CN111420661A - Bimetallic solid alkaline nano-catalyst and preparation method and application thereof - Google Patents
Bimetallic solid alkaline nano-catalyst and preparation method and application thereof Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title claims abstract description 22
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- 239000002105 nanoparticle Substances 0.000 claims abstract description 11
- 238000005809 transesterification reaction Methods 0.000 claims abstract description 10
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- 239000002127 nanobelt Substances 0.000 claims abstract description 8
- 239000011575 calcium Substances 0.000 claims description 34
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 16
- 239000002243 precursor Substances 0.000 claims description 12
- 238000003756 stirring Methods 0.000 claims description 12
- 238000001354 calcination Methods 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 10
- 238000001035 drying Methods 0.000 claims description 8
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- 229910001424 calcium ion Inorganic materials 0.000 claims description 6
- 238000001914 filtration Methods 0.000 claims description 5
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- 229910052709 silver Inorganic materials 0.000 claims description 4
- 239000004332 silver Substances 0.000 claims description 4
- -1 silver ions Chemical class 0.000 claims description 4
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 claims description 2
- 239000003054 catalyst Substances 0.000 abstract description 48
- 238000006243 chemical reaction Methods 0.000 abstract description 19
- 239000011148 porous material Substances 0.000 abstract description 16
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- 238000012546 transfer Methods 0.000 abstract description 4
- 239000000292 calcium oxide Substances 0.000 description 70
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- 230000000052 comparative effect Effects 0.000 description 13
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- 238000012512 characterization method Methods 0.000 description 7
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- 238000010521 absorption reaction Methods 0.000 description 6
- 238000007630 basic procedure Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 5
- 239000003513 alkali Substances 0.000 description 5
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- 229910000019 calcium carbonate Inorganic materials 0.000 description 4
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- 238000001878 scanning electron micrograph Methods 0.000 description 4
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- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 3
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- 125000004185 ester group Chemical group 0.000 description 3
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- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
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- 238000011068 loading method Methods 0.000 description 2
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- 239000002699 waste material Substances 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 229910014472 Ca—O Inorganic materials 0.000 description 1
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- 235000019738 Limestone Nutrition 0.000 description 1
- 229930182555 Penicillin Natural products 0.000 description 1
- JGSARLDLIJGVTE-MBNYWOFBSA-N Penicillin G Chemical compound N([C@H]1[C@H]2SC([C@@H](N2C1=O)C(O)=O)(C)C)C(=O)CC1=CC=CC=C1 JGSARLDLIJGVTE-MBNYWOFBSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 150000004703 alkoxides Chemical class 0.000 description 1
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- 239000002585 base Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
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- 229910021645 metal ion Inorganic materials 0.000 description 1
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/66—Silver or gold
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
- B01J35/64—Pore diameter
- B01J35/647—2-50 nm
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
- B01J35/64—Pore diameter
- B01J35/651—50-500 nm
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L1/00—Liquid carbonaceous fuels
- C10L1/02—Liquid carbonaceous fuels essentially based on components consisting of carbon, hydrogen, and oxygen only
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- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
- C11C3/00—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom
- C11C3/04—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom by esterification of fats or fatty oils
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
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Abstract
The invention discloses a bimetallic solid alkaline nano-catalyst and a preparation method and application thereof, wherein the catalyst is a CaO/Ag nano-catalyst with a porous structure, and Ag nano-particles cover the surfaces of the CaO nano-particles; the preparation method comprises preparing Ca (MAA)2Nanobelt and placing it in AgNO3The obtained solution is placed still, filtered and dried, then calcined to 650 ℃ at room temperature, and kept at the temperature for 10min to prepare the CaO/Ag nano catalyst; the catalyst is applied to transesterification reaction for preparing biodiesel. The CaO/Ag nano catalyst has large aperture, large pore volume and rich porous structure, and can effectively improve the quality of triglyceride macromolecules when being applied to the preparation of biodieselThe mass transfer rate is increased, the overall reaction rate is improved, the reaction temperature is low, the catalyst stability is strong, and the quality yield of the biodiesel reaches 90 percent or more; meanwhile, the preparation method is simple and has strong operability.
Description
Technical Field
The invention belongs to the field of catalyst preparation, and particularly relates to a bimetallic solid alkaline nano-catalyst, and a preparation method and application thereof.
Background
Biodiesel is a biodegradable and renewable fuel, a typical "green energy source". Compared with the traditional diesel, the biodiesel has lower sulfur content and aromatic compound content, and has the advantages of high flash point, low viscosity, high ignition point, environmental protection, and the like. Under the background of increasingly exhausted fossil fuels and increasingly serious environmental pollution, the development and research of biodiesel have important practical significance on energy supply and natural environment in China. The most widely used and mature process in biodiesel production is the transesterification process. The ester exchange reaction refers to the reaction of raw oil such as animal and vegetable oil and low-carbon chain alcohol under the action of a catalyst to generate fatty acid alkyl ester (i.e. biodiesel) and a byproduct of glycerin.
A key issue in the biodiesel industry is the choice of catalyst. Homogeneous acid/base catalysts are commonly used in transesterification reactions. Under the condition of no water and a small amount of free fatty acid, the activity of the alkaline catalyst is stronger than that of the acidic catalyst, and the alkaline catalyst is usually selected for biodiesel produced industrially at present. The most commonly used homogeneous basic catalysts at present include sodium hydroxide, potassium hydroxide and their alkoxides. The method for producing the biodiesel by using the homogeneous catalyst has the advantages of high reaction speed, high conversion rate and the like. But has the problems of more side reactions, complex subsequent catalyst separation process, generation of a large amount of waste water in the washing process, resource waste and the like. Therefore, the search for highly efficient, environmentally friendly and easily separable solid basic catalysts is becoming a focus of research.
The solid alkali as ester exchange catalyst has the advantages of repeated use of ① catalyst, environment friendship of ②, cheap ③ material, such as limestone or calcium hydroxide, and alkali produced ④⑤ has almost the same catalytic activity as homogeneous alkali catalyst under the same operation condition, and among several solid alkali catalysts, CaO has low cost, rich material, strong alkali and very low solubility in methanol, so that it has wide application foreground in preparing biodiesel oil through ester exchange reaction2Leading to the reduction of the activity of the catalyst, and the inactivation of the active sites of the byproduct glycerol is also easy to cause; secondly, in the reaction system, Ca2+Easy leaching and reduced catalyst activity.
Disclosure of Invention
The purpose of the invention is as follows: the first purpose of the invention is to provide a bimetallic solid alkaline nano-catalyst with high catalytic activity, low reaction temperature, short reaction time and strong catalyst stability;
the second purpose of the invention is to provide a preparation method of the catalyst;
the third purpose of the invention is to provide the application of the catalyst.
The technical scheme is as follows: the bimetallic solid alkaline nano-catalyst is a CaO/Ag nano-catalyst with a porous structure, and the aperture is 20-80 nm; wherein the Ag nano-particles cover the surfaces of the CaO nano-particles.
According to the invention, the nano Ag and the CaO are combined to form a porous structure in which Ag nano particles cover the surface of the CaO, so that not only are the active sites on the surface of the CaO protected, the stability of the CaO is improved, and the catalytic performance is improved, but also the Ag covering the surface of the CaO and lone-pair electrons of ester group oxygen atoms generate coordination and complexation, so that the electrophilicity is improved, and the O-H bond of alcohol can be effectively activated, and the catalytic performance of the catalyst is further enhanced.
The method for preparing the bimetallic solid alkaline nano catalyst comprises the following steps: preparation of Ca (MAA)2Nanoribbons placing them in AgNO3The obtained solution is placed still, filtered and dried, then calcined to 650 ℃ at the room temperature at the speed of 1 ℃/min, and kept at the temperature for 10min to prepare the CaO/Ag nano catalyst; wherein the molar ratio of the calcium ions to the silver ions is 1: 0.02.
The invention adopts Ca (MAA) when preparing the catalyst2Nanobelt, MMA-COO of (1)-Can be mixed with Ca2+Bound, and C ═ C pi electrons, can be bound to Ag+Ca can be bound through a coordinate bond2+And Ag+The incorporation of the polymer ensures a homogeneous dispersion of the metal ions at the molecular level. Further, Ca (MAA)2The nanobelt is prepared by the following steps: reacting Ca (OH)2Mixing with methacrylic acid solution, stirring to obtain Ca (MAA)2·H2O precursor solution, and adding the Ca (MAA)2·H2Dissolving the O precursor solution in absolute ethyl alcohol, standing to obtain Ca (MAA)2A nanoribbon.
Furthermore, the standing time for preparing the catalyst can be 24 hours, and the drying is carried out for 10 to 12 hours at the temperature of between 38 and 42 ℃.
Further, in the preparation of Ca (MAA)2Standing for 15-30min, stirring at 380r/min, and stirring for 0.5 h.
The bimetallic solid alkaline nano-catalyst is applied to transesterification reaction for preparing biodiesel.
Has the advantages that: compared with the prior art, the invention has the following remarkable advantages: the CaO/Ag nano catalyst has large aperture, large pore volume and rich porous structure, can effectively improve the mass transfer rate of triglyceride macromolecules and the overall reaction rate when being applied to the preparation of biodiesel, and has low reaction temperature, strong catalyst stability and the biodiesel quality yield of up to 90 percent and above; meanwhile, the preparation method is simple and has strong operability.
Drawings
FIG. 1 shows Ca (MMA)2SEM image of precursor, 20 KX;
FIG. 2 is an SEM image of 20KX of a CaO nanocatalyst;
FIG. 3 is an SEM image of 20KX of CaO/Ag nanocatalyst;
FIG. 4 is an SEM image of 50KX of CaO/Ag nanocatalyst;
FIG. 5 is an XRD pattern of a CaO nanocatalyst and a CaO/Ag nanocatalyst;
FIG. 6 is a FT-IR chart of CaO nanocatalyst and CaO/Ag nanocatalyst;
FIG. 7 is a BET plot of a CaO nanocatalyst;
FIG. 8 is a BET plot of a CaO/Ag nanocatalyst;
FIG. 9 is a graph showing the effect of catalytic reaction time of CaO/Ag nanocatalyst on biodiesel yield.
Detailed Description
The technical solution of the present invention will be further described in detail with reference to the following examples.
EXAMPLE 1 CaO/Ag nanocatalyst
The preparation method of the CaO/Ag nano-catalyst of the embodiment comprises the following steps:
(1)Ca(MAA)2preparation of hydrate: reacting Ca (OH)2Dissolving the powder (7.4g, 0.1mol) and MAA solution (17.2g, 0.2mol) in 200m L deionized water, stirring continuously for 0.5h at room temperature (stirring rate 380r/min), and vacuum-filtering with circulating water vacuum pump to obtain Ca2+And MAA-Ca (MAA)2·H2O precursor solution in transparent colorless state;
(2) preparation of CaO/Ag nano-catalyst 10m L Ca (MAA)2·H2Mixing the O precursor solution in 200m L anhydrous ethanol, standing for 20min to form uniform white viscous Ca (MAA)2Washing the nanobelt with absolute ethyl alcohol and collecting the nanobelt; 0.34g of AgNO3(2mmol) completely dissolved in 200m L anhydrous ethanol, collected Ca (MAA)2Dissolving the nanobelt in the solution, placing the mixed solution in a sample bottle wrapped with tinfoil, standing for 24h, filtering with anhydrous ethanol, and drying the collected sample in a 42 ℃ vacuum drying oven for 12 h; finally, taking out the sample, putting the sample into a tubular furnace for thermal process, calcining the sample in the air to 650 ℃ (the heating rate is 1 ℃/min), reacting the calcined sample at constant temperature for 10min to prepare a CaO/Ag nano catalyst, sealing and storing the CaO/Ag nano catalyst in a drying dish for later use, and adding Ca (OH)2And silica gel, preventing the catalyst from being mixed with water and CO2Of the contact of (a).
Comparative example 1 CaO nanocatalyst
The preparation method of the comparative example CaO nanocatalyst comprises the following steps:
(1)Ca(MAA)2preparation of hydrate: reacting Ca (OH)2Dissolving the powder (7.4g, 0.1mol) and MAA solution (17.2g, 0.2mol) in 200m L deionized water, stirring continuously for 0.5h at room temperature (stirring rate 380r/min), and vacuum-filtering with circulating water vacuum pump to obtain Ca2+And MAA-Ca (MAA)2·H2O precursor solution in transparent colorless state;
(2) preparation of CaO nano-catalyst 10m L Ca (MAA)2·H2Mixing the O precursor solution in 200m L anhydrous ethanol, standing for 20min to form uniform white viscous Ca (MAA)2A nanoribbon; washing with anhydrous ethanol, filtering, collecting nanobelt, and drying in 42 deg.C vacuum drying oven for 12 hr; then taking out the sample and putting the sample into a tubular furnace for thermal process, calcining the sample to 650 ℃ (the heating rate is 1 ℃/min) at room temperature, keeping the temperature at 650 ℃ for 10min to prepare a CaO nano catalyst, sealing and storing the CaO nano catalyst in a drying dish for later use, and adding Ca (OH)2And silica gel, preventing the catalyst from being mixed with water and CO2Of the contact of (a).
Structural characterization 1
Mixing Ca (MAA)2The precursor, the CaO nanocatalyst prepared in comparative example 1, and the CaO/Ag nanocatalyst prepared in example 1 were subjected to structural characterization, and the obtained results are shown in fig. 1 to 4. From this figure, Ca (MAA)2The precursor is in a fiber strip shape, the thickness of the precursor is different, and the thick fiber body consists of a plurality of thin fiber strips. The long-strip fiber structure of the CaO nano catalyst obtained after high-temperature calcination is destroyed to form a porous structure, and regular calcium oxide nano particles are presented, and the diameter of the calcium oxide nano catalyst is between 148 and 426 nm. In the CaO/Ag nano-catalyst, besides regular CaO nano-particles, spherical nano-silver particles with different sizes are also present on the surface of CaO.
The CaO/Ag nanocatalyst prepared in example 1 was characterized and the results obtained are shown in fig. 5. It can be seen from the figure that the CaO nanocatalyst shows derivatives at 2 θ of 32.72 °, 37.89 °, 54.34 °, 64.5 ° and 67.82 °The peaks are respectively assigned to the (111), (200), (220), (311) and (222) crystal planes of the cubic-centered CaO (jcpdno.040777) with the unit parameter a being 4.810. Diffraction peaks at 23.06 °, 30.09 °, 40.01 °, 43.75 °, 47.71 ° and 49.01 ° corresponding to the unit parameters a 4.990 cubic center CaCO3Crystal planes (JCPDno.471743) of (012), (104), (113), (202), (018), and (116) indicate that trace amounts of CaO and CO in air are present during storage and handling2A reaction takes place. As can be seen from the figure, CaCO is present in CaO/Ag3The intensity of the correlation peak is lower than CaO. The peaks at 2 θ ═ 38.66 °, 44.81 °, 64.88 ° and 77.82 ° are respectively assigned to the (111), (200), (220), (311) and (222) crystal planes of the unit parameters a ═ 4.086 cubic face center Ag (JCPDS No.040783), confirming successful loading of the nano-silver particles.
Structural characterization 3
The CaO/Ag nanocatalyst prepared in example 1 was subjected to infrared detection, and the obtained results are shown in FIG. 6. CaO and CaO/Ag at 3647cm-1、1428cm-1、873cm-1There is a major absorption peak. Among these absorption peaks, 3647cm-1The absorption peak at (A) was attributed to O-H stretching vibration, indicating that a small amount of Ca (OH) was found in both samples2. At 1428cm-1、873cm-1At the peak value of CaCO3Stretching vibration peak of C-O bond of (2). 2871cm-1The small absorption peak can be attributed to the carbonate C ═ O double bond, 548cm-1The absorption peak at (A) can be attributed to the Ca-O bond. In summary, CaO is compared to CaO/Ag, CaCO3The absorption peak is more obvious, which shows that CaO is easier to react with CO2The reaction takes place. The results are consistent with the above XRD results, confirming that the silver nanoparticles protect CaO and CO to some extent2The reaction of (1). However, during storage and handling, small amounts of CaO/Ag will still be associated with CO2Reaction takes place to form CaCO3。
Structural characterization 4
The CaO nanocatalyst and the CaO/Ag nanocatalyst prepared in example 1 and comparative example 1 were subjected to N2 adsorption/desorption isotherms and their corresponding pore size distributions, and the results obtained are shown in fig. 7 and 8. The CaO nanocatalyst has pores with most of the volume being 20-60nmThe diameter is occupied, the pore diameter at the highest peak is about 40nm, the average pore diameter is about 37.08nm, and the specific surface area is 2.045m2G, pore volume 0.016cm3(ii) in terms of/g. The CaO/Ag nano catalyst has wider mesopores and narrower macropores, the pore diameter is between 20 and 80nm, the average pore diameter is about 58.838nm, and the specific surface area is 7.022m2Per g, pore volume 0.070cm3And g, the diameter of the Ag nano particles is 2-6 nm. The total alkalinity of CaO and CaO/Ag is respectively 13.15mmol/g and 10.81mmol/g, which is obviously higher than that of CaO catalysts reported in the prior literature. Compared with CaO, CaO/Ag has larger specific surface area, pore size and pore volume, and is beneficial to the mass transfer of triglyceride molecules, thereby better contacting with active sites on the surface of a catalyst and improving the yield of biodiesel.
Detection of catalytic Performance
The catalyst prepared in example 1 was subjected to catalytic transesterification including the following steps:
(1) drying soybean oil purchased from a supermarket in an oven at 120 ℃ for 24 hours to remove moisture in the soybean oil;
(2) performing transesterification in a penicillin bottle, and mixing soybean oil, methanol and catalyst at a certain ratio (shown in Table 1 below); putting the mixture into a constant-temperature heating magnetic stirrer to react for 3 hours (reaction temperature: 72 ℃, stirring speed: 400r/min), wherein the obtained product is a mixture of biodiesel and triglyceride;
(3) centrifuging the obtained product in a centrifuge (rotation speed: 10000r/min, time: 7min) to obtain a liquid layer and a solid layer; the upper layer of the liquid is biodiesel, the lower layer of the liquid is triglyceride, the upper layer of the liquid is sucked out and transferred into a round-bottom flask, a rotary evaporator is used for rotary evaporation for 10min at 35 ℃, then the biodiesel is washed by hot water at 80 ℃ until the pH value of the washing waste liquid is neutral, the prepared biodiesel product is put into an oven for drying (120 ℃, 12h), and the catalyst in the solid layer is directly recovered and reused.
TABLE 2 CaO/Ag nanocatalyst catalytic performance
As can be seen from Table 1, the effect of reaction time on biodiesel yield was compared and analyzed at an alcohol to oil ratio of 13:1 and a catalyst loading of 5% (based on oil weight), and the results are shown in FIG. 9. The CaO/Ag catalyst of the invention obviously improves the reaction rate and shortens the reaction time, and the highest yield (about 90%) of the biodiesel is higher than that (about 86%) of the biodiesel under the CaO condition.
Comparative example 2
The basic procedure is as in example 1, except that 0.17g of AgNO is added3(2mmol) was completely dissolved in 200m L absolute ethanol.
Comparative example 3
The basic procedure is as in example 1, except that 0.51g of AgNO is added3(3mmol) was completely dissolved in 200m L absolute ethanol.
The structural and performance characterization of the catalysts prepared in the comparative examples 2 and 3 shows that when the concentration of silver ions is low, the spherical nano silver particles on the surface of the catalyst are less and cannot completely cover the surface of CaO; when the concentration of silver ions is higher, the alkalinity of the catalyst CaO/Ag is improved, but serious saponification reaction occurs in the preparation of the biodiesel through transesterification reaction, and the yield of the biodiesel is reduced.
Comparative example 4
The basic procedure is the same as in example 1, except that calcination is carried out in air to 500 ℃.
Comparative example 5
The basic procedure is the same as in example 1, except that calcination is carried out in air to 800 ℃.
The catalysts prepared in comparative examples 4 and 5 were subjected to structural and performance characterization, and it was found that different calcination temperatures resulted in differences in the contents of the components in the catalysts and changes in the crystal lattice structures of the catalysts, forming new active centers, resulting in different catalytic activities of the catalysts. Calcination at too low a temperature, dried Ca (MAA)2During the calcination processThe catalyst can not be completely degraded to be CaO, the catalyst is weak in alkalinity, and the activity is reduced; the calcination temperature is too high, the abundant porous structure of the catalyst is destroyed, the phenomenon of collapse is generated, the specific surface area is reduced, the catalytic activity is reduced, and the yield of the biodiesel is reduced when the catalyst is applied to the transesterification reaction.
Comparative example 6
The basic procedure was the same as in example 1 except that the temperature increase rate of calcination was 10 deg.C/min.
Comparative example 7
The basic procedure was the same as in example 1 except that the temperature increase rate of calcination was 2 deg.C/min.
The catalysts prepared in comparative examples 6 and 7 were characterized by their structure and performance and found to have a faster rate of temperature rise, Ca (MAA)2The organic complex in (1) can not be completely degraded into CO, but is completely carbonized, so that the product is a mixture of black carbide and calcium oxide; at the temperature rise rate of 2 ℃/min, CaO has the pore-like characteristic, but the pore diameter is small (10-30nm), triglyceride macromolecules can not pass through the channels in the transesterification reaction, and the conversion rate of the biodiesel is reduced.
The results of the above embodiments show that the CaO/Ag nano catalyst has large pore diameter, large pore volume and rich pore structure, can effectively improve the mass transfer rate of triglyceride macromolecules and the overall reaction rate when being applied to the preparation of biodiesel, and has low reaction temperature, strong catalyst stability and the biodiesel quality yield of up to 90% and above.
Claims (7)
1. A bimetallic solid alkaline nano-catalyst is characterized in that: the nano catalyst is a CaO/Ag nano catalyst with a porous structure, and the aperture is 20-80 nm; wherein the diameter of the Ag nano-particles is 2-6 nm, and the Ag nano-particles cover the surfaces of the CaO nano-particles.
2. A method for preparing the bimetallic solid basic nanocatalyst of claim 1, comprising the steps of: preparation of Ca (MAA)2Nanoribbons placing them in AgNO3Standing in ethanol solution, filtering, and dryingThen, calcining at room temperature to 650 ℃ at the speed of 1 ℃/min, and keeping the temperature for 10min to prepare the CaO/Ag nano catalyst; wherein the molar ratio of the calcium ions to the silver ions is 1: 0.02.
3. The method of preparing a bimetallic solid basic nanocatalyst as claimed in claim 2, characterized in that: said Ca (MAA)2The nanobelt is prepared by the following steps: reacting Ca (OH)2Mixing with methacrylic acid solution, stirring to obtain Ca (MAA)2·H2O precursor solution, and adding the Ca (MAA)2·H2Dissolving the O precursor solution in absolute ethyl alcohol, standing to obtain Ca (MAA)2A nanoribbon.
4. The method of preparing a bimetallic solid basic nanocatalyst as claimed in claim 2, characterized in that: the standing is carried out for 24 hours, and the drying is carried out for 10 to 12 hours at the temperature of between 38 and 42 ℃.
5. The method of preparing a bimetallic solid basic nanocatalyst as claimed in claim 3, characterized in that: and standing for 15-30 min.
6. The method of preparing a bimetallic solid basic nanocatalyst as claimed in claim 3, characterized in that: the stirring speed of the mixing stirring is 380r/min, and the stirring is carried out for 0.5 h.
7. The bimetallic solid basic nano-catalyst of claim 1 is applied to transesterification reaction to prepare biodiesel.
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