Indirectly heated moving-bed reactor

Abstract

A reactor for carrying out an endothermic reaction, in particular a high-temperature reaction, in which a product gas is obtained from a feed gas, is provided. The reactor is configured to provide a passage for downward flow of particles as a dense bed under gravity flow, the passage comprising a reaction zone. Moreover, the reactor is configured to heat the particles in the reaction zone; and to guide the feed gas into the passage from below and upwardly through the reaction zone. The passage has one of the following configurations A) or B): A) the passage comprises a plurality of vertical tubes and heating means arranged outside the vertical tubes for heating a section of each tube, which heated section houses the reaction zone; B) the passage is comprised of a continuous reactor inner volume, wherein heating means extend into the continuous reactor inner volume for heating a region of the reactor inner volume, which heated region defines the reaction zone, and the particles flow downwardly along outer surfaces of the heating means, and the outer surfaces of the heating means have a roughness Rz of lower than 1 mm. Further provided is a method for carrying out an endothermic reaction, in particular a high-temperature reaction, for obtaining a product gas from a feed gas in such a reactor. The reactor allows for continuous operation of methane pyrolysis.

Description

[0001] Indirectly Heated Moving-Bed Reactor

[0002] The present invention relates to a reactor and method for carrying out an endothermic reaction, in particular a high-temperature reaction.

[0003] The moving-bed reactor concept has proven to be a suitable apparatus for methane pyrolysis and for other endothermic high-temperature reactions such as hydrocarbon cracking or hydrocarbon dry reforming. These processes require heat supply at a temperature level of up to 1400 °C. A possible solution for providing thermal energy to the reaction is direct electric heating, whereby the moving bed comprises electrically conductive particles and two electrodes are immersed in the packing of the moving bed. The resistance of the discrete yet interconnecting electrically conductive particles to electrical current results in the particles being heated.

[0004] Directly electrically heated moving bed reactors, while representing a great improvement over the previous methods used in the art, still suffer from serious operational problems. A disadvantage is the influence of the conversion and the geometry of the reaction path on the electrical resistance of the moving bed. Accordingly, the control of the heat supply in the moving bed is a complex issue. In addition, the choice of the carrier particles is limited to electrically conductive materials. Finally, the requirement of galvanic insulation between the reaction chamber and the pressure-bearing jacket or the periphery of the reactor complicates the feeding of particles to and removal of particles from the reactor.

[0005] US 2022 / 0152568 discloses a reactor for carrying out an endothermic reaction in which a product gas is obtained from a feed gas, wherein the reactor is configured to provide a gravity-driven moving bed in a reaction zone, which moving bed comprises a large number of solid material particles. The reactor is configured to guide the feed gas into the reaction zone, wherein, in order to heat the feed gas, the reactor is configured to heat the solid material particles in the reaction zone by generating an electric current in the solid material particles.

[0006] Indirect heating by, e.g., heating elements embedded in the reaction section has been considered inadequate, due to the risk that carbon deposition on the heat exchanger surface would deteriorate heat conduction and thus impair the heat supply. In addition, internals in the reaction chamber would hinder the flow of solid particles and create stagnation zones. As a result, the cohesive nature of the deposited material may give rise to formation of agglomerates that may completely block the cross section of the reaction chamber.

[0007] The problem of coke depositions on indirectly heated surfaces has been reported in literature. For example, coke deposits on the wall of cracker coils cause serious problems to the operation of steam crackers, see Jakobi, D., & Gommans, R. (2003), “Typical failures in pyrolysis coils for ethylene cracking”, Materials and Corrosion, 54(11), p. 881- 887). In steam crackers, hydrocarbons such as ethane, propane or naphtha are cleaved into unsaturated compounds. To this end, a process stream is passed through coils of pipes suspended in a furnace chamber, which is heated by burners. Despite steamcracking being a long-established technique, the formation of coke deposits is still an unsolved issue. Coke deposits form on the wall of the cracker coils during the cracking process and can form thick, solid layers. As the coke layer grows, heat transport is hindered and the tube walls tend to overheat. For this reason, the cracker coils must be regenerated at regular intervals. Regeneration is carried out by burning off the coke deposits in an oxygenated gas stream. Care must be taken to avoid overheating and destruction of the cracker coils.

[0008] In addition, the fouling of internals in fluidized bed cokers has been reported, where high- boiling petroleum fractions are converted into petroleum coke and light hydrocarbons. For example, in the Exxon- Flexicoke process, massive coke deposits can form in the reactors and reheaters, which spoil the thermal management of the process or the distribution of the fluidization gas, see Rooijmans, A., “Flexicoking at Esso Rotterdam”, Lecture at Til Delft, October 06, 2003. As a result, a massive coke layer may form, which can only be removed by shutting down the system and breaking off the coke layers. However, this often causes severe damage to the structure of the apparatuses.

[0009] On the basis of these experiences, there is a widespread prejudice among persons skilled in the art that solid-forming reactions, especially carbon-forming reactions, cannot be carried out continuously in indirectly heated reactors.

[0010] WO 2021 / 130107 A1 discloses an electrically heated reactor wherein the reactor is a tube surrounded by electrical heating means. The electrical heating means is positioned at a certain distance and the electrical heating means comprises radiative sheeting.

[0011] WO 2022 / 074212 A1 relates to a reactor shell for producing olefins via steam cracking from a reactive mixture stream composed of steam and hydrocarbons. The reactor shell has a coated structured ceramic bed with electrical resistance heating elements.

[0012] The invention relates to a reactor for carrying out an endothermic reaction, in particular a high-temperature reaction, in which a product gas is obtained from a feed gas; wherein the reactor is configured to provide a passage for downward flow of particles as a dense bed under gravity flow, the passage comprising a reaction zone; the reactor is configured to indirectly heat the particles in the reaction zone; and the reactor is configured to guide the feed gas into the passage from below and upwardly through the reaction zone; wherein the passage has one of the following configurations A) or B):

[0013] A) the passage comprises a plurality of vertical tubes and heating means arranged outside the vertical tubes for heating a section of each tube, which heated section houses the reaction zone;

[0014] B) the passage is comprised of a continuous reactor inner volume, wherein heating means extend into the continuous reactor inner volume for heating a region of the reactor inner volume, which heated region defines the reaction zone, configured such that the particles flow downwardly along outer surfaces of the heating means, and the outer surfaces of the heating means have a roughness Rz, defined according to DIN EN ISO 21920, of lower than 1 mm.

[0015] Surprisingly, continuous operation of chemical conversions such as methane pyrolysis has been found to be feasible in an indirectly heated tubular reactor with a bed of particles moving along a vertical axis. Without wishing to be bound by theory, it is presumed that the motion of the particles along the wall scrapes off the carbon deposited thereon, resulting in only a thin carbon layer remaining instead of a continually growing layer which ultimately leads to blocking of the reactor, as previously reported. This thin layer does not affect the diathermy of the wall, and is smooth, which favors the sliding of the moving bed along the wall.

[0016] Different concepts can be used to heat the reaction zone. These concepts are characterized by the heat source and by the heat transfer mechanism from the heat source to the heat-transferring surfaces of the reaction chamber. The heat source can be combustion heating or electric heating.

[0017] Preferably, the heating means envisaged in the present invention are electrical heating means. The use of electric energy as a heat source instead of heating by combustion of natural gas allows considerable advantages, in particular with regard to the ease of control. The use of electricity offers opportunities for the use of compact, modular, high performance and energy efficient reactors. When the electricity comes from a non-fossil resource, the allothermic reaction can be implemented without net emission of carbon dioxide. The heating energy can be generated directly in the heat-transferring surfaces or in separate heating elements. Heat transport to the thermally permeable wall of the reaction chamber can be achieved by radiation and / or by conduction and / or by convection. In convective heating, gaseous heat carriers, such as flue gases, or liquid heat carriers, such as molten metals or molten salts, can be used.

[0018] The reactor is preferably a vertical elongated reactor.

[0019] The present invention is embodied in two configurations. According to configuration A, the reaction volume is divided into a plurality of vertical tubes, that form a multi-tubular reactor. Preferably, the inner walls of the tubes are smooth tube to favor the solids flow and ensure a uniform flow distribution over the tube cross section. Heating means are arranged outside the vertical tubes for heating a section of each tube, which heated section houses the reaction zone. Preferably, the heating means are electrical heating means. The electrical heating means may be selected from resistance heating and induction heating. For induction heating, the tubes may be surrounded by an induction coil energizable by a power source capable of supplying alternating current.

[0020] Preferably, the heating means comprises resistive heating elements. Such a heating element converts electricity into heat through the process of Joule heating. Electric current through the element encounters resistance, resulting in heating of the element. Heating elements can take the shape of a wire, ribbon, sheet or strip and can be straight, meandering or coiled. The heating means preferably comprise electrical heating jackets surrounding a section of each tube.

[0021] Alternatively, heating elements are installed in a common, heated chamber.

[0022] The vertical tubes are typically configured such that the particles flow downwardly along the inner surfaces of the tubes. This means that the particles flow downwardly in direct contact with the inner surfaces of the tubes. In order to minimize friction between the moving particles and the tubes, the inner surfaces of the tubes are preferably substantially smooth. Thus, the roughness Rz of the inner surfaces of the tubes is lower than 1 mm, preferably lower than 0.5 mm and particularly lower than 0.2 mm, wherein the roughness Rz is defined according to DIN EN ISO 21920.

[0023] The tubes may be made of a physically strong, non-corrosive material, for example a metal such as molybdenum.

[0024] The reactor has a feed gas inlet via which the feed gas can be distributed and introduced in the vertical tubes from below. To this end, the feed gas may be introduced underneath a tube sheet to which the lower ends of the vertical tubes are tightly attached in a gastight manner, for example via a clamping ring seal.

[0025] The reactor according to configuration A has the following advantages:

[0026] 1. The heating power and its spatial distribution are adjustable without interference by the reaction conditions.

[0027] 2. The particles may consist of both electrically conductive or non-conductive materials.

[0028] 3. The tube wall can be made of both electrically conductive and non-conductive materials.

[0029] 4. There is no requirement for a galvanic insulation between the reaction chamber and the reactor housing, or the reactor periphery.

[0030] 5. The ohmic resistance of the heating means can be specifically adjusted, in particular a high ohmic resistance can be realized. Furthermore, the resistance of the heating section can be adjusted by serial connection of the heating elements. This facilitates the contacting of the heater.

[0031] 6. The power density can be specifically adjusted along the reaction section, either by varying the specific resistance along the heating section or by arranging independently controllable heating segments along the heating section.

[0032] 7. Replicative scale up ensures scale transfer. A single tube has already a technically relevant production capacity. A world-scale system can be realized with a few hundred tubes. 8. Unlike in a conventional shaft reactor, the walls of the reaction tubes are tight. As a result, the gas flow and its distribution over the cross-section in the reaction tube is well defined.

[0033] According to configuration B, the passage is formed by a continuous reactor inner volume. Heating means extend into the continuous reactor inner volume for heating a region of the reactor inner volume, which heated region defines the reaction zone. Generally, the heating means are designed and arranged in such a way that the downward flow of particles is essentially not obstructed.

[0034] In order to avoid stagnation of the particle flow or accumulation of particles at upward facing surfaces of the heating means (which upward facing surfaces are located below the fill level of particles in the reactor inner volume), for example protrusions or shoulders thereof, any upward facing surface of the heating means should be suitably sloped. Suitably, the slope angle is larger than the wall friction angle. The wall friction angle represents the angle to which a wall surface must be inclined to cause the particles to slip. It is a function of the particles and the wall surface.

[0035] Hence in an embodiment, the angle between a normal to the surface at each point of an upward facing surface and the upwards directed vertical vector is equal to or larger than the wall friction angle. In most instances, the angle between a normal to the surface at each point of the surface and the upwards directed vertical vector is in the range of 60° to 90°, preferably 75° to 90°.

[0036] Preferably, the heating elements have essentially vertical lateral heat exchange surfaces. The term “essentially vertical” is intended to mean that a normal to the lateral surface includes an angle of 90° ± 15°, with the vertical line. In particular, the lateral heat exchange surfaces are oriented vertically.

[0037] The heating means are configured such that the particles flow downwardly along outer surfaces of the heating means. This means that the particles flow downwardly in direct contact with the outer surfaces of the heating means. In order to minimize friction between the moving particles and the heating means, the outer surfaces, in particular the outer surfaces of the lateral walls, of the heating means are substantially smooth. Thus, the roughness Rz of the outer surfaces, in particular the outer surfaces of the lateral walls, of the heating means is lower than 1 mm, preferably lower than 0.5 mm and particularly lower than 0.2 mm, wherein the roughness Rz is defined according to DIN EN ISO 21920.

[0038] Suitably, the heating means are spaced apart from each other and the side wall of the reactor inner volume.

[0039] The heating means achieve indirect heating. Indirect heating is understood to mean the transfer of heat from the heating means to the particles using conduction, radiation or convection. In an embodiment, the heating means comprise electrical heating cartridges. Several heating cartridges may be distributed over the cross-section of the reactor inner volume. Preferably, the heating cartridges are evenly spaced within the reactor inner volume.

[0040] The lateral wall of the heating cartridge can be cylindrical or polygonal. In order to improve heat exchange with the flow of particles, the heating cartridges may comprise heat exchange fins.

[0041] The heating cartridges may be suspended from above the particles feed to the reactor inner volume. Alternatively, the heating means comprise heating elements that may be completely immersed into the continuous reactor inner volume and may be held, e.g., by protrusions from the reactor shell. To minimize the resistance to the downward flow of particles, the immersed heating elements may have a leading edge, i.e., an edge that faces the flow of particles, behind which the elements widen in a wedge shape, such as heating elements having a lentil-shaped cross-section.

[0042] In another embodiment, the heating means comprise vertically arranged electrical heating sheets or flat heating elements, preferably vertically arranged electrical heating sheets. In an embodiment, the heating sheets are circularly curved and arranged coaxially with respect to a central axis of the reactor inner volume. This forms annular gaps through which the particles can flow downwardly. The sheet-shaped heating elements preferably comprise a heater strip arranged in a meandering pattern.

[0043] As heating means extend into the continuous reactor inner volume, the heat transport between the heating elements and the reaction volume is intensified. This concept could be particularly suitable for processes with high power density.

[0044] The reactor has a feed gas inlet via which the feed gas can be introduced to the bottom of the reactor inner volume.

[0045] Generally, a refractory lining thermally insulates the moving particles from the reactor shell. Typically, refractory bricks advantageously comprising aluminum oxide, zirconium oxide and mixed oxides of aluminum, magnesium, chromium, silicon are used for the refractory lining.

[0046] The reactor includes an outer pressure jacket. For ease of assembly and disassembly, the pressure jacket is preferably split in sections with flanged ends that may be secured by bolts or the like to the flange of an adjacent section of the pressure jacket or the flange of the terminal hoods of the reactor.

[0047] In order to optimize heat integration achieved by the counterflow of solid particles and gas, the passage preferably comprises a first heat integration zone for transferring heat from the product gas leaving the reaction zone to the particles which are to be guided into the reaction zone, and a second heat integration zone for transferring heat from particles leaving the reaction zone to the feed gas. Generally, the first heat integration zone is located above the reaction zone and immediately adjacent to the reaction zone; while the second heat integration zone is located underneath the reaction zone and immediately adjacent to the reaction zone. There is an uninterrupted particle flow through the first heat integration zone, the reaction zone and the second heat integration zone. In most cases there is no clear border between the reaction zone and the adjacent heat integration zones.

[0048] Heat exchange in the heat integration zones can be optimized by varying the downward flow velocity of the particles and / or the flow rate of the feed gas to the reactor. As the heat capacities of the product gas and the particles entering the reactor may not match exactly, an undesired loss of thermal energy may occur via the product gas. Hence, a discharge may be provided so as to permit a portion of the hot gaseous reaction product to leave the reaction zone or the first heat integration zone at a point adjacent to the reaction zone, just after the reaction has taken place.

[0049] Hence, in an embodiment, the reactor comprises gas withdrawal means for discharging a portion of the product gas from the reaction zone while bypassing the first heat integration zone. This allows discharging a portion of the gaseous reaction product from the reaction zone so as to withdraw sufficient heat such that the to maintain the outlet temperature below a predetermined maximum value.

[0050] The heat of the discharged portion of the gaseous reaction product can be recovered by heat exchange and used elsewhere in the process or provided to other heat-accepting processes.

[0051] The design of the gas withdrawal means is not particularly limited and depends on the configuration of the reactor of the invention.

[0052] Where the passage has configuration A, the upper end of each vertical tube may have an outer annular duct for withdrawing the discharged portion of the product gas, which outer annular duct constitutes the gas withdrawal means; an inner annular duct for collecting the product gas leaving the first heat integration zone; and an inside tube for guiding the particles into the vertical tubes. Hence, a pipe may be concentrically inserted into the vertical tube at the upper end thereof, the pipe extending to the border of the reaction zone to the first heat integration zone to provide the outer annular duct. The outer annular ducts culminate in a conduit for the discharged portion of the product gas. An inside tube is inserted in the pipe for guiding the particles into the vertical tubes, the inside tube extending to the upper end of the first heat integration zone. Via the annular duct formed between the pipe and the inner tube, the product gas leaving the first heat integration zone can be collected. The inner annular ducts culminate in a conduit for the product gas. The conduit for the discharged portion of the product gas may be the interspace between a tube sheet to which the vertical tubes are tightly attached and a tube sheet to which the inserted pipes are attached. The conduit for the product gas may be the interspace between the latter tube sheet and a tube sheet to which the inside tubes are welded.

[0053] Where the passage has configuration B, the gas withdrawal means may be gas vent pipes extending into the continuous reactor inner volume having vent openings located at the border of the reaction zone to the first heat integration zone.

[0054] Generally, the reactor has a particle inlet and particle distribution means for distributing the particles to the individual tubes according to configuration A); or over the crosssection of the reactor inner volume according to configuration B).

[0055] The distribution means for distributing the particles to the individual tubes may be a tube sheet with welded tube sockets or filling funnels that guide the particles into the tubes.

[0056] Generally, the reactor has particle discharging means for withdrawing the particles from the passage. Discharging the particles may be accomplished by conventional discharge means, e.g., by rotary valve.

[0057] The nature of the particles constituting the particle bed will depend largely on the process being carried out. In many instances, the particles act as a support for the deposition of a solid reaction product which can be withdrawn from the reactor together with the particles. Alternatively or in addition to acting as a support, the particles may exert a catalytic activity on the chemical conversion. In still other embodiments, the particles may form a reactant to the process being carried out.

[0058] In exemplary embodiments, the particles are selected from carbonaceous particles, silicon carbide particles, metallic particles or composites thereof. The particles may be in the form of fines, or be agglomerated such as pelletised or granulated, if required. Carbonaceous particles may include particles of char or coke, in particular graphite particles. Metallic particles, may be metallic throughout or have a metallic coating over a non-metallic core. Metallic particles include conductive prereduced oxidic particles.

[0059] In other embodiments, the particles are selected from metal oxides or ceramic materials, which may be vitreous or non-vitreous materials. Ceramic particles include, but are not limited to, alumina, zirconia, stabilized zirconia, mullite, zirconia toughened alumina, spinel, aluminosilicates, mullite, cordierite, silicon carbide, silicon nitride, titanium carbide, titanium nitride, aluminum carbide, aluminum nitride, zirconium carbide, zirconium nitride, aluminum oxynitride, silicon aluminum oxynitride, silicon dioxide, aluminum titanate, tungsten carbide, tungsten nitride, steatite, and the like.

[0060] The particle size may be in the range of 0.3 to 15 mm, preferably 0.5 to 10 mm, more preferably 1 to 8 mm.

[0061] The downward particle velocity suitably may be in the range of 0,1 to 50 m / h, preferably 0,2 to 20 m / h, more preferably 0,5 to 10 m / h. The invention further relates to a method for carrying out an endothermic reaction, in particular a high-temperature reaction, for obtaining a product gas from a feed gas, comprising providing a passage for downward flow of particles as a dense bed under gravity flow, the passage comprising a reaction zone; heating the particles in the reaction zone; guiding the feed gas into the passage from below and upwardly through the reaction zone; wherein the passage has one of the following configurations A) or B):

[0062] A) the passage comprises a plurality of vertical tubes and heating means arranged outside the vertical tubes for heating a section of each tube, which heated section houses the reaction zone;

[0063] B) the passage is comprised of a continuous reactor inner volume, wherein heating means extend into the continuous reactor inner volume for heating a region of the reactor inner volume, which heated region defines the reaction zone, and the particles flow downwardly along outer surfaces of the heating means, and the outer surfaces of the heating means have a roughness Rz, defined according to DIN EN ISO 21920, of lower than 1 mm.

[0064] The reactor and method of the invention may be applied to a wide variety of chemical conversions. The term “chemical conversion” as used herein is meant to include unit operations that involve primarily physical transformations such as the drying or calcination of substrates. The chemical conversion may simply involve the decomposition of the feed gas or a constituent thereof, but may also involve other reactants, in particular other gaseous reactants or solid reactants such as particles constituting the particle bed.

[0065] In preferred embodiments, the chemical conversion is selected from

[0066] (i) reforming of ammonia according to the idealized equation over a bed of particles of transition metal (such as Fe or Ni) supported on a refractory support material;

[0067] (ii) decomposition of methanol according to the idealized equation CH3OH -> CO + 2 H2over a bed of Cu catalyst;

[0068] (iii) reforming of methanol according to the idealized equation over a bed of Cu catalyst; (iv) Reverse Water Gas Shift Reaction according to the idealized equation CO2+ H2CO + H2O over a bed of Ni catalyst;

[0069] (v) Methane Steam Reforming according to the idealized equation CH4+ H2O -> CO + 3 H2over a bed of SiC, C, Ni catalyst or Fe catalyst;

[0070] (vi) Methane Dry Reforming according to the idealized equation over a bed of SiC, C, Ni catalyst or Fe catalyst;

[0071] (vii) formation of hydrocyanic acid by the reaction of ammonia with hydrocarbons according to the idealized equation

[0072] CH4+ NH3^> HCN + 3 H2over a bed of carbon particles;

[0073] (viii) formation of hydrocyanic acid by formamide cleavage according to the idealized equation over a bed of stain less particles or Fe catalyst;

[0074] (ix) Boudouard reaction according to the idealized equation over a bed of carbon particles;

[0075] (x) Methane Pyrolysis according to the idealized equation CH4^> C + 2 H2over a bed of carbon particles;

[0076] (xi) dehydroaromatization of methane according to the idealized equation over a bed of Mo catalyst, optionally a mixed bed of Mo catalyst and carbon particles;

[0077] (xii) alkane dehydrogenation according to the idealized equation

[0078] CnH(2n+2) CnH(2n) + H2, wherein n = 2,3,4 over a bed of FeO / Pt catalyst, optionally over a mixed bed of FeO / Pt catalyst and carbon particles;

[0079] (xiii) styrene synthesis according to the idealized equation over a bed of FeO / Pt catalyst, optionally over a mixed bed of FeO / Pt catalyst and carbon particles;

[0080] (xiv) formation of anhydrous formaldehyde according to the idealized equation over a bed of Ag catalyst;

[0081] (xv) cyclohexane dehydrogenation according to the idealized equation C6Hi2 C6H6+ 3 H2over a bed of Pt catalyst; (xvi) alcohol dehydration according to the idealized equation

[0082] CnH(2n+i)OH CnH(2n) + H2O, wherein n = 2,3,4 over a bed of zeolith catalyst, optionally including carbon particles;

[0083] (xvii) vinyl formamide synthesis from cyanoethyl formamide according to the idealized equation CH3CH(CN)(NH-COH) CH2CH(NH-COH) + HCN over a mixed bed of potassium hydroxide on alumina and carbon particles, or carbonized catalyst of potassium hydroxide on alumina;

[0084] (xviii) melamine synthesis according to the idealized equation

[0085] 6 (NH2)2CO C3N6H6+ 6 NH3+ 3 CO2over a mixed bed of bauxite and carbon particles, or carbonized bauxite;

[0086] (xix) calcination of catalysts by decomposition of, e.g., nitrates, carbonates and hydroxides;

[0087] (xx) drying of granulates in agricultural, wood and food industries; in paper, animal feed and pellet production; or in cement and recycling industry;

[0088] (xxi) regeneration of adsorbents, e.g., activated carbon; and

[0089] (xxii) regeneration of carbonized catalysts, e.g., desulfurization catalysts like Mo-Co on gamma-alumina, MTO catalysts and styrene catalysts.

[0090] Preferably, the chemical conversion is selected from (iv) to (viii), (x) to (xv) and (xvii). More preferably, the chemical conversion is selected from (v), (vii), (x), (xii).

[0091] A particularly preferred embodiment of the invention relates to a methane pyrolysis process (or, more generally, hydrocarbon pyrolysis process; however, the conventionally used term methane pyrolysis will be used in the following). Methane pyrolysis is a technology that splits hydrocarbons, especially aliphatic hydrocarbons such as methane, ethane, propane and / or butane directly into hydrogen and solid carbon. Most often, natural gas comprising methane is used as feedstock for methane pyrolysis. For methane, the pyrolysis proceeds according to the following main reaction:

[0092] CH4— ► C + 2H2

[0093] The process is moderately endothermic (standard reaction enthalpy: 37.8 kJ / mole of H2). It is evident from the reaction equation above that in methane pyrolysis, the release of greenhouse gases is prevented. Therefore, in the event that the energy originates from renewable resources, methane pyrolysis is a CCh-free, i.e., clean technology to obtain emission-free hydrogen. Methane pyrolysis is a one-step process which produces hydrogen in high volume.

[0094] As the energy demand of the methane pyrolysis contributes to the energy-penalty of the carbon fixture, a methane pyrolysis process having an as high as possible energy efficiency is preferred. Moving carbon bed methane pyrolysis is preferred due to its low energy demand and its higher hydrogen yields as compared to other methane pyrolysis methods. The hydrocarbon feedstock contains at least one hydrocarbon which may be selected from methane, saturated hydrocarbons, in particular saturated C2 to C3 hydrocarbons, or C5-9 hydrocarbons. The hydrocarbon feedstock preferably includes methane as a main hydrocarbon constituent, e.g., at least 75 vol.-% of methane, preferably at least 85 vol.-% of methane. In an embodiment, the hydrocarbon feedstock is natural gas.

[0095] The obtained solid carbon can be sold as a commercial product for selected applications, depending on the carbon morphology and physical / chemical properties. For example, the solid carbon from methane pyrolysis may be used for aluminum and steel production, tire manufacturing, electrode manufacturing, polymer blending, additive for construction materials, carbon devices like heat exchangers, soil conditioning, or storage.

[0096] The pyrolysis is preferably carried out at temperatures ranging from 1000 to 2500 K and at pressures ranging from 0.5 to 10000 kPa (abs).

[0097] The invention is further illustrated by the example below and the appended drawings.

[0098] Fig. 1 shows a vertical cross-section along the longitudinal axis of a first embodiment of a reactor of the present invention, having a passage according to configuration A.

[0099] Fig. 2 shows a vertical cross-section along the longitudinal axis of the reactor of Fig. 1 , showing the upper end of a vertical tube in detail.

[0100] Fig. 3 shows a horizontal cross-section perpendicular to the longitudinal axis of the reactor of Fig. 1.

[0101] Fig. 4 shows a horizontal cross-section of the reactor of Fig. 3, showing a vertical tube in detail.

[0102] Fig. 5 shows a vertical cross-section along the longitudinal axis of a second embodiment of a reactor of the present invention, having a passage according to configuration B with heating cartridges.

[0103] Figs. 6 shows a horizontal cross-section perpendicular to the longitudinal axis of the reactor of Fig. 5.

[0104] Figs. 7 shows a horizontal cross-section perpendicular to the longitudinal axis of an alternative design of the reactor of Fig. 5.

[0105] Fig. 8 shows a vertical cross-section of a vertical tube of the reactor of the second embodiment.

[0106] Fig. 9 shows a horizontal cross-section of the vertical tube of Fig. 8. Fig. 10 shows a vertical cross-section along the longitudinal axis of a third embodiment of a reactor of the present invention, having a passage according to configuration B with heating cartridges and incorporating gas withdrawal means for discharging a portion of the product gas from the reaction zone.

[0107] Fig. 11 shows a horizontal cross-section perpendicular to the longitudinal axis of a fourth embodiment of a reactor of the present invention, having a passage according to configuration B with heating sheets.

[0108] Fig. 12 shows a cross section of the inner wall of a ceramic tube after several hundred hours of operation.

[0109] A first embodiment of a reactor 1 of the present invention is described with reference to Figures 1 to 4:

[0110] The reactor 1 is an elongated vertical reactor, as shown by the arrow V in Figure 1 . The reactor 1 comprises a particle inlet 2 to feed particles into the reactor 1 . The upper section of the reactor 1 comprises a particle distribution means. In the first embodiment, the particle distribution means includes inlet filling funnels 3 that guide the particles into vertical tubes 4 below the inlet filling funnels 3. The particle inlet and the inlet filling funnels 3 are arranged so that the particles are evenly distributed to the plurality of vertical tubes 4. The downward flow of the particles from the particle inlet 2 through the inlet filling funnels 3 to the vertical tubes 4 is caused by gravity.

[0111] As shown in Figure 2, the lower opening of the inlet-filling funnel 3 is connected to an upper opening of an inside tube 16 that extends downward into the upper end 5 of the vertical tube 4. Particles that are introduced into the upper opening of the inlet filling funnel 3 flow downward under gravity flow, so that the particles enter the inside tube 16 and finally the vertical tube 4.

[0112] Referring again to Figure 1 , the vertical tubes 4 extend downward through a reaction zone 7 of the reactor 1 . The lower openings of the vertical tubes 4 lead to a particle discharging means. This particle discharging means is formed by an outlet hopper 8 and a cellular wheel sluice (not shown). Accordingly, the reactor 1 provides a passage for downward flow of particles as a dense bed under gravity flow. The passage is configured to distribute the particles to the vertical tubes 4, to guide the particles through the vertical tubes 4 into the outlet hopper 8, where the particles are discharged at the lower end of the reactor 1 by a rotary valve.

[0113] Furthermore, the reactor 1 comprises a gas feed inlet 9 as well as a gas outlet 10. Feed gas may be introduced through the gas feed inlet 9, so that the feed gas is guided through the vertical tubes 4 upwards through the reaction zone 7 forming a counterflow with the particles that move downward. As shown in detail in Figure 2, at the upper end 5 of each vertical tube 4, an inner annular duct 15 is arranged inside an outer annular duct 14 that in turn is arranged inside the vertical tube 4. Furthermore, the inside tube 16 is arranged inside the inner annular duct 15. The inside tube 16, the inner annular duct 15, the outer annular duct 14 and the vertical tube 4 are arranged concentrically with respect to a central vertical axis of the vertical tube 4.

[0114] In the vertical direction V, the outer annular duct 14 extends with the lower end to the beginning of the reaction zone 7 and with the upper end into a channel that finally leads into a side discharge opening for gas withdrawal. The inner annular duct 15 extends with the lower end to an upper section of a first heat integration zone 11. Such first heat integration zone 11 is located directly above the reaction zone 7. The upper end of the inner annular duct 15 leads to a further channel that finally leads to a gas outlet 10.

[0115] By means of the outer annular duct 14, a portion of the product gas may be withdrawn before entering the first heat integration zone 11 . This portion of the product gas is withdrawn through the outer annular duct 14 at the border of the reaction zone 7 to the first heat integration zone 11 so that this portion of the product gas from the reaction zone 7 bypasses the first heat integration zone 11. This withdrawn portion of the product gas is fed to the side discharge opening 13, where the heat of the withdrawn portion of the gaseous reaction product can be recovered by heat exchange and used elsewhere.

[0116] The other portion of the product gas from the reaction zone 7 forms a counterflow with the particles that move downward within the first heat integration zone 11. This counterflow of product gas and particles within the first heat integration zone 11 provides heat transfer from the product gas leaving the reaction zone 7 to the particles, which are to be guided into the reaction zone 7. By means of the inner annular duct 15, the product gas leaving the first heat integration zone 11 is collected, so that a product gas that is obtained from the feed gas is discharged through the gas outlet 10.

[0117] Below the reaction zone 7, a second heat integration zone 12 is formed, where heat is transferred from particles leaving the reaction zone 7 to the upward feed gas.

[0118] Figure 3 shows a horizontal cross-section of the reactor 1 of the first embodiment. Within the reactor shell 21 , the plurality of vertical tubes 4 is arranged, so that a multi-tubular reactor 1 is formed.

[0119] The inner surface of the reactor shell 21 is thermally insulated, e.g. by refractory bricks. From outside the reactor 1 is insulated by a thermal insulation 17 that surrounds the reactor shell 21.

[0120] As it can be seen in Figure 4 in detail, each vertical tube 4 is surrounded by an electrical heating jacket 19. The electrical heating jackets 19 provide resistive heating elements for heating the vertical tubes 4 from outside the passage that is provided for the particle flow. In the first embodiment, heat is transferred from the electrical heating jackets 19 through the vertical tubes 4 to the particles 20 inside the vertical tubes 4. Such arrangement of the passage with a plurality of vertical tubes, wherein heating means are arranged outside the vertical tubes for heating a section of each tube is also designated as configuration A).

[0121] In a vertical direction V, the electrical heating jackets 19 surrounding the vertical tubes 4 heat a section of each vertical tube 4. The heated section houses the reaction zone 7. Above and below the reaction zone 7, the reactor 1 comprises electrical contacts 18 that are connected to the electrical heating jackets 19. The electrical heating jackets 19 are configured to at least be heated within the vertical extension of the reaction zone 7, so that particles within the vertical tubes 4 can be heated in the reaction zone 7.

[0122] With reference to Figures 5 to 9, a second embodiment of the reactor 1 is described:

[0123] In the reactor 1 of the second embodiment, the passage for downward flow of particles as a dense bed under gravity flow is comprised of a continuous reactor inner volume 22. For distribution of the particles within the continuous reactor inner volume 22, a displacement element 23 is arranged within the continuous reactor inner volume 22 extending vertically at the center of the continuous reactor inner volume 23. At the upper end, the displacement element 23 is tapered. Above the tapered end of the displacement element 23, the particle inlet 2 is arranged. Particles that are fed from the particle inlet 2 into the continuous reactor inner volume 22 are distributed by the displacement element 23 to evenly fill the continuous reactor inner volume 22 and flow downward under gravity flow. The displacement element 23 is mounted via struts 24 within the reactor 1. Accordingly, the particles are fed into the continuous reactor in a volume 22 through particle inlet 2 and flow down through the continuous reactor inner volume 22. Then the particles are discharged by the outlet hopper 8 and a rotary valve (not shown).

[0124] The reactor 1 is insulated by refractory bricks and a thermal insulation 17 that lines the reactor shell 21.

[0125] The reactor 1 of the second embodiment comprises several electrical heating cartridges 25 that are suspended from above the particle inlet 2 into the continuous reactor inner volume 22 and that are evenly distributed over the horizontal cross-section of the continuous reactor inner volume 22. The heating cartridges 25 are spaced apart from each other as well as from the reactor shell 21. The lateral walls 26 of the heating cartridges 25 are cylindrical and oriented vertically. The outer surfaces of the heating cartridges 25 are smooth. Therefore, the heating cartridges 25 do not obstruct the vertical flow of the particles within the continuous reactor inner volume 22.

[0126] Figure 6 shows a horizontal cross-section of the reactor 1 of the second embodiment. In particular, the central displacement element 23 and the evenly distributed electrical heating cartridges 25 that are located within the continuous reactor inner volume 22 are shown. Figure 7 shows a horizontal cross-section of an alternative design of the reactor 1 of Figures 5 and 6. In this alternative design, the electrical heating cartridges 25 comprise heat exchange fins 27 that extend outwardly from the electrical heating cartridges 25. The particular embodiment of a heat cartridge comprises three heat exchange fins spaced equidistantly on the circumference of the heat cartridge. The heat exchange fins 27 are made from a material providing high thermal conductivity. The heat exchange fins may be made from metal.

[0127] The electrical heating cartridges 25 of the second embodiment are further described with reference to Figures 8 and 9:

[0128] The electrical heating cartridge 25 comprises a vertically lateral wall 26. At the low end, the electrical heating cartridge 25 is rounded. Inside the electrical heating cartridge 25, a coil-shaped resistor heating element 28 is arranged. At the upper end and at the lower end the resistor heating element 28 is connected to contact leads 29. The electrical heating cartridges 25 are located within the continuous reactor inner volume 22, so that the reaction zone 7 extends vertically in line with the vertical extension of the resistor heating elements 28 of the electrical heating cartridges 25.

[0129] Furthermore, thermoelements 30 are located vertically at the center of the electrical heating cartridge 25 as well as at the inner surface of the lateral wall 26 of the electrical heating cartridge 25. The thermoelements 30 measure the temperature within the electrical heating cartridge 25. The thermoelements 30 are connected with a control unit (not shown) that is configured to control the resistor heating element 28, so that the heat transfer to the particles within the continuous reactor inner volume 22 can be controlled.

[0130] Moreover, a gas purging line 31 extends vertically within the electrical heating cartridge 25. The electrical heating cartridge 25 is gas-tight. However, in case of a leakage, product gas may leak into the electrical heating cartridge 25. In this case, hydrogen gas that is fed by the gas purging line 31 into the electrical heating cartridge 25 can provide protection against damage of the inside of a electrical heating cartridge 25 caused by the product gas.

[0131] In the reactor 1 of the second embodiment, the heating means that is provided by the electrical heating cartridges 25 extends into a continuous reactor inner volume 22 for heating the reaction zone 7 that is formed within the reactor inner volume 22.

[0132] Such arrangement of the passage that is comprised of a continuous reactor inner volume 22, wherein heating means extend into the continuous reactor inner volume 22 for heating a region of the reactor inner volume, which heated region defines the reaction zone is also designated as configuration B).

[0133] A third embodiment of the reactor 1 is described with reference to Figure 10: The third embodiment of the reactor 1 is similar to the second embodiment as shown in Figure 5, so that only the differences to the second embodiment are described in the following.

[0134] The reactor 1 of the third embodiment comprises a gas withdrawal means for discharging a portion of the product gas from the reaction zone 7 while bypassing the first heat integration zone 11. The gas withdrawal means are formed by gas vent pipes 32 that extend into the continuous reactor inner volume 22. The gas vent pipes 32 have lower vent openings 34 located at the border of the reaction zone 7 to the first heat integration zone 11 and upper vent openings 35 leading to the channel that guides the withdrawn gas to side discharge opening 13

[0135] The particle inlet 2 of the reactor 1 of the third embodiment is adapted so as to feed the particles past the gas vent pipes 32 into the continuous reactor inner volume 22.

[0136] A fourth embodiment of the reactor 1 is described with reference to Figure 11 :

[0137] Like the second and third embodiment, the fourth embodiment of the reactor 1 has also a passage of configuration B).

[0138] The reactor 1 of the fourth embodiment comprises electrical heating sheets 33 that are vertically arranged, circularly curved and arranged coaxially with respect to a central vertical axis of the reactor inner volume 22. Heat transfer capability of a electrical heating sheet 33 is controlled by the choice of the thickness and width of sections of the electrical heating sheet 33 located in particular regions within the reactor inner volume 22.

[0139] In the intersections between adjacent electrical heating sheets 33 gaps are formed that have an annular horizontal cross-section and that vertically extend from the upper to the lower section of the reactor inner volume 22. Therefore, particles can flow downwardly through the gaps thereby heated by the electrical heating sheets 33.

[0140] The electrical heating sheets 33 are connected to electrical contacts 18 above and below the reaction zone 7 of the reactor 1 .

[0141] With reference to the following example, Fig. 12 shows a cross section of the inner wall of a ceramic tube after several hundred hours of operation of a methane pyrolysis process. On the inner surface of the wall, only a thin carbon layer (black) is evident. Between the carbon layer and the ceramic tube, a corrosion layer is visible. Example

[0142] A methane pyrolysis process was carried out in a tubular reactor. The reactor wall had a sandwich structure comprising an inner, 10 mm thick layer of mullite (Pythagoras®, from Haldenwanger) and an outer, 3 mm thick layer of oxide ceramic matrix composite (FW12, from WPS). The dimensions of the reactor tube were 216 mm * 190 mm x 3000 mm (outer diameter x inner diameter x length). The heated zone had a length of 1400 mm and comprised four heating segments.

[0143] A heating resistor concentrically surrounded the tubular reactor. The resistor consisted of a molybdenum wire (diameter: 3 mm; resistance: 0.4 Ohm at ambient temperature) which was helically wound around a cylindrical support. The cylindrical support was an alumina tube (Plascera®, from LWK), with dimensions of 270 mm x 250 mm (outer diameter x inner diameter).

[0144] The temperature set point for all segments of the heater was 1250 °C. The operating pressure as measured at the top of the reactor was 1.4 bar gauge.

[0145] A particles feed, comprising a carrier grain (carbon content: > 99 wt.-%; particle size: 2 to 4 mm according to DIN 66165), was fed to the top of the reactor tube and at a flow rate of 20 kg / h. The descent rate of particles of the moving bed was 0.65 h.

[0146] A gas feed, comprising 20 Nm3 / h of hydrogen and 3 Nm3 / h of natural gas, was fed to the bottom of the reactor in counter current to the particles feed. The natural gas comprised methane (90.8 mol-%); carbon dioxide (1.4 mol-%), nitrogen (1.2 mol-%), ethane (4.9 mol-%), propane (1.2 mol-%) and residuals (0.5 mol-%)

[0147] The process was carried out at a production rate of hydrogen of 2.4 Nm3 / h and a production rate of carbon of 600 g / h. The operating time of the reactor in pyrolysis mode was 912 h. During this time, 550 kg of pyrolysis carbon were produced in the reactor. The productivity of the reactor and the settings of the reactor heating were maintained unchanged over the entire operating time. It is thus evident that the heat transfer properties of the reactor remained constant.

[0148] Following the experiment, the reaction tube was inspected. Fig. 12 shows a segment of the used reactor tube, taken from the heated section of the reactor. It is clearly visible that a smooth and glossy layer of carbon has formed on the inner wall of the pipe. The thickness of this layer was less than 1 mm and the amount of carbon adhering to the wall was less than 80 g. List of reference signs:

[0149] 1 reactor

[0150] 2 particle inlet

[0151] 3 inlet filling funnels

[0152] 4 vertical tubes

[0153] 5 upper ends of vertical tubes

[0154] 6 heated sections of vertical tubes

[0155] 7 reaction zone

[0156] 8 outlet hopper

[0157] 9 gas feed inlet

[0158] 10 gas feed outlet

[0159] 11 first heat integration zone

[0160] 12 second heat integration zone

[0161] 13 side discharge opening

[0162] 14 outer annular duct

[0163] 15 inner annular duct

[0164] 16 inside tube

[0165] 17 thermal insulation

[0166] 18 electrical contacts

[0167] 19 electrical heating jackets

[0168] 20 particles

[0169] 21 reactor shell

[0170] 22 continuous reactor inner volume

[0171] 23 displacement element

[0172] 24 struts

[0173] 25 electrical heating cartridges

[0174] 26 lateral walls of electrical heating cartridges

[0175] 27 heat exchange fins

[0176] 28 resistive heating element

[0177] 29 contact leads

[0178] 30 thermoelements

[0179] 31 gas purging line

[0180] 32 gas vent pipes

[0181] 33 electrical heating sheets

[0182] 34 lower vent openings

[0183] 35 upper vent openings

Claims

Claims1. A reactor for carrying out an endothermic reaction, in particular a high-temperature reaction, in which a product gas is obtained from a feed gas; wherein the reactor is configured to provide a passage for downward flow of particles as a dense bed under gravity flow, the passage comprising a reaction zone; the reactor is configured to indirectly heat the particles in the reaction zone; and the reactor is configured to guide the feed gas into the passage from below and upwardly through the reaction zone; wherein the passage has one of the following configurations A) or B):A) the passage comprises a plurality of vertical tubes and heating means arranged outside the vertical tubes for heating a section of each tube, which heated section houses the reaction zone;B) the passage is comprised of a continuous reactor inner volume, wherein heating means extend into the continuous reactor inner volume for heating a region of the reactor inner volume, which heated region defines the reaction zone, configured such that the particles flow downwardly along outer surfaces of the heating means, and the outer surfaces of the heating means have a roughness Rz, defined according to DIN EN ISO 21920, of lower than 1 mm.

2. The reactor according to claim 1, wherein the passage has configuration A and the heating means comprise electrical heating jackets surrounding a section of each tube.

3. The reactor according to claim 1 , wherein the passage has configuration B, wherein the angle between a normal to the surface at each point of the outer surface of the heating means and the upwards directed vertical vector is equal to or larger than the wall friction angle of the particles.

4. The reactor according to claim 1 or 3, wherein the passage has configuration B and the heating means comprise electrical heating cartridges.

5. The reactor according to claim 4, wherein the heating cartridges comprise heat exchange fins.

6. The reactor according to claim 1 , wherein the passage has configuration B and the heating means comprise vertically arranged electrical heating sheets.

7. The reactor according to claim 6, wherein the heating sheets are circularly curved and arranged coaxially with respect to a central axis of the reactor inner volume.

8. The reactor according to any one of the preceding claims, wherein the passage comprises a first heat integration zone for transferring heat from the product gas leaving the reaction zone to the particles which are to be guided into the reaction zone, and a second heat integration zone for transferring heat from particles leaving the reaction zone to the feed gas.

9. The reactor according to claim 8, wherein the reactor comprises gas withdrawal means for discharging a portion of the product gas from the reaction zone while bypassing the first heat integration zone.

10. The reactor according to claim 9, wherein the passage has configuration A and the upper end of each vertical tube has an outer annular duct for withdrawing the discharged portion of the product gas, which outer annular duct constitutes the gas withdrawal means; an inner annular duct for collecting the product gas leaving the first heat integration zone; and an inside tube for guiding the particles into the vertical tubes.

11. The reactor according to claim 9, wherein the passage has configuration B and the gas withdrawal means are gas vent pipes extending into the continuous reactor inner volume having vent openings located at the border of the reaction zone to the first heat integration zone.

12. The reactor according to any one of the preceding claims, wherein the reactor has a particle inlet and particle distribution means for distributing the particles to the individual tubes according to configuration A); or over the cross-section of the reactor inner volume according to configuration B).

13. The reactor according to any one of the preceding claims, wherein the reactor has particle discharging means for withdrawing the particles from the passage.

14. A method for carrying out an endothermic reaction, in particular a high- temperature reaction, for obtaining a product gas from a feed gas, comprising providing a passage for downward flow of particles as a dense bed under gravity flow, the passage comprising a reaction zone; indirectly heating the particles in the reaction zone; guiding the feed gas into the passage from below and upwardly through the reaction zone; wherein the passage has one of the following configurations A) or B):A) the passage comprises a plurality of vertical tubes and heating means arranged outside the vertical tubes for heating a section of each tube, which heated section houses the reaction zone;B) the passage is comprised of a continuous reactor inner volume, wherein heating means extend into the continuous reactor inner volume for heating a region of the reactor inner volume, which heated region defines the reaction zone, and the particles flow downwardly along outer surfaces of the heating means, and the outer surfaces of the heating means have a roughness Rz, defined according to DIN EN ISO 21920, of lower than 1 mm.

15. The method according to claim 14, wherein the endothermic conversion is selected from(i) reforming of ammonia according to the idealized equationover a bed of particles of transition metal (such as Fe or Ni) supported on a refractory support material;(ii) decomposition of methanol according to the idealized equation CH3OH -> CO + 2 H2over a bed of Cu catalyst;(iii) reforming of methanol according to the idealized equation CH3OH + H2O CO2+ 3 H2over a bed of Cu catalyst;(iv) Reverse Water Gas Shift Reaction according to the idealized equation CO2+ H2-> CO + H2O over a bed of Ni catalyst;(v) Methane Steam Reforming according to the idealized equation CH4+ H2O -> CO + 3 H2over a bed of SiC, C, Ni catalyst or Fe catalyst;(vi) Methane Dry Reforming according to the idealized equationCH4+ CO2-> 2 CO + 2 H2over a bed of SiC, C, Ni catalyst or Fe catalyst;(vii) formation of hydrocyanic acid by the reaction of ammonia with hydrocarbons according to the idealized equationover a bed of carbon particles;(viii) formation of hydrocyanic acid by formamide cleavage according to the idealized equation HCONH2HCN + H2O over a bed of stain less particles or Fe catalyst;(ix) Boudouard reaction according to the idealized equationover a bed of carbon particles;(x) Methane Pyrolysis according to the idealized equationCH4^> C + 2 H2over a bed of carbon particles;(xi) dehydroaromatization of methane according to the idealized equation6 CH4C6H6+ 9 H2over a bed of Mo catalyst, optionally a mixed bed of Mo catalyst and carbon particles;(xii) alkane dehydrogenation according to the idealized equationCnH(2n+2) CnH(2n) + H2, wherein n = 2,3,4 over a bed of FeO / Pt catalyst, optionally over a mixed bed of FeO / Pt catalyst and carbon particles;(xiii) styrene synthesis according to the idealized equationover a bed of FeO / Pt catalyst, optionally over a mixed bed of FeO / Pt catalyst and carbon particles;(xiv) formation of anhydrous formaldehyde according to the idealized equationover a bed of Ag catalyst;(xv) cyclohexane dehydrogenation according to the idealized equationover a bed of Pt catalyst;(xvi) alcohol dehydration according to the idealized equationCnH(2n+i)OH CnH(2n) + H2O, wherein n = 2,3,4 over a bed of zeolith catalyst, optionally including carbon particles;(xvii) vinyl formamide synthesis from cyanoethyl formamide according to the idealized equation CH3CH(CN)(NH-COH) CH2CH(NH-COH) + HCN over a mixed bed of potassium hydroxide on alumina and carbon particles, or carbonized catalyst of potassium hydroxide on alumina;(xviii) melamine synthesis according to the idealized equationover a mixed bed of bauxite and carbon particles, or carbonized bauxite;(xix) calcination of catalysts by decomposition of, e.g., nitrates, carbonates and hydroxides;(xx) drying of granulates in agricultural, wood and food industries; in paper, animal feed and pellet production; or in cement and recycling industry;(xxi) regeneration of adsorbents, e.g., activated carbon; and(xxii) regeneration of carbonized catalysts, e.g., desulfurization catalysts like Mo- Co on gamma-alumina, MTO catalysts and styrene catalysts.

Images