WO2018209665A1 - 一种限域结构六面体形貌纳米镍基催化剂的制备方法及其催化加氢的应用 - Google Patents

一种限域结构六面体形貌纳米镍基催化剂的制备方法及其催化加氢的应用 Download PDF

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WO2018209665A1
WO2018209665A1 PCT/CN2017/084988 CN2017084988W WO2018209665A1 WO 2018209665 A1 WO2018209665 A1 WO 2018209665A1 CN 2017084988 W CN2017084988 W CN 2017084988W WO 2018209665 A1 WO2018209665 A1 WO 2018209665A1
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nickel
catalyst
hexahedral
nano
organic acid
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张法智
韩静静
贾会敏
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北京化工大学
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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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/74—Iron group metals
    • B01J23/755—Nickel
    • 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
    • B01J35/20—Catalysts, in general, characterised by their form or physical properties characterised by their non-solid state
    • B01J35/23—Catalysts, in general, characterised by their form or physical properties characterised by their non-solid state in a colloidal state
    • 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
    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • B01J35/391—Physical properties of the active metal ingredient
    • B01J35/393—Metal or metal oxide crystallite size
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C213/00—Preparation of compounds containing amino and hydroxy, amino and etherified hydroxy or amino and esterified hydroxy groups bound to the same carbon skeleton
    • C07C213/02—Preparation of compounds containing amino and hydroxy, amino and etherified hydroxy or amino and esterified hydroxy groups bound to the same carbon skeleton by reactions involving the formation of amino groups from compounds containing hydroxy groups or etherified or esterified hydroxy groups
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
    • C07C5/02—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by hydrogenation
    • C07C5/10—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by hydrogenation of aromatic six-membered rings
    • C07C5/11—Partial hydrogenation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D307/00—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom
    • C07D307/02—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings
    • C07D307/34—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members
    • C07D307/38—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members with substituted hydrocarbon radicals attached to ring carbon atoms
    • C07D307/40—Radicals substituted by oxygen atoms
    • C07D307/42—Singly bound oxygen atoms
    • C07D307/44—Furfuryl alcohol
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
    • C07C2523/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of the iron group metals or copper
    • C07C2523/74—Iron group metals
    • C07C2523/755—Nickel

Definitions

  • the invention belongs to the technical field of catalyst preparation, and particularly relates to a method for controlling the explosive in-situ uniform reduction of an organic carbon source by using a hydrotalcite layer to prepare a hexahedral morphology with high crystallinity and small size, and is limited to Ni ( Al) Nickel-based catalyst on O x /C and its application in catalytic hydrogenation of p-nitrophenol.
  • Para-aminophenol is of great commercial importance as an intermediate for the preparation of analgesics and antipyretics.
  • PNP p-nitrophenol
  • Liquid phase hydrogenation of p-nitrophenol is also an efficient and green way. Therefore, PNP catalytic hydrogenation to form PAP becomes very important.
  • liquid phase PNP hydrogenation using Raney nickel, nano-sized metallic nickel and several precious metal catalysts such as Pt/C, Au, etc. has been reported.
  • Precious metal catalysts have excellent catalytic properties, but are expensive and difficult to purify.
  • non-precious metals have received more and more attention due to their low price and excellent performance.
  • the metal and its supporting interface region can be considered as the catalytic active sites for the hydrogenation reaction.
  • the PNP hydrogenation is the surface reaction of the metal particles, the particle size of the nanoparticles is reduced, and the exposure is more More active sites can greatly improve its catalytic performance.
  • LDHs are compounds formed by the orderly assembly of interlayer anions and positively charged layers.
  • the chemical composition is generally as follows: [M 2+ 1-x M 3+ x (OH) 2 ] x+ [A n- ] x/n ⁇ yH 2 O.
  • the LDHs have the characteristics of tunable denaturation of the metal ion composition of the main layer, the charge density of the main layer and its variability, the variability of the type and amount of intercalated anion, the variability of the intra-layer space, and the variability of the interaction between the host and the guest.
  • Such structural features make LDHs a meaningful platform for the development of new catalysts, catalyst precursors and catalyst supports with variable structure and properties.
  • the use of hydrotalcite as a single precursor has significant advantages in preparing high-content, highly-dispersed heterogeneous catalyst materials through lamellar stripping, lattice confinement, and intercalation assembly machine arraying.
  • metal catalytic materials can be obtained by heat treatment under reducing conditions under certain conditions (temperature, time).
  • the structure of such materials is good, but the prepared active metal nanoparticles are large, and the dispersion is not high. Activity is limited.
  • carbon materials as catalyst carriers to load and disperse metal particles are very attractive. prospect.
  • the object of the present invention is to provide a novel small-sized structure-limited Ni-based catalyst prepared by explosive reduction, a preparation method and the catalytic hydrogenation of the catalyst to p-nitrophenol.
  • the invention firstly synthesizes a nickel-aluminum hydrotalcite precursor intercalated with an organic carbon chain, and uses the explosive in-situ uniform reduction of an organic carbon source to prepare a nanoparticle having a high crystallinity and a small size and a hexahedral morphology to be limited to Ni (Al).
  • a structural catalyst on O x /C Small-sized hexahedral morphology nanoparticle limits expose more active sites in the matrix carrier, which can be used to catalytically hydrogenate p-nitrophenol, which can effectively improve the conversion and stability of the catalyst. Selective hydrogenation of phenylacetylene and hydrogenation of furfural.
  • a hexahedral morphology nano-nickel catalyst with limited domain structure using inter-layer carbon reduction method under inert gas conditions, using intercalated organic carbon source between hydrotalcite layers to control explosive in-situ uniform reduction to prepare hexahedral metal nickel nanoparticles
  • the small-sized hexahedral metal nickel nanoparticles are bounded by an aluminum-doped metal oxide edge surrounded by an amorphous carbon phase, and the prepared catalyst Ni/Ni(Al)O x /C is a black powdery substance.
  • the particle size is 3-5 nm.
  • a preparation method of a nano-nickel catalyst with a hexahedral morphology and a hexahedral morphology wherein a nickel-aluminum hydrotalcite intercalated with a catalyst precursor organic acid is placed in an atmosphere furnace, and a reduction reaction is carried out by using a nitrogen gas having a flow rate of 30-80 mL/min.
  • the temperature is 300-600 ° C
  • the heating rate is 2-10 ° C / min
  • the reduction time is 1-5 h
  • the nano-nickel catalyst with hexahedral morphology is obtained after the reaction is completed.
  • the catalyst precursor organic acid intercalated nickel aluminum hydrotalcite is prepared by dissolving a nitrate intercalated nickel aluminum hydrotalcite precursor and an organic acid in de-CO 2 water, and transferring to a four-necked flask, nitric acid
  • the mass ratio of the intercalated nickel-aluminum hydrotalcite precursor to the organic acid ranges from 0.5 to 1; in a 60-70 ° C water bath, with inert gas protection and constant stirring, a concentration of 1-2 mol/ is added to the four-necked flask.
  • the NaOH solution of L is adjusted to pH value of 6-7, stirred for 1-2 h, filtered, washed, and dried under vacuum at 60-70 ° C for 20-24 h to obtain a catalyst precursor organic acid intercalated nickel aluminum hydrotalcite.
  • Another preparation method of the catalyst precursor organic acid intercalated nickel aluminum hydrotalcite is:
  • the nitrate intercalated nickel aluminum hydrotalcite precursor is dissolved in de-CO 2 water and transferred to a four-necked flask; the organic acid is dissolved in de-CO 2 water and transferred to a syringe; the NaOH is dissolved in de-CO 2 water and transferred to In another syringe, the mass ratio of the nitrate intercalated nickel-aluminum hydrotalcite precursor to the organic acid ranges from 0.5 to 1; the organic acid solution and the NaOH solution are adjusted in a 60-70 ° C water bath with inert gas protection and constant stirring.
  • the dropping rate was simultaneously dropped into a four-necked flask to maintain a pH of 6, and after filtration, washing, and drying under vacuum at 60-70 ° C for 20-24 hours, a nickel-aluminum hydrotalcite intercalated with a catalyst precursor organic acid was obtained.
  • the molar ratio of nickel ions to aluminum ions in the nitrate intercalated nickel aluminum hydrotalcite precursor is 2-3.
  • the organic acid is tartaric acid or lauric acid.
  • the limited-domain hexahedral nano-nickel catalyst prepared by the above method is applied to the catalytic hydrogenation of p-nitrophenol, and the process conditions are as follows: the concentration of 2 mL is 1 ⁇ 10 -3 -1 ⁇ 10 -4 mol/ L-p-nitrophenol in ethanol solution, adding 0.003-0.005 g of a limited-domain hexahedral nano-nickel catalyst, 17-20 mg of excess sodium borohydride, and stirring rapidly at room temperature.
  • the time-dependent absorption spectra were recorded in the UV-Vis spectrophotometer scanning range of 250-500 nm and scanned every 30 s to analyze the conversion of the reactants to the product.
  • the limited-domain hexahedral morphology nano-nickel catalyst prepared by the above method is applied to the selective hydrogenation of phenylacetylene and the furfural hydrogenation reaction.
  • the invention firstly synthesizes a nickel-aluminum hydrotalcite precursor intercalated with an organic carbon chain, and adopts a hydrotalcite precursor controlled reduction method to prepare a nano-nickel catalyst with a limited structure by using an in-situ homogeneous reduction of an organic carbon source.
  • the high-crystallinity and small-sized hexahedral morphology nano-particles obtained by the explosive reduction method are limited to the matrix Ni(Al)O x /C, which enhances the interaction with the carrier and is exposed at the same time. More active sites greatly improve the catalytic hydrogenation reaction of p-nitrophenol.
  • the catalytic reaction is carried out after reduction treatment at 400 ° C.
  • the conversion of p-nitrophenol at room temperature is only 180 s.
  • the catalyst preparation process does not need to use an organic solvent or an additive, and the method is simple and rapid, and the environment is green and friendly.
  • the catalyst can also be used in the reaction of selective hydrogenation of phenylacetylene and hydrogenation of furfural.
  • Example 1 is a XRD (a), FT-IR (b), TG-DTA (c, d) spectrum of NiAl-LDHs-NO 3 - and NiAl-LDHs-TA before and after exchange in Example 1.
  • Example 2 is a SEM (a, b) spectrum of NiAl-LDHs-NO 3 - and NiAl-LDHs-TA before and after exchange in Example 1, and an HRTEM chart of a catalyst sample under 400 ° C reduction treatment.
  • Example 3 is an XRD chart of a catalyst sample prepared by treating at different reduction temperatures in a N 2 atmosphere in Example 1.
  • Example 4 is a HRTEM image of a catalyst sample prepared by treating at different reduction temperatures in Example 1. The particle size distribution is shown in the figure (calculated based on 100 particles per sample).
  • Figure 5 is an ultraviolet absorption spectrum of Ni/Ni(Al)O x /C catalyzed p-nitrophenol obtained by treatment at different reduction temperatures in Example 2.
  • Figure 6 is a graph showing the relationship between ln(A/A 0 )-t of p-nitrophenol catalyzed by different sample catalysts in Example 2, according to the absorbance A at 400 nm at different times in the corresponding ultraviolet absorption spectrum.
  • Figure 7 is a graph showing the conversion and selectivity curves of benzene acetylene catalyzed by a sample of a catalyst treated at 500 ° C and 600 ° C in Example 5.
  • Figure 8 is a graph showing the conversion and selectivity of catalyzed furfural in a catalyst sample treated at 500 ° C and 600 ° C in Example 6.
  • the hydrotalcite NiAl-LDHs-TA prepared in the step A is placed in a high-temperature atmosphere furnace, and the N 2 purity is 99.999%, the flow rate is 40 mL/min, and the temperature in the furnace is raised to 300 ° C and 350 ° C, respectively. 400 ° C, 500 ° C and 600 ° C, the heating rate is 5 ° C / min, for 3 h, and then naturally cooled to room temperature, to obtain a limited structure hexahedral morphology nano-nickel-based catalyst recorded as Ni / NiAlO x / C (XRD diagram 3).
  • Fig. 3 The XRD patterns of the reduced products under NiAl-LDHs-TA and N 2 at different temperatures are shown in Fig. 3. It can be seen from the figure that the structure of the hydrotalcite laminate gradually collapses with the increase of temperature. From the starting point of explosive reduction at 300 °C, several broad peak Ni(Al)O x characteristic diffraction peaks gradually move toward the metallic Ni characteristic diffraction peak. It is proved that the C in-situ in-situ reduction process still has some Ni(Al)O x present in the R500°C/R600°C sample, indicating that the intercalation C prepared by us is an explosive reduction in a narrow temperature range.
  • the HRETEM characterization of the reduced catalyst was carried out. The results are shown in Fig. 4. It can be seen from Fig. 4 that the hexahedral metal Ni nanoparticles with a nanometer size of 3-5 nm from 350 ° C and 400 ° C were converted into 500 with increasing temperature. Spherical particles having a grain size of about 7-9 nm at °C and 600 °C. At low temperatures, we obtained a Ni/Ni(Al)O x /C catalyst with a small hexahedral morphology confined to the Ni(Al)O x /C substrate.
  • the nickel-based nanoparticle catalyst prepared by the above-mentioned limited structure has a composition structure in which a small-sized hexahedral metal nanoparticle is bounded by an aluminum-doped metal oxide edge and surrounded by an amorphous carbon phase.
  • the catalyst is a black powdery substance having a particle size of about 3-5 nm.
  • the nickel-based nanoparticle catalyst prepared by the above-mentioned limited structure is applied to the catalytic hydrogenation reaction of p-nitrophenol, and the process conditions are as follows: the concentration of 1 ⁇ 10 -4 mol/L of p-nitrophenol is prepared by measuring 2 ml of ethanol. The solution was dissolved in a standard (1 cm x 1 cm x 3 cm) 3 mL volumetric quartz cuvette. 0.005 g of a nickel-based catalyst having a confinement structure was added, and an excess of sodium borohydride was about 17 mg, and the reaction was rapidly stirred at room temperature. The time-dependent absorption spectra were recorded in the UV-Vis spectrophotometer scanning range of 250-500 nm and scanned every 30 s to analyze the conversion of the reactants to the product.
  • the invention provides a hexahedral morphology nickel-based nano particle catalyst with a limited structure, which is particularly suitable for use in the treatment of nitrate
  • the phenol is catalytically hydrogenated.
  • Figure 5 and Figure 6 the results are shown in Figure 5 and Figure 6:
  • Ni/Ni(Al)O x /C has a higher reaction rate than the higher temperature reduced sample and the H 2 reduced and purchased metal Ni based catalyst. This is not only reflected in the catalytic performance advantages of small particle size for the surface reaction of p-nitrophenol, but also in the morphology has a greater impact on the catalytic activity, the special hexahedral morphology reveals more active sites, and In Ni(Al)O x -C, the contact of the metal with the reactants plays a crucial role, which also promotes the activity of the catalytic reaction.
  • Synthetic hydrotalcite prepared using the precursor bis drop method, the 2g NiAl-LDHs-NO 3 - precursor to CO 2 was dissolved in 60ml water, transferred four-necked flask, 4g of organic acids to CO 2 was dissolved in 60ml water and transferred to In the syringe 1, the NaOH was dissolved in 60 ml of de-CO 2 water at a concentration of 1 mol/L, transferred to a syringe 2, and stirred in a water bath at 70 ° C under an inert gas atmosphere to adjust the dropping speed of the organic acid and the alkali, and the double drop.
  • the other conditions were the same, and in the same manner as in Step B of Example 1, the effects of different conditions on the preparation of the catalyst were investigated.
  • Example 2 The amount of catalyst for catalyzing p-nitrophenol in Example 2 was changed to 0.003 g, and the influence of different catalyst amounts on the catalytic reaction was investigated.
  • the limited-domain hexahedral morphology nano-nickel-based catalyst sample obtained in Example 1 was applied to the selective hydrogenation reaction of phenylacetylene, and the results are shown in FIG. Figure a is a sample treated at 500 ° C and Figure b is a sample treated at 600 ° C. It can be seen from the figure that the reaction can be completely converted in about 130s, the conversion rate reaches 100%, and the selectivity of styrene formation at this time can still be maintained at about 75%. It can be seen that in the selective hydrogenation reaction of phenylacetylene, the Ni/Ni(Al)O x /C catalyst with confinement structure has higher catalytic activity and selectivity.
  • FIG. 8 The limited-domain hexahedral nano-nickel catalyst sample obtained in Example 1 was applied to the furfural selective hydrogenation reaction, and the results are shown in Fig. 8.
  • Figure a is a sample treated at 500 ° C
  • Figure b is a sample treated at 600 ° C. It can be seen from the figure that the sample treated at 500 °C catalyzes the complete reaction of furfural in 8h, and the selectivity of sterol is about 65%.
  • the sample treated at 600 °C catalyzes the reaction of furfural in 7h, and the choice of sterol is selected at this time.
  • the sex is about 75%. It can be seen that the elevated temperature of the reduction treatment has higher catalytic activity and selectivity for the catalytic activity of the Ni/Ni(Al)O x /C catalyst.

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Abstract

一种限域结构六面体形貌纳米镍基催化剂的制备方法，该方法首先合成出有机碳链插层的镍铝水滑石前体，利用有机碳源的爆发性原位均匀还原制备得到限域结构的镍基催化剂。该催化剂结构特点为结晶度高、小尺寸的六面体形貌的金属镍纳米粒子限域在Ni(Al)O x/C上。小尺寸的六面体形貌金属镍纳米颗粒限域在基体载体中暴露出更多的活性位点，将其用于对硝基苯酚催化加氢反应中，可有效提高催化剂的转化率及稳定性，还可用于苯乙炔选择加氢和糠醛加氢反应。

Description

一种限域结构六面体形貌纳米镍基催化剂的制备方法及其催化加氢的应用 技术领域
本发明属于催化剂制备技术领域，特别涉及一种利用水滑石层板间插入有机碳源后控制其爆发性原位均匀还原制备结晶度高、小尺寸的六面体形貌的纳米粒子限域在Ni(Al)Ox/C上的纳米镍基催化剂，及其在对硝基苯酚催化加氢反应的应用。
背景技术
对氨基苯酚(PAP)是作为中间体用于止痛和退热药的制备有巨大的商业重要性。同时，对硝基苯酚(PNP)是在工业废水一种有毒的污染物，对硝基苯酚液相加氢也是一种高效，绿色环保的途径，因此PNP催化加氢生成PAP变得非常重要。到现在为止，报道了一些采用雷尼镍，纳米尺寸金属镍和几个贵金属催化剂如Pt/C、Au等的液相PNP加氢。贵金属催化剂具有优异的催化性能，但价格昂贵，不易净化。现在，非贵重金属由于其低廉的价格和优异的性能，受到了越来越多的关注。在PNP的催化加氢中，金属和其支撑界面区可被认为是用于氢化反应的催化活性位点，此外由于PNP加氢是金属颗粒的表面反应，降低纳米颗粒的粒径大小，暴露更多的活性位能大大提高其催化性能。
LDHs是由层间阴离子与带正电荷层板有序组装而形成的化合物，其化学组成通式一般如下：[M2+ 1-xM3+ x(OH)2]x+[An-]x/n·yH2O。由于LDHs具有主体层板金属离子组成可调变性、主体层板电荷密度及其分布可调变性、插层阴离子客体种类及数量可调变性、层内空间可调变性、主客体相互作用可调变性等结构特点，使得LDHs为我们发展新型催化剂、催化剂前体以及可调变结构及性质的催化剂载体提供了很有意义的平台。利用水滑石材料作为单一前驱体，经层板剥离、晶格限域、插层组装机阵列化等途径制备高含量、高度分散的多相催化剂材料具有显著的优势。
以LDHs作为前驱体，在一定条件(温度、时间)下经过还原气氛下热处理可得到金属催化材料，这类材料的结构良好，但是制备得到的活性金属纳米颗粒较大，分散性不高，反应活性受到限制。目前对于C材料负载已有大量研究，在非均相催化领域中，碳材料作为催化剂载体来负载和分散金属粒子具有十分诱人的 前景。
发明内容
本发明的目的是提供一种新的爆发性还原方式制备的小尺寸限域结构Ni基催化剂，制备方法以及将该催化剂应用于对硝基苯酚的催化加氢。
本发明首先合成出有机碳链插层的镍铝水滑石前体，利用有机碳源的爆发性原位均匀还原制备得到结晶度高、小尺寸的六面体形貌的纳米粒子限域在Ni(Al)Ox/C上的结构催化剂。小尺寸的六面体形貌纳米颗粒限域在基体载体中暴露出更多的活性位点，将其用于对硝基苯酚催化加氢反应中，可有效提高催化剂的转化率及稳定性，还可用于苯乙炔选择加氢和糠醛加氢反应。
一种限域结构六面体形貌纳米镍基催化剂，使用惰性气体条件下层间碳还原法，利用水滑石层板间插入有机碳源控制爆发性原位均匀还原制备六面体形貌的金属镍纳米粒子，小尺寸六面体形貌的金属镍纳米粒子限域在铝掺杂的金属氧化物边缘，外围由无定型碳相包围，制备得到的催化剂Ni/Ni(Al)Ox/C为黑色粉末状物质，颗粒粒径大小为3-5nm。
一种限域结构六面体形貌纳米镍基催化剂的制备方法，将催化剂前驱体有机酸插层的镍铝水滑石置于气氛炉中，采用流速为30-80mL/min的氮气进行还原反应，还原温度为300-600℃，升温速率为2-10℃/min，还原时间为1-5h，反应完成后得到限域结构六面体形貌纳米镍基催化剂。
优选的，所述催化剂前驱体有机酸插层的镍铝水滑石的制备方法为：将硝酸根插层镍铝水滑石前体与有机酸溶于去CO2水中，转移至四口烧瓶中，硝酸根插层镍铝水滑石前体与有机酸的质量比范围为0.5-1；在60-70℃水浴锅中，惰性气体保护及不断搅拌下，向四口烧瓶中滴加浓度为1-2mol/L的NaOH溶液至pH值＝6-7，搅拌1-2h，经过过滤，洗涤，在60-70℃真空条件下干燥20-24h，得到催化剂前驱体有机酸插层的镍铝水滑石。
优选的，所述催化剂前驱体有机酸插层的镍铝水滑石的另一种制备方法为：
将硝酸根插层镍铝水滑石前体溶于去CO2水中，转移至四口烧瓶中；将有机酸溶于去CO2水中，转移至注射器中；将NaOH溶于去CO2水中，转移至另一注射器中；硝酸根插层镍铝水滑石前体与有机酸的质量比范围为0.5-1；在60-70℃水浴锅中，惰性气体保护及不断搅拌下，调节有机酸溶液和NaOH溶液的滴速，同时滴入四口 烧瓶中，维持pH值＝6，经过过滤，洗涤，在60-70℃真空条件下干燥20-24h，得到催化剂前驱体有机酸插层的镍铝水滑石。
优选的，所述硝酸根插层镍铝水滑石前体中镍离子与铝离子摩尔比为2-3。
优选的，所述有机酸为酒石酸或月桂酸。
将上述方法制备得到的限域结构六面体形貌纳米镍基催化剂应用于对硝基苯酚催化加氢反应，其工艺条件是：量取2mL浓度为1×10-3-1×10-4mol/L的对硝基苯酚的乙醇溶液，加入限域结构六面体形貌纳米镍基催化剂0.003-0.005g，17-20mg的过量硼氢化钠，在室温下搅拌快速反应。在紫外可见分光光度计扫描范围250-500nm内记录时间依赖性吸收光谱，每30s扫一次，来分析反应物向产物的转化。
上述方法制备得到的限域结构六面体形貌纳米镍基催化剂应用于苯乙炔选择加氢和糠醛加氢反应中。
本发明首先合成出有机碳链插层的镍铝水滑石前体，采用水滑石前驱体控制还原的方法，利用有机碳源的爆发性原位均匀还原制备得到限域结构的纳米镍基催化剂。所述的爆发性的还原方式得到的结晶度高、小尺寸的六面体形貌纳米粒子，其限域在基体Ni(Al)Ox/C上，增强了与载体间的相互作用，同时暴露出更多的活性位点，大大提高了对硝基苯酚催化加氢反应性能，其在400℃还原处理后进行催化反应，常温下紫外测试对硝基苯酚转化完全仅需要180s。并且该催化剂制备过程无需使用有机溶剂或添加剂，方法简便快速，环境绿色友好。该催化剂还可用于苯乙炔选择加氢和糠醛加氢等反应中。
附图说明
图1是实施例1中交换前后NiAl-LDHs-NO3 -和NiAl-LDHs-TA的XRD(a)，FT-IR(b)，TG-DTA(c,d)谱图。
图2是实施例1中交换前后NiAl-LDHs-NO3 -和NiAl-LDHs-TA的SEM(a,b)谱图，以及400℃还原处理下催化剂样品的HRTEM图。
图3是实施例1中N2气氛下不同还原温度处理制备得到的催化剂样品XRD图。
图4是实施例1中不同还原温度处理制备得到催化剂样品的HRTEM图。颗粒尺寸分布如图所示(基于每个样品100个颗粒计算)。
图5是实施例2中不同还原温度处理得到的Ni/Ni(Al)Ox/C催化对硝基苯酚的紫外吸收图谱。
图6是实施例2中不同样品催化剂催化对硝基苯酚的ln(A/A0)-t的关系图，依据相应紫外吸收图谱中不同时间的400nm处吸光度A。
图7是实施例5中500℃、600℃处理催化剂样品催化苯乙炔的转化率和选择性曲线图。
图8是实施例6中500℃、600℃处理催化剂样品催化糠醛的转化率和选择性曲线图。
具体实施方式
实施例1
A.将14.4g的Ni(NO3)2·6H2O、6.19g的Al(NO3)2·9H2O加入到100mL去CO2水中(摩尔比Ni2+:Al3+＝3:1)，超声溶解得到混合盐溶液，转移至四口烧瓶中；将6.0g的氢氧化钠加入到100mL去CO2水中，超声溶解得到碱溶液，转移至恒压滴管中；在70℃水浴锅中，氮气保护下搅拌，然后逐步滴入碱溶液至pH为10；滴加完成后，将得到的浆液转移到250mL的特氟龙高压釜中，120℃下晶化24h，过滤，用去CO2水洗涤并过滤至pH为7，最后在70℃下干燥24h，得到硝酸根插层镍铝水滑石NiAl-LDHs-NO3 -前体。将2g NiAl-LDHs-NO3 -前体与4g酒石酸溶于100ml去CO2水中，超声溶解得到混合溶液，转移至四口烧瓶中，称取4g NaOH溶于100ml去CO2水中，转移至恒压滴定管中。在70℃水浴锅中，氮气保护下搅拌搅拌，碱滴盐直至pH＝7，搅拌2h，经过过滤，洗涤，在70℃真空条件下干燥24h，得到有机酸插层的镍铝水滑石NiAl-LDHs-TA；交换前后XRD，FT-IR，TG-DTA谱图见图1，SEM谱图见图2；
B.将步骤A中制备的水滑石NiAl-LDHs-TA放置于高温气氛炉中，通入纯度为99.999％的N2，流速为40mL/min，升高炉内温度分别至300℃、350℃、400℃、500℃和600℃，升温速率为5℃/min，保持3h，然后自然冷却至室温，得到限域结构六面体形貌纳米镍基催化剂记为Ni/NiAlOx/C(XRD图见图3)。
对得到的交换前后NiAl-LDHs-NO3 -前体和NiAl-LDHs-TA进行XRD，FTIR，TG-DTA表征，结果见图1，SEM表征见图2，由图可以看出得到了类水滑石的层状结构，插层前后水滑石的XRD图可以看出，(003)(006)(009)衍射峰位置向低角度移动，层间距对应酒石酸分子大小。红外，热重分析同样证明酒石酸成功插入水滑石层间，且材料整体结构均匀一致。SEM结果显示交换前后，都保持规整的大约30nm水滑石特征六方片结构。
不同温度下NiAl-LDHs-TA，N2下还原产物的XRD图谱，结果见图3。由图可知随着温度的升高，水滑石层板结构逐渐坍塌，从300℃下爆发性还原的起点，几个宽峰Ni(Al)Ox特征衍射峰逐渐向金属Ni特征衍射峰移动，证明了C爆发性原位还原过程，R500℃/R600℃样品中仍有部分Ni(Al)Ox存在，说明我们制备的插层C是一种窄温度范围的爆发性的还原。
对还原后催化剂进行HRETEM表征，结果见图4，由图4可以看出随着温度升高，从350℃、400℃纳米尺寸3-5nm的六面体形貌的金属Ni纳米粒子，转化成了500℃、600℃下晶粒尺寸大约7-9nm的类球形颗粒。其中低温度下我们得到了限域在Ni(Al)Ox/C基底上的小尺寸六面体形貌的Ni/Ni(Al)Ox/C催化剂。
上述制备的限域结构的镍基纳米粒子催化剂，其组成结构为：小尺寸的六面体形貌的金属纳米粒子限域在铝掺杂的金属氧化物边缘，外围由无定型碳相包围的结构。该催化剂为黑色粉末状物质，颗粒粒径大小约为3-5nm。
实施例2
将上述制备的限域结构的镍基纳米粒子催化剂应用于对硝基苯酚催化加氢反应，其工艺条件是：量取2ml乙醇配制的浓度为1×10-4mol/L的对硝基苯酚溶液，溶于标准(1cm×1cm×3cm)3mL体积石英比色皿中。加入限域结构镍基催化剂0.005g，过量硼氢化钠约为17mg，在室温下搅拌快速反应。在紫外可见分光光度计扫描范围250-500nm内记录时间依赖性吸收光谱，每30s扫一次，来分析反应物向产物的转化。
对不同还原温度及催化剂用量、反应物浓度对反应对硝基苯酚催化加氢活性进行考察。反应条件如下，紫外测试反应物转化率随各条件的变化如图5所示：
a)0.005g还原处理350℃镍基催化剂，2ml的1×10-4mol/L的对硝基苯酚溶液，17mg硼氢化钠，室温搅拌(图5)；
b)0.005g还原处理400℃镍基催化剂，2ml的1×10-4mol/L的对硝基苯酚溶液，17mg硼氢化钠，室温搅拌(图5)；
c)0.005g还原处理500℃镍基催化剂，2ml的1×10-4mol/L的对硝基苯酚溶液，17mg硼氢化钠，室温搅拌(图5)；
d)0.005g还原处理600℃镍基催化剂，2ml的1×10-4mol/L的对硝基苯酚溶液，17mg硼氢化钠，室温搅拌(图5)。
本发明提供的限域结构的六面体形貌镍基纳米粒子催化剂，特别适合用于对硝 基苯酚催化加氢反应。与传统的Ni基催化剂相比较，结果如图5图6所示：
1)从图5图6中可以看出，在特定还原温度下形成的六面体形貌的Ni/Ni(Al)Ox/C催化剂催化对硝基苯酚，400nm为反应物对硝基苯酚的吸收峰，300nm左右为生成物对氨基苯酚的吸收峰，反应在180s内迅速的反应完全，斜率代表为速率常数计算为3.4×10-2s-1。
2)从图5图6中可以看出，相比较于较高温度的还原样品及H2还原和购买的金属Ni基催化剂，Ni/Ni(Al)Ox/C有较高的反应速率。这不仅体现在小颗粒尺寸对对硝基苯酚这种表面反应的催化性能优势，还体现在形貌对催化反应活性有较大影响，特殊的六面体形貌暴露出较多的活性位来，并且限域在Ni(Al)Ox-C中，金属与其接触面对反应物的吸附起到了至关重要的作用，因此也促进了其催化反应的活性提高。
实施例3
采用双滴法合成制备水滑石前体，将2g NiAl-LDHs-NO3 -前体溶于60ml去CO2水中，转移至四口烧瓶中，4g有机酸溶于60ml去CO2水中，转移至注射器1中，将NaOH溶于60ml去CO2水中，浓度为1mol/L，转移至注射器2中，在70℃水浴锅中，惰性气体保护下搅拌，调节有机酸和碱的滴速，双滴前体溶液，维持pH值＝6，经过过滤，洗涤，在60℃真空条件下干燥24h，得到NiAl-LDHs-有机酸前体。其他条件不变，同实施例1的步骤B，探究不同条件合成前体对催化剂制备的影响。
实施例4
将实施例2中催化对硝基苯酚的催化剂用量改为0.003g，探究不同催化剂用量对催化反应的影响。
实施例5
将实施例1中得到的限域结构六面体形貌纳米镍基催化剂样品应用于苯乙炔选择加氢反应，结果如图7。图a为500℃处理样品，图b为600℃处理样品。由图可知，反应都能在130s左右转化完全，转化率达到100％，并且此时生成苯乙烯的选择性仍能保持在75％左右。由此可知在催化苯乙炔选择加氢反应中，限域结构Ni/Ni(Al)Ox/C催化剂有较高的催化活性和选择性。
实施例6
将实施例1中得到的限域结构六面体形貌纳米镍基催化剂样品应用于糠醛选 择加氢反应，结果如图8。图a为500℃处理样品，图b为600℃处理样品。由图可知，500℃处理样品催化糠醛在8h反应完全，且此时选择生成糠醇的选择性为65％左右，600℃处理样品催化糠醛在7h就能反应完全，且此时选择生成糠醇的选择性为75％左右。由此可知升高还原处理的温度对限域结构Ni/Ni(Al)Ox/C催化剂催化糠醛有较高的催化活性和选择性。
可以理解的是，以上是为了阐述本发明的原理和可实施性的示例，本发明并不局限于此。对于本领域内的普通技术人员而言，在不脱离本发明的精神和实质的情况下，可以做出各种变型和改进，这些变型和改进也视为本发明的保护范围。

Claims (8)

  1. 一种限域结构六面体形貌纳米镍基催化剂，其特征在于，使用惰性气体条件下层间碳还原法，利用水滑石层板间插入有机碳源控制爆发性原位均匀还原制备六面体形貌的金属镍纳米粒子，小尺寸六面体形貌的金属镍纳米粒子限域在铝掺杂的金属氧化物边缘，外围由无定型碳相包围，制备得到的催化剂为黑色粉末状物质，颗粒粒径大小为3-5nm。
  2. 一种限域结构六面体形貌纳米镍基催化剂的制备方法，其特征在于，将催化剂前驱体有机酸插层的镍铝水滑石置于气氛炉中，采用流速为30-80mL/min的氮气进行还原反应，还原温度为300-600℃，升温速率为2-10℃/min，还原时间为1-5h，反应完成后得到限域结构六面体形貌纳米镍基催化剂。
  3. 根据权利要求2所述的限域结构六面体形貌纳米镍基催化剂的制备方法，其特征在于，所述催化剂前驱体有机酸插层的镍铝水滑石的制备方法为：将硝酸根插层镍铝水滑石前体与有机酸溶于去CO2水中，转移至四口烧瓶中，硝酸根插层镍铝水滑石前体与有机酸的质量比范围为0.5-1；在60-70℃水浴锅中，惰性气体保护及不断搅拌下，向四口烧瓶中滴加浓度为1-2mol/L的NaOH溶液至pH值＝6-7，搅拌1-2h，经过过滤，洗涤，在60-70℃真空条件下干燥20-24h，得到催化剂前驱体有机酸插层的镍铝水滑石。
  4. 根据权利要求2所述的限域结构六面体形貌纳米镍基催化剂的制备方法，其特征在于，所述催化剂前驱体有机酸插层的镍铝水滑石的制备方法为：将硝酸根插层镍铝水滑石前体溶于去CO2水中，转移至四口烧瓶中；将有机酸溶于去CO2水中，转移至注射器中；将NaOH溶于去CO2水中，转移至另一注射器中；硝酸根插层镍铝水滑石前体与有机酸的质量比范围为0.5-1；在60-70℃水浴锅中，惰性气体保护及不断搅拌下，调节有机酸溶液和NaOH溶液的滴速，同时滴入四口烧瓶中，维持pH值＝6，经过过滤，洗涤，在60-70℃真空条件下干燥20-24h，得到催化剂前驱体有机酸插层的镍铝水滑石。
  5. 根据权利要求3或4所述的限域结构六面体形貌纳米镍基催化剂的制备方法，其特征在于，所述硝酸根插层镍铝水滑石前体中镍离子与铝离子摩尔比为2-3。
  6. 根据权利要求3或4所述的限域结构六面体形貌纳米镍基催化剂的制备方法，其特征在于，所述有机酸为酒石酸或月桂酸。
  7. 将权利要求1所述的限域结构六面体形貌纳米镍基催化剂应用于对硝基苯 酚催化加氢反应，其特征在于，量取2mL浓度为1×10-3-1×10-4mol/L的对硝基苯酚的乙醇溶液，加入限域结构六面体形貌纳米镍基催化剂0.003-0.005g，17-20mg的过量硼氢化钠，在室温下搅拌快速反应。
  8. 将权利要求1所述的限域结构六面体形貌纳米镍基催化剂应用于苯乙炔选择加氢和糠醛加氢反应中。
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