Indian Patents. 256014:PROCESS FOR THE PRODUCTION OF HIGH-OCTANE HYDROCARBON COMPOUNDS BY THE SELECTIVE DIMERIZATION OF ISOBUTENE CONTAINED IN A STREAM WHICH ALSO CONTAINS C5 HYDROCARBONS

Title of Invention	PROCESS FOR THE PRODUCTION OF HIGH-OCTANE HYDROCARBON COMPOUNDS BY THE SELECTIVE DIMERIZATION OF ISOBUTENE CONTAINED IN A STREAM WHICH ALSO CONTAINS C5 HYDROCARBONS
Abstract	A process is described for the production of high-octane hydrocarbon compounds by means of the selective dimerization of isobutene, in the presence of C5 hydrocarbons and oxygenated compounds (branched alcohols or alternatively blends of linear or branched alcohols and alkyl ethers) characterized in that it utilizes a catalytic distillation as second reaction step.

Full Text	"PROCESS FOR THE PRODUCTION OF HIGH-OCTANE HYDROCARBON COM¬POUNDS BY THE SELECTIVE DIMERIZATION OF ISOBUTENE CONTAINED IN A STREAM WHICH ALSO CONTAINS C5 HYDROCARBONS" SNAMPR0GETTI S.p.A - Via De Gasperi 1-20097-S.Donato Milanese-MI Description The present invention relates to a process for the production of high-octane hydrocarbon compounds by means of the selective dimerization of isobutene and, to a lesser extent, of possible linear olefins, in the presence of C5 hydrocarbons and oxygenated compounds, which favour the formation of higher selectivities on the part of the cata¬lyst. The mixture obtained can then be hydrogenated with conventional methods to obtain a product with further en¬hanced octane characteristics. For mainly environmental reasons, the composition of gasolines is being reformulated and the general tendency is towards the production of fuels which burn better and have lower evaporative emissions. The main measures for achiev¬ing this objective are listed below (D. Sanfilippo, F. An-cillotti, M.Marchionna, Chim.& Ind., 76,(1994), 32): - reduction in the content of aromatic compounds and elimi¬ nation of benzene; - reduction in the volatility of gasolines to minimize evaporative losses; - reduction in the content of light olefins, photochemi-cally extremely reactive; - reduction in the sulfur content and final boiling point of the gasolines. All these measures consequently create the necessity of projecting new production processes of purely hydrocar¬bon compoionds capable of positively contributing to the above demands. Among these, alkylated products are extremely impor¬tant as they have a high octane number, a low volatility and are practically free of olefins and aromatic compounds. The alkylation process in liquid phase is a reaction be¬tween isoparaffinic hydrocarbons, such as isobutane, and olefins, for example propylene, butenes, pentenes and rela¬tive mixtures, in the presence of an acid catalyst for the production of C7-C9 hydrocarbons with a high octane number to be used in gasolines (A. Corma, A. Martinez, Catal.Rev,-Sci.Eng., 3^,(1993),483). The main problem of alkylation processes is due to the fact that, with growing environmental regulations, both of the traditional processes (with hydrofluoric and sulfuric - 2 - acid) are encountering considerable difficulties, which create uncertainties for the future; the process with hy¬drofluoric acid due to the toxicity of this acid, espe¬cially in populated areas, and that using sulfuric acid, as a result of the large production of acid sludge as well as the considerably corrosive nature of the catalyst. Alternative processes with solid acid catalysts are being developed but their commercial applicability has yet to be demonstrated. A hydrocarbon product of this type, on the other hand, is becoming increasingly more requested due to its octane characteristics (both the Research Octane Number (RON) and the Motor Octane Number (MON) are high) and those relating to the boiling point (limited volatility but low end-point) which position it in the group of compositions of great in¬terest for obtaining gasolines which are more compatible with current environmental requirements. An alternative refinery process for obtaining products with characteristics similar to those of alkylated products can be offered by the hydrogenation of so-called "polymer" gasoline. Oligomerization processes (often inaccurately called polymerization in the refining industry) were widely used in the '30s' and '40s' for converting low-boiling C3-C4 olefins into gasolines. The process leads to the production - 3 - of a gasoline with a high octane number (RON about 97) but with a high sensitivity (difference between RON and MON) due to the purely olefinic nature of the product (J.H.Gary, G.E. Handwerk, 'Petroleum Refining : Technology and Econom- 5 ics", 3rd Ed., M. Dekker, New York, (1994), 250). Typical olefins which are oligomerized are mainly pro¬pylene, which gives dimers or slightly higher oligomers de¬pending on the process used, and isobutene which mainly gives dimers but is always accompanied by a considerable quantity of higher oligomers. With particular attention to the oligomerization of isobutene, it is known that this reaction can be carried out either batchwise, semi-batchwise or in continuous, ei¬ther in gas or liquid phase, generally at temperatures 5 ranging from 50 to 300°C and at atmospheric pressure or such pressures as to maintain the reagents in liquid phase, if necessary. Typical catalysts for the industrial oligomerization process of isobutene are represented by phosphoric acid, generally supported on a solid (for example kieselguhr), or cation-exchange acid resins. The latter allow blander con¬ditions to be used compared with supported phosphoric acid both in terms of temperature and pressure (50-100*0 and 0.2-3 MPa with respect to 200-220°C and 3-10 MPa) . Other catalysts are also claimed in literature, both - 4 - liquid acids such as H2SO4 and derivatives of sulfonic ac¬ids, and solids such as silico-aluminas, mixed oxides, zeo¬lites, fluorinated or chlorinated aluminas, etc.; none of these catalysts however has so far enabled an industrial I process to be set up, as in the case of supported phospho¬ric acid (F. Asinger, "Mono-olefins: Chemistry and Technol¬ogy", Pergamon Press, Oxford, pages 435-456) and that of cation resins (G. Scharfe, Hydrocarbon Proc, April 1973, 171) . From the product point of view, the main problem of this process lies in the fact that excessive percentages of heavy oligomers such as trimers (selectivity of 20-40%) and tetramers (selectivity of 1-5%) of isobutene, are produced in the oligomerization phase. Tetramers are completely out- side the gasoline fraction as they are too high-boiling and therefore represent a net loss in yield to gasoline; as far as trimers are concerned, their concentration should be greatly reduced as they have a boiling point (170-180°C) at the limit of future specifications on the final point of reformulated gasolines. The problem of reducing the formation of oligomers higher than dimers to percentages lower than 15% is, on the other hand, a problem typical of the oligomerization of isobutene, as also indicated in literature (C.T.O'Connor, M. Kojima, K.W. Shcumann, Appl.Catal., 16,(1985),193), This - 5 - level of heavy compounds is slightly higher than that of an alkylated product and is still tolerated in the gasoline pool. From what is specified above, there is evidently great interest in obtaining a new dimerization process of isobu-tene which allows the synthesis of a higher-quality prod¬uct, through reaching greater selectivities. By carrying out the selective dimerization reaction of isobutene in the presence of moderate quantities of oxygen¬ated products, the production of a fraction of oligomers is selectively obtained, which is particular rich in dimers (>85%) and practically free of tetramers and higher oli¬gomers ( The reaction product is then preferably hydrogenated to give a completely saturated end-product with a high oc¬tane number and low sensitivity. The hydrogenation can be carried out with conventional methods as described, for example, in F. Asinger, "Mono-olefins: Chemistry and Technology", Pergamon Press, Oxford, page 455. For illustrative purposes. Table 1 indicates the oc¬tane number and relative boiling, points of some of the products obtained, by means of the process, object of the present invention. - 6 - The process, object of the present invention, for the production of high-octane hydrocarbon compounds by the ser lective dimerization of isobutene contained in a stream also containing C5 hydrocarbons, is characterized in that: - the reaction is carried out^in two di'stinct steps, - a catalytic distillation is used as second step, - the reaction is carried out in the presence of oxygenated products selected from a branched alcohol alone or in a blend with linear alcohols and alkyl ethers, in such a quantity as to have in the feeding, in the case of the presence of a branched alcohol alone, a molar ratio oxygen¬ ated product/isobutene higher than 0.005, in the case of the presence of a branched alcohol in a blend, a molar ra¬tio oxygenated product/isobutene higher than 0.01 - a C5 /branched alcholm atetropic separatiion step is camed out. It should also be pointed out that in the of hy- It should also be pointed out that in the case of by- drocarbon streams also comprising other olefins, it has been observed that at least a part of the latter can be converted by reaction with isobutene into the hydrocarbon - 7 -AMENDED SHEET product without altering the octane value. It is therefore preferable to effect an enriching treatment, by means of pre-isomerization, of the internal linear olefins, in order to favour the overall octane number of the mixture. 5 The process claimed herein can be applied to cuts mainly containing isobutane, isobutene, n-butane, n-butenes and saturated and olef inic C5 hydrocarbons. Although a wide variety of sources are available for the supply of these streams, the most common are those de- 0 riving from Dehydrogenation processes of iso-paraf f ins, from FCC units. Steam Cracking or processes for the produc¬tion of pure isobutene such as the dehydration of tert-butyl alcohol (TEA) or the Cracking of MTBE and/or. ETBE; these streams differ from each other in the content of iso- 5 butene and linear butenes, as shown in Table 2. Should streams from Steam Cracking contain diolefins in addition to the desired mono-olef ins, they must be 5 eliminated by means of typical removal treatment (for exam- - 8 - ple solvent extraction or selective hydrogenation). Saturated and olefinic C5 hydrocarbons can be present in these streams, in various amounts (0.2 - 20%), depending on the efficiency of- the C4-C5 separation step. The C5 ole¬fins possibly present can be involved in dimerization reac¬tions . The stream sent to the reaction steps can contain branched alcohols or a blend of alcohols and alkyl ethers, in addition to the hydrocarbon components.The branched alcohol can also be formed by feeding water in the stream sent to the naction steps, which is The linear alcohols used contain a number of carbon atoms ranging from 1 to 6 and those preferred are methanol and/or ethanol. The branched alcohols have from 3 to 6 car¬bon atoms and those preferred are tert-butyl alcohol (TBA) and/or tert-amyl alcohol (TAA). The alkyl ether used can be selected from those, con- taining a number of carbon atoms ranging from 5 to 10: MTBE (methyl tert-butyl ether), ETBE (ethyl tert-butyl ether), MSBE (methyl sec-butyl ether), ESSE (ethyl sec-butyl ether), TAME (methyl tert-amyl ether), TAEE (ethyl tert- amyl ether) or mixtures thereof are preferred. Isobutene, together with the hydrocarbon stream in which it is contained, is sent with the oxygenated prod¬ucts, in stoichiometric defect, into contact with the acid catalyst where the dimerization takes place. The linear primary alcohol, possibly present, in addition to interact-capable of foeming the brabched alcohol by reacting with the tertiary olefin undert the naction - 9 - AMENDED SHEET ing with the catalysts, also helps to limit the possible cracking of the alkyl ether and can possibly react with the ditners and linear C4 olefins, whereas the branched alcohol (tertiary) does not react with the olefins due to its steric hindrance. In order to obtain the dimerization product with the desired selectivity to dimers, it is essential to maintain a constant level of oxygenated products in the reaction en¬vironment to form the catalytic species with the correct activity and stability. The optimal level of oxygenated products present in the reaction environment, to obtain se-lectivities to dimers close to 85% by weight, depends on the composition of the hydrocarbon charge. The higher the olefin content in the charge, the lower the amount of oxy¬genated products to be used. A wide variety of acid catalysts can be used for this process, but those preferred are styrene-divinyl benzene polymeric resins having sulphonic groups as catalytic cen¬tres . A large range of operative conditions can be used to produce high-octane hydrocarbons from isobutene in the de¬sired selectivities. It is possible to operate in vapour or liquid-vapour phase, but operating conditions in liquid phase are preferred. The pressure is preferably higher than the atmospheric value, in order to maintain the reagents in liquid phase, generally below 5 MPa, more preferably between 0.2 - 2.5 MPa. The reaction temperature preferably ranges from 30 to 120°C. The feeding space velocities of the oxygenated-hydrocarbon stream are preferably lower than 30 h-1, more preferably ranging from 1 and 15 h-1. Isobutene is mainly converted in the reaction zone, however portions of the other olefins which are present can also be converted to useful product; in principle, there are no limits to the concentration of iso-olefin in the hy¬drocarbon fraction, even if concentrations ranging from 2 to 60% are preferred; in case of streams having a high iso¬butene concentration (dehydration or cracking) it is there¬fore convenient to dilute the charge with C4-C7 hydrocar¬bons. There are no limits, on the contrary, for the ratio between isobutene and linear olefins. The process, object of the present invention, can be effected batchwise or in continuous, bearing in mind how¬ever that the latter is much more advantageous in indus¬trial practice. The reactor configuration selected includes a first reaction step (one or more fixed bed reactors) and a second step consisting of a catalytic distillation which avoids the use of a reactor and a distillation column, as in a - 11 - conventional plant. • The presence of C5 hydrocarbons in the feed, however, complicates the process schemes, as these compounds have intermediate boiling temperatures between C4 and oxygenated products, and they also form azeotropic mixtures with the branched alcohols as shown in Table 3, which indicates the boiling points of the most representative low-boiling com¬ponents present in the streams plant together with the C4 products, as they would intro¬duce oxygenated products (branched alcohols) into the stream, which are difficult to remove by means of the tra¬ditional techniques used for removing methanol (water wash- ing) and which are poisonous for the subsequent treatment processes of the streams (polymerization, alkylation and metathesis), The C5 products, on the other hand, cannot be main¬tained in the oxygenated stream as they would rapidly accu- mulate. With respect to the schemes shown in literature (US 6,011,191), it is therefore necessary to introduce a C5/branched alcohol azeotropic separation step, which can be inserted in several positions of the plant, in relation to the C5 content in the charge and also the relative con- centration of the C5 products present. When the oxygenated product is a branched alcohol alone, the process is, in particular, preferably effected with a molar ratio of oxygenated product/isobutene lower than 0.6, through the following essential steps: a) feeding the C4-C5 hydrocarbon cut containing isobutene to the first reaction step (consisting of one or more reactors) , together with one or more streams containing oxygenated products; b) using a catalytic distillation column as second reac- tion step, wherein the isobutene conversion is com- - 13 - pleted, in addition to the separation of the rea- gents/products; c) recovering the C5 hydrocarbon/branched alcohol azeo- tropic product, in one or more fractionation columns, i also catalytic, as head stream, side cut or bottom stream; d) recycling the stream containing the oxygenated products and possibly the reintegrated oxygenated products, to the two reaction steps; e) possibly recycling part of the C4 products to the first reaction step, in order to maximize the isobutene con¬version. The first reaction step can consist of one or more fixed bed, tubular and/or adiabatic reactors. The separation of the C5/branched alcohol azeotropic product of step (c) is preferably effected starting from blends: a) C5 - oxygenated products - reaction product, wherein the C5 hydrocarbons are recovered as azeotropic com- pound with the branched alcohol, as head effluent, using a scheme based on one or two fractionation columns; b) C4 - C5 - oxygenated products - reaction product, wherein the C5 hydrocarbons are recovered as azeo- tropic compound with the branched alcohol as side - 14 - cut of a catalytic distillation column from whose head the C4 products are recovered and at the bottom a blend containing the oxygenated products and the reaction product; c) C4 - C5 - oxygenated products, wherein the C5 hydro¬carbons are recovered as azeotropic compound with the branched alcohol as the bottom effluent of a fractionation column from whose head the C4 products are recovered. When the oxygenated product is a branched alcohol in a mixture with linear alcohols and alkyl ethers, the process is preferably effected, in particular, with a molar ratio of oxygenated product/isobutene lower than 0.7, by means of the following essential steps: a) feeding the C4-C5 hydrocarbon cut containing isobutene to the first reaction step (consisting of one or more reactors), together with one or more streams contain¬ing oxygenated products (linear and branched alcohols, ethers and water) ; b) using a catalytic distillation column as second reac¬tion step, wherein the isobutene conversion is com¬pleted, in addition to the separation of the rea¬gents/products ; c) separating the C4/linear alcohol azeotropic product and possibly C4 products from the remaining oxygenated - 15 - compounds and from the hydrocarbon product, in one or more distillation columns, also catalytic; d) recovering the linear alcohol from the azeotropic product with the C4 compounds, by means of conven- tional processes such as water washing or adsorption on inorganic solids; e) recovering the C5/branched alcohol azeotropic product, in one or more fractionation columns, also catalytic, as head stream, side cut or bottom stream; f) recycling the stream containing the oxygenated prod¬ucts (branched alcohol and ether) and possibly the re¬integrated oxygenated products and recovered linear alcohol, to the two reaction steps; g) possibly recycling part of the C4 products to the first reaction step, in order to maximize the isobu-tene conversion. The first reaction step can consist of one or more adia-batic reactors, such as traditional, boiling point, ex¬panded bed reactors. The separation of the Cs/branched alcohol azeotropic product of step (e) is preferably effected starting from blends of: a) C5 - oxygenated products (ethers and branched alco¬hols) - reaction product, wherein the C5 hydrocarbons are recovered as an azeotropic compound with the - 16 - branched alcohol, as head effluent, using a scheme based on one (recovery of the remaining oxygenated products as side cut) or two fractionation columns; b) C5 - oxygenated products (ethers and branched alcohols i - dimers, in which the Cs hydrocarbons are recovered as azeotropic product with the branched alcohol as head effluent of a fractionation column; c) C4-CS - oxygenated products (ethers and linear and branched alcohols) - reaction product, effluent from a reaction step, wherein the C5 hydrocarbons are recov¬ered as an azeotropic compound with the branched alco¬hol as side cut of a fractionation column from whose head the C4/linear alcohol azeotropic product and pos¬sibly the C4 products are recovered, whereas a mixture containing the oxygenated products and the reaction product is recovered at the bottom/ d) C4-C5 - oxygenated products (linear and branched alco¬ hols) wherein the C5 hydrocarbons are recovered as an azeotropic compound with the branched alcohol as bot- torn effluent of a fractionation column from whose head the C4/linear alcohol azeotropic product and possibly C4 products are recovered. For the two processes comprising the essential steps The C5/branched alcohol atetropic prouct is mixed with the reaction product of specified above (a-e and a-g) the C5 products are present in the streams prevalently containing C4 products in a - 17 -AMENDED SHEET quantity preferably ranging from 0.5 to 10% by weight. S'even process schemes are shown in figures 1-1, in order to clearly illustrate the present invention. Figure 1 shows a process scheme with catalytic distilla¬tion, when C5 products are not present in the charge and the oxygenated product is a branched alcohol (TBA). The stream (1) containing isobutene, together with the reintegration feeding of TBA (or possibly water) (2) and the recycled stream of oxygenated products (9), is sent to a first reaction step (Rl), which can consist of one or more fixed bed reactors, in which the C4 iso-olefin is se¬lectively converted to dimers. The effluent (4) from the first reaction step, is sent to a catalytic distillation (C1) in which the isobutene conversion is completed. A stream (5) essentially contain¬ing C4 hydrocarbons is removed from the head of this col¬umn, whereas a stream (6) essentially containing the reac¬tion product and the oxygenated compounds, is collected at the bottom. This stream (6) is sent to a further separation column (C2) wherein a stream (8) is collected at the head, con¬taining the dimers/TEA azeotropic product which is recycled to the two reaction steps (streams 9 and 10) , whereas the reaction product (7) essentially consisting of dimers and \ trimers, is collected from the bottom, - 18 -. The introduction of catalytic distillation allows a con-siderable simplification of the plant scheme, which is in¬stead based on two reaction steps (fixed bed reactors) and three fractionation columns, as shown in figure 2. When C5 hydrocarbons are present in the charge, different plant configurations can be used to recover the C5/TBA azeotropic product, depending on the quantity of C5 prod¬ucts present and the required purity of the streams. Figure 3 shows a possible process scheme which differs from that of figure 1 due to the fact that the C5/TBA azeo¬tropic product (11) is recovered from the head of the col¬umn C2, which can possibly be joined to the reaction prod¬uct, whereas the stream containing the oxygenated products to be recycled (TBA/dimers azeotropic product) is removed from the column C2 as side cut (8). The process scheme is more complex when a more efficient separation of the two C5/TBA and dimers/TBA azeotropic products is to be effected, as a new fractionation column (C3) must be inserted, as shown in figure 4. In this new scheme, the head stream of the column C2 (8) is sent to a new column (C3) wherein the C5/TBA azeotropic product (11) is separated at the head and the dimers/TBA azeotropic product (12) which is recycled to the two reaction steps (streams 9 and 10), is separated at the bottom. Alternatively, the C5/TBA azeotropic product can be re- - 19 - covered as side cut (11) in the column reactor CI (figure 5V. A further option, shown in figure 6, consists in sending this azeotropic product to the head stream of the catalytic 5 distillation column together with the C4 products and in using a new column (C3) to recover the C5/TBA azeotropic product at the bottom (11) and C4 products at the head (12) . Ficfure 7 shows a possible process scheme when a mixture of oxygenated products, consisting of alkyl ether (MTBE), linear alcohol (Methanol) and branched alcohol (TBA), is used. In this case, the stream (1) containing isobutene, together with the reintegration feeding of methanol and TBA (or water) (2) and the recycled streams of oxygenated prod- 5 ucts (MTBE and TBA) (9) and methanol (14), is sent to the first reaction step (Rl) , which can consist of one or more reactors, in which the C4 iso-olefin is selectively con¬verted to dimers. The effluent (4) from the first reaction step is sent to 3 catalytic distillation (CI), which represents the second reaction step, together, possibly, with the recycled streams of oxygenated products (ID) and methanol (13). A stream (5) is collected from the head of this column, es¬sentially containing C4 hydrocarbons and methanol, which is 5 fed to a unit for the recovery of the alcohol (MR) which - 20 - can consist, for example, of an adsorption system on mo-lecular sieves, or a water washing column. In both cases, the alcohol recovered (12) can be sent back to the two re¬action steps (streams 13 and 14) , whereas the hydrocarbon stream (11) can be used in subsequent operations. The bottom stream (6) of the column C1 is sent to a fur¬ther separation column (C3) wherein a stream (15) contain¬ing the Cs/branched alcohol azeotropic product is collected at the head, a stream (8) essentially containing MTBE, TEA ) and dimers, as side cut, which is recycled to the two, reac¬tion steps (streams 9 and 10), whereas the reaction product (7) , essentially consisting of dimers, trimers and small quantities of oligomers is recovered from the bottom. CLAIMS 1. ' Propess for the production of high-octane hydrocarbon compounds by the selective dimerization of isobutene con¬tained in a stream also containing C5 hydrocarbons, charac¬terized in that: - the reaction is carried out with acid catalysts in two distinct steps, - a catalytic distillation is used as second step, - the reaction is carried out in the presence of oxygenated products selected from a branched alcohol alone or in a blend with linear alcohols and alkyl ethers, in such a quantity as to have in the feeding, in the case of the. presence of a branched alcohol alone, a molar ratio of oxy¬genated product/ isobutene higher than 0.005, in the case of the presence of a branched alcohol in a blend, a molar ra¬tio of oxygenated product/isobutene higher than 0,01; - a C5/branched alcohol azeotropic separation step is car¬ried out. 2. The process according to claim 1, wherein the first reaction step is carried out at a reaction temperature ranging from 30 to 120°C, at a pressure lower than 5 MPa and feeding space velocities lower than 30 h-1. 3. The process according to claim 2, wherein the feeding space velocities range from 1 to 15 h-1. 4. The process according to claim l, wherein the branched - 22 - AMENDED SHEET alcohol has a number of carbon atoms ranging from 3 to 6 . 5. . The process according to claim 4, wherein the branched alcohol is selected from tert-butyl alcohol or tert-amyl alcohol. 6. The process according to claim 1, wherein water is fed, which is capable of forming the branched alcohol by reacting with the tertiary olefin under the reaction condi¬tions . 7. The process according to claim 1, wherein the linear alcohol has a number of carbon atoms ranging from 1 to 6. 8. The process according to claim 7, wherein the linear alcohol is selected from methanol and/or ethanol. 9. The process according to claim 1, wherein the alkyl ether has a number of carbon atoms ranging from 5 to 10. 10. The process according to claim 9, .wherein the alkyl ether is selected from MTBE, ETBE, MSBE, ESBE, TAME, TAEE or mixtures thereof. 11. The process according to claim i, wherein the oxygen¬ated product is the branched alcohol alone, comprising the following essential steps: a) feeding the C4-C5 hydrocarbon cut containing isobutene to the first reaction step (consisting of one or more reactors), together with one or more streams contain¬ing oxygenated products; b) using a catalytic distillation column as second reac- - 23 -AMENDED SHEET tion step, wherein the isobutene ' conversion is com¬pleted, in addition to the separation of the re¬agents/products; c) recovering the C5 hydrocarbon/branched alcohol azeo-tropic product, in one or more fractionation columns, also catalytic, as head stream, side cut or bottom stream; d) recycling the stream containing the oxygenated prod¬ucts and possibly the reintegrated oxygenated prod¬ucts, to the two reaction steps- e) possibly recycling part of the C4 products to the first reaction step, in order to maximize the isobu¬tene conversion. 12. The process according to claim 11, wherein the recov¬ering of the Cs/branched alcohol azeotropic product can be effected starting from blends of: a. Cs - oxygenated products - reaction product, wherein the Cs hydrocarbons are recovered as an azeotropic com¬ pound with the branched alcohol, as head effluent, us¬ ing a scheme based on one or two fractionation columns; b. C4 - C5 - oxygenated products - reaction product, wherein the C5 hydrocarbons are recovered as an azeo¬ tropic compound with the branched alcohol as side cut of a catalytic distillation column from whose head C4 products are recovered and from the bottom a blend con- - 24 -AMENDED SHEET taining the oxygenated products and the reaction prod- uct c) C4 - C5 - oxygenated products, wherein the C5 hydrocar¬bons are recovered as an azeotropic compound with the branched alcohol,, as bottom effluent of a fractionation column from whose head the C4 products are recovered. 13. The process according to claim 11, wherein the first reaction step consists of one or more .fixed bed, tubular and/or adiabatic reactors. 14. The process according to claim 11, wherein the molar ratio of oxygenated product/isobutene is lower than 0.6. 15. The process according to claim 1, wherein the oxygen¬ated product is the branched alcohol in a blend with linear alcohols and alkyl ethers, comprising the following essen¬tial steps: a) feeding the C4-C5 hydrocarbon cut containing isobutene to the first reaction step (consisting of one or more reactors), together with one or more streams contain¬ing oxygenated products (linear and branched alcohols, ethers and water); b) using a catalytic distillation column as second reac¬tion step, wherein the isobutene conversion is com¬pleted, in addition to the separation of the re¬agents/products c) separating the C4 products and C4/linear alcohol azeo- - 25 -AMENDED SHEET tropic product from the C5 hydrocarbons, from the re¬maining oxygenated compounds and from the hydrocarbon product, in one or more distillation columns, also catalytic; d) recovering the linear alcohol from. the azeotropic product with the C4 compounds, by means of conven¬tional processes such as water washing or adsorption on inorganic solids; e) recovering the Cs/branched alcohol azeotropic product, in one or more fractionation columns, also catalytic, as head stream, side cut or bottom stream; f) recycling the stream containing the oxygenated prod¬ucts (branched alcohol and ether) and possibly the re¬integrated oxygenated products and the linear alcohol recovered, to the two reaction steps; g) possibly recycling part of the C4 products to the first reaction step, on order to maximize the isobu-tene conversion. 16. The process according to claim 15, wherein the recov¬ering of the Cs/branched alcohol azeotropic product can be effected starting from blends of; a) Cs - oxygenated products (ethers and branched alco¬hols) - reaction product, wherein the C5 hydrocarbons are recovered as an azeotropic compound with the branched alcohol, as head effluent, using a scheme - 26 -AMENDED SHEET based on one (recovery of the remaining oxygenated products as side cut) or two fractionation columns; b) C5 - oxygenated products (ethers and branched alco¬hols) - dimers, in which the C5 hydrocarbons are re¬covered as an azeotropic product with branched alcohol as head effluent of a fractionation column; c) C4-C5 - oxygenated products (ethers and linear and branched alcohols) - reaction product, effluent from a reaction step, wherein the C5 hydrocarbons are recov¬ered as an azeotropic compound with the branched alco¬hol as side cut of a fractionation column from whose head the C4/linear alcohol azeotropic product and pos¬sibly the C4 products are recovered, whereas a mixture containing the oxygenated products and the reaction product is recovered at the bottom; d) C4-CS - oxygenated products (linear and branched alco¬hols) wherein the Cs hydrocarbons are recovered as an azeotropic compound with the branched alcohol as bot¬tom effluent of a fractionation column from whose head the azeotropic product C4/linear alcohol and possibly C4 products are recovered. 17. The process according to claim 15, wherein the first reaction step consists of one or more adiabatic reactors such as traditional, boiling point, expanded bed reactors. 18. The process according to claim 15, wherein the molar - 27 -AMENDED SHEET ratio oxygenated product/isobutene is lower than 0.7. 19. The process according to claim 11 or 15, wherein the C5/branched alcohol azeotropic product is mixed with the reaction product. 5 20. The process according to claim 1, wherein, in the case of concentrated isobutene streams, the charge is diluted with C4-C7 hydrocarbons. - 28 -AMENDED SHEET

Full Text

"PROCESS FOR THE PRODUCTION OF HIGH-OCTANE HYDROCARBON COM¬POUNDS BY THE SELECTIVE DIMERIZATION OF ISOBUTENE CONTAINED IN A STREAM WHICH ALSO CONTAINS C5 HYDROCARBONS" SNAMPR0GETTI S.p.A - Via De Gasperi 1-20097-S.Donato Milanese-MI Description
The present invention relates to a process for the production of high-octane hydrocarbon compounds by means of the selective dimerization of isobutene and, to a lesser extent, of possible linear olefins, in the presence of C5 hydrocarbons and oxygenated compounds, which favour the formation of higher selectivities on the part of the cata¬lyst.
The mixture obtained can then be hydrogenated with conventional methods to obtain a product with further en¬hanced octane characteristics.
For mainly environmental reasons, the composition of gasolines is being reformulated and the general tendency is towards the production of fuels which burn better and have lower evaporative emissions. The main measures for achiev¬ing this objective are listed below (D. Sanfilippo, F. An-cillotti, M.Marchionna, Chim.& Ind., 76,(1994), 32):

- reduction in the content of aromatic compounds and elimi¬
nation of benzene;
- reduction in the volatility of gasolines to minimize
evaporative losses;
- reduction in the content of light olefins, photochemi-cally extremely reactive;
- reduction in the sulfur content and final boiling point of the gasolines.
All these measures consequently create the necessity of projecting new production processes of purely hydrocar¬bon compoionds capable of positively contributing to the above demands.
Among these, alkylated products are extremely impor¬tant as they have a high octane number, a low volatility and are practically free of olefins and aromatic compounds. The alkylation process in liquid phase is a reaction be¬tween isoparaffinic hydrocarbons, such as isobutane, and olefins, for example propylene, butenes, pentenes and rela¬tive mixtures, in the presence of an acid catalyst for the production of C7-C9 hydrocarbons with a high octane number to be used in gasolines (A. Corma, A. Martinez, Catal.Rev,-Sci.Eng., 3^,(1993),483).
The main problem of alkylation processes is due to the fact that, with growing environmental regulations, both of the traditional processes (with hydrofluoric and sulfuric
- 2 -

acid) are encountering considerable difficulties, which create uncertainties for the future; the process with hy¬drofluoric acid due to the toxicity of this acid, espe¬cially in populated areas, and that using sulfuric acid, as
a result of the large production of acid sludge as well as the considerably corrosive nature of the catalyst.
Alternative processes with solid acid catalysts are being developed but their commercial applicability has yet to be demonstrated.
A hydrocarbon product of this type, on the other hand, is becoming increasingly more requested due to its octane characteristics (both the Research Octane Number (RON) and the Motor Octane Number (MON) are high) and those relating to the boiling point (limited volatility but low end-point)
which position it in the group of compositions of great in¬terest for obtaining gasolines which are more compatible with current environmental requirements.
An alternative refinery process for obtaining products with characteristics similar to those of alkylated products
can be offered by the hydrogenation of so-called "polymer" gasoline.
Oligomerization processes (often inaccurately called polymerization in the refining industry) were widely used in the '30s' and '40s' for converting low-boiling C3-C4
olefins into gasolines. The process leads to the production
- 3 -

of a gasoline with a high octane number (RON about 97) but with a high sensitivity (difference between RON and MON) due to the purely olefinic nature of the product (J.H.Gary, G.E. Handwerk, 'Petroleum Refining : Technology and Econom-
5 ics", 3rd Ed., M. Dekker, New York, (1994), 250).
Typical olefins which are oligomerized are mainly pro¬pylene, which gives dimers or slightly higher oligomers de¬pending on the process used, and isobutene which mainly gives dimers but is always accompanied by a considerable
quantity of higher oligomers.
With particular attention to the oligomerization of isobutene, it is known that this reaction can be carried out either batchwise, semi-batchwise or in continuous, ei¬ther in gas or liquid phase, generally at temperatures
5 ranging from 50 to 300°C and at atmospheric pressure or such pressures as to maintain the reagents in liquid phase, if necessary.
Typical catalysts for the industrial oligomerization process of isobutene are represented by phosphoric acid,
generally supported on a solid (for example kieselguhr), or cation-exchange acid resins. The latter allow blander con¬ditions to be used compared with supported phosphoric acid both in terms of temperature and pressure (50-100*0 and 0.2-3 MPa with respect to 200-220°C and 3-10 MPa) .
Other catalysts are also claimed in literature, both
- 4 -

liquid acids such as H2SO4 and derivatives of sulfonic ac¬ids, and solids such as silico-aluminas, mixed oxides, zeo¬lites, fluorinated or chlorinated aluminas, etc.; none of these catalysts however has so far enabled an industrial
I process to be set up, as in the case of supported phospho¬ric acid (F. Asinger, "Mono-olefins: Chemistry and Technol¬ogy", Pergamon Press, Oxford, pages 435-456) and that of cation resins (G. Scharfe, Hydrocarbon Proc, April 1973, 171) .
From the product point of view, the main problem of this process lies in the fact that excessive percentages of heavy oligomers such as trimers (selectivity of 20-40%) and tetramers (selectivity of 1-5%) of isobutene, are produced in the oligomerization phase. Tetramers are completely out-
side the gasoline fraction as they are too high-boiling and therefore represent a net loss in yield to gasoline; as far as trimers are concerned, their concentration should be greatly reduced as they have a boiling point (170-180°C) at the limit of future specifications on the final point of
reformulated gasolines.
The problem of reducing the formation of oligomers higher than dimers to percentages lower than 15% is, on the other hand, a problem typical of the oligomerization of isobutene, as also indicated in literature (C.T.O'Connor, M. Kojima, K.W. Shcumann, Appl.Catal., 16,(1985),193), This
- 5 -

level of heavy compounds is slightly higher than that of an alkylated product and is still tolerated in the gasoline pool.
From what is specified above, there is evidently great interest in obtaining a new dimerization process of isobu-tene which allows the synthesis of a higher-quality prod¬uct, through reaching greater selectivities.
By carrying out the selective dimerization reaction of isobutene in the presence of moderate quantities of oxygen¬ated products, the production of a fraction of oligomers is selectively obtained, which is particular rich in dimers (>85%) and practically free of tetramers and higher oli¬gomers ( The reaction product is then preferably hydrogenated to give a completely saturated end-product with a high oc¬tane number and low sensitivity.
The hydrogenation can be carried out with conventional methods as described, for example, in F. Asinger, "Mono-olefins: Chemistry and Technology", Pergamon Press, Oxford, page 455.
For illustrative purposes. Table 1 indicates the oc¬tane number and relative boiling, points of some of the products obtained, by means of the process, object of the present invention.
- 6 -

The process, object of the present invention, for the production of high-octane hydrocarbon compounds by the ser lective dimerization of isobutene contained in a stream also containing C5 hydrocarbons, is characterized in that:
- the reaction is carried out^in two di'stinct steps,
- a catalytic distillation is used as second step,
- the reaction is carried out in the presence of oxygenated
products selected from a branched alcohol alone or in a
blend with linear alcohols and alkyl ethers, in such a
quantity as to have in the feeding, in the case of the
presence of a branched alcohol alone, a molar ratio oxygen¬
ated product/isobutene higher than 0.005, in the case of
the presence of a branched alcohol in a blend, a molar ra¬tio oxygenated product/isobutene higher than 0.01
- a C5 /branched alcholm atetropic separatiion step is camed out.
It should also be pointed out that in the of hy-
It should also be pointed out that in the case of by-
drocarbon streams also comprising other olefins, it has
been observed that at least a part of the latter can be
converted by reaction with isobutene into the hydrocarbon
- 7 -AMENDED SHEET

product without altering the octane value. It is therefore preferable to effect an enriching treatment, by means of pre-isomerization, of the internal linear olefins, in order to favour the overall octane number of the mixture.
5 The process claimed herein can be applied to cuts mainly containing isobutane, isobutene, n-butane, n-butenes and saturated and olef inic C5 hydrocarbons.
Although a wide variety of sources are available for the supply of these streams, the most common are those de-
0 riving from Dehydrogenation processes of iso-paraf f ins, from FCC units. Steam Cracking or processes for the produc¬tion of pure isobutene such as the dehydration of tert-butyl alcohol (TEA) or the Cracking of MTBE and/or. ETBE; these streams differ from each other in the content of iso-
5 butene and linear butenes, as shown in Table 2.

Should streams from Steam Cracking contain diolefins
in addition to the desired mono-olef ins, they must be
5 eliminated by means of typical removal treatment (for exam-
- 8 -

ple solvent extraction or selective hydrogenation).
Saturated and olefinic C5 hydrocarbons can be present in these streams, in various amounts (0.2 - 20%), depending on the efficiency of- the C4-C5 separation step. The C5 ole¬fins possibly present can be involved in dimerization reac¬tions .
The stream sent to the reaction steps can contain
branched alcohols or a blend of alcohols and alkyl ethers,
in addition to the hydrocarbon components.The branched alcohol can also be formed by feeding water in the stream sent to the naction steps, which is
The linear alcohols used contain a number of carbon
atoms ranging from 1 to 6 and those preferred are methanol and/or ethanol. The branched alcohols have from 3 to 6 car¬bon atoms and those preferred are tert-butyl alcohol (TBA) and/or tert-amyl alcohol (TAA).
The alkyl ether used can be selected from those, con-
taining a number of carbon atoms ranging from 5 to 10: MTBE (methyl tert-butyl ether), ETBE (ethyl tert-butyl ether), MSBE (methyl sec-butyl ether), ESSE (ethyl sec-butyl ether), TAME (methyl tert-amyl ether), TAEE (ethyl tert-
amyl ether) or mixtures thereof are preferred.
Isobutene, together with the hydrocarbon stream in which it is contained, is sent with the oxygenated prod¬ucts, in stoichiometric defect, into contact with the acid catalyst where the dimerization takes place. The linear
primary alcohol, possibly present, in addition to interact-capable of foeming the brabched alcohol by reacting with the tertiary olefin undert the naction
- 9 -
AMENDED SHEET

ing with the catalysts, also helps to limit the possible cracking of the alkyl ether and can possibly react with the ditners and linear C4 olefins, whereas the branched alcohol (tertiary) does not react with the olefins due to its steric hindrance.
In order to obtain the dimerization product with the desired selectivity to dimers, it is essential to maintain a constant level of oxygenated products in the reaction en¬vironment to form the catalytic species with the correct activity and stability. The optimal level of oxygenated products present in the reaction environment, to obtain se-lectivities to dimers close to 85% by weight, depends on the composition of the hydrocarbon charge. The higher the olefin content in the charge, the lower the amount of oxy¬genated products to be used.
A wide variety of acid catalysts can be used for this process, but those preferred are styrene-divinyl benzene polymeric resins having sulphonic groups as catalytic cen¬tres .
A large range of operative conditions can be used to produce high-octane hydrocarbons from isobutene in the de¬sired selectivities. It is possible to operate in vapour or liquid-vapour phase, but operating conditions in liquid phase are preferred.
The pressure is preferably higher than the atmospheric

value, in order to maintain the reagents in liquid phase, generally below 5 MPa, more preferably between 0.2 - 2.5 MPa. The reaction temperature preferably ranges from 30 to 120°C.
The feeding space velocities of the oxygenated-hydrocarbon stream are preferably lower than 30 h-1, more preferably ranging from 1 and 15 h-1.
Isobutene is mainly converted in the reaction zone, however portions of the other olefins which are present can also be converted to useful product; in principle, there are no limits to the concentration of iso-olefin in the hy¬drocarbon fraction, even if concentrations ranging from 2 to 60% are preferred; in case of streams having a high iso¬butene concentration (dehydration or cracking) it is there¬fore convenient to dilute the charge with C4-C7 hydrocar¬bons. There are no limits, on the contrary, for the ratio between isobutene and linear olefins.
The process, object of the present invention, can be effected batchwise or in continuous, bearing in mind how¬ever that the latter is much more advantageous in indus¬trial practice.
The reactor configuration selected includes a first reaction step (one or more fixed bed reactors) and a second step consisting of a catalytic distillation which avoids the use of a reactor and a distillation column, as in a
- 11 -

conventional plant.
• The presence of C5 hydrocarbons in the feed, however, complicates the process schemes, as these compounds have intermediate boiling temperatures between C4 and oxygenated products, and they also form azeotropic mixtures with the branched alcohols as shown in Table 3, which indicates the boiling points of the most representative low-boiling com¬ponents present in the streams

plant together with the C4 products, as they would intro¬duce oxygenated products (branched alcohols) into the stream, which are difficult to remove by means of the tra¬ditional techniques used for removing methanol (water wash-
ing) and which are poisonous for the subsequent treatment processes of the streams (polymerization, alkylation and metathesis),
The C5 products, on the other hand, cannot be main¬tained in the oxygenated stream as they would rapidly accu-
mulate. With respect to the schemes shown in literature (US 6,011,191), it is therefore necessary to introduce a C5/branched alcohol azeotropic separation step, which can be inserted in several positions of the plant, in relation to the C5 content in the charge and also the relative con-
centration of the C5 products present.
When the oxygenated product is a branched alcohol alone, the process is, in particular, preferably effected with a molar ratio of oxygenated product/isobutene lower than 0.6, through the following essential steps:
a) feeding the C4-C5 hydrocarbon cut containing isobutene
to the first reaction step (consisting of one or more
reactors) , together with one or more streams containing
oxygenated products;
b) using a catalytic distillation column as second reac-
tion step, wherein the isobutene conversion is com-
- 13 -

pleted, in addition to the separation of the rea- gents/products;
c) recovering the C5 hydrocarbon/branched alcohol azeo-
tropic product, in one or more fractionation columns,
i also catalytic, as head stream, side cut or bottom stream;
d) recycling the stream containing the oxygenated products
and possibly the reintegrated oxygenated products, to
the two reaction steps;
e) possibly recycling part of the C4 products to the first reaction step, in order to maximize the isobutene con¬version.
The first reaction step can consist of one or more fixed bed, tubular and/or adiabatic reactors. The separation of the C5/branched alcohol azeotropic product of step (c) is preferably effected starting from blends:
a) C5 - oxygenated products - reaction product, wherein
the C5 hydrocarbons are recovered as azeotropic com-
pound with the branched alcohol, as head effluent, using a scheme based on one or two fractionation columns;
b) C4 - C5 - oxygenated products - reaction product,
wherein the C5 hydrocarbons are recovered as azeo-
tropic compound with the branched alcohol as side
- 14 -

cut of a catalytic distillation column from whose head the C4 products are recovered and at the bottom a blend containing the oxygenated products and the reaction product; c) C4 - C5 - oxygenated products, wherein the C5 hydro¬carbons are recovered as azeotropic compound with the branched alcohol as the bottom effluent of a fractionation column from whose head the C4 products are recovered. When the oxygenated product is a branched alcohol in a mixture with linear alcohols and alkyl ethers, the process is preferably effected, in particular, with a molar ratio of oxygenated product/isobutene lower than 0.7, by means of the following essential steps:
a) feeding the C4-C5 hydrocarbon cut containing isobutene to the first reaction step (consisting of one or more reactors), together with one or more streams contain¬ing oxygenated products (linear and branched alcohols, ethers and water) ;
b) using a catalytic distillation column as second reac¬tion step, wherein the isobutene conversion is com¬pleted, in addition to the separation of the rea¬gents/products ;
c) separating the C4/linear alcohol azeotropic product and possibly C4 products from the remaining oxygenated
- 15 -

compounds and from the hydrocarbon product, in one or more distillation columns, also catalytic;
d) recovering the linear alcohol from the azeotropic
product with the C4 compounds, by means of conven-
tional processes such as water washing or adsorption
on inorganic solids;
e) recovering the C5/branched alcohol azeotropic product,
in one or more fractionation columns, also catalytic,
as head stream, side cut or bottom stream;
f) recycling the stream containing the oxygenated prod¬ucts (branched alcohol and ether) and possibly the re¬integrated oxygenated products and recovered linear alcohol, to the two reaction steps; g) possibly recycling part of the C4 products to the first reaction step, in order to maximize the isobu-tene conversion. The first reaction step can consist of one or more adia-batic reactors, such as traditional, boiling point, ex¬panded bed reactors. The separation of the Cs/branched alcohol azeotropic product of step (e) is preferably effected starting from blends of:
a) C5 - oxygenated products (ethers and branched alco¬hols) - reaction product, wherein the C5 hydrocarbons are recovered as an azeotropic compound with the
- 16 -

branched alcohol, as head effluent, using a scheme based on one (recovery of the remaining oxygenated products as side cut) or two fractionation columns;
b) C5 - oxygenated products (ethers and branched alcohols
i - dimers, in which the Cs hydrocarbons are recovered
as azeotropic product with the branched alcohol as head effluent of a fractionation column;
c) C4-CS - oxygenated products (ethers and linear and
branched alcohols) - reaction product, effluent from a
reaction step, wherein the C5 hydrocarbons are recov¬ered as an azeotropic compound with the branched alco¬hol as side cut of a fractionation column from whose head the C4/linear alcohol azeotropic product and pos¬sibly the C4 products are recovered, whereas a mixture
containing the oxygenated products and the reaction product is recovered at the bottom/
d) C4-C5 - oxygenated products (linear and branched alco¬
hols) wherein the C5 hydrocarbons are recovered as an
azeotropic compound with the branched alcohol as bot-
torn effluent of a fractionation column from whose head
the C4/linear alcohol azeotropic product and possibly
C4 products are recovered.
For the two processes comprising the essential steps The C5/branched alcohol atetropic prouct is mixed with the reaction product of specified above (a-e and a-g) the C5 products are present
in the streams prevalently containing C4 products in a
- 17 -AMENDED SHEET

quantity preferably ranging from 0.5 to 10% by weight.
S'even process schemes are shown in figures 1-1, in order to clearly illustrate the present invention.
Figure 1 shows a process scheme with catalytic distilla¬tion, when C5 products are not present in the charge and the oxygenated product is a branched alcohol (TBA).
The stream (1) containing isobutene, together with the reintegration feeding of TBA (or possibly water) (2) and the recycled stream of oxygenated products (9), is sent to a first reaction step (Rl), which can consist of one or more fixed bed reactors, in which the C4 iso-olefin is se¬lectively converted to dimers.
The effluent (4) from the first reaction step, is sent to a catalytic distillation (C1) in which the isobutene conversion is completed. A stream (5) essentially contain¬ing C4 hydrocarbons is removed from the head of this col¬umn, whereas a stream (6) essentially containing the reac¬tion product and the oxygenated compounds, is collected at the bottom.
This stream (6) is sent to a further separation column (C2) wherein a stream (8) is collected at the head, con¬taining the dimers/TEA azeotropic product which is recycled to the two reaction steps (streams 9 and 10) , whereas the reaction product (7) essentially consisting of dimers and \ trimers, is collected from the bottom,
- 18 -.

The introduction of catalytic distillation allows a con-siderable simplification of the plant scheme, which is in¬stead based on two reaction steps (fixed bed reactors) and three fractionation columns, as shown in figure 2.
When C5 hydrocarbons are present in the charge, different plant configurations can be used to recover the C5/TBA azeotropic product, depending on the quantity of C5 prod¬ucts present and the required purity of the streams.
Figure 3 shows a possible process scheme which differs
from that of figure 1 due to the fact that the C5/TBA azeo¬tropic product (11) is recovered from the head of the col¬umn C2, which can possibly be joined to the reaction prod¬uct, whereas the stream containing the oxygenated products to be recycled (TBA/dimers azeotropic product) is removed
from the column C2 as side cut (8).
The process scheme is more complex when a more efficient separation of the two C5/TBA and dimers/TBA azeotropic products is to be effected, as a new fractionation column (C3) must be inserted, as shown in figure 4. In this new
scheme, the head stream of the column C2 (8) is sent to a
new column (C3) wherein the C5/TBA azeotropic product (11)
is separated at the head and the dimers/TBA azeotropic
product (12) which is recycled to the two reaction steps
(streams 9 and 10), is separated at the bottom.
Alternatively, the C5/TBA azeotropic product can be re-
- 19 -

covered as side cut (11) in the column reactor CI (figure 5V.
A further option, shown in figure 6, consists in sending this azeotropic product to the head stream of the catalytic
5 distillation column together with the C4 products and in using a new column (C3) to recover the C5/TBA azeotropic product at the bottom (11) and C4 products at the head (12) .
Ficfure 7 shows a possible process scheme when a mixture
of oxygenated products, consisting of alkyl ether (MTBE), linear alcohol (Methanol) and branched alcohol (TBA), is used. In this case, the stream (1) containing isobutene, together with the reintegration feeding of methanol and TBA (or water) (2) and the recycled streams of oxygenated prod-
5 ucts (MTBE and TBA) (9) and methanol (14), is sent to the first reaction step (Rl) , which can consist of one or more reactors, in which the C4 iso-olefin is selectively con¬verted to dimers.
The effluent (4) from the first reaction step is sent to
3 catalytic distillation (CI), which represents the second reaction step, together, possibly, with the recycled streams of oxygenated products (ID) and methanol (13). A stream (5) is collected from the head of this column, es¬sentially containing C4 hydrocarbons and methanol, which is
5 fed to a unit for the recovery of the alcohol (MR) which
- 20 -

can consist, for example, of an adsorption system on mo-lecular sieves, or a water washing column. In both cases, the alcohol recovered (12) can be sent back to the two re¬action steps (streams 13 and 14) , whereas the hydrocarbon
stream (11) can be used in subsequent operations.
The bottom stream (6) of the column C1 is sent to a fur¬ther separation column (C3) wherein a stream (15) contain¬ing the Cs/branched alcohol azeotropic product is collected at the head, a stream (8) essentially containing MTBE, TEA
) and dimers, as side cut, which is recycled to the two, reac¬tion steps (streams 9 and 10), whereas the reaction product (7) , essentially consisting of dimers, trimers and small quantities of oligomers is recovered from the bottom.

CLAIMS 1. ' Propess for the production of high-octane hydrocarbon compounds by the selective dimerization of isobutene con¬tained in a stream also containing C5 hydrocarbons, charac¬terized in that:
- the reaction is carried out with acid catalysts in two
distinct steps,
- a catalytic distillation is used as second step,
- the reaction is carried out in the presence of oxygenated products selected from a branched alcohol alone or in a blend with linear alcohols and alkyl ethers, in such a quantity as to have in the feeding, in the case of the. presence of a branched alcohol alone, a molar ratio of oxy¬genated product/ isobutene higher than 0.005, in the case of the presence of a branched alcohol in a blend, a molar ra¬tio of oxygenated product/isobutene higher than 0,01;
- a C5/branched alcohol azeotropic separation step is car¬ried out.

2. The process according to claim 1, wherein the first reaction step is carried out at a reaction temperature ranging from 30 to 120°C, at a pressure lower than 5 MPa and feeding space velocities lower than 30 h-1.
3. The process according to claim 2, wherein the feeding space velocities range from 1 to 15 h-1.
4. The process according to claim l, wherein the branched
- 22 -
AMENDED SHEET

alcohol has a number of carbon atoms ranging from 3 to 6 .
5. . The process according to claim 4, wherein the branched
alcohol is selected from tert-butyl alcohol or tert-amyl
alcohol.
6. The process according to claim 1, wherein water is fed, which is capable of forming the branched alcohol by reacting with the tertiary olefin under the reaction condi¬tions .
7. The process according to claim 1, wherein the linear alcohol has a number of carbon atoms ranging from 1 to 6.
8. The process according to claim 7, wherein the linear alcohol is selected from methanol and/or ethanol.
9. The process according to claim 1, wherein the alkyl ether has a number of carbon atoms ranging from 5 to 10.
10. The process according to claim 9, .wherein the alkyl ether is selected from MTBE, ETBE, MSBE, ESBE, TAME, TAEE or mixtures thereof.
11. The process according to claim i, wherein the oxygen¬ated product is the branched alcohol alone, comprising the following essential steps:

a) feeding the C4-C5 hydrocarbon cut containing isobutene to the first reaction step (consisting of one or more reactors), together with one or more streams contain¬ing oxygenated products;
b) using a catalytic distillation column as second reac-
- 23 -AMENDED SHEET

tion step, wherein the isobutene ' conversion is com¬pleted, in addition to the separation of the re¬agents/products;
c) recovering the C5 hydrocarbon/branched alcohol azeo-tropic product, in one or more fractionation columns, also catalytic, as head stream, side cut or bottom stream;
d) recycling the stream containing the oxygenated prod¬ucts and possibly the reintegrated oxygenated prod¬ucts, to the two reaction steps-
e) possibly recycling part of the C4 products to the first reaction step, in order to maximize the isobu¬tene conversion.
12. The process according to claim 11, wherein the recov¬ering of the Cs/branched alcohol azeotropic product can be effected starting from blends of:
a. Cs - oxygenated products - reaction product, wherein
the Cs hydrocarbons are recovered as an azeotropic com¬
pound with the branched alcohol, as head effluent, us¬
ing a scheme based on one or two fractionation columns;
b. C4 - C5 - oxygenated products - reaction product,
wherein the C5 hydrocarbons are recovered as an azeo¬
tropic compound with the branched alcohol as side cut
of a catalytic distillation column from whose head C4
products are recovered and from the bottom a blend con-
- 24 -AMENDED SHEET

taining the oxygenated products and the reaction prod- uct c) C4 - C5 - oxygenated products, wherein the C5 hydrocar¬bons are recovered as an azeotropic compound with the branched alcohol,, as bottom effluent of a fractionation column from whose head the C4 products are recovered.
13. The process according to claim 11, wherein the first reaction step consists of one or more .fixed bed, tubular and/or adiabatic reactors.
14. The process according to claim 11, wherein the molar ratio of oxygenated product/isobutene is lower than 0.6.
15. The process according to claim 1, wherein the oxygen¬ated product is the branched alcohol in a blend with linear alcohols and alkyl ethers, comprising the following essen¬tial steps:

a) feeding the C4-C5 hydrocarbon cut containing isobutene to the first reaction step (consisting of one or more reactors), together with one or more streams contain¬ing oxygenated products (linear and branched alcohols, ethers and water);
b) using a catalytic distillation column as second reac¬tion step, wherein the isobutene conversion is com¬pleted, in addition to the separation of the re¬agents/products
c) separating the C4 products and C4/linear alcohol azeo-
- 25 -AMENDED SHEET

tropic product from the C5 hydrocarbons, from the re¬maining oxygenated compounds and from the hydrocarbon product, in one or more distillation columns, also catalytic;
d) recovering the linear alcohol from. the azeotropic product with the C4 compounds, by means of conven¬tional processes such as water washing or adsorption on inorganic solids;
e) recovering the Cs/branched alcohol azeotropic product, in one or more fractionation columns, also catalytic, as head stream, side cut or bottom stream;
f) recycling the stream containing the oxygenated prod¬ucts (branched alcohol and ether) and possibly the re¬integrated oxygenated products and the linear alcohol recovered, to the two reaction steps;
g) possibly recycling part of the C4 products to the first reaction step, on order to maximize the isobu-tene conversion.
16. The process according to claim 15, wherein the recov¬ering of the Cs/branched alcohol azeotropic product can be effected starting from blends of;
a) Cs - oxygenated products (ethers and branched alco¬hols) - reaction product, wherein the C5 hydrocarbons are recovered as an azeotropic compound with the branched alcohol, as head effluent, using a scheme
- 26 -AMENDED SHEET

based on one (recovery of the remaining oxygenated products as side cut) or two fractionation columns;
b) C5 - oxygenated products (ethers and branched alco¬hols) - dimers, in which the C5 hydrocarbons are re¬covered as an azeotropic product with branched alcohol as head effluent of a fractionation column;
c) C4-C5 - oxygenated products (ethers and linear and branched alcohols) - reaction product, effluent from a reaction step, wherein the C5 hydrocarbons are recov¬ered as an azeotropic compound with the branched alco¬hol as side cut of a fractionation column from whose head the C4/linear alcohol azeotropic product and pos¬sibly the C4 products are recovered, whereas a mixture containing the oxygenated products and the reaction product is recovered at the bottom;
d) C4-CS - oxygenated products (linear and branched alco¬hols) wherein the Cs hydrocarbons are recovered as an azeotropic compound with the branched alcohol as bot¬tom effluent of a fractionation column from whose head the azeotropic product C4/linear alcohol and possibly C4 products are recovered.

17. The process according to claim 15, wherein the first reaction step consists of one or more adiabatic reactors such as traditional, boiling point, expanded bed reactors.
18. The process according to claim 15, wherein the molar
- 27 -AMENDED SHEET

ratio oxygenated product/isobutene is lower than 0.7. 19. The process according to claim 11 or 15, wherein the C5/branched alcohol azeotropic product is mixed with the reaction product. 5 20. The process according to claim 1, wherein, in the case of concentrated isobutene streams, the charge is diluted with C4-C7 hydrocarbons.

- 28 -AMENDED SHEET

Documents:

2390-CHENP-2008 AMENDED CLAIMS 05-04-2013.pdf

2390-CHENP-2008 AMENDED PAGES OF SPECIFICATION 05-04-2013.pdf

2390-CHENP-2008 FORM-3 05-04-2013.pdf

2390-CHENP-2008 PCT NOTIFICATION 05-04-2013.pdf

2390-CHENP-2008 CORRESPONDENCE OTHERS 19-06-2012.pdf

2390-CHENP-2008 EXAMINATION REPORT REPLY RECEIVED 05-04-2013.pdf

2390-chenp-2008 abstract.pdf

2390-chenp-2008 claims.pdf

2390-chenp-2008 correspondences-others.pdf

2390-chenp-2008 description(complete).pdf

2390-chenp-2008 drawings.pdf

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Patent Number

256014

Indian Patent Application Number

2390/CHENP/2008

PG Journal Number

17/2013

Publication Date

26-Apr-2013

Grant Date

19-Apr-2013

Date of Filing

14-May-2008

Name of Patentee

SNAMPROGETTI S.P.A

Applicant Address

VIALE DE GASPERI, 16I-20097 SAN DONATO MILANESE

Inventors:

#	Inventor's Name	Inventor's Address
1	DI GIROLAMO, MARCO	VIA I MAGGIO 7, I-20097 SAN DONATO MILANESE
2	SANFILIPPO, DOMENICO	VIA SALVO D' ACQUISTO, 4, I-20067 PAULLO-MILANO
3	CONTE, MASSIMO	VIA UGO LA MALFA 92, I-20068 PESCHIERA BORROMEO-MILANO

PCT International Classification Number

C07C 2/08

PCT International Application Number

PCT/EP06/10895

PCT International Filing date

2006-11-14

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	MI2005A002199	2005-11-17	Italy