US-12624294-B2 - Process and plant for improving oxygenate to gasoline conversion

US12624294B2US 12624294 B2US12624294 B2US 12624294B2US-12624294-B2

Abstract

Process and plant for producing a gasoline product from an oxygenate feed stream, the process including the provision of a methanol-to-gasoline reactor in a gasoline synthesis loop. The process and plant may include combination of an overhead stream from a de-ethanizer, e.g. a fractionation column, located downstream the cooling and separation of the raw gasoline produced in the methanol-to-gasoline reactor, in the gasoline synthesis loop.

Inventors

Arne Knudsen
Kumar RABI

Assignees

TOPSOE A/S

Dates

Publication Date: 20260512
Application Date: 20221028
Priority Date: 20211029

Claims (6)

1 . Plant for producing a gasoline product from an oxygenate feed stream comprising: an oxygenate-to-gasoline reactor comprising a catalyst for converting the oxygenate feed stream into a first raw gasoline stream; the reactor being arranged to receive the oxygenate feed stream and comprising an outlet for withdrawing the first raw gasoline stream; a mixing point arranged downstream a feed/effluent heat exchanger or downstream one or more heat exchangers, said mixing point being arranged to receive the first raw gasoline stream or cooled first raw gasoline stream or further cooled first raw gasoline stream, and an overhead gas stream comprising C2 compounds from a de-ethanizer arranged downstream, for forming a combined first raw gasoline stream as a second raw gasoline stream; a cooling unit arranged to receive the combined first raw gasoline stream as a second raw gasoline stream, for cooling said second raw gasoline stream; a gasoline synthesis product separator arranged to receive the thus cooled second raw gasoline stream or the second raw gasoline stream, and comprising an outlet for withdrawing a bottom water stream, an outlet for withdrawing an overhead recycle stream, and an outlet for withdrawing a third raw gasoline stream comprising C2 compounds, C3-C4 paraffins and C5+ hydrocarbons; a recycle compressor arranged to receive said overhead recycle stream and discharge a compressed overhead recycle stream; a de-ethanizer arranged downstream said gasoline synthesis product separator and further arranged to receive said third raw gasoline stream comprising C2 compounds, C3-C4 paraffins and C5+ hydrocarbons; the de-ethanizer comprising an outlet for withdrawing a bottom gasoline stream as said gasoline product, and an outlet for withdrawing the overhead gas stream comprising C2 compounds; and wherein the de-ethanizer is configured to operate at a higher pressure than the oxygenate-to-gasoline reactor.
2 . The plant according to claim 1 , in which the de-ethanizer is arranged to provide the entire overhead gas stream comprising C2 compounds in direct fluid communication with the first raw gasoline stream.
3 . The plant according to claim 1 , wherein the plant further comprises: the feed/effluent heat exchanger which is arranged to receive said first raw gasoline stream and to receive said oxygenate-feed stream as heat exchanging medium for generating the cooled first raw gasoline stream; the one or more heat exchangers arranged downstream said feed/effluent heat exchanger to receive the cooled first raw gasoline stream and arranged to receive as heat exchanging medium an oxygenate stream, or an overhead recycle stream from a gasoline synthesis product separator arranged downstream, for generating the further cooled first raw gasoline stream; a conduit for withdrawing, from said overhead recycle stream, a fuel gas stream.
4 . The plant according to claim 3 , wherein said compressed overhead recycle stream is conducted to said feed/effluent heat exchanger and/or said one or more heat exchangers arranged downstream the feed/effluent heat exchanger.
5 . The plant according to claim 1 , further comprising a LPG-splitter for converting said bottom gasoline stream into a stabilized gasoline product; in which the LPG-splitter is a fractionation column arranged to receive said gasoline product from the de-ethanizer, and comprises an outlet for withdrawing an overhead C3-C4 fraction stream as LPG stream, and an outlet for withdrawing a bottom gasoline stream as said stabilized gasoline stream.
6 . The plant according to claim 1 , configured such that the higher pressure at which the de-ethanizer is configured to be operated compared to the oxygenate-to-gasoline reactor causes said overhead gas stream comprising C2 compounds to be directed toward the mixing point.

Description

The present invention relates to a process and plant for converting an oxygenate feed stream such as methanol e.g. e-methanol into a gasoline product including the provision of a methanol-to-gasoline (MTG) reactor in a gasoline synthesis loop. Embodiments of the invention include combination of an overhead stream from a de-ethanizer, e.g. a fractionation column, located downstream the cooling and separation of the raw gasoline produced in the MTG reactor, in the gasoline synthesis loop, i.e. combination with raw gasoline produced in the gasoline synthesis loop. The known technology for gasoline synthesis from oxygenates such as methanol involves plants comprising a MTG section (methanol-to-gasoline section) and a downstream distillation section. The MTG section may also be referred as MTG loop or gasoline synthesis loop and comprises: a MTG reactor; a gasoline synthesis product separator for withdrawing a bottom water stream, an overhead recycle stream from which an optional fuel gas stream (also referred to as purge gas) may be derived, as well as a raw gasoline stream comprising C2 compounds, C3-C4 paraffins (LPG) and C5+ hydrocarbons (gasoline boiling components); and a recycle compressor for recycling the overhead recycle stream and combining it with an oxygenate stream, e.g. a methanol stream, thus generating the oxygenate feed stream to the MTG reactor. The overhead recycle stream (or simply, recycle stream) acts as diluent, thereby reducing the exothermicity of the oxygenate conversion. From the MTG reactor a raw gasoline stream is withdrawn and cooled in one or more heat exchangers by providing heat to the recycle stream and the combined recycle-oxygenate stream, i.e. the oxygenate feed stream. The raw gasoline is further cooled in a cooling train comprising a condenser such as an air cooler and a water cooler. In the distillation section, C2 compounds are first removed in a de-ethanizer, hereinafter also referred to as de-ethanizer column and then a C3-C4 fraction is removed as LPG as the overhead stream in a downstream LPG-splitting column (LPG splitter), while stabilized gasoline is withdrawn as the bottoms product. The stabilized gasoline or the heavier components of the stabilized gasoline, such as the C9-C11 fraction, may optionally be further treated and thereby refined, e.g. by conducting hydroisomerization (HDI) into an upgraded gasoline product. The MTG process for producing gasoline is well-known, as for instance disclosed in U.S. Pat. Nos. 4,788,369, 4,481,305 or 4,520,216. Normally, as for instance illustrated in appended FIG. 1, the overhead gas from the de-ethanizer, which is suitably a fractionation column, passes to an overhead system where it is condensed, and the liquid fraction is separated out in a separator, typically a 3-phase separator. Hydrocarbons in the liquid fraction are pumped back to the column as a reflux stream. Water withdrawn from the separator is sent to a process condensate stripper, while fuel gas is also withdrawn from the separator and sent to a fuel system. When the catalyst of the MTG reactor in the gasoline synthesis loop is less active, the production of gas over the catalyst is not enough to maintain the pressure in the loop. It would therefore be desirable to provide a process and plant (system) for gasoline production in which the gasoline loop is capable of overcoming the above problem in a simple manner. It would also be desirable to provide better integration in the process and plant for producing a gasoline product, more particularly better integration between the MTG section (methanol-to-gasoline section) comprising the MTG reactor and gasoline synthesis product separator, and the downstream distillation section comprising the de-ethanizer a gasoline product is withdrawn and subsequent LPG-splitter from which a stabilized gasoline is withdrawn. US2021078921 discloses methods for methanol-to-gasoline conversion featuring a separation operation following a heavy gasoline treatment, in particular methanol-to-gasoline conversion processes featuring post-processing of heavy gasoline hydrocarbons prior to forming final product gasoline. EP337759 discloses a method converting an oxygenate feedstock, such as methanol and dimethyl ether, in a reactor containing a catalyst, such as a zeolite, to hydrocarbons, such as gasoline boiling components. The process may further comprise separating various hydrocarbons in the reactor effluent, e.g., C2-light gas can be separated from C3+ product in in the reactor effluent, in for example, a fractionating column {e.g., de-ethanizer), and additionally or alternatively, the C3+ product can be sent to a stabilizer {e.g., de-butanizer) where the C3 and part of the C4 hydrocarbon components can be removed from C5+ gasoline product. U.S. Pat. No. 9,938,205 discloses a system and process for converting an oxygenate feedstock, such as methanol and dimethyl ether, in a fluidized bed reactor containing a catalyst to hydrocarbons