CN111253226B - A kind of method that catalyzes dihydroxyacetone and/or glyceraldehyde to prepare lactic acid - Google Patents

Abstract

The invention relates to a method for preparing lactic acid by catalyzing dihydroxyacetone and/or glyceraldehyde, which comprises the following steps: contacting reaction raw materials, water and a catalyst in a reactor and carrying out reaction to obtain a product containing lactic acid; wherein: the reaction raw materials contain dihydroxyacetone and/or glyceraldehyde, and the molar ratio of dihydroxyacetone and/or glyceraldehyde: water =1: (50-450), 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 weight of dihydroxyacetone and/or glyceraldehyde to the weight of the tin-titanium-silicon molecular sieve on a dry basis is 1: (1-6). The process of the present invention has high dihydroxyacetone/glyceraldehyde conversion and lactic acid yield.

Description

A kind of method that catalyzes dihydroxyacetone and/or glyceraldehyde to prepare lactic acid

technical field

The invention relates to a method for preparing lactic acid by catalyzing dihydroxyacetone and/or glyceraldehyde.

Background technique

Lactic acid (scientific name: 2-hydroxypropionic acid) is a chemical compound with the molecular formula C ₃ H ₆ O ₃ , which plays a role in various biochemical processes. It is a carboxylic acid containing a hydroxyl group and is therefore an alpha-hydroxy acid. In aqueous solution, its carboxyl group releases a proton to produce lactate ion. Lactate dehydrogenase converts pyruvate to L-lactate during fermentation. Lactate is continuously produced during normal metabolism and exercise, but its concentration generally does not rise. Lactic acid is a colorless liquid, and the industrial product is a colorless to pale yellow liquid. Odorless, hygroscopic, relative density 1.200, melting point 18°C, boiling point 122°C, flash point greater than 110°C, miscible with ethanol, ether, water, glycerin, insoluble in chloroform, carbon disulfide and petroleum ether, widely used in the food industry , pharmaceutical industry, industry, cosmetics industry, agriculture and livestock industry.

Traditional lactic acid production methods mainly use sugar fermentation and chemical synthesis. The fermentation method uses carbohydrates as raw materials, and the pH value of the fermentation system needs to be maintained in the range of 5.5-6.5, but with the continuous generation of lactic acid, the pH value gradually decreases, so it is necessary to continuously add calcium oxide or calcium carbonate during the reaction process. Balance the pH of the system. The generated calcium lactate is treated with sulfuric acid to obtain crude lactic acid, and a large amount of waste salt (calcium sulfate) is produced at the same time. However, it is difficult to separate crude lactic acid, which needs to be reacted with alcohol to form lactic acid ester with a relatively low boiling point, and then separated by distillation and hydrolyzed to obtain high-purity lactic acid. The process has a long reaction route, high production cost, and produces a large amount of solid waste, which makes it impossible to realize large-scale production and application of lactic acid at present. The commonly used chemical synthesis methods are the lactonitrile method and the propionic acid method. The lactonitrile method uses acetaldehyde and highly toxic hydrocyanic acid as the reaction raw materials, and concentrated sulfuric acid as the catalyst. Therefore, the production process is seriously polluted and has potential safety hazards. The propionic acid method uses toxic chlorine gas as a raw material, which not only requires high operational safety and airtightness, but also easily pollutes the atmospheric environment.

Contents of the invention

The purpose of the present invention is to provide a kind of method that catalyzes dihydroxyacetone and/or glyceraldehyde to prepare lactic acid, and the method of the present invention has the conversion rate of high dihydroxyacetone/glyceraldehyde and the productive rate of lactic acid.

In order to achieve the above object, the present invention provides a method of catalyzing dihydroxyacetone and/or glyceraldehyde to prepare lactic acid, the method comprising:

The reaction raw materials and water are contacted with the catalyst in a reactor and reacted to obtain a product containing lactic acid; wherein:

The reaction raw material contains dihydroxyacetone and/or glyceraldehyde, in terms of moles, dihydroxyacetone and/or glyceraldehyde:water=1:(50-450), the reaction temperature is 30-180°C, and the reaction time is 1- 10h, the catalyst contains tin-titanium-silicon molecular sieve, and the ratio of the weight of dihydroxyacetone and/or glyceraldehyde to the weight of the tin-titanium-silicon molecular sieve on a dry basis is 1:(1-6).

Optionally, the tin-titanium-silicon molecular sieve is selected from MFI tin-titanium-silicon molecular sieve, MEL tin-titanium-silicon molecular sieve, BEA tin-titanium-silicon molecular sieve, MWW tin-titanium-silicon molecular sieve, MOR tin-titanium-silicon molecular sieve, hexagonal structure tin One or more of titanium-silicon molecular sieves and FAU-type tin-titanium-silicon molecular sieves.

Optionally, the tin-titanium-silicon molecular sieve is selected from 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 - one or more of 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 silicon, titanium, tin and oxygen;

Preferably, at least part of the crystal grains of the tin-titanium-silicon molecular sieve have a cavity structure;

Preferably, the ratio of the external specific surface area of the tin-titanium-silicon molecular sieve to the total specific surface area is above 10%, the total specific surface area is above 300m ² /g, and the external specific surface area is above 20m ² /g;

Preferably, the tin-titanium-silicon molecular sieve has a diffraction peak at 2θ in the XRD pattern at 0.5°-9°;

Preferably, the tin-titanium-silica molecular sieve has absorption near 460cm ^-1 , 975cm ^-1 , 800cm ^-1 and 1080cm ^-1 in the FT-IR spectrum;

Preferably, the tin-titanium-silicon molecular sieve has absorption at 200-300nm in the 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%, the total specific surface area is 310-600m ² /g, and the external specific surface area is 31-150m ² /g;

Preferably, the tin-titanium-silicon molecular sieve has a benzene adsorption capacity of at least 35 mg/g measured under the conditions of 25°C, P/P ₀ =0.10 and an adsorption time of 1 hour; at a relative pressure around P/P ₀ =0.60 , the difference between the nitrogen adsorption amount during desorption of the tin-titanium-silicon molecular sieve and the nitrogen adsorption amount during adsorption is greater than 2% of the nitrogen adsorption amount during the adsorption of the tin-titanium-silicon molecular sieve;

Preferably, there is a hysteresis loop 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 internal cavity structure of the tin-titanium-silicon molecular sieve is 0.5-300nm;

Preferably, the molar ratio of tin to silicon in the tin-titanium-silicon molecular sieve is 0.05-10:100, and the molar ratio of titanium to silicon is 0.05-10:100.

Optionally, the preparation method of the tin-titanium-silicon molecular sieve comprises:

(1) contacting the tin source, the titanium source and the templating agent in the presence of an aqueous solvent to obtain the first mixture;

(2) mixing the first mixture with silicon molecular sieves to obtain a second mixture;

(3) Under hydrothermal crystallization conditions, the second mixture is crystallized.

Optionally, in step (1), the contact conditions include: the contact temperature is 20-80°C, and the contact time is 1-240min;

Preferably, the amount of the silicon molecular sieve and the tin source is such that the molar ratio of tin to silicon in the prepared tin-titanium-silicon molecular sieve is 0.05-10:100; the amount of the silicon molecular sieve and the titanium source is such that the prepared tin The molar ratio of titanium element to silicon element in the titanium silicon molecular sieve is 0.05-10:100;

Preferably, the molar ratio of the silicon molecular sieve, template, titanium source, tin source and water is 100:0.005-20:0.05-20:0.0005-15:200-10000, wherein the silicon molecular sieve is calculated as _SiO2 , The tin source is counted as tin element, and the titanium source is counted as _TiO2 ;

Preferably, the hydrothermal crystallization conditions include: the crystallization temperature is 80-200°C under airtight conditions, and the crystallization time is 6-150h;

Preferably, 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 is an aliphatic amine compound, an aliphatic alcohol amine compound and a quaternary One or more of ammonium base compounds; the silicon molecular sieve is selected from one or more of S-1, S-2, BETA, MOR, MCM-22, MCM-41, SBA-15 and MCM-48 various;

Preferably, at least part of the crystal grains of the tin-titanium-silicon molecular sieve have a cavity structure, and there are diffraction peaks at 0.5°-9° at 2θ in the XRD spectrum; 460cm ^-1 and 975cm ^-1 in the FT-IR spectrum ^1. There is absorption near 800cm ^-1 and 1080cm ^-1 ; there is absorption at 200-300nm in the UV-Vis spectrum, and the total specific surface area of the tin-titanium-silicon molecular sieve is above 300m ² /g, and the external specific surface area is 30m ² /g or more, and the ratio of the outer specific surface area to the total specific surface area is more than 10%.

Optionally, the tin-titanium-silicon molecular sieve is synthesized on the basis of titanium-silicon molecular sieve by secondary hydrothermal synthesis with tin-containing source compound, template agent, alkali and water at 100-160°C, and then separated by filtration and dried and roasting operation, the tin content in the molecular sieve is 1-5% by weight based on the oxide;

Preferably, the tin-titanium-silicon molecular sieves are Sn-TS-1, Sn-TS-2, Sn-Ti-BETA, Sn-Ti-MCM-22, Sn-Ti-MCM-41 and Sn-Ti-MCM- 48 in a mixture of one or more.

Optionally, the Sn-TS-1 is a titanium-silicon molecular sieve with an MFI crystal structure, the grains are hollow, and the radial length of the hollow portion of the hollow grains is 5-300 nanometers; the molecular sieve sample is 25 °C, P/P ₀ =0.10, and adsorption time of 1 hour, the measured benzene adsorption amount is at least 70 mg/g, and there is a hysteresis loop between the adsorption isotherm and desorption isotherm of the low-temperature nitrogen adsorption of the molecular sieve.

Optionally, in terms of moles, dihydroxyacetone and/or glyceraldehyde:water=1:(60-200), the weight of dihydroxyacetone and/or glyceraldehyde and the weight of the tin-titanium-silicon molecular sieve in terms of dry weight The ratio is 1:(1.2-3), the reaction temperature is 40-120°C, 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 suspension bed or a slurry bed reactor.

The method of the present invention adopts a catalyst containing a binary tin-titanium-silicon molecular sieve, and the tin atoms in the skeleton of the molecular sieve activate the carbonyl in dihydroxyacetone and/or glyceraldehyde to generate aceguvaldehyde, and the tin atoms in the skeleton of the molecular sieve and the titanium atoms in the skeleton cooperate to catalyze the aceguvaldehyde Lactic acid is generated, which improves the reaction efficiency. Compared with the existing technology, a higher conversion rate of dihydroxyacetone/glyceraldehyde and a yield of lactic acid can be obtained under milder reaction conditions in a short period of time. The subsequent separation of products consumes less energy, and the process is safer and more efficient. It is suitable for large-scale Industrial production applications.

Other features and advantages of the present invention will be described in detail in the following detailed description.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the description, together with the following specific embodiments, are used to explain the present invention, but do not constitute a limitation to the present invention. In the attached picture:

Fig. 1 is the reaction mechanism diagram that the present invention relates to dihydroxyacetone and glyceraldehyde conversion into lactic acid.

Detailed ways

Specific embodiments of the present invention will be described in detail below. It should be understood that the specific embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

In the present invention, the weight on a dry basis refers to the weight measured after the sample is calcined at 550° C. for 3 hours.

The invention provides a method for preparing lactic acid by catalyzing dihydroxyacetone and/or glyceraldehyde, the method comprising: contacting the reaction raw materials and water with the catalyst in a reactor and reacting to obtain a product containing lactic acid; wherein: the reaction The raw material contains dihydroxyacetone and/or glyceraldehyde, in terms of moles, dihydroxyacetone and/or glyceraldehyde: water = 1: (50-450), the reaction temperature is 30-180°C, and the reaction time is 1-10h. The catalyst contains tin-titanium-silicon molecular sieve, and the ratio of the weight of dihydroxyacetone and/or glyceraldehyde to the weight of the tin-titanium-silicon molecular sieve in terms of dry weight is 1: (1-6). The reaction mechanism diagram is shown in Figure 1.

Those skilled in the art can understand that, as shown in Figure 1, the method of the present invention actually includes the following three situations:

1. Dihydroxyacetone reacts with water. At this time, dihydroxyacetone and/or glyceraldehyde: water is dihydroxyacetone: water. The conversion rate of dihydroxyacetone/glyceraldehyde refers to the conversion rate of dihydroxyacetone, dihydroxyacetone and/or glycerin The weight of aldehyde is the weight of dihydroxyacetone;

2. Glyceraldehyde reacts with water. At this time, dihydroxyacetone and/or glyceraldehyde: water is glyceraldehyde: water, and the conversion rate of dihydroxyacetone/glyceraldehyde refers to the conversion rate of glyceraldehyde, the weight of dihydroxyacetone and/or glyceraldehyde Be the weight of glyceraldehyde;

3. Dihydroxyacetone and glyceraldehyde react with water at the same time. At this time, dihydroxyacetone and/or glyceraldehyde: water is dihydroxyacetone and glyceraldehyde: water, and the conversion rate of dihydroxyacetone/glyceraldehyde refers to dihydroxyacetone and glyceraldehyde The mole-weighted conversion rate (i.e. the weight is the molar ratio), the weight of dihydroxyacetone and/or glyceraldehyde is the total weight of dihydroxyacetone and glyceraldehyde, and dihydroxyacetone and glyceraldehyde can be reacted together with water in any mixing ratio .

According to the present invention, a tin-titanium-silicon molecular sieve refers to a molecular sieve obtained by substituting tin atoms and titanium atoms for a part of the silicon atoms in the molecular sieve lattice framework. The tin atoms and titanium atoms in the framework can be measured by ultraviolet or infrared spectroscopy. For example, using ultraviolet spectroscopy to analyze tin-titanium-silicon molecular sieve samples, the characteristic absorption peak of the skeleton tin atom appears near 190nm, and the skeleton Ti atom appears near 210nm. characteristic absorption peaks. The peak near 1450cm ^-1 in pyridine infrared spectrum reflects the L-acidity characteristic of molecular sieve, which is provided by the skeleton tin atoms and skeleton titanium atoms.

According to the present invention, the tin-titanium-silicon molecular sieve can be the product of tin atoms and titanium atoms replacing part of the skeleton silicon of molecular sieves with various topological structures. The topological structure of molecular sieves can refer to the website of the International Zeolite Association (IZA, International Zeolite Association), such as the tin Titanium silicon molecular sieve can be selected from MFI tin titanium silicon molecular sieve, MEL tin titanium silicon molecular sieve, BEA tin titanium silicon molecular sieve, MWW tin titanium silicon molecular sieve, MOR tin titanium silicon molecular sieve, hexagonal structure tin titanium silicon molecular sieve and FAU type One or more of tin-titanium-silicon molecular sieves, the MFI-type tin-titanium-silicon molecular sieves are, for example, Sn-Ti-MFI molecular sieves, the MEL-type tin-titanium-silicon molecular sieves are, for example, Sn-Ti-MEL molecular sieves, BEA-type tin-titanium molecular sieves Silicon molecular sieves are, for example, Sn-Ti-Beta molecular sieves, MWW-type tin-titanium-silicon molecular sieves are, for example, Sn-Ti-MCM-22 molecular sieves, MOR-type tin-titanium-silicon molecular sieves are, for example, Sn-Ti-MOR molecular sieves, tin-titanium-silicon molecular sieves with hexagonal structure For example, it is Sn-Ti-MCM-41 molecular sieve, Sn-Ti-SBA-15 molecular sieve, and the FAU type tin-titanium-silicon molecular sieve is such as Sn-Ti-USY molecular sieve; preferably, the tin-titanium-silicon molecular sieve is preferably MFI type tin-titanium One or more of silicon molecular sieves, BEA-type tin-titanium-silicon molecular sieves and FAU-type tin-titanium-silicon molecular sieves, more preferably MFI-type tin-titanium-silicon molecular sieves, the MFI-type tin-titanium-silicon molecular sieves can be commercially available, or It is prepared by the methods disclosed in Chinese patents CN105217645A and CN102452918A, and provides the following two specific implementations of tin-titanium-silicon molecular sieves.

The implementation of the first tin-titanium-silicon molecular sieve comes from patent CN105217645A.

According to the first embodiment, the tin-titanium-silicon molecular sieve contains silicon element, titanium element, tin element and oxygen element, wherein at least part of the crystal grains of the tin-titanium-silicon molecular sieve have a hole structure inside. At least part of the grains of the tin-titanium-silicon molecular sieve has a hole structure, which means that in a large number of tin-titanium-silicon molecular sieve grains, at least some of the grains of the tin-titanium-silicon molecular sieve have a hole structure, preferably more than 50% of tin The crystal grains of the titanium-silicon molecular sieve have a cavity structure inside, and more preferably 70-100% of the tin-titanium-silicon molecular sieves have a cavity structure inside the crystal grains.

According to the first embodiment, it is preferred that the ratio of the external specific surface area of the tin-titanium-silicon molecular sieve to the total specific surface area is more than 10%, preferably 10-25%, more preferably 10-20%, more preferably 12-18% %. Preferably the total specific surface area is above 300m ² /g, more preferably 310-600m ² /g, more preferably 350-460m ² /g. The external specific surface area is above 20m ² /g, preferably above 30m ² /g, more preferably 31-150m ² /g, still more preferably 35-120m ² /g, most preferably 40-70m ² /g.

According to the 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, which may also be referred to as the external area for short. Both the total specific surface area and the external specific surface area can be measured according to the ASTM D4222-98 standard method.

According to the first embodiment, the tin-titanium-silicon molecular sieve whose crystal grains have a hole structure has the spectroscopic properties of a conventional tin-titanium-silicon molecular sieve. Specifically, the 2θ of the tin-titanium-silicon molecular sieve in the XRD spectrum is between 0.5°- There is a diffraction peak at 9°, preferably there is a diffraction peak at 5°-9° at 2θ.

According to the first embodiment, preferably, the tin-titanium-silica molecular sieve has absorptions near 460 cm ^-1 , 975 cm ^-1 , 800 cm ^-1 and 1080 cm ^-1 in the FT-IR spectrum. Preferably, the tin-titanium-silicon molecular sieve has absorption at 200-300 nm in the UV-Vis spectrum, preferably at 200-260 nm.

According to the first embodiment, preferably the molar ratio of the tin element to the silicon element in the tin-titanium-silicon molecular sieve is 0.05-10:100, more preferably 0.1-5:100, particularly preferably 0.2-2:100. Preferably, the molar ratio of titanium element to silicon element in the tin-titanium-silicon molecular sieve is 0.05-10:100, more preferably 0.1-5:100, particularly preferably 0.5-4:100. Such proportions of tin, titanium and silicon can further optimize the catalytic activity of the tin-titanium-silicon molecular sieve of the present invention.

According to the first embodiment, it is preferred that the benzene adsorption capacity of the tin-titanium-silicon molecular sieve measured under the conditions of 25°C, P/P ₀ =0.10 and an adsorption time of 1 hour is at least 25 mg/g, preferably at least 35 mg/g. g, preferably 40-100 mg/g.

According to the first embodiment, preferably when the tin-titanium-silicon molecular sieve is near the relative pressure P/P ₀ =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 the adsorption of the tin-titanium-silicon molecular sieve, preferably the difference between the nitrogen adsorption amount during the desorption of the tin-titanium-silicon molecular sieve and the nitrogen adsorption amount during adsorption is greater than the adsorption amount of the tin-titanium-silicon molecular sieve 5% of the nitrogen adsorption amount during the desorption of the tin-titanium-silicon molecular sieve, and the difference between the nitrogen adsorption amount during the desorption of the tin-titanium-silicon molecular sieve and the nitrogen adsorption amount during the adsorption is 6% of the nitrogen adsorption amount during the adsorption of the tin-titanium-silicon molecular sieve -10%.

According to the first embodiment, preferably, there is a hysteresis loop 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 internal cavity structure of the tin-titanium-silicon molecular sieve is 0.1-500 nm, preferably 0.5-300 nm.

According to the first embodiment, the preparation method of the tin-titanium-silicon molecular sieve comprises:

(1) contacting the tin source, the titanium source and the templating agent in the presence of an aqueous solvent to obtain the first mixture;

(2) mixing the first mixture with silicon molecular sieves to obtain a second mixture;

(3) Under hydrothermal crystallization conditions, the second mixture is crystallized.

According to the first embodiment, the temperature of the contact can be selected in a wide range. For the preferred step (1) of the present invention, the conditions of the contact include: the temperature of the contact is 20-80°C, more preferably 25-60°C °C, more preferably 25-40 °C. In this way, the activity of the tin-titanium-silicon molecular sieve can be improved. The contact time can be determined according to specific needs. Preferably, in step (1), the contact conditions further include: the contact time is 1-240 min, more preferably 5-120 min, further preferably 20-60 min.

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 0.05-10:100, preferably 0.1-5:100, more preferably Preferably 0.5-2:100; the amount of the silicon molecular sieve and the titanium source makes the molar ratio of the titanium element to the silicon element in the prepared tin-titanium-silicon molecular sieve be 0.05-10:100, preferably 0.1-5:100, more preferably Preferably 0.5-4:100.

According to the first embodiment, in order to achieve the aforementioned purpose, preferably the molar ratio of the silicon molecular sieve, template agent, titanium source, tin source and water is 100:0.005-20:0.05-20:0.0005-15:200-10000 , more preferably 100:0.005-20:0.1-10:0.001-15:200-5000, particularly preferably 100:1-19:0.1-5:0.1-8:200-2000, most preferably 100:1- 18:0.2-1.5:0.5-2:150-200, wherein the silicon molecular sieve is counted as SiO ₂ , the tin source is counted as tin element, and the titanium source is counted as TiO ₂ .

According to the first embodiment, the mixing conditions in step (2) preferably include: the mixing temperature is 25-60° C., and the mixing time is 20-60 minutes. Preferably, the hydrothermal crystallization conditions include: the crystallization temperature under airtight conditions is 80-200°C, more preferably 100-180°C, further preferably 110-175°C, most preferably 160-170°C. The preferred crystallization time is 6-150 hours, more preferably 24-96 hours.

According to the first embodiment, the type of the tin source can be selected in a wide range, and any substance containing tin (such as a compound containing tin element and/or tin element) can achieve the purpose of the present invention. Among them, it is preferred that the tin source is a compound containing tin element, which may be one or more of inorganic tin compounds and organic tin compounds. The inorganic tin compound is, for example, a water-soluble inorganic tin salt, and the water-soluble inorganic tin salt can be, for example, tin chloride, tin chloride pentahydrate, stannous chloride, tin nitrate, tin sulfate, tin phosphate, chlorinated hydrate One or more of stannous, metastannic acid, calcium stannate, potassium stannate, sodium stannate, lithium stannate, magnesium stannate, stannous sulfate, stannous pyrophosphate and tin pyrophosphate; The organic acid salts are preferably C2-C10 organic acid salts, 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 stannate. Among them, the most preferred organotin compound is tin acetate.

According to the first embodiment, the titanium source can be a conventional choice in the art, and can be an inorganic titanium compound and/or an organic titanium compound. For the present invention, it is preferred that the titanium source is selected from inorganic titanium salts and/or organic titanium acid ester, preferably organic titanate.

According to the first embodiment, the inorganic titanium salt is selected from various hydrolyzable titanium salts, such as titanium-containing salts in various forms such as TiX ₄ , TiOX ₂ or Ti(SO ₄ ) ₂ , where X is halogen, preferably chlorine, wherein, preferably, the inorganic titanium salt is selected from one or more of titanium trichloride, TiCl ₄ , Ti(SO ₄ ) ₂ and TiOCl ₂ .

According to the first embodiment, the organic titanate is preferably an organic titanate with the structural formula M ₄ TiO ₄ , wherein M is preferably an alkyl group with 1-4 carbon atoms, and the 4 Ms can be the same Or different, preferably the organic titanate is selected from one or more of isopropyl titanate, n-propyl titanate, tetrabutyl titanate and tetraethyl titanate, in the specific implementation of the present invention In the examples, tetrabutyl titanate and tetraethyl titanate are used as examples, but the scope of the present invention is not limited thereby.

According to the 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 type of template agent can be selected in a wide range, specifically, it can be selected according to the type of tin-titanium-silicate molecular sieve to be prepared, which is known to those skilled in the art. For the present invention, preferably, the template agent is one or more of aliphatic amine compounds, aliphatic alcohol amine compounds and quaternary ammonium base compounds.

上式中，R₅、R₆、R₇和R₈各自为C1-C4的烷基，包括C1-C4的直链烷基和C3-C4的支链烷基，例如：R₅、R₆、R₇和R₈各自可以为甲基、乙基、正丙基、异丙基、正丁基、仲丁基、异丁基或叔丁基。更优选所述季铵碱为四丙基氢氧化铵、四乙基氢氧化铵和四丁基氢氧化铵中的一种或多种。According to the first embodiment, the quaternary ammonium base can be various organic quaternary ammonium bases, specifically, the quaternary ammonium base can be a quaternary ammonium base as shown in the following formula:

In the above formula, each of R ₅ , R ₆ , R ₇ and R ₈ is a C1-C4 alkyl group, including a C1-C4 straight-chain alkyl group and a C3-C4 branched-chain alkyl group, for example: R ₅ , R ₆ , R ₇ and R ₈ can each 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 the first embodiment, the aliphatic amine may be a compound formed after at least one hydrogen in various _NH3 is replaced by an aliphatic hydrocarbon group (preferably an alkyl group), specifically, the aliphatic amine may be the following Aliphatic amine represented by the formula: R ₉ (NH ₂ ) _n ; in the above formula, n is an integer of 1 or 2. When n is 1, R _is C1-C6 alkyl, including C1-C6 straight chain alkyl and C3-C6 branched chain alkyl, such as methyl, ethyl, n-propyl, isopropyl, n- Butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, isopentyl, tert-pentyl and n-hexyl. When n is 2, R _is C1-C6 alkylene, including C1-C6 straight-chain alkylene and C3-C6 branched-chain 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, butylenediamine and hexamethylenediamine.

According to the first embodiment, the aliphatic alcohol amine may be a compound formed after at least one hydrogen in various _NH3 is replaced by a hydroxyl-containing aliphatic hydrocarbon group (preferably an alkyl group), specifically, the aliphatic Alcohol amine can be the aliphatic alcohol amine represented by the following formula: (HOR ₁₀ ) _m NH _(3-m) ; In the above formula, m R ₁₀ are the same or different, and each is a C1-C4 alkylene group, including C1- C4 straight-chain alkylene and C3-C4 branched-chain alkylene, 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 the first embodiment, preferably, the templating agent is tetrapropylammonium hydroxide and/or tetraethylammonium hydroxide.

According to the first embodiment, the silicon molecular sieve can be of MFI structure (such as S-1), MEL structure (such as S-2), BEA structure (such as Beta), MWW structure (such as MCM-22), two-dimensional hexagonal Structure (such as MCM-41, SBA-15), MOR structure (such as MOR), TUN structure (such as TUN) and silicon molecular sieves with other structures (such as 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 a 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 S One or more of -1, S-2 and Beta, preferably S-1.

According to the first embodiment, the silicon molecular sieve is commercially available or can be prepared, and the method for preparing the silicon molecular sieve is well known to those skilled in the art, and will not be repeated here.

According to the first embodiment, preferably, the method further includes: filtering and washing the crystallized product to obtain a solid, drying or not drying the obtained solid, and then roasting. The methods of filtering the crystallized product, drying and roasting the filtered solid are well known to those skilled in the art. In the present invention, the optional range of the drying conditions is relatively wide, which can be carried out with reference to the prior art . For the present invention, preferably, the drying conditions include: the temperature is from room temperature to 200°C, more preferably 80-120°C; the time is 1-24h, preferably 2-10h.

According to the first embodiment, the optional range of the roasting conditions is relatively wide. For the present invention, the preferred roasting conditions include: the roasting temperature is 300-800°C, preferably 450-550°C; the roasting time It is 2-12h, preferably 2-4h; more preferably, the calcination conditions include: first calcination at 350-600°C in nitrogen atmosphere for 0.5-6h, and then sintering at 350-600°C in air atmosphere for 0.5-12h. The methods of filtering and washing are also well known to those skilled in the art, and will not be repeated here.

The implementation of the second tin-titanium-silicon molecular sieve comes from patent CN102452918A.

According to the second embodiment, the tin-titanium-silicon molecular sieve is synthesized on the basis of a titanium-silicon molecular sieve through secondary hydrothermal synthesis with a tin-containing source compound, a templating agent, an alkali and water at 100-160°C, and then filtered It is obtained by separation, drying and roasting operations. The tin content in the molecular sieve is 1-5% by weight based on the oxide, and a strong Lewis acid center is formed at the skeleton position, so as to enhance its activation of the substrate in the organic reaction.

According to the second embodiment, the tin-titanium-silicon molecular sieves are Sn-TS-1, Sn-TS-2, Sn-Ti-BETA, Sn-Ti-MCM-22, Sn-Ti-MCM-41 and Sn- One or more mixtures of Ti-MCM-48. Among them, TS-1 is preferred. In US Patent No. 4,410,501, the synthesis method of titanium-silicon molecular sieve TS-1 is disclosed for the first time. As a more preferred embodiment, the present invention adopts a TS-1 titanium-silicon molecular sieve with a hollow structure, the molecular sieve has a titanium-silicon molecular sieve with an MFI crystal structure, and the crystal grain is a hollow structure, and the radial direction of the cavity part of the hollow grain The length is 5-300 nanometers; the molecular sieve sample has a benzene adsorption capacity of at least 70 mg/g measured under the conditions of 25 ° C, P/P0 = 0.10, and an adsorption time of 1 hour, and the adsorption isotherm of the low-temperature nitrogen adsorption of the molecular sieve There is a hysteresis loop between the desorption isotherm. The so-called TS-1 titanium-silicon molecular sieve with a hollow structure has a large mesoporous volume, usually above 0.16mL/g, while the conventional TS-1 titanium-silicon molecular sieve generally has a mesoporous volume of about 0.084mL/g . The TS-1 titanium-silicon molecular sieve with a hollow structure can be bought commercially, or can be prepared by referring to the method disclosed in the Chinese patent ZL99126289.1.

According to the present invention, preferably, on a molar basis, dihydroxyacetone and/or glyceraldehyde: water=1: (60-200), the weight of dihydroxyacetone and/or glyceraldehyde is the same as that of tin titanium silicon by weight on a dry basis The weight ratio of molecular sieves is preferably 1:(1.2-3), the reaction temperature is preferably 40-120°C, the reaction time is preferably 2-8h, and the reaction pressure is preferably 0.1-2MPa.

According to the present invention, the reaction described in the present invention can be carried out in conventional catalytic reactor, and the present invention does not do special limitation, for example, the reaction of the present invention can be carried out in batch tank reactor or three-necked flask, or in suitable In other reactors such as fixed bed, moving bed, suspended bed etc., preferably carry out in tank reactor, fixed bed reactor, moving bed, suspended bed or slurry bed reactor, the specific mode of operation of above-mentioned reactor is this Those skilled in the art are well-known, and the present invention will not repeat them here.

According to the present invention, those skilled in the art can understand that, depending on the reactor used, the tin-titanium-silicon molecular sieve described in the present invention can be the original molecular sieve powder, or a molded catalyst formed by mixing molecular sieve and carrier. The separation of the product containing lactic acid and the catalyst can be achieved in many ways. For example, when the original powdery molecular sieve is used as the catalyst, the separation of the product and the recovery of the catalyst can be realized by means of sedimentation, filtration, centrifugation, evaporation, membrane separation, etc. Alternatively, the catalyst can also be molded and loaded into a fixed-bed reactor, and the catalyst can be recovered after the reaction is completed. The separation and recovery methods of various catalysts are mostly involved in the existing literature, and will not be repeated here.

The present invention will be further described below by way of examples, but content of the present invention is not limited thereto.

Unless otherwise specified, the raw materials used in the preparation examples, preparation comparative examples, examples and comparative examples are all chemically pure reagents.

In the present invention, the X-ray diffraction (XRD) crystal phase diagram of the sample is measured on a Siemens D5005 X-ray diffractometer, the ray source is Kα (Cu), and the test range 2θ is 0.5°-30°. The Fourier transform infrared (FT-IR) spectrum of the sample was measured on a Nicolet 8210 Fourier transform infrared spectrometer, and the test range was 400-4000cm ⁻¹ . The sample solid ultraviolet-visible diffuse reflectance spectrum (UV-vis) is measured on a SHIMADZU UV-3100 ultraviolet-visible spectrometer, and the test range is 200-1000nm. The total specific surface area and external specific surface area of the samples were measured on ASAP2405 static nitrogen adsorption instrument of Micromeritics Company according to ASTM D4222-98 standard method. The transmission electron micrograph TEM of the sample was obtained on a Tecnai G2F20S-TWIN transmission electron microscope of FEI Company.

In the present invention, the determination of the benzene adsorption amount adopts the conventional static adsorption method, and the determination of the adsorption isotherm and desorption isotherm of low-temperature nitrogen adsorption is carried out according to the ASTM D4222-98 standard method.

In the present invention, the molecular sieve yield refers to the percentage of the actually obtained product quality and the theoretically calculated quality (based on the total amount of input silicon dioxide, titanium dioxide and tin dioxide).

In the present invention, in the transmission electron microscope test, a certain number of crystal grains within a certain field of view is used as a representative such as 100 crystal grains, and the ratio of the number of holes in the crystal grains to the total number of crystal grains is observed. Calculate the ratio of tin-titanium-silicon molecular sieves with hole structure inside the grains to the total amount of tin-titanium-silicon molecular sieves.

In the present invention, the analysis of each component in the activity evaluation system is carried out by gas chromatography, and the analysis results are quantified by the internal standard method, and the internal standard is naphthalene. Among them, the chromatographic analysis conditions are: Agilent-6890 chromatograph, HP-5 capillary chromatographic column, injection volume 0.5 μL, inlet temperature 280°C. The column temperature was kept at 100°C for 2min, then increased to 200°C at a rate of 15°C/min, and kept for 3min. FID detector, detector temperature 300°C.

In the present invention:

Dihydroxyacetone/glyceraldehyde conversion %=(the molar number of dihydroxyacetone/glyceraldehyde in the raw material-the molar number of dihydroxyacetone/glyceraldehyde in the product) ÷ the molar number of dihydroxyacetone/glyceraldehyde in the raw material×100% ;

Lactic acid selectivity %=the molar number of lactic acid in the product ÷ (the molar number of dihydroxyacetone/glyceraldehyde in the raw material-the molar number of dihydroxyacetone/glyceraldehyde in the product) × 100%;

Lactic acid yield%=the molar number of lactic acid in the product÷the molar number of dihydroxyacetone/glyceraldehyde in the raw material×100%, that is, the lactic acid yield%=lactic acid selectivity%×dihydroxyacetone/glyceraldehyde conversion rate%.

Preparation Examples and Preparation Comparative Examples are used to provide catalysts used in Examples and Comparative Examples.

Preparation Example 1

In this preparation example, a Sn-Ti-MFI-1 molecular sieve is prepared according to the method of Example 1 of the Chinese patent CN 105217645A specification, and the specific preparation method is as follows:

(1) At 25°C, stirring and contacting tetrapropylammonium hydroxide aqueous solution (concentration: 15% by weight) with tetrabutyl titanate and tin tetrachloride pentahydrate for 30 minutes to obtain a mixture;

(2) At 60°C, add silicon molecular sieve S-1 to the above mixture and stir for 0.5h to obtain the mixture (during this contact process, add water or not add water as required, if the feeding in step (1) can meet the requirement of water Feeding requirements, there is no need to add water, if it is not met, you can add water when the mixture containing tetrapropylammonium hydroxide, tetrabutyl titanate and tin chloride is stirred and contacted with silicon molecular sieve, or distill off water, and the rest The preparation examples are similar, and will not be repeated); wherein, the molar ratio of each material is guaranteed to be: silicon source (silicon molecular sieve): alkali source template (tetrapropylammonium hydroxide): titanium source (tetrabutyl titanate ): tin source (crystalline tin tetrachloride): water=100:10:1.0:0.5:200, wherein, the silicon source is in SiO ₂ , the titanium source is in TiO ₂ , and the tin source is in tin element;

(3) Transfer the above mixture into a sealed stainless steel reaction kettle, crystallize at a temperature of 170°C and autogenous pressure for 144 hours, filter the resulting crystallized product, wash with water, and dry at 110°C for 120 minutes, and then dry it at 550°C Roasting at high temperature for 3 hours to obtain tin-titanium-silicon molecular sieve.

According to XRF composition analysis, the mass percentage of tin in the tin-titanium-silicon molecular sieve is 1.8, and the mass percentage of titanium is 0.9; 100% of the tin-titanium-silicon molecular sieve grains have a cavity structure through TEM; in the XRD crystal phase diagram , there are diffraction peaks at 2θ of 5°-9°; in FT-IR, there are absorptions near 460cm ^-1 , 800cm ^-1 , 975cm ^-1 , and 1080cm ^-1 ; in UV-Vis, there are absorptions at 220nm There is a hysteresis loop between the adsorption isotherm and the desorption isotherm of low-temperature nitrogen adsorption, the molecular sieve yield is 94%, the benzene adsorption capacity is 62mg/g, the ratio of the adsorption-desorption difference and the adsorption capacity (the ratio of the tin-titanium-silicon molecular sieve The difference between the nitrogen adsorption amount during desorption and the nitrogen adsorption amount during adsorption is greater than the nitrogen adsorption amount during adsorption of the tin-titanium-silicon molecular sieve) is 6%, the total specific surface area is ^440m2 /g, and the external specific surface area is ^46m2 /g, the ratio of the external specific surface area to the total specific surface area is 10.5%.

Preparation Example 2

This preparation example prepares the Sn-Ti-MFI-2 molecular sieve according to the method of the Chinese patent CN105217645A specification example 2, and the specific preparation method is as follows:

(1) At 25°C, stirring and contacting tetrapropylammonium hydroxide aqueous solution (concentration: 20% by weight) with tetrabutyl titanate and tin tetrachloride pentahydrate for 30 minutes to obtain a mixture;

(2) At 25°C, add silicon molecular sieve S-1 to the above mixture and stir for 0.5h to obtain the mixture; wherein, ensure that the molar ratio of each substance is: silicon source (silicon molecular sieve): alkali source template (four Propyl ammonium hydroxide): titanium source (tetrabutyl titanate): tin source (tin tetrachloride): water=100:15:2:0.1:200, wherein, silicon source is in SiO ₂ meter, titanium source is in Calculated as _TiO2 , tin source as tin element;

(3) Transfer the above mixture into a sealed stainless steel reaction kettle, crystallize at 160°C for 120 hours under autogenous pressure, filter the resulting crystallized product, wash with water, and dry at 110°C for 120 minutes, then heat at 550°C Roasting at high temperature for 3 hours to obtain tin-titanium-silicon molecular sieve.

According to the XRF composition analysis, the Sn mass percentage of the tin-titanium-silicon molecular sieve is 1.0, and the titanium mass percentage is 2.6; in the XRD crystal phase diagram, there is a diffraction peak at 2θ of 5°-9°; it is characterized by TEM 100 % of the molecular sieve grains have a hole structure; in FT-IR, there is absorption near 460cm ^-1 , 800cm ^-1 , 975cm ^-1 , and 1080cm ^-1 ; in UV-Vis, there is absorption at 220nm; low temperature nitrogen There is a hysteresis loop between the adsorption isotherm and the desorption isotherm of adsorption, and its molecular sieve yield is 93%, the benzene adsorption capacity is 68mg/g, the ratio of adsorption-desorption difference and adsorption capacity (desorption of tin-titanium-silicon molecular sieve The difference between the nitrogen adsorption amount during adsorption and the nitrogen adsorption amount during adsorption is greater than the nitrogen adsorption amount during adsorption of the tin-titanium-silicon molecular sieve) is 8%, the total specific surface area is 424m ² /g, and the external specific surface area is 45m ² /g , the ratio of the external specific surface area to the total specific surface area is 10.6%.

Preparation Example 3

This preparation example prepares the Sn-Ti-MFI-3 molecular sieve according to the method of the Chinese patent CN105217645A specification example 3, and the specific preparation method is as follows:

(1) At 35° C., an aqueous solution of tetraethylammonium hydroxide (concentration: 28% by weight) was stirred and contacted with titanium tetrachloride and tin nitrate for 30 minutes to obtain a mixture;

(2) At 50°C, add silicon molecular sieve S-1 into the above mixture and stir for 0.5h to obtain the mixture; wherein, ensure that the molar ratio of each substance is: silicon source (silicon molecular sieve): alkali source template (four Ethyl ammonium hydroxide): titanium source (titanium tetrachloride): tin source (tin nitrate): water=100:10:0.2:1:200, wherein, the silicon source is in _SiO2 , and the titanium source is in _TiO2 , tin source is calculated as tin element;

(3) Transfer the above mixture into a stainless steel sealed reaction kettle, crystallize at a temperature of 170°C and autogenous pressure for 96 hours, filter the resulting crystallized product, wash with water, and dry at 110°C for 120 minutes, then heat at 550°C Roasting at high temperature for 3 hours to obtain tin-titanium-silicon molecular sieve.

According to the XRF composition analysis, the Sn mass percentage of the tin-titanium-silicon molecular sieve is 0.8, and the titanium mass percentage is 0.3; in the XRD crystal phase diagram, there is a diffraction peak at 2θ of 5°-9°; it is characterized by TEM 100 % of the molecular sieve grains have a hole structure; in FT-IR, there is absorption near 460cm ^-1 , 800cm ^-1 , 975cm ^-1 , and 1080cm ^-1 ; in UV-Vis, there is absorption at 230nm; low temperature nitrogen There is a hysteresis loop between the adsorption isotherm and the desorption isotherm of adsorption, the molecular sieve yield is 94%, the benzene adsorption capacity is 54mg/g, the ratio of the adsorption-desorption difference and the adsorption capacity (the desorption time of the tin-titanium-silicon molecular sieve The difference between the nitrogen adsorption amount and the nitrogen adsorption amount during adsorption is greater than the nitrogen adsorption amount during the adsorption of the tin-titanium-silicon molecular sieve) is 5%, the total specific surface area is 431m ² /g, and the external specific surface area is 43m ² /g, The ratio of the external specific surface area to the total specific surface area is 10%.

Preparation Example 4

This preparation example prepares the Sn-Ti-MFI-4 molecular sieve according to the method in Example 4 of the Chinese patent CN105217645A specification, and the specific preparation method is as follows:

(1) At 30°C, stirring and contacting tetrapropylammonium hydroxide aqueous solution (concentration: 15% by weight) with tetraisopropyl titanate and tin tetrachloride for 30 minutes to obtain a mixture;

(2) At 60°C, add silicon molecular sieve S-1 into the above mixture and stir and contact for 0.5h to obtain the mixture; wherein, ensure that the molar ratio of each substance is: silicon source (silicon molecular sieve): alkali source template (four Propyl ammonium hydroxide): titanium source (tetraisopropyl titanate): tin source (tin tetrachloride): water=100:5:3:1:200, wherein, silicon source is in SiO ₂ meter, titanium source Calculated as _TiO2 , tin source as tin element;

(3) Transfer the above mixture into a stainless steel sealed reaction kettle, crystallize at a temperature of 120°C and an autogenous pressure for 72 hours, filter the obtained crystallized product, wash with water, and dry at 110°C for 120 minutes, and then at 550°C Roasting at high temperature for 3 hours to obtain tin-titanium-silicon molecular sieve.

According to the XRF composition analysis, the Sn mass percentage of the tin-titanium-silicon molecular sieve is 6.6, and the titanium mass percentage is 2.1; in the XRD crystal phase diagram, there is a diffraction peak at 2θ of 5°-9°; it is characterized by TEM 96 % of the molecular sieve grains have a hole structure; in FT-IR, there is absorption near 460cm ^-1 , 800cm ^-1 , 975cm ^-1 , and 1080cm ^-1 ; in UV-Vis, there is absorption near 240nm; low temperature nitrogen There is a hysteresis loop between the adsorption isotherm and the desorption isotherm of adsorption, and its molecular sieve yield is 94%, and the benzene adsorption capacity is 83mg/g, and the ratio of adsorption-desorption difference and adsorption capacity (the desorption of tin-titanium-silicon molecular sieve The difference between the nitrogen adsorption amount during adsorption and the nitrogen adsorption amount during adsorption is greater than the nitrogen adsorption amount during the adsorption of the tin-titanium-silicon molecular sieve) is 9%, the total specific surface area is 416m ² /g, and the external specific surface area is 50m ² /g , the ratio of the external specific surface area to the total specific surface area is 12.1%.

Preparation Example 5

In this preparation example, a Sn-Ti-MFI-5 molecular sieve was prepared according to the method in Example 7 of the specification of Chinese patent CN105217645A. The specific preparation method is as follows:

(1) At 25° C., an aqueous solution of tetrapropylammonium hydroxide (concentration of 15% by weight) was stirred and contacted with titanium trichloride and tin tetrachloride pentahydrate for 30 minutes to obtain a mixture;

(2) At 40°C, add silicon molecular sieve S-1 into the above mixture and stir for 0.5h to obtain the mixture; wherein, ensure that the molar ratio of each substance is: silicon source (silicon molecular sieve): alkali source template (four Propyl ammonium hydroxide): titanium source (titanium trichloride): tin source ₍ crystalline tin tetrachloride): water=100:1:2:12:150, wherein, the silicon source is in SiO , and the titanium source is in Calculated as _TiO2 , tin source as tin element;

(3) Transfer the above mixture into a stainless steel sealed reaction kettle, crystallize for 36 hours at a temperature of 170°C and autogenous pressure, filter the resulting crystallized product, wash with water, and dry at 110°C for 120 minutes, then dry it at 550°C ℃ for 3 hours to obtain tin-titanium-silicon molecular sieves.

According to the XRF composition analysis, the Sn mass percentage of the tin-titanium-silicon molecular sieve is 9.6, and the titanium mass percentage is 2.5; in the XRD crystal phase diagram, there is a diffraction peak at 2θ of 5°-9°; it is characterized by TEM61 % of the molecular sieve grains have a hole structure; in FT-IR, there is absorption near 460cm ^-1 , 800cm ^-1 , 975cm ^-1 , and 1080cm ^-1 ; in UV-Vis, there is absorption at 230-260nm; There is a hysteresis loop between the adsorption isotherm and the desorption isotherm of low-temperature nitrogen adsorption, the molecular sieve yield is 93%, the benzene adsorption capacity is 41mg/g, the ratio of the adsorption-desorption difference and the adsorption capacity (desorption of tin-titanium-silicon molecular sieve The difference between the nitrogen adsorption amount during adsorption and the nitrogen adsorption amount during adsorption) is 5%, the total specific surface area is 356m ² /g, and the external specific surface area is 51m ² / g, the ratio of the external specific surface area to the total specific surface area is 14.3%.

Preparation Example 6

This preparation example prepares the tin-titanium-silicon molecular sieve according to the method of CN102452918A catalyst preparation example 1, and the specific preparation method is as follows:

Mix 22.5 grams of tetraethyl orthosilicate with 7.0 grams of tetrapropylammonium hydroxide, add 59.8 grams of distilled water, mix well, and then hydrolyze at normal pressure and 60°C for 1.0 hour to obtain a hydrolysis solution of tetraethyl orthosilicate A solution consisting of 1.1 g of tetrabutyl titanate and 5.0 g of anhydrous isopropanol was slowly added under vigorous stirring, and the resulting mixture was stirred at 75° C. for 3 hours until it became a clear and transparent colloid. Put this colloid into a stainless steel sealed reaction kettle, and place it at a constant temperature of 170°C and autogenous pressure for 6 days to obtain a mixture of crystallized products; filter the mixture, wash it with water until the pH is 6-8, and dry it at 110°C After 60 minutes, unroasted TS-1 powder was obtained. The TS-1 raw powder was calcined in an air atmosphere at 550°C for 4 hours to obtain TS-1 molecular sieve.

Then TS-1 is in the system that tetrapropyl ammonium hydroxide is template agent, and anhydrous tin tetrachloride is tin source, according to molecular sieve (gram): anhydrous tin tetrachloride (mol): tetrapropyl hydroxide The ratio of ammonium (mol): water (mol)=100:0.06x:0.15:180 is mixed evenly, wherein the value of x is the mass percentage of tin oxide in molecular sieves, the mixture is passed through a closed autoclave, and 140°C passes through secondary water The thermal synthesis method introduces 2.2wt% tin element in terms of oxides into its MFI framework, and the obtained catalyst is denoted as Sn-TS-1, wherein the mass percent of _SnO2 is 2.2wt%, and the mass percent of _TiO2 is 3.9wt %.

Preparation Example 7

Take the TS-1 molecular sieve obtained in Preparation Example 6 and mix evenly according to the ratio of molecular sieve (g): sulfuric acid (mol): water (mol) = 100: 0.15: 15, react at 90 ° C for 5.0 hours, and then filter according to conventional methods , washing and drying to obtain acid-treated TS-1 molecular sieves.

The above-mentioned acid-treated TS-1 molecular sieves were mixed uniformly according to the ratio of molecular sieve (gram): triethanolamine (mol): tetrapropylammonium hydroxide (mol): water (mol) = 100: 0.20: 0.15: 180, and put into A stainless steel sealed reaction kettle was placed at a constant temperature of 190°C and autogenous pressure for 0.5 days. After cooling and pressure relief, it was filtered, washed, dried according to conventional methods, and roasted in an air atmosphere at 550°C for 3 hours to obtain a hollow structure molecular sieve.

According to X-ray diffraction analysis, it is a titanium-silicon molecular sieve with an MFI structure. There is a hysteresis loop between the adsorption isotherm and desorption isotherm of the low-temperature nitrogen adsorption of the molecular sieve. The crystal grains are hollow grains and the radial length of the cavity part is 15-180 nanometers; the molecular sieve sample has a benzene adsorption capacity of 78 mg/g measured under the conditions of 25°C, P/P0=0.10, and adsorption time of 1 hour.

Then the hollow structure molecular sieve is in the system of 140 ℃, tetrapropyl ammonium hydroxide as template, and anhydrous tin tetrachloride as tin source, according to molecular sieve (gram): anhydrous tin tetrachloride (mol): tetrapropyl ammonium hydroxide (mol): water (mol) = 100: 0.06x: 0.15: 180 ratio mixed evenly, the value of x is the mass percent of tin oxide in molecular sieve, the mixture is passed through a closed autoclave, hydrothermal at 140 ℃ Synthesized for 72 hours, introduced in its MFI skeleton in terms of oxides, 2.1wt% tin element, the catalyst was denoted as Sn-HTS, wherein, in terms of oxides, the mass percent of _SnO2 was 2.1wt%, and the mass percent of _TiO2 The percentage is 4.3 wt%.

Prepare comparative example 1

This preparation comparative example prepares Sn-MFI molecular sieve, and specific preparation method is:

Dissolve tin tetrachloride pentahydrate (SnCl ₄ .5H ₂ O) in water, add tetrapropylammonium hydroxide (TPAOH, 20% aqueous solution) to this aqueous solution and stir with tetraethyl orthosilicate (TEOS) and water, continuously stirred for 30 minutes to obtain a clear liquid with a chemical composition of 0.03SnO ₂ : SiO ₂ :0.45TPA: 35H ₂ O, and then crystallized at a temperature of 433K for 2 days, after which the obtained solid was filtered and washed with distilled water , dried at 393K for 5 hours, and then calcined at 823K for 10 hours to obtain a molecular sieve sample. Among them, 15.31 g of TEOS, 33.67 g of TPAOH, 0.38 g of SnCl ₄ .5H ₂ O, and 39.64 g of water are used.

Prepare comparative example 2

This preparation comparative example reference "Nemeth L, Moscoso J, Erdman N, et al.Synthesis and characterization of Sn-Beta as a selective oxidation catalyst [J]. Studies in Surface Science & Catalysis, 2004, 154 (04): 2626-2631" Method prepares Sn-Beta molecular sieve, the preparation method of the adopted Sn-Beta molecular sieve is:

Dissolve tin tetrachloride pentahydrate (SnCl ₄ .5H ₂ O) in water, add this aqueous solution to ethyl orthosilicate (TEOS) and stir, add tetraethylammonium hydroxide (TEAOH) under stirring, stir until TEOS Evaporation gave the alcohol, and hydrogen fluoride (HF) was added to the clear liquid to form a creamy thin layer. Finally, a suspension of dealuminated nano Beta seeds (20nm) and water was added to obtain a clear liquid with a chemical composition of 0.03SnO ₂ : SiO ₂ : 6TEA: 15H ₂ O: 10HF, and then crystallized at 413K for 10 days. Afterwards, the obtained solid was filtered, washed with distilled water, dried at 393K for 5 hours, and then calcined at 823K for 10 hours to obtain a molecular sieve sample. Among them, the amount of TEOS is 20.81g, the amount of TEAOH is 88.42g, the amount of SnCl ₄ .5H ₂ O is 1.05g, the amount of water is 27.01g, and the amount of HF is 20g.

Prepare comparative example 3

The reference of this preparation comparison example "Yang X, Wu L, Wang Z, et al. Conversion of dihydroxyacetone to methyl lactate catalyzed by highly active hierarchical Sn-USY at room temperature [J]. Catalysis Science & Technology, 2016, 6 (6): 1757- 1763" method to prepare Sn-USY molecular sieve, the preparation method of the adopted Sn-USY molecular sieve is:

H-USY molecular sieve was mixed with nitric acid, treated at 85°C for 8h, the sample was filtered and washed with deionized water, and dried at 120°C for 12h to obtain a solid sample. The solid sample was mixed with tin tetrachloride pentahydrate (SnCl ₄ .5H ₂ O) for 1 hour to obtain a mixed liquid with a chemical composition of 0.03SnO ₂ : 100SiO ₂ , dried at 100°C for 12 hours, and finally calcined at 550°C for 3 hours to obtain Molecular sieve samples. Among them, the amount of H-USY is 2.0 g, the amount of nitric acid is 50 mL, and the amount of SnCl ₄ .5H ₂ O is 0.6 g.

Prepare comparative example 4

This preparation comparative example prepares TS-1 molecular sieve, and specific preparation method is:

Add about 3/4 of the tetrapropylammonium hydroxide (TPAOH, 20%) solution to the tetraethyl orthosilicate (TEOS) solution to obtain a liquid mixture with a pH of about 13, and then to the The required amount of n-butyl titanate [Ti(OBu) ₄ ] in anhydrous isopropanol was added dropwise to the obtained liquid mixture, and a clear liquid was obtained after stirring for 15 minutes. Finally, the remaining TPAOH was slowly added to the In the clarified liquid, stir at 348-353K for about 3 hours to obtain a sol with a chemical composition of 0.03TiO ₂ : SiO ₂ : 0.36TPA: 35H ₂ O, and then carry out crystallization at 443K for 3 days, and then the obtained solid Filter, wash with distilled water, dry at 373K for 5 hours, and then roast at 823K for 10 hours to obtain a molecular sieve sample. Wherein, the consumption of TEOS is 42g, the consumption of TPAOH is 73g, the consumption of Ti(OBu) ₄ is 2g, the consumption of anhydrous isopropanol is 10g, and the consumption of water is 68g.

Prepare comparative example 5

This preparation comparative example prepares TS-2 molecular sieve, and specific preparation method is:

A certain amount of tetrabutylammonium hydroxide solution (TBAOH, 20%) is mixed with tetraethyl orthosilicate (TEOS), and then the required amount of n-butyl titanate is added dropwise to the obtained transparent liquid mixture under vigorous stirring Anhydrous isopropanol solution of [Ti(OBu) ₄ ] was stirred for 30 minutes to obtain a clear liquid after hydrolysis was completed. Finally, 2 times the required amount of distilled water was added, and the resulting sol was stirred at 348-353K for 2 hours to remove alcohol. The chemical composition of the obtained sol is 0.03TiO ₂ : SiO ₂ :0.2TBA:20H ₂ O. The sol was crystallized at 443K for 3 days, and the obtained crystallized product was filtered, washed with water, dried at 373K for 6 hours, and then calcined at 823K for 16 hours to obtain a molecular sieve sample. Wherein, the consumption of TEOS is 42g, the consumption of TBAOH is 52g, the consumption of Ti(OBu) ₄ is 2g, the consumption of anhydrous isopropanol is 10g, and the consumption of water is 30g.

Preparation of Comparative Example 6

This preparation comparative example prepares Ti-Beta molecular sieve, and concrete preparation method is:

A certain amount of tetraethylammonium hydroxide solution (TEAOH, 20%) and hydrogen peroxide was added into a solution of measured tetraethylammonium hydroxide solution (TEAOH, 20%), and hydrolyzed for 2 hours under stirring. Then add the weighed anhydrous isopropanol solution of tetrabutyl titanate [Ti(OBu) ₄ ] into the hydrolyzed solution of ethyl orthosilicate, and continue to stir for 3 hours to remove alcohol, and finally the chemical composition can be obtained as TiO ₂ : Sol of 60SiO ₂ :33TEA:400H ₂ O:20H ₂ O ₂ . Finally, dealuminated P-type molecular sieve seed crystals were added and vigorously stirred (the amount of seed crystals added was calculated as sol by silica, and 100 g of silica was added with 4 g of seed crystals). After the obtained mixture was crystallized at 413K for 14 days, the resulting slurry was filtered, washed with water, dried at 373K for 6 hours, and then calcined at 823K for 12 hours to obtain a molecular sieve sample. Wherein, the consumption of TEOS is 42g, the consumption of TEAOH is 81g, the consumption of Ti(OBu) ₄ is 1.16g, the consumption of anhydrous isopropanol is 10g, and the consumption of hydrogen peroxide is 7.5g.

Preparation of Comparative Example 7

The hollow titanium-silicon molecular sieve HTS prepared in this preparation comparison example is prepared according to the method described in Example 1 of the Chinese patent CN1301599A specification, and the specific preparation method is as follows:

Mix 22.5 grams of tetraethyl orthosilicate with 7.0 grams of tetrapropylammonium hydroxide, add 59.8 grams of distilled water, mix well, and then hydrolyze at normal pressure and 60°C for 1.0 hour to obtain a hydrolysis solution of tetraethyl orthosilicate A solution consisting of 1.1 g of tetrabutyl titanate and 5.0 g of anhydrous isopropanol was slowly added under vigorous stirring, and the resulting mixture was stirred at 75° C. for 3 hours to obtain a clear transparent colloid. Put this colloid into a stainless steel sealed reaction kettle, and place it at a constant temperature of 170°C and autogenous pressure for 6 days to obtain a mixture of crystallized products; filter the mixture, wash with water until the pH is 6-8, and dry at 110°C After 60 minutes, unroasted TS-1 powder was obtained. The TS-1 raw powder was calcined in air atmosphere at 550°C for 4 hours to obtain TS-1 molecular sieve.

Get the obtained TS-1 molecular sieve according to the ratio of molecular sieve (gram): sulfuric acid (mol): water (mol) = 100: 0.15: 150 and mix evenly, react at 90 ℃ for 5.0 hours, then filter, wash and dry according to conventional methods , to obtain acid-treated TS-1 molecular sieves.

The above-mentioned acid-treated TS-1 molecular sieves were mixed uniformly according to the ratio of molecular sieve (gram): triethanolamine (mol): tetrapropylammonium hydroxide (mol): water (mol) = 100: 0.20: 0.15: 180, and put into A stainless steel sealed reaction kettle was placed at a constant temperature of 190°C and autogenous pressure for 0.5 days. After cooling and pressure relief, it was filtered, washed, dried according to conventional methods, and roasted in an air atmosphere at 550°C for 3 hours to obtain HTS molecular sieves.

The HTS molecular sieve has a hollow structure with a radial length of 5-100 nanometers, and the benzene adsorption measured by static adsorption method at 25°C, P/P0=0.10, and adsorption time of 1 hour is 85 mg/gram molecular sieve; The adsorption isotherm and desorption isotherm of low-temperature nitrogen adsorption determined according to the ASTM D4222-98 standard method show that there is a hysteresis loop between the adsorption isotherm and desorption isotherm of low-temperature nitrogen adsorption.

Preparation of Comparative Example 8

The preparation method of the titanium-silicon molecular sieve Sn/TS-1 loaded with tin in this preparation comparative example is as follows:

Tin tetrachloride pentahydrate (SnCl ₄ .5H ₂ O) and TS-1 molecular sieve (prepared by the method of Comparative Example 7) were mechanically mixed directly and then calcined at 550°C for 5 hours to obtain a chemical composition of 0.03TiO ₂ :SiO ₂ : 0.03SnO ₂ molecular sieve. Wherein, the amount of TS-1 is 2 g, and the amount of SnCl ₄ .5H ₂ O is 0.76 g.

The examples and comparative examples are used to illustrate the method for preparing lactic acid by using different catalysts to catalyze dihydroxyacetone and/or glyceraldehyde.

Example 1

Weigh 0.15g of the tin-titanium-silicon molecular sieve Sn-Ti-MFI-1 prepared in Preparation Example 1 as a catalyst and put it in a 15mL glass reaction tube, then add a magnetic stirrer, 8g of water, and 0.1g of dihydroxyacetone in sequence, and screw on the glass Reaction tube caps. Put the glass reaction tube in an oil bath on a temperature-controlled magnetic stirrer, start the magnetic stirrer and heating device, and start the reaction. The reaction temperature was controlled at about 60° C., and the reaction was carried out for 7 hours. The specific reaction results are shown in Table 1.

Comparative example 1

Weigh 0.15g of the tin-silica molecular sieve Sn-MFI prepared in Preparation Comparative Example 1 as a catalyst and put it in a 15mL glass reaction tube, then add a magnetic stirrer, 8g of water, and 0.1g of dihydroxyacetone in sequence, and screw on the glass reaction tube cover. Put the glass reaction tube in an oil bath on a temperature-controlled magnetic stirrer, start the magnetic stirrer and heating device, and start the reaction. The reaction temperature was controlled at about 60° C., and the reaction was carried out for 7 hours. The specific reaction results are shown in Table 1.

Comparative example 2

Weigh 0.15g of the tin-silicon molecular sieve Sn-Beta prepared in Preparation Comparative Example 2 as a catalyst and put it in a 15mL glass reaction tube, then add a magnetic stirrer, 8g of water, and 0.1g of dihydroxyacetone in sequence, and screw on the glass reaction tube cover. Put the glass reaction tube in an oil bath on a temperature-controlled magnetic stirrer, start the magnetic stirrer and heating device, and start the reaction. The reaction temperature was controlled at about 60° C., and the reaction was carried out for 7 hours. The specific reaction results are shown in Table 1.

Comparative example 3

Weigh 0.15g of the tin-silica molecular sieve Sn-USY prepared in Preparation Comparative Example 3 as a catalyst and put it in a 15mL glass reaction tube, then add a magnetic stirrer, 8g of water, and 0.1g of dihydroxyacetone in sequence, and screw on the glass reaction tube cover. Put the glass reaction tube in an oil bath on a temperature-controlled magnetic stirrer, start the magnetic stirrer and heating device, and start the reaction. The reaction temperature was controlled at about 60° C., and the reaction was carried out for 7 hours. The specific reaction results are shown in Table 1.

Comparative example 4

Weigh 0.15g of the titanium-silicon molecular sieve TS-2 prepared in Comparative Example 5 as a catalyst and put it in a 15mL glass reaction tube, then add a magnetic stirrer, 8g of water, and 0.1g of dihydroxyacetone in sequence, and screw on the cap of the glass reaction tube. Put the glass reaction tube in an oil bath on a temperature-controlled magnetic stirrer, start the magnetic stirrer and heating device, and start the reaction. The reaction temperature was controlled at about 60° C., and the reaction was carried out for 7 hours. The specific reaction results are shown in Table 1.

Comparative example 5

Weigh 0.15g of the titanium-silicon molecular sieve Ti-Beta prepared in Comparative Example 6 as a catalyst and put it in a 15mL glass reaction tube, then add a magnetic stirrer, 8g of water, and 0.1g of dihydroxyacetone in sequence, and screw on the glass reaction tube cover. Put the glass reaction tube in an oil bath on a temperature-controlled magnetic stirrer, start the magnetic stirrer and heating device, and start the reaction. The reaction temperature was controlled at about 60° C., and the reaction was carried out for 7 hours. The specific reaction results are shown in Table 1.

Comparative example 6

Weigh 0.15g of the titanium-silicon molecular sieve TS-1 prepared in Preparation Comparative Example 4 as a catalyst and put it in a 15mL glass reaction tube, then add a magnetic stirrer, 8g of water, and 0.1g of glyceraldehyde in sequence, and screw on the glass reaction tube cover. Put the glass reaction tube in an oil bath on a temperature-controlled magnetic stirrer, start the magnetic stirrer and heating device, and start the reaction. The reaction temperature was controlled at about 60° C., and the reaction was carried out for 0.5 hour. The specific reaction results are shown in Table 1.

Comparative example 7

Weigh 0.10g of the tin-silicon molecular sieve Sn-MFI prepared in Comparative Example 1 and 0.05g of the titanium-silicon molecular sieve TS-1 prepared in Comparative Example 4 as catalysts and put them in a 15mL glass reaction tube, then add a magnetic stirrer, 8g of water , 0.1g dihydroxyacetone, screw on the glass reaction tube cover. Put the glass reaction tube in an oil bath on a temperature-controlled magnetic stirrer, start the magnetic stirrer and heating device, and start the reaction. The reaction temperature was controlled at about 60° C., and the reaction was carried out for 7 hours. The specific reaction results are shown in Table 1.

Comparative example 8

Weigh 0.05g of the tin-silicon molecular sieve Sn-MFI prepared in Comparative Example 1 and 0.10g of the titanium-silicon molecular sieve TS-1 prepared in Comparative Example 4 as catalysts and put them in a 15mL glass reaction tube, then add a magnetic stirrer, 8g of water , 0.1g dihydroxyacetone, screw on the glass reaction tube cover. Put the glass reaction tube in an oil bath on a temperature-controlled magnetic stirrer, start the magnetic stirrer and heating device, and start the reaction. The reaction temperature was controlled at about 60° C., and the reaction was carried out for 7 hours. The specific reaction results are shown in Table 1.

Comparative example 9

Weigh 0.15g of the tin-titanium-silicon molecular sieve Sn-Ti-MFI-4 prepared in Preparation Example 4 as a catalyst and put it in a 15mL glass reaction tube, then add a magnetic stirrer, 8g of water, and 0.1g of dihydroxyacetone in sequence, and screw on the glass Reaction tube caps. Put the glass reaction tube in an oil bath on a temperature-controlled magnetic stirrer, start the magnetic stirrer and heating device, and start the reaction. The reaction temperature was controlled at about 10°C, and the reaction was carried out for 0.5 hours. The specific reaction results are shown in Table 1.

Comparative example 10

Weigh 0.15g of the hollow titanium-silicate molecular sieve HTS catalyst prepared in Comparative Example 7 and put it in a 15mL glass reaction tube, then add a magnetic stirrer, 8g of water, and 0.1g of dihydroxyacetone in sequence, and screw on the cap of the glass reaction tube. Put the glass reaction tube in an oil bath on a temperature-controlled magnetic stirrer, start the magnetic stirrer and heating device, and start the reaction. The reaction temperature was controlled at about 60° C., and the reaction was carried out for 7 hours. The specific reaction results are shown in Table 1.

Comparative example 11

Weigh 0.15g of the tin-loaded titanium-silicon molecular sieve Sn/TS-1 catalyst prepared in Comparative Example 8 and put it in a 15mL glass reaction tube, then add a magnetic stirrer, 8g of water, and 0.1g of dihydroxyacetone in sequence, and screw on the glass reaction tube. Tube lid. Put the glass reaction tube in an oil bath on a temperature-controlled magnetic stirrer, start the magnetic stirrer and heating device, and start the reaction. The reaction temperature was controlled at about 60° C., and the reaction was carried out for 7 hours. The specific reaction results are shown in Table 1.

Comparative example 12

It is basically the same as Example 1, except that the reaction temperature is 200° C., and the reaction time is 12 hours. The reaction raw materials and the catalyst are packed into a polytetrafluoroethylene liner, and then sealed in a stainless steel reactor. react in a phase reactor. The specific reaction results are shown in Table 1.

Example 2

Weigh 0.15g of the tin-titanium-silicon molecular sieve Sn-Ti-MFI-2 prepared in Preparation Example 2 as a catalyst and put it in a 15mL glass reaction tube, then add a magnetic stirrer, 8g of water, and 0.1g of glyceraldehyde in sequence, and screw on the glass to react Tube lid. Put the glass reaction tube in an oil bath on a temperature-controlled magnetic stirrer, start the magnetic stirrer and heating device, and start the reaction. The reaction temperature was controlled at about 60° C., and the reaction was carried out for 7 hours. The specific reaction results are shown in Table 1.

Example 3

Weigh 0.15g of the tin-titanium-silicon molecular sieve Sn-Ti-MFI-3 prepared in Preparation Example 3 as a catalyst and put it in a 15mL glass reaction tube, then add a magnetic stirrer, 8g of water, and 0.1g of dihydroxyacetone in sequence, and screw on the glass Reaction tube caps. Put the glass reaction tube in an oil bath on a temperature-controlled magnetic stirrer, start the magnetic stirrer and heating device, and start the reaction. The reaction temperature was controlled at about 60° C., and the reaction was carried out for 7 hours. The specific reaction results are shown in Table 1.

Example 4

Weigh 0.15g of the tin-titanium-silicon molecular sieve Sn-Ti-MFI-4 prepared in Preparation Example 4 as a catalyst and put it in a 15mL glass reaction tube, then add a magnetic stirrer, 8g of water, and 0.1g of glyceraldehyde in sequence, and screw on the glass to react Tube lid. Put the glass reaction tube in an oil bath on a temperature-controlled magnetic stirrer, start the magnetic stirrer and heating device, and start the reaction. The reaction temperature was controlled at about 60° C., and the reaction was carried out for 7 hours. The specific reaction results are shown in Table 1.

Example 5

Weigh 0.15g of the tin-titanium-silicon molecular sieve Sn-Ti-MFI-5 prepared in Preparation Example 5 as a catalyst and put it in a 15mL glass reaction tube, then add a magnetic stirrer, 8g of water, and 0.1g of dihydroxyacetone in sequence, and screw on the glass Reaction tube caps. Put the glass reaction tube in an oil bath on a temperature-controlled magnetic stirrer, start the magnetic stirrer and heating device, and start the reaction. The reaction temperature was controlled at about 60° C., and the reaction was carried out for 7 hours. The specific reaction results are shown in Table 1.

Example 6

It is basically the same as Example 1, except that the tin-titanium-silica molecular sieve provided in Preparation Example 6 is used as the catalyst. The specific reaction results are shown in Table 1.

Example 7

It is basically the same as Example 1, except that the tin-titanium-silica molecular sieve provided in Preparation Example 7 is used as the catalyst. The specific reaction results are shown in Table 1.

Example 8

It is basically the same as Example 1, except that the molar ratio of dihydroxyacetone to water is 1:50, the reaction temperature is 30°C, the reaction time is 1 hour, and the weight ratio of dihydroxyacetone to tin-titanium-silicon molecular sieve is 1:1. The specific reaction results are shown in Table 1.

Example 9

It is basically the same as Example 1, except that the molar ratio of dihydroxyacetone to water is 1:450, the reaction temperature is 180°C, the reaction time is 10 hours, and the weight ratio of dihydroxyacetone to tin-titanium-silicon molecular sieve is 1:6, the reaction raw materials and catalysts are loaded into a polytetrafluoroethylene liner, and then placed in a stainless steel reactor to seal and react in a homogeneous reactor. The specific reaction results are shown in Table 1.

Example 10

It is basically the same as Example 1, except that dihydroxyacetone is replaced by a mixture of equimolar dihydroxyacetone and glyceraldehyde, and the molar ratio of dihydroxyacetone to glyceraldehyde in the mixture is 1:1. The specific reaction results are shown in Table 1.

Can find out by the result of above-mentioned embodiment and comparative example, adopt the method for the present invention to prepare lactic acid, operating process is simple, and reaction condition is gentle, and raw material conversion rate and lactic acid selectivity are higher; , and the molar ratio of dihydroxyacetone and/or glyceraldehyde to water is 1:(50-450), the reaction temperature is 30-180°C, the reaction time is 1-10h, and the reaction pressure is 0.1-3.0MPa. When the ratio of the weight of hydroxyacetone and/or glyceraldehyde to the weight of the tin-titanium-silicon molecular sieve in terms of dry weight is 1: (1-6), the molar ratio of dihydroxyacetone and/or glyceraldehyde to water is further preferred At 1:(60-200), the reaction temperature is 40-120°C, the reaction time is 2-8h, the reaction pressure is 0.1-2.0MPa, the weight of dihydroxyacetone and/or glyceraldehyde is equal to the tin on a dry basis The weight ratio of the titanium-silicon molecular sieve is 1:(1.2-3), which is more conducive to improving the conversion rate of dihydroxyacetone/glyceraldehyde and the yield of lactic acid.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention. These simple modifications All belong to the protection scope of the present invention.

In addition, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way if there is no contradiction. The combination method will not be described separately.

In addition, various combinations of different embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the idea of the present invention, they should also be regarded as the content of the present invention.

Table 1

serial number Dihydroxyacetone/glyceraldehyde conversion/% Lactic acid selectivity/% Example 1 99 99 Example 2 95 99 Example 3 95 98 Example 4 96 95 Example 5 98 98 Example 6 95 96 Example 7 97 96 Example 8 95 98 Example 9 99 95 Example 10 96 97 Comparative example 1 81 75 Comparative example 2 80 74 Comparative example 3 80 71 Comparative example 4 43 60 Comparative example 5 42 61 Comparative example 6 43 60 Comparative example 7 87 91 Comparative example 8 89 90 Comparative example 9 32 31 Comparative example 10 60 65 Comparative example 11 63 54 Comparative example 12 97 64

Claims (11)

1. A method of catalyzing dihydroxyacetone and/or glyceraldehyde to produce lactic acid, the method comprising:

contacting reaction raw materials, water and a catalyst in a reactor and carrying out reaction to obtain a product containing lactic acid; wherein:

the reaction raw materials contain dihydroxyacetone and/or glyceraldehyde, and the molar ratio of dihydroxyacetone and/or glyceraldehyde: water =1: (50-450), 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 weight of dihydroxyacetone and/or glyceraldehyde to the weight of the tin-titanium-silicon molecular sieve on a dry basis is 1: (1-6); the tin-titanium-silicon molecular sieve is selected from an MFI type tin-titanium-silicon molecular sieve; the molar ratio of tin element to silicon element in the tin-titanium-silicon molecular sieve is 0.05-10.

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 the tin-titanium-silicon molecular sieve contains elemental silicon, elemental titanium, elemental tin, and elemental oxygen;

at least part of crystal grains of the tin-titanium-silicon molecular sieve have a cavity structure;

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 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;

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;

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, whichIn the method, 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 the method of preparing the 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.

6. The method of claim 5, wherein in step (1), the contacting conditions comprise: the contact temperature is 20-80 ℃, and the contact time is 1-240min;

the dosage of the silicon molecular sieve and the tin source ensures 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;

the dosage mole ratio of the silicon molecular sieve, the template agent, the titanium source, the tin source and the water is (100) ₂ The tin source is calculated by tin element, and the titanium source is calculated by TiO ₂ Counting;

the hydrothermal crystallization conditions include: 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 one or more selected from S-1, S-2, BETA, MOR, MCM-22, MCM-41, SBA-15 and MCM-48;

at least of the tin-titanium-silicon molecular sieveA cavity structure is arranged in part of the crystal grains, and a diffraction peak is arranged at the position of 0.5-9 degrees of 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.

7. The method of claim 1, wherein the tin-titanium-silicon molecular sieve is obtained by performing a second hydrothermal synthesis on a titanium-silicon molecular sieve with a compound containing a tin source, a template agent, alkali and water at 100-160 ℃, and performing filtering separation, drying and roasting, wherein the tin content of the molecular sieve is 1-5 wt% calculated by oxide;

the tin-titanium-silicon molecular sieve is 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.

8. The method of claim 7, 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.

9. The method of claim 1, wherein, on a molar basis, the molar ratio of dihydroxyacetone and/or glyceraldehyde: water =1: (60-200), the weight ratio of the dihydroxyacetone and/or glyceraldehyde to the weight of the tin-titanium-silicon molecular sieve on a dry basis 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.

10. The process according to claim 9, wherein the reaction pressure is 0.1-2MPa.

11. 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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