A chromium-based catalyst and its application in fluorine-chlorine exchange of olefins

Abstract

The invention discloses a chromium-based catalyst and its application in olefin fluorine-chlorine exchange reaction. The chromium-based catalyst comprises a chromium oxide composition, which comprises 5-80% of Cr(OH)3, 5-60% of CrOOH, 5-50% of CrO2 and 5-20% of Cr2O3 by mass percentage. The chromium-based catalyst is used in olefin fluorine-chlorine exchange reaction to improve the conversion rate of raw materials and the selectivity of products at the same time.

Description

Technical Field

[0001] The present invention relates to the preparation of fluoroolefins, and in particular to a chromium-based catalyst containing a chromium oxide composition with a specific mass distribution and its application in the fluorine-chlorine exchange of olefins. Background Art

[0002] HFOs are considered to be a new generation of environmentally friendly refrigerants and foaming agents due to their ODP value of 0 and low GWP value. Among them, HFO-1234yf is one of the most popular varieties in HFOs research. It is mainly prepared by gas-phase fluorine-chlorine exchange reaction using HCFO-1233xf (2-chloro-3,3,3-trifluoropropene) as raw material. For this reaction, the research focus is mainly on the research of catalysts.

[0003] The article "Cr2O3 Catalysts for Fluorination of 2-Chloro-3,3,3trifluoropropene to 2,3,3,3-Tetrafluoropropene" (Ind.Eng.Chem.Res.2013,52,3295-3299) discloses the application of Cr2O3 in the gas phase synthesis of HFO-1234yf from HCFO-1233xf, focusing on the effect of calcination temperature on the grain size and acidity of Cr2O3. The conversion rate of HCFO-1233xf is 63%, and the selectivity of HFO-1234yf and HFC-245cb is 59% and 38%, respectively.

[0004] Patent CN108367285A discloses a method for preparing HFO-1234yf from HCFO-1233xf, wherein the catalyst is chromium dioxide doped with zinc or zinc oxide, and the catalyst is fluorinated, and the reaction conditions are: 5 bar, 350°C, HF:1233xf:O2=20:1:0.04, and the HCFO-1233xf conversion rate is 61% after 48 hours. The catalyst is then regenerated, and the regeneration conditions are: (1) 350°C, atmospheric pressure, 5 L / h air treatment for 48 hours; (2) 325°C, H2 (1.25 L / h), N2 (25 L / h) treatment for 5 hours; (3) 350°C, P=1.6 bar, 10 L / h N2 treatment for 24 hours. After regeneration, the sum of the selectivity of HFO-1234yf and HFC-245cb is 95%.

[0005] Therefore, the current understanding of the catalyst used in the preparation of HFO-1234yf from HCFO-1233xf is that most people believe that it is necessary to convert as much Cr(OH)3 as possible into Cr2O3, or to use CrO2 as a catalyst, but neither can achieve a high conversion rate and selectivity at the same time. Summary of the invention

[0006] In order to solve the above technical problems, the present invention proposes a chromium-based catalyst for olefin fluorine-chlorine exchange, which can simultaneously improve the conversion rate of raw materials and the selectivity of products by adjusting the ratio of Cr(OH)3, CrOOH, CrO2 and Cr2O3 in the precursor.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] A chromium-based catalyst comprises a chromium oxide composition, wherein the chromium oxide composition comprises, by mass percentage, 5-80% of Cr(OH)3, 5-60% of CrOOH, 5-50% of CrO2 and 5-20% of Cr2O3.

[0009] Preferably, the chromium oxide composition comprises 10-70% Cr(OH)3, 10-55% CrOOH, 10-40% CrO2 and 6-10% Cr2O3.

[0010] More preferably, the chromium oxide composition comprises 20-50% Cr(OH)3, 15-50% CrOOH, 15-30% CrO2 and 8-10% Cr2O3.

[0011] Furthermore, the chromium-based catalyst also includes a co-component composition, which includes a co-component oxide and / or a co-component hydroxide, and the co-component is selected from at least one of magnesium, zinc, aluminum, calcium, copper, lanthanum, iron, indium, zirconium, nickel, manganese, titanium, gallium or cobalt, and the molar ratio of chromium in the chromium oxide composition to the co-component in the co-component composition is 1:0.001 to 1:1.

[0012] Preferably, the auxiliary component is selected from at least one of zinc, aluminum or lanthanum, and the molar ratio of chromium in the chromium oxide composition to the auxiliary component in the auxiliary component composition is 1:0.01 to 1:0.05.

[0013] Furthermore, the auxiliary component composition includes 50-60% of auxiliary component oxide and 40-50% of auxiliary component hydroxide.

[0014] In a specific embodiment, the magnesium oxide composition comprises 50-60% MgO and 40-50% Mg(OH)2.

[0015] Any of the above-mentioned chromium-based catalysts of the present invention can be obtained by the following steps:

[0016] A1. Add ammonia water to the chromium salt solution and the auxiliary component salt solution to cause precipitation reaction. When the pH value of the slurry is ≈6-10, stop adding the material, filter the slurry, and wash the filter cake with deionized water until it is neutral;

[0017] A2. The filter cake is dried at 80-120°C and sieved into particles;

[0018] A3. The sieved particles are roasted.

[0019] In the step A2, particles of 1 to 3 mm are preferably obtained after screening.

[0020] In the step A3, the calcination temperature is 150-400°C, the calcination pressure is 0.01-1.0Mpa, the calcination atmosphere is a mixture of oxidizing gas and nitrogen, and the oxidizing gas accounts for 0.1-50% of the volume of the mixed gas. The oxidizing gas is selected from oxygen or chlorine. Preferably, the calcination temperature is 240-380°C, the pressure is 0.02-0.8Mpa, and the oxidizing gas accounts for 1-40% of the volume of the mixed gas.

[0021] The chromium salt solution of the present invention is selected from at least one of soluble chromium salts, such as chromium chloride, chromium nitrate, chromium sulfate, chromium oxalate or chromium carbonate.

[0022] The auxiliary component salt solution of the present invention is selected from chloride, nitrate, sulfate or oxalate of the auxiliary component. Preferably, the auxiliary component salt solution is selected from chloride, nitrate or sulfate of the auxiliary component.

[0023] The present invention also provides the use of any of the above-mentioned chromium-based catalysts, in particular, the chromium-based catalyst is used for the fluorine-chlorine exchange reaction of olefins. Further, the chromium-based catalyst is used for preparing HFO-1234yf from HCFO-1233xf and preparing HFO-1234ze from HCFO-1233zd.

[0024] The present invention also provides a method for preparing 2,3,3,3-tetrafluoropropene, which is specifically prepared by using any of the above-mentioned chromium-based catalysts and exchanging fluorine with chlorine from HCFO-1233xf.

[0025] Furthermore, the preparation method comprises:

[0026] B1. Activation step: 150 to 400 ° C, activating the chromium-based catalyst in a 1 to 90% HF / N2 atmosphere;

[0027] B2. Reaction step: 50~2000h -1 HCFO-1233xf, HF and an oxidizing gas are introduced at an air velocity of , wherein the oxidizing gas is oxygen or chlorine, and the molar ratio of HCFO-1233xf, HF and the oxidizing gas is (1-40):1:(0.001-1), and the reaction temperature is 200-400°C.

[0028] Preferably, the temperature of the activation step is 250-380° C., and the activation atmosphere is 20-80% HF / N2 atmosphere.

[0029] The reaction step space velocity is 100~1500h -1 The molar ratio of HCFO-1233xf, HF and oxidizing gas is (5-30):1:(0.05-0.5), and the reaction temperature is 250-380°C.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention studies different chromium forms in chromium-based catalysts and proposes a composition with different chromium form ratios, so that the catalyst surface has a suitable ratio of B acid to L acid, thereby improving the raw material conversion rate and product selectivity at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the XPS peak fitting curve of the chromium-based catalyst Cat 5# prepared in the embodiment of the present invention. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all possible alternatives, improvements and equivalents within the scope of the claims.

[0034] Preparation Example 1

[0035] Dissolve 50g CrCl3·6H2O and 0.02g MgCl2·6H2O in 200mL deionized water, then slowly add ammonia solution to adjust the pH value to 9. After the precipitation reaction is completed, filter the slurry and wash it repeatedly with deionized water. When the filter cake pH value is ≈ 7, place the filter cake in a blast oven at 120°C and dry it for 6h. Sieve the dried catalyst into particles of 1 to 3mm. Take 20mL of catalyst particles and fill them in a nickel alloy tube (19×2mm) of a fixed bed reactor. Roast them at 200°C with 10v% O2 / N2 (200mL / min) for 14h and the pressure is 0.04Mpa. The prepared chromium-based catalyst is recorded as cat 1#.

[0036] Preparation Example 2-7

[0037] The operations of Preparation Examples 2-7 are the same as those of Preparation Example 1, with the only difference being that the catalysts are calcined at 240°C, 280°C, 320°C, 360°C, 400°C, and 420°C with 10v% O2 / N2 (200mL / min) for 14h, and the chromium-based catalysts prepared are designated as cat 2#, cat 3#, cat 4#, cat 5#, cat 6#, and cat 7#, respectively.

[0038] Preparation Example 8

[0039] 50g CrCl3·6H2O and 0.02g MgCl2·6H2O were dissolved in 200mL deionized water, and then ammonia solution was slowly added dropwise thereto to adjust the pH value to 9. After the precipitation reaction, the slurry was filtered and washed repeatedly with deionized water. When the pH value of the filter cake was ≈7, the filter cake was placed in a blast oven and dried at 120°C for 6h. The dried catalyst was sieved into particles of 1 to 3mm, and 20mL of the catalyst particles were loaded into the nickel alloy tube (19×2mm) of the fixed bed reactor, and calcined at 360°C with 20v% O2 / N2 (200mL / min) for 14h. The prepared chromium-based catalyst was recorded as cat 8#.

[0040] Preparation Examples 9-11

[0041] The operations of Preparation Examples 9-11 are the same as those of Preparation Example 8, with the only difference being that the calcinations were carried out under calcination atmospheres of 40v% O2 / N2 (200mL / min), 60v% O2 / N2 (200mL / min), and 80v% O2 / N2 (200mL / min), respectively. The chromium-based catalysts prepared were designated as cat 9#, cat 10#, and cat 11#, respectively.

[0042] Preparation Example 12

[0043] 50g CrCl3·6H2O and 0.02g MgCl2·6H2O were dissolved in 200mL deionized water, and then aqueous ammonia solution was slowly added dropwise to adjust the pH value to 9. After the precipitation reaction, the slurry was filtered and washed repeatedly with deionized water. When the pH value of the filter cake was ≈7, the filter cake was placed in a blast oven and dried at 120°C for 6h. The dried catalyst was sieved into particles of 1-3mm, and 20mL of the catalyst particles were loaded into the nickel alloy tube (19×2mm) of the fixed bed reactor, and calcined at 360°C with 60v% O2 / N2 (200mL / min) for 4h. The prepared catalyst was recorded as cat 12#.

[0044] Preparation Examples 13-15

[0045] The operations of Preparation Examples 13-15 are the same as those of Preparation Example 12, with the only difference being that the calcination times are 8 h, 12 h, and 16 h, respectively, and the chromium-based catalysts prepared are denoted as cat 13#, cat 14#, and cat 15#, respectively.

[0046] Preparation Example 16

[0047] 50g CrCl3·6H2O and 0.02g MgCl2·6H2O were dissolved in 200mL deionized water, and then ammonia solution was slowly added dropwise to adjust the pH value to 9. After the precipitation reaction, the slurry was filtered and washed repeatedly with deionized water. When the pH value of the filter cake was ≈7, the filter cake was placed in a blast oven and dried at 120°C for 6h. The dried catalyst was sieved into particles of 1-3mm, and 20mL of catalyst particles were respectively loaded into the nickel alloy tube (19×2mm) of the fixed bed reactor. The system pressure was 0.1Mpa, and it was calcined at 360°C with 60v% O2 / N2 (200mL / min) for 12h, recorded as cat 16#.

[0048] Preparation Examples 17-18

[0049] The operations of Preparation Examples 17-18 are the same as those of Preparation Example 16, with the only difference being that the pressures of the calcination system are 0.3 MPa and 0.5 MPa, respectively, and the chromium-based catalysts prepared are denoted as cat 17# and cat 18#, respectively.

[0050] Comparative Preparation Example 1

[0051] 20 mL of purchased Cr2O3 (specific surface area of ​​250 m 2 / g, particle size is 3mm), loaded into a reactor, and dried with N2 (200mL / min) at 150°C to remove water, and recorded as Cat D1#.

[0052] The chromium-based catalysts Cat 1# to Cat 18# prepared above and the purchased Cat D1# after treatment were characterized by XPS according to Cr2P. The content distribution of different forms of chromium oxide on the surface of each catalyst is shown in Table 1 below.

[0053] Table 1. Distribution of chromium oxide content on the surface of chromium-based catalysts

[0054]

[0055] Example 1

[0056] This example is the application of the prepared chromium-based catalyst in the preparation of HFO-1234yf by fluorine-chlorine exchange of HCFO-1233xf.

[0057] The chromium-based catalysts Cat 1#~Cat 18# and Cat D1# were activated with HF (150 mL / min) and N2 (70 mL / min), and then HCFO-1233xf (28 mL / min), HF (170 mL / min) and O2 (0.3 mL / min) were introduced at 350°C. The products at the reactor outlet were treated with dehydration and deacidification and then sent to gas chromatography for quantitative analysis. The gas phase analysis results are shown in Table 2 below.

[0058] Table 2. HFO-1234yf preparation reaction results

[0059]

[0060] Example 2

[0061] This example is the application of the prepared chromium-based catalyst in the preparation of HFO-1234ze via the fluorine-chlorine exchange reaction of HCFO-1233zd.

[0062] Catalysts cat 1#~cat 18# and Cat D1# were activated with HF (150 mL / min) and N2 (70 mL / min), and then HCFO-1233zd (18 mL / min) and HF (110 mL / min) were introduced at 400°C. The product at the reactor outlet was dehydrated and deacidified, and then sent to gas chromatography for quantitative analysis. The gas phase analysis results are shown in Table 3 below.

[0063] Table 3 HFO-1234ze preparation reaction results

[0064]

Claims

1. An application of a chromium-based catalyst, characterized in that: The chromium-based catalyst comprises a chromium oxide composition, which comprises, by mass percentage, 5-80% of Cr(OH)3, 5-60% of CrOOH, 5-50% of CrO2 and 5-20% of Cr2O3; the chromium-based catalyst is used for preparing HFO-1234yf from HCFO-1233xf and preparing HFO-1234ze from HCFO-1233zd.

2. The use of the chromium-based catalyst according to claim 1, characterized in that: The chromium oxide composition comprises 10-70% Cr(OH)3, 10-55% CrOOH, 10-40% CrO2 and 6-10% Cr2O3.

3. The use of the chromium-based catalyst according to claim 1, characterized in that: The chromium-based catalyst also includes a co-component composition, which includes a co-component oxide and / or a co-component hydroxide, and the co-component is selected from at least one of magnesium, zinc, aluminum, calcium, copper, lanthanum, iron, indium, zirconium, nickel, manganese, titanium, gallium or cobalt, and the molar ratio of chromium in the chromium oxide composition to the co-component in the co-component composition is 1:0.001 to 1:

1.

4. The use of the chromium-based catalyst according to claim 3, characterized in that: In terms of mass percentage, the auxiliary component composition includes 50-60% of auxiliary component oxide and 40-50% of auxiliary component hydroxide.

5. The use of a chromium-based catalyst according to any one of claims 1 to 4, characterized in that: The chromium-based catalyst is obtained by the following steps: A1. Add ammonia water to the chromium salt solution and the auxiliary component salt solution to cause precipitation reaction. When the pH value of the slurry is ≈6-10, stop adding the material, filter the slurry, and wash the filter cake with deionized water until it is neutral; A2. The filter cake is dried at 80-120°C and sieved into particles; A3. The sieved particles are roasted.

6. The use of the chromium-based catalyst according to claim 5, characterized in that: The calcination temperature in step A3 is 150-400° C., the calcination pressure is 0.01-1.0 MPa, the calcination atmosphere is a mixture of oxidizing gas and nitrogen, and the oxidizing gas accounts for 0.1-50% of the volume of the mixture.

7. The use of the chromium-based catalyst according to claim 6, characterized in that: The oxidizing gas is selected from oxygen or chlorine.

8. A method for preparing 2,3,3,3-tetrafluoropropene, which is prepared by fluorine-chlorine exchange of HCFO-1233xf, characterized in that: A chromium-based catalyst is used, which includes a chromium oxide composition. In terms of mass percentage, the chromium oxide composition includes 5-80% Cr(OH)3, 5-60% CrOOH, 5-50% CrO2 and 5-20% Cr2O3.

9. The method for preparing 2,3,3,3-tetrafluoropropene according to claim 8, characterized in that: The preparation method comprises: B1. Activation step: 150 to 400 ° C, activating the chromium-based catalyst in a 1 to 90% HF / N2 atmosphere; B2. Reaction step: 50~2000h -1 HCFO-1233xf, HF and an oxidizing gas are introduced at an air velocity of , wherein the oxidizing gas is oxygen or chlorine, and the molar ratio of HF, HCFO-1233xf to the oxidizing gas is (1-40):1:(0.001-1), and the reaction temperature is 200-400°C.

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