CN108114730A - Molybdenum-vanadium-tellurium-niobium catalytic agent composition - Google Patents

Abstract

The invention discloses a molybdenum vanadium tellurium niobium catalyst composition, which is a mixture of molybdenum vanadium tellurium niobium catalyst and a stabilizer, and the stabilizer is _SiO2 or its mixture with SiC in any proportion. Based on previous work, the present invention creatively introduces a stabilizer with catalytic stabilizing effect, which can stabilize the catalyst under severe reaction conditions and significantly reduce the production cost of the catalyst.

Description

Molybdenum vanadium tellurium niobium catalyst composition

technical field

The present invention relates to the reaction of oxidizing ethane to prepare ethylene, especially to the catalyst in the reaction.

Background technique

In the field of petrochemicals, the technical route of ethylene production has always been one of the hot spots of research and development personnel. Introducing an oxidant (such as O ₂ or Air, etc.) to change the ethylene dehydrogenation reaction from a strong endothermic reaction to a simple exothermic reaction has become one of the ideas of many researchers. According to the literature [Chem.Week, 137 (4), 36, 1985], the energy consumption of this process can be reduced by 20% to 30%. However, the thermodynamics of this process support the formation of deep oxidation products CO ₂ and CO, so how to improve the selectivity of ethylene has become the core technical problem. As early as 1981, U.S. Patent No. 4,250,346 disclosed Mo-V-Nb-O catalysts used in ethane oxidation reactions. The ethylene selectivity can reach 90%, but the conversion rate of ethane does not exceed 10%. U.S. Patent US44100752 in 1983 used VPO catalyst in the ethane oxidation reaction, and the ethane conversion ratio was 52.53%, but the ethylene selectivity was low, only 43.16%; When ethylene selectivity was higher (76.58%), ethane The alkane conversion rate is very low, only 4.13%. Canadian patent CA122910358 introduces the fourth element Sb, which is Mo-V-Sb-Nb-O catalyst, which is used for ethane oxidation reaction. At 375 ° C, the conversion rate of ethane is 38%, and the selectivity of ethylene is 78%. %, the conversion rate has improved significantly. Chinese patent CN1069907 discloses a kind of fluoride as ethane oxidation ethylene catalyst, can react under very high space velocity, but needs to use a large amount of _N in raw material gas as diluent (N ₂ :O ₂ :C ₂ H ₆ =85:5:10), the main reaction results are: when the reaction space velocity is 18000h ^-1 and the reaction temperature is 470°C, the ethane conversion rate is 37.2%, and the ethylene selectivity is 95.9%; when the reaction space velocity is 12000h ^-1 and When the reaction temperature is 490°C, the ethane conversion rate is 59.1%, and the ethylene selectivity is 84.7%. Similar to this, the fluoride catalyst provided by CN1120470 requires higher reaction temperatures (640°C and 640°C), and the conversion rate of ethane is higher, up to 80.82%, but unfortunately, the ethylene selectivity is not Ideally, it is 70.0% to 80.0%, and the life of the catalyst is about 100h. The catalyst disclosed in CN1172790 is Na ₂ WO ₄ -Mn ₂ O ₃ /-S (S is SiO ₂ , TiO ₂ or MgO). This catalyst is used for the reaction of ethane oxidation to ethylene. The ethane conversion rate is 69.8%, and the ethylene selectivity 76.5%, but it needs to be carried out at a high temperature of 750°C. In this way, the significance of reducing energy consumption and equipment investment through exothermic reactions is lost to a certain extent. And EP0544372 then uses a kind of heteropolyacid as ethane oxidation to prepare ethylene catalyst, and reaction temperature is also on the high side, is 470 ℃, although selectivity is higher (90%), conversion rate is very low (no more than 10%), And at such high reaction temperatures, the structural stability of such catalysts is a problem. When searching the relevant journal literature of ethylene production technology, we found that Mo-V-Nb-O catalyst was used in ethane oxidation reaction very early, and the main products were acetic acid and ethylene (J.Catal.52,116(1978)), Later, in the literature (Appl.Catal.70,129(1991), Catal.Lett.19,17(1993), J.Catal.175,16(1998), J.Catal.175,27(1998)) obtained More in-depth and systematic research, generally speaking, this type of catalyst is often the co-production of ethylene and acetic acid, does not produce ethylene selectively, and the conversion rate of ethane is often relatively low (usually not more than 20%). Later, M.Roussel et al. (Appl.Catal.A: General, 308, 62 (2006)) replaced Nb with Pd, and compared the results in the ethane oxidation reaction between the two, but in general, Ethane conversion is still relatively low. What caused the performance of this type of metal oxide catalyst to change greatly is that, such as literature (Chem. As reported by Catal.Today, 142,272 (2009), Catal.Commu., 22 (2012), Appl.Catal.A: Gen., 433-424, 41 (2012)), a fourth element Te is introduced, which can Ethylene can be obtained with high selectivity (more than 90% on some catalysts), and at the same time, the conversion rate of ethane is very high (usually not lower than 35%). Under specific conditions, some catalysts (Chem.Commu., 1906 (2002)) obtained ethylene yield at 400°C as 71.5% (88.5% ethane conversion, 80.8% ethylene selectivity), with good Industrial application prospects. However, as we all know, if a catalyst has good industrial application prospects, it must have good stability, and the price of the catalyst itself should not be too high. We did not find information about the stability of Mo-V-Te-Nb-O catalysts in the oxidation of ethane to ethylene from the literature. According to our early research results, the Mo-V-Te-Nb-O catalyst itself is relatively stable under mild reaction conditions in the oxidation of ethane to ethylene, but it is relatively stable when the reaction conditions are relatively severe (such as high space velocity and high temperature acceleration). pressure, etc.), the catalyst performance may gradually decrease due to the sharp increase in hot spot temperature. The reason may be that Te in the active component is easier to be reduced and precipitated when the hot spot temperature is higher. The composition and structure changes, and ultimately affect the performance of the catalyst in the ethane oxidation reaction. Therefore, it is particularly meaningful to provide a catalytic catalyst or catalyst product.

Contents of the invention

The purpose of the present invention is firstly to provide a kind of molybdenum vanadium tellurium niobium catalyst composition, and this composition is the mixture that molybdenum vanadium tellurium niobium catalyst and stabilizing agent are formed, and described stabilizing agent is SiO ₂ or its composition with SiC according to any ratio mixture.

In the technical solution of the above catalyst combination, if a SiO ₂ -SiC binary stabilizer is used, it is preferable to make the mass percentage of SiC in the stabilizer be 0-60%.

In the molybdenum vanadium tellurium niobium catalyst composition of the present invention, the mass percentage of the stabilizer is not more than 95%, preferably 30-70%, more preferably 30-50%.

In the above catalyst composition of the present invention, the molybdenum vanadium tellurium niobium catalyst can be obtained according to the methods of CN1795987A and CN101612564. In the present invention, the molybdenum vanadium tellurium niobium catalyst in the composition has the general formula Mo1.0VxTeyNbzOn, wherein x is 0.2 to 1.0, y is 0.2 to 1.0, z is 0.1 to 0.5, n and Mo, V, The valence and content of Te and Nb are related.

More specifically, it can be prepared by hydrothermal synthesis, including the following steps:

(1) Put the mixed reaction solution of ammonium molybdate, vanadyl sulfate, telluric acid, and niobium oxalate in a stainless steel reaction kettle, raise the temperature from room temperature to 160-230°C at a heating rate of 2-10°C/min, and keep it warm for 2- 20 hours, then naturally lowered to room temperature.

(2) After aging, the reaction product is taken out, filtered and dried. The obtained product is roasted in two stages: the first stage is roasted at 150-300°C in air for 1-3 hours, and the second stage is roasted at 400-700°C in nitrogen. Calcining for 1-5 hours, the molybdenum vanadium tellurium niobium catalyst powder is prepared.

Further, on the basis of the prepared molybdenum vanadium tellurium niobium catalyst powder, the composition of the present invention is prepared by mixing molybdenum vanadium tellurium niobium catalyst powder and a stabilizer by one of the following methods:

a. Internal mixing method: the catalyst powder is mixed with the stabilizer and then ground and shaped;

b. External mixing method: shape the catalyst powder first and then mix it with the stabilizer.

In another aspect, the present invention provides a method for preparing the molybdenum vanadium tellurium niobium catalyst composition, comprising the following steps:

(1) Put the mixed reaction solution of ammonium molybdate, vanadyl sulfate, telluric acid, and niobium oxalate in a stainless steel reaction kettle, raise the temperature from room temperature to 160-230°C at a heating rate of 2-10°C/min, and keep it warm for 2-20°C. 20 hours, then naturally lowered to room temperature;

(2) After aging, the reaction product is taken out, filtered and dried. The obtained product is roasted in two stages: the first stage is roasted at 150-300°C in air for 1-3 hours, and the second stage is roasted at 400-700°C in nitrogen. Roasting for 1 to 5 hours to obtain molybdenum vanadium tellurium niobium catalyst powder;

(3) The molybdenum vanadium tellurium niobium catalyst powder prepared in step (2) is mixed with a stabilizer by one of the following methods:

a. Internal mixing method: the catalyst powder is mixed with the stabilizer and then ground and shaped;

b. External mixing method: shape the catalyst powder first and then mix it with the stabilizer.

In another aspect, the present invention provides the application of the catalyst composition for oxidation reaction in the oxidation reaction of ethane to ethylene.

More specific conditions for the oxidation reaction of ethane to ethylene suitable for the above application include: reaction temperature 300-450°C, reaction pressure 0.5-15amt, total reaction space velocity ^1000h -1-50000h ^-1 . Preferably, the reaction temperature is 340-400°C, the reaction pressure is 1-10 amt, and the total reaction space velocity is 2000h ^-1 -8000h ^-1 .

On the basis of previous work, the present invention creatively introduces a diluent with catalytic stabilizing effect. The introduction of the stabilizer has two important meanings: first, it can stabilize the catalyst under harsh reaction conditions, because the stabilizer is conducive to the dispersion and transfer of reaction heat, thereby avoiding the high hot spot temperature inside the catalyst; Second, the stabilizer itself, as a cheap diluent, can also significantly reduce the production cost of the catalyst.

Detailed ways

In the selective oxidation of ethane to ethylene, the reaction product is divided into gas and liquid phases. The gas phase products include CO, CO ₂ and C ₂ H ₄ , and the liquid phase products are mainly a very small amount of acetic acid.

Conversion, selectivity and yield are calculated according to the following formula:

Conversion (%)=(∑Mi×ni)/[2×(the amount of ethane in the feed)]×100%

Selectivity (%)=(Mi×ni)/(∑Mi×ni)×100%

Yield (%)=conversion rate×selectivity×100

In the above formula, Mi: the amount of substance of a certain product i; ni: the number of carbon atoms contained in a molecule of a certain product i.

Without special instructions, the mild reaction conditions for the selective oxidation of ethane mentioned in the present invention are: reaction temperature 350°C, total reaction volume space velocity 1500h ^-1 , ethane/oxygen/nitrogen (volume ratio) 30/ 20/50, the reaction pressure is 1atm (atmospheric pressure); the harsh reaction conditions are: reaction temperature 380°C, total reaction volume space velocity 4000h ^-1 , ethane/oxygen/nitrogen (volume ratio) 30/20/50, The reaction pressure was 3 atm (3 atmospheres).

In the present invention, the percentage values used when referring to the added amount of the stabilizer all represent the mass percentage of the added stabilizer in the entire catalyst composition. For example, when it is mentioned that "30% of alpha-Al ₂ O ₃ is added", it means that in the finally obtained catalyst composition, the mass percentage of stabilizer alpha-Al ₂ O ₃ is 30%.

The following examples will further illustrate the present invention, but do not limit the present invention thereby.

Example 1

The Mo-V-Te-Nb-O catalyst (catalytic active component (CN101612564) is prepared by a temperature-programmed hydrothermal synthesis method, and the steps include: first weighing the proportioned ammonium molybdate, vanadyl sulfate, telluric acid and niobium oxalate respectively Dissolve in hot deionized water, heat each solution for 30 minutes, slowly mix each solution together, continue to stir for 10 minutes, transfer it to a stainless steel tube synthesis kettle, and raise the temperature from room temperature at a rate of 10°C/min. to 190°C, keep warm for 20h and then drop to room temperature naturally, then take it out, filter, and dry. After grinding the obtained black solid, place it in a roasting container, rise from room temperature to 300°C at a heating rate of 3°C/min and keep it warm After 2 hours (atmosphere is air), then rise to 600° C. at the same heating rate and continue to keep warm for 2 hours (atmosphere is nitrogen) to naturally cool down, and the product obtained is the calcined Mo-V-Te-Nb-O catalyst. Finally, shape and granulate and sieve into catalyst particles with a particle size of 20-30 meshes for catalyst evaluation.

Take 1g of 20-30 mesh catalyst for the selective oxidation reaction of ethane, the reaction conditions are: reaction temperature 350°C, total reaction volume space velocity 1500h ^-1 , ethane/oxygen/nitrogen (volume ratio) 30/20/50 , The reaction pressure is 1 atm (atmospheric pressure). The reaction lasted for 900 hours, and the reaction results are listed in Table 1. The results show that the performance of the catalyst is very stable under relatively mild conditions.

Table 1

Example 2

The Mo-V-Te-Nb-O catalyst was prepared according to the method of Example 1.

Take 1g of 20-30 mesh prepared Mo-V-Te-Nb-O catalyst for the selective oxidation reaction of ethane. The reaction conditions are different from those in Example 1. The specific reaction conditions are: the reaction temperature is 380°C, and the total volume of the reaction is empty. The speed is 4000h ^-1 , ethane/oxygen/nitrogen (volume ratio) is 30/20/50, and the reaction pressure is 3atm (3 atmospheres). The reaction lasted for 900 hours, and the reaction results are listed in Table 2. The results showed that under relatively severe reaction conditions, the activity of the catalyst decreased significantly with time, and the conversion rate of ethane decreased by about 26.8% within 900 hours.

Table 2

Example 3

The Mo-V-Te-Nb-O catalyst composition of this example was obtained by referring to the preparation method of Example 1, and adding 30% of alpha-Al ₂ O ₃ by external mixing during the preparation process.

1 g of the 20-30 mesh catalyst composition prepared above was used for the selective oxidation of ethane, and the reaction conditions were the same as in Example 2. The reaction lasted for 900 hours, and the reaction results are listed in Table 3. The results show that the addition of Al ₂ O ₃ is beneficial to stabilize the active components of the catalyst performance. Even if the reaction conditions are relatively harsh, the ethane conversion rate drops by about 15.6% within 900 hours, which obviously inhibits or delays the decline rate of the catalyst performance.

table 3

Example 4

The Mo-V-Te-Nb-O catalyst composition of this example was prepared by referring to the preparation method of Example 1, and adding 30% SiO ₂ by external mixing during the preparation process.

1 g of 20-30 mesh catalyst was used for the selective oxidation of ethane, and the reaction conditions were the same as in Example 2. The reaction lasted for 900 hours, and the reaction results are listed in Table 4. The results showed that the addition of SiO ₂ basically stabilized the active components of the catalyst, and the conversion rate of ethane only decreased by 2.4% within 900 hours, which obviously inhibited or delayed the decline rate of the catalyst performance. And the catalytic stabilization effect is obviously better than that of Al ₂ O ₃ (Example 3).

Table 4

Example 5

Referring to the preparation method of Example 1, 25% SiC and 25% SiO ₂ were added by external mixing during the preparation process to prepare the Mo-V-Te-Nb-O catalyst composition of this example.

1 g of 20-30 mesh catalyst was used for the selective oxidation of ethane, and the reaction conditions were the same as in Example 2. The reaction lasted for 900 hours, and the reaction results are listed in Table 5.

table 5

Example 6

The Mo-V-Te-Nb-O catalyst composition of this example was prepared by referring to the preparation method of Example 1, and adding 30% SiO ₂ by external mixing during the preparation process.

Take 1 g of 20-30 mesh catalyst for the selective oxidation of ethane, and the reaction conditions are the same as in Example 1. The reaction lasted for 900 hours, and the reaction results are listed in Table 6. The results show that under mild reaction conditions, the addition of _SiO2 has no effect on the performance of the active components of the catalyst, it only acts as a diluent, and the ethane conversion rate does not decrease within 900 hours.

Table 6

Example 7

Referring to the preparation method of Example 1, 50% SiC and 45% SiO ₂ were added by external mixing during the preparation process to prepare the Mo-V-Te-Nb-O catalyst composition of this example.

1 g of 20-30 mesh catalyst was used for the selective oxidation of ethane, and the reaction conditions were the same as in Example 2. The reaction lasted for 900 hours, and the reaction results are listed in Table 12. The results showed that, same as Example 7, the mixed incorporation of 50% SiC and 45% _SiO completely stabilized the catalyst active components, and the ethane conversion was almost unchanged within 900 hours.

Table 12

Claims (10)

1. molybdenum-vanadium-tellurium-niobium catalytic agent composition, which is characterized in that said composition is made of molybdenum-vanadium-tellurium-niobium catalytic agent and stabilizer Mixture, the stabilizer is SiO₂Or its mixture for being formed with SiC according to arbitrary proportion.

2. composition according to claim 1, which is characterized in that the mass percentage of SiC is 0 in the stabilizer ~60%.

3. composition according to claim 1, which is characterized in that the mass percentage of stabilizer is not in the composition More than 95%.

4. composition according to claim 1, which is characterized in that molybdenum-vanadium-tellurium-niobium catalytic agent has general formula in the composition Mo1.0VxTeyNbzOn, wherein, x is that 0.2~1.0, y is the valence state that 0.2~1.0, z is 0.1~0.5, n and Mo, V, Te and Nb And content is related.

5. composition according to claim 1, which is characterized in that the molybdenum-vanadium-tellurium-niobium catalytic agent passes through hydrothermal synthesis method It prepares, includes the following steps：

(1) mixed reaction solution of ammonium molybdate, vanadic sulfate, telluric acid, niobium oxalate is placed in stainless steel cauldron, from room temperature with 2 ~10 DEG C/min of heating rate is warming up to 160~230 DEG C, when heat preservation 2-20 is small, is then down to room temperature naturally；

(2) reaction product is taken out after aging, filters, is dry, products therefrom is handled using two-segment calcining：First segment is in air At 150~300 DEG C roasting 1~3 it is small when, second segment in nitrogen 400~700 DEG C roasting 1~5 it is small when, be made molybdenum vanadium tellurium niobium urge Agent powder.

6. composition according to claim 5, which is characterized in that the composition is by molybdenum-vanadium-tellurium-niobium catalytic agent powder and surely Determine agent to be mixed by one of following methods：

A. interior mixed method：It grinds and is molded after catalyst powder is mixed with stabilizer；

B. outer mixed method：It is mixed again with stabilizer after catalyst powder is first molded.

7. the preparation method of molybdenum-vanadium-tellurium-niobium catalytic agent composition described in claim 1, includes the following steps：

(1) mixed reaction solution of ammonium molybdate, vanadic sulfate, telluric acid, niobium oxalate is placed in stainless steel cauldron, from room temperature with 2 ~10 DEG C/min of heating rate is warming up to 160~230 DEG C, when heat preservation 2~20 is small, is then down to room temperature naturally；

(2) reaction product is taken out after aging, filters, is dry, products therefrom is handled using two-segment calcining：First segment is in air At 150~300 DEG C roasting 1~3 it is small when, second segment in nitrogen 400~700 DEG C roasting 1~5 it is small when, be made molybdenum vanadium tellurium niobium urge Agent powder；

(3) the molybdenum-vanadium-tellurium-niobium catalytic agent powder prepared by step (2) is mixed with stabilizer by one of following methods：

A. interior mixed method：It grinds and is molded after catalyst powder is mixed with stabilizer；

B. outer mixed method：It is mixed again with stabilizer after catalyst powder is first molded.

8. application of the molybdenum-vanadium-tellurium-niobium catalytic agent composition described in claim 1 in ethane to ethylene oxidation reaction.

9. application according to claim 8, which is characterized in that the ethane to ethylene oxidation reaction condition includes：Instead 300~450 DEG C of temperature, 0.5~15amt of reaction pressure are answered, reacts total air speed 1000h^-1~50000h^-1。

10. application according to claim 9, which is characterized in that the ethane to ethylene oxidation reaction condition includes：Instead It answers that temperature is 340~400 DEG C, reaction pressure is 1~10amt, reacts total air speed for 2000h^-1~8000h^-1。