CN114887653A - High-selectivity catalyst and application thereof in preparation of p-xylene from methanol and toluene - Google Patents
High-selectivity catalyst and application thereof in preparation of p-xylene from methanol and toluene Download PDFInfo
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- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
- B01J29/42—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing iron group metals, noble metals or copper
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Abstract
The invention relates to the field of petrifaction, and discloses a high-selectivity catalyst and application thereof in preparation of p-xylene from methanol and toluene. According to the invention, the surface of the molecular sieve is coated with the silica gel, so that the acid active sites on the outer surface of the molecular sieve can be covered, and the acid active sites in the inner pore diameter of the molecular sieve are utilized to improve the generation selectivity of p-xylene. In addition, the catalyst of the invention contains Pt and TiB with strong interaction 2 The catalyst is used for catalyzing methanol and toluene to prepare p-xylene, and can obviously improve the catalytic activity and stability.
Description
Technical Field
The invention relates to the field of petrifaction, in particular to a high-selectivity catalyst and application thereof in preparation of p-xylene from methanol and toluene.
Background
Paraxylene is a fundamental organic chemical raw material which plays a significant role, and is an important source raw material for producing polyester fibers, polyester plastics and polyester films. The production of paraxylene is usually industrially increased by technical means such as C8 arene isomerization, toluene disproportionation and transalkylation, and the traditional processes all adopt the technology for increasing the production of PX by taking various arenes as raw materials, have high and limited raw material cost, and simultaneously need to combine a plurality of units together to reduce the operation cost, have huge investment, and the high-purity paraxylene still needs to be obtained by complex separation.
In order to solve the problems, the technical research of selectively producing PX by toluene and methanol alkylation is carried out at home and abroad, and the technology is characterized in that: the toluene and the methanol are used as raw materials, the raw materials are cheap and easy to obtain, and the utilization rate of the toluene is high; the high-selectivity p-xylene can be directly obtained through one-time reaction, isomerization, separation and refining are not needed, purification and separation are easy, and the process flow is short; the benzene content in the product is low, and the harm to the environment is less; the whole development cost is low, and the application value is high. Although the selective alkylation of toluene and methanol to produce p-xylene is widely studied in laboratory scale, the industrial production thereof has certain technical difficulties, including the development of a suitable catalyst modification preparation technology, the service life of the catalyst and the like, which are difficult points to be overcome by the technology.
TiB 2 Is the only stable metalloid compound of boron and titanium, having the hexagonal C32 type structure. The boron atom planes and the titanium atom planes in the crystal structure alternately appear to form a two-dimensional layered network structure. In which the boron atom absorbs an electron to form B - Ions, which have four electrons in their outer layer and form an SP 2 Hybridization of each B - Three electrons in (1) and the other three B - The electrons in (2) are combined by covalent bonds, and the excessive unhybridized free electrons form a large pi bond. The graphite-like structure enables the material to have good thermal conductivity and electrical conductivity due to the existence of free electrons in the boron atom layered structure. And the Ti-B ionic bond and the B-B covalent bond between the boron atom surface and the titanium atom surface determine that the titanium-based alloy has the characteristics of high melting point and hardness, low density, good impact resistance, corrosion resistance, oxidation resistance, high brittleness and the like. Due to TiB 2 The method has the characteristics, so the application background is very wide. TiB 2 The composite material is widely applied to the fields of aerospace, automobiles, military equipment, machinery, nonferrous metals, electronics and electricians and the like, is mainly used as a structural material and a functional material, but has less application as a catalytic material, and particularly has no report at present as a reaction catalyst for preparing p-xylene from methanol and toluene in the petrochemical field.
Disclosure of Invention
In order to solve the technical problems, the invention provides a high-selectivity catalyst and application thereof in preparation of p-xylene from methanol and toluene. According to the invention, the surface of the molecular sieve is coated with the silica gel, so that the acid active sites on the outer surface of the molecular sieve can be covered, and the acid active sites in the inner pore diameter of the molecular sieve are utilized to improve the generation selectivity of p-xylene. In addition, the catalyst of the invention contains Pt and TiB with strong interaction 2 The catalyst is used for catalyzing methanol and toluene to prepare p-xylene, and can obviously improve the catalytic activity and stability.
The specific technical scheme of the invention is as follows:
in a first aspect, the invention provides a high-selectivity catalyst for preparing p-xylene from methanol and toluene, which comprises a molecular sieve, silica gel coated on the surface of the molecular sieve, and nano TiB loaded on the surface of the silica gel 2 Loaded on the surface layer of the molecular sieve, silica gel and nano TiB 2 Nano Pt in (b).
The catalyst of the invention takes a molecular sieve as a carrier, a layer of wet silicon gel is coated on the carrier by utilizing a chemical synthesis method, a layer of nano titanium diboride powder is adhered to the surface of the wet silicon gel, and noble metal Pt is loaded by adopting an impregnation method after drying and calcining, thereby preparing the catalyst with high selectivity to p-xylene in the reaction of preparing the p-xylene from methanol and toluene.
On one hand, the surface of the molecular sieve is coated with the silica gel, so that the acid active sites on the outer surface of the molecular sieve can be covered, and the acid active sites in the inner pore diameter of the molecular sieve are utilized to improve the generation selectivity of p-xylene.
On the other hand, B in titanium boride - With Ti 2+ Due to the presence of electrostatic interactions, ionic bonds are formed, and thus both covalent and ionic bonds are present in the diboride. The covalent bond comprises a B-B bond and a delocalized big pi bond, and the boron atom is connected with the titanium atom by an ionic bond. TiB 2 The intermediate boron atoms are in sp2 hybridization form, electrons in large pi bonds formed by hybridization can migrate on the surface, so TiB 2 Has good electrical conductivity, thermal conductivity and electron donating ability. Boron atomic planes and titaniumThe existence of Ti-B ionic bonds and B-B covalent bonds between atomic planes enables TiB 2 The catalytic reaction can not be deactivated because the structure is damaged as the catalytic reaction is carried out. Meanwhile, slippage does not easily occur between layers in the titanium boride layered structure, and the d orbit of the titanium atom in the titanium boride is hybridized with the p orbit of the boron atom, so that certain covalency exists between the layers, and the layered structure is more stable compared with the traditional layered material. The research of the invention group shows that the catalyst has excellent catalytic effect on the preparation of p-xylene from methanol and toluene. The concrete expression is as follows: firstly, the catalyst is loaded with nano Pt, so that on one hand, the reaction activity of hydrogen in the hydrogenation reaction can be promoted, the generation of byproducts such as heavy aromatics and the like is reduced, and the carbon deposition and the like on the catalyst can be removed; on the other hand, the reaction of methanol and water vapor can be promoted to generate hydrogen, so that the concentration of the hydrogen is improved, and the hydrogen reaction is further facilitated. ② also finds that when the Pt nanoparticle and the nano TiB are used for catalyzing methanol and toluene to prepare paraxylene 2 The strong interaction exists between the two, which has great influence on the activity and catalytic performance of the catalyst. Specifically, the method comprises the following steps: when Pt is supported on TiB 2 After neutralization, TiB 2 Partial charges can be transferred to Pt, so that the valence state of Pt is changed, the adsorption capacity of Pt gas is influenced, the electron cloud density of carbon-hydrogen bonds of the adsorbed gas can be influenced, the reaction activity of the catalyst is improved, and the catalyst has better catalytic activity. And the strong interaction can also effectively inhibit the agglomeration of Pt nano particles, thereby greatly prolonging the service life of the catalyst. In summary, Pt and TiB 2 The strong interaction between them can lead Pt-TiB 2 Interfacial charge transfer, metal structure change, molecular adsorption modulation, and the like; experiments prove that the effect in the catalyst can obviously improve the catalytic activity and stability of the reaction of preparing p-xylene from toluene and methanol.
Preferably, the preparation method of the high selectivity catalyst comprises the following steps:
A) uniformly mixing tetrapropylammonium hydroxide with water, adding tetraethoxysilane under stirring, standing and aging; and transferring the obtained mixed solution into a reactor, adding a molecular sieve, heating for a rotation reaction to generate wet silica gel on the surface of the molecular sieve, centrifuging and washing the obtained product to be neutral, and removing the excessive wet silica gel to obtain the molecular sieve with the surface coated with the wet silica gel.
B) Placing the molecular sieve coated with wet silica gel on the nano TiB 2 Mixing and dispersing the powder to obtain the nano TiB 2 Adhering the powder to wet silica gel, sieving, drying the sieved matter, and roasting to obtain the product with outer layer loaded with nanometer TiB 2 Molecular sieves of the powder.
C) Loading the outer layer with nano TiB 2 Soaking the powdery molecular sieve in a platinum-containing compound aqueous solution, drying after soaking, then heating and calcining, then purging with argon and hydrogen sequentially under the condition of heat preservation, and finally heating and calcining under the protection of argon to prepare the high-selectivity catalyst.
In the preparation method, a layer of wet silica gel is coated on the outer surface of the molecular sieve carrier by adopting a chemical synthesis method, so that the acid active sites on the outer surface of the molecular sieve carrier can be covered, the generation selectivity of p-xylene can be improved by utilizing the acid active sites in the inner pore diameter of the molecular sieve, and the nano TiB can be bonded in the preparation process of the catalyst 2 The powder can be dried and sintered to obtain the nanometer TiB 2 The powder is fixed on the outer surface of the carrier. Then, precious metal Pt is loaded on the obtained modified molecular sieve carrier in the form of salt or oxide by adopting an impregnation method, at the moment, part of precious metal Pt is directly loaded on the surface layer of the nano molecular sieve carrier, and part of precious metal Pt is loaded on silica gel and nano TiB 2 And (3) coating the powder. After being dried, reduced and calcined, the nano TiB is loaded 2 Noble metals Pt and TiB on powder 2 Formation of Pt/TiB with Strong interaction 2 And (5) structure.
Preferably, in the step A), the mass ratio of the tetrapropylammonium hydroxide, the water, the tetraethoxysilane and the molecular sieve is 10-20:1000-1200:50-100: 5-10.
Further, in the step A), aging is carried out for 4-6h at room temperature; the molecular sieve is an HZSM-5 molecular sieve with the mass ratio of silicon to aluminum of 130-170: 1; the rotation reaction conditions are that the temperature is 180-.
Preferably, in step B), the surface is coated with the molecular sieve of the wet silica gel and the nano TiB 2 The mass ratio of the powder is 5-10: 50-100.
Further, in the step B), the drying temperature is 50-60 ℃, and the drying time is 5-6 h; the roasting temperature is 500-550 ℃, and the roasting time is 10-12 h.
Preferably, in step C), the outer layer is loaded with nano TiB 2 The mass ratio of the molecular sieve of the powder to the platinum-containing compound aqueous solution is 5-10: 5-10. The platinum content of the platinum-containing compound aqueous solution is 0.003 to 0.007 g/mL.
Further, in step C), the platinum-containing compound is chloroplatinic acid; the dipping time is 20-24 h; the drying temperature is 120-; the primary roasting temperature is 400-450 ℃, and the roasting time is 2-3 h; the argon purging time is 0.5-1h, and the hydrogen purging time is 1-2 h; the second calcination temperature is 600-650 ℃, and the calcination time is 3-4 h.
In a second aspect, the invention provides an application of the high-selectivity catalyst in preparation of p-xylene from methanol and toluene.
Preferably, the preparation method of the p-xylene prepared from methanol and toluene comprises the following steps: filling the high-selectivity catalyst in a fixed bed reactor, taking water vapor and hydrogen as carrier gases, and taking methanol and toluene as raw materials to heat and react; the reaction conditions are 460-480 ℃, 0.1-0.3MPa, the molar ratio of methanol to toluene is 0.75-0.90:1, and the mass space velocity of toluene is 0.8-1.2h -1 The molar ratio of water to toluene is 1.5-2.5:1 and the molar ratio of hydrogen to toluene is 1.5-2.5: 1.
Compared with the prior art, the invention has the following technical effects:
(1) the catalyst comprises a molecular sieve, silica gel coated on the surface of the molecular sieve, and nano TiB loaded on the surface of the silica gel 2 Loaded on the surface layer of the molecular sieve, silica gel and nano TiB 2 Nano Pt in (b). When the catalyst is used for catalyzing methanol and toluene to prepare p-xylene, the surface of the molecular sieve is coated with silica gel, so that the outer surface of the molecular sieve can be coveredThereby utilizing the acid active site in the inner pore diameter of the molecular sieve to improve the generation selectivity of the p-xylene. In addition, the catalyst of the invention contains Pt and TiB with strong interaction 2 The catalyst is used for catalyzing methanol and toluene to prepare p-xylene, and can obviously improve the catalytic activity and stability.
(2) In the preparation method of the catalyst, a layer of wet silica gel is coated on the outer surface of a molecular sieve carrier by adopting a chemical synthesis method, and then the wet silica gel is used for adhering the nano TiB 2 Powder, then drying and sintering to obtain the nano TiB 2 The powder is fixed on the outer surface of the carrier. Then, precious metal Pt is loaded on the obtained modified molecular sieve carrier in the form of salt or oxide by adopting an impregnation method, at the moment, part of precious metal Pt is directly loaded on the surface layer of the nano molecular sieve carrier, and part of precious metal Pt is loaded on silica gel and nano TiB 2 And (3) coating the powder. After being dried, reduced and calcined, the nano TiB is loaded 2 Noble metals Pt and TiB on powder 2 Formation of Pt/TiB with Strong interaction 2 And (5) structure.
Detailed Description
The present invention will be further described with reference to the following examples.
General examples
A high-selectivity catalyst for preparing p-xylene from methanol and toluene comprises a molecular sieve, silica gel coated on the surface of the molecular sieve, and nano TiB loaded on the surface of the silica gel 2 Loaded on the surface layer of the molecular sieve, silica gel and nano TiB 2 Nano Pt in (b).
The preparation method of the high-selectivity catalyst comprises the following steps:
A) uniformly mixing tetrapropylammonium hydroxide with water, adding tetraethoxysilane under stirring, standing and aging at room temperature for 4-6 h; transferring the obtained mixed solution to a reactor, adding an HZSM-5 molecular sieve with the mass ratio of silicon to aluminum of 130-170:1, performing rotation reaction at the temperature of 180-200 ℃ and the rotating speed of 5-15rpm for 20-24h to generate wet silica gel on the surface of the molecular sieve, centrifuging and washing the obtained product to be neutral, and removing the excess wet silica gel to obtain the molecular sieve with the surface coated with the wet silica gel. Wherein the mass ratio of the tetrapropylammonium hydroxide, the water, the ethyl orthosilicate and the molecular sieve is 10-20:1000-1200:50-100: 5-10.
B) Placing the molecular sieve coated with wet silica gel on the nano TiB according to the mass ratio of 5-10: 50-100 2 Mixing and dispersing the powder to obtain the nano TiB 2 Adhering the powder to wet silica gel, sieving, drying the sieved substance at 50-60 deg.C for 5-6h, and calcining at 500-550 deg.C for 10-12h to obtain the final product with outer layer loaded with nanometer TiB 2 Molecular sieves of the powder.
C) The outer layer is loaded with the nano TiB according to the mass ratio of 5: 10:5-10 2 The molecular sieve powder is soaked in a platinum-containing compound (preferably chloroplatinic acid) aqueous solution with the platinum content of 0.003-0.007g/mL, soaked for 20-24h, dried at 140 ℃ for 4-5h, heated to 450 ℃ and calcined for 2-3h, purged with argon for 0.5-1h under the condition of heat preservation, purged with hydrogen for 1-2h, and finally heated to 650 ℃ under the protection of argon and calcined for 3-4h to prepare the high-selectivity catalyst.
A preparation method for preparing p-xylene from methanol and toluene comprises the following steps: filling the high-selectivity catalyst in a fixed bed reactor, taking water vapor and hydrogen as carrier gases, and taking methanol and toluene as raw materials to heat and react; the reaction conditions are 460-480 ℃, 0.1-0.3MPa, the molar ratio of methanol to toluene is 0.75-0.90:1, and the mass space velocity of toluene is 0.8-1.2h -1 The molar ratio of water to toluene is 1.5-2.5:1 and the molar ratio of hydrogen to toluene is 1.5-2.5: 1.
Example 1
A) Uniformly mixing 15g of tetrapropylammonium hydroxide and 1100g of water, adding 75g of tetraethoxysilane under stirring, standing and aging at room temperature for 5 hours; and transferring the obtained mixed solution into a reactor, adding 8g of HZSM-5 molecular sieve with the silicon-aluminum mass ratio of 150: 1, performing rotation reaction for 22 hours at 190 ℃ and the rotating speed of 10rpm, generating wet silica gel on the surface of the molecular sieve, repeatedly centrifuging and washing the obtained product to be neutral, removing the excessive wet silica gel, and obtaining the molecular sieve coated with the wet silica gel on the surface.
B) Placing 8g of the molecular sieve coated with wet silica gel on 75g of nano TiB 2 Mixing the powderDispersing and making nano TiB 2 Adhering the powder to wet silica gel, sieving, oven drying at 55 deg.C for 5.5 hr, and roasting at 530 deg.C for 11 hr to obtain outer layer loaded with nanometer TiB 2 Molecular sieves of the powder.
C) Loading 8g of the outer layer with nano TiB 2 Soaking the powdery molecular sieve in 8g of chloroplatinic acid aqueous solution with the platinum content of 0.005g/mL for 22h, drying at 130 ℃ for 4.5h, heating to 430 ℃ and calcining for 2.5h, purging with argon for 0.8h under the condition of heat preservation, purging with hydrogen for 1.5h, heating to 630 ℃ under the protection of argon and calcining for 3.5h to prepare the high-selectivity catalyst.
Example 2
A) Uniformly mixing 10g of tetrapropylammonium hydroxide and 1200g of water, adding 50g of tetraethoxysilane under stirring, standing and aging at room temperature for 4 hours; transferring the obtained mixed solution to a reactor, adding 10g of HZSM-5 molecular sieve with the silicon-aluminum mass ratio of 130: 1, performing rotation reaction for 20 hours at 180 ℃ and the rotating speed of 5rpm, generating wet silica gel on the surface of the molecular sieve, repeatedly centrifuging and washing the obtained product to be neutral, removing the excessive wet silica gel, and obtaining the molecular sieve coated with the wet silica gel on the surface.
B) 10g of the molecular sieve coated with wet silica gel on the surface is placed in 50g of nano TiB 2 Mixing and dispersing the powder to obtain the nano TiB 2 Adhering the powder to wet silica gel, sieving, oven drying at 50 deg.C for 5 hr, and calcining at 500 deg.C for 10 hr to obtain outer layer loaded with nanometer TiB 2 Molecular sieves of the powder.
C) Loading 10g of the outer layer with nano TiB 2 Soaking the powdery molecular sieve in 5g of chloroplatinic acid aqueous solution with the platinum content of 0.003g/mL for 20h, drying at 120 ℃ for 4h, heating to 400 ℃ and calcining for 2h, purging with argon for 0.5h under the condition of heat preservation, purging with hydrogen for 1h, heating to 600 ℃ under the protection of argon and calcining for 3h to prepare the high-selectivity catalyst.
Example 3
A) Uniformly mixing 20g of tetrapropylammonium hydroxide and 1000g of water, adding 100g of tetraethoxysilane under stirring, standing and aging at room temperature for 6 hours; and transferring the obtained mixed solution into a reactor, adding 5g of HZSM-5 molecular sieve with the silicon-aluminum mass ratio of 170:1, performing rotation reaction for 24 hours at 200 ℃ and 15rpm, generating wet silica gel on the surface of the molecular sieve, repeatedly centrifuging and washing the obtained product to be neutral, removing the redundant wet silica gel, and obtaining the molecular sieve coated with the wet silica gel on the surface.
B) Placing 5g of the molecular sieve coated with wet silica gel on 100g of nano TiB 2 Mixing and dispersing the powder to obtain the nano TiB 2 Adhering the powder to wet silica gel, sieving, oven drying at 60 deg.C for 6 hr, and calcining at 550 deg.C for 12 hr to obtain outer layer loaded with nanometer TiB 2 Molecular sieves of the powder.
C) Loading 5g of the outer layer with nano TiB 2 Soaking the powder molecular sieve in 10g chloroplatinic acid aqueous solution with platinum content of 0.007g/mL for 24h, drying at 140 ℃ for 5h, heating to 450 ℃ and calcining for 3h, purging with argon for 1h under the condition of heat preservation, purging with hydrogen for 2h, heating to 650 ℃ under the protection of argon and calcining for 4h to prepare the high-selectivity catalyst.
Example 4
A) Uniformly mixing 10g of tetrapropylammonium hydroxide and 1000g of water, adding 100g of tetraethoxysilane under stirring, standing and aging at room temperature for 4 hours; transferring the obtained mixed solution to a reactor, adding 10g of HZSM-5 molecular sieve with the silicon-aluminum mass ratio of 150: 1, performing rotation reaction for 20 hours at 200 ℃ and 15rpm, generating wet silica gel on the surface of the molecular sieve, repeatedly centrifuging and washing the obtained product to be neutral, removing the redundant wet silica gel, and obtaining the molecular sieve coated with the wet silica gel on the surface.
B) Placing 5g of the molecular sieve coated with wet silica gel on 100g of nano TiB 2 Mixing and dispersing the powder to obtain the nano TiB 2 Adhering the powder to wet silica gel, sieving, oven drying at 60 deg.C for 5 hr, and calcining at 550 deg.C for 12 hr to obtain outer layer loaded with nanometer TiB 2 Molecular sieves of the powder.
C) Loading 10g of the outer layer with nano TiB 2 Soaking the powder molecular sieve in 5g chloroplatinic acid water solution containing 0.003g/mL platinum for 20 hr, drying at 120 deg.C for 4 hr, heating to 400 deg.C, and forgingBurning for 2h, purging with argon for 0.5h under heat preservation, purging with hydrogen for 1h, and heating to 600 ℃ under the protection of argon to calcine for 3h to obtain the high-selectivity catalyst.
Comparative example 1
A) Uniformly mixing 15g of tetrapropylammonium hydroxide and 1100g of water, adding 75g of tetraethoxysilane under stirring, standing and aging at room temperature for 5 hours; and transferring the obtained mixed solution into a reactor, adding 8g of HZSM-5 molecular sieve with the silicon-aluminum mass ratio of 150: 1, performing rotation reaction for 22 hours at 190 ℃ and the rotating speed of 10rpm, generating wet silica gel on the surface of the molecular sieve, repeatedly centrifuging and washing the obtained product to be neutral, removing the excessive wet silica gel, and obtaining the molecular sieve coated with the wet silica gel on the surface.
B) And (3) drying 8g of the molecular sieve coated with the wet silica gel on the surface at 55 ℃ for 5.5h, and roasting at 530 ℃ for 11h to obtain the molecular sieve loaded with the dry silica gel on the outer layer.
C) Soaking 8g of the molecular sieve loaded with the dry silica gel on the outer layer in 8g of chloroplatinic acid aqueous solution with the platinum content of 0.005g/mL for 22h, drying at 130 ℃ for 4.5h, heating to 430 ℃ and calcining for 2.5h, purging with argon for 0.8h under the condition of heat preservation, purging with hydrogen for 1.5h, and heating to 630 ℃ under the protection of argon and calcining for 3.5h to obtain the catalyst.
Comparative example 2
A) Uniformly mixing 10g of tetrapropylammonium hydroxide and 1200g of water, adding 50g of tetraethoxysilane under stirring, standing and aging at room temperature for 4 hours; transferring the obtained mixed solution to a reactor, adding 10g of HZSM-5 molecular sieve with the silicon-aluminum mass ratio of 130: 1, performing rotation reaction for 20 hours at 180 ℃ and the rotating speed of 5rpm, generating wet silica gel on the surface of the molecular sieve, repeatedly centrifuging and washing the obtained product to be neutral, removing the excessive wet silica gel, and obtaining the molecular sieve coated with the wet silica gel on the surface.
B) 10g of the molecular sieve coated with wet silica gel on the surface is placed in 50g of nano TiB 2 Mixing and dispersing the powder to obtain the nano TiB 2 Adhering the powder to wet silica gel, sieving, oven drying at 50 deg.C for 5 hr, and calcining at 500 deg.C for 10 hr to obtain outer layer loaded with nanometer TiB 2 Molecular sieves of the powder.
C) And (2) soaking 10g of the molecular sieve with the outer layer loaded with the nano TiB2 powder in 5g of water for 20h, drying for 4h at 120 ℃, heating to 400 ℃, calcining for 2h, purging with argon for 0.5h under the condition of heat preservation, purging with hydrogen for 1h, heating to 600 ℃ under the protection of argon, and calcining for 3h to obtain the catalyst.
Application example
The high-selectivity catalyst prepared in each example and each comparative example is used for a test of catalyzing methanol and toluene to prepare p-xylene, and the specific method comprises the following steps: the reactor is a six-section fixed bed, the catalyst is filled in sections, and the total filling amount is 600 g; taking water vapor and hydrogen as carrier gases, taking methanol and toluene as raw materials, and heating for reaction; the reaction conditions are 470 ℃, 0.2MPa, the molar ratio of methanol to toluene is 0.80: 1, and the mass space velocity of toluene is 1.0h -1 The water/toluene molar ratio was 2: 1 and the hydrogen/toluene molar ratio was 2: 1. After the reaction is finished, the product is detected, an Agilent GC6890N gas chromatograph is adopted to analyze an oil phase product, and an HP-INNOWAX capillary column (60m multiplied by 0.32mm multiplied by 0.5 mu m) and an FID detector are arranged.
The catalyst evaluation index includes the conversion rate (C) of p-toluene t ) Xylene selectivity (S) x ) And xylene selectivity (S) px )：
n t Is the amount of toluene species in the product, mol, n a Is the amount of toluene species in the reactants, mol;
n x is the molar amount, mol, of xylene in the product;
n px is the mole of p-xylene in the productMolar amount, mol.
The above result data are that the Ct, Sx and Spx values of each example and comparative example are respectively analyzed according to the sampled reaction products after the system is stably reacted for 10h and 500h, and the Ct, Sx and Spx values are calculated. According to the structural data, the Ct value, the Sx value and the Spx value measured by the 4 examples are relatively high, which shows that the catalyst prepared according to the technical scheme has relatively high reaction activity and reaction selectivity in the reaction of preparing p-xylene from methanol and toluene, and the activity and the like of the catalyst are stable after long-time reaction. In contrast, in comparative example 1, the TiB is not loaded on the surface of the molecular sieve 2 Powder, comparative 2 molecular sieve with silica gel loaded surface not impregnated with Pt salt solution, prepared catalyst without Pt and TiB 2 The strong interaction between the two components, thus leading to low activity and stability of the catalyst, and particularly having great influence on the reactivity and stability of the toluene conversion.
The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, alterations and equivalents of the above embodiments according to the technical spirit of the present invention are still within the protection scope of the technical solution of the present invention.
Claims (10)
1. A high selectivity catalyst characterized by: comprises a molecular sieve, silica gel coated on the surface of the molecular sieve, and nano TiB loaded on the surface of the silica gel 2 Loaded on the surface layer of the molecular sieve, silica gel and nano TiB 2 Nano Pt in (b).
2. The high selectivity catalyst of claim 1, wherein: the preparation method comprises the following steps:
A) uniformly mixing tetrapropylammonium hydroxide with water, adding tetraethoxysilane under stirring, standing and aging; transferring the obtained mixed solution into a reactor, adding a molecular sieve, heating for a rotation reaction to generate wet silica gel on the surface of the molecular sieve, centrifuging and washing the obtained product to be neutral, and removing the excessive wet silica gel to obtain the molecular sieve coated with the wet silica gel on the surface;
B) placing the molecular sieve coated with wet silica gel on the nano TiB 2 Mixing and dispersing the powder to obtain the nano TiB 2 Adhering the powder to wet silica gel, sieving, drying the sieved matter, and roasting to obtain the product with outer layer loaded with nanometer TiB 2 A molecular sieve of powder;
C) loading the outer layer with nano TiB 2 Soaking the powdery molecular sieve in a platinum-containing compound aqueous solution, drying after soaking, then heating and calcining, then purging with argon and hydrogen sequentially under the condition of heat preservation, and finally heating and calcining under the protection of argon to prepare the high-selectivity catalyst.
3. The high selectivity catalyst of claim 2, wherein: in the step A), the mass ratio of the tetrapropylammonium hydroxide, the water, the tetraethoxysilane and the molecular sieve is 10-20:1000-1200:50-100: 5-10.
4. A high selectivity catalyst as claimed in claim 2 or claim 3 wherein: in the step A), the step B) is carried out,
aging at room temperature for 4-6 h;
the molecular sieve is an HZSM-5 molecular sieve with the mass ratio of silicon to aluminum being 130-170: 1;
the conditions of the rotation reaction are that the temperature is 180 ℃ and 200 ℃, the rotating speed is 5-15rpm, and the time is 20-24 h.
5. The high selectivity catalyst of claim 2, wherein: in step B), the surface is coated with the molecular sieve of wet silica gel and the nano TiB 2 The mass ratio of the powders is5-10:50-100。
6. The high selectivity catalyst of claim 2 or 5, wherein: in the step B), the step (A) is carried out,
the drying temperature is 50-60 ℃, and the drying time is 5-6 h;
the roasting temperature is 500-550 ℃, and the roasting time is 10-12 h.
7. The high selectivity catalyst of claim 2 wherein: in the step C), the step C) is carried out,
the outer layer is loaded with nano TiB 2 The mass ratio of the molecular sieve powder to the platinum-containing compound aqueous solution is 5-10: 5-10;
the platinum content of the platinum-containing compound aqueous solution is 0.003 to 0.007 g/mL.
8. The high selectivity catalyst of claim 2 or 7, wherein: in the step C), the step C) is carried out,
the platinum-containing compound is chloroplatinic acid;
the dipping time is 20-24 h; the drying temperature is 120-140 ℃, and the drying time is 4-5 h;
the primary roasting temperature is 400-450 ℃, and the roasting time is 2-3 h;
the argon purging time is 0.5-1h, and the hydrogen purging time is 1-2 h;
the second calcination temperature is 600-650 ℃, and the calcination time is 3-4 h.
9. Use of the highly selective catalyst according to any one of claims 1 to 8 in the preparation of p-xylene from methanol and toluene.
10. The use of claim 9, wherein: filling the high-selectivity catalyst in a fixed bed reactor, taking water vapor and hydrogen as carrier gases, and taking methanol and toluene as raw materials to heat and react; the reaction conditions are 460-480 ℃, 0.1-0.3MPa, the molar ratio of methanol to toluene is 0.75-0.90:1, and the mass space velocity of toluene is 0.8-1.2h -1 Water/toluene molar ratio of 1.5-2.5:1 and hydrogen/toluene molar ratio of1.5-2.5:1。
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5120692A (en) * | 1991-02-04 | 1992-06-09 | Mobil Oil Corp. | Molecular sieves coated with non-oxide ceramics |
| US5191137A (en) * | 1991-02-04 | 1993-03-02 | Mobil Oil Corp. | Molecular sieves coated with non-oxide ceramics for toluene disproportionation |
| JP2002053526A (en) * | 2000-08-07 | 2002-02-19 | Teijin Ltd | Method for reactivating catalyst and method for producing aromatic carbonate using reactivated catalyst |
| CN101777654A (en) * | 2010-01-26 | 2010-07-14 | 武汉理工大学 | Fuel cell composite catalyst, high-durability membrane electrode and preparation method |
| CN102164849A (en) * | 2008-07-30 | 2011-08-24 | 布莱克光电有限公司 | Heterogeneous hydrogen-catalyst reactor |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5120692A (en) * | 1991-02-04 | 1992-06-09 | Mobil Oil Corp. | Molecular sieves coated with non-oxide ceramics |
| US5191137A (en) * | 1991-02-04 | 1993-03-02 | Mobil Oil Corp. | Molecular sieves coated with non-oxide ceramics for toluene disproportionation |
| JP2002053526A (en) * | 2000-08-07 | 2002-02-19 | Teijin Ltd | Method for reactivating catalyst and method for producing aromatic carbonate using reactivated catalyst |
| CN102164849A (en) * | 2008-07-30 | 2011-08-24 | 布莱克光电有限公司 | Heterogeneous hydrogen-catalyst reactor |
| CN101777654A (en) * | 2010-01-26 | 2010-07-14 | 武汉理工大学 | Fuel cell composite catalyst, high-durability membrane electrode and preparation method |
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