Application of composite oxide carrier catalyst in catalyzing reaction for preparing furan by decarbonylation of furfural

Abstract

The preparation method of the catalyst taking Al2O3-TiO2 composite oxide as the carrier and the application of the catalyst in the furan preparation reaction through furfural gas-phase decarbonylation comprise the following steps that furfural and hydrogen are mixed and pumped into a fixed bed reactor filled with the catalyst, and furfural is subjected to decarbonylation reaction on the catalyst to generate furan. According to the catalyst, Al2O3-TiO2 composite oxide is used as a carrier, the loading capacity of active component precious metal Pd and Pt is 0.15-0.3%, and the loading capacity of auxiliary component potassium and sodium is 1.0-20%. The catalyst has the advantages of low noble metal loading capacity, high activity, high product selectivity, long service life and the like. The reaction for preparing furan through furfural decarbonylation is carried out under normal pressure, the furfural conversion rate is greater than 95%, the furan selectivity is greater than 99%, the single-pass life of the catalyst exceeds 1000 hours, and the regeneration life can still exceed 800 hours. The method is characterized in that TiO2 is doped into a carrier, and precious metal nanoparticles are wrapped, so that the sintering resistance of the catalyst can be effectively improved, and the stability of the catalyst is improved.

Description

Technical Field

[0001] The present invention relates to the application of a catalyst with an Al 2 O 3 -TiO 2 composite oxide as a carrier in the reaction of furfural hydrodecarbonylation to furan, belonging to the field of fine chemical technology. Background Art

[0002] Furan is an important chemical raw material, widely used in organic synthesis and pharmaceutical production, used to produce pyrrole, thiophene, tetrahydrofuran, etc., and its market demand is increasing year by year. The traditional methods for preparing furan include decarboxylation of furoic acid, oxidation of furfural, and petroleum method (oxidation of butadiene), etc. Among them, the first two methods have been phased out due to reasons such as backward process, poor catalyst activity, and serious pollution, while the petroleum method has an unoptimistic market prospect due to the decreasing annual oil reserves and increasing prices. The raw material of the furfural decarbonylation method, furfural, comes from agricultural and sideline products, and has the advantages of good catalyst activity, etc., meeting the conditions for industrialization.

[0003] The process of furfural hydrodecarbonylation to furan is divided into liquid-phase and gas-phase decarbonylation methods. The operation temperature of the liquid-phase decarbonylation method is relatively mild, but the disadvantages are that the noble metal Pd content in the catalyst is too high and the catalyst is prone to coking and deactivation. Patent CN102000569A discloses a Pd / γ-Al 2 O 3 -MO catalyst (MO is an oxide of K, Cs, Li), the Pd loading reaches 5wt%, reacting at a pressure of 0 - 0.5MPa, under the conditions of 200 - 259 degrees, the furfural conversion rate is 92% - 98%, the furan selectivity is 85 - 94%, and the catalyst life is 100 - 120h. In contrast, although the reaction temperature of the furfural gas-phase decarbonylation process is relatively high (260 - 360 °C), it has obvious advantages in terms of the noble metal loading of the catalyst, furfural conversion rate, furan selectivity, and service life.

[0004] Patent US4780522 discloses a catalyst Pt / γ-Al 2 O 3 -CsCO 3 for the production of furan by gas-phase decarbonylation of furfural, the Pd loading reaches 0.75wt%, at normal pressure, 300 - 360 °C, with a furfural volume space velocity of 1.1h -1 and a molar ratio of furfural to hydrogen of 1.8 / 1.4, the furfural conversion rate is 70% - 99%, the average furan yield is 95%, the catalyst runs for 1430h, and 175 kg of furan is produced per kilogram of noble metal Pt.

[0005] Patent CN1308986A discloses a high-efficiency noble metal catalyst for the gas-phase decarbonylation of furfural to produce furan, using Al2 O 3 -TiO 2 The catalyst is prepared by impregnation method using a composite oxide as the carrier. The loading amount of the active component Pt is 0.4 - 0.7 wt%, and it also contains 0.5 - 2.0 wt% of K 2 O or Cs 2 O or MgO or CaO or BaO. Under normal pressure, at 280 °C, with a furfural volume space velocity of 0.9 h -1 , and a molar ratio of furfural to hydrogen of 0.5 - 2.0, the conversion rate can reach 80 - 97%, and the selectivity can reach 85 - 92%.

[0006] Patent CN113398911B discloses a catalyst using CeO 2 -ZrO 2 -Al 2 O 3 composite oxide as the carrier. The loading amount of the active component Pd is 0.25 wt%, and the loading amount of the promoter K is 1.0 wt%. It catalyzes the decarbonylation reaction of furfural to furan. Under normal pressure and a reaction temperature of 260 °C, the furfural feed volume space velocity is 0.8 h -1 , when the molar ratio of hydrogen to furfural is 1.0, the furfural conversion rate is greater than 98%, the selectivity reaches 95%, and the single-pass life of the catalyst reaches 500 hours. Compared with the existing work, this catalyst has the advantages of low noble metal loading, high activity, good selectivity, and long catalyst life. 165 kg of furan is produced per kilogram of noble metal Pd.

[0007] The core of the process for the gas-phase hydrogenation decarbonylation of furfural to furan is the catalyst. Currently, during the operation of the catalyst, due to sintering and coking, the single-pass service life of the catalyst is relatively short, the furan yield per kilogram of noble metal is relatively low, and the catalyst cost is relatively high. TiO 2 The carrier has a strong interaction with the noble metal, which can improve the dispersion of the noble metal; moreover, during the preparation of the catalyst, melamine is introduced, so that the noble metal nanoparticles are wrapped by an amorphous and permeable TiOx coating layer, and this coating layer remains stable after calcination in air at 400 - 600 °C, which can effectively improve the anti-sintering ability of the catalyst and improve the catalyst stability (ACS Catal. 2021, 11, 6081 - 6090). In addition, Al 2 O 3 The carrier has the advantages of high specific surface area and good thermal stability. Therefore, the present invention combines Al 2 O 3 and TiO 2 to prepare a composite oxide of Al 2 O 3 -TiO 2 to solve the problems of poor anti-sintering ability and low stability of the noble metal catalyst during the hydrogenation decarbonylation of furfural to furan in the prior art. SUMMARY OF THE INVENTION

[0008] To solve the problems existing in the prior art, the present invention prepares an Al 2 O 3 -TiO 2 composite oxide. The catalyst prepared with this composite oxide as the carrier has a high dispersion of noble metals, has very high activity for the gas-phase decarbonylation of furfural to furan, has good anti-sintering ability, and has a long catalyst life.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] The present invention relates to the application of a catalyst with an Al 2 O 3 -TiO 2 composite oxide as the carrier in the reaction of the hydrogenation decarbonylation of furfural to furan. The catalyst further includes active components of noble metals Pd and Pt and promoters potassium and sodium. The mass of the noble metals Pd and Pt is 0.15 - 0.3% (preferably 0.18 - 0.25%) of the total mass of the catalyst. The promoters potassium and sodium exist in the form of oxides or salts. The loading amount of potassium and sodium (calculated based on the mass of the corresponding salts input) is 1.0 - 20% (preferably 5.0 - 10%) of the total mass of the catalyst.

[0011] For the preparation method of the catalyst, first, the salt solution of the noble metal is impregnated on the Al 2 O 3 -TiO 2 composite oxide, dried at 100 - 120 °C, and calcined at 250 - 600 °C; then the salt solution of potassium or sodium is impregnated on the carrier, dried at 100 - 120 °C, and calcined at 250 - 600 °C to obtain Pd / Al 2 O 3 -TiO 2 . Then Pd / Al 2 O 3 -TiO 2 is added to a solution containing melamine or urea, heated at 40 - 100 °C with stirring for 2 - 24 h, and the slurry is filtered, washed, and dried to obtain M / Pd / Al 2 O 3 -TiO 2 , and calcined at 300 - 600 °C for 2 - 10 h under nitrogen conditions and at 400 - 1000 °C for 2 - 10 h under air conditions.

[0012] The concentration of the melamine or urea solution is 0.1 - 10.0 mg / mL (preferably 1.0 - 5.0 mg / mL).

[0013] The Al 2 O3 -TiO 2 The preparation method of the composite oxide is the co-precipitation method. The specific process is as follows: A mixed solution of metal aluminum salt and metal titanium salt is adjusted to pH = 9 - 10.5 with ammonia water. The obtained precipitate is aged, filtered, washed, dried, and calcined to obtain the titanium-aluminum composite oxide. The aging time of the titanium-aluminum composite oxide precipitate in the mother liquor is 1 - 24 hours (preferably 2 - 12 hours); the drying temperature is 80 - 150 °C (preferably 100 - 120 °C); the calcination temperature is 40 °C - 1200 °C (preferably 500 °C - 800 °C), and the calcination time is 1 - 12 hours (preferably 2 - 4 hours). The Al 2 O 3 -TiO 2 The mass of titanium oxide in the composite oxide is 1.0 wt% - 25 wt% (preferably 5 wt% - 15 wt%) of the mass of the composite oxide.

[0014] The metal aluminum salts include one or more of aluminum nitrate, aluminum trichloride, aluminum sulfate, sodium metaaluminate, and aluminum isopropoxide; the metal titanium salts include one or more of titanium tetrachloride, titanyl sulfate, titanium isopropoxide, and titanium sulfate.

[0015] The noble metal palladium salts are at least one of palladium chloride, palladium nitrate, palladium acetate, chloropalladic acid, sodium chloropalladate, and ammonium chloropalladate; the noble metal platinum salts are at least one of chloroplatinic acid, platinum tetrachloride, platinum nitrate, and platinum acetylacetonate; the salt solution of potassium or sodium is at least one of carbonate, acetate, sulfate, nitrate, and chloride.

[0016] The reaction conditions for the decarbonylation of furfural to furan are as follows: at atmospheric pressure, the reaction temperature is 250 - 360 °C (preferably 280 - 320 °C), the mass space velocity of furfural feed is 0.5 - 5.0 h -1 (preferably 1.2 - 3.5 h -1 ), and the molar ratio of hydrogen to furfural is 0.6 - 7.5:1 (preferably 1.5 - 4.5:1).

[0017] The decarbonylation reaction of furfural proceeds according to the following steps: Furfural is heated in a vaporizer and then enters the catalyst bed of a fixed-bed reactor together with hydrogen. Furfural undergoes a decarbonylation reaction on the catalyst to produce furan. The liquid raw material and the product are collected as the reaction solution after low-temperature condensation, and the gas product is quantitatively analyzed by on-line chromatography. The content of furfural and furan in the reaction solution is quantitatively analyzed by internal standard in gas chromatography to calculate the furfural conversion rate. The gas product is analyzed by on-line chromatography to calculate the CO yield, the content of furan and by-products, and the sum of the furan content in the gas product and the liquid product is used to calculate the furan selectivity and the total yield.

[0018] Preferably, the inner diameter of the fixed-bed reactor is 7 mm, and the catalyst addition amount is about 0.9 grams.

[0019] This catalyst has the advantages of low noble metal loading, high activity, high product selectivity, and long catalyst life. The reaction of furfural decarbonylation to furan is carried out under atmospheric pressure, with a reaction temperature of 250 - 360 °C, a mass space velocity of furfural feed of 0.5 - 5.0 h -1 , a molar ratio of hydrogen to furfural of 0.6 - 7.5:1, a furfural conversion rate greater than 95%, a furan selectivity greater than 99%, a single-pass life of the catalyst exceeding 1000 hours, and a regeneration life still exceeding 800 hours. The characteristics of this method are that TiO 2 is incorporated into the carrier, and by encapsulating noble metal nanoparticles, the sintering resistance of the catalyst can be effectively improved and the catalyst stability can be enhanced.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) The present invention uses Al 2 O 3 -TiO 2 composite oxide as the catalyst carrier, and the prepared catalyst has a high noble metal dispersion. With a relatively low noble metal Pd, Pt loading of 0.15 - 0.3%, at a mass space velocity of furfural feed of 2.32 h -1 (volume space velocity 1.48 h -1 ), the furfural conversion rate is still close to 100%, and the furan selectivity exceeds 99%.

[0022] (2) In the present invention, TiO 2 is incorporated into the carrier, and by encapsulating noble metal nanoparticles, a permeable coating layer is formed, which can effectively improve the sintering resistance of the catalyst and enhance the catalyst stability. The single-pass life of the catalyst can exceed 2000 hours; the regeneration life after deactivation can still exceed 200 hours. Detailed implementation manners

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention. The scope of protection required by the present invention is defined by the appended claims and their equivalents.

[0024] There are no particular restrictions on the purity of all raw materials of the present invention, and the reagents used in the following examples are all commercially available. Qualitative analysis of reaction raw materials and liquid products: Agilent gas chromatography-mass spectrometry was used to qualitatively analyze furfural, furan, 2-methylfuran, tetrahydrofuran, 2-methyltetrahydrofuran, furfuryl alcohol, and tetrahydrofurfuryl alcohol, and it was confirmed by retrieving the mass spectrometry library and comparing with the retention time of the reference substance. Quantitative analysis of reaction liquid products: An Agilent gas chromatograph (with an HP-5 capillary column and an FID hydrogen flame detector) was used to quantitatively analyze the products by the internal standard method, and the internal standard was n-heptanol. Drawing of the internal standard working curve: Accurately weigh a total of 4.0 g of the reference substances of furfural, furan, 2-methylfuran, tetrahydrofuran, 2-methyltetrahydrofuran, furfuryl alcohol, and tetrahydrofurfuryl alcohol to prepare a standard stock solution, and then respectively pipette 0.02 g, 0.05 g, 0.15 g, 0.25 g, 0.45, 0.65, 0.85, 1.0 g from the stock solution, dissolve 0.05 g of n-heptanol, add 1.5 mL of ethanol to make up the volume, and then perform gas phase analysis. Respectively record the peak area ratio (Ai / As, where Ai represents the chromatographic peak area of the analyte and As represents the chromatographic peak area of the reference substance) of the analytes (furfural, furan, 2-methylfuran, tetrahydrofuran, 2-methyltetrahydrofuran, furfuryl alcohol, tetrahydrofurfuryl alcohol) and the reference substance n-heptanol as the abscissa, and calculate the mass ratio mi / ms of furfural, furan, 2-methylfuran, tetrahydrofuran, 2-methyltetrahydrofuran, furfuryl alcohol, tetrahydrofurfuryl alcohol and n-heptanol in each solution as the ordinate to draw the standard working curve of raw materials and products and calculate the amount of products; Quantitative analysis of reaction gas products: A Penray gas chromatograph was connected online with a fixed bed reactor (with a TCD\FID hydrogen flame detector), and the products of CO, C2, C3, C4, furan, 2-methylfuran, tetrahydrofuran, and 2-methyltetrahydrofuran were quantitatively analyzed by the external standard method to calculate the amount of products. In the following examples, the conversion rate of furfural, the selectivity and yield of furan are defined by the following formulas:

[0025]

[0026]

[0027]

[0028]

[0029] Yield of 3,4-dihydropyran (%) = Selectivity of 3,4-dihydropyran * Conversion rate of tetrahydrofurfuryl alcohol * 100

[0030] Yield of tetrahydropyran (%) = Selectivity of tetrahydropyran * Conversion rate of tetrahydrofurfuryl alcohol * 100

[0031] Selectivity of 2 - Hydroxytetrahydropyran (%) = Selectivity of 2 - Hydroxytetrahydropyran * Conversion of Tetrahydrofurfuryl Alcohol * 100

[0032] Catalyst Preparation:

[0033] Al 2 O 3 -TiO 2 Preparation of Composite Oxide Support:

[0034] Weigh 63.15 g of aluminum nitrate (Al(NO 3 ) 3 .9H 2 O) and dissolve it in 100 mL of deionized water. Drop titanium tetrachloride into 20 mL of hydrochloric acid solution with pH = 5 - 6 (here pH = 5.5), and hydrolyze it in an ice - water bath for 1 hour. Slowly mix the aluminum nitrate solution and the titanium tetrachloride solution, and then drop concentrated ammonia water (ammonia mass content 25% - 28%) while stirring, controlling pH ≈ 9.5; age the obtained precipitate in the reaction solution at room temperature for 12 hours, then wash it with deionized water and filter it until there is no chloride ion, put it in an oven and dry it at 105 °C for 12 hours, and then calcine it in a muffle furnace at 500 °C for 2 hours to obtain Al 2 O 3 -TiO 2 Composite Oxide. Obtain composite oxide supports (TA) with TiO 2 mass percentages of 1%, 5%, 10%, 15%, 25%. The TA samples are respectively labeled as TA - X, where X is the mass percentage of TiO 2 . The dosage of titanium tetrachloride is as shown in Table 1 below:

[0035]

[0036] Al 2 O 3 -TiO 2 The pore volume of the Al

[0037] Example A1

[0038] Weigh 11.0 mL of palladium chloride solution (1.0 g of palladium chloride dissolved in 250 mL of dilute hydrochloric acid with a concentration of 49.8 mmol / L). Put 10 g of TA-10 into the above solution and impregnate for 8 hours. Dry at 120 °C for 12 hours and calcine at 400 °C for 4 hours. Weigh 1.0 g of potassium carbonate, dissolve it with 11.2 g of pure water, impregnate the TA-10 support loaded with palladium for 8 hours, dry at 120 °C for 12 hours, and calcine at 400 °C for 4 hours. Then add the TA-10 support loaded with palladium and potassium into a solution containing 2.0 mg / mL of melamine in 2500 ml, stir at 60 °C for 24 h, filter, wash and dry the slurry. Then calcine at 600 °C for 3 h under nitrogen conditions, calcine at 800 °C for 3 h under air conditions, and reduce at 200 °C for 2 h under hydrogen atmosphere to obtain catalyst 1#, and the loading amount of palladium relative to the support is 0.25%, and the loading amount of potassium salt relative to the support is 10%.

[0039] Example A2: The catalyst support is TA-1 (instead of TA-10), and the others (processes and conditions) are the same as in Example A1 to obtain catalyst 2#.

[0040] Example A3: The catalyst support is TA-5 (instead of TA-10), and the others (processes and conditions) are the same as in Example A1 to obtain catalyst 3#.

[0041] Example A4: The catalyst support is TA-15 (instead of TA-10), and the others (processes and conditions) are the same as in Example A1 to obtain catalyst 4#.

[0042] Example A5: The catalyst support is TA-25 (instead of TA-10), and the others (processes and conditions) are the same as in Example A1 to obtain catalyst 5#.

[0043] Example A6: Weigh 6.5 mL of palladium chloride solution, and the others (processes and conditions) are the same as in Example A1 to obtain catalyst 6#, and the theoretical loading amount of palladium is 0.15%.

[0044] Example A7: Weigh 13.0 mL of palladium chloride solution, and the others (processes and conditions) are the same as in Example A1 to obtain catalyst 7#, and the theoretical loading amount of palladium is 0.3%.

[0045] Example A8: Weigh 0.1 g of potassium carbonate, and the others (processes and conditions) are the same as in Example A1 to obtain catalyst 8#, and the theoretical loading amount of potassium salt is 1.0%.

[0046] Example A9: Weigh 0.5 g of potassium carbonate, and the others (processes and conditions) are the same as in Example A1 to obtain catalyst 9#, and the theoretical loading amount of potassium salt is 5.0%.

[0047] Example A10: Weigh 2.0 grams of potassium carbonate. Keep other (processes and conditions) the same as in Example A1 to obtain Catalyst 10#. The theoretical loading of the potassium salt is 20%.

[0048] Example A11: The concentration of the melamine solution is 0.1 mg / mL. Keep other (processes and conditions) the same as in Example A1 to obtain Catalyst 11#.

[0049] Example A12: The concentration of the melamine solution is 1.0 mg / mL. Keep other (processes and conditions) the same as in Example A1 to obtain Catalyst 12#.

[0050] Example A13: The concentration of the melamine solution is 5.0 mg / mL. Keep other (processes and conditions) the same as in Example A1 to obtain Catalyst 13#.

[0051] Example A14: The concentration of the melamine solution is 10.0 mg / mL. Keep other (processes and conditions) the same as in Example A1 to obtain Catalyst 14#.

[0052] Example A15: Replace the melamine solution with a urea solution. Keep other (processes and conditions) the same as in Example A1 to obtain Catalyst 15#.

[0053] Example A16: Replace the palladium chloride solution with a platinum nitrate solution (1.0 gram of platinum nitrate solution is dissolved in 100 mL of ultrapure water), 11.0 mL. Keep other (processes and conditions) the same as in Example A1 to obtain Catalyst 16#. The theoretical loading of platinum is 0.25%.

[0054] Comparative Example 1: Weigh 11.0 mL of a palladium chloride solution (1.0 gram of palladium chloride is dissolved in 250 mL of dilute hydrochloric acid with a concentration of 49.8 mmol / L). Put 10 grams of activated Al 2 O 3 balls (crushed and screened to 20 - 40 mesh) into the above solution for impregnation for 8 hours, dry at 120 °C for 12 hours, and calcine at 400 °C for 4 hours; Weigh 1.0 gram of potassium carbonate, dissolve it in 11.2 grams of pure water, and impregnate the above palladium-loaded Al 2 O 3 balls for 8 hours, dry at 120 °C for 12 hours, and calcine at 400 °C for 4 hours; Reduce it at 200 °C for 2 h under a hydrogen atmosphere to obtain Catalyst 17#. The theoretical loading of palladium is 0.25%, and the theoretical loading of the potassium salt is 10%.

[0055] Comparative Example 2: Weigh 11.0 mL of palladium chloride solution (1.0 g of palladium chloride dissolved in 250 mL of dilute hydrochloric acid with a concentration of 49.8 mmol / L), put 10 g of TA-10 into the above solution and impregnate for 8 hours, dry at 120 °C for 12 hours, and calcine at 400 °C for 4 hours; weigh 1.0 g of potassium carbonate, dissolve it with 11.2 g of pure water, impregnate the above palladium-loaded TA-10 support for 8 hours, dry at 120 °C for 12 hours, and calcine at 400 °C for 4 hours; reduce it at 200 °C for 2 h under a hydrogen atmosphere to obtain Catalyst 18#, the theoretical loading of palladium is 0.25%, and the theoretical loading of potassium salt is 10%.

[0056] Catalyst Stability Evaluation of Examples B1 - B16

[0057] The above-obtained powdered catalyst was tabletted, the catalyst was crushed, and particles with a mesh size of 20 - 40 were screened. The evaluation was carried out on a fixed-bed reactor with an inner diameter of 7 mm. The reaction was at atmospheric pressure, the reaction temperature was 280 °C, and the mass space velocity of furfural feed was 2.32 h -1 , the molar ratio of hydrogen to furfural was 1.48, and a long-term stability test of the catalyst was carried out. The products at the outlet of the hydrogenation reactor were collected for analysis, and the analysis results are shown in Table 2.

[0058] The furfural decarbonylation reaction is carried out according to the following steps: Furfural is vaporized with hydrogen at 40 - 150 °C in a vaporizer and enters the catalyst bed of a fixed-bed reactor. Furfural undergoes a decarbonylation reaction on the catalyst to form furan. The liquid raw materials and products are collected as the reaction solution after low-temperature condensation, and the gas products are quantitatively analyzed by on-line chromatography.

[0059]

[0060]

[0061] The two numbers before and after "-" represent the conversion rate and selectivity at the initial reaction and the end of the reaction respectively;

[0062] It can be seen from Table 2 and Comparative Example 4 of Example B1 that by using Al 2 O 3 -TiO 2 composite oxide as the catalyst support and performing a calcination treatment by adding a nitrogen-containing compound, the catalyst stability is significantly improved; it can be seen from Comparative Examples 3 and 4 that by using Al 2 O 3 -TiO 2 composite oxide as the catalyst support, compared with using Al 2 O 3 as the support, the catalyst stability is also improved.

[0063] Catalyst Regeneration Life Experiment of Example B17

[0064] When the stability experiments of Catalysts - 1#, 2#, 3#, 4#, 5#, 15#, and 16# exceed 1000 hours respectively, increase the space velocity by 5 times to reduce the furfural conversion rate to 70%, then stop the furfural feeding, switch the hydrogen to nitrogen for purging until the room temperature is reached; switch the nitrogen to air and raise the temperature programmedly to 400 °C and hold for 4 hours; then switch the air to nitrogen for purging until the room temperature is reached; switch the nitrogen to hydrogen and raise the temperature programmedly to 200 °C and hold for 2 hours to reduce the catalyst; after the reduction is completed, raise the temperature to 300 °C, turn on the furfural feeding pump, and carry out the furfural decarbonylation reaction. The reaction is at atmospheric pressure, the reaction temperature is 280 °C, and the mass space velocity of the furfural feeding is 2.32 h -1 , the molar ratio of hydrogen to furfural is 1.48, carry out the regeneration life test of the catalyst, and collect and analyze the products at the outlet of the hydrogenation reactor. Catalyst - 17# and Catalyst - 18# carry out the above operations respectively after the stability experiments of Comparative Example 1 and Comparative Example 2 are completed. All the analysis results are shown in Table 3.

[0065] The furfural decarbonylation reaction proceeds according to the following steps: Furfural is vaporized with hydrogen at 40 - 150 °C in a vaporizer and then enters the catalyst bed of a fixed - bed reactor. Furfural undergoes a decarbonylation reaction on the catalyst to produce furan. The liquid raw material and the product are collected as the reaction solution after low - temperature condensation, and the gas product is quantitatively analyzed by on - line chromatography.

[0066]

[0067]

[0068] The two numbers before and after "-" respectively represent the conversion rate and selectivity at the initial reaction and the end of the reaction;

[0069] As can be seen from Table 3 for Examples B17 - B23 and Comparative Example 6, using Al 2 O 3 -TiO 2 composite oxide as the catalyst support and preparing the catalyst by adding a nitrogen - containing compound for calcination treatment still has good stability after regeneration treatment. After reacting for 800 h, the furfural conversion rate still reaches 98.8% and the furan selectivity is 98.9%; as can be seen from Comparative Examples 5 and 6, using Al 2 O 3 -TiO 2 composite oxide as the catalyst support, compared with using Al 2 O 3 as the support, the regenerated catalyst has higher stability, but compared with the catalyst before regeneration, the stability still decreases significantly after regeneration. This is mainly due to TiO 2Incorporated into the carrier, by encapsulating noble metal nanoparticles, the anti-sintering ability of the catalyst can be effectively improved and the stability of the catalyst during long-term use can be improved. The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions and substitutions can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. Application of a composite oxide supported catalyst in the decarbonylation of furfural to furan, characterized in that: Using Al 2 O 3 -TiO 2 Composite oxide as the carrier; the catalyst further comprises one or two of the active components noble metals Pd and Pt, and one or two of the promoters potassium and sodium; the mass of the noble metal is 0.15 - 0.3% (preferably 0.18 - 0.25%) of the mass of the carrier, and the promoters potassium and sodium exist in the form of one or more of their oxides or salts, and the loading amount of the promoter is 1.0 - 20% (preferably 5.0 - 10%) of the mass of the carrier.

2. The application according to claim 1, characterized in that: The preparation process of the catalyst is as follows: first, impregnate the salt solution of the noble metal on the Al 2 O 3 -TiO 2 composite oxide, dry at 100 - 120 °C, and calcine at 250 - 600 °C for 2 - 10 h; then impregnate the salt solution of potassium and / or sodium on the carrier, dry at 100 - 120 °C, and calcine at 250 - 600 °C for 2 - 10 h to obtain Pd / Al 2 O 3 -TiO 2 ; then add Pd / Al 2 O 3 -TiO 2 to the solution containing melamine and / or urea, stir at 40 - 100 °C for 2 - 24 h, filter, wash, and dry the slurry to obtain M / Pd / Al 2 O 3 -TiO 2 , calcine at 300 - 600 °C for 2 - 10 h under nitrogen atmosphere, calcine at 400 - 1000 °C for 2 - 10 h under air atmosphere, and reduce at 200 - 600 °C for 1 - 4 h under hydrogen atmosphere.

3. The application according to claim 2, characterized in that: The solution concentration of the melamine or urea is 0.1 - 10.0 mg / mL (preferably 1.0 - 5.0 mg / mL).

4. The application according to claim 1 or 2, characterized in that: The said Al 2 O 3 -TiO 2 The preparation method of the composite oxide is the co-precipitation method, and the specific process is as follows: A mixed solution of metal aluminum salt and metal titanium salt is adjusted to pH = 9 - 10.5 with ammonia water having a mass concentration of 10% - 30%. The obtained precipitate is aged, filtered, washed, dried, and calcined to obtain the titanium-aluminum composite oxide; The aging time of the titanium-aluminum composite oxide precipitate in the mother liquor is 1 - 24 hours (preferably 2 - 12 hours); the drying temperature is 80 - 150 °C (preferably 100 - 120 °C); the calcination temperature is 400 °C - 1200 °C (preferably 500 °C - 800 °C), and the calcination time is 1 - 12 hours (preferably 2 - 4 hours); The described Al 2 O 3 -TiO 2 In the composite oxide, the mass of titanium oxide is 1.0 wt% - 25 wt% (preferably 5 wt% - 15 wt%) of the mass content of the composite oxide.

5. The application according to claim 4, characterized in that: The metal aluminum salt includes one or more of aluminum nitrate, aluminum trichloride, aluminum sulfate, sodium metaaluminate, and aluminum isopropoxide; The metal titanium salt includes one or more of titanium tetrachloride, titanium oxysulfate, titanium isopropoxide, and titanium sulfate.

6. The application according to claim 2, characterized in that: The noble metal palladium salt is at least one of palladium chloride, palladium nitrate, palladium acetate, chloropalladic acid, sodium chloropalladate, and ammonium chloropalladate; the noble metal platinum salt is at least one or more of chloroplatinic acid, platinum tetrachloride, platinum nitrate, and platinum acetylacetonate; the salt solution of potassium or sodium is at least one or more of carbonate, acetate, sulfate, nitrate, and chloride.

7. The application according to claim 1, characterized in that: The reaction conditions for the decarbonylation of furfural to furan are as follows: under atmospheric pressure, the reaction temperature is 250 - 360 °C (preferably 280 - 320 °C), and the mass space velocity of furfural feed is 0.5 - 5.0 h -1 (preferably 1.2 - 3.5 h -1 ), and the molar ratio of hydrogen to furfural is 0.6 - 7.5:1 (preferably 1.5 - 4.5:1).

8. The application according to claim 1, characterized in that: The furfural decarbonylation reaction proceeds according to the following steps: Furfural is heated to 40 - 150 °C in a vaporizer and then enters the catalyst bed of a fixed-bed reactor together with hydrogen. Furfural undergoes a decarbonylation reaction on the catalyst to produce furan. The liquid raw material and the product are collected by low-temperature condensation, and the gas product is quantitatively analyzed by an on-line chromatograph.

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