MXPA99007567A - Olefin plant recovery system employing catalytic distillation - Google Patents

Abstract

The C2 to C5 and heavier acetylenesand dienes in a thermally cracked feed stream are hydrogenated without significantly hydrogenating the C2 and C3 olefins. Additionally, the C4 and heavier olefins may be hydrogenated. Specifically, the cracked gas feed in an olefin plant is hydrogenated in a distillation reaction column containing a hydrogenation catalyst without the necessity of separating the hydrogen out of the feed and without any significant hydrogenation of the ethylene and propylene. A combined reaction-fractionation step known as catalytic distillation hydrogenation is used to simultaneously carry out the reactions and separations while maintaining the hydrogenation conditions such that the ethylene and propylene remain substantially unhydrogenated and essentially all of the other C2 and heavier unsaturated hydrocarbons are hydrogenated. Any unreacted hydrogen can be separated by a membrane and then reacted with separated C9 and heavier materials to produce hydrogenated pyrolysis gasoline.

Description

SYSTEM FOR OILFIELD PLANT RECOVERY, WHICH USES CATALYTIC DISTILLATION Background of the Invention The present invention relates to a process for the production of olefins and particularly to process the charge gas feed to recover more effectively the product and process the by-products. Ethylene, propylene and other petrochemicals valuable, are produced by thermal cracking of a variety of hydrocarbon feedstocks, which are in the range from ethane to heavy vacuum gas oil? In the thermal cracking of these feedstocks, a wide variety of products are produced in the range from hydrogen to pyrolysis fuel oil. The t. effluent from the cracking stage, commonly referred to as charge or cracked gas, is constituted by this complete range of materials that must then be separated (fractionated) into various streams of products and sub-products, followed by reaction (hydrogenation) of minus some of the unsaturated by-products. The typical charge gas stream, in addition to the desired ethylene and propylene products, contains C2 acetylenes, acetylenes and C3 dienes and acetylenes, dienes and C4 olefins and heavier, as well as a significant amount of hydrogen. In most of the previous processes acetylenes C2 and acetylenes and C3 dienes and the dienes, acetylenes and C5-olefins and heavier, are catalytically hydrogenated in fixed-bed reactors using a series of commercially available catalysts. In an increasing number of applications, acetylenes, dienes and C4 olefins are also catalytically hydrogenated in fixed-bed reactors. These separate hydrogenation steps are carried out in one of two process sequences. ~ In the first sequence, the charge gas is compressed between 2.76 and 4.14 MPa (400 and 600 psia). Then it is progressively cooled by condensing the C2 and heavier components. Hydrogen is recovered cryogenically and methane is fractionated from the stream. The remaining C2 and heavier currents enter a series of fractionation towers. The first tower produces an upper stream containing the C2 acetylenes, olefins, and paraffins. This stream is sent to a fixed phase, steam phase reactor, where the C2 acetylene is selectively hydrogenated using the cryogenically separated hydrogen prior to the charge gas stream. The second tower, in this sequence, produces an upper stream containing acetylenes, dienes, olefins and C3 paraffins. This stream is sent to a liquid phase or fixed-bed reactor, where acetylenes and C3 dienes are selectively hydrogenated using cryogenically separated hygrogens prior to the charge gas stream. The third tower, in this first sequence, produces an upper stream containing the acetylenes dienes, olefins and C4 paraffins. This stream is then sent either to battery limits with a final product or a fixed-bed liquid phase reactor, where the dienes, acetylenes and in some cases the olefins, are hydrogenated using the cryogenically recovered hydrogen previously from the gas. load. The bottoms of the third tower contain the dienes acetylenes, olefins and paraffins C5 and heavier. This current is sent to a series of liquid phase reactors with two fixed beds. In the first, acetylenes and dienes are catalytically hydrogenated. The olefins are catalytically hydrogenated in the second reactor. Both reactors use the cryogenically recovered hydrogen in advance of the charge gas. In some applications, the third tower produces an upper stream containing both acetylenes, dienes, olefins, and C4 and Cs paraffins. These are hydrogenated as discussed above for the C4 's alone, in a single fixed bed liquid phase reactor. Acetylene dienes, olefins and paraffins C6 and heavier, leave the bottom third tower and are hydrogenated as previously discussed in two reactors of liquid phase, fixed bed. In the second process sequence, the cracked gas is compressed between 2.07 and 3.45 MPa (300 and 500 psia) and sent to a fractional fraction tower. The product of the. The upper part of the tower is C3 and the lighter portion of the loading gas. It is sent to a series of fixed-bed vapor phase reactors, where acetylene C2 and a portion of acetylenes and dienes C3 are hydrogenated using a small portion (typically less than 10%) of the hydrogen contained in stream C3 and more light. The non-hydrogenated portion of the acetylenes and C3 dienes as well as the C4 and heavier acetylenes, dienes and olefins, are hydrogenated in a manner similar to that described above for the first process sequence. This still leaves more than 90% of the hydrogen to recover cryogenically. Also in said system it is necessary to fractionate the C4 and heavier materials from the load before the hydrogenation step. Otherwise, the heat of the hydrogenation reaction will be excessive and there would be a high proportion of hydrogenation catalyst scale. Since this fractionation occurs in an environment of high hydrogen and methane content, the energy requirements are high.

In most of the previous processes, acetylenes C2 and C3 and dienes C3 are hydrogenated after the hydrogen separation / recovery step. Hydrogenation of C4 and heavier acetylenes, dienes and olefins always occurs after the hydrogen preparation stage and will consume up to 80% of the total available hydrogen. This hydrogenation also occurs in fixed bed catalytic reactors using selected catalysts for the selectivity and degree of hydrogen saturation dictated or not dictated by the particular process. While widely practiced, both of the process sequences described above have a number of disadvantages. First, the cracked gas must be acquired and condensed in the presence of hydrogen. Due to the high partial pressure of hydrogen, the mechanical refrigeration requirements to achieve the condensation of the C2 and heavier material are high, thus increasing energy consumption and capital investment in the process. Also, hydrogen must be separated cryogenically to supply hydrogen for the various downstream reactors that are both intense in both power and capital. In addition, hydrogenation steps occur in a series of fixed bed reactor requiring between 3 and 6 separate reactor systems, thus increasing capital investment and plant complexity. Various hydrogenation processes and characteristics of the prior art are illustrated in U.S. Patents. Nos. 3,692,864; 4,020,119; 4,404,124; 4,443,559 and 4,973,790. Also, a selective catalytic hydrogenation process is disclosed in Published International Patent Application WO 95/15934. SUMMARY OF THE INVENTION An object of the present invention is to hydrogenate in the liquid phase in a boiling point reactor the acetylenes and dienes of C2 to C5 and possibly heavier in a feed stream without hydrogenation of the C2 and C3 olefins in the stream of food. Additionally, the C4 / C5 olefins and some or all of the heavier olefins can still be hydrogenated without hydrogenating the C2 and C3 olefins. More specifically, it is an object of the present invention to provide a system and method for hydrogenating the cracked gas in an olefin plant before the separation of hydrogen and methane from the cracked gas, in a form to hydrogenate the C2 acetylene byproducts, C3 acetylenes and dienes and acetylenes and C4 dienes and heavier and, if desired, C4 and heavier olefins, without significant hydrogenation of ethylene and propylene. This involves the use of a combined reaction-fractionation stage known as hydrogenation with catalytic distillation upstream of the cooling and condensation of the C2 material and heavier, to be carried out simultaneously in the reactions and separations in a way to avoid or minimize hydrogenation of the desired main products and consume hydrogen unnecessarily for the costly with hydrogen separation. The hydrogenation of the C4 and heavier acetylenes, dienes and olefins increases the hydrogen reduction between 70% and 100% and more typically from 90% to 95%. This high removal of hydrogen reduces the partial pressure of hydrogen, thus reducing the requirement for mechanical cooling to cool and condense the material C2 and heavier, thus saving energy and capital investment. The cryogenic separation of hydrogen from cracked gas, It is eliminated. Since all hydrogenation reactions occur upstream of the hydrogen-methane separation stages, the hydrogen required for the hydrogenation reactions that is present in the charge gas. The elimination of the cryogenic separation of hydrogen results in energy savings, lower capital investments and less complexity in the process. Alternatively, the present invention can be used to hydrogenate the acetylenes and dienes without significant hydrogenation of olefins. In the two processing sequences currently practiced, the incrustation in the bottoms of the fractionation towers typically occurs due to the presence of acetylenes and dienes. The bottom operating temperature of these towers is limited to minimizing incrustation tendencies but replacement equipment must often be provided to ensure continuity of plant operation. Hydrogenation of the dienes and acetylenes before the fractionation towers eliminates the incrustation tendencies in the bottoms of the fractionation towers. Brief Description of the Drawings Figure 1 is a flow chart for an olefin plant for the conventional prior art; Figure 2 is a flow chart for a portion of an olefin plant according to the present invention. Figure 3 is a flow diagram for the remaining portion of an olefin plant according to the present invention, illustrating the downstream processing of the olefin-containing vapors.

Figure 4 is a flow diagram similar to the flow chart of Figure 2, but illustrating an alternative embodiment of the present invention. Detailed Description of the Preferred Modes First with reference to Figure 1, which illustrates an olefin plant of the conventional prior art such as the first process sequence previously discussed, first a charge gas 10 is compressed in 12 to a pressure of 2.76 at 4.14 MPa (400 to 600 psia). Most of the gas obtained is then subjected to cryogenic treatment at 14 to separate the hydrogen followed by separation of methane at 16. A small portion of C3 and heavier material condenses in the compression train and often derives the stages of de-ethanization and cryogenic denatanisation passing directly to the depropanizer 30 as stream 31. The gas stream 18 is then decatanized at 20 with the gas stream C2 which is hydrogenated at 22 and fractionated at 24 to produce essentially ethylene 26 and ethane 28. The bottoms of the deethanizer 20 they are depropanied at 30 with the separate stream C3 32 which is hydrogenated at 34 and fractionated at 36 to essentially produce propylene 38 and propane 40. Likewise, the bottoms of the depropanizer 30 are debutanized at 42, with the stream C4 being hydrogenated at 44 and the Cs + stream that is hydrogenated at 46. As can be seen, almost all the feed stream is subjected to cryogenic treatment and hydr before any hydrogenations or fractions are carried. The separated hydrogen is then used downstream in the hydrogenation units 22, 24, 44 and 46. This scheme with its cryogenic treatment and hydrogen separation has the disadvantages previously discussed. Figure 2 illustrates the present invention wherein the charge gas 50 is compressed at 52 but only up to a pressure of 0.69 to 1.72 MPa (100 to 250 psia) and preferably of 1.21 MPa (175 psia). The compressed charge gas stream is supplied in the feed zone 54 of a catalytic distillation tower 56. This catalyst distillation tower is a device that simultaneously performs a catalytic reaction and distillation and comprises an extraction section 58 below of the feed zone 54 and a reaction / rectification section 60 on the feed zone 54. The extraction section 58 contains any desired internal distillation components such as conventional trays 62 illustrated in Figure 2. The boiler 63 returns the bottoms heated to the column. The reaction / rectification section 60 of column 56 has the dual function of reacting (hydrogenating) selected components of the feed and distilling the components. Therefore, this section contains beds of a conventional 64-hydrogenation catalyst. The criteria for this reaction / rectification section are that the conditions are created where the unsaturated hydrocarbons, except for ethylene and propylene, are hydrogenated and where the distillation required to essentially separate all C4 and lighter material as superior products and essentially all C6 materials and heavier as bottoms. A portion of the materials C5, 10 to 90% and typically 70%, leaves the top of the column and the remaining portion, typically 30%, leaves the bottom column. In some cases, all C5 will leave the top of the tower depending on the process requirements, feed materials and by-products of the individual plants. In order to selectively hydrogenate the acetylenes C2, the acetylenes and dienes C3 and the acetylenes, dienes and olefins C4 and heavier while leaving the ethylene and propylene unhydrogenated, the reaction / rectification section 60 of the column 56 is operated in a manner such that there is a substantial concentration gradient of materials C4 and C5 with respect to materials C2 and C3 in the liquid phase where the majority of the hydrogenation reaction occurs. In the preferred mode, this is achieved by the use until downward flow of liquid, for example the use of a high proportion of reflux and large intercondensing services. The reflux of the column that is produced by the upper condensers 86 and 88 and the intercoolers or column intercalenders 80 also removes the high reaction heating. As illustrated in Figure 2, the catalyst is separated into a series of discrete beds 66, 68 and 70. Although three beds are illustrated, this is only by way of example and can be any number of beds depending on the dynamics of any particular plant. These catalyst beds are retained between the sieves or perforated plates 72. Located between the catalyst beds, are trays or trays that collect liquids 74 that include with chimneys or gates for steam flow 76. The liquid descending from a catalyst bed is collected in the respective discharge trays in the collectors 78. The liquid is withdrawn from the collectors 78 as side streams through the intercondenser 80 and then reinjected back into the column on the next lower catalyst bed through the header heads. distribution 82. This allows a portion of the heat of reaction to be removed in the intercapacitors. By arranging the intercapacitors in this manner, the cooling medium may be cooling water while the cooling medium in the upper condensers may require to be partially by mechanical refrigeration use. Therefore, the use of intercapacitors can significantly reduce the portion of the heat of reaction that requires removal by mechanical cooling. The upper part 84 of the column is cooled in the condenser of the upper part 86, with cooling water and in the condenser 88, with cooling and the resulting vapor and liquid are separated by 90. The steam processing collected in the line 94 It will be discussed below. The liquid resulting from separator 90 is pumped through line 96 back to the column, as reflux. A number of trays are provided to fractionate ethylene and propylene from the liquid phase by preventing them from entering the catalyst beds at high concentrations relative to materials C4 and C5. In the present invention, it is imperative to limit the loss of ethylene and propylene in the hydrogenation reaction because these are the main products of an ethylene or olefin plant. However, under conventional conditions that would allow the hydrogenation of olefins, ethylene and C4 propylene and heavier ones, hydrogenation losses would be unacceptably high. This is the primary reason why one of the prior art process sequences currently practiced only hydrogenates the C2 acetylenes and a portion of the C3 acetylenes and dienes upstream in the cooling and condensation step. The hydrogenation in column 56 occurs primarily in the liquid phase. The extent of the reaction depends on the relative reactivity of the various components and the concentration of these components in the liquid phase and any particular point in the column. The acetylenes and dienes C2 and C3 are far more reactive than ethylene and propylene, so that they react first and quickly. However, the relative reactivities of ethylene, propylene and the heavier olefins, dienes and acetylenes C4 are much closer. In order to react a significant amount of the olefins dienes and acetylenes C4 and heavier without any significant loss of ethylene and propylene, the concentrations of ethylene and propylene in the liquid phase must be minimized and the profiles of temperature concentration of the upper part must control yourself Since hydrogenation occurs in a tower. fractionation, this control can be achieved by adjusting the upper (external) reflux produced by the upper capacitors 86 and 88 and the sidestream reflow from the intercapacitors 80. The feed 54 of the column at the aforementioned pressure of 1.25 MPa (0.69 a 1.72 MPa) of the temperature range 25 to 120 ° C and preferably to 70 -90 ° C. At the feeding point, the hydrogen concentration is the highest, the temperature (in the rectification / reaction section) is the highest and the concentration of ethylene and propylene in the liquid phase is the lowest. At this point, the concentration of C4 and Cs components in the liquid phase relative to the propylene concentration is maintained in the range of 10 to 80 and preferably to approximately 25 while the concentration of C4 and C5 in the liquid phase respect ethylene is maintained in the range of 30 to 100 and preferably to about 80. This low concentration of C2 and C3 in the rectification / reaction section is achieved by high rate of downward flow of liquid. This high rate of downward flow of liquid can be achieved by a high proportion of higher reflux and / or reflux created by the intercapacitors 80. As will be explained later with respect to Figure 4, this high proportion of downward flow of liquid can also be provided. by the recycling and cooling of heavy materials from the bottom of the column. More specifically, the proportion of liquid downward reflux that is provided by the upper reflux 96, the intercoolers 80 and the heavy material recycling (160 in Figure 4), is equivalent to the liquid downflow that would be supplied by a reflux ratio? ? lower in the range of 0.2 to 10 without intercapacitors and recycling of heavy materials. This is compared to a reflux ratio of less than 0.2 for a conventional column operated to achieve a top product specification. At the top of the rectification / reaction section 60, where the temperature is 38 to 80 ° C and preferably 60 ° C and where the concentration of hydrogen is low because most have reacted, the proportion of components C4 and Cs to components C2 and C3, is similarly high. The reflux ratio by the top and intercondenser temperatures are adjusted to maintain these operating parameters. With the hydrogenation of the C2 acetylenes, the C3 acetylenes and the acetylenes, dienes and C4 olefins and a major portion of the C5 and C6 acetylenes, dienes and olefins, 50 to 90% of the hydrogen contained in the cracked feed gas is reacted. The bottoms 98 of the column 56 contain a portion of the material C5 and essentially all of the material C6 and heavier. In the preferred embodiment, this bottom product is sent to a second column of hydrogenation by catalytic distillation 10Q for the production of hydrogenated pyrolysis gasoline. Alternatively, the bottom product may be burned in the plant bottom system or pumped and sent to a conventional fixed pyrolysis gas hydrotreater as previously described under the prior art. Also, in the preferred embodiment illustrated in Figure 2, the total of materials or products of the upper portion 94 of column 56, which contains a portion of the C5 material and essentially all of the C4 and lighter material, is first compressed into 102 and sends to hydrogen recovery membrane devices 104. These membrane devices are commercially available for the separation of hydrogen. The intention of the membrane is to recover most of the hydrogen remaining in the stream through the top 94. The resulting hydrogen stream 106 is then fed to the hydrogenation column of gasoline by pyrolysis 100, together with the bottoms of column 56 The compression step may or may not be required depending on the specific composition of the cracked gas, membrane selection to hydrogen and the operating condition of column 56. Alternatively, a conventional fixed bed pyrolysis gasoline hydrotreater may be employed without a membrane separator.

In this case, the hydrogen now significantly reduced in stream 94 by the hydrogenation reactions occurring in column 56 will be cryogenically recovered as discussed above. Pyrolysis gasoline is a complex mixture of hydrocarbons in the range of C5 compounds to materials with a boiling point of approximately 200 ° C. The raw feed to the gasoline column by pyrolysis 100 is highly unstable due to its high content of diolefins. Therefore, in the production of gasoline with pyrolysis, the feed is hydrogenated in column 100. Column 100 is similar to column 56 since it has a typical bottom extraction section 108, a reboiler 110 and a reaction section. / upper rectification 112 containing the hydrogenation catalyst. It includes an upper capacitor 114- and separator 116 from which reflux 118 is returned to the column. The column may or may not include intercoolers or intercondensers similar to the intercapacitors for column 56. In this column 100, the feed of the remaining acetylenes, dienes and olefins C5 and all acetylenes, dienes and C6 olefins and heavier, are hydrogenated. This column operates between 0.21 and 0.86 MPa and preferably at 0.34 MPa. The C8 and lighter materials in the feed enter the catalyst bed where the acetylenes dienes and olefins are hydrogenated. The C9 and heavier materials leave the bottoms of the column 100. The heat of reaction is removed by the reflux stream 118. The reflux stream 118 also serves to control the selectivity of the hydrogenation reaction. There is a small amount of ethylene in stream 106 and as noted, this ethylene is a valuable product and its hydrogenation should be avoided. By proper control of the reflux column 118, the concentration of ethylene in the liquid phase in the column It can be minimized. This is a technique that is preferable to improve the membrane separation process, to exclude that essentially pass ethylene through with hydrogen. The ethylene pitch can be minimized by decreasing the pressure differential across the membrane and / or by increasing the membrane surface area. However, adding the membrane surface area is an expensive capital cost and increasing the pressure differential is both intense in energy and capital. The capacity to selectively hydrogenate in column 100 allows a process of lower capital cost, and less intense in energy. Steam from the top 120 of the column that contains primarily C4 and lighter material is recycled to the feed for the process.

The net condensed liquid top product is removed at 122 as pyrolysis gasoline. Figure 3 illustrates the processing of the top 94 current after it passes through the hydrogen separation stage at 104 and emerges as the current 124. Alternatively, this system can be used to process the current 94 directly in the case that portions of gasoline pyrolysis and membrane separation of the process described above were not used. In this case, the additional provisions will be made for cryogenic hydrogen separation. The vapor stream 124 is cooled to 128 as required to liquefy the C2 and heavier components. The top methane material 130 is then separated in demetallizing towers 132 from bottoms C2 and heavier 134. These bottoms 134 are then separated in the de-nailing tower 136 to produce a top product C2 138 and bottoms C3 and heavier 140. The top product C2 138 may pass through a drying step (not shown), then it is separated in tower 142 at the bottom of ethane 144 and product of ethylene top 146. The backgrounds 140 of the deethanizer 136 are then separated in the tower 148 at bottoms of C4 and heavier 150 and product from the top C3 152. This product from the top 152, it can also be dried, it is fed to the tower 154 for the separation of propane 156 and propylene 158. Figure 4 illustrates an alternate preferred embodiment of the present invention, which incorporates recycling the extraction section 58 of column 56. In this embodiment , a recycle stream 160 of the extraction section 58 is recycled to either the product of the column top 84 through line 161 and / or to the catalytic zone the rectification / reaction section 60 through line 163 Recycling through line 163 to the catalyst zone is usually usually preferable. For example, this recycling may be a portion 162 of the bottoms 98 and / or a portion 164 of the interior of the extraction section. This recycling 160 serves to recycle the heavier Cs +, to the products of the upper part or to the catalytic zone of the column. This increases the amount of dienes and acetylenes and probably some olefins that will be hydrogenated, thus increasing hydrogen consumption. Also, it provides another control variable for increasing the temperature of products from the top of the tower and / or the catalyst bed. Increasing the temperature of products in the upper part of the tower is convenient since it will decrease or eliminate the cooling requirements to generate reflux. Increasing the temperature of the catalyst bed provides another variable for controlling the reaction rate of the catalytic reaction beds. Although this mode achieves distillation internally in the column, it is not classical distillation, since there are now some heavy products in the upper part. In this case, some additional downstream distillation will be provided to make the final desired separations. The purpose of this method is to improve the control of the reactions that take place in tower 56, even though this also sacrifices some of the separation by distillation. When the catalytic distillation column is operated with a heavy recycling to the top products, the heavy stream is preferably cooled to 165. This cooling effect can be considerable, especially if it uses a high recycling ratio of these heavy ones . This reduces the reflux ratio of the catalytic distillation column to equal proportions of liquid downflow. The reflux ratio is further reduced if lateral enfiration is used. The net effect of all cooling stages is to significantly decrease the reflux ratio. This can also reduce the cooling requirements, since some of the cooling required to condense reflux can be provided at higher condensing temperatures. This may be another benefit of heavy recycling from the bottom section to the upper section of the column, especially recycling to steam outlet 84 as this will raise the temperature of products from the top and reduce the cooling requirements. When operating the catalytic distillation column with bottom recycling, the reflux ratio of top products is in the range of 0.05 to 0.4 and preferably 0.1 to 0.2, when the bottom recycle is directed to the top of the catalytic bed through line 163. When the recycling of funds is directed to the products of the upper part of the column through line 161, the reflux ratio is 0.2 to 10. Even with this rate of reflux of products from the lower upper part, a high proportion of downward flow of liquid is maintained in the catalyst beds by intercapacitors and the recycling and cooling of weighings. Heavy recycling does not meet what would be considered a "classic" distillation because recycling results in the loss of some of the benefits of the net separation of the distillation. However, this loss is outweighed by the benefit of minimizing ethylene and propylene concentrations in the liquid in the catalyst zone by the use of high rates of downward flow of liquid and by the benefits of raising the temperature in the catalyst bed. The ability of the present invention to remove 85 to almost 100%, typically 90% of the hydrogen contained in the charge gas before the cooling and condensation stages, reduces energy consumption and reduces capital costs. By using the hydrogen contained in the charge gas as the source of hydrogen for the various hydrogenation reactions, the need for the cryogenic separation of independent hydrogen is eliminated. By proper control of the concentration profiles in the hydrogenation column by catalytic distillation, the C4 and heavier olefins can be hydrogenated, without significant hydrogenation of either ethylene or propylene. Therefore, the hydrogenation reactions are combined in one or two reactor systems.

Claims (10)

1. CLAIMS 1. - A method to process a thermally cracked feed stream containing hydrogen, ethylene, propylene and other C2, C3, C4, C5, C6 and heavier, unsaturated hydrocarbons, which are produced in thermal cracking, to separate ethylene and propylene of at least some of the other unsaturated hydrocarbons and hydrogenating at least some of the other unsaturated hydrocarbons with the hydrogen contained in the feed stream prior to the prior separation of the hydrogen and without significant hydrogenation of the ethylene and propylene, comprising the steps of: (a) introducing the feed stream into the feed zone of a by-distillation reaction column containing a distillation extraction zone below the feed zone and a catalytic reaction and rectification by distillation zone in coation on the feeding area; (b) concurrently: (i) contacting the feed stream in the distillation reaction column with a vertically oriented bed of hydrogenation catalyst in the catalytic reaction zone and distillation rectification in coation; (ii) maintaining a high proportion of the total hydrocarbons C4 and C5 with respect to the total hydrocarbons C2 and C3 at the bottom of the vertical oriented bed of the hydrogenation catalyst, the high proportion is chosen so that ethylene and propylene remain essentially unhydrogenated and at least some of the other unsaturated hydrocarbons are hydrogenated; (iii) fractionating the resulting mixture of hydrogenated and non-hydrogenated products; (c) removing a stream of products from the upper part that contains essentially all hydrocarbons C2, C3 and C4 and a portion of the C5 hydrocarbons and a bottom stream containing essentially all of the C6 and heavier hydrocarbons and a portion of the C5 hydrocarbons; and (d) process the product stream from the top to recover ethylene and propylene.
2. 2. Method for processing according to claim 1, characterized in that the feed stream includes C9 and heavier material and step (d) of processing the product stream of the upper part comprises the steps of: (a) separating hydrogen from the product stream from the top; (b) feeding the separated hydrogen and bottom stream from the reaction column with distillation to a reaction column with gasoline distillation by pyrolysis containing a hydrogenation catalyst; (c) reacting the separated hydrogen with the bottom stream in the reaction column by distillation of pyrolysis gasoline, to produce a top product of hydrogenated liquid of pyrolysis gasoline and bottoms of material C9 and heavier.
3. 3. Method for processing according to claim 2, characterized in that the step of separating hydrogen comprises the step of separating hydrogen from the product stream of the upper part through a hydrogen separation membrane.
4. 4. Method for processing according to claim 1, characterized in that the step of maintaining a high proportion includes the step of removing at least a portion of descending liquid as one. side stream at a selected point from the bed of the hydrogenation catalyst, cool the side stream and inject the cooled side stream back into the bed of the hydrogenation catalyst.
5. 5. - Method for processing according to claim 4, characterized in that the lateral stream is injected back into the bed at a point below the selected point.
6. 6. Method for processing according to claim 1, characterized in that the hydrogenation reactions occur essentially in the liquid phase in the reaction column by distillation.
7. 7. - A method for processing a thermally cracked feed stream containing hydrogen, ethylene, propylene and other C2, C3, C4 and heavier hydrocarbons, to hydrogenate at least some of the unsaturated hydrocarbons with hydrogen contained in the feed stream without hydrogenating ethylene and propylene, comprising the steps of: (a) introducing the feed stream in the feed zone of a distillation reaction column containing an extraction zone with distillation below the feed zone and a catalytic reaction zone and rectification by distillation in combination on the feed zone; (b) concurrently: (i) contacting the feed stream in the distillation reaction column, with a vertically oriented catalyst bed of hydrogenation of the catalytic reaction and rectification column with combined distillation; (ii) maintaining the hydrogenation conditions within the bed of the hydrogenation catalyst including a high proportion of the C4 hydrocarbons and heavier hydrocarbons C2 and C3, the high proportion is chosen whereby the ethylene and propylene remain essentially unhydrogenated and essentially all other C2, C3, and C4 and heavier unsaturated hydrocarbons are hydrogenated; (iii) fractionating the resulting mixture of hydrogenated and non-hydrogenated products; (iv) recycling the heavy materials from the extraction zone to a site in the column above the catalytic reaction zone to help maintain the high proportion and increase the temperature in the catalytic reaction columns and provide additional unsaturates to be hydrogenated; (c) removing a stream of products from the upper part that contains essentially all hydrocarbons C2, C3 and C4 and a portion of the heavier hydrocarbons and a stream of bottoms containing the remaining portion of the heavier hydrocarbons; (d) process the product stream from the top to recover ethylene and propylene.
8. 8. Method for processing according to claim 7, characterized in that the stage of recycling heavy materials includes the step of cooling the heavy materials before, to enter the column.
9. 9. Method for processing according to claim 8, characterized in that the step of maintaining a high proportion includes the step of removing at least a portion of descending liquid as a side stream at a selected point from the bed of the hydrogenation catalyst, cool the side stream and inject the cooled side stream back into the bed of the hydrogenation catalyst. 10. Method for processing according to claim 9, characterized in that the step of maintaining a high proportion also includes the step of maintaining a high proportion of reflux back to the catalytic reaction zone and rectification by distillation in combination. 11. Method for processing according to claim 10, characterized in that the reflux ratio is in the range of 0.05 to 0.4. 12. Method for processing according to claim 10, characterized in that the reflux ratio is in the range of 0.1 to 0.2. 13. Method for processing according to claim 7, characterized in that the step of recycling heavy materials to a site in the column on the catalytic reaction zone, comprises recycling in the stream of products from the top removed. 14. Method for processing according to claim 13, characterized in that the step of maintaining a high proportion further includes the step of maintaining a high reflux ratio back to the catalytic reaction zone and rectification by distillation in combination. 15. Method for processing according to claim 14, characterized in that the reflux ratio is in the range of 0.5 to 1.5. 16. - Method for processing according to claim 14, characterized in that the reflux ratio is in the range of 0.2 to
10. 10.