Method for converting a high-boiling hydrocarbon feedstock into lighter boiling hydrocarbon products

Abstract

A process for converting high boiling hydrocarbon feedstock into lighter boiling hydrocarbon products in which the lighter boiling hydrocarbon products are suitable feedstock for petrochemical processes.

Claims

1. A process for converting a high-boiling hydrocarbon feedstock into lighter-boiling hydrocarbon products, said lighter-hydrocarbon products being suitable as feedstocks for petrochemical processes, said converting process comprising: feeding a heavy hydrocarbon feedstock to a cascade of hydrocracking unit(s), wherein the cascade of hydrocracking units comprises at least two hydrocracking units, wherein on of the units is a last hydrocracking unit in said cascade of hydrocracking units; cracking said feedstock in the hydrocracking units; separating said cracked feedstock into at least a stream comprising a light-boiling hydrocarbon fraction and a bottom stream comprising a heavier hydrocarbon fraction than said light-boiling fraction; feeding said bottom stream of such a hydrocracking unit as a feedstock for a subsequent hydrocracking unit in said cascade of hydrocracking units, wherein process conditions in each hydrocracking unit are different from each other, in which temperature conditions from first to subsequent hydrocracking units increases, wherein a reactor type design of the last hydrocracking unit is of a slurry phase type; sending the light-boiling hydrocarbon fractions from each of said hydrocracking units to petrochemical processes, comprising at least a gas steam cracking unit, a propane dehydrogenation unit, and a butane dehydrogenation unit and one or more units chosen from a pentane dehydrogenation unit and a mixed propane-butane dehydrogenation unit; separating said light boiling hydrocarbon fractions into a stream comprising C2, a stream comprising C3 and a stream comprising C4; feeding said stream comprising C3 to the propane dehydrogenation unit; feeding said stream comprising C4 to the butane dehydrogenation unit; and feeding said stream comprising C2 to the gas steam cracker unit.

2. The process according to claim 1, wherein the lighter boiling hydrocarbon fractions from all hydrocracking units in said cascade of hydrocracking units are hydrocarbons having a boiling point higher than methane and equal to or lower than that of cyclobutane.

3. The process according to claim 1, further comprising separating said cracked feedstock into a stream comprising hydrogen; and feeding said stream comprising hydrogen to a hydrocracking unit in said cascade of hydrocracking units.

4. The process according to claim 1, wherein said heavy hydrocarbon feedstock is chosen from crude oil atmospheric distillation unit (ADU) including naphtha, ADU bottom stream, and atmospheric gas oils, and products from refinery processes.

5. The process according to claim 1, wherein said hydrocracking units preceded by a hydrotreating unit and bottom stream of said hydrotreating unit is used as a feedstock for said first hydrocracking unit, wherein temperature in said hydrotreating unit is higher than in said first hydrocracking unit.

6. The process according to claim 5, wherein a temperature in the cascade of hydrocracking units increases and temperature in said second hydrocracking unit is higher than in said hydrotreating unit.

7. The process according to claim 5, wherein the reactor type design of said hydrotreating unit is of the fixed bed type.

8. The process according to claim 5, wherein the reactor type design of said first hydrocracking unit is of the ebulated bed reactor type.

9. The process according to claim 1, wherein a bottom stream of a final hydrocracking unit is recycled to an inlet of said final hydrocracking unit.

10. A process for converting a high-boiling hydrocarbon feedstock into lighter-boiling hydrocarbon products, said lighter-hydrocarbon products being suitable as feedstocks for petrochemical processes, said converting process comprising: feeding a heavy hydrocarbon feedstock to a cascade of hydrocracking unit(s), cracking said feedstock in the hydrocracking unit(s), separating said cracked feedstock into a stream comprising hydrogen, a stream comprising a light-boiling hydrocarbon fraction and a bottom stream comprising a heavier hydrocarbon fraction, feeding said bottom stream of such a hydrocracking unit as a feedstock for a subsequent hydrocracking unit in said cascade of hydrocracking units, wherein process conditions in each hydrocracking unit are different from each other, in which the hydrocracking conditions from the first to subsequent hydrocracking units increase from least severe to most severe, wherein a reactor type design of the last hydrocracking unit is of a slurry phase type, and sending the light-boiling hydrocarbon fractions from each of said hydrocracking units to petrochemical processes, comprising at least a gas steam cracking unit, a propane dehydrogenation unit, and a butane dehydrogenation unit and one or more units chosen from a pentane dehydrogenation unit and a mixed propane-butane dehydrogenation unit, wherein a catalyst is present in the cascade of hydrocracking units and a particle size of the catalyst present in the cascade of hydrocracking units decreases from the first hydrocracking unit to the subsequent hydrocracking unit.

Description

(1) The invention will be described in further detail below and in conjunction with the attached drawings in which the same or similar elements are referred to by the same number.

(2) FIG. 1 is a schematic illustration of an embodiment of the process of the invention.

(3) Referring now to the process and apparatus schematically depicted in the sole FIG. 1, there is shown crude oil feed 1, an atmospheric distillation unit 2 for separating the crude oil into stream 29, comprising hydrocarbons having a boiling point of cyclobutane, i.e. 12 C., and lower. Bottom stream 3 leaving distillation unit 2 is fed to a hydro processing unit 4, for example a hydro treating unit, wherein the thus treated hydrocarbons 5 are sent to a separation unit 6 producing a gaseous stream 8, a hydrogen comprising stream 10 and a bottom stream 13 comprising hydrocarbons having a boiling point of cyclobutane and higher. Although separation unit 6 has been identified as a single separation unit, in practice such a separation unit may comprise several separation units. Stream 13 is fed into a hydrocracking unit 15 and its effluent 16 is sent to a separation unit 17 producing gaseous stream 18, a hydrogen comprising stream 10 and a bottom stream 20 comprising hydrocarbons having a boiling point of cyclobutane and higher. Hydrogen make up is indicated with reference number 41. The effluent 20 from separation unit 17 is sent to a further hydrocracking unit 22 and its effluent 23 is sent to a separation unit 24 producing a gaseous top stream 28, a hydrogen comprising stream 10 and a bottom stream 27. Bottom stream 27 can be partly recycled as stream 25 to the inlet of hydrocracking unit 22. Bottom stream 27 can be further separated in separation units (not shown here). The hydrogen containing stream 10 leaving separation unit 24 is sent to a compressor and returned to the inlet of hydrocracking unit 22. Since hydrocracking unit 22 in this FIGURE is the last hydrocracking unit in the cascade, the reactor type design of this hydrocracking unit 22 is of the slurry phase type.

(4) The top stream 29 coming from distillation unit 2 and streams 8, 18 and 28 are and sent to a number of processing units. According to a preferred embodiment the combined streams 29, 8, 18, and 28, i.e. light boiling hydrocarbon fractions, are separated in separator section 30, which section 30 may comprise several separation units. In the FIGURE three separated streams 31, 32, 33 have been shown, but the present invention is not restricted to any number of streams. Stream 33, for example a stream comprising C2, is sent to gas steam cracker unit 34, and its effluent 36 is sent to a further separation section 38, which section 38 may comprise several separation units. Streams 31, 32 are sent to a dehydrogenation unit 35, such as one or more of pentane dehydrogenation unit, propane dehydrogenation unit, butane dehydrogenation unit and mixed propane-butane dehydrogenation unit. For example a stream comprising C3 31 is sent to a propane dehydrogenation unit 35 and a stream comprising C4 32 is sent to a butane dehydrogenation unit 35. The effluent 37 is sent to a further separation section 38, which section 38 may comprise several separation units. Although not shown, other examples of petrochemicals processes, in addition to gas steam cracking unit 34 and dehydrogenation unit 35, are one or more chosen form aromatization unit, alkylation processes, high severity catalytic cracking (including high severity FCC), light naphtha aromatization (LNA), reforming and mild hydrocracking. Separation section 38 produces into individual streams 39, 40, 41. From individual streams 39, 40, 41 olefins and aromatics can be recovered. Although only three individual streams 39, 40, 41 have been shown, the present invention is not restricted to any number of individual streams.

(5) As shown here it is possible to separate the combined streams 29, 8, 18, 28 into a into a stream comprising C1, a stream comprising C2, a stream comprising C3 and a stream comprising C4 and feeding said stream comprising C3 to a propane dehydrogenation unit 35 and feeding the stream comprising C4 to a butane dehydrogenation unit 35, and feeding the stream comprising C2 to a gas steam cracker unit 34.

(6) In addition, it is also possible to run hydroprocessing unit 4, hydrocracking unit 15 and hydrocracking unit 22 under such processing conditions that the composition of streams 8, 18 and 28 are such that each of streams 8, 18 and 28 is sent to one or more different processing units, as mentioned before. Although the FIGURE shows that streams 8, 18 and 28 are combined and sent as one single feed to unit 30, some embodiments prefer to have separate streams 8, 18 and 28 sent to individual processing units. This means that separator section 30 can be by-passed.