Method for mitigating reaction of hydrogen bromide with ethylenically unsaturated compounds

Abstract

The present invention relates to a process for mitigating the reaction of hydrogen bromide and optionally bromine with one or more ethylenically unsaturated compounds, said process comprising i) a step of adding hydrogen to a composition comprising hydrogen bromide and ethylenically unsaturated compounds to obtain a composition comprising hydrogen, hydrogen bromide and ethylenically unsaturated compounds, and / or ii) a step of adding hydrogen to a precursor composition containing one or more brominated hydrocarbons from which a composition containing hydrogen, hydrogen bromide and an ethylenically unsaturated compound is formed.

Description

[0001] The present invention relates to a process for mitigating the reaction of hydrogen bromide with olefinically unsaturated compounds.

[0002] Olefins or alkenes, and especially C 2-10 Olefins, such as ethylene and propylene, are valuable raw materials for chemical synthesis and in fact belong to the most important starting materials in the petrochemical industry. For example, ethylene is the starting material for the preparation of polyethylene, and propylene is the starting material for the preparation of polypropylene, and polyethylene and polypropylene are two most widely used polymers because they are odorless, skin-friendly, physiologically harmless and have excellent mechanical properties. For example, polyethylene and polypropylene are used for packaging, films, textiles, lids, medical products, mattress covers and many other products. In addition, ethylene and propylene are used to prepare other important chemicals, such as for the preparation of ethylene glycol, propylene glycol, acrylonitrile, acrylic acid and propylene oxide.

[0003] C 2-10 Alkenes are usually synthesized by the corresponding C 2-10 Propylene is produced by direct catalytic dehydrogenation of alkanes, such as propylene produced by direct catalytic dehydrogenation of propane. The catalytic dehydrogenation of propane to propylene is usually carried out at a relatively high temperature of 550 to 680°C and at a relatively low pressure, usually below atmospheric pressure. However, if non-renewable fuels (such as coal, etc.) that form a large amount of carbon dioxide during their combustion are used to generate the energy required to maintain the required high reaction temperature, the energy required to generate the carbon dioxide based on the C 2-10 Such processes for direct catalytic dehydrogenation of alkanes are energy intensive and ecologically harmful, especially due to the high reaction temperatures required. The predominantly used direct dehydrogenation processes utilize circulating catalysts or multiple reactors that cycle in a preparation-purge-regeneration-purge sequence. This requirement is derived from alkane-olefin equilibrium limitations, which are mitigated by high temperature and / or low pressure operation. In summary, these C-based 2-10 Direct catalytic dehydrogenation of alkanes has the disadvantages of high capital expenditure, high operating cost and the production of large amounts of carbon dioxide.

[0004] In view of this, a method for preparing olefinically unsaturated compounds (especially C 2-10Alternative method of alkene).A kind of promising alternative scheme is the method comprising the following steps: with bromine, alkane is brominated into the mixture that comprises bromoalkane, and subsequently bromoalkane is dehydrobrominated into the mixture of corresponding alkene and hydrogen bromide, subsequently hydrogen bromide is separated from alkene, for example, by first distilling said mixture so that therefrom separate the heavy component (heavies) as tower bottom fraction, and the overhead fraction containing hydrogen bromide and alkene is subjected to water absorption.In addition, the mixture that comprises bromoalkene also may contain some unreacted bromine, and it can be delivered to the dehydrobromination step together with bromoalkene.In addition, in some cases, bromine may also be formed during the regeneration of dehydrobromination catalyst or different process confusions.The composition that contains alkene and hydrogen bromide and optional trace bromine that obtains during dehydrobromination reaction is very sensitive to the rebromination reaction of alkene and hydrogen bromide or bromine. Such rebromination is extremely undesirable because the (poly)alkyl bromides formed need to be separated and recycled back to the dehydrobromination reaction or burned in a thermal oxidizer to recover the bromine, which results in significant energy losses, additional carbon dioxide emissions and reduced yields of olefinically unsaturated compounds. Therefore, methods for mitigating the rebromination of the reaction mixture obtained after the dehydrobromination step are very important for such processes.

[0005] Olefins react very rapidly with pure liquid bromine or with solutions of bromine in water or an organic solvent under cooling. Double bonds are broken, and bromine atoms attach to each carbon. This reaction is an example of electrophilic addition. Bromine is a very polarizable molecule, and the proximity of the pi bond in ethylene induces a dipole in the bromine molecule. However, the reaction in the gas phase is not very rapid in the presence of only trace amounts of bromine and can be avoided. However, it is advantageous to neutralize the bromine before preparing the olefin.

[0006] The interaction between hydrogen bromide and olefinically unsaturated compounds is a free radical chain reaction. Typically, the presence of trace amounts of oxygen or light significantly increases the rate of this reaction. However, heavy compounds, such as aromatic compounds, for example, benzene, toluene, and xylene, and mixtures thereof, can be used as free radical scavengers to reduce the risk of rebromination. However, before separating hydrogen bromide from the olefinically unsaturated compounds by water absorption, the aromatic compounds used as free radical scavengers must be removed from the mixture. Otherwise, the aromatic compounds will contaminate the absorption medium, necessitating separation of the aromatic compounds from the absorption medium to allow for recycling of the absorption medium, which involves high energy costs and capital expenditures. Therefore, if the aromatic compounds are removed from the mixture before separating hydrogen bromide from the olefinically unsaturated compounds, the remaining mixture is once again susceptible to rebromination of the olefinically unsaturated compounds. Therefore, alternative mitigation measures are needed. It has been proposed to reduce the temperature of the mixture containing hydrogen bromide and olefinically unsaturated compounds to below 10°C, up to -80°C. However, such cooling consumes a large amount of energy and creates significant technical challenges for the water absorption step. Alternatively, it has been suggested to add sulfur- or oxygen-containing compounds as free radical scavengers to the mixture containing hydrogen bromide and olefinically unsaturated compounds. However, such treatment results in water contamination of the water used in the absorption step and thus requires further separation and purification steps, which increases operating costs and capital expenditures.

[0007] In view of the above, it is a basic object of the present invention to provide an efficient and economical process for mitigating the reaction of hydrogen bromide and optionally bromine with one or more olefinically unsaturated compounds in a composition containing the same in order to protect the one or more olefinically unsaturated compounds from rebromination, particularly in a subsequent separation step in which hydrogen bromide is separated from the one or more olefinically unsaturated compounds.

[0008] According to the present invention, this object is solved by providing a process for mitigating the reaction of hydrogen bromide and optionally bromine with one or more olefinically unsaturated compounds, said process comprising i) the step of adding hydrogen to a composition comprising hydrogen bromide and an olefinically unsaturated compound to obtain a composition comprising hydrogen, hydrogen bromide and an olefinically unsaturated compound, and / or ii) the step of adding hydrogen to a precursor composition comprising one or more brominated hydrocarbons, from which a composition comprising hydrogen, hydrogen bromide and an olefinically unsaturated compound is formed.

[0009] This solution is based on the discovery that the addition of small amounts of hydrogen to a composition containing hydrogen bromide and, optionally, bromine, and one or more olefinically unsaturated compounds reliably reduces any rebromination of the olefinically unsaturated compounds by hydrogen bromide and, optionally, bromine. Without wishing to be bound by any theory, it is believed that the hydrogen acts to neutralize any free radicals in the composition and further reduce the effects of oxidation and salts on the walls of the apparatus through which the composition flows. In the case of bromine, the added hydrogen reacts very rapidly with the bromine in the gas phase, resulting in the formation of hydrogen bromide, thereby eliminating any traces of bromine.

[0010] Since any rebromination of the olefinically unsaturated compounds by hydrogen bromide is reliably mitigated by the addition of hydrogen, the resulting composition containing hydrogen, hydrogen bromide, and the olefinically unsaturated compounds can be subjected to a separation step involving absorption with an absorption medium (e.g., water or an aqueous solution) because the hydrogen can be easily separated from the olefinically unsaturated compounds and from the absorbate. Another advantage is that the hydrogen effectively reacts with trace amounts of bromine present in the absorption medium, which is recycled in the process. For example, in the case of recovering the absorption medium from an absorbate containing the absorption medium and hydrogen bromide by electrolysis, during which the hydrogen bromide is electrolyzed into a mixture containing the hydrogen obtained at one of the two electrodes and the bromide, the absorption medium, and a hydrogen bromide residue (which was not converted to hydrogen and bromide during the electrolysis) obtained at the other electrode, the bromine is subsequently removed from the mixture of the absorption medium, for example, by distillation, the hydrogen bromide residue remaining in the absorption medium along with the trace amounts of bromine obtained during the electrolysis. In the absence of hydrogen in the composition containing hydrogen bromide and olefinically unsaturated compounds, such residual traces of bromine would immediately lead to rebromination of the olefinically unsaturated compounds during the absorption step. In summary, the process according to the present invention allows for the efficient and economical mitigation of the reaction of hydrogen bromide with olefinically unsaturated compounds in a composition containing both, in order to protect the olefinically unsaturated compounds from rebromination, in particular in the subsequent separation step of separating hydrogen bromide from the olefinically unsaturated compounds.

[0011] Compositions containing hydrogen, hydrogen bromide and olefinically unsaturated compounds are understood according to the present invention to mean any composition containing hydrogen, hydrogen bromide and one or more olefinically unsaturated compounds. Likewise, compositions containing hydrogen bromide and olefinically unsaturated compounds are understood according to the present invention to mean any composition containing hydrogen bromide and one or more olefinically unsaturated compounds.

[0012] According to a preferred embodiment of the present invention, the composition comprising hydrogen, hydrogen bromide and olefinically unsaturated compounds further comprises bromine and / or the precursor composition comprising one or more brominated hydrocarbons from which the composition comprising hydrogen, hydrogen bromide and olefinically unsaturated compounds is formed further comprises bromine.

[0013] In order to sufficiently mitigate the reaction of hydrogen bromide and olefinically unsaturated compounds in the composition, a further development of the concept of the invention proposes to adjust the molar concentration of hydrogen in the composition containing hydrogen, hydrogen bromide and olefinically unsaturated compounds to at least 0.1 mol %. Preferably, the molar concentration of hydrogen in the composition containing hydrogen, hydrogen bromide and olefinically unsaturated compounds is adjusted to 0.2 to 90 mol % and more preferably 0.5 to 60 mol %.

[0014] Good results are particularly obtained when the molar ratio of hydrogen to olefinically unsaturated compound in the composition comprising hydrogen, hydrogen bromide and olefinically unsaturated compound is adjusted to between 2:1 and 1:10.

[0015] Likewise, particularly good results are obtained when the molar ratio of hydrogen to hydrogen bromide in the composition comprising hydrogen, hydrogen bromide and the olefinically unsaturated compound is adjusted to between 2:1 and 1:5.

[0016] The present invention is not particularly limited in terms of the type of the ethylenically unsaturated compound. For example, the ethylenically unsaturated compound is an ethylenically unsaturated hydrocarbon, more preferably C 2-10 Olefins, more preferably C 2-5 Monoolefins or C 4-8 A diene, still more preferably ethylene or propylene and most preferably propylene.

[0017] According to the present invention, i) hydrogen can be added to an already formed composition comprising hydrogen bromide and olefinically unsaturated compounds, or ii) hydrogen can be added before the composition comprising hydrogen bromide and olefinically unsaturated compounds is formed, i.e., to a precursor composition comprising one or more brominated hydrocarbons from which the composition comprising hydrogen, hydrogen bromide and olefinically unsaturated compounds is formed, for example, by dehydrobromination of a brominated olefin.

[0018] In the first-mentioned embodiment, in which hydrogen is added to an already formed composition containing hydrogen bromide and olefinically unsaturated compounds, preferably hydrogen is added to a composition containing 1 to 90 weight percent, and preferably 20 to 50 weight percent, of hydrogen bromide and 20 to 90 weight percent, and preferably 30 to 50 weight percent, of one or more olefinically unsaturated compounds. Such a composition can be prepared, for example, by a dehydrobromination reaction as described in further detail below.

[0019] In the second-mentioned embodiment, in which hydrogen is added prior to forming the composition comprising hydrogen bromide and the olefinically unsaturated compounds, i.e., to a precursor composition comprising one or more brominated hydrocarbons, from which the composition comprising hydrogen, hydrogen bromide and the olefinically unsaturated compounds is formed, for example, by a reaction such as a dehydrobromination reaction, it is preferred that hydrogen is added to a precursor composition comprising one or more brominated hydrocarbons, which comprises one or more brominated hydrocarbons, and the mixture thus obtained is subsequently subjected to a dehydrobromination reaction in order to form the composition comprising hydrogen, hydrogen bromide and one or more olefinically unsaturated compounds.

[0020] According to the present invention, a precursor composition is any composition containing one or more brominated hydrocarbons which can be reacted, for example and in particular by dehydrobromination, to form a composition containing hydrogen, hydrogen bromide and an olefinically unsaturated compound. The present invention is not particularly limited as to the type of the one or more brominated hydrocarbons contained in the precursor composition. Suitable examples of such brominated hydrocarbons are C 1-10 Bromohydrocarbon, more preferably C 1-10 Bromoalkanes, more preferably C 1-5 Monobrominated alkanes or C 4-8 Dibromoalkanes, more preferably bromomethane, bromoethane or bromopropane, and most preferably 1-bromopropane or 2-bromopropane. In addition, the brominated hydrocarbons may be brominated olefins so that they are dehydrobrominated to dialkanes. Specific examples of suitable brominated hydrocarbons are monobromomethane, monobromoethane, 1,2-dibromoethane, 1-bromopropane, 2-bromopropane, 1,2-dibromopropane, 1,3-dibromopropane, 1-bromo-1-propene, 2-bromo-1-propene, 3-bromo-1-propene, monobromobutane, dibromobutane, monobromopentane, dibromopentane, and any mixture of two or more of the foregoing compounds.

[0021] Good results are particularly obtained when the precursor composition contains from 10 to 99% by weight and preferably from 20 to 75% by weight of one or more brominated hydrocarbons. In addition to the brominated hydrocarbons, the precursor composition may contain any other compounds, such as one or more compounds selected from the group consisting of olefinically unsaturated hydrocarbons, C 6-9 Aromatic hydrocarbons, other than olefinically unsaturated hydrocarbons and C 6-9 Aromatic hydrocarbons, carbon dioxide, inert gases, nitrogen, hydrogen bromide, and any combination of two or more of the foregoing compounds.

[0022] Preferably, hydrogen is added to the precursor composition so that the resulting mixture has a molar ratio of brominated hydrocarbon(s) to hydrogen of from 1:10 to 10:1 and preferably from 1:5 to 5:1.

[0023] In a particularly preferred embodiment of the present invention, a mixture obtained by adding hydrogen to a precursor composition comprising one or more brominated hydrocarbons is subjected to a catalytic dehydrobromination reaction. Good results are particularly obtained when the catalyst comprises a support material and at least 200 ppm of at least one metal selected from transition metals, noble metals, and any combination of two or more thereof. This solution is based on the discovery that a catalyst comprising a support material and at least 200 ppm of at least one metal selected from transition metals, noble metals, and any combination of two or more thereof is particularly effective in catalyzing the dehydrobromination of brominated hydrocarbons (such as C 1-10 Dehydrobromination of bromoalkanes) to corresponding and / or similar alkenes, such as C 2-10 For the sake of completeness, it must be mentioned that methyl bromide can react during the dehydrobromination to form ethylene and / or propylene. Another advantage of the aforementioned catalyst is that it is very stable.

[0024] Preferably, the catalyst used to catalyze the dehydrobromination reaction comprises at least 75 wt%, more preferably at least 75 wt% to 99.6 wt%, still more preferably at least 85 wt% to 99.6 wt%, and most preferably at least 95 wt% to 99.6 wt% support material.

[0025] In a further development of the concept of the invention it is proposed that the support material for the catalyst for the catalytic dehydrobromination reaction has at least 5 m 2 / g or more, preferably at least 20m 2 / g and more preferably at least 50m 2 / g of specific surface area measured by nitrogen adsorption.

[0026] The present invention is not particularly limited with respect to the chemical nature of the support material. However, particularly good results are obtained when the support material is selected from the group consisting of alumina, silica, silica gel, silica-alumina, zeolites, zirconia, titania, niobium oxide, silicon carbide, carbon, aluminophosphate molecular sieves, metalloaluminophosphate molecular sieves, amorphous aluminophosphates, and any combination of two or more thereof.

[0027] According to a particularly preferred embodiment of the present invention, the support material of the catalyst is gamma-alumina and / or boehmite.

[0028] Preferably, high purity alumina of 99.99% or even higher is synthesized via the alkoxide route. The alkoxide route is a known production technology based on the hydrolysis of aluminum alkoxides. In this process, the alcohol of the aluminum alkoxide is recycled back to the synthesis. Alumina is produced as a co-product with a synthetic linear alcohol (Ziegler process) or directly from aluminum metal (dedicated route). The Ziegler route for the synthesis of alumina involves the oligomerization of ethylene using triethylaluminum and subsequent oxidation. Triethylaluminum can be produced by reacting aluminum, ethylene and hydrogen. In this production process, two-thirds of the triethylaluminum produced is recycled back to the reactor and only one-third is used to produce the alcohol. The recycling step is used to produce triethylaluminum with higher yields and shorter times. Triethylaluminum reacts with ethylene to form a higher molecular weight trialkylaluminum. The number of ethylene equivalents, n, is equal to the total number of monomer units grown on the initial ethylene chain, where n=x+y+z, where x, y and z are the number of ethylene units per chain. The trialkylaluminum is oxidized with air to form an aluminum alkoxide, which is ultimately hydrolyzed to aluminum hydroxide and the desired alcohol.

[0029] Al+3C2H4+1.5H2→Al(C2H5)3

[0030] Al(C2H5)3+nethylene→Al((CH2CH2) n CH2CH3)3

[0031] Al((CH2CH2) n CH2CH3)3+O2→Al(O(CH2CH2) n CH2CH3)3

[0032] Al(O(CH2CH2) n CH2CH3)3→Al(OH)3+CH3CH2(CH2C2) m OH

[0033] According to another embodiment of the present invention, the alumina used as the support material is selected from the group consisting of aluminum oxyhydroxide, gamma-alumina, boehmite, diaspore, transition alumina, rho-alumina, and any combination of two or more thereof. Suitable examples of transition alumina are alpha-alumina, beta-alumina, gamma-alumina, delta-alumina, epsilon-alumina, and kappa-alumina, while suitable examples of rho-alumina are aluminum trihydroxides such as gibbsite, bayerite, nordstrandite, and doyelite.

[0034] According to an alternative embodiment of the present invention, the support material for the catalyst of catalytic dehydrobromination reaction is silicon dioxide. Suitable examples of the source of silicon dioxide are silicates, precipitated silica, such as the Zeosil series available from Rhodia, fumed silica, such as the Aerosil-200 available from Degussa Inc., New York, NY, silicon compounds, such as tetraalkyl orthosilicates, such as tetramethyl orthosilicate (TMOS) and tetraethyl orthosilicate (TEOS), colloidal silicon dioxide or its aqueous suspension, such as the Ludox-HS-40 sol available from EI du Pont de Nemours, Wilmington, Del., silicic acid, alkali metal silicate or its arbitrary combination. Other suitable examples of amorphous silicon dioxide include silicon dioxide powder, such as Ultrasil VN3SP (commercially available from Degussa).

[0035] According to a particular embodiment of the invention, silica sol or a combination of silica sol and precipitated or fumed silica is used as silicon source for the preparation of the catalyst.

[0036] One or more zeolites may also be used as a support material for the catalyst catalyzing the dehydrobromination reaction. The zeolite may contain 0.01 to 10% by weight of phosphorus. In addition, the zeolite may be exchanged with Ca-, Mg-, La-, and / or Ce-compounds, or directly with salts of transition metals and / or noble metals provided on the support material of the catalyst to be used for the dehydrobromination reaction.

[0037] According to another alternative embodiment of the present invention, carbon is used as the silicon source for preparing the catalyst for catalyzing the dehydrobromination reaction. Preferably, the carbon is selected from graphite, carbon black, coke, petroleum coke, and any combination of two or more thereof. Graphite is particularly preferred.

[0038] According to an alternative embodiment of the present invention, silicon carbide is used as a silicon source for preparing a catalyst for catalyzing the dehydrobromination reaction. Suitable examples are therefore sintered silicon carbide, nitride-bonded silicon carbide, recrystallized silicon carbide, reaction-bonded silicon carbide, and any combination of two or more thereof.

[0039] According to yet another alternative embodiment of the present invention, aluminophosphates (ALPO) and / or metalloaluminophosphates (MeAPO) are used as silicon sources for the preparation of the catalyst for catalyzing the dehydrobromination reaction.

[0040] As described above, the catalyst preferably comprises a support material and at least 200 ppm of at least one metal selected from transition metals, noble metals, and any combination of two or more thereof. Preferably, the support material comprises from 200 ppm to 20% by weight of one or more transition metals. The present invention is not particularly limited with respect to the type of transition metal. However, particularly good results are achieved when the catalyst comprises at least one compound selected from iron, cobalt, nickel, molybdenum, manganese, lead, copper, chromium, zinc, gallium, and any combination of two or more thereof as the transition metal.

[0041] Furthermore, it is preferred to use a catalyst in the process which comprises a support material and thereon 200 ppm to 5 wt % of one or more noble metals. The one or more noble metals may be provided on the support material in place of or in addition to one or more transition metals.

[0042] The present invention is not particularly limited in the type of noble metal. However, particularly good results are achieved when the catalyst comprises at least one compound selected from silver, platinum, palladium, ruthenium, iridium, and any combination of two or more thereof as the noble metal.

[0043] The transition metal and / or noble metal can be introduced onto the support material in any known manner, such as by precipitation, by deposition, by impregnation, by ion exchange, by grafting, by anchoring, by chemical vapor deposition (CVD), by atomic layer epitaxy (ALE) or by encapsulation. Preferably, the transition metal and / or noble metal is introduced onto the support material by impregnation, since this technique allows a given porous support material to be loaded with transition metal and / or noble metal in a solid state manner (i.e. a physical mixture of the two components in the solid state) or more preferably via wet impregnation (i.e. a physical mixture of the support in the solid state with the metal component dissolved in a liquid solution).

[0044] Before the transition metal and / or noble metal is loaded onto the support material, the support material is preferably shaped, which allows it to be processed into a catalyst with the desired particle size and good crush strength. This is advantageous because it allows limiting the pressure drop during the reaction and prevents the catalyst from decomposing into a powdered material during the reaction. For this reason, the support material is preferably shaped alone or with the addition of a binder. The binder can be selected to withstand the temperature and other conditions used in the method for using the catalyst, and the binder can be an inorganic material selected from the same chemical group as the material of the support material, i.e., silica, metal silicates, zirconium oxide, borates, aluminum oxide, silica-alumina, phosphates (e.g., amorphous aluminum phosphates), calcium phosphates, clays, xonotlite, magnesium oxide, metal oxides (e.g., zirconium dioxide), metals, and gels (comprising mixtures of silica and metal oxides). Clays are known to be substantially inert under a wide range of reaction conditions. Suitable clays include commercially available products such as kaolin, kaolinite, montmorillonite, attapulgite, saponite, and bentonite. These clays can be used in their natural state as mined, or they can be used in a highly active form, such as activated by an acid treatment process. Clays contribute strength by acting as a binder that enhances the anti-wear properties of the catalyst particles, and clays in combination with other binders contribute to the hardness of the particles. Clays also start out as small particles and have a higher density, which provides a denser particle when combined with the molecular sieve and binder, imparting the desirable property of higher density.

[0045] Once the support material is formed, the transition metal and / or noble metal is loaded onto the support material, and the catalyst is present in a substantially dry or dried state, it is preferably subjected to a heat treatment (e.g., calcination) to harden and / or activate the composition. Preferably, the heat treatment is carried out at a temperature of at least 400° C. for a period of 1 to 48 hours. Calcination can be carried out, for example, in a rotary calciner, a fluidized bed calciner, or a batch furnace.

[0046] According to another preferred embodiment of the present invention, the catalyst has a silicon dioxide content of less than 0.4% by weight, a sulfur and sulfur-containing compound content of less than 0.5% by weight, and a sodium and sodium-containing compound content of less than 200 ppm.

[0047] Good results are particularly achieved when the catalyst contains alkaline earth metals, rare earth metals, compounds containing at least one alkaline earth metal and compounds containing at least one rare earth metal in an amount of 0.1% to 5% by weight in total. Preferred alkaline earth metals and rare earth metals are calcium, magnesium, yttrium and lanthanum.

[0048] Good results are particularly achieved when the catalyst contains a small amount of alkali metal or, better, even no alkali metal. In view of this, it is preferred that the catalyst contains alkali metal and a compound containing at least one alkali metal in an amount of less than 1,000 ppm, preferably less than 200 ppm, more preferably less than 100 ppm in total.

[0049] According to another preferred embodiment of the present invention, the catalyst contains chlorine in an amount of less than 1,000 ppm, preferably less than 200 ppm, more preferably less than 100 ppm, even more preferably less than 50 ppm, still more preferably less than 20 ppm and most preferably less than 10 ppm in total.

[0050] Since the dehydrobromination reaction is endothermic, an inert component is preferably added to the mixture as a heat carrier to provide energy to the reactor. 1-10 The weight ratio of the brominated hydrocarbon to the inert component is preferably from 1:10 to 10:1 and preferably from 1:5 to 5:1. Suitable examples of inert components are C 1-10 Alkanes, steam, nitrogen, argon, methane, carbon dioxide, naphtha and any combination of two or more of the foregoing inert compounds. 3-7 Alkanes, more preferably C 4-6 Particularly good results are obtained with alkanes and most preferably pentane.

[0051] The present invention has no particular restrictions on the type of reactor in which the dehydrobromination reaction is carried out. Preferably, the reaction is carried out in a fixed-bed reactor, a radial reactor, a multi-tubular reactor, a moving-bed reactor or a fluidized-bed reactor. A suitable fluidized-bed reactor is one of the FCC types used for fluidized-bed catalytic cracking in oil refineries. A typical moving-bed reactor is a continuous catalytic reforming type. Alternatively, the dehydrobromination reaction can be carried out in a fixed-bed reactor configuration using a pair of parallel "swing" reactors. This is possible due to the high stability of the aforementioned catalyst.

[0052] In a further development of the concept of the invention, it is provided that the dehydrobromination reaction is carried out at an absolute pressure of 50 kPa to 3 MPa, more preferably 50 kPa to 1 MPa, even more preferably 50 kPa to 500 kPa, still more preferably 120 kPa to 500 kPa and most preferably 120 kPa to 400 kPa. Preferably, the pressure is adjusted so that the one or more olefinically unsaturated compounds (such as one or more C 2-10 The partial pressure of the olefins) is lower than 2 bar and more preferably lower than 1 bar.

[0053] The dehydrobromination reaction is an endothermic reaction and thus requires the input of reaction heat to maintain sufficiently high catalyst activity and to shift the thermodynamic equilibrium to a sufficiently high reaction level. In view of this, the dehydrobromination reaction is preferably carried out at a temperature of 200° C. to 500° C., more preferably 225° C. to 450° C., and most preferably 250° C. to 400° C.

[0054] In the case of carrying out the reaction in a fluidized bed reactor using a fixed fluidized bed without catalyst circulation, the reaction temperature is substantially uniform throughout the catalyst bed. However, in the case of carrying out the reaction in a fluidized bed reactor using a circulating fluidized bed to circulate the catalyst between the reaction zone and the catalyst regeneration zone, the temperature in the catalyst bed, depending on the degree of catalyst backmixing, approaches a uniform condition in the case of a large amount of backmixing, or approaches a plug flow condition in the case of almost no backmixing and therefore forms a decreasing temperature distribution as the reaction proceeds. In the case of carrying out the reaction in a fixed bed reactor or a moving bed reactor, a decreasing temperature distribution will be formed as the reaction proceeds. In this case, reaction heat can be introduced by the following method: using multiple (several) catalyst beds in series, wherein the reactor effluent from the first bed is heated to a higher temperature in the middle (inter), and the heated effluent is introduced into a second catalyst bed, etc. When carrying out the reaction in a fixed bed reactor, a multi-tube reactor can be used, wherein the catalyst is loaded in a small diameter tube installed in the reactor shell. On the shell side, a heating medium can be introduced, which provides the required reaction heat by heat transfer to the catalyst via the reactor tube wall. Radial or spherical reactors can be used to overcome excessively high input pressure drops.

[0055] According to another preferred embodiment of the present invention, the weight hourly space velocity (WHSV) of the composition catalyzing the dehydrobromination reaction is 1 to 100 h -1 , more preferably 2 to 50h -1 , still more preferably 3 to 20h -1 and most preferably 4 to 12 hours -1 Preferably, as one or more C 1-10 The ratio of the weight of the brominated hydrocarbon to the weight of the catalyst measures the weight hourly space velocity of the composition without regard to diluent flow.

[0056] In a further development of the concept of the invention, it is proposed to periodically regenerate the catalyst by subjecting it to temperatures of 400 to 525° C. and preferably 420 to 500° C. in an oxygen-containing atmosphere. Thereby, the carbon on the catalyst is burned together with the oxygen. Taking into account the noble metals and / or transition metals contained in the catalyst, it is preferred to limit the exposure of the catalyst to temperatures of at most 525° C. and preferably 500° C. Preferably, the regeneration is carried out at approximately 450° C., with a temperature variation of at most 50° C. on the reactor. This is usually achieved by limiting the amount of oxygen in the regeneration circuit to at most 1 mol % in the initial stage. After the removal of the main part of the carbon, the oxygen content can be raised to at most 5 mol %. Water vapor, hydrogen bromide and / or carbon dioxide may be present in the regeneration circuit. After the end of the regeneration, it is preferred to remove all traces of oxygen from the catalyst, since the presence of oxygen catalyzes the carbonization of the catalyst. 2-10 Rebromination of olefins with hydrogen bromide.

[0057] Preferably, the composition containing hydrogen, hydrogen bromide and olefinically unsaturated compounds is subjected to at least one separation step in order to separate it into a composition rich in hydrogen bromide and a composition rich in olefinically unsaturated compounds. Thus, any suitable separation technique may be used. According to a particularly preferred embodiment of the present invention, at least one separation step comprises at least one and preferably two distillation steps and / or comprises at least one absorption step.

[0058] According to a particularly preferred embodiment of the present invention, at least one separation step comprises a (first) distillation step, in which the composition comprising hydrogen, hydrogen bromide and olefinically unsaturated compounds is distilled in order to separate it into a composition rich in polybrominated hydrocarbons as a bottoms composition and an overhead composition comprising olefinically unsaturated compounds, hydrogen bromide and hydrogen.

[0059] Furthermore, it is preferred that at least one separation step comprises an absorption step wherein the composition comprising hydrogen, hydrogen bromide and olefinically unsaturated compounds is contacted with water or an aqueous solution in order to obtain purified olefinically unsaturated compound-rich and hydrogen bromide-rich compositions.

[0060] When at least one separation step comprises (first) a distillation step, wherein a composition containing hydrogen, hydrogen bromide and olefinically unsaturated compounds is distilled so as to separate it into a composition rich in polybrominated hydrocarbons as a bottoms composition and an overhead composition containing olefinically unsaturated compounds, hydrogen bromide and hydrogen, and further comprises an absorption step, wherein the overhead composition obtained in the distillation step is contacted with water or an aqueous solution so as to obtain a purified composition rich in olefinically unsaturated compounds and a composition rich in hydrogen bromide, particularly good results are obtained. When water or an aqueous composition is used as an absorbent in the absorption step, particularly good results are obtained. The absorbent can contain at least 80% by weight and preferably at least 95% by weight of water, and one or more compounds such as, for example, hydrogen bromide to 100% by weight. Particularly preferably, the aqueous composition used as absorbent contains hydrogen bromide, such as hydrogen bromide from the recycled absorbent, which is preferably used in the loop, i.e. recycled after the absorption step. In addition, the aqueous composition used as an absorbent may contain from its recovery (particularly after the use of an electrolysis step and a ternary column to convert hydrogen bromide into hydrogen and bromide) greater than 0 to 1,000 ppm of bromine, preferably 1 to 100 ppm of bromine, and more preferably 1 to 10 ppm of bromine. In addition, it is preferred that the hydrogen bromide-rich composition has a hydrogen bromide concentration of at least 30% by weight and more preferably at least 40% by weight, and an absorbent content of at most 60% by weight and more preferably at most 48% by weight. Similarly, if the absorbent is water, in practice the hydrogen bromide-rich composition is an aqueous solution containing hydrogen bromide.

[0061] It is further preferred in this embodiment that the bottoms composition obtained in the first distillation step is subjected to a further second distillation step in order to obtain a light hydrocarbon composition as overhead composition and a polybrominated propane-rich composition as bottoms composition.

[0062] In a further development of the concept of the invention, it is proposed to subject the composition rich in hydrogen bromide obtained in the washing step to electrolysis in order to obtain hydrogen at one of the two electrodes and a mixture containing bromine, water and hydrogen bromide at the other electrode, and subsequently to distill the mixture containing hydrogen bromide, water and bromine to obtain as bottom product a mixture containing hydrogen bromide, water and more than 0 to 1,000 ppm of bromine, preferably from 1 to 100 ppm of bromine and more preferably from 1 to 10 ppm of bromine, which mixture is recycled to the absorption step.

[0063] Furthermore, it is preferred that the at least one separation step comprises a pressure swing adsorption step in order to remove hydrogen from the composition enriched in olefinically unsaturated compounds or from the purified olefinically unsaturated compounds.

[0064] The brominated hydrocarbon contained in the precursor composition, such as C 1-10Bromoalkanes, such as bromopropane, can be obtained by any suitable reaction. For example, brominated hydrocarbons can be obtained by reacting a hydrocarbon containing the corresponding hydrocarbon (such as C 1-10 alkanes, such as propane) and further comprising bromine to produce a mixture containing brominated hydrocarbons (such as C 1-10 The reaction mixture is obtained by mixing a bromoalkane (e.g., bromopropane) and hydrogen bromide. Good results are particularly achieved when the molar ratio of hydrocarbon to bromine in the reaction mixture is from 10:1 to 1:1 and preferably from 3:1 to 2:1. Preferably, the reaction is carried out in the absence of a catalyst at a temperature of preferably from 200 to less than 420° C., more preferably from 230 to 410° C., even more preferably from 240 to 400° C., and most preferably from 240 to 300° C. Furthermore, it is preferred that the mixture be reacted under elevated pressure, more preferably at a pressure of at least 400 kPa, even more preferably at a pressure of at least 1 MPa, and most preferably from 1 to 4 MPa. Elevated pressure results in high conversion per time unit and advantageously avoids or at least minimizes the formation of unsaturated products (e.g., allyl bromide or propylene) in the reaction mixture. Good results are particularly achieved when the residence time of the mixture in the reactor is at least 10 seconds and more preferably from 20 seconds to 2 minutes. In this regard, residence time refers to the time period between the mixture entering the reactor (in which the reaction is carried out) and the reaction mixture leaving the reactor. In practice, not all bromine and / or hydrocarbons will react to form bromopropanes during the bromination reaction, but polybrominated propanes will also be formed, and small amounts of bromine and propane will remain in the reaction mixture as unreacted educts. Therefore, the reaction mixture obtained in the bromination reaction will, in practice, further contain one or more polybrominated propanes, unreacted propane and optionally at least trace amounts of unreacted bromine. Therefore, it is preferred that the reaction mixture be subjected to one or more separation steps, such as preferably one or two distillation steps and / or at least one absorption step with water or an aqueous absorption medium.

[0065] According to another aspect, the present invention relates to an apparatus comprising:

[0066] a reactor for catalytically reacting one or more brominated hydrocarbons to produce a reaction mixture containing olefinically unsaturated hydrocarbons and hydrogen bromide, wherein the reactor comprises an inlet line for the one or more brominated hydrocarbons and an outlet line for the reaction mixture,

[0067] a separation unit comprising an inlet line for the reaction mixture connected to the outlet line for the reaction mixture of the reactor, an outlet line for the olefinically unsaturated hydrocarbon and an outlet line for a composition rich in hydrogen bromide,

[0068] wherein i) the inlet line for one or more brominated hydrocarbons of the reactor is connected to the inlet line for hydrogen, or ii) the reactor comprises a further inlet line for hydrogen, or iii) the line connecting the outlet line for the reaction mixture of the reactor and the inlet line for the reaction mixture of the separation unit is connected to the inlet line for hydrogen, or iv) the separation unit is connected to the inlet line for hydrogen, or v) any combination of two or more of the aforementioned features i) to iv) is met.

[0069] Preferably, the separation unit comprises at least one and preferably two distillation columns and / or at least one absorption column.

[0070] Good results are particularly achieved when the separation unit comprises the following components:

[0071] a first distillation column comprising an inlet line connected to the outlet line for the reaction mixture, an overhead outlet line and a bottoms outlet line,

[0072] an absorption column comprising an inlet line connected to the overhead outlet line of the first distillation column, an inlet line for an absorbent, an outlet line for a composition rich in hydrogen bromide and an outlet line for a mixture of olefinically unsaturated compounds and hydrogen, and

[0073] - a second distillation column comprising an inlet line connected to the bottom outlet line of the first distillation column, an overhead outlet line, and a bottom outlet line.

[0074] In a further development of the concept of the invention, it is proposed that the separation unit further comprises a separation device, which comprises an inlet pipeline connected to the outlet pipeline of the absorption column for the mixture of olefinically unsaturated compounds and hydrogen, an outlet pipeline for hydrogen and an outlet pipeline for olefinically unsaturated compounds, wherein the separation device is preferably a pressure swing adsorption column.

[0075] Furthermore, it is preferred that the apparatus further comprises a purification unit, wherein the purification unit comprises an electrolysis cell comprising an anode, a cathode and a membrane sandwiched between the anode and the cathode, and an inlet line for a composition comprising hydrogen bromide, an outlet line for hydrogen and an outlet line for a composition comprising bromine, wherein the inlet line of the electrolysis cell is connected to the outlet line for a composition rich in hydrogen bromide of the separation unit, and wherein the outlet line for the bromine-containing composition is connected to the inlet line of a reactor for catalytically reacting one or more brominated hydrocarbons.

[0076] According to another preferred embodiment of the present invention, the device further comprises:

[0077] a reactor for reacting a mixture comprising a hydrocarbon and bromine to produce a reaction mixture comprising brominated hydrocarbon and hydrogen bromide, wherein the reactor comprises an inlet line for the mixture and an outlet line for the reaction mixture comprising brominated hydrocarbon and hydrogen bromide,

[0078] a first separation unit comprising an inlet line for a reaction mixture containing brominated hydrocarbons and hydrogen bromide, an outlet line for a composition enriched in brominated hydrocarbons and an outlet line for a composition enriched in hydrogen bromide, connected to the outlet line for the reaction mixture of a reactor for reacting a mixture containing hydrocarbons and bromine,

[0079] The outlet line for the composition rich in brominated hydrocarbons is connected to an inlet line for one or more brominated hydrocarbons of a reactor for catalytically reacting one or more brominated hydrocarbons.

[0080] Preferably, the separation unit comprises at least one and preferably two distillation columns and / or at least one absorption column.

[0081] Good results are particularly achieved when the separation unit comprises the following components:

[0082] a first distillation column comprising an inlet line connected to the outlet line for the reaction mixture of a reactor for reacting a mixture comprising hydrocarbons and bromine, an overhead outlet line and a bottoms outlet line,

[0083] an absorption column comprising an inlet line connected to the overhead outlet line of the first distillation column, an inlet line for an absorbent, an outlet line for a composition rich in hydrogen bromide and an outlet line for a purified propane composition, and

[0084] a second distillation column comprising an inlet line connected to the bottom outlet line of the first distillation column, an overhead outlet line for a composition rich in bromopropane, and a bottom outlet line.

[0085] Next, specific embodiments according to the present invention will be described with reference to the accompanying drawings.

[0086] Figure 1 is a schematic diagram of an apparatus according to one embodiment of the present invention.

[0087] Figure 1 The apparatus 10 shown in FIG. 1 and its operation subsequently uses propane as a hydrocarbon (e.g., C 1-10 alkane), propylene is used as the olefinically unsaturated compound (such as C 2-10 olefins), and the use of bromopropane as a brominated hydrocarbon (such as C 1-10 The device 10 comprises:

[0088] i) a bromination reactor 12 for reacting a mixture comprising propane and bromine to produce a first reaction mixture comprising bromopropane and hydrogen bromide,

[0089] ii) a first separation unit 14 for separating a bromopropane-rich composition, a propane-rich composition, a polybrominated propane-rich composition, and a hydrogen bromide-rich composition from the first reaction mixture,

[0090] iii) a dehydrobromination reactor 16 for catalytically reacting the bromopropane-rich composition obtained in the first separation unit 14 to obtain a second reaction mixture containing propene and hydrogen bromide,

[0091] iv) a second separation unit 18 for separating propylene, a polybrominated propane-rich composition, and a hydrogen bromide-rich composition from the second reaction mixture,

[0092] v) a thermal oxidizer 20 for oxidizing the polybrominated propane-rich composition obtained in the first and second separation units,

[0093] vi) an absorption column 22 for contacting the composition rich in hydrogen bromide obtained in the first and second separation units with the oxidation product obtained in the thermal oxidizer 20,

[0094] vii) an electrolysis cell 24 for producing hydrogen and a bromine-containing composition from the hydrogen bromide-rich composition treated in the absorption column 22, and

[0095] viii) A purification unit 26 for obtaining pure bromine from the bromine-containing composition obtained in the electrolytic cell 24 .

[0096] More specifically, the bromination reactor 12 comprises an inlet line 28 for a mixture comprising propane and bromine and an outlet line 30 for a first reaction mixture. The inlet line 28 is connected to a feed line 32 for a propane-containing gas (e.g., natural gas), a recycle line 34 for propane, and a recycle line 36 for bromine, wherein a heat exchanger 38 is arranged so that the first reaction mixture withdrawn from the bromination reactor 12 via the outlet line 30 preheats the propane-containing gas introduced through the feed line 32. The outlet line 30 passes through another heat exchanger 40 before it is introduced into the first separation unit 14. Viewed from upstream to downstream of the first separation unit 14, the first separation unit 14 comprises a first distillation column 42, an absorption column 44, and a second distillation column 46. The first distillation column 42 includes an inlet line 48 connected to the outlet line 30 for the first reaction mixture of the bromination reactor 12, an overhead outlet line 50, and a bottom outlet line 52, while the absorption column 44 includes an inlet line 54 connected to the overhead outlet line 50 of the first distillation column 42, an inlet line 56 for the absorbent, an outlet line 58 for a composition rich in hydrogen bromide, and an outlet line for a purified propane composition 60. The outlet line for the purified propane composition 60 is introduced into the recycle line 34 for propane via a compressor 62. In turn, the second distillation column 46 includes an inlet line 64 connected to the bottom outlet line 52 of the first distillation column 42, an overhead outlet line 66 for a composition rich in bromopropanes, and a bottom outlet line 68 for a composition rich in polybrominated propanes.

[0097] Dehydrobromination reactor 16 for catalytically reacting the bromopropane-rich composition to produce a second reaction mixture containing propylene and hydrogen bromide comprises an inlet line 70 for the bromopropane-rich composition connected to overhead outlet line 66 for the bromopropane-rich composition of second distillation column 46 of first separation unit 14 via heat exchanger 72, and an outlet line 74 for the second reaction mixture directed to second separation unit 18 via heat exchanger 72 and compressor 76. Viewed from upstream to downstream of second separation unit 18, second separation unit 18 comprises a first distillation column 80, an absorption column 82, and a second distillation column 84. First distillation column 80 comprises an inlet line 78 for the second reaction mixture of bromination reactor 12 connected to outlet line 74 of dehydrobromination reactor 16, an overhead outlet line 86, and a bottoms outlet line 88, while absorption column 82 comprises an inlet line 90 connected to overhead outlet line 86 of first distillation column 80, an inlet line 92 for absorbent, an outlet line 94 for a composition rich in hydrogen bromide, and an outlet line 96 for (purified) propylene. Outlet line 96 for (purified) propylene leads to pressure swing adsorption column 98, which comprises an outlet line 100 for propylene and an outlet line 102 for hydrogen, which divides into a take-off line 104 for hydrogen and a recycle line 106 leading back to inlet line 70 for the second reaction mixture of dehydrobromination reactor 16. Furthermore, the second distillation column 84 of the second separation unit 18 comprises an inlet line 108 connected to the bottom outlet line 88 of the first distillation column 80, a 4-5 An overhead outlet line 110 for the hydrocarbon composition, a bottoms outlet line 112 for a composition rich in polybrominated propanes, and a recycle line 114 for the composition rich in polybrominated propanes that leads to the overhead outlet line 66 of the second distillation column 44 of the first separation unit 14 .

[0098] The oxidation unit 20 includes an inlet line 116 for air, an inlet line 118 connected to the bottom outlet line 68 of the second distillation column 46 of the first separation unit 14 and to the bottom outlet line 112 of the second distillation column 84 of the second separation unit 18, and an outlet line 120. Furthermore, the absorption column 22 includes an inlet line connected to the outlet line 120 of the oxidation unit 20, an inlet line 122 for a composition rich in hydrogen bromide connected to the outlet line 58 for a composition rich in hydrogen bromide of the absorption column 44 of the first separation unit 14 and to the outlet line 94 for a composition rich in hydrogen bromide of the absorption column 82 of the second separation unit 18, an outlet line 124 for air, and an outlet line 126 for a composition rich in hydrogen bromide connected to the inlet line for a composition containing hydrogen bromide of the electrolysis cell 24. Electrolyzer 24 comprises an outlet line 128 for the bromine-containing composition, an outlet line 130 for hydrogen connected to compressor 132, a recycle line 134 leading to recycle line 106, and a hydrogen removal line 136. Finally, purification unit 26 comprises a distillation column 138 comprising an inlet line connected to outlet line 128 for the bromine-containing composition of electrolyzer 24, a bottoms outlet line for a mixture of water and hydrogen bromide, a recycle line 140, and an overhead outlet line 142 for hydrogen. The bottom outlet line and recycle line 140 of the purification unit 26 lead to the absorbent inlet lines 56, 92 of the second distillation columns 44, 82 of the first and second separation units 14, 18, while the overhead outlet line 142 leads to a condenser 144 and from there to a container 146, from which a return line 148 leads back to the distillation column 138, and an outlet line 150 leads to a dryer column 152. The dryer column 152 comprises a bottom outlet line for bromine connected to the recycle line 36 and an overhead outlet 156 that leads back to the overhead outlet line 142 of the distillation column 138.

[0099] During operation of the apparatus 10, a mixture comprising propane and bromine is introduced via line 28 into the bromination reactor 12, where the propane reacts with bromine to form bromopropane and hydrogen bromide. Furthermore, the (first) reaction mixture contains unreacted propane, unreacted bromine, and by-products such as polybrominated propanes. Subsequently, the (first) reaction mixture is introduced via lines 30 and 48 into the first distillation column 42 of the first separation unit, where the reaction mixture is separated into a bottoms composition comprising primarily bromopropane and a small amount of polybrominated propanes, and an overhead composition comprising primarily hydrogen bromide, unreacted propane, and unreacted bromine. The overhead composition is fed to an absorption column 44 via lines 50, 54 and contacted there with an absorbent, which is an aqueous solution containing a small amount of hydrogen bromide that is recycled to the absorption column 44 via lines 140, 56, to obtain a purified propane composition that is recycled to the mixture used in step a) via lines 60, 34 and compressor 62, and a composition rich in hydrogen bromide is withdrawn from the absorption column 44 via line 58. The bottoms composition of the first distillation column 42 of the first separation unit 14, which contains mainly bromopropane and a small amount of polybrominated propanes, is introduced into the second distillation column 46 via lines 52, 64, where polybrominated propanes are separated from bromopropanes as a bottoms composition. Simultaneously with the withdrawal of a polybrominated propane composition from the second distillation column 46 via line 68, a bromopropane composition rich in propane is withdrawn from the second distillation column 46 via line 66. Subsequently, the bromopropane-rich composition is dehydrobrominated in the presence of hydrogen in the dehydrobromination reactor 16 to obtain a second reaction mixture containing propylene, hydrogen bromide, hydrogen and polybrominated propanes. The second reaction mixture is then separated in the second separation unit 18 into pure propylene withdrawn via line 100, pure hydrogen withdrawn via line 102 and partially recycled to the dehydrobromination reactor 16 via lines 102, 106, and 70, a polybrominated propane-rich composition withdrawn via line 112, and a hydrogen bromide-rich composition withdrawn via line 94. The two polybrominated propane-rich compositions withdrawn from the first and second separation units via lines 68 and 112 are oxidized primarily to bromine in the thermal oxidizer 20, which are then contacted together with the two hydrogen bromide-rich compositions withdrawn from the first and second separation units via lines 58 and 94 in the absorption tower 22, from which the hydrogen bromide-rich composition (which is actually an aqueous solution containing hydrogen bromide) is withdrawn via line 126 and introduced into the electrolysis cell 24. Electrolyzer 24 produces hydrogen from the composition at the cathode and bromine from the composition at the anode. While hydrogen is withdrawn from electrolyzer 24 via line 130 and partially recycled to dehydrobromination reactor 16 via lines 134, 106, 70, a bromine-containing composition (which is an aqueous solution containing bromine and hydrogen bromide) is withdrawn from electrolyzer 24 via line 128.Subsequently, the bromine-containing composition is separated in a distillation column 138 into an aqueous solution containing hydrogen bromide, which is withdrawn via line 140 and recycled as absorbent to the absorption columns 44, 82 of the first and second separation units 14, 18 via lines 56, 92, and a composition rich in bromine. The latter is withdrawn from the distillation column 138 via line 142 and dehydrated in a distillation column 152 to obtain pure bromine, which is introduced via lines 154, 36 into the mixture introduced via line 28 into the bromination reactor 12.

[0100] The second reaction mixture contains propylene, hydrogen bromide, hydrogen, and polybrominated propanes, wherein the hydrogen protects the propylene from rebromination by hydrogen bromide generated from the second reaction mixture and throughout the separation step until the hydrogen is removed from the purified propylene. Figure 1 In the embodiment shown, hydrogen is added to the precursor composition of the reaction mixture, ie, to the bromopropane-rich composition withdrawn from distillation column 46 via overhead outlet line 66 . Example

[0101] comparison

[0102] An empty quartz tube with a length of 50 cm and an inner diameter of 10 mm was covered with aluminum foil to prevent light from penetrating. The tube was heated to 120° C. The inlet of the reactor was connected to an online GC analysis.

[0103] A blank test was performed for 10 minutes during a 2-hour run at 120° C. under atmospheric pressure using 30 ml / min of He, 3 ml / min of propylene, and 2 ml / min of nitrogen. The total gas flow (i.e., the flow of hydrogen bromide, propylene, and nitrogen) to the reactor was 35 ml / min. No changes in the reaction mixture were observed.

[0104] Comparative Example 1

[0105] The experiment was repeated under the same conditions as the control, except that the He flow rate was replaced by an equivalent hydrogen bromide flow rate (i.e., 30 ml / min), while the propylene flow rate was maintained at 3 ml / min and the nitrogen flow rate was maintained at 2 ml / min. The total gas flow rate (i.e., hydrogen bromide, propylene, and nitrogen) entering the reactor at atmospheric pressure during a 2-hour run at 120° C. was 35 ml / min. The hydrogen bromide / propylene molar ratio was approximately 10. Approximately 55% of the propylene was converted to bromopropane, i.e., rebrominated.

[0106] Comparative Example 2

[0107] Comparative Example 1 was repeated, except that the hydrogen bromide flow rate was changed to 6 ml / min, the propylene flow rate was maintained at 3 ml / min, and the nitrogen flow rate was increased to 26 ml / min. The total gas flow rate (i.e., hydrogen bromide, propylene, and nitrogen) entering the reactor at atmospheric pressure during a 2-hour run at 120°C was 35 ml / min. The hydrogen bromide / propylene molar ratio was approximately 2. Approximately 12% of the propylene was converted to bromopropane, i.e., rebromination. Due to the lower hydrogen bromide partial pressure (i.e., lower hydrogen bromide / propylene molar ratio), a lower amount of rebromination was observed compared to Comparative Example 1.

[0108] Comparative Example 3

[0109] Comparative Example 2 was repeated, except that the hydrogen bromide flow rate was adjusted to 6 ml / min, the propylene flow rate was adjusted to 3 ml / min, and the nitrogen flow rate was adjusted to 26 ml / min. The total gas flow rate (i.e., hydrogen bromide, propylene, and nitrogen) entering the reactor at atmospheric pressure during a 2-hour run at 120°C was 35 ml / min. The hydrogen bromide / propylene molar ratio was approximately 2. Propane bromide reappeared in the effluent mixture. Approximately 9% of the propylene was converted back to propane bromide, i.e., rebrominated.

[0110] Example 1

[0111] The differences from Comparative Example 1 were that the hydrogen bromide flow rate was adjusted to 6 ml / min, the propylene flow rate was adjusted to 3 ml / min, the hydrogen flow rate was adjusted to 6 ml / min, and the nitrogen flow rate was adjusted to 20 ml / min. The total gas flow rate (i.e., hydrogen bromide, propylene, and nitrogen) entering the reactor at atmospheric pressure during a 2-hour run at 120°C was 35 ml / min. The hydrogen bromide / propylene molar ratio was approximately 2. No bromopropane was detected.

[0112] Reference Signs List

[0113] 10 Equipment

[0114] 12 Bromination Reactor

[0115] 14. First separation unit

[0116] 16 Dehydrobromination Reactor

[0117] 18 Second separation unit

[0118] 20 Thermal Oxidizer

[0119] 22 Absorption Tower

[0120] 24 electrolytic cells

[0121] 26 purification units

[0122] 28 Inlet line for the first reaction mixture of the bromination reactor

[0123] 30 Reactor outlet pipeline

[0124] 32 for feed lines containing propane gas

[0125] 34 Recirculation line for propane

[0126] 36 Recycle line for bromine

[0127] 38 Heat Exchanger

[0128] 40 heat exchanger

[0129] 42 The first distillation column of the first separation unit

[0130] 44 Absorption tower of the first separation unit

[0131] 46 The second distillation column of the first separation unit

[0132] 48 inlet pipeline of the first distillation column of the first separation unit

[0133] 50 overhead distillate outlet pipeline of the first distillation tower

[0134] 52 Bottom outlet pipeline of the first distillation tower

[0135] 54 Inlet pipeline of absorption tower

[0136] 56 Inlet line for absorbent

[0137] 58 outlet line for a composition rich in hydrogen bromide

[0138] 60 Export line for purified propane composition

[0139] 62 compressor

[0140] 64 Inlet pipeline of the second distillation column

[0141] 66 The top distillate outlet pipeline of the second distillation tower

[0142] 68 Bottom outlet pipeline of the second distillation tower

[0143] 70 Inlet line for the second reaction mixture of the dehydrobromination reactor

[0144] 72 heat exchanger

[0145] 74 outlet line for the second reaction mixture

[0146] 76 compressor

[0147] 78 Inlet pipeline of the first distillation column of the second separation unit

[0148] 80 The first distillation column of the second separation unit

[0149] 82 Absorption tower of the second separation unit

[0150] 84 The second distillation column of the second separation unit

[0151] 86 overhead distillate outlet pipeline of the first distillation tower

[0152] 88 Bottom outlet pipeline of the first distillation tower

[0153] 90 Inlet pipeline of absorption tower

[0154] 92 Inlet line for absorbent

[0155] 94 outlet line for a composition rich in hydrogen bromide

[0156] 96 Export line for purified propylene

[0157] 98 Pressure Swing Adsorption Tower

[0158] 100 Export line for propylene

[0159] 102 Export pipeline for hydrogen

[0160] 104 Take-out line for hydrogen

[0161] 106 Recirculation line for hydrogen

[0162] 108 inlet pipeline of the second distillation column of the second separation unit

[0163] 110 for C 4-5 Overhead distillate outlet line for hydrocarbon composition

[0164] 112 The bottom outlet pipeline of the second distillation tower of the second separation unit

[0165] 114 Recycle line for polybrominated propane-rich composition

[0166] 116 Inlet line for air

[0167] 118 Inlet line for polybrominated propane-rich composition

[0168] 120 thermal oxidizer outlet pipeline

[0169] 122 Inlet line for a composition rich in hydrogen bromide

[0170] 124 outlet line for air

[0171] 126 outlet line for a composition rich in hydrogen bromide

[0172] 128 Export pipeline for bromine-containing composition

[0173] 130 Export pipeline for hydrogen

[0174] 132 compressor

[0175] 134 Recirculation line for hydrogen

[0176] 136 Hydrogen removal line

[0177] 138 Distillation column of purification unit

[0178] 140 bottom outlet pipeline for mixture of water and hydrogen bromide

[0179] 142 Overhead distillate outlet line for hydrogen

[0180] 144 Condenser

[0181] 146 Container

[0182] 148 return line

[0183] 150 Container outlet line

[0184] 152 Dryer Tower

[0185] 154 Bottom outlet of dryer tower

[0186] 156 Dryer tower overhead distillate outlet

Claims

1. A method for mitigating the reaction of hydrogen bromide with one or more olefinically unsaturated compounds, the method comprising the steps of i) adding hydrogen to a composition comprising hydrogen bromide and an olefinically unsaturated compound to obtain a composition comprising hydrogen, hydrogen bromide, and an olefinically unsaturated compound, and / or ii) adding hydrogen to a precursor composition comprising one or more brominated hydrocarbons, from which the composition comprising hydrogen, hydrogen bromide, and an olefinically unsaturated compound is formed.

2. The process according to claim 1, wherein the composition comprising hydrogen, hydrogen bromide and olefinically unsaturated compounds further comprises bromine and / or the precursor composition from which the composition comprising hydrogen, hydrogen bromide and olefinically unsaturated compounds is formed further comprises bromine.

3. The process according to claim 1 or 2, wherein the molar concentration of hydrogen in the composition comprising hydrogen, hydrogen bromide and olefinically unsaturated compounds is adjusted to at least 0.1 mol %, preferably 0.2 to 90 mol % and more preferably 0.5 to 60 mol %.

4. The process according to claim 1 , wherein the molar ratio of hydrogen to hydrogen bromide in the composition comprising hydrogen, hydrogen bromide and olefinically unsaturated compounds is adjusted to a range of from 2:1 to 1:10, and / or wherein the molar ratio of hydrogen to hydrogen bromide in the composition comprising hydrogen, hydrogen bromide and olefinically unsaturated compounds is adjusted to a range of from 2:1 to 1:

5.

5. The process according to claim 1 , wherein the ethylenically unsaturated compound is an ethylenically unsaturated hydrocarbon, preferably C 2-10 Olefins, more preferably C 2-5 Monoolefins or C 4-8 A diene, still more preferably ethylene or propylene and most preferably propylene.

6. The process according to claim 1 , wherein hydrogen is added to a composition comprising 1 to 90% by weight and preferably 20 to 50% by weight of hydrogen bromide and 20 to 90% by weight and preferably 30 to 50% by weight of one or more olefinically unsaturated compounds.

7. A process according to any one of claims 1 to 4, wherein hydrogen is added to a precursor composition comprising one or more brominated hydrocarbons, and the mixture thus obtained is subsequently subjected to a dehydrobromination reaction to form a composition comprising hydrogen, hydrogen bromide and one or more olefinically unsaturated compounds, wherein preferably the precursor composition comprises one or more C 1-10 Bromohydrocarbon, preferably C 1-10 Bromoalkanes, more preferably C 1-5 Monobrominated alkanes or C 4-8 Dibrominated alkanes, still more preferably methyl bromide, ethyl bromide or propyl bromide, and most preferably 1-bromopropane or 2-bromopropane, and wherein preferably the precursor composition contains 10 to 99 wt% and preferably 20 to 75 wt% of one or more brominated hydrocarbons.

8. The process according to claim 6 or 7, wherein hydrogen is added to the precursor composition so as to obtain a mixture having a molar ratio of one or more brominated hydrocarbons and hydrogen of from 1:10 to 10:1 and preferably from 1:5 to 5:

1.

9. The process of claim 7 or 8, wherein the mixture is subjected to a catalytic dehydrobromination reaction, wherein the catalyst comprises a support material and at least 200 ppm of at least one metal selected from the group consisting of transition metals, noble metals, and any combination of two or more thereof.

10. The process according to any one of the preceding claims, wherein the composition comprising hydrogen, hydrogen bromide and olefinically unsaturated compounds is subjected to at least one separation step in order to separate it into a composition rich in hydrogen bromide and a composition rich in olefinically unsaturated compounds, wherein preferably the at least one separation step comprises a distillation step in which the composition comprising hydrogen, hydrogen bromide and olefinically unsaturated compounds is distilled in order to separate it into a composition rich in polybrominated hydrocarbons as a bottoms composition and an overhead composition comprising the olefinically unsaturated compounds, hydrogen bromide and hydrogen.

11. The process according to claim 10, wherein the at least one separation step comprises an absorption step, wherein the composition containing hydrogen, hydrogen bromide and olefinically unsaturated compounds or the overhead composition obtained in the distillation step is contacted with water or an aqueous solution, wherein the water or aqueous solution contains from greater than 0 to 1,000 ppm of bromine, preferably from 1 to 100 ppm of bromine and more preferably from 1 to 10 ppm of bromine, to obtain a purified composition rich in olefinically unsaturated compounds and a composition rich in hydrogen bromide, and wherein the composition rich in hydrogen bromide is preferably subjected to electrolysis so as to obtain hydrogen at one of two electrodes and a mixture containing bromine, water and hydrogen bromide at the other electrode, followed by distillation of the mixture containing hydrogen bromide, water and bromine to obtain as a bottom product a mixture containing hydrogen bromide, water and from greater than 0 to 1,000 ppm of bromine, preferably from 1 to 100 ppm of bromine and more preferably from 1 to 10 ppm of bromine, which mixture is recycled to the absorption step.

12. An apparatus comprising: a reactor for catalytically reacting one or more brominated hydrocarbons to produce a reaction mixture containing olefinically unsaturated hydrocarbons and hydrogen bromide, wherein the reactor comprises an inlet line for the one or more brominated hydrocarbons and an outlet line for the reaction mixture, a separation unit comprising an inlet line for the reaction mixture connected to the outlet line for the reaction mixture of the reactor, an outlet line for the olefinically unsaturated hydrocarbon and an outlet line for a composition rich in hydrogen bromide, wherein i) the inlet line for one or more brominated hydrocarbons of the reactor is connected to the inlet line for hydrogen, or ii) the reactor comprises a further inlet line for hydrogen, or iii) the line connecting the outlet line for the reaction mixture of the reactor and the inlet line for the reaction mixture of the separation unit is connected to the inlet line for hydrogen, or iv) the separation unit is connected to the inlet line for hydrogen, or v) any combination of two or more of the aforementioned features i) to iv) is met.

13. The apparatus according to claim 12, wherein the separation unit comprises at least one and preferably two distillation columns and / or at least one absorption column.

14. The apparatus according to claim 12 or 13, further comprising a purification unit, wherein the purification unit comprises an electrolysis cell comprising an anode, a cathode and a membrane sandwiched between the anode and the cathode, and an inlet line for a composition comprising hydrogen bromide, an outlet line for hydrogen and an outlet line for a composition comprising bromine, wherein the inlet line of the electrolysis cell is connected to the outlet line of the separation unit for a composition rich in hydrogen bromide, and wherein the outlet line for the bromine-containing composition is connected to the inlet line of a reactor for catalytically reacting one or more brominated hydrocarbons.

15. The apparatus according to claim 12 or 13, further comprising: a reactor for reacting a mixture comprising a hydrocarbon and bromine to produce a reaction mixture comprising brominated hydrocarbon and hydrogen bromide, wherein the reactor comprises an inlet line for the mixture and an outlet line for the reaction mixture comprising brominated hydrocarbon and hydrogen bromide, a first separation unit comprising an inlet line for a reaction mixture containing brominated hydrocarbons and hydrogen bromide, an outlet line for a composition enriched in brominated hydrocarbons and an outlet line for a composition enriched in hydrogen bromide, connected to the outlet line for the reaction mixture of a reactor for reacting a mixture containing hydrocarbons and bromine, The outlet line for the composition rich in brominated hydrocarbons is connected to an inlet line for one or more brominated hydrocarbons of a reactor for catalytically reacting one or more brominated hydrocarbons.

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