阅读说明：本技术 从烃进料除去含氮化合物的方法 (Process for removing nitrogen-containing compounds from hydrocarbon feedstocks ) 是由 B·H·布莱德尔 P·汉密尔顿 M·简森 P·J·奥斯特雷斯 C·泰勒 L·马滕斯 B· 于 2018-06-15 设计创作，主要内容包括：从包含至少一种选自C3、C4、C5和非必要的C6烯烃和它们的混合物中的烯烃的烃进料除去含氮化合物的方法,包括溶剂萃取,包括监测所述溶剂的降解。(A process for removing nitrogen-containing compounds from a hydrocarbon feed comprising at least one olefin selected from the group consisting of C3, C4, C5, and optionally C6 olefins and mixtures thereof, comprising solvent extraction, comprising monitoring the degradation of the solvent.)

1. A process for removing nitrogen-containing compounds from a hydrocarbon feed comprising at least one olefin selected from the group consisting of C3, C4, C5, and optionally C6 olefins and mixtures thereof, comprising the steps of:

a) contacting the hydrocarbon feed with an extraction solvent comprising propylene carbonate to obtain a hydrocarbon phase having a reduced content of nitrogen-containing compounds and a solvent phase comprising dissolved nitrogen-containing compounds;

b) separating the hydrocarbon phase with reduced content of nitrogen-containing compounds from the solvent phase containing dissolved nitrogen-containing compounds;

c) subjecting the hydrocarbon phase from step (b) to a distillation step to separate a heavy phase containing the solvent and optionally heavy hydrocarbon compounds from a light hydrocarbon fraction containing the C3, C4 and C5 olefins;

d) optionally, subjecting the light fraction to further processing; and

e) subjecting the solvent phase from step (b), optionally together with the heavy phase from step (c), to a regeneration step; and

f) recycling the regenerated solvent back to step (a),

the method further comprises monitoring the degradation of the solvent as follows:

maintaining the content of propylene carbonate present in the recycled solvent, measured by gas chromatography, greater than 94% by weight with respect to said solvent;

maintaining the Total Acid Number (TAN) of the recycled solvent, measured according to ISO 1843/2, less than 0.1mg KOH/g;

maintaining the distribution coefficient of said nitrogen-containing compounds between said recycled solvent and said hydrocarbon feed greater than 50% of the value measured with fresh solvent;

maintaining the settling time of the recycled solvent in the hydrocarbon feed less than 200% of the settling time of the starting propylene carbonate; or

Keeping the surface tension of the circulating solvent greater than 25mN/m as measured by the tear ring method or keeping the interfacial tension of the circulating solvent greater than 6mN/m as measured by the Du Nouy ring method.

2. The process according to claim 1, wherein the accumulation of solvent degradation products and heavy hydrocarbons in the recycle loop can be avoided or at least minimized by one or more of the following steps:

filtering the solvent before feeding it back to step (a);

depending on the monitoring result, the appropriate amount of solvent is purged and replaced with fresh solvent;

operating the regeneration step in such a way that the heavy hydrocarbon compounds and the solvent degradation products are removed in the regeneration step, for example by reducing the reflux ratio in the stripper or modifying the regeneration temperature; and

a distillation step is added between the regeneration and the extraction step.

3. The process according to claim 1 or 2, wherein the regeneration step (e) is operated in a stripping column by using an inert gas or a light hydrocarbon containing from 1 to 7 carbon atoms.

4. The process according to any one of the preceding claims, wherein the solvent comprises propylene carbonate.

5. The process of any one of the preceding claims wherein the hydrocarbon feed is a C5 olefin feed comprising an FCC light naphtha stream, a steam cracker C5 rich stream that has been treated to remove dienes, a C5 olefin containing stream from a natural Gas To Olefins (GTO) unit or a Fischer-Tropsch unit.

6. The process according to any of the preceding claims, wherein the stripping column is equipped with an overhead reflux resulting in a column configuration comprising a stripping section in the bottom and a distillation section at the top.

7. A process according to claims 1-3, wherein, depending on the monitoring result, the appropriate amount of solvent is purged and replaced with fresh solvent in step (e).

8. A process for converting a hydrocarbon feed to a hydrocarbon product, the hydrocarbon feed comprising at least one olefin selected from the group consisting of C3, C4, C5, and optionally C6 olefins and mixtures thereof, contaminated with at least one nitrogen-containing compound, the process comprising the steps of:

i) providing a hydrocarbon feed contaminated with at least one nitrogen-containing compound;

ii) removing the nitrogen-containing compounds from the feed to produce a hydrocarbon feed stream having a reduced content of nitrogen-containing compounds; and

iii) contacting the hydrocarbon feed stream having a reduced content of nitrogen-containing compounds with a catalyst to convert the feed stream to hydrocarbon products,

wherein nitrogen-containing compounds are removed from the feed by using a process as defined in any one of the preceding claims.

9. The process according to claim 8, wherein step (iii) is an isomerization, alkylation, hydrogenation, aromatization or oligomerization step.

10. The process according to claim 9, wherein step (ii) is an oligomerization step using an oligomerization catalyst comprising a material selected from the group consisting of zeolites, phosphoric acid, supported metal oxides, and combinations thereof.

11. The process according to claim 10, wherein the oligomerization catalyst comprises a zeolite, especially a zeolite selected from the group consisting of ZSM-5, ZSM-11, ZSM-12, ZSM-18, ZSM-22, ZSM-23, ZSM-35, ZSM-38, ZSM-48, ZSM-50, ZSM-57, ITQ-39 and mixtures thereof.

Background

Hydrocarbon feed streams containing light olefins, typically C3-C6 olefins, are used in catalytic oligomerization processes to obtain oligomers and/or polymers, typically heptenes, octenes, nonenes, and dodecenes. These products can be converted into further products such as alcohols, plasticizers, adipates, mercaptans and solvents.

Hydrocarbon feed streams derived from various sources, including refinery operations such as catalytic or steam cracking, are known to contain certain amounts of impurities, including but not limited to nitrogen-containing compounds such as nitriles. These impurities can have an adverse effect on the catalysts used in the oligomerization process, such as phosphoric acid-based catalysts, zeolite-based catalysts, and supported metal catalysts. In particular, nitrogen-containing compounds may act as catalyst poisons (contaminants) that reduce the activity and life of the catalyst and/or cause non-sustainable operating conditions and should be removed from these hydrocarbon feed streams.

Prior art approaches to the removal of nitrogen-containing compounds include removal via liquid-liquid extraction techniques or adsorption techniques using so-called guard beds.

Liquid-liquid extraction is for example disclosed in WO 2009/058229 and WO 2012/078218. The latter document discloses the removal of nitriles and/or pyrroles from a feed stream comprising olefins and paraffins as follows: contacting the feed stream with a solvent and removing at least a portion of the nitriles and pyrroles from the feed stream. The process conditions are based on the distribution coefficient of the nitrogen-containing compound in the feed stream and the solvent.

Solvents such as sulfone compounds or alkyl/alkenyl/aryl carbonates, typically propylene carbonate, are generally used. Such solvents can be recycled or reused in the extraction process, but typically are followed by regeneration processes such as vacuum and steam distillation, stripping, adsorption, and anion-cation exchange resin columns. The regeneration process involves contacting the solvent after it has been used in the extraction process with an inert gas or a light hydrocarbon.

Continuous solvent circulation will also produce solvent degradation products in the solvent circulation loop as well as an accumulation of heavy hydrocarbon compounds that may be present in the hydrocarbon feed stream. These components collected in the solvent circulation loop may also strongly influence the effectiveness of the removal process and need to be removed in a timely manner. These compounds are not considered in WO 2012/078218.

Thus, there remains a need for further processes that allow for long term operation while maintaining good operating conditions that allow for effective removal of nitrogen-based impurities.

Disclosure of Invention

According to a first aspect, the present invention solves the above problem(s) by providing a process for removing nitrogen-containing compounds from a hydrocarbon feed, preferably from a hydrocarbon feed comprising at least one olefin selected from the group consisting of C3, C4, C5 and optionally C6 olefins and mixtures thereof, said process comprising the steps of:

a) contacting the hydrocarbon feed with an extraction solvent comprising propylene carbonate to obtain a hydrocarbon phase having a reduced content of nitrogen compounds and a solvent phase comprising dissolved nitrogen compounds therein;

b) separating the hydrocarbon phase with reduced content of nitrogen-containing compounds from the solvent phase containing dissolved nitrogen-containing compounds therein;

c) subjecting the hydrocarbon phase obtained in step (b) to a distillation step to separate a heavy phase comprising the solvent and optionally heavy hydrocarbon compounds from a light hydrocarbon fraction comprising at least one olefin selected from the group consisting of C3, C4 and C5 olefins and mixtures thereof;

d) optionally, subjecting the light fraction to further processing; and

e) subjecting the solvent phase obtained in step (b), optionally together with the heavy phase from step (c), to a regeneration step; and

f) recycling the regenerated solvent back to step (a),

the method further comprises monitoring the degradation of the solvent as follows:

maintaining the content of propylene carbonate present in the recycled solvent, measured by gas chromatography, greater than 94% by weight relative to the total amount of recycled solvent; or

Maintaining the Total Acid Number (TAN) of the recycled solvent, measured according to ISO 1843/2, less than 0.1mg KOH/g; or

Maintaining the distribution coefficient of the nitrogen-containing compounds between the recycled solvent and the hydrocarbon feed greater than 50% of the value measured for fresh solvent.

According to the invention, the degradation of the solvent can also be monitored as follows:

maintaining the surface tension of the circulating solvent measured by the Ring tearing method (Ring Tear Off method) higher than 25 mN/m; or

An interfacial tension measured by the Du Nouy Ring method (Du Nouy Ring method) of greater than 6mN/m to maintain the circulating solvent; or

Maintaining the settling time of the recycled solvent in the hydrocarbon feed to be less than 200% of the settling time of the starting propylene carbonate.

The regeneration step (e) is preferably operated in a stripper by using an inert gas such as nitrogen or one or more of the inert gases of group 18 of the periodic table of the elements (Wikipedia-2017) or a light hydrocarbon as defined below.

According to a second aspect, the present invention relates to a process for converting a hydrocarbon feed contaminated with at least one nitrogen-containing compound into a hydrocarbon product, the hydrocarbon feed comprising at least one olefin selected from the group consisting of C3, C4, C5 and optionally C6 olefins and mixtures thereof, the process comprising the steps of:

i) providing a hydrocarbon feed contaminated with at least one nitrogen-containing compound;

ii) removing nitrogen-containing compounds from the feed by using a process according to the first aspect of the invention to produce a hydrocarbon feed stream having a reduced content of nitrogen-containing compounds; and

iii) contacting the hydrocarbon feed stream having a reduced content of nitrogen-containing compounds with a catalyst to convert the feed stream to hydrocarbon products.

Other and preferred embodiments are disclosed in the dependent claims and in the following description, including examples and figures illustrating the invention.

Brief Description of Drawings

FIG. 1 is a schematic representation of steps (a) - (e) of the present invention, including monitoring for solvent degradation.

FIG. 2 is a schematic diagram of a preferred distillation column layout used in step (c).

Fig. 3 shows the content of different nitrogen compounds in different process streams in the process according to the invention.

Detailed Description

Before the present materials, compounds, components, compositions, and/or methods are disclosed in more detail, it should be noted that the singular forms "a," "an," and "the" include plural referents unless otherwise specified.

Additionally, the words "comprise" (and any form thereof), have (and any form thereof), include (and any form thereof), or contain (and any form thereof) are inclusive or open-ended and do not exclude additional, unrecited elements, such as materials, compounds, or compositions, or additional method steps.