Bifunctional molecular sieve catalytic material as well as preparation method and application thereof

Abstract

The invention provides a bifunctional molecular sieve catalytic material as well as a preparation method and application thereof. The hierarchical pore molecular sieve catalytic material DIC-TMG / ZrO2 / MFI comprises a molecular sieve MFI and active components loaded on the molecular sieve MFI, and the active components mainly comprise ZrO2 and DIC-TMG. The preparation method of the DIC-TMG / ZrO2 / MFI mainly comprises the step of introducing ZrO2 and DIC-TMG into the molecular sieve MFI through a calcination method and covalent bond grafting. The catalytic material DIC-TMG / ZrO2 / MFI is an acid-base bifunctional solid catalyst with double active centers, and has a porous structure and a high specific surface area, macropores are beneficial to transfer and diffusion of oil reactants and products, and carbon accumulation is reduced; acid and alkali double catalytic sites in the catalytic material show synergistic catalysis, so that the invention further provides application of the catalytic material in production of biofuel from catalytic oil, the catalytic activity of the catalytic material is remarkably improved, and low-quality oil is converted into the biofuel in one step under normal-pressure mild conditions; reaction conditions are mild and safe, the yield is high, and industrial application is facilitated.

Description

Technical Field

[0001] The present invention relates to the field of preparation and application of multiphase catalysts, and in particular to a dual-functional molecular sieve catalytic material and a preparation method and application thereof. Background Art

[0002] At present, biodiesel is produced industrially by reacting oils (triglycerides) or fatty acids with low-carbon alcohols (such as methanol). The catalyst used can be acid, alkali or lipase. In actual production, the cost of raw materials accounts for about 60-80% of the total cost of biodiesel production, which is a key factor restricting the development of biodiesel. Therefore, it is more economically feasible to use low-cost oil raw materials (such as waste oils or non-edible oils) as raw materials for biodiesel production. However, low-quality oils often contain a large amount of impurities such as free fatty acids (FFA) and water, which can deactivate the catalyst. For transesterification reactions, alkaline catalysts usually have higher catalytic activity than acid catalysts, but because saponification reactions are prone to occur in the presence of FFA and water, alkaline catalysts will lose their activity, so alkaline catalysts are not suitable for low-quality waste oils. In addition to catalyzing oil transesterification reactions, acidic catalysts also have catalytic esterification reaction activity, but their catalytic transesterification reaction activity is low, and higher reaction temperatures or longer reaction times are required to obtain satisfactory oil conversion rates. Generally, when low-quality waste oil is used to produce biofuels, an acid catalyst is used to catalyze the esterification of FFA, and then a base catalyst is used to catalyze the transesterification of triglycerides. This complex "two-step method" involves multiple separation and purification processes, with high production costs and large amounts of wastewater. Therefore, developing acid-base bifunctional catalysts that have the advantages of both acid and base catalysts and reducing the catalytic process flow has important practical significance and good application prospects for increasing raw material utilization efficiency, reducing production costs, and reducing environmental pollution.

[0003] In order to improve biodiesel yield and feedstock utilization efficiency, two catalytic processes, esterification and transesterification, are required when using low-quality oils with high FFA and water content. Acid-base bifunctional heterogeneous solid catalysts are able to convert triglycerides and FFA into biodiesel at the same time. This is mainly due to the dual functional properties of these heterogeneous catalysts, where both acidic and basic sites are able to perform biofuel conversion of triglycerides and FFA in one process operation unit. In addition, by adjusting the performance of the bifunctional solid catalyst, the serious effects of high free fatty acids and high water content on the catalyst activity can be reduced or eliminated.

[0004] Invention patent application CN118807823 A discloses an acid-base bisexual ester exchange catalyst with clinoptilolite as carrier, and its preparation method and application. The catalyst is an acid-base bisexual ester exchange catalyst with clinoptilolite as carrier, and zirconium oxide and calcium oxide are loaded on the carrier; the catalyst has acid-base bisexuality, high catalytic activity, and can show good catalytic effect on methanol and crude oil to synthesize biodiesel at a temperature of 131°C. However, since the boiling point of methanol at normal pressure is 65°C, the above-mentioned catalyst disclosed in the invention patent application needs to be carried out in a high-pressure reactor to synthesize biodiesel with a high yield at normal pressure, which is difficult to achieve, and the cost is high, which is not conducive to industrial application. Summary of the invention

[0005] Transition metal oxides are acidic and are effective active ingredients for biomass conversion solid catalysts. They show good catalytic activity for oils with high acid values. Organic guanidine, as an organic base, has strong alkalinity. The simultaneous introduction of metal oxides and organic biguanide compounds on the molecular sieve carrier can produce new and Lewis acid-base sites, effectively improving the acidity and alkalinity of the catalyst surface. The strength and amount of acid-base sites on the catalyst surface are key factors affecting the catalytic activity and selectivity of bifunctional acid-base solid catalysts in the process of producing biodiesel from low-quality oil. In the oil conversion reaction, macromolecular oil raw materials have the characteristics of high viscosity and large molecules, which have mass transfer barriers and resistance on the surface of conventional heterogeneous catalysts, significantly affecting the catalyst activity. Therefore, in terms of heterogeneous catalyst carriers, multi-level pore structure carriers are superior to traditional microporous structure carriers. Their large pore size structure and abundant through-hole channels can reduce the diffusion resistance of macromolecular reactants and enhance the mass transfer of macromolecular oil materials. In addition, the multi-level pore structure is also easy to functionalize its surface. Multi-level pore carriers have a large specific surface area and a higher total porosity, which can provide more catalytic active sites and improve the exposure of catalytic active sites. The catalytic center activity, availability, and surface mass transfer properties of heterogeneous catalysts determine the performance of the catalyst. The pore size distribution and continuity of the catalyst carrier have an important influence on its specific surface area, availability of active centers, and material mass transfer rate.

[0006] In view of this, the present invention mainly provides a multiphase acid-base bifunctional molecular sieve catalytic material with a large surface area. The molecular sieve is used as a carrier and is assembled with metal oxides and organic biguanide compound active centers. When used to catalyze the production of biofuels from low-quality oil, the catalyst is endowed with the multifunctionality of co-catalyzing oil ester exchange and free fatty acid esterification, which can effectively improve the contact between the oil reactants and the active sites to solve the mass transfer resistance and obstacle problems of triglyceride macromolecules on the surface of the multiphase catalyst, increase the stability of the catalytic active center, and significantly improve its catalytic performance in the conversion of low-quality oil. At the same time, the reaction temperature of biofuel synthesis is significantly reduced, and biofuel synthesis is achieved at normal pressure and low temperature using methanol and low-quality oil as raw materials. The reaction conditions are mild, and low-cost, efficient and safe synthesis of biofuels is further achieved, which is conducive to industrial application.

[0007] Specifically, the first aspect of the present invention provides a method for preparing a bifunctional molecular sieve catalytic material, comprising: using molecular sieve MFI, ZrO(NO3)2·xH2O, 3-chloropropyltriethoxysilane and DIC-TMG as raw materials, and adopting calcination and covalent bonding methods to graft ZrO2 and DIC-TMG onto the molecular sieve MFI to obtain the target catalytic material DIC-TMG / ZrO2 / MFI; wherein DIC-TMG is the compound 1,2-diisopropyl-4,4,5,5-tetramethylbiguanide, and the ratio of the total mass of ZrO(NO3)2·xH2O (hydrated zirconium oxynitrate) and DIC-TMG to the mass of the molecular sieve MFI is 0.35-0.6:1.

[0008] In order to increase the catalyst activity, the mass ratio of ZrO(NO3)2·xH2O and DIC-TMG biguanide is 1:0.4-1.3.

[0009] Wherein, the molecular sieve MFI is a microporous MFI molecular sieve (C-MIF) or a multi-level porous MFI molecular sieve. In the present invention, the microporous MFI molecular sieve is a common MFI molecular sieve, represented by C-MIF, which is mainly prepared by hydrothermal synthesis using tetraethyl orthosilicate (TEOS) as a silicon source and tetrapropylammonium hydroxide (TPAOH) as a microporous template.

[0010] In the present invention, the multi-level pore MIF molecular sieve is represented by H-MIF, and the H-MFI is a "coal ball type", which is an MFI type molecular sieve with a three-dimensional ordered macropore-mesopore-micropore multi-level pore structure. Preferably, the macropore diameter of the H-MFI is about 450-550nm, the average pore diameter is 2-2.5nm, and the specific surface area is 380-450m 2 / g, pore volume is 0.28-0.42cm 3 / g. H-MFI is mainly synthesized by steam-assisted crystallization method using mesoporous silica particles (MSP) as silicon source and template for macropore formation, TPAOH as microporous template and etchant. Preferably, the particle size of the MSPs is 240-260nm, and the specific surface area is 321-348m 2 / g, pore volume is 0.12-0.14cm 3 / g.

[0011] Further, the synthesis method of H-MFI includes: mixing a TPAOH solution with a concentration of 30-50wt% and MSP in a crucible, placing the crucible containing the TPAOH solution and MSP in a hydrothermal kettle containing deionized water by a steam-assisted crystallization method, and reacting at 100-120°C for 60-84h; then washing, filtering and drying at 60-80°C, and finally calcining at 500-600°C for 4-8h to obtain a multi-level porous carrier material H-MFI; wherein the mass ratio of the TPAOH solution to the MSP is 1:1.1-1.5. If the calcination temperature of the H-MFI carrier precursor is too low and the calcination time is too short, the precursor will not be completely decomposed; if the calcination temperature is too high and the calcination time is too long, it is easy to cause multi-level structure destruction. Therefore, preferably, the calcination temperature of the H-MFI carrier precursor is 500-600°C and the calcination time is 4-8h.

[0012] The MSP synthesis method comprises: adding hexadecyltrimethylammonium bromide (CTAB) to an ethanol-water solution, stirring and dissolving; then adding an ammonia solution with a concentration of 25-30wt%, stirring for 1-2h; then adding tetraethyl orthosilicate (TEOS), and continuing to stir at room temperature for 1-2h; after the reaction is completed, centrifugation and drying, and then calcining at 500-600°C for 6-8h to obtain MSP, wherein the volume ratio of ethanol to water in the ethanol-water solution is 1:3-4. The molar ratio of TEOS, NH3, CTAB, EtOH, and H2O is 1:20-22:0.15-0.2:520-550:560-600.

[0013] Furthermore, the preparation method of the bifunctional molecular sieve catalytic material comprises the steps of:

[0014] Preparation of ZrO2 / MFI: Using molecular sieve MFI and ZrO(NO3)2·xH2O as raw materials, calcining at 500-600°C for 4-8h to obtain molecular sieve MFI loaded with ZrO2, expressed as ZrO2 / MFI;

[0015] Preparation of target catalytic material: firstly, using ZrO2 / MFI and 3-chloropropyltriethoxysilane as raw materials, chloropropyl-functionalized ZrO2 / MFI is prepared; then, using chloropropyl-functionalized ZrO2 / MFI and DIC-TMG as raw materials, the target catalytic material DIC-TMG / ZrO2 / MFI is prepared by covalent grafting.

[0016] The steps of preparing ZrO2 / MFI include: using an impregnation method to immerse the molecular sieve MFI in a ZrO(NO3)2·xH2O solution to obtain a MFI porous material loaded with ZrO(NO3)2·xH2O; calcining the MFI porous material loaded with ZrO(NO3)2·xH2O at 500-600°C for 4-8h to obtain the porous material ZrO2 / H-MFI. The mass ratio of the molecular sieve MFI to the ZrO(NO3)2·xH2O solid is 1:0.2-0.4. The mass ratio of ZrO(NO3)2·xH2O to water in the ZrO(NO3)2·xH2O solution is 1:12-18.

[0017] The step of preparing the target catalytic material includes: firstly preparing a chloropropyl functionalized ZrO2 / MFI molecular sieve using 3-chloropropyltriethoxysilane and ZrO2 / MFI as raw materials, and then covalently grafting DIC-TMG onto the chloropropyl functionalized ZrO2 / MFI using the chloropropyl functionalized ZrO2 / MFI molecular sieve and the organic biguanide DIC-TMG as raw materials, so as to obtain the target catalytic material DIC-TMG / ZrO2 / MFI. The molecular sieve MFI and DIC-TMG solid mass ratio is 1:0.1-0.35. The organic biguanide DIC-TMG is synthesized using N,N'-diisopropylcarbodiimide (DIC) and 1,1,3,3-tetramethylguanidine (TMG) as raw materials.

[0018] The chloropropyl functionalized ZrO2 / MFI molecular sieve contains a bonded silane coupling agent, and its preparation method comprises: placing 3-chloropropyltriethoxysilane and molecular sieve MFI into anhydrous toluene, refluxing for 20-28 hours under a nitrogen environment, filtering the mixture after the reaction is completed, washing with toluene, and drying at 45-55°C for 5-7 hours.

[0019] The step of covalent grafting of DIC-TMG comprises: under the catalysis of sodium methoxide, DIC-TMG and the chloropropyl functionalized ZrO2 / H-MFI are refluxed at 105-115°C for 20-28h in a nitrogen environment, after the reaction is completed, the reaction mixture is filtered and washed with toluene, and then dried at 75-85°C for 10-14h; then the dried reaction mixture is Soxhlet extracted with a mixed solution of ether / dichloromethane for 5-7h, and then dried at 45-55°C for 3.5-4.5h to obtain the target catalytic material DIC-TMG / ZrO2 / MFI. Among them, the amount of sodium methoxide is preferably 18-22% of the mass of ZrO2 / H-MFI.

[0020] The preparation method of the DIC-TMG biguanide compound comprises: refluxing N,N'-diisopropylcarbodiimide (DIC) and 1,1,3,3-tetramethylguanidine (TMG) at 105-115° C. for 20-28 hours.

[0021] The second aspect of the present invention provides a bifunctional molecular sieve catalytic material prepared by the above method, represented by DIC-TMG / ZrO2 / MFI, comprising a molecular sieve MFI and an active component loaded on the molecular sieve MFI, wherein the active component comprises ZrO2 and DIC-TMG.

[0022] The above-mentioned dual-functional molecular sieve catalytic material DIC-TMG / ZrO2 / MFI has a multi-level pore structure and a surface area of ​​145-182m 2 / g, average pore diameter 2-5.2nm, pore volume 0.10-0.16cm 3 Preferably, when the molecular sieve MFI is H-MFI, the bifunctional molecular sieve catalytic material DIC-TMG / ZrO2 / H-MFI has a macroporous-mesoporous-microporous multi-level pore structure with a surface area of ​​159-182 m 2 / g, macropore diameter 450-550nm, average pore diameter 2.3-4nm, pore volume 0.12-0.16cm 3 / g.

[0023] The third aspect of the present invention provides an application of the above-mentioned bifunctional molecular sieve catalytic material DIC-TMG / ZrO2 / MFI in catalyzing oil to produce biofuel. Further, the application of the bifunctional molecular sieve catalytic material in catalyzing oil to synthesize biofuel under normal pressure. Among them, the oil described in the present invention can be pure oil or waste oil, and the pure oil includes vegetable oil, animal oil, etc. The vegetable oil can be soybean oil, peanut oil, melon seed oil, rapeseed oil, cottonseed oil, jatropha seed oil, etc. The waste oil described in the present invention has a moisture content of 0-3wt.%, and a free fatty acid content of 0-4wt.%; the waste oil can be waste frying oil, waste kitchen oil, waste rancid oil, etc. Preferably, the amount of the multi-level porous catalytic material DIC-TMG / ZrO2 / MFI is 4-8wt.% of the mass of the oil.

[0024] The fourth aspect of the present invention provides a method for preparing biodiesel, comprising using oil and methanol as raw materials, using the multi-level porous catalytic material DIC-TMG / ZrO2 / MFI as a catalyst, and preparing biodiesel at a temperature not higher than 65° C. and normal pressure. The amount of the catalytic material DIC-TMG / ZrO2 / MFI added is 4-8wt.% of the mass of the oil, such as 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, etc. Preferably, the moisture content in the oil is 0-2.4wt%, such as 0, 0.5wt%, 1wt%, 1.2wt%, 1.4wt%, 1.6wt%, 1.8wt%, 2wt%, 2.2wt%, 2.4wt% and the like; the acid value is preferably 0-2.4mg(KOH) / g, such as 0, 0.5mg(KOH) / g, 1mg(KOH) / g, 1.5mg(KOH) / g, 2.0mg(KOH) / g, 2.1mg(KOH) / g, 2.2mg(KOH) / g, 2.3mg(KOH) / g, 2.4mg(KOH) / g.

[0025] The above technical solution provided by the present invention has the following advantages:

[0026] (1) The bifunctional molecular sieve catalytic material DIC-TMG / ZrO2 / MFI has a porous structure and a high specific surface area, especially DIC-TMG / ZrO2 / H-MFI with H-MFI as the carrier also has a macropore-mesopore-micropore multi-level pore structure and an excellent specific surface area. The macropores are conducive to the transfer and diffusion of oil reactants and products, reducing carbon accumulation; and it has acid / base dual catalytic sites, showing a synergistic catalytic effect, so that the catalytic activity of the bifunctional molecular sieve catalytic material is significantly improved;

[0027] (2) The active components ZrO2 and DIC-TMG in the bifunctional molecular sieve catalytic material DIC-TMG / ZrO2 / MFI are evenly distributed on the molecular sieve MFI carrier, have acid / base dual catalytic active centers, and have strong acidity and strong alkalinity; have good water resistance and acid resistance, can synergistically catalyze triglyceride transesterification and free fatty acid esterification reactions, and can also convert low-quality waste oil into biofuels in one pot at normal pressure and low temperature. It is a promising, environmentally friendly solid acid-base bifunctional catalyst;

[0028] (3) Compared with solid base catalysts, the solid acid-base bifunctional catalyst has better acid and water resistance and has the ability to catalyze transesterification and esterification reactions at the same time; compared with solid acid catalysts, the solid acid-base bifunctional catalyst has higher catalytic oil transesterification activity, and can undergo transesterification reaction under normal pressure and mild conditions (not higher than 65° C.) to prepare biodiesel, with mild reaction conditions and an oil conversion rate of up to 97.04%;

[0029] (4) The bifunctional molecular sieve catalytic material DIC-TMG / ZrO2 / MFI has good recyclability as a catalyst for catalyzing oil to produce biofuel.

[0030] Therefore, the entire production process of producing biofuels using oil and methanol as raw materials using the above-mentioned dual-functional molecular sieve catalytic material DIC-TMG / ZrO2 / MFI provided by the present invention has the characteristics of mild reaction conditions, safety, high yield, short process, simplified process, and green process, and has good prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 XRD patterns of the microporous carrier C-MFI, the multi-level porous carrier H-MFI, ZrO2 / H-MFI and the bifunctional molecular sieve catalytic material DIC-TMG / ZrO2 / H-MFI with different organic biguanide loadings provided in Example 1 of the present invention;

[0032] Figure 2 SEM images of MSP (a), H-MFI (b) and bifunctional molecular sieve catalytic material 0.48DIC-TMG / ZrO2 / H-MFI (c) provided in Example 1 of the present invention; EDS spectrum of bifunctional molecular sieve catalytic material 0.48DIC-TMG / ZrO2 / H-MFI (d);

[0033] Figure 3TEM images of the H-MFI carrier (a, b) and the bifunctional molecular sieve catalytic material 0.48DIC-TMG / ZrO2 / H-MFI (c, d) provided in Example 1 of the present invention; Mapping image of the bifunctional molecular sieve catalytic material 0.48DIC-TMG / ZrO2 / H-MFI;

[0034] Figure 4 N2 adsorption-desorption curve diagram of the H-MFI carrier and the bifunctional molecular sieve catalytic material 0.48DIC-TMG / ZrO2 / H-MFI provided in Example 1 of the present invention;

[0035] Figure 5 NH3-TPD (a) and CO2-TPD (b) spectra of the H-MFI carrier and the bifunctional molecular sieve catalytic material 0.48DIC-TMG / ZrO2 / H-MFI provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described in detail below through specific implementation methods.

[0037] The terms used in the present invention are all commonly used terms in the relevant field. The raw materials, equipment, preparation processes, testing methods, etc. used, unless otherwise specified, are all existing technologies or common knowledge and conventional conditions in the relevant field.

[0038] The measurement method used in each embodiment is as follows:

[0039] XRD test: Determined by using German Rigaku D / MAX-3B X-ray diffractometer. Test conditions: Incident wavelength Voltage 40kV, current 20mA, scanning rate 10° / min -1 .

[0040] SEM and EDS test: A German ZEISS Sigma 300 scanning electron microscope was used to observe and analyze the catalyst morphology (size, pore size, particle size and morphology, etc.). An American Thermo ESCALAB 250XI X-ray energy spectrometer was used to analyze the samples and determine the types and contents of elements in the sample micro-area.

[0041] TEM test: A Japanese JEOL JEM-F200 transmission electron microscope (TEM) was used to analyze and observe the catalyst morphology and particle size distribution. Before the test, the sample must be prepared. The solid powder is evenly dispersed in the ethanol solvent by ultrasound, and then a drop of sample solution is dropped on the TEM copper grid and dried at room temperature to evaporate the solvent.

[0042] BET specific surface area test: The specific surface area and pore size distribution of the sample were determined by nitrogen adsorption-desorption at 120°C for 8 hours using the Micromeritics ASAP 2460 fully automatic specific surface and porosity analyzer. After the determination, the BET formula was used to calculate the specific surface area of ​​the sample based on the experimental data, and the pore volume and pore size distribution were calculated using the BJH method.

[0043] TPD test: Xianquan Tp-5080 programmed temperature desorber was used to characterize and analyze the acid content of the sample. The sample was first pretreated in helium (30mL / min) at a rate of 10℃ / min to 200℃ for 1h, then cooled to the adsorption temperature of 50℃. After the temperature stabilized, the carrier gas / reference gas was switched to the adsorption gas, and adsorbed at a flow rate of 30mL / min for 1h. The carrier gas was then switched to helium (30mL / min) and purged for 1h. After the baseline was stable, the temperature was raised to 600℃ at a rate of 10℃ / min for chemical desorption, and the desorbed chemically absorbed NH3 or CO2 was recorded by the TCD detector.

[0044] Triglyceride conversion rate (oil conversion rate) determination: Agilent 7890N gas chromatography was used for determination, and the detector was an FID detector. In this method, methyl heptadecanoate was used as the internal standard, n-hexane was used as the solvent, and fatty acid methyl esters were determined based on the retention time of the reference standard. The oil conversion rate was calculated according to the following formula:

[0045]

[0046] In the formula, X ME is the oil conversion rate, ∑A ME It can be defined as the total peak integrated area of ​​oil. As represents the peak integrated area of ​​the internal standard, Vs represents the volume of the internal standard, unit: mL; Cs represents the concentration of the internal standard, unit: mg / mL; m represents the mass of the sample, unit: mg.

[0047] Example 1-3 Dual-functional multi-level pore molecular sieve catalytic material DIC-TMG / ZrO2 / H-MFI

[0048] Examples 1-3 respectively provide a bifunctional molecular sieve catalytic material and a preparation method thereof, which preparation method mainly includes the steps of synthesis of mesoporous silica particles (MSP), preparation of H-MFIH-MFI carrier, preparation of multi-level pore molecular sieve ZrO2 / H-MFI and preparation of bifunctional multi-level pore molecular sieve DIC-TMG / ZrO2 / H-MFI.

[0049] S1. MSP synthesis: CTAB was dissolved in an ethanol-water solution under vigorous stirring, stirred to dissolve, and then ammonia water was added. After stirring for 1 hour at room temperature, TEOS was added to form a mixed solution with a molar composition of 1TEOS:21NH3:0.18CTAB:540EtOH:584H2O (molar ratio). The solution was further stirred for 2 hours at room temperature. Then, a white precipitate was obtained by centrifugation and dried at 75°C overnight. Finally, the obtained solid was calcined at 550°C for 6 hours to remove CTAB, generating 4.46g of MSP. In this embodiment, the volume ratio of ethanol to water in the ethanol-water solution is 1:3.5.

[0050] S2. Preparation of H-MFIH-MFI carrier: 34g of 40wt% TPAOH solution and 25g MSP were mixed evenly in a crucible, and after being completely dried, they were transferred to a hydrothermal reactor filled with 2400mL deionized water and reacted at 110°C for 72h. After the reaction was completed, it was cooled to room temperature, and the solid product was recovered by filtration, washed with deionized water, and dried at 75°C overnight. Finally, it was calcined at 550°C for 4h to remove the TPAOH therein, and 12g of a multi-level porous carrier H-MFI was obtained. The macropore diameter of the H-MFIH-MFI carrier was 500nm, the average pore diameter was 2.3nm, and the specific surface area was 420.85m 2 / g, pore volume 0.36cm 3 / g.

[0051] S3. Preparation of multi-level porous molecular sieve ZrO2 / H-MFI: First, the metal oxide is grafted onto the multi-level porous carrier by calcination to synthesize the multi-level porous molecular sieve ZrO2 / H-MFI. Specifically, ZrO(NO3)2·xH2O of the mass shown in Table 1 is slowly added to an appropriate amount of water as a precursor of zirconium oxide. After dissolution, a ZrO(NO3)2·xH2O solution is formed. The mass ratio of ZrO(NO3)2·xH2O to water in the ZrO(NO3)2·xH2O solution is 1:15; 1gH-MFIH-MFI carrier is added to the ZrO(NO3)2·xH2O solution. After stirring at 60°C for 3h, dry in an oven at 110°C for 12h. Then, place it in a muffle furnace and calcine it at 550°C for 6h to obtain ZrO2 / H-MFI.

[0052] Secondly, prepare chloropropyl functionalized ZrO2 / H-MFI molecular sieve. Specifically, 0.1 mol of 3-chloropropyltriethoxysilane and 1 g of H-MFI molecular sieve are placed in 30 mL of anhydrous toluene and refluxed for 24 hours under a nitrogen environment. After the reaction is completed, the mixture is filtered, washed with toluene, and dried at 50°C for 6 hours to prepare a chloropropyl functionalized multi-level pore molecular sieve ZrO2 / H-MFI with a bonded silane coupling agent.

[0053] S4. Preparation of target catalytic material DIC-TMG / ZrO2 / H-MFI: The organic biguanide DIC-TMG is fixed on the ZrO2 / H-MFI molecular sieve by condensation of biguanide and chloropropyl.

[0054] Specifically, 0.1 mol N,N'-diisopropylcarbodiimide (DIC) and 0.1 mol 1,1,3,3-tetramethylguanidine (TMG) were placed in a three-necked flask and refluxed at 110°C for 24 hours to obtain a DIC-TMG biguanide compound. Then, the DIC-TMG biguanide prepared above was placed in a certain amount of toluene together with a chloropropyl-functionalized ZrO2 / H-MFI with a bonded silane coupling agent and a sodium methoxide catalyst with a mass percentage of 20% of ZrO2 / H-MFI according to the dosage shown in Table 1, and refluxed at 110°C for 24 hours under nitrogen protection. After the reaction was completed, the reaction mixture was filtered and washed with toluene, and then dried at 80°C for 12 hours. Finally, the dried reaction mixture was Soxhlet extracted with a mixed solution of ether / dichloromethane (volume ratio of 1:1) for 6 hours, and then dried at 50°C for 4 hours to obtain a new acid-base bifunctional molecular sieve catalytic material, yDIC-TMG / ZrO2 / H-MFI, where "y" represents the mass ratio of the total mass of the raw materials ZrO(NO3)2·xH2O and DIC-TMG to the corresponding MFI carrier during the preparation of the bifunctional molecular sieve catalytic material DIC-TMG / ZrO2 / H-MFI.

[0055] Table 1 Raw material ratio of catalytic material DIC-TMG / ZrO2 / H-MFI

[0056]

[0057] Example 4: Dual-functional molecular sieve catalytic material DIC-TMG / ZrO2 / C-MFI

[0058] This embodiment is a bifunctional molecular sieve catalytic material 0.48DIC-TMG / ZrO2 / C-MFI and a preparation method thereof. The preparation method is basically the same as that of Example 1, and the main difference is that this embodiment uses ordinary microporous molecular sieve C-MFI to replace the multi-level pore structure H-MFI carrier in step S3 of Example 1, and other methods and parameters are the same. Among them, C-MFI in this embodiment is prepared by hydrothermal synthesis, and the specific steps are: adding 20g of TEOS to a solution containing 21.3g of TPAOH and 25g of deionized water under stirring, and stirring the resulting mixture for 4h to obtain a colloidal solution with a molar composition of: 1SiO2:4.5TPAOH:28.8H2O (molar ratio); stirring the synthetic mixture at room temperature for 1h, and then crystallizing it under static conditions at 175°C in a hydrothermal reactor for 48h. Then, the solid product is recovered by centrifugation, washed with deionized water and ethanol, and dried overnight at 80°C to obtain C-MFI.

[0059] Comparative Example 1-2

[0060] Comparative Example 1 provides a 0.48ZrO2 / H-MFI multilevel porous material, which is prepared by a method substantially the same as that of the 0.48DIC-TMG / ZrO2 / H-MFI multilevel porous material provided in Example 1. The main difference is that this comparative example does not have step S4, i.e., the step of loading DIC-TMG.

[0061] Comparative Example 2 provides a 0.48DIC-TMG / H-MFI multilevel porous material, which is basically the same as the preparation method of the 0.48DIC-TMG / ZrO2 / H-MFI multilevel porous material provided in Example 1, the main difference being that: this comparative example does not have step S3, and step S4 of this comparative example is: 0.1 mol N,N'-diisopropylcarbodiimide (DIC) and 0.1 mol 1,1,3,3-tetramethylguanidine (TMG) are placed in a three-necked flask, refluxed at 110°C for 24 hours under a nitrogen atmosphere, to obtain a DIC-TMG biguanide compound; then the prepared DIC-TMG biguanide, H-MFI carrier and a small amount of sodium methoxide are placed in a certain amount of toluene, and refluxed for 24 hours under nitrogen protection. Then the reaction mixture is Soxhlet extracted with a mixed solution of ether / dichloromethane (volume ratio 1:1) for 6 hours. Then, after drying at 50°C for 4 h, DIC-TMG / H-MFI was obtained.

[0062] Application Test 1 Application of Dual-Functional Molecular Sieve Catalytic Materials in Oil-to-Biofuel Conversion

[0063] In order to study the catalytic performance of the above catalytic materials in the conversion of oil to biodiesel, this experiment provides an application of a catalytic material in the conversion of oil to biodiesel. The specific method includes: using soybean oil and methanol as raw materials, the conversion of soybean oil to biodiesel is carried out in a 1000mL round-bottom flask equipped with a reflux condenser and a magnetic stirrer, 200g soybean oil and 220g methanol are added to the round-bottom flask, and then 6wt.% of the catalytic material of soybean oil mass is added respectively, and the reaction is stirred at 65°C for 3h, and the stirring speed is 500rpm. After the reaction is completed, it is cooled to room temperature, the catalyst is filtered, and the excess methanol is evaporated under reduced pressure. Then, glycerol is separated by centrifugation, and the oil conversion rate of the product is detected by gas chromatography. The biodiesel conversion rate is shown in Table 2.

[0064] The catalytic materials used in this experiment are respectively the catalytic materials prepared in Examples 1-4, the H-MFI and DIC-TMG used in Example 1, the molecular sieve C-MFI used in Example 4, and the catalytic materials prepared in Comparative Examples 1-2.

[0065] Table 2 Conversion rate of soybean oil catalyzed by different porous materials

[0066]

[0067] As can be seen from Table 2, H-MFI and C-MFI carrier materials have almost no catalytic activity. The homogeneous DIC-TMG active ingredient can produce an oil conversion rate of 88.69%. Using the catalytic materials prepared in Examples 1-4 and Comparative Examples 1-2, the H-MFI and DIC-TMG catalytic materials used in Example 1, and the molecular sieve C-MFI in Example 4 as catalysts, the results of the catalytic soybean oil conversion rate show that the multi-level porous catalytic material DIC-TMG / ZrO2 / MFI provided in the example has a high catalytic activity, and the active components ZrO2 and DIC-TMG have a synergistic catalytic effect, which can achieve efficient synthesis of biodiesel at low temperatures, mild reaction conditions, and an oil conversion rate of more than 91%.

[0068] Judging from the oil conversion rates of Examples 1-3, the oil conversion rate in the multi-level porous catalytic material first increases with the increase in the amount of DIC-TMG used, reaches a maximum when the mass ratio of the total mass of hydrated zirconium oxynitrate and DIC-TMG to the mass ratio of H-MFI is 0.48, and then its catalytic activity decreases.

[0069] From the oil conversion rates of Examples 1 and 4, the catalyst activity of the single pore structure C-MFI loaded with active components is lower than that of H-MFI, and its oil conversion rate is significantly lower than that of the multi-level porous catalytic material 0.48DIC-TMG / ZrO2 / H-MFI provided in Example 1. This shows that the macropore-mesopore-micropore structure in the multi-level porous molecular sieve H-MFI used in the example has a significant effect on improving the catalytic performance of the catalytic material in the process of converting oil to biofuel.

[0070] From the oil conversion rates of Example 1 and Comparative Examples 1-2, ZrO2@H-MFI and DIC-TMG / H-MFI with a single active center showed lower catalytic activity in the process of low-temperature biodiesel synthesis.

[0071] The above conclusions are further verified from the perspective of microstructure. (1) XRD analysis

[0072] In order to confirm the crystal structure of the DIC-TMG / ZrO2 / H-MFI multi-level porous catalytic material, the molecular sieve C-MFI prepared in Example 4, the H-MFIH-MFI carrier prepared in Example 1, the ZrO2 / H-MFI provided in Comparative Example 1, and the 0.48DIC-TMG / ZrO2 / H-MFI provided in Example 1, the 0.37DIC-TMG / ZrO2 / H-MFI provided in Example 2, and the 0.59DIC-TMG / ZrO2 / H-MFI provided in Example 3 were subjected to XRD analysis. The results are as follows: Figure 1 shown.

[0073] The crystal structure of the catalysts prepared under different conditions was studied by XRD analysis. Figure 1It can be seen that in the X-ray diffraction pattern, sharp diffraction peaks appear at the characteristic peaks of the H-MFI topological structure at 2θ=8°, 8.8°, 13.9°, 14.8°, 23.3°, 24° and 24.4°, which are completely consistent with the diffraction peaks of the (011), (200), (102), (301), (051), (033) and (133) crystal planes (JCPDS 00-044-0696) of the standard MFI. After the introduction of the Zr element, the characteristic peaks corresponding to the structure of ZrO2 (JCPDS 00-049-1642) appear at 2θ=30.1°(111) and 35°(200), indicating the presence of ZrO2 compounds. In addition, after the organic biguanide DIC-TMG is further introduced, the XRD spectrum does not change much. However, compared with H-MFI, the crystal diffraction peak of the catalyst sample after loading biguanide shifted slightly to the left, and the peak height decreased slightly, which may be due to the reduction in pore size. The characteristic diffraction peaks mentioned above can be detected in the XRD spectra of all samples, which is attributed to the unique two-dimensional hexagonal pore structure of MFI molecular sieve. After loading ZrO2 and biguanide, the two-dimensional hexagonal pore structure of H-MFI is well preserved.

[0074] The above XRD results show that metal oxide ZrO2 and biguanide compound DIC-TMG are loaded on H-MFIH-MFI. The simultaneous introduction of ZrO2 and DIC-TMG on the carrier makes the generated catalyst acidic and alkaline and bifunctional, which is suitable for the one-step conversion of low-quality oil into biofuels under normal pressure and mild conditions.

[0075] (2) Scanning electron microscopy (SEM) and EDS spectral analysis

[0076] The SEM analysis of MSP nanoparticles, H-MFIH-MFI carrier and multi-level porous catalytic material 0.48DIC-TMG / ZrO2 / H-MFI was carried out. Figure 2 As shown. The calcined MSP nanoparticles are uniformly spherical with a diameter of about 500nm ( Figure 2 a). Figure 3 (b) and Figure 3 (c) The macroporous structure of the H-MFI support and the 0.48DIC-TMG / ZrO2 / H-MFI catalyst can be clearly observed. There is almost no difference in the SEM images between H-MFI and 0.48DIC-TMG / ZrO2 / H-MFI, and both samples have a "coal ball-like" multi-level pore structure. These results show that the catalyst preparation process has no obvious effect on the macroporous morphology of the 0.48DIC-TMG / ZrO2 / H-MFI catalyst. Compared with the conventional catalyst C-MFI, the multi-level structure catalyst H-MFI significantly reduces the oil mass transfer resistance and increases the oil conversion rate.

[0077] The EDS analysis of the catalytic material 0.48DIC-TMG / ZrO2 / H-MFI was performed, and the results were as follows: Figure 3 (d). The mass percentages of C, N, O, Si and Zr elements in the catalytic material 0.48DIC-TMG / ZrO2 / H-MFI are 16.84%, 6.42%, 52.41%, 10.52% and 13.82%, respectively, indicating that the metal zirconium and biguanide are successfully immobilized on the H-MFI carrier. According to elemental analysis, the mass percentage of zirconium content is 13.82%, which is almost consistent with the addition amount of the initial precursor ZrO(NO3)2·xH2O (14%). Through EDS analysis, it can be calculated that the mass percentage of the active component DIC-TMG relative to the loading amount of the H-MFI carrier is approximately 22%, which is consistent with the theoretical addition value of DIC-TMG in Example 1 (22%).

[0078] (3) Transmission electron microscopy (TEM) characterization

[0079] In order to further confirm the structure of the multi-level porous catalytic material 0.48DIC-TMG / ZrO2 / H-MFI, TEM was used to characterize it. The results are as follows Figure 3 shown. Figure 3 (a, b) are transmission electron micrographs of H-MFIH-MFI. It can be clearly seen that the H-MFIH-MFI carrier has abundant macropores, and the pore structure is evenly arranged with almost the same pore size. Figure 3 (c, d) are TEM images of the multi-level porous catalytic material 0.48DIC-TMG / ZrO2 / H-MFI. It can be seen that after the introduction of the active center ZrO2 and DIC-TMG, the multi-level porous structure of H-MFIH-MFI is well preserved and not destroyed, so that the multi-level porous catalytic material 0.48DIC-TMG / ZrO2 / H-MFI also has a three-dimensional multi-level porous structure. In addition, the element mapping (Mapping) of 0.48DIC-TMG / ZrO2 / H-MFI shows that Si, O, C, N, and Zr are evenly distributed in the catalyst, further confirming that ZrO2 and DIC-TMG are successfully immobilized in the multi-level porous carrier H-MFI. The rich pore size structure and large specific surface area of ​​the multi-level porous catalytic material can effectively reduce the mass transfer resistance of the transesterification reaction and improve the catalytic activity.

[0080] (4) N2 adsorption-desorption measurement

[0081] The H-MFI multi-level porous carrier and the multi-level porous catalytic material DIC-TMG / ZrO2 / H-MFI provided in Examples 1-3 were subjected to nitrogen adsorption-desorption measurements. The results are as follows: Figure 4As shown. The N2 adsorption isotherm curves of the samples confirmed their porous characteristics. All samples had an adsorption tendency and showed a mixed type I and type IV curve, indicating the presence of micropores and mesopores in the samples. The inclined and obvious hysteresis loops in the region of 0.4 < P / P0 < 0.9 were attributed to the adsorption of N2 in the mesopores and macropores of the samples. Especially after P / P0 > 0.9, obvious hysteresis loops appeared in the isotherms of the support H-MFI and the catalyst 0.48DIC-TMG / ZrO2 / H-MFI, and their pore size distributions showed an obvious macropore distribution. With the increase of the organic guanidine loading, the N2 adsorption-desorption performance of the catalyst decreased, indicating that the ZrO2 particles and organic guanidine supported on the zeolite blocked the pore space. The specific surface area of the hierarchical pore catalytic material DIC-TMG / ZrO2 / H-MFI was 159 - 182 m 2 / g, the pore volume was 0.12 - 0.16 cm 3 / g, and the average pore size was 3.1 - 3.4 nm.

[0082] (5) TPD analysis

[0083] The acidity and acid strength of the H-MFI support and the 0.48DIC-TMG / ZrO2 / H-MFI catalyst were detected by NH3-TPD. As can be seen from Figure 4 (a), the acid amount of the H-MFI support was 0.049 mmol / g in the temperature range of 50 - 210 °C; the acid amount was 0.133 mmol / g in the temperature range of 210 - 440 °C. The 0.48DIC-TMG / ZrO2 / H-MFI catalyst had a weak NH3 desorption peak in the temperature range of 50 - 280 °C, corresponding to the weak acid sites of the catalyst, and the acid amount was 0.182 mmol / g; in the temperature range of 280 - 530 °C, corresponding to the strong acid sites of the catalyst, and the acid amount was 0.219 mmol / g at this time. After introducing the metal oxide ZrO2 into H-MFI, the strength of the acidic sites of the catalytic material was significantly improved. The basic properties of the H-MFI support and the 0.48DIC-TMG / ZrO2 / H-MFI catalytic material were studied by CO2-TPD. As can be seen from Figure 4 (b), the base amount of the H-MFI support was 0.022 mmol / g in the temperature range of 50 - 210 °C; the base amount was 0.091 mmol / g in the temperature range of 210 - 440 °C. Introducing the organic guanidine group could improve the basic properties of the catalyst. The desorption peak of the 0.48DIC-TMG / ZrO2 / H-MFI catalyst in the temperature range of 50 - 260 °C corresponded to the weak basic sites of the surface CO2, and the base amount was 0.288 mmol / g; the desorption peak in the temperature range of 260 - 490 °C was for the medium and strong basic sites, and the base amount was 0.562 mmol / g. The above characterization results further indicated that the DIC-TMG / ZrO2 / H-MFI catalytic material had stable acid-base bifunctional active sites.

[0084] In short, the multi-level porous catalytic material DIC-TMG / ZrO2 / H-MFI provided in the embodiment of the present invention uses H-MFIH-MFI as a carrier. The micropores and mesopores in the multi-level porous structure of H-MFI can increase the specific surface area and pore volume of the catalyst, providing more reaction sites and interface area; the macropores can improve the mass transfer efficiency of oil macromolecules, reduce their transmission distance in mesopores or micropores, and greatly reduce the diffusion restriction of materials. Compared with the ordinary microporous material C-MFI, the H-MFI carrier has the advantages of high surface area and low mass transfer resistance in catalyzing oil transesterification reaction, which can significantly improve the efficiency of oil transesterification reaction.

[0085] Application test 2 Application of dual-functional multi-level pore molecular sieve catalytic material DIC-TMG / ZrO2 / MFI in simulating low-quality waste oil conversion into biofuel at low temperature

[0086] In order to explore the effects of free fatty acids (FFA) and water content on the transesterification activity of oils, different amounts of oleic acid were added to soybean oil to simulate low-quality waste oil, wherein the FFA and water content in oleic acid were 0-4wt.% and water 0-3wt.%, respectively. This experiment used simulated low-quality waste oil and methanol as raw materials, and carried out biodiesel conversion in a 1000mL round-bottom flask equipped with a reflux condenser and a magnetic stirrer. 200g of simulated low-quality waste oil and 220g of methanol were added to the round-bottom flask, and then 0.48DIC-TMG / ZrO2 / H-MFI multi-stage porous catalytic material provided in Example 1 with a mass of 6wt% of simulated low-quality oil was added as a catalyst, and the reaction was stirred at normal pressure and 65°C for 3h, with a stirring speed of 500rpm. After the reaction was completed, it was cooled to room temperature, the catalyst was filtered, and the excess methanol was evaporated under reduced pressure. Then, glycerol was separated by centrifugation, and the product was tested for the conversion rate of fatty acid methyl esters by gas chromatography. The main impurity composition of the simulated oil and the biofuel conversion rate are shown in Table 3. The FFA content in the simulated oil samples 1-5 is 0.8wt%, and the water content in the simulated oil samples 6-10 is 0.6wt%.

[0087] Table 3 Application of DIC-TMG / ZrO2 / H-MFI catalytic materials in the conversion of low-quality oil to biofuels

[0088] Simulated oil samples Moisture Oil conversion rate Simulated oil samples FFA Oil conversion rate 1 0.6％ 94.42％ 6 0.8％ 93.9％ 2 1.2％ 93.9％ 7 1.6％ 87.12％ 3 1.8％ 88.95％ 8 2.4％ 81.38％ 4 2.4％ 84.51％ 9 3.2％ 75.65％ 5 3.0％ 81.12％ 10 4.0％ 67.82％

[0089] It can be seen from Table 3 that, under the same conditions, as the water content increases, the catalytic activity of the DIC-TMG / ZrO2 / H-MFI catalytic material in catalytic synthesis of biodiesel at low temperature decreases, and the oil conversion rate gradually decreases; but when the water content is 3.0%, the DIC-TMG / ZrO2 / H-MFI catalytic material can still catalytically synthesize biodiesel at low temperature, and the oil conversion rate reaches more than 80%. In addition, under the same conditions, as the FFA content increases, the catalytic activity of the DIC-TMG / ZrO2 / H-MFI catalytic material in catalytic synthesis of biodiesel at low temperature also gradually decreases, and the oil conversion rate gradually decreases; but when the FFA content is 2.4%, the oil conversion rate of low-temperature synthesis of biodiesel using the catalytic material DIC-TMG / ZrO2 / H-MFI can still reach 81.38%.

[0090] Therefore, the catalytic material DIC-TMG / ZrO2 / H-MFI provided in the embodiment of the present invention has higher catalytic activity than the multiphase solid acid catalyst, and can obtain higher oil conversion rate at lower reaction temperature. Compared with the multiphase solid base catalyst, the DIC-TMG / ZrO2 / H-MFI catalytic material has higher acid and alkali resistance. The solid base catalysts such as DIC-TMG and DIC-TMG / H-MFI are deactivated and have no catalytic activity under the simulated oil FFA and water content conditions of this application test.

[0091] Application test 3 Application of bifunctional molecular sieve catalytic material DIC-TMG / ZrO2 / MFI in the conversion of waste cooking oil into biofuel

[0092] In this application test, waste cooking oil and methanol are used as raw materials, the 0.48DIC-TMG / ZrO2 / H-MFI multi-level catalytic material provided in Example 1 is used as a catalyst, and a normal pressure batch reaction is used to prepare biodiesel; its preparation method is basically the same as that of application test 2. In this application test, waste cooking oil is used instead of the simulated low-quality waste oil in application test 2, and the main impurity composition and biofuel conversion rate of the waste cooking oil are shown in Table 4.

[0093] Table 4 Application of DIC-TMG / ZrO2 / H-MFI in the conversion of waste cooking oil into biodiesel

[0094] Waste cooking oil samples Moisture Acid value (mg(KOH) / g) Oil conversion rate 1 1.2％ 1.5 92.1％ 2 1.4％ 2.1 84.3％ 3 2.6％ 2.3 76.5％ 4 2.8％ 3.0 68.2％

[0095] Application test 4: Recycling of bifunctional molecular sieve catalytic material DIC-TMG / ZrO2 / MFI in oil-to-biofuel conversion

[0096] The 0.48DIC-TMG / ZrO2 / H-MFI multilevel porous material used in Example 1 was recovered as a catalyst, washed three times with cyclohexane and methanol respectively, and then dried and the method provided in Example 1 was repeated to prepare biodiesel. The catalytic effect of the reuse is shown in Table 5.

[0097] Table 5 Oil conversion rate of DIC-TMG / ZrO2 / H-MFI catalytic material reuse

[0098] raw material Use once Use 2 times Use 3 times Use 4 times Use 5 times Soybean Oil 97.04％ 93.9％ 91.3％ 86.9％ 82.4％

[0099] As can be seen from Table 5, as the number of reuses increases, the catalytic activity of DIC-TMG / ZrO2 / H-MFI decreases. After DIC-TMG / ZrO2 / H-MFI is reused 5 times, the oil conversion rate of the catalytic oil to produce biofuel at normal pressure and low temperature is still over 80%, indicating that the catalytic material DIC-TMG / ZrO2 / MFI provided by the present invention has good reuse performance.

[0100] In the embodiment of the present invention, metal oxide ZrO2 and organic biguanide compound DIC-TMG are introduced into the molecular sieve MFI carrier by impregnation method and covalent grafting, and a porous solid acid-base bifunctional catalytic material DIC-TMG / ZrO2 / MFI with dual active centers is prepared. The heterogeneous bifunctional molecular sieve catalytic material DIC-TMG / ZrO2 / MFI with acid and base sites can not only avoid equipment corrosion and waste liquid treatment problems caused by homogeneous catalysts, but also can realize the simultaneous conversion of triglycerides and FFA into biodiesel in one reactor, thereby improving the catalytic efficiency of converting low-quality oil into biodiesel.

[0101] Furthermore, in the field of catalysis, homogeneous catalysis will encounter great difficulties for chemical processes that require both acid and base catalysis. Free movement and full contact will cause the acid and base to neutralize and lose activity. In acid-base bifunctional catalysts, the acid and base groups are each fixed in a specific position and cannot be completely free to contact, and their respective acid-base properties can be retained. Compared with existing multiphase solid acid catalysts, the bifunctional molecular sieve catalytic material DIC-TMG / ZrO2 / H-MFI provided by the present invention has higher activity and can obtain a higher oil conversion rate at normal pressure and lower reaction temperature; compared with multiphase solid base catalysts, it has higher acid and water resistance. Generally, solid base catalysts are deactivated in the presence of FFA and water and have no catalytic activity.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the specific implementation of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution claimed for protection by the present invention.

Claims

1. A method for preparing a bifunctional molecular sieve catalytic material, comprising: Using molecular sieve MFI, ZrO(NO3)2·xH2O, 3-chloropropyltriethoxysilane and DIC-TMG as raw materials, ZrO2 and DIC-TMG are grafted onto the molecular sieve MFI by calcination and covalent bonding, so as to obtain the target catalytic material DIC-TMG / ZrO2 / MFI; wherein DIC-TMG is the compound 1,2-diisopropyl-4,4,5,5-tetramethylbiguanide, and the ratio of the total mass of ZrO(NO3)2·xH2O and DIC-TMG to the mass of the molecular sieve MFI is 0.35-0.6:

1.

2. The preparation method according to claim 1, characterized in that: The mass ratio of ZrO(NO3)2·xH2O and DIC-TMG biguanide is 1:0.4-1.

3.

3. The preparation method according to claim 1 or 2, characterized in that: The molecular sieve MFI is a microporous MFI molecular sieve or a multi-level pore MIF molecular sieve; wherein the microporous MFI molecular sieve is prepared by a hydrothermal synthesis method; the multi-level pore MIF molecular sieve is a "coal ball type", which is an MFI type molecular sieve with a macropore-mesopore-micropore multi-level pore structure.

4. The preparation method according to claim 3, characterized in that: The multi-level pore MIF molecular sieve is mainly composed of mesoporous silica particles as silicon source and macroporous template agent, and tetrapropylammonium hydroxide as microporous template and etchant. The macropore diameter is 450-550 nm, the average pore diameter is 2-2.5 nm, the specific surface area is 380-450 m² / g and the pore volume is 0.28-0.42 cm 3 / g multi-level pore structure.

5. The preparation method according to claim 3, characterized in that: Includes steps: Preparation of ZrO2 / MFI: using the molecular sieve MFI and ZrO(NO3)2·xH2O as raw materials, calcining at 500-600°C for 4-8h to obtain the molecular sieve MFI loaded with ZrO2, represented by ZrO2 / MFI; Preparation of target catalytic material: firstly, using ZrO2 / MFI and 3-chloropropyltriethoxysilane as raw materials, chloropropyl-functionalized ZrO2 / MFI is prepared; then, using chloropropyl-functionalized ZrO2 / MFI and DIC-TMG as raw materials, the target catalytic material DIC-TMG / ZrO2 / MFI is prepared by covalent grafting.

6. The preparation method according to claim 5, characterized in that: The steps of preparing ZrO2 / MFI include: using an impregnation method to immerse the molecular sieve MFI in a ZrO(NO3)2·xH2O solution to obtain a MFI porous material loaded with ZrO(NO3)2·xH2O; calcining the MFI porous material loaded with ZrO(NO3)2·xH2O at 500-600°C for 4-8 h to obtain the ZrO2 / HMFI; the mass ratio of the H-MFI to the ZrO(NO3)2·xH2O solid is 1:0.2-0.

4.

7. The preparation method according to claim 5 or 6, characterized in that: The steps of preparing the target catalytic material include: firstly, using 3-chloropropyltriethoxysilane and ZrO2 / MFI as raw materials to prepare a chloropropyl functionalized ZrO2 / MFI molecular sieve, and then using the chloropropyl functionalized ZrO2 / MFI molecular sieve and DIC-TMG as raw materials to covalently graft DIC-TMG onto the chloropropyl functionalized ZrO2 / MFI, so as to obtain the target catalytic material DIC-TMG / ZrO2 / MFI; wherein the solid mass ratio of the molecular sieve MFI to DIC-TMG is 1:0.1-0.

35.

8. The preparation method according to claim 7, characterized in that: The preparation method of the chloropropyl functionalized ZrO2 / MFI molecular sieve comprises: placing 3-chloropropyltriethoxysilane and molecular sieve MFI in anhydrous toluene, refluxing for 20-28 hours under a nitrogen environment, filtering the mixture after the reaction is completed, washing with toluene, and drying at 45-55°C for 5-7 hours.

9. The preparation method according to claim 7, characterized in that: The step of covalently grafting DIC-TMG onto the chloropropyl functionalized ZrO2 / MFI comprises: under the catalysis of sodium methoxide, DIC-TMG and the chloropropyl functionalized ZrO2 / H-MFI are refluxed at 105-115°C for 20-28 hours in a nitrogen environment. After the reaction is completed, the reaction mixture is filtered and washed with toluene, and then dried at 75-85°C for 10-14 hours; then the dried reaction mixture is Soxhlet extracted with a mixed solution of ether / dichloromethane for 5-7 hours, and then dried at 45-55°C for 3.5-4.5 hours to obtain the target catalytic material DIC-TMG / ZrO2 / MFI.

10. A bifunctional molecular sieve catalytic material prepared by the preparation method according to any one of claims 1 to 9, comprising a molecular sieve MFI and an active component supported on the molecular sieve MFI, wherein: The active components include ZrO2 and DIC-TMG.

11. Use of the bifunctional molecular sieve catalytic material according to claim 10 in catalyzing oil to produce biofuel, wherein: The amount of the bifunctional molecular sieve catalytic material used is 4-8 wt.% of the mass of the oil.

12. The use according to claim 11, characterized in that: The bifunctional molecular sieve catalytic material is used in catalyzing oil to synthesize biofuel under normal pressure, wherein the oil is pure oil or waste oil, and the water content of the waste oil is 0-3 wt.%, and the free fatty acid content is 0-4 wt.%.

13. A method for preparing biodiesel, comprising using oil and methanol as raw materials, using the bifunctional molecular sieve catalytic material according to claim 10 as a catalyst, and preparing biodiesel at a temperature not higher than 65°C under normal pressure.

14. The preparation method according to claim 13, characterized in that: The addition amount of the bifunctional molecular sieve catalytic material is 4-8 wt.% of the mass of the oil, and the water content in the oil is 0-2.4 wt%, and the acid value is 0-2.4 mg (KOH) / g.

Images