阅读说明：本技术 一种用于3,5-二甲基吡啶和吡啶反应的催化剂改性方法 (Catalyst modification method for reaction of 3, 5-dimethylpyridine and pyridine ) 是由 赵彦平 李袁 谢朝 郭彦超 颜明 于 2021-08-10 设计创作，主要内容包括：本发明公开了一种用于3,5-二甲基吡啶和吡啶反应的催化剂改性方法,包括以下步骤,将HZSM-5分子筛与二氧化硅粘结剂混捏、挤条、干燥、焙烧和水蒸汽处理,制成ZSM-5催化剂。本发明采用上述结构的一种用于3,5-二甲基吡啶和吡啶反应的催化剂改性方法,制成的ZSM-5催化剂应用于3,5-二甲基吡啶和吡啶生成3-甲基吡啶的化学反应,与未经水蒸汽处理或氧化铝粘结剂制备的催化剂相比,ZSM-5催化剂进一步提高了吡啶转化率和3-甲基吡啶的选择性。(The invention discloses a catalyst modification method for reaction of 3, 5-dimethylpyridine and pyridine, which comprises the following steps of kneading an HZSM-5 molecular sieve and a silica binder, extruding, drying, roasting and carrying out steam treatment to prepare a ZSM-5 catalyst. According to the invention, by adopting the catalyst modification method for the reaction of 3, 5-dimethylpyridine and pyridine with the structure, the prepared ZSM-5 catalyst is applied to the chemical reaction of 3, 5-dimethylpyridine and pyridine to generate 3-methylpyridine, and compared with a catalyst prepared without water vapor treatment or an alumina binder, the ZSM-5 catalyst further improves the pyridine conversion rate and the selectivity of 3-methylpyridine.)

1. A method for modifying a catalyst used for reaction of 3, 5-lutidine and pyridine is characterized in that: the method comprises the following steps of mixing and kneading the HZSM-5 molecular sieve and a silicon dioxide binder, extruding strips, drying, roasting and carrying out steam treatment to prepare the ZSM-5 catalyst.

2. The process of claim 1 for modifying a catalyst for the reaction of 3, 5-lutidine and pyridine, wherein: the silica comprises at least one of silica gel, silica sol or white carbon black.

3. The process of claim 1 for modifying a catalyst for the reaction of 3, 5-lutidine and pyridine, wherein: the weight ratio of the HZSM-5 molecular sieve to the silicon dioxide is 40-90: 10 to 60.

4. The process of claim 1 for modifying a catalyst for the reaction of 3, 5-lutidine and pyridine, wherein: the drying temperature is 80-120 ℃, and the drying time is 2-10 hours.

5. The process of claim 1 for modifying a catalyst for the reaction of 3, 5-lutidine and pyridine, wherein: the roasting temperature is 450-600 ℃, and the roasting time is 2-5 hours.

6. The process of claim 1 for modifying a catalyst for the reaction of 3, 5-lutidine and pyridine, wherein: the water vapor treatment temperature is 500-700 ℃, and the time is 4-10 hours.

7. The ZSM-5 catalyst prepared according to claims 1-6, when used in the reaction of 3, 5-lutidine with pyridine, wherein: the 3, 5-dimethylpyridine and the pyridine are subjected to chemical reaction under the following conditions that the pressure is 0.1-1.0 MPa, the temperature is 350-550 ℃, and the weight space velocity of the 3, 5-dimethylpyridine and the pyridine is 0.5-1.5 h^-1And the weight ratio of the 3, 5-dimethylpyridine to the pyridine is 3-10.

Technical Field

The invention relates to the technical field of molecular sieve catalysts, in particular to a catalyst modification method for reaction of 3, 5-dimethylpyridine and pyridine.

Background

3-methylpyridine is a main raw material for preparing nicotinic acid and ammonium nicotinate, can also be used for preparing vitamins, is an important intermediate for synthesizing pyridine spices and novel insecticides, and is in short supply in the market at present. The 3-methylpyridine is firstly recovered from coal coking fractional distillation by-products, but because the pyridine components in the coking by-products are more, the products are complex, the separation is difficult, and the yield is less, the aldehyde ammonia synthesis method is mainly adopted for production at present.

The method for synthesizing 3-methylpyridine by adopting an aldehyde ammonia synthesis method is mainly characterized in that pyridine and 3-methylpyridine are prepared by adding a large amount of formaldehyde into raw materials on the basis of synthesizing 2-methylpyridine and 4-methylpyridine by adopting an acetaldehyde and ammonia gas phase method. A process for synthesizing 2-methylpyridine and 4-methylpyridine from acetaldehyde and ammonia gas features use of Ag-Pb-Si-Al-O and Ag-Ca-Si-Al-O as catalyst, temp about 440 deg.C and space velocity of 800 hr^-1Mixed gas of acrolein/ammonia gas/water vapor/nitrogen gas (1/1/4/2) is introduced to obtain pyridine base with pyridine content of about 88%, pyridine content of 13%, 2-methylpyridine of 38% and pyridine content of 4-methylpyridine of 37%. The heteropolyacid is used as a catalyst, acetaldehyde and ammonia are used as raw materials, about 70% of 2-methylpyridine and 4-methylpyridine are obtained, when the 3-methylpyridine is required to be obtained, the raw materials are only required to be changed into a mixture of acetaldehyde and formaldehyde, and the method is mature and simple in process operation, so that the 3-methylpyridine is industrially prepared at present.

Formaldehyde/acetaldehyde/ammonia gas (1/2/4.5) is adopted, Co-Pb-ZSM5 is used as a catalyst, the temperature is about 450 ℃, and the space velocity is 1000h^-1Under the conditions, the pyridine base yield is 83%, wherein the pyridine yield is 68%, the 2-methylpyridine yield is 4%, the 3-methylpyridine yield is 4.5%, and the 4-methylpyridine yield is 6.5%. When formaldehyde/acetaldehyde/ammonia gas was 1/1/4.5, pyridine base yield was 81.5%, wherein pyridine yield was 56%, 3-methylpyridine yield reached 24.5%, and 2-methylpyridine and 4-methylpyridine were not substantially produced. It can be seen that the yield of 3-methylpyridine can be improved by increasing the amount of formaldehyde, but it is difficult to completely avoid the formation of 4-methylpyridine. It is known that 3-picoline and 4-picoline are difficult to separate, and thus it is difficult to obtain high-purity 3-picoline.

Since it is necessary to avoid acetaldehyde from the starting material in order to avoid the formation of 4-methylpyridine as much as possible, there have been many studies on a process for producing 3-methylpyridine from acrolein and synthesizing pyridine and 3-methylpyridine from acrolein and ammonia gas in a gas phase without producing a productContains 4-methylpyridine. Using acrolein/ammonia/water 1/5/1, as B-P/SiO₂-Al₂O₃Is used as a catalyst, the temperature is about 350 ℃, the contact time is 5 seconds, and the pyridine base yield is 60 percent, wherein the pyridine yield is 25 percent, and the 3-methylpyridine yield is 35 percent. Since the 3-methylpyridine product generated by gas phase reaction of acrolein and ammonia gas generates a large amount of pyridine, the pyridine should be generated by high-temperature cracking of acrolein or by demethylation generated by cracking of 3-methylpyridine. Meanwhile, because acrolein is relatively active and easily self-polymerized, some patents consider adding other organic substances instead of acrolein as raw materials, such as acetaldehyde, propylene oxide, ketone, propanol or paraldehyde.

In the industrial production process of formaldehyde, acetaldehyde and ammonia, pyridine in pyridine base products is the main component, 3-methylpyridine is about 1/2 of pyridine, at present, 3-methylpyridine is not in demand, a large amount of pyridine is excessive, and how to digest pyridine to obtain 3-methylpyridine is a subject of industrial attention, for example, in the process of preparing 3-methylpyridine by reacting 3, 5-dimethylpyridine with pyridine, pyridine can be digested, and the 3, 5-dimethylpyridine obtained by the reaction of acrolein, propionaldehyde and ammonia can be fully utilized. At present, the patent of preparing 3-methylpyridine by reacting 3, 5-dimethylpyridine with pyridine is not reported, and the industrial industry may pay attention to how to obtain high-yield pyridine before, so that the situation is obviously changed, the pyridine is excessive, and the research on the modification of a ZSM-5 catalyst for the process is not reported.

Disclosure of Invention

The invention aims to provide a catalyst modification method for the reaction of 3, 5-dimethylpyridine and pyridine, which aims to solve the problems that the pyridine is excessive, the yield and selectivity of the chemical reaction for preparing 3-methylpyridine are too low, and the market supply of the 3-methylpyridine is insufficient.

In order to achieve the purpose, the invention provides a catalyst modification method for reaction of 3, 5-dimethylpyridine and pyridine, which comprises the following steps of kneading an HZSM-5 molecular sieve and a silica binder, extruding, drying, roasting and carrying out steam treatment to prepare the ZSM-5 catalyst.

The HZSM-5 molecular sieve and the silica binder are directly purchased, the HZSM-5 molecular sieve is powder, the mechanical strength is poor (<5N/cm), the HZSM-5 molecular sieve can not be directly used as a catalyst in the actual industrial process, generally the HZSM-5 molecular sieve and the alumina or the silica are kneaded, extruded, dried and roasted to obtain the catalyst with certain mechanical strength (>60N/cm), the physical and chemical changes can be generated between the material interfaces of the HZSM-5 molecular sieve and the silica binder, the porosity of a sample can be reduced by adding the alumina binder, the porosity of the catalyst can be increased by adding the silica, the diffusion of reaction raw materials and products is facilitated, and the reaction performance is improved, because the particle sizes of the HZSM-5 molecular sieve and the silica binder are different, and an irregular porous structure is formed on the contact interface in the compounding process of the HZSM-5 molecular sieve and the silica binder, thereby increasing porosity. Both alumina and silica binders can be added to increase the mechanical strength of the catalyst.

Preferably, the silica includes at least one of silica gel, silica sol, or white carbon black.

Preferably, the weight ratio of the HZSM-5 molecular sieve to the silicon dioxide is 40-90: 10 to 60.

Preferably, the drying temperature is 80-120 ℃, and the drying time is 2-10 hours.

Preferably, the roasting temperature is 450-600 ℃, and the roasting time is 2-5 hours.

Preferably, the water vapor treatment temperature is 500-700 ℃, and the time is 4-10 hours.

The ZSM-5 catalyst is applied to the reaction of 3, 5-dimethylpyridine and pyridine, and the 3, 5-dimethylpyridine and pyridine are subjected to chemical reaction under the following reaction conditions that the pressure is 0.1-1.0 MPa, the temperature is 350-550 ℃, and the weight space velocity of the 3, 5-dimethylpyridine and the pyridine is 0.5-1.5 h^-1And the weight ratio of the 3, 5-dimethyl pyridine to the pyridine is 3-10.

Therefore, according to the catalyst modification method for the reaction of the 3, 5-lutidine and the pyridine with the structure, the ZSM-5 catalyst activates the 3, 5-lutidine and the pyridine to perform chemical reaction, so that the excess pyridine is converted into the 3-methylpyridine, and meanwhile, the 4-methylpyridine is not generated, so that the yield and the selectivity of the 3-methylpyridine are improved.

The technical solution of the present invention is further described in detail by the following examples.

Detailed Description

The following examples further illustrate the technical solution of the present invention, but the present invention is not limited thereto.

Comparative example 1

Mixing 8g of HZSM-5 molecular sieve and 2g of silica gel, kneading, extruding, drying at 120 ℃ for 4 hours, and roasting at 540 ℃ for 3 hours to obtain the catalyst Cat-A.

Comparative example 2

8g of HZSM-5 molecular sieve and 2.6g of boehmite (dry basis 77%) are kneaded, extruded into strips, dried at 120 ℃ for 4 hours and roasted at 540 ℃ for 3 hours to prepare the catalyst Cat-B.

Example 1

Kneading 8g of HZSM-5 molecular sieve and 2g of silica gel, extruding into strips, drying at 120 ℃ for 4 hours, roasting at 540 ℃ for 3 hours, then placing the roasted catalyst in a steam environment for steam treatment at 600 ℃ for 4 hours to obtain the catalyst Cat-C. The reaction properties of the prepared catalyst are shown in table 1.

Example 2

4.5g of HZSM-5 molecular sieve and 18.3g of silica sol (with the solid content of 30 wt%) are kneaded, extruded, dried at 85 ℃ for 9 hours, calcined at 580 ℃ for 4.5 hours, and then subjected to steam treatment at 500 ℃ for 4 hours to prepare the catalyst Cat-D. The reaction properties of the prepared catalyst are shown in table 1.

Example 3

9g of HZSM-5 molecular sieve and 1.25g of white carbon black (dry basis 80 wt%) are kneaded, extruded, dried at 100 ℃ for 7 hours, calcined at 480 ℃ for 3 hours, and then subjected to steam treatment at 680 ℃ for 7 hours to prepare the catalyst Cat-E. The reaction properties of the prepared catalyst are shown in table 1.

Example 4

7g of HZSM-5 molecular sieve, 1.25g of white carbon black (dry basis is 80 wt%) and 2g of silica gel are kneaded, extruded into strips, dried at 110 ℃ for 6 hours, calcined at 550 ℃ for 3 hours, and then subjected to steam treatment at 480 ℃ for 9 hours to prepare the catalyst Cat-F. The reaction properties of the prepared catalyst are shown in table 1.

The evaluation of the reaction properties was carried out on a fixed-bed reactor, 5g of catalyst being placed in a constant-temperature zone in the middle of a stainless steel reactor (internal diameter 12mm, length 50 cm). Catalyst before reaction in N₂The atmosphere is raised to 450 ℃ (60mL/min), the raw materials are 3, 5-dimethyl pyridine and pyridine, and the reaction conditions are as follows: 0.1-1.0 MPa, 350-450 ℃, and the weight space velocity of the 3, 5-dimethyl pyridine and the pyridine is 0.5-1.5 h^-1And the weight ratio of the 3, 5-dimethyl pyridine to the pyridine is 3-10. The outlet of the reactor is connected with a condenser, the outlet is connected with a receiving bottle, and tail gas is washed and absorbed by three-stage methylbenzene. Pyridine base concentration was analyzed by HPLC external standard method.

The experimental results in Table 1 show that the catalyst prepared with alumina binder (Cat-B) has a lower reactivity than the catalyst prepared with silica binder (Cat-A), and that the catalysts prepared with appropriate steam treatment (Cat-C to Cat-F) have higher pyridine conversion and 3-picoline selectivity than the corresponding values (Cat-A) for the samples that were not steam treated.

After the HZSM-5 molecular sieve and the silicon dioxide adhesive are kneaded, extruded, dried and roasted, an irregular porous structure is formed on a contact interface of the HZSM-5 molecular sieve and the silicon dioxide adhesive, the porosity is increased, water vapor can enter pores during water vapor treatment, and the ZSM-5 catalyst contains adsorbed water vapor, so that the acid content of the ZSM-5 catalyst is adjusted. The acid amount being a molecular sieve catalystAcid or Lewis acid) acidity, generally expressed as the specific number of hydrogen ions provided by a unit sample, e.g., x. mu. mol H⁺Per g (1 gram of catalyst can provide x. mu. mol of hydrogen ions).

For the chemical reaction of 3, 5-dimethyl pyridine and pyridine to generate 3-methyl pyridine, the acid amount is too low, the conversion rate of raw materials is low, and the selectivity of 3-methyl pyridine is high; if the amount of acid is too high, the conversion of 3, 5-lutidine is high, but 3, 5-lutidine tends to be excessively converted, and in addition to 3-picoline, much methane, pyridine and coke are formed, resulting in a decrease in the conversion of pyridine. Therefore, the 3, 5-lutidine can be activated to 3-methylpyridine only under the condition of proper acid amount, the ZSM-5 catalyst is adopted to catalyze the reaction of the 3, 5-lutidine and pyridine to generate the 3-methylpyridine in the invention, and the methyl ions on the activated 3, 5-lutidine and the pyridine are immediately alkylated to generate the 3-methylpyridine. The ZSM-5 catalyst produced by the invention is treated by proper steam, so that the catalyst has proper acid amount, thereby achieving the purpose of increasing the pyridine conversion rate and the 3-methylpyridine selectivity.

TABLE 1 catalyst reactivity

Therefore, the ZSM-5 catalyst prepared by the method for modifying the catalyst for the reaction of the 3, 5-lutidine and the pyridine with the structure is applied to the chemical reaction of the 3-methylpyridine generated by the 3, 5-lutidine and the pyridine, and compared with the catalyst prepared without steam treatment or an alumina binder, the ZSM-5 catalyst further improves the pyridine conversion rate and the selectivity of the 3-methylpyridine.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the invention without departing from the spirit and scope of the invention.