MX2008006876A - Process for producing ethylene - Google Patents

Abstract

The present invention relates to a process for the production of ethylene from a feedstock comprising ethanol.

Description

PROCESS FOR THE PRODUCTION OF ETHYLENE Field of the Invention The present invention relates to a process for the production of ethylene from a feedstock comprising ethanol. BACKGROUND OF THE INVENTION Olefins have traditionally been produced by cracking with water vapor or hydrocarbon catalytic. However, as oil resources fall, the price of oil inevitably increases, which makes the production of light olefmas an expensive process. Thus, there is a growing need to use non-petroleum-based pathways to produce C2 + defines, essentially ethylene and propylene. Said defines are useful as starting materials for numerous chemical products, including polymeric products such as polyethylene and polypropylene. In recent years, research to find alternative materials for the production of C2 + olefins has led to the use of alcohols such as methanol, ethanol and higher alcohols. Said alcohols can be produced by fermentation, for example, of sugars and / or cellulosic materials.

Alternatively, the alcohols can be produced from synthesis gas (also known as "syngas"). The synthesis gas refers to a combination of hydrogen and oxides of carbon produced in a plant of the synthesis gas from a carbon source such as natural gas, petroleum liquids, biomass and carbon materials including carbon, plastic materials. recycled, municipal waste or any other organic material. Thus, alcohols and their derivatives can provide non-petroleum-based routes for the production of olefms and other related hydrocarbons. In general, the production of oxygenates, mainly methanol, takes place via three procedural steps. The three stages of the process are: i synthesis gas preparation, methanol synthesis and methanol purification. In the step of preparing synthesis gas, an additional step in which the feed material is treated can be used, for example, the feed material is purified to remove sulfur and other potential poisons from the catalysts before becoming synthesis gas This additional step can also be carried out after the preparation of the synthesis gas; for example, when coal or biomass is used. Methods for producing mixtures of oxide or oxides of carbon and hydrogen (synthesis gas) are well known. Each of them has its advantages and disadvantages and the choice of the use of a particular reforming process is governed by economic and technical considerations. for the availability of feed streams, as well as for the desired molar ratio of H2-CO in the feed material resulting from the reforming reaction The synthesis gas can be prepared using any of the methods known in the art, including the partial oxidation of hydrocarbons, cl reformed with steam, reforming heated with gases, reforming into microchannels (as described, for example, in US 6,284,217, which is incorporated herein for reference purposes only), reformed with plasma, autothermal reforming and any combination of the above. An exhibition of these synthesis gas production technologies is offered in "Hydrocarbon Processing" V78, N.4, 8 / -90, 92-93 (April 1999) and "Petrole et Techmques", N.415, 86 93 ( July-August 1998). It is also contemplated that the synthesis gas can be obtained by oxidation Partial catalytic hydrocarbons in a structured reactor as exemplified in "IMRET 3. Proceedmgs of the Third International Conference on Microreaction Technology", Editor W. Ehrfeld, Spremger Vcrlag, 1999, pages 187-196. Alternatively, gas from The synthesis can be obtained by partial catalytic oxidation, with a short contact time, of hydrocarbon feedstocks as described in EP 0303438. Preferably, the synthesis gas is obtained by a procedure in "Compact Reformer" as described in EP-A-0303438. described in "Hydrocarbon Engineermg", 2000, 6, (5), 67-69; "Hydrocarbon Processing", 79/9, 34 (September 2000); "Today's Refmery", 3/15, 9 (August 2000); WO 99/02254; and WO 200023689. Typically, for the commercial production of gas from In synthesis, the pressure at which the synthesis gas is obtained ranges from approximately 20 to 75 bar and the temperature at which the synthesis gas of the reformer exits ranges from approximately 700 to 1100 ° C. The synthesis gas contains a molar of hydrogen to ! ^ carbon oxide (which depends on the synthesis gas feed material) that oscillates between 0.8 and 3. The synthesis of alcohol from syngas requires a molar ratio H2: CO that is usually between 1: 1 and 2: 1. The Applicant entity believes that the production reaction of alcohol, such as ethanol, from synthesis gas can be written so that: 2CO + 4H2? EtOH t H20 reaction stoichiometry 2: 1. However, in addition to this reaction, the The water gas afterburning reaction and, thus, the equilibrium under the usual conditions of the alcohol synthesis strongly favors the production of carbon dioxide and hydrogen: CO + H20 = C02 + H2> of this Thus, the overall synthesis of the alcohol can be written in such a way that: 3C0 + 3H2 - EtCH + C02 stoichiometry 1: 1 reaction In addition to this, the displacement reaction of water gas allows the substitution of CO2 and H2 by CO. In this way, the molar ratio of syngas required for the synthesis of alcohol can be written in terms of (H2-C02) (COtC02) and, in this case, the required ratio is 2. However, 3a relation molar H2 CO used in the practice is usually greater due to the formation of by-products, such as alkanes The synthesis gas preparation, also known, in addition to the above, as reforming, can take place in a single stage, where all the s reactions of reformed consumers and generators of energy. For example, in a single reformer with steam, tubular, the reaction is generally endothermic, while in the autothermal reforming, the combustion of part of the feed and product is used to compensate the performance Autotérm co The steam reformer in a single step normally results in the production of an excess of hydrogen.In a preferred alternative, the preparation of the synthesis gas can take place in a two-stage reforming process wherein The primary reforming in a tubular steam reformer is combined with a secondary reforming stage activated with oxygen and which, if used alone, produces a synthesis gas with a deficiency in hydrogen. the composition of the synthesis gas to obtain the most suitable composition for the methanol synthesis As an alternative, the autothermal reforming results in a simplified procedure scheme with a lower cost of capital Autothermal reforming is when a single activated reformer for oxygen it produces in First of all a hydrogen-deficient synthesis gas and then separates at least a part of the carbon dioxide present, in order to obtain the desired molar ratio of hydrogen to carbon oxides. The reaction from synthesis gas to oxygenates, 2o such as methanol, is a limited exothermic reaction in terms of balance. Conversion to methanol is favored by low temperatures but, for economic considerations, a balance between speed and conversion must be maintained. It also requires high pressures on a heterogeneous catalyst since the reactions that produce methanol exhibit a decrease in volume. As described in US Pat. No. 3,326,956, the synthesis of methanol at ba under pressure is based on a copper oxide-zinc oxide-alumina catalyst that usually operates at a nominal pressure of 5-10 MPa and at temperatures that oscillate approximately between 150 and 450 ° C on a variety of catalysts, including CuO / ZnO / Al203, CuO / ZnO / Cr? 03, ZnO / Cr203, Faith, Co, N, Ru, Os, Pt and Pd. The catalysts based on ZnO are preferred for the production of methanol and dimethyl ether. The copper-based catalyst for the synthesis of low pressure methanol is commercially supplied by suppliers such as BASF, ICI Ltd of the United Kingdom and Haldor-Topsoe. The methanol yields from copper-based catalysts are generally above 99.5% of the converted CO + C02 present. Water is a known by-product of the conversion of synthesis gas to oxygenates. An article entitled "Selection of Technology for Large Mcthanol Plants", by Helge Hi-Larsen, presented at the 1994 World Methanol Conference, Nov. 30-Dec 1, 1994, in Geneva, Switzerland, and incorporated here for reference purposes only, reviews the developments in methanol production and shows how a further reduction in the costs of methanol production will result in the construction of very large plants with capacities approaching 10,000 metric tons per day. US Patent No. 4,543,435 discloses a process for converting an oxygenate feedstock comprising methanol, dimethyl ether or the like, into an oxygenate conversion reactor, to liquid hydrocarbons comprising C2-C4 olefms and C5 + hydrocarbons. The C2-C4 olefms are compressed to recover a gas rich in ethylene. The ethylene-rich gas is recycled to the oxygenation conversion reactor. US Pat. No. 4,076,761 describes a process for converting oxygenates to gasoline with the return of a hydrogen-rich gas product to a synthesis gas plant or to the conversion reaction zone of the 1 - . 1 - > Oxygenate US Patent No. 5,177,114 discloses a process for the conversion of natural gas to liquid hydrocarbons with quality of gasoline and / or olefmas by conversion of natural gas to a synthesis gas and conversion of synthesis gas to methanol and / or crude dimethyl ether and subsequent conversion of the crude methanol / dimethyl ether to gasoline and to the effluents. International patent application No. 93/13013 of Kvisle et al. refers to an improved method to produce "A silane-alummo-phosphate catalyst that is more stable to deactivation by coking." The patent discloses that, after a period of time, all such catalysts used to convert methanol to olefins (MTO) lose the active capacity to converting methanol to hydrocarbons, mainly because the microporous crystalline structure is coked, that is, it is filled with carbonaceous compounds of volatility that block the porous structure. Carbon compounds can be separated by conventional methods such as combustion in air. EPO Publication No. 0 407 038A1 discloses a method for preparing dialkylethers which comprises feeding a stream containing an alkyl alcohol to a distillation column reactor within a feed zone, contacting the stream with an acid catalytic distillation structure solid in a fixed bed to form the corresponding dialkyl ether and water and, simultaneously, fractionate the product ether with respect to water and materials to react. US Patent No. 5,817,906 describes a process for producing light defines from a crude oxygenate feedstock comprising alcohol and water. The process uses two reaction steps. First, the alcohol is converted, using a distillation reaction, to an ether. The ether is then passed to an oxygenate conversion zone containing a metal aluminosilicate catalyst to produce a stream of light defines. There is a well-known chemistry that can be used to produce one or more olefins from one or more alcohols, ie, the methanol to olefin or olefmas-MTO process (as described in Handbook of Petroleum refmmg processes third edition, Chapter 15.1 RA publisher Meyers published by McGra Hill). The said MTO process can be described as the dehydrating coupling of methanol to one or more olefmas. It is believed that this mechanism proceeds via a coupling of Cl fragments generated by the dehydration of methanol catalyzed by acid, 1 ^ possibly via an intermediate methyloxonium. However, the main drawback of said MTO process is that a variety of defines are co-produced together with aromatic and alcanic by-products, which in turn makes it very difficult and expensive to recover the olefme 2nd desired defines with high purity. It is known that molecular sieves such as zeolitic and non-zeolitic, crystalline, microporous catalysts, in particular silicoalumomophosphates (SAPO), promote the conversion of oxygenates by the chemistry of ^ methanol to olefmas (MTO) to hydrocarbon mixtures.

Numerous patents describe this process for various types of such catalysts: US Patent Nos. 3,928,483, 4,025,575, 4,252,479 (Chang et al.); 4,496,786 (Santilli et al.); 4,547,616 (Avidan et al.); 4,677,243 (Kaiser); 4,843,183 (Inuí); 4,499,314 (Seddon et al.); 4 44/669 (Harmon et al.); 5,095,163 (Barger); 5,191,141 (Barger); 5 126 308 (Barger); 4,973,792 (Lewis); and 4 861,938 (Lew s). The MTO reaction comprises a stage of high activation energy (possibly in the production stage of methane! Or methether) so that to achieve a high conversion it is necessary to employ high temperatures, for example 300-450 ° C. However, unfortunately the fact of working at such high temperatures leads to major problems such as deactivation of the catalyst, coking and formation of by-products. In order to minimize such problems, the reactions can be carried out at lower temperatures, but this requires larger reactors and a large and expensive recycling of intermediates and reactants. Another important drawback associated with the MTO process is that aromatic and alcanic byproducts are co-obtained along with the definition or defines and both are difficult and expensive to separate from the desired products, for example, the separation of ethylene and ethane is an expensive process . These and other disadvantages of the state of the art demonstrate that there is a need to have an improved and / or alternative procedure for the production of defines C2 and C3 from alcohols. The solution to these and other disadvantages is provided by the present invention, which refers specifically to a new non-MTO process that proceeds via the dcshydratation of ethanol to olefms. This dehydration reaction is characterized because carbon-carbon double bonds are formed by the elimination of water only and does not include the coupling of carbon fragments as in the case of MTO chemistry. 1 ^ during the dehydration of ethanol, by-products are formed. This can be formed by coupling alkyl fragments, for example, olefin oligomerization catalyzed by acids, such as: 2-propylene - > Hexene The by-products can also be formed by dehydrogenation of alcohol, for example, ethanol-acetaldehyde + H2 (J. Catalysis 1989, 117, pp. 135-143 Y. Matsummura, K. Hashimoto and S. Yoshida). The state of hydrogen released may not be like ^ free hydrogen, but as chemosorbed hydrogen, of particular relevance is the hydrogenation reaction by transfer, for example: ethylene + H2-ethane 2-ethanol-acetaldehyde + ethane + water ^ It is known that the formation of alkanes of the same number of carbon atoms it adds significantly to the complexity and cost of producing purified olefmas for the preparation of polymers. For example, industrially practiced catalytic cracking of Hydrocarbon feedstocks, to produce olefins useful in the preparation of polymers, is a high cost process, with a high proportion of the cost involved in the separation of olefins and alkanes of the same number of carbon atoms. That is, the separation 1 ^ of ethylene ethane and propylene propane (as described in Handbook of Petroleum refming processes third edition, Chapter 3 editor R.A. Meyers published by McGraw Hill). This is also a drawback for the MTO process (Ibid chapter 15.1). Dehydration ethanol to ethylene has been practiced commercially in places such as Brazil and India, albeit on a small scale. the reaction conditions indicated are such that a high conversion per pass to olefin is achieved, for example at 1-2 bar relative, > 350C. It's about a ^ procedure of high selectivity but produces unacceptable levels of alkanes for direct use in the preparation of polyethylene. Usually, acceptable levels of less than 500 ppm of ethane and methane are combined. The actual practice of dehydration leads to olefms > which need expensive purification before being used in the current polymerization processes, as in the case of MTO. US Pat. No. 5,475,183 describes a process for the production of light defins by dehydration of lower alcohols having lower molecular weight. -4 carbon atoms on a vapor phase alumina catalyst. The typical reaction conditions offered in the examples are 300-400 ° C to 8-18 bar relative, indicating selectivities to olefms comprised between 65 and 97%. 1 ^ GB Patent No. 2094829 describes how ethylene can be produced in a plurality of adiabatic vapor phase reactors, wherein parts of the liquid products containing unconverted alcohol are recycled. The reaction conditions described, for the feed charge, are 400-520 ° C and a pressure of 19 39 bar relative The output product is maintained at at least 18 bar relative before being cryogenically purified. No examples of predicted selectivity are offered. US Patent No. 4,232,179 also describes "How can ethanol be dehydrated in adiabatic reactors.

The examples, with silica / alumina and alumina, show that the ethane content of the ethylene product is above 923-100,000 ppm by weight with respect to ethylene. This is unacceptable for polyethylene production without further purification. DD Patent No. 245866 describes how C2 to C4 defines can be obtained from singas derived alcohol mixtures by vapor phase treatment with a zeolitic catalyst at temperatures of 300-500 ° C and pressures of 200-2,000 kPa. The analysis of the examples has shown that a significant conversion to C5 and higher hydrocarbons occurs. The examples describe the dcshidratation of mixtures of Cl to C7 alcohols. Example 1 describes the dehydration of a mixture of 76% of 1 ^ methanol, 7.1% ethanol, 4.3% ethanol, 0.5% isopropanol, 4.3% n-propanol, 3.9% iso-butanol, 2% butanols, 2, 1% amyl alcohol, 0.9% hexanols, 0.2% heptanols + rest other oxygenates, to provide 143.2 g of ethylene, 96.8 g of propene, 77.9 g of butene, 1 / 4.3 g of C5-t hydrocarbons. A clearly significant conversion of lower carbonate moieties to higher carbon fragments occurs over the modified zeolitic catalyst. US Patent No. 4,398,050 describes the synthesis of "^ a mixed stream of alcohols and purification to provide a mixture of ethanol and propane which is subsequently dehydrated at 0.5-1 bar, 350-500 ° C (Example 1) . The main claim mentions the separation of methanol before dehydration, but not ^ the separation of C4 and higher alcohols. US Patent No. 4,423,270 describes the dehydration of ethanol in vapor phase and atmospheric pressure on a supported phosphoric acid catalyst with additional water and an alkyl-substituted phosphoric acid. The reaction temperatures used are 300-400 ° C and the experiments were carried out at atmospheric pressure in a glass tube. The registered ethylene yields were 88-101%, without providing details regarding the formation of by-products. US Patent No. 4,727,214 describes dehydration Ethanol on a crystalline aluminosilicate zeolite. The claimed conditions are between 1 and 10 bar and 126 and 526 ° C. Details of the formation of by-products in a decimal fraction are given and a 100% ethylene selectivity is indicated. However, from the It is not clear whether it is possible to prepare suitable material for polymer-grade ethylene without further purification to remove ethane. Limited experimental information is available for the dehydration of n-propanol (Journal of Catalysis ^ 169, 67-75 (1997) G. Larsen et al., J. Phy. Chem. B 109 / 3345-3354). The applicant entity has verified that the two-hydration proceeds in a manner similar to that indicated above for ethanol, with similar formation of by-products, for example, alkanes, aldehydes, ketones, oligomers. However, the proportion of oligomer formation is the most important. SUMMARY OF THE INVENTION The present invention relates to a process for the production of ethylene from ethanol. DESCRIPTION OF THE DRAWING Figure 1 depicts one embodiment of a process scheme according to the present invention. This embodiment comprises optional and / or preferred process steps according to the present invention. The reference letters indicated in Figure 1 correspond to those used in the present description and claims adtas. DETAILED DESCRIPTION The present invention relates to a process for the production of ethylene from an ethanol feedstock A, characterized by the following steps: 1. the feedstock of ethanol A is reacted in a reactor in the vapor phase wherein the ethanol is converted to a stream of product B comprising ethylene, diethyl ethers, water and unconverted ethanol, said product stream B is cooled, 3 said stream of cooled product B -> is cooled. in a separation unit to provide a first stream C comprising ethylene and diethyl ethers and a second stream of product D comprising water, di ethyl ethers and unconverted ethanol, said product stream D is fed to a unit of dehydration in where the stream of water F is separated from the stream of diethyl ethers and ethanol without converting E, 5. said stream E is recycled to the dehydration reactor of stage 1, and said stream of product C is cooled. said stream of cooled product C is fed to a purification unit where the stream of diethyl ethers G ee separates from the stream of ethylene H, and 8. optionally, the stream of ethylene glycols G is recycled either to the dehydration unit of the stage 4 or directly to the dehydration reactor of step 1. According to a preferred embodiment, the present invention provides a method for the conversion ^ from a hydrocarbon to ethylene wherein the feed of ethanol A of the above step 1 proceeds from the separation of a mixed feed material from ethanol and propanol oxygenates. According to another preferred embodiment, the present invention provides a method for the conversion from hydrocarbons to ethylene, comprising the steps of: converting the hydrocarbons, in a singas reactor, to a mixture of carbon oxides or oxides and hydrogen, b. converting said mixture of oxide or carbon oxides and hydrogen of step (a), in the presence of a particulate catalyst in a reactor at a temperature comprised between 200 and 400 ° C and a pressure of 5 to 20 MPa, to a material of feed comprising ethanol, c using at least part of said feed material comprising ethanol as the feed of ethanol A and proceeding according to steps 1 to 8 described above and according to the present invention, to produce said ethylene. In the methods of the invention, any feed stream containing hydrocarbons that can be converted to a feed material comprising carbon monoxide and hydrogen, most preferably a synthesis gas (or "syngas") is useful.

The hydrocarbon feedstock used for the generation of syngas is preferably a carbonaceous material, for example biomass, plastic, naphtha, refinery glues, metallurgical gases, urban waste, coal, coke and / or natural gas; carbon and natural gas being the preferred carbon material and most preferably the hydrocarbon feed material in natural gas . Feeding materials comprising carbon monoxide and hydrogen, for example synthesis gas, can undergo a reaction before being fed into any of the reaction zones. The purification of the synthesis gas can be effected by methods known in the art. See, for example, Weissermel, K. 1 ^ and Arpe H J, Industrial Organic Chemistry, Second, Revised and Extended Edition, 1993, p. 19-21. According to the present invention, the method for the production of olefins from alcohols proceeds via the dehydration of said alcohols. These dehydration reactions are distinguished from the aforementioned MTO process in that although a coupling of the carbon fragments in the dehydration process is not required, a CC double bond is formed during the removal of water and, as a result, can be achieved. a very high selectivity In general, the conditions used in the MTO process are much more severe than those used in the dehydration of alcohols described herein It is believed that the dehydration of the feedstock according to the present invention (Chem.

Eng. Comm. 1990 vol. 95 pp. 27-39 C.L Chang, A.L. DeVera and D J Millar) proceeds either by direct dehydration to one or more defines and water Equation 1 • = \ + H20 R ' or via an intermediate ether: Equation 2 2 ROH - ^ ^ ROR + H20 Equation 3 ROR R0I] + = R ' wherein R is an ethyl group and R 'is hydrogen. The direct conversion of the ether to two moles of define and water has also been described (Chem. Eng Res and Design 1984 Vol 6? Pp 81-91). All the reactions shown above are normally catalyzed by Lewis and / or Bronsted acids. Equation 1 shows the direct endothermic migration of alcohol to one or more defines and water. Competing with equation 1 are equations 2 and 3; the exothermic etherification reaction (equation 2) and the endothermic elimination of one or more ethers to produce one or more defines and alcohol (equation 3) However, it is said that the dehydration reaction of alcohols to one or more defines is in general endothermic As it mentioned above, the process according to the present invention preferably begins with an oxygenated feedstock comprising ethanol and propanol, for example a mixture of ethanol and n-propanol and / or iso-propanol. Said oxygenate feedstock may comprise homo and mixed ethers of these alcohols, for example, d-ethyl ether, n-propyl ether, ethyl n-propyl ether, ethyl isopropyl ether, n-propyl isopropyl ether and iso-propyl ether.

The oxygenates used as feedstock preferably comprise, as alcohols, only a mixture of ethanol and n-propanol. According to the present invention, the molar ratio of ethanol to n-propanol in the oxygenate feedstock to be separated in the ethanol feed A is preferably greater than 1: 2 but less than 20-1 and more preferably, it is greater than 1: 1 but less than 10.1, most preferably greater than 2: 1 and less than 5: 1.

According to a preferred embodiment of the present invention, the oxygenate feedstock and / or the feedstock A have an isopropanol content of less than 5% by weight, preferably less than 1% by weight, most preferably less than 0.1% by weight and ideally do not contain iso-propanol. A preferred characterizing measure according to the present invention is that the oxygenate feedstock and / or feedstock A have a total content of C3 + alcohols (defined as alcohols having at least 4 carbon atoms, for example, n-butanol, iso-butanol, pentanol) less than 5% by weight, preferably less than 1% by weight, most preferably less than 0.1% by weight and ideally do not contain C3 + alcohols. Conventional distillation according to the present invention can be employed in order to reduce / eliminate the C * of the corresponding feed material A. In fact, the applicant entity has surprisingly discovered that the presence of C3 + alcohols can be harmful to the production process of one or more defines of the present invention, for example, the applicant entity believes that they are responsible for an increase of the alkane prepared during the production of the olefma.

Another preferred embodiment according to the present invention is that the oxygenate feedstock and / or feedstock A have a methanol content of less than 5% by weight, preferably less than 2% by weight, most preferably less of 0.5% by weight and ideally there is no methanol. As a result of the removal of methanol the corresponding advantages can arise, namely (i) prevention of dimethyl ether formation - the DME is difficult to separate from propylene and ethylene compared with diethyl ether, (n) prevention of MTO chemistry , (ni) prevention of alkylation of olefins, for example, propylene to butene, 1 ^ (iv) prevention of the formation of methylethylether (which is more difficult to separate from ethylene), (v) less waste, (vi) lower toxicity, (vn) lower vapor pressure - easier to transport, (vm) a better CO ratio in the feed material for transport, ie, less water production According to the present invention can be used " ^ conventional distillation in order to reduce / eliminate methanol and C3 + alcohols from the corresponding feedstock When a mixed feedstock of ethanol and propanol is obtained from step b) above, &Thus, a separation of the feed material of ethanol and propanol is preferably carried out in an ethanol feed material A and a propanol A2 feed material. Said separation is preferably carried out in a conventional distillation column.

The separation is preferably carried out in such a way that the resulting ethanol feedstock can tolerate the presence of some propanol. Therefore, the propanol content of the feed material A is preferably at least 50 ppm, more preferably at 1 ^ less 0.1% in propanol or at least 1% propanol. According to a preferred embodiment of the present invention, the feed material A comprises less than 10% by weight, more preferably less than 2% by weight of propanol. The preferred reaction conditions of the vapor phase dehydration according to step 1 of the present invention are such that a moderate conversion to olefin occurs in the reactor. The liquid product stream after separating the olefin comprises "^ fundamentally unreacted alcohols, ethers and water.

It is preferable to recycle most of the alcohols and ethers to the dehydration reactor after removal of the by-product water. For the purposes of the present invention and the appended claims, a moderate conversion of the feed material from ethanol A to ethylene means that it is converted, per step, less than 10% to 80% and more preferably 20 to 60% of said ethanol introduced in the dehydration reactor. The term "conversion" is defined as the ratio between the number of moles of ethylene produced versus the number of moles of ethanol (and fragments derived from ethanol in ethers) that are fed to the reactor or dehydration reactors in the vapor phase. According to the present invention, for the ethylene generator reactor, some ethanol and optionally limited amounts of one or more ethers derived from propanol such as diethyl ether, n-propyl ether, ethyl-n are produced during the dehydration step. -propyl ether, ethyl isopropyl ether, n-propyl isopropyl ether and iso-propyl ether.

In accordance with the present invention it is preferable to proceed with an additional separation step; thus, preferably at least 80% by weight, more preferably at least 90% by weight, most preferably at least 99% by weight, even more preferably at least 99.9% by weight of the ether or The ethers are separated from the define or defines, at least part, preferably all, of the separated ether or ethers are then preferably recycled to the respective reactor or dewatering reactors in the vapor phase according to a preferred embodiment of the present invention.

The invention, at least part, preferably all of said ether recycle, is pre-mixed with the new ethanol feed (stream A) before entering the steam phase dehydration reactor of step 1. The formation of ethers is thermodynamically favorable. This formation of ethers facilitates the separation of water from the recycle. Ethanol, n-propanol and iso-propanol are totally or significantly miscible in water and easily form azeotropes with water, which thus prevents the separation of water, a by-product of the reaction, from the ] * • recycle streams. However, the formation of ethers, such as diethyl ether and di-n-propyl ether (both of which have a limited water solubility and a very low azeotrope or water content), allow water to be recovered by using a decanter , even in the presence alcohols sm react. In accordance with the present invention, the presence of water is permissible in the feed materials of ethanol and propanol A to be dehydrated; said feed material may comprise up to 50% by weight of water, "but preferably said feedstock comprises less than 25% by weight of water and most preferably the feedstock comprises less than 20% by weight of water, however, due to labor costs such as reactor size. , the heat of vaporization and the thermal capacity of the water, it is preferable to work with feed materials containing lower water levels, for example, less than 10% by weight, preferably less than 5% by weight of water. heteropolyacids as catalysts, the level of water in contact with the catalyst can affect the stability and activity of the catalyst For example, the heteropolyacids show a lower catalytic stability at low water levels (<1% by weight) and a less activity at high water levels (> 50% by weight) For the expert in the matter it is evident that the optimum level of water will depend on the interaction of a complex set of variables including the composition of the alcohol feed, the pressure, the temperature and the nature of the heteropolyacid employed. You can say that this The procedure has a good capacity to separate water and therefore facilitates the use of bioethanol and other bioalcohol.es. The operation at an average conversion with separation of water during recycling, has the advantage that it allows a convergence towards the conditions of Optimal reactions of the process The presence of water in the feed can also increase the difficulty of separation of the alcohol due to the presence of alcohol-water azeotropes which serves to narrow the difference of boiling point during the separation. with the highly preferred embodiment of the present invention, the ethanol and the diethyl ether together with the water represent at least 90% by weight and preferably at least 99% by weight of the feed material A introduced in the steam phase dehydration reactor. other sources of ethanol can be added either to the alcohol separation column or directly to the reactor feeds, for example, bioethanol to stream A. The vapor phase reactor used to dehydrate the ethanol feed material A in accordance with The present invention is preferably operated at a temperature between 160 and 270 ° C, preferably between 180 and 27 ° C. 0 ° C, more preferably between 190 and 260 ° C and most preferably between 200 and 250 ° C. The vapor phase reactor used for the dehydration of the feed material A according to the present invention is preferably operated at a pressure above 0.1 MPa but less than 4.5 MPa, more preferably at a pressure of above 1.5 MPa but less than 3.5 MPa and most preferably at a pressure of above 1.8 MPa but less than 2.8 MPa. According to the present invention, the operating conditions are such that the dehydration process > always works in the vapor phase state. A preferred embodiment is that the operating pressure in the dehydration process is always at least 0.1 MPa, preferably 0.2 MPa, below the pressure at the dew point and / or that the operating temperature in the process dehydration is at least 10 ° C above the dew point temperature of the feed entering the steam phase dehydration reactor (the alcohol feed mixture and / or the mixture resulting from the addition of the recycle) and of the composition of the product that is present inside the dehydration reactor. The latter will depend on factors such as the composition of the initial feed and the degree of conversion in the reactor. For the purposes of the present invention, the 2nd "dew point temperature" is defined as a threshold temperature For example, for a given mixture, at a given pressure, s the system temperature rises above the dew point temperature, the mixture will exist as a dry gas Similarly, below the "^ Dew point temperature, the mixture will exist as a vapor containing some liquid. Similarly, the" dew point pressure "is defined as a threshold pressure. For example, for a given mixture, at a certain temperature, if the system pressure is • below the dew point pressure, the mixture will exist as a dry gas, above the dew point pressure, the mixture will exist as a vapor containing some liquid Reactors are built to compete with the exothermic formation of ethers and with the endothermic dehydration to definas.The reaction temperature is preferably maintained within a small range of temperatures, since too low a temperature reduces the proportion of defina produced and can lead to the condensation of reactants, and too high a temperature can lead to the definition being contaminated by unacceptable levels of subproduct ucts, such as alkanes of the same number of carbon atoms. Preferably, the temperature profile of the bed of The catalyst is less than 30 ° C, more preferably less than 15 ° C and most preferably less than 10 ° C. For a single-bed adiabatic reactor, the overall endothermic reaction, if it were to proceed to thermodynamic equilibrium, could result in a theoretical fall of "^ temperature of 180 ° C Obviously, the problem lies in the thermal control by the reactor design Suitable reactor designs include those capable of handling thermal flows, such as fixed bed, fluidized bed, multitubular and multiple fixed bed reactors with •> heaters between the stages Optionally, the thermal control can be improved by injecting new, preheated alcohol feed at several points of the reactor bed, at which points the exothermic etherification reaction can partially counteract the global endothermy. The feed can also be heated additionally to a temperature above the reaction temperature, in order to provide an additional source of heat. A portion of the recycle stream can also be added at several points along the 1 reactor with additional heating, but it is preferable to add the main proportion of this current to the front end of the reactor. According to another embodiment of the present invention, the dehydration process, described in The present invention is not carried out in a reactive distillation column The expression "reactive distillation column" refers to a combination of distillation column and reactor. Surprisingly, the requesting entity has "It has been proven that the use of a mixed ether and alcohol feed results in a higher yield and selectivity to defines." This surprising discovery has shown that performing the process of the present invention with a recycle is advantageous for productivity and The selectivity of the olefin production process In addition to this, the option of conducting separate separation on the alcohol feedstock, prior to dehydration, also constitutes a modality of this invention, in this way, according to a preferred embodiment of the present invention, the ethanol feedstock A comprises at least 10% by weight, preferably at least 15% by weight, preferably at least 30% by weight and most preferably at least 50% by weight of ethers, but less than or equal to 85% by weight of ethers. Such ethers are preferably ethers derived from ethanol, such as diethyl ether for the food material. A. Since propanol can also be tolerated in the ethanol feed material A, these ethers can also be ethers derived from propanol, such as di-n-propyl ether, n-propyl isopropyl ether, di-iso-propyl ether, n-propylethyl ether and o-propyl ethyl ether. Said ethers can be produced during the dehydration step, during the alcohol synthesis step, during an additional step of etherification separately, or simply added to the feed material or materials. A preferred characterizing aspect according to the present invention is that the feed material A has a content of ethers derived from Cl (for example, methylethylether, methylpropyl ether) and from C3 + (defined as having at least one chain of 4 carbon atoms, for example, n-buti 1 ethether, butylpropyl ether) less than 5% by weight, preferably less than 1% by weight, with preference being less than 0.1% by weight and ideally there are no ethers derived from Cl and / or C3 +. According to another embodiment of the present invention, it has been found that the presence of aldehydes in the oxygenate feed material and / or material The feed A is detrimental to the service life of the catalyst. Thus, the content of aldehydes in said feedstocks is preferably less than 1% by weight, more preferably less than 0.1% by weight. In order to get the absence It is preferable to separate said aldehydes from the feed materials of alcohols to be dehydrated, by subjecting said alcohol feedstocks to any of the following treatments: a washing with bisulfite; a hydrogenation with borohydride; ^ a hydrogenation with hydrogen, or a distillation treatment The deethylation treatment can be combined with a chemical treatment such as a caustic-catalyzed Aldol condensation or a borohydride treatment to improve its efficiency in the separation of aldehydes. The dehydration reaction can also produce small amounts of aldehydes which can be preferably separated by treatment in a similar manner. According to another embodiment of the present invention, the The oxygenate feedstock and / or the feedstock A and / or the recycle streams should preferably be substantially free of volatile bases and metal ions which can cause deactivation of the catalyst. Transition metal ions such as l - > The common corrosion metalee, for example, Cu, Fe and Ni, can also catalyze hydrogen transfer reactions and lead to loss of quality of the olefinic currents as a consequence of an increased production of aldehydes and alkanes. Volatile amines can be Conveniently separate by treatments such as distillation and / or by the use of protection beds (usually acid ion exchange ream beds) Metal ions can also be conveniently separated by the use of protective beds, "^ but the careful design of the feed and unit or units of vaporization can provide an important protection olefms such as ethylene and propylene, used in the production of polymers, by virtue of the high indexes of activity and renewal of the catalysts used for polymerization, they are susceptible to the presence of low amounts of impurities, these can be separated by well-known treatments for olefins. Alternatively, some of these impurities, such as sulfur compounds, which may be present in bioethanol, are can separate by pre-treatment from the feed material According to a preferred embodiment of the present invention, the alcohols present in the feed material of oxygenates are transported from a distant place before being separated and dehydrated to one or more define by the above procedure For the purposes of this invention and the claims In the appended claims, the term "distant place" refers to a location that is located more than 100 km from the alcohol dehydration units. In accordance with a preferred embodiment of the present invention, the catalyst used for the dehydration of the feedstock of ethanol A consists of one or more "> heterogeneous catalysts Means include, but are not limited to, heteropolyacids, sulphonated carriers (eg, Naphion and ion exchange resins, sulphonated sulcoma, sulfur-containing zircoma), Niobia, foetophobic acid on siliceous supports (silica). , Kiesselguhr, clays), zeolites, metal-modified zeolites, mordenites and mixtures thereof, preferably heteropolyacids and ion exchange reams, more preferably heteropolyacids, and most preferably 12-tungstosilicic acid, 12-tungstophosphoric acid, acid 18- tungstophosphoc and 18-tungstosilicic acid and partial salts thereof The term "heteropolyacid" as used herein and throughout the description of the present invention, is intended to include, inter alia, alkali metal salts, alkaline earth metals, ammonium, free acids, bulky cations and / or metal salts (where salts may be salts Thus, the heteropolyacids used in the present invention are high molecular weight complex anions comprising oxygen-bonded polyvalent metal atoms. Usually, each anion comprises 12-18 polyvalent metal atoms bonded with oxygen. of polyvalent metals, known as peripheral atoms, surround one or more central atoms in a symmetric way. Peripheral atoms may be one or more of molybdenum, tungsten, vanadium, niobium, tantalum or any other polyvalent metal. The central atoms are preferably silicon or phosphorus, but alternatively can comprise any of a large variety of atoms of Groups I-VIII of the Periodic Table of the Elements. These include copper, beryllium, zinc, cobalt, nickel, boron, aluminum, gallium, iron, cinder, arsenic, antimony, bismuth, chromium, rhodium, silicon, germ, tin, titanium, zirconium, vanadium, sulfur, tellurium, manganese, nickel, platinum, thorium, hafnium, ceno, arsenic, vanadium, antimony ions, tellurium and iodine. Suitable heteropoly acids include the heteropoly acids Keggm, Wells-Da son and? Nderson-Evans-Perloff. Specific examples of heteropo l.? The following are suitable compounds: 18-tungstophosphocid acid 116 [P2W18062] .xH20 12-tungstophosphoric acid H3 [PW12O40] xH20 12 -molybophosphate acid 0 H3 [PMO12040]. xH20 12-tungstosilicic acid H4 [S? W12O40]. xH20 12-molded acid? lic? co H4 [S? Mol2O40] .xH20 cesium hydrogenase-sulphide CS3H [S1W12O40] .xH20 and the free acid or partial salts of the following heteropolyacids: monopotassium tungstophosphate KH5 [P2W18062]. xH20 monosodium 12-tungstocyclic acid NaK3 [S? W12O40]. x H20 potassium tungstophosphate K6 [P2W18062]. xH20 sodium molybdophosphate Na3 [PMO12O40] .xH20 ammonium molybdodiphosphate (NH4) 6 [P2Mol 8062]. H20 potassium molybindovanadiosphate K5 [PMoV2O40] .xH20 In addition, mixtures of different heteropolyacids and salts can be used. Preferred heteropolyacids for use in the process described by the present invention consist of one or more heteropolyacids which are based on the structures of Keggm or Wells-Dawson; more preferably, the heteropolyacid chosen for use in the process described by the present invention consists of one or more of the following: cotungic acid, phosphotungstic acid, silicomolybdic acid and foefomolybdic acid; and most preferably, the heteropolyacid chosen for use in the process described by the present invention consists of one or more silicotungstic acids. The heteropolyacids employed in the present invention may have molecular weights greater than 700 and less than 8,500, preferably greater than 2,800 and less than 6,000. Said heteropoly acids also include dimer complexes. The supported catalyst can be conveniently prepared by dissolving the selected heteropolyacid in a suitable solvent, wherein suitable solvents include polar solvents such as water, ethers, alcohols, carboxylic acids, ketones and aldehydes; being The preferred solution is preferably distilled water and / or ethanol. The resulting acid solution has a concentration of heteropolyacid preferably comprised between 10 and 80% by weight, more preferably between 20 and 70% by weight and most preferably between 30 and 60%. in weigh. This solution is then added to the chosen support (or alternatively the support is immersed in the solution). The actual volume of acid solution added to the support is not limited and, therefore, may be a sufficient volume to achieve incipient moisture or wet impregnation, where wet impregnation (ie, the preparation employing an excess volume of solution acid with respect to the pore volume of the support) constitutes the known method for the purposes of the present invention. The resulting supported heteropolyacid can be modified and various salts of the heteropolyacid can then be formed in the aqueous solution either before or during the impregnation of the acid solution on the support, subjecting the supported heteropolyacid to prolonged contact with a solution of a suitable metal salt or by the addition of phosphoric acid and / or other mineral acids. When a soluble metal salt is used to modify the support, the salt is taken at the desired concentration, with the heteropolyacid solution. The support is then allowed to impregnate in said acid solution for a suitable time (for example, a few hours), with periodic agitation, after which it is filtered, using suitable means, in order to remove any or excess of acid. When the salt is more soluble, it is preferable to impregnate the catalyst with the HPA and then titrate with the salt precursor. This method can improve the dispersion of the HPA salt. Other techniques such as;; vacuum impregnation.

The impregnated support can then be washed and dried. This can be achieved using any conventional separation technique including, for example, decanting and / or filtration. Once recovered, the impregnated support can be dried, preferably by placing the support in an oven at elevated temperature. Alternatively or additionally, a desiccant may be employed. On a commercial scale, this drying step is usually accomplished by a purge of a hot inert gas such as nitrogen. The amount of heteropolyzed impregnated on the resulting support is suitably 10 to 80% by weight and preferably 20 to 50% by weight based on the total weight of the heteropolyacid and support. The weight of the catalyst after drying and the weight of the 1 • > used support, can be used to obtain the acid peeo on the support by deducting the latter from the first, providing the load of the catalyst as "g of heteropolyacid / kg of catalyst" You can also calculate the load of the catalyst in "g of heteropoly acid / liter of support "using the known bulk density or measurement of the support The preferred heteropoly acid catalyst load is 150 to 600 g of HPA / kg of catalyst It should be noted that the oxidation states "Polyvalent and hydration states of the heteropolyacids, indicated above and as represented in the usual formulas of some specific compounds, only apply to the new acid before being impregnated on the support, and especially before being subjected to the conditions of the Dehydration process The degree of hydration of the heteropolyacid can affect the acidity of the supported catalyst and, therefore, its activity and selectivity Thus, either or both of these impregnation and dehydration actions can change the hydration and oxidation state of the metals in the heteropolyacids, ie, the actual catalytic species used, under the given process conditions, may not provide the hydration / oxidation states of the metals in the heteropoly acids used to impregnate the support., therefore, it can be expected that said hydration and oxidation states may also be different in the depleted catalysts after the reaction. Suitable catalyst supports may be in powder form or may be granules, pellets, spheres or extrudates and include, but not limitatively, mordetate, for example montmorillonite, clays, bentonite, diatomaceous earth, titania, active carbon, alumina, silica-alumina, silica-lime-titania, silica-zirconia-silica, carbon-coated alumina, zeolites, oxide of zinc, oxides pyrolysed to the flame. The supports may consist of mixed oxides, neutral or weakly basic oxides. Silica supports are preferred, "I such as silica gel supports and supports produced by S? Cl4 flame hydrolysis." Preferred supports are usually free of metals or foreign elements that could adversely affect the catalytic activity of the system. The suitable silica supports have a purity of at least 99% w / w The impurities amount to less than 1% w / w, preferably less than 0.60% w / w, and more preferably less than 0.30% The pore volume of the support is preferably greater than 0.50 ml / g, preferably greater than 0.8 ml / g.The average radius of the pores (before its run) of the support ee of 10 to 500 A, preferably from 30 to 175 A, more preferably from 50 to 150 A and most preferably from 60 to 120 A. The BET surface area is preferably from 50 to 600 m2 / g and most preferably from 150 to 400 m2 / g.

The preferred support has an average crushing strength of a single particle of at least 1 kg strength, suitably at at least 2 kg strength, preferably at least 6 kg and more preferably at least 7 kg. The apparent density of the support is at least 380 g / l, with "• preference at least 395 g / l.

The crushing strength of an individual particle was determined using a Mecmesm force gauge that m the minimum force required to crush a particle between parallel plates. Resistance to > Crushing is based on the mean value of those determined for a series of 50 catalytic particles. The BET surface area, the pore volume, the pore size distribution and the average pore radius were determined from the adsorption isotherm of 0 nitrogen at 77 ° K, using a static volumetric adsorption analyzer Micromeptics TRISTAR 3000. The procedure used was an application of the methods of the British Standards BS4359: Part 1: 1984"Recommendations for gas adsorption (BET) methods" and BS7591: Part 2: 1992, > "Porosity and pore eize dietpbution de matepals" - Method of evaluation by gas adsorption. The resulting data were reduced using the BET method (in the 0.05-0.20 P / Po pressure range and the method of Barrett, Joyner & Halcnda (BJH) (for pore diameters of 20-1,000 Á), to provide the surface area and the pore size distribution respectively. Suitable references for the aforementioned data reduction methods are Brunauer, S. Emmett, P.H. & Teller, E.J. Amer. Chem. Soc. 60, 309, (1938) and Barret, E.P.

Joyner, LG & Halenda P.P. J. Am. Chem. Soc. 1951, 73 373-380. Samples of the supports were gassed for 16 hours at approximately 120 ° C under a vacuum of i 5 and 10-3 Torr before analysis. Suitable silica supports include, but are not limited to, GraceDavison G57, GraceDavison 1252, GraceDavison 1254, Fuj i Silysia CariAct Q15, Fuj i Silysia CariAct Q10, Aerolyst 3045 and Aerolyst 3043. The mean diameter of the particles of the support ee from 2 to 10 mm, preferably from 3 to 6 mm. However, these particles can be crushed and sieved to smaller sizes, for example, 0.5-2 mm, if desired. Another embodiment of the invention is one in which the selected catalyst support is first treated with a fluorinating agent; the applicant entity believes that by fully complying with this embodiment, the catalyst will become more inert and / or acidic thereby improving the selectivity and / or effectiveness of the catalyst during the aforementioned dehydration process. Figure 1 depicts an embodiment of a procedural scheme according to the present invention. Said embodiment comprises optional and / or preferred process steps according to the present invention.

The letters used to illustrate the respective feed / product streams correspond to the definitions given in the foregoing text and related claims.

Claims (1)

1. NOVELTY OF THE INVENTION MODIFIED CLAIMS Process for the production of ethylene from an ethanol feed material A, characterized by the following steps: 1. the ethanol feed material A is reacted in a steam reactor where the ethanol is converted to a temperature between 160 and 270 ° C and at a pressure greater than 0.1 MPa but less than 4.5 MPa, to a stream of product B comprising ethylene, di eti 1 ethers, water and unconverted ethanol 2. said stream of product B is cooled, 3. said stream of cooled product B is disconnected in a separation unit to provide a first stream C comprising ethylene and diethyl ethers and a second stream of product D comprising water, diethyl ethers and sm converting ethanol, 4 said product stream D is fed to a dehydration unit where the water stream F is separated from the stream of diethyl ethers and ethanol without converting E, 5 said current stream E is recirculated to the dehydration reactor of step 1, 6 said product stream C is cooled, 7. said stream of cooled product C is fed to a purification unit where the stream of di ethers G is separated from the stream of ethylene H, and 8. optionally, the stream of ethylethers G is recycled either to the dehydration unit of the stage 4 or directly to the dehydration reactor of stage 1 Process for the conversion of hydrocarbons to ethylene, characterized in that it comprises the steps of: a. converting hydrocarbons, in a singas reactor, to a mixture of oxides or carbon oxides and hydrogen, b. converting said mixture of oxide or carbon oxides and hydrogen of step (a), in the presence of a particulate catalyst in a reactor at a temperature between 200 and 400 ° C and a pressure of 5 to 20 MPa, to a oxygenate feedstock comprising ethanol, c. using at least part of said feed material comprising ethanol as the feed of ethanol A and proceeding according to steps 1 to 8 of claim 1, to produce said ethylene. Method according to any of the preceding claims, characterized in that the material of The oxygenate feed and / or feed material A have an iso-propanol content of less than 5% by weight, preferably less than 1% by weight, most preferably less than 0.1% by weight and ideally do not contain isopropanol - > Process according to any of the preceding claims, characterized in that the oxygenate feedstock and / or the feedstock A have a content of C3 + alcohols less than 5% by weight, preferably less than 1% by weight, most preferably 10 smaller than 0.1% by weight and ideally do not contain C3 + alcohols. Method according to any of the preceding claims, characterized in that the oxygenate feedstock and / or the feedstock ] * > A have a methanol content of less than 5% by weight, preferably less than 2% by weight, most preferably less than 0.5% by weight and ideally do not contain methanol. Process according to any of the preceding claims, characterized in that ethanol, diethyl ether and The water represents at least 90% by weight, preferably at least 99% by weight, of the ethanol feed A introduced in the vapor phase dehydration reactor. Process according to any of the preceding claims, characterized in that the ethanol feed A comprises at least 10% by weight, preferably at least 15% by weight, preferably at least 30% by weight and most preferably at least 50% by weight of ether, but less than or equal to 85% by weight of ethers; said ethers consisting of diethyl ether and optionally di-n-propyl ether and / or n-propyl isopropylether and / or diisopropyl ether. Process according to any of the preceding claims, characterized in that the feed of ethanol A comprises less than 5% by weight, preferably less than 1% by weight, most preferably less than 0.1% by weight of ethers Cl and / or ethers derived of C3 + and ethers derived from Cl and / or C3 + are ideally not present.