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.
Claims17
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 first 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 from the effluent of step (a) wherein a first high boiling fraction 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 second 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), wherein the second cracking catalyst has a higher acidic density than the first cracking catalyst;
- (d) isolating propylene from the effluent of step (c) wherein a second high boiling fractions remains;
- (e) recycling all or part of the second high boiling fraction to step (a) and/or to step (c);
- and
- (f) contacting part of the first high boiling fraction and/or all or part of the second high boiling fraction with hydrogen in the presence of an aromatic conversion catalyst as present in a reactor to obtain a fraction rich in aromatics, wherein all or part of the fraction rich in aromatics is recycled to step (c) and/or to step (f), and wherein the aromatic conversion catalyst is a heterogenous catalyst comprising ZnO, a medium pore zeolite, and a binder.
The process according to 16, 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.
Dependencies are inferred from the claim text.