JP2005509083A - Countercurrent hydrotreatment - Google Patents

Abstract

  In the reaction zone (10) having a fixed bed containing porous catalyst particles (11), in order to ensure that the upward flow gas and the descending liquid are in countercurrent contact, heavy carbonization is performed at high temperature under super atmospheric treatment conditions. The hydrogen feed is distributed in a downward flow mainly on the catalyst bed (11) into the liquid phase and brought into contact with the catalyst particles, and the hydrogen-containing gas in the reaction zone (10) is introduced under the catalyst bed (11). Under conditions, the feedstock is brought into contact with the hydrogen-containing gas, the treated liquid under the catalyst bed (11) is removed and the hydrogen-depleted fluid on the catalyst bed (11) is removed to remove the heavy hydrocarbon feedstock to hydrogen. In which the void ratio of the catalyst bed (11) is less than 0.5 and the countercurrent gas-liquid contact is performed under such conditions that the Peclet number of the liquid is in the range of 0 to 10. The method performed.

Description

  The present invention relates to a process for hydrotreating hydrocarbonaceous feedstocks at high temperature and pressure, wherein products, in particular fuels and / or middle distillates, are obtained in high yields with relatively low consumption of hydrogen.

BACKGROUND OF THE INVENTION Hydroprocessing is well known in the art and has been practiced for many years, but is still one of the important refinery processes. Over the years, various feedstocks, catalysts and processing conditions for hydroprocessing have been described, many of which are in practical use. For example, in hydrocracking, the feedstock to be hydrocracked together with a hydrogen-containing gas, one or more metal compounds with inherent ability to break carbon-carbon bonds, and fragments present after the end of the cracking operation are hydrogenated. It is common to pass through a fixed bed-containing catalyst bed of particles having one or more metal compounds with the inherent ability to be converted.

  A hydrocracking process in which feedstock and hydrogen-containing gas are typically passed through the catalyst bed in the same direction from the top to the bottom using gravity is known as cocurrent hydroprocessing. This is the hydrocracking method that has been applied commercially since the oldest. In the early 70's it was proposed to operate the hydrotreatment process in a so-called “split flow” manner. In such a process, in particular in US 3,607,723, US 3,671,420 and US 3,897,329, the feedstock is constantly introduced between the two catalyst beds in the reaction zone, Hydrogen is introduced from the bottom of the catalyst bed. The feedstock is distributed over the catalyst bed and passed downward through the catalyst bed. In essence, processing performed in the downstream bed (as viewed from the feedstock introduction point) is operated in a countercurrent manner (feedstock moves downward facing the rising hydrogen), while the catalyst bed The processing performed in the upper catalyst bed (on which the feedstock is distributed) is performed in a co-current manner (rising hydrogen and fluid stripped by rising hydrogen move in the same direction). Such a “split flow” process utilizes two reaction zones that are preferably operated under the same process conditions.

It has been observed that countercurrent flow operation can slightly mitigate the inadequate flow distribution of the mixed phase present in the cocurrent flow, but still has the major limitation of severely affecting the countercurrent hydrotreatment.
A major limitation in countercurrent hydroprocessing is that conventional fixed beds are usually susceptible to the phenomenon called “catalyst bed flooding”. This catalyst bed flood occurs when the rate of the rising hydrogen-containing gas prevents the feedstock to be hydrotreated from passing downwardly due to gravity of the feedstock through the catalyst bed. As the catalyst bed approaches flood conditions, catalyst contact may be improved, but the process becomes vulnerable to pressure or temperature fluctuations or fluid flow rate fluctuations. If there is a disturbance that can initiate a flood, the process will be disrupted, even to the extent of an unplanned shutdown, to restore stable operation.

  In order to minimize the occurrence of floods in reactors operating in countercurrent mode, in particular in patent publication WO 99/00181, hydroprocessing with gas bypass means that can be operated to the vicinity of the reactor flood point with self-regulation. A reactor is proposed. However, additional facilities need to be installed and the risk of flooding that has yet to be eliminated.

US 4,775,281 is directed to treating countercurrent heavy hydrocarbons with special foam control, and if the porous solid bed catalyst is properly distributed and shaped, this solid A uniform vertical flow through the floor is obtained. US Pat. No. 4,775,281 specifically teaches that using a densely packed (spherical) solid (retaining a low void ratio in the reaction zone) is advantageous in terms of catalyst concentration, especially 2 When a two-phase countercurrent flow is required, fluid flow interference can also occur. Therefore, the patent specification strongly recommends that the catalyst bed used usually has a porosity higher than 1/2 of the catalyst bed. When using loosely packed polylobular or cylindrical extrudates, the void fraction can be between 0.5 and 0.9. This represents a significant sacrifice in the effective volume of the reactor that greatly affects the yield of the scheduled process.
Patent Publication WO 99/00181 US 4,775,281 Chemical Reactor Design and Operation, K.M. Westerp et al. ISBN 0 471 90183 0 Advantages, Possibilities and Limitations of Small Scale Testing of Catalysts for Fixed-Bed Processes: S. T.A. Sie, 210th National Meeting, American Chemical Society, Chicago, Ill. , August 20-25, 1995, p463-472.

  It has now been found that countercurrent hydrogenation can be carried out in a reaction zone with a low porosity ratio and that no special means for preventing flooding of the catalyst bed are required. The countercurrent hydrotreatment method of the present invention is preferably performed under flood conditions. In addition, this counterflow method provides a higher yield than the cocurrent flow hydrogenation process. It has also been found that the method of the present invention consumes less expensive hydrogen, has a high conversion rate of heavy terminals (ends), and has a high selectivity in removing sulfur from components having a high boiling point.

  Accordingly, the present invention provides heavy carbonization at high temperatures under superatmospheric treatment conditions to ensure countercurrent contact between the upflowing gas and the descending liquid in a reaction zone having a fixed array of porous catalyst particles. The hydrogen feed is distributed in a downward flow mainly on the catalyst bed into the liquid phase and brought into contact with the catalyst particles, and the feedstock is supplied with the hydrogen-containing gas under the condition that the hydrogen-containing gas in the reaction zone is introduced under the catalyst bed. And removing the treated liquid under the catalyst bed and removing the hydrogen depleted fluid on the catalyst bed to hydrotreat the heavy hydrocarbon feedstock, wherein the catalyst bed has a void ratio of 0.5. And counter-current gas-liquid contact relates to the process performed under conditions such that the Peclet number of the liquid is in the range of 0-10.

  While not wishing to be bound by any particular theory, operation in a gas / liquid regime characterized by low Peclet number liquids (ie, allowing backmixing of specific amounts of liquids) is a relatively densely packed catalyst particle. And thus substantially improve the yield of the desired product. In other words, given processing conditions that reduce static liquid retention and thereby increase dynamic liquid retention, unwanted reactions are reduced and more intermediate distillations than without this processing condition. Things are made. When the low void ratio of the catalyst is used in combination with the reduction ratio of the static retention amount and the dynamic retention amount of the liquid phase, the performance of the countercurrent hydrogenation treatment is improved.

  Parameters that help in countercurrent gas / liquid contact include gas velocities (increase gas velocities that reduce unnecessary static retention), liquid flow, and the size of the constraints, especially in the introduction to the gas. It is done. Methods of applying one or more of these parameters to reach the appropriate Peclet number in the countercurrent hydroprocessing method of the present invention are known to those skilled in the art.

  For the purposes of the present invention, the void ratio of the catalyst bed is defined as “1- (ratio of the occupied volume of catalyst particles to the total volume of the reaction zone)”. The internal pore volume of the solid catalyst is not included in this void ratio definition. The void ratio is constituted by a gap between the catalyst particles and a gap between appropriate catalyst particles and a reaction zone wall containing these catalyst particles.

  The pore ratio of the catalyst bed that can be used in the process according to the invention is preferably above 0.25 (and below 0.50). Preferable values are in the range of 0.30 to 0.48, and particularly preferable values are in the range of 0.35 to 0.47. Impressive results were obtained with catalyst particles packed so that the gap ratio was 0.45 (operating under conditions where the liquid Peclet number was 0-10).

  In systems where the liquid and gas are in contact with each other while the solid phase is fixed, the Peclet number is the same as in the case of hydrotreating using a fixed array of porous solid catalyst particles, Chemical Reactor Design and Operation, K.M. Westerp et al. ISBN 0 471 90183 0 can be defined as the ratio of the transport rate by convection and the transport rate by dispersion. In a totally backmixed system (usually occurring when operating under CSTR (continuous stirred tank reactor) conditions), the Peclet number is defined as 0, while by definition, an occluded flow without backmixing. The Peclet number of a system operating in (eg conventional trickle hydrocracking) is defined as indefinite (∞). In the method of the present invention, the preferred range of the Peclet number of the liquid is 1-8. It will be clear to those skilled in the art how to calculate the actual Peclet number in a given situation. As described above, a catalyst bed with a low void ratio is used in combination under conditions that allow a low Peclet number liquid that can improve the performance of the hydrotreating method of the present invention.

  The catalysts used in the hydroprocessing method of the present invention are well known in the art. These catalysts usually contain one or more metals from Group VI of the Periodic Table of Elements and / or one or more non-noble metals from Group VIII. These metals are conveniently present as oxides and / or sulfides. Preferred Group VI elements are molybdenum and tungsten, and preferred Group VIII metals are nickel and cobalt. The amount of metal compound used can vary widely. The preferred range is 2 to 40% by weight, expressed as a metal, for a Group VI metal compound, and the Group VIII metal compound is 1-10% by weight, expressed as a metal.

  Usually, the catalyst particles are those in which a catalytically active metal is present on a support. Suitable carrier materials are inorganic refractory oxides such as alumina, silica, silica-alumina, magnesia, titania, zirconia and mixtures of two or more of these materials. It may be advantageous that the catalyst particles comprise (further) a dedicated degradable component such as zeolite and / or amorphous silica-alumina. Examples of suitable degradable components are well known in the art. Suitable zeolites include zeolite Y and zeolite β, although non-zeolitic components such as (silico) -aluminophosphate and related compounds can also be used.

  The hydrotreating method of the present invention can use a wide variety of catalyst shapes such as spherical particles, cylindrical particles, and multilobal particles such as trilobes and quadrulobes. Good results have been obtained with trilobal catalyst particles. Particles having a maximum diameter of 0.5 to 3.5 mm are preferably used. Good results have been obtained with 1.6 mm diameter trilobal catalyst particles.

  The hydrotreatment process of the present invention is conveniently carried out using a temperature in the range of 200 to 475 ° C, preferably in the range of 250 to 425 ° C and a pressure of 20 to 250 bar, preferably 40 to 160 bar. obtain. This process can be carried out with LHSV in the range of 1-20 Nl feed / liter of catalyst / hour and hydrogen / hydrocarbon feed ratio in the range of 100-2000 Nl / l, preferably 250-1500 Nl / l. It is clear that the processing conditions should be selected so that the Peclet number of the liquid is in the range of 0 to 10 (the void ratio of the catalyst bed in the reaction zone is less than 0.5 as described above). Will.

  The heavy hydrocarbon feedstock used in the process of the present invention includes conventional feedstock used commercially in hydrocracking such as heavy gas oil. Suitable feedstocks can sufficiently process feedstocks having an initial boiling point of 200 ° C. or higher, while containing substantial amounts of materials with boiling points above 520 ° C., for example, 40% by weight or less of this type of material.

  In the method of the present invention, commercially available hydrogen can be preferably used. Hydrogen may contain intrinsic impurities to the extent that they do not substantially affect the catalyst activity. In the method of the present invention, a hydrogen stream containing 50% by volume or more, particularly 80% by volume or more of hydrogen is preferable. Typical impurities contain light hydrocarbons and nitrogen.

  There are a number of processing arrangements that can be advantageously used in the method of the present invention. Five device-ups of particular interest are described below, but those skilled in the art will recognize that equivalent device sequences can be used. FIG. 1 describes the basic equipment arrangement for countercurrent hydroprocessing. 2A and 2B describe first and second preferred device arrangements. FIG. 3 describes a third preferred device arrangement, and FIG. 4 describes a fourth preferred device arrangement. In each figure, the same numbers are used for the same parts.

Fig. 1 (Basic equipment arrangement)
Liquid feed is introduced from line 1 to the top of reaction zone 10 having catalyst bed 11 and distributed (means not shown) on the catalyst bed, while hydrogen-containing gas is passed from line 2 to the catalyst bed in reaction zone 10. 11 and rises in the catalyst bed. The treated liquid (treatment liquid) is removed from the reaction zone 10 via line 3 and can be used as is or further processed / quality-enhanced (not shown). The liquid present inside is separated from the reaction zone 10 via a line 4 which can be cooled to separate the liquid (means not shown). The method described with reference to FIG. 1 is performed under conditions that allow the liquid in the catalyst bed 11 to have a low Peclet number.

FIG. 2A (Further processing of processing solution)
The apparatus arrangement described in FIG. 1 has another reaction zone 20 having a catalyst bed 21 that can be operated downstream under the catalyst bed 11 under trickle conditions (i.e. conditions that produce a high Peclet number in the liquid phase). It is expanded by. The treatment liquid exiting from the bottom of the reaction zone 10 passes through the catalyst bed 21 in the reaction zone 20 and is taken out from there through line 5. This processing solution can be used as it is or further processing (not shown) can be performed. There is no separate inlet for the hydrogen-containing gas in this arrangement (which may be present if desired).

FIG. 2B (Further treatment of both treatment liquid and hydrogen depleted fluid)
The apparatus arrangement shown in FIG. 2B is obtained by adding a reaction zone 30 having a catalyst bed 31 to the reaction zone 10 having the catalyst bed 11 in the apparatus arrangement of FIG. 2A. The catalyst bed 31 is operated in a trickle mode (high Peclet number liquid) and the hydrogen depleted fluid is withdrawn via line 7 which can be cooled to separate the liquid present therein (means not shown). Liquid feedstock can optionally be additionally introduced from line 8 at the top of catalyst bed 31 in reaction zone 30.

Figure 3 (Three catalyst beds, two of which are operated countercurrently)
The arrangement of the apparatus described in FIG. 2B is varied to the extent that hydrogen-containing fluid is not introduced from line 2 but from line 12 at the bottom of reaction zone 20 having catalyst bed 21. This arrangement of equipment allows the process to be carried out countercurrently in the catalyst beds 21, 11 while the catalyst bed 31 is operated in a trickle manner. It is possible to operate the catalyst beds 21 and / or 11 under flood conditions.

Figure 4 (Combination of further processing)
The liquid feed is introduced from line 1 at the top of reaction zone 10 having catalyst bed 11 and distributed (means not shown) on this catalyst, while the hydrogen-containing gas passes through the catalyst in reaction zone 10. It is introduced from the line 2 under the bed 11 and rises in the catalyst bed 11. The treatment liquid is removed from the reaction zone 10, sent via line 3 (at least in part), and combined with the hydrogen depleted fluid removed from reaction zone 10 via line 4 (at least in part). Of course, a portion of the liquid exiting reaction zone 10 via line 4 is condensed so that the gas / liquid mixture combines with the process fluid in line 3 to form a feedstock entering reaction zone 40 via line 13. It is actually possible and preferred. The mixture is thus sent via line 13 to a reaction zone 40 having a catalyst bed 41. The catalyst bed 41 is operated in a trickle mode (high Peclet number liquid) (as a hydrotreating unit). The hydrogen required for this part of the process can be fed from line 14 at the top of reaction zone 40 so that the mixture entering reaction zone 40 via line 13 can be cocurrently hydrotreated or It can be fed via line 14 at the bottom, thereby operating the catalyst bed 41 in a countercurrent manner. Process liquid is removed from line 15 and hydrogen depleted fluid is removed from line 16.
The method of the present invention is illustrated in detail by the following non-limiting examples.

Example 1
Trilobal catalyst particles of 65 mm in length and 2 cm in inner diameter and 1.6 mm (alumina-based silica-alumina 80 wt. In a cylindrical reactor (generally as shown in FIG. 1) with heavy gas oil introduced downward into the catalyst bed and hydrogen from the bottom of the catalyst bed into heavy gas oil. It was introduced counter-currently. The catalyst bed was loaded so that the void ratio was 0.45. Gas oil has an initial boiling point (IBP) of 230 ° C. and a boiling point exceeding 340 ° C. of 62%, and a final boiling point (FBP) of 450 ° C. The gas oil contained 2.1 wt% sulfur and 317 ppm nitrogen. Two experiments were carried out, changing only the applicable hydrogen gas velocity. Details of Experiments 1 and 2 are shown in Table I below.

Table I

^* ) The method was performed in the conventional trickle mode commonly referred to as “occlusive flow” under the conditions associated with Experiment 1 (Advantages, Possibilities and Limitations of Small Scales of Catalysts for Fixed-Beds: Sie, 210th National Meeting, American Chemical Society, Chicago, Ill., August 20-25, 1995, p463-472). The liquid Peclet number 16 arises from this set-up.

The condition attached to Experiment 2 can be described as a flood countercurrent that produces a Peclet number 6 liquid (calculated using the above-mentioned Westerterp literature (reference)).
Not only did the conversion of the 340 ° C. + portion of the feed (ie, the fraction of the boiling point of the feed 340-450 ° C.) increase under conditions that allowed a low Peclet number (according to the invention) (approximately 50%), At the same time, it can be seen that the selectivity to the desired product also increased from 86.0% to 92.1%.

Example 2
The experiment described in Example 1 was repeated under the same conditions except that the space velocity was changed. Details of Experiments 3 and 4 are shown in Table II.

^*）第Ｉ表参照 Table II

^* ) See Table I

  It can be seen that a similar tendency is seen when operating at high space velocities. In particular, it should be noted that the conversion can be doubled while still increasing the selectivity to the desired product.

2 shows a basic equipment arrangement for countercurrent hydroprocessing according to the method of the present invention. 2A and 2B show the first and second preferred device arrangements used in the method of the present invention. Figure 3 shows a third preferred device arrangement for use in the method of the present invention. Figure 4 shows a fourth preferred device arrangement for use in the method of the present invention.

Explanation of symbols

1, 8, 13 Liquid feed lines 2, 12, 14 Hydrogen-containing gas lines 3, 5, 15 Process liquid lines 4, 7, 16 Hydrogen depleted fluid lines 10, 20, 30, 40 Reaction zones 11, 21, 31, 41 catalyst bed

Claims (9)

  In a reaction zone with a bed containing a fixed array of porous catalyst particles, to ensure countercurrent contact between the upflowing gas and the descending liquid, the heavy hydrocarbon feedstock is directed downward at high temperatures under superatmospheric conditions. The feedstock is contacted with the hydrogen-containing gas under conditions that allow the hydrogen-containing gas in the reaction zone to be introduced under the catalyst bed while being mainly distributed in the liquid phase on the catalyst bed in a stream. Removing the treated liquid and removing the hydrogen depleted fluid on the catalyst bed to hydrotreat the heavy hydrocarbon feedstock, wherein the catalyst bed void ratio is less than 0.5, and The method in which the flowing liquid contact is performed under conditions such that the Peclet number of the liquid is in the range of 0 to 10.   The process of claim 1, wherein the void ratio of the catalyst bed exceeds 0.25.   The process according to claim 2, wherein the catalyst bed has a void ratio of 0.30 to 0.48, preferably 0.35 to 0.47.   The method according to any one of claims 1 to 3, wherein the countercurrent gas-liquid contact is performed under conditions such that the Peclet number of the liquid is in the range of 1 to 8.   The treatment liquid that passed down the further catalyst particle-containing bed before removal from the process and / or the hydrogen-depleted fluid that passed upwards through the catalyst bed are directed upward in the vapor phase before being removed from the process as hydrogen-depleted fluid. The process according to any one of claims 1 to 4, which is passed through a bed containing further catalyst particles.   The process of claim 5, wherein at least a portion of the upwardly flowing hydrogen-containing gas is introduced into the bottom of a reaction zone having a further catalyst particle-containing bed, through which process liquid is removed from the process. .   6. The process of claim 1, wherein at least a portion of the processing liquid and at least a portion of the hydrogen depleted fluid are combined and then subjected to a second hydroprocessing step performed in cocurrent or countercurrent. Method.   The process according to any one of claims 1 to 7, wherein the hydrotreatment is carried out under hydrocracking conditions comprising a temperature in the range of 200 to 475 ° C and a pressure of 20 to 250 bar. 9. A process according to claim 8, wherein the catalyst particles are used in a spherical, cylindrical or multilobal shape with a maximum diameter of 0.5 to 3.5 mm.

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