CN115518656A - A kind of lignin-PVC carbon-based solid acid and its preparation method and application - Google Patents

Abstract

The invention discloses a lignin-PVC carbon-based solid acid and its preparation method and application, belonging to the technical field of preparation of solid acid catalysts. The invention uses biomass waste lignin and white pollutant polyvinyl chloride (PVC) as raw materials, and prepares lignin-PVC carbon-based porous material under the activation of strong alkali potassium hydroxide. Using p-aminobenzenesulfonic acid as a sulfonic acid source to carry out sulfonation treatment on lignin-PVC carbon base to obtain lignin-PVC solid acid catalyst to catalyze xylose hydrolysis to prepare furfural porous carbon-based solid acid catalyst and preparation method, the method sulfonates The conditions are relatively mild, and it is safer and more environmentally friendly than traditional high-temperature sulfonation of concentrated sulfuric acid, and the total acidity of the solid acid obtained is higher, which is in line with the concept of green, environmentally friendly and sustainable development.

Description

A kind of lignin-PVC carbon-based solid acid and its preparation method and application

technical field

The invention belongs to the technical field of solid acid catalyst preparation, and in particular relates to a lignin-PVC carbon-based solid acid and its preparation method and application.

Background technique

Furfural is currently the only important chemical raw material completely dependent on biomass extraction. At present, furfural is mainly produced in industry by homogeneous acid hydrolysis, which has a high catalytic efficiency, but due to the use of liquid acid, the catalyst cannot be recovered and the equipment is severely corroded. The heterogeneous solid acid has the advantages of stability, low pollution, high yield, and reusability, and can solve the problem that the existing methods are not environmentally friendly, and the prepared solid acid has low surface acid content, easy loss of active sites, and poor catalytic activity. Technical problems make it have huge application potential in industrial production. Therefore, it is extremely important to develop a carbon-based solid acid with good stability and high content of active functional groups. Lignin, the most abundant and renewable biomass in the world, is a waste by-product or low-value product of biorefineries. In the industry, most of the conversion of biomass sugars (xylose, fructose, glucose and hemicellulose) into furan compounds is a homogeneous acid catalyst. Although the conversion rate is high and the rate is fast, the furan product is easy to polymerize so that the yield Low; the requirements for the corrosion resistance of the reactor are high, which increases the cost; the waste acid generated in the reaction is difficult to deal with, and the environmental pollution is serious.

Contents of the invention

In order to overcome the above-mentioned shortcoming of the prior art, the object of the present invention is to provide a kind of lignin-PVC carbon-based solid acid and its preparation method and application.

In order to achieve the above object, the present invention adopts the following technical solutions to achieve:

The invention discloses a preparation method of lignin-PVC carbon-based solid acid, which comprises the following steps:

S1: Carbonize the lignin, PVC and KOH to obtain a carbon-based material; perform ultrasonic treatment, washing and drying on the carbon-based material in sequence to obtain a pretreated carbon-based material;

S2: The pretreated carbon-based material is subjected to sulfonation treatment with p-aminobenzenesulfonic acid in an oil bath, and then washed and dried to obtain a lignin-PVC carbon-based solid acid.

Further, in S1, the weight ratio of lignin, PVC and KOH is 1.0:1.0:1.0.

Further, in S1, the carbonization treatment is carried out under N ₂ atmosphere, the temperature of the carbonization treatment is 400-800° C., and the time is 4 hours.

Further, in S1, the ultrasonic treatment is ultrasonic treatment with hydrochloric acid with a mass concentration of 15%-20%; the washing treatment is washing with ultrapure water until the pH of the washing solution is 7-8.

Further, in S2, the step of sulfonation treatment is: mix the pretreated carbon-based material with water, then add p-aminobenzenesulfonic acid after the oil bath is heated up, add NaNO ₂ for 30-35 minutes of reaction, and carry out again After reacting for 10-12 hours, take out the reactant, wash and filter the reactant with dilute hydrochloric acid, water and methanol, and dry at 80-85°C for 12-24 hours.

Further, the amount ratio of the pretreated carbon-based material, water, p-aminobenzenesulfonic acid and NaNO ₂ is 1:(150-200)mL:(4-5)g:6g.

Further, in S2, the temperature of the oil bath is 80-100°C.

The invention also discloses a lignin-PVC carbon-based solid acid prepared by the above preparation method.

The present invention also discloses the application of the above-mentioned lignin-PVC carbon-based solid acid. When the lignin-PVC carbon-based solid acid is used as a catalyst in the reaction of preparing furfural from biomass conversion, it includes the following steps:

Add the biomass and lignin-PVC carbon-based solid acid into the pressure-resistant reaction tube according to the mass ratio of (1:1)~(2:1), and add an organic solvent, and react at a temperature of 150~170°C for 60 minutes, to furfural.

Compared with the prior art, the present invention has the following beneficial effects:

The invention discloses a preparation method of a lignin-PVC carbon-based solid acid, which uses lignin and PVC as carbon sources, and then adopts a p-aminobenzenesulfonic acid sulfonation method to prepare a carbon-based solid acid catalyst grafted with sulfonic acid groups. The sulfonation conditions of this method are relatively mild, and it is safer and more environmentally friendly than the high-temperature sulfonation of traditional concentrated sulfuric acid; at the same time, this method uses PVC as raw material to make full use of waste PVC plastics; at the same time, chlorine is introduced into the carbon-based solid acid material through PVC, Utilize the hydrogen bond formed by chlorine element and biomass to promote the improvement of reaction performance. In addition, the carbon carrier used in this method is derived from lignin in biomass and PVC, which is a plastic waste in life, which is in line with the concept of green and sustainable development. The raw materials used are low in cost, the synthesis route is simple, and it is easy to scale up production and preparation.

The present invention also discloses the lignin-PVC carbon-based solid acid prepared by the above-mentioned preparation method, because the total acidity first decreases with the increase of the calcination temperature, because the -COOH group is the main acid site at this time, At high temperatures -COOH groups decompose resulting in a decrease in overall acidity. On the contrary, the content of -SO ₃ H groups increases with the increase of calcination temperature, indicating that higher temperature is beneficial to the sulfonation process, and when the temperature is higher than 600 °C, the enhanced -SO ₃ H acidity contributes to the total acidity However, when the calcination temperature is higher than 750 °C, the content of -SO ₃ H will decrease, which means that too high temperature is not conducive to sulfonation, resulting in a decrease in the total acidity of carbon-based solid acids. Therefore, the lignin-PVC-750 carbon-based solid acid catalyst calcined at 750 °C possessed the highest acidity.

The lignin-PVC carbon-based solid acid prepared by the method has high surface acid content, active sites are not easily lost, and has good catalytic activity.

The present invention also discloses the application of the above-mentioned lignin-PVC carbon-based solid acid as a catalyst in the reaction of biomass conversion to prepare furfural. It is proved by relevant experimental results that the total acidity of the solid acid obtained by the application is relatively high (0.66～1.54mmol/g ), the furfural yield obtained reaches 82.5%, has excellent catalytic effect, and shows high activity and high selectivity to catalyze the conversion of biomass to prepare furfural.

Description of drawings

Fig. 1 is the SEM figure of solid acid catalyst of the present invention;

Fig. 2 is the FT-IR figure of solid acid catalyst of the present invention;

Fig. 3 is an XRD pattern of the solid acid catalyst of the present invention.

Among them: a- lignin-PVC-400 carbon-based solid acid; b- lignin-PVC-600 carbon-based solid acid; c- lignin-PVC-800 carbon-based solid acid; d- lignin-PVC-750 carbon base solid acid; e-lignin-PVC-750-PVCF; f-lignin-PVC-750-POF.

detailed description

In order to enable those skilled in the art to understand the features and effects of the present invention, the terms and terms mentioned in the specification and claims are generally described and defined below. Unless otherwise specified, all technical and scientific terms used herein have the usual meanings understood by those skilled in the art for the present invention. In case of conflict, the definitions in this specification shall prevail.

The theories or mechanisms described and disclosed herein, whether true or false, should not limit the scope of the present invention in any way, ie, the present invention can be practiced without being limited by any particular theory or mechanism.

Herein, all the features defined in the form of numerical range or percentage range, such as numerical value, quantity, content and concentration, are only for the sake of brevity and convenience. Accordingly, the recitation of a numerical range or a percentage range should be deemed to encompass and specifically disclose all possible subranges and individual values (including integers and fractions) within those ranges.

In this article, unless otherwise specified, "comprising", "comprising", "comprising", "having" or similar expressions cover the meanings of "consisting of" and "consisting mainly of", for example, "A contains a " covers the meanings of "A contains a and others" and "A contains only a".

Herein, for the sake of concise description, all possible combinations of the technical features in each embodiment or embodiment are not described. Therefore, as long as there is no contradiction in the combination of these technical features, each technical feature in each embodiment or example can be combined arbitrarily, and all possible combinations should be regarded as within the scope of this specification.

This patent revolves around the preparation of furfural from biomass waste, and develops a porous solid acid catalyst composed of biomass waste polyvinyl chloride (PVC) plastic, using p-aminobenzenesulfonic acid as the sulfonic acid precursor to increase the acid density of the catalyst and stability. Invented lignin and PVC high temperature pyrolysis to prepare sulfonic solid acid catalyst by hydrolysis of xylose to prepare furfural to evaluate its catalytic activity. The lignin-PVCx carbon-based solid acid catalyst prepared by the invention has low raw material cost, simple synthesis path, and easy scale-up production and preparation.

So far, the research on the preparation of solid acid catalysts by pyrolysis and sulfonation of lignin-PVC has not been reported. So far, the research on the preparation of solid acid catalysts by pyrolysis and sulfonation of lignin-PVC has not been reported.

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Conventional instruments and equipment in the art are used in the following examples. For the experimental methods without specific conditions indicated in the following examples, the conventional conditions or the conditions suggested by the manufacturer are usually followed. Various raw materials are used in the following examples. Unless otherwise specified, conventional commercially available products are used, and their specifications are conventional specifications in the art. In the description of the present invention and the following examples, unless otherwise specified, "%" means percentage by weight, "part" means parts by weight, and proportions mean ratio by weight.

Example 1

A preparation method of lignin-PVC carbon-based solid acid, comprising the following steps:

S1: Put 5.0g of lignin, 5.0g of PVC and 5.0g of KOH in a mortar and grind them evenly, then transfer them to a porcelain ark, put them into a tube furnace, use nitrogen to purge the tube furnace for 5-10min, and heat the tube furnace at 10°C Raise the temperature to 750°C/min, carbonize at high temperature for 4 hours, take it out after natural cooling to room temperature, and obtain the carbon-based material; then put the carbon-based material in a mortar and grind for 5 minutes, and put the obtained solid powder into dilute hydrochloric acid solution for 2 hours and sonicate Filtrate, collect the filtrate, rinse with distilled water until the pH of the rinse solution is between 7 and 8, then put the rinsed filtrate into an oven, dry at 80°C for 24h, and obtain the pretreated carbon-based material ( Lignin-PVC-750 carbon-based);

S2: Weigh 1.0g lignin-PVC-750 carbon base and pour it into a three-necked bottle, add 150mL water, heat the oil bath to 80°C, add 4.0g p-aminobenzenesulfonic acid, react for 30min, add 6.0g after it dissolves NaNO ₂ , take it out after 10 hours of reaction, alternately wash and filter with methanol and water until the pH of the washing solution is between 7 and 8, and dry at 80°C for 24 hours to obtain lignin-PVC carbon-based solid acid (lignin-PVC -750 carbon-based solid acid).

After measuring, the acid value of this sample is 1.54mmol/g; When the prepared lignin-PVC-750 carbon-based solid acid is used in the application of biomass conversion to prepare furfural, 0.10g xylose, 0.05g lignin -PVC-750 carbon-based solid acid and 5mL of γ-valerolactone were added to a 25mL pressure-resistant reaction tube. Under magnetic stirring, the reaction temperature was 160°C and kept for 60min. The yield of furfural obtained was 82.5%.

Example 2

S1: Put 5.0g of lignin, 5.0g of PVC and 5.0g of KOH in a mortar and grind them evenly, then transfer them to a porcelain ark, put them into a tube furnace, use nitrogen to purge the tube furnace for 5-10min, and heat the tube furnace at 10°C Raise the temperature to 400°C/min, carbonize at high temperature for 4 hours, take it out after natural cooling to room temperature, and obtain the carbon-based material; then put the carbon-based material in a mortar and grind for 5 minutes, and put the obtained solid powder into dilute hydrochloric acid solution for 2 hours and sonicate Filtrate, collect the filtrate, rinse with distilled water until the pH of the rinse solution is between 7 and 8, then put the rinsed filtrate into an oven, dry at 80°C for 24h, and obtain the pretreated carbon-based material ( Lignin-PVC-400 carbon base);

S2: Weigh 1.0g lignin-PVC-400 carbon base and pour it into a three-necked bottle, add 150mL water, heat the oil bath to 80°C, add 4.0g p-aminobenzenesulfonic acid, react for 35min, add 6.0g after it dissolves NaNO ₂ , take it out after 10 hours of reaction, alternately wash and filter with methanol and water until the pH of the washing solution is between 7 and 8, and dry at 80°C for 24 hours to obtain lignin-PVC carbon-based solid acid (lignin-PVC -400 carbon-based solid acid).

After measuring, the acid value of this sample is 1.26mmol/g; When the prepared lignin-PVC-400 carbon-based solid acid is used in the application of biomass conversion to prepare furfural, 0.10g xylose, 0.05g lignin -PVC-450 carbon-based solid acid and 5mL of γ-valerolactone were added to a 25mL pressure-resistant reaction tube. Under magnetic stirring, the reaction temperature was 160°C and kept for 60min. The yield of furfural obtained was 45.3%.

Example 3

A preparation method of lignin-PVC carbon-based solid acid, comprising the following steps:

S1: Put 5.0g of lignin, 5.0g of PVC and 10.0g of KOH in a mortar and grind them evenly, then transfer them to a porcelain ark, put them into a tube furnace, use nitrogen to purge the tube furnace for 5-10min, and heat at 10°C Raise the temperature to 500°C/min, carbonize at high temperature for 4 hours, take it out after natural cooling to room temperature, and obtain the carbon-based material; then put the carbon-based material in a mortar and grind for 5 minutes, and put the obtained solid powder into dilute hydrochloric acid solution for 2 hours and sonicate Filtrate, collect the filtrate, rinse with distilled water until the pH of the rinse solution is between 7 and 8, then put the rinsed filtrate into an oven, dry at 80°C for 24h, and obtain the pretreated carbon-based material ( Lignin-PVC-500 carbon base);

S2: Weigh 1.0g lignin-PVC-500 carbon base and pour it into a three-necked bottle, add 150mL water, heat the oil bath to 100°C, add 4.0g p-aminobenzenesulfonic acid, react for 30min, add 6.0g after it dissolves NaNO ₂ , take it out after 12 hours of reaction, alternately wash and filter with methanol and water until the pH of the washing solution is between 7 and 8, and dry at 80°C for 12 hours to obtain lignin-PVC carbon-based solid acid (lignin-PVC -500 carbon-based solid acid).

After measurement, the acid value of the sample is 1.26mmol/g; when the prepared lignin-PVC-500 carbon-based solid acid is used in the application of biomass conversion to prepare furfural, 0.10g xylose, 0.05g lignin -PVC-500 carbon-based solid acid and 5mL of γ-valerolactone were added to a 25mL pressure-resistant reaction tube. Under magnetic stirring, the reaction temperature was 160°C and kept for 60min. The yield of furfural obtained was 34.5%.

Example 4

A preparation method of lignin-PVC carbon-based solid acid, comprising the following steps:

S1: Put 5.0g of lignin, 5.0g of PVC and 10.0g of KOH in a mortar and grind them evenly, then transfer them to a porcelain ark, put them into a tube furnace, use nitrogen to purge the tube furnace for 5-10min, and heat at 10°C Raise the temperature to 600°C/min, carbonize at high temperature for 4 hours, take it out after natural cooling to room temperature, and obtain the carbon-based material; then put the carbon-based material in a mortar and grind for 5 minutes, and put the obtained solid powder into dilute hydrochloric acid solution for 2 hours and ultrasonic Filtrate, collect the filtrate, rinse with distilled water until the pH of the rinse solution is between 7 and 8, then put the rinsed filtrate into an oven, dry at 80°C for 24h, and obtain the pretreated carbon-based material ( Lignin-PVC-600 carbon base);

S2: Weigh 1.0g of lignin-PVC-600 carbon base and pour it into a three-necked bottle, add 150mL of water, heat the oil bath to 80°C, add 4.0g of p-aminobenzenesulfonic acid, react for 30min, and add 6.0g after it dissolves NaNO ₂ , take it out after 10 hours of reaction, alternately wash and filter with methanol and water until the pH of the washing solution is between 7 and 8, and dry at 80°C for 24 hours to obtain lignin-PVC carbon-based solid acid (lignin-PVC -600 carbon-based solid acid).

After measuring, the acid value of this sample is 0.90mmol/g; When the prepared lignin-PVC-600 carbon-based solid acid is used in the application of biomass conversion to prepare furfural, 0.10g xylose, 0.05g lignin -PVC-600 carbon-based solid acid and 5mL of γ-valerolactone were added to a 25mL pressure-resistant reaction tube. Under magnetic stirring, the reaction temperature was 160°C and kept for 60min. The yield of furfural obtained was 49.4%.

Example 5

S1: Put 5.0g of lignin, 5.0g of PVC and 10.0g of KOH in a mortar and grind them evenly, then transfer them to a porcelain ark, put them into a tube furnace, use nitrogen to purge the tube furnace for 5-10min, and heat at 10°C Raise the temperature to 700°C/min, carbonize at high temperature for 4 hours, take it out after natural cooling to room temperature, and obtain the carbon-based material; then put the carbon-based material in a mortar and grind for 5 minutes, and put the obtained solid powder into dilute hydrochloric acid solution for 2 hours and sonicate Filtrate, collect the filtrate, rinse with distilled water until the pH of the rinse solution is between 7 and 8, then put the rinsed filtrate into an oven, dry at 80°C for 24h, and obtain the pretreated carbon-based material ( Lignin-PVC-700 carbon base);

S2: Weigh 1.0g lignin-PVC-700 carbon base and pour it into a three-necked bottle, add 200mL water, heat the oil bath to 80°C, add 4.0g p-aminobenzenesulfonic acid, react for 30min, add 6.0g after it dissolves NaNO ₂ , take it out after 10 hours of reaction, alternately wash and filter with methanol and water until the pH of the washing solution is between 7 and 8, and dry at 80°C for 24 hours to obtain lignin-PVC carbon-based solid acid (lignin-PVC -700 carbon-based solid acid).

After measuring, the acid value of this sample is 1.20mmol/g; When the prepared lignin-PVC-700 carbon-based solid acid is used in the application of biomass conversion to prepare furfural, 0.10g xylose, 0.05g lignin -PVC-700 carbon-based solid acid and 5mL of γ-valerolactone were added to a 25mL pressure-resistant reaction tube. Under magnetic stirring, the reaction temperature was 160°C and kept for 60min. The yield of furfural obtained was 74.7%.

Example 6

S1: Put 5.0g of lignin, 5.0g of PVC and 10.0g of KOH in a mortar and grind them evenly, then transfer them to a porcelain ark, put them into a tube furnace, use nitrogen to purge the tube furnace for 5-10min, and heat at 10°C Raise the temperature to 800°C/min, carbonize at high temperature for 4 hours, take it out after natural cooling to room temperature, and obtain the carbon-based material; then put the carbon-based material in a mortar and grind for 5 minutes, and put the obtained solid powder into dilute hydrochloric acid solution for 2 hours and sonicate Filtrate, collect the filtrate, rinse with distilled water until the pH of the rinse solution is between 7 and 8, then put the rinsed filtrate into an oven, dry at 80°C for 24h, and obtain the pretreated carbon-based material ( Lignin-PVC-800 carbon base);

S2: Weigh 1.0g lignin-PVC-800 carbon base and pour it into a three-necked bottle, add 180mL water, heat the oil bath to 80°C, add 5.0g p-aminobenzenesulfonic acid, react for 30min, add 6.0g after it dissolves NaNO ₂ , take it out after 10 hours of reaction, alternately wash and filter with methanol and water until the pH of the washing solution is between 7 and 8, and dry at 80°C for 24 hours to obtain lignin-PVC carbon-based solid acid (lignin-PVC -800 carbon-based solid acid).

After measuring, the acid value of this sample is 0.66mmol/g; When the prepared lignin-PVC-800 carbon-based solid acid is used in the application of biomass conversion to prepare furfural, 0.10g xylose, 0.05g lignin -PVC-800 carbon-based solid acid and 5mL of γ-valerolactone were added to a 25mL pressure-resistant reaction tube. Under magnetic stirring, the reaction temperature was 160°C and kept for 60min. The yield of furfural obtained was 33.3%.

Example 7

S1: Put 5.0g of lignin, 5.0g of PVC and 10.0g of KOH in a mortar and grind them evenly, then transfer them to a porcelain ark, put them into a tube furnace, use nitrogen to purge the tube furnace for 5-10min, and heat at 10°C Raise the temperature to 750°C/min, carbonize at high temperature for 4 hours, take it out after natural cooling to room temperature, and obtain the carbon-based material; then put the carbon-based material in a mortar and grind for 5 minutes, and put the obtained solid powder into dilute hydrochloric acid solution for 2 hours and sonicate Filtrate, collect the filtrate, rinse with distilled water until the pH of the rinse solution is between 7 and 8, then put the rinsed filtrate into an oven, dry at 80°C for 24h, and obtain the pretreated carbon-based material ( Lignin-PVC-750 carbon-based);

S2: Weigh 1.0g lignin-PVC-750 carbon base and pour it into a three-necked bottle, add 150mL water, heat the oil bath to 80°C, add 4.0g p-aminobenzenesulfonic acid, react for 30min, add 6.0g after it dissolves NaNO ₂ , take it out after 10 hours of reaction, alternately wash and filter with methanol and water until the pH of the washing solution is between 7 and 8, and dry at 80°C for 24 hours to obtain lignin-PVC carbon-based solid acid (lignin-PVC -750 carbon-based solid acid).

Comparative example 1

A preparation method of carbon-based solid acid, comprising the following steps:

S1: Put 5.0g lignin and 5.0g PV in a mortar and grind them evenly, then transfer them to a porcelain ark, put them into a tube furnace, use nitrogen to purge the tube furnace for 5-10 minutes, and heat up to 10°C/min. Carbonize at 750°C for 4 hours at high temperature, cool naturally to room temperature, and take out to obtain carbon-based materials; then put the carbon-based materials in a mortar and grind for 5 minutes, put the obtained solid powder into dilute hydrochloric acid solution for 2 hours, and then filter, collect and filter Rinse with distilled water until the pH of the rinse solution is between 7 and 8, then put the rinsed filtrate into an oven, and dry it at 80°C for 24 hours to obtain lignin-PVC-750-POF carbon-based (POF stands for Potassium oxyhydrogen of free);

S2: Weigh 1.0g of lignin-PVC-750-POF carbon base and pour it into a three-necked bottle, add 150mL of water, heat the oil bath to 80°C, add 4.0g of p-aminobenzenesulfonic acid, react for 30min, and add after it dissolves 6.0g NaNO ₂ , take it out after 10 hours of reaction, alternately wash and filter with methanol and water until the pH of the washing solution is between 7 and 8, and dry at 80°C for 24 hours to obtain lignin-PVC-750-POF carbon-based solid acid.

After measuring, the acid value of this sample is 1.96mmol/g; When the prepared lignin-PVC-750-POF carbon-based solid acid is used in the application of biomass conversion to prepare furfural, 0.10g xylose, 0.05g Lignin-PVC-750-POF carbon-based solid acid and 5mL γ-valerolactone were added to a 25mL pressure-resistant reaction tube. Under magnetic stirring, the reaction temperature was 160°C and kept for 60min. The yield of furfural obtained was 11.9%.

Comparative example 2

A preparation method of carbon-based solid acid, comprising the following steps:

S1: Put 5.0g lignin and 5.0g KOH in a mortar and grind them evenly, transfer them to a porcelain ark, put them into a tube furnace, use nitrogen to purge the tube furnace for 5-10 minutes, and heat up at 10°C/min to Carbonize at 750°C for 4 hours at high temperature, cool naturally to room temperature, and take out to obtain carbon-based materials; then put the carbon-based materials in a mortar and grind for 5 minutes, put the obtained solid powder into dilute hydrochloric acid solution for 2 hours, and then filter, collect and filter Rinse with distilled water until the pH of the rinse solution is between 7 and 8, then put the rinsed filtrate into an oven, and dry it at 80°C for 24 hours to obtain lignin-750-PVCF carbon base (PVCF stands for PVCof free);

S2: Weigh 1.0g of lignin-750-PVCF carbon base and pour it into a three-necked flask, add 150mL of water, heat the oil bath to 80°C, add 4.0g of p-aminobenzenesulfonic acid, react for 30min, and add 6.0g after it dissolves NaNO ₂ , taken out after 10 hours of reaction, alternately washed and filtered with methanol and water until the pH of the washing solution was between 7 and 8, and dried at 80°C for 24 hours to obtain lignin-750-PVCF carbon-based solid acid.

After measurement, the acid value of the sample is 0.54mmol/g; when the prepared 0.54mmol/g is used in the application of biomass conversion to prepare furfural, 0.10g xylose, 0.05g 0.54mmol/g and 5mL gamma-pentane The lactone was added into a 25mL pressure-resistant reaction tube, under magnetic stirring, the reaction temperature was 160° C., and kept for 60 minutes, and the yield of furfural obtained was 3.0%.

Comparative example 3

A preparation method of carbon-based solid acid, comprising the following steps:

S1: Put 5.0g of PVC and 5.0g of KOH (without lignin) in a mortar and grind them evenly, transfer them to a porcelain ark, put them into a tube furnace, use nitrogen to purge the tube furnace for 5-10min, and heat the tube furnace at 10°C Raise the temperature to 750°C/min, carbonize at high temperature for 4 hours, take it out after natural cooling to room temperature, and obtain the carbon-based material; then put the carbon-based material in a mortar and grind for 5 minutes, and put the obtained solid powder into dilute hydrochloric acid solution for 2 hours and sonicate Filtrate, collect the filtrate, rinse with distilled water until the pH of the rinse solution is between 7 and 8, then put the rinsed filtrate into an oven, dry at 80°C for 24 hours, and obtain the pretreated carbon-based material as follows: Lignin-PVC-750-LF carbon base (LF stands for Lignin of free);

S2: Weigh 1.0g of lignin-PVC-750-LF carbon base and pour it into a three-necked bottle, add 150mL of water, heat the oil bath to 80°C, add 4.0g of p-aminobenzenesulfonic acid, react for 30min, and add after it dissolves 6.0g NaNO ₂ , take it out after 10 hours of reaction, alternately wash and filter with methanol and water until the pH of the washing solution is between 7 and 8, and dry at 80°C for 24 hours to obtain lignin-PVC-750-LF carbon-based solid Acid (Lignin-PVC-750-LF Carbon Based Solid Acid).

After measuring, the acid value of the sample is 0.90mmol/g; when the prepared lignin-PVC-750-LF carbon-based solid acid is used in the application of biomass conversion to prepare furfural, 0.10g xylose, 0.05g Lignin-PVC-750-LF carbon-based solid acid and 5mL γ-valerolactone were added to a 25mL pressure-resistant reaction tube. Under magnetic stirring, the reaction temperature was 160°C and kept for 60min. The yield of furfural obtained was 49.4%.

A cycle study was carried out on the above catalysts, and the used catalysts were washed with water and ethanol for three times. After measurement, the acid value of the sample was circulated five times to 0.48mmol/g; when the lignin-PVC-750 carbon-based solid acid obtained after use was used again in the application of biomass conversion to prepare furfural, 0.10g xylose , 0.05g of lignin-PVC-750 carbon-based solid acid and 5mL of γ-valerolactone were added to a 25mL pressure-resistant reaction tube. Under magnetic stirring, the reaction temperature was 160°C and kept for 60min. The yield of furfural obtained was 56.9%. .

Figure 1 shows the SEM images of the samples. It can be seen from the figure that lignin and PVC present a smooth irregular polygonal block structure under the scanning electron microscope. It can be seen from the figure that the carbon-based catalyst calcined at different temperatures presents different morphologies, and the lignin-PVC-400 carbon-based solid acid catalyst calcined at 400°C is a block with a relatively smooth surface and some channels inside. structure, while the lignin-PVC-600 carbon-based solid acid is a block with a large number of pores on the surface and inside. When the temperature rises to 750 ° C, the surface of the lignin-PVC-750 carbon-based solid acid catalyst presents a large Porous lamellar structure with a large increase in surface area. At 800°C, the surface of the lignin-PVC-800 carbon-based solid acid catalyst has a porous thin-layer sheet structure, which shows that the calcination temperature has a great influence on the carbon structure. Comparing lignin-PVC-750-PVCF carbon-based solid acid catalyst and lignin-PVC-750-POF carbon-based solid acid catalyst, it can be seen that the carbon-based sheet structure is more abundant after adding PVC, while lignin-PVC- The morphology and structure of 750-PVCF carbon-based solid acid catalyst and lignin-PVC-750-POF carbon-based solid acid catalyst did not change much, indicating that the introduction of -SO ₃ H had no effect on the surface structure of carbon-based.

Figure 2 shows the FT-IR spectrum of the sample. It can be seen from the figure that various oxygen-containing functional groups of lignin, such as 3600~3000cm ^-1 are OH stretching vibration peaks, and the peaks at 2850~2930cm ^-1 are mainly from various aliphatic groups (-CH, -CH ₂ and -CH ₃ ), the peak at about 1720cm ^-1 is the C=O stretching vibration peak, the strong broad peak in the range of 1390～1647cm ^-1 , the center around 1430cm ^-1 is the aromatic skeleton vibration. This is because lignin is a biopolymer with a three-dimensional network structure, which is formed by connecting three kinds of phenylpropane units through ether bonds and carbon-carbon bonds, and contains rich aromatic ring structures, aliphatic and aromatic hydroxyl groups, and quinone groups. and other active groups. Strong broad peaks from 1000 to 1390 cm ^-1 , several peaks around 1351, 1230, 1128 cm- ¹ , and 1047 cm ^-1 attributed to complex results of CO stretching, aromatic ring respiration, aromatic CH deformation, CO deformation , the peaks from 600 to 800 cm ^-1 are C-Cl vibrating haloalkanes and aromatic rings. In addition, it can be observed that the relative intensities of the peaks at 1232, 1128 and 1047 cm ^-1 are enhanced, which are the characteristic absorption peaks of -SO ₃ H, because the stretching vibrations of S=O and O=S=O are at 1035, 1164 and 1260 cm ^-1 , It indicated that the -SO ₃ H group was successfully introduced through the sulfonation process.

Figure 3 shows the XRD spectrum of the sample. It can be seen from the figure that there is a strong peak at 20° to 30°, and a weak peak at 40° to 50°, corresponding to the (002) crystal of carbon. and (101) crystal plane, the peak at 2θ at 20-30° is mainly aromatic amorphous carbon structure, and the peak at 2θ at 40-50° is corresponding to the graphitic carbon structure. Compare lignin-PVC-400 carbon-based solid acid catalyst, lignin-PVC-600 carbon-based solid acid catalyst, lignin-PVC-750 carbon-based solid acid catalyst and lignin-PVC-800 carbon-based solid acid catalyst. It can be seen that the higher the calcination temperature of the catalyst carbon support, the stronger the 2θ peak between 40° and 50°, and the higher the degree of graphitization of the catalyst. Comparing lignin-PVC-750-PVCF carbon-based solid acid catalyst and lignin-PVC-750-POF carbon-based solid acid catalyst, it can be seen that the addition of PVC has no effect on the crystal structure of lignin carbon-based. Comparing the lignin-PVC-750-PVCF carbon-based solid acid catalyst and the lignin-PVC-750-POF carbon-based solid acid catalyst, it can be seen that the peak of the sulfonated catalyst on the (002) crystal plane of carbon becomes wider, Indicates that the amorphous structure of the carbon group is enhanced, indicating that the access of the phenylsulfonic acid group increases the disorder of the carbon structure.

The invention utilizes lignin and PVC as carbon sources to directly carbonize and sulfonate a carbon-based solid acid catalyst. The preparation method is environmentally friendly and simple to operate. No corrosion, easy separation after reaction and many other advantages; the catalyst can realize the one-step conversion of biomass to prepare furfural, and has good catalytic performance.

The above content is only to illustrate the technical ideas of the present invention, and cannot limit the protection scope of the present invention. Any changes made on the basis of the technical solutions according to the technical ideas proposed in the present invention shall fall within the scope of the claims of the present invention. within the scope of protection.

Claims (10)

1. a preparation method of lignin-PVC carbon-based solid acid, is characterized in that, comprises the following steps: S1: Carbonize the lignin, PVC and KOH to obtain a carbon-based material; perform ultrasonic treatment, washing and drying on the carbon-based material in sequence to obtain a pretreated carbon-based material; S2: The pretreated carbon-based material is subjected to sulfonation treatment with p-aminobenzenesulfonic acid in an oil bath, and then washed and dried to obtain a lignin-PVC carbon-based solid acid. 2. The preparation method of a kind of lignin-PVC carbon-based solid acid according to claim 1, characterized in that, in S1, the weight ratio of the lignin, PVC and KOH is 1.0:1.0:1.0. 3. the preparation method of a kind of lignin-PVC carbon-based solid acid according to claim ₁ , is characterized in that, in S1, described carbonization treatment is to carry out under N atmosphere, and the temperature of described carbonization treatment is 400 ~800°C, the time is 4h. 4. the preparation method of a kind of lignin-PVC carbon-based solid acid according to claim 1, is characterized in that, in S1, described ultrasonic treatment is to adopt the hydrochloric acid that mass concentration is 15%～20% to carry out ultrasonic treatment; The washing treatment is to use ultrapure water to wash until the pH value of the washing liquid is 7-8. 5. the preparation method of a kind of lignin-PVC carbon-based solid acid according to claim 1, is characterized in that, in S2, the step of described sulfonation treatment is: the carbon-based material after pretreatment is mixed with water After water, add p-aminobenzenesulfonic acid after heating up the oil bath, add NaNO ₂ after 30-35 minutes of reaction, take out the reactant after another 10-12 hours of reaction, wash and filter the reactant with dilute hydrochloric acid, water and methanol, at 80-85 Dry at ℃ for 12-24 hours. 6. the preparation method of a kind of lignin-PVC carbon-based solid acid according to claim 5 is characterized in that, the carbon-based material after the pretreatment, water, _p -aminobenzenesulfonic acid and NaNO Consumption ratio It is 1: (150-200) mL: (4-5) g: 6g. 7. The preparation method of a lignin-PVC carbon-based solid acid according to claim 1, characterized in that, in S2, the temperature of the oil bath is 80-100°C. 8. A lignin-PVC carbon-based solid acid, characterized in that, the lignin-PVC carbon-based solid acid adopts a kind of lignin-PVC carbon-based solid acid described in any one of claims 1 to 7 prepared by the preparation method. 9. The application of a kind of lignin-PVC carbon-based solid acid according to claim 8, characterized in that, the lignin-PVC carbon-based solid acid is used as a catalyzer in the furfural reaction prepared from biomass conversion. 10. the application of a kind of lignin-PVC carbon-based solid acid as claimed in claim 9, is characterized in that, when described lignin-PVC carbon-based solid acid prepares the catalyzer in the furfural reaction as biomass conversion, comprises the following steps : Add the biomass and lignin-PVC carbon-based solid acid into the pressure-resistant reaction tube according to the mass ratio of (1:1)~(2:1), and add an organic solvent, and react at a temperature of 150~170°C for 60 minutes, to furfural.

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