CN110882716A - Preparation method of novel solid acid catalyst for one-pot multi-step catalytic conversion of biomass-derived furfural to γ-valerolactone - Google Patents

Abstract

The invention discloses a preparation method for converting biomass derived furfural into gamma-valerolactone by a novel solid acid catalyst through one-pot multi-step catalysis, which comprises the following steps: uniformly mixing a precursor generated by 0.3g-0.7g of zirconium nitrate with distilled water; adding a ZSM-5 carrier into the solution prepared in the last step; adding 6g-10g of urea for regulating the PH; heating the mixed solution to 95 ℃ and stirring vigorously for 5 hours; the solution was filtered, washed with distilled water and then dried at 90 ℃ for 14 hours; calcining the mixture in an oven at 550 ℃ for 4 hours; before the reaction, introducing nitrogen into the reaction kettle for discharging air in the kettle to keep the reaction environment in a nitrogen atmosphere; adding 20mL of solution formed by mixing isopropanol and water into a stainless steel high-pressure reaction kettle, adding furfural, a solid acid catalyst and a magnetic stirring rotor, and setting experimental conditions for reaction; after the reaction was completed, the reactor was placed in cold water to be rapidly cooled to room temperature, and the catalyst was recovered.

Description

One-pot multi-step catalytic conversion of biomass-derived furfural to γ- The preparation method of valerolactone

technical field

The invention belongs to the field of acid catalyst preparation, and relates to a novel multifunctional solid acid catalyst HZSM-5-ZrO ₂ , in particular to a preparation method for catalyzing the catalytic conversion of furfural into γ-valerolactone.

Background technique

The large-scale utilization of fossil resources has greatly promoted the development of human society and economy, but also caused many inevitable derived problems, including global warming, air pollution and energy shortages, to improve environmental degradation, pollution and global energy crisis, researchers In recent years, it has gradually sought to develop new green and renewable resource utilization strategies. As a natural and clean renewable energy with extensive sources, abundant reserves and low prices, biomass energy can be converted into various important high value-added fuels and chemicals, and has great potential to replace traditional fossil energy , the exploration of more efficient biomass resource utilization methods is attracting extensive attention from academia and industry. γ-Valerolactone has attracted much attention of researchers due to its excellent physical properties. The basic properties of γ-valerolactone mainly include high boiling point, high flash point, low melting point, and low toxicity. γ-Valerolactone can participate in various reactions and is widely used in the production of fuel additives, pharmaceutical intermediates, advanced olefin fuels, green regeneration solvents, nylon intermediates, etc. The preparation of γ-valerolactone from furfural involves two hydrolysis reactions and one hydrogenation reaction. At present, γ-valerolactone is prepared from the biomass platform compound furfural. The hydrogen donor mostly uses hydrogen, and the catalyst mostly uses liquid acid, composite catalyst, introduction of precious metals, etc., resulting in poor safety, difficult catalyst recovery, and high manufacturing costs. The invention uses molecular sieve ZSM-5 to support ZrO ₂ to prepare a single bifunctional solid acid catalyst, which is used in the reaction of furfural catalytically converting into γ-valerolactone.

SUMMARY OF THE INVENTION

In order to solve the problem of existing catalysts. The invention focuses on a novel single dual-function solid acid catalyst, uses molecular sieves to support non-precious metal oxide ZrO ₂ , uses a co-precipitation method to synthesize the catalyst, and the catalyst after drying is in the form of white powder.

The present invention adopts the following technical scheme, and the preparation method of the novel solid acid catalyst one-pot multi-step catalyzing biomass-derived furfural into γ-valerolactone comprises the following steps:

1) Evenly mix the precursor generated by 0.3g-0.7g of zirconium nitrate with distilled water;

2) adding the ZSM-5 carrier to the solution configured in the previous step;

3) add 6g-10g urea for adjusting pH;

4) The mixed solution was heated to 95°C and vigorously stirred for 5 hours;

5) The solution was filtered, washed with distilled water, and then dried at 90°C for 14 hours;

6) calcined in an oven at 550°C for 4 hours;

7) feed nitrogen into the reaction kettle before the reaction, in order to discharge the air in the kettle, so that the reaction environment is kept under the nitrogen atmosphere;

8) adding the 20mL solution of isopropanol and water to the stainless steel autoclave, adding furfural, solid acid catalyst and magnetic stirring rotor, and setting experimental conditions to react;

9) After the reaction is completed, the reactor is placed in cold water to rapidly cool to room temperature, and the catalyst is recovered to obtain a solution containing γ-valerolactone.

In the step 2), the ratio of silicon to aluminum is 27.

In described step 3), the mass ratio of urea and ZSM-5 molecular sieve is 5-10g molecular sieve: 1g urea, and the regulation of pH is to form ammoniacal liquor by thermal decomposition of urea, thereby controlling Ph to be between 9-11.6.

The precursor containing equimolar Zr ions generated by zirconium nitrate in the step 2).

In described step 8), isopropanol and water are mutually soluble in any proportion.

In the step 8), the amount of catalyst is controlled between 0.15g-0.6g.

The step 2) metal loading is controlled at 5wt%-20wt%.

The step 8) reaction temperature is controlled at 125-200°C.

The step 8) reaction time is controlled at 16-22h.

The step 8) the solid acid catalyst HZSM-5-ZrO2 can be recycled after being recovered.

experimental method:

1. Add the 20mL solution of isopropanol and water into the stainless steel autoclave, add furfural, solid acid catalyst catalyst and magnetic stirring rotor, set five factors (metal load, catalyst dosage, reaction temperature, reaction time, isopropanol) Dosing amount) four-level orthogonal experiment.

2. Pour nitrogen into the reaction kettle before the reaction to discharge the air in the kettle and keep the reaction environment under nitrogen atmosphere. Tighten the screws of the reaction kettle to maintain a closed environment in the kettle, connect the power supply, connect the temperature sensor, then set the temperature and reaction time of the reaction kettle, and keep the magnetic stirring speed at 500 rpm to start the reaction.

3. After the reaction was completed, the reactor was placed in cold water to rapidly cool to room temperature. The catalyst was recovered to obtain a solution containing γ-valerolactone, waiting for testing.

Product testing method:

1. The furfural and γ-valerolactone concentrations of the filtrate were determined using a Bio-Rad Aminex HPX-87H column at 65°C with high performance liquid chromatography and a refractive index detector.

2. Use 5mM aqueous sulfuric acid as the mobile phase at a flow rate of 0.6mL/min.

3. Configure standard samples with different concentration gradients for the fitting of the standard curves of furfural and γ-valerolactone.

4. Product detection, calculate the concentration and γ-valerolactone yield according to the peak area.

Description of drawings

Figure 1 shows the results based on experimental condition nine in the table.

In the figure: 0.2 ml furfural, 15 wt% Zr, 0.4 g catalyst, 17.4 mL isopropanol, 175°C, 16 hours; only one variable was changed to obtain new reaction conditions and yields.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

The 20mL solution that furfural and isopropanol mixed solution is formed is added in autoclave together with catalyst, add solid acid catalyst catalyst and magnetic stirring rotor, set five factors (metal load, catalyst consumption, reaction temperature, reaction time, isopropanol Dosing amount) four-level orthogonal experiment, as shown in Table 1 below. Nitrogen was introduced into the reaction kettle before the reaction to discharge the air in the kettle, so that the reaction environment was kept under a nitrogen atmosphere. Tighten the screws of the reaction kettle to maintain a closed environment in the kettle, connect the power supply, connect the temperature sensor, then set the temperature and reaction time of the reaction kettle, and keep the magnetic stirring speed at 500 rpm to start the reaction. After the reaction was completed, the reactor was placed in cold water to rapidly cool to room temperature. The catalyst was recovered to obtain a solution containing γ-valerolactone, waiting for testing. The furfural and γ-valerolactone concentrations of the filtrate were determined using a Bio-Rad Aminex HPX-87H column at 65°C with high performance liquid chromatography and a refractive index detector. Using high performance liquid chromatography to test the product, firstly configure 0.05mol/L dilute sulfuric acid solution as the mobile phase, put the prepared dilute sulfuric acid solution into the volumetric flask; pour the dilute sulfuric acid into the beaker and put it into the ultrasonic oscillator to shake for 30 The solution after shaking is filtered with a filter membrane to remove air bubbles in the mobile phase; open the high performance liquid chromatography according to the operation procedure to take the baseline; the flow rate of the mobile phase is controlled to 0.6mL/min; when the baseline becomes stable, use the injection needle Samples were injected, and concentrations and γ-valerolactone yields were calculated from the peak areas.

Zr can be used as a metal with the function of promoting the dehydrogenation of hydrogen donors. Compared with CuO or _SnO2 , ZrO2 supported by molecular sieves has obvious catalytic effect. It is believed that Zr/ZSM-5 catalyst has the effect of catalyzing furfural to produce γ-valerolactone , which can complete the MPV reaction and acid hydrolysis reaction in series in the process. The results in Table 1 show that different reaction conditions have a greater impact on the yield of γ-valerolactone, and when the metal loading reaches 15%, the catalytic performance is the best. Under the conditions of the ninth group in the table (metal loading 15wt%, catalyst dosage 0.4, reaction temperature 175°C, reaction time 16 hours, isopropanol consumption 17.4ml), the yield of γ-valerolactone reached 49.71% . The possible reason is that the Zr/ZSM-5 catalyst has more suitable Bronsted acid sites and Lewis acid sites, the ratio and number of B acid sites and L acid sites are suitable, and the catalytic conditions are more suitable for the reaction, which is It is ensured that the reaction can be carried out sufficiently.

Table 1: Reaction conditions of Zr/ZSM-5

(a: volume of IPA in 20 mL solution)

After that, the catalytic effect of the novel multifunctional solid acid catalyst HZSM-5-ZrO2 was optimized in detail.

The reaction conditions suitable for γ-valerolactone production were further investigated by using Zr/ZSM-5 catalyst to obtain higher γ-valerolactone yield, in Table 1, the 9th set of experimental conditions (metal loading 15% wt , catalyst dosage 0.4g, reaction temperature 175°C, reaction time 16 hours, isopropanol consumption 17.4ml), 10 groups of univariate reactions were continued. For example, the reaction conditions corresponding to the two sets of reactions for the first univariate are: 0.2ml furfural, 10wt% Zr or 20wt% Zr, 0.4g catalyst, 17.4mL isopropanol, 175°C, 16h, modified The condition is only the change of the metal loading, and the change rule of the subsequent experimental conditions is the same as that of the first group. At this time, the γ-valerolactone yield was significantly improved, and most of the GVL yields reached more than 40%. It is obvious from the figure that the metal loading of Zr on the molecular sieve plays a crucial role in FAL conversion and GVL generation, and the effect of catalysts with high metal loading is significantly reduced. The possible reason is that the metal loading on the molecular sieve carrier has reached saturation, and if it continues to increase at this time, it will block the molecular sieve pores, significantly reduce the acidity of the molecular sieve, and reduce the overall specific surface area of the catalyst, so the catalytic performance will decline. In addition, the variation of reaction temperature and reaction time had a moderate effect on the GVL yield, with the temperature controlled at 165°C and 185°C, the γ-valerolactone yield changed slightly. Extending the time from 14 hours to 18 hours increases the yield of γ-valerolactone, thus pushing the reaction forward as the reaction time increases. However, the amount of catalyst and IPA has little effect on it, indicating that the dosage of 0.3g of catalyst and the amount of 18.5ml of isopropanol have met the conditions required for the reaction under this condition. By optimizing the catalytic conditions of Zr/ZSM-5, using 0.4 g of 15 wt% Zr/ZSM-5 as catalyst and 17.4 mL of isopropanol as hydrogen donor, the yield of GVL reached the highest value of 52.43% at 175 °C for 18 h. .

Claims (10)

1. The preparation method for converting biomass derived furfural into gamma-valerolactone by using the novel solid acid catalyst through one-pot multi-step catalysis is characterized by comprising the following steps of:

1) uniformly mixing a precursor generated by 0.3g-0.7g of zirconium nitrate with distilled water;

2) adding a ZSM-5 carrier into the solution prepared in the last step;

3) adding 6g-10g of urea for regulating the PH;

4) heating the mixed solution to 95 ℃ and stirring vigorously for 5 hours;

5) the solution was filtered, washed with distilled water and then dried at 90 ℃ for 14 hours;

6) calcining the mixture in an oven at 550 ℃ for 4 hours;

7) before the reaction, introducing nitrogen into the reaction kettle for discharging air in the kettle to keep the reaction environment in a nitrogen atmosphere;

8) adding 20mL of solution formed by mixing isopropanol and water into a stainless steel high-pressure reaction kettle, adding furfural, a solid acid catalyst and a magnetic stirring rotor, and setting experimental conditions for reaction;

9) after the reaction was completed, the reactor was placed in cold water to be rapidly cooled to room temperature, and the catalyst was recovered to obtain a solution containing γ -valerolactone.

2. The method according to claim 1, wherein the ratio of Si to Al in step 2) is 27.

3. The preparation method of claim 1, wherein the mass ratio of urea to ZSM-5 molecular sieve in the step 3) is 5-10g of molecular sieve to 1g of urea, and the pH is adjusted by heating urea to decompose into ammonia water, so that the pH is controlled to be 9-11.6.

4. The method according to claim 1, wherein the zirconium nitrate is generated as a precursor containing Zr ions in an equimolar amount in the step 2).

5. The method of claim 1, wherein the isopropanol in step 8) is miscible with water in any ratio.

6. The method as claimed in claim 1, wherein the amount of the catalyst used in the step 8) is controlled to be 0.15g to 0.6 g.

7. The method of claim 1, wherein the metal loading of step 2) is controlled to be in the range of 5 wt% to 20 wt%.

8. The method as set forth in claim 1, wherein the reaction temperature in the step 8) is controlled to be 125-200 ℃.

9. The preparation method according to claim 1, wherein the reaction time of the step 8) is controlled to 16 to 22 hours.

10. The preparation method according to claim 1, wherein the solid acid catalyst HZSM-5-ZrO2 in step 8) is recovered and recycled.

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