WO2022007387A1 - 丙烯直接环氧化制备环氧丙烷的方法和系统 - Google Patents

丙烯直接环氧化制备环氧丙烷的方法和系统 Download PDF

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WO2022007387A1
WO2022007387A1 PCT/CN2021/073744 CN2021073744W WO2022007387A1 WO 2022007387 A1 WO2022007387 A1 WO 2022007387A1 CN 2021073744 W CN2021073744 W CN 2021073744W WO 2022007387 A1 WO2022007387 A1 WO 2022007387A1
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gas
propylene
reaction
feed
hydrogen
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PCT/CN2021/073744
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English (en)
French (fr)
Inventor
孙冰
赵辰阳
杨哲
朱红伟
王林
姜杰
石宁
李娜
王世强
王浩志
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中国石油化工股份有限公司
中国石油化工股份有限公司青岛安全工程研究院
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Priority claimed from CN202010662738.XA external-priority patent/CN113912570B/zh
Priority claimed from CN202010662746.4A external-priority patent/CN113912573B/zh
Priority claimed from CN202010662744.5A external-priority patent/CN113912572B/zh
Application filed by 中国石油化工股份有限公司, 中国石油化工股份有限公司青岛安全工程研究院 filed Critical 中国石油化工股份有限公司
Priority to US18/004,985 priority Critical patent/US20230339833A1/en
Priority to EP21837621.8A priority patent/EP4163275A4/en
Publication of WO2022007387A1 publication Critical patent/WO2022007387A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C41/00—Preparation of ethers; Preparation of compounds having groups, groups or groups
    • C07C41/01—Preparation of ethers
    • C07C41/02—Preparation of ethers from oxiranes
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D301/00—Preparation of oxiranes
    • C07D301/02—Synthesis of the oxirane ring
    • C07D301/03—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds
    • C07D301/04—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen
    • C07D301/08—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen in the gaseous phase
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/0006—Controlling or regulating processes
    • B01J19/0013—Controlling the temperature of the process
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/14—Production of inert gas mixtures; Use of inert gases in general
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/064—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof containing iron group metals, noble metals or copper
    • B01J29/068—Noble metals
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D303/00—Compounds containing three-membered rings having one oxygen atom as the only ring hetero atom
    • C07D303/02—Compounds containing oxirane rings
    • C07D303/04—Compounds containing oxirane rings containing only hydrogen and carbon atoms in addition to the ring oxygen atoms

Definitions

  • the invention relates to the field of propylene oxide preparation, in particular to a method and system for preparing propylene oxide by epoxidizing propylene.
  • Propylene oxide is a chemical with huge production and consumption worldwide. It can be used to produce intermediate chemicals such as polyether, propylene glycol, isopropanolamine, and allyl alcohol, and then generate unsaturated polymer resins, polyurethanes, surfactants and other chemicals. Taste. Propylene oxide is widely used in food, textile, pharmaceutical, chemical and other fields.
  • the industrial production methods of propylene oxide mainly include chlorohydrin method, co-oxidation method and direct oxidation (HPPO) method.
  • chlorohydrin method the main disadvantage of the chlorohydrin method is the use of toxic chlorine gas, the equipment is seriously corroded and a large amount of chlorine-containing wastewater that pollutes the environment is generated, which does not meet the requirements of green chemistry and clean production. Therefore, with the increasing environmental protection requirements, this process will eventually Be eliminated.
  • the co-oxidation method overcomes the shortcomings of the chlorohydrin method such as polluting the environment and corroding equipment, it is a relatively cleaner production process than the chlorohydrin method, but the disadvantage is that it has higher quality requirements for raw materials, a longer process, a large investment scale, and benefits from co-production. The price of the product has a greater impact.
  • the HPPO method is a relatively novel process, which is a direct oxidation method using titanium-silicon molecular sieve as the catalyst and hydrogen peroxide as the oxidant.
  • the outstanding advantages of this reaction are mild reaction conditions (room temperature to 80° C.), high selectivity, and green cleanliness.
  • this technology also has certain problems, such as the need to build a hydrogen peroxide production unit.
  • the purpose of the present invention is to provide a method and system for preparing propylene oxide by epoxidizing propylene in order to overcome the defect of high amount of diluent gas in the process of preparing propylene oxide by epoxidation of propylene in the prior art.
  • Using the technical solution of the present invention can significantly reduce the amount of diluent gas.
  • one aspect of the present invention provides a method for preparing propylene oxide by epoxidizing propylene, the method comprising: under the reaction conditions of propylene epoxidation, mixing a mixture containing a first feed gas and a second feed gas The mixed gas is contacted and reacted with the catalyst to obtain propylene oxide;
  • the first feed gas contains oxygen and is free or substantially free of hydrogen
  • the second feed gas contains hydrogen and is free or substantially free of oxygen
  • the first feed gas and/or the second feed gas contains propylene
  • At least one of the first feed gas and the second feed gas also contains a diluent gas.
  • the diluent gas is an inert diluent gas and/or a non-inert diluent gas; in the first feed gas and the mixed gas, the concentrations of oxygen independently satisfy the following formula:
  • X O2 is the volume fraction (%) of oxygen in the gas mixture
  • Xm is the volume fraction (%) of the inert diluent gas m in the mixture
  • Xn is the volume fraction (%) of the non-inert diluent gas n in the mixture
  • X propylene is the volume fraction (%) of propylene in the mixed gas
  • X hydrogen is the volume fraction (%) of hydrogen in the mixed gas
  • Nn is the lower explosion limit (%) of the non-inert diluent gas n in the mixed gas
  • N propylene is the lower explosion limit (%) of propylene in mixed gas
  • N hydrogen is the lower explosion limit (%) of hydrogen in mixed gas
  • Ln is the explosion upper limit (%) of the non-inert diluent gas n in the mixture
  • L propylene is the explosion upper limit (%) of propylene in mixed gas
  • LHydrogen is the explosion upper limit (%) of hydrogen in the mixed gas.
  • the dilution gas is at least one of propylene, propane, methane and ethane.
  • the catalyst and the inert packing are packed in the reactor in an alternate layered manner.
  • the volume space velocity of the mixed gas is 500-30000 ml g cat -1 h -1 .
  • the method further comprises preheating the mixed gas.
  • the present invention provides a reaction system for the direct epoxidation of propylene to prepare propylene oxide, the reaction system comprising:
  • Gas supply unit for supplying propylene, oxygen, hydrogen and diluent gas
  • a mixing unit comprising a first feeding zone, a second feeding zone and a third feeding zone;
  • the first feed zone is used for mixing oxygen, optional hydrogen, optional propylene and optional diluent gas to obtain the first feed gas;
  • the second feed zone is used for mixing hydrogen, optional oxygen, optional propylene and optional diluent gas to obtain the second feed gas;
  • each material in the first feed gas and the second feed gas is selected such that the first feed gas contains oxygen and does not contain or substantially contains hydrogen, and the second feed gas contains hydrogen and contains no or substantially no hydrogen. contains oxygen, the first feed gas and/or the second feed gas contains propylene, and at least one of the first feed gas and the second feed gas further contains a diluent gas;
  • the third feed zone is used for mixing the first feed gas, the second feed gas and the recycle gas to obtain a mixed gas
  • a catalyst is arranged in the reaction unit for contacting the mixed gas with the catalyst and reacting under propylene epoxidation reaction conditions to obtain propylene oxide
  • the product separation unit is used for separating the product obtained by the propylene epoxidation reaction to obtain the target product propylene oxide, organic by-products and recycle gas;
  • a gas circulation unit in communication with the mixing unit, for receiving the circulating gas, and then delivering the circulating gas to the mixing unit as at least part of the reaction raw material gas and the dilution gas.
  • the present invention can obtain the following beneficial effects:
  • the present invention obtains a mixed gas by mixing a first feed gas containing oxygen and no or substantially no hydrogen and a second feed gas containing hydrogen and no or substantially no oxygen to obtain a mixed gas, and the first feed
  • the gas and/or the second feed gas contains propylene, and at least one of the first feed gas and the second feed gas also contains a diluent gas, which can prevent the concentration of hydrogen from rapidly decreasing when mixing hydrogen and oxygen.
  • the method of the present invention achieves the purpose of mixing the reaction raw materials more uniformly and further reducing the risk of explosion.
  • the technical scheme of the present invention can simultaneously reduce the amount of diluent gas, and under the precursor that reduces the separation pressure of subsequent products, the concentration of the reaction gas is also increased, thereby improving the reaction selectivity and conversion rate, and reducing energy. consumption.
  • the technical solution of the present invention can mix the reaction gas more effectively, and reduces the influence on the catalyst when it is in contact with the catalyst, thereby significantly prolonging the service life of the catalyst. 100 hours extended to more than 500 hours.
  • the present invention adopts a gas-phase circulation process, and the unreacted raw material gas is specifically treated and then circulated back to the reactor for further reaction, thereby realizing a substantial increase in the utilization rate of raw materials, and ensuring the epoxy Under the premise of the propane space-time yield, the comprehensive conversion rate of propylene is significantly improved.
  • the reaction tail gas is recycled under the precursor that ensures the safety of the reaction, which reduces the production cost and the tail gas treatment pressure.
  • the technical solution of the present invention can more effectively utilize the reaction gas without affecting the life of the catalyst.
  • Fig. 1 is the packing method of the catalyst provided by the present invention.
  • FIG. 2 is a schematic diagram of a reaction system for preparing propylene oxide by direct epoxidation of propylene provided by the present invention.
  • the present invention provides a method for preparing propylene oxide by epoxidizing propylene, the method comprising: under the reaction conditions of propylene epoxidation, mixing a mixed gas containing a first feed gas and a second feed gas Contact reaction with catalyst to obtain propylene oxide;
  • the first feed gas contains oxygen and is free or substantially free of hydrogen
  • the second feed gas contains hydrogen and is free or substantially free of oxygen
  • the first feed gas and/or the second feed gas contains propylene
  • At least one of the first feed gas and the second feed gas also contains a diluent gas.
  • the diluent gas can be any diluent gas that can be used for the direct epoxidation of propylene, it can be an inert gas, a non-inert gas, or a mixed diluent gas of an inert gas and a non-inert gas . Therefore, the diluent gas is an inert diluent gas and/or a non-inert diluent gas.
  • the inert diluent gas may be selected from N 2 , Ar and CO 2 .
  • the non-inert gas is gaseous alkane and/or gaseous olefin.
  • the gaseous alkanes are C1-C4 alkanes.
  • the gaseous alkanes are methane, ethane and propane, more preferably propane.
  • the gaseous olefin is a C2-C4 olefin.
  • the gaseous olefin is propylene.
  • the ratio of the diluent gas is not particularly limited, and it can be any value or range between 0 and 100% of the total diluent gas, For example, 0, 0.01%, 0.1%, 1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 0.05-100%, 50- 90% and so on.
  • the proportion of propylene is not particularly limited, and it can be any value or range between 0 and 100% of the total propylene, for example, 0, 0.01%, 0.1%, 1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 0.05-100%, 50-90% etc.
  • substantially free of hydrogen means that the amount of hydrogen contained in the first feed gas is insufficient to cause an explosion, for example, the volume fraction of hydrogen in the first feed gas is below 4% (excluding this number) For example, it may be 3.5% or less, 3% or less, 2.5% or less, 2% or less, 1.5% or less, 1% or less, 0.5% or less, and 0.1% or less.
  • substantially free of oxygen means that the amount of oxygen contained in the first feed gas is insufficient to cause an explosion, for example, the volume fraction of oxygen in the second feed gas is below 25% (excluding this number), for example , can be 20% or less, 15% or less, 10% or less, 8% or less, 5% or less, 4% or less, 3% or less, 2% or less, 1% or less, 0.5% or less, 0.1% or less.
  • the first feed gas contains oxygen and no or substantially no hydrogen, contains at least part of propylene and at least part of diluent gas;
  • the second feed gas contains hydrogen and does not contain hydrogen or substantially free of oxygen, with the remainder of the propylene and the remainder of the diluent; or
  • the second feed gas contains hydrogen and no or substantially no oxygen, contains at least a portion of propylene and at least a portion of the diluent gas; the second feed gas contains oxygen and no or substantially no hydrogen, and contains the remainder of propylene and the remainder of the dilution gas.
  • the first feed gas contains oxygen and is free or substantially free of hydrogen, all propylene and all dilution gas; the second feed gas contains hydrogen and is free or substantially free Contains oxygen.
  • the first feed gas contains oxygen and is free or substantially free of hydrogen, all propylene and part of the dilution gas (>0); the second feed gas contains hydrogen and no hydrogen With or substantially free of oxygen and the remainder of the dilution gas.
  • the first feed gas contains oxygen and is free or substantially free of hydrogen, part of propylene (>0) and part of dilution gas (>0);
  • the second feed gas Contains hydrogen and no or substantially no oxygen, the remainder of the propylene and the remainder of the dilution gas.
  • the first feed gas contains oxygen and is free or substantially free of hydrogen, part of propylene (>0) and all dilution gas; the second feed gas contains hydrogen and no hydrogen With or substantially free of oxygen and the remainder of propylene.
  • the first feed gas contains oxygen and is free or substantially free of hydrogen and all dilution gases; the second feed gas contains hydrogen and is free or substantially free of oxygen and All acrylic.
  • the first feed gas contains oxygen and is free or substantially free of hydrogen and part of the dilution gas (>0); the second feed gas contains hydrogen and is free or substantially free Free of oxygen, remaining part of diluent and all propylene.
  • the first feed gas contains oxygen and is free or substantially free of hydrogen and part of propylene (>0); the second feed gas contains hydrogen and is free or substantially free Contains oxygen, all diluent and some propylene.
  • the first feed gas contains oxygen and is free or substantially free of hydrogen; the second feed gas contains hydrogen and is free or substantially free of oxygen, all dilution gas and All acrylic.
  • partial dilution gas refers to any value between 0-100% by volume (excluding the endpoint value), for example, 0.1% by volume, 1% by volume, 5% by volume, 10% by volume, 15% by volume, 20% by volume, 25% by volume, 30% by volume, 35% by volume, 40% by volume, 45% by volume, 50% by volume, 55% by volume, 60% by volume, 65% by volume, 70% by volume, 75% by volume %, 80% by volume, 85% by volume, 90% by volume, 91% by volume, 92% by volume, 93% by volume, 94% by volume, 95% by volume, 96% by volume, 97% by volume, 98% by volume, 99% by volume, 99.5% by volume.
  • partial propylene refers to any value between 0 and 100 vol% (excluding endpoint values), for example, 0.1 vol%, 1 vol%, 5 vol%, 10 vol%, 15 vol% vol%, 20vol%, 25vol%, 30vol%, 35vol%, 40vol%, 45vol%, 50vol%, 55vol%, 60vol%, 65vol%, 70vol%, 75vol% , 80% by volume, 85% by volume, 90% by volume, 91% by volume, 92% by volume, 93% by volume, 94% by volume, 95% by volume, 96% by volume, 97% by volume, 98% by volume, 99% by volume, 99.5 volume%.
  • the concentrations of oxygen independently satisfy the following formula:
  • X O2 is the volume fraction (%) of oxygen in the gas mixture
  • Xm is the volume fraction (%) of the inert diluent gas m in the mixture
  • Xn is the volume fraction (%) of the non-inert diluent gas n in the mixture
  • X propylene is the volume fraction (%) of propylene in the mixed gas
  • X hydrogen is the volume fraction (%) of hydrogen in the mixed gas
  • Nn is the lower explosion limit (%) of the non-inert diluent gas n in the mixed gas
  • N propylene is the lower explosion limit (%) of propylene in mixed gas
  • N hydrogen is the lower explosion limit (%) of hydrogen in mixed gas
  • Ln is the explosion upper limit (%) of the non-inert diluent gas n in the mixture
  • L propylene is the explosion upper limit (%) of propylene in mixed gas
  • LHydrogen is the explosion upper limit (%) of hydrogen in the mixed gas.
  • the above mixed gas refers to the first feed gas
  • the above mixed gas refers to the mixed gas
  • the diluent gas when the diluent gas is only an inert diluent gas, the sum of the non-inert diluent gas in the formula is 0; when the diluent gas is only a non-inert diluent gas, Xm in the formula is 0; when the dilution gas is a mixed dilution gas of an inert gas and a non-inert gas, the calculation of the formula is performed according to the respective ratios.
  • the explosion limit range of propylene refers to the explosion limit range determined by the combustible gas explosion test method in a closed space (tested according to relevant regulations of GB/T12474-2008) under the conditions of room temperature and normal pressure, and its explosion range is 2 -11%.
  • the lower explosion limit is 2% and the upper explosion limit is 11%.
  • X propylene can refer to the volume fraction of all propylene in the system, and the sum of propylene used as diluent gas is 0 at this time; in addition, propylene can also be used as diluent gas according to the above formula The amount of propylene and the amount of propylene as the reactant gas were used to calculate the formula.
  • the explosion limit range of hydrogen refers to the explosion limit range determined by the test method of combustible gas explosion in a closed space (tested according to relevant regulations of GB/T12474-2008) under the conditions of room temperature and normal pressure, and its explosion range is 4 -75%.
  • the lower explosion limit is 4% and the upper explosion limit is 75%.
  • the explosion limit range of methane refers to the explosion limit range determined by the test method of combustible gas explosion in a closed space (tested according to relevant regulations of GB/T12474-2008) under the conditions of room temperature and normal pressure, and its explosion range is 5 -15%.
  • the lower explosion limit is 5% and the upper explosion limit is 15%.
  • the explosion limit range of ethane refers to the explosion limit range determined by the combustible gas explosion test method in a closed space (tested according to relevant regulations of GB/T12474-2008) under the conditions of room temperature and normal pressure, and the explosion range is 3-16%.
  • the lower explosion limit is 3% and the upper explosion limit is 16%.
  • the explosion limit range of propane refers to the explosion limit range determined by the combustible gas explosion test method in a closed space (tested according to relevant regulations of GB/T12474-2008) under the conditions of room temperature and normal pressure, and its explosion range is 2 -10%.
  • the lower explosion limit is 2% and the upper explosion limit is 10%.
  • propylene acts as both the diluent gas and the reaction gas, which can further promote the forward progress of the reaction.
  • propane is used as the diluent gas
  • the occurrence of side reactions can be effectively suppressed, thereby improving the selectivity of propylene oxide.
  • propylene when used as the diluent gas, it means that at least part of the diluent gas is replaced by propylene, thereby causing a large excess of propylene in the reaction raw material gas. Therefore, in this case, it cannot be simply considered that propylene is in excess, which is different from the excess in the sense of conventional understanding.
  • the concentration of oxygen satisfies the formula (1).
  • the first feed gas can be pure oxygen, or a mixture of oxygen and diluent gas.
  • the first feed gas is the latter, there is no difference in the concentration of oxygen. special restrictions.
  • the concentration of oxygen preferably satisfies the formula (1), and the concentration of oxygen in the first feed gas is preferably not higher than 82 vol%, for example, can be at 15 vol%, 20 vol%, 25 vol%, 30 vol%, 35 vol%, 40 vol%, 45 vol%, 50 vol%, 55 vol%, 60 vol%, 69 vol% %, 76% by volume, 79% by volume or less, in this preferred case, the first feed gas can be controlled within a safe range.
  • the concentration of the diluent gas in the mixed gas can be reduced to below 70% by volume, for example, 65% by volume, 60% by volume, 55% by volume, 50% by volume, 45% by volume, 40% by volume vol%, 35 vol%, etc.
  • the concentration of its diluent gas is generally above 70% by volume. It can be seen that the method of the present invention can effectively reduce the concentration of the diluent gas, thereby further increasing the concentration of the reaction gas and improving the reaction efficiency.
  • the concentration of oxygen in the mixed gas preferably satisfies the formula (1), and the concentration of oxygen in the mixed gas can be increased to 5% by volume, preferably more than 10% by volume, preferably not higher than 60% by volume %, eg, 11 vol%, 12 vol%, 13 vol%, 14 vol%, 15 vol%, 16 vol%, 17 vol%, 18 vol%, 19 vol%, 20 vol%, 21 vol%, 22 vol% %, 23% by volume, 24% by volume, 25% by volume, 26% by volume, 27% by volume, 28% by volume, 29% by volume, 30% by volume, 32% by volume, 34% by volume, 36% by volume, 38% by volume, 40 vol%, 42 vol%, 44 vol%, 46 vol%, 48 vol%, 50 vol%, 52 vol%, 54 vol%, 56 vol%, 58 vol%, 60 vol%.
  • the oxygen concentration is generally below 10% by volume, more preferably below 5% by volume
  • the second feed gas and the first feed gas are designed to be counter-mixed. This can be achieved by arranging the delivery pipeline of the second feed gas and the delivery pipeline of the first feed gas.
  • the hedging described in this article refers to the mixing of two airflows in the form of collision, and the collision may be that the two collide at an angle of 90-270°, for example, 180°, wherein The two airflows are defined as 0° in the same direction, and the opposite direction is defined as 180°.
  • the mixed gas in order to further improve the efficiency of the reaction, it is also preferable to preheat the mixed gas before bringing it into contact with the catalyst.
  • the degree of preheating is preferably at least 50% of the target reaction temperature, eg 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, preferably greater than 80% .
  • the propylene epoxidation reaction can be carried out in a conventional reactor in the art, for example, can be various tubular reactors conventional in the art, such as stainless steel, resin, quartz, plexiglass, ceramic glass reactor.
  • the reactor can be various microchannel reactors conventional in the art.
  • the catalyst may have any size and shape suitable for the tubular reactor or the microchannel reactor.
  • the catalyst can be any catalyst disclosed in the prior art that can catalyze the reaction of propylene, oxygen, hydrogen and diluent gas to generate propylene oxide
  • the catalyst is a supported metal catalyst
  • the supported Metal catalysts contain supports and active metal components.
  • the active metal component can be selected from at least one of gold, silver, copper, ruthenium, palladium, platinum, rhodium, cobalt, nickel, tungsten, bismuth, molybdenum and their oxides, preferably gold
  • the carrier for supporting the metal can be carbon black, activated carbon, silica, alumina, cerium oxide and zeolite, preferably zeolite, more preferably titanium-silicon molecular sieve.
  • the content of metals in terms of metallic elements can be varied within a wide range, for example, in terms of the total weight of the catalyst, the active metal components in the catalyst in terms of metallic elements
  • the content is 0.01-50% by weight, for example, it can be 0.01% by weight, 0.05% by weight, 0.06% by weight, 0.07% by weight, 0.08% by weight, 0.09% by weight, 0.1% by weight, 0.2% by weight, 0.3% by weight, 0.4% by weight wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt% , 1.7% by weight, 1.8% by weight, 1.9% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, 10% by weight, 15%
  • the catalyst is a gold-supported titanium-silicon molecular sieve (Au@TS-1), wherein the supported amount of the active metal component in terms of gold element is 0.1-2 wt%.
  • Au@TS-1 gold-supported titanium-silicon molecular sieve
  • the TS-1 molecular sieve can be prepared by hydrothermal synthesis, and the active metal component Au can be loaded by the method of deposition and precipitation.
  • the catalyst can be filled in the reactor for propylene epoxidation reaction alone (as shown in Fig. 1a ), or can be packed in the reactor in combination with other inert substances.
  • the catalyst is packed in a combination of the catalyst and the inert filler. in the reactor.
  • the inert filler can be an inert solid phase substance commonly used in the art, preferably, the inert filler is selected from at least one of quartz sand, Al 2 O 3 , porous silica gel and ceramic rings.
  • the amount of the inert filler can be changed in a wide range, but preferably, the amount of the inert filler is 1-200 parts by weight relative to 1 part by weight of the catalyst (for example, it can be 1 part by weight parts, 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, 35 parts by weight, 40 parts by weight, 45 parts by weight, 50 parts by weight, 80 parts by weight, 90 parts by weight, 95 parts by weight, 100 parts by weight, 105 parts by weight, 110 parts by weight, 115 parts by weight, 120 parts by weight, 125 parts by weight, 130 parts by weight, 135 parts by weight, 140 parts by weight, 145 parts by weight, 150 parts by weight, 160 parts by weight, 170 parts by weight parts, 180 parts by weight, 190 parts by weight, 200 parts by weight), preferably 15-50 parts by weight, more preferably 30-45 parts by weight.
  • the combination form of the catalyst and the inert packing may not be particularly limited, for example, the two may be directly mixed and then filled in the reactor, or the two may be designed into a sandwich structure ( Figure 1b), wherein the catalyst or inert packing is located in the middle.
  • Figure 1b sandwich structure
  • the inventors of the present invention found that the catalyst and the inert packing are packed in the reactor in a layered manner, and the catalyst and the inert packing are alternately packed in the reactor in a layered manner.
  • the life of the catalyst, the selectivity of the reaction, the conversion rate, the space-time yield and the hydrogen utilization rate can be further improved, and the amount of the catalyst can be reduced.
  • each layer of catalyst and each layer of inert packing can be selected in a wide range, and they can be layered in a way of equal height or in a way of unequal height, preferably, each layer
  • the catalyst and each layer of inert packing are independently 1-2000 layers/meter, for example, it can be 1 layer/meter, 2 layers/meter, 3 layers/meter, 4 layers/meter, 5 layers/meter, 6 layers/meter m, 7 floors/m, 8 floors/m, 9 floors/m, 10 floors/m, 15 floors/m, 18 floors/m, 20 floors/m, 50 floors/m, 100 floors/m, 200 floors/ m, 300 floors/m, 400 floors/m, 500 floors/m, 600 floors/m, 700 floors/m, 800 floors/m, 900 floors/m, 1000 floors/m, 1200 floors/m, 1400 floors/ meter, 1600 layers/meter, 1800 layers/meter, 2000 layers/meter; preferably 1000-2000 layers/meter, or 10-20 layers/meter.
  • the layer height ratio of each layer of catalyst and each layer of inert packing can be changed in a wide range.
  • the layer height ratio of each layer of catalyst and each layer of inert packing 1:1-10 for example, can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10 , preferably 1:1-3, more preferably 1:1.5-2.5.
  • the manner of filling the catalyst in the reactor may not be particularly limited, for example, a coating method, an electrodeposition method, a solution electroplating method, a mechanical filling method and the like may be used.
  • the filling amount of the catalyst is 10-50g.
  • the filling amount of the catalyst needs to be at least 100 g, and it can be seen that the technical solution of the present invention can also reduce the filling amount of the catalyst.
  • the temperature of the propylene epoxidation reaction can be a conventional reaction temperature in the art, for example, can be 20-300 ° C, but in order to further improve the conversion rate, selectivity, space-time yield and hydrogen utilization rate of the reaction , and improve the service life of the catalyst and reduce the amount of the catalyst, preferably, the temperature of the reaction is 50-250 ° C, more preferably 120-200 ° C, for example, it can be 120 ° C, 125 ° C, 130 ° C, 135 ° C , 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, 200°C.
  • the temperature of the reaction is 50-250 ° C, more preferably 120-200 ° C, for example, it can be 120 ° C, 125 ° C, 130 ° C, 135 ° C , 140°C, 145°
  • the heating rate of the system can also further affect the conversion rate, selectivity, space-time yield and hydrogen utilization rate of the reaction, the service life of the catalyst, and the amount of catalyst used.
  • the temperature of the reaction system is raised to the temperature required for the propylene epoxidation reaction, the conversion rate, selectivity, space-time yield and hydrogen utilization rate of the reaction can be further improved, the service life of the catalyst can be improved, and the amount of the catalyst and the dilution gas can be reduced. dosage.
  • the intermittent heating method includes: maintaining the temperature for 5-10 min ( For example, 5min, 6min, 7min, 8min, 9min, 10min).
  • the temperature is 0.1-10°Cmin -1 , preferably 0.5-5°Cmin -1 , more preferably 0.5-2°Cmin -1 (for example, it can be 0.5°Cmin -1 , 0.8°Cmin -1 , 1.0°Cmin -1 , 1.2°Cmin -1 , 1.5°Cmin -1 , 2.0°Cmin -1 , more preferably 0.8-1.5°Cmin -1 ) to raise the temperature of the reaction system to the level required for the propylene epoxidation reaction.
  • the temperature is high, the conversion rate, selectivity, space-time yield and hydrogen utilization rate of the reaction can be further improved, the service life of the catalyst can be increased, and the amount of the catalyst and the amount of diluent gas can be reduced.
  • the pressure of the propylene epoxidation reaction can be the conventional reaction pressure in the art, for example, can be 0-5MPa, but in order to further improve the conversion rate, selectivity, space-time yield and hydrogen utilization rate of the reaction, And improve the service life of the catalyst and reduce the amount of the catalyst, preferably, the pressure of the reaction is 0-1.5MPa, more preferably 0.05-0.25MPa, for example, can be 0.05MPa, 0.06MPa, 0.07MPa, 0.08MPa, 0.09MPa, 0.1MPa, 0.11MPa, 0.12MPa, 0.13MPa, 0.14MPa, 0.15MPa, 0.17MPa, 0.19MPa, 0.21MPa, 0.23MPa, 0.25MPa.
  • the space velocity of the propylene epoxidation reaction can be the conventional reaction space velocity in the field, but in order to further improve the conversion rate, selectivity, space-time yield and hydrogen utilization rate of the reaction, and improve the service life of the catalyst , reduce the amount, the catalyst is preferably mixed gas hourly space velocity of 500-30000ml g cat -1 h -1, more preferably 1000-20000ml g cat -1 h -1, more preferably 2000-15000ml g cat - 1 h -1 , for example, can be 2000ml g cat -1 h -1 , 3000ml g cat -1 h -1 , 4000ml g cat -1 h -1 , 5000ml g cat -1 h -1 , 6000ml g cat -1 h -1, 7000ml g cat -1 h -1, 8000ml g cat -1 h -1, 9000ml g cat -1 h -1,
  • the propylene epoxidation reaction provided by the method of the present invention is preferably carried out in the absence of a solvent.
  • the solvent includes any externally-incorporated liquid phase.
  • the method further comprises: separating the reaction product to obtain the target product propylene oxide, organic by-products and tail gas, and then post-processing the tail gas as at least part of the reaction raw material gas It is mixed with the diluent gas into the mixed gas for recycling.
  • the utilization rate of raw materials is greatly improved, and the comprehensive conversion rate of propylene is significantly improved on the premise of ensuring the space-time yield of propylene oxide.
  • the post-treatment includes sequential washing, optional condensation, optional component adjustment and pressurization.
  • the washing is alcohol washing.
  • the alcohol can be one or more of methanol, ethanol, propanol, n-butanol, isobutanol and ethylene glycol.
  • alcohol is used to perform low-temperature washing on the tail gas, and more preferably, the reacted gas is subjected to multi-stage low-temperature alcohol washing, for example, 2-3 stages.
  • the low temperature may be 2-20°C.
  • the post-processing includes:
  • composition of the non-condensable process gas is regulated by feeding at least one of propylene, hydrogen, oxygen and diluent gas, and the obtained regulated process gas is analyzed for composition, if the regulated process gas composition is within a predetermined range , then it is mixed into the mixed gas as a circulating gas for recycling, and if the composition of the adjusted process gas is not within the predetermined range, it is discharged to the outside.
  • composition analysis can be completed by gas chromatography analysis.
  • the gas to be analyzed is introduced into a gas chromatograph equipped with TCD and FID detectors for analysis.
  • the concentration of each component in the gas is obtained after the composition analysis, and the concentration of each component in the gas is adjusted to a predetermined concentration by a mass flow meter according to the reaction requirements, and then recycled.
  • the alcohol washing tail gas in step (b), can be condensed by a low temperature cold trap, and each component in the alcohol washing tail gas can be condensed separately according to the difference of its boiling point to form a condensate, and then the condensate is cooled by a low temperature circulating refrigeration pump. Separated by cyclone.
  • the composition within the predetermined range means that the composition content of the corresponding gas is stable and within a safe range, and does not exceed the limit oxygen content.
  • each process gas to be subjected to component analysis is transported to the gas chromatographic analysis under the heating condition of 50-200 ° C.
  • a heating belt can be set to maintain the temperature of 50-200 ° C.
  • 80-150°C eg, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C.
  • the present invention provides a reaction system for the direct epoxidation of propylene to prepare propylene oxide, the reaction system comprising:
  • Gas supply unit 1 for supplying propylene, oxygen, hydrogen and diluent gas
  • Mixing unit 2 comprising a first feeding zone, a second feeding zone and a third feeding zone;
  • the first feed zone is used for mixing oxygen, optional hydrogen, optional propylene and optional diluent gas to obtain the first feed gas;
  • the second feed zone is used for mixing hydrogen, optional hydrogen, optional propylene and optional diluent gas to obtain the second feed gas;
  • each material in the first feed gas and the second feed gas is selected such that the first feed gas contains oxygen and does not contain or substantially contains hydrogen, and the second feed gas contains hydrogen and contains no or substantially no hydrogen. contains oxygen, the first feed gas and/or the second feed gas contains propylene, and at least one of the first feed gas and the second feed gas further contains a diluent gas;
  • the third feed zone is used for mixing the first feed gas, the second feed gas and the recycle gas to obtain a mixed gas
  • Reaction unit 3 a catalyst is arranged in the reaction unit, and is used for contacting the mixed gas with the catalyst therein, and reacting under propylene epoxidation reaction conditions to obtain propylene oxide;
  • the product separation unit 4 is used for separating the product obtained by the propylene epoxidation reaction to obtain the target product propylene oxide, organic by-products and recycle gas;
  • the gas circulation unit 5 communicated with the mixing unit, is used for receiving the circulating gas, and then delivering the circulating gas to the mixing unit as at least part of the reaction raw material gas and the dilution gas.
  • the pipeline for introducing the first feed gas and the pipeline for introducing the second feed gas or hydrogen are arranged in such a way that the first feed gas is connected to the second feed gas.
  • the second feed gas is hedging mixed.
  • the hedging described herein refers to the mixing of the two air streams in the form of collision, and the collision may be that the two air streams collide at an angle of 90-270°, for example, 180°, wherein the two air streams collide at an angle of 90-270°, for example, 180°
  • the jet of air flow in the same direction is defined as 0°, and the opposite direction is defined as 180°.
  • the mixing unit further includes a gas preheating zone arranged downstream of the third feeding zone, wherein a preheating device is arranged in the gas preheating zone, the The device can be designed to be the same as the reactor structure, or it can be different.
  • the device is also provided with a heating element and a temperature control element to heat the reaction raw material gas to a predetermined temperature.
  • the preheating device is of a coil type design, and the reaction raw material gas can be heated in the form of heat-conducting oil, molten salt, electric heating, and the like.
  • the product separation unit comprises a product separation zone, a gas washing zone, a gas condensation zone and a gas conditioning zone which are connected in series in sequence, and the product separation zone,
  • the gas washing zone, the gas condensing zone and the gas conditioning zone are independently communicated with the gas circulation unit.
  • a regulating valve such as a back pressure valve, is also provided at the outlet of the reaction unit to control the pressure and flow rate of the reacted gas. The flow rate is adjusted.
  • the reaction system further includes an analysis unit 6 for performing component analysis on the process gas requiring component analysis.
  • the reaction unit is also communicated with the analysis unit. Therefore, the reacted product can be divided into at least two branches, wherein one branch is used to transport part of the reacted product to the analysis unit, Another branch is used to convey the remaining reacted product to the product separation unit for work-up.
  • the product separation zone is used to separate the product obtained by the propylene epoxidation reaction to obtain the target product propylene oxide, organic by-products and tail gas (containing dilution gas and insufficiently reacted raw material gas), so
  • the tail gas is transported to the analysis unit through one branch for analysis of all components; the remaining part of the tail gas is transported to the gas washing area through another branch for washing the tail gas to obtain the washing process gas. Therefore, preferably, the product separation zone is also communicated with the analysis unit.
  • the gas scrubbing zone is preferably provided with a gas scrubbing device, for example, a gas scrubbing tank, wherein a gas distributor is preferably provided in the gas scrubbing device, so as to uniformly distribute the introduced gas, thereby making the scrubbing more efficient. full.
  • a gas scrubbing device for example, a gas scrubbing tank
  • a gas distributor is preferably provided in the gas scrubbing device, so as to uniformly distribute the introduced gas, thereby making the scrubbing more efficient. full.
  • the gas scrubbing device is further provided with a cooling element, for example, circulating water arranged outside the gas scrubbing device Jacket, through heat exchange to reduce the temperature of the washing liquid.
  • a cooling element for example, circulating water arranged outside the gas scrubbing device Jacket, through heat exchange to reduce the temperature of the washing liquid.
  • the heated water can be used as other heat sources for full use.
  • the gas scrubbing zone includes multi-stage alcohol washing tanks connected in series in sequence, the alcohol washing tanks are filled with alcohol liquid, and the tail gas is in contact with the alcohol in the form of bubbling through the gas distributor arranged in the alcohol washing tank. for alcohol washing.
  • the alcohol can be methanol, ethanol, propanol, n-butanol, isobutanol, ethylene glycol and the like.
  • the gas scrubbing area is communicated with the analysis unit, so that all components of the scrubbing process gas are detected to determine the content of each component in the scrubbing process gas. Therefore, the scrubbing process gas It is divided into at least two branches, one of which is communicated with the analysis unit and is used for full-component analysis, and the other branch is further processed according to the situation.
  • the scrubbing process gas can be treated in the following situations.
  • the gas scrubbing area is communicated with the analysis unit and the gas circulation unit respectively, and a valve is provided on the communication pipeline.
  • the content of a certain component in the scrubbing process gas is abnormal, exceeds the limit oxygen content control range or the content of combustible organic matter exceeds the explosion limit, it will be transported to the gas condensation area for further processing.
  • the temperature of the gas condensation area cold trap temperature
  • the components of the scrubbing process gas are condensed separately according to their boiling points to achieve a safe mixed gas range, and then the uncondensed part of the gas enters the analysis unit again for component analysis. If the conditions in 1 are met, it is directly sent to the gas circulation unit as circulating gas. If the conditions in 1 are not met, continue to adjust the condensation temperature and further separate the scrubbing process gas to reach the safe control range.
  • the gas condensation area is communicated with the analysis unit and the gas circulation unit respectively, and a valve is provided on the communication pipeline.
  • the non-condensable process gas is transported to the gas adjustment area to adjust the gas ratio.
  • the ratio of the process gas For example, if the content of hydrogen in the non-condensable process gas is relatively high, and it is in the explosion limit range, the utilization rate of hydrogen can be increased by increasing the content of propylene and oxygen, thereby reducing the concentration of hydrogen at the outlet), so as to realize the selective consumption of reaction raw material gas, Further, the safe operation of the mixed gas components entering the gas circulation unit is realized.
  • the gas adjustment area is communicated with the analysis unit and the gas circulation unit respectively, and a valve is provided on the communication pipeline.
  • a tail gas discharge area is further provided downstream of the air conditioning area.
  • the gas circulation unit in order to complete the circulation of the tail gas, preferably includes a gas pressurization zone for pressurizing the circulating gas, so as to be delivered to the mixing unit as at least part of the reaction feed gas and diluent gas.
  • the gas pressurization zone is preferably provided with a low-pressure gas buffer tank and a high-pressure gas buffer tank in series, wherein a pressurization device is arranged in the low-pressure gas buffer tank, and the high-pressure gas buffer tank is connected to the high-pressure gas buffer tank.
  • the mixing unit is connected. Specifically, the circulating gas enters the low-pressure gas buffer tank through the pipeline.
  • the pressurizing device is turned on to pressurize the gas, and the pressurized gas is sent to the high-pressure gas buffer tank as a At least part of the reaction feed gas and diluent gas is sent to the mixing unit.
  • a pressure sensor is also provided in the low-pressure gas buffer tank.
  • the booster device can be turned on through the pressure sensor, for example, the electromagnetic solenoid on the gas path can be activated by opening the booster device valve.
  • the booster device is a gas booster pump.
  • a gas return pipeline is further provided between the high-pressure gas buffer tank and the low-pressure gas buffer tank to return part of the gas in the high-pressure gas buffer tank to the low-pressure gas buffer tank.
  • the low-pressure gas buffer tank and the high-pressure gas buffer tank are also independently provided with a safety valve and a drainage structure at the bottom.
  • the overall control of the reaction system is preferably PLC control, and data such as heating, gas intake flow, circulating gas volume, measurable temperature, pressure, flow, etc. can be controlled by a computer, and the control software has recording and exporting functions.
  • the PLC control cabinet is preferably an explosion-proof design, equipped with a one-key power-off button, and the device is equipped with a computer.
  • the gas supply unit may include a hydrogen intake branch, an oxygen intake branch, a propylene intake branch and a dilution gas intake branch, and each intake branch may include a corresponding gas storage tank ,
  • the pressure reducing valve, flow regulator and reducing joint etc. are arranged on the gas flow pipeline.
  • a reactor is provided in the reaction unit, and corresponding heating and/or cooling elements and temperature control elements can also be arranged in the reactor according to the situation, so as to heat and/or cool the target area , so that the reaction temperature is controlled within the scope of the present invention.
  • the gas in the reactor is heated by means of heat transfer oil, molten salt, electric heating, etc. to make it reach a predetermined reaction temperature.
  • the analytical unit may be a gas chromatograph equipped with TCD and FID detectors.
  • the system preferably further includes a heat preservation unit, such as a heat preservation pipeline, arranged between the reaction unit and the analysis unit and between the product separation unit and the analysis unit, so as to keep the gas to be analyzed in the heat preservation unit. delivered to the analysis unit under non-condensing conditions.
  • a heat preservation unit such as a heat preservation pipeline
  • the present invention also provides a method for preparing propylene oxide by utilizing the above system for epoxidizing propylene, the method comprising:
  • oxygen, optional hydrogen, optional propylene and optional diluent gas are mixed to obtain a first feed gas
  • each material in the first feed gas and the second feed gas is selected such that the first feed gas contains oxygen and does not contain or substantially contains hydrogen, and the second feed gas contains hydrogen and contains no or substantially no hydrogen. contains oxygen, the first feed gas and/or the second feed gas contains propylene, and at least one of the first feed gas and the second feed gas further contains a diluent gas;
  • the first feed gas, the second feed gas and the recycle gas are mixed to obtain a mixed gas
  • the mixed gas is contacted with the catalyst, and reacted under the propylene epoxidation reaction conditions to obtain propylene oxide;
  • the circulating gas is pressurized, and then the pressurized circulating gas is recycled into the mixing unit as at least part of the reaction raw material gas and the dilution gas.
  • the first feed gas and the second feed gas are subjected to hedging mixing.
  • the mixed gas is preheated.
  • At least one-stage condensation is performed on the scrubbing process gas to obtain a condensed liquid and a non-condensable process gas, and the non-condensable process gas is subjected to component analysis, if the composition of the non-condensable process gas is within a predetermined range If the composition of the non-condensable process gas is not within the predetermined range, the gas adjustment treatment is performed;
  • the composition of the non-condensable process gas is adjusted by feeding at least one of propylene, hydrogen, oxygen and diluent gas, and the obtained adjusted process gas is analyzed for composition. If the gas composition is within the predetermined range, it is sent to the gas circulation unit as a circulating gas, and if the adjusted process gas composition is not within the predetermined range, it is discharged to the outside.
  • the reaction system used for the direct epoxidation of propylene to prepare propylene oxide includes:
  • Air supply unit 1 including:
  • each intake branch may include a corresponding gas storage tank, a pressure reducing valve arranged on the gas flow pipeline , flow regulator and reducing joint;
  • Hybrid unit 2 including:
  • a first feed zone for mixing oxygen, optional hydrogen, optional propylene and optional diluent gas to obtain a first feed gas
  • the second feed zone is used for mixing hydrogen, optional hydrogen, optional propylene and optional diluent gas to obtain a second feed gas
  • the third feed zone is used to mix the first feed gas, the second feed gas and the circulating gas to obtain a mixed gas, wherein the conveying pipeline of the first feed gas and the conveying pipeline of the second feed gas relative settings;
  • the gas preheating zone is equipped with a coil type preheater, and the outer periphery is provided with heat conduction oil to heat the mixed gas;
  • Reaction unit 3 including:
  • the reaction zone is provided with a tubular reactor (316L stainless steel material), the outer periphery is provided with heat-conducting oil for heating, and the preheated gas is reacted here; wherein, the length of the tubular reactor is 3m, and the catalyst is filled in the tubular reactor;
  • the reaction product outlet of the tubular reactor is the same as that of the analysis unit 6 through the pipeline to analyze the composition of the reaction product;
  • Product separation unit 4 including:
  • the product separation zone, the gas washing zone, the condensation zone, the gas adjustment zone and the tail gas discharge zone are connected in series in sequence, wherein, the gas washing zone, the condensation zone and the gas adjustment zone are respectively provided with the gas circulation unit 5 and the analysis unit 6.
  • pipeline, and the pipeline is provided with a valve;
  • the product separation zone is used to separate the product obtained by the propylene epoxidation reaction to obtain the target product propylene oxide, organic by-products and tail gas.
  • a back pressure valve is provided at the outlet of the product separation zone, and a part of the tail gas passes through the insulation pipeline (150° C.).
  • the gas scrubbing area includes a two-stage alcohol washing tank, and the inner air inlet pipeline of each grade of the alcohol washing tank is provided with a gas distributor, and the exhaust gas passes through the gas
  • the distributor performs alcohol washing in the form of bubbling, and a circulating water jacket is arranged outside the alcohol washing tank to reduce the temperature of the alcohol washing liquid.
  • Part of the scrubbing process gas enters the analysis unit 6 through the four-way valve for full component analysis;
  • the composition of the mixture obtained by entering the analysis unit 6 is still within the range of the flammable gas explosion limit, enter the gas adjustment area to adjust the raw material components (for example, the hydrogen content in the mixture is high and is in the In the explosion limit range, by increasing the content of propylene and oxygen to improve the utilization rate of hydrogen, thereby reducing the concentration of hydrogen at the outlet), the selective consumption of the reaction raw material gas is realized, and the safe operation of the mixed gas components entering the circulation unit is realized.
  • the raw material components for example, the hydrogen content in the mixture is high and is in the In the explosion limit range, by increasing the content of propylene and oxygen to improve the utilization rate of hydrogen, thereby reducing the concentration of hydrogen at the outlet
  • Gas circulation unit 5 including:
  • the gas pressurization area includes a low-pressure gas buffer tank and a high-pressure gas buffer tank.
  • the circulating gas is divided into two paths, one is vented through the rotameter, and the other enters the low-pressure gas buffer tank.
  • the solenoid valve of the booster equipment gas booster pump
  • the solenoid valve of the booster equipment is turned on through the pressure sensor to start the gas circuit, so that the booster equipment starts to run.
  • a part of the gas enters the gas mixing area through the mass flow meter to realize the gas pressurization cycle, and the other part of the gas returns to the previous upper-level low-pressure gas buffer tank through the back pressure valve to prevent the gas from being evacuated. liquid structure.
  • the overall control of the device is PLC control.
  • the computer can control heating, gas intake flow, circulating gas volume, measurable temperature, pressure, flow and other data.
  • the control software has the function of recording and exporting.
  • the PLC control cabinet is an explosion-proof design with one-key disconnect Electric button, the unit is equipped with a computer.
  • Analysis unit 6 including:
  • gas chromatographs were used to sample the products for gas chromatographic analysis.
  • the two analytical chromatographic models are Agilent 7890B, and the chromatographic columns of gas chromatograph A are (1) HayeSep Q column (SFt 0.9m, OD 1/8, ID 2mm), (2) Molsieve 5A column (SFt 2.44m, OD 1/8, ID 2mm), (3) PoraBOND U column (25m, 0.32mm, 7 ⁇ m); equipped with TCD and FID detectors for analysis of permanent gases such as H 2 , O 2 , diluent gas and propylene, propane, cyclic Oxypropane, acrolein, acetone, propionaldehyde, acetaldehyde, etc., among which the peak positions of propylene and hydrogen are similar, and the mutual influence of the two cannot be accurately distinguished, so gas chromatography B is used to assist the analysis.
  • permanent gases such as H 2 , O 2 , diluent gas and propylene, propane
  • the TS-1 molecular sieve catalyst was prepared by hydrothermal synthesis, and the active metal Au was supported by the method of deposition and precipitation.
  • reaction space velocity 4000ml g cat -1 h -1
  • reaction pressure of the control system is 0.2 MPa
  • reaction pressure is 1.5
  • the temperature was programmed to 200°C at a rate of °C min -1.
  • the reaction system does not explode within 20 minutes.
  • the reaction system does not explode within 20 minutes.
  • the safety of the reaction can also be guaranteed under the condition of reducing the amount of diluent gas.
  • the diluent gas is nitrogen
  • the mixed gas is passed into the gas preheating zone, preheated to 160 °C, and then enters the reaction unit for reaction, and the reaction space velocity is 4000ml g cat -1 h -1
  • the reaction pressure of the system was controlled at 0.15 MPa
  • the temperature was programmed to 200 °C at a rate of 1.5 °C min -1 .
  • reaction product After the reaction product is processed by the product separation unit and the gas circulation unit, it is introduced into the mixed gas for recycling.
  • the diluent gas is nitrogen
  • the mixed gas is passed into the gas preheating zone, preheated to 130 °C, and then enters the reaction unit for reaction, and the reaction space velocity is 9000ml g cat -1 h -1
  • the reaction pressure of the system was controlled at 0.05 MPa
  • the temperature was programmed to 170 °C at a rate of 1.2 °C min -1 .
  • reaction product After the reaction product is processed by the product separation unit and the gas circulation unit, it is introduced into the mixed gas for recycling.
  • the diluent gas is nitrogen
  • the mixed gas is passed into the gas preheating zone, preheated to 100 °C, and then enters the reaction unit for reaction, and the reaction space velocity is 15000ml g cat -1 h -1
  • the reaction pressure of the system was controlled at 0.25 MPa
  • the temperature was programmed to 120 °C at a rate of 0.8 °C min -1 .
  • reaction product After the reaction product is processed by the product separation unit and the gas circulation unit, it is introduced into the mixed gas for recycling.
  • the diluent gas is nitrogen
  • the mixed gas is passed into the gas preheating zone, preheated to 80 °C, and then enters the reaction unit for reaction, and the reaction space velocity is 20000ml g cat -1 h -1 , control the reaction pressure of the system to 0.5 MPa, and program the temperature to 110 °C at a rate of 0.3 °C min -1 .
  • reaction product After the reaction product is processed by the product separation unit and the gas circulation unit, it is introduced into the mixed gas for recycling.
  • the diluent gas is nitrogen
  • the mixed gas is passed into the gas preheating zone, preheated to 100 °C, and then enters the reaction unit for reaction, and the reaction space velocity is 1000ml g cat -1 h -1
  • the reaction pressure of the system was controlled at 0.02 MPa
  • the temperature was programmed to 230 °C at a rate of 5 °C min -1 .
  • reaction product After the reaction product is processed by the product separation unit and the gas circulation unit, it is introduced into the mixed gas for recycling.
  • the direct epoxidation of propylene is carried out to prepare propylene oxide, the difference is that the diluent gas is propylene.
  • This comparative example is used to illustrate the method for the direct epoxidation of reference propylene
  • the conversion rate of propylene in Example 9 is only calculated for propylene as the reaction gas, and does not take into account the amount of propylene as the dilution gas, that is, after analyzing the amount of each component of the gas after the reaction. In the case of the conversion of propylene, the amount of propylene as the diluent gas needs to be subtracted, and it is considered that the diluent gas does not participate in the reaction.
  • (2) described second feed gas is mixed with oxygen 180° as the first feed gas hedging mix, obtains mixed gas, in the mixed gas, the ratio of hydrogen, oxygen, propylene and diluent gas is 1:1:1: 1;
  • reaction space velocity is 4000ml g cat -1 h -1
  • reaction pressure of the control system is 0.2MPa
  • reaction pressure is 0.2MPa per The temperature was increased to 200°C with a programmed temperature of 5°C and maintained for 5 min.
  • the reaction system does not explode within 20 minutes.
  • the reaction system does not explode within 20 minutes.
  • the safety of the reaction can also be guaranteed under the condition of reducing the amount of diluent gas.
  • reaction unit for reaction The reaction space velocity was 9000ml g cat -1 h -1 , the reaction pressure of the control system was 0.15MPa, and the temperature was increased to 200°C by a program maintained at 5°C for every 10min.
  • the reacted product is separated by product to obtain the target product, organic by-products and incompletely reacted tail gas, and the tail gas is treated and introduced into the third mixed gas for recycling.
  • reaction unit for reaction The reaction space velocity was 15000ml g cat -1 h -1 , the reaction pressure of the system was controlled to 0.05MPa, and the temperature was increased to 170°C by a program maintained at 8°C for every 8min.
  • the reacted product is separated by product to obtain the target product, organic by-products and incompletely reacted tail gas, and the tail gas is treated and introduced into the third mixed gas for recycling.
  • reaction unit for reaction The reaction space velocity was 4000ml g cat -1 h -1 , the reaction pressure of the control system was 0.25MPa, and the temperature was increased to 120°C with a program of maintaining 5min for each temperature increase of 10°C.
  • the reacted product is separated by product to obtain the target product, organic by-products and incompletely reacted tail gas, and the tail gas is treated and introduced into the third mixed gas for recycling.
  • reaction unit for reaction The reaction space velocity was 1000ml g cat -1 h -1 , the reaction pressure of the control system was 0.5MPa, and the temperature was increased to 100°C by a program maintained at 2°C for 1 min.
  • the reacted product is separated by product to obtain the target product, organic by-products and incompletely reacted tail gas, and the tail gas is treated and introduced into the third mixed gas for recycling.
  • reaction unit for reaction The reaction space velocity was 20000 ml g cat -1 h -1 , the reaction pressure of the control system was 0.01 MPa, and the temperature was increased to 250 °C with a program of maintaining 10 min for each temperature increase of 15 °C.
  • the reacted product is separated by product to obtain the target product, organic by-products and incompletely reacted tail gas, and the tail gas is treated and introduced into the third mixed gas for recycling.
  • This comparative example is used to illustrate the method for the direct epoxidation of reference propylene
  • the present invention can effectively reduce the amount of catalyst (compared to a 1000ml reactor, usually, the amount of catalyst needs to be at least 100g), and the amount of diluent gas is significantly reduced. Therefore, the concentration of reactants is significantly improved , the energy consumption is significantly reduced. At the same time, the conversion rate of propylene, the selectivity of propylene oxide and the utilization rate of hydrogen have been significantly improved. It can be seen that under the condition of using the same catalyst dosage, the technical solution of the present invention can achieve better effects, and therefore, the present invention can reduce the dosage of the catalyst.
  • the stable operation of the propylene gas-phase direct epoxidation process for at least 500 hours is realized, and combined with the more preferable conditions of the present invention, for example, specific reaction conditions, specific catalyst filling methods, etc. , which can make stable operation at least more than 1000 hours.
  • the propylene conversion rate can be improved without affecting the life of the catalyst through the recycling of the gas, and the full utilization of the raw materials is realized.

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Abstract

本发明涉及环氧丙烷制备领域，具体涉及一种丙烯直接环氧化制备环氧丙烷的方法和系统。该方法包括: 在丙烯环氧化反应条件下，将含有第一进料气和第二进料气的混合气体与催化剂进行接触反应，以得到环氧丙烷; 其中，第一进料气含有氧气且不含或基本不含氢气，第二进料气含有氢气且不含或基本不含氧气，第一进料气和/或第二进料气含有丙烯，所述第一进料气和第二进料气中至少一者还含有稀释气。使用本发明的技术方案能够降低稀释气的用量，优选对所述尾气进行循环使用，在不影响催化剂寿命的情况下显著提高了丙烯的转化率。

Description

丙烯直接环氧化制备环氧丙烷的方法和系统
相关申请的交叉引用
本申请要求2020年07月10日提交的中国专利申请202010662746.4的权益，该申请的内容通过引用被合并于本文。
本申请要求2020年07月10日提交的中国专利申请202010662744.5的权益，该申请的内容通过引用被合并于本文。
本申请要求2020年07月10日提交的中国专利申请202010662738.X的权益，该申请的内容通过引用被合并于本文。
技术领域
本发明涉及环氧丙烷制备领域，具体涉及一种丙烯环氧化制备环氧丙烷的方法和系统。
背景技术
环氧丙烷是全球范围内产量和用量巨大的化学品，可用于生产聚醚、丙二醇、异丙醇胺、丙烯醇等中间化学品，进而生成不饱和聚合物树脂、聚氨酯、表面活性剂等化学品。环氧丙烷广泛应用于食品、纺织、医药、化工等领域。
目前工业上的环氧丙烷生产方法主要有氯醇法、共氧化法和直接氧化(HPPO)法。其中，氯醇法的主要缺点是使用有毒氯气，设备腐蚀严重并产生大量污染环境的含氯废水，不符合绿色化学和清洁生产的要求，因此随着环境保护要求的日益提高，该工艺将最终被淘汰。共氧化法虽克服了氯醇法的污染环境和腐蚀设备等缺点，是比氯醇法相对清洁的生产工艺，但缺点是对原料质量要求高，工艺较长，投资规模大，效益受到联产产物的价格影响较大。
HPPO法是一种较为新颖的工艺，是以钛硅分子筛为催化剂，过氧化氢为氧化剂的直接氧化法。该反应突出的优势是反应条件温和(室温～80℃)，选择性高，绿色清洁。但该技术也存在一定的问题，例如需要配套建设过氧化氢生产装置。
有关研究报道TiO 2负载的Au纳米粒子可以催化氧气与丙烯反应生成环氧丙烷，具体反应方程式如下：
Figure PCTCN2021073744-appb-000001
该工作引起了国内外广泛的关注，研究人员对此展开了大量的研究，开发了多种金属催化剂，如Au、Ag、Cu等。普遍认同的反应机理为：TiO 2、TS-1等负载的Au催化剂首先催化H 2与O 2反应生成H 2O 2或者-OOH物种，然后中间物种与Ti作用形成Ti-OOH，进一步与丙烯反应生成环氧丙烷。该方法在反应器中，并且在催化剂和稀释气的存在下，直接对丙烯进行氧化得到环氧丙烷。该反应突出的优势是反应条件温和，选择性高，绿色清洁。但也存在明显问题：例如，为了解决安全性问题，研究人员大多数选择掺杂大量惰性保护气(例如，70-95体积％)来避免体系的爆炸。
发明内容
本发明的目的是为了克服现有技术存在的丙烯环氧化制备环氧丙烷的过程中，稀释气用量高的缺陷，提供一种丙烯环氧化制备环氧丙烷的方法和系统。使用本发明的技术方案能够显著降低稀释气的用 量。
为了实现上述目的，本发明一方面提供一种丙烯环氧化制备环氧丙烷的方法，该方法包括：在丙烯环氧化反应条件下，将含有第一进料气和第二进料气的混合气体与催化剂进行接触反应，以得到环氧丙烷；
其中，第一进料气含有氧气且不含或基本不含氢气，第二进料气含有氢气且不含或基本不含氧气，第一进料气和/或第二进料气含有丙烯，所述第一进料气和第二进料气中至少一者还含有稀释气。
优选的，所述稀释气为惰性稀释气和/或非惰性稀释气；在第一进料气和混合气体中，氧气的浓度各自独立地满足如下公式：
Figure PCTCN2021073744-appb-000002
其中，
X O2为氧气在混合气中的体积分数(％)；
Xm为惰性稀释气m在混合气中的体积分数(％)；
Xn为非惰性稀释气n在混合气中的体积分数(％)；
X丙烯为丙烯在混合气中的体积分数(％)；
X氢气为氢气在混合气中的体积分数(％)；
Nn为非惰性稀释气n在混合气中的爆炸下限(％)；
N丙烯为丙烯在混合气中的的爆炸下限(％)；
N氢气为氢气在混合气中的爆炸下限(％)；
Ln为非惰性稀释气n在混合气中的爆炸上限(％)；
L丙烯为丙烯在混合气中的爆炸上限(％)；
L氢气为氢气在混合气中的爆炸上限(％)。
优选的，所述稀释气为丙烯、丙烷、甲烷和乙烷中的至少一种。
优选的，所述催化剂与惰性填充物以交替分层堆积的方式填充于反应器中。
优选的，所述丙烯环氧化反应中，混合气体的体积空速为500-30000ml g cat -1h -1。
优选地，该方法还包括对所述混合气体进行预热。
第二方面，本发明提供了一种用于丙烯直接环氧化制备环氧丙烷的反应系统，该反应系统包括：
供气单元，用于提供丙烯、氧气、氢气和稀释气；
混合单元，包括第一进料区、第二进料区和第三进料区；
所述第一进料区用于将氧气、可选的氢气、可选的丙烯和可选的稀释气进行混合，得到第一进料气；
所述第二进料区用于将氢气、可选的氧气、可选的丙烯和可选的稀释气进行混合，得到第二进料气；
其中，所述第一进料气和第二进料气中各物料的选择使得第一进料气含有氧气且不含或基本不含氢气，第二进料气含有氢气且不含或基本不含氧气，第一进料气和/或第二进料气含有丙烯，所述第一进料气和第二进料气中至少一者还含有稀释气；
所述第三进料区用于将所述第一进料气、所述第二进料气和循环气混合，得到混合气体；
反应单元，所述反应单元内布置有催化剂，用于使所述混合气体与所述催化剂进行接触，并在丙烯环氧化反应条件下反应，得到环氧丙烷；
产物分离单元，用于分离丙烯环氧化反应得到的产物，得到目标产物环氧丙烷、有机副产物和循环气；
气体循环单元，与所述混合单元相连通，用于接收所述循环气，然后将循环气作为至少部分反应原料气和稀释气输送至所述混合单元。
通过上述技术方案，本发明可取得如下的有益效果：
1.本发明通过将含有氧气且不含或基本不含氢气的第一进料气和含有氢气且不含或基本不含氧气的第二进料气混合，得到混合气体，且第一进料气和/或第二进料气含有丙烯，所述第一进料气和第二进料气中至少一者还含有稀释气，可避免氢气和氧气的混合时氢气的浓度迅速降至混合可燃气体系的爆炸极限以内，由此可见，本发明的方法达到了反应原料气混合更加均匀混合且更进一步降低燃爆风险的目的。
2.本发明的技术方案，可同时降低稀释气的用量，在降低了后续产物分离压力的前体下，还提高了反应气的浓度，从而提高了反应选择性和转化率，并且降低了能耗。
3.本发明的技术方案能够对反应用气体更为有效的混合，在与催化剂接触时，降低了对催化剂的影响，从而显著延长了催化剂的使用寿命，在管式反应器中，可由常规的100小时延长至500小时以上。
4.在优选的情况下，本发明采用气相循环工艺，对没有反应的原料气针对性地进行处理后循环返回反应器，进一步进行反应，实现了原料利用率的大幅度提高，在保障环氧丙烷空时产率的前提下，丙烯综合转化率得到显著提高。此外，在保障反应安全的前体下，对反应尾气进行循环利用，降低了生产成本以及尾气处理压力。
5.在优选的情况下，本发明的技术方案能够对反应用气体更为有效的利用，且不会对催化剂的寿命造成影响。
附图说明
图1是本发明提供的催化剂的填充方式。
图2是是本发明提供的丙烯直接环氧化制备环氧丙烷的反应系统的示意图。
附图标记说明
1供气单元               2混合单元               3反应单元
4产物分离单元       5气体循环单元       6分析单元
具体实施方式
在本文中所披露的范围的端点和任何值都不限于该精确的范围或值，这些范围或值应当理解为包含接近这些范围或值的值。对于数值范围来说，各个范围的端点值之间、各个范围的端点值和单独的点值之间，以及单独的点值之间可以彼此组合而得到一个或多个新的数值范围，这些数值范围应被视为在本文中具体公开。
第一方面，本发明提供了一种丙烯环氧化制备环氧丙烷的方法，该方法包括：在丙烯环氧化反应条件下，将含有第一进料气和第二进料气的混合气体与催化剂进行接触反应，以得到环氧丙烷；
其中，第一进料气含有氧气且不含或基本不含氢气，第二进料气含有氢气且不含或基本不含氧气，第一进料气和/或第二进料气含有丙烯，所述第一进料气和第二进料气中至少一者还含有稀释气。
根据本发明，所述稀释气可以为任意的能够用于丙烯直接环氧化反应的稀释气，可以为惰性气体，也可以为非惰性气体，还可以为惰性气体和非惰性气体的混合稀释气。因此，所述稀释气为惰性稀释气和/或非惰性稀释气。
根据本发明，所述惰性稀释气可以选自N 2，Ar和CO 2。
根据本发明，优选的，所述非惰性气体为气态烷烃和/或气态烯烃。
优选的，所述气态烷烃为C1-C4的烷烃，根据本发明另一种特别优选的实施方式，所述气态烷烃为甲烷、乙烷和丙烷，更优选为丙烷。
优选的，所述气态烯烃为C2-C4的烯烃，根据本发明一种特别优选的实施方式，所述气态烯烃为丙烯。
根据本发明，在所述第一进料气或所述第二进料气中，稀释气的比例不受特别的限制，其可以为0至100％之间任意值或范围的总稀释气，例如，0、0.01％、0.1％、1％、10％、20％、30％、40％、50％、60％、70％、80％、90％、100％，0.05-100％、50-90％等等。
根据本发明，在所述第一进料气或所述第二进料气中，丙烯的比例不受特别的限制，其可以为0至100％之间任意值或范围的总丙烯，例如，0、0.01％、0.1％、1％、10％、20％、30％、40％、50％、60％、70％、80％、90％、100％，0.05-100％、50-90％等等。
根据本发明，“基本不含氢气”是指第一进料气中含有的氢气的量不足以引发爆炸，例如，氢气在第一进料气中的体积分数在4％以下(不包括本数)，例如，可以在3.5％以下、3％以下、2.5％以下、2％以下、1.5％以下、1％以下、0.5％以下、0.1％以下。
其中，“基本不含氧气”是指第一进料气中含有的氧气的量不足以引发爆炸，例如，氧气在第二进料气中的体积分数在25％以下(不包括本数)，例如，可以在20％以下、15％以下、10％以下、8％以下、5％以下、4％以下、3％以下、2％以下、1％以下、0.5％以下、0.1％以下。
根据本发明一种优选的实施方式，所述第一进料气含有氧气且不含或基本不含氢气，含有至少部分丙烯和至少部分稀释气；所述第二进料气含有氢气且不含或基本不含氧气，含有剩余部分丙烯和剩余部分稀释气；或者
所述第二进料气含有氢气且不含或基本不含氧气，含有至少部分丙烯和至少部分稀释气；所述第二进料气含有氧气且不含或基本不含氢气，含有剩余部分丙烯和剩余部分稀释气。
根据本发明进一步优选的实施方式A，所述第一进料气含有氧气且不含或基本不含氢气、全部丙烯和全部稀释气；所述第二进料气含有氢气且不含或基本不含氧气。
根据本发明进一步优选的实施方式B，所述第一进料气含有氧气且不含或基本不含氢气、全部丙烯和部分稀释气(＞0)；所述第二进料气含有氢气且不含或基本不含氧气和剩余部分稀释气。
根据本发明进一步优选的实施方式C，所述第一进料气含有氧气且不含或基本不含氢气、部分丙烯(＞0)和部分稀释气(＞0)；所述第二进料气含有氢气且不含或基本不含氧气、剩余部分丙烯和剩余部分稀释气。
根据本发明进一步优选的实施方式D，所述第一进料气含有氧气且不含或基本不含氢气、部分丙烯(＞0)和全部稀释气；所述第二进料气含有氢气且不含或基本不含氧气和剩余部分丙烯。
根据本发明进一步优选的实施方式E，所述第一进料气含有氧气且不含或基本不含氢气和全部稀 释气；所述第二进料气含有氢气且不含或基本不含氧气和全部丙烯。
根据本发明进一步优选的实施方式F，所述第一进料气含有氧气且不含或基本不含氢气和部分稀释气(＞0)；所述第二进料气含有氢气且不含或基本不含氧气、剩余部分稀释气和全部丙烯。
根据本发明进一步优选的实施方式G，所述第一进料气含有氧气且不含或基本不含氢气和部分丙烯(＞0)；所述第二进料气含有氢气且不含或基本不含氧气、全部稀释气和部分丙烯。
根据本发明进一步优选的实施方式H，所述第一进料气含有氧气且不含或基本不含氢气；所述第二进料气含有氢气且不含或基本不含氧气、全部稀释气和全部丙烯。
本发明中，如上所述的“部分稀释气”是指0-100体积％之间的任意数值(不包括端点值)，例如，0.1体积％、1体积％、5体积％、10体积％、15体积％、20体积％、25体积％、30体积％、35体积％、40体积％、45体积％、50体积％、55体积％、60体积％、65体积％、70体积％、75体积％、80体积％、85体积％、90体积％、91体积％、92体积％、93体积％、94体积％、95体积％、96体积％、97体积％、98体积％、99体积％、99.5体积％。
本发明中，如上所述的“部分丙烯”是指0-100体积％之间的任意数值(不包括端点值)，例如，0.1体积％、1体积％、5体积％、10体积％、15体积％、20体积％、25体积％、30体积％、35体积％、40体积％、45体积％、50体积％、55体积％、60体积％、65体积％、70体积％、75体积％、80体积％、85体积％、90体积％、91体积％、92体积％、93体积％、94体积％、95体积％、96体积％、97体积％、98体积％、99体积％、99.5体积％。
根据本发明一种优选的实施方式，在第一进料气和混合气体中，氧气的浓度各自独立地满足如下公式：
Figure PCTCN2021073744-appb-000003
Figure PCTCN2021073744-appb-000004
其中，
X O2为氧气在混合气中的体积分数(％)；
Xm为惰性稀释气m在混合气中的体积分数(％)；
Xn为非惰性稀释气n在混合气中的体积分数(％)；
X丙烯为丙烯在混合气中的体积分数(％)；
X氢气为氢气在混合气中的体积分数(％)；
Nn为非惰性稀释气n在混合气中的爆炸下限(％)；
N丙烯为丙烯在混合气中的爆炸下限(％)；
N氢气为氢气在混合气中的爆炸下限(％)；
Ln为非惰性稀释气n在混合气中的爆炸上限(％)；
L丙烯为丙烯在混合气中的爆炸上限(％)；
L氢气为氢气在混合气中的爆炸上限(％)。
在如上优选的实施方式下，通过将氧气控制在如上式(1)或式(2)的范围内，可有效避免反应体 系的爆炸，从而使得反应安全进行。
需要说明的是，当控制第一进料气中氧气浓度时，如上的混合气是指第一进料气，当控制混合气体中氧气浓度时，如上的混合气是指混合气体。
能够理解的是，当所述稀释气仅为惰性稀释气时，公式中对于非惰性稀释气的加和为0；当所述稀释气仅为非惰性稀释气时，公式中Xm为0；当所述稀释气为惰性气体和非惰性气体的混合稀释气时，按照各自的比例进行公式的运算。
根据本发明，丙烯的爆炸极限范围是指在室温、常压条件下通过密闭空间的可燃气体燃爆实验方法(GB/T12474-2008相关规定进行测试)测定的爆炸极限范围，其爆炸范围为2-11％。爆炸下限为2％，爆炸上限为11％。
能够理解的是，当丙烯作为稀释气时，X丙烯可以指体系中全部的丙烯的体积分数，此时作为稀释气的丙烯的加和为0；此外，也可以按照如上公式以丙烯作为稀释气的量和丙烯作为反应气的量进行公式的运算。
根据本发明，氢气的爆炸极限范围是指在室温、常压条件下通过密闭空间的可燃气体燃爆实验方法(GB/T12474-2008相关规定进行测试)测定的爆炸极限范围，其爆炸范围为4-75％。爆炸下限为4％，爆炸上限为75％。
根据本发明，甲烷的爆炸极限范围是指在室温、常压条件下通过密闭空间的可燃气体燃爆实验方法(GB/T12474-2008相关规定进行测试)测定的爆炸极限范围，其爆炸范围为5-15％。爆炸下限为5％，爆炸上限为15％。
根据本发明，乙烷的爆炸极限范围是指在室温、常压条件下通过密闭空间的可燃气体燃爆实验方法(GB/T12474-2008相关规定进行测试)测定的爆炸极限范围，其爆炸范围为3-16％。爆炸下限为3％，爆炸上限为16％。
根据本发明，丙烷的爆炸极限范围是指在室温、常压条件下通过密闭空间的可燃气体燃爆实验方法(GB/T12474-2008相关规定进行测试)测定的爆炸极限范围，其爆炸范围为2-10％。爆炸下限为2％，爆炸上限为10％。
本发明的发明人独创的发现，在采用丙烯作为稀释气的情况下，丙烯既作为稀释气又作为反应气，能够进一步推动反应的正向进行。在采用丙烷作为稀释气的情况下，可以有效抑制副反应的发生，从而提高环氧丙烷的选择性。本发明需要说明的是，丙烯作为稀释气的情况下，是指至少部分稀释气被丙烯所取代，从而导致反应原料气中丙烯的量大大过量，该过量程度超出了一般情况下通过提高反应原料的用量从而达到促进反应正向进行的程度，因此，在该情况下，不能简单的认为丙烯是过量的，其和常规理解意义上的过量是不同的。
根据本发明，为了更有利于工业化生产以及提高本发明的效果，优选的，在混合气体中，氧气的浓度满足式(1)。
根据本发明，由以上可知，所述第一进料气可以为纯氧气，可以为氧气与稀释气的混合气，当所述第一进料气为后者情况时，对于其氧气的浓度没有特别的限制。
根据本发明，当所述第一进料气含有氧气、稀释气、丙烯和可选的氢气时，氧气的浓度优选满足公式(1)中，第一进料气中氧气的浓度优选不高于82体积％，例如，可以在15体积％、20体积％、25体积％、30体积％、35体积％、40体积％、45体积％、50体积％、55体积％、60体积％、69体积％、76体积％、79体积％以下，在该优选的情况下，可以将第一进料气控制在安全范围。
根据本发明，在本发明的技术方案下，混合气体中稀释气的浓度可以降低至70体积％以下，例如，65体积％、60体积％、55体积％、50体积％、45体积％、40体积％、35体积％等等。而按照现有技术 方案方法，其稀释气的浓度一般在70体积％以上。由此可见，本发明的方法可有效降低稀释气的浓度，从而进一步提高了反应气的浓度，提高了反应效率。
根据本发明，在本发明的技术方案下，混合气体中氧气的浓度优选满足公式(1)，混合气体中氧气的浓度可以提高至5体积％，优选10体积％以上，优选不高于60体积％，例如，11体积％、12体积％、13体积％、14体积％、15体积％、16体积％、17体积％、18体积％、19体积％、20体积％、21体积％、22体积％、23体积％、24体积％、25体积％、26体积％、27体积％、28体积％、29体积％、30体积％、32体积％、34体积％、36体积％、38体积％、40体积％、42体积％、44体积％、46体积％、48体积％、50体积％、52体积％、54体积％、56体积％、58体积％、60体积％。而按照现有技术方案方法，其氧气浓度一般在10体积％以下，更优选在5体积％以下。由此可见，本发明的方法可有效提高氧气的浓度。
根据本发明，为了更加充分的混合，第二进料气与第一进料气设计为对冲混合。这可以通过对第二进料气的输送管路与第一进料气的输送管路的设置实现。其中，需要说明的是，本文所述的对冲是指两股气流以相撞的形式进行混合，所述相撞可以是两股在90-270°，例如，180°角度下相撞，其中，以两股气流喷向同一方向界定为0°，喷向相反的反向界定为180°。
根据本发明，为了进一步提高反应的效率，在将混合气体与催化剂进行接触之前，还优选对其进行预热。
根据本发明，所述预热的程度优选至少达到目标反应温度的50％，例如，50％、55％、60％、65％、70％、75％、80％、85％，优选大于80％。
根据本发明，所述丙烯环氧化反应可以在本领域常规的反应器中进行，例如，可以为本领域常规的各种管式反应器，例如，不锈钢、树脂、石英、有机玻璃、陶瓷玻璃反应器。又例如，所述反应器可以为本领域常规的各种微通道反应器。
根据本发明，所述催化剂可以具有任意适合所述管式反应器或所述微通道反应器的尺寸和形状。
根据本发明，所述催化剂可以为现有技术公开的任意能够将丙烯、氧气、氢气和稀释气催化反应以生成环氧丙烷的催化剂，优选的，所述催化剂为负载型金属催化剂，该负载型金属催化剂含有载体和活性金属组分。其中，所述活性金属组分可以选自金、银、铜、钌、钯、铂、铑、钴、镍、钨、铋、钼及它们的氧化物中的至少一种，优选为金；用于负载所述金属的载体可以为炭黑、活性炭、二氧化硅、三氧化二铝、氧化铈和沸石，优选为沸石，更优选为钛硅分子筛。
根据本发明，在所述负载型金属催化剂中，以金属元素计的金属的含量可以在较宽的范围内改变，例如，以催化剂的总重量计，催化剂中以金属元素计的活性金属组分的含量为0.01-50重量％，例如，可以为0.01重量％、0.05重量％、0.06重量％、0.07重量％、0.08重量％、0.09重量％、0.1重量％、0.2重量％、0.3重量％、0.4重量％、0.5重量％、0.6重量％、0.7重量％、0.8重量％、0.9重量％、1重量％、1.1重量％、1.2重量％、1.3重量％、1.4重量％、1.5重量％、1.6重量％、1.7重量％、1.8重量％、1.9重量％、2重量％、3重量％、4重量％、5重量％、10重量％、15重量％、20重量％、25重量％、30重量％、35重量％、40重量％、45重量％、50重量％，优选为0.05-5重量％，更优选0.1-2重量％。
根据本发明一种优选的实施方式，所述催化剂为负载金的钛硅分子筛(Au@TS-1)，其中，以金元素计的活性金属组分的负载量为0.1-2重量％。其中，TS-1分子筛可以通过水热合成的方式制备，活性金属组分Au可以通过沉积沉淀的方法进行负载。
根据本发明，所述催化剂可以单独填充在丙烯环氧化反应的反应器中(如图1a所示)，也可以与其他惰性物质结合填充在所述反应器中。但为了进一步提高催化剂的使用寿命，提高反应的选择性、转化率、时空产率以及氢气利用率，降低催化剂的用量，优选的，所述催化剂以与催化剂和惰性填充物相结合的形式填充于所述反应器中。其中，所述惰性填充物可以为本领域常规使用的惰性固相物质，优选 的，所述惰性填充物选自石英砂、Al 2O 3、多孔硅胶和陶瓷环中的至少一种。
其中，所述惰性填充物的用量可以在较宽的范围内改变，但优选的，相对于1重量份的催化剂，所述惰性填充物的用量为1-200重量份(例如，可以为1重量份、10重量份、15重量份、20重量份、25重量份、30重量份、35重量份、40重量份、45重量份、50重量份、80重量份、90重量份、95重量份、100重量份、105重量份、110重量份、115重量份、120重量份、125重量份、130重量份、135重量份、140重量份、145重量份、150重量份、160重量份、170重量份、180重量份、190重量份、200重量份)，优选为15-50重量份，更优选为30-45重量份。
根据本发明，所述催化剂与所述惰性填充物的结合形式可以不受特别的限制，例如，可以直接将二者混合后填充于所述反应器中，也可以将二者设计成三明治结构(如图1b)，其中，催化剂或者惰性填充物位于中间。然而本发明的发明人在研究中发现，所述催化剂与惰性填充物以分层堆积的方式填充于所述反应器中，更所述催化剂与惰性填充物以交替分层堆积的方式填充于反应器中(如图1c所示)，能够进一步提高催化剂的寿命，反应的选择性、转化率、时空产率以及氢气利用率，以及降低催化剂的用量。其中，在该方式中，每层催化剂和每层惰性填充物的高度可以在较宽的范围内选择，他们可以以等高度的方式或不等高度的方式进行分层堆积，优选的，每层催化剂和每层惰性填充物各自独立地为1-2000层/米，例如，可以为1层/米、2层/米、3层/米、4层/米、5层/米、6层/米、7层/米、8层/米、9层/米、10层/米、15层/米、18层/米、20层/米，50层/米、100层/米、200层/米、300层/米、400层/米、500层/米、600层/米、700层/米、800层/米、900层/米、1000层/米、1200层/米、1400层/米、1600层/米、1800层/米、2000层/米；优选为1000-2000层/米，或者10-20层/米。
根据本发明，每层催化剂和每层惰性填充物的层高比可以在较宽的范围内改变，优选的，为了进一步提高本发明的效果，每层催化剂和每层惰性填充物的层高比为1:1-10，例如，可以为1:1、1:2、1:3、1:4、1:5、1:6、1:7、1:8、1:9、1:10，优选为1:1-3，进一步优选为1:1.5-2.5。
根据本发明，将所述催化剂填充于所述反应器中的方式可以不受特别的限制，例如，可以采用涂层法、电沉积法、溶液电镀法、机械填充法等。
根据本发明，优选的，相对于1000ml的反应器，所述催化剂的填充量为10-50g。通常情况下，催化剂的填充量至少需要100g，而可以看出，本发明的技术方案还可以降低催化剂的填充量。
根据本发明，所述丙烯环氧化反应的温度可以为本领域常规的反应温度，例如，可以为20-300℃，但为了进一步提高反应的转化率、选择性、时空产率以及氢气利用率，以及提高催化剂的使用寿命，降低催化剂的用量，优选的，所述反应的温度为50-250℃，更优选为120-200℃，例如，可以为120℃、125℃、130℃、135℃、140℃、145℃、150℃、155℃、160℃、165℃、170℃、175℃、180℃、185℃、190℃、195℃、200℃。
本发明的发明人在研究中发现，体系的升温速度也能够进一步影响反应的转化率、选择性、时空产率以及氢气利用率，催化剂的使用寿命，催化剂的用量，当以间歇式升温的方式将反应体系的温度升温至丙烯环氧化反应所需温度时，能够进一步提高反应的转化率、选择性、时空产率以及氢气利用率，以及提高催化剂的使用寿命，降低催化剂的用量和稀释气用量。优选的，所述间歇式升温的方式包括：每升温5-10℃(例如，5℃、6℃、7℃、8℃、9℃、10℃)后在升至温度下维持5-10min(例如，5min、6min、7min、8min、9min、10min)。
更为优选的，当以0.1-10℃min -1，优选0.5-5℃min -1，更优选0.5-2℃min -1(例如，可以为0.5℃min -1、0.8℃min -1、1.0℃min -1、1.2℃min -1、1.5℃min -1、2.0℃min -1，更优选0.8-1.5℃min -1)的速率将反应体系的温度升温至丙烯环氧化反应所需温度时，能够再进一步提高反应的转化率、选择性、时空产率以及氢气利用率，以及提高催化剂的使用寿命，降低催化剂的用量和稀释气用量。
根据本发明，所述丙烯环氧化反应的压力可以为本领域常规的反应压力，例如，可以为0-5MPa，但为了进一步提高反应的转化率、选择性、时空产率以及氢气利用率，以及提高催化剂的使用寿命，降低催化剂的用量，优选的，所述反应的压力为0-1.5MPa，更优选为0.05-0.25MPa，例如，可以为0.05MPa、0.06MPa、0.07MPa、0.08MPa、0.09MPa、0.1MPa、0.11MPa、0.12MPa、0.13MPa、0.14MPa、0.15MPa、0.17MPa、0.19MPa、0.21MPa、0.23MPa、0.25MPa。
根据本发明，所述丙烯环氧化反应的空速可以为本领域常规的反应空速，但为了进一步提高反应的转化率、选择性、时空产率以及氢气利用率，以及提高催化剂的使用寿命，降低催化剂的用量，优选的，混合气体的体积空速为500-30000ml g cat -1h -1，更优选为1000-20000ml g cat -1h -1，进一步优选为2000-15000ml g cat -1h -1，例如，可以为2000ml g cat -1h -1、3000ml g cat -1h -1、4000ml g cat -1h -1、5000ml g cat -1h -1、6000ml g cat -1h -1、7000ml g cat -1h -1、8000ml g cat -1h -1、9000ml g cat -1h -1、10000ml g cat -1h -1、12000ml g cat -1h -1、13000ml g cat -1h -1、14000ml g cat -1h -1、15000ml g cat -1h -1。
根据本发明，本发明的方法提供的所述丙烯环氧化反应优选在不存在溶剂的情况下进行。其中，所述溶剂包括任意的外援引入的液相。
根据本发明一种优选的实施方式，该方法还包括：将反应产物进行分离，得到目标产物环氧丙烷、有机副产物和尾气，然后将所述尾气进行后处理，并作为至少部分反应原料气和稀释气混合入所述混合气体中进行循环使用。通过该循环使用，实现了原料的利用率的大幅度提高，在保障环氧丙烷空时产率的前提下，丙烯综合转化率得到显著提高。
优选的，所述后处理包括依次进行的洗涤、可选的冷凝、可选的组分调整和增压。
优选的，所述洗涤为醇洗。其中，所述醇可以为甲醇、乙醇、丙醇、正丁醇、异丁醇和乙二醇等中的一种或多种。
根据本发明一种优选的实施方式，使用醇对所述尾气进行低温洗涤，更优选对反应后的气体进行多级低温醇洗，例如，2-3级。所述低温可以为2-20℃。
根据本发明一种优选的实施方式，所述后处理包括：
1)对所述尾气进行洗涤，并对所得洗涤工艺气进行组成分析，若洗涤工艺气组成在预定范围内，则将其作为循环气混入混合气体中进行循环使用，若洗涤工艺气组成不在预定范围内，则进行冷凝处理；
2)将洗涤工艺气进行至少一级冷凝，得到凝液和不凝工艺气，并对所述不凝工艺气进行组分分析，若不凝工艺气组成在预定范围内，则将其作为循环气混入混合气体中进行循环使用，若不凝工艺气组成不在预定范围内，则进行调气处理；
3)通过通入丙烯、氢气、氧气和稀释气中的至少一种对所述不凝工艺气的组成进行调节，并对得到的调节工艺气进行组成分析，若调节工艺气组成在预定范围内，则将其作为循环气混入混合气体中进行循环使用，若调节工艺气组成不在预定范围内，将其外排。
其中，所述组成分析可以通过气相色谱分析来完成。例如，将待分析的气体引入到配备有TCD和FID检测器的气相色谱中进行分析。
优选的，组成分析后得到气体中各组分的浓度，并根据反应需求通过质量流量计将气体中各组分浓度调节至预定浓度，然后进行循环使用。
其中，步骤(b)中，可以通过低温冷阱对醇洗尾气进行冷凝，醇洗尾气中各组分能够根据其沸点的不同分别冷凝下来，形成冷凝液，然后通过低温循环制冷泵将冷凝液经旋风分离。
根据本发明，所述组成在预定范围内是指相应气体的组成含量稳定、处于安全的范围内，没有超出极限氧含量。
更优选的，为了保证分析的效果，各待进行组分分析的工艺气在50-200℃的加热条件下输送至气 相色谱分析中，具体可以通过设置加热带以维持50-200℃的温度，优选80-150℃，例如，80℃、90℃、100℃、110℃、120℃、130℃、140℃、150℃。
第二方面，如图2所示，本发明提供了一种用于丙烯直接环氧化制备环氧丙烷的反应系统，该反应系统包括：
供气单元1，用于提供丙烯、氧气、氢气和稀释气；
混合单元2，包括第一进料区、第二进料区和第三进料区；
所述第一进料区用于将氧气、可选的氢气、可选的丙烯和可选的稀释气进行混合，得到第一进料气；
所述第二进料区用于将氢气、可选的氢气、可选的丙烯和可选的稀释气进行混合，得到第二进料气；
其中，所述第一进料气和第二进料气中各物料的选择使得第一进料气含有氧气且不含或基本不含氢气，第二进料气含有氢气且不含或基本不含氧气，第一进料气和/或第二进料气含有丙烯，所述第一进料气和第二进料气中至少一者还含有稀释气；
所述第三进料区用于将所述第一进料气、所述第二进料气和循环气混合，得到混合气体；
反应单元3，所述反应单元内布置有催化剂，用于使所述混合气体与其中的催化剂进行接触，并在丙烯环氧化反应条件下反应，得到环氧丙烷；
产物分离单元4，用于分离丙烯环氧化反应得到的产物，得到目标产物环氧丙烷、有机副产物和循环气；
气体循环单元5，与所述混合单元相连通，用于接收所述循环气，然后将循环气作为至少部分反应原料气和稀释气输送至所述混合单元。
优选的，在所述第三进料区，用于引入第一进料气的管路和用于引入第二进料气或氢气的管路的设置方式使得第一进料气与所述第二进料气进行对冲混合。需要说明的是，本文所述的对冲是指两股气流以相撞的形式进行混合，所述相撞可以是两股在90-270°，例如，180°角度下相撞，其中，以两股气流喷向同一方向界定为0°，喷向相反的反向界定为180°。
根据本发明，为了进一步提高本发明的效果，所述混合单元还包括设置在所述第三进料区下游的气体预热区，其中，所述气体预热区内设置有预热装置，该装置可以设计为与所述反应器的结构相同，也可以不同。该装置还设置有加热元件以及温控元件，以将所述反应原料气加热至预定的温度。
根据本发明一种优选的实施方式，所述预热装置为盘管式设计，可以通过导热油、熔盐、电加热等形式对所述反应原料气进行加热。
根据本发明，为了提高丙烯转化率，根据本发明一种优选的实施方式，所述产物分离单元包括依次串联的产物分离区、气体洗涤区、气体冷凝区和调气区，且产物分离区、气体洗涤区、气体冷凝区和调气区各自独立地与所述气体循环单元相连通。
根据本发明，为了更好的控制反应后所得反应产物气的压力和流速，优选的，在反应单元的出口处还设置有调节阀，例如，背压阀，以对反应后的气体的压力和流速进行调节。
根据本发明，优选的，所述反应系统还包括分析单元6，用于对需要组分分析的工艺气进行组分分析。
根据本发明，优选的，所述反应单元还与分析单元相通，因此，反应后的产物可分为至少2条支路，其中，一条支路用于将部分反应后的产物输送至分析单元，另一条支路用于将剩余的反应后的产物输送至产物分离单元，以进行后处理。
根据本发明，优选的，所述产物分离区用于分离丙烯环氧化反应得到的产物，得到目标产物环氧 丙烷、有机副产物和尾气(含有稀释气和未充分反应的原料气)，所述尾气通过一条支路输送至分析单元用于全组分分析；剩余部分尾气通过另一条支路输送至气体洗涤区，用于对所述尾气进行洗涤，得到洗涤工艺气。因此，优选的，所述产物分离区还与所述分析单元相连通。
优选的，所述气体洗涤区优选设置有气体洗涤设备，例如，气体洗涤罐，其中，所述气体洗涤设备中优选设置有气体分布器，以对引入的气体进行均匀的分布，从而使得洗涤更充分。
根据本发明，由于反应后的气体仍然具有较高的温度，因此，为了及时的将热量移除，所述气体洗涤设备还设置有降温元件，例如，设置在所述气体洗涤设备外部的循环水夹套，通过换热以降低洗涤液温度。而换热升温后的水可以用作其他的热源进行充分利用。
根据本发明一种优选的实施方式，使用醇对所述尾气进行洗涤，更优选对所述尾气进行多级醇洗，例如，2-3级。因此，所述气体洗涤区包括依次串联的多级醇洗罐，所述醇洗罐中装有醇液，所述尾气通过设置在醇洗罐中的气体分布器以鼓泡的形式与醇接触以进行醇洗。其中，所述醇可以为甲醇、乙醇、丙醇、正丁醇、异丁醇、乙二醇等。
根据本发明一种优选的实施方式，所述气体洗涤区与分析单元相通，从而对洗涤工艺气进行全组分检测，以确定洗涤工艺气中各组分的含量，因此，所述洗涤工艺气至少分为两条支路，其中一条支路与分析单元相通，用于对其进行全组分分析，另一条支路根据情况将其进一步处理。
根据本发明，所述洗涤工艺气可以通过如下几种情况来处理。
1：如果洗涤工艺气各组分含量达到预期要求，且处于安全的混合气体系范围，没有超出极限氧含量的控制条件，各种有机组分的含量稳定，该洗涤工艺气直接作为循环气输送至气体循环单元。
在这样的情况下，所述气体洗涤区分别与分析单元和气体循环单元相通，并在连通管路上设置有阀门。
2：如果洗涤工艺气中某组分含量异常，超出极限氧含量控制范围或者可燃性有机物的含量超过爆炸极限，则将其输送至气体冷凝区进行进一步处理，此时通过控制气体冷凝区的温度(冷阱温度)，将该洗涤工艺气各组分根据其沸点的不同分别冷凝下来，以达到安全的混合气范围，然后未冷凝的部分气体再次进入分析单元进行组分分析。如果满足1中的条件，则直接作为循环气输送至气体循环单元。如果不满足1中的条件，则继续调节冷凝温度，将洗涤工艺气进一步分离以达到安全控制区间。
因此，优选的，所述气体冷凝区分别与分析单元和气体循环单元相通，并在连通管路上设置有阀门。
3：如果经过多次冷凝操作后，不凝工艺气组成仍然处于可燃气体爆炸极限范围以内，则将所述不凝工艺气输送至调气区进行气体比例的调节，通过调节工艺气的比例(例如，不凝工艺气中氢气的含量较高，且处于爆炸极限范围，则通过提高丙烯和氧气含量以提高氢气的利用率，从而降低出口氢气浓度)，从而实现反应原料气的选择性消耗，进而实现进入气体循环单元的混合气组分安全化操作。
因此，优选的，所述调气区分别与分析单元和气体循环单元相通，并在连通管路上设置有阀门。
4：如果1、2、3均不能解决混合气安全范围的控制问题，则将该部分混合气进入尾气泄放区排空，移出本反应体系。
因此，优选的，所述调气区下游还设置有尾气泄放区。
根据本发明，为了完成尾气的循环，所述气体循环单元优选包括气体增压区，用于循环气的增压，从而作为至少部分反应原料气和稀释气输送至所述混合单元。
根据本发明，所述气体增压区优选设置有依次串联的低压气体缓冲罐和高压气体缓冲罐，其中，所述低压气体缓冲罐中设置有增压设备，所述高压气体缓冲罐与所述混合单元连通。具体的，循环气通过管路进入低压气体缓冲罐，当低压气体缓冲罐中的气体压力达到阈值时，增压设备开启以对气体进行 增压，增压后的气体进行高压气体缓冲罐，作为至少部分反应原料气和稀释气输送至混合单元。
其中，优选的，在所述低压气体缓冲罐中还设置有压力传感器，当其中的气体压力达到阈值时，可以通过该压力传感器开启增压设备，例如，通过开启增压设备启动气路上的电磁阀。
优选的，所述增压设备为气体增压泵。
根据本发明，为了防止气体抽空，优选的，高压气体缓冲罐和低压气体缓冲罐之间还设置有气体回流管路，以将高压气体缓冲罐中的部分气体返回至低压气体缓冲罐。
优选的，所述低压气体缓冲罐和所述高压气体缓冲罐还各自独立地设置有安全阀以及底部的排液结构。
根据本发明，所述反应系统整体的控制优选为PLC控制，通过计算机可控制加热、气体进气流量，循环气量、可测量温度、压力、流量等数据，控制软件具有记录与导出功能。其中，PLC控制柜优选为防爆设计，配有一键断电按钮，装置配有计算机。
根据本发明，所述供气单元可以包括氢气进气支路、氧气进气支路、丙烯进气支路和稀释气进气支路，每个进气支路中均可以包括相应气体储罐，设置在气体流动管路上的减压阀、流量调节器和变径接头等。
根据本发明，在所述反应单元中设置有反应器，在所述反应器内还可以根据情况设置相应的加热和/或冷却元件，以及温控元件，以对目标区域进行加热和/或冷却，以使的反应温度控制在本发明的范围内。
根据本发明一种优选的实施方式，通过导热油、熔盐、电加热等形式对反应器内的气体进行加热以使其达到预定的反应温度。
根据本发明，分析单元可以为配备有TCD和FID检测器的气相色谱仪。
其中，为了确保分析的准确性，该系统还优选包括设置在反应单元和分析单元之间以及产物分离单元和分析单元之间的保温单元，例如，保温管路，以将待分析的气体在保温的不冷凝的条件下输送至分析单元。
相应的，本发明还提供了一种利用如上的系统进行丙烯环氧化制备环氧丙烷的方法，该方法包括：
(1)在混合单元中，
在第一进料区，将氧气、可选的氢气、可选的丙烯和可选的稀释气进行混合，得到第一进料气；
在第二进料区，将氢气、可选的氢气、可选的丙烯和可选的稀释气进行混合，得到第二进料气；
其中，所述第一进料气和第二进料气中各物料的选择使得第一进料气含有氧气且不含或基本不含氢气，第二进料气含有氢气且不含或基本不含氧气，第一进料气和/或第二进料气含有丙烯，所述第一进料气和第二进料气中至少一者还含有稀释气；
在第三进料区，将所述第一进料气、所述第二进料气和循环气混合，得到混合气体；
(2)在反应单元中，将所述混合气体与催化剂进行接触，并在丙烯环氧化反应条件下反应，得到环氧丙烷；
(3)在产物分离单元中，将丙烯环氧化反应得到的产物分离，得到目标产物环氧丙烷、有机副产物和循环气；
(4)在气体循环单元中，对所述循环气进行增压处理，然后将增压处理的循环气作为至少部分反应原料气和稀释气循环至所述混合单元中。
优选的，在所述第三进料区，将第一进料气和第二进料气进行对冲混合。
优选的，在气体预热区，对所述混合气进行预热。
优选的，在所述产物分离单元中：
(a)在产物分离区，将丙烯环氧化反应得到的产物分离，得到目标产物环氧丙烷、有机副产物和尾气；
(b)在气体洗涤区，对所述尾气进行洗涤，并对所得洗涤工艺气进行组成分析，若洗涤工艺气组成在预定范围内，则将其作为循环气输送至气体循环单元，若洗涤工艺气组成不在预定范围内，则进行冷凝处理；
(c)在气体冷凝区，将洗涤工艺气进行至少一级冷凝，得到凝液和不凝工艺气，并对所述不凝工艺气进行组分分析，若不凝工艺气组成在预定范围内，则将其作为循环气输送至气体循环单元，若不凝工艺气组成不在预定范围内，则进行调气处理；
(d)在调气区，通过通入丙烯、氢气、氧气和稀释气中的至少一种对所述不凝工艺气的组成进行调节，并对得到的调节工艺气进行组成分析，若调节工艺气组成在预定范围内，则将其作为循环气输送至气体循环单元，若调节工艺气组成不在预定范围内，将其外排。
对于丙烯环氧化制备环氧丙烷的方法中具体的条件设置、催化剂选择和填充等，在如上第一方面进行了详细的介绍，此处不再重复赘述。
以下将通过实施例对本发明进行详细描述。
如图2所示，用于丙烯直接环氧化制备环氧丙烷的反应系统：包括：
供气单元1，包括：
氢气进气支路、氧气进气支路、丙烯进气支路和稀释气进气支路，每个进气支路中均可以包括相应气体储罐，设置在气体流动管路上的减压阀、流量调节器和变径接头；
混合单元2，包括：
第一进料区，用于氧气、可选的氢气、可选的丙烯和可选的稀释气进行混合，得到第一进料气；
所述第二进料区用于将氢气、可选的氢气、可选的丙烯和可选的稀释气进行混合，得到第二进料气
第三进料区，用于将第一进料气、第二进料气和循环气混合，得到混合气体，其中，第一进料气的输送管路与第二进料气的输送管路相对设置；
气体预热区，设置有盘管式预热器，外周设置导热油加热，对混合气体进行预热；
反应单元3，包括：
反应区，设置有管式反应器(316L不锈钢材质)，外周设置导热油加热，预热后的气体在此进行反应；其中，管式反应器长度为3m，催化剂填充在管式反应器中；管式反应器的反应产物出口与分析单元6通过管路相同，以对反应产物的组成进行分析；
产物分离单元4，包括：
依次串联的产物分离区、气体洗涤区、冷凝区、调气区和尾气泄放区，其中，气体洗涤区、冷凝区和调气区均分别设置有与气体循环单元5和分析单元6相通的管路，并且管路上设置有阀门；
所述产物分离区用于分离丙烯环氧化反应得到的产物，得到目标产物环氧丙烷、有机副产物和尾气，产物分离区出口处设置有背压阀，尾气一部分通过保温管路(150℃)进入分析单元6进行全组分分析，其余尾气进入气体洗涤区；所述气体洗涤区包括两级醇洗罐，每级醇洗罐内部进气管路设有气体分布器，所述尾气通过气体分布器以鼓泡形式进行醇洗，醇洗罐外部设有循环水夹套，用于降低醇洗液温度。洗涤工艺气一部分通过四通阀进入分析单元6进行全组分分析；
1：如果洗涤工艺气各组分含量达到预期要求，且处于安全的混合气体系范围，没有超出极限氧含量的控制条件，各种有机组分的含量稳定，该洗涤工艺气可直接进入气体循环单元。
2：如果洗涤工艺气中某组分含量异常，超出极限氧含量控制范围或者可燃性有机物的含量超过爆炸极限，此时通过控冷凝区的温度(冷阱温度)，将该洗涤工艺气各组分根据其沸点的不同分别冷凝下来，以达到安全的混合气范围，然后未冷凝的部分气体再次进入分析单元6进行组分分析。如果满足1中的条件，则进行后续的循环处理。如果不满足1中的条件，则继续调节冷凝温度，将洗涤工艺气进一步分离以达到混合物浓度的安全控制区间。
3：如果经过多次冷凝操作后，进入分析单元6得到的混合物组成仍然处于可燃气体爆炸极限范围以内，则进入调气区调节各原料组分(例如，混合物中氢气的含量较高，且处于爆炸极限范围，则通过提高丙烯和氧气含量以提高氢气的利用率，从而降低出口氢气浓度)，从而实现反应原料气的选择性消耗，进而实现进入循环单元的混合气组分安全化操作。
4：如果1、2、3均不能解决混合气安全范围的控制问题，则将该部分混合气进入尾气泄放区排空，移出本反应体系。
气体循环单元5，包括：
气体增压区，包括低压气体缓冲罐和高压气体缓冲罐，循环气分为两路，一路通过转子流量计放空，另一路进入低压气体缓冲罐。当气体缓冲罐压低达到阈值时，通过压力传感器开启增压设备(气体增压泵)启动气路的电磁阀，使增压设备开始运行，增压后气体进入气体高压缓冲罐，高压缓冲罐中一部分气体通过质量流量计进入气体混合区，实现气体增压循环，另一部分气体通过背压阀返回前上级低压气体缓冲罐，防止气体抽空，高压缓冲罐设有安全阀，罐底设有可排液结构。
装置整体控制为PLC控制，通过计算机可控制加热、气体进气流量，循环气量、可测量温度、压力、流量等数据，控制软件具有记录与导出功能，PLC控制柜为防爆设计，配有一键断电按钮，装置配有计算机。
分析单元6，包括：
2台气相色谱仪，对产物采样进气相色谱分析。两台分析色谱型号均为安捷伦7890B，其中气相色谱A的色谱柱为(1)HayeSep Q柱(SFt 0.9m，OD 1/8，ID 2mm)，(2)Molsieve 5A柱(SFt 2.44m，OD 1/8，ID 2mm)，(3)PoraBOND U柱(25m，0.32mm，7μm)；配有TCD和FID检测器用于分析H 2、O 2、稀释气等永久性气体和丙烯、丙烷、环氧丙烷、丙烯醛、丙酮、丙醛、乙醛等，其中丙烯和氢气的出峰位置相似，两者相互影响不能准确区分，所以用气相色谱B辅助分析。气相色谱B的色谱柱为(1)HayeSep Q柱(SFt 1.83m，OD 1/8，ID 2mm)，(2)Molsieve 5A柱(SFt 2.44m，OD 1/8，ID 2mm)，(3)HP-AL\S柱(25m，0.32mm，8μm)；配有TCD和FID检测器用于分析H 2、O 2、稀释气等永久性气体和丙烯、丙烷。
Au@TS-1分子筛催化剂中，TS-1分子筛通过水热合成的方式制备，活性金属Au通过沉积沉淀的方法进行负载。
实施例一
燃爆实验
在如上反应系统中，相对于1000ml的反应器，填充30g Au@TS-1分子筛催化剂(Au的负载量为1重量％)，其与1200g石英砂分层堆积在反应器中，如图1中(c)所示，其中，催化剂层和石英砂层的层高比为1:2，所述催化剂层和惰性填充物层各自独立地为15层/米，按照如下方式进行丙烯气相直接环氧化反应：
(1)将稀释气、丙烯与氧气1:1:1的比例进行混合，得到第一进料气，氧气浓度符合式(1)；
(2)将所述第一进料气与作为第二进料气的氢气180°对冲混合，得到混合气体，混合气体中， 氢气、氧气、丙烯和稀释气的比例为1:1:1:1，氧气浓度符合式(1)；
(3)将所述混合气体通入气体预热区，预热至160℃后进入反应单元，进行反应，反应空速4000ml g cat -1h -1，控制体系的反应压力0.2MPa，以1.5℃min -1的速率程序升温至200℃。
在稀释气为氮气的情况下，反应20min时间内，反应体系不爆炸。
而不按照如上分步通入气体的方式，体系不能安全进行。
在稀释气为丙烯、丙烷和甲烷的情况下，反应20min时间内，反应体系不爆炸。
由此可见，采用本发明的方法，在降低稀释气用量的情况下，也能够保障反应的安全性。
实施例1
本实施例用于说明本发明提供的丙烯直接环氧化的方法
在如上反应系统中，相对于1000ml的反应器，填充30g Au@TS-1分子筛催化剂(Au的负载量为1重量％)，其与1200g石英砂分层堆积在反应器中，如图1中(c)所示，其中，催化剂层和石英砂层的层高比为1:1.5，所述催化剂层和惰性填充物层各自独立地为10层/米，按照如下方式进行丙烯气相直接环氧化反应：
按照“燃爆实验”中气体混合方式进行混合，稀释气为氮气，然后将所述混合气通入气体预热区，预热至160℃后进入反应单元，进行反应，反应空速4000ml g cat -1h -1，控制体系的反应压力0.15MPa，以1.5℃min -1的速率程序升温至200℃。
反应后的产物经产物分离单元和气体循环单元处理后，引入至混合气体中进行循环使用。
反应稳定后，丙烯气相直接环氧化反应分析如表1所示，并记录丙烯转化率、环氧丙烷选择性等指标开始下降时的大概时间(每50小时记录一次)。
实施例2
本实施例用于说明本发明提供的丙烯直接环氧化的方法
在如上反应系统中，相对于1000ml的反应器，填充30g Au@TS-1分子筛催化剂(Au的负载量为1重量％)，其与900g石英砂分层堆积在反应器中，如图1中(c)所示，其中，催化剂层和石英砂层的层高比为1:2.5，所述催化剂层和惰性填充物层各自独立地为20层/米，按照如下方式进行丙烯气相直接环氧化反应：
按照“燃爆实验”中气体混合方式进行混合，稀释气为氮气，然后将所述混合气通入气体预热区，预热至130℃后进入反应单元，进行反应，反应空速9000ml g cat -1h -1，控制体系的反应压力0.05MPa，以1.2℃min -1的速率程序升温至170℃。
反应后的产物经产物分离单元和气体循环单元处理后，引入至混合气体中进行循环使用。
反应稳定后，丙烯气相直接环氧化反应分析如表1所示，并记录丙烯转化率、环氧丙烷选择性等指标开始下降时的大概时间(每50小时记录一次)。
实施例3
本实施例用于说明本发明提供的丙烯直接环氧化的方法
在如上反应系统中，相对于1000ml的反应器，填充30g Au@TS-1分子筛催化剂(Au的负载量为1重量％)，其与1350g石英砂分层堆积在反应器中，如图1中(c)所示，其中，催化剂层和石英砂层的层高比为1:2，所述催化剂层和惰性填充物层各自独立地为15层/米，按照如下方式进行丙烯气相直接环氧化反应：
按照“燃爆实验”中气体混合方式进行混合，稀释气为氮气，然后将所述混合气通入气体预热区，预热至100℃后进入反应单元，进行反应，反应空速15000ml g cat -1h -1，控制体系的反应压力0.25MPa，以0.8℃min -1的速率程序升温至120℃。
反应后的产物经产物分离单元和气体循环单元处理后，引入至混合气体中进行循环使用。
反应稳定后，丙烯气相直接环氧化反应分析如表1所示，并记录丙烯转化率、环氧丙烷选择性等指标开始下降时的大概时间(每50小时记录一次)。
实施例4
本实施例用于说明本发明提供的丙烯直接环氧化的方法
在如上反应系统中，相对于1000ml的反应器，填充30g Au@TS-1分子筛催化剂(Au的负载量为1重量％)，其与500g石英砂分层堆积在反应器中，如图1中(c)所示，其中，催化剂层和石英砂层的层高比为1:1.2，所述催化剂层和惰性填充物层各自独立地为8层/米，按照如下方式进行丙烯气相直接环氧化反应：
按照“燃爆实验”中气体混合方式进行混合，稀释气为氮气，然后将所述混合气体通入气体预热区，预热至80℃后进入反应单元，进行反应，反应空速20000ml g cat -1h -1，控制体系的反应压力0.5MPa，以0.3℃min -1的速率程序升温至110℃。
反应后的产物经产物分离单元和气体循环单元处理后，引入至混合气体中进行循环使用。
反应稳定后，丙烯气相直接环氧化反应分析如表1所示，并记录丙烯转化率、环氧丙烷选择性等指标开始下降时的大概时间(每50小时记录一次)。
实施例5
本实施例用于说明本发明提供的丙烯直接环氧化的方法
在如上反应系统中，相对于1000ml的反应器，填充30g Au@TS-1分子筛催化剂(Au的负载量为1重量％)，其与1500g石英砂分层堆积在反应器中，如图1中(c)所示，其中，催化剂层和石英砂层的层高比为1:4，所述催化剂层和惰性填充物层各自独立地为15层/米，按照如下方式进行丙烯气相直接环氧化反应：
按照“燃爆实验”中气体混合方式进行混合，稀释气为氮气，然后将所述混合气通入气体预热区，预热至100℃后进入反应单元，进行反应，反应空速1000ml g cat -1h -1，控制体系的反应压力0.02MPa，以5℃min -1的速率程序升温至230℃。
反应后的产物经产物分离单元和气体循环单元处理后，引入至混合气体中进行循环使用。
反应稳定后，丙烯气相直接环氧化反应分析如表1所示，并记录丙烯转化率、环氧丙烷选择性等指标开始下降时的大概时间(每50小时记录一次)。
实施例6
本实施例用于说明本发明提供的丙烯直接环氧化的方法
按照实施例2的方法进行丙烯直接环氧化制备环氧丙烷，不同的是，所述催化剂按照图1中(b)中所示进行填装。分析如表1所示。
实施例7
本实施例用于说明本发明提供的丙烯直接环氧化的方法
按照实施例2的方法进行丙烯直接环氧化制备环氧丙烷，不同的是，所述催化剂按照图1中(a)中所示进行填装。分析如表1所示。
实施例8
本实施例用于说明本发明提供的丙烯直接环氧化的方法
按照实施例2的方法进行丙烯直接环氧化制备环氧丙烷，不同的是，在进入反应单元之前不进行预热。分析如表1所示。
实施例9
本实施例用于说明本发明提供的丙烯直接环氧化的方法
按照实施例2的方法进行丙烯直接环氧化制备环氧丙烷，不同的是，稀释气为丙烯。
实施例10
本实施例用于说明本发明提供的丙烯直接环氧化的方法
按照实施例2的方法进行丙烯直接环氧化制备环氧丙烷，不同的是，稀释气为甲烷。
实施例11
本实施例用于说明本发明提供的丙烯直接环氧化的方法
按照实施例2的方法进行丙烯直接环氧化制备环氧丙烷，不同的是，稀释气为丙烷。
实施例12
本实施例用于说明本发明提供的丙烯直接环氧化的方法
按照实施例1的方法进行丙烯直接环氧化制备环氧丙烷，不同的是，不对反应的后气体进行循环。
对比例1
本对比例用于说明参比的丙烯直接环氧化的方法
按照实施例12的方法进行丙烯直接环氧化制备环氧丙烷，不同的是，不通过分步进行气体的混合，而是直接将各路气体混合，但为了确保反应的顺利进行，调节H 2:O 2:C 3H 6:N 2＝1:1:1:7。分析如表1所示。
表1
Figure PCTCN2021073744-appb-000005
Figure PCTCN2021073744-appb-000006
注：实施例9中丙烯转化率仅针对作为反应气的丙烯计算而得，并没有把作为稀释气的丙烯的量计算在内，也即，在通过分析反应后气体的各组分的量计算丙烯转化率时，需要将作为稀释气的丙烯的量减去，认为稀释气不参与反应。
实施例二
燃爆实验
在管式反应器中，相对于1000ml的反应器，填充30g Au@TS-1分子筛催化剂(Au的负载量为1重量％)，其与1200g石英砂分层堆积在反应器中，如图1中(c)所示，其中，催化剂层和石英砂层的层高比为1:2，所述催化剂层和惰性填充物层各自独立地为15层/米，按照如下气体通入方式进行丙烯气相直接环氧化反应：
(1)将稀释气、丙烯与氢气1:1:1的比例进行混合，得到第二进料气；
(2)将所述第二进料气与作为第一进料气的氧气180°对冲混合，得到混合气体，混合气体中，氢气、氧气、丙烯和稀释气的比例为1:1:1:1；
(3)将所述混合气体通入气体预热区，预热至160℃后进入反应单元，进行反应，反应空速4000ml g cat -1h -1，控制体系的反应压力0.2MPa，以每升温5℃维持5min的程序升温至200℃。
在稀释气为水蒸气的情况下，反应20min时间内，反应体系不爆炸。
而不按照如上分步通入气体的方式，体系不能安全进行。
在稀释气为一氧化碳和氮气的情况下，反应20min时间内，反应体系不爆炸。
由此可见，采用本发明的方法，在降低稀释气用量的情况下，也能够保障反应的安全性。
实施例1
本实施例用于说明本发明提供的丙烯直接环氧化的方法
在管式反应器中，相对于1000ml的反应器，填充30g Au@TS-1分子筛催化剂(Au的负载量为1重量％)，其与1200g石英砂分层堆积在反应器中，如图1中(c)所示，其中，催化剂层和石英砂层的层高比为1:2，所述催化剂层和惰性填充物层各自独立地为15层/米，按照如下方式进行丙烯气相直接环氧化反应。
按照“燃爆实验”中第二种气体混合方式进行混合，稀释气为水蒸气，然后将所述第三混合气通入气体预热区，预热至160℃后进入反应单元，进行反应，反应空速9000ml g cat -1h -1，控制体系的反应压力0.15MPa，以每升温5℃维持10min的程序升温至200℃。
反应后的产物经产物分离，得到目标产物、有机副产物和未完全反应的尾气，尾气经处理后引入至第三混合气中进行循环使用。
反应稳定后，丙烯气相直接环氧化反应分析如表2所示，并记录丙烯转化率、环氧丙烷选择性等 指标开始下降时的大概时间(每50小时记录一次)。
实施例2
本实施例用于说明本发明提供的丙烯直接环氧化的方法
在管式反应器中，相对于1000ml的反应器，填充30g Au@TS-1分子筛催化剂(Au的负载量为1重量％)，其与900g石英砂分层堆积在反应器中，如图1中(c)所示，其中，催化剂层和石英砂层的层高比为1:1.5，所述催化剂层和惰性填充物层各自独立地为10层/米，按照如下方式进行丙烯气相直接环氧化反应。
按照“燃爆实验”中第二种气体混合方式进行混合，稀释气为水蒸气，然后将所述第三混合气通入气体预热区，预热至130℃后进入反应单元，进行反应，反应空速15000ml g cat -1h -1，控制体系的反应压力0.05MPa，以每升温8℃维持8min的程序升温至170℃。
反应后的产物经产物分离，得到目标产物、有机副产物和未完全反应的尾气，尾气经处理后引入至第三混合气中进行循环使用。
反应稳定后，丙烯气相直接环氧化反应分析如表2所示，并记录丙烯转化率、环氧丙烷选择性等指标开始下降时的大概时间(每50小时记录一次)。
实施例3
本实施例用于说明本发明提供的丙烯直接环氧化的方法
在管式反应器中，相对于1000ml的反应器，填充30g Au@TS-1分子筛催化剂(Au的负载量为1重量％)，其与1350g石英砂分层堆积在反应器中，如图1中(c)所示，其中，催化剂层和石英砂层的层高比为1:2.5，所述催化剂层和惰性填充物层各自独立地为20层/米，按照如下方式进行丙烯气相直接环氧化反应。
按照“燃爆实验”中第二种气体混合方式进行混合，稀释气为水蒸气，然后将所述第三混合气通入气体预热区，预热至100℃后进入反应单元，进行反应，反应空速4000ml g cat -1h -1，控制体系的反应压力0.25MPa，以每升温10℃维持5min的程序升温至120℃。
反应后的产物经产物分离，得到目标产物、有机副产物和未完全反应的尾气，尾气经处理后引入至第三混合气中进行循环使用。
反应稳定后，丙烯气相直接环氧化反应分析如表2所示，并记录丙烯转化率、环氧丙烷选择性等指标开始下降时的大概时间(每50小时记录一次)。
实施例4
本实施例用于说明本发明提供的丙烯直接环氧化的方法
在管式反应器中，相对于1000ml的反应器，填充30g Au@TS-1分子筛催化剂(Au的负载量为1重量％)，其与500g石英砂分层堆积在反应器中，如图1中(c)所示，其中，催化剂层和石英砂层的层高比为1:1，所述催化剂层和惰性填充物层各自独立地为15层/米，按照如下方式进行丙烯气相直接环氧化反应。
按照“燃爆实验”中第二种气体混合方式进行混合，稀释气为水蒸气，然后将所述第三混合气通入气体预热区，预热至100℃后进入反应单元，进行反应，反应空速1000ml g cat -1h -1，控制体系的反应压力0.5MPa，以每升温2℃维持1min的程序升温至100℃。
反应后的产物经产物分离，得到目标产物、有机副产物和未完全反应的尾气，尾气经处理后引入至第三混合气中进行循环使用。
反应稳定后，丙烯气相直接环氧化反应分析如表2所示，并记录丙烯转化率、环氧丙烷选择性等指标开始下降时的大概时间(每50小时记录一次)。
实施例5
本实施例用于说明本发明提供的丙烯直接环氧化的方法
在管式反应器中，相对于1000ml的反应器，填充30g Au@TS-1分子筛催化剂(Au的负载量为1重量％)，其与1500g石英砂分层堆积在反应器中，如图1中(c)所示，其中，催化剂层和石英砂层的层高比为1:3，所述催化剂层和惰性填充物层各自独立地为15层/米，按照如下方式进行丙烯气相直接环氧化反应。
按照“燃爆实验”中第二种气体混合方式进行混合，稀释气为水蒸气，然后将所述第三混合气通入气体预热区，预热至100℃后进入反应单元，进行反应，反应空速20000ml g cat -1h -1，控制体系的反应压力0.01MPa，以每升温15℃维持10min的程序升温至250℃。
反应后的产物经产物分离，得到目标产物、有机副产物和未完全反应的尾气，尾气经处理后引入至第三混合气中进行循环使用。
反应稳定后，丙烯气相直接环氧化反应分析如表2所示，并记录丙烯转化率、环氧丙烷选择性等指标开始下降时的大概时间(每50小时记录一次)。
实施例6
本实施例用于说明本发明提供的丙烯直接环氧化的方法
按照实施例1的方法进行丙烯直接环氧化制备环氧丙烷，不同的是，所述催化剂按照图1中(b)中所示进行填装。分析如表2所示。
实施例7
本实施例用于说明本发明提供的丙烯直接环氧化的方法
按照实施例1的方法进行丙烯直接环氧化制备环氧丙烷，不同的是，所述催化剂按照图1中(a)中所示进行填装。分析如表2所示。
实施例8
本实施例用于说明本发明提供的丙烯直接环氧化的方法
按照实施例1的方法进行丙烯直接环氧化制备环氧丙烷，不同的是，在进入反应单元之前不进行预热。分析如表2所示。
实施例9
本实施例用于说明本发明提供的丙烯直接环氧化的方法
按照实施例1的方法进行丙烯直接环氧化制备环氧丙烷，不同的是，不对反应的后气体进行循环。分析如表2所示。
实施例10
本实施例用于说明本发明提供的丙烯直接环氧化的方法
按照实施例1的方法进行丙烯直接环氧化制备环氧丙烷，不同的是，稀释气为氮气。分析如表2所示。
实施例11
本实施例用于说明本发明提供的丙烯直接环氧化的方法
按照实施例1的方法进行丙烯直接环氧化制备环氧丙烷，不同的是，稀释气为一氧化碳。分析如表2所示。
对比例1
本对比例用于说明参比的丙烯直接环氧化的方法
按照实施例9的方法进行丙烯直接环氧化制备环氧丙烷，不同的是，不通过分步进行气体的混合，而是直接将各路气体混合，稀释气为氮气，但为了确保反应的顺利进行，调节H 2:O 2:C 3H 6:N 2＝1:1:1:7。分析如表2所示。
表2
Figure PCTCN2021073744-appb-000007
如表1和表2所示，本发明能够有效降低催化剂的用量(相对于1000ml的反应器，通常情况下，催化剂的用量至少需要100g)，稀释气用量显著降低，因此，反应物浓度显著提升，能耗显著降低。同时在丙烯转化率、环氧丙烷的选择性、氢气的利用率上均有了显著的提高。由此可见，在使用相同催化剂用量的情况下，本发明技术方案可以达到更好的效果，因此，本发明可以降低催化剂的用量。
通过使用本发明的管式反应器，实现了丙烯气相直接环氧化过程至少500小时以上的稳定运行，再结合本发明更为优选的条件，例如，特定的反应条件、特定的催化剂填充方式等，可使得稳定运行至少达到1000小时以上。
此外，采用本发明的技术方案，通过气体的循环利用，能够在不影响催化剂寿命的情况下，提高 丙烯转化率，实现了原料的充分利用。
以上详细描述了本发明的优选实施方式，但是，本发明并不限于此。在本发明的技术构思范围内，可以对本发明的技术方案进行多种简单变型，包括各个技术特征以任何其它的合适方式进行组合，这些简单变型和组合同样应当视为本发明所公开的内容，均属于本发明的保护范围。

Claims (15)

  1. 一种丙烯环氧化制备环氧丙烷的方法，其特征在于，该方法包括：在丙烯环氧化反应条件下，将含有第一进料气和第二进料气的混合气体与催化剂进行接触反应，以得到环氧丙烷；
    其中，第一进料气含有氧气且不含或基本不含氢气，第二进料气含有氢气且不含或基本不含氧气，第一进料气和/或第二进料气含有丙烯，所述第一进料气和第二进料气中至少一者还含有稀释气。
  2. 根据权利要求1所述的方法，其中，所述稀释气为惰性稀释气和/或非惰性稀释气；
    优选的，在第一进料气和混合气体中，氧气的浓度各自独立地满足如下公式：
    Figure PCTCN2021073744-appb-100001
    或
    Figure PCTCN2021073744-appb-100002
    其中，
    X O2为氧气在混合气中的体积分数(％)；
    Xm为惰性稀释气m在混合气中的体积分数(％)；
    Xn为非惰性稀释气n在混合气中的体积分数(％)；
    X丙烯为丙烯在混合气中的体积分数(％)；
    X氢气为氢气在混合气中的体积分数(％)；
    Nn为非惰性稀释气n在混合气中的爆炸下限(％)；
    N丙烯为丙烯在混合气中的爆炸下限(％)；
    N氢气为氢气在混合气中的爆炸下限(％)；
    Ln为非惰性稀释气n在混合气中的爆炸上限(％)；
    L丙烯为丙烯在混合气中的爆炸上限(％)；
    L氢气为氢气在混合气中的爆炸上限(％)。
  3. 根据权利要求2所述的方法，其中，所述惰性稀释气选自N 2，Ar和CO 2；和/或
    所述非惰性稀释气为气态烷烃。
  4. 根据权利要求3所述的方法，其中，所述气态烷烃为C2-C4的烷烃，优选为甲烷、乙烷和丙烷，更优选为丙烷。
  5. 根据权利要求1-4中任意一项所述的方法，其中，在所述第一进料气或所述第二进料气中，稀释气的含量为0-100体积％，优选50-90体积％的总稀释气；
    优选的，所述第一进料气含有氧气且不含或基本不含氢气，含有至少部分丙烯和至少部分稀释气；所述第二进料气含有氢气且不含或基本不含氧气，含有剩余部分丙烯和剩余部分稀释气；或者，
    所述第二进料气含有氢气且不含或基本不含氧气，含有至少部分丙烯和至少部分稀释气；所述第一进料气含有氧气且不含或基本不含氢气，含有剩余部分丙烯和剩余部分稀释气。
  6. 根据权利要求1-5中任意一项所述的方法，其中，第二进料气与第一进料气以对冲的方式进行混合。
  7. 根据权利要求1-6中任意一项所述的方法，其中，在将混合气体与催化剂进行接触之前，还包括将所述混合气体进行预热。
  8. 根据权利要求1-7中任意一项所述的方法，其中，所述催化剂为负载型金属催化剂，该负载型金属催化剂含有载体和活性金属组分，所述活性金属组分选自金、银、铜、钌、钯、铂、铑、钴、镍、钨、铋、钼及它们的氧化物中的至少一种，所述载体为炭黑、活性炭、二氧化硅、三氧化二铝、氧化铈和沸石中的至少一种，以催化剂的总重量计，催化剂中以金属元素计的活性金属组分的含量为0.01-50重量％；
    优选的，所述载体为钛硅分子筛，所述活性金属组分为金。
  9. 根据权利要求1-8中任意一项所述的方法，其中，所述催化剂以与惰性填充物结合的形式填充于反应器中；
    优选的，所述惰性填充物选自石英砂、Al 2O 3、多孔硅胶和陶瓷环中的至少一种；
    优选的，相对于1重量份的催化剂，所述惰性填充物的用量为1-200重量份；
    优选的，所述催化剂与惰性填充物以分层堆积的方式填充于反应器中；
    更优选的，所述催化剂与惰性填充物以交替分层堆积的方式填充于反应器中；
    更优选的，每层催化剂和每层惰性填充物的层高比为1∶1-10。
  10. 根据权利要求1-9中任意一项所述的方法，其中，所述丙烯环氧化反应条件包括：反应温度为20-300℃，优选为50-250℃；反应压力为0-5MPa，优选为0-1.5MPa；混合气体的体积空速为500-30000ml g cat -1h -1，优选为1000-20000ml g cat -1h -1。
  11. 根据权利要求1-10中任意一项所述的方法，其中，所述丙烯环氧化反应在不存在溶剂的情况下进行。
  12. 根据权利要求1-11中任意一项所述的方法，其中，该方法还包括：分离丙烯环氧化反应得到的产物，得到目标产物环氧丙烷、有机副产物和循环气，并将所述循环气引入至所述混合气体中。
  13. 一种用于丙烯直接环氧化制备环氧丙烷的反应系统，其特征在于，该反应系统包括：
    供气单元，用于提供丙烯、氧气、氢气和稀释气；
    混合单元，包括第一进料区、第二进料区和第三进料区；
    所述第一进料区用于将氧气、可选的氢气、可选的丙烯和可选的稀释气进行混合，得到第一进料气；
    所述第二进料区用于将氢气、可选的氧气、可选的丙烯和可选的稀释气进行混合，得到第 二进料气；
    其中，所述第一进料气和第二进料气中各物料的选择使得第一进料气含有氧气且不含或基本不含氢气，第二进料气含有氢气且不含或基本不含氧气，第一进料气和/或第二进料气含有丙烯，所述第一进料气和第二进料气中至少一者还含有稀释气；
    所述第三进料区用于将所述第一进料气、所述第二进料气和循环气混合，得到混合气体；
    反应单元，所述反应单元内布置有催化剂，用于使所述混合气体与所述催化剂进行接触，并在丙烯环氧化反应条件下反应，得到环氧丙烷；
    产物分离单元，用于分离丙烯环氧化反应得到的产物，得到目标产物环氧丙烷、有机副产物和循环气；
    气体循环单元，与所述混合单元相连通，用于接收所述循环气，然后将循环气作为至少部分反应原料气和稀释气输送至所述混合单元。
  14. 根据权利要求13所述的反应系统，其中，在所述第三进料区，用于引入第一进料气的管路和用于引入第二进料气的管路的设置方式使得第一进料气与所述第二进料气进行对冲混合。
  15. 根据权利要求13或14所述的反应系统，其中，所述产物分离单元包括依次串联的产物分离区、气体洗涤区、气体冷凝区和调气区，且产物分离区、气体洗涤区、气体冷凝区和调气区各自独立地与所述气体循环单元相连通。
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