RU2422422C2 - Method of removing oxygenates from stream of paraffins - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of removing oxygenate from a stream containing 50-99.99 wt % paraffins and 0-50 wt % olefins, which involves the following steps: a) passing a supply stream containing 50-99.99 wt % of one or more starting C₁₀-C₁₅-paraffins, 0-50 wt % olefins and one or more oxygenates through an adsorbent layer which is an exchange alkali or alkali-earth cation of zeolite X in order to remove virtually all said oxygenates; and b) removing paraffin(s) from the adsorbent layer to obtain a clean stream.

EFFECT: use of present method enables to remove a wide range of oxygenates from raw materials, a large portion of which contains C₁₀-C₁₅-paraffins.

4 cl, 2 tbl, 1 ex, 4 dwg

Description

Technical field

The present invention relates to a method for removing oxygenates from paraffins or a mixture of paraffins and olefins. The present invention is particularly useful for removing oxygenates from C ₁₀ -C ₁₅ paraffins or mixtures of paraffins and olefins before using said paraffins or olefins or mixtures thereof in subsequent processes or reactions.

State of the art

There are a number of industrial applications of paraffins or olefins or mixtures thereof in the range of C ₁₀ -C ₁₅ . These applications include hydrocarbons as a precursor to n-alkylbenzene, which is used to produce n-alkylbenzenesulfonic acid, which is the main surfactant in the production of detergents. These paraffins or olefins or mixtures thereof can also be used as precursors to convert them to more valuable fuels. Due to the pollution caused by the increase in traditional fossil fuels, and due to the fact that the sources of oil are running out, there is an increased interest in other sources of energy. One of the promising sources of energy is the synthetic production of fuels, lubricants and other products from natural gas or coal. The process of converting gas to fuel is often referred to as "gas to liquid fuel" (GTL) and is often carried out using the Fischer-Tropsch process. An example is US Pat. No. 4,973,453, which is incorporated herein by reference. Normal paraffins and olefins in the range of C ₁₀ -C ₁₅ are of particular value for the above processes.

The synthetic production of hydrocarbons using a catalytic synthesis gas reaction is well known and is usually called the Fischer-Trochp reaction. The Fischer-Tropsch process was invented at the beginning of the 20th century in Germany. It was used on an industrial scale in Germany during World War II and was later used in South Africa.

Synthesis gas (mainly hydrogen and carbon monoxide) is obtained from coal or natural gas (methane). After that, the synthesis gas is converted into liquid hydrocarbons. The Fischer-Tropsch reaction for converting synthesis gas is in some cases described as the following general reaction:

The Fischer-Tropsch hydrocarbon products range from methane to high molecular weight paraffin waxes containing more than 50 carbon atoms.

When carrying out the reaction, numerous catalysts are used, including active metals such as iron, cobalt, ruthenium, rhenium, etc., and both saturated and unsaturated hydrocarbons can be obtained. The synthesis reaction is very exothermic and temperature sensitive, and therefore temperature control is required to maintain the selectivity of the desired hydrocarbon product.

The synthesis gas used in the Fischer-Tropsch reaction can be obtained from natural gas, gasified coal, and other sources. To obtain synthesis gas (syngas), used as a feedstock in the Fischer-Tropsch reaction, a number of basic methods are used. Numerous methodologies and systems used to produce synthesis gas include partial oxidation, steam reforming, autoreforming, or autothermal reforming. Both a fixed bed system and a fluidized bed system are used.

Reforming reactions are endothermic and often use a nickel-containing catalyst for them. Partial oxidation (non-catalytic or catalytic) involves the substoichiometric burning of light hydrocarbons, such as methane, to produce synthesis gas. The partial oxidation reaction is usually carried out on an industrial scale using oxygen of high purity.

In some situations, these synthesis gas production methods may be combined to form another method. To date, the synthesis of partial oxidation and steam reforming, known as autothermal reforming, in which air can be used as an oxygen-containing gas for the partial oxidation reaction, is also used to produce synthesis gas. Autothermal reforming - the combination of partial oxidation and steam reforming, allows you to use the exothermic heat of partial oxidation as the heat needed for the endothermic reaction of steam reforming. The autothermal reforming process can be carried out in a relatively inexpensive carbon steel reactor with refractory lining, due to which, as a rule, the cost of the process is reduced.

The Fischer-Tropsch process for producing paraffins and paraffin / olefin mixtures also leads to the formation of a wide variety of oxygenates. These oxygenates, which include aldehydes, acids, ketones and alcohols, are harmful in many applications of these paraffins or olefins or mixtures thereof. In particular, oxygenates poison the catalysts used to facilitate the conversion of paraffin and paraffin / olefin mixture to the desired end products. In order for paraffins or olefins or their mixtures to be processed without poisoning the adsorbent / catalyst or causing any other harm during the processing of these paraffins or olefins or mixtures thereof, the oxygenate content should be reduced by amounts of the order of 200-400 ppm in the untreated paraffin stream and / or olefins up to 1 ppm or less.

To remove oxygenates from paraffins with a small number of carbon atoms, i.e. averaging around C ₅ , several different adsorption schemes have been proposed. For example, in US Pat. No. 6,111,162, hydrocarbons containing 3 to 8 carbon atoms were treated with an adsorbent including silica gel to remove oxygenated pollutants. In US 5,427,689, many polar substances, including water, alcohols, esters, aldehydes, ketones, amines, mercaptans, organic sulfides and carboxylic acids, were removed from hydrocarbons containing 1-10 carbon atoms using a sorbent composition comprising aluminum borate and zirconium borate . US 4,404,118 teaches the removal of oxygenates from a stream containing C ₄ hydrocarbons. However, to date, no method has been proposed for the sufficient removal of oxygenates from a paraffin and paraffin / olefin mixture with a high content of carbon atoms (C ₁₀ -C ₁₅ ) used in the method of the present invention. These mixtures include from 0 to 50 wt.% Olefins and from 50 to 99 wt.% Paraffins. Dozens of different oxygenate compounds are present in the paraffin and paraffin / paraffin / olefin mixtures obtained by the Fischer-Tropsch process, and in order to use these paraffins and paraffin / olefin mixtures in a wide variety of processes, it is necessary to have a common method that is suitable for removing all oxygenate compounds. Accordingly, it is believed that it is desirable to remove the co-presence of these compounds from the starting paraffin and paraffin / olefin mixture. In addition, in many applications of the present invention, it is desirable to be able to regenerate the adsorbents used to remove oxygenates from the starting paraffin and paraffin / olefin mixture. If it is possible to reuse adsorbents after regeneration of the adsorbent layer, instead of frequently replacing the layers, a significant reduction in costs can be achieved.

Disclosure of invention

The present invention includes a method for removing oxygenates from a stream containing from 50 to 99.99% by weight of paraffins and from 0 to 50% by weight of olefins, comprising passing a feed stream containing one or more starting C ₁₀ -C ₁₅ paraffins and a mixture of olefins and one or more oxygenates, through an adsorbent bed in order to remove substantially all oxygenates and to obtain paraffins and olefins as a product (if they are present). The level of oxygenates is below the level that is detected using standard laboratory methods, such as gas chromatography. In some embodiments of the present invention, to ensure complete removal of oxygenate impurities, it is considered necessary to direct the paraffin-rich stream to a second adsorbent bed including a molecular sieve. Typically, a “stripping” layer with a pore size of 5 A is used to complete the removal of these impurities from the paraffin-enriched stream. The present invention is particularly useful in the purification of feed streams for certain reactions. Trace amounts of oxygenates can be harmful to the adsorbent / catalyst. Among the processes that can be improved by removing oxygenates according to the present invention are the dehydrogenation of normal paraffins to olefins and the processes of separating normal paraffins from branched and cyclic hydrocarbons. In the case where the feed is a mixture of paraffins and olefins, this stream is suitable for direct alkylation of benzene after the operation to remove oxygenates and before the formation of alkylated benzene. Accordingly, one embodiment of the present invention includes a process for the dehydrogenation of normal paraffins to olefins, comprising first passing a stream of paraffins containing C ₁₀ -C ₁₅ paraffins through at least one adsorbent layer containing one or more adsorbents selected from the group consisting of silica gel, activated alumina and exchanging the alkaline or alkaline-earth cation X-zeolite, where adsorbents by adsorption remove almost all oxygenates from the paraffin stream, and ATEM direction paraffinic stream to a reactor containing a dehydrogenation catalyst to convert at least a portion of the paraffinic stream to olefins. Another embodiment of the present invention includes a process comprising first passing a stream of paraffins containing C ₁₀ -C ₁₅ paraffins through at least one adsorbent layer containing one or more adsorbents selected from the group consisting of silica gel, activated alumina and exchanging the alkaline or alkaline-earth cation X-zeolite, where adsorbents by adsorption remove almost all oxygenates from the paraffin stream, and the subsequent direction of the paraffin stream to the adsorbent bed, including conductive molecular sieve to separate from the paraffin stream of normal paraffins.

Another embodiment of the present invention includes a process comprising first passing a stream containing 50-99.99% C ₁₀ -C ₁₅ paraffins and 0-50% olefins through at least one adsorbent layer containing one or more adsorbents, selected from the group consisting of silica gel, activated alumina, and exchanging the alkaline or alkaline-earth cation X-zeolite, where adsorbents remove almost all oxygenates from the stream by adsorption, and then combining the stream with benzene and directing the resulting stream a alkylation to a reactor containing a catalyst for converting at least a portion of the olefins to alkyl benzene.

Brief Description of the Figures

Figure 1 - demonstration of the slip with the raw material through an adsorbent of aluminum oxide at 1000 ppm of 2-undecanol, 2-undecanol, decyl alcohol, lauric acid and 2-dodecanol.

Figure 2 - demonstration of a slip with the feed through a silica gel adsorbent of 1000 ppm of 2-undecanone, 2-undecanol, decyl alcohol, lauric acid and 2-dodecanol.

Figure 3 - demonstration of a slip with the feed through another silica gel adsorbent of 1000 ppm of 2-undecanone, 2-undecanol, decyl alcohol, lauric acid and 2-dodecanol.

Figure 4 is a demonstration of the slip along with the feed through a 13X adsorbent of 1000 ppm of 2-undecanone, 2-undecanol, decyl alcohol, lauric acid and 2-dodecanol.

The implementation of the invention

The present invention includes a method for removing oxygenates from a mixture of paraffins and olefins or a paraffin-rich stream, which comprises passing a feed stream containing one or more starting C ₁₀ -C ₁₅ paraffins or a mixture of paraffins and olefins and one or more oxygenates through an adsorbent bed to removing substantially all oxygenates; and obtaining paraffins or a mixture of paraffins and olefins. Typically, a mixture of paraffins and olefins, referred to herein as an olefin-rich stream, contains up to 50 wt.% Olefins, while the rest contains paraffins plus impurities. Up to 1% of a mixture of paraffins and olefins or paraffin-rich streams are oxygenate impurities that must be removed by the present invention. In the case of paraffin-rich streams, the streams typically include 99% by weight of paraffins, and in some cases up to 99.99% by weight of paraffins. It has been found that in such a typical paraffin-rich or olefin-rich paraffin stream produced in a gas to liquid Fischer-Tropsch process, a variety of hydrocarbon oxygenates are formed, including alcohols, aldehydes, ketones and acids. In order to use these paraffins or olefin-rich paraffins without poisoning the adsorbent / catalyst used in processes such as the conversion of paraffins to olefins, the alkylation of paraffins with benzene and the separation of n-paraffins from other paraffins, it is necessary to use the process of removing almost all oxygenates . Table 1 illustrates an extensive list of oxygenates contained in three samples of paraffins or olefin-rich paraffins prior to processing in the process of the present invention, all of which are removed using the method of the present invention. All numbers are expressed in ppm.

Table 1 Compound Raw 1 Raw materials 2 Raw materials 3 1 nonanol 1,6 12.1 3.6 2-nonanol <0.4 1,6 1.8 1-decanol 2.2 14.0 12.1 2-decanol 0.4 4,5 3.3 3-decanol <0.4 <0.4 9.2 4-decanol 0.3 4.2 3,1 Unknown C ₁₀ alcohols <0.4 <0.4 <0.4 1-undecanol 1,6 9.0 4.3 2-undecanol 1.4 4,5 3.9 3-undecanol 0.9 3.3 4.8 4-undecanol 0.6 2.1 5.2 Unknown C ₁₀ alcohols 0.8 3.2 5.7 1-dodecanol 0.5 1,0 1.4 2-dodecanol 4.6 8.0 <0.4 Unknown C ₁₂ alcohols 6.0 15.3 <1.0 1-tridecanol <0.4 <0.4 <0.4 Unknown C ₁₃ alcohols 3,1 6.7 <0.4 1-tetradecanol <0.4 <0.4 <0.4 Unknown C ₁₄ alcohols 1,0 0.5 <0.4 1-octanal 4,5 4.9 4.3 1 nonanal 4.2 6.7 7.7 1-decanal 3.9 8.3 16.9 1-undecanal 3.0 7.2 17.1 1-dodecanal <0.6 1.4 <1.0 1-channel <0.5 <0.5 <1.0 2-heptanone 0.7 1,6 <0.4 2-octananone 1,5 3.8 <0.4 2-nonanone 2,4 6.6 0.6 2-decanon 3,1 10.1 2.9 2-undecanon 3.3 11.3 3,5 2-dodecanon 1,6 5.7 1,0 Unknown C ₁₁ -contains 2.2 1,0 5.2 Unknown C ₁₂ -contains 1.3 5,4 6.1 butanoic acid 3.3 1,2 1,6 pentanoic acid 6.7 2,4 1,6 hexanoic acid 10,4 3.6 3.3 heptanoic acid 12.8 4,5 4.3 octanoic acid 14.3 4.7 6.7 nonanoic acid 16,0 5.3 9,4 decanoic acid 16.7 5.1 10.1 undecanoic acid 12.0 4.0 15.4 lauric acid 6.6 2,4 12.6

Table 2 summarizes all types of oxygenates contained in the feed.

table 2 Compound Raw 1 Raw materials 2 Raw materials 3 Alcohols 25.0 90.0 58.4 Aldehydes 15.6 28.5 46.0 Ketones 12.6 39.1 8.0 Acids 98.8 33,2 65.0

In the practice of the present invention, a paraffin-rich or olefin-rich paraffin stream is first passed through an adsorbent bed containing at least one adsorbent selected from the group consisting of silica gel, activated alumina and exchanging alkaline or alkaline earth X-zeolite cation. The ratio of Si / Al ₂ in X-zeolite is from 2.0 to 3.0. Preferred is X-zeolite with a ratio of Si / Al ₂ equal to 2, 2.3 or 2.5.

In addition to removing oxygenates, in some embodiments of the present invention, it is necessary to remove compounds containing other elements from group VIB of the Periodic Table of the Elements. In particular, when a low-quality condensate is used from a gas well containing up to 0.7% by weight of mercaptans, sulfides and disulfides, it is highly desirable to process such a stream in order to reduce the level of sulfur compounds that are harmful to the platinum catalyst used to produce n-alkylbenzenes up to below 5 parts by weight / million Sulfur compounds can be removed using adsorbents known to those of ordinary skill in the art. Advantageous results can be achieved using an adsorbent bed containing ADS-102 and PEP adsorbent, which can be obtained from UOP LLC, Des Plaines, Illinois.

The adsorbent layer may be designed exclusively for processing a paraffin-rich or olefin-rich paraffin stream, or it may be integrated with a chemical conversion process that uses a paraffin stream to effect other types of separation. A specialized adsorbent layer is such a layer, the sole purpose of which is to remove oxygenates from the paraffin stream, regardless of whether only the paraffin stream passes through the layer or the paraffin stream is combined with the chemical conversion stream and the combined stream passes through the layer. In the integrated adsorbent layer, the paraffin stream and the chemical conversion process are combined and the adsorbent layer is used to remove at least one component in the chemical conversion process stream. For example, in the processes for alkylation and the process for producing alkylbenzenes from paraffins, paraffins are dehydrated and, in order to remove undesirable aromatic compounds, the dehydrated stream is usually passed through an adsorbent layer such as 13X zeolite. In such processes, the paraffin stream enters the process mainly after dehydrogenation and before adsorption of water and aromatic compounds in the adsorbent layer.

Being specialized, the adsorbent layer operates, as a rule, at a temperature of from 25 to 60 ° C and preferably at a temperature slightly above ambient (40 ° C). Although it was found that this adsorbent layer reduces the level of oxygenate below the level measured by gas chromatography, since it was found that under certain conditions these adsorbent layers remove oxygenates less efficiently over time to ensure complete removal of oxygenates, additional measurements are required . Accordingly, in preferred embodiments of the present invention, it has been found that a second adsorbent layer operating at an elevated temperature of 150 to 200 ° C. and containing 5 A adsorbent removes possibly present residual oxygenates not removed by the first layer. Adsorbent layers integrated with a process that uses a paraffin-rich or olefin-rich paraffin stream typically operate under conditions that are suitable for the process.

After the adsorbent layers have exhausted their capacity to remove oxygenates from paraffin-rich streams, a layer regeneration step follows to remove adsorbed oxygenates from the adsorbent layer. A gas or liquid is passed through the layer while maintaining an elevated temperature for a time sufficient to regenerate it by removing oxygenates. In one embodiment of the regeneration process, nitrogen was used as a regenerating gas at a gas hourly space velocity of 3000 h ^-1 , the layer was first heated to 130 ° C for two hours and then the temperature was raised to 250 ° C for another three hours. Other regenerating gases or liquids, such as those involved in the process, may be used. The layer can also be regenerated in accordance with the procedure proposed in US 6225518 B1, fully incorporated into the present description as a reference material. As a rule, due to the low concentration of oxygenates, the integrated adsorbent layer is regenerated or replaced in the process depending on the productivity of the process.

EXAMPLE

Laboratory tests were performed to determine the degree of removal of oxygenates from hydrocarbons. The process is carried out in a 20 ml stainless steel column. The column is installed in a closed box and filled with 20 ml of adsorbent. Initially, the temperature of the closed box is raised to the desired temperature, which in this example is 40 ° C. After stabilization of the temperature, the hydrocarbon feed containing oxygenates is introduced at a flow rate of 4 h ⁻¹ . The effluent is collected and analyzed for the presence of impurity oxygenates. The tested raw materials contained 1000 ppm of each of the five typical oxygenates contained in kerosene: 2-undecanol, 2-undecanol, decyl alcohol, lauric acid and 2-dodecanol. In the case of alumina, silicate gel, and NaX type adsorbents, very noticeable breakthroughs were noted. 1, the alumina tested as an adsorbent was spherical activated alumina sold by UOP LLC, Des Plaines, Illinois, under the name Activated Alumina 9139A. The adsorbent has a capacity of 21.95 wt.%. 2, the adsorbent was Eagle 32-950 silica gel sold by Eagle Chemical Co, Inc., Mobile, Alabama. The adsorbent has a capacity of 19.76 wt.%. 3, the adsorbent used was Grace 408 silica gel sold by WRGrace, Grace Davison division, Columbia, Maryland. The adsorbent has a capacity of 32.33 wt.%. Figure 4 used the adsorbent Molsiv MRG-E, sold by UOP, Des Plaines, Illinois. The adsorbent has a capacity of 23.57 wt.%. Each of the figures shows a significant capacity of these adsorbents for oxygenates, as well as a sharp slip after reaching the maximum capacity of the adsorbent. It was also noted that lauric acid is strongly bound by adsorbents in all four cases.

Claims (4)

1. The method of removing oxygenate from a stream containing from 50 to 99.99 wt.% Paraffins and from 0 to 50 wt.% Olefins, which includes the following stages:
a) passing a feed stream containing from 50 to 99.99% by weight of one or more initial C ₁₀ -C ₁₅ paraffins, from 0 to 50% by weight of olefins and one or more oxygenates through an adsorbent alkaline exchange layer or alkaline earth cation X-zeolite in order to remove almost all of these oxygenates; and
b) removing paraffin (s) from the adsorbent layer to obtain a purified stream. 2. The method according to claim 1, wherein the adsorbent layer comprises a NaX zeolite. 3. The method according to one of claims 1 or 2, in which the adsorbent layer is regenerated by removing oxygenates, the regeneration includes heating the adsorbent layer to a sufficient temperature and for a sufficient period of time, and passing the regenerating gas through the adsorbent layer to remove from the specified adsorbent of the desired portion of oxygenates. 4. The method according to claim 1, in which, after passing the stream of paraffins and olefins through the adsorbent layer, a purified stream is passed through a second adsorbent layer comprising 5 A adsorbent to further remove oxygenates from the purified stream.

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