CN111253239B - Method for preparing lactic acid by catalyzing methylglyoxal - Google Patents

Method for preparing lactic acid by catalyzing methylglyoxal Download PDF

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CN111253239B
CN111253239B CN201811456825.9A CN201811456825A CN111253239B CN 111253239 B CN111253239 B CN 111253239B CN 201811456825 A CN201811456825 A CN 201811456825A CN 111253239 B CN111253239 B CN 111253239B
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tin
molecular sieve
titanium
silicon molecular
silicon
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CN111253239A (en
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朱斌
刘聿嘉
夏长久
林民
彭欣欣
罗一斌
舒兴田
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Sinopec Research Institute of Petroleum Processing
China Petroleum and Chemical Corp
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China Petroleum and Chemical Corp
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • B01J29/405—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing rare earth elements, titanium, zirconium, hafnium, zinc, cadmium, mercury, gallium, indium, thallium, tin or lead
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/584—Recycling of catalysts

Abstract

The invention relates to a method for preparing lactic acid by catalyzing methylglyoxal, which comprises the following steps: the method comprises the following steps of (1) enabling methylglyoxal and water to contact with a catalyst in a reactor and reacting to obtain a product containing lactic acid; wherein the molar ratio of the methylglyoxal to the water is 1: (40-350), the reaction temperature is 30-180 ℃, the reaction time is 1-10h, the catalyst contains a tin-titanium-silicon molecular sieve, and the weight ratio of the methylglyoxal to the tin-titanium-silicon molecular sieve based on the dry weight is 1: (1-6). The method of the present invention has high methylglyoxal conversion and lactic acid yield.

Description

Method for preparing lactic acid by catalyzing methylglyoxal
Technical Field
The invention relates to a method for preparing lactic acid by catalyzing methylglyoxal.
Background
Lactic acid (2-hydroxypropionic acid, scientific name) is a compound that functions in a variety of biochemical processes, and has the molecular formula C 3 H 6 O 3 . It is a carboxylic acid containing a hydroxyl group and is therefore an alpha-hydroxy acid. Its carboxyl group in aqueous solution releases a proton, producing lactate ions. Lactate dehydrogenase converts pyruvate to L-lactate during fermentation. Lactic acid is produced continuously during normal metabolism and exercise, but its concentration does not generally rise. Lactic acid is a colorless liquid, and the industrial product is a colorless to pale yellow liquid. The natural plant extract is odorless, has hygroscopicity, has a relative density of 1.200, a melting point of 18 ℃, a boiling point of 122 ℃ and a flash point of more than 110 ℃, is miscible with ethanol, ether, water and glycerin, is insoluble in chloroform, carbon disulfide and petroleum ether, and is widely applied to the food industry, the pharmaceutical industry, the cosmetic industry and the agricultural and livestock industry.
The traditional lactic acid production method mainly adopts a sugar fermentation method and a chemical synthesis method. The fermentation method uses saccharides as raw materials, and the pH value of a fermentation system needs to be maintained within the range of 5.5-6.5, but the pH value is gradually reduced along with the continuous generation of lactic acid, so that calcium oxide or calcium carbonate needs to be continuously added in the reaction process to balance the pH value of the system. The generated calcium lactate is treated by sulfuric acid to obtain crude lactic acid, and simultaneously, a large amount of waste salt (calcium sulfate) is generated. However, crude lactic acid is difficult to separate, and it is necessary to react with alcohol to produce lactate having a relatively low boiling point, and then to obtain high-purity lactic acid through distillation separation and hydrolysis reaction. The reaction route of the process is long, the production cost is high, and a large amount of solid waste residue is generated, so that the large-scale production and application of the lactic acid cannot be realized at present. The commonly used chemical synthesis method is a lactonitrile method and a propionic acid method, the lactonitrile method uses acetaldehyde and hypertoxic hydrocyanic acid as reaction raw materials, and concentrated sulfuric acid is a catalyst, so that the pollution in the production process is serious, and potential safety hazards exist. The propionic acid method uses toxic chlorine as a raw material, has high requirements on operation safety and tightness, and is easy to cause pollution to the atmospheric environment.
Disclosure of Invention
The invention aims to provide a method for preparing lactic acid by catalyzing methylglyoxal, which has high methylglyoxal conversion rate and lactic acid yield.
In order to achieve the above objects, the present invention provides a method for preparing lactic acid by catalyzing methylglyoxal, the method comprising:
contacting methylglyoxal and water with a catalyst in a reactor and reacting to obtain a product containing lactic acid; wherein the molar ratio of the methylglyoxal to the water is 1: (40-350), the reaction temperature is 30-180 ℃, the reaction time is 1-10h, the catalyst contains a tin-titanium-silicon molecular sieve, and the weight ratio of the methylglyoxal to the tin-titanium-silicon molecular sieve based on the dry weight is 1: (1-6).
Optionally, the tin-titanium-silicon molecular sieve is selected from one or more of an MFI type tin-titanium-silicon molecular sieve, an MEL type tin-titanium-silicon molecular sieve, a BEA type tin-titanium-silicon molecular sieve, an MWW type tin-titanium-silicon molecular sieve, an MOR type tin-titanium-silicon molecular sieve, a hexagonal structure tin-titanium-silicon molecular sieve and an FAU type tin-titanium-silicon molecular sieve.
Optionally, the tin-titanium-silicon molecular sieve is selected from one or more of Sn-Ti-MFI molecular sieve, sn-Ti-MEL molecular sieve, sn-Ti-Beta molecular sieve, sn-Ti-MCM-22 molecular sieve, sn-Ti-MOR molecular sieve, sn-Ti-MCM-41 molecular sieve, sn-Ti-SBA-15 molecular sieve and Sn-Ti-USY molecular sieve.
Optionally, the tin-titanium-silicon molecular sieve contains a silicon element, a titanium element, a tin element and an oxygen element;
preferably, at least part of the inner part of crystal grains of the tin-titanium-silicon molecular sieve has a cavity structure;
preferably, the proportion of the external specific surface area of the tin-titanium-silicon molecular sieve in the total specific surface area is more than 10%, and the total specific surface area is 300m 2 More than g, and the external specific surface area is 20m 2 More than g;
preferably, the tin-titanium-silicon molecular sieve has a diffraction peak at 0.5-9 degrees in 2 theta in an XRD pattern;
preferably, the tin-titanium-silicon molecular sieve is 460cm in FT-IR spectrum -1 、975cm -1 、800cm -1 And 1080cm -1 There is absorption nearby;
preferably, the tin-titanium-silicon molecular sieve has absorption at 200-300nm in a UV-Vis spectrum;
preferably, the ratio of the external specific surface area of the tin-titanium-silicon molecular sieve to the total specific surface area is 10-25%, and the total specific surface area is 310-600m 2 Per g, external specific surface area of 31-150m 2 /g；
Preferably, the tin-titanium-silicon molecular sieve is P/P at 25 DEG C 0 An amount of benzene adsorbed of at least 35mg/g as measured with an adsorption time of 1 hour and 0.10; at a relative pressure P/P 0 If the molar ratio is about 0.60, the difference between the nitrogen adsorption amount during desorption and the nitrogen adsorption amount during adsorption of the tin-titanium-silicon molecular sieve is greater than 2% of the nitrogen adsorption amount during adsorption of the tin-titanium-silicon molecular sieve;
preferably, a hysteresis loop exists between the adsorption isotherm and the desorption isotherm of the low-temperature nitrogen adsorption of the tin-titanium-silicon molecular sieve;
preferably, the radial length of the cavity part of the cavity structure inside the crystal grains of the tin-titanium-silicon molecular sieve is 0.5-300nm;
preferably, the molar ratio of the tin element to the silicon element in the tin-titanium-silicon molecular sieve is 0.05-10.
Optionally, the preparation method of the tin-titanium-silicon molecular sieve comprises the following steps:
(1) Contacting a tin source, a titanium source and a template agent in the presence of an aqueous solvent to obtain a first mixture;
(2) Mixing the first mixture with a silicon molecular sieve to obtain a second mixture;
(3) And crystallizing the second mixture under the hydrothermal crystallization condition.
Optionally, in step (1), the contacting conditions include: the contact temperature is 20-80 ℃, and the contact time is 1-240min;
preferably, the silicon molecular sieve and the tin source are used in such an amount that the molar ratio of tin element to silicon element in the prepared tin-titanium-silicon molecular sieve is 0.05-10; the dosage of the silicon molecular sieve and the titanium source ensures that the molar ratio of the titanium element to the silicon element in the prepared tin-titanium-silicon molecular sieve is 0.05-10;
preferably, the silicon molecular sieve, the template agent, the titanium source, the tin source andthe molar ratio of the water is 100-0.005-20 2 The tin source is calculated by tin element, and the titanium source is calculated by TiO 2 Counting;
preferably, the hydrothermal crystallization conditions include: the crystallization temperature is 80-200 ℃ under the closed condition, and the crystallization time is 6-150h;
preferably, the tin source is an inorganic tin compound and/or an organotin compound; the titanium source is an inorganic titanium compound and/or an organic titanium compound; the template agent is one or more of aliphatic amine compound, aliphatic alcohol amine compound and quaternary ammonium base compound; the silicon molecular sieve is one or more selected from S-1, S-2, BETA, MOR, MCM-22, MCM-41, SBA-15 and MCM-48;
preferably, at least part of the inner part of crystal grains of the tin-titanium-silicon molecular sieve has a cavity structure, and a diffraction peak is arranged at 0.5-9 degrees in 2 theta in an XRD pattern; 460cm in the FT-IR spectrum -1 、975cm -1 、800cm -1 、1080cm -1 Nearby absorption; the absorption is carried out at 200-300nm in a UV-Vis spectrum, and the total specific surface area of the tin-titanium-silicon molecular sieve is 300m 2 More than g, and the external specific surface area is 30m 2 More than g, and the proportion of the external specific surface area in the total specific surface area is more than 10 percent.
Optionally, the tin-titanium-silicon molecular sieve is obtained by performing secondary hydrothermal synthesis on a titanium-silicon molecular sieve and a compound containing a tin source, a template agent, alkali and water at 100-160 ℃, and performing filtering separation, drying and roasting operations, wherein the tin content in the molecular sieve is 1-5 wt% calculated by oxides;
preferably, the tin-titanium-silicon molecular sieve is one or a mixture of more of Sn-TS-1, sn-TS-2, sn-Ti-BETA, sn-Ti-MCM-22, sn-Ti-MCM-41 and Sn-Ti-MCM-48.
Optionally, the Sn-TS-1 is a titanium silicalite molecular sieve having an MFI crystal structure, crystal grains are hollow, and the radial length of a cavity portion of the hollow crystal grains is 5 to 300 nanometers; the molecular sieve sample is at 25 ℃ and P/P 0 =0.10, adsorbed benzene amount measured under the condition of adsorption time of 1 hour is at least 70 mg/gA hysteresis loop exists between the adsorption isotherm and the desorption isotherm of the low temperature nitrogen adsorption of the sub-sieve.
Optionally, the molar ratio of methylglyoxal to water is 1: (60-200), wherein the weight ratio of the methylglyoxal to the tin-titanium-silicon molecular sieve based on the dry weight is 1: (1.2-3), the reaction temperature is 40-120 ℃, the reaction time is 2-8h, the reaction pressure is 0.1-3MPa, and the reaction pressure is preferably 0.1-2MPa.
Optionally, the reactor is a tank reactor, a fixed bed reactor, a moving bed, a suspended bed or a slurry bed reactor.
The method adopts the catalyst containing the binary tin-titanium-silicon molecular sieve, and the framework tin atoms and the framework titanium atoms of the molecular sieve cooperatively catalyze the methylglyoxal and the water to generate the lactic acid, so that the reaction efficiency is improved. Compared with the prior art, higher methylglyoxal conversion rate and lactic acid yield can be obtained in a short time under mild reaction conditions, the subsequent separation energy consumption of products is lower, the process is safer and more efficient, and the method is suitable for large-scale industrial production and application.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a diagram of the reaction mechanism involved in the conversion of methylglyoxal to lactic acid according to the present invention.
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
In the present invention, the dry weight refers to the weight measured after the sample is baked at 550 ℃ for 3 hours.
The invention provides a method for preparing lactic acid by catalyzing methylglyoxal, which comprises the following steps: the method comprises the following steps of (1) enabling methylglyoxal and water to contact with a catalyst in a reactor and reacting to obtain a product containing lactic acid; wherein the molar ratio of the methylglyoxal to the water is 1: (40-350), the reaction temperature is 30-180 ℃, the reaction time is 1-10h, the catalyst contains a tin-titanium-silicon molecular sieve, and the weight ratio of the methylglyoxal to the tin-titanium-silicon molecular sieve based on the dry weight is 1: (1-6). The reaction mechanism is shown in figure 1.
According to the present invention, the tin-titanium-silicon molecular sieve refers to a molecular sieve obtained by substituting tin atoms and titanium atoms for a part of silicon atoms in a lattice framework of the molecular sieve, wherein the content of the tin atoms and the titanium atoms in the molecular sieve can be determined by using an XRF method which is conventional in the art, and the content of the tin atoms and the titanium atoms in the framework of the molecular sieve can be determined by using an ultraviolet spectrum or an infrared spectrum, for example, when a tin-titanium-silicon molecular sieve sample is analyzed by using an ultraviolet spectrum, a characteristic absorption peak of the framework tin atoms appears at a position near 190nm, and a characteristic absorption peak of the framework Ti atoms appears at a position near 210 nm. Pyridine infrared spectrum at 1450cm -1 The peaks around the molecular sieve show the L-acidic character of the molecular sieve and are provided by framework tin atoms and framework titanium atoms.
According to the invention, the tin-titanium-silicon molecular sieve can be a product of replacing partial framework silicon of various topological structures of molecular sieves by tin atoms and titanium atoms, the topological structure of the molecular sieve can refer to the website of International Zeolite Association (IZA), for example, the tin-titanium-silicon molecular sieve can be one or more selected from MFI type tin-titanium-silicon molecular sieve, MEL type tin-titanium-silicon molecular sieve, BEA type tin-titanium-silicon molecular sieve, MWW type tin-titanium-silicon molecular sieve, MOR type tin-titanium-silicon molecular sieve, hexagonal structure tin-titanium-silicon molecular sieve and FAU type tin-titanium-silicon molecular sieve, the MFI type tin-titanium-silicon molecular sieve is Sn-Ti-MFI molecular sieve, the MEL type tin-titanium-silicon molecular sieve is Sn-Ti-MEL molecular sieve, the BEA type tin-titanium-silicon molecular sieve is Sn-Ti-Beta molecular sieve, the MWW type tin-titanium-silicon molecular sieve is Sn-Ti-MCM-22 molecular sieve, the MOR type tin-titanium-silicon molecular sieve is Sn-Ti-MOR molecular sieve, the hexagonal structure tin-titanium-silicon molecular sieve is Sn-Ti-MCM-41 molecular sieve, sn-Ti-SBA-15 molecular sieve, the FAU type tin-titanium-silicon molecular sieve is Sn-Ti-USY molecular sieve; preferably, the tin-titanium-silicon molecular sieve is one or more of an MFI-type tin-titanium-silicon molecular sieve, a BEA-type tin-titanium-silicon molecular sieve and an FAU-type tin-titanium-silicon molecular sieve, and more preferably is an MFI-type tin-titanium-silicon molecular sieve, which can be obtained by commercial purchase or prepared by the methods disclosed in chinese patents CN105217645A and CN102452918A, and specific embodiments of the following two tin-titanium-silicon molecular sieves are provided.
An embodiment of the first tin-titanium-silicon molecular sieve is from patent CN105217645A.
According to a first embodiment, the tin-titanium-silicon molecular sieve contains silicon, titanium, tin and oxygen, wherein at least part of the crystal grains of the tin-titanium-silicon molecular sieve have a cavity structure inside. The fact that at least part of the tin titanium silicalite molecular sieves have a cavity structure inside the crystal grains means that at least part of the tin titanium silicalite molecular sieves in a large number of the tin titanium silicalite molecular sieves have a cavity structure inside the crystal grains, preferably more than 50% of the tin titanium silicalite molecular sieves have a cavity structure inside the crystal grains, and more preferably 70-100% of the tin titanium silicalite molecular sieves have a cavity structure inside the crystal grains.
According to the first embodiment, the ratio of the external specific surface area of the tin-titanium-silicon molecular sieve to the total specific surface area is preferably 10% or more, preferably 10 to 25%, more preferably 10 to 20%, and still more preferably 12 to 18%. The total specific surface area is preferably 300m 2 More preferably 310 to 600 m/g 2 G, more preferably from 350 to 460m 2 (ii) in terms of/g. The external specific surface area is 20m 2 A ratio of at least 30 m/g, preferably 2 A ratio of one to more than g, more preferably 31 to 150m 2 Per g, more preferably 35 to 120m 2 Per g, most preferably 40 to 70m 2 /g。
According to a first embodiment, the total specific surface area refers to the BET specific surface area; and the external specific surface area refers to the surface area of the external surface of the tin-titanium-silicon molecular sieve, and can also be referred to as the external surface area for short. The total specific surface area, the external specific surface area and the like can be measured according to the standard method of ASTM D4222-98.
According to a first embodiment, the crystalline tin-titanium-silicon molecular sieve with a cavity structure has the spectral properties of a conventional tin-titanium-silicon molecular sieve, and specifically, the tin-titanium-silicon molecular sieve has a diffraction peak at 0.5 to 9 degrees in 2 theta, preferably a diffraction peak at 5 to 9 degrees in 2 theta in an XRD pattern.
According to a first embodiment, the tin-titanium-silicon molecular sieve is preferably 460cm in the FT-IR spectrum -1 、975cm -1 、800cm -1 And 1080cm -1 There is absorption in the vicinity. Preferably, the tin-titanium-silicon molecular sieve has absorption at 200-300nm in a UV-Vis spectrum, and preferably has absorption at 200-260 nm.
According to the first embodiment, the molar ratio of the tin element to the silicon element in the tin titanium silicalite molecular sieve is preferably from 0.05 to 10, more preferably from 0.1 to 5, and particularly preferably from 0.2 to 2. Preferably, the molar ratio of titanium element to silicon element in the tin-titanium-silicon molecular sieve is from 0.05 to 10, more preferably from 0.1 to 5. The tin element, the titanium element and the silicon element in the proportion can further optimize the catalytic activity of the tin-titanium-silicon molecular sieve.
According to a first embodiment, the tin-titanium-silicon molecular sieve is preferably P/P at 25 ℃ 0 An amount of benzene adsorbed of at least 25mg/g, preferably at least 35mg/g, preferably from 40 to 100mg/g, as measured at 0.10 and an adsorption time of 1 hour.
According to the first embodiment, the tin-titanium-silicon molecular sieve is preferably at a relative pressure P/P 0 When the molar ratio is about 0.60, the difference between the nitrogen adsorption amount during desorption and the nitrogen adsorption amount during adsorption of the tin-titanium-silicon molecular sieve is greater than 2% of the nitrogen adsorption amount during adsorption of the tin-titanium-silicon molecular sieve, preferably, the difference between the nitrogen adsorption amount during desorption and the nitrogen adsorption amount during adsorption of the tin-titanium-silicon molecular sieve is greater than 5% of the nitrogen adsorption amount during adsorption of the tin-titanium-silicon molecular sieve, and more preferably, the difference between the nitrogen adsorption amount during desorption and the nitrogen adsorption amount during adsorption of the tin-titanium-silicon molecular sieve is 6 to 10% of the nitrogen adsorption amount during adsorption of the tin-titanium-silicon molecular sieve.
According to the first embodiment, a hysteresis loop is preferably present between the adsorption isotherm and the desorption isotherm of the low temperature nitrogen adsorption of the tin titanium silicalite molecular sieve. Preferably, the radial length of the cavity part of the cavity structure in the crystal grain of the tin-titanium-silicon molecular sieve is 0.1-500nm, and the preferred length is 0.5-300nm.
According to a first embodiment, the method of making a tin-titanium-silicon molecular sieve comprises:
(1) Contacting a tin source, a titanium source and a template agent in the presence of an aqueous solvent to obtain a first mixture;
(2) Mixing the first mixture with a silicon molecular sieve to obtain a second mixture;
(3) And crystallizing the second mixture under the hydrothermal crystallization condition.
According to the first embodiment, the contact temperature can be selected in a wide range, and for the preferred step (1) of the present invention, the contact conditions include: the contact temperature is 20 to 80 deg.C, more preferably 25 to 60 deg.C, and still more preferably 25 to 40 deg.C. Thus, the activity of the tin-titanium-silicon molecular sieve can be improved. The contacting time can be determined according to specific needs, and preferably in step (1), the contacting conditions further include: the contact time is 1 to 240min, more preferably 5 to 120min, and still more preferably 20 to 60min.
According to the first embodiment, the amount of the silicon molecular sieve and the tin source is preferably such that the molar ratio of the tin element to the silicon element in the prepared tin-titanium-silicon molecular sieve is from 0.05 to 100, preferably from 0.1 to 5, and more preferably from 0.5 to 2; the dosage of the silicon molecular sieve and the titanium source is such that the molar ratio of the titanium element to the silicon element in the prepared tin-titanium-silicon molecular sieve is 0.05-10, preferably 0.1-5, more preferably 0.5-4.
According to a first embodiment, to achieve the above object, the molar ratio of the silicalite, the templating agent, the titanium source, the tin source and the water is preferably from 100, from 0.005 to 20 2 The tin source is calculated by tin element, and the titanium source is calculated by TiO 2 And (6) counting.
According to the first embodiment, it is preferable that the conditions for mixing in the step (2) include: the mixing temperature is 25-60 deg.C, and the mixing time is 20-60min. Preferably, the hydrothermal crystallization conditions include: the crystallization temperature under a closed condition is 80 to 200 ℃, more preferably 100 to 180 ℃, still more preferably 110 to 175 ℃, and most preferably 160 to 170 ℃. The crystallization time is preferably 6 to 150 hours, more preferably 24 to 96 hours.
According to the first embodiment, the variety of the tin source can be widely selected, and any substance containing tin (for example, a compound containing tin element and/or a simple substance of tin) can achieve the object of the present invention. The inorganic tin compound is, for example, a water-soluble inorganic tin salt, which may be, for example, one or more of tin chloride, tin chloride pentahydrate, stannous chloride, tin nitrate, tin sulfate, tin phosphate, stannous chloride hydrate, metastannic acid, calcium stannate, potassium stannate, sodium stannate, lithium stannate, magnesium stannate, stannous sulfate, stannous pyrophosphate, and tin pyrophosphate; the organic acid salt of tin is preferably C2-C10 organic acid salt, including but not limited to one or more of tin acetate, stannous acetate and stannous octoate. The organotin compound may be an organic acid salt of tin and/or an organic ligand compound of tin, preferably a stannic acid ester. Among them, the most preferred organotin compound is tin acetate.
According to a first embodiment, the titanium source may be a conventional choice in the art, and may be an inorganic titanium compound and/or an organic titanium compound, preferably for the purposes of the present invention, the titanium source is selected from inorganic titanium salts and/or organic titanates, preferably organic titanates.
According to a first embodiment, the inorganic titanium salt is chosen from various hydrolysable titanium salts, such as may be chosen from TiX 4 、TiOX 2 Or Ti (SO) 4 ) 2 And the like, wherein X is halogen, preferably chlorine, wherein preferably the inorganic titanium salt is selected from titanium trichloride, tiCl 4 、Ti(SO 4 ) 2 And TiOCl 2 One or more of (a).
According to a first embodiment, the organic titanate is preferably of formula M 4 TiO 4 Wherein M is preferably an alkyl group having 1 to 4 carbon atoms, and 4M's may be the same or different, preferably the organotitanic acidThe ester is selected from one or more of isopropyl titanate, n-propyl titanate, tetrabutyl titanate and tetraethyl titanate, and tetrabutyl titanate and tetraethyl titanate are used as examples in specific embodiments of the invention, but do not limit the scope of the invention.
According to a first embodiment, preferably the titanium source is one or more of tetrabutyl titanate, titanium tetrachloride, tetraisopropyl titanate and titanium trichloride.
According to the first embodiment, the selection range of the template agent is wide, and the template agent can be specifically selected according to the type of the tin-titanium-silicon molecular sieve to be prepared, and those skilled in the art can know the type. For the present invention, it is preferable that the templating agent is one or more of an aliphatic amine compound, an aliphatic alcohol amine compound, and a quaternary ammonium base compound.
According to the first embodiment, the quaternary ammonium hydroxide may be various organic quaternary ammonium hydroxides, and specifically, the quaternary ammonium hydroxide may be a quaternary ammonium hydroxide represented by the following formula:
Figure BDA0001887905210000081
in the above formula, R 5 、R 6 、R 7 And R 8 Each C1-C4 alkyl, including C1-C4 straight chain alkyls and C3-C4 branched chain alkyls, such as: r 5 、R 6 、R 7 And R 8 Each may be methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl. More preferably, the quaternary ammonium base is one or more of tetrapropylammonium hydroxide, tetraethylammonium hydroxide and tetrabutylammonium hydroxide.
According to a first embodiment, the aliphatic amine may be any NH 3 Is substituted with an aliphatic hydrocarbon group (preferably an alkyl group), and specifically, the aliphatic amine may be an aliphatic amine represented by the following formula: r 9 (NH 2 ) n (ii) a In the above formula, n is an integer of 1 or 2. When n is 1, R 9 Is C1-C6 alkyl, including C1-C6 straight chain alkyl and C3-C6 branched chain alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butylSec-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, isopentyl, tert-pentyl and n-hexyl. When n is 2, R 9 Is C1-C6 alkylene, including C1-C6 linear alkylene and C3-C6 branched alkylene, such as methylene, ethylene, n-propylene, n-butylene, n-pentylene, or n-hexylene. More preferably, the aliphatic amine compound is one or more of ethylamine, n-butylamine, butanediamine and hexamethylenediamine.
According to a first embodiment, the aliphatic alcohol amine can be any of various NH 3 In the above formula (b), at least one hydrogen of the aliphatic alcohol amine is substituted by a hydroxyl group-containing aliphatic hydrocarbon group (preferably an alkyl group), and specifically, the aliphatic alcohol amine may be represented by the following formula: (HOR) 10 ) m NH (3-m) (ii) a In the above formula, m are R 10 Identical or different, each being a C1-C4 alkylene group, including C1-C4 linear alkylene groups and C3-C4 branched alkylene groups, such as methylene, ethylene, n-propylene and n-butylene; m is 1, 2 or 3. More preferably, the aliphatic alcohol amine compound is one or more of monoethanolamine, diethanolamine and triethanolamine.
According to a first embodiment, the templating agent is preferably tetrapropylammonium hydroxide and/or tetraethylammonium hydroxide.
According to a first embodiment, the silicalite may be at least one of an MFI structure (e.g., S-1), an MEL structure (e.g., S-2), a BEA structure (e.g., beta), an MWW structure (e.g., MCM-22), a two-dimensional hexagonal structure (e.g., MCM-41, SBA-15), an MOR structure (e.g., MOR), a TUN structure (e.g., TUN), and other structures of silicalite (e.g., ZSM-48, MCM-48). Preferably, the silicon molecular sieve is one or more of a silicon molecular sieve with an MFI structure, a silicon molecular sieve with an MEL structure and a silicon molecular sieve with a BEA structure, more preferably a silicon molecular sieve with an MFI structure, and preferably, the silicon molecular sieve is one or more of S-1, S-2 and Beta, preferably S-1.
According to a first embodiment, the silicalite is commercially available or can be prepared, and methods for preparing the silicalite are well known to those skilled in the art and will not be described herein.
According to the first embodiment, it is preferred that the method further comprises: and filtering and washing the crystallized product to obtain a solid, and roasting the obtained solid after drying or not drying. The methods of filtering the product obtained by crystallization, drying the solid obtained by filtering, and calcining are well known to those skilled in the art, and in the present invention, the optional range of the drying conditions is wide, and the drying can be specifically performed with reference to the prior art. For the present invention, it is preferable that the drying conditions include: the temperature is between room temperature and 200 ℃, and is more preferably between 80 and 120 ℃; the time is 1-24h, preferably 2-10h.
According to a first embodiment, the conditions of the calcination can be chosen within a wide range, and for the purposes of the present invention, it is preferred that the conditions of the calcination include: the roasting temperature is 300-800 ℃, preferably 450-550 ℃; the roasting time is 2-12h, preferably 2-4h; more preferably, the firing conditions include: firstly, roasting for 0.5-6h at 350-600 ℃ in a nitrogen atmosphere, and then roasting for 0.5-12h at 350-600 ℃ in an air atmosphere. Methods of filtration and washing are also well known to those skilled in the art and will not be described in detail herein.
An embodiment of the second tin titanium silicalite molecular sieve is from patent CN102452918A.
According to a second embodiment, the tin-titanium-silicon molecular sieve is obtained by performing a second hydrothermal synthesis on a titanium-silicon molecular sieve together with a compound containing a tin source, a template agent, alkali and water at 100-160 ℃, and performing filtering separation, drying and roasting operations, wherein the tin content in the molecular sieve is 1-5 wt% calculated by oxides, and a strong Lewis acid center is formed at a framework position, so that the activation of the molecular sieve on a substrate is enhanced in an organic reaction.
According to a second embodiment, the tin-titanium-silicon molecular sieve is a mixture of one or more of Sn-TS-1, sn-TS-2, sn-Ti-BETA, sn-Ti-MCM-22, sn-Ti-MCM-41 and Sn-Ti-MCM-48. TS-1 is preferred, and a synthesis method of the titanium silicalite TS-1 is disclosed for the first time in U.S. Pat. No. 4,4410501. As a more preferable embodiment, the invention adopts a TS-1 titanium silicalite molecular sieve with a hollow structure, the molecular sieve has a titanium silicalite molecular sieve with an MFI crystal structure, crystal grains have a hollow structure, and the radial length of a cavity part of each hollow crystal grain is 5-300 nanometers; the molecular sieve sample has a benzene adsorption capacity of at least 70 mg/g measured at 25 ℃, P/P0=0.10, and an adsorption time of 1 hour, and a hysteresis loop exists between an adsorption isotherm and a desorption isotherm of low temperature nitrogen adsorption of the molecular sieve. The TS-1 titanium silicalite molecular sieve with a hollow structure has larger mesoporous volume, which is usually more than 0.16mL/g, while the conventional TS-1 titanium silicalite molecular sieve has the mesoporous volume of about 0.084 mL/g. The TS-1 titanium silicalite molecular sieve with the hollow structure can be prepared by a method disclosed in Chinese patent ZL99126289.1, and is commercially available.
According to the invention, the molar ratio of methylglyoxal to water is preferably 1: (60-200), the weight ratio of methylglyoxal to tin titanium silicalite on a dry basis is preferably 1: (1.2-3), the reaction temperature is preferably 40-120 ℃, the reaction time is preferably 2-8h, and the reaction pressure (absolute pressure) can be 0.1-3MPa, preferably 0.1-2MPa.
The reaction according to the present invention may be carried out in a conventional catalytic reactor according to the present invention, and the present invention is not particularly limited, for example, the reaction according to the present invention may be carried out in a batch tank reactor or a three-neck flask, or in a suitable other reactor such as a fixed bed, a moving bed, a suspended bed, etc., preferably in a tank reactor, a fixed bed reactor, a moving bed, a suspended bed, or a slurry bed reactor, the specific operation of which is well known to those skilled in the art, and the detailed description of the present invention will be omitted.
According to the present invention, it can be understood by those skilled in the art that, depending on the reactor used, the tin-titanium-silicon molecular sieve of the present invention may be a molecular sieve raw powder, or may be a molded catalyst formed by mixing a molecular sieve and a carrier. The separation of the lactic acid-containing product from the catalyst can be achieved in various ways, for example, when the raw powdery molecular sieve is used as the catalyst, the separation of the product and the recovery and reuse of the catalyst can be achieved by settling, filtration, centrifugation, evaporation, membrane separation, or the like, or the catalyst can be molded and then packed in a fixed bed reactor, and the catalyst can be recovered after the reaction is completed.
The present invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.
The starting materials used in the preparation examples, preparation comparative examples, examples and comparative examples were all chemically pure reagents, except where otherwise specified.
In the invention, the X-ray diffraction (XRD) crystal phase diagram of a sample is determined on a Siemens D5005 type X-ray diffractometer, the radiation source is Ka (Cu), and the test range 2 theta is 0.5-30 degrees. The Fourier infrared (FT-IR) spectrum of the sample is measured on a Nicolet8210 type Fourier infrared spectrometer, and the measuring range is 400-4000cm -1 . The solid ultraviolet-visible diffuse reflectance spectrum (UV-vis) of the sample is measured on a SHIMADZU UV-3100 model ultraviolet-visible spectrometer, and the measuring range is 200-1000nm. The total specific surface area and the external specific surface area of the sample were measured on a Micromeritics ASAP2405 static nitrogen adsorption apparatus according to ASTM D4222-98 standard method. TEM is a transmission electron microscope of the sample obtained on a transmission electron microscope of the type Tecnai G2F20S-TWIN from FEI.
In the present invention, the benzene adsorption amount is measured by a conventional static adsorption method, and the adsorption isotherm and desorption isotherm of low-temperature nitrogen adsorption are measured according to the ASTM D4222-98 standard method.
In the present invention, the molecular sieve yield refers to the percentage of the mass of the product actually obtained to the theoretically calculated mass (based on the total amount of silica, titanium dioxide and tin dioxide charged).
In the invention, in a transmission electron microscope test, a certain number of crystal grains in a certain visual field range are taken as representatives, such as 100 crystal grains, the proportion of the number of the crystal grains with the cavity structures in the crystal grains in the total number of the crystal grains is observed, and the proportion of the tin-titanium-silicon molecular sieves with the cavity structures in the crystal grains in the total number of the tin-titanium-silicon molecular sieves is calculated.
In the invention, the gas chromatography is adopted to analyze each component in the activity evaluation system, the analysis result is quantified by an internal standard method, and the internal standard substance is naphthalene. Wherein, the chromatographic analysis conditions are as follows: agilent-6890 type chromatograph, HP-5 capillary chromatographic column, sample amount of 0.5 μ L, and sample inlet temperature of 280 deg.C. The column temperature was maintained at 100 ℃ for 2min, then ramped up to 200 ℃ at a rate of 15 ℃/min and maintained for 3min. FID detector, detector temperature 300 ℃.
In the invention:
methylglyoxal conversion% = (moles of methylglyoxal in raw material-moles of methylglyoxal in product)/moles of methylglyoxal in raw material x 100%;
lactic acid selectivity% = mole of lactic acid in product/(mole of methylglyoxal in raw material-mole of methylglyoxal in product) × 100%;
the yield of lactic acid is% = mole of lactic acid in product/mole of methylglyoxal in raw material x 100%, namely the yield of lactic acid is% = selectivity of lactic acid x conversion of methylglyoxal%.
Preparation examples and preparation comparative examples catalysts used in the examples and comparative examples were provided.
Preparation of example 1
The preparation example prepares the Sn-Ti-MFI-1 molecular sieve according to the method of the specification example 1 of the Chinese patent CN105217645A, and the specific preparation method is as follows:
(1) Stirring and contacting tetrapropylammonium hydroxide aqueous solution (with the concentration of 15 weight percent) with tetrabutyl titanate and stannic chloride pentahydrate for 30min at 25 ℃ to obtain a mixture;
(2) Adding the silicalite molecular sieve S-1 into the mixture at 60 ℃, stirring and contacting for 0.5h to obtain a mixture (in the contact process, water is added or not added according to the requirement, if the feeding of the step (1) can meet the feeding requirement of the water, the water is not added, if the feeding can not meet the feeding requirement of the water, the water can be additionally added when the mixture containing tetrapropylammonium hydroxide, tetrabutyl titanate and tin chloride is stirred and contacted with the silicalite molecular sieve, or the water is removed by distillation, and other preparation examples are similar and are not repeated); wherein, the feeding molar ratio of each substance is ensured as follows: silicon source (silicon molecular sieve), alkali source template agent (tetrapropylammonium hydroxide), titanium source (tetrabutyl titanate): tin source (crystalline tin tetrachloride): water =100 2 The titanium source is calculated as TiO 2 The tin source is calculated by the tin element;
(3) And transferring the mixture into a stainless steel sealed reaction kettle, crystallizing for 144 hours at the temperature of 170 ℃ and the autogenous pressure, filtering the obtained crystallized product, washing with water, drying for 120 minutes at the temperature of 110 ℃, and then roasting for 3 hours at the temperature of 550 ℃ to obtain the tin-titanium-silicon molecular sieve.
By XRF composition analysis, the tin-titanium-silicon molecular sieve has the tin content of 1.8 percent by mass and the titanium content of 0.9 percent by mass; TEM indicates that 100% of the tin-titanium-silicon molecular sieve crystal grains have a cavity structure; in an XRD crystal phase diagram, diffraction peaks exist at 5-9 degrees of 2 theta; in FT-IR, 460cm -1 、800cm -1 、975cm -1 、1080cm -1 Nearby absorption; in UV-Vis, there is an absorption at 220 nm; a hysteresis loop exists between an adsorption isotherm and a desorption isotherm of low-temperature nitrogen adsorption, the molecular sieve yield is 94%, the benzene adsorption capacity is 62mg/g, the ratio of an adsorption-desorption difference value to an adsorption capacity (the difference between the nitrogen adsorption capacity during desorption and the nitrogen adsorption capacity during adsorption of the tin-titanium-silicon molecular sieve is greater than the nitrogen adsorption capacity during adsorption of the tin-titanium-silicon molecular sieve) is 6%, and the total specific surface area is 440m 2 A specific surface area of 46m 2 The proportion of the external specific surface area to the total specific surface area was 10.5%.
Preparation of example 2
The preparation example prepares the Sn-Ti-MFI-2 molecular sieve according to the method of the specification example 2 of the Chinese patent CN105217645A, and the specific preparation method is as follows:
(1) Stirring and contacting tetrapropylammonium hydroxide aqueous solution (with the concentration of 20 weight percent) with tetrabutyl titanate and stannic chloride pentahydrate for 30min at 25 ℃ to obtain a mixture;
(2) Adding a silicon molecular sieve S-1 into the mixture at 25 ℃, and stirring and contacting for 0.5h to obtain a mixture; wherein, the feeding molar ratio of each substance is ensured as follows: silicon source (silicon molecular sieve), alkali source template agent (tetrapropylammonium hydroxide), titanium source (tetrabutyl titanate): tin source (tin tetrachloride): water =100 2 The titanium source is calculated as TiO 2 The tin source is calculated by the tin element;
(3) And transferring the mixture into a stainless steel sealed reaction kettle, crystallizing for 120 hours at the temperature of 160 ℃ under autogenous pressure, filtering the obtained crystallized product, washing with water, drying for 120 minutes at the temperature of 110 ℃, and roasting for 3 hours at the temperature of 550 ℃ to obtain the tin-titanium-silicon molecular sieve.
By XRF composition analysis, the Sn mass percent of the tin-titanium-silicon molecular sieve is 1.0, and the titanium mass percent is 2.6; in an XRD crystal phase diagram, diffraction peaks exist at 5-9 degrees of 2 theta; TEM indicates that the inside of 100% molecular sieve crystal grains is a cavity structure; in FT-IR, 460cm -1 、800cm -1 、975cm -1 、1080cm -1 Nearby absorption; in UV-Vis, there is an absorption at 220 nm; a hysteresis loop exists between the adsorption isotherm and the desorption isotherm of low-temperature nitrogen adsorption, the molecular sieve yield is 93 percent, the benzene adsorption capacity is 68mg/g, the ratio of the adsorption-desorption difference value to the adsorption capacity (the difference value between the nitrogen adsorption capacity during desorption and the nitrogen adsorption capacity during adsorption of the tin-titanium-silicon molecular sieve is greater than the nitrogen adsorption capacity during adsorption of the tin-titanium-silicon molecular sieve) is 8 percent, and the total specific surface area is 424m 2 A specific surface area of 45m 2 The proportion of the external specific surface area to the total specific surface area was 10.6%.
Preparation of example 3
In the preparation example, the method of example 3 of the specification of the Chinese patent CN105217645A is used for preparing the Sn-Ti-MFI-3 molecular sieve, and the specific preparation method is as follows:
(1) A mixture was obtained by contacting an aqueous tetraethylammonium hydroxide solution (concentration of 28% by weight) with titanium tetrachloride and tin nitrate at 35 ℃ for 30 minutes with stirring;
(2) Adding a silicon molecular sieve S-1 into the mixture at 50 ℃, and stirring and contacting for 0.5h to obtain a mixture; wherein, the feeding molar ratio of each substance is ensured as follows: silicon source (silicon molecular sieve), alkali source templating agent (tetraethylammonium hydroxide), titanium source (titanium tetrachloride), tin source (tin nitrate), water =100 2 The titanium source is calculated as TiO 2 The tin source is calculated by the tin element;
(3) And transferring the mixture into a stainless steel sealed reaction kettle, crystallizing for 96 hours at the temperature of 170 ℃ and the autogenous pressure, filtering the obtained crystallized product, washing with water, drying for 120 minutes at the temperature of 110 ℃, and then roasting for 3 hours at the temperature of 550 ℃ to obtain the tin-titanium-silicon molecular sieve.
By XRF composition analysis, the Sn mass percent of the tin-titanium-silicon molecular sieve is 0.8, and the titanium mass percent is 0.3; in an XRD crystal phase diagram, a diffraction peak exists at the 2 theta position of 5-9 degrees; TEM indicates that the inside of 100% molecular sieve crystal grains is a cavity structure; in FT-IR, 460cm -1 、800cm -1 、975cm -1 、1080cm -1 Nearby absorption; in UV-Vis, there is an absorption at 230 nm; a hysteresis loop exists between an adsorption isotherm and a desorption isotherm of low-temperature nitrogen adsorption, the molecular sieve yield is 94%, the benzene adsorption capacity is 54mg/g, the ratio of an adsorption-desorption difference value to an adsorption capacity (the difference between the nitrogen adsorption capacity during desorption and the nitrogen adsorption capacity during adsorption of the tin-titanium-silicon molecular sieve is greater than the nitrogen adsorption capacity during adsorption of the tin-titanium-silicon molecular sieve) is 5%, and the total specific surface area is 431m 2 Per g, external specific surface area 43m 2 The proportion of the external specific surface area to the total specific surface area was 10%.
Preparation of example 4
The preparation example prepares the Sn-Ti-MFI-4 molecular sieve according to the method of the specification example 4 of the Chinese patent CN105217645A, and the specific preparation method is as follows:
(1) Stirring and contacting tetrapropylammonium hydroxide aqueous solution (with the concentration of 15 weight percent) with tetraisopropyl titanate and stannic chloride for 30min at the temperature of 30 ℃ to obtain a mixture;
(2) Adding a silicon molecular sieve S-1 into the mixture at 60 ℃, and stirring and contacting for 0.5h to obtain a mixture; wherein, the feeding molar ratio of each substance is ensured as follows: silicon source (silicon molecular sieve), alkali source template (tetrapropylammonium hydroxide), titanium source (tetraisopropyl titanate), tin source (tin tetrachloride), water =100 2 The titanium source is calculated as TiO 2 The tin source is calculated by the tin element;
(3) And transferring the mixture into a stainless steel sealed reaction kettle, crystallizing for 72 hours at the temperature of 120 ℃ and the autogenous pressure, filtering the obtained crystallized product, washing with water, drying for 120 minutes at the temperature of 110 ℃, and then roasting for 3 hours at the temperature of 550 ℃ to obtain the tin-titanium-silicon molecular sieve.
The tin titanium silicon component is analyzed by XRF compositionThe mass percent of Sn of the sub-sieve is 6.6, and the mass percent of titanium of the sub-sieve is 2.1; in an XRD crystal phase diagram, diffraction peaks exist at 5-9 degrees of 2 theta; TEM indicates that 96% of molecular sieve crystal grains have a cavity structure; in FT-IR, 460cm -1 、800cm -1 、975cm -1 、1080cm -1 There is absorption nearby; in UV-Vis, there is absorption around 240 nm; a hysteresis loop exists between the adsorption isotherm and the desorption isotherm of low-temperature nitrogen adsorption, the molecular sieve yield is 94 percent, the benzene adsorption capacity is 83mg/g, the ratio of the adsorption-desorption difference value to the adsorption capacity (the difference value between the nitrogen adsorption capacity during desorption and the nitrogen adsorption capacity during adsorption of the tin-titanium-silicon molecular sieve is greater than the nitrogen adsorption capacity during adsorption of the tin-titanium-silicon molecular sieve) is 9 percent, and the total specific surface area is 416m 2 Per g, external specific surface area of 50m 2 The proportion of the external specific surface area to the total specific surface area was 12.1%.
Preparation of example 5
In the preparation example, the Sn-Ti-MFI-5 molecular sieve is prepared according to the method in the specification example 7 of the Chinese patent CN105217645A. The preparation method comprises the following steps:
(1) Stirring and contacting tetrapropylammonium hydroxide aqueous solution (with the concentration of 15 weight percent) with titanium trichloride and stannic chloride pentahydrate for 30min at the temperature of 25 ℃ to obtain a mixture;
(2) Adding a silicon molecular sieve S-1 into the mixture at 40 ℃, and stirring and contacting for 0.5h to obtain a mixture; wherein, the feeding molar ratio of each substance is ensured as follows: silicon source (silicon molecular sieve), alkali source template (tetrapropylammonium hydroxide), titanium source (titanium trichloride), tin source (crystalline tin tetrachloride), water =100 2 The titanium source is calculated as TiO 2 The tin source is calculated by the tin element;
(3) And transferring the mixture into a stainless steel sealed reaction kettle, crystallizing for 36 hours at the temperature of 170 ℃ under autogenous pressure, filtering the obtained crystallized product, washing with water, drying for 120 minutes at the temperature of 110 ℃, and roasting for 3 hours at the temperature of 550 ℃ to obtain the tin-titanium-silicon molecular sieve.
By XRF composition analysis, the Sn mass percentage content of the tin-titanium-silicon molecular sieve is 9.6, and the titanium mass percentage content is 2.5; in XRD crystal phase diagram, 2 theta is 5-9 °Has diffraction peak; TEM indicates that 61% of the molecular sieve crystal grains have a cavity structure; in FT-IR, 460cm -1 、800cm -1 、975cm -1 、1080cm -1 Nearby absorption; in UV-Vis, there is absorption at 230-260 nm; a hysteresis loop exists between an adsorption isotherm and a desorption isotherm of low-temperature nitrogen adsorption, the yield of the molecular sieve is 93 percent, the benzene adsorption capacity is 41mg/g, the ratio of an adsorption-desorption difference value to an adsorption capacity (the difference value between the nitrogen adsorption capacity during desorption and the nitrogen adsorption capacity during adsorption of the tin-titanium-silicon molecular sieve is greater than the nitrogen adsorption capacity during adsorption of the tin-titanium-silicon molecular sieve) is 5 percent, and the total specific surface area is 356m 2 (g) an external specific surface area of 51m 2 The proportion of the external specific surface area to the total specific surface area was 14.3%.
Preparation of example 6
In the preparation example, the tin-titanium-silicon molecular sieve is prepared according to the method of preparation example 1 of the CN102452918A catalyst, and the specific preparation method is as follows:
tetraethyl orthosilicate 22.5 g and tetrapropylammonium hydroxide 7.0 g are mixed, and then distilled water 59.8 g is added, after uniform mixing, the mixture is hydrolyzed at normal pressure and 60 ℃ for 1.0 hour to obtain a hydrolysis solution of tetraethyl orthosilicate, a solution consisting of tetrabutyl titanate 1.1 g and anhydrous isopropanol 5.0 g is slowly added under vigorous stirring, and the obtained mixture is stirred at 75 ℃ for 3 hours, and the clear and transparent colloid is obtained. Placing the colloid in a stainless steel sealed reaction kettle, and standing at a constant temperature of 170 ℃ and a self-generated pressure for 6 days to obtain a mixture of crystallized products; the mixture was filtered, washed with water to pH 6-8, and dried at 110 ℃ for 60 minutes to give raw, unfired TS-1 powder. Roasting the TS-1 raw powder in air atmosphere at 550 ℃ for 4 hours to obtain the TS-1 molecular sieve.
Then TS-1 is evenly mixed according to the proportion of molecular sieve (g) to anhydrous stannic chloride (mol) to tetrapropylammonium hydroxide (mol) to water (mol) =100: 0.06 x: 0.15: 180 in a system with tetrapropylammonium hydroxide as a template agent and anhydrous stannic chloride as a tin source, wherein the value of x is the mass percent of stannic oxide in the molecular sieve, the mixture is processed by a closed autoclave, and 2.2 percent of oxide is introduced into an MFI framework by a secondary hydrothermal synthesis method at 140 DEGThe obtained catalyst is marked as Sn-TS-1, wherein SnO 2 2.2wt%, tiO 2 The mass percentage of (b) is 3.9wt%.
Preparation of example 7
The TS-1 molecular sieve obtained in the preparation example 6 is uniformly mixed according to the proportion of the molecular sieve (g): (sulfuric acid (mol):) water (mol) =100: 0.15: 15), reacted for 5.0 hours at 90 ℃, and then filtered, washed and dried according to a conventional method to obtain the acid-treated TS-1 molecular sieve.
Mixing the acid treated TS-1 molecular sieve uniformly according to the proportion of molecular sieve (g), triethanolamine (mol), tetrapropylammonium hydroxide (mol) and water (mol) =100: 0.20: 0.15: 180, placing the mixture into a stainless steel sealed reaction kettle, standing the mixture for 0.5 day at the constant temperature of 190 ℃ and the autogenous pressure, cooling and relieving the pressure, filtering, washing and drying the mixture according to a conventional method, and roasting the mixture for 3 hours at the temperature of 550 ℃ in an air atmosphere to obtain the hollow-structure molecular sieve.
The molecular sieve is analyzed to be a titanium-silicon molecular sieve with an MFI structure through X-ray diffraction, a hysteresis ring exists between an adsorption isotherm and a desorption isotherm of low-temperature nitrogen adsorption of the molecular sieve, the crystal grains are hollow crystal grains, and the radial length of a cavity part is 15-180 nanometers; the molecular sieve sample has a benzene adsorption of 78 mg/g measured at 25 ℃, P/P0=0.10, and an adsorption time of 1 hour.
Then, in a system with a hollow structure molecular sieve, at 140 ℃, tetrapropylammonium hydroxide as a template agent and anhydrous stannic chloride as a tin source, uniformly mixing the molecular sieve with anhydrous stannic chloride (mol), tetrapropylammonium hydroxide (mol) and water (mol) =100: 0.06 x: 0.15: 180 according to the proportion of the molecular sieve (g) to the anhydrous stannic chloride (mol), wherein the value of x is the mass percent of stannic oxide in the molecular sieve, subjecting the mixture to hydrothermal synthesis at 140 ℃ for 72 hours in a closed autoclave, introducing 2.1wt% of tin element (calculated by oxide) into an MFI framework of the mixture, and recording a catalyst as Sn-HTS, wherein SnO (stannic oxide) is calculated by oxide 2 2.1wt%, tiO 2 The mass percentage of (B) is 4.3wt%.
Preparation of comparative example 1
The preparation comparative example is used for preparing the Sn-MFI molecular sieve, and the specific preparation method comprises the following steps:
the pentahydrate stannic chloride (SnCl) 4 .5H 2 O) was dissolved in water, the aqueous solution was added to tetraethyl orthosilicate (TEOS) and stirred, tetrapropylammonium hydroxide (TPAOH, 20% aqueous solution) and water were added with stirring, and stirring was continued for 30 minutes to obtain 0.03SnO 2 ：SiO 2 :0.45TPA：35H 2 And crystallizing the clear liquid of O at 433K for 2 days, filtering the obtained solid, washing the solid with distilled water, drying the solid for 5 hours at 393K, and roasting the solid for 10 hours at 823K to obtain a molecular sieve sample. Wherein the dosage of TEOS is 15.31g, the dosage of TPAOH is 33.67g, the dosage of SnCl is 4 .5H 2 The amount of O was 0.38g and the amount of water was 39.64g.
Preparation of comparative example 2
The present preparation comparative example reference "Nemeth L, moscoso J, erdman N, et al. Synthesis and Catalysis of Sn-Beta as a selective oxidation catalyst [ J ]. Studies in Surface Science & Catalysis,2004,154 (04): 2626-2631" describes the preparation of a Sn-Beta molecular sieve by:
the pentahydrate stannic chloride (SnCl) 4 .5H 2 O) dissolving in water, adding tetraethyl orthosilicate (TEOS) into the water solution, stirring, adding tetraethyl ammonium hydroxide (TEAOH) while stirring, stirring until TEOS is evaporated to obtain alcohol, and adding Hydrogen Fluoride (HF) into the clear solution to form a paste thin layer. Finally, a suspension of dealuminized nano Beta seed crystals (20 nm) and water is added to obtain the product with a chemical composition of 0.03SnO 2 ：SiO 2 ：6TEA：15H 2 O:10HF, then crystallized at the temperature of 413K for 10 days, and then the obtained solid is filtered, washed by distilled water, dried at the temperature of 393K for 5 hours, and then roasted at the condition of 823K for 10 hours to obtain a molecular sieve sample. Wherein the dosage of TEOS is 20.81g, the dosage of TEAOH is 88.42g 4 .5H 2 The amount of O used was 1.05g, the amount of water used was 27.01g and the amount of HF used was 20g.
Preparation of comparative example 3
The Sn-USY molecular sieve is prepared by the method of "Yang X, wu L, wang Z, et al. Conversion of dihydroxy monomer to methyl lactate catalyzed by high active Sn-USY at room temperature [ J ]. Catalysis Science & Technology,2016,6 (6): 1757-1763", and the Sn-USY molecular sieve is prepared by the following method:
mixing the H-USY molecular sieve with nitric acid, treating at 85 ℃ for 8H, filtering and washing a sample with deionized water, and drying at 120 ℃ for 12H to obtain a solid sample. This solid sample was mixed with tin tetrachloride pentahydrate (SnCl) 4 .5H 2 O) for 1 hour to obtain a mixture with a chemical composition of 0.03SnO 2 ：100SiO 2 Drying the mixed liquid at 100 ℃ for 12h, and finally roasting at 550 ℃ for 3 hours to obtain a molecular sieve sample. Wherein the dosage of H-USY is 2.0g, the dosage of nitric acid is 50mL 4 .5H 2 The amount of O used was 0.6g.
Preparation of comparative example 4
The preparation comparative example is used for preparing the TS-1 molecular sieve, and the specific preparation method comprises the following steps:
a tetrapropylammonium hydroxide (TPAOH, 20%) solution in an amount of about 3/4 was added to a tetraethyl orthosilicate (TEOS) solution to obtain a liquid mixture having a pH of about 13, and then a desired amount of n-butyl titanate [ Ti (OBu) ] was added dropwise to the obtained liquid mixture under vigorous stirring 4 ]Stirring the anhydrous isopropanol solution for 15 minutes to obtain a clear liquid, and finally slowly adding the rest TPAOH into the clear liquid, and stirring the mixture for about 3 hours at 348-353K to obtain the anhydrous isopropanol solution with the chemical composition of 0.03TiO 2 ：SiO 2 ：0.36TPA：35H 2 And crystallizing the sol of O at the temperature of 443K for 3 days, filtering the obtained solid, washing the solid with distilled water, drying the solid for 5 hours at the temperature of 373K, and roasting the solid for 10 hours at the condition of 823K to obtain a molecular sieve sample. Wherein the amount of TEOS is 42g, the amount of TPAOH is 73g, ti (OBu) 4 The amount of (b) was 2g, the amount of anhydrous isopropyl alcohol was 10g, and the amount of water was 68g.
Preparation of comparative example 5
The preparation comparative example is used for preparing the TS-2 molecular sieve, and the specific preparation method comprises the following steps:
a certain amount of tetrabutylammonium hydroxide solution (TBAOH, 20%) was mixed with Tetraethylorthosilicate (TEOS),then, a desired amount of n-butyl titanate [ Ti (OBu) ] was added dropwise to the obtained transparent liquid mixture under vigorous stirring 4 ]Stirring for 30 minutes to obtain a clear liquid after hydrolysis. Finally, 2 times the amount of distilled water required was added and the sol was stirred at 348-353K for 2h to remove the alcohol. The chemical composition of the sol obtained was 0.03TiO 2 ：SiO 2 :0.2TBA：20H 2 And O. And (3) crystallizing the sol at 443K for 3 days, filtering and washing the obtained crystallized product, drying for 6 hours under 373K, and roasting for 16 hours under 823K to obtain a molecular sieve sample. Wherein the amount of TEOS is 42g, the amount of TBAOH is 52g, ti (OBu) 4 The amount of (A) was 2g, the amount of anhydrous isopropyl alcohol was 10g, and the amount of water was 30g.
Preparation of comparative example 6
The preparation comparative example is used for preparing the Ti-Beta molecular sieve, and the specific preparation method comprises the following steps:
a certain amount of tetraethyl orthosilicate (TEOS) was added to a solution of metered tetraethylammonium hydroxide solution (TEAOH, 20%) and hydrogen peroxide and hydrolyzed under stirring for 2h. Then weighed tetrabutyl titanate [ Ti (OBu) 4 ]Adding the anhydrous isopropanol solution into hydrolysate of ethyl orthosilicate, continuously stirring for 3h to remove alcohol, and finally obtaining the chemical composition of TiO 2 ：60SiO 2 :33TEA：400H 2 O:20H 2 O 2 The sol of (4). Finally, adding dealuminized P-type molecular sieve seed crystals and stirring vigorously (the seed crystal adding amount is that the sol is calculated by silica, and 4g of seed crystals are added into 100g of silica). After the mixture is crystallized under 413K for 14 days, the obtained slurry is filtered, washed by water, dried under 373K for 6h, and then calcined under 823K for 12h to obtain a molecular sieve sample. Wherein the amount of TEOS is 42g, the amount of TEAOH is 81g, ti (OBu) 4 The dosage of the compound is 1.16g, the dosage of the anhydrous isopropanol is 10g, and the dosage of the hydrogen peroxide is 7.5g.
Preparation of comparative example 7
The hollow titanium silicalite molecular sieve HTS prepared by the preparation comparative example is prepared by the method described in the specification example 1 of the Chinese patent CN1301599A, and the specific preparation method is as follows:
22.5 g tetraethyl orthosilicate and 7.0 g tetrapropylammonium hydroxide were mixed, 59.8 g distilled water was added, after mixing uniformly, hydrolysis was carried out at 60 ℃ for 1.0 hour under normal pressure to obtain a hydrolysis solution of tetraethyl orthosilicate, a solution consisting of 1.1 g tetrabutyl titanate and 5.0 g anhydrous isopropyl alcohol was slowly added with vigorous stirring, and the resulting mixture was stirred at 75 ℃ for 3 hours to obtain a clear transparent colloid. Placing the colloid in a stainless steel sealed reaction kettle, and standing at a constant temperature of 170 ℃ and a self-generated pressure for 6 days to obtain a mixture of crystallized products; the mixture was filtered, washed with water to pH 6-8, and dried at 110 ℃ for 60 minutes to give raw, unfired TS-1 powder. And roasting the TS-1 raw powder for 4 hours at 550 ℃ in an air atmosphere to obtain the TS-1 molecular sieve.
And (3) uniformly mixing the obtained TS-1 molecular sieve according to the proportion of molecular sieve (g) to sulfuric acid (mol) to water (mol) =100: 0.15: 150, reacting for 5.0 hours at 90 ℃, and then filtering, washing and drying according to a conventional method to obtain the acid-treated TS-1 molecular sieve.
Mixing the acid treated TS-1 molecular sieve uniformly according to the proportion of molecular sieve (g), triethanolamine (mol), tetrapropylammonium hydroxide (mol) and water (mol) =100: 0.20: 0.15: 180, placing the mixture into a stainless steel sealed reaction kettle, placing the stainless steel sealed reaction kettle at the constant temperature of 190 ℃ and the autogenous pressure for 0.5 day, cooling and releasing the pressure, filtering, washing and drying the mixture according to a conventional method, and roasting the mixture for 3 hours at the temperature of 550 ℃ in an air atmosphere to obtain the HTS molecular sieve.
The HTS molecular sieve has a hollow structure with the radial length of 5-100 nanometers, and the benzene adsorption quantity measured by a static adsorption method under the conditions of 25 ℃, P/P0=0.10 and 1 hour of adsorption time is 85 mg/g molecular sieve; the adsorption isotherm and the desorption isotherm of the low-temperature nitrogen adsorption determined according to the standard method of astm d4222-98 show that there is a hysteresis loop between the adsorption isotherm and the desorption isotherm of the low-temperature nitrogen adsorption.
Preparation of comparative example 8
The preparation method of the tin-loaded titanium silicalite Sn/TS-1 in the preparation comparative example is as follows:
the pentahydrate stannic chloride (SnCl) 4 .5H 2 O) and TS-1 molecular sieve (prepared by the method of comparative preparation example 7) are directly and mechanically mixed and then are roasted for 5 hours at 550 ℃ to obtain the molecular sieve with the chemical composition of 0.03TiO 2 :SiO 2 :0.03SnO 2 The molecular sieve of (4). Wherein the dosage of TS-1 is 2g 4 .5H 2 The amount of O used was 0.76g.
The examples and comparative examples illustrate the preparation of lactic acid using a different catalyst to catalyze methylglyoxal.
Example 1
Weighing 0.15g of the tin-titanium-silicon molecular sieve Sn-Ti-MFI-1 provided in preparation example 1 as a catalyst, putting the catalyst into a 15mL glass reaction tube, sequentially adding a magnetic stirrer, 8g of water and 0.1g of pyruvaldehyde, and screwing a cover of the glass reaction tube. And putting the glass reaction tube in an oil bath, putting the glass reaction tube on a temperature control magnetic stirrer, and starting the magnetic stirrer and a heating device to start reaction. The reaction temperature is controlled to be about 60 ℃ and the reaction is carried out for 7 hours. The specific reaction results are shown in Table 1.
Comparative example 1
0.15g of the Sn-MFI as catalyst provided in comparative example 1 was weighed and placed in a 15mL glass reaction tube, and then a magnetic stirrer, 8g of water and 0.1g of methylglyoxal were sequentially added, and the lid of the glass reaction tube was screwed on. And putting the glass reaction tube in an oil bath, putting the glass reaction tube on a temperature control magnetic stirrer, and starting the magnetic stirrer and a heating device to start reaction. The reaction temperature is controlled to be about 60 ℃ and the reaction is carried out for 7 hours. The specific reaction results are shown in Table 1.
Comparative example 2
0.15g of the Sn-Beta molecular sieve provided in preparation comparative example 2 is weighed and loaded into a 15mL glass reaction tube as a catalyst, then a magnetic stirrer, 8g of water and 0.1g of methylglyoxal are sequentially added, and the cover of the glass reaction tube is screwed on. And putting the glass reaction tube in an oil bath, putting the glass reaction tube on a temperature control magnetic stirrer, and starting the magnetic stirrer and a heating device to start reaction. The reaction temperature is controlled to be about 60 ℃ and the reaction is carried out for 7 hours. The specific reaction results are shown in Table 1.
Comparative example 3
0.15g of the Sn-USY molecular sieve provided in preparation comparative example 3 is weighed and loaded into a 15mL glass reaction tube as a catalyst, then a magnetic stirrer, 8g of water and 0.1g of methylglyoxal are sequentially added, and the cover of the glass reaction tube is screwed on. And (3) placing the glass reaction tube in an oil bath, placing the glass reaction tube on a temperature control magnetic stirrer, starting the magnetic stirrer and a heating device, and starting the reaction. The reaction temperature is controlled to be about 60 ℃ and the reaction is carried out for 7 hours. The specific reaction results are shown in Table 1.
Comparative example 4
Weighing 0.15g of the titanium silicalite TS-2 provided in preparation comparative example 5 as a catalyst, filling the catalyst into a 15mL glass reaction tube, sequentially adding a magnetic stirrer, 8g of water and 0.1g of methylglyoxal, and screwing a cover of the glass reaction tube. And putting the glass reaction tube in an oil bath, putting the glass reaction tube on a temperature control magnetic stirrer, and starting the magnetic stirrer and a heating device to start reaction. The reaction temperature is controlled to be about 60 ℃ and the reaction is carried out for 7 hours. The specific reaction results are shown in Table 1.
Comparative example 5
Weighing 0.15g of the Ti-Si molecular sieve Ti-Beta provided by the preparation comparative example 6 as a catalyst, putting the catalyst into a 15mL glass reaction tube, sequentially adding a magnetic stirrer, 8g of water and 0.1g of methylglyoxal, and screwing a cover of the glass reaction tube. And putting the glass reaction tube in an oil bath, putting the glass reaction tube on a temperature control magnetic stirrer, and starting the magnetic stirrer and a heating device to start reaction. The reaction temperature is controlled to be about 60 ℃ and the reaction is carried out for 7 hours. The specific reaction results are shown in Table 1.
Comparative example 6
Weighing 0.15g of the titanium silicalite molecular sieve TS-1 provided in preparation comparative example 4 as a catalyst, putting the catalyst into a 15mL glass reaction tube, sequentially adding a magnetic stirrer, 8g of water and 0.1g of methylglyoxal, and screwing a cover of the glass reaction tube. And putting the glass reaction tube in an oil bath, putting the glass reaction tube on a temperature control magnetic stirrer, and starting the magnetic stirrer and a heating device to start reaction. The reaction temperature is controlled to be about 60 ℃ and the reaction is carried out for 7 hours. The specific reaction results are shown in Table 1.
Comparative example 7
0.10g of Sn-MFI provided in preparation comparative example 1 and 0.05g of TS-1 provided in preparation comparative example 4 were weighed as catalysts and placed in a 15mL glass reaction tube, and then a magnetic stirrer, 8g of water and 0.1g of methylglyoxal were sequentially added, and a cover of the glass reaction tube was screwed on. And putting the glass reaction tube in an oil bath, putting the glass reaction tube on a temperature control magnetic stirrer, and starting the magnetic stirrer and a heating device to start reaction. The reaction temperature is controlled to be about 60 ℃ and the reaction is carried out for 7 hours. The specific reaction results are shown in Table 1.
Comparative example 8
0.05g of Sn-MFI of the Sn-Si molecular sieve provided by the preparation comparative example 1 and 0.10g of TS-1 of the Ti-Si molecular sieve provided by the preparation comparative example 4 are weighed as catalysts and filled in a 15mL glass reaction tube, then a magnetic stirrer, 8g of water and 0.1g of methylglyoxal are sequentially added, and a cover of the glass reaction tube is screwed on. And putting the glass reaction tube in an oil bath, putting the glass reaction tube on a temperature control magnetic stirrer, and starting the magnetic stirrer and a heating device to start reaction. The reaction temperature is controlled to be about 60 ℃ and the reaction is carried out for 7 hours. The specific reaction results are shown in Table 1.
Comparative example 9
Weighing 0.15g of the tin-titanium-silicon molecular sieve Sn-Ti-MFI-1 provided in preparation example 1 as a catalyst, putting the catalyst into a 15mL glass reaction tube, sequentially adding a magnetic stirrer, 8g of water and 0.1g of pyruvaldehyde, and screwing a cover of the glass reaction tube. And putting the glass reaction tube in an oil bath, putting the glass reaction tube on a temperature control magnetic stirrer, and starting the magnetic stirrer and a heating device to start reaction. The reaction temperature is controlled to be about 10 ℃ and the reaction is carried out for 0.5 hour. The specific reaction results are shown in Table 1.
Comparative example 10
0.15g of the hollow titanium silicalite molecular sieve HTS catalyst provided in preparation comparative example 7 was weighed and placed in a 15mL glass reaction tube, and then a magnetic stirrer, 8g of water and 0.1g of methylglyoxal were sequentially added, and the cover of the glass reaction tube was screwed on. And putting the glass reaction tube in an oil bath, putting the glass reaction tube on a temperature control magnetic stirrer, and starting the magnetic stirrer and a heating device to start reaction. The reaction temperature is controlled to be about 60 ℃ and the reaction is carried out for 7 hours. The specific reaction results are shown in Table 1.
Comparative example 11
0.15g of the Sn/TS-1 catalyst for preparing the Sn-loaded titanium silicalite molecular sieve provided in the comparative example 8 is weighed and placed in a 15mL glass reaction tube, then a magnetic stirrer, 8g of water and 0.1g of methylglyoxal are sequentially added, and a cover of the glass reaction tube is screwed on. And (3) placing the glass reaction tube in an oil bath, placing the glass reaction tube on a temperature control magnetic stirrer, starting the magnetic stirrer and a heating device, and starting the reaction. The reaction temperature is controlled to be about 60 ℃ and the reaction is carried out for 7 hours. The specific reaction results are shown in Table 1.
Comparative example 12
The same as example 1 except that: the reaction temperature is 200 ℃, the reaction time is 12 hours, the reaction raw materials and the catalyst are filled in a polytetrafluoroethylene lining, then the polytetrafluoroethylene lining is placed in a stainless steel reaction kettle for sealing, and the reaction is carried out in a homogeneous reactor. The specific reaction results are shown in Table 1.
Example 2
Weighing 0.15g of the tin-titanium-silicon molecular sieve Sn-Ti-MFI-2 provided in preparation example 2 as a catalyst, putting the catalyst into a 15mL glass reaction tube, sequentially adding a magnetic stirrer, 8g of water and 0.1g of pyruvaldehyde, and screwing a cover of the glass reaction tube. And putting the glass reaction tube in an oil bath, putting the glass reaction tube on a temperature control magnetic stirrer, and starting the magnetic stirrer and a heating device to start reaction. The reaction temperature is controlled at about 60 ℃ and the reaction is carried out for 7 hours. The specific reaction results are shown in Table 1.
Example 3
Weighing 0.15g of the tin-titanium-silicon molecular sieve Sn-Ti-MFI-3 provided in preparation example 3 as a catalyst, putting the catalyst into a 15mL glass reaction tube, sequentially adding a magnetic stirrer, 8g of water and 0.1g of pyruvaldehyde, and screwing a cover of the glass reaction tube. And (3) placing the glass reaction tube in an oil bath, placing the glass reaction tube on a temperature control magnetic stirrer, starting the magnetic stirrer and a heating device, and starting the reaction. The reaction temperature is controlled to be about 60 ℃ and the reaction is carried out for 7 hours. The specific reaction results are shown in Table 1.
Example 4
Weighing 0.15g of the tin-titanium-silicon molecular sieve Sn-Ti-MFI-4 provided in preparation example 4 as a catalyst, putting the catalyst into a 15mL glass reaction tube, sequentially adding a magnetic stirrer, 8g of water and 0.1g of pyruvaldehyde, and screwing a cover of the glass reaction tube. And (3) placing the glass reaction tube in an oil bath, placing the glass reaction tube on a temperature control magnetic stirrer, starting the magnetic stirrer and a heating device, and starting the reaction. The reaction temperature is controlled to be about 60 ℃ and the reaction is carried out for 7 hours. The specific reaction results are shown in Table 1.
Example 5
Weighing 0.15g of the Sn-Ti-MFI-5 provided in preparation example 5 as a catalyst, filling the catalyst into a 15mL glass reaction tube, sequentially adding a magnetic stirrer, 8g of water and 0.1g of methylglyoxal, and screwing a cover of the glass reaction tube. And putting the glass reaction tube in an oil bath, putting the glass reaction tube on a temperature control magnetic stirrer, and starting the magnetic stirrer and a heating device to start reaction. The reaction temperature is controlled to be about 60 ℃ and the reaction is carried out for 7 hours. The specific reaction results are shown in Table 1.
Example 6
The same as example 1 except that the tin-titanium-silicon molecular sieve provided in preparation example 6 was used as a catalyst. The specific reaction results are shown in Table 1.
Example 7
The same as example 1 except that the tin-titanium-silicon molecular sieve provided in preparation example 7 was used as a catalyst. The specific reaction results are shown in Table 1.
Example 8
The same as example 1 except that: the molar ratio of methylglyoxal to water is 1:40, the reaction temperature is 30 ℃, the reaction time is 1 hour, and the weight ratio of the methylglyoxal to the tin-titanium-silicon molecular sieve is 1. The specific reaction results are shown in Table 1.
Example 9
The same as example 1 except that: the molar ratio of methylglyoxal to water is 1:350, the reaction temperature is 180 ℃, the reaction time is 10 hours, the weight ratio of the methylglyoxal to the tin-titanium-silicon molecular sieve is 1. The specific reaction results are shown in Table 1.
As can be seen from the results of the above examples and comparative examples, the method of the present invention for preparing lactic acid has the advantages of simple operation process, mild reaction conditions, high conversion rate of raw materials and high selectivity of lactic acid; especially when the catalyst is a binary tin titanium silicon molecular sieve, the molar ratio of the methylglyoxal to the water is 1: (40-350), the reaction temperature is 30-180 ℃, the reaction time is 1-10h, and the reaction pressure is 0.1-3.0MPa, and the molar ratio of the methylglyoxal to the water is further preferably 1: (60-200), the reaction temperature is 40-120 ℃, the reaction time is 2-8h, and the reaction pressure is 0.1-2.0MPa, which is more beneficial to improving the conversion rate of the methylglyoxal and the yield of the lactic acid.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that, in the above embodiments, the various features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, the present invention does not separately describe various possible combinations.
In addition, any combination of the various embodiments of the present invention can be made, and the same should be considered as the content of the present invention as long as the idea of the present invention is not violated.
TABLE 1
Numbering Methylglyoxal conversion/%) Lactic acid selectivity/%)
Example 1 97 97
Example 2 96 97
Example 3 99 97
Example 4 95 99
Example 5 97 97
Example 6 95 96
Example 7 96 98
Example 8 93 95
Example 9 99 95
Comparative example 1 80 67
Comparative example 2 78 74
Comparative example 3 77 75
Comparative example 4 45 15
Comparative example 5 47 14
Comparative example 6 49 18
Comparative example 7 87 84
Comparative example 8 89 85
Comparative example 9 24 14
Comparative example 10 54 22
Comparative example 11 62 58
Comparative example 12 97 75

Claims (10)

1. A method of catalyzing methylglyoxal to produce lactic acid, the method comprising:
contacting methylglyoxal and water with a catalyst in a reactor and reacting to obtain a product containing lactic acid; wherein the molar ratio of the methylglyoxal to the water is 1: (40-350), the reaction temperature is 30-180 ℃, the reaction time is 1-10h, the catalyst contains a tin-titanium-silicon molecular sieve, and the weight ratio of the methylglyoxal to the tin-titanium-silicon molecular sieve based on the dry weight is 1: (1-6); the molar ratio of tin element to silicon element in the tin-titanium-silicon molecular sieve is 0.2-2; the tin-titanium-silicon molecular sieve is selected from an MFI type tin-titanium-silicon molecular sieve; the tin-titanium-silicon molecular sieve contains silicon element, titanium element, tin element and oxygen element;
the preparation method of the tin-titanium-silicon molecular sieve comprises the following steps:
(1) Contacting a tin source, a titanium source and a template agent in the presence of an aqueous solvent to obtain a first mixture;
(2) Mixing the first mixture with a silicon molecular sieve to obtain a second mixture;
(3) Crystallizing the second mixture under hydrothermal crystallization conditions;
the conditions of the contacting include: the contact temperature is 20-80 ℃, and the contact time is 1-240min;
or, the tin-titanium-silicon molecular sieve is obtained by carrying out secondary hydrothermal synthesis on a compound containing a tin source, a template agent, alkali and water at 100-160 ℃ on the basis of a titanium-silicon molecular sieve, and then carrying out filtering separation, drying and roasting operations, wherein the tin content in the molecular sieve is 1-5 wt% calculated by oxides.
2. The method of claim 1, wherein the tin-titanium-silicon molecular sieve is selected from Sn-Ti-MFI molecular sieves.
3. The method of claim 1, wherein at least a portion of the crystallites of the tin titanium silicalite have a void structure therein;
the proportion of the external specific surface area of the tin-titanium-silicon molecular sieve in the total specific surface area is more than 10 percent, and the total specific surface area is 300m 2 More than g, and the external specific surface area is 20m 2 More than g;
the tin-titanium-silicon molecular sieve has a diffraction peak at 0.5-9 degrees of 2 theta in an XRD pattern;
460cm of the tin-titanium-silicon molecular sieve in an FT-IR spectrum -1 、975cm -1 、800cm -1 And 1080cm -1 Nearby absorption;
the tin-titanium-silicon molecular sieve has absorption at 200-300nm in a UV-Vis spectrum;
the tin-titanium-silicon molecular sieve is P/P at 25 DEG C 0 An adsorbed amount of benzene of at least 35mg/g as measured under conditions of 0.10 and an adsorption time of 1 hour; at a relative pressure P/P 0 A difference between the nitrogen adsorption amount during desorption and the nitrogen adsorption amount during adsorption of the tin-titanium-silicon molecular sieve of about 0.60% is greater than 2% of the nitrogen adsorption amount during adsorption of the tin-titanium-silicon molecular sieve;
a hysteresis loop is arranged between an adsorption isotherm and a desorption isotherm of low-temperature nitrogen adsorption of the tin-titanium-silicon molecular sieve;
the radial length of the cavity part of the cavity structure in the crystal grain of the tin-titanium-silicon molecular sieve is 0.5-300nm.
4. The method of claim 3, wherein the ratio of the external specific surface area of the tin-titanium-silicon molecular sieve to the total specific surface area is 10-25%, and the total specific surface area is 310-600m 2 Per g, external specific surface area of 31-150m 2 /g。
5. The method of claim 1, wherein in the step (1), the silicon molecular sieve and the tin source are used in an amount such that the molar ratio of tin element to silicon element in the prepared tin-titanium-silicon molecular sieve is 0.5-2; the molar ratio of the titanium element to the silicon element in the prepared tin-titanium-silicon molecular sieve is 0.5-4;
the molar ratio of the silicon molecular sieve to the template agent to the titanium source to the tin source to the water is (100-18) 2 The tin source is calculated by tin element, and the titanium source is calculated by TiO 2 Counting;
the hydrothermal crystallization conditions comprise: the crystallization temperature is 80-200 ℃ under the closed condition, and the crystallization time is 6-150h;
the tin source is an inorganic tin compound and/or an organic tin compound; the titanium source is an inorganic titanium compound and/or an organic titanium compound; the template agent is one or more of aliphatic amine compound, aliphatic alcohol amine compound and quaternary ammonium base compound; the silicon molecular sieve is S-1;
at least part of the interior of crystal grains of the tin-titanium-silicon molecular sieve has a cavity structure, and a diffraction peak is arranged at a position of 0.5-9 degrees of 2 theta in an XRD (X-ray diffraction) pattern; 460cm in the FT-IR spectrum -1 、975cm -1 、800cm -1 、1080cm -1 Nearby absorption; the absorption is carried out at 200-300nm in a UV-Vis spectrum, and the total specific surface area of the tin-titanium-silicon molecular sieve is 300m 2 More than g, and the external specific surface area is 30m 2 More than g, and the proportion of the external specific surface area to the total specific surface area is more than 10 percent.
6. The method of claim 1, wherein the tin-titanium-silicon molecular sieve is Sn-TS-1.
7. The method of claim 6, wherein the Sn-TS-1 is a titanium silicalite molecular sieve having an MFI crystal structure, the grains have a hollow structure, and the radial length of the hollow part of the hollow grains is 5 to 300nm; the molecular sieve sample is at 25 ℃ and P/P 0 =0.10, the benzene adsorption amount measured under the condition of adsorption time of 1 hour is at least 70 mg/g, and a hysteresis loop exists between the adsorption isotherm and the desorption isotherm of low-temperature nitrogen adsorption of the molecular sieve.
8. The method of claim 1, wherein the molar ratio of methylglyoxal to water is 1: (60-200), wherein the weight ratio of the methylglyoxal to the tin-titanium-silicon molecular sieve is 1: (1.2-3), the reaction temperature is 40-120 ℃, the reaction time is 2-8h, and the reaction pressure is 0.1-3MPa.
9. The process according to claim 8, wherein the reaction pressure is 0.1-2MPa.
10. The process of claim 1, wherein the reactor is a tank reactor, a fixed bed reactor, a moving bed, a suspended bed, or a slurry bed reactor.
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