CN103084187B - Carbon-based solid acid and preparation method thereof - Google Patents

Abstract

The invention provides a carbon-based solid acid and a preparation method thereof. The invention uses fresh fruit shells as raw materials. After the fresh fruit shells are washed with water, dried and crushed to a required particle size, they are added to an activator solution for soaking and activation. After the activated fruit shell is dried, it is carbonized under heating conditions to prepare activated carbon. After the activated carbon material is ground into powder, it is boiled in an acid solution, then suction filtered, rinsed with distilled water and dried. The dried The activated carbon material is heated and sulfonated by a sulfonating agent. The sulfonated mixture is slowly poured into cold water and stirred continuously. The black solid powder obtained by suction filtration and drying is carbon-based solid acid. The carbon-based solid acid prepared by the invention has the advantages of large specific surface area and high catalytic performance.

Description

A kind of carbon-based solid acid and preparation method thereof

technical field

The invention relates to a solid acid and a preparation method thereof, in particular to a carbon-based solid acid and a preparation method thereof.

Background technique

Due to the wide application of acid catalysts and the requirements of green chemical industry, the development of green catalytic processes and catalysts targeting low-carbon production has become a hotspot in catalytic research in recent years. Only by improving the process and catalyst can the combination of scientific and technological innovation and green environmental protection be realized, and the simultaneous growth of high corporate and social benefits can be brought about. In order to overcome the corrosiveness of liquid acid catalysts to production equipment; often form a homogeneous body with raw materials and products, resulting in complicated post-reaction treatment; the process is not conducive to the realization of continuous production requirements and other shortcomings, solid acid gradually replaces traditional liquid acid catalysts It is an inevitable development direction to make it widely used in various fields of chemical production. Through the development of solid acid for nearly half a century, so far, a large number of chemical processes previously involved in liquid acid have been replaced by solid acid.

In recent years, carbon-based sulfonated solid acids have attracted much attention as a new solid acid that can maintain strong protic acidity and stability in water. According to the summary of the literature, there are roughly two ideas for the synthesis of carbon-based sulfonated solid acids: the first is the incomplete carbonization of sulfonated polycyclic aromatic compounds. In this synthesis method, the sulfonation of aromatic compounds is the first stage of the reaction, and then the obtained sulfonated aromatic compounds are heated under the action of concentrated sulfuric acid for incomplete carbonization. However, the solid acid prepared by this method is prone to elution or severe deactivation of the aromatized compound in the liquid phase reaction at a temperature exceeding 100 °C. In addition, the experimental operation of carbonization under the condition of high-temperature concentrated sulfuric acid is very dangerous, so it also limits the promotion of this test method; the second synthesis method is to carry out incomplete carbonization and then sulfonation of organic compounds. This synthesis method is proposed on the basis of safe synthesis, and the target material is prepared from low-toxic or non-toxic substances as raw materials. Sucrose, glucose, starch, and cellulose, which are common in daily life, are used as carbon sources and roasted at high temperatures in isolation from the air to decompose them into amorphous carbon containing many small carbon sheets. Then introduce sulfonic acid groups on the amorphous carbon by sulfonation. Compared with the first method, this method is not only simple but also safe. In addition, the ability to synthesize highly active solid acids with practical value from abundant resources in nature is also the advantage of this synthesis method.

Takagaki et al prepared carbon-based solid acid with glucose as raw material (Acid-catalyzed reactions on flexible polycyclic aromatic carbon in amorphous carbon, Takagaki et al, Catal Today, 2006); Wang Du et al prepared a new type of carbon-based solid acid with starch as raw material Catalyst (carbon-based solid acid catalyzed acid reduction effect of high acid value biodiesel feedstock, Wang Du et al., Journal of Agricultural Engineering, 2009, 25); Ma Fang et al. prepared carbon-based solid acid catalyst (corn stalk solid Acid catalyst and catalytic synthesis of biodiesel, Ma Fang et al., Journal of Northwest A&F University, 2010, 38); Li Liqiang prepared composite carbon-based solid acid (composite carbon-based solid acid (composite Preparation and Application of Carbon-Based Solid Acid Catalyst, Li Liqiang, Master Thesis of Ningxia University, 2010).

In the prior art, the starting materials for the synthesis of carbon-based solid acids are mostly sucrose, glucose, starch, and cellulose, which are costly and cause waste of resources. In the prior art of preparing carbon-based solid acids, the final products are mostly non-porous, with low specific surface area and poor mechanical properties, which limits many reactant molecules, especially those macromolecular reactants close to the surface of the catalyst. Active site.

Contents of the invention

The technical problem to be solved by the present invention is: in the prior art, the cost of raw materials used in the preparation of carbon-based solid acid is relatively high and causes waste of resources; the specific surface area of the prepared product is relatively low.

In order to solve this technical problem, the technical solution adopted by the present invention is: the present invention provides a carbon-based solid acid, which is prepared by using fresh fruit shells as raw materials, and the prepared carbon-based solid acid The specific surface area of solid acid is above 1000m ² /g, and the acid value is above 2.5mmol/L.

The present invention also provides a method for preparing the above-mentioned carbon-based solid acid, the specific steps are:

(1) Pretreatment of fresh husks: Wash the air-dried fresh husks repeatedly with water until no impurities exist, then put the washed husks in an oven to dry, remove water, and screen out better-looking husks. Crushing in a crusher to 10-50 meshes for later use, preferably: fresh shells are nut shells, selected from one or more of chestnut shells, pine nut shells, walnut shells, coconut shells, water chestnut shells or peanut shells combination,

Preferably: the particle size after crushing is 10-30 mesh, further: the particle size is 20 mesh;

(2) Activation of fruit shells: According to the ratio of material to liquid 1:2 ~ 20g/mL, add the pretreated fruit shells into a solution with an activator concentration of 20 ~ 50wt% and soak for 2 ~ 12 hours, and then soak the soaked The husks are oven dried to remove excess moisture,

As preferred: the ratio of solid to liquid is 1:2～10g/mL, further: the ratio of solid to liquid is 1:5g/mL,

Preferably: the activator is a metal salt or an inorganic acid, selected from one or more of zinc chloride, aluminum chloride, ammonium chloride, calcium chloride, hydrogen chloride, phosphoric acid, sulfuric acid, nitric acid, potassium sulfide or iron salt The composition, further: activator solution is the zinc chloride of 30wt%;

(3) Carbonization of fruit shells: heat the shells obtained in step (2) to 400-600°C under a protective atmosphere, carbonize them for 2-15 hours to prepare activated carbon, grind the activated carbon into powder, and boil in acid solution , then suction filtered, rinsed with distilled water, and dried to obtain an activated carbon material,

Preferably: the protective atmosphere is selected from one or more combination atmospheres of nitrogen, carbon dioxide, argon, helium or neon, further: the protective atmosphere is nitrogen and/or carbon dioxide,

As preferably: heating temperature is 400～500 ℃, further: temperature is 450 ℃,

Preferably: the carbonization time is 2 to 10 hours, further: the carbonization time is 2 to 6 hours,

Preferably: the acid solution is selected from one or more of hydrochloric acid, phosphoric acid, citric acid, sulfuric acid or oxalic acid, and its concentration is 0.5-1.5 mol/L, further: the acid solution is 1 mol/L hydrochloric acid;

(4) Sulfonation of activated carbon material: The activated carbon material obtained in step (3) is sulfonated with a sulfonating agent for 6-15 hours at 80-200°C, and the sulfonated mixture is slowly poured into cold water and stirring continuously, the black solid powder obtained by suction filtration and drying is the carbon-based solid acid.

Preferably: the sulfonation temperature is 120-200°C, further: the sulfonation temperature is 150°C,

Preferably: the sulfonation time is 6-10h, further: the sulfonation time is 8-10h,

Preferably: the sulfonating agent is selected from one or more combinations of concentrated sulfuric acid, oleum, chlorosulfonic acid or sulfamic acid, further: the sulfonating agent is selected from concentrated sulfuric acid, oleum and chlorosulfonic acid A combination of one or more, and further: the sulfonating agent is concentrated sulfuric acid.

The present invention has following beneficial effect:

Using fresh fruit shells as raw materials to prepare carbon-based solid acids reduces the cost of solid acid preparation, opens up a new way to improve the quality of fruit shells, and effectively improves the utilization of fruit shells, which is in line with the current sustainable development of the country. policy. Compared with the prior art, the reaction conditions for preparing carbon-based solid acid from condensed ring compounds are safe, the product has good color, and the prepared carbon-based solid acid has a large specific surface area and good catalytic effect.

Description of drawings

Fig. 1 is the process flow diagram of the method for preparing carbon-based solid acid by fresh fruit shell of the present invention.

Detailed ways

In order to facilitate understanding of the present invention, the present invention enumerates the following examples. It should be clear to those skilled in the art that the embodiments are only for helping to understand the present invention, and should not be regarded as specific limitations on the present invention.

Example 1:

Pretreatment of fresh husks:

Take fresh chestnut shells (yellow brown) from Xinyang, Henan, and repeatedly wash off the dust and impurities on the surface of the chestnut shells with water until the washed water is clear and transparent, then put the chestnut shells in an oven at 120°C, dry for 2 hours, and remove the chestnut shells moisture in. Screen the chestnut shells with better appearance from the dried chestnut shells, crush them in a crusher to 10-30 mesh, weigh 200g, and count them as shell 1.

Example 2:

Pretreatment of fresh husks:

Take fresh Jilin Tonghua pine nut shells (brown), wash the dust and impurities on the surface of the pine nut shells repeatedly with water until the washed water is clear and transparent, then put the pine nut shells in an oven at 120°C, dry for 2 hours, and remove the pine nut shells of moisture. Screen the pine nut shells with better appearance from the dried pine nut shells, crush them in a crusher to 10-30 mesh, weigh 200g, and count them as shell 2.

Example 3:

Pretreatment of fresh husks:

Take fresh Xinjiang Kuqa walnut shells (yellow brown), wash the dust and impurities on the surface of the walnut shells repeatedly with water until the washed water is clear and transparent, then put the walnut shells in an oven at 120°C and dry for 2 hours to remove the walnuts moisture in the shell. Screen the walnut shells with better appearance from the dried walnut shells, crush them in a crusher to 10-30 mesh, weigh 200g, and count them as shell 3.

Example 4:

Pretreatment of fresh husks:

Take fresh Shandong Luhua peanut shells (yellow brown), wash the dust and impurities on the surface of the peanut shells repeatedly with water until the washed water is clear and transparent, then put the peanut shells in an oven at 120°C, dry for 2 hours, and remove the peanut shells. moisture in the shell. Screen the peanut shells with better appearance from the dried peanut shells, crush them in a crusher to 10-30 mesh, weigh 200g, and count them as shell 4.

Example 5:

Pretreated fresh fruit shells were selected as raw materials to be soaked in an activator solution, and then carbonized and activated under a protective atmosphere to prepare activated carbon materials.

Add 43g of activator to a 400mL beaker, pour 100mL of distilled water into the beaker, stir to dissolve, add 30g of pretreated fresh fruit shells to the activator solution, stir for 5min, and soak for 8h at room temperature. Then put the impregnated sample in an oven at 110°C for 2 hours to remove moisture. The dried samples were placed in a dry pot, placed in a tube electric furnace, and activated carbon was prepared by carbonization and activation at 450°C for 3 hours under a nitrogen protective atmosphere. After the tube-type electric furnace is cooled, take out the activated carbon, grind it, boil it with 1mol/L hydrochloric acid for 30 minutes, then wash it with distilled water until the pH is about 7, and dry it to obtain the activated carbon material.

Choose fruit shell 1 as a raw material, impregnate it with zinc chloride solution as an activator, and prepare activated carbon 1;

Choose fruit shell 1 as raw material, impregnate with phosphoric acid solution as activator, make activated carbon 2;

Selecting the fruit shell 2 as a raw material, impregnating it with a zinc chloride solution as an activator to obtain activated carbon 3;

Select the fruit shell 2 as a raw material, impregnate it with a phosphoric acid solution as an activator, and obtain activated carbon 4;

Selecting the fruit shell 3 as a raw material, impregnating it with a zinc chloride solution as an activator to obtain activated carbon 5;

Select the fruit shell 3 as a raw material, impregnate it with a phosphoric acid solution as an activator, and obtain activated carbon 6;

Choose fruit shell 4 as raw material, use zinc chloride solution as activator impregnation, make activated carbon 7;

Embodiment 6:

Select activated carbon 1 as raw material to prepare carbon-based solid acid:

Add 10g of activated carbon into a 250mL four-necked flask, pour 100mL of concentrated sulfuric acid (98% concentrated sulfuric acid), put the four-necked flask into an oil bath, connect nitrogen gas to one port of the four-necked flask, and As the nitrogen outlet, the nitrogen outlet is connected to the water. The oil bath was heated to 120°C for sulfonation for 8h. After the reaction, the mixture was slowly poured into cold water with constant stirring. After cooling, the solution was filtered with suction, the black solid was washed with distilled water until neutral, and dried in vacuum for 5 hours to finally obtain a carbon-based solid acid. The product was characterized by means of X-ray diffraction (XRD) and infrared spectroscopy (FT-IR). The results showed that the carbon-based solid acid is an amorphous form composed of aromatic carbon sheets connected with sulfonic acid groups (-SO ₃ H). Carbon; the specific surface area measured by nitrogen adsorption BET method is 1269m ² /g, and the acid density measured by NaOH solution titration method is 2.83mmol/L.

Embodiment 7:

Select activated carbon 2 as raw material to prepare carbon-based solid acid:

Add 10g of activated carbon into a 250mL four-necked flask, pour 135mL of fuming sulfuric acid into it, put the four-necked flask into an oil bath, connect nitrogen to one port of the four-necked flask, and use the other port as the nitrogen outlet, The nitrogen outlet is connected to the water. The oil bath was heated to 130°C for sulfonation for 8h. The treatment method is the same as in Example 6, and finally a carbon-based solid acid is obtained. The product was characterized by means of X-ray diffraction (XRD) and infrared spectroscopy (FT-IR). The results showed that the carbon-based solid acid is an amorphous form composed of aromatic carbon sheets connected with sulfonic acid groups (-SO ₃ H). Carbon; the specific surface area measured by nitrogen adsorption BET method is 1127m ² /g, and the acid density measured by NaOH solution titration method is 2.48mmol/L.

Embodiment 8:

Select activated carbon 3 as raw material to prepare carbon-based solid acid:

Add 10g of activated carbon to a 250mL four-necked flask, pour 150mL of concentrated sulfuric acid (98% concentrated sulfuric acid), put the four-necked flask into an oil bath, connect nitrogen gas to one port of the four-necked flask, and As the nitrogen outlet, the nitrogen outlet is connected to the water. The oil bath was heated to 150°C for sulfonation for 9h. The treatment method is the same as in Example 6, and finally a carbon-based solid acid is obtained. The product was characterized by means of X-ray diffraction (XRD) and infrared spectroscopy (FT-IR). The results showed that the carbon-based solid acid is an amorphous form composed of aromatic carbon sheets connected with sulfonic acid groups (-SO ₃ H). Carbon; the specific surface area measured by nitrogen adsorption BET method is 1326m ² /g, and the acid density measured by NaOH solution titration method is 3.52mmol/L.

Embodiment 9:

Select activated carbon 4 as raw material to prepare carbon-based solid acid:

Add 10g of activated carbon to a 250mL four-necked flask, pour 80mL of fuming sulfuric acid into it, put the four-necked flask into an oil bath, connect nitrogen to one port of the four-necked flask, and use the other port as the nitrogen outlet. The nitrogen outlet is connected to the water. The oil bath was heated to 150°C for sulfonation for 9h. The treatment method is the same as in Example 6, and finally a carbon-based solid acid is obtained. The product was characterized by means of X-ray diffraction (XRD) and infrared spectroscopy (FT-IR). The results showed that the carbon-based solid acid is an amorphous form composed of aromatic carbon sheets connected with sulfonic acid groups (-SO ₃ H). Carbon; the specific surface area measured by nitrogen adsorption BET method is 1274m ² /g, and the acid density measured by NaOH solution titration method is 1.93mmol/L.

Example 10:

Select activated carbon 5 as raw material to prepare carbon-based solid acid:

Add 10g of activated carbon into a 250mL four-necked flask, pour 110mL of concentrated sulfuric acid (98% concentrated sulfuric acid), put the four-necked flask into an oil bath, connect nitrogen gas to one port of the four-necked flask, and As the nitrogen outlet, the nitrogen outlet is connected to the water. The temperature of the oil bath was raised to 160°C for sulfonation for 10 hours. The treatment method is the same as in Example 6, and finally a carbon-based solid acid is obtained. The product was characterized by means of X-ray diffraction (XRD) and infrared spectroscopy (FT-IR). The results showed that the carbon-based solid acid is an amorphous form composed of aromatic carbon sheets connected with sulfonic acid groups (-SO ₃ H). Carbon; the specific surface area measured by nitrogen adsorption BET method is 982m ² /g, and the acid density measured by NaOH solution titration method is 1.63mmol/L.

Example 11:

Select activated carbon 6 as raw material to prepare carbon-based solid acid:

Add 10g of activated carbon into a 250mL four-necked flask, pour oleum 95mL, put the four-necked flask into an oil bath, connect nitrogen to one port of the four-necked flask, and use the other port as the nitrogen outlet. The nitrogen outlet is connected to the water. The oil bath was heated to 180°C for sulfonation for 8h. The treatment method is the same as in Example 6, and finally a carbon-based solid acid is obtained. The product was characterized by means of X-ray diffraction (XRD) and infrared spectroscopy (FT-IR). The results showed that the carbon-based solid acid is an amorphous form composed of aromatic carbon sheets connected with sulfonic acid groups (-SO ₃ H). Carbon; the specific surface area measured by nitrogen adsorption BET method is 1073m ² /g, and the acid density measured by NaOH solution titration method is 2.47mmol/L.

Example 12:

Select activated carbon 7 as raw material to prepare carbon-based solid acid:

Add 10g of activated carbon into a 250mL four-necked flask, pour 120mL of concentrated sulfuric acid (98% concentrated sulfuric acid), put the four-necked flask into an oil bath, connect nitrogen gas to one port of the four-necked flask, and As the nitrogen outlet, the nitrogen outlet is connected to the water. The oil bath was heated to 200°C for sulfonation for 9h. The treatment method is the same as in Example 6, and finally a carbon-based solid acid is obtained. The product was characterized by means of X-ray diffraction (XRD) and infrared spectroscopy (FT-IR). The results showed that the carbon-based solid acid is an amorphous form composed of aromatic carbon sheets connected with sulfonic acid groups (-SO ₃ H). Carbon; the specific surface area measured by nitrogen adsorption BET method is 856m ² /g, and the acid density measured by NaOH solution titration method is 1.68mmol/L.

Example 13:

The carbon-based solid acid in Example 6 is used to catalyze the preparation of biodiesel, and soybean oil and methanol (molar ratio 1:3) are added to a 250mL three-necked flask. The amount of carbon-based solid acid added is 8% of the total mass of soybean oil and methanol. %, reacted at 65°C for 2 hours, and the conversion rate of biodiesel reached 93.6%.

Example 14:

The carbon-based solid acid in Example 7 was used to catalyze the preparation of ethyl acetate, and acetic acid and ethanol (molar ratio 1:1) were added to a 250mL three-necked flask. The amount of carbon-based solid acid added was 8% of the total mass of acetic acid and ethanol. %, reacted at 65°C for 2 hours, and the yield of ethyl acetate reached 89.3%.

Example 15:

The carbon-based solid acid in Example 8 is used to catalyze the isomerization reaction of α-pinene, catalyst: α-pinene=1:20 (wt), react at 165°C for 4h, the conversion rate of α-pinene Reached 94.87%.

Example 16:

The carbon-based solid acid in Example 12 is used to catalyze the preparation of epoxy fatty acid esters, add fatty acid methyl esters in a 250mL three-necked flask, add hydrogen peroxide that accounts for 30% of the quality of fatty acid methyl esters dropwise at a constant rate, and add the carbon-based solid acids The amount is 8% of the mass of fatty acid methyl ester, reacted at 80°C for 6 hours, and the epoxy value reaches 4.4%.

The method for preparing carbon-based solid acid from fresh fruit shells of the present invention provides a waste utilization method of plant fruit shells. The performance index of the carbon-based solid acid prepared by the method needs to be tested according to the field of application. Only after passing the qualification can it be used in related fields. The carbon-based solid acid prepared by the method of the present invention is preferably used in industries such as chemical industry, detergent, agriculture and animal husbandry, and textiles, and is not recommended to be directly used in fields such as food, medicine, and cosmetics. If it is necessary to apply the carbon-based solid acid prepared by the present invention to the fields of food, medicine, cosmetics, etc., relevant laws and regulations should be strictly followed, and the carbon-based solid acid should be fully tested or further processed to eliminate the harmful effects on human health. Unfavorable factors can be used in these fields.

Claims (1)

1. a preparation method for carbon-based solid acid, is characterized in that: described carbon-based solid acid utilizes fresh shell District, Xinyang Area, Henan Province chestnut shell to be prepared from for raw material, and obtained carbon-based solid acid specific area is 1127m ²/ g, acid number is 2.48mmol/L,

The concrete steps of described preparation method are,

(1) pretreatment of fresh shell: air-dry fresh shell District, Xinyang Area, Henan Province chestnut shell water is washed till repeatedly and does not have impurity, then the shell of wash clean is put into baking oven dry, remove moisture, the shell that screening product is compared, in disintegrating machine, be crushed to 10 ~ 30 orders for subsequent use;

(2) activation of shell: add 43g activator phosphoric acid in 400mL beaker, 100mL distilled water is poured in beaker, stirring and dissolving obtains activator solution, add through the pretreated fresh shell District, Xinyang Area, Henan Province chestnut shell 30g of step (1) in described activator solution, stir 5min, flood 8h under normal temperature, then the sample flooded is put into 110 DEG C of baking ovens and dry 2h, remove moisture;

(3) carbonization of shell: the shell obtained will be activated in step (2), 450 DEG C are heated under nitrogen protection atmosphere, carbonization 3h, prepare active carbon, by active carbon grind into powder, in the hydrochloric acid solution of 1mol/L, boil 30min, then suction filtration, obtain absorbent charcoal material with after distilled water rinsing, drying;

(4) sulfonation of absorbent charcoal material: by the absorbent charcoal material obtained in step (3), under 130 DEG C of conditions, through oleum sulfonation 8h, the solid-liquid ratio of absorbent charcoal material and sulfonating agent solution is 1:13.5g/mL, mixed liquor after sulfonation is gently poured in cold water and is also constantly stirred, and suction filtration, oven dry gained black solid powder are carbon-based solid acid.