KR20050016887A - System and process for pyrolysis gasoline hydrotreatment - Google Patents

Abstract

The present invention relates to a water treatment method and system for pyrolysis gasoline comprising a reactor, a monolith catalyst bed and a hydrogen-containing process gas, and according to the present invention the efficiency and productivity are improved over conventional water treatment trickle bed methods and systems.

Description

System and process for pyrolysis gasoline hydrotreatment

The present invention relates to a method for treating water of pyrolysis gasoline, and more particularly, to a method and apparatus for treating water by reducing costs and increasing efficiency.

Pyrolysis gasoline (also called "pygas") is a liquid byproduct of the steam cracking process for the production of ethylene and propylene. Pyrolysis gasoline is a high unsaturated hydrocarbon mixture (approximately C ₅ -C ₁₄ carbon range) rich in dienes, olefins and aromatics, especially benzene. Pyrolysis gasoline also includes undesirable heteroatom-containing hydrocarbons such as sulfur- and nitrogen-containing compounds. To use pyrolysis gasoline as a gasoline combination, it must be at least partially hydrogenated or water treated to reduce the amount of unsaturated and heteroatom-containing hydrocarbons. If left untreated, gasoline is typically broken down to form gums and varnishes in the fuel system.

Pyrolysis gasoline is currently commonly treated in fixed bed reactors using pellet catalysts. In general, trickle flow rate operation is applied. One of the problems of this kind of operation is the incomplete wetting of the layers by the liquid reactants and the channeling of the gas flow through the flow paths first, thus reducing the utilization of the layers. In addition, the bed pressure drop is limited by the catalyst particle size, and in many cases it is desirable to reduce the catalyst particle size if the limitation of the pressure drop can be overcome. In addition, conventional fixed bed reactors present problems associated with health, stability and environmental issues. These problems arise when the catalyst is insufficiently wetted by the liquid feed and the gaseous unsaturated hydrocarbon continues to react to release heat. Since the reaction rate is proportional to temperature, these problems may arise, thus causing high temperatures and even explosions.

Water treatment methods have been studied using alternative catalysts. For example, Smits et al. (Chemical Engineering Science, 1996 (51), 3019-3025) describe a method of water treatment of styrene and 1-octene mixtures in toluene on a monolithic catalyst. However, the mixture used by Smits et al. In the model experiments was significantly different from the actual pyrolysis gasoline composition. For example, while actual pygas contains at least 130 different compounds, the model system studied by Smits et al. Contains only three other compounds, and recent data shows that hydrogenation of styrene in pygas metrics The reaction rate is known to be 15 to 20 times slower than the same rate of ethylbenzene or toluene matrix. Thus, the discovery of Smits et al. Is difficult to apply to the water treatment of actual pyrolysis gasoline compositions on an industrial scale.

In view of the above-mentioned problems and inefficiencies associated with conventional pyrolysis gasoline water treatment methods currently in place, there is a constant need to improve the problems. There is a need to improve reactor and pyrolysis gasoline water treatment to reduce reactor size and cost, use hydrogen reactants more effectively, use power and water more effectively, and apply better hydrodynamics to improve overall bed utilization. have. From the above description will be able to solve this need.

Summary of the Invention

An important aspect of the water treatment process of the pyrolysis gasoline feed of the present invention includes contacting the pyrolysis gasoline feed with a hydrogen-containing treatment gas in the presence of at least one catalyst bed comprising a monolith catalyst. Preferred monolith catalysts are generally honeycomb structures, ie monolithic structures in which there are a number of equilibrium channels from the inlet side to the outlet side of the structure defined by the channel walls formed or coated or immersed in the catalyst.

In a preferred embodiment the support portion of the monolith catalyst comprises [theta] -alumina as a structural component of the monolith or as a coating on another metal or ceramic material support, for example an alumina coating on cordierite ceramic honeycomb. Suitable catalysts for use in combination with the support include hydrogenation catalysts selected from the group consisting of nickel, platinum, palladium, rhodium, silver, iron, cobalt, iridium, tin and mixtures thereof. The monolithic catalyst channel or so-called cell density ranges from 1.5 to 310 cells / cm 2 (10 to 2000 cells / in ² ) of the honeycomb cross section.

The feed for carrying out the water treatment process of the invention comprises both gas and liquid components. Preferably, part of the liquid product is recycled from the pyrolysis gasoline reactor. The gas component of the reactor feed usually contains at least about 50 mole percent molecular hydrogen. In a preferred embodiment of the invention, the gas and liquid feed traverses a plurality of catalyst beds with a hydrogen-containing process gas introduced between the catalyst beds to replace the volume of hydrogen consumed in the process.

Another aspect of the invention includes a reactor system for water treatment of pyrolysis gasoline feed. The system includes one or more reactor vessels comprising at least one monolith catalyst bed, each reactor vessel including a liquid feed inlet, an outlet, and a hydrogen-containing process gas inlet. In a preferred embodiment, a portion of the liquid exiting the outlet is recycled to the feed inlet. Also preferably, the at least one reactor vessel comprises at least one catalyst bed, the vessel comprising means capable of introducing a hydrogen-containing process gas into each catalyst bed through a hydrogen-containing process gas inlet.

1 is a graph showing a diene reduction rate with time in a pyrolysis gasoline water treatment reactor according to the present invention.

2 is a schematic view of a pyrolysis gasoline water treatment apparatus and method according to the present invention;

3 is a view showing an alternative method and reactor design of the heat treatment gasoline water treatment method.

The key of the present invention is the use of monolithic catalysts in systems and methods for the hydrogenation of pyrolysis gasoline (also referred to herein as "water treatment"). Monolith catalyst means a catalyst deposited on a solid support that is well known in the art and exhibits a substantially single structure (or geometry) throughout the structure. In a preferred embodiment the monolith catalyst has a honeycomb-type structure, which is typically characterized by a geometrical arrangement comprising a plurality of parallel, open-channel channels leading from the first or inlet side to the second or outlet side of the structure. Can be.

The "geometric arrangement" or "geometric structure" of a honeycomb-type catalyst refers not only to the structural features of the catalyst but also to the material features where some degree of unity can be found in the whole material. For example, the geometric arrangement may specifically include pore size, channel structure, channel diameter, cell density, wall thickness, void fraction, open front area (i.e., the percentage of total surface area occupied by the channel or pore face), and Analogues thereof. Monolith catalysts may also be referred to as "monolith" or "honeycomb catalysts".

The monolith catalyst is formed of, or dispersed in, or made of a monolithic structure consisting of channels defined across channel walls extending from one end of the structure to the other. The channels have a variety of cross sections including triangles, squares, rectangles, and hexagons, and the channel sizes in a relatively wide range of channel diameters range from millimeters to centimeters or more. Preferred honeycombs generally have a cell density in the range of about 7 to 160 cells / cm 2 (50 to 1000 cells / in ² ) of the honeycomb cross section.

Monolith catalysts and their preparation are known throughout the art and are described, for example, by Nijhuis et al. (Catalysis Reviews, 43 (4), 345-380). Monolith catalysts can be made of any material that can provide a porous structure. Suitable catalyst support materials include oxides of silicon, magnesium, aluminum, titanium, zirconium, transition metal oxides and mixtures and compounds thereof. Thus, some catalyst support materials include ceramics and zeolites. Examples of suitable ceramic materials are described, for example, in US Pat. No. 3,885,977; US Patent No. 4,483,944; US Patent No. 4,631,267; And US Pat. No. 5,633,217, which is incorporated by reference herein. Cordierite honeycomb specifically constitutes a suitable catalyst support.

The catalyst structure may support washcoats, catalysts or catalyst mixtures suitable for water treatment. For example, the support comprises alumina, such as γ-alumina or θ-alumina, extruded in monolithic form or washcoat onto other monolithic support structures. Another function of the washcoat is to provide a high surface area support for the active catalyst component.

The hydrogenation catalyst component is dispersed on the monolith catalyst support surface through dipping or coating. The hydrogenation catalyst component can include materials that help catalyze the hydrogenation of unsaturated organic compounds. Examples thereof include metals such as nickel, platinum, palladium, rhodium, ruthenium, silver, iron, copper, cobalt, chromium, iridium, tin and alloys and mixtures thereof. Preferred hydrogenation catalyst components are nickel, platinum and palladium.

The monolith catalyst aids in hydrogenation of the unsaturated pyrolysis gasoline component upon contact with the hydrogen-containing process gas. "Hydrogen-containing process gas" means a gas containing molecular hydrogen used to convert unsaturated organic compounds into their saturated form in whole or in part. The hydrogen-containing process gas typically contains at least about 50 mole percent molecular hydrogen. The hydrogen-containing process gas consists of 100 mole percent hydrogen or includes other gases such as inert gases. Examples of suitable inert gases include, but are not limited to, nitrogen, carbon dioxide, methane, ethane, propane, butane, and mixtures thereof and other gases.

“Contacting” the pygas and hydrogen-containing process gas with the monolith catalyst in accordance with the purpose of the present invention is a reaction with the catalyst bed for a sufficient temperature and time to effect efficient molecular interactions to increase the hydrocarbon saturation of the feed vapor. It includes the step of importing. The reaction conditions applied to the process depend in part on the reactor design specifically chosen, but a reaction temperature of about 20 to about 350 ° C. and a gas pressure of about 5 to about 100 bar are usually preferred. Preferably, the contacting step may be performed at a liquid hourly space velocity of greater than 0.1 hr ⁻¹ . Under these conditions, however, at least about 10% of the diene conversion present in the pyrolysis gasoline feed of conventional composition was found in a single pass through the reactor system.

As mentioned above, the mixed feed used for pygas conversion in accordance with the present invention typically consists of a gas and liquid mixture. The volume ratio of gas to liquid (“G: L ratio”) at reactor operating conditions ranges from about 0.1 to 20: 1, more typically from 0.1 to about 10: 1. However, conditions that provide a G: L ratio close to 1: 1, such as Taylor's flow, are usually preferred. Process operations under Taylor flow are known in the art and are described, for example, in US patent application Ser. No. 10 / 027,645, filed Dec. 21, 2001, which is incorporated herein by reference. Nevertheless, Taylor flow retention is not a prerequisite for practicing the present invention, and the methods and apparatus of the present invention can be operated with other flows, including film flow and turbulence, as desired.

According to various preferred operating methods of the present invention, the hydrogen-containing process gas consumed in the progress of the hydrogenation reaction occurring in the reactor system is replenished periodically depending on the location. Preferably, the replenishment takes place at an effective position and speed to maintain the desired G: L value for control of the flow mode, while at the same time providing the amount of hydrogen required for catalyst protection and total reaction stoichiometry. A suitable way to achieve this result is to inject hydrogen into the process stream at several points along the length of the reactor. Suitable flow control methods are further described in US patent application Ser. No. 10 / 027,645.

The process of the invention is carried out in a system having one or more reactor vessels. In one embodiment, the system includes two or more reactor vessels connected in series, so that the discharge from the upstream vessel includes the feed for the downstream vessel. The reactor vessel contains at least one catalyst bed containing a monolith catalyst. In one embodiment, the reaction vessel may contain two or more catalyst beds, or the reactor system may comprise two or more reactor vessels. An example of a reactor system having two or more reactor vessels is schematically shown in the drawings, which is described in detail below. Suitable systems contain two reactor vessels, where one vessel, such as an upstream vessel, comprises two catalyst beds, and another vessel, such as a downstream vessel, includes one catalyst layer. As with many reactor bed systems, a mixture of conventionally packed and monolith layers may be used.

In general, each reactor vessel includes one or more inlets, for example for pygas or emissions from the upstream reactor vessel and for the hydrogen-containing process gas. The vessel comprises, for example, one or more outlets for the pi gas product (emission) and / or vented process gas. In order to locally supply replenishment hydrogen-containing process gas in a vessel having one or more catalyst layers, an inlet to the gas is positioned to inject gas between the catalyst layers. This injection process additionally helps to better control the reactor temperature.

The catalyst bed can be operated according to any suitable mode, including upflow, downflow, or horizontal flow arrangements. In addition, the monolith catalyst bed can be operated using a countercurrent or countercurrent gas / liquid flow. In the same flow, the gas and liquid move in the same direction, while in the reverse flow the gas and liquid move in the opposite direction. Any combination of catalyst bed arrangements and flows is suitable and includes, for example, systems with multiple reactors operating independently under different arrangements and flows.

In one embodiment of the invention, the process can recycle the unreacted portion of the hydrogen-containing process gas back to the reactor so that unreacted hydrogen can be effectively used in the water treatment process. Thus, in one embodiment, the reactors have inlet and outlet valves capable of recirculating gas. In another embodiment, a recycle gas is added to the hydrogen-containing process gas prior to injection into the reactor vessel.

The process of the present invention further provides a portion of the liquid reactor discharge that is recycled. Thus, the liquid fraction of the vapor / liquid separator downstream from the reactor can be introduced directly into the reactor, for example in the reactor zone between the catalyst beds or in the reactor upstream zone of the catalyst bed. Liquid recirculation can also be combined with a pygas feed prior to injection into the reactor.

The system of the present invention may further comprise vapor / liquid separators, heat exchangers, pumps, and / or gas presses used in components of conventional systems. Examples of suitable pumps may include, but are not limited to, feed pumps, liquid recycle pumps, and equivalents thereof. Gas presses are used, for example, to recycle unreacted hydrogen-containing process gas.

The operating parameters of the systems and methods according to the invention are somewhat dependent on the design and capacity of the system to which they are applied. Generally, however, the liquid space velocity (feed volume per hour per catalyst volume) for the liquid pygas feed component is at least about 0.1 hr ⁻¹ . The primary purpose of performing a water treatment system is to convert dienes into more saturated molecules. The conversion of dienes present in a typical pygas feed is at least about 5% in a single system pass of the liquid space velocity.

Other advantages of the water treatment system and method described in the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited thereto. One of the important advantages is the use of monolithic catalysts to achieve the same level of conversion that less reactor volume is used than conventional methods such as trickle bed flow / pellet packed bed. The methods and systems of the present invention also allow for reduced hydrogen recycle rates compared to conventional methods.

Example 1

Preparation of Monolith Catalyst

A monolith catalyst support consisting of cordierite monolith washwashed with cita-alumina was catalyzed by nickel through the following procedure. A water-soluble nickel dipping solution was prepared by dissolving 600 grams of nickel nitrate in 1 liter of distilled water. The catalyst support was immersed in the solution at room temperature for about 30 minutes, after which the solution was removed and excess solution was drained. Excess solution was further removed by air blowing. The sample was dried by heating in an oven at 120 ° C. for 2 hours and finally calcined under air flow for at least 2 hours in a furnace at 250 ° C. The characteristics of the catalyst thus finished are shown in Table 1 below.

Nickel Properties on Wash-Coated Cita-Alumina Catalysts Cell density, cpsi 400 Cordierite web thickness, 0.001 inches 6.5 θ-alumina washcoat loading, wt% 19-23 Nickel loading,% by weight 1.7 BET surface area, ㎡ / g 12.3

Example 2

Nickel-catalyzed conversion of pygas

Nickel on the washcoated θ-alumina monolith catalyst described in Example 1 was tested for pyrolysis gasoline hydrogenation activity and selectivity in a fixed bed pilot reactor. The catalyst was first pretreated by flowing hydrogen for 16 hours at a temperature of 400 ° C. and 3.5 bar pressure to reduce nickel and create an active hydrogen site.

To run the test, the test unit was operated in a recycle or "differential" reactor in batch recycle mode. The mode includes a continuous recycle of liquid feed and hydrogen-containing gas over the monolith layer. Fresh hydrogen was added continuously to compensate for hydrogen consumption by reaction with the pygas feed. Periodically, water-treated pygas product samples were taken from the process stream and the reaction progress was measured using gas chromatography.

The graph of total diene concentration change over time shown in FIG. 1 shows the total mole fraction of diene remaining in the recycled pygas feed according to the reaction time in minutes. As a result, it can be seen that the diene concentration obtained with the actual pyrolysis gasoline feed is reduced using the monolith catalyst having the geometry and composition described in the present invention.

Example 3

Sprinkling layer pygas water treatment (comparative example)

Conventional methods of water treatment of heat treated gasoline are based on a fixed bed reactor method employing a bead catalyst bed randomly packed in a trickle bed flow mode. In this process, the raw petroleum gas is first combined with a hydrogen containing process gas and the gas and liquid mixture is preheated by a heat exchanger. The preheated mixture was fed to a reactor vessel comprising one or more catalyst beds.

In the case of a dual catalyst bed reactor, the two beds can be composed of the same or different catalyst volumes. The gas and liquid mixture first passes through the first catalyst bed and then through the second catalyst bed. The reactor discharge is cooled through a heat exchanger and then the gas and liquid phases are separated. The separated gas stream is generally recycled again and mixed again with fresh pygas and at this stage the hydrogen-containing feed gas is replenished for spent hydrogen. The separated liquid product was sent downstream.

Conventional methods use some of the cooled liquid product to control the overall temperature rise inside the reactor due to exothermic hydrogenation. A portion of the cooled liquid product for this purpose is typically recycled and introduced into the reactor between the two catalyst beds via quench internals.

Typical liquid space velocities (LHSVs) for operating layers of spraying layers commonly used for pygas hydrogenation, for example layers consisting of commercial nickel (10% by weight) catalysts on alumina beads, range from 1 to 3hr ⁻¹ . In actual conditions, the ratio of gas to liquid at the reactor inlet is generally in the range of 4 to 10 m 3 / m 3.

Table 2 shows the characteristics of a typical pygas feed normally processed in such a reactor. As mentioned above, pygas often consists of more than 100 components. However, for comparison, the components were grouped into smaller numbers according to unsaturated bonds, molecular weight, carbon number and boiling point. For example, a linear branched C6 component was classified into a C6 component group with a methyl group attached to a cyclic C5 ring. The components of this simplified pygas composition are shown in Table 3 together with the weight percent of the components in the raw pygas mixture.

Pygas Feed Characteristics density 842㎏ / ㎥ Molecular Weight 86.9㎏ / kmole BTX aromatic 69.67% by weight Composition Gross dienes 10.6% by weight Total olefins 7.36% by weight Styrene content 1.93 wt% ASTM D86 Distillation IBP 13.4 ℃ 5% 30 ℃ 50% 91.7 ℃ 95% 170 ℃ FBP 180 ℃

Simplified Pyrolysis Gasoline Composition (% by weight) n-butane2M-1-butenei-pentane1,3-cyclopentadienecyclopentenecyclopentane1,4-pentadiene1-pentene n-pentane2M-1pentene2Mpentanemethylcyclopentadiene1methylcyclopentenemethylcyclone Pentanebenzenestyrene E-benzenetoluene xylenedicyclopentadiene (C ₁₀ H ₁₂ ) dihydrodicyclopentene (C ₁₀ H ₁₄ ) tetrahydrodicyclopentane (C ₁₀ H ₁₆ ) methyl-dicyclopentadiene (C ₁₁ H ₁₄₎ methyl-di-hydro-cyclopentene (C ₁₁ H ₁₆₎ methyl-tetrahydro-di cyclopentane (C ₁₁ H ₁₈₎ 0.333.401.141.660.450.351.810.701.950.391.111.600.711.9839.151.937.3717.995.153.841.531.581.680.172.02 Sum 100

Typical results of conventional trickle bed pygas water treatment methods can easily predict reactor inlet and operating conditions based on pilot plant tests and specific simulation processes. Table 4 below describes the operation for a conventional trickle bed reactor design, and it is possible to predict the conversion results typical for reactors operated under these conditions.

The results shown in Table 4 below are based on two pellet bed reactors in which the liquid product for process temperature control is recycled. The volume of the first catalyst bed represents 29% of the total catalyst volume and 71% of the remaining catalyst volume is located in the second bed. Recirculation of the liquid product for process temperature control is achieved by injecting the recycled liquid product between the catalyst pellet beds at a rate of 7.6% by weight of the raw pygas feed, the rate being not higher than 70K above the reactor inlet temperature. It is efficient to control. The gas and liquid reactor emissions are separated into a liquid product stream and a recycle gas stream, the latter being temperature controlled to 40 ° C.

Data on the operation of the reactor described in Table 4 include the liquid space velocity of the pygas feed, the reactor inlet temperature, the reactor inlet pressure, the gas: liquid ratio at the reactor inlet, and the hydrogen content of the gas feed to the reactor. Typical process results reported for products under these operating conditions include the total product of dienes, olefins, and styrene and the density and molecular weight of the product.

Method variables LHSV Reactor Inlet Temperature Reactor Inlet Pressure Gas-to-Oil Ratio (Reactor at Inlet, Actual Conditions) Hydrogen Content of Treated Gas (Before Mixing Pigas) 1.8h ^-1 70 ℃ 36.7bar4.64㎥ / ㎥85.5% mol Product data Content conversion rate Total diene total olefin total styrene density ^a) Molecular weight ^a) 1.00% by weight 90.56% 8.48% by weight -16.01% 0.25% by weight 87.16% 833㎏ / ㎥87.1㎏ / kmole

a) after a simple flash at 1 bar and 20 ° C

Example 4

Monolith Catalytic Pigas Water Treatment Method

The pyrolysis gasoline water treatment system and method according to the invention was designed based on using the Ni-θ-wash coated monolith catalyst of Example 1. The reactor unit was designed and sized to operate at the same total pygas feed rate as the trickle bed reactor of Example 3, to produce the same product quality, and to be temperature controlled.

The particular catalyst design chosen for the reactor was a cordierite support having a cell density of 400 cells per square inch washcoated with θ-alumina coating applied to the main catalyst active phase at a concentration of about 1.69% by weight of the nickel coated monolith. Is made of. The dynamics based on pygas conversion data developed in bench and pilot tests of the reactor incorporating such a catalyst was used as basic information for the design of the system.

2 shows a system component and method flow diagram of a system employing the catalyst. 2, the raw pygas feed 1 enters the unit via the feed pump 2 and is mixed with the first fraction 13 of the process gas from the recycle compactor 12. The gas / liquid mixture is then preheated to the reactor inlet temperature by the feed-emitting heat exchanger 3 and fed to the reactor 4.

The reactor 4 comprises monolith catalyst layers 18, 19, 20 containing honeycomb catalysts. From the recycle compactor 12 the second fraction 14 of the process gas is divided into two parts. One of the portions 15 is injected into the reactor between the first 18 and second 19 catalyst beds. A second portion of the process gas 16 is injected into the reactor between the second (19) and third (20) catalyst beds together with the recycle liquid (17) from the liquid recycle pump (8). Recycle liquid 17 is provided to control the reactor temperature.

The process variables and product characteristics obtained by the method are shown in Table 5 below, which are based on the catalyst bed design and process parameters described in Table 6 below. Table 5 includes reactor operating data including the liquid space velocity of the pygas feed, reactor inlet temperature, reactor inlet pressure, gas to liquid ratio at the reactor inlet, and hydrogen content of the gas feed fed to the reactor. Typical process results for products under these operating conditions include the total product of dienes, olefins and styrene and the density and molecular weight of the product. Table 6 shows the relative volumes of each of the three catalyst beds, along with the inlet and outlet gas: liquid (G: L) ratios and the temperature of each of the three layers.

Method variables LHSV Reactor Inlet Temperature Reactor Inlet Pressure Gas-to-Oil Ratio (Reactor at Inlet, Actual Conditions) Hydrogen Content of Treated Gas (Before Mixing Pigas) 11.8h ^-1 70 ℃ 36.7bar0.84㎥ / ㎥89.5% mol Product data Content conversion rate Total diene total olefin total styrene density ^a) Molecular weight ^a) 1.00 wt% 90.56% 8.62 wt% -18.01% 0.27 wt% 86.10% 833㎏ / ㎥87.1㎏ / kmole

a) after a simple flash at 1 bar and 20 ° C

Monolith Catalyst Layer Materials Catalyst bed compartment (FIG. 2) (18) (19) 20 Relative Catalyst Volume Inlet G: L Outlet G: L Inlet Temperature Outlet Temperature 30% 0.840.5770 ℃ 92 ℃ 20% 0.900.6891 ℃ 112 ℃ 50% 1.030.63 102 ℃ 140 ℃

 The above described gas / liquid injection strategy applied to the design allows the reactor to be operated in a very layered gas / oil (G: L) profile. At the same time, control over the reactor temperature and a sufficient hydrogen supply to the reactor are ensured. For example, controlling the maximum reaction temperature so that it is no more than 70 ° C. above the reactor inlet is possible by maintaining the liquid recycle rate at 19% of the raw pygas flow rate.

When the actual gas volume for the liquid flow rate is in the range of about G: L = 0.2 to 2, preferably 0.5 to 1, excellent conversion efficiency through the monolith catalyst layer of the specific geometry described above has been demonstrated. This is generally below the ratio obtainable in a trickle bed with a G: L ratio of greater than 5. In addition, the reactors are designed to operate at a higher linear speed than is possible in a trickle bed reactor, and there is no problem of pressure drop across the catalyst bed. This is due to the low flow resistance inside the monolithic channel of the monolith. The trickle bed reactor requires a significant excess of hydrogen in the reactor feed so that sufficient hydrogen can be supplied through the reactor at an attainable mass transfer rate, and excess hydrogen is also needed to enhance mass transfer in the pellet catalyst bed.

The design according to the invention thus has two important advantages over the conventional trickle bed reactor design. Firstly, the use of a monolith catalyst allows for higher mass transfer when operating under the conditions described above, thus reducing the high hydrogen partial pressure required in the trickle bed process. In other words, since limiting the rate at which hydrogen is supplied to the catalyst surface to the process speed is the result of mass transfer coefficients and driving forces, higher mass transfer coefficients result in reduced power.

Secondly, the process design allows for adequate hydrogen supply along the entire reactor length, thus maintaining a gas to liquid ratio and thus allowing hydrogen to be used in an appropriately controlled range. This can be achieved by dividing the total process gas demand of the system by at least two parts of the proper flow rate, and by placing at least one additional location typically along the length of the reactor (between the monolith catalyst beds) and along the length of the reactor (between the monolith catalyst beds).

The substantial benefits of the system features are evident from the data. First, high performance, for example, for 1.8h 11.8h ^-1 as ^-1, in the same liquid Example 3 significantly higher space velocities compared to the trickle-bed reactor in order to produce the same product in the reactor feed of the monolith catalytic reactor It is possible to operate. This reduces catalyst requirements and saves significant costs for new reactor installations. In general, the presence of a water treatment unit can be upgraded to increase unit capacity or increase circulation length to obtain improved catalytic performance.

In addition, since it can be operated at a low G: L ratio in the monolith reactor, the amount of process gas required for recycling is significantly reduced. Thus, it is possible to reduce the specific energy required for the recycle gas press, for example using a less expensive gas press, 2.28 kWh per tonne of pygas for a trickle bed reactor and 0.96 kWh per tonne of pygas for a monolith reactor. Is reduced.

Another advantage is that the purity of the hydrogen at the reactor inlet is increased due to the reduced hydrogen recycle requirements of the monolith catalyst system, for example 85.5% of the monolith reactor while 85.5% of the monolith reactor. This is because when the feed gas is supplied at 90 mol% hydrogen purity, the volume of the process gas recycled and used is smaller, to the extent of hydrogen consumption or to approximately the same amount of feed gas added.

One consequence of these and other advantages of the monolith catalytic reactor is that the reactor operation costs are low. Table 7 below summarizes the results of comparing the trickle bed and monolith catalytic reactors as described in Examples 3 and 4, based on the useful cost of operating reactors of the same process capacity. In other words, the advantages of using a monolith catalytic reactor for the water treatment of pyrolysis gasoline feed are evident, including that the volume of catalyst required is reduced so that the reactor volume is significantly reduced.

Utility Sprinkle layer operation (comparative example) Monolith Operation (Invention) Difference between Monoliths and Aqueducts Diffusion Hydrogen Consumption Volume of Catalysts per Load Gas Power Cooled Water Reactor 512㎏ / h35㎏ / h256kW175㎥ / h44㎥ 498㎏ / h35㎏ / h170kW174㎥ / h6.6㎥ -14㎏ / h0-86kw-1㎥ / h-37.6㎥

As described above, multiple monolithic catalyst beds are used to efficiently multistage gas injection along the reactor length. This helps to better control the dual-phase flow mode, especially when the main components of the gas are consumed in the reaction, and to better control the exothermic temperature occurring across the catalyst bed. Reactors incorporating 2-4 catalyst beds provide excellent performance in a variety of applications, and more layers may be used if desired. Alternative systems and methods employing a large number of monolith catalysts and the like are described in the Examples below.

Example 5

Alternative Monolith Catalytic Reactor Design

The reactor based on the same process layout, feed conditions and catalyst as in Example 4 was evaluated, but in this case the catalyst bed arrangement and gas injection scheme were slightly modified. Six instead of three monolith catalyst beds of the type described in Example 1 were used in this reactor and provided 5 gas injection points. This arrangement makes it possible to control the gas to oil ratio in the reactor in a very narrow range. For example, it may be easy to maintain a gas to liquid volume ratio higher than 0.5: 1 at all points in the reactor.

The catalyst volume fractions and operating parameters for each monolith catalyst bed section are shown in Table 8 below. The operating parameters and planned conversion performance designed for this reactor design are summarized in Table 9. In this specific reactor design, the recycle liquid for reactor temperature control was injected between the fourth and fifth catalyst beds and the pygas feed rate to the reactor was adjusted to 19%.

6-bed reactor catalytic design and operation Catalyst bed I Ⅱ Ⅲ Ⅳ Ⅴ Ⅵ Catalyst Volume% Inlet G; L Outlet G: L Inlet Temperature Outlet Temperature 15.3% 0.720.6070 ℃ 80 ℃ 15.3% 0.720.5879 ℃ 92 ℃ 12.2% 0.700.5691 ℃ 104 ℃ 7.6% 0.740.65103 ℃ 113 ℃ 23% 0.820.66102 ℃ 119 ℃ 26.6% 0.970.66118 ℃ 140 ℃

Method variables LHSV Reactor Inlet Temperature Reactor Inlet Pressure Gas-to-Oil Ratio (Reactor at Inlet, Actual Conditions) Hydrogen Content of Treated Gas (Before Mixing Pigas) 11.9h ^-1 70 ℃ 36.7bar0.84㎥ / ㎥89.8% mol Product data Content conversion rate Total diene total olefin total styrene 0.97% by weight 90.78% 8.57% by weight -17.16% 0.26% by weight 86.56%

Example 6

Second Alternative Monolith Catalytic Reactor Design

The reactor based on the same process layout, feed conditions and catalyst as in Example 4 was evaluated, but the catalyst bed arrangement and gas injection scheme were slightly modified. Only two monolith catalyst beds of the kind described in Example 1 were used in this reactor and only one gas injection point was provided. While this arrangement is less in control of the gas-to-oil ratio in the reactor than is possible in the design described above, this control retains the advantages of the pellet bed reactor.

Catalyst volume fractions and operating parameters for each of the two monolith catalyst bed sections are shown in Table 10 below. The operating parameters and planned conversion performance designed for the reactor design are summarized in Table 11. The recycle liquid for reactor temperature control between the two monolith catalyst beds was adjusted to 19% of the pygas feed for the reactor.

Two-bed reactor catalyst design and operation Catalyst bed I Ⅱ Relative Catalyst Volume Inlet G: L Outlet G: L Inlet Temperature Outlet Temperature 47% 0.870.3470 ℃ 111 ℃ 53% 0.980.61 100 ℃ 141 ℃

Method variables LHSV Reactor Inlet Temperature Reactor Inlet Pressure Gas-to-Oil Ratio (Reactor at Inlet, Actual Conditions) Hydrogen Content of Treated Gas (Before Mixing Pigas) 11.8h ^-1 70 ℃ 36.7bar0.84㎥ / ㎥89.4% mol Product data Content conversion rate Total diene total olefin total styrene 1.00% by weight 90.49% 8.60% by weight -17.80% 0.265% by weight 86.14%

Various other designs are possible within the scope of the present invention with a monolith catalytic reactor for pyrolysis gasoline water treatment. Two other examples are shown in FIGS. 3A and 3B. These reactors each comprise three catalyst beds 18a, 19a and 20a with intermediate injection of gas containing hydrogen at injection points 15a and 16a to maintain sufficient hydrogen in the reactor to maintain high conversion efficiency. In this design, however, the catalyst beds are divided into two reactor vessels 4a and 4a 'to accommodate the reactor system present during the conversion to a monolith catalyst system, for example through a system upgrade.

The system shown in FIG. 3A represents a system operated in a simultaneous upflow mode in reactor 4a, ie a system in which gas and liquid phases 1 and 13 flow upward through the reactor vessel. The system shown in FIG. 3B is a simultaneous downflow system with separated catalyst beds. In a specific example, if maintenance of the layer is desired in such a system, it is also possible to use catalyst pellet beds in place of one or two monolith catalysts.

The foregoing materials, components, detailed descriptions and examples merely illustrate examples of possible variations within the scope of the invention as claimed below.

Claims (10)

Contacting the pyrolysis gasoline feed with a hydrogen-containing process gas in the presence of at least one catalyst bed comprising a monolith catalyst to provide a reacted pyrolysis gasoline product. The honeycomb catalyst of claim 1, wherein the monolith catalyst is a honeycomb catalyst comprising an Al ₂ O ₃ -containing catalyst support surface of gamma-alumina, cita-alumina, or mixtures thereof, wherein the monolith catalyst is nickel, platinum, Palladium, rhodium, silver, iron, copper, cobalt, chromium, iridium, tin, and mixtures and alloys thereof. The method of claim 2, wherein the catalyst support surface is an alumina coating on cordierite monolith and the honeycomb catalyst has a cell density of about 10 to 2000 cpsi. The method of claim 1 wherein the contacting step is performed at a temperature range of 20 to 350 ° C. and a pressure range of 5 to 100 bar. The process of claim 1, wherein the hydrogen-containing process gas comprises at least about 50 mole percent molecular hydrogen, and the contacting step comprises a gas to liquid volume ratio of 0.1 to 10: 1 and a liquid space velocity of greater than 0.1 hr ⁻¹ . Characterized in that it is carried out. The method of claim 1, wherein the pyrolysis gasoline feed flows through a plurality of catalyst beds and at least a portion of the hydrogen-containing process gas flows between the catalyst beds. The method of claim 1, wherein the feed flows through 2 to 4 catalyst beds and the contacting step provides a diene conversion of more than 10% of the pyrolysis gasoline feed. The method of claim 1 wherein the liquid portion of the reacted pyrolysis gasoline is recycled. At least one reactor vessel including at least one monolith catalyst layer, each of the at least one reactor vessel further comprising at least one feed inlet, at least one outlet, and at least one hydrogen-containing process gas inlet. A system for water treatment of pyrolysis gasoline feeds. 10. The reactor vessel of claim 9, wherein the at least one reactor vessel comprises two or more catalyst beds, wherein a hydrogen-containing process gas is introduced through a gas inlet between the at least two catalyst beds, and the hydrogen-containing process gas is in the reactor vessel. And at a rate sufficient to maintain a volumetric ratio of liquid to gas greater than 0.5: 1 at all points.