CN114210342B - Catalyst for synthesizing dimethyl carbonate from methanol in gas phase, preparation method and dimethyl carbonate synthesizing method - Google Patents
Catalyst for synthesizing dimethyl carbonate from methanol in gas phase, preparation method and dimethyl carbonate synthesizing method Download PDFInfo
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Abstract
The invention discloses a catalyst for synthesizing dimethyl carbonate by methanol gas phase, which comprises a carrier and active components, wherein the carrier comprises manganese dioxide, pseudo-boehmite and active carbon, and the active components comprise soluble palladium salt, chloride salt and hypochlorite; also disclosed is a method for preparing a catalyst for synthesizing dimethyl carbonate from methanol in a gas phase, comprising: step 1, preparing a carrier, namely uniformly mixing manganese dioxide, pseudo-boehmite, active carbon and first deionized water, and drying and calcining; step 2, dispersing soluble palladium salt, chloride salt and hypochlorite in second deionized water to obtain an impregnating solution; and 3, dipping the carrier obtained in the step 1 into the dipping liquid obtained in the step 2, and drying to obtain the catalyst for synthesizing the dimethyl carbonate by using the methanol gas phase. The catalyst has higher conversion rate and selectivity, and the service life of the catalyst is greatly improved.
Description
Technical Field
The invention belongs to the technical field of chemical technology, and particularly relates to a catalyst for synthesizing methyl carbonate from methanol in a gas phase, a preparation method and a methyl carbonate synthesis method.
Background
Dimethyl carbonate (DMC) is an environment-friendly chemical raw material, and is widely applied to the fields of pesticides, medicines, plastics, dyes, electronic chemicals, food additives, color imaging and the like. As carbonylation agent and methylation agent to synthesize various valuable chemical products, it can be used as non-toxic high-octane gasoline additive and organic solvent, and its application is getting more and more attention.
In recent years, dimethyl carbonate (DMC) is attracting attention as a new basic organic chemical raw material. Some researchers at home and abroad research the reaction process, and have made certain progress in aspects of activity selection of catalysts, process operation conditions and the like, and DMC synthesis methods mainly comprise a phosgene-methanol method, a transesterification method, a gas (liquid) phase methanol oxidative carbonylation method and the like. The phosgene method is gradually eliminated due to the extremely toxic raw materials, high corrosion equipment and high cost; the transesterification method is to prepare dimethyl carbonate by using ethylene carbonate and methanol as raw materials, and simultaneously, the byproduct ethylene glycol, which is not industrialized yet, mainly because of poor economic feasibility; the liquid-phase methanol oxidative carbonylation method adopts Cu or Pd halide as a catalyst, has very strong corrosiveness and short service life, and has problems in the aspect of product recovery; the methanol vapor phase oxidative carbonylation process overcomes the disadvantages of the liquid phase process.
Patent CN1736595a provides a method for preparing DMC by reacting propylene carbonate with methanol, wherein a catalyst is selected from monoalkoxides and polyethylene glycol, and the addition of polyethylene glycol can slow down the decomposition of monoalkoxides, but is not absolute, and as can be seen from the examples, the DMC selectivity of the catalyst is relatively low, and no data is supported that the catalyst is not deactivated when continuously used.
Patent CN1736595A provides a method using CuX or CuX-CuX 2 Catalyst as active component, which is used for synthesizing D by methanol gas phase carbonylation after being impregnated into corresponding carrierMC, however, from the reaction results, the catalytic system is unstable, the conversion rate of methanol is lower, the fluctuation range is 5-20% and the DMC space-time yield is low, the maximum is 170g/Kgcath, and the industrialization cost is too high.
Patent CN01102306.6 provides a method for utilizing CO 2 Method for directly synthesizing DMC with methanol, and catalyst mainly is K 2 CO 3 Cocatalysts CH are also required 3 I, the method has the advantage that CO can be utilized 2 The disadvantage of this greenhouse gas is that the methanol conversion is not about 10% higher and there is no information about DMC selectivity, and it is not clear what DMC is in the product after methanol conversion.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a catalyst for synthesizing methyl carbonate by methanol gas phase, which has higher conversion rate and selectivity and greatly improves the service life of the catalyst.
The invention is realized by the following technical scheme:
a catalyst for synthesizing dimethyl carbonate by methanol gas phase, which comprises a carrier and an active component, wherein the carrier comprises a catalyst carrier and an active component;
the carrier comprises manganese dioxide, pseudo-boehmite and active carbon, wherein the mass ratio of the manganese dioxide to the pseudo-boehmite is 1 (1-10), and the mass of the active carbon is 0.1-2.5% of the sum of the mass of the manganese dioxide and the mass of the pseudo-boehmite;
the active components comprise soluble palladium salt, chloride salt and hypochlorite, wherein the mass of the soluble palladium salt is 0.1-1% of that of the carrier, the molar ratio of the chloride salt to the soluble palladium salt is (5-20): 1, and the molar ratio of the hypochlorite to the soluble palladium salt is (1-10): 1.
In the technical scheme, the soluble palladium salt is one or more of palladium chloride, palladium nitrate, palladium acetate and palladium sulfate; the chloride salt is one or more of copper chloride, manganese chloride, chromium chloride, nickel chloride, vanadium chloride, molybdenum pentachloride, tungsten chloride and cobalt chloride; the hypochlorite is one or more of potassium hypochlorite, sodium hypochlorite, calcium hypochlorite, lithium hypochlorite and copper hypochlorite.
It is another object of the present invention to provide a method for preparing a catalyst for vapor phase synthesis of dimethyl carbonate from methanol.
A method for preparing a catalyst for synthesizing dimethyl carbonate by methanol gas phase, which comprises the following steps:
step 1, evenly mixing manganese dioxide, pseudo-boehmite, active carbon and first deionized water to obtain a first material, granulating the first material to obtain first particles, drying the first particles, and calcining at 200-500 ℃ to obtain a carrier;
in the first material, the mass ratio of manganese dioxide to pseudo-boehmite is 1 (1-10), and the mass of the activated carbon is 0.1% -5% of the sum of the mass of manganese dioxide and pseudo-boehmite; the weight of the deionized water accounts for 4.5% -20% of that of the first material;
step 2, dispersing soluble palladium salt, chloride salt and hypochlorite in second deionized water to obtain an impregnating solution;
the mass of the soluble palladium salt is 0.1-1% of the mass of the carrier, the molar ratio of the chloride salt to the soluble palladium salt is (5-20): 1, and the molar ratio of the hypochlorite salt to the soluble palladium salt is (1-10): 1;
the second deionized water amount is the maximum absorption mass of the carrier to deionized water in the step 1;
step 3, dipping the carrier obtained in the step 1 into the dipping liquid obtained in the step 2 for 2-24 hours to obtain a dipped carrier; and drying the impregnated carrier to constant weight to obtain the catalyst for synthesizing the dimethyl carbonate by using the methanol gas phase.
In the above technical scheme, the drying temperature of the first particles is 100 ℃.
In the above technical scheme, the mass of the activated carbon in the carrier after the calcination process in the step 1 is completed is less than 50% of the mass of the activated carbon before calcination.
In the technical scheme, in the step 1, the process of uniformly mixing manganese dioxide, pseudo-boehmite, activated carbon and deionized water is completed by adopting a kneader; and granulating the first material by adopting a strip extruder.
In the technical scheme, in the step 2, soluble palladium salt, chloride salt and hypochlorite are stirred and dispersed in a solvent at 20-60 ℃ to obtain an impregnating solution.
In the technical scheme, the soluble palladium salt is one or more of palladium chloride, palladium nitrate, palladium acetate and palladium sulfate; the chloride salt is one or more of copper chloride, manganese chloride, chromium chloride, nickel chloride, vanadium chloride, molybdenum pentachloride, tungsten chloride and cobalt chloride; the hypochlorite is one or more of potassium hypochlorite, sodium hypochlorite, calcium hypochlorite, lithium hypochlorite and copper hypochlorite.
In the above technical scheme, the activated carbon is one or more of coconut shell type activated carbon powder, coal-based activated carbon powder or wood type activated carbon powder.
In the technical scheme, in the step 3, the impregnated carrier is dried to constant weight at 60-120 ℃.
In the above technical scheme, the raw material adopted in step 2 may have any water of crystallization, and if the raw material containing water of crystallization is used in step 2, the amount of the solvent is the maximum absorption mass of the carrier to the solvent minus the total mass of the water of crystallization in step 1.
It is another object of the present invention to provide a method for synthesizing dimethyl carbonate.
The synthesis method adopts methyl nitrite, CO and HCl as raw materials, and the methyl carbonate is obtained by reaction synthesis under the action of the catalyst for synthesizing the methyl carbonate by the methanol gas phase, wherein the catalyst is prepared by the technical scheme;
the synthesis temperature is 110-130 ℃, and the volume airspeed is 1700-2400 h -1 The molar ratio of methyl nitrite to CO is 1-1.5: 1, a step of;
the concentration of the HCl gas is 50-500ppm.
In the technical scheme, the methyl nitrite adopts NO and O 2 Anhydrous methanol as raw material, nitrogenAs balance gas, under the conditions of reaction temperature of 110-130 ℃ and reaction pressure of 0.3-0.7 MPa, the catalyst is obtained by reaction;
the NO and O 2 The molar ratio of the anhydrous methanol is (2-3): 1-2): 5-10; the volume of nitrogen is CO and O 2 1 to 5 times of the sum of the volumes.
The invention has the advantages and beneficial effects that:
1. the surface and a part of the inside active carbon of the catalyst carrier disclosed in the technical proposal of the invention can be carbonized in the calcining process, and a great amount of heat and CO can be generated in the carbonizing process 2 The manganese dioxide and the alumina in the carrier are crosslinked and form a wide micropore structure, the impregnating solution can be perfectly impregnated into the pore structure of the carrier, and the manganese dioxide surrounds Pd through the micropore effect 2+ 、Cu 2+ Around, the positive effect generated avoids Pd 2+ 、Cu 2+ The catalyst life is longer because the catalyst is deactivated by reducing +2 to 0 in the reaction process, and the specific surface area of the carrier is greatly improved by the micropore structure, and the C remained in the pore structure of the carrier has strong adsorption effect on-OH bonds, so that methanol molecules are adsorbed in Pd in the pore structure of the carrier more easily 2+ The DMC is generated by carbonylation reaction under catalysis, so that the conversion rate of the catalyst is improved.
2. The active carbon in a large number of micropore structures of the catalyst carrier has an adsorption effect, can adsorb and prepare HCl gas added in the DMC reaction system to supplement Cl ions, can slow down the loss of Cl ions of palladium chloride and copper chloride, and can play a role in improving DMC selectivity.
3. H is produced during DMC reactions in methanol production 2 O, add HCl and H 2 O can form a weak acid environment after contact, hypochlorite in the active component of the catalyst is combined with weak acid HCl to generate strong oxidizing property, and the synergistic effect between hypochlorite on the macroscopic surface of the carrier and manganese dioxide with a microscopic pore structure is Pd 2+ Provides complete oxidation environment and protects the active center Pd of the catalyst 2+ 、Cu 2+ Is not reduced by the CO of the raw material gas, so that the conversion rate and the selectivity of the catalyst are more stable and efficient, and the catalyst is prolongedLong catalyst life.
4. The catalyst has high CO conversion rate maintained over 30%, DMC selectivity higher than 95%, low reaction temperature, low reaction pressure and long catalyst life.
Drawings
FIG. 1 shows a catalyst evaluation apparatus;
FIG. 2 shows a gas chromatograph GC-2014C
FIG. 3 shows a gas chromatograph GC-2014C with vaporization chamber
FIG. 4 is a SEM photograph of a catalyst before evaluation of the catalyst of example 1
FIG. 5 is a SEM photograph of the catalyst after evaluation of the catalyst of example 1
FIG. 6 shows a catalyst EDS point-taking image of example 1
FIG. 7 shows an EDS apparatus resolution of the catalyst of example 1
FIG. 8 shows EDS equipment analysis data for the catalyst of example 1
FIG. 9 shows XPS spectra of the catalyst of example 1 after 500h of evaluation
FIG. 10 shows XPS spectrum after 500h of evaluation of the catalyst of comparative example 1c
FIG. 11 example 1 shows XRD patterns of the catalyst before and after 500 hours of evaluation, with the upper curve being 500 hours after evaluation and the lower curve being 500 hours before evaluation. .
Other relevant drawings may be made by those of ordinary skill in the art from the above figures without undue burden.
Detailed Description
In order to make the person skilled in the art better understand the solution of the present invention, the following describes the solution of the present invention with reference to specific embodiments.
The materials used in the examples do not contain crystal water
Example 1
A method for preparing a catalyst for synthesizing dimethyl carbonate, comprising the following steps:
step 1: adding manganese dioxide, pseudo-boehmite, coconut shell type activated carbon and deionized water 1 into a kneader for kneading, pouring the materials into a strip extruder for strip extrusion after the kneading is finished, drying the extruded strips at 100 ℃, and calcining at 300 ℃ to obtain a carrier, wherein the mass ratio of manganese dioxide to pseudo-boehmite is 1:1, the addition amount of the coconut shell type activated carbon is 0.1% of the sum of the mass of manganese dioxide and the mass of the pseudo-boehmite, and the addition amount of the deionized water 1 is 5% of the total mass.
Step 2: mixing deionized water 2, palladium chloride and copper chloride, stirring at 20 ℃ until the mixture is completely dissolved, then adding a certain amount of sodium hypochlorite, and continuing stirring until the mixture is completely dissolved to obtain an impregnating solution, wherein the adding amount of the palladium chloride is 0.1% of the mass of the carrier, the molar ratio of the adding amount of the copper chloride to the sodium hypochlorite to the palladium chloride is 5:1 and 1:1 respectively, and determining the using amount of the deionized water 2 by adopting an equal volume impregnation method;
step 3: and (3) dipping the carrier in the step (1) into the dipping liquid in the step (2), wherein the dipping process lasts for 2 hours, and after the dipping is finished, putting the material into a baking oven, and drying at 60 ℃ to constant weight to obtain the catalyst.
Comparative example 1
Comparative example 1 was different from example 1 only in that no activated carbon was added in step 1 of comparative example 1, and the other raw material ratios and reaction parameters were the same as those of example 1, to prepare a No. 1a catalyst.
Comparative example 2
Comparative example 2 was different from example 1 only in that no manganese dioxide was added in comparative example 2, and the other raw material ratios and reaction parameters were the same as those of example 1, to prepare a No. 1b catalyst.
Comparative example 3
Comparative example 3 was different from example 1 only in that no hypochlorite was added in comparative example 3, and other raw material ratios and reaction parameters were the same as those of example 1, to prepare a catalyst No. 1 c.
Comparative example 4
Comparative example 4 differs from example 1 only in that comparative example 4 was not supplemented with HCl during the evaluation, and the result data is recorded as catalyst No. 1 d.
Example 2
A method for preparing a catalyst for synthesizing dimethyl carbonate, comprising the following steps:
step 1: adding manganese dioxide, pseudo-boehmite, coconut shell type activated carbon and deionized water 1 into a kneader for kneading, pouring the materials into a strip extruder for strip extrusion after the kneading is finished, drying the extruded strips at 100 ℃, and calcining at 500 ℃ to obtain a carrier, wherein the mass ratio of manganese dioxide to pseudo-boehmite is 1:5, the addition amount of the coconut shell type activated carbon is 0.5% of the sum of the mass of manganese dioxide and the mass of the pseudo-boehmite, and the addition amount of the deionized water 1 is 12.5% of the total mass.
Step 2: mixing deionized water 2, palladium acetate and manganese chloride, stirring at 20 ℃ until the mixture is completely dissolved, then adding a certain amount of potassium hypochlorite, and continuing stirring until the mixture is completely dissolved to obtain an impregnating solution, wherein the adding amount of the palladium acetate is 0.5% of the mass of the carrier, the molar ratio of the adding amount of the manganese chloride, the adding amount of the potassium hypochlorite and the palladium acetate is 5:1 and 1:1 respectively, and determining the using amount of the deionized water 2 by adopting an equal volume impregnation method;
step 3: and (3) dipping the carrier in the step (1) into the dipping liquid in the step (2), wherein the dipping process lasts for 12 hours, and after the dipping is finished, putting the material into a baking oven, and drying at 90 ℃ to constant weight to obtain the catalyst.
Example 3
A method for preparing a catalyst for synthesizing dimethyl carbonate, comprising the following steps:
step 1: adding manganese dioxide, pseudo-boehmite, coconut shell type activated carbon and deionized water 1 into a kneader for kneading, pouring the materials into a strip extruder for strip extrusion after the kneading is finished, drying the extruded strips at 100 ℃, and calcining at 700 ℃ to obtain a carrier, wherein the mass ratio of manganese dioxide to pseudo-boehmite is 1:10, the addition amount of the coconut shell type activated carbon is 1% of the sum of the mass of manganese dioxide and the mass of the pseudo-boehmite, and the addition amount of the deionized water 1 is 20% of the total mass.
Step 2: mixing deionized water 2, palladium sulfate and chromium chloride, stirring at 20 ℃ until the mixture is completely dissolved, then adding a certain amount of calcium hypochlorite, and continuing stirring until the mixture is completely dissolved to obtain an impregnating solution, wherein the adding amount of the palladium sulfate is 1% of the mass of the carrier, the molar ratio of the adding amount of the chromium chloride and the calcium hypochlorite to the palladium sulfate is 5:1 and 1:1 respectively, and determining the using amount of the deionized water 2 by adopting an equal volume impregnation method;
step 3: and (3) dipping the carrier in the step (1) into the dipping liquid in the step (2), wherein the dipping process lasts for 24 hours, and after the dipping is finished, putting the material into a baking oven, and drying at 120 ℃ to constant weight to obtain the catalyst.
Example 4
A method for preparing a catalyst for synthesizing dimethyl carbonate, comprising the following steps:
step 1: adding manganese dioxide, pseudo-boehmite, coal-based activated carbon and deionized water 1 into a kneader for kneading, pouring the materials into a strip extruder for strip extrusion after the kneading is finished, drying the extruded strips at 100 ℃, and calcining at 300 ℃ to obtain a carrier, wherein the mass ratio of manganese dioxide to pseudo-boehmite is 1:1, the addition amount of the coal-based activated carbon is 0.1% of the sum of the mass of manganese dioxide and the mass of the pseudo-boehmite, and the addition amount of the deionized water 1 is 5% of the total mass.
Step 2: mixing deionized water 2, palladium nitrate and nickel chloride, stirring at 40 ℃ until the mixture is completely dissolved, adding a certain amount of lithium hypochlorite, and continuously stirring until the mixture is completely dissolved to obtain an impregnating solution, wherein the adding amount of the palladium nitrate is 0.1% of the mass of the carrier, the molar ratio of the adding amount of the nickel chloride, the lithium hypochlorite to the palladium nitrate is 10:1 and 5:1 respectively, and determining the using amount of the deionized water 2 by adopting an equal volume impregnation method;
step 3: and (3) dipping the carrier in the step (1) into the dipping liquid in the step (2), wherein the dipping process lasts for 2 hours, and after the dipping is finished, putting the material into a baking oven, and drying at 60 ℃ to constant weight to obtain the catalyst.
Example 5
A method for preparing a catalyst for synthesizing dimethyl carbonate, comprising the following steps:
step 1: adding manganese dioxide, pseudo-boehmite, coal-based activated carbon and deionized water 1 into a kneader for kneading, pouring the materials into a strip extruder for strip extrusion after the kneading is finished, drying the extruded strips at 100 ℃, and calcining at 300 ℃ to obtain a carrier, wherein the mass ratio of manganese dioxide to pseudo-boehmite is 1:1, the addition amount of the coal-based activated carbon is 0.1% of the sum of the mass of manganese dioxide and the mass of the pseudo-boehmite, and the addition amount of the deionized water 1 is 5% of the total mass.
Step 2: mixing deionized water 2, palladium chloride and vanadium chloride, stirring at 60 ℃ until the mixture is completely dissolved, adding a certain amount of copper hypochlorite, and continuously stirring until the mixture is completely dissolved to obtain an impregnating solution, wherein the adding amount of the palladium chloride is 0.5% of the mass of the carrier, the molar ratio of the adding amount of the vanadium chloride to the copper hypochlorite to the palladium chloride is 20:1 and 10:1 respectively, and determining the using amount of the deionized water 2 by adopting an equal volume impregnation method;
step 3: and (3) dipping the carrier in the step (1) into the dipping liquid in the step (2), wherein the dipping process lasts for 12 hours, and after the dipping is finished, putting the material into a baking oven, and drying at 90 ℃ to constant weight to obtain the catalyst.
Example 6
A method for preparing a catalyst for synthesizing dimethyl carbonate, comprising the following steps:
step 1: adding manganese dioxide, pseudo-boehmite, coal-based activated carbon and deionized water 1 into a kneader for kneading, pouring the materials into a strip extruder for strip extrusion after the kneading is finished, drying the extruded strips at 100 ℃, and calcining at 500 ℃ to obtain a carrier, wherein the mass ratio of manganese dioxide to pseudo-boehmite is 1:5, the addition amount of the coal-based activated carbon is 0.5% of the sum of the mass of manganese dioxide and the mass of the pseudo-boehmite, and the addition amount of the deionized water 1 is 12.5% of the total mass.
Step 2: mixing deionized water 2, palladium acetate and molybdenum pentachloride, stirring at 40 ℃ until the mixture is completely dissolved, then adding a certain amount of potassium hypochlorite, and continuing stirring until the mixture is completely dissolved to obtain an impregnating solution, wherein the adding amount of the palladium acetate is 1% of the mass of the carrier, the molar ratio of the adding amount of the molybdenum pentachloride to the potassium hypochlorite to the palladium acetate is 10:1 and 5:1 respectively, and determining the using amount of the deionized water 2 by adopting an equal volume impregnation method;
step 3: and (3) dipping the carrier in the step (1) into the dipping liquid in the step (2), wherein the dipping process lasts for 12 hours, and after the dipping is finished, putting the material into a baking oven, and drying at 90 ℃ to constant weight to obtain the catalyst.
Example 7
A method for preparing a catalyst for synthesizing dimethyl carbonate, comprising the following steps:
step 1: adding manganese dioxide, pseudo-boehmite, wooden activated carbon and deionized water 1 into a kneader for kneading, pouring the materials into a strip extruder for strip extrusion after the kneading is finished, drying the extruded strips at 100 ℃, and calcining at 500 ℃ to obtain a carrier, wherein the mass ratio of the manganese dioxide to the pseudo-boehmite is 1:5, the addition amount of the wooden activated carbon is 0.5% of the sum of the mass of the manganese dioxide and the mass of the pseudo-boehmite, and the addition amount of the deionized water 1 is 12.5% of the total mass.
Step 2: mixing deionized water 2, palladium sulfate and tungsten chloride, stirring at 60 ℃ until the mixture is completely dissolved, adding a certain amount of sodium hypochlorite, and continuously stirring until the mixture is completely dissolved to obtain an impregnating solution, wherein the adding amount of the palladium sulfate is 0.1% of the mass of the carrier, the molar ratio of the adding amount of the tungsten chloride and the sodium hypochlorite to the palladium sulfate is 20:1 and 10:1 respectively, and determining the using amount of the deionized water 2 by adopting an equal volume impregnation method;
step 3: and (3) dipping the carrier in the step (1) into the dipping liquid in the step (2), wherein the dipping process lasts for 24 hours, and after the dipping is finished, putting the material into a baking oven, and drying at 120 ℃ to constant weight to obtain the catalyst.
Example 8
A method for preparing a catalyst for synthesizing dimethyl carbonate, comprising the following steps:
step 1: adding manganese dioxide, pseudo-boehmite, wooden activated carbon and deionized water 1 into a kneader for kneading, pouring the materials into a strip extruder for strip extrusion after the kneading is finished, drying the extruded strips at 100 ℃, and calcining at 700 ℃ to obtain a carrier, wherein the mass ratio of the manganese dioxide to the pseudo-boehmite is 1:10, the addition amount of the wooden activated carbon is 1% of the sum of the mass of the manganese dioxide and the mass of the pseudo-boehmite, and the addition amount of the deionized water 1 is 20% of the total mass.
Step 2: mixing deionized water 2, palladium nitrate and cobalt chloride, stirring at 40 ℃ until the mixture is completely dissolved, adding a certain amount of calcium hypochlorite, and continuously stirring until the mixture is completely dissolved to obtain an impregnating solution, wherein the adding amount of the palladium nitrate is 0.5% of the mass of the carrier, the molar ratio of the adding amount of the cobalt chloride and the calcium hypochlorite to the palladium nitrate is 10:1 and 5:1 respectively, and determining the using amount of the deionized water 2 by adopting an equal volume impregnation method;
step 3: and (3) dipping the carrier in the step (1) into the dipping liquid in the step (2), wherein the dipping process lasts for 2 hours, and after the dipping is finished, putting the material into a baking oven, and drying at 60 ℃ to constant weight to obtain the catalyst.
Example 9
A method for preparing a catalyst for synthesizing dimethyl carbonate, comprising the following steps:
step 1: adding manganese dioxide, pseudo-boehmite, wooden activated carbon and deionized water 1 into a kneader for kneading, pouring the materials into a strip extruder for strip extrusion after the kneading is finished, drying the extruded strips at 100 ℃, and calcining at 700 ℃ to obtain a carrier, wherein the mass ratio of the manganese dioxide to the pseudo-boehmite is 1:10, the addition amount of the wooden activated carbon is 1% of the sum of the mass of the manganese dioxide and the mass of the pseudo-boehmite, and the addition amount of the deionized water 1 is 20% of the total mass.
Step 2: mixing deionized water 2, palladium chloride and copper chloride, stirring at 60 ℃ until the mixture is completely dissolved, then adding a certain amount of calcium hypochlorite, and continuing stirring until the mixture is completely dissolved to obtain an impregnating solution, wherein the adding amount of the palladium chloride is 1% of the mass of the carrier, the molar ratio of the adding amount of the copper chloride and the calcium hypochlorite to the palladium chloride is 20:1 and 10:1 respectively, and determining the using amount of the deionized water 2 by adopting an equal volume impregnation method;
step 3: and (3) dipping the carrier in the step (1) into the dipping liquid in the step (2), wherein the dipping process lasts for 12 hours, and after the dipping is finished, putting the material into a baking oven, and drying at 90 ℃ to constant weight to obtain the catalyst.
Example 10
This example is a performance evaluation of the liquid-phase chlorine-free catalysts No. 1 to 9 prepared in examples 1 to 9 and the catalysts No. 1a, 1b and 1c prepared in comparative examples 1 to 3.
The synthesis reaction of the experimental case adopts a low-pressure fixed bed reactor, and adopts a gas phase method for CO coupling and regeneration. The prior process flow for synthesizing and preparing the dimethyl carbonate comprises the following specific steps:
(1) NO, O 2 Introducing anhydrous methanol into a packed tower respectively for reaction to obtain a component CH 3 ONO, NO and N 2 Wherein the reaction pressure is 0.6MPa, the reaction temperature is 20 ℃ and the space velocity is 2800h -1 ；NO、O 2 And anhydrous methanol in a molar ratio of 4.9:1:5, nitrogen being the balance gas, the volumes of which are CO and O 2 1.5 times the total volume. Wherein NO is in sufficient quantity and anhydrous methanol is in excess. The height of the packed tower is 1500mm, the diameter is 120+/-5 mm, the flow rate of the liquid phase is 50ml/min, the liquid phase is fed from the upper section of the packed tower and circulates from top to bottom, the gas phase is fed from the lower section of the packed tower, and the product is discharged from the middle part;
(2) Mixing the first mixed gas, CO and HCl gas, and introducing the mixed gas into a fixed bed reactor as raw material gas, wherein the pressure of a catalyst bed layer is 0.5Mpa, the temperature of a reaction bed layer is 125 ℃, and the volume space velocity is 3500h -1 The retention time is 1.5s, and finally the dimethyl carbonate product is obtained, wherein the intake gas comprises the following components in percentage by volume: CO 11.12%, N 2 57.68％、NO7.17％、CH 3 19.64% of ONO, wherein the fixed bed reactor is a tubular reactor loaded with a catalyst, the internal diameter is 50mm, the length is 500mm, the catalyst loading is 10ml, and the concentration of HCl gas is 50-500ppm.
(3) Gas phase component analysis
(4) The gas phase component analysis adopts an Shimadzu GC-2014C gas chromatograph for on-line analysis.
(5) Analysis of liquid phase Components
(6) Liquid phase product analysis of the reaction was also performed using Shimadzu GC-2014C with vaporization chamber.
(7) Coupling CO gas phase to CH 3 Calculation of catalyst performance evaluation for ONO synthesis of DMC shows:
(8) CO conversion (x) =converted CO (mol)/CO (mol) of feed x 100%
(9) DMC Selectivity(s) =amount of product DMC (mol)/amount of total product (mol). Times.100%
(10) Mass space time yield of DMC (sty) =weight of product DMC (g) ×product DMC content%/[ catalyst volume (L) ×time (h) ]×100%
(11) The evaluation time of the implementation cases is 500h
The results of the performance evaluation are shown in the following table:
according to the results of Table 1, the initial CO conversion was 25.23% -33.68% when DMC was synthesized using the methanol gas phase catalysts No. 1-9 prepared in examples 1-9; DMC selectivity from 90.23% to 98.21%; DMC space-time yield is 564.87-754.65g (g/Lcat.h), and CO conversion rate is 20.42% -31.69% after 500 h; DMC selectivity is 84.22% -96.10%; DMC space-time yield was 457.54-710.066g (g/Lcat.h).
From the two scanning electron microscope pictures shown in FIG. 4 and FIG. 5, the catalyst of example 1 had a microporous structure before and after evaluation, and FIG. 6 and FIG. 7 and FIG. 8 are EDS pictures of the catalyst of example 1. As shown in FIG. 6, example 1 contains C element, it was confirmed that the catalyst carrier of example 1 was prepared to contain activated carbon, a part of the activated carbon on the surface and inside was carbonized during calcination, and a large amount of heat and CO were generated during carbonization 2 The manganese dioxide and the alumina in the carrier are crosslinked and form a wide micropore structure, the impregnating solution can be perfectly impregnated into the pore structure of the carrier, and the manganese dioxide surrounds Pd through the micropore effect 2+ 、Cu 2+ Around, the positive effect generated avoids Pd 2+ 、Cu 2+ The catalyst life is longer because the catalyst is deactivated by reducing +2 to 0 in the reaction process, and the specific surface area of the carrier is greatly improved by the micropore structure, and the C remained in the pore structure of the carrier has strong adsorption effect on-OH bonds, so that methanol molecules are adsorbed in Pd in the pore structure of the carrier more easily 2+ The DMC is generated by carbonylation reaction under catalysis, so that the conversion rate of the catalyst is improved. The catalyst conversion in example 1 was evaluated over 500 hours and decreased by 4.81% and in comparative example 1a by 10.77%, so that the conversion in example 1 was higher and the life was longer.
On the other hand, the activated carbon in the catalyst carrier with a large number of micropore structures has an adsorption effect, can adsorb and prepare HCl gas added in the DMC reaction system to supplement Cl ions, can slow down the loss of Cl ions of palladium chloride and copper chloride, and can play a role in improving DMC selectivity, because the selectivity of the embodiment 1 is reduced by 3.91% and the selectivity of the comparative embodiment 1a is reduced by 25.17% after 500h evaluation
Example 1H is generated during DMC reaction in methanol preparation 2 O, add HCl and H 2 O can form a weak acid environment after contact, hypochlorite in the active component of the catalyst is combined with weak acid HCl to generate strong oxidizing property, and the synergistic effect between hypochlorite on the macroscopic surface of the carrier and manganese dioxide with a microscopic pore structure is Pd 2+ Provides complete oxidation environment and protects the active center Pd of the catalyst 2+ 、Cu 2+ Without reduction by feed gas CO, the conversion and selectivity of example 1 were reduced by 4.81% and 3.91% respectively, and the conversion and selectivity of comparative examples 1b and 1c were reduced by 10.49%, 12.47% and 9.67% and 21.60% respectively, as evaluated over 500h, which indicated that the catalyst of example 1 was higher in conversion and selectivity and longer in lifetime.
As can be seen from the evaluation results of example 1 and comparative example 1d, the catalyst conversion rate of example 1 was evaluated over 500 hours, and was reduced by 4.81%, the catalyst conversion rate of comparative example 1d was reduced by 20.03%, the catalyst conversion rate of selective example 1 was reduced by 3.91%, and the catalyst conversion rate of comparative example 1d was reduced by 18.97%, which fully demonstrates that the addition of HCl can make the catalyst conversion rate, selectivity higher and more stable, and the catalyst life longer.
FIGS. 9 and 10 are XPS spectra of the catalyst of example 1 and the catalyst of comparative example 1c, respectively, after 500h evaluation, it can be seen from FIG. 9 that the catalyst of example 1 has a higher strength Pd at 342ev after 500h 2+ Peak at 338ev with higher intensity Pd 4 + Pd at 335ev 0 The peak was very weak and FIG. 10, comparative example 1c, was a Pd having a relatively high intensity at 342ev 2+ Peak, pd at 335ev 0 The peaks are also very strong, which indicates that the Pd of comparative example 1c has been reduced to the 0-valence state for the most part, which is also the main reason for the low selectivity of the conversion of the comparative example, while the reduction of the active center Pd to the 0-valence state for the most part indicates a lower lifetime.
Fig. 11 shows XRD spectra before (lower curve) and after (upper curve) evaluation of the catalyst of example 1, respectively, and it can be seen from the spectra that the XRD characteristic peak position before and after the evaluation does not change, but the peak intensity is reduced to some extent, which indicates that the evaluation process has an influence on the crystallinity of the catalyst, but the influence is not great, that is, the catalyst has a longer service life.
Relational terms such as "first" and "second", and the like may be used solely to distinguish one element from another element having the same name, without necessarily requiring or implying any actual such relationship or order between such elements.
The foregoing has described exemplary embodiments of the invention, it being understood that any simple variations, modifications, or other equivalent arrangements which would not unduly obscure the invention may be made by those skilled in the art without departing from the spirit of the invention.
Claims (10)
1. A catalyst for synthesizing dimethyl carbonate by methanol gas phase, which is characterized by comprising a carrier and an active component, wherein the carrier comprises a catalyst carrier and an active component;
the carrier comprises manganese dioxide, pseudo-boehmite and active carbon, wherein the mass ratio of the manganese dioxide to the pseudo-boehmite is 1 (1-10), and the mass of the active carbon is 0.1-2.5% of the sum of the mass of the manganese dioxide and the mass of the pseudo-boehmite;
the active components comprise soluble palladium salt, chloride salt and hypochlorite, wherein the mass of the soluble palladium salt is 0.1-1% of that of the carrier, the molar ratio of the chloride salt to the soluble palladium salt is (5-20): 1, and the molar ratio of the hypochlorite to the soluble palladium salt is (1-10): 1;
the chloride salt is one or more of copper chloride, manganese chloride, chromium chloride, nickel chloride, vanadium chloride, molybdenum pentachloride, tungsten chloride and cobalt chloride.
2. The catalyst for vapor phase synthesis of dimethyl carbonate from methanol according to claim 1, wherein the soluble palladium salt is one or more of palladium chloride, palladium nitrate, palladium acetate, palladium sulfate; the hypochlorite is one or more of potassium hypochlorite, sodium hypochlorite, calcium hypochlorite, lithium hypochlorite and copper hypochlorite.
3. A method for preparing a catalyst for synthesizing dimethyl carbonate by methanol gas phase, which is characterized by comprising the following steps:
step 1, evenly mixing manganese dioxide, pseudo-boehmite, active carbon and first deionized water to obtain a first material, granulating the first material to obtain first particles, drying the first particles, and calcining at 200-500 ℃ to obtain a carrier;
in the first material, the mass ratio of manganese dioxide to pseudo-boehmite is 1 (1-10), and the mass of the activated carbon is 0.1% -5% of the sum of the mass of manganese dioxide and pseudo-boehmite; the weight of the deionized water accounts for 4.5% -20% of that of the first material;
step 2, dispersing soluble palladium salt, chloride salt and hypochlorite in second deionized water to obtain an impregnating solution;
the mass of the soluble palladium salt is 0.1-1% of the mass of the carrier, the molar ratio of the chloride salt to the soluble palladium salt is (5-20): 1, and the molar ratio of the hypochlorite salt to the soluble palladium salt is (1-10): 1;
the second deionized water amount is the maximum absorption mass of the carrier to the deionized water in the step 1;
step 3, dipping the carrier obtained in the step 1 into the dipping liquid obtained in the step 2 for 2-24 hours to obtain a dipped carrier; drying the impregnated carrier to constant weight to obtain the catalyst for synthesizing the dimethyl carbonate by using the methanol gas phase;
the chloride salt is one or more of copper chloride, manganese chloride, chromium chloride, nickel chloride, vanadium chloride, molybdenum pentachloride, tungsten chloride and cobalt chloride.
4. The method according to claim 3, wherein in the step 1, the drying temperature of the first particles is 100 ℃; the mass of the activated carbon in the carrier after the calcination process is completed is less than 50% of the mass of the activated carbon before the calcination.
5. The method according to claim 3, wherein the step 1 of uniformly mixing manganese dioxide, pseudo-boehmite, activated carbon and deionized water is performed by a kneader; and granulating the first material by adopting a strip extruder.
6. The preparation method of claim 3, wherein in the step 2, soluble palladium salt, chloride salt and hypochlorite are stirred and dispersed in a solvent at 20-60 ℃ to obtain an impregnating solution, and the soluble palladium salt is one or more of palladium chloride, palladium nitrate, palladium acetate and palladium sulfate; the hypochlorite is one or more of potassium hypochlorite, sodium hypochlorite, calcium hypochlorite, lithium hypochlorite and copper hypochlorite.
7. The method of claim 3, wherein the activated carbon is one or more of coconut shell activated carbon powder, coal-based activated carbon powder, or wood-based activated carbon powder.
8. A method according to claim 3, wherein in step 3, the impregnated support is dried to constant weight at 60-120 ℃.
9. A method for synthesizing dimethyl carbonate, which is characterized in that methyl nitrite, CO and HCl are adopted as raw materials in the synthesis method, and the dimethyl carbonate is obtained through reaction synthesis under the action of the catalyst for synthesizing the dimethyl carbonate by methanol gas phase, wherein the catalyst is prepared by the preparation method according to any one of claims 3 to 8;
the synthesis temperature is 110-130 ℃, and the volume airspeed is 1700-2400 h -1 The molar ratio of methyl nitrite to CO is 1-1.5: 1, a step of;
the concentration of the HCl gas is 50-500ppm.
10. The method for synthesizing dimethyl carbonate according to claim 9, characterized in thatThe methyl nitrite adopts NO and O 2 Anhydrous methanol is used as a raw material, nitrogen is used as balance gas, and the reaction is carried out at the reaction temperature of 110-130 ℃ and the reaction pressure of 0.3-0.7 MPa;
the NO and O 2 The molar ratio of the anhydrous methanol is (2-3): 1-2): 5-10; the volume of nitrogen is CO and O 2 1 to 5 times of the sum of the volumes.
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| CN112823879A (en) * | 2019-11-21 | 2021-05-21 | 中国科学院大连化学物理研究所 | Application of cerium-based catalyst in preparation of dimethyl carbonate through direct conversion of carbon dioxide and methanol |
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| CN112823879A (en) * | 2019-11-21 | 2021-05-21 | 中国科学院大连化学物理研究所 | Application of cerium-based catalyst in preparation of dimethyl carbonate through direct conversion of carbon dioxide and methanol |
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