CN106609151B - A kind of method for producing low-carbon alkene - Google Patents

Abstract

The invention relates to the field of catalytic cracking of Fischer-Tropsch synthetic oil, and specifically discloses a method for producing low-carbon olefins. The method includes: performing a first catalytic cracking reaction on conventional petroleum and a catalytic cracking catalyst, and then performing the first catalytic cracking reaction The obtained reaction mixture and the Fischer-Tropsch synthetic oil are subjected to the second catalytic cracking reaction, wherein the weight ratio of the Fischer-Tropsch synthetic oil to the amount of conventional petroleum is 40-85:15-60, and the conventional petroleum is selected from straight-run At least one of vacuum distillate, straight run bitumen, and heavy distillates produced by coking, thermal cracking, and visbreaking processes. According to the method for producing low-carbon olefins provided by the present invention, the conversion of Fischer-Tropsch synthetic oil and conventional petroleum can be promoted, the selectivity of low-carbon olefins can be improved, and the heat balance of the self-reaction-regeneration system can be satisfied at the same time.

Description

A method for producing low-carbon olefins

technical field

The present invention relates to a method for converting hydrocarbon oil feedstocks in the absence of hydrogen, in particular to a method for producing light olefins.

Background technique

With the decreasing reserves of conventional petroleum resources and the rapid increase in consumption, the technology of producing synthetic oil by Fischer-Tropsch synthesis has attracted much attention. Fischer-Tropsch synthetic oil is quite different from natural petroleum in composition, and is a hydrocarbon mainly composed of alkanes and olefins.

At present, the processing and utilization of Fischer-Tropsch synthetic oil obtained by cryogenic method is mainly divided into the following aspects: naphtha fraction is usually used as raw material for steam cracking unit to produce ethylene after hydrotreating. The diesel fraction has a high cetane number and is generally used as a diesel blending component. For heavy oil and wax fractions, the hydrocracking process is generally used to cut long-chain hydrocarbons, or isomerize them into short-chain normal or isoparaffins with good low-temperature performance, to obtain high-quality jet fuel and diesel blending components, or use Hydroisomerization dewaxing technology synthesizes lubricating base oils with better properties. How to optimize the final product structure of Fischer-Tropsch synthetic oil, produce products that meet market demand, and improve economic benefits is the basis for improving the sustainable development of the technology of converting unconventional oil such as biomass, natural gas or coal into liquid fuels. In recent years, there have also been studies on converting Fischer-Tropsch synthetic oil into clean transportation fuels and high-value low-carbon olefins by using thermal cracking or catalytic cracking technology.

EP0584879A1 discloses a method for preparing light olefins from synthetic oil. In this method, the synthetic oil is used as part of the feed for thermal cracking after undergoing hydrogenation and/or hydroconversion and/or hydrocracking. The main purpose of the hydrogenation process is to increase the saturation of synthetic oil and remove oxygen. The treated synthetic oil is subjected to thermal cracking reaction under the conditions of a temperature of 700-900° C. and a residence time of 0.04-0.5 seconds. After the C5-C9 fraction in the Fischer-Tropsch synthetic oil is hydrotreated, it can be subjected to thermal cracking reaction to obtain 47% by weight of ethylene and 15% by weight of propylene.

CN101102983A discloses a method for producing light olefins from heavy synthetic oil fractions prepared by the Fischer-Tropsch process. In this method, the heavy synthetic oil fraction with a boiling point higher than 550°C is subjected to mild thermal cracking after dehydration or hydrogenation pretreatment to remove oxygenates and/or olefins, and then the mild thermal cracking products are subjected to short residence time High temperature thermal cracking. The mild thermal cracking process includes melting furnace cracking or soaking furnace cracking, wherein melting furnace cracking is carried out at a temperature of 500-700° C. and a residence time of up to 6 minutes; soaking furnace cracking is carried out at a temperature of 400-500° C. and a residence time of 10-60 minutes to carry out. The mildly thermally cracked product is then subjected to high temperature (700-1000°C) thermal cracking with a short residence time either directly or after hydrogenation saturation. The method can obtain higher ethylene or propylene yield, less by-products such as methane and/or higher hydrocarbons, especially aromatic hydrocarbons, and low coke formation.

CN102533322A discloses a method for producing propylene by catalytic cracking of Fischer-Tropsch synthetic oil. After the method is heated and gasified, the stream rich in small molecular olefins is used as all or part of the atomization medium of Fischer-Tropsch synthetic oil raw material and Fischer-Tropsch synthetic oil. The raw materials are mixed and injected into the reactor. This method can not only process heavy Fischer-Tropsch synthetic oil fractions, but also light Fischer-Tropsch synthetic oil fractions. Under the same reaction conditions, this method can increase the yield of propylene by 6.74 percentage point.

Contents of the invention

The purpose of the present invention is to provide a kind of Fischer-Tropsch synthetic oil and the method for blending catalytic cracking of conventional petroleum to produce light olefins, can not only produce more light olefins like this, can satisfy the heat balance of catalytic cracking reaction-regeneration system simultaneously.

The inventors of the present invention have found through research that the yield of low-carbon olefins (ethylene+propylene+butene) in the product is relatively high when the Fischer-Tropsch synthetic oil is processed by the catalytic cracking method. At the same time, due to the raw material composition characteristics of Fischer-Tropsch synthetic oil, its catalytic coke formation is very low, which cannot meet the heat balance in the catalytic cracking process. It is found in the experimental research that the blending of Fischer-Tropsch synthetic oil and conventional petroleum with a certain composition and certain catalytic cracking technology can not only produce more low-carbon olefins, but also satisfy its own heat balance, thus completing the present invention.

For this reason, the present invention provides a kind of method of producing light olefins, and this method comprises: carry out first catalytic cracking reaction with conventional oil and catalytic cracking catalyst, then with the reaction mixture obtained by described first catalytic cracking reaction and Fischer-Tropsch synthesis The oil is subjected to the second catalytic cracking reaction, wherein the weight ratio of the Fischer-Tropsch synthetic oil to the amount of conventional petroleum is 40-85:15-60, and the conventional petroleum is selected from straight-run vacuum distillate, straight-run bitumen , and at least one of the heavy fractions produced by coking, thermal cracking and visbreaking processes.

According to the method for producing low-carbon olefins provided by the present invention, the conversion of Fischer-Tropsch synthetic oil and conventional petroleum can be promoted, the selectivity of low-carbon olefins can be improved, and the heat balance of the self-reaction-regeneration system can be satisfied at the same time.

Other features and advantages of the present invention will be described in detail in the detailed description that follows.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the description, together with the following specific embodiments, are used to explain the present invention, but do not constitute a limitation to the present invention. In the attached picture:

Figure 1 is a schematic flow diagram of the method for producing light olefins provided by the present invention.

Explanation of reference signs

1: Pre-lift medium delivery pipeline

2: Conventional oil pipeline

3: Riser reactor

4: Fluidized bed reactor

5: Fischer-Tropsch synthetic oil pipeline

6: Settler

7: Reaction oil and gas pipeline

8: Stripper

9: Stripping steam pipeline

10: Inclined tube to be born

11: Oxygen-containing gas pipeline

12: Regenerator

13: Regenerative flue gas transmission pipeline

14: Regenerated inclined pipe

Detailed ways

Specific embodiments of the present invention will be described in detail below. It should be understood that the specific embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

All ranges disclosed herein are inclusive of endpoints and are independently combinable. Neither the endpoints of the ranges nor any values disclosed herein are limited to that precise range or value, and these ranges or values are understood to include values approaching these ranges or values.

The method for producing low-carbon olefins provided by the present invention comprises: performing a first catalytic cracking reaction on conventional petroleum and a catalytic cracking catalyst, and then performing a second catalytic cracking reaction on the reaction mixture obtained by the first catalytic cracking reaction and Fischer-Tropsch synthetic oil reaction, wherein the weight ratio of the Fischer-Tropsch synthetic oil to the conventional petroleum is 40-85:15-60.

Preferably, the weight ratio of the Fischer-Tropsch synthetic oil to the conventional petroleum is 50-75:25-50.

In the present invention, the catalytic cracking catalyst is reacted with conventional petroleum and then reacted with Fischer-Tropsch synthetic oil. Preferably, the first catalytic cracking reaction is such that the carbon content of the catalytic cracking catalyst is between 0.3% and 1.0% by weight. The carbon content on the catalytic cracking catalyst is measured by an infrared absorption method, and the specific operation is as follows: put the catalyst sample in contact with the Fischer-Tropsch synthetic oil together with a flux into a high-frequency induction furnace, and burn it in the presence of oxygen to form The CO ₂ and SO ₂ gases flow through the infrared absorption cell to determine the carbon content in the catalyst.

In the present invention, the conditions of the first catalytic cracking reaction and the second catalytic cracking reaction may each include: a temperature of 480-700° C., a time of 0.5-20 seconds, and an agent-to-oil weight ratio of 6-40. Preferably, the conditions of the first catalytic cracking reaction and the second catalytic cracking reaction each include: a temperature of 520-600° C., a time of 1-10 seconds, and an agent-to-oil weight ratio of 10-30. Further preferably, the reaction temperature of the first catalytic cracking reaction is 10-60°C higher than the reaction temperature of the second catalytic cracking reaction, preferably 20-40°C.

In the present invention, the first catalytic cracking reaction and the second catalytic cracking reaction can be carried out in the same reactor, or in two different reactors. Preferably, the first catalytic cracking reaction and the second catalytic cracking reaction are respectively implemented in different reactors. Specifically, the first catalytic cracking reaction is carried out in a first reactor, and the first reactor can be a riser reactor or a downcomer reactor; the second catalytic cracking reaction is carried out in a second reactor , the second reactor may be a fluidized bed reactor or a downcomer reactor. Most preferably, the first catalytic cracking reaction is carried out in a riser reactor, and the second catalytic cracking reaction is carried out in a fluidized bed reactor.

In the present invention, the Fischer-Tropsch synthetic oil may be at least one of the whole fraction or partial fraction of the low-temperature Fischer-Tropsch synthesis product with a boiling point ranging from 23° C. to the final boiling point.

In the present invention, the conventional petroleum may be selected from at least one of straight-run vacuum distillate, straight-run bitumen, and heavy distillate produced by coking, thermal cracking and visbreaking processes.

In the present invention, the catalytic cracking catalyst may be a conventional catalytic cracking catalyst in the art. Preferably, the catalytic cracking catalyst contains 1-60% by weight of zeolite, 5-99% by weight of refractory inorganic oxide and 0-70% by weight of clay. The zeolite may be selected from at least one of ZSM-5 series zeolites, ZSP series zeolites, silica zeolites with a five-membered ring structure, beta zeolites and Y-type zeolites. The inorganic oxide as a binder is preferably selected from silicon dioxide (SiO ₂ ) and/or aluminum oxide (Al ₂ O ₃ ). The clay as a matrix (ie carrier) is preferably selected from kaolin and/or halloysite.

In the present invention, in order to realize the recycling of the catalytic cracking catalyst, the method preferably further includes: performing gas-solid separation on the reaction oil gas and carbon deposit catalyst obtained after the second catalytic cracking reaction, and the separated carbon deposit The catalyst is stripped and regenerated and returned to the first catalytic cracking reactor for recycling. The gas-solid separation process is carried out in a settler, and the pressure of the settler can be 1.5×10 ⁵ Pa to 4×10 ⁵ Pa. Specifically, the gas-solid separation process is generally: firstly separate the coke-deposited catalyst from the reaction oil and gas to obtain the coke-deposited catalyst and reaction oil and gas, and then further separate the obtained reaction oil and gas into gas, gasoline and diesel oil through a subsequent separation system Equal fractions, gas components were analyzed by gas chromatography, and the yields of ethylene, propylene and butene were obtained by calculation. The operation of stripping the separated carbon deposit and regenerating the catalyst is well known to those skilled in the art and will not be repeated here. In the present invention, due to the blending of conventional petroleum and Fischer-Tropsch synthetic oil, the coking performance of hydrocarbon oil is improved, so that the method can meet the heat balance of the self-reaction-regeneration system.

The method provided by the present invention will be described in detail below in conjunction with the accompanying drawings, but the present invention is not limited thereto.

As shown in FIG. 1 , the hot regenerated catalyst enters the bottom of the riser reaction 3 through the regenerant delivery line 14 , and is accelerated to flow upward under the action of the pre-lift medium injected from the line 1 . The heated conventional petroleum is mixed with the atomizing medium through the delivery pipeline 2 at a weight ratio of (0.05-0.1):1, and then injected into the bottom of the riser reactor 3, where the conventional petroleum contacts the regenerated catalyst and undergoes catalytic cracking reaction. After the heated Fischer-Tropsch synthetic oil is mixed with the atomizing medium in the atomization nozzle at a weight ratio of (0.05-0.1):1 through the delivery pipeline 5, it is injected into the bottom of the fluidized bed reactor 4, and the Fischer-Tropsch synthetic oil and carbon content Between 0.3% and 1.0% by weight of catalyst contact and cracking reactions occur. The catalyst that reacts oil gas and carbon deposits is separated in the settler 6 from the catalyst that reacts oil gas and carbon deposits. The reaction oil gas is sent to the subsequent separation system through pipeline 7. The coke-deposited catalyst after the reaction separated in the settler 6 enters the stripper 8 through the fluidized bed reactor 4 under the action of gravity, and the stripping steam is injected through the pipeline 9, and the reaction oil gas carried by the coke-deposited catalyst is removed as much as possible. Stripped clean. The hydrocarbon products adsorbed on the carbon-deposited catalyst stripped by the stripping steam enter the settler 6 through the fluidized bed reactor 4 . The spent catalyst is sent to the regenerator 12 through the inclined tube 10 of the spent catalyst. Oxygen-containing gas such as air or oxygen is injected into the regenerator 12 from the bottom through the pipeline 11 to carry out coke regeneration. The regeneration flue gas is drawn out through the pipeline 13. The regenerated catalyst is returned to the riser reactor 3 for recycling through the regenerated catalyst delivery pipeline 14 .

The method provided by the present invention is further illustrated below by way of examples, but the present invention is not thereby limited in any way.

The catalytic cracking catalyst used in the Examples and Comparative Examples was industrially produced by China Petroleum & Chemical Corporation Catalyst Qilu Branch, and the trade name was MMC-2. The catalyst contains ultra-stable Y-type zeolite and ZSP zeolite with an average pore size of less than 0.7 nanometers. Before use, it was subjected to hydrothermal aging with saturated steam for 14 hours at a temperature of 800°C. The main physical and chemical properties of the catalyst are shown in Table 1.

The Fischer-Tropsch synthetic oil raw material used in the examples and comparative examples is distillate oil with a distillation range of 268-700° C., and the conventional petroleum used is Daqing vacuum residue. The basic properties of the two distillates are shown in Table 2.

Table 1

Table 2

Example 1-3

This example is used to illustrate the method for producing light olefins provided by the present invention.

A medium-sized device with continuous reaction-regeneration operation was used for experiments. The first reactor was a riser reactor, and the inner diameter of the riser reactor was 16 mm, and the height was 6 meters; the second reactor was a fluidized bed reactor with a fluidized bed. The bed reactor has an internal diameter of 60 mm and a height of 0.3 m. Wherein, in Example 1, the riser reactor was injected with 25% by weight of Daqing vacuum residue, and the fluidized bed reactor was injected with 75% by weight of Fischer-Tropsch synthetic oil. In Example 2, 40% by weight of Daqing vacuum residue was injected into the riser reactor, and 60% by weight of Fischer-Tropsch synthetic oil was injected into the fluidized bed reactor. In Example 3, 50% by weight of Daqing vacuum residue was injected into the riser reactor, and 50% by weight of Fischer-Tropsch synthetic oil was injected into the fluidized bed reactor.

The MMC-2 regenerated catalyst with a temperature of about 700°C is introduced into the bottom of the riser reactor through the regenerated inclined tube, and flows upward under the action of pre-lift steam. Daqing vacuum residue is mixed with atomized water and then sprayed into the riser reactor, then enters the riser and fluidized bed in turn, and contacts with the hot catalyst for catalytic cracking reaction. Fischer-Tropsch synthetic oil is mixed with atomized water and then sprayed Into the fluidized bed reactor, contact with the catalyst for catalytic cracking reaction. The reacted oil gas and unborn catalyst enter the settler from the outlet of the fluidized bed, and the reacted oil gas and the catalyst are quickly separated in the settler. The reaction oil and gas are further separated into gaseous products and liquid products. The raw catalyst separated from the settler enters the stripper by gravity, and the stripped raw catalyst enters the regenerator through the raw inclined pipe, where it contacts with heated air and is heated at 700 regeneration at a temperature of °C. The regenerated catalyst recovered from charred regeneration is returned to the riser reactor for recycling. The main operating conditions and results are listed in Table 3.

Comparative example 1

This comparative example is used to illustrate: under the same reaction conditions as in Example 1, only the Fischer-Tropsch synthetic oil and the Daqing vacuum residue are mixed and injected into the riser reactor for catalytic cracking to produce light olefins.

The reaction apparatus that adopts is with embodiment 1. The used Fischer-Tropsch synthetic oil and Daqing vacuum residue, the main experimental steps are the same as in Example 1, the difference is that the Fischer-Tropsch synthetic oil is not injected into the fluidized bed reactor, and the Fischer-Tropsch synthetic oil and Daqing vacuum residue are Injected into the riser reactor. The main operating conditions and results are listed in Table 3.

Comparative example 2

This comparative example is used to illustrate: under the same reaction conditions as in Example 1, only Fischer-Tropsch synthetic oil is injected into the reactor for catalytic cracking to produce light olefins.

The reaction apparatus that adopts is with embodiment 1. The Fischer-Tropsch synthetic oil used and the main experimental procedures are the same as in Example 1, except that the Daqing vacuum residue is not injected into the riser reactor, but the Fischer-Tropsch synthetic oil is injected into the riser reactor. The main operating conditions and results are listed in Table 3.

Comparative example 3

This comparative example is used to illustrate: under the same reaction conditions as in Example 1, only Daqing vacuum residue is injected into the reactor for catalytic cracking to produce light olefins.

The reaction apparatus that adopts is with embodiment 1. The Daqing vacuum residue used and the main experimental procedures are the same as in Example 1, except that the Fischer-Tropsch synthetic oil is not injected into the fluidized bed reactor, but the Daqing vacuum residue is injected into the fluidized bed reactor. The main operating conditions and results are listed in Table 3.

Comparative example 4

This comparative example is used to illustrate: under the same reaction conditions as in Example 1, only 70% by weight of the Daqing vacuum residue that accounts for the hydrocarbon oil feedstock is injected into the riser reactor, and 30% by weight of the Fischer-Tropsch residue that accounts for the hydrocarbon oil feedstock is injected into the riser reactor. The effect of producing light olefins when synthetic oil is injected into the reaction system.

The reaction apparatus that adopts is with embodiment 1. The used Fischer-Tropsch synthetic oil, Daqing vacuum residue and main experimental steps are the same as in Example 1, except that the Daqing vacuum residue injected into the riser reaction accounts for 70% by weight of the hydrocarbon oil raw material, and injected into the fluidized bed for reaction The Fischer-Tropsch synthetic oil of the reactor accounts for 30% by weight of the hydrocarbon oil feedstock. The main operating conditions and results are listed in Table 3.

table 3

As can be seen from the data in Table 3, using the method for producing light olefins provided by the present invention, by blending Fischer-Tropsch synthetic oil with conventional oil, the coke yield and the total yield of ethylene+propylene+butene are all higher, so that not only It can promote the generation of low-carbon olefins, and at the same time, it can also meet the heat balance of the self-reaction-regeneration system.

Claims (10)

1. a kind of method for producing low-carbon alkene, this method include：Conventional oil is carried out first with catalytic cracking catalyst to urge Change cracking reaction, reaction mixture obtained by first catalytic cracking reaction then is carried out the second catalysis with Fischer-Tropsch synthesis oil splits Change reaction, wherein, the weight ratio of the Fischer-Tropsch synthesis oil and the dosage of the conventional oil is 40-85：15-60, the routine Oil is in the heavy end that straight run reduced pressure distillate, straight asphalt and coking, thermal cracking and vis-breaking process produce It is at least one.

2. according to the method described in claim 1, wherein, the Fischer-Tropsch synthesis oil and the weight ratio of the dosage of the conventional oil For 50-75：25-50.

3. method according to claim 1 or 2, wherein, first catalytic cracking reaction causes the catalytic cracking to urge The carbon content of agent is in 0.3 weight % between 1.0 weight %.

4. method according to claim 1 or 2, wherein, first catalytic cracking reaction and second catalytic cracking The condition of reaction each includes：Temperature is 480-700 DEG C, and the time is 0.5-20 seconds, and agent weight of oil ratio is 6-40.

5. according to the method described in claim 4, wherein, first catalytic cracking reaction and second catalytic cracking reaction Condition each include：Temperature is 520-600 DEG C, and the time is 1-10 seconds, and agent weight of oil ratio is 10-30.

6. according to the method described in claim 4, wherein, the reaction temperature of first catalytic cracking reaction is urged than described second The reaction temperature for changing cracking reaction is 10-60 DEG C high.

7. method according to claim 1 or 2, wherein, first catalytic cracking reaction carries out in the first reactor, The first reactor is riser reactor or downer reactor；Second catalytic cracking reaction is in the second reactor It carries out, the second reactor is fluidized-bed reactor or downer reactor.

8. according to the method described in claim 7, wherein, first catalytic cracking reaction carries out in riser reactor, Second catalytic cracking reaction carries out in a fluidized bed reactor.

9. method according to claim 1 or 2, wherein, the Fischer-Tropsch synthesis oil is to be boiled in low temperature process Fischer-Tropsch synthetic Point range is 23 DEG C at least one of the full fraction of the end point of distillation or part fraction.

10. according to the method described in claim 1, wherein, the catalytic cracking catalyst contains the zeolite of 1-60 weight %, 5- The heat-resistant inorganic oxide of 99 weight % and the clay of 0-70 weight %, wherein, the zeolite is selected from ZSM-5 series zeolites, ZSP At least one of series zeolite, silica-rich zeolite, β zeolites and the y-type zeolite with five-membered ring structure.