Process to prepare propylene
AssigneeGasolfin B.V.
InventorsElbert Arjan DE GRAAF, Raymond Paul FLETCHER
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Abstract
The invention is directed to a process to prepare propylene from a mixture of hydrocarbons having an olefin content of between 5 and 50 wt. % and boiling for more than 90 vol. % between 35 and 280 ?C or from a hydrocarbon feed comprising paraffins, naphthenics and/or aromatics and optionally up to 10 wt. % of olefins, by first contacting the feed with a low acidic density cracking catalyst in a reactor, separating propylene and subsequently contacting the residue with a high acidic density cracking catalyst in a reactor at a more elevated temperature, separating propylene and recycling the residue to first and second cracking reactors. Aromatics may be added to first and second cracking step to improve cycle length.
Claims31
A process to prepare propylene from a mixture of hydrocarbons having an olefin content of between 5 and 50 wt. % and boiling for more than 90 vol. % between 35 and 280° C. or from a hydrocarbon feed comprising paraffins, naphthenics and/or aromatics, wherein the process comprises the following steps:
- (a) feeding the mixture of hydrocarbons, having a temperature between 450 and 750° C., to a reactor where the feed is contacted with a low acidic density cracking catalyst at a hydrocarbon partial pressure of below 3 bar and at a weight hourly space velocity of between 0.5 and 100 h−1;
- (b) isolating propylene the effluent of step (a) wherein a first high boiling fractions remains;
- (c) feeding all or part of the first high boiling fraction, having a temperature between 400 and 750° C., to a reactor where the first high boiling fraction is contacted with a high acidic density cracking catalyst at a hydrocarbon partial pressure of below 3 bar and at a weight hourly space velocity of between 0.5 and 100 h−1 and wherein the temperature of the mixture of hydrocarbons as fed to the reactor in step (a) is lower than the temperature of the first high boiling fraction as fed to the reactor in step (c);
- (d) isolating propylene from the effluent of step (c) wherein a second high boiling fractions remains;
- and
- (e) recycling all or part of the second high boiling fraction to step (a) and/or to step (c).
The process according to 18, wherein in step (d) propylene and other low boiling compounds are isolated from the effluent of step (c) in a debutanizer distillation column which is operated under partial vacuum and wherein the second high boiling fraction is obtained as a bottom product of the debutanizer distillation column.
A process to prepare propylene from a hydrocarbon starting feed comprising paraffins, naphthenics and/or aromatics by adding aromatic compounds to the hydrocarbon starting feed resulting in an upgraded feed containing between 10 and 70 wt % and wherein the upgraded feed is catalytically cracked in the presence of an acidic cracking catalyst to propylene and other reaction products.
A process to prepare propylene from a hydrocarbon feed comprising paraffins, naphthenics and/or aromatics wherein the process comprises the following steps:
- (aa) feeding the feed in admixture with a recycle stream and having a temperature of between 450 and 700° C. to a continuously operated reactor comprising a high acidic density cracking catalyst where the mixture is contacted with a high acidic density cracking catalyst at a hydrocarbon partial pressure, excluding aromatics, of below 3 bar and at a weight hourly space velocity of between 1 and 30 h−1,
- (bb) isolating propylene and optionally other low boiling compounds from the effluent of step (aa) wherein a high boiling fractions remains,
- (cc) recycling part of the high boiling fraction to the reactor of step (aa) wherein the total content of aromatics in the combined mixture as fed to the reactor in step (aa) is maintained at between 5 and 50 wt. %, optionally by additionally feeding an aromatic comprising further hydrocarbon mixture to the reactor.
The process according to 22, wherein in step (bb) propylene and other low boiling compounds are isolated from the effluent of step (aa) in a distillation column which is operated under partial vacuum and wherein the high boiling fraction is obtained as a bottom product of the distillation column.
A Process configuration suited to prepare propylene from an olefin comprising hydrocarbon mixture comprising:
- (i) one or more parallel operated first reactors comprising an amorphous heterogeneous cracking catalyst or a heterogeneous cracking catalyst comprising a medium or large pore zeolite having a silica to alumina ratio of between 1 and 1000;
- (ii) first distillation and/or flash separation units fluidly connected to an outlet of the one or more first reactors, and having at least an outlet for a propylene comprising fraction and an outlet for high boiling compounds;
- (iii) means to recycle the high boiling compounds from the outlet for high boiling compounds of the distillation and/or flash separation units to an inlet of the one or more parallel operated first reactors;
- (iv) one or more parallel operated second reactors comprising a heterogeneous cracking catalyst comprising up to 80 wt. % ZSM-5 having a silica to alumina ratio of between 2 and 1000, between 1-20 wt. % P2O5 and a binder, and wherein an inlet of the second reactors is fluidly connected to the outlet for high boiling compounds of the first distillation and/or flash separation unit;
- (v) second distillation and/or flash separation units fluidly connected to an outlet of the one or more second reactors of (iv), and having at least an outlet for a propylene comprising fraction and an outlet for high boiling compounds;
- and
- (vi) means to recycle the high boiling compounds from the outlet for high boiling compounds of the second distillation and/or flash separation units to the inlet of the one or more parallel operated first reactors and to the inlet of the one or more parallel operated second reactors.
Dependencies are inferred from the claim text.