Alkylene oxide separation system
阅读说明:本技术 环氧烷分离系统 (Alkylene oxide separation system ) 是由 E·I·罗斯-梅德戈德 D·W·莱申 K·P·鲁芬内尔 S·康卡基蒂苏普查 R·J·沃尔夫 于 2019-02-05 设计创作,主要内容包括:一种环氧丙烷分离系统,包括重质蒸馏塔和第一萃取蒸馏塔,重质蒸馏塔被配置为接收粗氧化丙烯流并排出重质清洗塔底物,重质清洗塔底物包含选自丙酮、甲醇、醛衍生物、水、包含C<Sub>5</Sub>+的重质烃或其组合的至少一种杂质,并排出包含与粗氧化丙烯流一起进入的大部分环氧丙烷的重质蒸馏塔塔顶流,第一萃取蒸馏塔被配置为接收重质蒸馏塔塔顶流和包含烃溶剂的第一萃取溶剂流,并排出包含选自醛(例如乙醛、甲醛等)、甲酸甲酯、甲醇、水、C<Sub>3</Sub>烃、C<Sub>4</Sub>烃或其组合的至少一种杂质的轻质清洗塔顶流,并排出包含经由重质蒸馏塔塔顶流进入的大部分环氧丙烷的富溶剂塔底流。还提供了一种环氧丙烷纯化方法。(An epoxypropane separation system comprises a heavy distillation column and a first extractive distillation column, the heavy distillation column is configured to receive a crude propylene oxide stream and discharge a heavy purge bottoms, the heavy purge bottoms comprises a component selected from the group consisting of acetone, methanol, aldehyde derivatives, water, C, and mixtures thereof 5 + a heavy hydrocarbon or a combination thereof, and withdrawing a heavy distillation column overhead stream comprising a majority of the propylene oxide entering with the crude propylene oxide stream, the first extractive distillation column being configured to receive the heavy distillation column overhead stream and a first extractive solvent stream comprising a hydrocarbon solvent, and withdrawing a heavy distillation column overhead stream comprising at least one impurity selected from aldehydes (e.g., acetaldehyde, formaldehyde, etc.), methyl formate, methanol, water, C, and mixtures thereof 3 Hydrocarbons, C 4 At least one hetero atom of a hydrocarbon or combination thereofA light, heavy purge overhead stream and a solvent-rich bottoms stream comprising a major portion of the propylene oxide entering via the heavy distillation overhead stream. A process for purifying propylene oxide is also provided.)
1. A propylene oxide separation system comprising:
A) a heavy distillation column configured to receive a crude propylene oxide stream and discharge:
a1) heavy purge bottoms comprising a compound selected from the group consisting of acetone, methanol, aldehydes, aldehyde derivatives, water, C5+ a heavy hydrocarbon or a combination thereof, and
a2) a heavy distillation column overhead stream comprising a major portion of the propylene oxide entering with the crude propylene oxide stream; and
B) a first extractive distillation column configured to receive the heavy distillation column overhead stream and a first extractive solvent stream comprising a hydrocarbon solvent and to discharge:
b1) a light wash overhead comprising at least one impurity selected from acetaldehyde, methyl formate, methanol, water, a C3 hydrocarbon, a C4 hydrocarbon, or a combination thereof, and
b2) a rich solvent bottoms stream comprising a majority of the propylene oxide entering via the heavy distillation column overhead stream.
2. The propylene oxide separation system of claim 1, wherein the first extractive distillation column is further configured to discharge a side extract, and wherein the propylene oxide separation system further comprises a decanter configured to receive the side extract, a hydrocarbon-lean solvent stream comprising the hydrocarbon solvent, and optionally water, allow formation of an aqueous phase and an organic phase, discharge an aqueous phase purge comprising water and methanol, one or more glycols, or a combination thereof, and discharge an organic phase stream comprising propylene oxide and the hydrocarbon solvent.
3. A propylene oxide separation system according to claim 2, further comprising a first solvent stripper configured to receive a rich solvent bottoms stream from the first extractive distillation column, discharge a first solvent stripper overhead comprising a majority of the propylene oxide entering with the rich solvent bottoms stream, and discharge a first solvent stripper bottoms comprising a lean hydrocarbon solvent.
4. A propylene oxide separation system as recited in claim 3, wherein the first extractive distillation column is fluidly connected to the first solvent stripper column, whereby at least a portion of the lean hydrocarbon solvent from the first solvent stripper column bottoms can be introduced into the first extractive distillation column via the first extractive solvent stream.
5. The propylene oxide separation system of claim 3, further comprising:
a second extractive distillation column configured to receive the first solvent stripper overhead and a second extractive solvent stream comprising the hydrocarbon solvent, to discharge an overhead propylene oxide product stream comprising a majority of the propylene oxide from the first solvent stripper overhead, and to discharge a second extractive distillation column bottoms comprising a hydrocarbon-rich solvent; and
a second solvent stripper configured to receive the second extractive distillation bottoms, discharge a hydrocarbon purge overhead stream, and discharge a second solvent stripper bottoms comprising a lean hydrocarbon solvent.
6. The propylene oxide separation system of claim 5, wherein the second solvent stripper is fluidly coupled to the first extractive distillation column, the decanter, or both, whereby a portion of the lean hydrocarbon solvent from the second solvent stripper bottoms can be introduced into the first extractive distillation column, the decanter, or both.
7. A propylene oxide separation system as recited in claim 5, wherein the second solvent stripper is fluidly coupled to the second extractive distillation column whereby at least a portion of the lean hydrocarbon solvent from the second solvent stripper bottoms can be introduced into the second extractive distillation column via the second extractive solvent stream.
8. The propylene oxide separation system of claim 1, which does not comprise a non-solvent distillation column upstream of the first extractive distillation column other than the heavies distillation column.
9. The propylene oxide separation system of claim 1, further comprising:
a decanter configured to receive at least a portion of the light wash overhead, a hydrocarbon solvent-lean stream comprising a hydrocarbon solvent, and optionally water, allow formation of an aqueous phase and an organic phase, and discharge an aqueous phase purge comprising water and methanol, one or more glycols, or a combination thereof, and discharge an organic phase stream comprising propylene oxide and the hydrocarbon solvent back to the first extractive distillation column.
10. The propylene oxide separation system of claim 1, further comprising:
a decanter configured to receive at least a portion of the light wash overhead, a hydrocarbon solvent-lean stream comprising a hydrocarbon solvent, and optionally water, allow formation of an aqueous phase and an organic phase, discharge an aqueous phase purge comprising water and methanol, one or more glycols, or a combination thereof, and discharge an organic phase stream comprising propylene oxide and the hydrocarbon solvent; and
a solvent stripper configured to receive the organic phase stream from the decanter, discharge a hydrocarbon purge overhead stream comprising at least a portion of the propylene oxide from the organic phase stream, and discharge a solvent stripper bottoms comprising a lean hydrocarbon solvent.
11. A method, comprising:
(i) subjecting the crude propylene oxide stream to non-solvent distillation in a heavy ends distillation column to produce a crude propylene oxide stream comprising a solvent selected from the group consisting of acetone, methanol, aldehydes, aldehyde derivatives, water, and C5+ a heavy purge bottoms of at least one impurity of a heavy hydrocarbon or combination thereof, and a heavy distillation column overhead stream comprising a majority of the propylene oxide entering the crude propylene oxide stream;
(ii) introducing the heavy distillation column overhead stream and a first extractive distillation solvent stream comprising a hydrocarbon solvent into a first extractive distillation column to produce a light wash overhead comprising at least one impurity selected from acetaldehyde, methyl formate, methanol, water, C3 hydrocarbons, C4 hydrocarbons, or a combination thereof, and a solvent-rich bottoms stream comprising a majority of the propylene oxide entering via the heavy distillation column overhead stream;
(iii) introducing the side extract from the first extractive distillation column into a decantation apparatus and allowing an aqueous phase purge comprising water and methanol, one or more glycols, or a combination thereof, and an organic phase stream comprising propylene oxide and the hydrocarbon solvent to form therein; and
(iv) the rich solvent bottoms stream from the first extractive distillation column is introduced into a first solvent stripper column to produce a first solvent stripper column overhead comprising a majority of the propylene oxide entering the first solvent stripper column via the rich solvent bottoms stream and a first solvent stripper column bottoms comprising the lean hydrocarbon solvent.
12. The method as set forth in claim 11 further comprising feeding a portion of the first solvent stripper bottoms comprising the lean hydrocarbon solvent to the first extractive distillation column and feeding another portion of the first solvent stripper bottoms comprising the lean hydrocarbon solvent to the decanter.
13. The process of claim 11, wherein the heavy purge bottoms comprises at least 10 wt% of the amount of methanol introduced with the crude propylene oxide stream, at least 40 wt% of the amount of water introduced with the crude propylene oxide stream, or both.
14. The method of claim 11, further comprising:
(v) subjecting the first solvent stripper overhead to extractive distillation by introducing the first solvent stripper overhead and a second extractive distillation solvent stream comprising the hydrocarbon solvent into a second extractive distillation column, thereby producing a purified propylene oxide product as an overhead stream and a second extractive distillation column bottoms comprising a hydrocarbon-rich solvent;
(vi) introducing the second extractive distillation column bottoms comprising hydrocarbon-rich solvent into a second solvent stripper column to produce a light hydrocarbon overhead purge stream and a second solvent stripper column bottoms comprising a lean hydrocarbon solvent; and
(vii) introducing at least a portion of the second solvent stripper bottoms into the second extractive distillation column, the first extractive distillation column, the decanter, or a combination thereof.
15. The process of claim 14, wherein the heavy distillation column is operated at a pressure in the range of from 0 to 60psig (0 to 414kPa gauge), at a temperature in the range of from 30 to 150 degrees celsius, or both; wherein the first extractive distillation column is operated at a pressure in the range of from 0 to 60psig (0 to 414kPa gauge), at a temperature in the range of from 30 to 200 degrees Celsius, or both; wherein the second extractive distillation column is operated at a pressure in the range of 0 to 60psig (0 to 414kPa gauge), at a temperature in the range of 30 to 200 degrees Celsius, or both; or a combination thereof.
16. A method, comprising:
(i) subjecting the crude propylene oxide stream to non-solvent distillation in a heavy ends distillation column to produce a crude propylene oxide stream comprising a solvent selected from the group consisting of acetone, methanol, aldehydes, aldehyde derivatives, water, and C5+ a heavy purge bottoms of at least one impurity of a heavy hydrocarbon or combination thereof, and a heavy distillation column overhead stream comprising a majority of the propylene oxide entering the crude propylene oxide stream;
(ii) introducing the heavy distillation column overhead stream and a first extractive distillation solvent stream comprising a hydrocarbon solvent into a first extractive distillation column to produce a light wash overhead comprising at least one impurity selected from acetaldehyde, methyl formate, methanol, water, C3 hydrocarbons, C4 hydrocarbons, or a combination thereof, and a solvent-rich bottoms stream comprising a majority of the propylene oxide entering via the heavy distillation column overhead stream;
(iii) introducing at least a portion of the light purge overhead from the first extractive distillation column into a decantation apparatus and allowing an aqueous phase purge comprising water and methanol, one or more glycols, or a combination thereof, and an organic phase stream comprising propylene oxide and a hydrocarbon solvent to form therein; and
(iv) the rich solvent bottoms stream from the first extractive distillation column is introduced into a first solvent stripper column to produce a first solvent stripper column overhead comprising a majority of the propylene oxide entering the first solvent stripper column via the rich solvent bottoms stream and a first solvent stripper column bottoms comprising the lean hydrocarbon solvent.
17. The method as set forth in claim 16 further comprising feeding a portion of the first solvent stripper bottoms comprising the lean hydrocarbon solvent to the first extractive distillation column and feeding another portion of the first solvent stripper bottoms comprising the lean hydrocarbon solvent to the decanter.
18. The process of claim 16, wherein the heavy purge bottoms comprises at least 10 wt% of the amount of methanol introduced with the crude propylene oxide stream, at least 40 wt% of the amount of water introduced with the crude propylene oxide stream, or both.
19. The method of claim 16, further comprising:
(v) subjecting the first solvent stripper overhead to extractive distillation by introducing the first solvent stripper overhead and a second extractive distillation solvent stream comprising the hydrocarbon solvent into a second extractive distillation column, thereby producing a purified propylene oxide product as an overhead stream and a second extractive distillation column bottoms comprising a hydrocarbon-rich solvent;
(vi) introducing the second extractive distillation column bottoms comprising hydrocarbon-rich solvent into a second solvent stripper column to produce a light hydrocarbon overhead purge stream and a second solvent stripper column bottoms comprising a lean hydrocarbon solvent; and
(vii) introducing at least a portion of the second solvent stripper bottoms into the second extractive distillation column, the first extractive distillation column, the decanter, or a combination thereof.
20. The process of claim 19 wherein the heavy distillation column is operated at a pressure in the range of from 0 to 60psig (0 to 414kPa gauge), at a temperature in the range of from 30 to 150 degrees celsius, or both; wherein the first extractive distillation column is operated at a pressure in the range of from 0 to 60psig (0 to 414kPa gauge), at a temperature in the range of from 30 to 200 degrees Celsius, or both; wherein the second extractive distillation column is operated at a pressure in the range of 0 to 60psig (0 to 414kPa gauge), at a temperature in the range of 30 to 200 degrees Celsius, or both; or a combination thereof.
Technical Field
The present disclosure relates to a system and process for purifying and recovering propylene oxide formed by epoxidation of propylene with a hydroperoxide derived from the oxidation of isobutane, ethylbenzene, cyclohexane, alkylate or cumene. More particularly, the present disclosure relates to a system and method that provides a reduced amount of propylene oxide in the purge stream and/or facilitates separation of impurities, such as light impurities in the first extractive distillation column, thereby increasing propylene oxide yield, increasing purity, or both. Still more particularly, the present disclosure relates to systems and methods for purifying and recovering propylene oxide via a configuration that first removes selected heavy impurities ("heavy-first" configuration).
Background
Approximately 145 million pounds of Propylene Oxide (PO) are produced per year. Propylene oxide has many uses. 60-70% of the propylene oxide is converted into polyether polyols for the production of polyurethane plastics. About 20% of the propylene oxide is hydrolyzed to propylene glycol via a process accelerated by thermal reaction or by acid or base catalysis. Other major products are polypropylene glycol, propylene glycol ethers and propylene carbonate. To produce these end products, propylene oxide is required which is substantially free of impurities.
Processes for the production of alkylene oxides, including propylene oxide, involve hydrochlorination, direct oxidation and epoxidation of their corresponding alkenes by peroxides or hydroperoxides. The oxides used in the epoxidation process are derived from secondary or tertiary hydrocarbons by direct oxidation with molecular oxygen; thus, the oxide contains both oxygenate impurities and precursors. Additional oxygenate impurities are also produced in the olefin epoxidation step. Crude alkylene oxides, such as propylene oxide, particularly those produced by epoxidation with hydrocarbyloxides, contain oxygen-containing impurities in amounts that are difficult to separate from the alkylene oxide. Impurities may include water, acids, alcohols, aldehydes, alkanes, ketones, and esters. There is a continuing need for improved systems and methods for separating alkylene oxide from these impurity components of a crude alkylene oxide hydrocarbon stream.
Although the purity of crude propylene oxide (e.g., crude propylene oxide from propylene oxide and tert-butyl alcohol (PO/TBA) processes) can be as high as 98.5%, crude propylene oxide typically contains near-boiling impurities including, but not limited to, water, methanol, methyl formate, formaldehyde, acetaldehyde, acetone, propionaldehyde, isobutylene oxide, aldehyde derivatives, and C5-C7One or more of hydrocarbons. To meet commercial grade product propylene oxide specifications, impurities are removed from the crude propylene oxide. Due to the proximity of the boiling point, these impurities are difficult to separate from propylene oxide without the use of elaborate propylene oxide refining or purification schemes involving extractive distillation techniques.
Conventional propylene oxide purification involves producing a purge stream comprising propylene oxide (also known as 'tilted propylene oxide cuts'), which may be equal to 18 to 22 wt% of the propylene oxide in the crude propylene oxide entering the refining section. Such a purge stream comprising propylene oxide is typically used to produce Propylene Glycol (PG) to obtain added value in a propylene oxide purification/purification section at reduced equipment and energy costs. A reduction in PO loss in the purge stream can provide greater overall recovery of product PO, which may be desirable relative to making PG.
Recovery of a purified propylene oxide product containing low levels of impurities such as aldehydes and alcohols, particularly for propylene oxide produced by free radical oxidation processes, including, for example, the t-butyl hydroperoxide process, remains a challenge. Accordingly, there is a need for improved systems and methods for recovering propylene oxide in a high purity state from the effluent streams of various crude propylene oxide production processes without excessive loss of propylene oxide product.
Disclosure of Invention
Disclosed herein is a propylene oxide separation system comprising: a heavy distillation column configured to receive a crude propylene oxide stream and discharge a heavy purge bottoms comprising a component selected from the group consisting of acetone, methanol, aldehyde derivatives, water, oxidized isobutylene, and C5+ a heavy hydrocarbon or a combination thereof and withdrawing a heavy distillation column overhead stream comprising a majority of the propylene oxide entering with the crude propylene oxide stream; and a first extractive distillation column configured to receive the heavy distillation column overhead stream and an extractive solvent stream comprising a hydrocarbon solvent and to discharge a stream comprising a hydrocarbon solvent selected from the group consisting of aldehydes, methyl formate, methanol, water, C3Hydrocarbons, C4A light purge overhead stream of at least one impurity of a hydrocarbon or combination thereof and withdrawing a solvent-rich bottoms stream comprising a majority of the propylene oxide entering via the heavy distillation column overhead stream.
Also disclosed herein is a method comprising: (i) subjecting the crude propylene oxide stream to non-solvent distillation in a heavy ends distillation column to produce a stream comprising a solvent selected from the group consisting of acetone, methanol, aldehydes, aldehyde derivatives, water, isobutylene oxide, C, and mixtures thereof5+ a heavy purge bottoms of at least one impurity of a heavy hydrocarbon or combination thereof, and a heavy distillation column overhead stream comprising a majority of the propylene oxide entering the crude propylene oxide stream; (ii) introducing the heavy distillation column overhead stream and an extractive distillation solvent stream comprising a hydrocarbon solvent into a first extractive distillation column to produce a stream comprising a solvent selected from the group consisting of aldehydes, methyl formate, methanol, water, C3Hydrocarbons, C4A light purge overhead of at least one impurity of a hydrocarbon or combination thereof, and a rich solvent comprising a majority of propylene oxide entering via a heavy distillation column overhead streamA bottoms stream; (iii) transferring the side extract from the first extractive distillation column into a decantation apparatus and allowing an aqueous phase purge comprising water and methanol, one or more glycols, or a combination thereof, and an organic phase stream comprising propylene oxide and the hydrocarbon solvent to form therein; and (iv) introducing the rich solvent bottoms stream from the first extractive distillation column into a first solvent stripper column to produce a first solvent stripper column overhead comprising a majority of the propylene oxide entering the first solvent stripper column via the rich solvent bottoms stream and a first solvent stripper column bottoms comprising the lean hydrocarbon solvent.
Also disclosed herein is a method comprising: (i) subjecting the crude propylene oxide stream to non-solvent distillation in a heavy ends distillation column to produce a stream comprising a solvent selected from the group consisting of acetone, methanol, aldehydes, aldehyde derivatives, water, isobutylene oxide, C, and mixtures thereof5+ a heavy purge bottoms of at least one impurity of a heavy hydrocarbon or combination thereof, and a heavy distillation column overhead stream comprising a majority of the propylene oxide entering the crude propylene oxide stream; (ii) introducing the heavy distillation column overhead stream and a first extractive distillation solvent stream comprising a hydrocarbon solvent into a first extractive distillation column to produce a light wash overhead comprising at least one impurity selected from aldehydes, methyl formate, methanol, water, C3 hydrocarbons, C4 hydrocarbons, or combinations thereof, and a solvent-rich bottoms stream comprising a majority of the propylene oxide entering via the heavy distillation column overhead stream; (iii) introducing at least a portion of the light purge overhead from the first extractive distillation column into a decantation apparatus and allowing an aqueous phase purge comprising water and methanol, one or more glycols, or a combination thereof, and an organic phase stream comprising propylene oxide and a hydrocarbon solvent to form therein; and (iv) introducing the rich solvent bottoms stream from the first extractive distillation column into a first solvent stripper column to produce a first solvent stripper column overhead comprising a majority of the propylene oxide entering the first solvent stripper column via the rich solvent bottoms stream and a first solvent stripper column bottoms comprising the lean hydrocarbon solvent.
While multiple embodiments are disclosed, other embodiments will become apparent to those skilled in the art from the following detailed description. As will be apparent, certain embodiments as disclosed herein can be modified in various respects, without departing from the spirit and scope of the claims presented herein. The following detailed description is, therefore, to be regarded as illustrative in nature and not as restrictive.
Drawings
The following figures illustrate embodiments of the subject matter disclosed herein. The claimed subject matter can be understood by reference to the following description taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a schematic diagram of a propylene oxide separation system 100 according to an embodiment of the present disclosure;
FIG. 2 is a schematic diagram of a propylene oxide separation system 100A according to an embodiment of the present disclosure;
FIG. 3 is a schematic diagram of a propylene
FIG. 4 is a schematic diagram of a propylene oxide separation system 100C according to an embodiment of the present disclosure; and is
Fig. 5 is a schematic diagram of a propylene
Detailed Description
SUMMARY
The present disclosure may be understood more readily by reference to the following detailed description of various embodiments and the examples included therein. As used herein, "substantial portion" means greater than 50% by weight.
The present disclosure relates to systems and methods for removing impurities from a crude propylene oxide stream. Propylene Oxide (PO) is also known as propylene oxide (epyppane), propylene oxide (epypropane), 1,2-propylene oxide (1,2-propylene oxide), methyl ethylene oxide (methyl oxirane), 1,2-propylene oxide (1, 2-epyppane), propylene oxide (propene oxide), methyl ethylene oxide (methyl ethylene oxide), and methyl ethylene oxide (methyl ethylene oxide). PO can be produced in a PO/TBA process in which PO and tert-butanol (TBA, also known as 2-methyl-2-propanol and tert-butanol) are formed. In this PO/TBA process, Isobutane (IB), also known as 2-methylpropane, may first be reacted with oxygen to form tert-butyl hydroperoxide (TBHP), also known as tert-butyl hydroperoxide. Subsequently, propylene (propylene), also known as propylene (propene), can be reacted with TBHP in the presence of a catalyst to form PO and TBA. Since this process produces both PO and TBA, it is referred to herein as a PO/TBA process.
The crude propylene oxide purified via the systems and methods disclosed herein may be produced via any process known in the art. In embodiments, a crude PO stream purified via the systems and methods disclosed herein is formed in a PO/TBA process. The production of a crude PO stream, for example from a PO/TBA process, is known to those skilled in the art.
The PO/TBA process can also produce a variety of undesirable by-products or near boiling impurities that remain in the crude PO. Without wishing to be bound by theory, a non-selective reaction may occur to produce impurities. These impurities may include, but are not limited to, acetone, alcohols such as, but not limited to, methanol, formaldehyde, propionaldehyde, water, formic acid, methyl formate, acetaldehyde, hydrocarbons, aldehydes, oxidized isobutylene, and the like. For example, such non-selective reactions may include, but are not limited to, the production of acetone and methanol from TBHP; producing formaldehyde and water from methanol in the presence of oxygen; producing formic acid from formaldehyde in the presence of oxygen; producing methyl formate and water from formic acid and methanol; acetaldehyde and methanol, etc. are produced from PO and water. Other reactions and impurities are possible.
The concentration of these impurities ending up in the crude PO stream from the PO/TBA process can vary and their removal is effected to provide a purified PO product. Systems and methods for removing impurities from such a crude PO stream are disclosed herein. It has been unexpectedly found that removing heavies upstream of the extractive distillation increases the effectiveness of the downstream extractive distillation. Without wishing to be bound by theory, the removal of aldehydes and/or aldehyde derivatives (e.g., formaldehyde and/or methylene glycol and/or dimethoxymethane) as heavies in the upstream heavy distillation column bottoms as disclosed herein prevents or minimizes the downstream travel of aldehydes and/or aldehyde derivatives, where there is a potential for heavy decomposition at higher temperatures to form near-boiling impurities (e.g., methanol, water, formaldehyde) that can end up in the purified PO product. Such aldehyde derivatives (e.g., formaldehyde derivatives) can form rapidly, but are unstable, making their quantification difficult.
A propylene oxide separation system and process (also referred to herein as a PO separation system or process or a propylene oxide purification system or process) will now be described with reference to fig. 1, fig. 1 being a schematic diagram of a PO separation system 100 (also referred to as a "PO purification system") according to embodiments of the present disclosure. For clarity, the respective reboilers and overhead condensers (including any reflux systems) for each column (except for the condenser and associated reflux for the first extractive distillation column 120) are not shown in fig. 1. The systems and methods of the present disclosure provide for separating heavy from a crude PO stream by (non-solvent) distillation prior to (e.g., upstream of) further separation of impurities such as, but not limited to, extractive distillation to remove light purge streams, solvent stripping to provide a lean solvent for recycle, separation of PO product by extractive distillation, separation of a hydrocarbon purge stream from a lean solvent stream that may be recycled, and the like. For example, the PO separation system 100 comprises a
A crude PO stream is introduced into the
Methyl formate may be present in the crude PO stream in an amount within a range having a lower limit and/or an upper limit, each expressed as a weight percentage of the total composition of the crude PO stream. The range may or may not include a lower limit and/or an upper limit. The lower and/or upper limit of methyl formate may be selected from 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.51, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.54, 0.82, 0.73, 0.54, 0.73, 0.75, 0.54, 0.73, 0.75, 0.73, 0.75, 0.54, 0.73, 0.75, 0.73, 0.75, 0.73, 0.54, 0.73, 0.75, 0.73, 0.54, 0.73, 0.75. For example, methyl formate may be present in an amount greater than 0.02, 0.04, or 0.06 wt% of the total composition of the crude PO stream.
The one or more alcohols (e.g., without limitation, methanol) can be present in the crude PO stream in an amount within a range having a lower limit and/or an upper limit, each expressed as a weight percentage of the total composition of the crude PO stream. The range may or may not include a lower limit and/or an upper limit. One or more alcohol (e.g., methanol) lower and/or upper limits may be selected from 0, 0.001, 0.002, 0.003, 0.0031, 0.0032, 0.0033, 0.0034, 0.0035, 0.0036, 0.0037, 0.0038, 0.0039, 0.0139, 0.0239, 0.0339, 0.0439, 0.0539, 0.0639, 0.0739, 0.0839, 0.0939, 0.1039, 0.1049, 0.1059, 0.1069, 0.1079, 0.1089, 0.1099, 0.1109, 0.1119, 0.1129, 0.1139, 0.1149, 0.1159, 0.116, 0.1161, 0.1162, 0.1163, 0.1164, 0.1167, 0.1164, 0.117, 0.1164, 0.1173, 0.1164, 0.1175, 0.1164, 365, 0.1164, 365, 364, and 364 weight percent. For example, methanol may be present in an amount greater than 0.003, 0.03, 0.1172, or 0.3 wt% of the total composition of the crude PO stream.
Acetaldehyde may be present in the crude PO stream in an amount within a range having a lower limit and/or an upper limit, each expressed as a weight percentage of the total composition of the crude PO stream. The range may or may not include a lower limit and/or an upper limit. The lower and/or upper limit of acetaldehyde may be selected from 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.53, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.54, 0.73, 0.75, 0.73, 0.54, 0.73, 0.75, 0.73, 0.54, 0.75, 0.73, 0.75, 0.73, 0.75, 0.73, 0.75, 0.49, 0.75, 0.9, 0.73, 0.75. For example, acetaldehyde may be present in an amount greater than 0.03, 0.01, or 0.005 wt.% of the total composition of the crude PO stream.
Formaldehyde can be present in the crude PO stream in an amount within a range having a lower limit and/or an upper limit, each expressed as a weight percentage of the total composition of the crude PO stream. The range may or may not include a lower limit and/or an upper limit. The formaldehyde may be present in an amount selected from 0, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.82, 0.54, 0.27, 0.54, 0.27, 0.54, 0.27, 0.54, 0.27, 0.54, 0.67, 0.54, 0.75, 0.54, 0.27. For example, formaldehyde may be present in an amount greater than 0.003, 0.005, 0.01, or 0.02 wt% of the total composition of the crude PO stream.
Water may be present in the crude PO stream in an amount within a range having a lower limit and/or an upper limit, each expressed as a weight percentage of the total composition of the crude PO stream. The range may or may not include a lower limit and/or an upper limit. The lower and/or upper limit of water may be selected from 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.53, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.52, 0.54, 0.73, 0.82, 0.73, 0.54, 0.73, 0.75, 0.54, 0.75, 0.73, 0.75, 0.73, 0.75, 0.49, 0.75, 0.73, 0.75, 0.9, 0.73, 0.54, 0.75, 0.73, 0.75, 0.95, 0.75, 0.73, 0.75, 0.9, 0.73, 0.75. For example, water may be present in an amount greater than 0.16, 0.2, 0.3, or 0.8 wt% of the total composition of the crude PO stream.
For example, the crude PO stream can comprise (each expressed as an average weight percentage of the total composition of the crude PO stream): 0.05 to 1.5, 0.02 to 1.0 or 0.01 to 0.07 wt.% of methyl formate (MeF), 0.05 to 1.5, 0.1 to 1.0 or 0.2 to 0.8 wt.% of methanol (MeOH), 0.001 to 0.03, 0.003 to 0.02 or 0.004 to 0.04 wt.% of aldehydes and/or aldehyde derivatives, 0.001 to 0.05, 0.003 to 0.03 or 0.006 to 0.04 wt.% of acetaldehyde (AA), 0.001 to 0.04, 0.002 to 0.03 or 0.003 to 0.02 wt.% of Formaldehyde (FA), 0.05 to 1.5, 0.1 to 1.0 or 0.2 to 0.8 wt.% of water, 0.001 to 0.5, 0.002 to 0.4 or 0.01 to 0.3 wt.% of hydrocarbons, 0.01 to 0.03 or 0.08 to 0.06 wt.% of light hydrocarbons (c.06 wt.%)3+ hydrocarbons, C3A hydrocarbon,C4Hydrocarbons or combinations thereof), 0.01 to 0.2, 0.02 to 0.15, or 0.03 to 0.1 wt.% of heavy hydrocarbons (C)5+、C6+、C5、C6Or a combination thereof) or a combination thereof.
Distillation of the crude PO stream within the
The heavy ends
In embodiments, the
Without wishing to be bound by theory, the PO separation system and method of the present disclosure including the prior heavies removal via
Since the higher content of methanol and/or water in the crude PO stream can provide enhanced removal of aldehydes and/or aldehyde derivatives (such as, but not limited to, formaldehyde derivatives) via the
The heavy purge bottoms removed via heavy purge bottoms line 102 can comprise one or more compounds selected from the group consisting of acetone, methanol, aldehydes and aldehyde derivatives, water, heavy hydrocarbons (i.e., C)5+、C6+、C5、C6Or a combination thereof), acrolein, Propionaldehyde (PA), isobutylene oxide (IBO), formic acid, or a combination thereof. In embodiments, the heavy purge bottoms comprises at least one selected from the group consisting of acetone, methanol, aldehydes and aldehyde derivatives, water, heavy hydrocarbons, or combinations thereof. The aldehyde and aldehyde derivative may comprise formaldehyde and/or a formaldehyde derivative. In embodiments, the heavy purge bottoms removed from the
The heavy distillation column overhead stream removed via heavy distillation column overhead line 103 comprises a majority of the PO introduced into heavy distillation column 110 with the crude PO stream, and may further comprise (each expressed as an average weight percentage of the total composition of the heavy distillation column overhead stream): 0.02 to 0.08, 0.03 to 0.07 or 0.04 to 0.06% by weight of methyl formate (MeF), 0.1 to 0.5, 0From 2 to 0.4 or from 0.25 to 0.35% by weight of methanol (MeOH), from 0.005 to 0.05, from 0.01 to 0.04 or from 0.015 to 0.03% by weight of aldehydes and/or aldehyde derivatives, from 0.002 to 0.04, from 0.003 to 0.03 or from 0.004 to 0.02% by weight of acetaldehyde (AA), from 0.0 to 0.01, from 0.0 to 0.005 or from 0.0 to 0.0001% by weight of Formaldehyde (FA), from 0.05 to 0.5, from 0.03 to 0.4 or from 0.01 to 0.3% by weight of water, from 0.01 to 0.2, from 0.03 to 0.5 or from 0.05 to 0.8% by weight of hydrocarbons, from 0.005 to 0.08, from 0.015 to 0.1 or from 0.02 to 0.3% by weight of light hydrocarbons (C)3+ hydrocarbons, C3Hydrocarbons, C4Hydrocarbons or combinations thereof), 0.001 to 0.02, 0.002 to 0.01, or 0.003 to 0.008 wt.% of heavy hydrocarbons (C)5+ hydrocarbons, C6+ hydrocarbons, C5Hydrocarbons, C6Hydrocarbons or combinations thereof) or combinations thereof.
The heavy distillation column overhead stream is introduced into an extractive distillation column 120 (which, as noted above, may be referred to as a "first" extractive distillation column in a system further comprising a second extractive distillation column downstream thereof) via heavy distillation column
The first
The first
In embodiments, the first
The first extractive distillation column overhead, or "light purge," comprises at least one impurity and is removed from the first
A separation (knock out) (K/O)121 may be used to separate the gas comprising the uncondensed components from the liquid comprising the condensed components. The uncondensed components or 'vapor purge'
A portion of the condensate from K/O121 may be returned to
The light purge removed via first edc
In embodiments, the first
The organic phase may be removed from
The water wash in
The first extractive distillation column extractive
Removal of the light and aqueous purge via the first
The impurities removed via the first
The solvent stripper 130 (which may be referred to herein as a 'first' solvent stripper when a second
The first
In embodiments, the first
First solvent stripper
The second
The second
In embodiments, the second
The PO product removed from
The second extractive distillation bottoms line 142 can be configured to introduce a second extractive distillation bottoms comprising rich solvent into the second
In embodiments, the second
The second solvent stripper
Fig. 2 is a schematic diagram of a propylene oxide separation system 100A according to another embodiment of the present disclosure. In the embodiment of fig. 2, the side extract line 127 of the embodiment shown in fig. 1 is replaced with
Fig. 3 is a schematic diagram of a propylene
Fig. 4 is a schematic diagram of a propylene oxide separation system 100C according to another embodiment of the present disclosure. In the embodiment of fig. 4, the liquid light purge in liquid
Fig. 5 is a schematic diagram of a propylene
Feature/potential benefit
The systems and methods of the present disclosure provide for the removal of heavies from a crude PO stream as an upstream step in a PO purification process. In embodiments, the heavy removal is the first step in the PO purification process according to the present disclosure. In embodiments, removal of heavies via non-solvent distillation is the only distillation step upstream of the (first) extractive distillation in the PO purification process according to the present disclosure. In embodiments, the system of the present disclosure does not include a non-solvent distillation column upstream of the first extractive distillation column other than the heavy distillation column. In embodiments, the process according to the present disclosure does not include a non-solvent distillation, other than a heavy distillation column, upstream of the first extractive distillation. In embodiments, the downstream separation (e.g., the first extractive distillation column, the second extractive distillation column, or both) may be conducted at a lower temperature than a corresponding separation/unit of a similar system in the absence of upstream heavies removal of the present disclosure. In embodiments, the system of the present disclosure does not include a caustic mixer and/or a backwash tower as described in U.S. patent No. 9,593,090.
In embodiments, the total PO purge is the total PO in a combined stream of (a) the heavy purge bottoms extracted from the
By positioning the non-solvent heavy distillation column prior to PO purification and removing heavy ends from its bottoms, a purer PO stream can be introduced to a subsequent extractive distillation column (e.g., first extractive distillation column 120). Unexpectedly, in embodiments, removal of the heavy fraction (which can remove aldehydes and/or aldehyde derivatives, such as, but not limited to, formaldehyde and formaldehyde derivatives) with the bottoms of the preliminary heavy
The systems and methods disclosed herein including upstream heavies removal may provide for reduced solvent flow in the front loop including the first
Upstream heavies removal in accordance with the present disclosure may enable the introduction of a crude PO stream having relatively high amounts of water and methanol, for example, directly to PO purification system 100 (e.g., directly to heavy distillation column 110).
The following examples merely illustrate the systems and methods of the present disclosure. Those skilled in the art will recognize many variations that are within the spirit of the disclosure and scope of the claims.
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