WO2009082930A1

WO2009082930A1 - Methods and apparatus for exothermic catalystic process

Info

Publication number: WO2009082930A1
Application number: PCT/CN2008/073548
Authority: WO
Inventors: Xinlei Hua; Youqi Wang; Rocco Fiato
Original assignee: Accelergy Shanghai R & D Center Co., Ltd.
Priority date: 2007-12-17
Filing date: 2008-12-17
Publication date: 2009-07-09
Also published as: CN101670253A

Abstract

Methods and apparatus for carrying out exothermic catalytic process are provided. In a particular implementation, an exothermic catalytic process is conducted in a catalyst bed (120) having a plurality of sections (S1, S2, &mldr; Sn), wherein the plurality of sections (S1, S2, &mldr; Sn) are configured such that a maximum temperature in each of at least two of the plurality of sections is within a predetermined range from a predetermined temperature.

Description

Method and Apparatus for Exothermic Catalytic Process

[Field]

This invention relates to a method and apparatus for exothermic catalytic process.

[Background]

Fischer-Tropsch (FT) processes have long been known to produce gaseous and liquid hydrocarbons. Also it is well known that FT processes are strongly exothermic and have highly temperature dependent reaction rate, so runaway or catalyst deterioration may happen if the temperature of an FT process is not kept below a specific critical temperature.

Thus, a commercial FT operation needs to have good cooling system and run under a well defined set of operation conditions in order to achieve a reasonable yield. Many efforts have been made to optimize the conditions and thus to increase the yield.

In conventional commercial fixed-bed FT operations, temperature profile along a single-catalyst bed typically has a peak, so called "hot spot". A part around where the peak temperature occurs has the highest reaction activity, while other parts of the catalyst bed are run at lower reaction activities due to being at lower temperatures. The hot spot limits the maximum flow rate of reactants in the feed allowed, because too high a flow rate can cause a temperature run away at the position where the hot spot occurs. Selectivity for desired products is poorer and deactivation of catalyst is more prominent at the position where the hot spot occurs, compared with other parts. And heat transfer is not optimum due to non-uniform catalyst temperature. Therefore, there is a need and room to improve the yield and thus the economic efficiency of conventional fixed-bed FT processes.

[Brief Description of the Drawings]

Fig. 1 illustrates a structured reactor.

Fig. 2 illustrates an exemplary temperature profile.

Fig.3 illustrates a flowchart of a method for carrying out an exothermic catalytic process.

Fig. 4 illustrates a flowchart of a method for forming a catalyst bed.

Fig. 5 illustrates a block diagram of a computer system for configuring an exothermic catalytic process.

Fig. 6 illustrates a flowchart of a method for optimizing an exothermic catalytic process.

Fig. 7 illustrates the temperature profile of the catalyst bed of example IA.

Fig. 8 illustrates the temperature profile of the catalyst bed of example IB.

Fig. 9 illustrates the temperature profile of the catalyst bed of example 1C.

Fig. 10 illustrates the temperature profile of the catalyst bed of example ID.

Fig. 11 illustrates the temperature profile of the catalyst bed of example 4.

Fig. 12 illustrates the temperature profile of the catalyst bed of example 5.

Fig. 13 illustrates the temperature profile of the catalyst bed of example 6.

Fig. 14 illustrates a structured reactor system including two serially connected reactors.

Fig. 15 illustrates another structured reactor system including three serially connected reactors.

Fig. 16 illustrates a flowchart of a method for forming catalyst beds in a reactor system.

Fig. 17 illustrates the temperature profile obtained in example 7.

Fig.18 illustrates a flowchart of a method for carrying out an exothermic catalytic process.

[ Description of Embodiments ]

To overcome the disadvantages and improve the yield and thus the economic efficiency of exothermic catalytic processes, Unitemp^® reactors or reactor systems designed by the applicant are provided. These reactors or reactor systems as well as their advantages when they are used to carry out exothermic catalytic processes are disclosed hereafter.

Fig. 1 illustrates a Unitemp^® reactor 100 for carrying out an exothermic catalytic process, such as an FT process. As shown in Fig. 1, the reactor 100 comprises a reactor tube 110 and a catalyst bed 120 disposed in the reactor tube 110. The reactor tube 110 has at least one reactant feed input 112 to allow one or more reactants to be fed into the reactor 100 and an effluent output 114 to allow reaction products and unreacted reactants to be output from the reactor 100. The catalyst bed 120 extends along a central axis A-A' of the reactor tube 110 and has a first end 122, which is closer to the feed input 112, a second end 124, which is closer to the effluent output 114, and a plurality of sections Sl, S2, ... Sn successively arranged along a flow direction F _of reactants between the first and second ends 122 and 124. In one embodiment, the plurality of sections Sl, S2, ... Sn are configured such that during the exothermic catalytic process, a maximum temperature in each of at least two of the plurality of sections is within a predetermined range from a predetermined temperature.

Fig. 2 illustrates an exemplary temperature profile 200 associated with the reactor 100 of Fig. 1 when n = 8. As shown in Fig. 2, the temperature profile 200 can be temperature along the central axis A-A' of the catalyst bed 120 as a function of a net volume of catalyst from the first end 122 of the catalyst bed to the respective points along the central axis. Of course, a radially averaged temperature from the axis to the wall can also be used to demonstrate the temperature profile. As further shown in Fig. 2, each of the sections Sl, S2, ... S 8 has a maximum temperature T_max, and seven of the eight sections Sl through S7, have their respective T_maχ within a predetermined range ΔT from a predetermined temperature T_c.

In one embodiment, to achieve a desirable temperature profile, such as the temperature profile shown in Fig. 2, in which a maximum temperature in each of at least two of the plurality of sections is within a predetermined temperature range from a predetermined temperature during the exothermic catalytic process, the plurality of sections Sl, S2, ... Sn should include at least two sections having different catalytic activities. In a further embodiment, at least two sections are loaded with a same catalyst diluted at different dilution rates with an inert substance, to achieve different catalytic activities. Alternatively, at least two sections are loaded with different catalysts to achieve different catalytic activities. Alternatively, at least two sections are loaded with a same catalyst diluted at different dilution rates with another catalyst, to achieve different catalytic activities. Alternatively, at least two sections are loaded with a same catalyst diluted at different dilution rates with different substances, to achieve different catalytic activities. In the following description, a different catalyst means a substance or a mixture of at least two substances having a different catalytic activity from another, e.g., a same catalyst diluted to a different catalytic activity.

In a further embodiment, the catalyst bed 120 is configured such that catalytic activity increases monotonously from section to section along the reactants flow direction F . In a further embodiment, the exothermic catalytic process is carried out under a predetermined feed flow rate and a predetermined composition of the feed, and the plurality of sections are configured based on either or both of the predetermined feed flow rate and the predetermined composition of the feed. In another embodiment, the exothermic catalytic process is carried out to achieve a predetermined conversion, and the plurality of sections are configured based on the predetermined conversion.

Fig. 3 is a flowchart illustrating a method 300 for carrying out an exothermic catalytic process according to one embodiment. As shown in Fig. 3, the method 300 comprises a step 310 in which the catalyst bed 120 is formed in the reactor tube 110 and a step 320 in which the exothermic catalytic process is conducted such that a maximum temperature in each of at least two of the plurality of sections is within a predetermined temperature range from a predetermined temperature, such as the temperature profile shown in Fig. 2.

Fig. 4 is a flowchart illustrating the step 310 for forming the catalyst bed 120 in the reactor tube 110. As shown in Fig. 4, the step 310 comprises a step 410 in which a feed flow rate and a catalyst bed configuration are selected, a step 420 in which a temperature profile along the catalyst bed 120 is obtained based on the feed flow rate and the catalyst bed configuration, a step 430 in which the temperature profile achieved in the step 420 is compared with a predetermined temperature using a predetermined temperature range, a step 440 in which it is determined whether the temperature profile meets a predetermined criteria , and a step 450 in which the catalyst bed 120 is built in the reactor tube 110 according to the catalyst bed configuration, wherein a temperature profile, which meets the predetermined criteria, is achieved using the catalyst bed configuration and a corresponding feed flow rate. In one embodiment, a temperature profile is achieved by calculation. In a further embodiment, a temperature profile is achieved by experiment. In one embodiment, part or all of method 300 can be performed using a computer system, such as the computer system 500 illustrated in Fig. 5. Referring to Fig. 5, the computer system 500 may include a processor such as a central processing unit (CPU) 501, a memory 503, and input and/or output devices 511, 513, 515 and 517 interconnected via a system bus 110.

The memory 503 may include a random access memory (RAM) 503a, and a computer readable medium 503b storing therein a modeling program product 505 such as AMP® of Accelergy Corporation, a Delaware corporation headquartered in California, and a database 507 for storing related data. The computer readable medium 503b can be part or all of a hard disk, portable hard disk, CDROM, memory stick, etc., or combinations thereof. The computer software AMP® is constructed with tool sets from Microsoft including Window2003 OS, Excel and VisualStudio C++, and employs some of the algorithms described in <Numerical Recipes in C> (William H. Press, Saul A. Teukolsky, William T. Vetterling and Brian P. Flannery, Cambridge University Press).

Referring to Fig. 6, the modeling program product 505 when executed by the CPU 501 causes the CPU 501 to perform a method 600 including the following steps: receiving a catalyst bed configuration and a feed configuration(step 610); calculating a temperature profile along the catalyst bed based on the catalyst bed configuration and the feed configuration (step 620). In one embodiment, the catalyst bed configuration specifies that the catalyst bed includes a plurality of sections, and that a catalyst loaded in one section is different from a catalyst loaded in an adjacent section. The method 600 may further include the following steps: comparing the temperature profile with a predetermined temperature using a predetermined temperature range (step 630); determining whether the temperature profile meets a predetermined criteria (step 640); if the temperature profile meets the criteria, outputing the catalyst bed configuration and the feed configuration (step 650); and if the temperature profile doesn't meet the criteria, and repeating steps 620-650 using an adjusted second catalyst bed configuration and an adjusted feed configuration (step 660).

In a further embodiment, the modeling program product 505 when executed by the CPU 501 causes the CPU 501 to create the adjusted catalyst bed configuration and the adjusted feed configuration, such that the exothermic catalytic process can be optimized by the computer system 500 automatically.

In one embodiment, step 420 in method 300 and/or step 620 in method 600 can be performed by modeling and simulation, in which a bed level reactant concentration

C^{B A} and temperature T are taken as dynamic variables while effect of catalyst and diluents are treated as external forces (so-called pseudo-homogeneous model). Following are a mass conservation equation (Equation 1) and an energy conservation equation (Equation 2) with respect to each of the reactants in terms of these variables in a cylindrical coordinate system suitable for a fixed bed reactor (See Section 11.7.2, "Continuity and Energy Equations," Gilbert F. Froment and Kenneth B. Bischoff, "Chemical Reactor Analysis And Design," second version, 1990, by John Wiley & Sons, Inc., which is incorporated here by reference):

where ^ΓA is reaction rate per catalyst weight, and^^s is catalyst volume density in catalyst pellet;

A U where T is temperature, ^κ is reaction heat, and subscript "A" in the above equations indicates a reactant.

Equations 1 and 2 are solved using the following boundary conditions:

C^B C^B 0 < r < R

^A= ^A0 , T=T₀ (at z=0, ^{~ l} , where R_t is internal radii of reactor tube)

a^r (at z=0 and r=R_t, for all z)

^3r (at i=0, for all z)

where T_R is temperature of the border of the catalyst bed and inner wall of the reactor tube, T_w is reactor wall temperature).

By assuming symmetry around the central axis of the catalyst bed of the reactor, Equations 1 and 2 become two-dimensional partial differential equations with respect to one of the terms, the reaction rate r( C^{B A} ,T), and a set of parameters like flow velocity along axial direction U₂ (cm/s), specific heat C_p, effective diffusivities D_e(cm²/s), thermal conductivity k_e (k_ez and k_er for axial and radial direction respectively), heat of reaction JH(kJ/mol), density of reactant p_g, density of catalyst in packed bed pe and heat transfer coefficient U_w(J/s-cm²-K).

To solve the two-dimensional partial differential equations, the following catalyst pallet level mass transfer conservation equation, Equation 3, is solved under the following boundary conditions:

^«!-%.₊-!. ^«!-k₊A._r; ₌o dr> r dr D₁ _ ₀₎

Boundary conditions: dC

= 0 dr r=0

C ^{A r}-^R = C^{B A} (R is radii of catalyst pellet)

In one embodiment, reactions are assumed to happen near catalyst surface inside normally porous catalyst pellets, so Γ_A in Equation 1 is normally expressed in terms of reactant concentration C_A inside the porous pellet, i.e., Γ_A = Γ_A (C_A5T). Under pseudo-homogeneous assumption, the pellet level mass equation (Equation 3) and one or more energy conservation equations can be solved to get the intra-pellet concentration profile, using the value at the pellet surface C^{B A} as boundary values. In one embodiment, thermal conductivity of catalyst pellet is assumed to be infinite, therefore energy conservation equation can be left out. Then, using the pellet-averaged rJA_for the reaction term in Equations 1 and 2, the reactor level equations can be solved at bed level, i.e., with a coarser spatial grid. For a spherical pellet spherical coordinates can be used. For first order reactions, closed-form solutions can be found.

In one embodiment one assumes a reaction network with the associated rate laws for corresponding reactions and assumes the values of the relevant parameters from thermal dynamics database, literature data and current experimental setups.

Numerical method can be used to solve the coupled bed-level and pellet-level equations. Conventional methods familiar to those skilled in the art, such as the "Shooting Method" for solving mixed-boundary condition for the pellet, and the "Crank-Nicholson Algorithm" for solving 2-dimensional partial differential equation, can be used to solve the bed-level equations (Equations 1 and 2).

In one embodiment one can first calculate the effectiveness factor η defined in Equation 4 by solving the pellet level rate laws and stores the resulting effectiveness factors corresponding to various reaction conditions, e.g., temperatures and pressures, into a database or a table. When solving bed-level equations one directly reads effectiveness factors off that database or table, thus saving computation time for solving of coupled pellet-bed equations.

Rate laws for the reactions being modeled may need to be known before the pellet level equations (e.g., Equation 3) can be solved. In one embodiment, lab-scale experimental results regarding a reactant conversion (such as CO conversion in FT synthesis) corresponding to a specific catalyst are used to find rate law parameters, such as rate constant, partial and overall orders of reaction, apparent activation energies, etc., for the said catalyst pellet, and heat transfer coefficient of reactor bed, etc., . Then the aforementioned method can be used to find bed-level rate law(s) based on the pellet level rate laws. So, a calibrated model fitted to a reaction system being modeled, such as a commercial scale reaction system (catalyst, bed, etc.), can be obtained.

In the following examples, the calibrated model is used to model and/or optimize a structured bed with n (n is an integer larger than or equal to 1) section(s), each of which has a particular catalytic activity factor, which indicates catalytic activity of a catalyst loaded in the section. During the modeling, two sides of a boundary between two adjacent sections are assumed to have the same radial concentrations and temperature distribution. For a selected structured bed configuration, conversion and product yield at different feed concentrations and/or specific reactant flow rates can be predicted using the calibrated model. Based on the prediction, the structured bed configuration can be adjusted and the conversion and product yield obtained based on the adjusted bed configuration. Therefore, the structured bed can be optimized to obtain superior product yield and/or other objective variables, such as conversion, selectivity, etc.

An FT process may include reactions that can be described using the following:

Paraffins production: (2n+l)H₂ + nCO -^■> C_nH_2n+2 + nH20, n=l, 2, 3,...

Olefins production: 2nH₂ + nCO -^■> C_nH_2n + nH20, n = 2, 3...

Water gas shift: CO+H₂O -> CO₂+H₂

Examples 1-6 discussed below are based on a simplified reaction network including reactions shown in Table 1, which also lists a rate law associated with the reactions.

Table 1

Where P_H2 is partial pressure of H₂ and is related to H₂ molar concentration via ideal gas law. R is the gas constant and equals to 8.314 Joule/(mol-K).

Also in Examples 1-2, some or all of the data shown in Table 2 are used to calculate temperature profiles.

In one embodiment, temperature profile is calculated using rate-law parameters shown in Table 3, which can be found by curve fitting using experimental results, such as those shown in Table 4, which are obtained by running experiments on Accelergy 32 channel parallel reactor system with four different catalyst loadings 0.45g, 0.6g, 0.9g and 1.2g and at four different temperatures 220⁰C, 230 ⁰C, 235 ⁰C and 240 ⁰C. Table 2

Table 3

Table 4

Example 1

In the Example 1, a three-section bed with different packing profiles under different syngas concentration, with the constraint that the temperature not to exceed a predetermined temperature, such as 250⁰C , which is about 10⁰C above a reactor wall temperature of 240⁰C, is used to illustrate a method for optimizing an FT process according to embodiments. Four examples IA- ID with different packing profiles are discussed.

In the examples IA- ID, a same catalyst will be used, and activity factor of the catalyst without dilution is set as 1. The catalyst bed configuration is represented by catalyst bed packing, which indicates activity factors of catalysts loaded in different sections of the catalyst bed.

In example IA, a conventional FT catalyst bed configuration is analyzed. Referring to Fig. 7, a temperature profile along the catalyst bed is illustrated. In order to compare with other examples, the conventional FT catalyst bed is divided into three equal sections along a longitudinal axis of the reactor, section I, section II and section III. The three sections are loaded with the same undiluted catalyst, so the catalyst bed packing of example 1 A is 1 : 1 : 1.

As shown in Fig. 7, the temperature curve of the catalyst bed reaches a peak in section I, and decreases afterwards. As mentioned above, FT processes are highly exothermic. Heat generated from the reactions causes temperature to rise, which in turn boosts speed of the reactions and heat generation. So the temperature of the catalyst bed increases very fast along the flow direction in section I. At the same time, the content of syngas decreases rapidly along the flow direction because of consumption, especially near the inlet of the catalyst bed. At certain position of the catalyst bed, the speed of the reactions begins to decrease because of the depletion of reactants, and the temperature of the catalyst bed begins to decrease, such that a peak temperature is formed. The following table 5 illustrates parameters and resulting product yield of example 1.

Table 5

Product Space Time Yield indicates quantity of carbon contained in products produced per gram of catalyst per hour, and it may be referred to as Product Yield for short hereafter. Total productivity, which indicates quantity of carbon contained in products produced per hour, can be used to measure performance of a catalyst bed. In the following examples, reactors used therein are the same as that of example 1. Since the amount (e.g., weight) of catalyst(s) loaded in a catalyst bed is assumed to be the same in each of these examples, there is no need to calculate total productivity based on actual weight of catalyst loaded in a catalyst bed for the purpose of comparing among these examples. Therefore, for ease of discussion, the Product Yield is used to represent total productivity in these examples.

In commercial FT operations, the peak temperature of a catalyst bed is usually set to be equal to or close to a critical temperature with a maximum syngas flow rate, which equals to feed flow rate multiplied by syngas concentration, to achieve a total productivity as high as possible. If the flow rate of syngas is further increased by increasing concentration of syngas, holding residence time unchanged, run-away or catalyst deactivation may occur. In order to control the peak temperature formed in section I so that it is below the critical temperature, the flow rate of syngas needs be controlled so that it is below a specific level. This however makes section II and section III under utilized.

An approach of increasing product yield of a process provided by this application, is to form a catalyst bed having a plurality of sections, which are loaded with catalysts of different activities. In one embodiment, the catalytic activity of the catalysts loaded in the sections increases monotonously along a flow direction of reactants, such that a maximum temperature in each of the sections is equal to or in a predetermined temperature range from a predetermined temperature.

In example IB, a catalyst bed is divided into three sections equably in longitudinal direction. It is intended to form a peak temperature in each section that is equal to or in a predetermined temperature range from the predetermined temperature, in order to increase the total yield. The three sections are loaded with catalysts having catalyst activities. For example, catalysts in section I and section II are diluted with an inert substance (e.g. quartzite), and catalyst in section III is undiluted. Meanwhile, syngas concentration in the feed is increased. The catalyst used in example IB is the same as that of example IA. The following table 6 illustrates parameters and resulting Product Yield of example IB.

Table 6

As shown in table 6, the catalyst loaded in section I is diluted with the inert substance to 65%. The catalyst loaded in section II is diluted with the inert substance to 80%. The catalyst loaded in section III is not diluted. At the same time, Syngas Content in Feed is increased to 81% from 69%, which is the maximum allowable concentration in example IA. A temperature profile illustrated in Fig. 8 and a Product Yield of 0.0683 mol/(gcat*h) are calculated based on the calibrated model discussed above. The peak temperature of section II is higher than that of section I, and the peak temperature of section III is higher than that of section II and exceeds the max temperature (25O⁰C), thus run-away may happen in section III. This example indicates that the Syngas Content in Feed has been increased too high and needs be lowered to avoid a run-away situation, and at the same time the catalytic activity of section I and II have been lowered too much, leading to lower productivity.

In example 1C, catalyst dilution rates in section I and II are decreased, in order to keep the peak temperatures of section I, II and III relatively uniform. The catalyst used in example 1C is the same as that of example IA. The following table 7 illustrates parameters and resulting Product Yield of example 1C.

Table 7

As shown in table 7, the catalyst loaded in section I is diluted with the inert substance to 90%. The catalyst loaded in section II is diluted with the inert substance to 95%. The catalyst loaded in section III is not diluted. Syngas Content In Feed is set as 76.5%. A temperature profile illustrated in Fig. 9 and a Product Yield of 0.0742 mol/(gcat*h), which is much more than that of example 1 and 2, is obtained using the calibrated model. The peak temperature of section I is 250⁰C. The peak temperature of section II is about 249.5⁰C. The peak temperature of section III is about 249⁰C. In order to make the peak temperatures more uniform, one can lower the catalytic activities of sections I and II and increase the Syngas Content In Feed at the same time.

In example ID, catalyst dilution rate of section I and II is increased compared to example 1C, at the same time, Syngas Content In Feed is increased. The following table 8 illustrates parameters and Product Yield of example ID.

As shown in Table 8, the catalyst loaded in section I is diluted with the inert substance to 85%. The catalyst loaded in section II is diluted with the inert substance to 90%. The catalyst loaded in section III is not diluted. Syngas Content In Feed is set as 81%. A temperature profile of the catalyst bed illustrated in Fig. 10 and Product Yield of 0.0779 mol/(gcat*h) are calculated based on the calibrated model. The peak temperature of section I is 250⁰C. The peak temperature of section II is about 249.5⁰C. The peak temperature of section III is about 249.8⁰C . Table 8

Compared with example 1C, the peak temperatures of example ID are more uniform and closer to the max temperature, and Product Yield is increased about 5%. Compared with example IA, Product Yield of example 4 has a 14.6% improvement.

According to the above examples, when intrinsic activity of catalyst(s) and number of sections of a catalyst bed are known, an optimum product yield can be obtain by optimizing a temperature profile using the calibrated model. In one embodiment, the temperature profile is optimized such that a peak temperature in each of at least two sections is within a predetermined range from a predetermined temperature. Such a temperature profile can be achieved by adjusting catalytic activities of the sections and reactants concentration in the feed.

Although these examples involve dividing the catalyst bed into three equal sections, in practice, to optimize product yield, the catalyst bed can be divided in more or less, equal or unequal sections.

In a further embodiment, different catalyst activities in different sections of a catalyst bed can be achieved by diluting one or more catalysts at different dilution rates. In another embodiment, different catalyst activities in different sections of a catalyst bed can be achieved by mixing different catalysts using different ratios or by using different catalysts for different sections.

Example 2

Provided that each section of a catalyst bed is formed with a peak temperature within a predetermined range, therefore the more sections the catalyst bed is divided into, the more uniform temperature profile can be achieved, leading to higher average temperature along the bed and thus higher product yield. But the increase of the product yield approaches a limit as the number of sections becomes large. These are illustrated by following examples, which used parameters in Table 2. A same catalyst will be used in the following examples.

In example 2A, 1.2 gram of said catalyst is loaded in a catalyst bed without dilution. When the syngas percentage in the feed is set at 61.50%, based on the mathematical model, the max temperature of the catalyst bed reaches 250⁰C, and Product Yield of the catalyst bed is 0.0352 mol/(gcat*h).

In example 2B, a catalyst bed is divided into two sections equably in longitudinal direction. The catalysts loaded in the two sections are diluted as indicated in the following table 9, and when the syngas percentage in the feed is set at 66.10%, one peak temperature reaches 250⁰C, and the other peak temperature is equal to or very close to 25O⁰C, and Product Yield of the catalyst bed is 0.0372 mol/(gcat*h). Compared with example 2A, Product Yield increases by 5.5%.

In example 2C, a catalyst bed is divided into three sections equably in longitudinal direction. The catalysts loaded in the three sections are diluted as indicated in the following table 9, and when the syngas percentage in the feed is set at 67.45%, and Product Yield of the catalyst bed is 0.0376 mol/(gcat*h). Compared with example 2A, Product Yield increases by 6.8%.

In example 2D, a catalyst bed is divided into four sections equably in longitudinal direction. The catalysts loaded in the four sections are diluted as indicated in the following table 9, and when the syngas percentage in the feed is set at 68.15%, and Product Yield of the catalyst bed is 0.0379 mol/(gcat*h). Compared with example 2 A, Product Yield increases by 7.7%.

In example 2E, a catalyst bed is divided into five sections equably in longitudinal direction. The catalysts loaded in the five sections are diluted as indicated in the following table 9, and when the syngas percentage in the feed is set at 68.75%, and Product Yield of the catalyst bed is 0.0381 mol/(gcat*h). Compared with example 2A, Product Yield increases by 8.1%.

In example 2F, a catalyst bed is divided into six sections equably in longitudinal direction. The catalysts loaded in the six sections are diluted as indicated in the following table 9, and when the syngas percentage in the feed is set at 69.15%, and Product Yield of the catalyst bed is 0.0382 mol/(gcat*h). Compared with example 2A, Product Yield increases by 8.5%.

In example 2G, a catalyst bed is divided into seven sections equably in longitudinal direction. The catalysts loaded in the seven sections are diluted as indicated in the following table 9, and when the syngas percentage in the feed is set at 69.28%, and Product Yield of the catalyst bed is 0.0383 mol/(gcat*h). Compared with example 2A, Product Yield increases by 8.8%.

In example 2H, a catalyst bed is divided into eight sections equably in longitudinal direction. The catalysts loaded in the eight sections are diluted as indicated in the following table 9, and when the syngas percentage in the feed is set at 69.35%, and Product Yield of the catalyst bed is 0.0384 mol/(gcat*h). Compared with example 2 A, Product Yield increases by 9.0%.

Table 9

According to the above examples, the more sections a catalyst bed is formed, the higher product yield can be achieved. However, forming more sections in a catalyst bed brings higher operation cost, so there is a balance in determining how many sections a catalyst bed should be formed.

In the case that a process (e.g. FT processes) favors higher temperature, it is expected to operate the process right below a run away temperature and in a structured catalyst bed to improve product yield.

In the case that a highest conversion or a highest selectivity for a specific product can be achieved under an optimum temperature or in an optimum temperature range, it is expected to operate the process under the optimum temperature or in the optimum temperature range and in a structured catalyst bed to improve product yield.

In addition to FT processes, the method for increasing product yield of the application can be used in other exothermic catalytic processes, e.g. syngas to alcohols etc.

In the above examples, some factors, which don't have much influence on the results, are not considered. But if it is necessary, they can be integrated in the calibrated model.

In one embodiment, an exothermic catalytic process is configured such that a peak temperature in each of at least two of a plurality of sections of a catalyst bed is in a predetermined temperature range from a predetermined temperature, although one or more sections may not form any peak temperature, or may have peak temperature that is outside the predetermined temperature range.

Example 3

Referring to table 10, two more examples on FT process, examples 3 A and 3B, are described. In example 3A, a catalyst bed is loaded with a catalyst uniformly, syngas content is set at 61.5%, and gas hourly space velocity of syngas is set at 138, such that max temperature of the catalyst bed reaches at 249.93⁰C, CO conversion is 70.71%, and Product Yield is 0.0225 mol/(gcat*h).

In example 3B, a catalyst bed having a same size as that in example 3A is divided into eight sections. The eight sections are loaded with the same catalyst used in the example 3A, and the catalysts loaded in the eight sections (Sections I- VIII) are diluted at dilution rates according to table 11. Syngas Content In Feed is set at 100%, and gas hourly space velocity of syngas is set at 225, such that a temperature profile illustrated in Fig. 2 is formed. Referring to Fig. 2, a peak temperature is formed in each of the eight sections. Peak temperatures of Sections I-VII are about 249.93⁰C, but the peak temperature of the Section VIII down stream is much lower than 249.93⁰C because of syngas depletion. Product Yield reaches 0.0363 mol/(gcat*h), which is 61.6% more than that of example 3 A. Apparently, the improvement is remarkable. Table 10

Example 4

In example 4, results obtained from two FT synthesis processes 4A and 4B are disclosed. The two FT synthesis processes 4A and 4B are carried out at substantially same conditions including pressure, syngas content in the feedstock, GHSV, temperature rise ΔT between a reactor entrance/wall temperature and a maximum temperature within the reactor, and catalyst, except reactor entrance/wall temperature, with a conventional reactor and a Unitemp^® reactor, respectively. Reaction conditions, factors and results of the FT synthesis processes 4A and 4B are shown in the table 11 below.

Table 11

In the FT synthesis processes 4A, the catalyst bed is loaded with catalysts in a conventional uniform way, a pressure in the reactor is set at 3.1 MPa, syngas content in the feedstock is set at 35%, GHSV is set at 435, a reactor entrance/wall temperature is set at 185⁰C, a temperature rise ΔT between the reactor entrance/wall temperature and a maximum temperature within the reactor is set at 15⁰C, and the maximum temperature within the reactor is 200⁰C. Based on such a catalyst bed configuration and these reaction conditions, a temperature profile curve 4A as shown in Fig.ll, a CO conversion of 84% and a Product Space Time Yield of 0.0725 mol/(gcat*h) are obtained. In the FT synthesis processes 4B, the catalyst bed is divided into three sections equably in longitudinal direction. The three sections are loaded with a catalyst the same as the catalyst used in the process 4A, but diluted as indicated in the table 11. A pressure in the reactor is set at 3.1 MPa, syngas content in the feedstock is set at 35%, GHSV is set at 435, a reactor entrance/wall temperature is set at 205⁰C, a temperature rise ΔT between the reactor entrance/wall temperature and a maximum temperature within the reactor is set at 15⁰C, and the maximum temperature within the reactor is 220⁰C. Based on such a catalyst bed configuration and these reaction conditions, a temperature profile curve 4B as shown in Fig.11, a CO conversion of 91% and a Product Space Time Yield of 0.0790 mol/(gcat*h) are obtained. Compared with process 4A, the CO conversion increases by 8.33% and the Product Space Time Yield increases by 8.97%.

By comparing the processes 4A and 4B, it is found that, based on a given target temperature rise ΔT, the Unitemp^® reactor can improve the single pass CO conversion and product yield via higher reactor entrance/wall temperature.

Example 5

In example 5, results obtained from two FT synthesis processes 5A and 5B are disclosed. The two FT synthesis processes 5A and 5B are carried out at substantially same conditions including pressure, GHSV, reactor entrance/wall temperature, temperature rise ΔT between the reactor entrance/wall temperature and a maximum temperature within the reactor, and catalyst, except syngas content in the feedstock, with a conventional reactor and a Unitemp^® reactor, respectively. Reaction conditions, factors and results of the FT synthesis processes 5 A and 5B are shown in the table 12 below.

Table 12

In the FT synthesis processes 5A, the catalyst bed is loaded with catalysts in a conventional uniform way, a pressure in the reactor is set at 3.1 MPa, syngas content in the feedstock is set at 35%, GHSV is set at 435, a reactor entrance/wall temperature is set at 185⁰C, a temperature rise ΔT between the reactor entrance/wall temperature and a maximum temperature within the reactor is set at 15⁰C, and the maximum temperature within the reactor is 200⁰C. Based on such a catalyst bed configuration and these reaction conditions, a temperature profile curve 5 A as shown in Fig.12, a CO conversion of 83% and a Product Space Time Yield of 0.070 mol/(gcat*h) are obtained.

In the FT synthesis processes 5B, the catalyst bed is divided into three sections equably in longitudinal direction. The three sections are loaded with a catalyst the same as the catalyst used in the process 5 A, but diluted as indicated in the table 12. A pressure in the reactor is set at 3.1 MPa, syngas content in the feedstock is set at 80%, GHSV is set at 435, a reactor entrance/wall temperature is set at 185⁰C, a temperature rise ΔT between the reactor entrance/wall temperature and the maximum temperature within the reactor is set at 15⁰C, and the maximum temperature within the reactor is 200⁰C. Based on such a catalyst bed configuration and these reaction conditions, a temperature profile curve 5B as shown in Fig.12, a CO conversion of 91% and a Product Space Time Yield of 0.170 mol/(gcat*h) are obtained. Compared with process 5A, the CO conversion increases by 9.64% and the Product Space Time Yield increases by 143%.

By comparing the processes 5A and 5B, it is found that, based on a given target temperature rise ΔT, the Unitemp^® reactor can improve the single pass CO conversion and product yield by increasing syngas content in the feedstock.

Example 6

In example 6, results obtained from two FT synthesis processes 6A and 6B are disclosed. The two FT synthesis processes 6A and 6B are carried out at substantially same conditions including pressure, syngas content in the feedstock, GHSV, reactor entrance/wall temperature, temperature rise ΔT between the reactor entrance/wall temperature and a maximum temperature within the reactor, except catalyst, with a conventional reactor and a Unitemp^® reactor, respectively. Reaction conditions, factors and results of the FT synthesis processes 6 A and 6B are shown in the table 13 below.

In the FT synthesis processes 6A, the catalyst bed is loaded with catalysts in a conventional uniform way, a pressure in the reactor is set at 3.1 MPa, syngas content in the feedstock is set at 35%, GHSV is set at 435, a reactor entrance/wall temperature is set at 185⁰C, a temperature rise ΔT between the reactor entrance/wall temperature and a maximum temperature within the reactor is set at 15⁰C, and the maximum temperature within the reactor is 200⁰C. Based on such a catalyst bed configuration and these reaction conditions, a temperature profile curve 6 A as shown in Fig.13, a CO conversion of 84% and a Product Space Time Yield of 0.072 mol/(gcat*h) are obtained.

In the FT synthesis processes 6B, the catalyst bed is divided into three sections equably in longitudinal direction. The three sections are loaded with a catalyst with 2 times higher activity than the catalyst used in the process 6A, and then diluted as indicated in the table 13. A pressure in the reactor is set at 3.1 MPa, syngas content in the feedstock is set at 80%, GHSV is set at 435, a reactor entrance/wall temperature is set at 185⁰C, a temperature rise ΔT between the reactor entrance/wall temperature and the maximum temperature within the reactor is set at 15⁰C, and the maximum temperature within the reactor is 200⁰C. Based on such a catalyst bed configuration and these reaction conditions, a temperature profile curve 6B as shown in Fig.13, a CO conversion of 90% and a Product Space Time Yield of 0.078 mol/(gcat*h) are obtained. Compared with process 6A, the CO conversion increases by 7.14% and the Product Space Time Yield increases by 8.33%.

By comparing the processes 6A and 6B, it is found that, based on a given target temperature rise ΔT, the Unitemp^® reactor can improve the single pass CO conversion and product yield by using higher activity catalysts.

As can be seen from the above 1-6 examples, in conventional FT operations, due to hot spot in an exothermic reaction in a fixed-bed reactor, to avoid runaway at the hotspot one has to limit reactor temperature, which reduces overall conversion and reactor efficiency, or limit reactant concentration in feed, which increases recycle and utility loads, or limit catalyst activity, which leads to requiring larger equipment. In Unitemp^® reactors on the other hand, with catalyst activity profile management the hotspot is distributed over the entire bed one can increase reactor temperature, or reactant concentration in feed, or using more active catalyst.

Through dividing a catalyst bed into a plurality of sections successively arranged along the flow direction of reactants and loading the plurality of sections with catalysts in a manner that, for example, catalytic activities of the catalyst bed increase along the flow direction for the reactants, Unitemp® reactors can boost the reaction rate, which would otherwise decreases along the flow direction due to the depletion of the reactants. In other embodiments, for further improving reaction conversions, besides loading bed sections with catalysts of different activities, reaction rates can further be controlled by adjusting the reaction temperatures. For example, in a situation as shown in Fig. 2, i.e., decrease of reaction rate in the 8th section can not be substantially prevented through adjusting the catalyst loading or activity, then temperature adjustment, such as increasing the temperature of the 8th section, may be additionally used to prevent or reduce decrease of reaction rate in the 8th section.

Example 7

Another embodiment of the present invention provides a Unitemp^® reaction system for exothermic catalytic process. In one embodiment, the Unitemp^® reaction system includes two or more serially connected reactors, and at least one of the serially connected reactors is a Unitemp^® reactor, which may be similar to those discussed above.

Referring to Fig. 14, a reactor system 700 includes a first reactor 710, a second rector 730 serially connected to the first reactor 710, a first product collecting device 721 for collecting a part of products contained in the effluent of the first reactor 710, a second product collecting device 723 for collecting a part of products contained in the effluent of the second rector 730 and a tail gas treating device 725 for treating tail gas. The first reactor 710 includes a first reactor tube 711 and a first heat exchanger (or temperature controller) 713 for controlling the external temperature of the first reactor tube 711 and thereby controlling the temperature of the exothermic catalytic reaction taking place in the first reactor tube 711. The first reactor tube 711 has a first inlet 715 for receiving reactants into the first reactor tube 711 and a first outlet 717 for outputting reaction results and unreacted reactants from the first reactor tube 711. The first reactor tube 711 further includes a first catalyst bed 719 for loading catalysts. The first catalyst bed 719 is formed with a plurality of first sections Bl, B2...Bn. Configuration or catalyst loading of the plurality of first sections Bl, B2...Bn is in such a manner that during an exothermic catalytic process, a temperature profile along the first catalyst bed 719 meeting a first predetermined criterion. The first catalyst bed can be configured by optimizing methods as described in the aforementioned embodiments.

If the first reactor 710 is provided with a first reactor tube 711 only, the first inlet and outlet of the first reactor tube 711 can be used as an inlet and outlet of the first reactor 710, respectively.

In one embodiment, the first predetermined criterion is that a maximum temperature in at least two of the plurality of first sections is within a predetermined range from a first predetermined temperature.

In one alternative embodiment, the first predetermined criterion is that a maximum temperature in at least two predetermined first sections is within a predetermined range from a first predetermined temperature.

In one embodiment, catalysts are loaded in the plurality of first sections in such a manner that during an exothermic catalytic process in the first reactor 710, a maximum temperature in each of the plurality of first sections is within a predetermined range from a first predetermined temperature.

The second reactor 730 includes a second reactor tube 731 and a second heat exchanger (or temperature controller) 733 for controlling the external temperature of the second reactor tube 731 and thereby controlling the temperature of the exothermic catalytic reaction taking place in the second reactor tube 731. The second reactor tube 731 has a second inlet 735 for receiving reactants into the second reactor tube 731 and a second outlet 737 for outputting reaction results and unreacted reactants from the second reactor tube 731. The second reactor tube 731 further includes a second catalyst bed 739 for loading catalysts. The second catalyst bed 739 is formed with a plurality of second sections Dl, D2...Dn. Configuration or catalyst loading of the plurality of second sections Dl, D2...Dn is in such a manner that during an exothermic catalytic process, a temperature profile along the second catalyst bed 739 meeting a second predetermined criterion. The second catalyst bed 739 can be configured by optimizing methods as described in the aforementioned embodiments.

In one embodiment, the second catalyst bed 739 has the plurality of sections Dl, D2...Dn thereof loaded with same catalysts, and the second criterion is that a maximum temperature in the second catalyst bed 739 is within a predetermined range from a second predetermined temperature.

In one embodiment, the second predetermined criterion is that a maximum temperature in at least two of the plurality of second sections is within a predetermined range from a second predetermined temperature.

In one alternative embodiment, the second predetermined criterion is that a maximum temperature in at least two predetermined second section is within a predetermined range from a second predetermined temperature.

In one embodiment, catalysts are loaded in the plurality of second sections in such a manner that during an exothermic catalytic process in the second reactor 730, a maximum temperature in each of the plurality of second sections is within a predetermined range from a second predetermined temperature.

As to FT synthesis process, a predetermined temperature may be a maximum temperature, below which runaway or catalyst deterioration may not happen (critical temperature). Generally, in practically operations, the predetermined temperature may be a temperature slightly below the critical temperature, based on the security consideration. As to a high-temperature FT synthesis process, a predetermined temperature is generally in the range of 300⁰C -350⁰C, and as to a low-temperature FT synthesis process, predetermined temperature is generally in the range of 200⁰C -240⁰C . A predetermined range may be 20⁰C below the predetermined temperature, or particularly, 10⁰C below the predetermined temperature, or more particularly, 5⁰C below the predetermined temperature.

In one embodiment, the activity of the catalyst loaded in each of the plurality of first sections is lower than the activity of the catalyst loaded in a first section further along the flow direction of reactants, and the activity of the catalyst loaded in each of the plurality of second sections is lower than the activity of the catalyst loaded in a second section further along the flow direction of reactants.

In one embodiment, the first catalyst bed 719 has the first sections thereof loaded with a same first catalyst diluted at different dilution rates with a first inert substance, to achieve different catalytic activities, and the second catalyst bed 739 has the second sections thereof loaded with a same second catalyst diluted at different dilution rates with a second inert substance, to achieve different catalytic activities. In one embodiment, the first and second catalysts are the same. In another embodiment, the first and second catalysts are different. For example, the first catalyst is suitable for relatively lower temperature reactions while the second catalyst is suitable for relatively higher temperature reactions, or the first catalyst is suitable for front-stage reactions and the second catalyst is suitable for rear-stage reactions for further converting results of the front-stage reactions to object products.

In one embodiment, the first reactor 710 may be provided with a plurality of first reactor tubes 711 and the second reactor 730 may be provided with a plurality of second reactor tubes 731, i.e., the first and second reactors 710 and 730 may either or both be multi-tubular fixed-bed reactors.

Referring to Fig. 14 again, a first product collecting device 721 is set between the first outlet 717 and the second inlet 735 for collecting liquid products, such as wax and water, discharged from the first reactor tube 711. Collecting of the liquid products may be carried out by condensation processes. The by-product of FT processes water will bring bad effects to Co-based catalysts, therefore, if the second reactor is loaded with co-based catalysts, it is good for the second reactor to remove water from the results of the first reactor.

The second product collecting device 723 is connected to the second outlet 737 and used to collect liquid products discharged from the second reactor 731. The tail gas treating device 725 is connected to the second product collecting device 723 and used to treat tail gas. In one embodiment, the tail gas treating device 725 includes tail gas burning device (not shown) in order to burn the tail gas to generate electrical power.

Taking FT synthesis as an example, based on the analysis in the examples 1-6, the first reactor 710 can have a syngas conversion much higher than conventional reactors due to its configuration. That is to say, even in the absence of the second reactor 730, the first reactor 710 is able to achieve an increased utilization of syngas. Due to a relatively higher conversion of syngas in the first reactor 710, a syngas content in the feedstock fed into the second reactor tube 731 is relatively lower. Therefore, heat produced in the second reactor tube 731 is much lower than the first reactor tube 711 if under a same condition and the temperature in the second reactor tube 731 is much lower than the critical temperature. In one embodiment, an exterior temperature of the second reactor tube 731 is set higher than an exterior temperature of the first reactor tube 711, to make the temperature in the second catalyst bed 739 more close to the critical temperature such that the conversion in the second reactor 730 can be increased, the syngas content in the tail gas can be reduced and the utilization of syngas can be greatly increased.

The number of reactors in a reactor system can be adjusted depending on specific needs. Referring to Fig. 15, a reactor system 750 including reactors 760, 770 and 780 connected in series is provided. Each of the reactors 760, 770 and 780 may be a rector with a plurality of sections, similar to those reactors described above. Exterior temperatures of the reactors 760, 770 and 780 are Tl ', T2' and T3', respectively, wherein T3' > T2' > Tl'.

Alternatively, since the results out of the first reactor 710 has a relatively lower syngas content, in one embodiment, more than one parallel first reactor may be provided in series connection with a same second reactor to increase the utilization of the second reactor.

Another aspect of the above embodiments provides a method for configuring an exothermic catalytic process. Referring to Fig. 16, a method 810 includes steps as follows: a step 811 in which a temperature profile along the first catalyst bed 719 is obtained based on the catalyst bed configuration and reaction conditions in the first reactor 710, a step 813 in which the temperature profile achieved in the step 811 is compared with a first predetermined temperature using a predetermined temperature range, a step 815 in which it is determined whether the temperature profile meets a first predetermined criteria, selectively a step 817 in which the catalyst bed configuration and reaction conditions in the first reactor 710 are adjusted following by repeating the steps 811 to 815 if the temperature profile achieved in the step 811 does not meet the first predetermined criteria or a step 819 in which a flow rate and a composition of the feedstock fed to the second reactor is obtained if the temperature profile achieved in the step 811 meets the first predetermined criteria, a step 821 in which a temperature profile along the second catalyst bed 739 is obtained based on the catalyst bed configuration and reaction conditions in the second reactor 730, a step 823 in which the temperature profile achieved in the step 821 is compared with a second predetermined temperature using a predetermined temperature range, a step 825 in which it is determined whether the temperature profile meets a second predetermined criteria, selectively a step 827 in which the catalyst bed configuration and reaction conditions in the second reactor 730 are adjusted following by repeating the steps 821 to 825 if the temperature profile does not meet the second predetermined criteria or a step 829 in which catalyst bed configurations and reaction conditions in the first and second reactors, which respectively meet the first and second criteria are obtained.

A part or all of method 810 can be simulated using a computer system, such as the computer system 500 illustrated in Fig. 5, or performed by experiment.

In one embodiment, the adjustment of reaction conditions in the step 817 may include adjustment of flow rates of reactants and/or compositions of reactants.

In one embodiment, the step 819 further includes obtaining the flow rate and composition of the material fed into the second reactor 730 based on the reaction conditions in the first reactor 710, the first catalyst bed configuration and conditions of the first product collecting device 721, such as temperature, pressure and etc.

In one embodiment, the first predetermined temperature is the same as the second predetermined temperature. In one embodiment, the first predetermined temperature range is the same as the second predetermined temperature range.

Three examples (examples I, J and K) performed by computer simulation will be discussed below to show advantages of the above embodiments. The data used to calculate temperature profiles for the three examples are shown in Table 14. Table 14

In one embodiment, temperature profile is calculated using rate-law parameters shown in Table 15. Table 15

Table 16 below shows the catalyst bed packing (activity factors in different sections of reactors of a reactor system), reaction conditions and reaction results of the examples I, J and K. Table 16

Referring to Fig. 17, curves i, j and k are temperature profiles obtained based on the reaction conditions, factors and catalyst bed configurations in the examples I, J and K. Temperature profiles for examples J and K are superposed as a same curve in Fig. 17, because the first reactors in examples J and K have same catalyst bed configurations and reaction conditions.

In the examples I, J and K, a first catalyst bed of 30cm is divided into three first sections equably in longitudinal direction and a second catalyst bed of 10cm is divided into three second sections equably in longitudinal direction.

In example I, both a first catalyst bed and a second catalyst bed are loaded with undiluted catalysts, i.e., both the catalyst bed packing of the first catalyst bed and the second catalyst bed is 1:1:1. When the syngas percentage in the feed is set at 65%, the external wall temperature of the first reactor tube is set at 185⁰C, and the external wall temperature of the second reactor tube is set at 193⁰C, a maximum temperature of the first catalyst bed is formed in the first of the first sections and is about 201⁰C (set as the maximum temperature allowed), a maximum temperature of the second catalyst bed is formed in the first of the second sections and is about 200⁰C, and the CO conversion is 76%.

In example J, both the catalyst bed packing of the first catalyst bed and the second catalyst bed is set at 0.69:0.8:1. When the syngas percentage in the feed is set at 90%, the external wall temperature of the first reactor tube is set at 185⁰C, and the external wall temperature of the second reactor tube is set at 193⁰C, each of the first sections has a maximum temperature in a range of 199-201⁰C and each of the second sections has a maximum temperature in a range of 199-201⁰C, and the CO conversion is 79%. In example K, the catalyst bed packing of the first catalyst bed is set at 0.69:0.8:1 and the catalyst bed packing of the second catalyst bed is 1:1:1. When the syngas percentage in the feed is set at 90%, the external wall temperature of the first reactor tube is set at 185⁰C, and the external wall temperature of the second reactor tube is set at 190.5⁰C, each of the first sections has a maximum temperature in a range of 199-201⁰C and a maximum temperature of the second catalyst bed is formed in the first of the second sections and is about 201⁰C, and the CO conversion is 79%.

Referring to Fig. 18, another embodiment provides a method 830 for carrying out exothermic catalytic process including: a step 831, in which a first catalyst bed is formed in a first reactor tube of a first reactor, the first catalyst bed having a plurality of sections arranged successively along a flow direction of reactants; a step 833, in which a second catalyst bed is formed in a second reactor tube of a second reactor serially connected to the first reactor and fed with at least a part of effluent from the first reactor as reactants, and a step 835, in which conducting the exothermic catalytic process such that a temperature profile along the first catalyst bed meets a first predetermined criterion and a temperature profile along the second catalyst bed meets a second predetermined criterion.

In one embodiment, the first predetermined criterion may be that a maximum temperature in each of at least two of the plurality of first sections is within a predetermined range from a first predetermined temperature. In one embodiment, the first predetermined criterion may be that a maximum temperature in at least two predetermined first sections is within a predetermined range from a first predetermined temperature.

In one embodiment, the second predetermined criterion may be that a maximum temperature in the second catalyst bed is within a predetermined range from a predetermined temperature.

In one embodiment, the second catalyst bed is formed with a plurality of sections successively arranged along the flow direction of reactants and loaded with catalysts, and the second predetermined criterion may be that a maximum temperature in each of at least two of the plurality of second sections is within a predetermined range from a second predetermined temperature. In one embodiment, the second predetermined criterion may be that a maximum temperature in at least two predetermined second sections is within a predetermined range from a second predetermined temperature.

As well known, there are many catalysts suitable for FT synthesis processes. Catalysts for FT synthesis may be active components either loaded on or not loaded on carriers. Carriers generally are porous materials providing physical support to the catalytically active components, and they may include, for example, boehmite, high temperature resistant oxide (such as, silicon, alumina, titanium oxide, thorium oxide, zirconia, or their combinations), aluminum fluoride and etc. Active components may be Group 8 metals, Group 9 metals, or Group 10 metals, and preferably may be iron, cobalt, nickel, ruthenium or their combinations. FT catalysts may further include one or more promoters, which may be metals from Group 1 to Group 13, including noble metals and boron. Generally, while used as catalysts, these metals are on oxidized or reduced state (such as metal state).

Claims

CLAIMS We claim:

1. A reactor for carrying out an exothermic catalytic process, comprising: a reactor tube; and a catalyst bed disposed in the reactor tube and extending along a flow direction of reactants, the catalyst bed having a plurality of sections successively arranged along the flow direction of reactants, the plurality of sections being configured such that during the exothermic catalytic process, a maximum temperature in each of at least two of the plurality of sections is within a predetermined range from a predetermined temperature.

2. A reactor according to claim 1, wherein each section is loaded with a catalyst having a different activity from a catalyst loaded in an adjacent section.

3. A reactor according to claim 2, wherein the activity of the catalyst loaded in each of the plurality of sections is lower than the activity of the catalyst loaded in a section further along the flow direction of reactants.

4. A reactor according to claim 1, wherein the exothermic catalytic process is carried out under a predetermined feed flow rate and a predetermined composition of the feed; and wherein the plurality of sections are configured based on at least one of the predetermined feed flow rate and the predetermined composition of the feed.

5. A reactor according to claim 1, wherein the exothermic catalytic process is a Fischer-Tropsch process.

6. A method for carrying out an exothermic catalytic process, comprising: forming a catalyst bed in a reactor tube, the catalyst bed having a plurality of sections arranged successively along a flow direction of reactants; and conducting the exothermic catalytic process such that a maximum temperature in each of at least two of the plurality of sections is within a predetermined range from a predetermined temperature during the exothermic catalytic process.

7. A method according to claim 6, wherein forming the catalyst bed comprises calibrating catalytic activities in the sections.

8. A method according to claim 7, wherein calibrating catalytic activities comprises: obtaining a temperature profile along the catalyst bed; comparing the temperature profile with the predetermined temperature using the predetermined range; and adjusting the catalytic activities of the plurality of sections based on the comparison.

9. A method according to claim 7, wherein forming the catalyst bed further comprises calibrating a feed flow rate so as to determine an optimal feed flow rate at which the maximum temperature in each of at least two of the plurality of sections is within the predetermined from the predetermined temperature during the exothermic catalytic process.

10. A computer readable medium storing therein program instructions which when executed by a processor cause the processor to perform a method for configuring an exothermic catalytic process, the method comprising: receiving a catalyst bed configuration specifying a catalyst bed having a plurality of sections along a reactant flow direction in a reactor tube, at least two of the plurality of sections having different catalytic activity values; and calculating a first temperature profile based on the catalyst bed configuration.

11. A computer readable medium according to claim 10, wherein the method further comprises: receiving an adjusted catalyst bed configuration; and calculating a second temperature profile based on the adjusted catalyst bed configuration.

12. A computer readable medium according to claim 11, wherein the adjusted catalyst bed configuration is derived based on a comparison of the first temperature profile with a predetermined temperature using a predetermined temperature range.

13. A computer readable medium according to claim 10, wherein the method further comprises receiving a feed configuration specifying a flow rate and composition of the feed, and wherein the first temperature profile is calculated based on the space velocity value for the first reactant.

14. A computer readable medium according to claim 13, wherein the method further comprises: receiving an adjusted feed configuration; and calculating a second temperature profile based on the adjusted feed configuration.

15. A computer readable medium according to claim 14, wherein the adjusted feed configuration is derived based on a comparison of the first temperature profile with a predetermined temperature using a predetermined temperature range.

16. A method for configuring an exothermic catalytic process, which is carried out in a catalyst bed having a plurality of sections along a flow direction of reactants in a reactor tube, the method comprising: receiving a catalyst bed configuration; calculating a first temperature profile based on the catalyst bed configuration; receiving an adjusted catalyst bed configuration; and calculating a second temperature profile based on the adjusted catalyst bed configuration.

17. A method according to claim 16, wherein the adjusted catalyst bed configuration is derived based on a comparison of the first temperature profile with a predetermined temperature using a predetermined temperature range.

18. A method according to claim 16, further comprising receiving a feed configuration, and wherein the first temperature profile is calculated based on the feed configuration.

19. A method according to claim 17, further comprising receiving an adjusted feed configuration, and wherein the second temperature profile is calculated based on the adjusted feed configuration.

20. A method according to claim 17, wherein the adjusted feed configuration is derived based on a comparison of the first temperature profile with a predetermined temperature using a predetermined temperature range.

21. A method for simulating an exothermic catalytic process carried out in a reactor, wherein the reactor includes a reactor tube and a catalyst bed arranged in the reactor tube, the method comprising: establishing mass conservation equations and energy conservation equations; receiving a catalyst bed configuration, wherein the catalyst bed has a plurality of sections arranged along a feed flow direction, and wherein a catalyst loaded in a section has a different catalytic activity from a catalyst loaded in an adjacent section; solving the mass conservation equations and energy conservation equations for a first section based on catalytic performance of the first section according to the catalyst bed configuration to achieve a temperature profile of the first section; and solving the mass conservation equations and energy conservation equations for a second section based on catalytic performance of the second section, which is the next section of the first section along the feed flow direction to achieve a temperature profile of the second section.

22. A reactor system for carrying out an exothermic catalytic process, comprising: a first reactor comprising: a first reactor tube with an external wall temperature thereof controlled at Tl, and a first catalyst bed disposed in the first reactor tube and extending along a flow direction of reactants, the first catalyst bed having a plurality of first sections successively arranged along the flow direction of reactants, the plurality of first sections being configured such that during the exothermic catalytic process, a maximum temperature in each of at least two of the plurality of first sections is within a first predetermined range from a first predetermined temperature, and a second reactor serially connected to the first reactor to receive at least a part of effluent including reaction results and un-reacted reactants from the first reactor, comprising: a second reactor tube with an external wall temperature thereof controlled at T2, wherein T2 is higher than Tl, and a second catalyst bed disposed in the first reactor tube.

23. A reactor system according to claim 22, wherein each first section is loaded with a catalyst having a different activity from a catalyst loaded in an adjacent first section.

24. A reactor according to claim 23, wherein the activity of the catalyst loaded in each of the plurality of first sections is lower than the activity of the catalyst loaded in a first section further along the flow direction of reactants.

25. A reactor according to claim 22, wherein second catalyst bed has a plurality of second sections successively arranged along a flow direction of reactants in the second catalyst bed, the plurality of second sections being configured such that during the exothermic catalytic process, a maximum temperature in each of at least two of the plurality of second sections is within a second predetermined range from a second predetermined temperature.

26. A reactor system according to claim 25, wherein each second section is loaded with a catalyst having a different activity from a catalyst loaded in an adjacent second section.

27. A reactor according to claim 26, wherein the activity of the catalyst loaded in each of the plurality of second sections is lower than the activity of the catalyst loaded in a second section further along the flow direction of reactants in the second catalyst bed.

28. A reactor according to claim 22, further comprising a first product collecting device arranged between the first and second reactors for collecting a first product from the first reactor.