阅读说明：本技术 一种负载Mo的纯硅沸石非均相催化剂及其制备方法与应用 (Mo-loaded pure silicalite heterogeneous catalyst and preparation method and application thereof ) 是由 吴国强 陈超 洪艳平 蔡雷 高秀 黎冬明 于 2020-08-11 设计创作，主要内容包括：本发明公开了一种纯硅沸石(Silicalite-1)负载钼(Mo)非均相催化剂的制备方法与其催化麻疯树籽油转酯化生产生物柴油的应用。本发明通过等体积浸渍法将含钼化合物负载在纯硅沸石Silicalite-1的外表面上,形成仅外表面上含金属位点的高效非均相催化剂。一方面,Mo物种在Silicalite-1沸石外表面上引入,使该固体催化剂具有高效催化麻疯树油转酯化的活性；另一方面,Silicalite-1沸石大表面积的结构特性让Mo能够稳定且高度分散在其表面,两者作用相辅相成。本发明通过在纯硅Silicalite-1沸石外表面上负载Mo,可以在相对温和的条件一步法高效生产生物柴油,而且催化剂后处理简单,显著地简化了生产工艺；另外,该催化剂的高催化活性和良好的催化稳定性,可以降低催化剂的使用成本,使其在工业推广中具有巨大的优势。(The invention discloses a preparation method of a pure Silicalite (Silicalite-1) loaded molybdenum (Mo) heterogeneous catalyst and application of the catalyst in catalyzing transesterification of barbadosnut seed oil to produce biodiesel. According to the invention, a molybdenum-containing compound is loaded on the outer surface of the pure Silicalite-1 by an isometric impregnation method, so that the high-efficiency heterogeneous catalyst containing metal sites on the outer surface only is formed. On one hand, Mo species is introduced on the outer surface of the Silicalite-1 zeolite, so that the solid catalyst has the activity of efficiently catalyzing the transesterification of the barbadosnut oil; on the other hand, the structural characteristics of the large surface area of the Silicalite-1 zeolite allow Mo to be stably and highly dispersed on the surface of the zeolite, and the two functions supplement each other. According to the invention, Mo is loaded on the outer surface of the pure silicon Silicalite-1 zeolite, so that the biodiesel can be efficiently produced in one step under relatively mild conditions, the post-treatment of the catalyst is simple, and the production process is remarkably simplified; in addition, the catalyst has high catalytic activity and good catalytic stability, and can reduce the use cost of the catalyst, so that the catalyst has great advantages in industrial popularization.)

1. A Mo-loaded pure silicalite heterogeneous catalyst, comprising: the non-porous structure pure silicon zeolite loaded metal Mo is prepared by calcining.

2. The Mo-loaded pure silicalite heterogeneous catalyst according to claim 1, wherein the loading of metallic Mo is 3-20 wt%.

3. The Mo-loaded pure silicalite heterogeneous catalyst according to claim 1, wherein the metallic Mo is loaded on the outer surface of the pure silicalite.

4. A process for the preparation of a Mo-loaded pure silicalite heterogeneous catalyst according to any one of claims 1 to 3, characterized in that: the method comprises the following specific steps:

(1) preparation of pure silicon Silicalite-1 material with non-porous structure

Accurately weighing 59.6g of 25% tetrapropylammonium hydroxide solution and 40g of deionized water, fully stirring for 10min, slowly dropwise adding 63g of tetraethoxysilane into the system under the condition of vigorous stirring, and continuing to age for 2h after dropwise adding; after the aging is finished, distilling the solution at 80 ℃ to remove alcohol until the weight is constant, and then transferring the solution into a stainless steel crystallization kettle for crystallization; after crystallization is finished, centrifugally washing the mixture solution to be neutral, drying the obtained solid overnight at 120 ℃, and grinding the dried solid to 100 meshes to obtain a pure silicon Silicalite-1 material with a non-porous structure;

(2) preparation of Mo-loaded Silicalite-1 heterogeneous catalyst

Taking a proper amount of the pure silicon Silicalite-1 material with the non-porous structure prepared in the step (1), dropwise adding the prepared ammonium molybdate solution into the pure silicon Silicalite-1 material by adopting an isometric impregnation method, and aging the mixture at room temperature overnight after the impregnation is finished; then the mixture is dried in an oven at 120 ℃ for 24 hours and finally calcined in a muffle furnace at high temperature to obtain the solid catalyst xMo/S-1 of the pure silicon Silicalite-1 with Mo supported on the outer surface.

5. The method of claim 4 for the preparation of a Mo supported pure silicalite heterogeneous catalyst characterized in that: the crystallization is specifically crystallization at 105 ℃ for 4 days.

6. The method of claim 4 for the preparation of a Mo supported pure silicalite heterogeneous catalyst characterized in that: and (3) calcining in the muffle furnace at 550 ℃ for 3 h.

7. Use of a Mo-loaded pure silicalite heterogeneous catalyst as claimed in any one of claims 1-3 in catalyzing the transesterification of Jatropha curcas seed oil to produce biodiesel.

8. The use of the Mo-loaded pure silicalite heterogeneous catalyst of claim 7 in catalyzing transesterification of Jatropha curcas seed oil to produce biodiesel, wherein: the method comprises the following specific steps:

placing the mixed solution of the barbadosnut seed oil and the methanol in a stainless steel crystallization reaction kettle; accurately weighing xMo/S-1, adding into the mixed solution, sealing the reaction kettle, and stirring at 100 deg.C for 16 hr; after the reaction is finished, taking out the reaction mixed liquid for centrifugation, rotary evaporation and centrifugation; the supernatant after centrifugation is the biodiesel.

9. The use of the Mo-loaded pure silicalite heterogeneous catalyst of claim 8 in catalyzing transesterification of Jatropha curcas seed oil to produce biodiesel, wherein: the mass ratio of the barbadosnut seed oil to the methanol in the mixed solution is 3: 1.

10. The use of the Mo-loaded pure silicalite heterogeneous catalyst of claim 8 in catalyzing transesterification of Jatropha curcas seed oil to produce biodiesel, wherein: the amount of xMo/S-1 is 2 wt% of the mass of jatropha curcas seed oil.

Technical Field

The invention relates to the field of catalytic material preparation and energy development and application, in particular to a Mo-loaded pure silicalite heterogeneous catalyst and a preparation method and application thereof.

Background

With the diminishing of fossil energy and the outstanding contradiction between population growth and energy consumption, it is important to find new renewable and rich resources, and the biodiesel as a sustainable energy source is concerned by people. At present, besides the technical difficulties in the production process, the source of raw oil is also one of the bottlenecks in inhibiting the development of biodiesel. With the continuous expansion of the production and use scale of biodiesel, the high cost and the conflict between eating and production result in that the traditional edible oil plants such as soybean, rapeseed, sunflower seed, corn and the like are not allowed to be used as raw materials for producing biodiesel. Therefore, jatropha curcas, one of the non-edible oil plants, has received much attention. Compared with edible oil such as rapeseed oil, soybean oil, etc., the jatropha curcas has strong adaptability to the growth environment and can be planted in a large area in arid areas. Therefore, the preparation of the biodiesel by using the jatropha curcas seed oil not only can better solve the problem of high raw material cost, but also can fully utilize idle resources. In addition, compared with non-edible oil plants such as pistacia chinensis bunge, cornus wilsoniana and the like, the oil content of the jatropha curcas seeds is higher, and the jatropha curcas seed oil becomes an ideal raw material for preparing the biodiesel.

At present, homogeneous acids (e.g.H) are mostly used in industry₂SO₄、HNO₃Etc.) or a base (e.g.: NaOH, KOH, etc.) catalyst to catalyze the transesterification of the raw oil to produce biodiesel. However, preparation by homogeneous acid-or base-catalyzed transesterificationThe biodiesel has the problems of difficult separation of product catalyst, environmental pollution, serious equipment corrosion and the like, and the saponification reaction of the biodiesel on high-acid-value raw oil is easy to occur, so that the raw oil needs to be pretreated. Therefore, the search for a novel heterogeneous catalyst with good catalytic performance is an urgent problem to be solved in the current biodiesel production. The existing biodiesel production is mostly prepared by traditional liquid acid or by base catalysis of deacidified raw oil. The former generates a large amount of acidic waste water in the preparation process and causes the problems of environmental pollution, equipment corrosion and the like; although the latter shortens the production time of the biodiesel, the production process is complex and is not beneficial to industrial popularization.

At present, there is a fresh report that under relatively mild conditions, a heterogeneous catalyst is adopted to efficiently catalyze the one-step transesterification of the jatropha curcas seed oil to produce the biodiesel; in addition, no report has been made on the preparation of a solid catalyst of molybdenum supported on Silicalite-1 zeolite having a low metal content, a high metal dispersion degree and a high catalytic transesterification activity by supporting Mo only on the outer surface of pure Silicalite (Silicalite-1).

Disclosure of Invention

Based on the characteristic that large-size jatropha curcas seed oil molecules cannot pass through microporous pore canals of zeolite, the invention develops the Mo-loaded pure-silica zeolite high-performance heterogeneous catalyst, which takes Silicalite-1 zeolite with simple preparation process as a carrier and only loads Mo on the outer surface of the carrier to prepare the Silicalite-1 zeolite-loaded molybdenum solid catalyst with low metal content, high metal dispersion degree and high catalytic transesterification activity. In order to obtain more efficient catalytic performance, the invention obtains the solid catalyst with efficient catalytic performance by loading Mo on the outer surface of the pure Silicalite (Silicalite-1).

In order to achieve the aim, the Mo-supported pure silicon (Silicalite-1) zeolite heterogeneous catalyst provided by the invention is prepared by carrying metal Mo on a pure silicon zeolite with a non-porous structure and then calcining.

Wherein the loading amount of Mo is 3-20 wt%; the metal Mo is loaded on the surface of the pure silicon zeolite.

Preferably, the loading of Mo is 5-15 wt%.

The invention also provides a preparation method of the Mo-loaded pure silicalite heterogeneous catalyst, which comprises the following specific steps:

(1) preparation of pure silicon Silicalite-1 material with non-porous structure

Accurately weighing 59.6g of 25% tetrapropylammonium hydroxide solution (TPAOH) and 40g of deionized water, fully stirring for 10min, slowly dropwise adding 63g of Tetraethoxysilane (TEOS) into the system under the condition of vigorous stirring, and continuously aging for 2h after dropwise adding; after the aging is finished, distilling the solution at 80 ℃ to remove alcohol until the weight is constant, and then transferring the solution into a stainless steel crystallization kettle for crystallization; after crystallization is finished, centrifugally washing the mixture solution to be neutral, drying the obtained solid overnight at 120 ℃, and grinding the dried solid to 100 meshes to obtain a pure silicon Silicalite-1 material with a non-porous structure;

wherein the crystallization is specifically crystallization at 105 ℃ for 4 days.

(2) Preparation of Mo-loaded Silicalite-1 heterogeneous catalyst

Taking a proper amount of the pure silicon Silicalite-1 material with the non-porous structure prepared in the step (1), dropwise adding the prepared ammonium molybdate solution into the pure silicon Silicalite-1 material by adopting an isometric impregnation method, and aging the mixture at room temperature overnight after the impregnation is finished; then it was dried in an oven at 120 ℃ for 24 hours and finally calcined in a muffle furnace at high temperature for a period of time to obtain a solid catalyst of Silicalite-1 with Mo supported on the outer surface (xMo/S-1, where the Mo loading is x wt%).

Preferably, the calcining temperature in the muffle furnace is 550 ℃, and the calcining time is 3 h.

The invention also provides application of the heterogeneous catalyst loaded with Mo pure silicalite in catalyzing transesterification of Jatropha curcas seed oil to produce biodiesel. The reaction equation for the catalytic reaction is shown below:

the method comprises the following specific steps of catalyzing the transesterification of the jatropha curcas seed oil to produce the biodiesel:

placing the mixed solution of the barbadosnut seed oil and the methanol in a stainless steel crystallization reaction kettle; accurately weighing xMo/S-1, adding into the mixed solution, sealing the reaction kettle, and stirring at 100 deg.C for 16 hr; after the reaction is finished, taking out the reaction mixed liquid for centrifugation, rotary evaporation and centrifugation; the supernatant after centrifugation is the biodiesel.

Wherein the mass ratio of the barbadosnut seed oil to the methanol in the mixed solution is 3: 1.

Wherein the amount of xMo/S-1 is 2 wt% of the jatropha curcas seed oil.

According to the invention, a molybdenum-containing compound is loaded on the outer surface of the pure Silicalite-1 by an isometric impregnation method, so that the high-efficiency heterogeneous catalyst containing metal sites on the outer surface only is formed. On one hand, Mo is introduced on the outer surface of the Silicalite-1 zeolite to promote the Mo to perform catalytic reaction with large-size grease molecules, so that the solid catalyst has the activity of efficiently catalyzing the transesterification of the barbadosnut oil; on the other hand, Silicalite-1 zeolite has a large external surface area (S)_Ext＝186m²The structural characteristics of the Mo and the Si-OH-rich surface enable the Mo to be stably and highly dispersed on the surface, and the two functions supplement each other.

The invention has the beneficial effects that:

the invention firstly prepares a pure Silicalite (Silicalite-1) material without a pore channel structure, and then loads Mo on the outer surface of the material to introduce a new metal catalytic active site, thereby preparing the Silicalite-1 loaded molybdenum (xMo/S-1) solid catalyst with low metal content, high metal dispersity and high catalytic transesterification activity. Meanwhile, due to the large outer surface area and good adsorption property of the Silicalite-1 zeolite, Mo can be uniformly and stably dispersed on the outer surface of the Silicalite-1 zeolite, the Silicalite-1 zeolite and the Silicalite-1 zeolite supplement each other, the yield of the xMo/S-1 solid catalyst in the transesterification reaction of the barbadosnut seed oil is remarkably improved, and the transesterification yield is only slightly reduced after the catalyst is repeatedly reacted for five times, so that the possibility is provided for the industrial application of the catalyst.

Drawings

FIG. 1 is a scanning electron micrograph (left) and a transmission electron micrograph (right) of 7Mo/S-1 prepared in example of the present invention

FIG. 2 is an X-ray diffraction pattern of S-1 prepared in comparative example 1 and 7Mo/S-1 prepared in example of the present invention

FIG. 3 is N of S-1 prepared in comparative example 1 and 7Mo/S-1 prepared in example in the present invention₂Physical adsorption de-attached drawing

The invention is further explained with reference to the drawings and the embodiments.

Detailed Description