CN105195215A - Multistage porous molecular sieve catalyst and preparation method thereof - Google Patents

Abstract

The invention discloses a multi-stage pore molecular sieve catalyst and a preparation method thereof, which belong to the technology field of resource utilization of waste plastics and clean vehicle fuel production. The composition of the catalyst and the mass percent of each component are: 30-70 wt% of micro-mesoporous composite MCM-41 molecular sieve containing microporous structural units, 0.5-3.0 wt% of La ₂ O ₃ , 0.5-3.0 wt% of P ₂ O ₅ 5.0 wt%, and the balance is composed of binder. The preparation method of the multi-stage molecular sieve catalyst: the above-mentioned molecular sieve, La ₂ O ₃ precursor, P ₂ O ₅ precursor, alumina precursor, clay and water are mixed and slurried uniformly, and the dry weight of each raw material in the mixture is The mass ratio of the sum to water is (0.2～0.6): 1, and the catalyst of the present invention is obtained by spray molding and roasting; the catalyst of the present invention is used in the catalytic conversion process of macromolecular raw materials such as polyolefins, and has a high utilization rate of catalyst active sites , Good diffusion and mass transfer performance, good hydrothermal stability and good regeneration performance.

Description

A kind of hierarchical porous molecular sieve catalyst and preparation method thereof

technical field

The invention belongs to the technical field of resource utilization of waste plastics and clean vehicle fuel production, and in particular relates to a multi-stage pore molecular sieve catalyst and a preparation method thereof.

Background technique

With the rapid development of the plastics industry, plastics have been widely used in various fields of the national economy due to their many advantages. In 2013, the annual output of plastic products in the world reached 300 million tons, and the output of plastic products in my country was more than 61 million tons. However, plastic products have a short service life, and after being discarded, due to their poor biodegradability (especially polyolefin plastics), serious environmental pollution and resource waste are caused. At present, the recycling rate of waste plastics in my country is only ~20%.

With the increasing shortage of petroleum resources and the increasing concern for environmental issues, the recycling and recycling of wastes has attracted more and more attention. In 2008, my country passed the "Circular Economy Promotion Law of the People's Republic of China", which regulates and guides the reuse and recycling of waste, promotes environmental protection, and achieves sustainable development. At present, the recycling and recycling of waste plastics mainly include landfill, incineration, melting regeneration and cracking conversion methods. Among them, the first three treatment methods have many shortcomings such as occupying cultivated land and secondary pollution, while the catalytic conversion of waste plastics to produce liquid fuels or chemical raw materials It can not only solve the problem of white pollution caused by waste plastics, but also promote the effective utilization and recycling of resources. It is the most effective resource utilization method for waste plastics. The core of the cracking conversion of waste plastics lies in the creation of high-performance cracking catalysts and the development of supporting processes. However, the existing waste plastics conversion technologies have low catalyst active site utilization, poor product distribution, and low octane number of gasoline products [Liu Xianxiang, Yin Dulin. Research progress on pyrolysis of waste plastics to fuel. Progress in Chemical Industry. 2008,27(3):348-351].

The invention provides a catalyst for converting waste plastics into a hierarchical porous molecular sieve and a preparation method thereof. The catalyst has a micro-mesoporous composite pore structure, which can effectively promote the diffusion and mass transfer of polyolefin macromolecular raw materials and products, and the catalyst has relatively high acidity. , good hydrothermal stability and regeneration performance, and has good cracking and conversion performance of polyolefin plastics.

Contents of the invention

In view of the above problems, the present invention provides a waste plastics conversion hierarchical porous molecular sieve catalyst and its preparation method. The catalyst has a micro-mesoporous composite pore structure, which can effectively promote the diffusion and mass transfer of polyolefin macromolecular raw materials and products, and the catalyst has relatively It has high acidity, good hydrothermal stability and regeneration performance, and has good cracking and conversion performance of polyolefin plastics. The catalyst is used in the catalytic conversion process of polyolefin and other macromolecular raw materials, and has the characteristics of high catalyst active site utilization rate, good diffusion and mass transfer performance, good hydrothermal stability and regeneration performance, and the like.

A multi-level porous molecular sieve catalyst, the composition of the catalyst and the mass percentage of each component are: micro-mesoporous composite MCM-41 molecular sieve containing microporous structural units 30-70wt%, _{La2O3 0.5-3.0wt} % %, P ₂ O ₅ 0.5-5.0 wt%, and the balance is composed of binder.

A preparation method of a multi-stage porous molecular sieve catalyst is carried out according to the following steps:

(1) Treat the microporous molecular sieve with NaOH alkali solution under certain conditions, specifically: the concentration of NaOH alkali solution is 0.5～2.0mol/L, and the liquid-solid ratio (mL/g) of NaOH alkali solution and microporous molecular sieve is (5～ 30): 1, the treatment temperature is 50-95°C, and the treatment time is 0.5-5h;

(2) Use the slurry or filtrate of the above system as the silicon-aluminum source or part of the silicon-aluminum source, cetyltrimethylammonium bromide (CTAB) as the template, hydrothermal crystallization, the molar ratio of each component of the system SiO ₂ :CTAB:Al ₂ O ₃ :H ₂ O＝1:(0.05～0.40):(0.01～0.03):(30～150), hydrothermal crystallization conditions: dynamic crystallization at 95～115℃ for 24～72 hours ;washing, drying, and roasting at 500-540°C for 2-5 hours; using ammonium salt/inorganic acid aqueous solution as an exchange agent for ion exchange, drying, and roasting at 500-540°C for 2-5 hours to prepare a hydrogen-type molecular sieve sample;

( ₃ ) Mix the above-mentioned hydrogen _- type molecular sieves, _La2O3 precursors, _P2O5 precursors, binder precursors and water uniformly, spray molding and then roasting to obtain the catalyst, the dry weight of each raw material in the mixture The mass ratio of the sum to water is (0.2-0.6):1, and the spray forming conditions are: the spray forming conditions are: the pressure is 4-10MPa, the inlet temperature of the drying tower is 450-620°C, the tail gas temperature is 150-300°C; the roasting temperature is 500°C ~620°C, time 1~5 hours.

The microporous molecular sieve is one or several molecular sieves with configurations such as MFI, AEL, MTT, TON, MEL, MOR, FER, MTW, MWW, and BEA.

The binder is a mixture of alumina and clay in a certain proportion, the alumina is derived from aluminum sol or aluminum nitrate, and its content in the catalyst is 15-30 wt%; the clay is kaolin, bentonite, seafoam One or more mixtures of stone, attapulgite, montmorillonite and diatomite, the content of which in the catalyst is 15-40wt%.

The La ₂ O ₃ precursor is one or more of lanthanum nitrate, lanthanum oxide, lanthanum chloride, lanthanum acetate, lanthanum carbonate, and lanthanum hydroxide, and the content of the La ₂ O ₃ is 0.5-3.0 wt %; The precursor of the P ₂ O ₅ is one or more of phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate or diammonium hydrogen phosphate, and the content of the P ₂ O ₅ is 0.5-5.0 wt%.

The catalyst is used in the catalytic conversion of waste plastics and other raw materials to produce aromatics or high-octane gasoline components; the waste plastics are one or more of waste polyethylene, polypropylene, and polystyrene; the The catalytic conversion process is carried out under the following conditions, the temperature is 330-500° C., and the pressure is 0.1-1.0 MPa.

The catalyst of the invention is used in the catalytic conversion process of polyolefin and other macromolecular raw materials, and has the characteristics of high catalyst active site utilization rate, good diffusion and mass transfer performance, good hydrothermal stability and regeneration performance, and the like.

Detailed ways

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

Example 1

Dissolve 10 g of molecular sieves with MFI configuration (molar ratio of silicon to aluminum: 50) in 200 ml of NaOH solution (1 mol/L), and treat for 1 hour under constant temperature water bath conditions at 80°C;

Dissolve 5g of CTAB in 50ml of distilled water, heat and stir for 30 minutes to clarify the solution; use alkali-treated MFI molecular sieve slurry as the source of silicon and aluminum, slowly add it to the CTAB solution, and stir for 2 hours to fully mix the solution. The molar ratio of raw materials SiO ₂ :CTAB:Al ₂ O ₃ :H ₂ O＝1:0.1:0.02:60;

The pH value of the above solution was adjusted to 10.5, and transferred to a synthesis kettle lined with polytetrafluoroethylene; crystallized at 110°C for 24 hours, washed, dried, and roasted to obtain MCM with a micro-mesoporous composite pore structure- 41 molecular sieves; use ammonium nitrate as an exchange agent to ion-exchange the sample, and make a hydrogen-type molecular sieve sample after roasting;

After the above-mentioned hydrogen-type molecular sieve, lanthanum nitrate, phosphoric acid, aluminum sol, kaolin, and deionized water are mixed and slurried uniformly and finely ground, the inlet temperature of the drying tower is 620°C, the tail gas temperature is 300°C, and the spray pressure is 10.0MPa. The catalyst A was prepared by spraying and calcination at 620° C. for 2 hours. The weight contents of molecular sieve, La ₂ O ₃ , P ₂ O ₅ , and alumina are 45%, 1.5%, 2.5% and 25% respectively, and the rest is kaolin; More than 80% of the volume, wear index <1.5%.

Example 2

Dissolve 10 g of molecular sieves with a MWW configuration (molar ratio of silicon to aluminum: 30) in 200 ml of NaOH solution (0.6 mol/L), and treat for 1 hour under the condition of a constant temperature water bath at 80 ° C;

Dissolve 10g of CTAB in 50ml of distilled water, heat and stir for 30 minutes to clarify the solution; the slurry obtained by alkali treatment of MWW molecular sieves is part of the source of silicon and aluminum, according to the composition ratio of each component of the raw material SiO2:CTAB:Al ₂ O ₃ :H ₂ O =1:0.2:0.03:40 Add the calculated amount of extra silicon source water glass and aluminum source sodium aluminate, after stirring evenly, slowly add CTAB solution, stir for 2 hours, so that the solution is fully mixed;

The pH value of the above solution was adjusted to 10.0, and transferred to a synthesis kettle with a polytetrafluoroethylene liner; crystallized at 105°C for 48 hours, washed, dried, and roasted to obtain MCM with a micro-mesoporous composite pore structure- 41 molecular sieves; use hydrochloric acid as an exchange agent to ion-exchange the sample, and make a hydrogen-type molecular sieve sample after roasting;

The above-mentioned molecular sieve, lanthanum acetate, ammonium dihydrogen phosphate, aluminum sol, hydrogen-based bentonite, and deionized water were mixed and slurried uniformly and finely ground. Catalyst B was prepared by spray molding under the conditions and calcined at 550°C for 3 hours. The weight contents of molecular sieve, La ₂ O ₃ , P ₂ O ₅ and alumina are 50%, 1.0%, 3.0% and 30% respectively, and the rest are bentonite; More than 80% of the volume, wear index <1.5%.

Example 3

The catalyst preparation process is the same as in Example 2, except that the alkali-treated ten-membered ring or twelve-membered ring microporous molecular sieve is an equal weight ratio mixture of AEL, MTT, TON and MEL configuration molecular sieves, and the concentration of NaOH solution is 2.0mol/ L, the liquid-solid ratio is 5:1, the processing temperature is 50°C, and the processing time is 5 hours; the external silicon and aluminum sources are silicon source silica sol and aluminum source aluminum sulfate; the precursors of lanthanum and phosphorus are lanthanum acetate and ammonium dihydrogen phosphate respectively, In the catalyst, molecular sieve accounts for 30wt%, La ₂ O ₃ accounts for 3.0wt%, P ₂ O ₅ accounts for 5.0wt%, alumina 30%, and the rest is composed of sepiolite, attapulgite, montmorillonite and diatomite in equal proportions During the molding process, the inlet temperature of the drying tower was 450°C, the tail gas temperature was 150°C, and the spray pressure was 7.5MPa. The catalyst C was obtained by roasting at 620°C for 1 hour.

Example 4

The catalyst preparation process is the same as in Example 3, except that the alkali-treated ten-membered ring or twelve-membered ring microporous molecular sieve is an equal weight ratio mixture of MOR, FER, MTW and BEA configuration molecular sieves, and the concentration of NaOH solution is 0.5mol/ L, the ratio of liquid to solid is 30:1, the treatment temperature is 95°C, and the treatment time is 0.5h; the precursors of lanthanum and phosphorus are lanthanum chloride and ammonium phosphate respectively, molecular sieves account for 70wt% _of the catalyst, and _La2O3 accounts for 0.5wt%. P ₂ O ₅ accounts for 0.5wt%, alumina 15%, and the rest is clay; during the molding process, the inlet temperature of the drying tower is 550°C, the tail gas temperature is 280°C, and the spray pressure is 4.0MPa. The spray molding is carried out at 500°C for 5 hours. Catalyst D is prepared.

Example 5

Under the conditions of reaction temperature of 380°C, pressure of 0.3MPa, and raw material space velocity of 1.0h ^-1 , in a fixed fluidized bed reactor equipped with catalyst A, polypropylene PP is used as raw material, and the conversion rate of raw material is ~100%. The total yield of C ₅ + liquid phase products and liquefied gas is >95%; the total content of high-octane aromatics, isoparaffins and olefins in gasoline distillation products is >85%, and it does not contain sulfur, which can be used as high-quality cleaning Fuel blending components.

Example 6

Under the conditions of reaction temperature of 410°C, pressure of 0.5MPa, and raw material space velocity of 0.8h ^-1 , in a fixed fluidized bed reactor equipped with catalyst B, low density polyethylene LDPE is used as raw material, and the conversion rate of raw material is >95 %, the total yield of C ₅ + liquid phase products and liquefied gas is >90%, and the total content of high-octane components aromatics, isoparaffins and olefins in gasoline distillation products is >85%, excluding sulfur,

It can be used as a blending component of high-quality clean fuel.

Example 7

Under the conditions of reaction temperature of 330°C, pressure of 1.0MPa, and raw material space velocity of 0.5h ^-1 , in a fixed fluidized bed reactor equipped with catalyst C, low density polyethylene LDPE, polypropylene PP, Polystyrene PS is used as raw material, the conversion rate of raw material is >90%, the total selectivity of C ₅ + liquid phase products and liquefied gas is >95%, and the total content of high-octane component aromatics, isoparaffins and olefins in gasoline distillation products >80%, sulfur-free, can be used as a blending component of high-quality clean fuels.

Example 8

Under the conditions of reaction temperature of 500°C, pressure of 0.1MPa, and raw material space velocity of 3.0h ^-1 , in a fixed fluidized bed reactor equipped with catalyst D, polypropylene PP is used as raw material, and the conversion rate of raw material is >96%. The total selectivity of C ₅ + liquid phase products and liquefied gas is >95%, and the total content of high-octane aromatics, isoparaffins and olefins in gasoline distillation products is >85%, which does not contain sulfur and can be used as high-quality clean fuel The blending components, or the high-content aromatics are extracted and further separated into chemicals such as benzene, toluene, xylene, etc., and the remaining components are used as blending components for clean fuels.

Claims (6)

1. A multi-stage porous molecular sieve catalyst, characterized in that the composition of the catalyst and the mass percentage of each component are: micro-mesoporous composite MCM-41 molecular sieve containing microporous structural units 30～70wt%, La ₂ O ₃ 0.5 ～3.0wt%, P ₂ O ₅ 0.5～5.0wt%, and the balance is composed of binder; the samples with the catalyst particle size between 40～100um accounted for more than 80% of the total, and the wear index was <1.5%; The preparation of described hierarchical porous molecular sieve catalyst is carried out according to the following steps: (1) Treat the microporous molecular sieve with NaOH alkali solution under certain conditions, specifically: the concentration of NaOH alkali solution is 0.5～2.0mol/L, and the liquid-solid ratio (mL/g) of NaOH alkali solution and microporous molecular sieve is (5～ 30): 1, the treatment temperature is 50-95°C, and the treatment time is 0.5-5h; (2) Use the slurry or filtrate of the above system as the silicon-aluminum source or part of the silicon-aluminum source, cetyltrimethylammonium bromide (CTAB) as the template, hydrothermal crystallization, the molar ratio of each component of the system SiO ₂ :CTAB:Al ₂ O ₃ :H ₂ O＝1:(0.05～0.40):(0.01～0.03):(30～150), dynamic crystallization at 95～115℃ for 24～72 hours; washing and drying , Calcining at 500-540°C for 2-5 hours; using ammonium salt/inorganic acid aqueous solution as an exchange agent for ion exchange, drying, roasting at 500-540°C for 2-5 hours, and then making a hydrogen-type molecular sieve sample; (3) Mix the above-mentioned hydrogen-type molecular sieve, La ₂ O ₃ precursor, P ₂ O ₅ precursor, binder precursor and water into slurry, grind it finely, spray molding and then roasting to obtain the catalyst: each The ratio of the sum of the dry basis mass of the raw materials to the water mass is (0.2-0.6): 1; the spray molding conditions are: the pressure is 4-10MPa, the inlet temperature of the drying tower is 450-620°C, the tail gas temperature is 150-300°C; the roasting temperature is 500-620°C °C, time 1-5 hours. 2. according to the described multi-level porous molecular sieve catalyst of claim 1, it is characterized in that described microporous molecular sieve is one of configuration molecular sieves such as MFI, AEL, MTT, TON, MEL, MOR, FER, MTW, MWW, BEA species or several. 3. according to the described hierarchical porous molecular sieve catalyst of claim 1, it is characterized in that said binding agent is the mixture of aluminum oxide and clay certain ratio, and described aluminum trioxide originates from aluminum sol or aluminum nitrate, and its content in catalyzer The content is 15-30 wt%. The clay is one or a mixture of kaolin, bentonite, sepiolite, attapulgite, montmorillonite and diatomite, and its content in the catalyst is 15-40 wt%. 4. according to the described hierarchical porous molecular sieve catalyst of claim ₁ , it is characterized in that said _La2O3 precursor is one or more of lanthanum nitrate, lanthanum oxide, lanthanum chloride, lanthanum acetate, lanthanum carbonate, lanthanum hydroxide species, the content of the _La2O3 is _0.5-3.0wt %wt% _; the precursor of the _P2O5 is one or more of phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate or diammonium hydrogen phosphate, The content of the P ₂ O ₅ is 0.5-5.0 wt%. 5. according to the preparation method of the described hierarchical porous molecular sieve catalyst of claim 1, it is characterized in that carrying out according to the following steps: (1) Treat the microporous molecular sieve with NaOH alkali solution under certain conditions, specifically: the concentration of NaOH alkali solution is 0.5～2.0mol/L, and the liquid-solid ratio (mL/g) of NaOH alkali solution and microporous molecular sieve is (5～ 30): 1, the treatment temperature is 50-95°C, and the treatment time is 0.5-5h; (2) Use the slurry or filtrate of the above system as the silicon-aluminum source or part of the silicon-aluminum source, cetyltrimethylammonium bromide (CTAB) as the template, hydrothermal crystallization, the molar ratio of each component of the system SiO ₂ :CTAB:Al ₂ O ₃ :H ₂ O＝1:(0.05～0.40):(0.01～0.03):(30～150), dynamic crystallization at 95～115℃ for 24～72 hours; washing and drying , Calcining at 500-540°C for 2-5 hours; using ammonium salt/inorganic acid aqueous solution as an exchange agent for ion exchange, drying, roasting at 500-540°C for 2-5 hours, and then making a hydrogen-type molecular sieve sample; (3) Mix the above-mentioned hydrogen-type molecular sieve, La ₂ O ₃ precursor, P ₂ O ₅ precursor, binder precursor and water into slurry, grind it finely, spray molding and then roasting to prepare the catalyst, in the mixture The mass ratio of the dry basis mass sum of each raw material to water is (0.2-0.6): 1, the spray forming conditions are: the spray forming conditions are: the pressure is 4-10MPa, the inlet temperature of the drying tower is 450-620°C, and the tail gas temperature is 150- 300°C; calcination temperature 500-620°C, time 1-5 hours. 6. according to the application of the described hierarchical porous molecular sieve catalyst of claim 1, it is characterized in that this catalyst is applied to raw materials such as waste plastics catalytic conversion to produce aromatics or high-octane gasoline component process; Said waste plastics is waste and old polyethylene , a mixture of one or more of polypropylene and polystyrene; the catalytic conversion process is carried out under the following conditions, the temperature is 330-500° C., and the pressure is 0.1-1.0 MPa.