50 ℃ to 250 ℃.

11. In Paragraph 6, A method for producing a catalyst for producing lactide from alkyl lactate, characterized by further adding the step of recovering and drying a titanium-containing zeolite having a MWW-type framework synthesized after the above hydrothermal synthesis, and calcining it at a temperature of 200 ℃ to 600 ℃.

12. A method for producing a catalyst for producing lactide from alkyl lactate, wherein (a) A step of preparing a boron-substituted MWW zeolite; (b) a step of swelling and exfoliating the boron-substituted MWW zeolite prepared in step (a) above to obtain a boron-substituted exfoliated MWW zeolite; (c) a step of deboration from the boron-substituted exfoliated MWW zeolite obtained in step (b) above; and (d) a step of producing a titanium-substituted exfoliated MWW zeolite by substituting titanium into the above-mentioned deborided exfoliated MWW zeolite; characterized by comprising a method for producing a catalyst for producing lactide from alkyl lactate.

13. In Paragraph 12, A method for producing a catalyst for producing lactide from alkyl lactate, characterized in that the swelling and peeling in step (b) above utilize one or more methods selected from the group consisting of surfactant treatment methods, alkali treatment methods, ultrasonic treatment methods, and acid treatment methods.

14. A method for producing lactide from alkyl lactate, characterized by cyclizing gaseous alkyl lactate in the presence of a catalyst for producing lactide according to any one of claims 1 to 5 or a catalyst produced by the method of any one of claims 6 to 13.

15. In Paragraph 14, A method for producing lactide from alkyl lactate, characterized in that the content of the catalyst for producing lactide is 0.1 to 90 parts by weight per 100 parts by weight of alkyl lactate.

16. In Paragraph 14, A method for producing lactide from alkyl lactate, characterized in that the cyclization reaction of the alkyl lactate is carried out at 150 ℃ to 300 ℃.

17. In Paragraph 14, A method for producing lactide from alkyl lactate, characterized by performing the cyclization reaction of the alkyl lactate at a pressure of 1 bar to 5 bar.

18. In Paragraph 14, The above alkyl lactate is 0.1 h -1 ~ 50 h -1 Supply at the spatial velocity of A method for producing lactide from alkyl lactate characterized by performing a cyclization reaction.

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