CN116410786A

CN116410786A - Method for improving viscosity reduction cracking efficiency and product distribution of heavy oil

Info

Publication number: CN116410786A
Application number: CN202111681199.5A
Authority: CN
Inventors: 王丽涛; 袁佩青; 王路海; 刘银东; 凌浩; 韩爽; 许倩; 杨行; 宋海朋; 于志敏
Original assignee: East China University of Science and Technology; Petrochina Co Ltd
Current assignee: East China University of Science and Technology; Petrochina Co Ltd
Priority date: 2021-12-31
Filing date: 2021-12-31
Publication date: 2023-07-11

Abstract

The invention relates to a method for improving the viscosity reduction cracking efficiency and product distribution of heavy oil. The method comprises the following steps: the heavy oil is used as raw oil, after preheating, visbreaking reaction is carried out for 5-40min at 360-460 ℃, and when the reaction is carried out to 1/4-1/2, a hydrogen donor is added into the reaction system. The introduction mode of the hydrogen donor maintains reasonable viscosity reducing cracking efficiency and inhibits undesired condensation. The product distribution is improved, the stability is improved, and the subsequent catalytic hydrogenation or transportation performance can be obviously improved while the viscosity of the obtained product is greatly reduced.

Description

Method for improving viscosity reduction cracking efficiency and product distribution of heavy oil

Technical Field

The invention relates to the technical field of heavy oil processing, in particular to a viscosity reduction cracking treatment of heavy oil, and specifically relates to a method for improving the distribution of a viscosity reduction cracking product of the heavy oil.

Background

Heavy oils (including extra heavy crude oil, oil sand bitumen, vacuum residuum, atmospheric residuum, and catalytically cracked slurry oils, etc.) have similar average molecular structural characteristics: 1) A condensed ring center formed by an aromatic ring, a cycloalkane ring and an aromatic heterocyclic ring; 2) Alkyl side chains exist between condensed ring centers or are linked by a bridge. The average structural characteristics of the heavy oil lead to large average scale and extremely high viscosity of heavy oil molecules, which brings great trouble to the catalytic processing and transportation of the heavy oil.

Visbreaking is one of the thermal processing forms of heavy oils based on free radical reaction mechanisms. Because there is no catalyst intervening, visbreaking has no particular requirement on the nature of heavy oils. At present, the main application of the visbreaking is as follows: 1) As pretreatment for heavy oil catalytic processing, the average molecular scale of the feed is reduced; 2) The viscosity of the heavy oil is reduced, so that the pipeline or shipping transportation of the heavy oil is possible; 3) And obtaining a part of gasoline and diesel oil light fraction products through reaction.

Visbreaking consists of reactions of various hydrocarbon radical groups including C-C cleavage, β -cleavage, hydrogen transfer, cyclization, dehydrogenation, and coupling. These hydrocarbon radical reactions can be categorized into two broad categories, dealkylation and condensation. Desirable visbreaking is to avoid condensation reactions, consisting of dealkylation reactions only. The fraction belonging to the vacuum residue (boiling point >500 ℃) is decomposed by dealkylation to produce vacuum gas oil (boiling point 350-500 ℃), atmospheric gas oil (boiling point 200-350 ℃), and even gasoline fraction (boiling point IBP-200 ℃). However, condensation is always present during the visbreaking process. Macromolecules and even asphaltenes formed by condensation are easy to coke and block catalyst pore channels and cover active centers in the catalytic processing process. In addition, asphaltene formation also leads to an increase in the viscosity of the upgraded heavy oil. Among these, the formation of aromatic carbon radicals is a key step in the condensation of heavy oil components. The formation of the aromatic carbon free radical under the medium-low temperature condition is formed by hydrogen abstraction of the aromatic ring by the methyl free radical, and the aromatic carbon free radical under the high temperature condition can be completed by direct dehydroaromatization. Through addition, cyclization, dehydrogenation and other reactions of aromatic carbon free radicals and olefins, the condensed ring center of the heavy oil component is extended in two-dimensional directions, and the extended condensed ring plane can form coke through interlayer superposition and further dehydrogenation. It is widely accepted in the academia that saturated aromatic carbon radicals are capable of inhibiting condensation from a source.

Therefore, hydrogen donors having active hydrogen such as tetrahydronaphthalene and decalin and the like are introduced into heavy oil thermal processing to suppress condensation and improve product distribution. These hydrogen donors are either present in the reaction system in large amounts in the form of solvents or added in small amounts in the form of auxiliaries. By providing active hydrogen saturated aromatic carbon radicals, condensation is partially inhibited during thermal cracking of heavy oils. For deep cracking (e.g., delayed coking) reactions characterized by condensation, the presence of a large amount of hydrogen donor can partially inhibit coke formation and increase the yield of light products. However, it should be noted that the presence of the hydrogen donor in the cracking system is not only capable of saturating the aromatic carbon radicals, but also the alkyl carbon radicals that initiate the thermal cracking reaction network. The alkyl carbon radicals are saturated so that the initiation time of thermal cracking is greatly prolonged. In addition, the activity of the formed naphthenic carbon radicals after the hydrogen donor gives active hydrogen is relatively low, which reduces the propagation efficiency of the chain radical reaction. Accordingly, the addition of hydrogen donors generally results in delays in initiation and chain propagation efficiency of the heavy oil thermal cracking network.

CN106883873a discloses a method for modifying and viscosity-reducing inferior heavy oil, which comprises the following steps: step one: distilling inferior heavy oil under reduced pressure to obtain straight-run distillate oil and vacuum residue oil, wherein the straight-run distillate oil comprises hydrogen donor fraction; step two: the vacuum residuum and the whole or part of the hydrogen donor fraction are mixed and then enter a hydrogen donor thermal cracking device for reaction to generate gas, distillate oil and residuum; step three: after heat exchange, the residual oil generated by the hydrogen-supplied thermal cracking reaction is pumped into a solvent deasphalting device to obtain deasphalted oil and deasphalted asphalt; and step four: mixing the rest straight-run distillate, deasphalted oil and distillate obtained by hydrogen-supplying thermal cracking reaction to produce modified oil with API more than 19. The invention can produce modified crude oil with API larger than 19 in maximum, meet the requirements of storage and pipeline transportation, has low investment and ensures the stability of the modified oil.

CN105733671a discloses a method and system for producing modified oil from inferior heavy oil, the system comprises an atmospheric and vacuum distillation unit, a solvent deasphalting unit and a hydrogen-supplying thermal cracking unit. The atmospheric and vacuum distillation unit has a bottom outlet, a distillate outlet, and a hydrogen donor fraction outlet. The solvent deasphalting unit is connected to the bottom outlet through a first connecting pipe and has a deasphalted asphalt outlet and a deasphalted oil outlet. The hydrogen-supplying thermal cracking device is connected with the deoiling asphalt outlet through a second connecting pipeline and is provided with a distillate oil outlet. The second connecting pipeline is provided with a hydrogen supply agent inlet which is connected with a hydrogen supply agent fraction outlet. The external hydrogen donor and the viscosity reducing raw material are mixed from the hydrogen supply fraction and then are together participated in the viscosity reducing cracking reaction.

CN105567319a discloses a method for treating heavy oil, which comprises the steps of: (1) Carrying out solvent deasphalting operation on the heavy oil to obtain deasphalted oil and deasphalted asphalt; (2) Hydrotreating the deoiled asphalt obtained in the step (1), coal and a hydrogen donor in the presence of a hydrogenation catalyst to obtain a hydrotreated product; (3) Fractionating the hydrogenated product obtained in the step (2) to obtain a fractionated product, wherein the fractionation conditions are such that the fractionated product at least comprises a gasoline fraction, a diesel fraction and a fraction having a boiling range of 350-500 ℃ which are separated from each other; (4) And (3) carrying out partial hydrogenation treatment on the fraction with the boiling range of 350-500 ℃ in the fractionation product obtained in the step (3) to obtain a product after partial hydrogenation, and returning the product after partial hydrogenation as a hydrogen donor to the step (2) for use. Through the combined processing technology for the heavy oil, the invention can effectively convert asphaltene in the heavy oil into light oil with higher value. In the patent of the invention, the hydrogen donor and the raw material synchronously participate in the hydrotreating process.

CN102504862B discloses a hydrogen donating thermal cracking process; adding a hydrogen donor into a conventional visbreaking raw material as a mixed feed, carrying out hydrogen-donor thermal cracking reaction, and blending the hydrogen-donor thermal cracking generated oil with gasoline and diesel oil fractions obtained in atmospheric and vacuum distillation to obtain hydrogen-donor thermal cracking modified oil; the temperature of the hydrogen-supplying thermal cracking reaction is 380-510 ℃, the reaction residence time is 0.1-180 min, and the reaction pressure is 0.1-4.0 MPa; the hydrogen donor is straight run wax oil or straight run wax oil narrow fraction; the distillation range is between 350 and 500 ℃; the hydrogen distribution is: h _A Accounting for 18.0 to 50.0 percent of the total hydrogen in the hydrogen donor, H _α 18.0 to 50.0 percent of the total hydrogen in the hydrogen donor; the addition amount of the hydrogen donor is 0.1-50% of the weight of the visbreaking raw material. In the disclosed invention, the hydrogen donor is premixed with conventional visbreaking material and then subjected to a hydrogen donor thermal cracking reaction.

CN102358846a discloses a combined process of hydrogen-supplying viscosity-reducing coking of heavy oil; mixing the narrow fraction of the coking distillate oil into raw oil, preheating to 350-380 ℃, entering into an viscosity-reducing reactor for thermal cracking reaction, and separating oil gas from the top of the viscosity-reducing reactor into a viscosity-reducing fractionating tower to obtain gas, light distillate oil and viscosity-reducing residual oil; preheating the visbreaking residual oil to coking temperature, entering a coke tower for coking reaction, separating oil gas discharged from the coke tower into coking gas, gasoline and narrow fraction of coking distillate oil by entering a coking fractionating tower, and mixing circulating oil and coking raw oil at the bottom of the fractionating tower to coking; the narrow fraction of the coking distillate oil is used as a hydrogen donor to be partially mixed into raw oil for hydrogen supply and viscosity reduction cracking reaction. In the disclosed invention, the self-hydrogen-supplying fraction which is the most hydrogen-supplying agent is mixed with raw oil to carry out hydrogen-supplying viscosity-reducing cracking reaction.

CN110885702a discloses a method for combining a coal hydrogenation liquefaction reaction process and a heavy oil hydrogenation thermal cracking reaction process, wherein a gas phase AR-APV of AR-a product AR-AP in a front reaction section AR of the coal hydrogenation liquefaction reaction process contains a large amount of light hydrogen-supplying solvent and hydrogen, and the light hydrogen-supplying solvent or its hydrogenation stabilized oil based on the gas phase AR-APV is introduced into the heavy oil hydrogenation thermal cracking reaction process for secondary use, or the hydrogen can be secondarily utilized; in the combined process, the hydrogen donor is introduced and mixed with the heavy oil to participate in the heavy oil hydrogenation thermal cracking process.

CN110028986a discloses a method for preparing fuel oil from biomass pyrolysis liquid. The biomass pyrolysis liquid which is not pretreated is added into a reaction area of the ebullated bed reactor for hydrotreatment under the protection of a hydrogen donor. The biomass pyrolysis liquid is hydrogenated and converted into fuel oil in a boiling bed reactor of a catalyst full mixed flow circulation system formed by the combined action of circulating oil, catalyst, hydrogen and internal components, wherein one part of fuel oil is used as circulating oil to return to the boiling bed reactor, and the other part of fuel oil is discharged as a product. Wherein the biomass pyrolysis liquid is mixed with a hydrogen supply agent before entering the ebullated bed reactor, and enters the reactor under the protection of the hydrogen supply agent.

In these prior arts, a hydrogen donor is previously mixed into the reaction mass. This manner of introducing the hydrogen donor has an adverse effect on the visbreaking with the aim of reducing the viscosity and producing small amounts of light components. The visbreaking realizes visbreaking through dealkylation, and the saturation of the hydrogen donor to the alkyl side chain carbon radical leads to low visbreaking efficiency, and the time required for reaching the specified visbreaking rate is greatly prolonged.

For the hydrogen donor, the process is economically viable only when it is added in small amounts in the form of an auxiliary. The hydrogen donor is also subjected to cracking dehydrogenation at high temperature. When the visbreaking reaches a certain depth to start forming aromatic carbon free radicals, the effective concentration of the hydrogen donor in the system is greatly reduced. At this time, the ability of the hydrogen donor to saturate aromatic carbon radicals is greatly reduced, and condensation cannot be effectively inhibited. Therefore, the existing hydrogen-supplying thermal cracking system in which the hydrogen-supplying agent and the raw material synchronously react mainly has two problems: 1) The hydrogen donor is consumed in advance, resulting in insufficient amount of hydrogen radicals supplied to the aromatic carbon radical saturation reaction, resulting in insufficient inhibition of condensation; 2) In the earlier stage of free radical initiation, the occurrence of hydrogen donor free radicals causes the saturation of free radical chains generated initially by cracking, inhibits the propagation of the free radical chains, and is unfavorable for improving the viscosity reducing efficiency. Thus, this is contrary to the original purpose of adding a hydrogen donor in the visbreaking process, which "ensures visbreaking efficiency and sufficiently inhibits condensation".

Disclosure of Invention

Based on the above, it is an object of the present invention to overcome the above-mentioned drawbacks of the prior art and to provide a method for improving the efficiency of visbreaking of heavy oil and the distribution of products, while suppressing condensation while ensuring the efficiency of visbreaking of heavy oil.

To this end, the present invention provides a method for improving the efficiency and product distribution of heavy oil visbreaking comprising the steps of: the heavy oil is used as raw oil, after preheating, visbreaking reaction is carried out for 5-40min at 360-460 ℃, and when the reaction is carried out to 1/4-1/2, a hydrogen donor is added into the reaction system.

Specifically, the visbreaking is operated under the condition of maximum conversion depth without damaging the colloidal stability of visbreaking residual oil, and the main operation control conditions are reaction temperature, reaction pressure and residence time according to a free radical reaction mechanism. The reaction pressure is controlled between 0.6 and 0.8MPa, the conversion depth is realized by controlling the reaction temperature and time, and the purpose of reducing viscosity can be achieved at low temperature for a long time and at high temperature for a short time. Therefore, at a certain temperature, the time of the viscosity reduction cracking plays an absolute role in the viscosity reduction effect. In the method provided by the invention, in the process of reducing the viscosity and cracking of the heavy oil by a free radical mechanism, the viscosity and cracking is firstly carried out by utilizing the breakage of alkyl side chains of heavy oil molecules and the propagation of hydrocarbon free radical chains. After the viscosity reduction reaches a certain depth, a hydrogen donor is introduced for saturation of aromatic carbon free radicals with key effects on condensation. Based on the introduction mode of the hydrogen donor, the efficient progress of the viscosity reduction is ensured, the occurrence of condensation is effectively inhibited, and the product distribution and the property of the heavy oil viscosity reduction cracking product can be improved.

The method for improving the viscosity breaking efficiency and the product distribution of heavy oil according to the present invention is preferably to add a hydrogen donor to the reaction system when the reaction is carried out for 2 to 30 minutes, more preferably 3 to 20 minutes.

The method for improving the viscosity breaking efficiency and the product distribution of heavy oil according to the present invention, wherein the addition amount of the hydrogen donor is preferably 0.5 to 10wt%, more preferably 0.5 to 2wt% of the heavy oil treatment amount.

The method for improving the viscosity reduction cracking efficiency and the product distribution of heavy oil according to the invention, wherein the temperature of the viscosity reduction cracking reaction is preferably 380-420 ℃.

The method for improving the viscosity reducing cracking efficiency and the product distribution of heavy oil according to the present invention, wherein it is preferable that the viscosity reducing cracking reaction is performed in a batch manner or a continuous manner.

The method for improving the viscosity reduction cracking efficiency and the product distribution of the heavy oil, which is disclosed by the invention, is preferable, wherein the heavy oil is one or a mixture of more than one of extra heavy crude oil, oil sand asphalt, atmospheric residuum, vacuum residuum or catalytic cracking slurry oil.

The method for improving the viscosity breaking efficiency and the product distribution of heavy oil according to the invention, wherein the hydrogen donor is preferably a partially saturated bi-or polycyclic aromatic compound, or a fraction oil rich in the partially saturated bi-or polycyclic aromatic compound.

The method for improving the viscosity reduction cracking efficiency and the product distribution of heavy oil, wherein the partially saturated bicyclo or polycyclic aromatic compound is preferably at least one selected from tetrahydronaphthalene, decalin, dihydroanthracene and cycloalkyl aromatic compounds; the distillate oil is at least one selected from diesel oil, light wax oil, heavy wax oil, ethylene tar, catalytic slurry oil, hydrotreated ethylene tar and hydrotreated catalytic slurry oil.

The method for improving the viscosity reduction cracking efficiency and the product distribution of heavy oil according to the invention is characterized in that a charging port is arranged at the middle lower part of a tower reactor when the viscosity reduction cracking reaction is carried out in the tower reactor.

The method for improving the viscosity breaking efficiency and the product distribution of heavy oil according to the present invention, wherein preferably, the feed inlet extends into the middle part of the tower reactor, and the end of the feed inlet is provided with a liquid product distributor with an upward opening, so that the hydrogen donor and the reactant stream are fully mixed.

The hydrogen donor is added in the middle of the visbreaking reaction, and has the following advantages:

(1) The existence of the hydrogen donor not only saturates aromatic carbon free radicals which have key influence on condensation, but also saturates alkyl carbon free radicals in the reaction system. Saturation of alkyl carbon radicals reduces initiation and chain propagation efficiency of the visbreaking network. Therefore, the hydrogen donor is added in the middle stage of heavy oil visbreaking, and does not interfere the initiation and chain propagation of a thermal cracking reaction network, so that the visbreaking efficiency in the early stage and the middle stage of the reaction is ensured.

(2) Under certain reaction pressure and temperature, the reaction effect is influenced by the reaction time, and the viscosity reducing effect is improved and then reduced along with the time extension, so that obvious condensation reaction is shown by the deterioration. The hydrogen donor is added in the middle stage of heavy oil viscosity reducing cracking, so that the effective concentration of the hydrogen donor can be ensured, the aromatic carbon free radical with key effect on condensation is fully saturated, and the condensation in the middle and later stages of the reaction is inhibited.

In summary, according to the method provided by the invention, the hydrogen donor is introduced in the middle stage of the heavy oil viscosity reduction cracking, so that the hydrogen donor does not interfere with initiation and chain propagation of a heavy oil viscosity reduction cracking reaction network, and a reaction system is ensured to reach a certain viscosity reduction depth at a reasonable speed; meanwhile, the hydrogen donor saturates aromatic carbon free radicals with key effects on condensation, so that on one hand, further reaction time is striven for viscosity reduction, and on the other hand, the occurrence of condensation is effectively inhibited. Based on the visbreaking of the hydrogen donor introduction mode, the obtained cracked product has the characteristics of low viscosity, small average molecular weight, light distillation range and the like. At the same time, condensed ring formation is suppressed and no coke is formed. The treated product can be used for subsequent catalytic hydrogenation or to improve its transport properties.

Drawings

FIG. 1 is a process flow diagram of a continuous visbreaking reaction with hydrogen donor;

FIG. 2 is a process flow diagram of a continuous visbreaking reaction with its own fraction as the hydrogen donor fraction.

FIG. 3 is a plot of product viscosity as a function of reaction time (reaction temperature 380 ℃ C.) during batch visbreaking of example 1 and its comparative examples;

FIG. 4 is a plot of asphaltene content in the product of the batch visbreaking process of example 1 and its comparative example as a function of reaction time (reaction temperature 380 ℃ C.).

Detailed Description

The following describes embodiments of the present invention in detail: the present example is implemented on the premise of the technical scheme of the present invention, and detailed implementation modes and processes are given, but the protection scope of the present invention is not limited to the following examples, and experimental methods without specific conditions are not noted in the following examples, and generally according to conventional conditions.

The method for improving the viscosity reduction cracking efficiency and the product distribution of heavy oil comprises the steps of taking heavy oil such as extra heavy crude oil, oil sand asphalt, atmospheric residuum, vacuum residuum or catalytic cracking slurry oil as raw oil, preheating, adding the raw oil into a kettle type reactor for viscosity reduction cracking reaction, or carrying out viscosity reduction cracking reaction on bottom residuum obtained after vacuum cutting to obtain a viscosity reduction product, adding a hydrogen donor or a hydrogen donor fraction in the middle stage of the viscosity reduction cracking reaction, and finally mixing the viscosity reduction product and the fraction oil to obtain the viscosity reduction product.

To further illustrate specific features of the present invention, reference is made to the accompanying drawings.

As shown in fig. 1, one process of the present invention is: the raw oil is heated and then enters a rectifying tower for cutting and distilling to obtain a fraction 1, a fraction 2 and tower bottom residual oil, the tower bottom residual oil is heated and then enters an viscosity reducing tower from the bottom, a hydrogen donor enters the viscosity reducing tower from the middle, and the obtained viscosity reducing oil is mixed with the fraction 1 and the fraction 2 through a pipeline mixer and then is used as a viscosity reducing product.

As shown in fig. 2, one process of the present invention is: the raw oil is heated and then enters a rectifying tower for cutting and distilling to obtain fraction 1, fraction 2 and bottom residual oil, and the cutting temperature of the fraction 1 and the fraction 2 is 300-420 ℃. The residual oil at the bottom of the tower enters the viscosity reducing tower from the bottom after being heated, the fraction 1 as a hydrogen supply fraction enters the viscosity reducing tower from the middle, and the obtained viscosity reducing oil is mixed with the fraction 2 through a pipeline mixer to be used as a viscosity reducing product.

In the following examples and comparative examples: a. product analysis: the dynamic viscosity of the product was measured on a TA Instruments advanced rheology extension system (Advanced Rheology Expand System, TA Instruments); b. four component separation was based on standard SY/T5119-2016.

Example 1:

the heavy oil feedstock is a vacuum residuum with basic properties shown in table 1. The hydrogen donor is tetrahydronaphthalene, and the addition amount is 0.5 weight percent of the heavy oil treatment amount. The visbreaking is carried out in a batch mode, the reaction temperature is 380 ℃, and the reaction pressure is 0.1MPa.

TABLE 1 basic Properties of vacuum residuum

30g of vacuum residuum were placed in an autoclave having a capacity of 100 ml. After nitrogen purging, the autoclave is closed and heated at a speed of 15 ℃/min, the reaction is carried out for 20min after the temperature reaches 380 ℃, then 0.15g of tetrahydronaphthalene is added into the reaction system, and the temperature of the reaction system is reduced after the continuous viscosity reduction cracking is carried out for 20min.

After visbreaking in a batch unit, the yield of coke in the product was 0, the gas yield was negligible and the yield of liquid product was nearly 100%. The viscosity of the liquid cracked product is shown in figure 3 and the asphaltene content of the product is shown in figure 4. As can be seen from fig. 3 and 4, the viscosity of the cracked product maintains a monotonically decreasing trend with the increase of the reaction time. The asphaltene content in the final product was maintained at substantially the same level as 20min.

Comparative examples 1 to 1

The difference from example 1 is that: without addition of hydrogen donor, 30g of vacuum residue was placed in an autoclave having a volume of 100 ml. After nitrogen purging, the autoclave was closed, the autoclave pressure was set at 0.1MPa, and the temperature was raised at a rate of 15 ℃/min. And after the temperature reaches 380 ℃, viscosity reduction cracking is continued for 40min, and then the temperature of the reaction system is reduced.

After visbreaking in a batch unit, the yield of coke in the product was 0, the gas yield was negligible and the yield of liquid product was nearly 100%. The viscosity of the liquid cracked product is shown in figure 3 and the asphaltene content of the product is shown in figure 4. As can be seen from fig. 3 and 4, the viscosity of the vacuum residue after visbreaking at 80 ℃ can be reduced to 0.5pa.s at 20min. However, the viscosity of the product is slightly raised with the extension of the reaction time. Condensation is always present during the reaction. As the reaction time was prolonged, the asphaltene content in the product increased from an initial value of 5.0wt% to about 8.5wt%. The increase in product viscosity after 20min of reaction was associated with a substantial increase in asphaltene content.

Comparative examples 1 to 2

The difference from example 1 is that: in a conventional manner of adding a hydrogen donor, 30g of vacuum residue and 0.15g of tetrahydronaphthalene were placed in an autoclave having a volume of 100 ml. After nitrogen purging, the autoclave was closed, the autoclave pressure was set to 0.1mPa, and the temperature was raised at a rate of 15 ℃/min. And after the temperature reaches 380 ℃, viscosity reduction cracking is continued for 40min, and then the temperature of the reaction system is reduced.

After visbreaking in a batch unit, the yield of coke in the product was 0, the gas yield was negligible and the yield of liquid product was nearly 100%. The viscosity of the liquid cracked product is shown in figure 3 and the asphaltene content of the product is shown in figure 4. As can be seen from fig. 3 and 4, the viscosity of the cracked product decreases monotonically with the increase of the reaction time. The viscosity was reduced only at a reaction time of 40min, which was comparable to that without the addition of the hydrogen donor, i.e. the viscosity reduction efficiency was reduced by the presence of the hydrogen donor. Despite the reduced asphaltene content in the product at the initial stage of the reaction, a rapid increase in asphaltene content still occurs at the later stage of the reaction.

As is clear from the comparison of example 1 with comparative examples 1-1 and 1-2, by timely introducing a hydrogen donor into a batch reactor, the viscosity of vacuum residuum at 80℃can be reduced from an initial value of 6.2Pa.s to about 0.1Pa.s, and the increase in asphaltene content in the system is only 1.5wt%. The addition of the hydrogen donor in the middle section has obvious advantages compared with the addition of no hydrogen donor and the initial addition of the hydrogen donor in the traditional reaction.

Example 2:

the heavy oil feedstock was oil sand bitumen, the basic properties of which are shown in table 2. The hydrogen donor is a mixture of decalin and dihydroanthracene according to a mass ratio of 1:1, and the addition amount of the hydrogen donor is 2.0wt% of the heavy oil treatment amount. The visbreaking is carried out in a continuous manner at a reaction temperature of 440 ℃.

Table 2 basic properties of oil sands bitumen

The oil sand bitumen to be fed was divided into two parts, wherein 95% of the raw oil sand bitumen was preheated to 440 ℃ and passed through a tubular reactor immersed in a fluidised sand bath maintained at the same temperature, the system pressure being set at 30MPa. The middle section of the reactor was fed with the remaining 5wt% of oil sand bitumen and 2.0wt% of hydrogen donor in side feed. The residence time of the material in the reactor was 5min. The properties of the resulting product are shown in Table 3.

Comparative example 2-1

The difference from example 2 is that: the raw oil sand asphalt is preheated to 440 ℃ completely without adding hydrogen donor, and then passes through a tubular reactor, the tubular reactor is immersed in a fluidized sand bath maintaining the same temperature, and the system pressure is set to be 30MPa. The residence time of the material in the reactor was 5min. The properties of the resulting product are shown in Table 3.

Comparative examples 2 to 2

The difference from example 2 is that: in the conventional hydrogen donor adding mode, the mixture of all raw oil sand asphalt and 2wt% of hydrogen donor is preheated to 440 ℃ and then passes through a tubular reactor, and the tubular reactor is immersed in a fluidized sand bath maintained at the same temperature, and the system pressure is set to be 30MPa. The residence time of the material in the reactor was 5min. The properties of the resulting product are shown in Table 3.

TABLE 3 basic Properties of oil sands bitumen visbroken products

From Table 3, it can be seen that comparative example 2-1, although the viscosity of the product can be significantly reduced, the asphaltene content in the product is almost doubled; the adhesion-reducing effect of the product of comparative example 2-2 was approximately equivalent to that without the addition of a hydrogen donor. Although the asphaltene content in the product was slightly reduced from that without the addition of hydrogen donor, it was still up to 27.8wt%. Example 2 by adding a hydrogen donor in the middle of the reaction, product viscosities as low as 0.45 (80 ℃) and 0.19 (120 ℃) Pa.s can be obtained. Meanwhile, the asphaltene content in the product only rises to 19.2wt% which is far lower than the case that no hydrogen donor is added or the hydrogen donor is added at the beginning of the reaction.

Comparing the data shown in Table 3, there are significant advantages in mid-stage addition of hydrogen donor over no addition of hydrogen donor and initial addition of hydrogen donor in conventional reactions.

Example 3:

the raw materials were the same as in example 2. The hydrogen donor is tetrahydronaphthalene, and the addition amount is 1wt% of the heavy oil treatment amount. The visbreaking is carried out in a continuous manner in a column reactor at a reaction temperature of 410 ℃.

The method comprises the steps of preheating raw oil sand asphalt, entering a rectifying tower, cutting the raw oil sand asphalt into fraction 1, fraction 2 and tower bottom residual oil at a vacuum degree of 10mmHg and using a cutting point at 350 ℃ and 420 ℃ as cutting points, enabling the tower bottom residual oil to enter an viscosity reducing tower with a reaction pressure of 1.0MPa from the bottom after being preheated to 410 ℃, enabling a hydrogen supply agent to enter the viscosity reducing tower from the middle part of the tower, arranging a feed inlet in the middle part of the viscosity reducing tower, enabling the feed inlet to extend into the middle part of the tower reactor, and arranging a liquid product distributor with an upward opening at the tail end of the feed inlet so as to enable the hydrogen supply agent and a reactant flow to be fully mixed. The obtained viscosity reducing oil is mixed with the fraction 1 and the fraction 2 through a pipeline mixer to obtain a viscosity reducing product. The residence time of the bottom residuum in the viscosity reducing tower is 20min, and the residence time of the hydrogen donor in the viscosity reducing tower is 10min. The properties of the resulting product are shown in Table 4.

Comparative example 3-1

The difference from example 3 is that: no hydrogen donor was added. The method comprises the steps of preheating raw oil sand asphalt, feeding the preheated raw oil sand asphalt into a rectifying tower, cutting the raw oil sand asphalt into fraction 1, fraction 2 and tower bottom residual oil at the vacuum degree of 10mmHg and the cutting point of 350 ℃ and 420 ℃, and feeding the tower bottom residual oil into an viscosity reducing tower with the reaction pressure of 1.0MPa from the bottom after the tower bottom residual oil is preheated to 410 ℃. The obtained viscosity reducing oil is mixed with the fraction 1 and the fraction 2 through a pipeline mixer to obtain a viscosity reducing product. The residence time of the bottom residuum in the visbreaking column was 20min. The properties of the resulting product are shown in Table 4.

Comparative example 3-2

The difference from example 3 is that: the traditional hydrogen donor is added. The method comprises the steps of preheating raw oil sand asphalt, feeding the preheated raw oil sand asphalt into a rectifying tower, cutting the raw oil sand asphalt into fraction 1, fraction 2 and tower bottom residual oil at a vacuum degree of 10mmHg and a cutting point of 350 ℃ and 420 ℃, mixing the tower bottom residual oil with a hydrogen supply agent, feeding the mixture into an viscosity reducing tower with a reaction pressure of 1.0MPa from the bottom after preheating to 410 ℃, and mixing the obtained viscosity reducing oil with the fraction 1 and the fraction 2 through a pipeline mixer to obtain a viscosity reducing product. The residence time of the bottom residuum in the visbreaking column was 20min. The properties of the resulting product are shown in Table 4.

Comparative examples 3 to 3

The difference from example 3 is that: the end of the charging hole arranged in the middle of the viscosity reducing tower is not provided with a liquid distributor with an upward opening. The method comprises the steps of preheating raw oil sand asphalt, feeding the preheated raw oil sand asphalt into a rectifying tower, cutting the raw oil sand asphalt into fraction 1, fraction 2 and tower bottom residual oil at the vacuum degree of 10mmHg and the cutting point of 350 ℃ and 420 ℃, feeding the tower bottom residual oil into an viscosity reducing tower with the reaction pressure of 1.0MPa from the bottom after preheating to 410 ℃, feeding a hydrogen supply agent into the viscosity reducing tower from the middle part of the tower, and mixing the viscosity reducing oil with the fraction 1 and the fraction 2 through a pipeline mixer to obtain a viscosity reducing product. The residence time of the bottom residuum in the visbreaking column was 20min. The properties of the resulting product are shown in Table 4.

TABLE 4 basic Properties of oil sands bitumen visbroken product

As can be seen from Table 4, comparative example 3-1, in which no hydrogen donor was added, the viscosity of the thermal cracking product was significantly reduced and the asphaltene content was slightly increased; comparative example 3-2 the conventional manner of adding the hydrogen donor, the viscosity reducing effect of the product was slightly increased as compared with the case where no hydrogen donor was added, and the asphaltene content was slightly decreased as compared with the asphaltene content in the raw material. In the embodiment 3, the hydrogen donor is added in the middle reaction section, so that the viscosity is obviously reduced, and meanwhile, the asphaltene content is also obviously reduced. The end of the charging port of comparative example 3-3 is not provided with a liquid distributor with an upward opening, the viscosity reducing effect is equivalent to that of example 3, and the asphaltene content is slightly reduced compared with the raw material.

As can be seen from the data shown in table 4, there are significant advantages in the case where the hydrogen donor is added in the middle section where the liquid distributor is provided at the end of the feed port, compared with the case where the hydrogen donor is not added, the hydrogen donor is initially added in the conventional reaction, and the liquid distributor is not provided at the end of the feed port.

Example 4:

the raw material is super-thick crude oil, and the properties are shown in Table 5. The hydrogen donor is self-distillate, and the addition amount is 8.5wt% of the processing amount of the ultra-thick crude oil. The visbreaking is carried out in a continuous manner in a column reactor at a reaction temperature of 425 ℃.

TABLE 5 basic Properties of ultra-heavy crude oil

The method comprises the steps of preheating raw oil sand asphalt, feeding the preheated raw oil sand asphalt into a rectifying tower, cutting the raw oil sand asphalt into fraction 1, fraction 2 and tower bottom residual oil at a vacuum degree of 10mmHg by taking 350 ℃ and 420 ℃ as cutting points, taking the fraction 1 as hydrogen supply fraction, feeding the tower bottom residual oil into an adhesion-reducing tower with a reaction pressure of 0.6MPa from the bottom after preheating the tower bottom residual oil to 425 ℃, feeding the fraction 1 into the adhesion-reducing tower from the middle part of the tower, arranging a feed inlet in the middle part of the adhesion-reducing tower, enabling the feed inlet to extend into the middle part of the tower reactor, and arranging a liquid product distributor with an upward opening at the tail end of the feed inlet so as to fully mix a hydrogen supply agent and a reactant flow. The obtained viscosity-reduced oil and the fraction 2 are mixed by a pipeline mixer to obtain a viscosity-reduced product. The residence time of the bottom residuum in the visbreaking tower is 20min, and the residence time of the hydrogen supply fraction in the visbreaking tower is 10min. The properties of the resulting product are shown in Table 6.

Comparative example 4-1

The difference from example 4 is that: the method comprises the steps of preheating raw oil sand asphalt without adding a hydrogen donor, feeding the preheated raw oil sand asphalt into a rectifying tower, cutting the raw oil sand asphalt into fraction 1, fraction 2 and bottom residual oil at the vacuum degree of 10mmHg and the cutting point of 350 ℃ and 420 ℃, feeding the bottom residual oil into an viscosity reducing tower with the reaction pressure of 0.6MPa from the bottom after preheating to 425 ℃, and mixing the obtained viscosity reducing oil with the fraction 1 and the fraction 2 through a pipeline mixer to obtain a viscosity reducing product. The residence time of the bottom residuum in the visbreaker was 10min and the properties of the resulting products are set forth in Table 6.

Comparative example 4-2

The difference from example 4 is that: in the traditional hydrogen supply agent adding mode, raw oil sand asphalt is preheated and then enters a rectifying tower, raw materials are cut into fraction 1, fraction 2 and tower bottom residual oil by taking the temperature of 350 ℃ and the temperature of 420 ℃ as cutting points, fraction 1 is taken as hydrogen supply fraction, the tower bottom residual oil and the hydrogen supply fraction are mixed and then enter an viscosity reducing tower with the reaction pressure of 0.6MPa from the bottom after being preheated to 425 ℃, and the obtained viscosity reducing oil and fraction 2 are mixed by a pipeline mixer to obtain a viscosity reducing product. The residence time of the bottom residuum in the visbreaking column was 10min.

The mixture of raw oil sand asphalt and hydrogen donor is preheated to 425 ℃ and then enters a tower reactor from the bottom, and the residence time of the materials in the reactor is 10min. The properties of the resulting product are shown in Table 6.

TABLE 6 basic Properties of cracked products of ultra-heavy crude

As can be seen from Table 6, comparative example 4-1, in which no hydrogen donor was added, the viscosity of the thermal cracking product was significantly reduced and the asphaltene content was slightly increased; comparative example 4-2 conventional hydrogen donor addition mode: the viscosity reducing effect of the product is slightly increased compared with that of the product without adding the hydrogen donor, and the asphaltene content is slightly reduced compared with that of the raw material; in the method of adding the hydrogen donor in the middle reaction section in the embodiment 4, the viscosity is obviously reduced, and meanwhile, the asphaltene content is also obviously reduced.

From the data shown in Table 6, there are significant advantages in mid-stage addition of the hydrogen donor over the non-addition of the hydrogen donor and the initial addition of the hydrogen donor in the conventional reaction.

Of course, the present invention is capable of other various embodiments and its several details are capable of modification and variation in light of the present invention by one skilled in the art without departing from the spirit and scope of the invention.

Claims

1. A method for improving the efficiency and product distribution of visbreaking of heavy oil, comprising the steps of: the heavy oil is used as raw oil, after preheating, visbreaking reaction is carried out for 5-40min under the temperature of 0.1-30 MPa and 360-460 ℃, and when the reaction is carried out to 1/4-1/2, a hydrogen donor is added into the reaction system.

2. The method according to claim 1, wherein a hydrogen donor is added to the reaction system when the reaction has proceeded for 2 to 30 minutes, preferably 3 to 20 minutes.

3. The method according to claim 1, wherein the hydrogen donor is added in an amount of 0.5 to 10wt%, preferably 0.5 to 2wt%, of the heavy oil treatment.

4. The method of claim 1, wherein the temperature of the visbreaking reaction is 380-420 ℃.

5. The method of claim 1, wherein the visbreaking reaction is performed in a batch or continuous mode.

6. The method of claim 1, wherein the heavy oil is one or a mixture of more of extra heavy crude oil, oil sand bitumen, atmospheric residuum, vacuum residuum, or catalytically cracked slurry oil.

7. The method of claim 1, wherein the hydrogen donor is a partially saturated bicyclic or polycyclic aromatic hydrocarbon compound, a distillate enriched in partially saturated bicyclic or polycyclic aromatic hydrocarbon compounds.

8. The method according to claim 7, wherein the partially saturated bi-or polycyclic aromatic hydrocarbon compound is selected from at least one of tetrahydronaphthalene, decalin, dihydroanthracene, cycloalkyl aromatic hydrocarbon; the distillate oil is at least one selected from diesel oil, light wax oil, heavy wax oil, ethylene tar, catalytic slurry oil, hydrotreated ethylene tar and hydrotreated catalytic slurry oil.

9. The method according to claim 1, wherein a feed inlet is provided in a middle lower portion of the tower reactor when the visbreaking reaction is performed in the tower reactor.

10. The method of claim 9 wherein said feed port extends into the middle of said tower reactor and said feed port terminates with an upwardly open liquid product distributor to provide thorough mixing of the hydrogen donor and reactant streams.