CN115888379A - Method for removing oxygen from oxygen-containing gas - Google Patents
Method for removing oxygen from oxygen-containing gas Download PDFInfo
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- CN115888379A CN115888379A CN202110955355.6A CN202110955355A CN115888379A CN 115888379 A CN115888379 A CN 115888379A CN 202110955355 A CN202110955355 A CN 202110955355A CN 115888379 A CN115888379 A CN 115888379A
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Abstract
The invention relates to the field of mixed gas purification, and discloses a method for removing oxygen in oxygen-containing gas. The method comprises the following steps: dividing the mixed gas containing hydrogen, other combustible gases and oxygen into n parts, and carrying out oxidation reaction on the 1 st to n th parts of the mixed gas according to the following steps: (a) Carrying out oxidation reaction on the mixed gas of the part 1 in the presence of stabilizing gas and a first catalyst to obtain deoxidized gas of the part 1; (b) Carrying out oxidation reaction on the part 2 mixed gas and the part 1 deoxidized gas obtained in the step (a) in the presence of stabilizing gas and a second catalyst to obtain part 2 deoxidized gas; and the operation is carried out according to the rule until the n part deoxidized gas is obtained. The invention can improve the deoxidization efficiency, reduce the circulating use amount of stabilizing gas, conveniently and better control the temperature of the oxidation reaction, prevent the temperature runaway of the reactor, reduce the phenomenon of carbon deposition on the catalyst, improve the service life of the catalyst and prolong the operation time of the system.
Description
Technical Field
The invention relates to the field of mixed gas purification, in particular to a method for removing oxygen in oxygen-containing gas.
Background
SH 3009-2013 'design Specification for petrochemical engineering combustible gas discharge System' 5.3.1 states that "combustible gas with oxygen content greater than 2% (v%) should not be discharged into whole plant combustible gas discharge systems, such as torches, incinerators, etc. Oxygen is accumulated in circulating gas in the epichlorohydrin production process, so that combustion and explosion are easily caused, the conventional process mostly adopts a measure of periodically discharging the diluted nitrogen to an incinerator to avoid oxygen accumulation, and the method not only causes organic gas waste, but also causes large VOC treatment load and environmental pollution. In addition, for deoxidation, three deoxidation modes, namely chemical adsorption deoxidation, activated carbon high-temperature deoxidation and catalytic deoxidation, are mainly adopted in the current industrial production. The chemical adsorption deoxidation mainly utilizes a deoxidizer (such as CN 1955150A) to cause chemical reaction with oxygen to consume the oxygen in a system so as to achieve the aim of deoxidation, but the method has the defects of short service life of the adsorbent and incapability of large-scale continuous use. The high-temperature deoxidation of the activated carbon is mainly used for deoxidation of inert gas, and the purpose of oxygen removal is achieved by the reaction of the activated carbon and oxygen under the high-temperature condition, but the development of the activated carbon is limited by the defects of high investment, difficult operation, difficult temperature control and the like. The catalytic deoxidation is realized by reacting oxygen in the environment with gases such as hydrogen, carbon monoxide, hydrocarbons and the like under the action of a catalyst (such as Liu Yingjie and the like, the development of a liquid propylene deoxidation catalyst, industrial catalysis, 2016,24 (1): 61-64).
In order to ensure the process safety in the existing catalytic deoxidation technology, nitrogen is mostly adopted to dilute the mixed gas before the mixed gas enters a deoxidation reactor so as to reduce the risk of burning and explosion of the mixed gas. However, the use of nitrogen as the diluent gas has very limited effect in reducing the risk of deflagration. Therefore, in order to improve the process safety of the light hydrocarbon hydro-catalytic deoxygenation technology, it is necessary to develop a more effective and safer treatment method for the system.
Disclosure of Invention
The invention aims to overcome the problems of effectiveness and safety in the prior art and provide a method for removing oxygen in oxygen-containing gas.
In order to achieve the above object, the present invention provides a method for removing oxygen from an oxygen-containing gas, the method comprising: dividing a mixed gas containing hydrogen, other combustible gases and oxygen into n parts, and carrying out oxidation reaction on the mixed gas of the 1 st part to the n th part according to the following steps:
(a) Carrying out oxidation reaction on the mixed gas of the part 1 in the presence of stabilizing gas and a first catalyst to obtain deoxidized gas of the part 1;
(b) Carrying out oxidation reaction on the part 2 mixed gas and the part 1 deoxidized gas obtained in the step (a) in the presence of stabilizing gas and a second catalyst to obtain part 2 deoxidized gas; and operating according to the rule until the n part deoxidized gas is obtained.
The invention can improve the deoxidization efficiency, reduce the circulating use amount of stabilizing gas, conveniently and better control the temperature of the oxidation reaction, prevent the temperature runaway of the reactor, reduce the phenomenon of carbon deposition on the catalyst, prolong the service life of the catalyst and prolong the operation time of the system.
Drawings
FIG. 1 is a schematic structural view of an apparatus for carrying out the deoxidation method of the invention according to one embodiment of the invention;
FIG. 2 is a schematic diagram of a multi-stage reactor for carrying out the multi-stage oxidation reaction of the present invention according to one embodiment of the present invention.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to these ranges or values. For ranges of values, one or more new ranges of values may be obtained from combinations of values between the endpoints of each range, the endpoints of each range and the individual values, and the individual values of the points, and these ranges of values should be considered as specifically disclosed herein.
In the present invention, unless otherwise specified, "pressure" refers to absolute pressure.
The present invention provides a process for removing oxygen from an oxygen-containing gas, said process comprising a plurality of oxidation reactions, i.e. the oxygen-containing gas may be divided into a plurality of fractions and the oxidation reactions are carried out in a stepwise manner, said process comprising: dividing the mixed gas containing hydrogen, other combustible gases and oxygen into n parts, and carrying out oxidation reaction on the 1 st to n th parts of the mixed gas according to the following steps:
(a) Carrying out oxidation reaction on the mixed gas of the part 1 in the presence of stabilizing gas and a first catalyst to obtain deoxidized gas of the part 1;
(b) And (b) carrying out oxidation reaction on the part 2 mixed gas and the part 1 deoxidized gas obtained in the step (a) in the presence of stabilizing gas and a second catalyst to obtain part 2 deoxidized gas, and operating according to the rule until the part n deoxidized gas is obtained.
In the present invention, the other combustible gas and oxygen are sometimes collectively referred to herein as "oxygen-containing gas", and the mixed gas is obtained by mixing an oxygen-containing gas with hydrogen. The mixed gas may be a gas mixture in which the respective components are mixed in advance, or may be a reaction system in which the components are mixed in real time at the time of the oxidation reaction. Similarly, the stabilising gas may be introduced from the outside or may be carried by the oxygen-containing gas itself, and in the above-described multiple oxidation reaction, at least part of the stabilising gas of the subsequent step may be introduced from the preceding step. The mixed gas of each part may also contain stabilizing gas, but the content of the stabilizing gas may be varied, but preferably, the content of the stabilizing gas is such that the stabilizing gas accounts for more than 60 vol% (such as 60 vol%, 70 vol%, 80 vol%, 90 vol%, 93 vol%, 96 vol%, 97 vol%, 99 vol% or any value therebetween) of the total volume of the gas in the oxidation reaction system in each step, so as to better prevent the occurrence of the explosion situation.
In embodiments of the invention that include multiple oxidation reactions, the oxygen-containing gas (other flammable gases and oxygen) is mixed with the stabilizing gas prior to mixing with the hydrogen gas in order to better prevent explosions.
In embodiments of the present invention involving multiple oxidation reactions, n can be any integer greater than 2 or greater than 2, preferably n is an integer from 3 to 20.
In the preferred embodiment of the invention comprising multi-stage oxidation reaction, the content c of oxygen in the oxidation reaction system of each step is more than or equal to 15 volume percent, and 20 is more than or equal to n and more than 12; or the content of oxygen in the oxidation reaction system of each step is more than 15 and more than c and more than or equal to 10 volume percent, and the content of oxygen in the oxidation reaction system of each step is more than or equal to 12 and more than n and more than 8; or the content of oxygen in the oxidation reaction system of each step is more than 10 < c > and more than 6 volume percent, and the content of oxygen in the oxidation reaction system of each step is more than 8 < n > and more than 5; or the content c of oxygen in the oxidation reaction system of each step is less than 6 volume percent, and n is more than or equal to 5 and more than or equal to 1. Thus, the selection of n according to the oxygen content in the oxidation reaction system of each step is particularly beneficial to more effectively preventing temperature runaway and increasing the treatment capacity of gas under the condition of lower usage of stabilizing gas, reducing the carbon deposition amount of the catalyst and prolonging the service life of the catalyst.
In a preferred embodiment of the present invention involving multiple oxidation reactions, the oxygen content of the gas mixture is greater than 5% by volume, n =4, the volume of the gas mixture of part 1 is 10-40% of the total volume of the gas mixtures of each part, the volume of the gas mixture of part 2 is 30-60% of the total volume of the gas mixtures of each part, the volume of the gas mixture of part 3 is 20-40% of the total volume of the gas mixtures of each part, and the volume of the gas mixture of part 4 is 1-10% of the total volume of the gas mixtures of each part.
In another preferred embodiment of the present invention involving multiple oxidation reactions, the oxygen content of the gas mixture is 2-5 vol%, n =4, the volume of the gas mixture in the 1 st portion is 30-60% of the total volume of the gas mixtures in each portion, the volume of the gas mixture in the 2 nd portion is 20-50% of the total volume of the gas mixtures in each portion, the volume of the gas mixture in the 3 rd portion is 20-30% of the total volume of the gas mixtures in each portion, and the volume of the gas mixture in the 4 th portion is 1-20% of the total volume of the gas mixtures in each portion.
In another preferred embodiment of the present invention comprising multiple oxidation reactions, the oxygen content of the gas mixture is less than 2% by volume, n =4, the volume of the gas mixture of part 1 is 40-65% of the total volume of the gas mixture of parts, the volume of the gas mixture of part 2 is 25-40% of the total volume of the gas mixture of parts, the volume of the gas mixture of part 3 is 10-30% of the total volume of the gas mixture of parts, and the volume of the gas mixture of part 4 is 1-25% of the total volume of the gas mixture of parts.
In embodiments of the present invention involving multiple oxidation reactions, the oxidation reaction temperature in each step may be controlled within the range of 30-380 ℃.
In the embodiment of the present invention including the multistage oxidation reaction, the oxidation reaction pressure in each step may be controlled in the range of 0.3 to 5 MPa.
In the embodiment of the invention comprising multi-stage oxidation reaction, the gas total volume space velocity of the oxidation reaction in each step can be controlled between 500 and 45000h -1 Within the range.
In embodiments of the present invention that include multiple oxidation reactions, the oxidation conditions in each step may be the same or different.
In embodiments of the present invention comprising multiple oxidation reactions, to ensure that the oxygen content of the gas after the oxidation reaction is kept at a low level, the method may further comprise: and (3) carrying out oxidation reaction on the n-th deoxidized gas in the presence of a post-treatment catalyst.
In the embodiment of the present invention including the multi-stage oxidation reaction, the catalysts (including the first catalyst, the second catalyst, the third catalyst … … and the post-treatment catalyst) mentioned in the above steps can be catalysts which are commonly used in the art and catalyze the reaction of oxygen and hydrogen to generate water, and can also be catalysts in the above preferred embodiments, and the catalysts in the steps can be the same or different.
The multistage oxidation reaction of the present invention may be carried out in a multistage reactor (as shown in fig. 2) comprising the following structure: the reactor main body and the reactor main body which are sequentially provided with a first-stage feed inlet 1, a second-stage feed inlet 2, a third-stage feed inlet 3, a fourth-stage feed inlet 4 and a discharge outlet 11 from top to bottom are sequentially provided with a first-stage reaction bed layer 6, a second-stage reaction bed layer 7, a third-stage reaction bed layer 8, a fourth-stage reaction bed layer 9 and a fifth-stage reaction bed layer 10 from top to bottom, the reactor main body is internally provided with corresponding clapboards, so that raw material gas introduced from the first-stage feed inlet 1 can flow through the first-stage reaction bed layer 6 and then flow through the second-stage reaction bed layer 7 together with raw material gas introduced from the second-stage feed inlet 2, gas flowing through the second-stage reaction bed layer 7 flows through the third-stage reaction bed layer 8 together with raw material gas introduced from the third-stage feed inlet 3, gas flowing through the third-stage reaction bed layer 8 and raw material gas introduced from the fourth-stage feed inlet 4 flow through the fourth-stage reaction bed layer 9 together, and gas flowing through the fourth-stage reaction bed layer 9 is further flows through the fifth-stage reaction bed layer 10 and then is discharged through the discharge outlet 11. A packing layer 12 is further arranged between each level of reaction bed layers in the reactor main body, so that gas from the previous level of reaction bed layer flows through the next level of reaction bed layer after passing through the corresponding packing layer, and the packing layer can enable the gas to be distributed more uniformly, so that the oxygen removal efficiency and the oxygen removal effect can be further improved. In order to timely discharge the gas in the reactor main body, a safety valve 5 may be provided at the top thereof. In order to facilitate cleaning and maintenance of the various stages of the reaction bed, corresponding manholes 15 may be provided in the reactor body. The reactor body may also include a base 18. A pressure detection alarm 19 can be arranged in the reactor main body, can detect the pressure in the reactor main body, and gives an alarm when the pressure in the reactor main body is detected to exceed a preset value. In order to make the gas distribution more uniform and further improve the oxygen removal effect and the oxygen removal efficiency, the reactor main body can also comprise a gas distributor 14 arranged before the five-stage reaction bed layer 10. The heat exchanger capable of exchanging heat with the five-stage reaction bed layer can be arranged in the five-stage reaction bed layer 10, so that the five-stage reaction bed layer can be effectively cooled, carbon deposition on the catalyst of the five-stage reaction bed layer is not easy to occur, and the service life of the catalyst is prolonged. The heat exchanger has a heat exchanger inlet 16 for the cooling medium to enter and a heat exchanger outlet 17 for the heat exchanged cooling medium to exit. The reactor may also be provided with an oxygen content on-line detection system 13 and a flow control system 20 to facilitate detection of oxygen content and control of feed flow.
In the present invention, the stabilizing gas is preferably a gaseous alkane. As mentioned before, the stabilising gas can be introduced from the outside. However, when the oxygen-containing gas contains gaseous alkane, it may not be necessary to introduce gaseous alkane from the outside as the stabilizing gas, or the amount of stabilizing gas introduced from the outside may be reduced accordingly, that is, the term "stabilizing gas" in the present invention may refer to only gaseous alkane contained in the oxygen-containing gas, only gaseous alkane introduced from the outside, and a mixture of gaseous alkane contained in the oxygen-containing gas and gaseous alkane introduced from the outside. In the present invention, the stabilizing gas is only gaseous alkane, and therefore, the content of other inactive gas (i.e. gas which does not react with any of hydrogen, oxygen, other flammable gas in the system, such as helium, nitrogen, argon, carbon dioxide, steam, etc.) in the oxidation reaction system is maintained at a low level, for example, less than 10 vol%, less than 5 vol%, less than 3 vol%, less than 2 vol%, less than 1 vol%, less than 0.5 vol%, less than 0.05 vol% or less.
According to a preferred embodiment of the invention, the volume ratio of the stabilizing gas to the oxygen (in the oxygen-containing gas) in the steps is not less than 4, more preferably more than 5, such as 6, 10, 12, 15, 18, 20, 22, 25, 30 or any value between the above values.
According to another preferred embodiment of the present invention, the stabilizing gas is at least 60 vol%, such as 60 vol%, 70 vol%, 80 vol%, 90 vol%, 93 vol%, 96 vol%, 97 vol%, 99 vol% or any value therebetween, based on the total volume of the gas in the oxidation reaction system in each step.
According to the invention, "gaseous alkane" means an alkane which is gaseous under the operating conditions of the invention, preferably said stabilizing gas is selected from C1-C4 (C1, C2, C3, C4) alkanes, including straight or branched alkanes, preferably at least one of methane, ethane and propane.
According to the invention, the oxygen-containing gas may also be a gas containing an unsaturated hydrocarbon, the process comprising, in order to avoid as far as possible an adverse effect of the unsaturated hydrocarbon on the oxidation reaction: in the presence of stabilizing gas, unsaturated hydrocarbon in oxygen-containing gas is removed, and the gas after removing unsaturated hydrocarbon is mixed with hydrogen gas for oxidation reaction. The unsaturated hydrocarbons may be removed by methods common in the art, such as at least one of direct gas-liquid separation, pressurized, absorption, and reduced temperature distillation separation. The direct gas-liquid separation means that: the oxygen-containing gas is directly fed into the container to naturally separate the gas phase and the liquid phase in the container, and no pressure or temperature control is applied in the process. Wherein, the gas after removing unsaturated hydrocarbon mainly contains stabilizing gas and oxygen, and may also contain nitrogen, carbon monoxide, hydrogen and the like.
According to the present invention, the oxygen content of the oxygen-containing gas may be greater than 2 vol%, preferably 3 to 99.5 vol% (e.g. 2.5 vol%, 2.8 vol%, 3 vol%, 4 vol%, 5 vol%, 6 vol%, 10 vol%, 20 vol%, 30 vol%, 40 vol%, 50 vol%, 55 vol%, 60 vol%, 70 vol%, 80 vol%, 90 vol%, 93 vol%, 96 vol%, 99 vol% or any value therebetween). The amount of the other flammable gas in the oxygen-containing gas may be from 0.5 to 99.99 volume percent (e.g., 0.1 volume percent, 1 volume percent, 10 volume percent, 20 volume percent, 30 volume percent, 40 volume percent, 50 volume percent, 60 volume percent, 70 volume percent, 80 volume percent, 90 volume percent, 93 volume percent, 96 volume percent, 99 volume percent, or any value therebetween).
In the present invention, the oxygen-containing gas may contain an organic gas other than oxygen, such as methanol, and may also contain an inorganic gas, such as argon, helium, hydrogen, nitrogen, carbon monoxide, and the like. Thus, the other flammable gas is a flammable gas other than hydrogen and gaseous alkanes and may be selected from various common flammable organic gases and/or flammable inorganic gases other than gaseous alkanes and hydrogen, including light hydrocarbons below C4, halogenated hydrocarbons below C4, alcohols below C4, ketones below C4, ethers below C4, carbon monoxide, and the like.
According to a preferred embodiment of the invention, the other flammable gas is selected from at least one of ethylene, ethylene oxide, propylene oxide, 1-butene, 2-butene, isobutylene, 1,3-butadiene, acetylene, propyne, 1-butyne, 2-butyne, vinyl chloride, 3-chloropropene, 1-chloropropane, 2-chloropropane and epichlorohydrin.
According to the present invention, the oxidation reaction means a reaction in which hydrogen reacts with oxygen to generate water. In this reaction, the amount of hydrogen used is not particularly limited as long as the oxygen in the oxygen-containing gas and hydrogen can be reacted as much as possible to produce water, and preferably the hydrogen is used in such an amount that the molar ratio of hydrogen to oxygen (in the oxygen-containing gas) is 0.5 to 5, more preferably 1 to 3.
According to the invention, the mixing (oxidation reaction) is carried out in the presence of a catalyst, and the catalyst of the invention is not particularly directed to a certain catalyst as long as the catalyst has the function of catalyzing the reaction of oxygen and hydrogen to generate water within a proper temperature range so as to achieve the purpose of removing oxygen. The catalyst is selected from at least one of noble metal catalysts (such as platinum-based catalysts and/or palladium-based catalysts) and non-noble metal catalysts (such as molybdenum-based catalysts, copper-based catalysts, nickel-based catalysts, manganese-based catalysts, and the like). The active component of the catalyst may be one or more of Pt, pd, ru, rh, ir, ag, fe, ni, mn, cu, ce, alkali metals and alkaline earth metals. The loading amount of the active component can be 0.01-95g/100g of the carrier by metal elements. The carrier of the catalyst can be one or more of alumina, a silicon-aluminum molecular sieve, an all-silicon molecular sieve, a phosphorus-aluminum molecular sieve, kaolin, diatomite and montmorillonite. The shape of the catalyst can be any one of a sphere, a dentate sphere, a Raschig ring, a cylinder, a clover shape or a clover shape.
According to a preferred embodiment of the present invention, in order to further improve the deoxygenation effect, reduce the hydrogenation selectivity of hydrocarbon materials and extend the service life of a catalyst, the catalyst comprises a carrier, and an active component and a co-agent supported on the carrier, the active component comprises a noble metal, the co-agent comprises an alkali metal and/or an alkaline earth metal, and the catalyst satisfies the following formulas I and II:
0.8<D 1 /(D 1 +D 2 +D 3 )<0.98 Formula I
5.2D 1 +2.5D 2 +160D 3 <W 1 /W 2 <100. Formula II
Wherein:
D 1 represents the percentage of the pore volume occupied by pores with a pore diameter of less than 20nm to the total pore volume;
D 2 representing the percentage of the pore volume occupied by pores with a pore diameter of 20-50nm to the total pore volume;
D 3 represents the percentage of the pore volume occupied by pores with a pore diameter of more than 50nm to the total pore volume;
W 1 represents the weight content of the active assistant in the catalyst;
W 2 represents the weight content of active components in the catalyst.
According to the present invention, in order to further increase the oxygen removal rate, it is preferable that D 1 Is 82-96% (e.g., 82%, 84%, 86%, 88%, 89%, 91%, 93%, 96%, or any value therebetween). Preferably, D 2 0-20% (e.g., 1%, 2%, 4%, 4.6%, 8%, 8.5%, 9%, 11%, 12%, 15%, 17%, 18%, 19%, 20%, or any value therebetween). Preferably, D 3 0-5% (e.g., 0.1%, 0.15%, 0.25%, 0.4%, 0.8%, 0.9%, 1%, 1.2%, 2%, 3%, 4%, 5%, or any value therebetween).
According to the invention, to furtherIncreasing the oxygen removal rate, preferably, W 1 /W 2 =6-100, more preferably W 1 /W 2 =10-75 (e.g., 10, 12, 15, 20, 25, 30, 32, 38, 40, 50, 60, 68, 70, 72, 75, or any value therebetween).
The content of carrier, active ingredient and coagent according to the invention is not particularly critical. Preferably, the content of the active component in terms of metal element is 0.01 to 5% by weight, more preferably 0.1 to 1% by weight, based on the total amount of the catalyst.
Preferably, the content of the coagent in terms of metal element is from 0.1 to 20% by weight, more preferably from 5 to 10% by weight, based on the total amount of the catalyst.
Preferably, the support is present in an amount of from 75 to 99.8 wt%, more preferably from 85 to 94 wt%, based on the total amount of catalyst.
In the present invention, unless otherwise specified, the total amount of the catalyst = the amount of the active component in terms of the metal element + the amount of the active assistant in terms of the metal element + the amount of the carrier.
According to the invention, the weight ratio of the active auxiliary agent to the active component, calculated as the metal element, is preferably 6 to 100:1.
according to the invention, preferably, the active assistant is alkali metal and alkaline earth metal, and the weight ratio of the alkali metal to the alkaline earth metal is 5-10:1, more preferably, the weight ratio of alkali metal to alkaline earth metal is from 6 to 9:1. the deoxidation performance of the catalyst can be further improved by blending an alkali metal with an alkaline earth metal. Further preferably, the coagent is selected from at least one of Na, K, and Cs and at least one of Mg, ca, and Ba; most preferably a combination of Na and Mg, or a combination of K and Ca.
According to the present invention, the active component is selected from noble metals commonly used in the art, preferably, the active component is selected from at least one of Pt, pd, ru, rh, ag, and Ir; more preferably, the active component is selected from at least one of Pt, pd and Ru.
According to another preferred embodiment of the invention, the catalyst may also comprise a fourth periodic group VIII transition metal, more preferably Fe. The weight ratio of the VIII group transition metal in the fourth period to the active component is 3-50:1. the introduction of the fourth period group VIII transition metal can further improve the sulfur resistance of the catalyst. In the present invention, when the catalyst contains a group VIII transition metal in the fourth period, W1 represents the weight content of only the alkali metal and the alkaline earth metal, and does not include the weight content of the group VIII transition metal in the fourth period.
According to the present invention, preferably, the support is selected from at least one of alumina (gamma-alumina), silica, titania and carbon nanotubes.
According to the invention, the specific surface area of the catalyst is preferably 120 to 260m 2 (ii) in terms of/g. Preferably, the catalyst has a pore volume of 0.4-0.8cm 3 (ii) in terms of/g. Preferably, the catalyst has an average pore diameter of 6 to 25nm.
The invention also provides a method for preparing the catalyst, which comprises the following steps: carrying out first roasting on the carrier precursor and the modifier at 450-1000 ℃; loading an active component precursor and an active auxiliary agent precursor on the first roasted product to obtain a catalyst precursor; then carrying out second roasting on the catalyst precursor; wherein the modifier is ammonium chloride and/or urea.
Preferably, the support precursor is selected from at least one of pseudo-boehmite, silica sol, water glass, alumina sol, tetrabutyl titanate, and activated carbon.
Preferably, the time of the first roasting is 1 to 10 hours.
Preferably, the first firing is performed in air.
Preferably, the first roasting mode is as follows: heating the carrier precursor and the modifier to 450-1000 ℃ (such as 450 ℃, 490 ℃, 510 ℃, 550 ℃, 590 ℃, 610 ℃, 640 ℃, 660 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃ or any value between the above values) at a heating rate of 200-600 ℃/h (such as 200 ℃/h, 210 ℃/h, 250 ℃/h, 290 ℃/h, 310 ℃/h, 350 ℃/h, 390 ℃/h, 410 ℃/h, 500 ℃/h, 600 ℃/h or any value between the above values), and roasting at the temperature for 1-10h (such as 1h, 2h, 3h, 4h, 5h, 6h, 8h, 10h or any value between the above values).
Preferably, the weight ratio of the support precursor to the modifier is 5-10:1.
in the above preparation method of the present invention, in order to obtain the catalyst having the active component and the co-agent as described above, a person skilled in the art can select the active component precursor and the co-agent precursor according to the kinds of the active component and the co-agent, and details thereof are not repeated.
Preferably, the active ingredient precursor is selected from at least one of nitrate, chloride, acetate and metal acetylacetonate of the active ingredient.
More preferably, the active component precursor is selected from palladium chloride and/or chloroplatinic acid.
Preferably, the coagent precursor is selected from at least one of a nitrate, chloride and acetate salt of the coagent.
Preferably, the active component precursor and the active assistant precursor are used in amounts such that the catalyst contains 0.01 to 5 wt% of active component calculated by metal element, 0.1 to 20 wt% of active assistant calculated by metal element, and 75 to 99.8 wt% of carrier; more preferably, the active component is present in an amount of 0.1 to 1 wt% calculated on the metallic element, the coagent is present in an amount of 5 to 10 wt% calculated on the metallic element, and the carrier is present in an amount of 85 to 94 wt%.
Preferably, the active component precursor and the coagent precursor are used in amounts such that the weight ratio of coagent to active component, calculated as metal element, in the resultant catalyst is from 6 to 100, preferably from 10 to 75.
Preferably, the alkali metal precursor and the alkaline earth metal precursor in the active assistant precursor are used in such amounts that the weight ratio of the alkali metal to the alkaline earth metal in the prepared catalyst is 5-10:1; more preferably, the weight ratio of alkali metal to alkaline earth metal is 6-9:1.
preferably, the temperature of the second firing is 0 to 50 ℃ lower than the temperature of the first firing. Preferably, the rate of temperature rise of the second firing is 140 to 240 ℃ lower than the rate of temperature rise of the first firing. More preferably, the second firing process comprises: carrying out second roasting at 300-800 ℃ for 1-5h; or, the temperature is raised to 300-800 ℃ at the speed of 60-160 ℃/h, and then the temperature is kept for 1-5h.
Preferably, the second firing is performed in air.
Preferably, the method for loading the active component precursor and the coagent precursor on the carrier is an impregnation method; more preferably, the method comprises a process of loading a reactive component precursor and a coagent precursor onto the carrier:
(1) Preparing an impregnation liquid containing an active component precursor and an active auxiliary agent precursor, wherein the pH value of the impregnation liquid is 0.5-4 or 9-13;
(2) Impregnating the support with the impregnation solution, optionally drying after impregnation is completed.
More preferably, the process of formulating the impregnation fluid containing the active ingredient precursor and the coagent precursor comprises: dissolving the active component precursor in acid solution or alkali solution, mixing with the active assistant precursor, and introducing water to regulate pH value of the system to 0.5-4 or 9-13. Preferably, the acid solution is selected from at least one of hydrochloric acid, nitric acid and acetic acid, and/or the alkali solution is selected from at least one of ammonia, sodium hydroxide and sodium carbonate.
More preferably, the time of the impregnation is 0.5 to 10h.
According to another preferred embodiment of the present invention, the method for preparing the catalyst may further comprise: and a step of supporting the fourth period group VIII transition metal. The method for supporting the fourth period group VIII transition metal may be a conventional impregnation method, but it is preferable that the fourth period group VIII transition metal is contacted with the carrier precursor together with the modifier to perform the first calcination, that is, preferably, an impregnation solution containing the modifier and the fourth period group VIII transition metal precursor is impregnated into the carrier precursor, followed by drying and performing the first calcination at 450 to 1000 ℃. The fourth period group VIII transition metal is preferably Fe. Preferably, the transition metal precursor of the fourth period is used in an amount such that the weight ratio of the transition metal to the active component of the fourth period in the prepared catalyst is 3-50:1.
according to the present invention, there is no particular requirement for the conditions of mixing (oxidation reaction) as long as the oxidation reaction can occur, and preferably, the conditions of mixing (oxidation reaction) are such that the oxygen content in the gas after the reaction is 1.5% by volume or less, more preferably 0.5% by volume or less. According to a more preferred embodiment of the invention, the temperature of the oxidation reaction is lower than the light-off temperature of the catalytic combustion of the ballast gas (gaseous alkane) in order to avoid the catalytic combustion reaction of the ballast gas with oxygen. According to a more preferred embodiment of the present invention, the conditions of the oxidation reaction include: the total volume space velocity of the gas is 2000-20000h -1 The pressure is 0.1-10MPa, and the temperature is 30-600 ℃.
According to a preferred embodiment of the invention, the stabilizing gas is methane and the oxidation conditions comprise: the total volume space velocity of the gas is 2000-20000h -1 The pressure is 0.1-5MPa, and the temperature is 30-500 deg.C (preferably 30-150 deg.C).
According to a preferred embodiment of the invention, the ballast gas is ethane and the oxidation conditions comprise: the total volume space velocity of the gas is 2000-15000h -1 The pressure is 0.1-4.5MPa, and the temperature is 30-400 deg.C (more preferably 30-120 deg.C).
According to a preferred embodiment of the present invention, the stabilizing gas is propane and the oxidation conditions comprise: the total volume space velocity of the gas is 2000-10000h -1 The pressure is 0.1-4MPa, and the temperature is 30-350 deg.C (more preferably 30-100 deg.C).
According to the present invention, in order to further improve the efficiency of the oxidation reaction, the method may further include: mixing the oxygen-containing gas and the hydrogen before the oxygen-containing gas is contacted with the hydrogen, preheating the mixed gas, and reacting the preheated gas under the condition that the hydrogen generates an oxidation reaction. Wherein the preheating brings the temperature of the gas to the activation temperature of the catalyst used (typically 50-300 c).
According to the invention, the residual gas after the reaction is mainly stable gas, and the direct recycling can further reduce the energy consumption of treatment. Thus, according to a preferred embodiment of the present invention, the method further comprises: and recycling the gas which does not undergo the oxidation reaction as stabilizing gas. After the gas which does not undergo the oxidation reaction is condensed, the temperature can be reduced to below 45 ℃, and the gas is separated from the liquid by a circulating pump for repeated use.
According to the present invention, water generated by the oxidation reaction can be discharged to a wastewater collection system (sewage treatment system) at a regular time.
The invention also provides the use of gaseous alkanes as stabilising gas to reduce the risk of explosion of oxygen-containing gases. The specific types or compositions of the gaseous alkane and the oxygen-containing gas are as described above and will not be described in detail herein.
The present invention will be described in detail below by way of examples. In the following examples, the method of analysis of the gas components was gas chromatography; the oxygen conversion is calculated as (volume of oxygen in the oxygen-containing gas-volume of oxygen in the reaction product)/volume of oxygen in the oxygen-containing gas x 100%.
Preparation example 1
(1) Preparing a carrier: mixing pseudo-boehmite powder and ammonium chloride solid according to the weight ratio of 5:1, heating to 500 ℃ at the heating rate of 300 ℃/h after mixing, and roasting for 5h at the temperature to obtain the carrier.
(2) Preparing a steeping fluid: feeding according to the stoichiometric ratio of each component in the catalyst, dissolving palladium chloride in 0.1mol/L dilute hydrochloric acid, adding sodium nitrate and magnesium nitrate after completely dissolving, uniformly stirring, and then introducing water to adjust the pH value to 3 to obtain an impregnation liquid.
(3) Preparation of catalyst C1: placing the carrier in the impregnation liquid, impregnating for 5h, stirring and evaporating at 120 ℃ after the impregnation is finished, and drying in an oven at 80 ℃ for 12h to obtain a catalyst precursor; then roasting in air, wherein the roasting conditions comprise: the temperature is raised to 500 ℃ at a speed of 100 ℃/h, and then the temperature is kept for 3h.
Preparation examples 2 to 3
The preparation of catalysts C2 and C3 was carried out according to the method of preparation 1, except that the stoichiometric ratios of the components in the catalyst were different from those in preparation 1 and the preparation conditions of the catalyst were different, as shown in Table 1.
TABLE 1
Preparation example 4
The preparation of catalyst C4 was carried out according to the method of example 1, except that the stoichiometric ratio of the components in the catalyst was different from that of preparation example 1 and the process for preparing the support was different: mixing Fe (NO) 3 ) 3 Dissolving urea in deionized water to obtain a soaking solution, soaking the pseudo-boehmite powder in the soaking solution for 3h, stirring at 80 deg.C, evaporating to dryness, and calcining at 500 deg.C for 7h to obtain the carrier.
Preparation example 5
Catalyst C5 was prepared according to the method of preparation example 1, except that the charge amount of the coagent was such that the weight ratio of sodium nitrate to magnesium nitrate, calculated as the metal element, was 1:1.
preparation example 6
Preparation of catalyst C6 was carried out as in preparation example 1, except that magnesium nitrate was replaced by sodium nitrate.
Preparation example 7
Preparation of catalyst C7 was carried out as in preparation example 1, except that sodium nitrate was replaced by magnesium nitrate.
Preparation example 8
Catalyst C8 was prepared according to the method of preparation example 1, except that the charge amount of the coagent was such that the weight ratio of sodium nitrate to magnesium nitrate, calculated as the metal element, was 1:5.
comparative preparation example 1
Preparation of catalyst C9 was carried out as in preparation example 1, except that the pseudo-boehmite was directly calcined at 1200 ℃ for 5 hours to obtain a carrier.
Comparative preparation example 2
Preparation of catalyst C10 was carried out as in preparation example 1, except that the ammonium chloride solid was replaced by N, N-dimethylformamide.
Comparative preparation example 3
Preparation of catalyst C11 was carried out as in preparation example 1, except that magnesium nitrate and sodium nitrate were replaced by iron nitrate.
Test example 1
The structural parameters of the catalysts prepared in the preparation examples and preparation ratios are characterized, and the results are shown in table 2. The elemental compositions of the catalysts prepared in the above preparation examples and comparative preparation examples were characterized, and the contents of the metal elements of the active component and the metal elements of the coagent were shown in table 2, and the balance was the carrier.
Specific surface area and pore size distribution test: using American microphones
II 3020 physical adsorption apparatus, analysis of specific surface area and pore structure. Specific test conditions included N at-196 deg.C (liquid nitrogen temperature) 2 Measuring surface area and pore structure by adsorption method, vacuum-pumping pretreatment of sample at 300 deg.C until pressure is less than 10 -3 Pa, and the measuring method is a static method. And calculating the specific surface area and the pore structure by adopting a BET method according to the adsorption isotherm.
The contents of the components in the catalyst are tested by adopting an ICP-AES method.
TABLE 2
Note: r represents the weight ratio of alkali metal to alkaline earth metal
Further analysis showed that the iron content and W in preparation example 4 and comparative preparation example 3 2 The ratios of (a) to (b) are 3 and 50, respectively.
Test example 2
(1) Prepared by the above preparation examples and comparative preparation examplesThe catalyst is used for the deoxidation treatment of the oxygen-containing gas, and the deoxidation treatment conditions comprise: the reaction temperature is 60 ℃, the pressure is 0.3MPa, and the gas volume space velocity is 5000h -1 The oxygen-containing gas contains oxygen and hydrocarbon gas, methane (stabilizing gas), hydrogen (reducing gas) and the oxygen-containing gas are mixed, and the molar ratio of the hydrogen to the oxygen in the mixed gas is 2.2:1, the volume ratio of methane to oxygen is 15. The oxygen concentration in the oxygen-containing gas and the oxygen concentration after the reaction are shown in Table 3.
(2) The catalysts prepared in the above preparation examples and comparative preparation examples were subjected to life test measurement according to the deoxidation treatment conditions in the step (1), and the life of the catalyst was characterized by the time of catalyst deactivation: catalyst deactivation is considered when the oxygen conversion of the catalyst is less than 80% of the initial conversion, when the total length of time the deoxygenation treatment is run is the life of the catalyst, longer than a certain time means that the treatment time is up to that length of time the catalyst is not deactivated, but the experiment is not continued. The results are shown in Table 3.
TABLE 3
Note: the indicated gas content values or selectivities refer to the mean values of the measurements of the system as it is run until the catalyst has deactivated
As can be seen from the results of table 3, the deoxidation performance is further improved and the selectivity and the service life of the catalyst are further improved by using the catalyst prepared according to the preferred embodiment of the present invention.
Examples 1 to 3 and comparative examples 1 to 2
The tail gas (oxygen-containing gas) was treated according to the procedure shown in FIG. 1, with the following specific operations:
the oxygen-containing gas is firstly mixed with the stabilizing gas in the pre-separation buffer tank V-1, so that the content of the stabilizing gas in the premixed gas is not lower than 90 percent. The premixed gas is pressurized by a first compressor C-1, cooled by a first heat exchanger E-1, enters a separation tower T-1, separation of unsaturated hydrocarbons with more than C2 and non-condensable gas (stabilizing gas and oxygen) is realized in the separation tower T-1, condensed hydrocarbons are discharged from the bottom of the separation tower T-1 and sent to a light hydrocarbon recovery system, the non-condensable gas consisting of stabilizing gas and oxygen is discharged from the top of the separation tower T-1, heat exchange is firstly carried out on the non-condensable gas and a deoxygenation product in a second heat exchanger E-2, then a third heat exchanger E-3 is heated to the activation temperature of deoxygenation reaction by steam, the non-condensable gas is mixed with hydrogen at an inlet of a deoxygenation reactor R-1 (the molar ratio of hydrogen to oxygen is 2.2) and then enters a reactor, the reactor is contacted with a catalyst in a deoxygenation reactor R-1 to carry out hydrogen catalytic deoxygenation reaction, the reaction product is separated from the bottom of the deoxygenation reactor R-1 after being separated from a catalyst bed layer, the product E-2 and a feed gas from the separation tower T-1 are firstly returned to a fourth heat exchanger E-1, a small amount of hydrogen-1 stable gas and a buffer tank, a small amount of residual gas containing hydrogen-1-stable reaction medium is discharged from a separation tank, and discharged from a top of a stable separation tank, and a stable reaction system.
The specific operating conditions of the above steps are shown in table 4, and the oxygen content at each stage is detected in real time by the oxygen content online detection control system (the result is shown in table 4), and the gas content values shown in table 4 all refer to the detection average value when the system runs for 500 h.
The catalysts described in table 4 and part of the catalysts described in table 5 were prepared by the following method: using a bar-extruding method to obtain Al with a diameter of 2X 4mm 2 O 3 50g of the spheres were treated by immersion in 50ml of a 5% by weight KOH solution for 50 minutes and then dried in a drying cabinet at 200 ℃. 0.15g of PdCl is taken 2 Preparing a solution, adjusting the pH value of the solution to 3, and pouring the solution to the dipped Al 2 O 3 Drying on carrier at 200 deg.C for 6 hr, calcining at 500 deg.C for 4 hr, and calcining at 150 deg.C with H 2 Reducing for 2 hours, cooling to room temperature to obtain Al with the Pd content of 0.18g/100g 2 O 3 The deoxygenation catalyst of (1), adjusting PdCl 2 The amount of the catalyst or the type of the carrier can be different to obtain different deoxygenation catalysts.
TABLE 4
The results show that the alkane auxiliary light hydrocarbon hydrocatalysis deoxidation technology has the technical characteristics of simple operation, low cost, long-period continuous deoxidation, high operation safety and reliability and the like, and has good application prospect.
Examples 4 to 6
Diluting oxygen-containing gas with stabilizing gas, separating unsaturated hydrocarbons with more than 2C from non-condensable gas (stabilizing gas and oxygen) in a separation tower according to the mode of example 1, mixing the non-condensable gas consisting of the stabilizing gas and the oxygen with hydrogen (the amount of the stabilizing gas is that the stabilizing gas accounts for the total volume of the gas in an oxidation reaction system in each step and is shown in table 5, the molar ratio of the hydrogen to the oxygen in the mixed gas is 2.2), then dividing the mixed gas into 4 parts to obtain a part 1 mixed gas, a part 2 mixed gas, a part 3 mixed gas and a part 4 mixed gas, and carrying out oxidation reaction on the part 1-4 mixed gas according to the following steps:
(a) Carrying out oxidation reaction on the mixed gas of the part 1 in the presence of a first catalyst to obtain a deoxidized gas of the part 1;
(b) Carrying out oxidation reaction on the part 2 mixed gas and the part 1 deoxidized gas obtained in the step (a) in the presence of a second catalyst to obtain a part 2 deoxidized gas;
(c) Carrying out oxidation reaction on the 3 rd part of mixed gas and the 2 nd part of deoxidized gas obtained in the step (b) in the presence of a third catalyst to obtain a 3 rd part of deoxidized gas;
(d) Carrying out oxidation reaction on the 4 th part of mixed gas and the 3 rd part of deoxidized gas obtained in the step (c) in the presence of a fourth catalyst to obtain a 4 th part of deoxidized gas;
(e) And (4) carrying out oxidation reaction on the deoxidized gas of the 4 th part in the presence of a post-treatment catalyst to obtain an outlet gas.
In each of the above steps, the pressure of the reaction was controlled to 0.5MPa, the kind of the active component of the catalyst used was the same, the amount of the active metal supported was different, and other operating conditions and the evaluation results of the catalyst life and the like in each step are shown in table 5.
TABLE 5
Note: the values of gas content shown refer to the average values detected during 500h operation of the system.
As can be seen from the results in tables 4 and 5, the multistage oxidation reaction mode can ensure the deoxidation effect and reduce the carbon deposition amount of the catalyst under the conditions of the catalyst with low precious metal content and high space velocity, so that the multistage oxidation reaction mode can further improve the deoxidation efficiency, and the consumption of the stabilizing gas is low and the system operation time is long.
Comparative example 3
An oxygen-containing gas was treated in the same manner as in example 4 except that the stabilizing gas was replaced with nitrogen, and the results are shown in Table 6.
TABLE 6
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (10)
1. A method for removing oxygen from an oxygen-containing gas, the method comprising: dividing a mixed gas containing hydrogen, other combustible gases and oxygen into n parts, and carrying out oxidation reaction on the mixed gas of the 1 st part to the n th part according to the following steps:
(a) Carrying out oxidation reaction on the mixed gas of the part 1 in the presence of stabilizing gas and a first catalyst to obtain deoxidized gas of the part 1;
(b) Carrying out oxidation reaction on the part 2 mixed gas and the part 1 deoxidized gas obtained in the step (a) in the presence of stabilizing gas and a second catalyst to obtain part 2 deoxidized gas; and the operation is carried out according to the rule until the n part deoxidized gas is obtained.
2. The method according to claim 1, wherein the volume ratio of the stabilizing gas to oxygen in each step is not less than 4, preferably more than 5.
3. The method as claimed in claim 1 or 2, wherein the stabilizing gas accounts for 60 vol% or more of the total volume of the gases in the oxidation reaction system in each step.
4. The method according to claim 1, wherein the stabilizing gas is selected from C1-C4 alkanes, preferably at least one of methane, ethane and propane.
5. The method of claim 1, wherein n is an integer from 2 to 20.
6. The method according to claim 1 or 5, wherein the content c of oxygen in the oxidation reaction system of each step is 15% by volume or more, 20n is more than 12;
or the content of oxygen in the oxidation reaction system of each step is more than 15 and more than c and more than or equal to 10 volume percent, and the content of oxygen in the oxidation reaction system of each step is more than or equal to 12 and more than n and more than 8;
or the content of oxygen in the oxidation reaction system of each step is more than 10 < c > and more than 6 volume percent, and the content of oxygen in the oxidation reaction system of each step is more than 8 < n > and more than 5;
or the content c of oxygen in the oxidation reaction system of each step is less than 6 volume percent, and n is more than or equal to 5 and more than or equal to 1.
7. The process of claim 1 wherein the other flammable gas is selected from at least one of ethylene, ethylene oxide, propylene oxide, 1-butene, 2-butene, isobutylene, 1,3-butadiene, acetylene, propyne, 1-butyne, 2-butyne, vinyl chloride, 3-chloropropene, 1-chloropropane, 2-chloropropane, and epichlorohydrin.
8. The process according to claim 1, wherein in each step the hydrogen is used in an amount such that the molar ratio of hydrogen to oxygen is between 0.5 and 5, preferably between 1 and 3;
and/or the temperature of the oxidation reaction is lower than the light-off temperature of the steady gas catalytic combustion.
9. The process as claimed in claim 1, 2 or 8, wherein the oxidation reaction temperature in each step is controlled within the range of 30-380 ℃, the pressure is controlled within the range of 0.3-5MPa, and the gas total volume space velocity is controlled within the range of 500-45000h -1 Within the range.
10. The process according to claim 1, wherein the oxidation reaction conditions are such that the oxygen content in the reacted gas is below 1.5 vol.%, preferably below 0.5 vol.%.
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