CN115368210B - Treatment method of tail gas hydrogen of hydrogenation reaction - Google Patents
Treatment method of tail gas hydrogen of hydrogenation reaction Download PDFInfo
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- CN115368210B CN115368210B CN202211081772.3A CN202211081772A CN115368210B CN 115368210 B CN115368210 B CN 115368210B CN 202211081772 A CN202211081772 A CN 202211081772A CN 115368210 B CN115368210 B CN 115368210B
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- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 192
- 239000001257 hydrogen Substances 0.000 title claims abstract description 192
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 176
- 238000005984 hydrogenation reaction Methods 0.000 title claims abstract description 111
- 239000007789 gas Substances 0.000 title claims abstract description 69
- 238000000034 method Methods 0.000 title claims abstract description 41
- 238000004519 manufacturing process Methods 0.000 claims abstract description 50
- 150000002431 hydrogen Chemical class 0.000 claims abstract description 16
- 239000007788 liquid Substances 0.000 claims abstract description 13
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims abstract description 8
- 238000000926 separation method Methods 0.000 claims abstract description 8
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 33
- 238000006243 chemical reaction Methods 0.000 claims description 19
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 claims description 16
- YIMQCDZDWXUDCA-UHFFFAOYSA-N [4-(hydroxymethyl)cyclohexyl]methanol Chemical compound OCC1CCC(CO)CC1 YIMQCDZDWXUDCA-UHFFFAOYSA-N 0.000 claims description 11
- 230000008569 process Effects 0.000 claims description 11
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 9
- -1 bis (4-methylcyclohexane) dimethyl terephthalate Chemical compound 0.000 claims description 7
- 239000003345 natural gas Substances 0.000 claims description 5
- PXGZQGDTEZPERC-UHFFFAOYSA-N 1,4-cyclohexanedicarboxylic acid Chemical compound OC(=O)C1CCC(C(O)=O)CC1 PXGZQGDTEZPERC-UHFFFAOYSA-N 0.000 claims description 4
- LNGAGQAGYITKCW-UHFFFAOYSA-N dimethyl cyclohexane-1,4-dicarboxylate Chemical compound COC(=O)C1CCC(C(=O)OC)CC1 LNGAGQAGYITKCW-UHFFFAOYSA-N 0.000 claims description 4
- WOZVHXUHUFLZGK-UHFFFAOYSA-N dimethyl terephthalate Chemical compound COC(=O)C1=CC=C(C(=O)OC)C=C1 WOZVHXUHUFLZGK-UHFFFAOYSA-N 0.000 claims description 4
- 239000002994 raw material Substances 0.000 claims description 3
- 239000003054 catalyst Substances 0.000 abstract description 14
- 230000008901 benefit Effects 0.000 abstract description 6
- 238000000746 purification Methods 0.000 abstract description 5
- 230000007613 environmental effect Effects 0.000 abstract description 2
- 239000012535 impurity Substances 0.000 description 17
- 239000000047 product Substances 0.000 description 9
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 7
- 239000007791 liquid phase Substances 0.000 description 5
- 229910002092 carbon dioxide Inorganic materials 0.000 description 4
- 229910002091 carbon monoxide Inorganic materials 0.000 description 4
- 238000010926 purge Methods 0.000 description 4
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 3
- YZCKVEUIGOORGS-OUBTZVSYSA-N Deuterium Chemical compound [2H] YZCKVEUIGOORGS-OUBTZVSYSA-N 0.000 description 3
- 239000001569 carbon dioxide Substances 0.000 description 3
- 239000005416 organic matter Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 231100000331 toxic Toxicity 0.000 description 3
- 230000002588 toxic effect Effects 0.000 description 3
- 239000002341 toxic gas Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 231100000252 nontoxic Toxicity 0.000 description 2
- 230000003000 nontoxic effect Effects 0.000 description 2
- 238000000053 physical method Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 229910052703 rhodium Inorganic materials 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 230000009849 deactivation Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 231100000572 poisoning Toxicity 0.000 description 1
- 230000000607 poisoning effect Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/17—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by hydrogenation of carbon-to-carbon double or triple bonds
- C07C29/19—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by hydrogenation of carbon-to-carbon double or triple bonds in six-membered aromatic rings
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
- C01B3/06—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents
- C01B3/12—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents by reaction of water vapour with carbon monoxide
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
- C01B3/22—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of gaseous or liquid organic compounds
- C01B3/24—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of gaseous or liquid organic compounds of hydrocarbons
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/50—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
- C07C1/02—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon
- C07C1/04—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon from carbon monoxide with hydrogen
- C07C1/0405—Apparatus
- C07C1/041—Reactors
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C2601/00—Systems containing only non-condensed rings
- C07C2601/12—Systems containing only non-condensed rings with a six-membered ring
- C07C2601/14—The ring being saturated
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- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Combustion & Propulsion (AREA)
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- Health & Medical Sciences (AREA)
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- Oil, Petroleum & Natural Gas (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention provides a method for treating tail gas hydrogen in hydrogenation reaction, wherein part of tail gas hydrogen obtained by gas-liquid separation after hydrogenation reaction is directly introduced into a hydrogenation reactor as internal recycle hydrogen, or the internal recycle hydrogen is treated by a methanation device and then directly introduced into the hydrogenation reactor, and the other part of tail gas hydrogen obtained by gas-liquid separation after hydrogenation reaction is introduced into a purification device in a hydrogen production system as external recycle hydrogen, hydrogen obtained by purifying and purifying the external recycle hydrogen and hydrogen prepared by the hydrogen production system are added into the hydrogenation reactor together as fresh high-purity hydrogen, and the fresh high-purity hydrogen and the internal recycle hydrogen which is treated by the methanation device or not together form total hydrogen for the hydrogenation reaction. The method can effectively reduce the hydrogen unit consumption and save the production cost. And meanwhile, the concentration of CO in the hydrogenation system is controlled, so that the influence of CO on the catalyst is reduced. The method can obtain remarkable economic benefit and environmental protection benefit.
Description
Technical Field
The invention relates to the field of hydrogenation reactions of organic matters, in particular to a method for treating tail gas hydrogen in a hydrogenation reaction.
Background
In the organic matter hydrogenation reaction (hydrogenation reaction), in order to increase the concentration of hydrogen in the reaction, the reaction conditions are usually high temperature and high pressure and hydrogen are largely excessive and the excessive amount of hydrogen is usually several times the theoretical required value of the reaction. Therefore, in order to reduce the unit consumption of the reaction hydrogen, it is necessary to recycle the hydrogen in the hydrogenation reaction.
The surface is quite simple in hydrogen circulation, and only a gas-liquid separator is arranged at the outlet of the reactor to separate organic matters in liquid phase, and then a compressor is added in gas phase to compensate pressure reduction, so that unreacted hydrogen can be returned to the hydrogenation reactor. However, the problem is not so simple in practice, and during the hydrogenation reaction, carbon monoxide, carbon dioxide or other gases are produced by decomposition of a very small portion of the organic matter (raw material), and if these by-product gases cannot be effectively separated and discharged, they are continuously accumulated in the hydrogen recycle gas. This not only affects the concentration of hydrogen in the hydrogen recycle gas, but also slowly affects the hydrogenation efficiency of the hydrogenation reactor, and there is a more important problem in that these impurity gases in the hydrogen recycle gas will have an important influence on the life of the hydrogenation catalyst. For example, pd and Rh are heavy metals commonly used in hydrogenation catalysts, while carbon monoxide and carbon dioxide are Pd and Rh toxic gases, and only ppm amounts of toxic gases are required to accelerate deactivation of the catalyst. These gases, which affect catalyst life, are commonly referred to in the art as CO.
In the prior art, a few researches have disclosed separating impurity gases from hydrogen recycle gas (tail gas hydrogen of hydrogenation reaction), such as US6179996, concentrating hydrogen by using a specially designed membrane, for reducing the loss of hydrogen in the hydrogenation reaction tail gas, and also effectively removing the impurity gases. Accordingly, the flow rate of the circulating hydrogen can be increased, and the concentration of CO in the hydrogenation reactor can be controlled within a reasonable range.
In addition to the removal of impurity gases using physical methods, these impurity gases may also be removed using chemical methods. Methanation reactions such as those described in US3967936 and CN102600771 are effective in converting CO toxic to the catalyst into methane. The method can effectively reduce the concentration of CO in the circulating hydrogen, but the concentration of methane in the circulating hydrogen is greatly increased, and the concentration of hydrogen in the circulating hydrogen is reduced, so that the reaction efficiency of hydrogenation reaction is affected.
The two hydrogenation reaction tail gas hydrogen treatment methods have certain advantages, but are not perfect. The first physical method, in which the concentration of impurity gas increases, tends to require an additional large investment. The second chemical method converts the impurity gas toxic to the hydrogenation catalyst into a gas non-toxic to the hydrogenation catalyst, which solves the problem of catalyst poisoning, but the newly generated impurity gas (e.g., methane) also needs to be effectively removed.
Thus, there is a need in the art for a new method of treating tail gas hydrogen from hydrogenation reactions.
Disclosure of Invention
The invention provides a method for treating tail gas hydrogen of hydrogenation reaction, wherein part of tail gas hydrogen obtained by gas-liquid separation after hydrogenation reaction is directly introduced into a hydrogenation reactor as internal recycle hydrogen, or the internal recycle hydrogen is firstly converted into methane by a methanation device and then is directly introduced into the hydrogenation reactor, and the other part of tail gas hydrogen obtained by gas-liquid separation after hydrogenation reaction is introduced into a purifying and purifying device in a hydrogen production system as external recycle hydrogen, hydrogen obtained by purifying and purifying the external recycle hydrogen and hydrogen prepared by a hydrogen production raw material through the hydrogen production system are jointly used as fresh high-purity hydrogen to be added into the hydrogenation reactor, and the fresh high-purity hydrogen and the internal recycle hydrogen which is treated by the methanation device or not are jointly used for forming total hydrogen.
In a specific embodiment, the ratio of the internal recycle hydrogen to the external recycle hydrogen is from 0.5 to 5:1, preferably 0.8 to 4: 1, more preferably 1 to 3:1.
In a specific embodiment, the hydrogenation reaction is one of the following reactions: hydrogenation of terephthalic acid to produce 1, 4-cyclohexanedicarboxylic acid, hydrogenation of 1, 4-cyclohexanedicarboxylic acid to produce 1, 4-cyclohexanedimethanol, continuous two-stage hydrogenation of terephthalic acid to produce 1, 4-cyclohexanedimethanol, hydrogenation of dimethyl terephthalate to produce dimethyl 1, 4-cyclohexanedicarboxylate, hydrogenation of dimethyl 1, 4-cyclohexanedicarboxylate to produce 1, 4-cyclohexanedimethanol, hydrogenation of bis (4-methylcyclohexane) dimethyl terephthalate to produce bis (4-methylcyclohexane) dimethyl 1, 4-cyclohexanedicarboxylate, and continuous two-stage hydrogenation of bis (4-methylcyclohexane) dimethyl terephthalate to produce 1, 4-cyclohexanedimethanol.
In a specific embodiment, the hydrogen production system is a natural gas hydrogen production system or a methanol hydrogen production system.
In a specific embodiment, the CO concentration of the internal recycle hydrogen after treatment by the methanation unit is less than 20ppm, preferably less than 10ppm.
In a specific embodiment, the hydrogen unit consumption in the hydrogenation reaction is not more than 1.1 times, preferably not more than 1.05 times, more preferably not more than 1.03 times the theoretical value.
In a specific embodiment, the total hydrogen used in the hydrogenation reaction has a CO concentration of less than 30ppm, preferably less than 25ppm, more preferably less than 20ppm.
In a specific embodiment, the exhaust hydrogen after the hydrogenation reaction and before a part of the exhaust hydrogen obtained by the gas-liquid separation enters the hydrogen production system is exhausted to zero.
The beneficial effects are that: the method can effectively reduce the hydrogen unit consumption and save the production cost. And meanwhile, the concentration of CO in the hydrogenation system is controlled, so that the influence of CO on the catalyst is reduced. The method can obtain remarkable economic benefit and environmental benefit.
Drawings
FIG. 1 is a flow chart of a prior art process for treating tail gas hydrogen from a hydrogenation reaction.
FIG. 2 is a flow chart of another prior art process for treating tail gas hydrogen from a hydrogenation reaction.
FIG. 3 is a schematic diagram of the introduction of tail gas hydrogen from a hydrogenation reaction into a hydrogen production system in accordance with the present invention.
FIG. 4 is a flow chart showing the case where a methanation device is not provided in the method for treating tail gas hydrogen of hydrogenation according to the present invention.
FIG. 5 is a flow chart of the method for treating tail gas hydrogen of hydrogenation reaction according to the present invention, when a methanation device is provided.
FIG. 6 is a flow chart of a method for treating tail gas hydrogen from a hydrogenation reaction for producing 1, 4-cyclohexanedimethanol from terephthalic acid in accordance with the present invention.
Detailed Description
FIG. 1 is a flow chart of a prior art process for treating tail gas hydrogen from a hydrogenation reaction. In FIG. 1, if stream ① is 100 moles of organics, stream ② is 300.074 moles of fresh hydrogen (containing 5ppm CO), stream ③ is 200 moles of internal recycle hydrogen, and the total hydrogen flow of stream ④ is 500 moles to achieve this reaction 5:1 (hydrogen: organics) 100 moles of organics react with 99.99 moles of hydrogen to produce 99.99 moles of product under the designed reaction conditions, and the remaining 0.01 moles of organics decompose to produce 0.01 moles of CO to form stream ⑤. In the gas-liquid separator, product ⑥ is separated in the liquid phase, the remaining gas being stream ⑦, the total emission of gas in stream ⑧ being 200 moles for emission of 0.01 moles of CO in stream ⑧. The corresponding stream balance for FIG. 1 is shown in Table 1.
TABLE 1
| Logistics material | ① | ② | ③ | ④ | ⑤ | ⑥ | ⑦ | ⑧ |
| Hydrogen gas | / | 300.07 | 200.04 | 500.11 | 400.12 | / | 400.08 | 200.04 |
| CO | / | 0.002 | 0.01 | 0.01 | 0.02 | / | 0.02 | 0.01 |
| Organic matter | 100.00 | / | / | / | / | / | / | / |
| Product(s) | 99.99 | 99.99 | ||||||
| Total flow rate | 100.00 | 300.07 | 200.05 | 500.12 | 500.13 | 99.99 | 400.10 | 200.05 |
In the above case, the purge ratio (percentage of purge ⑧ to total gas volume ⑦) was 50%, in this state the flow of fresh hydrogen ② was 300.07mol, while the CO concentration of the hydrogenation reactor feed was 25ppm. If the amount of fresh hydrogen ② is reduced, the CO concentration at the inlet of the hydrogenation reactor is increased and the corresponding purge ratio is reduced. As the purge ratio decreases, the CO concentration in the hydrogenation reactor increases, which is a significant hazard to the catalyst. Generally, the acceptable concentration of CO in the hydrogenation reactor is below 30ppm, so that the input amount of fresh hydrogen ② is required to be more than 250mol, which is 2.5 times of the theoretical value of the hydrogen consumption in the hydrogenation reactor, and the emptying amount ⑧ is required to be more than 150mol, which causes the unit consumption of hydrogen to be greatly increased, and the mode is not feasible for industrial production.
Therefore, in the industrial process of hydrogenation reaction in the prior art, a methanation device is generally added to treat tail gas hydrogen of hydrogenation reaction, so that CO in the tail gas hydrogen is hydrogenated into methane, and gas toxic to a hydrogenation catalyst is converted into non-toxic gas. FIG. 2 depicts a flow chart of another prior art process for treating tail gas hydrogen from a hydrogenation reaction.
In FIG. 2, stream ① is 100 moles of organics, stream ② is 160.75 moles of fresh hydrogen (containing 5ppm CO) plus 339.25 moles of internal recycle hydrogen of stream ③, and the total hydrogen flow of stream ④ is 500 moles to achieve this reaction 5:1 (hydrogen: organics) 100 moles of organics react with 99.99 moles of hydrogen to produce 99.99 moles of product under the designed reaction conditions, and the remaining 0.01 moles of organics decompose to produce 0.01 moles of CO to form stream ⑤. In the gas-liquid separator, product ⑥ is separated in the liquid phase, the remaining gas being stream ⑦, and the total gas discharge of stream ⑧ being 60.77 moles for the discharge of 0.01 moles of impurity gas in stream ⑧. The remaining internal recycle gas ⑨ enters the methanation unit, and the concentration of CO entering the hydrogenation reactor can be effectively reduced provided that 90% of the CO in the methanation unit is converted to CH 4.
Compared with fig. 1, the methanation device is added in fig. 2, so that the concentration of CO in the hydrogenation reactor can be effectively controlled, the normal operation of hydrogenation reaction is ensured, and the input amount of fresh hydrogen is obviously reduced. However, a new problem arises that new impurity methane is introduced into the hydrogenation reactor, and the concentration of methane is inversely proportional to the input amount of fresh hydrogen, if the unit consumption of hydrogen is to be reduced, the concentration of methane in the hydrogenation reactor tends to be increased, while the concentration and partial pressure of hydrogen in the hydrogenation reaction system are reduced by methane with high concentration, and the hydrogenation reaction is affected with uncertainty. Thus, the process is also worth further improvement.
According to the method, a part of tail gas hydrogen is introduced into the hydrogen production system, and the high-purity hydrogen obtained after the purification of the hydrogen production system is recycled to the hydrogenation reaction, so that the hydrogen unit consumption is effectively reduced, and the production cost is saved; the concentration of CO in the hydrogenation reaction system can be controlled, and the influence of CO on the hydrogenation catalyst is reduced.
The existing hydrogen production system generally comprises natural gas hydrogen production and methanol hydrogen production, and the advantages are more and more obvious due to the gradual reduction of the hydrogen production cost of the natural gas hydrogen production, namely, methane reacts with oxygen to generate carbon monoxide and hydrogen, and then reacts with water to generate carbon dioxide and hydrogen.
The chemical formula is as follows:
2CH4+O2→2CO+4H2
CO+H2O→CO2+H2
after the reaction, it is necessary to purify and separate gases such as CO 2, CO and CH 4 from H 2. Therefore, purification devices are required in hydrogen production systems to purify H 2 to remove impurities such as CO 2, CO, CH 4, and the like, and to provide H 2 in an amount greater than 99.999%. Thus, if the hydrogenation reaction process of the enterprise is equipped with a dedicated hydrogen production device (i.e., hydrogen production system), there is no need to additionally add a methanation device as shown in fig. 2 to treat the off-gas hydrogen in the hydrogenation reaction, but to use a purification device already equipped in the hydrogen production system to purify the off-gas hydrogen. Thus, the overall use efficiency of the hydrogen is improved, the tail gas circulation device corresponding to the hydrogenation reaction is correspondingly simplified, and the investment is reduced.
FIG. 3 provides a schematic diagram of a purification apparatus for introducing hydrogen, a tail gas from a hydrogenation reaction, into a hydrogen production system in accordance with the present invention. As shown in fig. 3, a part of the tail gas hydrogen of the hydrogenation reaction is introduced into a hydrogen production system, and enters a purifying device in the hydrogen production system together with the crude hydrogen after the reaction in the reformer, and after the S, CO 2、CO、CH4 and other impurities are removed, H 2 with the content of more than 99.999% is provided for the hydrogenation reaction.
Specifically, in the method for treating tail gas hydrogen of hydrogenation reaction according to the present invention, a methanation device as shown in fig. 2 may be provided, or a methanation device as shown in fig. 2 may not be provided. When the methanation device is not arranged, a flow chart of the treatment method is shown in fig. 4.
In FIG. 4, stream ① is 100 moles of organics, stream ② is 302.57 moles of fresh hydrogen (containing 5ppm CO) stream ③ is 197.43 moles of internal recycle hydrogen, and the total hydrogen flow of stream ④ is 500 moles to achieve this reaction 5:1 (hydrogen: organics) 100 moles of organics react with 99.99 moles of hydrogen to produce 99.99 moles of product under the designed reaction conditions, and the remaining 0.01 moles of organics decompose to produce 0.01 moles of CO to form stream ⑤. In the gas-liquid separator, product ⑥ is separated in the liquid phase, the remaining gas is stream ⑦, a portion of stream ⑦ is directly recycled back to the hydrogenation reactor as stream ③, a portion of stream ⑧ remaining in stream ⑦ is recycled to the hydrogen production system, impurities in stream ⑧ are discharged together with other impurities produced in the hydrogen production system, and hydrogen in stream ⑧ becomes a portion of fresh hydrogenHydrogen produced from hydrogen production feedstock is ⑩.
In the case of setting up a methanation unit in the process according to the invention, a flow chart of the treatment process is shown in FIG. 5.
In FIG. 5, stream ① is 100 moles of organics, stream ② is 249.98 moles of fresh hydrogen (containing 4ppm CO), stream ③ is 250.02 moles of internal recycle hydrogen, and the total hydrogen flow of stream ④ is 500 moles to achieve this reaction 5:1 (hydrogen: organics) 100 moles of organics react with 99.99 moles of hydrogen to produce 99.99 moles of product under the designed reaction conditions, and the remaining 0.01 moles of organics decompose to produce 0.01 moles of CO to form stream ⑤. In the gas-liquid separator, product ⑥ is separated in the liquid phase, the remaining gas being stream ⑦, the internal recycle gas streamEnters the methanation unit, assuming 90% of the CO in the methanation unit is converted to CH 4, and after conversion is directly refluxed to the hydrogenation reactor as stream ③. The remaining tail gas hydrogen stream ⑧ in stream ⑦ is recycled outside the hydrogen production system and impurities in stream ⑧ are removed along with other impurities produced in the hydrogen production system, and hydrogen in stream ⑧ becomes part of the fresh hydrogen/>Hydrogen produced from hydrogen production feedstock is ⑩.
In FIG. 5, stream ⑧ has a composition of 149.99 moles of hydrogen, 0.004 moles of CO and 0.07 moles of CH 4. After the material flow ⑧ is directly and externally circulated to the hydrogen production system by adopting the scheme, part of tail gas hydrogen is changed into fresh hydrogen through the hydrogen production system; the CO component is purified in a purifying device of the hydrogen production system and then is emptied; the CH 4 component of stream ⑧ then becomes the feedstock for a hydrogen production system (natural gas hydrogen production) for the production of fresh hydrogen. Thereby realizing 100% recycling of tail gas hydrogen of hydrogenation reaction, reducing hydrogen unit consumption of hydrogenation reaction and saving production cost; simultaneously, impurities in tail gas hydrogen of hydrogenation reaction are effectively treated, the concentration of CO and CH 4 in a hydrogenation system is controlled, and the influence of internal recycle hydrogen on a hydrogenation catalyst is reduced.
Example 1
Taking continuous hydrogenation of terephthalic acid (TPA) to produce 1, 4-Cyclohexanedimethanol (CHDM) as an example, in the prior art, a methanation device shown in FIG. 2 is adopted to treat hydrogen in tail gas of hydrogenation reaction, the emptying amount of the hydrogen is controlled to ensure that the concentration of CO at the inlet of a hydrogenation reactor is below 30ppm, and the average value of hydrogen unit consumption is 1250Nm 3/ton of CHDM after multi-month operation. After the method and the flow are adopted, as shown in fig. 6, fig. 6 is a flow chart of a treatment method of tail gas hydrogen in the hydrogenation reaction of producing 1, 4-cyclohexanedimethanol from terephthalic acid, wherein a part of the tail gas hydrogen in the hydrogenation reaction is introduced into a hydrogen production system. After a number of months of operation, the average hydrogen unit consumption is reduced to 1099Nm 3/ton CHDM, and the unit consumption is only 101% of the theoretical value. Compared with the prior art, the method reduces the hydrogen consumption by 12.1 percent. The annual hydrogen gas is saved by 45.3 ten thousand Nm 3 in terms of 3000 tons of CHDM per annual production.
The foregoing is a further detailed description of the invention in connection with specific preferred embodiments, and is not intended to limit the practice of the invention to such description. It will be apparent to those skilled in the art that several simple deductions and substitutions can be made without departing from the spirit of the invention, and these are considered to be within the scope of the invention.
Claims (10)
1. A method for treating tail gas hydrogen of hydrogenation reaction is characterized in that part of tail gas hydrogen obtained by gas-liquid separation after hydrogenation reaction is directly introduced into a hydrogenation reactor as internal recycle hydrogen, or most of CO in the internal recycle hydrogen is converted into methane by a methanation device and then the treated internal recycle hydrogen is directly introduced into the hydrogenation reactor, the other part of tail gas hydrogen obtained by gas-liquid separation after hydrogenation reaction is introduced into a purifying and purifying device in a hydrogen production system as external recycle hydrogen, hydrogen obtained by purifying and purifying the external recycle hydrogen and hydrogen prepared by a hydrogen production raw material through the hydrogen production system are jointly used as fresh high-purity hydrogen to be added into the hydrogenation reactor, and the fresh high-purity hydrogen and the internal recycle hydrogen which is treated by the methanation device or not are jointly used for forming total hydrogen; the ratio of the internal recycle hydrogen to the external recycle hydrogen is 0.5-5: 1 and the CO concentration of the total hydrogen used in the hydrogenation reaction is less than 30ppm.
2. The process of claim 1, wherein the total hydrogen used in the hydrogenation reaction has a CO concentration of less than 25ppm.
3. The method of claim 1, wherein the hydrogenation reaction is one of the following reactions: hydrogenation of terephthalic acid to produce 1, 4-cyclohexanedicarboxylic acid, hydrogenation of 1, 4-cyclohexanedicarboxylic acid to produce 1, 4-cyclohexanedimethanol, continuous two-stage hydrogenation of terephthalic acid to produce 1, 4-cyclohexanedimethanol, hydrogenation of dimethyl terephthalate to produce dimethyl 1, 4-cyclohexanedicarboxylate, hydrogenation of dimethyl 1, 4-cyclohexanedicarboxylate to produce 1, 4-cyclohexanedimethanol, hydrogenation of bis (4-methylcyclohexane) dimethyl terephthalate to produce bis (4-methylcyclohexane) dimethyl 1, 4-cyclohexanedicarboxylate, and continuous two-stage hydrogenation of bis (4-methylcyclohexane) dimethyl terephthalate to produce 1, 4-cyclohexanedimethanol.
4. The method of claim 1, wherein the hydrogen production system is a natural gas hydrogen production system or a methanol hydrogen production system.
5. The method of claim 1, wherein the internal recycle hydrogen has a CO concentration of less than 10ppm after treatment by the methanation unit.
6. The process of claim 1, wherein the hydrogen unit consumption in the hydrogenation reaction is not more than 1.03 times the theoretical value.
7. The process of claim 2, wherein the total hydrogen used in the hydrogenation reaction has a CO concentration of less than 20ppm.
8. The method according to any one of claims 1 to 7, wherein the amount of exhaust hydrogen that is discharged from the gas-liquid separation after the hydrogenation reaction before a part of the exhaust hydrogen enters the hydrogen production system is zero.
9. The method of claim 2, wherein the ratio of internal recycle hydrogen to external recycle hydrogen is from 0.8 to 4:1.
10. The method of claim 9, wherein the ratio of internal recycle hydrogen to external recycle hydrogen is 1 to 3:1.
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