CN114308117A - Method for in-situ iron removal of titanium-silicon molecular sieve - Google Patents
Method for in-situ iron removal of titanium-silicon molecular sieve Download PDFInfo
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Abstract
The invention provides an in-situ iron removal method for a titanium-silicon molecular sieve, which comprises the following steps: feeding the washing solution into a reaction device filled with the iron-inactivated titanium-silicon molecular sieve for a first-stage reaction, and discharging the washing solution after the first-stage reaction; feeding the acidic solution into the reaction device at the flow rate of 0.2-1.8BV/h, carrying out a second-stage reaction with the iron-deactivated titanium-silicon molecular sieve at the temperature of 20-150 ℃ and under the pressure of 0-2.8MPa, and discharging the acidic solution after the second-stage reaction; feeding the activated solution into the reaction device for flushing to obtain a regenerated titanium silicalite molecular sieve; according to the method, organic macromolecules in a pore channel are removed through a washing solution, iron enriched on a catalyst frame through chemical and physical adsorption in the process of pressure washing reaction by an acid solution is concentrated, the content of the regenerated catalyst iron is obviously reduced, the activity of the regenerated catalyst iron is equal to that of a fresh catalyst, and the method realizes in-situ iron removal of the titanium-silicon molecular sieve, does not need to be disassembled, and is convenient to operate.
Description
Technical Field
The invention belongs to the technical field of catalyst regeneration, and particularly relates to an in-situ iron removal method for a titanium-silicon molecular sieve.
Background
Epoxy chloropropane is also named epichlorohydrin, is an important organic chemical raw material intermediate, has wide application, and epoxy resin prepared from epoxy chloropropane has the characteristics of strong viscosity, chemical corrosion resistance, low shrinkage, good chemical stability, high impact strength, excellent dielectric property and the like, and is applied to coatings, adhesives, reinforcing materials, wind power blades, new energy materials and the like. The method for directly epoxidizing chloropropene to generate epichlorohydrin is used as a new green production process, can avoid environmental pollution caused by the saponification process of dichloropropanol by the traditional method, and meets the requirements of sustainable development chemistry and environment-friendly chemistry. Therefore, research and optimization of direct epoxidation process is still the mainstream trend in the future.
In the preparation process of epichlorohydrin, with the accumulation of catalytic times, the titanium-silicon molecular sieve catalyst is deactivated due to impurity poisoning, loss of self components and the like, and the deactivation of the titanium-silicon molecular sieve catalyst can be divided into temporary deactivation and permanent deactivation. The temporary inactivation is caused by the generation of macromolecular organic matters in the reaction process which block the pore channels of the molecular sieve; the permanent deactivation is caused by the reduction of the catalyst performance due to the flow rate of the framework titanium of the molecular sieve part. Meanwhile, in the long-time continuous reaction process, the catalyst can adsorb iron in the reaction liquid, and the enrichment of iron on the catalyst can influence the reaction activity of the catalyst.
CN109126864A discloses a regeneration method of deactivated titanium silicalite molecular sieve catalyst, which is a method of uniformly mixing deactivated titanium silicalite molecular sieve with alkaline compound solution, heat-treating, mixing with acidic solution, and heat-treating, wherein the method needs to disassemble the catalyst, and comprises the steps of drying, roasting, etc., the operation is complicated, and the catalyst is easy to be broken in the regeneration treatment process, which results in loss.
CN105665002A discloses a regeneration method of deactivated titanium silicalite molecular sieve catalyst, comprising the following steps: mixing the deactivated titanium-silicon molecular sieve catalyst with an acidic solution containing a cation trapping agent, stirring at 20-120 ℃ for 1-10 hours, washing to be neutral, and drying to obtain an acid-treated titanium-silicon molecular sieve catalyst; mixing the titanium silicalite molecular sieve catalyst after acid treatment with an alkaline solution, and reacting for 0.55 day at the temperature of 150 ℃ and 190 ℃ under autogenous pressure to obtain the titanium silicalite molecular sieve catalyst after alkali treatment: and filtering the titanium silicalite molecular sieve catalyst after alkali treatment, washing until the pH value is 7-10, and drying and roasting to obtain the regenerated titanium silicalite molecular sieve catalyst. The regeneration method needs to disassemble the catalyst in the device, the steps are complicated, and the regenerated titanium silicalite molecular sieve catalyst is easy to damage after being repeatedly roasted and has short service life.
CN110152726A discloses a regeneration method of a deactivated titanium-silicon molecular sieve catalyst in a process of producing epichlorohydrin by a hydrogen peroxide direct oxidation method, the deactivated titanium-silicon molecular sieve catalyst in the process is subjected to acid washing treatment to wash out metal ion impurities, byproducts blocking the inner pore channels of the catalyst are decomposed into micromolecular halohydrocarbon and alcohols, and then the micromolecular halohydrocarbon and the alcohols are dissolved by an organic solvent to separate out a catalyst system, and the catalyst regeneration is realized
In order to improve the regeneration effect of the deactivated titanium silicalite molecular sieve for producing epichlorohydrin, a titanium silicalite molecular sieve regeneration iron removal process needs to be further improved.
Disclosure of Invention
The invention provides a method for in-situ iron removal of a titanium-silicon molecular sieve, which aims at solving the problems that in the prior art, in the continuous reaction process of epoxy chloropropane, dissolved impurity iron is enriched on a catalyst to cause continuous reduction of the activity of the catalyst, and in the method for regenerating the catalyst, the operation of a high-temperature roasting method is complex, the operation time of a solvent washing regeneration method is long, the regeneration effect is not ideal and the like.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides an in-situ iron removal method for a titanium-silicon molecular sieve, which comprises the following steps:
(1) feeding the washing solution into a reaction device filled with the iron-inactivated titanium-silicon molecular sieve for a first-stage reaction, and discharging the washing solution after the first-stage reaction;
(2) feeding the acidic solution into the reaction device at the flow rate of 0.2-1.8BV/h, carrying out a second-stage reaction with the iron-deactivated titanium-silicon molecular sieve at the temperature of 20-150 ℃ and under the pressure of 0-2.8MPa, and discharging the acidic solution after the second-stage reaction;
(3) and feeding the activated solution into the reaction device for flushing to obtain the regenerated titanium silicalite molecular sieve.
The method for in-situ iron removal of the titanium-silicon molecular sieve adopts in-situ operation, firstly uses a washing solution to react to remove reaction byproducts blocked in a molecular sieve pore passage, then uses an acid solution to wash iron enriched on a catalyst frame through chemical and physical adsorption in the reaction process under pressure, and removes iron ions adsorbed on the catalyst in situ, thereby fully exposing the active site of the catalyst, improving the activity of the catalyst, having no need of disassembly in the catalyst regeneration process, having simple process, convenient operation and effectively removing the reaction byproducts in the catalyst.
The titanium silicalite molecular sieve is not particularly limited, and can be treated aiming at deactivated titanium silicalite molecular sieves commonly encountered by a person skilled in the art, and can also be treated aiming at improved titanium silicalite molecular sieves, such as TS-1 molecular sieves or improved TS-1 molecular sieves disclosed in CN 112408414A.
Preferably, the content of the iron element in the iron-deactivated titanium-silicon molecular sieve is 1000-1800 ppm.
Preferably, step (1) is preceded by: the organic solvent is sent into a reaction device to take out and flush the reaction liquid, and is discharged when the concentration of the original reaction raw material in the organic solvent is lower than a limit value.
Preferably, the limit is a concentration of the original reaction raw material in the organic solvent of 0 to 900ppm, preferably 200 to 800ppm, and may be, for example, 100ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm or 900ppm, but is not limited to the recited values, and other values not recited in the numerical range are also applicable.
Preferably, the original reaction feedstock comprises chloropropene;
preferably, the organic solvent in step (1) includes any one or a combination of two or more of ethanol, methanol, toluene, isopropanol, acetone, n-butanol or benzene, wherein typical but non-limiting combinations are a combination of ethanol and methanol, a combination of ethanol and toluene, a combination of methanol and methanol, a combination of isopropanol and acetone, and the like, but is not limited to the listed combinations, and other combinations not listed within the scope are also applicable.
Preferably, the organic solvent is fed to the fixed bed at a flow rate of 0.15 to 1.6BV/h, which may be, for example, 0.15BV/h, 0.2BV/h, 0.3BV/h, 0.5BV/h, 0.8BV/h, 1.0BV/h, 1.2BV/h, 1.3BV/h, 1.5BV/h or 1.6BV/h, but is not limited to the values recited, and other values not recited in this range are equally applicable.
Preferably, the temperature of the washing is 10-30 ℃, for example 10 ℃, 12 ℃, 13 ℃, 15 ℃, 18 ℃, 20 ℃, 22 ℃, 23 ℃, 25 ℃, 28 ℃ or 30 ℃, but is not limited to the recited values, and other values not recited in the range of values are equally applicable.
Preferably, the pressure of the flushing is 0-2.8MPa, and may be, for example, 0.1MPa, 0.2MPa, 0.3MPa, 0.5MPa, 0.8MPa, 1.0MPa, 1.2MPa, 1.5MPa, 1.8MPa, 2.0MPa, 2.2MPa, 2.5MPa or 2.8MPa, but is not limited to the values listed, and other values not listed within the range of values are equally applicable.
Preferably, the rinsing time is 12-28h, for example 12h, 15h, 18h, 20h, 21h, 24h or 28h, but not limited to the values listed, and other values not listed in this range of values are equally applicable.
Preferably, the washing solution in step (2) comprises an organic liquid and/or water, preferably an organic liquid.
Preferably, the organic liquid includes any one or a combination of two or more of methanol, ethanol, toluene, isopropanol, acetone, n-butanol or benzene, wherein typical but non-limiting combinations are a combination of methanol and ethanol, a combination of methanol and toluene, a combination of toluene and ethanol, a combination of methanol and isopropanol, a combination of methanol and acetone, and the like, but is not limited to the listed combinations, and other combinations not listed within the scope are equally applicable.
The invention uses the washing solution, according to the principle of similarity and compatibility, the organic solvent is used for washing and reacting under the conditions of high temperature and high pressure, most organic macromolecular byproducts blocking the inner holes of the catalyst can be removed, and most active center positions of the catalyst are released.
Preferably, the flow rate of the scrubbing solution to the reaction apparatus containing the iron-deactivated titanium silicalite molecular sieves is 0.2 to 1.8BV/h, for example, 0.2BV/h, 0.5BV/h, 1.0BV/h, 1.5BV/h or 1.8BV/h, but is not limited to the values recited, and other values not recited in this range are equally applicable.
Preferably, the first-stage reaction comprises a first-stage reaction after temperature rise and then temperature reduction.
Preferably, the rate of temperature increase is 0.2-1.8 deg.C/min, and may be, for example, 0.2 deg.C/min, 0.3 deg.C/min, 0.5 deg.C/min, 0.8 deg.C/min, 1.0 deg.C/min, 1.2 deg.C/min, 1.5 deg.C/min, or 1.8 deg.C/min, but is not limited to the values recited, and other values not recited within the range of values are equally applicable.
Preferably, the temperature of the end point of the temperature increase is 120-180 ℃, and may be, for example, 120 ℃, 130 ℃, 150 ℃, 160 ℃ or 180 ℃, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
Preferably, the rate of cooling is 0.2-1.8 deg.C/min, and may be, for example, 0.2 deg.C/min, 0.3 deg.C/min, 0.5 deg.C/min, 0.8 deg.C/min, 1.0 deg.C/min, 1.2 deg.C/min, 1.5 deg.C/min, or 1.8 deg.C/min, but is not limited to the values recited, and other values not recited within the range of values are equally applicable.
Preferably, the reaction time is 24-96h, such as 24h, 30h, 36h, 40h, 48h, 56h, 72h, 80h or 96h, but not limited to the recited values, and other values not recited in the range of values are also applicable.
Preferably, the pressure of the first stage reaction is 0 to 2.4MPa, and may be, for example, 0.1MPa, 0.5MPa, 1.0MPa, 1.5MPa, 1.6MPa, 1.8MPa, 2.0MPa or 2.4MPa, but is not limited to the values recited, and other values not recited within the range of values are also applicable.
Preferably, the acidic solution in step (3) comprises an inorganic acid and/or an organic acid.
Preferably, the acidic solution comprises any one or a combination of two or more of hydrochloric acid, nitric acid, citric acid, oxalic acid, acetic acid, acrylic acid, isobutyric acid or lactic acid, wherein typical but non-limiting combinations are combinations of hydrochloric acid and nitric acid, hydrochloric acid and citric acid, citric acid and nitric acid, hydrochloric acid and oxalic acid, oxalic acid and nitric acid, acetic acid and nitric acid, hydrochloric acid and isobutyric acid, hydrochloric acid and lactic acid, acrylic acid and isobutyric acid, and the like, but is not limited to the listed combinations, and other combinations not listed within the scope are equally suitable.
Preferably, the acidic solution further comprises any one or a combination of two or more of methanol, ethanol, acetonitrile, isopropanol, acetone, or water, wherein typical but non-limiting combinations are a combination of methanol and ethanol, a combination of methanol and acetonitrile, a combination of acetonitrile and ethanol, a combination of methanol and isopropanol, a combination of isopropanol and ethanol, a combination of acetone and water, and the like, but is not limited to the listed combinations, and other combinations not listed within this range are equally suitable.
The acidic solution needs to have a certain dissolving capacity for iron, and complex does not occur, and further the activity of the catalyst is damaged, so the selection of the solution also has a certain necessity.
Preferably, the amount of inorganic and/or organic acid in the acidic solution is 0.5 to 18 wt.%, for example 0.5 wt.%, 1 wt.%, 2 wt.%, 5 wt.%, 8 wt.%, 10 wt.%, 15 wt.% or 18 wt.%, but is not limited to the recited values, and other values not recited within this range are equally applicable.
The use of a certain concentration of acid not only removes the excess adsorbed iron on the catalyst framework, but also ensures that the acid concentration is moderate, does not react excessively with the catalyst to dissolve the framework and change the microenvironment around the framework. The concentration of the acid ranges from 0.5 to 18% by weight.
Preferably, the second stage reaction time is 1-48h, for example 1h, 2h, 5h, 10h, 12h, 20h, 24h, 36h or 48h, but not limited to the recited values, and other values not recited in the range of values are also applicable.
The iron element is enriched on the outer surface of the frame to form accumulation, which can affect the activity of active center titanium, causing the activity of the titanium-silicon molecular sieve to be attenuated rapidly, and the acidic solution is adopted for flushing, so that the metal enriched on the catalyst frame by chemical and physical adsorption in the catalytic reaction process can be further removed, and the purpose of regeneration is achieved.
Preferably, the activating solution in the step (4) comprises hydrogen peroxide.
Preferably, the concentration of hydrogen peroxide is 3 to 15 wt%, for example, 3 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 10 wt%, 12 wt%, 13 wt% or 15 wt%, but is not limited to the recited values, and other values not recited within the range of values are also applicable.
Preferably, the activating solution is fed to the reactor at a flow rate of 0.2 to 1.5BV/h, such as 0.2BV/h, 0.3BV/h, 0.5BV/h, 0.8BV/h, 1.0BV/h, 1.2BV/h or 1.5BV/h, but not limited to the values recited, and other values not recited in this range are equally applicable.
Preferably, the temperature of the washing in step (4) is 25-70 ℃, for example 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃ or 70 ℃, but is not limited to the recited values, and other values not recited in the range of values are also applicable.
Preferably, the pressure of the flushing in step (4) is 0-1MPa, and may be, for example, 0.1MPa, 0.2MPa, 0.3MPa, 0.5MPa, 0.8MPa or 1MPa, but is not limited to the values listed, and other values not listed in the range of values are equally applicable.
Preferably, the rinsing time in step (4) is 1-48h, for example, 1h, 2h, 5h, 10h, 12h, 20h, 24h, 36h or 48h, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
As a preferred technical solution of the present invention, the method comprises the steps of:
(1) feeding the organic solvent into a reaction device at a flow rate of 0.5-1.6BV/h to take out the reaction liquid, flushing the reaction liquid at 10-30 ℃ and 0-2.8MPa for 12-28h, and discharging the reaction liquid when the concentration of the reaction liquid is lower than 0-900 ppm; feeding the washing solution into a reaction device filled with the iron-deactivated titanium-silicon molecular sieve at the flow rate of 0.2-1.8BV/h, heating to 180 ℃ at the speed of 0.2-1.8 ℃/min, carrying out a first-stage reaction at 0-2.4MPa, cooling, and then discharging the washing solution;
(2) feeding the acid solution into the reaction device at the flow rate of 0.2-1.8BV/h, carrying out a second-stage reaction for 1-48h at the temperature of 20-150 ℃ and under the pressure of 0-2.8MPa, and then discharging the acid solution;
(3) the activating solution is sent into the reaction device at the flow rate of 0.2-1.5BV/h, and the regenerated titanium-silicon molecular sieve is obtained after flushing for 1-48h at the temperature of 25-70 ℃.
Compared with the prior art, the invention has the beneficial effects that:
(1) the in-situ iron removal method for the titanium-silicon molecular sieve provided by the invention can remove macromolecular byproducts blocking the pore channel of the catalyst, and can also remove iron adsorbed on the catalyst, wherein the iron impurity content of the catalyst before regeneration is more than or equal to 1360ppm, the iron impurity content after regeneration is less than or equal to 582ppm, and the iron content is remarkably reduced;
(2) the method for in-situ iron removal of the titanium-silicon molecular sieve provided by the invention has a good regeneration effect on the titanium-silicon molecular sieve, the average conversion rate of the catalyst regenerated by adopting a preferred scheme to hydrogen peroxide is more than or equal to 93.25%, the selectivity to epoxy chloropropane is more than or equal to 94.08%, the average yield of the catalytic epoxy chloropropane is more than or equal to 90.26%, the stable operation time after regeneration is more than or equal to 1380h, and the regenerated catalyst has a stable operation effect;
(3) the in-situ iron removal method for the titanium-silicon molecular sieve provided by the invention adopts in-situ online regeneration, does not need to be disassembled, and is convenient to operate.
Detailed Description
For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
The technical solution of the present invention is further explained by the following embodiments.
In one embodiment, the invention provides a method for in-situ iron removal of a titanium-silicon molecular sieve, which comprises the following steps:
(1) feeding the organic solvent into a reaction device at a flow rate of 0.5-1.6BV/h to take out the reaction liquid, flushing the reaction liquid at 10-30 ℃ and 0-2.8MPa for 12-28h, and discharging the reaction liquid when the concentration of the reaction liquid is lower than 0-800 ppm; feeding the washing solution into a reaction device filled with the iron-deactivated titanium-silicon molecular sieve at the flow rate of 0.2-1.8BV/h, heating to 120-180 ℃ at the speed of 0.2-1.8 ℃/min, carrying out a first-stage reaction at 0-2.4MPa for 24-96h, cooling, and then discharging the washing solution; (2) feeding the acid solution into the reaction device at the flow rate of 0.2-1.8BV/h, carrying out a second-stage reaction for 1-48h at the temperature of 20-150 ℃ and under the pressure of 0-2.8MPa, and then discharging the acid solution; (3) the activating solution is sent into the reaction device at the flow rate of 0.2-1.5BV/h, and the washing is carried out for 1-48h at the temperature of 25-70 ℃ and under the pressure of 0-1MPa, so as to obtain the regenerated titanium-silicon molecular sieve.
Wherein the organic solvent comprises one or a combination of at least two of ethanol, methanol, toluene, isopropanol, acetone, n-butanol, benzene or water; the washing solution comprises any one or combination of at least two of methanol, ethanol, toluene, isopropanol, acetone, n-butanol or benzene; the acid solution comprises any one or the combination of more than two of hydrochloric acid, nitric acid, citric acid, oxalic acid, acetic acid, acrylic acid, isobutyric acid or lactic acid, the concentration of the organic acid and/or the inorganic acid is 0.5 to 18 weight percent, and the acid solution also comprises any one or the combination of more than two of methanol, ethanol, acetonitrile, isopropanol, acetone or water; the activating solution comprises 3-15 wt% of hydrogen peroxide.
It is understood that processes or substitutions and variations of conventional data provided by embodiments of the present invention are within the scope and disclosure of the present invention. The following specific examples are given by way of example of conventional TS-1 molecular sieves.
Example 1
The embodiment provides an in-situ iron removal method for a titanium-silicon molecular sieve, which comprises the following steps:
(1) feeding acetone into a reaction device at the flow rate of 1.2BV/h to take out the reaction liquid, flushing the reaction liquid at 15 ℃ and 0.3MPa for 12h, and discharging the acetone when the concentration of chloropropene in the acetone is lower than 500 ppm; feeding the methanol/toluene (toluene content is 20 wt%) solution into a reaction device filled with the iron-deactivated titanium-silicon molecular sieve at the flow rate of 0.5BV/h, heating to 120 ℃ at the speed of 1.8 ℃/min, carrying out a first-stage reaction at 0.3MPa for 48h, cooling, and then discharging the washing solution; (2) an acid solution of 35% methanol containing 15 wt% nitric acid and 50% water was fed into the reaction apparatus at a flow rate of 1BV/h, and a second-stage reaction was carried out at 30 ℃ and 1MPa for 24 hours, followed by discharging the acid solution; (3)5 wt% hydrogen peroxide is fed into the reaction device at the flow rate of 1BV/h, and the regenerated titanium-silicon molecular sieve is obtained after 24h flushing at 35 ℃ and 0.3 MPa.
Example 2
The embodiment provides an in-situ iron removal method for a titanium-silicon molecular sieve, which comprises the following steps:
(1) feeding ethanol into a reaction device at a flow rate of 0.5BV/h to take out reaction liquid, flushing the reaction liquid at 10 ℃ and 0.6MPa for 10h, and discharging the reaction liquid when the concentration of chloropropene in the ethanol is lower than 200 ppm; feeding a methanol/benzene (benzene content is 30 wt%) solution into a reaction device filled with an iron-deactivated titanium-silicon molecular sieve at the flow rate of 0.6BV/h, heating to 150 ℃ at the speed of 1 ℃/min, carrying out a first-stage reaction at 0.6MPa for 24h, cooling, and then discharging the washing solution; (2) feeding an acidic solution containing 5 wt% of citric acid and 95 wt% of methanol into the reaction device at a flow rate of 1.5BV/h, carrying out a second-stage reaction at 50 ℃ and 0.5MPa for 48h, and then discharging the acidic solution; (3)3 wt% hydrogen peroxide is fed into the reaction device at the flow rate of 0.5BV/h, and the regenerated titanium-silicon molecular sieve is obtained after 36h flushing at 45 ℃ and 0.3 MPa.
Example 3
The embodiment provides an in-situ iron removal method for a titanium-silicon molecular sieve, which comprises the following steps:
(1) feeding methanol into a reaction device at a flow rate of 0.8BV/h to take out reaction liquid, flushing the reaction liquid at 20 ℃ and 1MPa for 12h, and discharging the reaction liquid when the concentration of chloropropene in the methanol is lower than 100 ppm; feeding the methanol/isopropanol (isopropanol content is 10 wt%) solution into a reaction device filled with the iron-deactivated titanium-silicon molecular sieve at the flow rate of 0.8BV/h, heating to 160 ℃ at the speed of 5 ℃/min, carrying out a first-stage reaction at 1MPa for 36h, cooling, and then discharging the washing solution; (2) feeding an acidic solution containing 3 wt% hydrochloric acid and 97 wt% water into the reaction device at a flow rate of 1BV/h, carrying out a second-stage reaction at 80 ℃ and 0.3MPa for 16h, and then discharging the acidic solution; (3)8 wt% hydrogen peroxide is fed into the reaction device at the flow rate of 0.3BV/h, and the regenerated titanium-silicon molecular sieve is obtained after 24h flushing at the temperature of 40 ℃ and the pressure of 0.3 MPa.
Example 4
The embodiment provides an in-situ iron removal method for a titanium-silicon molecular sieve, which comprises the following steps:
(1) feeding isopropanol into a reaction device at the flow rate of 1.2BV/h to take out reaction liquid, flushing the reaction liquid at the temperature of 24 ℃ and the pressure of 0.3MPa for 30h, and discharging the reaction liquid when the concentration of chloropropene in the isopropanol is lower than 200 ppm; feeding the ethanol/isopropanol (the content of isopropanol is 30 wt%) solution into a reaction device filled with the iron-deactivated titanium-silicon molecular sieve at the flow rate of 0.5BV/h, heating to 140 ℃ at the speed of 4 ℃/min, carrying out a first-stage reaction for 18h under the pressure of 0.3MPa, cooling, and then discharging the washing solution; (2) feeding an acidic solution containing 8 wt% of lactic acid and 92 wt% of water into the reaction device at a flow rate of 0.8BV/h, carrying out a second-stage reaction at 10 ℃ and 1.2MPa for 36h, and then discharging the acidic solution; (3) and (3) feeding 10 wt% of hydrogen peroxide into the reaction device at the flow rate of 1BV/h, and flushing for 24h at 45 ℃ and 0.5MPa to obtain the regenerated titanium-silicon molecular sieve.
Example 5
The embodiment provides an in-situ iron removal method for a titanium-silicon molecular sieve, which comprises the following steps:
(1) feeding n-butanol into a reaction device at a flow rate of 1BV/h to take out reaction liquid, washing at 24 ℃ for 30h under 0.1MPa, and discharging when the concentration of chloropropene in the n-butanol is lower than 200 ppm; feeding a n-butyl alcohol/benzene (benzene content is 30 wt%) solution into a reaction device filled with an iron-deactivated titanium-silicon molecular sieve at the flow rate of 1BV/h, heating to 200 ℃ at the speed of 3 ℃/min, carrying out a first-stage reaction for 10h under 0.3MPa, cooling, and then discharging the washing solution; (2) feeding an acidic solution containing 10 wt% of acetic acid and 90 wt% of acetone into the reaction device at a flow rate of 1BV/h, carrying out a second-stage reaction at 60 ℃ and 0.3MPa for 36h, and then discharging the acidic solution; (3)1 wt% hydrogen peroxide is fed into the reaction device at the flow rate of 1BV/h, and the regenerated titanium-silicon molecular sieve is obtained after 48h flushing at the temperature of 60 ℃ and the pressure of 0.1 MPa.
Example 6
Substantially the same as in example 1 except that in step (2), the concentration of nitric acid was 23 wt%.
Example 7
The method is basically the same as that of example 1, except that in step (3), the concentration of hydrogen peroxide is 15 wt%.
Comparative example 1
Essentially the same procedure as in example 1, except that the two-stage reaction was not carried out using an acidic solution, and rinsing was not carried out using an active solution.
Comparative example 2
And (3) testing a fresh TS-1 titanium silicalite molecular sieve.
The evaluation methods of the catalysts in examples 1 to 7 and comparative examples 1 to 2 were as follows:
20g of catalyst is loaded into a tubular reactor with the inner diameter of 10 mm, and then 50% of hydrogen peroxide, chloropropene and methanol are added according to the weight ratio of hydrogen peroxide: chloropropene: methanol molar ratio equal to 1: 3: 10, total liquid mass airspeed 6h-1And (3) feeding the titanium silicalite molecular sieve catalyst bed from the bottom of the tubular reactor, controlling the temperature of the catalyst bed to be 40 ℃ in a water bath, controlling the reaction pressure to be 2MPa, sampling every two hours, analyzing the conversion rate of hydrogen peroxide, the yield and the selectivity of propylene oxide on line, and evaluating the activity and the service life of the catalyst. The hydrogen peroxide conversion is less than 90%, i.e. the catalyst is considered to be deactivated and needs to be regenerated.
The parameters of the catalysts of examples 1-7 and comparative examples 1-2 are shown in Table 1:
TABLE 1
In Table 1 "-" indicates that there is no data on the iron content of the catalyst before regeneration because it is fresh molecular sieve that has not been used, and the iron content of the fresh molecular sieve is taken as the iron content of the catalyst after regeneration.
From the data in table 1 we can see that:
(1) the average conversion rate of the titanium silicalite molecular sieves obtained by regeneration in the embodiments 1-5 to hydrogen peroxide is more than or equal to 93.25%, the selectivity to epoxy chloropropane is more than or equal to 94.08%, the average yield of the catalytic epoxy chloropropane is more than or equal to 90.26%, the stable operation time of the regenerated epoxy chloropropane is more than or equal to 1380h, and the stable operation time of the fresh catalyst in the comparative example 2 is 1700h, which proves that the regenerated catalyst has stable operation effect; the content of iron impurities in the catalyst before regeneration is more than or equal to 1360ppm, the content of iron impurities after regeneration is less than or equal to 582ppm, and the content of iron is obviously reduced, wherein the content of iron impurities after regeneration is less than or equal to 364ppm by adopting the preferred schemes of examples 1-3 and example 5, which proves that the method provided by the invention can effectively remove the iron impurities and restore the catalytic effect after the regeneration of the iron-deactivated titanium-silicon molecular sieve;
(2) it can be seen from the combination of example 1 and example 6 that the concentration of nitric acid in the regeneration of example 1 is 15 wt%, compared with the concentration of nitric acid in example 6 of 23 wt%, the operation time of the titanium silicalite molecular sieve obtained in the regeneration of example 1 is 1380h, and the average conversion rate of hydrogen peroxide reaches 98.68%, while the operation time of the titanium silicalite molecular sieve in example 6 after regeneration is 892h, and the average conversion rate of hydrogen peroxide is 93.07%; therefore, the invention utilizes 0.5-18 wt% acid solution to remove the metal impurities blocking the pore channel, the framework of the invention can not be damaged, and the best dissolution effect can be achieved, thereby obtaining better regeneration effect;
(3) it can be seen from the combination of example 1 and example 7 that, the concentration of hydrogen peroxide in the regeneration of example 1 is 5 wt%, compared with the concentration of hydrogen peroxide of example 7 being 15 wt%, the operation time of the titanium silicalite molecular sieve obtained by the regeneration of example 1 is 1380h, the average conversion rate of hydrogen peroxide reaches 98.68%, while the operation time of the titanium silicalite molecular sieve after the regeneration of example 7 is only 1327h, and the average conversion rate of hydrogen peroxide is only 94.83%; therefore, the invention utilizes 3-15 wt% hydrogen peroxide solution to wash the impurity ions remained on the surface, thereby obtaining better regeneration effect;
(4) compared with the comparative example 1, the operation stability time of the catalyst obtained by the regeneration in the comparative example 1 is greatly shortened, although the average conversion rate of hydrogen peroxide is more than 90%, the catalyst has the catalytic performance, but the catalytic effect is far lower than that of the titanium silicalite molecular sieve regenerated in the example 1, the iron content after the regeneration in the example 1 is only 11.25% before the regeneration due to the adoption of the step of removing iron by the acid solution, and the iron content after the regeneration in the comparative example 1 is 98.68% before the regeneration, almost not reduced, and the catalyst has a good removal effect on iron impurities causing poisoning in the deactivated catalyst by the acid solution, so that the in-situ regeneration is realized.
In conclusion, the method for in-situ iron removal of the titanium-silicon molecular sieve provided by the invention removes the metal impurities enriched in the catalyst pore channel by using the acidic solution, realizes in-situ regeneration of the titanium-silicon molecular sieve, has the activity of the regenerated catalyst being equal to that of a fresh catalyst, has simple steps and remarkable iron removal effect, and is suitable for popularization and use in the green and environment-friendly synthesis process of epoxy chloropropane.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.
Claims (10)
1. An in-situ iron removal method for a titanium-silicon molecular sieve is characterized by comprising the following steps:
(1) feeding the washing solution into a reaction device filled with the iron-inactivated titanium-silicon molecular sieve for a first-stage reaction, and discharging the washing solution after the first-stage reaction;
(2) feeding the acidic solution into the reaction device at the flow rate of 0.2-1.8BV/h, carrying out a second-stage reaction with the iron-deactivated titanium-silicon molecular sieve at the temperature of 20-150 ℃ and under the pressure of 0-2.8MPa, and discharging the acidic solution after the second-stage reaction;
(3) and feeding the activated solution into the reaction device for flushing to obtain the regenerated titanium silicalite molecular sieve.
2. The method of claim 1, wherein step (1) is preceded by: the organic solvent is sent into a reaction device to carry out and flush the reaction liquid, and the reaction liquid is discharged when the concentration of the reaction liquid in the organic solvent is lower than a limit value;
preferably, the limit value is 0-900ppm, preferably 200-800ppm of the original reaction raw material in the organic solvent;
preferably, the original reaction feedstock comprises chloropropene;
preferably, the organic solvent in step (1) comprises any one or a combination of two or more of ethanol, methanol, toluene, isopropanol, acetone, n-butanol or benzene;
preferably, the flow rate of the organic solvent fed to the fixed bed is 0.15 to 1.6 BV/h.
3. The method of claim 2, wherein the temperature of the rinsing is 10-30 ℃;
preferably, the pressure of the flushing is 0-2.8 MPa;
preferably, the time for flushing is 12-28 h.
4. A method according to any of claims 1-3, characterized in that the washing solution in step (2) comprises an organic liquid and/or water, preferably an organic liquid;
preferably, the organic liquid comprises any one or a combination of more than two of methanol, ethanol, toluene, isopropanol, acetone, n-butanol or benzene;
preferably, the flow rate of the washing solution fed into the reaction device filled with the iron-deactivated titanium silicalite molecular sieve is 0.2-1.8 BV/h.
5. The method according to any one of claims 1 to 4, wherein the first-stage reaction comprises a first-stage reaction after temperature rise and subsequent temperature drop;
preferably, the rate of temperature rise is 0.2-1.8 ℃/min;
preferably, the temperature rise end temperature is 120-180 ℃;
preferably, the rate of cooling is 0.2-1.8 ℃/min.
6. The method according to any one of claims 1 to 5, wherein the period of time for the reaction is 24 to 96 hours;
preferably, the pressure of the first-stage reaction is 0-2.4 MPa.
7. The method according to any one of claims 1 to 6, wherein the acidic solution in step (3) comprises an inorganic acid and/or an organic acid;
preferably, the acidic solution comprises any one or a combination of more than two of hydrochloric acid, nitric acid, citric acid, oxalic acid, acetic acid, acrylic acid, isobutyric acid or lactic acid;
preferably, the acidic solution further comprises any one or a combination of two or more of methanol, ethanol, acetonitrile, isopropanol, acetone or water;
preferably, the content of the inorganic acid and/or the organic acid in the acidic solution is 0.5 to 18 wt%.
8. The process according to any one of claims 1 to 7, wherein the secondary reaction is carried out for a period of time ranging from 1 to 48 hours.
9. The method according to any one of claims 1 to 8, wherein the activating solution in step (4) comprises hydrogen peroxide;
preferably, the concentration of the hydrogen peroxide is 3-15 wt%;
preferably, the flow rate of the activating solution fed into the reaction device is 0.2-1.5 BV/h;
preferably, the temperature of the washing in the step (4) is 25-70 ℃;
preferably, the pressure of the washing in the step (4) is 0-1 MPa;
preferably, the time for the rinsing in step (4) is 1-48 h.
10. A method according to any of claims 1-9, characterized in that the method comprises the steps of:
(1) feeding the organic solvent into a reaction device at a flow rate of 0.5-1.6BV/h to take out the reaction liquid, flushing the reaction liquid at 10-30 ℃ and 0-2.8MPa for 12-28h, and discharging the reaction liquid when the concentration of the reaction liquid is lower than 0-900 ppm; feeding the washing solution into a reaction device filled with the iron-deactivated titanium-silicon molecular sieve at the flow rate of 0.2-1.8BV/h, heating to 180 ℃ at the speed of 0.2-1.8 ℃/min, carrying out a first-stage reaction at 0-2.4MPa, cooling, and then discharging the washing solution;
(2) feeding the acid solution into the reaction device at the flow rate of 0.2-1.8BV/h, carrying out a second-stage reaction for 1-48h at the temperature of 20-150 ℃ and under the pressure of 0-2.8MPa, and then discharging the acid solution;
(3) the activating solution is sent into the reaction device at the flow rate of 0.2-1.5BV/h, and the washing is carried out for 1-48h at the temperature of 25-70 ℃ and under the pressure of 0-1MPa, so as to obtain the regenerated titanium-silicon molecular sieve.
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| CN110152726A (en) * | 2019-05-28 | 2019-08-23 | 江苏扬农化工集团有限公司 | The regeneration method of inactive titanium silicon molecule sieve catalyst in a kind of HPPO technique |
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