CN110272324B

CN110272324B - Process for preparing butadiene by carbon tetraoxide dehydrogenation as by-product of catalytic cracking process

Info

Publication number: CN110272324B
Application number: CN201810215203.0A
Authority: CN
Inventors: 徐国辉; 李延生
Original assignee: Wison Engineering Ltd
Current assignee: Wison Engineering Ltd
Priority date: 2018-03-15
Filing date: 2018-03-15
Publication date: 2022-07-15
Anticipated expiration: 2038-03-15
Also published as: CN110272324A

Abstract

The invention relates to a process for preparing butadiene by carbon tetraoxide dehydrogenation as a byproduct in a catalytic cracking process, which comprises the following steps: (I): sequentially removing butadiene, isobutane and isobutene from the byproduct carbon IV of the FCC device to obtain n-butene material; (II): feeding the n-butene material, the ingredient air and the ingredient steam into a butene oxidative dehydrogenation unit together for reaction, compressing the obtained reaction generated gas by a generated gas compression unit, separating a carbon four product and a non-condensable gas, and removing oxide to obtain crude butadiene; (III): and (3) sending the crude butadiene to a butadiene extraction unit to obtain butadiene product output, sending a byproduct alkane-alkene mixture comprising butylene and n-butane to an alkane-alkene separation unit to separate butylene from n-butane, extracting n-butane as a product, and returning butylene to a butylene oxidative dehydrogenation unit for continuous reaction. Compared with the prior art, the invention reasonably sets up the process flow, reduces the processing load of the alkane-alkene separation device, and greatly reduces the public engineering consumption and the equipment investment.

Description

Process for preparing butadiene by carbon tetraoxide dehydrogenation as by-product of catalytic cracking process

Technical Field

The invention belongs to the technical field of chemical product separation, and relates to a process for preparing butadiene by carbon tetraoxide dehydrogenation as a byproduct in a catalytic cracking process.

Background

Butadiene is an important petrochemical basic material used for producing synthetic rubber, synthetic resin, adiponitrile, hexamethylenediamine, nylon 66, sulfolane, 1, 4-butanediol, etc. The butadiene production method comprises two methods of carbon four fraction separation and synthesis (including butane dehydrogenation, butene oxydehydrogenation and the like). Almost all butadiene in all countries of the world is directly derived from the carbon four fraction produced in the process of preparing ethylene by hydrocarbon cracking. The production of butadiene by the oxidative dehydrogenation of butenes is an important supplement to the butadiene source. Table 1 shows a typical FCC by-product carbon four composition.

TABLE 1 typical FCC by-product carbon four composition

Serial number	Composition of	Content,% wt
			1	Isobutane	34
2	N-butane	10
			3	Butene-1	13
4	Butene-2	28
			5	Isobutene	15
6	Butadiene	<0.5
				Total of	100

A process flow for preparing butadiene by oxidative dehydrogenation of butylene, which is widely adopted at present, as shown in figure 1. A byproduct carbon tetraolefin S601 from an FCC device is treated by a pretreatment unit 600, specifically, butadiene is removed by hydrotreating in a butadiene hydrogenation section 601, then isobutylene in the carbon tetraolefin is removed by an etherification system, a methanol raw material is introduced to react with the isobutylene to generate methyl tert-butyl ether (MTBE), and a reaction product from an MTBE reactor is sent to a reaction rectifying tower. The reactive distillation tower consists of an upper tower and a lower tower, an MTBE product is extracted from the tower bottom, the C4 extracted from the tower top is sent to a C four water washing tower to wash out unreacted methanol, and the C4 for washing out the methanol is sent to an alkane and alkene separation unit. And (3) feeding the methanol-containing washing water in the kettle of the carbon four-water washing tower to a methanol recovery tower, circulating the methanol extracted from the tower top to the etherification reactor, and circulating the water in the kettle of the tower to the tower top of the carbon four-water washing tower. The C4 with the isobutene removed is sent to an alkane and alkene separation unit 500, so that butane and butylene are separated, the butane is taken out as a byproduct, and the butylene is sent to a butylene oxidative dehydrogenation unit 100 for reaction.

In the butylene oxidative dehydrogenation unit 100, a butylene oxidative dehydrogenation reactor or two axial fixed bed reactors are connected in series in each production line, and 6 production lines are required to be connected in parallel for a butylene oxidative dehydrogenation device with the scale of 10 ten thousand tons/year; or a single production line is adopted, and three radial fixed beds are connected in series. The generated gas after reaction is sent to the generated gas compression unit 200 for pressure boosting after heat recovery and quenching acid washing, and the generated gas after pressure boosting is sent to the oil absorption desorption and oxide removal unit 300. The tail gas after oil absorption is sent to a tail gas absorption unit or a catalytic oxidation unit. And (3) sending the crude butadiene S331 extracted from the side line of the desorber to a butadiene extraction unit 400, and obtaining a butadiene product after two-stage extraction and common rectification. And the butylene obtained from the top of the first extraction tower is recycled to the alkane and alkene separation unit.

Through research and analysis, the carbon tetraene byproduct generated by the FCC device treated by the traditional process for preparing butadiene through oxidative dehydrogenation of butene is found to have the following defects:

1) butane components in the carbon tetraolefins byproduct of the FCC unit comprise isobutane and n-butane, wherein the isobutane, the n-butane and the butene components are separated through an extractive distillation process, the separation load is very large, the steam consumption is very high, and the equipment investment is large.

2) If the isobutane and normal butane products are obtained, the isobutane and normal butane are required to be further separated, and the equipment investment and the public and auxiliary consumption are required to be increased.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a process for preparing butadiene by carbon tetraoxide dehydrogenation as a byproduct in a catalytic cracking process.

The purpose of the invention can be realized by the following technical scheme:

the invention provides a process for preparing butadiene by carbon tetraoxide dehydrogenation as a byproduct of a catalytic cracking process, which is characterized by comprising the following steps of:

step (one): sequentially removing butadiene, isobutane and isobutene from the byproduct carbon IV of the FCC device to obtain n-butene material;

step (II): feeding the n-butene material, the ingredient air and the ingredient steam into a butene oxidative dehydrogenation unit together for reaction, compressing the obtained reaction generated gas by a generated gas compression unit, separating a carbon four product and a non-condensable gas, and removing oxide to obtain crude butadiene;

step (III): and (3) sending the crude butadiene to a butadiene extraction unit to obtain butadiene product output, sending a byproduct alkane-alkene mixture comprising butylene and n-butane to an alkane-alkene separation unit to separate butylene from n-butane, extracting n-butane as a product, and returning butylene to a butylene oxidative dehydrogenation unit for continuous reaction.

In a preferred embodiment of the invention, in the step (one), the byproduct carbon four is selectively hydrogenated to remove butadiene, then is sent to remove and output isobutane, and the remaining carbon four components are subjected to isobutene removal to obtain the n-butene material. And removing isobutane by adopting a conventional rectification process.

In a preferred embodiment of the present invention, in step (one), the removal of isobutylene is performed by an etherification process or a dimerization process, wherein,

when the etherification process is adopted, methanol raw material is introduced to react with isobutene to generate methyl tert-butyl ether, and then the methyl tert-butyl ether is separated and extracted to realize isobutene removal;

when the dimerization process is adopted, the catalyst is utilized to lead isobutene components in the butylene to carry out dimerization reaction to generate carbon octaolefin, and then the carbon octaolefin is separated and removed through fractionation, thus realizing isobutene removal. The etherification process or the isobutylene dimerization process are the prior art, and the catalyst used in the dimerization process can be the catalyst known in the prior art, such as cation exchange resin and the like.

In a preferred embodiment of the invention, in the butylene oxidative dehydrogenation unit, n-butene material reacts with ingredient air and ingredient steam in an oxidative dehydrogenation reactor, generated gas obtained after the reaction is sent to a water-cooled acid washing tower for further cooling and removing acid gas after heat recovery, waste water at the tower bottom is discharged for treatment, and generated gas obtained after cooling and acid washing at the tower top is sent to a generated gas compression unit. The reaction treatment process in the butylene oxidative dehydrogenation unit is just referred to the prior process.

In a more preferred embodiment of the present invention, the oxidative dehydrogenation reactor is a fixed bed reactor or a fluidized bed reactor or the like.

In a preferred embodiment of the present invention, the generated gas is compressed by the generated gas compression unit and then is pressurized to 0.50 to 1.80 MPaG.

In a preferred embodiment of the present invention, in the step (two), the removal of the C four products together with the non-condensable gases and the oxides is performed in an oil absorption desorption and oxides removal unit, which is divided into two steps of separation of C four from the non-condensable gases and separation of C four from the oxides, wherein the separation of C four from the oxides is arranged upstream or downstream of the operation of separation of C four from the non-condensable gases. The oil absorption desorption and oxide removal unit can adopt a traditional oil absorption desorption unit (such as an oil absorption tower and an oil desorption tower) and an oxide removal unit (such as an aldehyde washing tower) and can also be added with a preseparation unit on the traditional basis (such as a preseparation tank and a preseparation tower are additionally arranged, a gas is generated by utilizing the preseparation tank to carry out preliminary gas-liquid separation, a gas phase at the top of the tank is treated by the oil absorption tower and the oil desorption tower, crude butadiene is extracted from the side line, a liquid phase at the bottom of the tank is sent to the preseparation tower to be separated, non-condensable gas at the top of the tank and non-condensable gas at the oil desorption tower are returned to a gas compression unit, a liquid phase at the bottom of the tower is mixed with the crude butadiene extracted from the side line and then sent to the oxide removal unit),

In a preferred embodiment of the present invention, the butadiene extraction unit comprises an extractive distillation section and a common distillation section, wherein the extractive distillation section adopts two-stage extraction, the crude butadiene is extracted by the extractive distillation section and then subjected to common distillation in the common distillation section to obtain butadiene products, and the separated alkylene mixture including butylene and butane is sent to the alkylene separation unit. The specific treatment process of the butadiene extraction unit can be realized by adopting the prior art. The extraction solvent may be an acetonitrile solvent or an N-methylpyrrolidone solvent, etc.

In a preferred embodiment of the invention, the alkane-alkene separation unit comprises a butene extraction tower and a butene desorption tower, the alkane-alkene mixture comprising n-butane and butene is extracted and absorbed by the butene extraction tower, the obtained n-butane product is extracted, the extraction solvent comprising butene is sent to the butene desorption tower for desorption, and the obtained butene is returned to the butene oxidative dehydrogenation unit for continuous reaction. The adopted extraction solvent is consistent with the butadiene extraction unit, and the extraction solvent can be acetonitrile solvent or N-methylpyrrolidone solvent and the like.

The invention adopts the pretreatment measures of hydrogenation, isobutane removal and the like to directly send the carbon tetraolefin by-product of the FCC device to the oxidative dehydrogenation reactor for reaction, reasonably sets the process flow according to the composition distribution of the carbon four feed, and greatly reduces the public engineering consumption and the equipment investment. Compared with the traditional process, the method has more remarkable economic benefit.

Compared with the prior art, the invention has the following characteristics:

(1) the isobutane separation process is arranged in the pretreatment unit, isobutane is separated out firstly, an isobutane byproduct is obtained, and the normal butane and the normal butene mixture are sent to the oxidative dehydrogenation reactor together, so that the consumption of burdening water vapor can be effectively reduced, and the energy consumption is reduced;

(2) and the alkane-alkene separation unit is arranged at the downstream of butadiene extraction by adopting a post alkane-alkene separation process, so that the treatment load of an alkane-alkene separation device is reduced, the investment and the public engineering consumption are reduced, and the operation cost is saved.

Drawings

FIG. 1 is a flow chart of a conventional process for preparing butadiene by tetraoxidative dehydrogenation of FCC byproduct carbon;

FIG. 2 is a flow chart of the process for preparing butadiene by tetraoxidative dehydrogenation of FCC byproduct carbon according to the present invention;

the symbols in the figure illustrate:

100-600 represent six units of the device, wherein 100 is a butylene oxidative dehydrogenation unit, 200 is a generated gas compression unit, 300 is an oil absorption desorption and oxide removal unit, 400 is a butadiene extraction unit, 500 is an alkane-alkene separation unit, and 600 is a pretreatment unit, wherein 601 is a butadiene hydrogenation section, 602 is an isobutane removal section, and 603 is an isobutene removal section;

S101-S632 represent material flows, wherein S101 is ingredient air, S102 is ingredient steam, S321 is tail gas, S361 is stripping steam, S331 is crude butadiene, S421 is butylene after butadiene extraction, S440 is fuel gas, S450 is a butadiene product, S530 is n-butane, S531 is a mixture of isobutane and n-butane, S541 is butylene after alkane and alkene separation, S601 is FCC unit byproduct carbon four, S602 is hydrogen, S622 is isobutane, and S632 is carbon octaene or MTBE.

Detailed Description

The invention is described in detail below with reference to the figures and the specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

Example 1:

this example describes the process simulation for butadiene production by oxidative dehydrogenation of butene at a scale of 10 million tons/year, wherein the feed is the carbon tetraolefin as a by-product of the FCC unit.

The specific process flow is shown in fig. 2, the FCC unit by-product carbon four S601 is sent to a pretreatment unit 600, and hydrogen S602 is sent from a boundary area, the pretreatment unit 600 is composed of a butadiene hydrogenation section 601, an isobutane removal section 602 and an isobutene removal section 603, the FCC unit by-product carbon four S601 and hydrogen S602 enter the butadiene hydrogenation section 601 first to perform selective hydrogenation reaction to remove butadiene, the obtained carbon four enters the isobutane removal section 602 to perform isobutane removal, and an isobutane product S622 is obtained, next, the carbon four components after isobutane removal enter the isobutene removal section 603 to obtain MTBE or carbon octaolefin S632, and the remaining carbon four olefins are sent to the butene oxidative dehydrogenation unit 100. In the isobutylene removal section 603, if an etherification process is adopted, isobutylene is removed in a manner of reacting with a methanol raw material to generate MTBE, and if a dimerization process is adopted, isobutylene is subjected to selective dimerization to generate and remove carbon octants.

The method comprises the steps of adding ingredient air S101 and ingredient steam S102 according to the quantity and proportion of carbon tetraolefin, simultaneously feeding three strands of raw material gas into an oxidative dehydrogenation reactor for butylene oxidative dehydrogenation, carrying out heat recovery and water-cooling acid washing on the discharged material of the reactor, then feeding the discharged material into a gas generation compression unit 200, compressing and boosting the discharged material to 0.50 MPaG-1.80 MPaG, and then feeding the compressed material into an oil absorption desorption and oxide removal unit, wherein the unit comprises three sections of pre-separation, oil absorption desorption and oxide removal, and is mainly used for separating carbon tetrad from non-condensable gas and separating carbon tetrad from oxide.

The crude butadiene S331 without the non-condensable gas and the oxide is sent to a butadiene extraction unit 400, the butadiene extraction process can adopt acetonitrile or N-methylpyrrolidone as an extraction solvent, and the butadiene extraction process comprises two stages of extraction processes and a common rectification process, and finally the qualified butadiene product S450 and the byproduct fuel gas S440 are obtained. The extracted alkane-alkene mixture S421 is sent to an alkane-alkene separation unit 500 (which can be composed of a butene extraction tower system and a butene desorption tower system), butene and n-butane are separated, an n-butane product S530 extracted from the butene extraction tower system is sent to a tank area, and the desorbed and extracted butene S541 is circulated back to the butene oxidative dehydrogenation unit 100 for continuous reaction.

Comparative example 1

Referring to fig. 1, the currently widely adopted process flow for preparing butadiene by oxidative dehydrogenation of butene is adopted, and the process flow for preparing butadiene by oxidative dehydrogenation of FCC byproduct carbon four is also adopted.

The processes used in comparative example 1 and comparative example 1 were analyzed, and the same processes used in the comparison of the process of example 1 and the conventional process of comparative example 1 are shown in the dotted line frame.

Tables 1 and 2 are a comparison of the two process schemes, with the consumption criterion in the conventional scheme being 0.

TABLE 1 conversion of energy of electric power and energy consumption working medium

Categories	Unit	Energy conversion value (MJ)
			Electricity	kWh	10.89
Circulating water	t	4.19
			1.3MPaG steam	t	3349

TABLE 2 comparison of energy consumption for two process designs (hourly unit time)

The comparison in tables 1 and 2 is performed under the same process in the butene oxidative dehydrogenation unit 100, the product gas compression unit 200, the oil absorption desorption and oxide removal unit 300, the butadiene extraction unit 400, the alkane separation unit 500, the butadiene hydrogenation section 601, and the isobutene removal section 603.

According to the data, the alkane and alkene separation unit 500 is arranged at the downstream of the butadiene extraction unit 400, the isobutane removal section 602 is additionally arranged between the butadiene hydrogenation section 601 and the isobutene removal section 603, and isobutane is obtained through separation. Compared with the traditional process flow shown in the figure 1, the energy saving rate of the process flow of the invention for consuming butadiene per ton is reduced by about 14.25%, the production cost of butadiene is reduced by about 206.5 yuan per ton, the benefit can be increased by 2065 ten thousand yuan per year according to 8000h of annual operation time, and the benefit is considerable.

The invention provides a process for preparing butadiene by oxidative dehydrogenation of butene, which is used for preparing carbon tetraolefin as a byproduct in an FCC (fluid catalytic cracking) device, and has considerable economic benefit.

The embodiments described above are intended to facilitate a person of ordinary skill in the art in understanding and using the invention. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make modifications and alterations without departing from the scope of the present invention.

Claims

1. A catalytic cracking process for preparing butadiene from carbon byproduct by means of four-oxidation dehydrogenation is characterized by comprising the following steps:

Step (III): sending the crude butadiene to a butadiene extraction unit to obtain butadiene product output, sending a byproduct alkane-alkene mixture comprising butylene and n-butane to an alkane-alkene separation unit to separate butylene from n-butane, extracting n-butane as a product, and returning butylene to a butylene oxidative dehydrogenation unit for continuous reaction;

in the step (one), the byproduct carbon four is subjected to selective hydrogenation to remove butadiene, then is sent to remove and output isobutane, and the remaining carbon four components are subjected to isobutene removal to obtain n-butene material;

in the second step, the removal of the C4 products, the non-condensable gas and the oxides is carried out in an oil absorption desorption and oxide removal unit, which is divided into two steps of separation of C4 from the non-condensable gas and separation of C4 from the oxides, wherein the separation of C4 from the oxides is arranged upstream or downstream of the separation operation of C4 from the non-condensable gas.

2. The process for preparing butadiene through the tetraoxide dehydrogenation of carbon as a byproduct of the catalytic cracking process according to claim 1, wherein in the step (one), the removal of isobutene is performed by an etherification process or a dimerization process, wherein,

When the dimerization process is adopted, the catalyst is utilized to lead isobutene components in the butylene to carry out dimerization reaction to generate the carbon octaolefin, and then the carbon octaolefin is separated and removed through fractionation, thus realizing isobutene removal.

3. The process of claim 1, wherein in the butylene oxidative dehydrogenation unit, n-butene material reacts with ingredient air and ingredient steam in the oxidative dehydrogenation reactor, the generated gas after the reaction is sent to a water-cooled acid washing tower for further cooling and removal of acid gas after heat recovery, the wastewater at the bottom of the tower is discharged for treatment, and the generated gas after the tower top is cooled and acid washed is sent to the generated gas compression unit.

4. The process for preparing butadiene by tetraoxidative dehydrogenation of carbon byproduct of a catalytic cracking process according to claim 3, wherein the oxidative dehydrogenation reactor is a fixed bed reactor or a fluidized bed reactor.

5. The process of claim 1, wherein the pressure of the generated gas is increased to 0.50 MPaG-1.80 MPaG after the generated gas is compressed by the generated gas compression unit.

6. The process for preparing butadiene by tetraoxydehydrogenation of carbon as a byproduct of the catalytic cracking process according to claim 1, wherein the butadiene extraction unit comprises an extractive distillation section and a common distillation section, wherein two-stage extraction is adopted in the extractive distillation section, the crude butadiene is extracted in the extractive distillation section and then subjected to common distillation in the common distillation section to obtain butadiene products, and the extracted and separated mixture of alkane and alkene including butene and butane is sent to the alkane and alkene separation unit.

7. The process of claim 1, wherein the alkane-olefin separation unit comprises a butene extraction tower and a butene desorption tower, the alkane-olefin mixture comprising n-butane and butene is extracted and absorbed by the butene extraction tower, the n-butane product is extracted, the extraction solvent comprising butene is sent to the butene desorption tower for desorption, and the obtained butene is returned to the butene oxydehydrogenation unit for further reaction.