TW201402205A - A process for use with a catalytic reactor - Google Patents

Abstract

A process for use with a catalytic reactor is specified. The catalytic reactor comprises a catalyst for converting synthesis gas to a product which is liquid or solid at ambient conditions. The catalyst is in the form of solid catalytic bodies without free liquid. Operation of the reactor is stopped by performing a shutting-in procedure. After the shutting-in procedure, operation of the reactor is restarted. The restarting comprises removing products such as hydrocarbons and water from the surface of the catalyst gradually so as to avoid damage to the pore structure of the catalyst by purging the catalyst with a flowing gas that contains a reducing agent, for between 6 and 12 hours, at a temperature at or below the normal operating temperature of the catalyst.

Description

Method of using a catalytic reactor

The present invention relates to a process for using a catalytic reactor, in particular a catalyst comprising a catalyst for converting synthesis gas into a product which is liquid or solid under ambient conditions, such as Fischer-Tropsch synthesis or methanol. synthesis.

The Fischer-Tropsch synthesis process is a well-known method in which synthesis gas (i.e., a combination of hydrogen and carbon monoxide) is reacted in the presence of a suitable catalyst to produce hydrocarbons. This may form the second stage of the process of converting natural gas to liquid or solid hydrocarbons, since natural gas can react with steam or a small amount of oxygen to produce syngas. A range of different types of reactors are known for Fischer-Tropsch synthesis; and a range of different catalysts are suitable for Fischer-Tropsch synthesis. For example, cobalt, iron and nickel are known catalysts which have different properties for the resulting product.

During operation, it may occasionally be necessary to stop the operation of the catalytic reactor, which may be referred to as a shutdown process. It may be shut down regularly or irregularly. For example, this may be necessary for a modular plant where the number of reactors used varies depending on the flow rate of the gas being processed. The closing process involves introducing the gas Into the reactor, the catalytic reaction is stopped without destroying the catalyst. For example, hydrogen is used as a shut-off gas, and gases such as nitrogen and argon are also used as inert gases. When the operation of the reactor is subsequently restarted, it has been found to cause problems, and the performance of the catalyst and the productivity of the reactor will be significantly reduced.

For example, US 6 878 655 describes a process for regenerating a hydrocarbon synthesis catalyst in the form of a slurry, wherein the first stage relates to contacting the catalyst slurry with a dry stripping gas, It is possible to remove water from the catalyst slurry. The stripping process is preferably carried out at a temperature above 200 ° C, such as 230 ° C, but at a lower pressure than that used for Fischer-Tropsch synthesis. Some embodiments also include a second stage of reactivation of the catalyst, for example, using hydrogen at a temperature significantly above the Fischer-Tropsch operating temperature.

According to a first aspect of the invention, there is provided a method of using a catalytic reactor comprising a catalyst for converting synthesis gas to a product which is liquid or solid under ambient conditions, the catalyst The form is a solid-state catalytic object free of free liquid, wherein the operation of the reactor is stopped by performing a shutdown procedure, and the operation of the reactor is restarted after the shutdown process, wherein restarting includes gradually removing hydrocarbons from the catalyst surface A product such as water to avoid damage to the pore structure of the catalyst, which is purged with a flowing gas containing a reducing agent for 6 to 12 hours.

The flowing gas removes vapors of the product from the catalyst surface (such as hydrocarbons and water). Purging will syngas during normal operation of the reactor The temperature at which the product is converted (hereinafter referred to as "normal operating temperature") is performed at or below the temperature. Purging can be carried out at temperatures well below normal operating temperatures, for example at ambient temperatures.

This method may require reducing the pressure below 0.2 MPa (2 bar) (absolute pressure). The method may further include heating the catalyst to a high temperature unless the catalyst has been at or above this high temperature, the high temperature being lower than the normal operating temperature of the catalyst not exceeding 35 K, and the heating rate being less than 20 K/hour; The catalyst is purged with a flowing gas containing a reducing agent, which is carried out at elevated temperature for 6 to 12 hours. Purging can also be carried out during the heating process.

After performing this procedure, the catalyst can be returned to normal operating conditions by contacting the catalyst with syngas, increasing the pressure to normal operating pressure, and increasing the temperature to the normal operating temperature.

The catalyst is in the form of a solid catalytic material that does not contain a free liquid, that is, the catalytic object is not immersed or suspended in the liquid. In operation, a liquid film may be formed on the surface of the catalytic object, the liquid system being composed of the product of the synthesis reaction, but with a continuous flow path of the reactant gas through the catalytic object.

The depressurization step may require reducing the pressure below 0.5 MPa (5 bar), or below 0.2 MPa (2 bar), and possibly 0.1 MPa (1 bar). Low pressure increases the rate of evaporation of any liquid or solid on the surface of the catalyst.

The purging step can be carried out for a long time. For example, each purge step may last for at least 4 hours, for example, each step may last for 8 hours. In other words, the flowing gas or the purge gas may be syngas, or nitrogen/ The hydrogen mixture, and preferably the dry gas, does not contain significant concentrations of moisture.

Heating to a high temperature must be carried out slowly. It must be no more than 20 K/hour and can be significantly slower, such as 10 K/hour, 5K/hour or 3 K/hour. This slow temperature rise prevents rapid evaporation of any liquid (such as water) on the catalyst surface.

The high temperature can be higher, for example less than 20 K below normal operating temperature; but usually at least 10 K below normal operating temperature.

The purge gas may comprise less than 10% of a reducing agent in combination with at least one inert gas component. The purge gas may comprise 5% hydrogen combined with at least one inert gas component.

The restart may also include changing the composition of the flushing gas from an initial composition to a final composition equivalent to syngas for at least one hour. The temperature in this step may be the normal operating temperature of the catalyst, and the pressure may be the normal operating pressure.

According to a second aspect of the present invention, there is provided a catalytic reactor comprising: a catalyst for converting synthesis gas into a product which is liquid or solid under ambient conditions, the catalyst being in the form of a free-liquid solid-state catalytic object; and at least one controller capable of stopping the operation of the reactor by performing a shutdown procedure, and restarting the operation of the reactor after the shutdown procedure, wherein restarting includes gradually from the surface of the catalyst Removal of products such as hydrocarbons and water to avoid damage to the pore structure of the catalyst, which is carried out at a normal operating temperature of the catalyst or at a lower temperature than the lower temperature of the catalyst, with a flowing gas containing a reducing agent. 6 to 12 hours.

The at least one controller is operative to perform any one or more of the method steps described above.

According to a third aspect of the present invention, there is provided a catalytic reactor for converting synthesis gas into a product which is liquid or solid under ambient conditions, the reactor comprising: a structure designed to hold a solid catalytic object, Having a continuous flow path for passing the reactant gas through the catalytic object; and a controller operable to temporarily stop the conversion of the syngas into a product and subsequently purge the solid catalytic object 6 to 12 with a flowing gas containing a reducing agent In hours, it is carried out at a temperature at which the synthesis gas is converted into a product or a temperature lower than that, and the hydrocarbon and water are removed from the surface of the solid catalytic object without breaking the pore structure of the solid catalytic object.

This processing method not only avoids the degradation of catalyst performance that may occur separately, but surprisingly, the processing method has also been found to improve the performance of the catalyst. In one embodiment, when the treatment process is applied to a Fischer-Tropsch catalyst, it has been found that C5+ hydrocarbon productivity can be increased by at least 40%.

In order to inhibit the catalytic reaction, or in other words, in order to temporarily stop the conversion of the synthesis gas into a product, the shutdown procedure of the reactor may be periodic or irregular. The reactor is then returned to operation by restarting the supply of the reactant gas stream. It has been found that the process of the invention improves the performance of the catalyst when the catalytic reaction is restarted.

The purge gas may comprise, for example, off-gas from a Fischer-Tropsch synthesis reaction, which may be treated to remove at least some of the constituents if desired. It is to be recognized that such exhaust gas contains not only hydrogen And carbon monoxide, which also contains other components such as carbon dioxide, ethane and methane, which are inert under these conditions.

The invention will now be further and more specifically described by way of example only.

The invention is particularly applicable to the treatment of catalysts in small catalytic reactors, wherein each reactor is comprised of stacked plates that define a composite flow channel and a coolant flow channel that are alternately arranged in a stack. In each of the reactors, the first and second flow passages may be defined by a sheet of metal that is toothed and alternately stacked with the plates; the edges of the flow passage may be defined by a sealing strip. The stack is then joined together. Alternatively, the flow channels may be defined by spacer strips and stacked plates, or by grooves configured in stacked plates, and then stacked together. The stack of plates forming the reactor is joined together by, for example, diffusion bonding, brazing, or heat equalization.

In such a small catalytic reactor, the size of the first and second flow channels can be between 10 mm and 2 mm high (section) and the width of each channel is between about 3 mm and 25 mm. A good thermal contact between the syngas reaction and the coolant stream is achieved. For example, the possible width of the slab (in plan view) is in the range of 0.05 meters up to 1 meter, and the length is in the range of 0.2 meters up to 2 meters, and the preferred height of the flow channel is Between 1 mm and 20 mm. For example, the panels may be 0.5 meters wide and 0.8 meters long; and they may define channels such as 7 mm high and 6 mm wide, or 3 mm high and 10 mm wide, or 10 mm high, 5 mm wide. Catalyst structure is inserted for The channels of the synthesis reaction, and, if desired, can be removed and replaced, and the reactor strength is not provided, so the reactor itself must have sufficient strength to withstand any pressure or thermal stress during operation. In many cases, there may be two or more catalyst structures in the channel that are configured in an end-to-end configuration.

Each such catalyst structure is preferably shaped to subdivide the flow channel into a plurality of parallel flow secondary channels. Each of the catalyst structures preferably comprises a coating of a ceramic support material on a metal substrate that provides a carrier for the catalyst. The ceramic carrier is preferably in the form of a coating on a metal substrate, for example a coating having a thickness of 100 microns on each metal surface. The metal substrate provides catalyst structural strength and enhances heat transfer by thermal conduction. The metal substrate is preferably a steel alloy which forms an alumina adhesion surface coating upon heating, such as a fermented grain steel doped with aluminum (e.g., Fecralloy (TM)), but other materials may also be suitable, such as stainless steel. The substrate may be a foil, a wire mesh or a mat, which may be in the form of a corrugated, braided or pleated shape. The preferred substrate is a thin metal foil, for example having a thickness of less than 200 microns, which is undulated to define Longitudinal secondary channel. The catalytic element may be, for example, a foil comprising a single shape, for example a corrugated foil having a thickness of 50 microns; this would be particularly suitable if the minimum dimension of the channel is less than about 3 mm, but it can also be applied to larger channels. . Alternatively, and particularly where the channel depth or width is greater than about 2 mm, the catalyst structure can include a plurality of foils of such shape that are substantially separated by a flat foil. The active catalytic material will be incorporated into the ceramic coating.

The present invention relates to chemical equipment for converting natural gas (mainly methane) into a growing chain hydrocarbon. The first stage of the process is the production of syngas, and preferably with respect to steam recombination, which means the following reaction: H ₂ O+CH ₄ → CO+3H ₂

This reaction is an endothermic reaction and can be catalyzed by rhodium or platinum/ruthenium catalyst in the first gas flow path. The heat required to initiate this reaction can be provided by burning a fuel gas such as methane, or another short chain hydrocarbon such as ethane, propane, butane, carbon monoxide, hydrogen, or a mixture of such gases. It is an exothermic reaction and can be catalyzed by a palladium/platinum catalyst in an adjacent second gas flow channel. Alternatively, the synthesis gas can be produced by a partial oxidation process or an autothermal process, which are known methods; these processes can produce synthesis gases having slightly different compositions.

The synthesis gas mixture is then used for Fischer-Tropsch synthesis to produce long chain hydrocarbons, namely: nCO + 2nH ₂ → (CH ₂ ) _n + nH ₂ O

This is an exothermic reaction in the presence of a catalyst (such as iron, cobalt or molten magnetite), typically between 190 ° C and 280 ° C and typically between 1.8 MPa and 2.8 MPa. (Absolute value) occurs under high pressure. Preferred catalysts for Fischer-Tropsch synthesis include a gamma-alumina coating having a specific surface area of from 140 to 230 square meters per gram, having about 10-40% cobalt (compared to the weight of alumina). And a catalyst promoter such as ruthenium, platinum or rhodium, which weighs less than 10% by weight of the cobalt, and a basic catalyst promoter such as ruthenium oxide. Other suitable ceramic support materials are titanium oxide, zirconium oxide, or hafnium oxide. Preferred reaction conditions are temperatures between 200 ° C and 240 ° C and pressures ranging from 1.5 MPa up to 4.0 MPa, such as from 2.1 MPa up to 2.7 MPa, such as 2.6 MPa.

Although the described system is related to Fischer-Tropsch synthesis The method of the present invention can also be applied to a reactor in which methanol is produced, for example, from synthesis gas.

As previously described, the reaction channel contains a catalyst in the form of a solid catalytic material free of free liquid. For example, the object can include a coating of a ceramic carrier material on a corrugated metal foil substrate that provides a carrier for the catalytic material. Catalytic objects are located within the flow channels and reactant gases flow through the flow channels. The result of the reaction may be a thin film of liquid on the surface of the catalytic object, but the catalytic object is not immersed or suspended in the liquid and has a continuous flow path for the reactant gas to pass through the catalytic object.

It is important that the characteristics of the catalyst do not adversely affect during shutdown. The shut-off gas may comprise an inert gas such as argon or nitrogen and may comprise a reducing agent such as hydrogen or carbon monoxide. This reduces the risk of catalyst oxidation. However, it has been found that the capacity of the reactor will drop after the shutdown process.

The apparatus for performing Fischer-Tropsch synthesis may comprise a plurality of parallel operated Fischer-Tropsch synthesis reactors, each of which is provided with a shut-off valve to cut off its connection to the apparatus. Reactors that are cut off in this manner are typically flushed with an inert gas or with a shut-off gas to inhibit further reactions.

The shut-off gas can be the off-gas from the Fischer-Tropsch synthesis reaction, which can be treated to remove some of the constituents if desired. In particular, it may be advantageous to treat such exhaust gases to reduce the concentration of water vapor. The purge step of the catalyst treatment method can use the same gas as the shut-off gas.

It should be understood that at least one controller may be provided to fully or partially control one or more aspects of the reactor operation, such as the feed rate of various different gases or their composition.

Example 1

In the first embodiment, the normal operating conditions of a small catalytic Fischer-Tropsch reactor at a pressure of 2.6 MPa (26 bar) (absolute) are 220 °C. It was shut down using nitrogen with 5% hydrogen and the reactor was allowed to cool to room temperature. The subsequent processing is as follows.

The pressure in the reactor was then lowered to atmospheric pressure (0.1 MPa) and the reactor was purged with dry nitrogen containing 5% hydrogen for 8 hours at room temperature (between 15 and 25 °C). Then, while continuing to purge, it was gradually heated to 190 ° C at a rate of only 3 K/hr (i.e., 0.05 K/min) for more than 56 hours. The reactor was then purged with dry nitrogen containing 5% hydrogen for 8 hours at this high temperature of 190 °C.

After this purge method, the gas mixture was changed back to syngas, the pressure rose to a normal operating pressure of 2.6 MPa, and the temperature gradually rose back to the normal operating temperature. This may be done in a continuous rate-reducing manner, for example 6K/hour in the range of 190 ° C up to 212 ° C, then 1 K / h in the range of 212 ° C up to 217 ° C, then up to 217 ° C up to It is 0.2 K/hr in the range of 220 °C.

In this example, the reactor productivity of C5+ hydrocarbons (i.e., hydrocarbons having at least 5 carbon atoms) was 0.68 g/(gram catalyst ‧ hours). After the above shutdown and treatment, C5+ productivity was found to have increased to 0.95 g / (gram of catalyst ‧ hours). After the second closure and treatment described above, C5+ productivity has been found to have increased to 1.0 g / (gram Media ‧ hours). The third closure and processing did not change productivity.

Example 2

In a second example, the normal operating conditions of a small catalytic Fischer-Tropsch reactor at a pressure of 2.6 MPa (26 bar) (absolute) are 225 °C. It was shut down using nitrogen with 5% hydrogen and the reactor was allowed to cool to room temperature. The subsequent processing is as follows.

The pressure in the reactor was then lowered to atmospheric pressure (0.1 MPa) and the reactor was purged with dry nitrogen containing 5% hydrogen for 8 hours at room temperature (between 15 and 25 °C). Then, while continuing to purge, it was gradually heated to 190 ° C at a rate of only 3 K/hr (i.e., 0.05 K/min) for more than 56 hours. The reactor was then purged with dry nitrogen containing 5% hydrogen for 8 hours at this high temperature of 190 °C.

After this purge method, the gas mixture was changed back to syngas, the pressure rose to a normal operating pressure of 2.6 MPa, and the temperature gradually rose back to the normal operating temperature. It is carried out in a continuous rate-reducing manner, 6K/hour in the range of 190 ° C up to 215 ° C, then 1 K / h in the range of 215 ° C up to 222 ° C, then 222 ° C up to 225 ° C The range is 0.2K/hour.

In this example, the reactor productivity of the C5+ hydrocarbons was 0.51 g/(gram of catalyst ‧ hours). After the above shutdown and treatment, C5+ productivity was found to have increased to 0.85 g / (gram of catalyst ‧ hours).

Example 3

In a third example, the normal operating conditions of a small catalytic Fischer-Tropsch reactor at a pressure of 2.6 MPa (26 bar) (absolute) are 225 °C. It uses nitrogen with 5% hydrogen It was closed and the reactor was cooled to 195 °C. The subsequent processing is as follows.

The pressure inside the reactor was lowered to atmospheric pressure (0.1 MPa), and the reactor was purged with dry nitrogen containing 5% hydrogen at 195 ° C for 12 hours. This temperature is higher than the high temperature of the previous embodiment, and the step of gradual heating is not required.

After this purge method, the gas mixture was changed back to syngas, the pressure rose to a normal operating pressure of 2.6 MPa, and the temperature gradually rose back to the normal operating temperature. It can again be carried out in a continuous rate-reducing manner, 4 K/hr in the range of 195 ° C up to 215 ° C, then 1.5 K / h in the range of 215 ° C up to 221 ° C, then up to 221 ° C up to It is 0.3 K/hr in the range of 225 °C.

It is believed that in the shutdown procedure of such a Fischer-Tropsch reactor, the pores of the catalyst are at least partially filled with water and/or liquid or solid hydrocarbons, both of which are formed by a Fischer-Tropsch reaction. Long-term purging at initial temperatures and elevated temperatures promotes evaporation of this material from the pores, and slowly rising to high temperatures avoids any rapid phase changes that cause damage to the catalyst structure.

It is also to be understood that the purge method of the present invention can result in an increase in catalyst performance. It will be appreciated that no additional activation or regeneration of the catalyst is required.

Example 4

In a fourth example, the normal operating conditions of a small catalytic Fischer-Tropsch reactor at a pressure of 2.6 MPa (26 bar) (absolute) are 220 °C. The normal gas stream was syngas (1.9:1 H ₂ :CO) containing 12.7% nitrogen. The reactor was shut down at a normal operating temperature of 220 ° C by stopping the flow of gas. After the synthesis gas was shut down for 10 minutes, the subsequent treatment was as follows: the pressure and temperature in the reactor were maintained under normal operating conditions (2.6 MPa and 220 °C), and at a normal nitrogen feed rate, substantially Pure dry nitrogen was used to purge the reactor for 5 minutes.

The nitrogen feed rate is then increased (eg, doubled) and then introduced to the syngas at a small step, such as adding 2% of the normal feed rate to the additional feed every 3 to 10 minutes while slowly reducing the nitrogen feed rate to normal Nitrogen feed rate target. The process from stopping the feed to the reactor to achieve a normal or target syngas feed rate lasted for 7 hours.

In this example, the reactor productivity of the C5+ hydrocarbons was 0.42 g/(gram of catalyst ‧ hours). After the above shutdown and treatment, C5+ productivity was found to have increased to 0.65 g / (gram of catalyst ‧ hours).

It is believed that the reason for the performance improvement is as follows: initially introducing a syngas at a significantly lower flow rate, for example 2 to 25% of the normal flow rate, such that complete conversion of CO, which will increase the hydrogen concentration on the catalyst or is beneficial The catalyst is reduced in the syngas. This is believed to be beneficial for the reduction of partial cobalt oxide, the removal of liquid products and carbonaceous impurities and other impurities from the catalyst, or the selective removal of cobalt carbide (which has been identified in the used catalysts, and is known The catalyst is deactivated to form more active metal Co with hexagonal closest packed structure (hcp). In this mode, it is expected that the formation of methane and gaseous products on the catalyst will be significantly higher than the formation of liquid products, which is advantageous during normal operation. This will help the catalyst to be restored.

Example 5

In a fifth embodiment, a small catalytic Fischer-Tropsch reactor containing catalyst pellets has a normal operating condition of 235 ° C at a pressure of 2.6 MPa (26 bar) (absolute) and a CO conversion of about 56%. . CO stop feeding about 10-12 hours to the reactor, at the same time, at the same temperature and pressure, and the normal H ₂ N ₂ gas stream fed continuously to the reactor. Attempting to reintroduce normal CO gas flow under normal operating conditions (235 ° C, 26 bar) will result in an uncontrolled loss of temperature which will cause the reactor to trip. An alternative and more satisfactory way to reintroduce CO is as follows: Under normal operating conditions (235 ° C, 26 bar), the CO is reintroduced in a phased manner. For example, a 50% normal CO gas stream is first added and maintained for 30 minutes to ensure that all internal temperatures are approximately constant. The CO gas stream is then increased to 75% of the normal CO gas stream, then increased to 87.5%, and then the CO gas stream is increased to the normal CO gas stream target for 20 minutes between each increase.

In this example, the reactor productivity per unit channel volume of C5+ hydrocarbons was 231 g/l ‧ hours and the conversion was 56%. After the above treatment, C5+ productivity and CO conversion were found to have increased to 279 g/l ‧ hours and 69%, respectively.

It is believed that this performance increase is related to the hydrogen treatment of the catalyst during 10 to 12 hours, during which no CO flows into the reactor, and/or based on the reasons described in the previous Example 4.

Although the method of the invention previously described is directed to a method of a Fischer-Tropsch reactor, it should be understood that it is equally It is used in many different reactors, such as reactors that form methanol. Reactors in which the catalyst is supported on a corrugated metal foil have been described in some embodiments, but it is equally applicable to reactors in which the catalyst is coated on the walls of the channels, as well as in granular bed reactors suitable for fluidization. .

Claims (17)

A method of using a catalytic reactor comprising a catalyst for converting synthesis gas into a liquid or solid product under ambient conditions in the form of solid state catalysis free of free liquid An object wherein the operation of the reactor is stopped by performing a shutdown procedure and the operation of the reactor is restarted after the shutdown procedure, wherein restarting includes gradually removing products such as hydrocarbons and water from the surface of the catalyst to avoid damage The pore structure of the catalyst is at a temperature below or below the normal operating temperature of the catalyst, and the catalyst is purged with a flowing gas containing a reducing agent for 6 to 12 hours. The method of claim 1, wherein the pressure of the flowing gas is less than 0.2 MPa. The method of claim 1 or 2, wherein the temperature is a high temperature which is lower than a normal operating temperature of the catalyst of not more than 35 K. The method of claim 1 or 2, further comprising heating the catalyst to a high temperature which is lower than a normal operating temperature of the catalyst of not more than 35 K, and the heating rate is less than 20 K/hr. A method of claim 4, which comprises the subsequent step of purging the catalyst with a flowing gas containing a reducing agent, which is carried out at the elevated temperature for 6 to 12 hours. The method of claim 4, wherein the rate of heating to a high temperature does not exceed 3 K/hour. The method of claim 2, or the method of any one of claims 4 to 6, wherein the high temperature is less than 20 K below the normal operating temperature. The method of claim 7, wherein the high temperature is at least 10 K below the normal operating temperature. The method of any of the preceding claims, wherein the flowing gas comprises less than 10% of a reducing agent in combination with at least one inert gas component. The method of claim 9, wherein the flowing gas comprises 5% hydrogen, which is combined with at least one inert gas component. The method of claim 9, wherein the flowing gas system is obtained from exhaust gas generated during operation of the reactor. The method of claim 1, wherein the restarting comprises changing the composition of the flowing gas from an initial composition to a subsequent step corresponding to the final composition of the syngas for at least one hour. The method of claim 12, wherein the temperature during the subsequent step is the normal operating temperature of the catalyst and the pressure is the normal operating pressure. The method of any one of the preceding claims, wherein the catalyst is exposed by exposing the catalyst to syngas, raising the pressure to a normal operating pressure, and raising the temperature to a normal operating temperature. Returns to normal operating conditions. Substantially as previously described, reference is made to any of the embodiments. A catalytic reactor comprising: a catalyst for converting synthesis gas into a product that is liquid or solid under ambient conditions, the catalyst being in the form of a solid catalytic material free of free liquid; and at least one a controller capable of stopping the operation of the reactor by performing a shutdown procedure, and, in closing After the procedure, the operation of the reactor is restarted, wherein restarting includes gradually removing products such as hydrocarbons and water from the surface of the catalyst to avoid damaging the pore structure of the catalyst, which is at or above the normal operating temperature of the catalyst. At a low temperature, the catalyst is purged with a flowing gas containing a reducing agent for 6 to 12 hours. The catalytic reactor of claim 16, wherein the at least one controller is operable to perform the method of any one of claims 2 to 14.