Metal oxide in-situ loaded granular carbon catalyst as well as preparation method and application thereof

Abstract

The invention discloses a metal oxide in-situ loaded granular carbon catalyst and a preparation method and application thereof.The preparation method comprises the steps that a crosslinking system formed by cassava starch, citric acid, a nitrogen-containing compound and metal salt serves as a bonding substance, and crosslinking forming is promoted through interaction of the bonding substance and biomass raw materials; the granular carbon catalyst with good mechanical strength is prepared through processes such as kneading and strip extrusion, shaping and granulation, curing and high-temperature carbonization, and used metal ions not only are beneficial to acceleration of formation of a crosslinking system, but also can be converted into uniformly dispersed metal oxide nano-particles in the high-temperature carbonization process, and are loaded on granular carbon in situ, so that the metal oxide nano-particles are uniformly dispersed in the high-temperature carbonization process. The catalytic active sites of the granular carbon catalyst are increased, so that the granular carbon catalyst shows excellent catalytic performance in rosin esterification reaction. According to the present invention, the bonding molding and the high catalytic performance are considered, the obtained catalyst further has advantages of low cost and easy recovery, and the new approach is provided for the development of the environmentally-friendly catalytic material.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of granular carbon materials, and particularly relates to a granular carbon catalyst with in-situ loaded metal oxides, a preparation method thereof and an application thereof. Background Art

[0002] Biomass-derived carbon materials have become ideal carriers for preparing metal oxide-loaded carbon material catalysts due to their rich hierarchical pore structures, high specific surface areas and excellent chemical stabilities. Their unique pore structures can not only effectively disperse active components, but also increase the contact between active sites and reactants, thereby significantly enhancing catalytic activities. However, most of the carbon material carriers studied currently are in powder form, which have problems such as high packing density, large pressure drop and easy abrasion in practical applications, restricting their industrial applications. Therefore, powder carbon materials need to be transformed into shaped carbon through shaping technologies.

[0003] In the preparation of shaped carbon, the binder method is a widely used process method, and its basic principle is to bond powdered carbon materials into shape by adding specific binders. This method has advantages such as high process maturity, controllable operation and good mechanical strength. However, the binder method also faces technical challenges. The use of binders often fills or even blocks the pore structures of powdered carbon materials, thereby having an adverse effect on their adsorption functions. In addition, conventional binder components may cover catalytic active centers, reducing the accessibility and active site utilization rate of shaped carbon as a catalyst. Therefore, it is necessary to develop new binder systems to prepare granular carbon materials with good catalytic performance.

[0004] Therefore, the present invention proposes a preparation method of a granular carbon catalyst with in-situ loaded metal oxides, which has a developed pore structure, excellent catalytic activity and is easy to recycle. This method uses biomass powder as a raw material, and a cross-linking system formed by cassava starch, citric acid and metal ions as a binding substance, and a nitrogen-containing compound is introduced to further enhance the cross-linking network. During the shaping process, metal ions accelerate the cross-linking process through coordination with biomass raw materials and other components in the adhesive system, and promote the uniform dispersion of metal ions. After high-temperature carbonization, they can be transformed into metal oxide nanoparticles in-situ loaded on the granular carbon, increasing catalytic active sites, so as to achieve both bonding and shaping and high catalytic performance. The granular carbon with in-situ loaded metal oxides prepared by the present invention has good mechanical strength and exhibits excellent catalytic activity in the esterification reaction of rosin and glycerol. At the same time, the granular carbon catalyst after the reaction is easy to recycle and has good application prospects. Summary of the Invention

[0005] The object of the present invention is to provide a granular carbon catalyst with in-situ loading of metal oxide, its preparation method and application. The granular carbon catalyst obtained in the present invention has a developed pore structure, good mechanical strength, and uniform loading of metal oxide thereon, and can exhibit excellent catalytic activity in the esterification reaction of rosin and glycerol.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A preparation method of a granular carbon catalyst with in-situ loading of metal oxide, which comprises the following steps: (1) By washing with deionized water, drying, pulverizing and screening, the biomass raw material is processed into a powdered biomass raw material; (2) Citric acid, metal salt and nitrogen-containing compound are mixed and dissolved in water, and then tapioca starch is added, and a milky white viscous adhesive system is obtained through cross-linking reaction; (3) The powdered biomass raw material obtained in step (1) and the adhesive system obtained in step (2) are kneaded, extruded by a twin-screw extruder, and then subjected to shaping granulation and curing to obtain spherical particles; (4) The spherical particles obtained in step (3) are carbonized, and after cooling, they are washed thoroughly with deionized water to obtain the granular carbon catalyst with in-situ loading of metal oxide.

[0007] Further, in step (1), screening is carried out using a 100-200 mesh sieve.

[0008] Further, in step (1), the biomass raw material includes one or more of wood chips, bamboo powder, and peanut shells.

[0009] Further, in step (2), the metal salt is one or more of chlorides and / or acetates of metals such as magnesium and zinc.

[0010] Further, in step (2), the nitrogen-containing compound is melamine or urea.

[0011] Further, in step (2), the mass ratio of citric acid, metal salt, nitrogen-containing compound to tapioca starch is 3:(10-20):6.25:7.

[0012] Further, in step (2), the amount of water used is converted according to 40 mL per gram of citric acid.

[0013] Further, in step (2), the temperature of the cross-linking reaction is 70-90 °C, and the time is 10-60 min.

[0014] Further, by weight, in step (3), the amount of the powdered biomass raw material used is 50 parts, and the amount of the adhesive system used is 146.25-156.25 parts.

[0015] Furthermore, the kneading time in step (3) is 30 - 60 min, and the temperature is 80 - 100 °C.

[0016] Furthermore, the curing temperature in step (3) is 100 °C, and the time is 8 - 12 h.

[0017] Furthermore, in step (4), the carbonization is carried out under a nitrogen atmosphere, the temperature is raised to 700 - 900 °C at a rate of 5 - 15 °C / min, and the temperature is maintained for 1 - 4 h.

[0018] The granular carbon catalyst with in-situ loaded metal oxide prepared by the above method can be used for the esterification reaction of rosin and glycerol.

[0019] Furthermore, specifically, rosin and glycerol are used as reactants, and the reaction is carried out at 260 °C for 4 h to obtain rosin glyceride.

[0020] Furthermore, the mass ratio of rosin to glycerol used is 4:1.

[0021] Furthermore, the dosage of the granular carbon catalyst with in-situ loaded metal oxide in the reaction is 3% of the mass of rosin.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention utilizes the cross-linking interaction between the oxygen-containing functional groups of biomass raw materials and the components of the adhesive system to promote the forming process of biomass raw materials, and then obtains a granular carbon catalyst with in-situ loaded metal oxide and good mechanical strength through high-temperature carbonization.

[0023] (2) Compared with the traditional powdered metal oxide-supported carbon catalyst, in the catalyst forming process of the present invention, metal ions are introduced. Through the coordination action between metal ions and other components in the biomass raw materials and the adhesive system, not only can the formation of the cross-linking system be accelerated, but also the metal ions can be converted into uniformly dispersed metal oxide nanoparticles during the high-temperature carbonization process and be in-situ loaded on the granular carbon to increase the catalytic active sites of the granular carbon, so as to achieve both good bonding performance and high catalytic activity.

[0024] (3) The granular carbon catalyst with in-situ loaded metal oxide provided by the present invention has a developed pore structure, good mechanical strength and rich active sites, shows excellent catalytic performance in the esterification reaction of rosin and glycerol, and also has the advantages of low cost and easy recovery. Description of the Drawings

[0025] Figure 1 It is the N2 adsorption-desorption isotherm (A) and pore size distribution diagram (B) of the granular carbon catalyst with in-situ loaded magnesium oxide obtained in Example 1 and Comparative Example 1.

[0026] Figure 2 XRD diffraction patterns of the granular carbon catalyst with in-situ loaded magnesium oxide obtained in Example 1 and Comparative Example 1.

[0027] Figure 3 Sample diagram (A) and TEM diagram (B) of the granular carbon catalyst with in-situ loaded magnesium oxide obtained in Example 1. Detailed implementation mode

[0028] A method for preparing a granular carbon catalyst with in-situ loaded metal oxide, comprising the following steps: (1) Washing the biomass raw material with deionized water, drying, pulverizing, and screening through a 100-200 mesh sieve to obtain a powdered biomass raw material; (2) Mixing citric acid, metal salt, and nitrogen-containing compound, adding water to dissolve, then adding tapioca starch at 70-90 °C, and performing a cross-linking reaction for 10-60 min to obtain a milky white viscous adhesive system; (3) By weight, adding 50 parts of the powdered biomass raw material obtained in step (1) and 146.25-156.25 parts of the adhesive system obtained in step (2) into a kneader, kneading at 80-100 °C for 30-60 min, then extruding through a twin-screw extruder, granulating with a shaping granulator, and curing at 100 °C for 8-12 h to obtain spherical particles; (4) Placing the spherical particles obtained in step (3) in a muffle furnace, heating to 700-900 °C at a rate of 5-15 °C / min under a nitrogen atmosphere, holding for 1-4 h, and thoroughly washing with deionized water after cooling to obtain a granular carbon catalyst with in-situ loaded metal oxide.

[0029] Among them, the biomass raw material in step (1) includes one or more of sawdust, bamboo powder, and peanut shells.

[0030] The mass ratio of citric acid, metal salt, nitrogen-containing compound to tapioca starch used in step (2) is 3:(10-20):6.25:7. The metal salt is one or more of magnesium, zinc, etc. in the form of chloride salts and / or acetate salts, and the nitrogen-containing compound is melamine or urea. The amount of water is calculated according to 40 mL per gram of citric acid.

[0031] To make the content of the present invention more understandable, the technical solutions of the present invention are further described below in conjunction with specific implementation modes, but the present invention is not limited thereto.

[0032] Example 1 (1) Washing the sawdust with deionized water, drying, pulverizing, and screening through a 120-140 mesh sieve to obtain sawdust powder; (2) After mixing 3 g of citric acid, 15 g of magnesium chloride, 6.25 g of melamine and 120 mL of water at 80 °C, 7 g of tapioca starch was added, and a milky white viscous adhesive system was obtained after a 15-minute cross-linking reaction; (3) 50 g of the wood chip powder obtained in step (1) and 151.25 g of the adhesive system obtained in step (2) were kneaded in a kneader at 80 °C for 60 min, then extruded through a twin-screw extruder, and then granulated by a shaping granulator and cured at 100 °C for 12 h to obtain spherical particles; (4) The spherical particles described in step (3) were placed in a muffle furnace, heated to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere, kept for 2 h and then naturally cooled, and after being thoroughly washed with deionized water, a particulate carbon catalyst with in-situ loading of magnesium oxide was obtained, where the loading amount of magnesium oxide was 18.40 wt%.

[0033] Example 2 (1) The wood chips were washed with deionized water, dried, crushed, and screened through a 120-140 mesh sieve to obtain wood chip powder; (2) After mixing 3 g of citric acid, 15 g of zinc acetate dihydrate, 6.25 g of melamine and 120 mL of water at 80 °C, 7 g of tapioca starch was added, and a milky white viscous adhesive system was obtained after a 15-minute cross-linking reaction; (3) 50 g of the wood chip powder obtained in step (1) and 151.25 g of the adhesive system obtained in step (2) were kneaded in a kneader at 80 °C for 60 min, then extruded through a twin-screw extruder, and then granulated by a shaping granulator and cured at 100 °C for 12 h to obtain spherical particles; (4) The spherical particles described in step (3) were placed in a muffle furnace, heated to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere, kept for 2 h and then naturally cooled, and after being thoroughly washed with deionized water, a particulate carbon catalyst with in-situ loading of zinc oxide was obtained, where the loading amount of zinc oxide was 15.43 wt%.

[0034] Example 3 (1) The bamboo was washed with deionized water, dried, crushed, and screened through a 120-140 mesh sieve to obtain bamboo powder; (2) After mixing 3 g of citric acid, 15 g of magnesium chloride, 6.25 g of melamine and 120 mL of water at 80 °C, 7 g of tapioca starch was added, and a milky white viscous adhesive system was obtained after a 15-minute cross-linking reaction; (3) Knead 50 g of the bamboo powder obtained in step (1) and 151.25 g of the adhesive system obtained in step (2) at 80 °C for 60 min using a kneader, then extrude through a twin-screw extruder, and then granulate using a shaping granulator and cure at 100 °C for 10 h to obtain spherical particles; (4) Place the spherical particles described in step (3) in a muffle furnace, heat up to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere, hold for 2 h and then cool naturally. After washing thoroughly with deionized water, a granular carbon catalyst with in-situ loaded magnesium oxide is obtained.

[0035] Example 4 (1) Wash the wood chips with deionized water, dry, crush, and screen through a 120-140 mesh sieve to obtain wood chip powder; (2) Mix 3 g of citric acid, 15 g of magnesium chloride, 6.25 g of melamine and 120 mL of water at 80 °C, then add 7 g of tapioca starch, and obtain a milky white viscous adhesive system after a 15 min crosslinking reaction; (3) Knead 50 g of the wood chip powder obtained in step (1) and 151.25 g of the adhesive system obtained in step (2) at 80 °C for 60 min using a kneader, then extrude through a twin-screw extruder, and then granulate using a shaping granulator and cure at 100 °C for 12 h to obtain spherical particles; (4) Place the spherical particles described in step (3) in a muffle furnace, heat up to 700 °C at a rate of 5 °C / min under a nitrogen atmosphere, hold for 2 h and then cool naturally. After washing thoroughly with deionized water, a granular carbon catalyst with in-situ loaded magnesium oxide is obtained.

[0036] Example 5 (1) Wash the wood chips with deionized water, dry, crush, and screen through a 120-140 mesh sieve to obtain wood chip powder; (2) Mix 3 g of citric acid, 20 g of magnesium chloride, 6.25 g of melamine and 120 mL of water at 80 °C, then add 7 g of tapioca starch, and obtain a milky white viscous adhesive system after a 15 min crosslinking reaction; (3) Knead 50 g of the wood chip powder obtained in step (1) and 156.25 g of the adhesive system obtained in step (2) at 80 °C for 60 min using a kneader, then extrude through a twin-screw extruder, and then granulate using a shaping granulator and cure at 100 °C for 12 h to obtain spherical particles; (4) Place the spherical particles described in step (3) in a muffle furnace, heat them up to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere, keep them at this temperature for 2 h, then let them cool naturally. After being thoroughly washed with deionized water, a granular carbon catalyst with in-situ loaded magnesium oxide is obtained, where the loading amount of magnesium oxide is 22.37 wt%.

[0037] Example 6 (1) Wash the wood chips with deionized water, dry them, crush them, and sieve them through a 120 - 140 mesh sieve to obtain wood chip powder; (2) Mix 3 g of citric acid, 10 g of magnesium chloride, 6.25 g of melamine, and 120 mL of water at 80 °C, then add 7 g of tapioca starch. After a 15 - minute crosslinking reaction, a milky white viscous adhesive system is obtained; (3) Knead 50 g of the wood chip powder obtained in step (1) and 146.25 g of the adhesive system obtained in step (2) at 80 °C for 60 min using a kneader, then extrude them through a twin - screw extruder, and then granulate them using a shaping granulator and cure them at 100 °C for 12 h to obtain spherical particles; (4) Place the spherical particles described in step (3) in a muffle furnace, heat them up to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere, keep them at this temperature for 2 h, then let them cool naturally. After being thoroughly washed with deionized water, a granular carbon catalyst with in-situ loaded magnesium oxide is obtained, where the loading amount of magnesium oxide is 12.84 wt%.

[0038] Example 7 (1) Wash the wood chips with deionized water, dry them, crush them, and sieve them through a 120 - 140 mesh sieve to obtain wood chip powder; (2) Mix 3 g of citric acid, 15 g of magnesium chloride, 6.25 g of urea, and 120 mL of water at 80 °C, then add 7 g of tapioca starch. After a 15 - minute crosslinking reaction, a milky white viscous adhesive system is obtained; (3) Knead 50 g of the wood chip powder obtained in step (1) and 151.25 g of the adhesive system obtained in step (2) at 80 °C for 60 min using a kneader, then extrude them through a twin - screw extruder, and then granulate them using a shaping granulator and cure them at 100 °C for 12 h to obtain spherical particles; (4) Place the spherical particles described in step (3) in a muffle furnace, heat them up to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere, keep them at this temperature for 2 h, then let them cool naturally. After being thoroughly washed with deionized water, a granular carbon catalyst with in-situ loaded magnesium oxide is obtained.

[0039] Comparative Example 1 (1) Wash the wood chips with deionized water, dry them, crush them, and sieve them through a 120 - 140 mesh sieve to obtain wood chip powder; (2) After mixing 3 g of citric acid, 6.35 g of commercial magnesium oxide, 6.25 g of melamine and 120 mL of water at 80 °C, 7 g of tapioca starch was added, and a milky white viscous adhesive system was obtained after a 15-min cross-linking reaction; (3) 50 g of the wood chip powder obtained in step (1) and 142.60 g of the adhesive system obtained in step (2) were kneaded in a kneader at 80 °C for 60 min, then extruded through a twin-screw extruder, and then granulated by a shaping granulator and cured at 100 °C for 12 h to obtain spherical particles; (4) The spherical particles described in step (3) were placed in a muffle furnace, heated to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere, held for 2 h and then cooled naturally. After being thoroughly washed with deionized water, a granular carbon catalyst with in-situ loading of commercial magnesium oxide was obtained, wherein the loading amount of commercial magnesium oxide was 16.91 wt%.

[0040] Comparative Example 2 (1) The wood chips were washed with deionized water, dried, crushed, and screened through a 120-140 mesh sieve to obtain wood chip powder; (2) After mixing 3 g of citric acid, 15 g of magnesium chloride and 120 mL of water at 80 °C, 7 g of tapioca starch was added, and a milky white viscous adhesive system was obtained after a 15-min cross-linking reaction; (3) 50 g of the wood chip powder obtained in step (1) and 145 g of the adhesive system obtained in step (2) were kneaded in a kneader at 80 °C for 60 min, then extruded through a twin-screw extruder, and then granulated by a shaping granulator and cured at 100 °C for 12 h to obtain spherical particles; (4) The spherical particles described in step (3) were placed in a muffle furnace, heated to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere, held for 2 h and then cooled naturally. After being thoroughly washed with deionized water, a granular carbon catalyst with in-situ loading of magnesium oxide was obtained, wherein the loading amount of magnesium oxide was 14.52 wt%.

[0041] Comparative Example 3 (1) The wood chips were washed with deionized water, dried, crushed, and screened through a 120-140 mesh sieve to obtain wood chip powder; (2) After mixing 3 g of citric acid, 6.25 g of melamine and 120 mL of water at 80 °C, 7 g of tapioca starch was added, and a milky white viscous adhesive system was obtained after a 15-min cross-linking reaction; (3) Knead 50 g of the wood chip powder obtained in step (1) and 136.25 g of the adhesive system obtained in step (2) at 80 °C for 60 min using a kneader, then extrude through a twin-screw extruder, and then granulate using a shaping granulator and cure at 100 °C for 12 h to obtain spherical particles; (4) Place the spherical particles described in step (3) in a muffle furnace, heat up to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere, hold for 2 h, and then cool naturally. After thorough washing with deionized water, unloaded granular carbon is obtained.

[0042] (5) Take 10 g of the granular carbon obtained in step (4), pour it into a beaker containing 20 mL of MgCl2 solution (1 M), mix under magnetic stirring, ultrasonicate for 2 h, and then stir at room temperature overnight. After filtration, it is placed in an oven for drying. The dried sample is heated up to 800 °C at a heating rate of 5 °C / min under a nitrogen atmosphere, held for 2 h, and then cooled naturally. After thorough washing with deionized water, a magnesium oxide-supported granular carbon catalyst prepared by the impregnation method is obtained, where the loading amount of magnesium oxide is 4.14 wt%.

[0043] Comparative Example 4 (1) Wash the wood chips with deionized water, dry, crush, and screen through a 120 - 140 mesh sieve to obtain wood chip powder; (2) Mix 3 g of citric acid, 15 g of magnesium chloride, 6.25 g of melamine, and 120 mL of water at 80 °C, then add 7 g of corn starch, and obtain a milky white viscous adhesive system after a 15-min crosslinking reaction; (3) Knead 50 g of the wood chip powder obtained in step (1) and 151.25 g of the adhesive system obtained in step (2) at 80 °C for 60 min using a kneader, then extrude through a twin-screw extruder, and then granulate using a shaping granulator and cure at 100 °C for 12 h to obtain spherical particles; (4) Place the spherical particles described in step (3) in a muffle furnace, heat up to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere, hold for 2 h, and then cool naturally to obtain a magnesium oxide in-situ supported granular carbon catalyst.

[0044] Figure 1 N2 adsorption-desorption isotherms and pore size distribution diagrams of the magnesium oxide-supported granular carbon catalysts obtained in Example 1 and Comparative Example 1. As Figure 1As shown, the adsorption and desorption isotherms of Example 1 and Comparative Example 1 both exhibit the characteristics of type I isotherms, indicating that the material mainly consists of micropores with a small amount of mesopores, and the pore size distribution diagram further confirms this view. At the same time, the specific surface area of the granular carbon catalyst obtained in Example 1 is significantly higher than that in Comparative Example 1, indicating that the metal oxides are more uniformly distributed therein, avoiding the phenomenon of pore blockage and facilitating the exposure of active sites.

[0045] Figure 2 XRD diffraction patterns of the granular carbon catalysts with in-situ loaded magnesium oxide obtained in Example 1 and Comparative Example 1. The characteristic peaks at 42.8° and 62.2° in the figure are attributed to magnesium oxide, indicating the successful loading of magnesium oxide on the granular carbon.

[0046] Figure 3 Sample diagram and TEM diagram of the granular carbon catalyst with in-situ loaded magnesium oxide obtained in Example 1. As can be seen from the figure, the diameter of the obtained granular carbon catalyst with in-situ loaded magnesium oxide is about 3 mm, and it can be observed from the TEM diagram that magnesium oxide is uniformly dispersed on the granular carbon. Combining Figure 2 It shows that the in-situ generation and uniform loading of metal oxides can be achieved by introducing magnesium ions during the cross-linking and forming process.

[0047] Performance test 1. The mechanical strength (i.e., point crushing force) of the granular carbon catalysts prepared in Examples 1-7 and Comparative Examples 1-4 was determined according to the strength test standard HG / T 2782-2011.

[0048] 2. The granular carbon catalysts prepared in Examples 1-7 and Comparative Examples 1-4 were used to catalyze the esterification reaction of rosin and glycerol, and the acid value and rosin conversion rate of the obtained rosin glyceride were determined. The specific operation was to weigh 2.0 g of the granular carbon catalyst, 60 g of rosin, and 15 g of glycerol, add them to a 250 mL three-necked flask, react at 260 °C for 4 h under a nitrogen atmosphere, filter the reaction product to obtain the product rosin glyceride, and titrate to determine the acid value of the rosin glyceride after cooling to obtain the rosin conversion rate.

[0049] The specific data are shown in Table 1.

[0050] Table 1 Effects of different granular carbon catalysts on the esterification reaction of rosin and glycerol

[0051] Combined with the above results analysis, in Comparative Example 1, when directly using commercial magnesium oxide as the catalytic active component in the forming process of the granular carbon catalyst, its catalytic activity and mechanical strength are inferior to those of the granular carbon catalyst prepared in Example 1. The main reason is that in Example 1, metal magnesium ions are introduced during the forming process. Through the coordination effect between the metal magnesium ions and the components in the biomass raw material and the adhesive system, the formation of the crosslinking system is accelerated, which is beneficial to improving the mechanical strength. In addition, during the high-temperature carbonization process, the magnesium ions can be transformed into uniformly dispersed magnesium oxide nanoparticles and in-situ loaded on the granular carbon, increasing the catalytic active sites of the granular carbon, thereby improving the catalytic performance. However, commercial magnesium oxide is difficult to produce a coordination effect with the components in the biomass raw material and the adhesive system, resulting in uneven dispersion of magnesium oxide, blocking the pores of the granular carbon, reducing the specific surface area, and further affecting the mechanical strength and catalytic activity of the granular carbon catalyst.

[0052] In Comparative Example 2, the mechanical strength of the prepared granular carbon catalyst without introducing melamine decreased, and the catalytic activity also decreased slightly. This is mainly because the introduction of melamine can enhance the crosslinking network through the hydrogen bond interaction between the amino group and other components, enhancing the mechanical strength of the granular carbon catalyst. At the same time, nitrogen doping can adjust the surface chemical properties of the carbon material and improve the catalytic performance of the catalyst.

[0053] In the preparation process of Comparative Example 3, a magnesium oxide-loaded granular carbon catalyst was prepared by the method of forming first and then impregnating. However, the interaction force between the magnesium ions and the already carbonized and formed granular carbon is weak, resulting in a decrease in both the activity and mechanical strength of the prepared catalyst.

[0054] In Comparative Example 4, when replacing the cassava starch with the same mass of corn starch, the mechanical strength of the prepared granular carbon catalyst decreased significantly, and the catalytic activity also decreased slightly. This may be because cassava starch is mainly composed of amylopectin, while corn starch is mainly composed of amylose. Therefore, replacing cassava starch with corn starch leads to a decrease in the compactness of the crosslinking network of the adhesive system, weakening the adhesion force between particles, and ultimately resulting in a significant decrease in the mechanical strength of the granular carbon catalyst.

[0055] In contrast, through the interaction between magnesium ions and each component in the biomass raw material and the adhesive system, the present invention successfully prepared a magnesium oxide in-situ loaded granular carbon catalyst with high catalytic activity and good mechanical strength, showing more excellent performance. And through the comparison of Examples 1 to 7, it can be seen that the method of the present invention has good universality and controllability.

[0056] The above are only the preferred embodiments of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.

Claims

1. A preparation method of a granular carbon catalyst with in-situ loading of metal oxide, characterized in that: It includes the following steps: (1) The biomass raw material is processed into a powdery biomass raw material through deionized water washing, drying, pulverizing and sieving; (2) Citric acid, metal salt and nitrogen-containing compound are mixed and dissolved in water, and then tapioca starch is added. After cross-linking reaction, a milky white viscous adhesive system is obtained; (3) The powdery biomass raw material obtained in step (1) and the adhesive system obtained in step (2) are kneaded, extruded by a twin-screw extruder, and then subjected to shaping granulation and curing to obtain spherical particles; (4) The spherical particles obtained in step (3) are carbonized, and after cooling, they are thoroughly washed with deionized water to obtain the particulate carbon catalyst with in-situ loaded metal oxide.

2. The preparation method of the granular carbon catalyst with in-situ loading of metal oxide according to claim 1, characterized in that: In step (1), a 100-200 mesh sieve is used for sieving.

3. The preparation method of the granular carbon catalyst with in-situ loaded metal oxide according to claim 1, characterized in that: The biomass raw material described in step (1) includes one or more of wood chips, bamboo powder, and peanut shells.

4. The preparation method of the granular carbon catalyst with in-situ loading of metal oxide according to claim 1, characterized in that: In step (2), the mass ratio of citric acid, metal salt, nitrogen-containing compound to tapioca starch is 3:(10-20): 6.25:7, wherein the metal salt is one or more of magnesium chloride and / or zinc acetate of magnesium and zinc, and the nitrogen-containing compound is melamine or urea; the amount of water is calculated according to 40 mL per gram of citric acid.

5. The preparation method of the granular carbon catalyst with in-situ loading of metal oxide according to claim 1, wherein: In step (2), the temperature of the cross-linking reaction is 70-90 °C and the time is 10-60 min.

6. The preparation method of the granular carbon catalyst with in-situ loading of metal oxide according to claim 1, characterized in that: By weight, the amount of the powdery biomass raw material in step (3) is 50 parts, and the amount of the adhesive system is 146.25-156.25 parts.

7. The preparation method of the granular carbon catalyst with in-situ loading of metal oxide according to claim 1, characterized in that: In step (3), the kneading time is 30-60 min and the temperature is 80-100 °C; the curing temperature is 100 °C and the time is 8-12 h.

8. The preparation method of the granular carbon catalyst with in-situ loading of metal oxide according to claim 1, characterized in that: In step (4), the carbonization is carried out in a nitrogen atmosphere, heated to 700-900 °C at a rate of 5-15 °C / min, and kept warm for 1-4 h.

9. Application of a particulate carbon catalyst with in-situ loaded metal oxide prepared by the preparation method according to any one of claims 1-8 in the catalytic rosin esterification reaction.

10. The application according to claim 9, characterized in that: Using rosin and glycerol as reactants, reacting at 260 °C for 4 h to obtain rosin glyceride.

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