Modified titanium silicalite molecular sieve, and preparation method therefor and use thereof

Abstract

A modified titanium silicalite molecular sieve, which is characterized by containing titanium, silicon, oxygen and cesium, wherein the 133Cs MAS NMR spectrum thereof at least has resonance absorption peaks at -94±15 ppm, -73±15 ppm and -36±15 ppm. The modified titanium silicalite molecular sieve can be used in the aldol condensation reaction.

Description

Modified titanium silicate molecular sieve and its preparation method and application Technical Field

[0001] The present invention belongs to the technical field of molecular sieves, and more specifically relates to a modified titanium silicate molecular sieve, a preparation method of the modified titanium silicate molecular sieve, and application of the modified titanium silicate molecular sieve as a catalyst. Background Art

[0002] Aldol condensation, also known as aldol condensation, occurs when an aldehyde or ketone with an α-H bond undergoes nucleophilic addition reaction with another aldehyde or ketone under acid or base catalysis to form a β-hydroxyaldehyde or β-hydroxyketone. This β-hydroxyaldehyde or β-hydroxyketone can be dehydrated upon heating to form an α,β-unsaturated aldehyde or ketone. Aldol condensation can form new carbon-carbon bonds in a molecule and extend the carbon chain.

[0003] The aldol condensation reaction can produce a variety of high-value chemicals, such as 1,3-propylene glycol, 1,3-butanediol, neopentyl glycol, octenal and other β-hydroxy compounds, which can be used as monomers for the further production of fragrances, pharmaceuticals, plasticizers, polymers or polymers such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and polytrimethylene terephthalate (PTT).

[0004] The dehydration product of aldol condensation, α,β-unsaturated aldehydes, can be oxidized to the corresponding carboxylic acids, which are widely used as raw materials in fine chemical production. For example, 2,2-dimethylolpropionic acid can be used as a chain extender for water-based urethanes and in the preparation of polyesters, photosensitive resins, and liquid crystals. 2-Methyl-2-pentenoic acid is a fruity flavoring widely used in the food processing industry and other daily fragrance and flavor industries. Methyl methacrylate (MMA) is primarily used to produce polymethyl methacrylate (PMMA) and acrylic resins, but is also widely used in the manufacture of other resins, plastics, coatings, adhesives, lubricants, wetting agents, glazing agents, printing and dyeing auxiliaries, and insulating and potting materials. Methyl acrylate (MA) is an important organic intermediate widely used in the rubber, leather, pharmaceutical, and coatings industries. Furthermore, α,β-unsaturated aldehydes, when fully hydrogenated, yield saturated primary aldehydes, which can be used as solvents or in the manufacture of detergents and plasticizers.

[0005] The aldol condensation reaction can generally occur under the catalysis of either an acid or a base, but the reaction mechanisms differ. In the presence of an acidic catalyst, the aldehyde carbonyl group is activated at the cationic active center (Bronsted center or Lewis center) of the acidic catalyst to form an enolate carbonium ion, thereby causing the condensation reaction. Commonly used acidic catalysts include (VO)2P2O7, niobic acid, and MFI zeolite. Basic catalysts are frequently used in the aldol condensation reaction and include basic compounds (oxides, hydroxides, bicarbonates, carbonates, and carboxylates of alkali or alkaline earth metals), organic amine compounds, and anion exchange resins. In actual industrial applications, the basic catalysts used in the aldol condensation reaction can be weak bases (such as sodium carbonate, sodium bicarbonate, and sodium acetate) or strong bases (such as sodium hydroxide, calcium hydroxide, sodium hydride, and sodium alkoxide). The former is generally used for the condensation between more active aldehydes, and the products are mostly β-hydroxy compounds. The latter is used for the condensation between less active and sterically hindered aldehydes or ketones, and the reaction is mostly carried out in aprotic polar solvents.

[0006] The direct aldol condensation of methyl propionate and formaldehyde to produce methyl methacrylate does not use highly toxic raw materials. The raw materials are inexpensive and widely available, making it an important method for producing methyl methacrylate in the future. Currently, the most effective catalyst for the aldol condensation of methyl propionate and formaldehyde is a supported catalyst with silica as the primary support and cesium as the primary active component. However, this supported catalyst suffers from low activity, which prevents the complete conversion of the raw materials. Furthermore, because the catalyst is supported on amorphous silica, its specific surface area and strength gradually decrease over time in the reaction system.

[0007] CN103551148B discloses a water-resistant catalyst for aldol condensation, wherein the main active ingredient includes one or more oxides or salts of Cs, the active auxiliary agent is one or more oxides or salts of Sb, Nb, Ag, Al, and Zr, and the carrier includes SiO2 and a carrier auxiliary agent.

[0008] CN112675830A discloses an aldol condensation catalyst. The catalyst uses foamed porous silica as a carrier to load metal elements, which makes the catalyst have excellent water resistance, anti-carbon deposition performance and long-term activity stability. It is suitable for industrial application in the preparation of methyl methacrylate by aldol condensation of methyl propionate and formaldehyde.

[0009] The catalysts used in the aldol condensation reaction studied in existing literature are mostly alkaline catalysts of amorphous silica-supported alkali metals. Their carriers have poor stability, a single active center, low activity and selectivity, and cannot meet the requirements of industrial large-scale production.

[0010] Currently, there are several main methods for producing methyl acrylate: propylene oxidation, acrylonitrile hydrolysis, and propane oxidation. Propylene oxidation offers technical and economic advantages, but is inefficient and is the primary method for industrial production. Acrylonitrile hydrolysis yields low yields and the sulfuric acid cannot be recycled. Propane oxidation is inexpensive but has a low yield.

[0011] The preparation of methyl acrylate by the condensation reaction of coal-based methyl acetate (or acetic acid) and formaldehyde is a very important and highly productive process synthesis route. It not only has low production costs but also effectively controls the discharge of polluted waste liquids, making it a synthesis method with great application prospects.

[0012] "Chemical Industry Progress, 2021, 40(4): 2005-2015" reported on the research progress of acetic acid (ester)-formaldehyde condensation to acrylic acid (ester). The catalysts currently used in this route include VPO catalysts, alkali metal / alkaline earth metal catalysts and ionic liquid catalysts. Among them, VPO catalysts have high catalytic efficiency, but many side reactions and are easily deactivated. Compared with VPO, alkali metal catalysts have no oxidative by-products and higher selectivity, but their catalytic efficiency is slightly lower. Ionic liquid catalysts have mild reaction conditions and high selectivity, but product separation is difficult and the catalyst is difficult to reuse. In comparison, the preparation process of alkali metal catalysts is simpler, the adjustable space is large, the product selectivity is high, and it is easier to achieve industrial application.

[0013] CN 108097290A discloses a catalyst for preparing acrylic acid / methyl acrylate from raw materials containing carbon monoxide and formaldehyde compounds. The catalyst is primarily obtained by metal-modifying commercially available MOR molecular sieves with varying silicon-to-aluminum ratios with at least one of copper, silver, iron, cobalt, nickel, and gallium through impregnation, ion exchange, and in-situ synthesis. The catalyst achieves a maximum selectivity of 88.2% for acrylic acid and 5.3% for methyl acrylate.

[0014] The catalyst disclosed in CN 106693941A uses Li, Na, K, Rb, Cs, Mg, Ca, Sr, and Ba as active components, and an Al2O3 carrier prepared by a coprecipitation method. At a molar ratio of methyl acetate: formaldehyde: methanol of 1:2:2, the conversion of methyl acetate is 34.4%, and the selectivity for methyl acrylate is 93.4%.

[0015] CN 104258901A discloses a Cs-supported pure silicon molecular sieve catalyst, which uses KIT-6 as a carrier and Cs as an active component. The catalyst is used in the aldol condensation reaction of methyl acetate and formaldehyde to prepare methyl acrylate. The molar ratio of methyl acetate, formaldehyde, and methanol is 1:2:2. The conversion rate of methyl acetate can reach up to 35%, and the selectivity of methyl acrylate can reach up to 94%.

[0016] Teng He et al. reported in "Catalysis Letters, 2019, 149(2):373-389" that cesium-loaded SiO2 was used as a catalyst in the aldol condensation of methyl acetate and formaldehyde to prepare methyl acrylate. When the molar ratio of methyl acetate, formaldehyde, and methanol was 1:2:2 and the reaction temperature was 390°C, the conversion rate of methyl acetate was about 35%, and the selectivity of methyl acrylate was 85-90%.

[0017] Among various catalysts for catalyzing the aldol condensation reaction of methyl acetate and formaldehyde to prepare MA, the activity of silica-supported Cs alkali metal catalysts is not ideal, and the yield of the target product is low. Summary of the Invention

[0018] The purpose of the present invention is to provide a catalytic material different from the prior art, provide a preparation method thereof, provide a catalyst containing the catalytic material, and use of the catalyst in an aldol condensation reaction.

[0019] In order to achieve one of the purposes of the present invention, the present invention provides a modified titanium silicon molecular sieve in the first aspect, characterized in that it contains titanium, silicon, oxygen, and cesium elements; 133 The Cs MAS NMR spectrum has at least resonance absorption peaks at -94±15 ppm, -73±15 ppm, and -36±15 ppm, and the intensities of the resonance absorption peaks follow a specific relationship.

[0020] In order to achieve the second purpose of the present invention, the second aspect of the present invention provides a preparation method of the modified titanium silicate molecular sieve, characterized in that the method includes mixing the titanium silicate molecular sieve as the starting modified raw material with a cesium compound, especially a cesium hydroxide or a cesium salt, and then treating it under steam conditions, and drying and calcining the treated solid to obtain the modified titanium silicate molecular sieve.

[0021] In order to achieve the third purpose of the present invention, the third aspect of the present invention provides a catalyst containing the modified titanium silicalite described in the first aspect of the present invention or the modified titanium silicalite obtained by the preparation method of the second aspect of the present invention, characterized in that it contains the titanium silicalite provided by the first aspect of the present invention or the titanium silicalite prepared by the method provided by the second aspect of the present invention, and the weight ratio of the titanium silicalite to the titanium silicalite catalyst is preferably 5%-100%.

[0022] In order to achieve the fourth object of the present invention, the fourth aspect of the present invention provides a method for aldol condensation, which is a method in which a carbonyl-containing compound having an α-H and another carbonyl-containing compound undergo a carbon-carbon bond coupling reaction in the presence of the titanium silicalite catalyst provided by the third aspect of the present invention to generate a carbonyl-containing compound having a β-hydroxyl group or a carbonyl-containing compound having an α,β-unsaturated bond.

[0023] The modified titanium silicalite molecular sieve of the present invention uses cesium and titanium as its main active components. The interaction between cesium and titanium produces appropriate catalytic active centers, ensuring high conversion rates and good product selectivity in the aldol condensation reaction. The preparation method of this modified titanium silicalite molecular sieve is simple, requires only a few steps, and utilizes a wide range of raw material sources, making it suitable for large-scale industrial applications and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the following detailed description, they are used to explain the present application but do not constitute a limitation of the present application. In the accompanying drawings:

[0025] Figure 1 is a comparative example 1 of the catalyst Cs / SiO2 133 Cs MAS NMR spectrum.

[0026] Figure 2 is the comparative catalyst Cs / S-1 of Comparative Example 2 133 Cs MAS NMR spectrum.

[0027] FIG3 is an XRD spectrum of TS-1-0.02 titanium silicalite molecular sieve prepared in Preparation Example 1.

[0028] FIG4 is an infrared spectrum of the hydroxyl group of TS-1-0.02 titanium silicalite molecular sieve of Preparation Example 1.

[0029] FIG5 is a UV-Vis spectrum of TS-1-0.02 titanium silicalite molecular sieve of Preparation Example 1.

[0030] FIG6 is an XRD spectrum of catalyst Cs / TS-1-A of Example 1.

[0031] Figure 7 shows the catalyst Cs / TS-1-A of Example 1 133 Cs MAS NMR spectrum.

[0032] FIG8 is an infrared spectrum of the hydroxyl group of catalyst Cs / TS-1-A of Example 1.

[0033] FIG9 is a UV-Vis spectrum of catalyst Cs / TS-1-A of Example 1.

[0034] FIG10 is an XRD spectrum of the comparative catalyst Cs / TS-1-A1 of Comparative Example 3.

[0035] Figure 11 shows the comparative catalyst Cs / TS-1-A1 of Comparative Example 3. 133 Cs MAS NMR spectrum.

[0036] FIG12 is an infrared spectrum of the hydroxyl group of the comparative catalyst Cs / TS-1-A1 of Comparative Example 3.

[0037] FIG13 is a UV-Vis spectrum of the comparative catalyst Cs / TS-1-A1 of Comparative Example 3.

[0038] FIG14 is an XRD spectrum of the comparative catalyst Cs / TS-1-A2 of Comparative Example 4.

[0039] Figure 15 is the comparative catalyst Cs / TS-1-A2 of Comparative Example 4 133 Cs MAS NMR spectrum.

[0040] FIG16 is an infrared spectrum of the hydroxyl group of the comparative catalyst Cs / TS-1-A2 of Comparative Example 4.

[0041] FIG17 is a UV-Vis spectrum of the comparative catalyst Cs / TS-1-A2 of Comparative Example 4.

[0042] FIG18 is an XRD spectrum of comparative catalyst K / TS-1-A of Comparative Example 5.

[0043] FIG19 is an infrared spectrum of the hydroxyl group of comparative catalyst K / TS-1-A of Comparative Example 5.

[0044] FIG20 is a UV-Vis spectrum of comparative catalyst K / TS-1-A of Comparative Example 5. DETAILED DESCRIPTION

[0045] The first aspect of the present invention provides a modified titanium silicon molecular sieve, characterized in that it contains titanium, silicon, oxygen, and cesium elements; 133 The Cs MAS NMR spectrum has at least resonance absorption peaks at -94±15ppm, -73±15ppm and -36±15ppm.

[0046] 133 The resonance absorption peak in the Cs MAS NMR spectrogram is the specific spectral peak produced by cesium in different chemical environments. The number of peaks represents the number of different chemical environments. The chemical shift of the peak indicates the degree of influence of the chemical environment in which it is located on the cesium element. The more negative the chemical shift, the stronger the effect of the environment on it, and the stronger the shielding effect on the nucleus of cesium. The modified titanium silicon molecular sieve of the present invention has characteristic peaks at -94 ± 15ppm, -73 ± 15ppm, and -36 ± 15ppm, indicating that its cesium element is present in a specific chemical environment, which will inevitably bring specific catalytic performance. Due to the very complex nuclear magnetic spectrum analysis, the present invention can not fully confirm the physicochemical meaning of each spectral peak under existing knowledge and research conditions, and only confirms its characteristics and effects by comparison. However, since the present invention produces new signal peaks through the effect of cesium and titanium silicon molecular sieve, the new characteristics and effects produced are mainly derived from the effect of cesium and titanium.

[0047] In the modified titanium silicalite of the present invention, when the spectral peak intensities of the resonance absorption peaks of -94±15ppm, -73±15ppm, and -36±15ppm are I1, I2, and I3, respectively, preferably, the spectral peak intensities have the following relationship: I2≥I1>I3, more preferably I2>I1>I3; even more preferably, the spectral peak intensities have the following relationship: I1 / I2=0.3-1, I3 / I2=0.2-0.9, further preferably, the spectral peak intensities have the following relationship: I1 / I2=0.5-0.95, I3 / I2=0.4-0.8, most preferably, the spectral peak intensities have the following relationship: I1 / I2=0.7-0.9, I3 / I2=0.65-0.8.

[0048] Preferably, in the modified titanium silicalite of the present invention, the chemical shift of the resonance absorption peak at -94±15ppm is -94±10ppm, more preferably -94±5ppm; the chemical shift of the resonance absorption peak at -73±15ppm is -73±10ppm, more preferably -73±5ppm; and / or the chemical shift of the resonance absorption peak at -36±15ppm is -36±10ppm, more preferably -36±5ppm.

[0049] When the modified titanium silicate molecular sieve of the present invention is characterized by infrared spectroscopy, it can be found that the infrared hydroxyl spectrum of the modified titanium silicate molecular sieve is 3200-3720cm -1 There is no hydroxyl signal peak. Infrared hydroxyl characterization method is usually used to characterize the hydroxyl state in solid catalytic materials such as molecular sieves. It is generally believed that the wavelength is at 3520cm -1 The broad peak near the hydroxyl group represents the nested hydroxyl group, which is the four silanol structures left after the skeleton atoms are removed; the wavelength is at 3690 cm -1 The signal peak near the vicinal hydroxyl group is that the two silicon atoms of the silanol group are connected by oxygen; 3720cm -1 The signal peak near 3740cm is titanium hydroxyl; -1 The signal peak near 3740cm is the terminal silanol group. -1 The hydroxyl signal peaks other than 3740 cm -1 The signal peaks are also very weak or difficult to distinguish.

[0050] The modified titanium silicate molecular sieve of the present invention is characterized by ultraviolet-visible spectroscopy (UV-Vis), and it can be found that its UV-Vis spectrum has a tetracoordinate titanium signal peak of 210±10nm and a hexacoordinate titanium signal peak of 270±15nm; further in the UV-Vis spectrum, there may also be an anatase signal peak of 330±15nm. In the UV-Vis spectrum, based on the total area of ​​the peaks in the range of 200-800nm ​​in the spectrum, the tetracoordinate titanium signal peak area of ​​210±10nm is preferably 50%-95%, more preferably 50%-90%, even more preferably 55%-85%, and further preferably 60%-75%; the hexacoordinate titanium signal peak area of ​​270±15nm is preferably 10%-45%, more preferably 20%-40%, and further preferably 25%-35%; the anatase signal peak area of ​​330±15nm is preferably 0-40%, more preferably 0-20%, and further preferably 0-10%.

[0051] In the modified titanium silicalite molecular sieve of the present invention, the molar ratio of cesium element to silicon element can be (0.0001-0.1):1, preferably (0.001-0.08):1, further preferably (0.005-0.06):1, more preferably (0.008-0.04):1, and most preferably (0.01-0.03:1); the molar ratio of titanium element to silicon element can be (0.0001-0.1):1, preferably (0.001-0.08):1, further preferably (0.004-0.06):1, more preferably (0.008-0.04):1, and most preferably (0.01-0.03:1; the molar ratio of each element is obtained by X-ray fluorescence spectrometer analysis method (XRF).

[0052] The modified titanium silicalite molecular sieve of the present invention may, in principle, include any suitable structure type or any suitable combination of structure types. Therefore, the available molecular sieve crystal structure types may, in principle, include the following structure crystal types: ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFY, AHT, ANA, APC, APD, AST, ASV, AFX, ATN, ATO, ATS, ATT, ATV, AWO, AWW, BCT, BEA, BEC, BIK, BOF, BOG, BOZ, BPH, BRE, BSV, CAN, CAS, CDO, CFI, CGF, SCO, CFI, SGF, CGS, CHA, CHI, CLO, C ON, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EWT, EON, EPI, ERI, ESV, ETR, EUO, FAU, FER, FRA, GIS, GIU, GME, GON, GOO, HEU, IFR, IHW, ISV, I TE, ITH, ITW, IWR, IWW, IWV, JBW, JNT, JOZ, JRY, JSN, JSR, JST, JSW, KFI, LAU, LEV, LIO, LIT, LOS, LOV, LTA, LTF, LTJ, LTL, LTN, MAR, MAZ, MEI, ME L, MEP, MER, MFI, MFS, MON, MOR, MOZ, MRT, MSE, MSO, MTF, MTN, MTT, MTW, MVY, MWF, MWW, NAB, NAT, NES, NON, NPO, NPT, NSI, OBW, OFF, OKO, OSI, OS O,OWE,PAR,PAU,PCR,PHI,PON,POR,POS,PSI,PTY,PUN,PWN,PWO,PWW,RHO,RON,RRO,RSN,RTE,RTH,RUT,RWR,RWY,SAF,SAO,SAS,SAT,SAV,SBE , SBN, SBS, SBT, SFE, SFF, SFG, SFH, SFN, SFO, SFS, SFW, SGT, SIV, SOD, SOF, SOR, SOS, SOV, SSF, SSY, STF, STI, STT, STW, SVR, SVV, SWY, SYT, SSN, TER, THO, TOL, TON, TSC, TUN, UEI, UFI, UOS, UOV, UOZ, USI, UTL, UWY, VET, VFI, VNI, VSV, WEI, WEN, YFI, YUG, ZON, and a mixed structure composed of two or more of these structure types.The modified titanium silicalite molecular sieve of the present invention may also be an amorphous structure, wherein the amorphous structure includes MCM-41, MCM-48, and SBA-15. Preferably, the structural crystal type of the modified titanium silicalite molecular sieve of the present invention is MFI, MEL, BEA, MWW, MOR, or SVR structure, or the modified titanium silicalite molecular sieve of the present invention is an amorphous structure of at least one of MCM-41, MCM-48, and SBA-15.

[0053] The modified titanium silicate molecular sieve of the present invention preferably has at least one crystal structure of MFI, MEL, and BEA. The modified titanium silicate molecular sieve may have multi-level pore characteristics or mesoporous structure characteristics within a pore distribution range of 2-50 nm. The multi-level pores or mesoporous structure may be obtained by direct synthesis or post-processing of the titanium silicate molecular sieve. For example, it may be synthesized by soft or hard template synthesis methods (silanization method, cellulose method, carbon black method, etc.), and expanded by acid or alkali treatment (for example, by hydrochloric acid, hydrofluoric acid, ammonium bifluoride, ammonium fluoride, sodium hydroxide, potassium hydroxide, ammonia water, ammonium carbonate, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, etc.). The multi-level pores or mesoporous structure may contain micropores and at least one mesopore and / or macropore. The micropores have a pore diameter of less than 2 nm; the mesopores have a pore diameter of 2-50 nm; and the macropores have a pore diameter greater than 50 nm.

[0054] The second aspect of the present invention provides a method for preparing a modified titanium silicate molecular sieve, which is characterized in that the method includes mixing a titanium silicate molecular sieve as a starting modified raw material with a cesium compound, especially a cesium hydroxide or a cesium salt, and then treating it under steam conditions, and drying and calcining the treated solid to obtain the modified titanium silicate molecular sieve.

[0055] In the preparation method of the modified titanium silicate molecular sieve provided by the present invention, the mixing can be carried out by one or more of an impregnation method, an ion exchange method, a spraying method, a solid-phase ion exchange method, a grinding method, and a stirring method, and the method can be repeated multiple times. Since the grinding method can better contact the cesium element with the titanium silicate molecular sieve than other methods, the grinding chemical reaction occurs, which is more conducive to the formation of catalytic active centers of the titanium silicate molecular sieve of the present invention, the grinding method is preferably used. The mixing is preferably carried out in the presence of a solvent.

[0056] In the preparation method of the modified titanium silicate molecular sieve provided by the present invention, the titanium silicate molecular sieve used as the starting modified raw material can be obtained by a hydrothermal synthesis method or a post-synthesis method. Among them, the post-synthesis method can be a rearrangement method, a silicon aluminum molecular sieve dealumination titanium insertion method, a silicon boron molecular sieve deboronation titanium insertion method, a silicon germanium molecular sieve degermanation titanium insertion method, etc.; it can be a liquid phase titanium insertion method or a vapor phase titanium insertion method. The present invention is not particularly limited, and preferably uses a titanium silicate molecular sieve obtained by a hydrothermal synthesis method as the starting modified raw material.

[0057] In the preparation method of the modified titanium silicalite provided by the present invention, there is no restriction on the skeleton structure of the titanium silicalite as the starting modified raw material, and in principle, the following structural crystal types can be included: ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFY, AHT, ANA, APC, APD, AST, ASV, AFX, ATN, ATO, ATS, ATT, ATV, AWO, AWW, BCT, BEA, BEC, BIK, BOF, BOG, BOZ, BPH, BRE, BSV, CAN, CAS, CDO, CFI, CGF, SCO, C FI, SGF, CGS, CHA, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EWT, EON, EPI, ERI, ESV, ETR, EUO, FAU, FER, FRA, GIS, GIU, GME, GON, G OO, HEU, IFR, IHW, ISV, ITE, ITH, ITW, IWR, IWW, IWV, JBW, JNT, JOZ, JRY, JSN, JSR, JST, JSW, KFI, LAU, LEV, LIO, LIT, LOS, LOV, LTA, LTF, LTJ, LTL, LT N, MAR, MAZ, MEI, MEL, MEP, MER, MFI, MFS, MON, MOR, MOZ, MRT, MSE, MSO, MTF, MTN, MTT, MTW, MVY, MWF, MWW, NAB, NAT, NES, NON, NPO, NPT, NSI, OBW, OF F, OKO, OSI, OSO, OWE, PAR, PAU, PCR, PHI, PON, POR, POS, PSI, PTY, PUN, PWN, PWO, PWW, RHO, RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, SAF, SAO, SAS, SAT , SAV, SBE, SBN, SBS, SBT, SFE, SFF, SFG, SFH, SFN, SFO, SFS, SFW, SGT, SIV, SOD, SOF, SOR, SOS, SOV, SSF, SSY, STF, STI, STT, STW, SVR, SVV, SWY, SYT, SSN, TER, THO, TOL, TON, TSC, TUN, UEI, UFI, UOS, UOV, UOZ, USI, UTL, UWY, VET, VFI, VNI, VSV, WEI, WEN, YFI, YUG, ZON, and a mixed structure composed of two or more of these structure types.The titanium silicalite molecular sieve used as the starting material for modification may also be an amorphous structure including MCM-41, MCM-48, SBA-15, etc. Preferably, the titanium silicalite molecular sieve used as the starting material for modification has one or more crystal structures of MFI, MEL, MWW, BEA, MOR, SVR, or an amorphous structure of MCM-41, MCM-48, or SBA-15, more preferably one or more crystal structures of MFI, MEL, or BEA. The titanium silicalite molecular sieve used as the starting material for modification may contain a multi-level pore structure or a mesoporous structure.

[0058] In the preparation method of the modified titanium silicate molecular sieve provided by the present invention, the molar ratio of titanium element to silicon element in the titanium silicate molecular sieve used as the starting modified raw material can be (0.0001-0.1):1, preferably (0.001-0.08):1, further preferably (0.004-0.06):1, more preferably (0.008-0.04):1, and most preferably (0.01-0.03):1.

[0059] In the preparation method of the modified titanium silicate molecular sieve provided by the present invention, the cesium salt can be selected from the group consisting of cesium hydrochloride, hypochlorite, chlorite, metachlorate, perchlorate, nitrate, sulfate, bisulfate, sulfite, bisulfite, phosphate, hydrogen phosphate, dihydrogen phosphate, high phosphate, metaphosphate, phosphite, hypophosphite, carbonate, bicarbonate, pyrophosphate, C1-C 20 The cesium salt is preferably a nitrate or a carbonate. Preferably, the cesium hydroxide or cesium salt is exemplified by, but not limited to, one or more of cesium hydroxide, cesium nitrate, cesium carbonate, cesium bicarbonate, and cesium acetate.

[0060] In the preparation method of the modified titanium silicate molecular sieve provided by the present invention, the molar ratio of the cesium element to the silicon element in the titanium silicate molecular sieve as the starting material can be (0.0001-0.1):1, preferably (0.001-0.08):1, further preferably (0.005-0.06):1, more preferably (0.008-0.04):1, and most preferably (0.01-0.03):1.

[0061] In the preparation method of the modified titanium silicalite provided by the present invention, a solvent may be optionally added. The solvent may be an inorganic solvent or an organic solvent. The inorganic solvent may be water, such as distilled water or deionized water; the organic solvent may include a C1-C 10 Alcohol, C3-C 10 Ketone, C2-C 10 Esters, C6-C 10The organic solvent may be an alkane or aromatic hydrocarbon. The solvent may also be a chlorinated solvent, such as one or more of chloroform, dichloromethane, chloroform, carbon tetrachloride, chloroethane, dichloroethane, trichloroethane, and tetrachloroethane. The solvent may be an aliphatic alcohol, typically a C1-C6 alkanol, such as methanol, ethanol, propanol, isopropanol, butanol, pentanol, and hexanol, preferably methanol, ethanol, or propanol. The amount of solvent added depends on the carrier. In the preparation method, the solvent is preferably at least one of water, methanol, ethanol, propanol, chloroform, dichloromethane, and chloroform, and a further preferred solvent is at least one of water, methanol, ethanol, and propanol. The molar ratio of the titanium silicalite (calculated as SiO2) as the starting material to the solvent may be 1:(0-10), preferably 1:(1-8), more preferably 1:(1.5-6), and most preferably 1:(1.5-4).

[0062] In the preparation method of the modified titanium silicalite provided by the present invention, the mixing can be carried out at 20-150°C and an absolute pressure of 10-100KPa for 5-120 minutes; the mixing is preferably carried out at 25-100°C, more preferably at 30-70°C, and an absolute pressure of 20-80KPa, more preferably 30-50KPa, for 5-60 minutes, more preferably 10-30 minutes. The mixing is carried out under a certain vacuum degree, which is more conducive to the dispersion of cesium in the titanium silicalite and forms a better interaction between cesium and titanium. The mixing can be carried out on equipment that meets the processing requirements, such as a vacuum glove box or a vacuum ball mill.

[0063] In the preparation method of the modified titanium silicalite provided by the present invention, if mixing is performed in the presence of a solvent, the solvent must be removed. The method for removing the solvent may be pressure evaporation, atmospheric evaporation, reduced pressure evaporation, filtration, centrifugation, sedimentation, or natural volatilization during the mixing process, and is not particularly limited in the present invention.

[0064] Preferably, in the method for preparing the modified titanium silicate molecular sieve provided by the present invention, the steam refers to water vapor.

[0065] Preferably, in the preparation method of the modified titanium silicalite provided by the present invention, the treatment under steam conditions is carried out with water vapor at 100-200°C, preferably 120-180°C, more preferably 130-160°C, at a gauge pressure of 0-1MPa, preferably 0.1-0.8MPa, more preferably 0.3-0.6MPa for 0.1-24h, preferably 1-12h, and further preferably 2-8h. The steam may be superheated steam or saturated steam. The pressure may be adjusted by supplementing gas such as nitrogen, argon, air, etc. The inventors have found that cesium exists on the surface of the titanium silicalite mainly in three forms, namely cesium oxide, active centers formed by reaction with silicon, and active centers formed by reaction with titanium. Among them, cesium oxide exists in an aggregated state with low dispersion, and its activity and selectivity in catalyzing aldol condensation are low. Increasing its content to a certain level does not significantly improve the catalytic reaction. When the cesium content is high, it primarily exists on the support surface as cesium oxide. Active centers formed with silicon and titanium are highly dispersed, resulting in superior catalytic performance, with those formed with titanium providing the highest catalytic performance. Steam treatment increases the mesopore volume, promotes cesium distribution, and interacts with titanium, forming highly efficient active centers.

[0066] In the preparation method of the modified titanium silicalite provided by the present invention, the drying is preferably carried out at a temperature range of 60-150°C, more preferably 90-140°C, and more preferably 100-130°C; the drying time is preferably 0.5-24 hours, more preferably 1-12 hours, and more preferably 2-6 hours. The calcination is preferably carried out at 250-800°C for 0.5-24 hours, more preferably 350-550°C for 1-12 hours. The calcination atmosphere is preferably an oxygen-containing atmosphere, more preferably an air atmosphere; the calcination temperature is determined by the decomposition temperature of the alkali element precursor of the modifier. The calcination is preferably carried out at less than 550°C, and more preferably a calcination temperature of 400-500°C to prevent decomposition of the alkali element precursor. To prevent significant changes in the support structure or specific surface area, the calcination time is more preferably 3-8 hours. The calcination atmosphere is preferably an oxygen-containing atmosphere, more preferably an air atmosphere.

[0067] A third aspect of the present invention provides a titanium silicate molecular sieve catalyst, characterized in that the catalyst comprises the titanium silicate molecular sieve of the first aspect of the present invention or the titanium silicate molecular sieve prepared by the method described in the second aspect of the present invention. Furthermore, the titanium silicate molecular sieve accounts for 5% to 100% by weight of the titanium silicate molecular sieve catalyst.

[0068] The fourth aspect of the present invention provides a method for aldol condensation, characterized in that, in the presence of the titanium silicon molecular sieve catalyst provided in the third aspect above, a carbonyl-containing compound having α-H undergoes a carbon-carbon bond coupling reaction with another carbonyl-containing compound to generate a carbonyl-containing compound having a β-hydroxyl group or a carbonyl-containing compound having an α,β-unsaturated bond.

[0069] The α and β positions refer to the first ortho and second ortho carbon atoms of the functional groups of hydrocarbon molecules, such as carbonyl, hydroxyl, carboxyl, etc. Wherein, the carbonyl-containing compound may include the first carbonyl compound and the second carbonyl compound, and the number of carbon atoms thereof is preferably C1-C 20 The carbonyl compound may include the following structure:

[0070] C1-C 12 Alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl, 1,2-dimethylpropyl, isopentyl, n-hexyl, isohexyl, sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl, n-decyl and n-dodecyl; preferably C1-C6 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl, 1,2-dimethylpropyl, isopentyl, n-hexyl, isohexyl, sec-hexyl, particularly preferably C1-C4 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isohexyl, sec-butyl, tert-butyl;

[0071] C3-C 12 Cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl and cyclododecyl; preferably cyclopentyl, cyclohexyl and cycloheptyl;

[0072] Substituted cycloalkyl groups, examples of which are: 2-methylcyclopentyl, 3-methylcyclopentyl, 2-methylcyclohexyl, 3-methylcyclohexyl, 4-methylcyclohexyl, 2-methoxycyclopentyl, 2-chlorocyclopentyl, 2-methylthiocyclohexyl and other derivatives;

[0073] C7-C 13 Arylalkyl, preferably C7-C 12 Phenylalkyl, such as benzyl, 1-phenylethyl, 2-phenylethyl, 1-phenylpropyl, 2-phenylpropyl, 3-phenylpropyl, 1-phenylbutyl, 2-phenylbutyl, 3-phenylbutyl and 4-phenylbutyl, particularly preferably benzyl;

[0074] C6-C 14Aryl, for example phenyl, 1-naphthyl, 2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthrenyl, 2-phenanthrenyl, 3-phenanthrenyl, 4-phenanthrenyl, 9-phenanthrenyl, preferably phenyl, which is unsubstituted or substituted with one or more of the following groups:

[0075] C1-C 12 Alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl, 1,2-dimethylpropyl, isopentyl, n-hexyl, isohexyl, sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl, n-decyl and n-dodecyl; preferably C1-C6 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl, 1,2-dimethylpropyl, isopentyl, n-hexyl, isohexyl, sec-hexyl, particularly preferably C1-C4 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isohexyl, sec-butyl, tert-butyl,

[0076] Halogen, such as fluorine, chlorine, bromine, iodine, preferably chlorine, and

[0077] C1-C 12 Alkoxy, preferably C1-C6 alkoxy, such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, n-pentoxy, isopentylpropoxy, n-hexyloxy and isohexyloxy, particularly preferably methoxy, ethoxy, n-propoxy, n-butoxy.

[0078] Preferably, the first carbonyl compound contains α-H, and the second carbonyl compound contains α-H or does not contain α-H. Further preferably, the carbonyl compound not containing α-H is preferably formaldehyde, benzaldehyde, furfural, 5-hydroxyfurfural, 5-methylfurfural or a derivative thereof, and further preferably formaldehyde; the carbonyl compound containing α-H is preferably acetaldehyde, propionaldehyde, acetone, butyraldehyde, butanone, valeraldehyde, pentanone, hexanal, hexanone, cyclohexanone, cyclopentanone, acetic acid, propionic acid, malonic acid, butyric acid, succinic acid, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, cyclohexyl acetate, methyl propionate, ethyl propionate, butyl propionate, dimethyl malonate, methyl butyrate, dimethyl succinate, ethyl butyrate or at least one of a derivative thereof.

[0079] In the aldol condensation method provided by the present invention, the molar ratio of the first carbonyl compound to the second carbonyl compound is preferably 1:(0.1-10), further preferably 1:(0.2-6), more preferably 1:(0.4-4), more preferably 1:(0.8-3), and more preferably 1:(1-2).

[0080] In the method for aldol condensation provided by the present invention, one or more diluents can also be included in the mixed stream of the carbonyl compound. The diluent can include at least one of alcohols, ethers, alkanes, halogenated alkanes, and toluene, and preferred diluents are methanol, cycloalkane, ether, and toluene. The molar ratio of diluent to carbonyl compound can be (30-0.5):1, preferably (20-0.7):1, further preferably (10-0.8):1, more preferably (5-0.9):1, and most preferably (3-1):1.

[0081] In the aldol condensation method provided by the present invention, the aldol condensation reaction can be carried out in an atmosphere containing at least one gas selected from N2, He, Ar, CH4, C2H6, H2, CO, and CO2, preferably N2.

[0082] In the aldol condensation method provided by the present invention, the aldol condensation reaction temperature can be 200-500°C, preferably 250-480°C, and more preferably 300-400°C. Before the reaction, the temperature of the mixed solution is preferably raised to between 250-400°C, more preferably between 300-400°C; the reaction pressure (gauge pressure) is 0-2.5 MPa, preferably 0.2-1.5 MPa, and more preferably 0.5-1.0 MPa; the reaction liquid hourly space velocity is 0.05-5 h / min based on the total mass of the carbonyl compound and the diluent. -1 , further preferably 0.08-3h -1 , more preferably 0.1-2h -1 The space velocity should be understood as the mass space velocity, which means the ratio of the mass flow rate of the total mass of the carbonyl compound and the diluent (in units of (mass / time)) to the mass of the catalyst. Therefore, the unit of space velocity is h -1 .

[0083] The present inventors have found that the catalysts of the present invention are capable of surprisingly greatly improving the activity and selectivity for the condensation of a methylene source, such as formaldehyde, with a carboxylic acid or a hydrocarbyl ester, such as methyl acetate, to form an ethylenically unsaturated carboxylic acid ester. The formaldehyde source is an anhydrous formaldehyde source, preferably methylal, trioxymethylene, and paraformaldehyde.

[0084] In a specific embodiment of the present invention, the aldol condensation reaction conditions of formaldehyde and methyl acetate include: methyl acetate: formaldehyde molar ratio of 1:2 to 1:1, methanol: methyl acetate molar ratio of 1:1 to 3:1, preferably 1:1 to 2:1, reaction temperature of 320 to 400 ° C, reaction pressure (gauge pressure) of 0 to 1 MPa, nitrogen flow rate of 30 to 100 mL / min, reaction liquid hourly space velocity of 0.1 to 2 h -1 .

[0085] In a specific embodiment of the present invention, the aldol condensation reaction conditions of formaldehyde and methyl propionate include: a methyl propionate: formaldehyde molar ratio of 1:2 to 1:0.2, a methanol: methyl propionate molar ratio of 1:1 to 5:1, a reaction temperature of 320 to 400°C, a reaction pressure (gauge pressure) of 0 to 1 MPa, a nitrogen flow rate of 30 to 100 mL / min, and a reaction liquid hourly space velocity of 0.1 to 2 h -1 .

[0086] In another specific embodiment of the present invention, the reaction conditions for preparing octenal by the aldol condensation reaction of butyraldehyde include: a methanol: n-butyraldehyde molar ratio of 0:1 to 10:1, a reaction temperature of 300 to 380°C, a reaction pressure (gauge pressure) of 0 to 1 MPa, a nitrogen flow rate of 30 to 100 mL / min, and a reaction liquid hourly space velocity of 0.1 to 2 h -1 .

[0087] The aldol condensation method provided by the present invention can be carried out in a fixed bed reactor, a fluidized bed reactor, a microchannel reactor or a kettle reactor. It will be understood by those skilled in the art that, depending on the different reactors used, the catalyst of the present invention can be the modified titanium silicon molecular sieve raw powder or a shaped catalyst after the modified titanium silicon molecular sieve is shaped. The separation of the aldol condensation reaction product and the catalyst can be achieved in a variety of ways. For example, when the raw powder is used as the catalyst, the separation of the product and the recovery and reuse of the catalyst can be achieved by sedimentation, filtration, centrifugation, evaporation, membrane separation, etc.; the shaped catalyst is loaded into a fixed bed reactor, and the catalyst is recovered after the reaction is completed. Various catalyst separation and recovery methods are widely involved in existing literature and will not be described here.

[0088] Example

[0089] The present invention is described in detail below by way of examples. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0090] Sample 133 The Cs MAS NMR characterization instrument was an AVANCE III 500WB nuclear magnetic resonance spectrometer, which used a 7 mm double resonance probe, a Ø4 mm SnO2 rotor, and was calibrated with cesium chloride.

[0091] The hydroxyl infrared spectrum of the sample was measured on a NICOLET 6700. The sample was placed on a self-supporting sheet and tested after being treated at 473K for 2h.

[0092] The ultraviolet-visible (UV-Vis) spectra of the samples were detected on a Cary 300 Agilent UV-visible spectrometer, and the signals in the range of 190–800 nm were measured under ambient conditions.

[0093] The chemical composition of the samples was determined using a Rigaku 3721E X-ray fluorescence spectrometer at a measurement voltage of 40 kV.

[0094] The XRD patterns of the samples were measured on a Philips Panalytical X'pert X-ray diffractometer equipped with a Cu Kα light source, a scanning step size of 0.04°, and a scanning range of 5–35°.

[0095] The prepared modified titanium silicalite catalyst was used to catalyze the aldol condensation of methyl acetate and formaldehyde to synthesize methyl acrylate. The catalytic performance test of the aldol condensation reaction was conducted in a fixed-bed reactor at atmospheric pressure, wherein the molar ratio of methyl acetate to formaldehyde was 1:1.8, methanol was used as the solvent, the molar ratio of methyl acetate to methanol was 1:3, and the raw material mixture was fed at a space velocity of 1.5h. -1 The catalyst dosage was 5 g. The carrier gas (N2) flow rate was maintained at 30 mL / min and the reaction temperature was 350°C. The product was condensed and then analyzed by chromatography. Unless otherwise specified, the raw materials in the examples of this application were purchased from commercial sources.

[0096] The composition of the aldol condensation reaction product was analyzed by gas chromatography, and the results were quantified using an external standard method. The chromatographic analysis conditions were: an Agilent-6890 chromatograph, an HP-5 capillary column, an injection volume of 0.5 μL, and an injection port temperature of 280°C. The column temperature was maintained at 100°C for 2 minutes, then increased to 200°C at a rate of 15°C / min and held there for 3 minutes. The FID detector was set at 300°C.

[0097] The calculations of conversion, selectivity and yield in the examples are as follows: Y 丙烯酸甲酯 =C 醋酸甲酯 ×S 丙烯酸甲酯

[0098] Comparative Example 1

[0099] This comparative example is used to illustrate the preparation of a comparative catalyst Cs / SiO2 containing cesium supported on an amorphous silica carrier.

[0100] Preparation of SiO2: 100 mL of water and 50 g of tetraethyl silicate were mixed at room temperature. Ammonia was added dropwise to the mixture until the pH reached 13. The mixture was then stirred at 40°C for 60 minutes. The hydrolyzed silica was filtered and dried in a drying oven at 110°C overnight. After cooling and grinding at room temperature, the amorphous silica support was obtained. XRD analysis of the SiO2 revealed an amorphous structure.

[0101] Preparation of the Cs / SiO2 catalyst: Weigh a certain amount of cesium nitrate and dissolve it in deionized water. Then, immerse the SiO2 in the cesium nitrate solution. The molar ratio of cesium to silicon is 0.03:1, and the molar ratio of SiO2 (calculated as silicon dioxide) to solvent is 1:40. Immerse for 30 minutes at an absolute pressure of 101 kPa and 40°C to evenly distribute the cesium ions on the silica. The solvent is then evaporated, and the mixture is dried in a drying oven at 120°C for 6 hours. Finally, the mixture is calcined in a muffle furnace at 400°C for 6 hours to obtain the Cs / SiO2 catalyst.

[0102] XRF characterization, UV-Vis characterization, 133 Cs MAS NMR characterization and evaluation of the aldol condensation reaction of methyl acetate and formaldehyde. The characterization and evaluation results are shown in Tables 1 and 2.

[0103] 133 The Cs MAS NMR characterization spectrum showed two signal peaks at -12 ppm and -36 ppm (Figure 1).

[0104] Comparative Example 2

[0105] This comparative example is used to illustrate the preparation of a comparative catalyst Cs / S-1 of MFI type all-silicon molecular sieve S-1 loaded with cesium.

[0106] Preparation of MFI-type all-silica molecular sieve S-1: Tetraethyl orthosilicate (TEOS), tetrapropylammonium hydroxide (TPAOH, 25 wt%) solution, and water were mixed in a molar ratio of SiO2:0.2TPAOH:30H2O, stirred for 60 minutes, and then stirred at 80°C for approximately 3 hours to obtain a clear sol. The mixture was then crystallized at 170°C for 72 hours. The resulting solid was filtered, washed with distilled water, dried at 120°C for 5 hours, and then calcined at 550°C for 5 hours to obtain molecular sieve S-1. XRD analysis of S-1 revealed an MFI structure.

[0107] Catalyst Cs / S-1 was prepared by dissolving a certain amount of cesium nitrate in deionized water. S-1 was then immersed in the cesium nitrate solution. The molar ratio of cesium to silicon was 0.03:1, and the molar ratio of S-1 (calculated as silica) to solvent was 1:40. The catalyst was immersed at an absolute pressure of 101 kPa and 40°C for 30 minutes to uniformly distribute the cesium ions on the S-1. The solvent was then evaporated, and the catalyst was dried in a drying oven at 120°C for 6 hours. The catalyst was then calcined in a muffle furnace at 400°C for 6 hours to obtain the comparative catalyst Cs / S-1.

[0108] XRF characterization, UV-Vis characterization, 133Cs MAS NMR characterization and evaluation of the aldol condensation reaction of methyl acetate and formaldehyde. The characterization and evaluation results are shown in Tables 1 and 2.

[0109] 133 The Cs MAS NMR characterization spectrum showed two signal peaks at -19 ppm and -36 ppm (Figure 2).

[0110] Preparation Example 1

[0111] Preparation Example 1 illustrates the preparation of TS-1-0.02 titanium silicalite molecular sieve.

[0112] The preparation steps of TS-1-0.02 titanium silicalite molecular sieve are as follows: tetraethyl orthosilicate (TEOS), tetrabutyl titanate (TBOT), tetrapropylammonium hydroxide (TPAOH, 25wt%) solution and water are mixed in a molar ratio of SiO2:0.02TiO2:0.2TPAOH:30H2O, then stirred for 60 minutes, and then stirred at 80°C for about 5 hours to obtain a clear sol, which is then crystallized at 170°C for 72 hours. The obtained solid is then filtered, washed with distilled water, dried at 120°C for 6 hours, and then calcined at 550°C for 6 hours to obtain titanium silicalite molecular sieve, numbered TS-1-0.02.

[0113] XRD analysis of TS-1-0.02 revealed that it had an MFI structure ( FIG3 ).

[0114] TS-1-0.02 was analyzed by infrared spectroscopy and the presence of hydroxyl groups at 3520 cm -1 、3690cm -1 、3720cm -1 and 3740cm -1 The hydroxyl peak of

[0115] UV-Vis analysis of TS-1-0.02 revealed a signal peak at 210 nm ( FIG. 5 ).

[0116] Example 1

[0117] This example illustrates the preparation of a cesium-loaded catalyst Cs / TS-1-A using titanium silicalite TS-1-0.02.

[0118] The specific steps for the Cs / TS-1-A catalyst are as follows: a certain amount of cesium nitrate is weighed and dissolved in deionized water. TS-1-0.02 is then immersed in the cesium nitrate solution. The molar ratio of cesium to silicon is 0.03:1, and the molar ratio of TS-1-0.02 (calculated as silica) to solvent is 1:2. In a glove box, the solid is ground at 50 kPa absolute pressure and 40°C for 30 minutes to uniformly distribute the cesium ions throughout the TS-1-0.02. The solid is then treated with steam at 120°C and 0.4 MPa gauge pressure for 3 hours. The solvent is further evaporated, and the solid is dried in a drying oven at 120°C for 6 hours. Finally, it is calcined in a muffle furnace at 400°C for 6 hours to obtain the Cs / TS-1-A catalyst.

[0119] XRF characterization, UV-Vis characterization, 133 Cs MAS NMR characterization and evaluation of the aldol condensation reaction of methyl acetate and formaldehyde. The characterization and evaluation results are shown in Tables 1 and 2.

[0120] XRD analysis of Cs / TS-1-A revealed that it had an MFI structure ( FIG6 ).

[0121] Cesium nuclear magnetic spectrum analysis of Cs / TS-1-A revealed the presence of -36ppm, -73ppm, and -94ppm signal peaks (Figure 7), with peak intensities I2(-73)>I1(-94)>I3(-36).

[0122] Infrared analysis of Cs / TS-1-A revealed the presence of only hydroxyl groups at 3740 cm -1 The hydroxyl peak of

[0123] UV-Vis analysis of Cs / TS-1-A revealed signal peaks at 210 nm, 270 nm, and 330 nm ( FIG9 ).

[0124] Comparative Example 3

[0125] This comparative example illustrates the preparation of the cesium-loaded catalyst Cs / TS-1-A1 of titanium silicalite TS-1-0.02.

[0126] The specific steps for preparing the Cs / TS-1-A1 catalyst are as follows: a certain amount of cesium nitrate is weighed and dissolved in deionized water. TS-1-0.02 is then immersed in the cesium nitrate solution. The molar ratio of cesium to silicon is 0.03:1, and the molar ratio of TS-1-0.02 (calculated as silica) to solvent is 1:2. In a glove box, the mixture is ground at 50 kPa absolute pressure and 40°C for 30 minutes to uniformly distribute the cesium ions on the TS-1-0.02. The solvent is evaporated, and the mixture is dried in a drying oven at 120°C for 6 hours. Finally, the mixture is calcined in a muffle furnace at 400°C for 6 hours to obtain the Cs / TS-1-A1 catalyst.

[0127] XRF characterization, UV-Vis characterization, 133 Cs MAS NMR characterization and evaluation of the aldol condensation reaction of methyl acetate and formaldehyde. The characterization and evaluation results are shown in Tables 1 and 2.

[0128] XRD analysis of Cs / TS-1-A1 revealed that it had an MFI structure ( FIG. 10 ).

[0129] Cesium nuclear magnetic spectrum analysis of Cs / TS-1-A1 revealed the presence of signal peaks at -41 ppm, -73 ppm, and -97 ppm ( FIG. 11 ), with peak intensities I(-41)>I(-73)>I(-97).

[0130] Infrared analysis of Cs / TS-1-A1 revealed the presence of only hydroxyl groups at 3740 cm -1 The hydroxyl peak of

[0131] UV-Vis analysis of Cs / TS-1-A1 revealed that it had obvious signal peaks at 210 nm and 270 nm ( FIG. 13 ).

[0132] Comparative Example 4

[0133] This comparative example illustrates the preparation of the cesium-loaded catalyst Cs / TS-1-A2 of titanium silicalite molecular sieve TS-1-0.02.

[0134] The specific steps for the Cs / TS-1-A2 catalyst are as follows: a certain amount of cesium nitrate is weighed and dissolved in deionized water. TS-1-0.02 is then immersed in the cesium nitrate solution. The molar ratio of cesium to silicon is 0.03:1, and the molar ratio of TS-1-0.02 (calculated as silica) to solvent is 1:2. In a glove box, the sample is ground at 50 kPa absolute pressure and 40°C for 30 minutes to uniformly distribute the cesium ions on the TS-1-0.02. The resulting solid sample is then mixed with water at a solid-to-liquid ratio of 1:5 and treated at 120°C under autogenous pressure for 3 hours. The solvent is then evaporated, the sample is dried in a drying oven at 120°C for 6 hours, and calcined in a muffle furnace at 400°C for 6 hours to obtain the Cs / TS-1-A2 catalyst.

[0135] XRF characterization, UV-Vis characterization, 133 Cs MAS NMR characterization and evaluation of the aldol condensation reaction of methyl acetate and formaldehyde. The characterization and evaluation results are shown in Tables 1 and 2.

[0136] XRD analysis of Cs / TS-1-A2 revealed that it had an MFI structure ( FIG. 14 ).

[0137] Cs / TS-1-A2 was subjected to cesium nuclear magnetic spectrum analysis, revealing the presence of -48 ppm, -74 ppm, and -96 ppm signal peaks ( FIG. 15 ), with peak intensities I(-48)>I(-74)>I(-96).

[0138] Infrared analysis of Cs / TS-1-A2 revealed the presence of only hydroxyl groups at 3740 cm -1 The hydroxyl peak of

[0139] UV-Vis analysis of Cs / TS-1-A2 revealed that it had obvious signal peaks at 210 nm and 270 nm ( FIG. 17 ).

[0140] Comparative Example 5

[0141] This example illustrates the preparation of the potassium-loaded catalyst K / TS-1-A of titanium silicalite TS-1-0.02.

[0142] The K / TS-1-A catalyst is prepared as follows: a certain amount of potassium nitrate is weighed and dissolved in deionized water. TS-1-0.02 is then immersed in the potassium nitrate solution. The molar ratio of potassium to silicon is 0.03:1, and the molar ratio of TS-1-0.02 (calculated as silica) to solvent is 1:2. In a glove box, the solid is ground at 50 kPa absolute pressure and 40°C for 30 minutes to uniformly distribute the potassium ions throughout the TS-1-0.02. The solid is then treated with steam at 120°C and 0.4 MPa gauge pressure for 3 hours. The solvent is further evaporated, and the solid is dried in a drying oven at 120°C for 6 hours. Finally, it is calcined in a muffle furnace at 400°C for 6 hours to obtain catalyst K / TS-1-A.

[0143] Catalyst K / TS-1-A was characterized by XRF and UV-Vis spectrometry, and evaluated for the aldol condensation reaction of methyl acetate and formaldehyde. The characterization and evaluation results are shown in Tables 1 and 2.

[0144] XRD analysis of K / TS-1-A revealed that it had an MFI structure ( FIG. 18 ).

[0145] The infrared analysis of K / TS-1-A showed the presence of hydroxyl groups at 3740 cm -1 and 3530cm -1 The hydroxyl peak of

[0146] K / TS-1-A was subjected to UV-Vis analysis, and was found to have signal peaks at 210 nm, 270 nm, and 330 nm ( FIG. 20 ).

[0147] Example 2

[0148] This example illustrates the preparation of a cesium-loaded catalyst Cs / TS-1-B using titanium silicalite TS-1-0.02.

[0149] The specific steps for the Cs / TS-1-B catalyst are as follows: a certain amount of cesium carbonate is weighed and dissolved in deionized water. TS-1-0.02 is then immersed in the cesium carbonate solution. The molar ratio of cesium to silicon is 0.02:1, and the molar ratio of TS-1-0.02 (calculated as silica) to solvent is 1:4. In a glove box, the solid is ground at 30 kPa absolute pressure and 60°C for 60 minutes to uniformly distribute the cesium ions throughout the TS-1-0.02. The solid is then treated with steam at 180°C and 0.3 MPa gauge pressure for 2 hours. The solvent is further evaporated, and the solid is dried in a drying oven at 100°C for 3 hours. Finally, it is calcined in a muffle furnace at 500°C for 3 hours to obtain the Cs / TS-1-B catalyst.

[0150] XRF characterization, UV-Vis characterization, 133 Cs MAS NMR characterization and evaluation of the aldol condensation reaction of methyl acetate and formaldehyde. The characterization and evaluation results are shown in Tables 1 and 2.

[0151] XRD analysis of Cs / TS-1-B revealed that it had an MFI structure.

[0152] Cesium nuclear magnetic spectrum analysis of Cs / TS-1-B revealed the presence of -36ppm, -73ppm and -94ppm signal peaks, with peak intensities I2(-73)>I1(-94)>I3(-36).

[0153] Infrared analysis of hydroxyl groups in Cs / TS-1-B revealed the presence of only hydroxyl groups at 3740 cm -1 hydroxyl peak.

[0154] UV-Vis analysis of Cs / TS-1-B revealed signal peaks at 210 nm, 270 nm, and 330 nm.

[0155] Preparation Example 2

[0156] This preparation example illustrates the preparation of TS-1-0.04 titanium silicalite molecular sieve.

[0157] The preparation steps of TS-1-0.04 molecular sieve are as follows: tetraethyl orthosilicate (TEOS), tetrabutyl titanate (TBOT), tetrapropylammonium hydroxide (TPAOH, 25wt%) solution and water are mixed in a molar ratio of SiO2:0.04TiO2:0.25TPAOH:35H2O, then stirred for 60 minutes, and then stirred at 80°C for about 6 hours to obtain a clear sol, which is then crystallized at 170°C for 72 hours. After that, the obtained solid is filtered, washed with distilled water, dried at 120°C for 6 hours, and then calcined at 550°C for 6 hours to obtain molecular sieve TS-1-0.04.

[0158] XRD analysis of TS-1-0.04 revealed that it had an MFI structure.

[0159] TS-1-0.04 was subjected to infrared analysis of hydroxyl groups, and the presence of hydroxyl groups at 3520 cm -1 、3690cm -1 、3720cm -1 and 3740cm -1 hydroxyl peak.

[0160] UV-Vis analysis of TS-1-0.04 revealed signal peaks at 210 nm, 270 nm, and 330 nm.

[0161] Example 3

[0162] This example illustrates the preparation of a cesium-loaded catalyst Cs / TS-1-C using titanium silicalite TS-1-0.04.

[0163] The specific steps for the Cs / TS-1-C catalyst are as follows: a certain amount of cesium nitrate is weighed and dissolved in isopropanol. TS-1-0.04 is then immersed in the cesium nitrate solution. The molar ratio of cesium to silicon is 0.04:1, and the molar ratio of TS-1-0.04 (calculated as silica) to solvent is 1:8. In a glove box, the mixture is stirred at 100 kPa absolute pressure and 40°C for 30 minutes to uniformly distribute the cesium ions on the TS-1-0.04. The solid is then treated with steam at 120°C and 0 MPa gauge pressure for 3 hours. The solvent is further evaporated, and the mixture is dried in a drying oven at 120°C for 6 hours. Finally, the mixture is calcined in a muffle furnace at 400°C for 6 hours to obtain the Cs / TS-1-C catalyst.

[0164] XRF characterization, UV-Vis characterization, 133 Cs MAS NMR characterization and evaluation of the aldol condensation reaction of methyl acetate and formaldehyde. The characterization and evaluation results are shown in Tables 1 and 2.

[0165] XRD analysis of Cs / TS-1-C showed that it had an MFI structure.

[0166] Cesium nuclear magnetic spectrum analysis of Cs / TS-1-C showed the presence of -36ppm, -73ppm and -94ppm signal peaks, with peak intensities I2(-73)>I1(-94)>I3(-36).

[0167] Infrared analysis of hydroxyl groups in Cs / TS-1-C revealed only the presence of hydroxyl groups at 3740 cm -1 hydroxyl peak.

[0168] UV-Vis analysis of Cs / TS-1-C revealed signal peaks at 210 nm, 270 nm, and 330 nm.

[0169] Example 4

[0170] This example illustrates the preparation of a cesium-loaded catalyst Cs / TS-1-D using titanium silicalite TS-1-0.04.

[0171] The specific steps for the Cs / TS-1-D catalyst are as follows: a certain amount of cesium carbonate is weighed and dissolved in deionized water. TS-1-0.04 is then immersed in the cesium carbonate solution. The molar ratio of cesium to silicon is 0.03:1, and the molar ratio of TS-1-0.04 (calculated as silica) to solvent is 1:6. In a glove box, the solid is ground at 80 kPa absolute pressure and 50°C for 15 minutes to uniformly distribute the cesium ions on the TS-1-0.04. The solid is then treated with steam at 180°C and 0.8 MPa gauge pressure for 5 hours. The solvent is further evaporated, and the solid is dried in a drying oven at 130°C for 2 hours. Finally, it is calcined in a muffle furnace at 450°C for 8 hours to obtain the Cs / TS-1-D catalyst.

[0172] XRF characterization, UV-Vis characterization, 133 Cs MAS NMR characterization and evaluation of the aldol condensation reaction of methyl acetate and formaldehyde. The characterization and evaluation results are shown in Tables 1 and 2.

[0173] XRD analysis of Cs / TS-1-D showed that it had an MFI structure.

[0174] Cesium nuclear magnetic spectrum analysis of Cs / TS-1-D showed the presence of -36ppm, -73ppm and -94ppm signal peaks, with peak intensities I2(-73)>I1(-94)>I3(-36).

[0175] Infrared analysis of hydroxyl groups in Cs / TS-1-D revealed only the presence of hydroxyl groups at 3740 cm -1 hydroxyl peak.

[0176] UV-Vis analysis of Cs / TS-1-D revealed signal peaks at 210 nm, 270 nm, and 330 nm.

[0177] Preparation Example 3

[0178] This preparation example illustrates the synthesis of titanium silicalite HTS-0.02 having a mesoporous structure (referring to the method of Chinese patent CN1260241A).

[0179] HTS-0.02 was prepared as follows: tetraethyl silicate, tetrabutyl titanate, a 25 wt% tetrapropylammonium hydroxide solution, and deionized water were mixed in a molar ratio of silicon source (as SiO2): titanium source (as TiO2): template: water of 1:0.02:0.2:25, stirred at 30°C for approximately 2 hours, and then at 80°C for approximately 8 hours to produce a sol. The resulting sol was treated at 170°C for 72 hours. The resulting slurry was then filtered, washed with deionized water until the filtrate pH was below 9, dried at 120°C for 6 hours, and calcined at 550°C for 6 hours to produce the intermediate TS-1 product. TS-1 was then mixed with tetrapropylammonium hydroxide and water in a weight ratio of 1:0.4:5, and treated at 170°C for 24 hours. The resulting slurry was then filtered, dried, and calcined as described above to produce the titanium silicate molecular sieve HTS-0.02.

[0180] XRD analysis of HTS-0.02 showed that it had an MFI structure.

[0181] Infrared analysis of HTS-0.02 showed the presence of hydroxyl groups at 3520 cm -1 、3690cm -1 、3720cm - 1 and 3740cm -1 hydroxyl peak.

[0182] UV-Vis analysis of HTS-0.02 revealed signal peaks at 210 nm and 330 nm.

[0183] Example 5

[0184] This example illustrates the preparation of a cesium-loaded catalyst Cs / HTS-A using titanium silicalite molecular sieve HTS-0.02.

[0185] The Cs / HTS-A catalyst is prepared as follows: a certain amount of cesium nitrate is weighed and dissolved in ethanol. The HTS-A and cesium nitrate solutions are then mixed. The molar ratio of cesium to silicon is 0.02:1, and the molar ratio of HTS-A (calculated as silica) to solvent is 1:4. In a glove box, the mixture is ground at 40 kPa absolute pressure and 60°C for 30 minutes to uniformly distribute the cesium ions on the HTS-A. The solid is then treated with steam at 150°C and 0.3 MPa gauge pressure for 8 hours. The solvent is further evaporated, and the mixture is dried in a drying oven at 120°C for 3 hours. Finally, the mixture is calcined in a muffle furnace at 400°C for 5 hours to obtain the Cs / HTS-A catalyst.

[0186] XRF characterization, UV-Vis characterization and 133 Cs MAS NMR characterization and evaluation of the aldol condensation reaction of methyl acetate and formaldehyde. The characterization and evaluation results are shown in Tables 1 and 2.

[0187] XRD analysis of Cs / HTS-A showed that it had an MFI structure.

[0188] Cs / HTS-A was analyzed by cesium nuclear magnetic spectrum, and the presence of -36ppm, -73ppm and -94ppm signal peaks were observed, with peak intensities I2(-73)>I1(-94)>I3(-36).

[0189] Infrared analysis of hydroxyl groups in Cs / HTS-A revealed only the presence of hydroxyl groups at 3740 cm -1 hydroxyl peak.

[0190] UV-Vis analysis of Cs / HTS-A revealed signal peaks at 210 nm, 270 nm, and 330 nm.

[0191] Example 6

[0192] This example illustrates the preparation of a cesium-loaded catalyst Cs / HTS-B using titanium silicalite molecular sieve HTS-0.02.

[0193] The Cs / HTS-B catalyst is prepared as follows: a certain amount of cesium hydroxide is weighed and dissolved in deionized water. HTS-0.02 is then immersed in the cesium hydroxide solution. The molar ratio of cesium to silicon is 0.03:1, and the molar ratio of HTS-0.02 (calculated as silica) to solvent is 1:3. In a glove box, the solid is ground at 50 kPa absolute pressure and 70°C for 30 minutes to uniformly distribute the cesium ions on the HTS-0.02. The solid is then treated with steam at 130°C and 0.5 MPa gauge pressure for 4 hours. The solvent is further evaporated, and the solid is dried in a drying oven at 110°C for 5 hours. Finally, it is calcined in a muffle furnace at 500°C for 8 hours to obtain the Cs / HTS-B catalyst.

[0194] XRF characterization, UV-Vis characterization, 133 Cs MAS NMR characterization and evaluation of the aldol condensation reaction of methyl acetate and formaldehyde. The characterization and evaluation results are shown in Tables 1 and 2.

[0195] XRD analysis of Cs / HTS-B showed that it had an MFI structure.

[0196] Cs / HTS-B was analyzed by cesium nuclear magnetic spectrum, and the presence of -36ppm, -73ppm and -94ppm signal peaks were found, with peak intensities I2(-73)>I1(-94)>I3(-36).

[0197] The infrared analysis of hydroxyl groups in Cs / HTS-B showed that only hydroxyl groups at 3740 cm -1 hydroxyl peak.

[0198] UV-Vis analysis of Cs / HTS-B revealed signal peaks at 210 nm, 270 nm, and 330 nm.

[0199] Preparation Example 4

[0200] This preparation example illustrates the preparation of TS-2-0.02 titanium silicalite molecular sieve.

[0201] The preparation steps of TS-2-0.02 molecular sieve are as follows: tetraethyl orthosilicate (TEOS), tetrabutyl titanate (TBOT), tetrabutylammonium hydroxide (TBAOH, 40wt%) solution and water are mixed in a molar ratio of SiO2:0.02TiO2:0.2TPAOH:30H2O, then stirred for 120 minutes, and then stirred at 70°C for about 4 hours to obtain a clear sol, which is then crystallized at 170°C for 72 hours. After that, the obtained solid is filtered, washed with distilled water, dried at 120°C for 6 hours, and then calcined at 550°C for 6 hours to obtain titanium silicon molecular sieve TS-2-0.02.

[0202] XRD analysis of TS-2-0.02 showed that it had a MEL structure.

[0203] TS-2-0.02 was subjected to infrared analysis and the presence of hydroxyl groups at 3520 cm -1 、3690cm -1 、3720cm -1 and 3740cm -1 hydroxyl peak.

[0204] UV-Vis analysis of TS-2-0.02 revealed a signal peak at 210 nm.

[0205] Example 7

[0206] This example illustrates the preparation of a cesium-loaded catalyst Cs / TS-2-A using titanium silicalite TS-2-0.02.

[0207] The specific steps for the Cs / TS-2-A catalyst are as follows: a certain amount of cesium nitrate is weighed and dissolved in ethanol. TS-2-0.02 is then immersed in the cesium nitrate solution. The molar ratio of cesium to silicon is 0.02:1, and the molar ratio of TS-2-0.02 (calculated as silica) to solvent is 1:2. In a glove box, the solid is ground at 40°C and 40°C for 20 minutes to uniformly distribute the cesium ions throughout the TS-2-0.02. The solid is then treated with steam at 140°C and 0.4 MPa gauge pressure for 3 hours. The solvent is further evaporated, and the solid is dried in a drying oven at 120°C for 6 hours. Finally, it is calcined in a muffle furnace at 400°C for 6 hours to obtain the Cs / TS-2-A catalyst.

[0208] XRF characterization, UV-Vis characterization, 133 Cs MAS NMR characterization and evaluation of the aldol condensation reaction of methyl acetate and formaldehyde. The characterization and evaluation results are shown in Tables 1 and 2.

[0209] XRD analysis of Cs / TS-2-A showed that it had a MEL structure.

[0210] Cesium nuclear magnetic spectrum analysis of Cs / TS-2-A showed the presence of -36ppm, -73ppm and -94ppm signal peaks, with peak intensities I2(-73)>I1(-94)>I3(-36).

[0211] Infrared analysis of hydroxyl groups in Cs / TS-2-A revealed only the presence of hydroxyl groups at 3740 cm -1 hydroxyl peak.

[0212] UV-Vis analysis of Cs / TS-2-A revealed signal peaks at 210 nm, 270 nm, and 330 nm.

[0213] Example 8

[0214] This example is used to prepare the cesium-loaded catalyst Cs / TS-2-B of titanium silicalite molecular sieve TS-2-0.02.

[0215] The specific steps for the Cs / TS-2-B catalyst are as follows: a certain amount of cesium hydroxide is weighed and dissolved in deionized water. TS-2-0.02 is then immersed in the cesium hydroxide solution. The molar ratio of cesium to silicon is 0.015:1, and the molar ratio of TS-2-0.02 (calculated as silica) to solvent is 1:3. In a glove box, the solid is ground at 70°C and 30 kPa absolute pressure for 30 minutes to uniformly distribute the cesium ions throughout the TS-2-0.02. The solid is then treated with steam at 160°C and 0.6 MPa gauge pressure for 5 hours. The solvent is further evaporated, and the solid is dried in a drying oven at 130°C for 5 hours. Finally, it is calcined in a muffle furnace at 400°C for 3 hours to obtain the Cs / TS-2-B catalyst.

[0216] XRF characterization, UV-Vis characterization, 133 Cs MAS NMR characterization and evaluation of the aldol condensation reaction of methyl acetate and formaldehyde. The characterization and evaluation results are shown in Tables 1 and 2.

[0217] XRD analysis of Cs / TS-2-B showed that it had a MEL structure.

[0218] Cesium nuclear magnetic spectrum analysis of Cs / TS-2-B showed the presence of -36ppm, -73ppm and -94ppm signal peaks, with peak intensities I2(-73)>I1(-94)>I3(-36).

[0219] Infrared analysis of hydroxyl groups in Cs / TS-2-B revealed only the presence of hydroxyl groups at 3740 cm -1 hydroxyl peak.

[0220] UV-Vis analysis of Cs / TS-2-B revealed signal peaks at 210 nm, 270 nm, and 330 nm.

[0221] Table 1

[0222] From the comparison between Examples 1-8 and Comparative Examples 1-5, it can be seen that the modified titanium silicon molecular sieve catalyst of the present invention has obvious characteristic peaks at -93ppm and -73ppm, and there is a specific intensity relationship between the peaks. The infrared spectrum of hydroxyl is at 3200-3720cm -1 There is no hydroxyl signal peak within the range, and the signal peak area of ​​210±10nm in the UV-Vis spectrum accounts for 50%-90%, and the signal peak area of ​​270±15nm accounts for 10%-45%.

[0223] Table 2

[0224] GC-MS characterization and analysis showed that the aldol condensation reaction of methyl acetate and formaldehyde using the modified titanium silicalite catalyst was mainly produced by methyl acrylate, and the main by-products were isobutyraldehyde, methacrolein, and methyl methacrylate. In contrast, the by-products of the aldol condensation in the comparative example included acetone, acetic acid, and the like.

[0225] As can be seen from the data in Table 2, the aldol condensation method provided by the present invention has a good conversion rate of methyl acetate and selectivity for the target product methyl acrylate.

[0226] Example 9

[0227] This example illustrates the use of the prepared catalyst to catalyze the aldol condensation reaction of methyl propionate and formaldehyde to prepare methyl methacrylate.

[0228] The catalysts prepared in Comparative Examples 1-5 and Examples 1-8 catalyzed the aldol condensation of methyl propionate and formaldehyde to synthesize methyl methacrylate. A fixed bed reactor was used at atmospheric pressure, wherein the molar ratio of methyl propionate to formaldehyde was 1:0.5, methanol was used as the solvent, the molar ratio of methyl propionate to methanol was 1:2, and the raw material mixture was fed at a space velocity of 0.3 h -1 The catalyst dosage was 5 g. During the reaction, the carrier gas (N2) flow rate was maintained at 30 mL / min, and the reaction temperature was 360°C. The product was condensed and then subjected to chromatographic analysis, with quantification performed using an external standard method. The chromatographic analysis conditions were: Agilent-6890 chromatograph, HP-5 capillary column, injection volume 0.5 μL, injection port temperature 300°C. The column temperature was maintained at 100°C for 2 minutes, then increased to 260°C at a rate of 15°C / min and maintained there for 5 minutes. The FID detector was operated at a detector temperature of 380°C.

[0229] The conversion, selectivity and yield were calculated as follows: Y 甲基丙烯酸甲酯 =C 丙酸甲酯 ×S 甲基丙烯酸甲酯

[0230] The reaction results are shown in Table 3.

[0231] Table 3

[0232] According to GC-MS characterization and analysis, the aldol condensation reaction of methyl propionate and formaldehyde was carried out using the modified titanium silicalite catalyst. The main product of the embodiment of the present invention was methyl methacrylate, and the main by-products were methyl isobutyrate, α-methyl-γ-butyrolactone, 2,4-dimethyldimethyl glutarate, etc., while the by-products of the aldol condensation in the comparative example mainly contained acetone, 3,4-dimethyl-2-cyclopentenone, methyl isobutyrate, propionic acid, etc.

[0233] As can be seen from the data in Table 3, the aldol condensation method provided by the present invention has a good conversion rate of methyl propionate and selectivity for the target product methyl methacrylate.

[0234] Example 10

[0235] This example illustrates the use of the prepared catalyst in catalyzing the aldol condensation reaction of butyraldehyde to produce octenal.

[0236] The catalysts prepared in Comparative Examples 1-5 and Examples 1-8 catalyzed the aldol condensation of n-butyraldehyde to synthesize octenal. Using a fixed bed reactor at normal pressure, n-butyraldehyde was introduced into the fixed bed reactor at a feed space velocity of 2 h -1 The catalyst dosage was 5 g. During the reaction, the carrier gas (N2) flow rate was maintained at 30 mL / min, and the reaction temperature was 330°C. The product was condensed and then subjected to chromatographic analysis, using an external standard method for quantification. The chromatographic analysis conditions were: Agilent-6890 chromatograph, HP-5 capillary column, injection volume 0.5 μL, injection port temperature 300°C. The column temperature was maintained at 100°C for 2 minutes, then increased to 260°C at a rate of 15°C / min and maintained there for 5 minutes. The FID detector was set at a detector temperature of 380°C.

[0237] The conversion, selectivity and yield were calculated as follows: Y 辛烯醛 =C 正丁醛 ×S 辛烯醛

[0238] The reaction results are shown in Table 4.

[0239] Table 4

[0240] GC-MS characterization and analysis showed that the main product of the aldol condensation reaction of n-butyraldehyde using the modified titanium silicalite catalyst was octenal, and the main by-product was hydroxyoctanal.

[0241] As can be seen from the data in Table 4, the aldol condensation method provided by the present invention has a good conversion rate of n-butyraldehyde and selectivity of the target product octenal.

[0242] Any embodiment described herein may be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas thus formed shall be deemed as part of the original disclosure or original record of the present invention, and shall not be regarded as new content that has not been disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

Claims

1. A modified titanium silicalite molecular sieve, characterized in that, It contains titanium, silicon, oxygen and cesium elements; it 133 In the Cs MAS NMR spectrum, there are at least resonance absorption peaks at -94±15 ppm, -73±15 ppm and -36±15 ppm. When the peak intensities of the resonance absorption peaks at -94±15 ppm, -73±15 ppm and -36±15 ppm are I1, I2 and I3 respectively, I2≥I1>I3.

2. The modified titanium silicalite molecular sieve according to claim 1, characterized in that, I2 > I1 > I3. Preferably, the spectral peak intensities have the following relationships: I1 / I2 = 0.3 - 1, I3 / I2 = 0.2 - 0.

9. More preferably, I1 / I2 = 0.5 - 0.95, I3 / I2 = 0.4 - 0.

8. Even more preferably, I1 / I2 = 0.7 - 0.9, I3 / I2 = 0.65 - 0.

8.

3. The modified titanium silicalite molecular sieve according to claim 1 or 2, wherein In its infrared hydroxyl spectrum, there is no hydroxyl signal peak at 3200 - 3720 cm -1 ; and / or Its UV-Vis spectrum has a tetracoordinated titanium signal peak at 210 ± 10 nm and a hexacoordinated titanium signal peak at 270 ± 15 nm.

4. The modified titanium silicalite molecular sieve according to claim 3, wherein, Based on the total area of the spectral peaks in the range of 200 - 800 nm in the UV-Vis spectrum, the peak area ratio of the tetracoordinated titanium signal peak at 210 ± 10 nm is 50% - 90%, and the peak area ratio of the hexacoordinated titanium signal peak at 270 ± 15 nm is 10% - 45%.

5. The modified titanium silicalite molecular sieve according to any one of claims 1-4, characterized in that, The molar ratio of cesium element to silicon element is (0.0001 - 0.1):1, preferably (0.001 - 0.08):1, further preferably (0.005 - 0.06):1, more preferably (0.008 - 0.04):1, and most preferably (0.01 - 0.03):1; and / or The molar ratio of titanium element to silicon element is (0.0001 - 0.1):1, preferably (0.001 - 0.08):1, further preferably (0.004 - 0.06):1, more preferably (0.008 - 0.04):1, and most preferably (0.01 - 0.03):

1.

6. The modified titanium silicalite molecular sieve according to any one of claims 1-5, characterized in that, It has a crystal structure selected from at least one of MFI, MEL, MWW, BEA, MOR, SVR, or an amorphous structure selected from at least one of MCM-41, MCM-48, SBA-15.

7. The preparation method of the modified titanium silicalite molecular sieve according to any one of claims 1-6, characterized in that, The method includes the steps of mixing a titanium silicalite as a starting modification raw material with a cesium compound, especially cesium hydroxide or cesium salt, then treating under steam conditions, and drying and calcining the treated solid to obtain the modified titanium silicalite.

8. The preparation method according to claim 7, wherein, The mixing is carried out by impregnation, ion exchange, spraying, solid-phase ion exchange, or grinding methods, with grinding being preferred; and / or The mixing is carried out in the presence of a solvent.

9. The preparation method according to claim 7 or 8, wherein, The titanium silicalite as the starting modification raw material has one or more of the molecular sieves with MFI, MEL, MWW, BEA, MOR, SVR crystal structures, or one or more of MCM-41, MCM-48, SBA-15 amorphous structures; and / or The titanium silicalite as the starting modification raw material is obtained by hydrothermal synthesis or post-synthesis methods; and / or For the titanium silicalite as the starting modification raw material, the molar ratio of titanium element to silicon element is (0.0001 - 0.1):1, preferably (0.001 - 0.08):1, further preferably (0.004 - 0.06):1, more preferably (0.008 - 0.04):1, and most preferably (0.01 - 0.03):1; and / or The molar ratio of the cesium compound (especially cesium hydroxide or cesium salt) calculated as cesium to the titanium silicalite as the starting modification raw material calculated as silicon element is (0.0001 - 0.1):1, preferably (0.001 - 0.08):1, more preferably (0.005 - 0.06):1, still more preferably (0.008 - 0.04):1, and most preferably (0.01 - 0.03):

1.

10. The preparation method according to any one of claims 7-9, characterized in that, The cesium compound is a cesium salt selected from one or more of cesium hydrochloride, hypochlorite, chlorite, metachlorite, perchlorate, nitrate, sulfate, bisulfate, sulfite, bisulfite, phosphate, hydrogen phosphate, dihydrogen phosphate, metaphosphate, hypophosphite, carboxylate, pyrophosphate, carboxylates of C1-C 20 ; and / or The cesium compound is cesium hydroxide.

11. The preparation method according to any one of claims 7-10, characterized in that, The mixing is carried out at 20 - 150 °C and an absolute pressure of 10 - 100 KPa for 5 - 120 min; the mixing is preferably carried out at 25 - 100 °C, more preferably at 30 - 70 °C, and an absolute pressure of 20 - 80 KPa, more preferably 30 - 50 KPa for 5 - 60 min, more preferably for 10 - 30 min; and / or The steam mentioned refers to water vapor; and / or The steam is superheated steam or saturated steam; and / or The treatment under the steam condition is carried out with water vapor at 100 - 200 °C, preferably 120 - 180 °C, more preferably 130 - 160 °C, and at a gauge pressure of 0 - 1 MPa, preferably 0.1 - 0.8 MPa, more preferably 0.3 - 0.6 MPa for 0.1 - 24 h, preferably 1 - 12 h, further preferably 2 - 8 h.

12. A titanium silicalite molecular sieve catalyst, characterized in that, The modified titanium silicalite as claimed in any one of claims 1 - 6 or the modified titanium silicalite obtained by the preparation method as claimed in any one of claims 7 - 11.

13. The titanium-silicate molecular sieve catalyst according to claim 12, wherein, The weight ratio of the modified titanium silicalite is 5% - 100%.

14. A method for aldol condensation, characterized in that, In the presence of the titanium silicalite catalyst as claimed in claim 12 or 13, a carbonyl - containing compound having α - H reacts with another carbonyl - containing compound to undergo a carbon - carbon bond coupling reaction to form a carbonyl - containing compound having β - hydroxy or a carbonyl - containing compound having α,β - unsaturated bond.

15. The aldol condensation method according to claim 14, characterized in that, The reaction temperature is 200 - 500 °C, preferably 250 - 480 °C, more preferably 300 - 400 °C, and the reaction pressure is 0 - 2.5 MPa, preferably 0.2 - 1.5 MPa, more preferably 0.5 - 1.0 MPa. Based on the total mass of the carbonyl compound and the diluent, the space velocity of the reaction liquid is 0.05 - 5 h -1 , preferably 0.08 - 3 h -1 , more preferably 0.1 - 2 h -1 .

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