SU767080A1 - Method of isolating highest normal alkanes - Google Patents

Description

The invention relates to the separation of hydrocarbons by adsorption and can be applied in the refining and petrochemical industries. There is a method for separating n-alkanes from a mixture with other hydrocarbons of crude oil using type 5A zeolite. The method involves contacting the evaporated raw material with a layer of zeolite and selecting the fraction depleted in H-alkanes (denormalized), purging the layer of zeolite with low molecular weight H-alkane vapors and selecting the intermediate fraction, stripping the adsorbed H-alkanes with low-molecular H-alkane and stripping the desorption of H-alkanes with low-molecular H-alkane and stripping the desorption of the H-alkanes with low molecular weight H-alkane and desorption . The process is carried out under isothermal and isobaric conditions at 30 ° C to 400 ° C and a pressure of 0-7 atm. As desorbent and purge agent use N-hexane l. There is also known a method for isolating N-allans, according to which the intermediate fraction is returned to the feedstock at the adsorption stage. Blowing and desorption is carried out with n-hexane, they also dilute the raw material before adsorption. M The disadvantage of these methods is the low purity of the H-alkanes obtained and a large amount of n-hexane circulating in the process (desorbent and blowing agent), which complicates the regeneration of n-hexane. hexane from finished products. The closest to the invention according to the technical essence and the achieved result is a method of separating higher H-alkanes by adsorbing them on the zeolite from the oil fraction in the vapor phase, followed by blowing the zeolite with a low molecular weight alkane, to obtain an intermediate fraction and desorbing the zeolite, with obtaining a mixture of H-alkanes and desorbent, which is fed to the rectification, with the release of the target product and desorbent and recycling the latter into the process. The raw material, the hydrotreated kerosene gasoil fraction, is diluted with a low molecular weight n-alkane, mixed with a circulating intermediate fraction, evaporated, and fed to an adsorber loaded with type 5A zeolite, which absorbs H-slippers. In this case, a stream consisting of

1 | 1 ШШШШМ) Ш 1 §wbpuebJSfa с6р6ён77 Become after the desorption stage, and denormalized, non-adsorbent part of the raw material. The stream is separated by distillation into a catalyst and desorbene. Denormalized is the finished product, and the desorbent is returned to the process ..; G After the end of the adsorption stage

It is the stage of Purging, for which the adsorber is supplied with a Preliminary Evaporating Purge Agent - a low molecular weight H-alkane, for example, H-pentane, which removes the raw material and denormalized wastes between the zeolite grains. At the same time, some of the adsorbed N-alkanes are desorbed. The stream leaving adsorber1a and consisting of the non-adsorbed part of the raw material (denormalization), the remainder -. - -. ------- .- ...-.: .- KOV of the raw material, partially desorbed 14-alkyns and The purge agent (in particular, desorbentai-pentane) is referred to as intermediate fraudy. The intermediate fraction is recovered in the process and is mixed with fresh raw material.

For desorption of H-alkanes from the pores of the zeolite, evaporated desorbent — low molecular weight n-alkane, in particular H-pentane, is fed to the adsorber. The flow of the displaced N-alkanes and desorbent is separated by rectification. The n-alkanes are the TOT product and the desorbent is returned to the process. After the end of the desorption process, the process steps are repeated in the same sequence.

The process is carried out under thermal and isobaric conditions at 300-400 ° C and a pressure of 0-7 atm. The duration of the adsorption, blowing and desorption stages is usually 1: 1; n, where n is 2-3, and adsorption lasts 5-6 minutes.

At the stage of blowing with short-term supply of desorbent, the latter blows out hydrocarbons, it is found -. spread between the zeolite grains. Hydrocarbons of abnormal structure, adsorbed on the ma; Cropars, are not displaced, and upon subsequent desorption they are contaminated by desorbed in CLO-O molecular h-alkanes. With an increase in the duration of the purge and the amount of missed desorbent, the latter desorbs the hydrocarbons of the zeolite and partly high-yield H-alkanes from micropores. With an increase in the amount of desorbent missed, it comes to the purity of the n-alkanes desorbed in the next stage, but their content in the intermediate fraction is determined, and then their number decreases.

The content of H-alkanes in the intermediate fraction is usually 5-30% higher than in the raw materials (calculated on high).

The nucleus is the hydrocarbon part of the intermediate fraction), and its amount is 10-50% of the feed mixture.

The disadvantage of this method is the low purity of the desorbed high molecular weight n-alkanes, a large number of intermediate fraction and desorbent circulating in the system.

The aim of the invention is to increase the quality and yield of the target product.

The goal is achieved by isolating higher-alkanes by adsorbing them to the zeolite from the oil fraction in the vapor phase followed by subsequent production, with the first stage purging is carried out to obtain an intermediate fraction that is fed for rectification together with a mixture of desorbent and deiormal ata , With the subsequent carrying out of the second stage of purging with either the desired higher n-alkanes or nizkoMOAYAET an alkane alkane containing 5-75 wt.% Of the higher alkanes for 1 / 6-1 / 3 the duration of the entire process a purge, with Niemi blowdown, rotsirkulirue1myh The feedstock zeolite desorption to obtain a mixture of higher n-alkanes and desorbent, which is fed to a rectification and separation of the desired product and recycle of desorbent in the last process. g The raw material, the hydrofined kerosene gas – gas fraction, is mixed with the intermediate fraction obtained in the second stage of the purge, evaporated and formed into the adsorber loaded with type 5A zeolite.

H-alkanes C, o-Cjj, contained in the mixture, are adsorbed in internal electrolytes; the desorbent, replaced by previous adsorption, is expelled at this stage. The stream coming out of the still-sorber, consisting of the denormalized product (non-adsorbing part of the raw material) and desorbent, is separated by a certificate. Dyenabethyl is the finished product and the desorbent is returned to the process.

At the end of the adsorption, a two-stage purging step is carried out, predating to remove the denormalized zeolite from the volume between the grains. For carrying out the first stage into the adsorber, the evaporated purge agent (in particular, the -H-hexane desorbent. The mixture coming out of the vapor adsorber, consisting mainly of the desorbent and denormalization (intermediate fraction 1), is sent to the flow of denormalization. After the first stage is exhausted, the adsorber feeds n-alkanes and their mixture with a blowing agent. Thus, the second stage of the purge is carried out;

from desorbent, denormalized and n-alkanoE C, d-C22 (intermediate fractions are sent for mixing with the raw materials entering the adsorption step.

After the completion of the purge, the evaporated desorbent (in particular, n-hexane) is fed into the adsorber, which displaces H-alkanes from the internal pores of the zeolite. The stream consisting of desorbent and H-alkanes is separated by distillation. And the alkanes are the finished product and the desorbent is returned to the process. Part of the N-alkanes C | Q-C22 is directed to the second stage of the blowdown.

At the end of the desorption, all stages of the process are repeated in the same sequence.

The process is carried out under isothermal and isobaric conditions at 300-400 s and a pressure of 0-7 atm. The duration of the purge stage is 2-3 minutes.

Example 1. A raw material, a hydrotreated kerosene-gas oil fraction boiling in the range of 200-320 ° C, containing 21.5% H-alkanes C, d-C22 in an amount of 464.8 kg, is mixed with intermediate fraction II leaving the second blowing steps (110.6 kg and consisting of,%: n-hexane 74, H-alkanes C | / j-C2220.8, denormalized 5.2. The mixture in the amount of 575.4 kg is fed to the adsorber for 6 minutes loaded with 5 tons of type 5A zeolite in which the desorption stage was completed. The stream leaving the adsorber was separated by rectification into denormalized (401.6 kg) and n-hexane, desorbent, in an amount of 241.5 kg.

At the end of the adsorption, the first stage of purging is carried out, for which 260 kg of evaporated n-hexane are passed through the adsorber for 2 minutes. The output stream from the adsorber in the amount of 281.5 kg and consisting of N-hexane (66.8%), non-adsorbing cix hydrocarbons, denormalized acid (32.4% and n-alkanes C | g-C22 (0.8%) ), mixed with the previous stage denormalization stream and sent for rectification. H-Hexane is returned to the process, and the rest of the hydrocarbons are a component of the finished denormalized product. Then, the second stage of purging is carried out for 1 min, feeding H-hexane mixture to the adsorber ( 87.1 kg) and H-Gshkans C | 0-C22 (34.6 kg).

The stream exiting the adsorber

consisting of n-hexane (73.9%), n-alkanes (20.8%) and residues of denormalization (5.2%) (intermediate fraction P1 is directed to mixing with the raw material.

For desorption of the absorbed n-alkanes, evaporated desorbent H-hexane (500 kg) is passed through the adsorber for 9 minutes. The effluent from the adsorber is a distillation stream.

the column is divided into n-alkanes (111.5 kg) and n-hexane (418.2 kg). The purity of the extracted n-alkanes is 99.2%, the yield of n-alkanes on the potential is 73.2 wt.% Per cycle.

Example 2. Conditions are similar to example 1, with the exception of purging. After the adsorption is completed, the first stage of purging is carried out, for which 305 kg are supplied to the adsorber for 2.5 minutes.

0 evaporated hexane. The effluent from the adsorber (intermediate fraction 1 in the amount of 328.2 kg, consisting of is-hexane (73.1%), non-adsorbing hydrocarbons

5 (26.0%) and n-alkanes C, o-C22 (0.91%), is mixed with the stream of the denormalized product of the previous stage and sent for rectification. N-Hexane is returned to the process, and the remainder of the carbon of hydrogens is a component of the final denormalization. Then, within 0, 5 minutes, the second stage of purging is carried out, supplying the EI adsorber with 55 kg of evaporated C | o-C22 alkanes obtained at the desorption stage in the previous 5th cycle. The effluent from the adsorber consists of H-hexane (74.6 kg), n-alkanes (22.3 kg) and. residues denormalized (3.1 kg), sent for mixing with raw materials.

0

The purity of the desorbed i-alkanes is 99.6%, the output potential of alkanes is 71.7% by weight per cycle.

Example 3. Conditions are similar to example 1, with the exception of purging. After termination of adsorption, the first stage of purging is carried out, for which the adsorber in those. For 2 minutes, 260 kg of evaporated H-hexane are fed. The effluent from the adsorbent (intermediate fraction 11

0 in the amount of 281.5 kg, consisting of H-hexane (66.8% by weight), non-adsorbing hydrocarbons (32.4% by weight) and n-alkanes CiQ-Cj COS% by weight, is mixed with a stream of denormalized and on the 5th rule for rectification, H-hexane is returned to the process. The remainder of the hydrocarbons is a component of the final denormalysis. Then for 1 min the second

0 stage purge, submitting to the adsorber mixed hexane (123.5 kg) and H-alkanes C, o-C22 (6/5 kg). The stream leaving the adsorber consisting of N-hexane (88.9 wt.%), N-alkanes

5 C | Q-C2j (8.9 wt.%) And residues of denormalizate (2.2 wt.%) (Intermediate fraction I are directed for mixing in the raw materials.

The purity of the desorbed N-alkanes C | Q-C2298,8 wt.%, The output of n-alkanes

0 on potential 72.4 wt.% Per cycle.

Example 4. Conditions are similar to example 1, except for the second stage of purging. After the end of the first stage purge

During 0.7 min, the second stage of purging is carried out by feeding into the adsorber a mixture of i-hexane (25%) and n-alkanes CjQ-Cjj (75%) in an amount of 122 kg.

The stream leaving the adsorber, consisting of H-hexane (16.7%), H-alkanes (76.2%) and residues of denormalized (7.1%) (intermediate fraction P), is directed to mixing with raw material.

The purity of the obtained rt-alkanes CIQ-CJIJ is 99.4%, the yield of m-alkanes from the potential is 72.5%.

The table shows the comparative data indicators for the known and proposed methods.

Claims (3)

100 105.3 106.3 106 100 117 118 117.8 65.8 73.2 71.7 72.4 The use of high molecular weight H-cloths as a blowing agent or its component will increase the purity of the desorbed H-alkanes. A positive effect is achieved due to the displacement of macropores from the volume between the grains of the zeolite to non-adsorbing components of the raw material. The presence of high-molecular n-alkanes (of the same composition as inside the micropores of the zeolite) prevents desorption of the latter on the thickening of the purge. Due to this, high purity of desorbed n-alkanes (98.8-99.6%) is achieved and the yield of H-gshcans increases by 6-7%. When the content of K-alkanes in the stream is received, we go to the second stage of the purge, 5%, yield 72.4%, purity 98.8%; at 28%, respectively, 73.2%, 99.2%; at 75% - 72.5, 99.4%; Yri 100% - 71.7%, 99.6%. If it is necessary to obtain the purest n-alkanes (99.6%), it is optimal to use 100% H-alkanes in the second stage of purging. To achieve maximum output with relatively high purity, the optimal range is 30-75% H-gc 8. Intensification of the purge by conducting the second stage reduces the total purge time (and hence the total cycle time) and the amount of n-hexane circulating in the system. Reducing the total cycle time allows for an increase in daily production by 17–18% for fresh raw materials. Claims The method of isolating higher H-apanes by adsorbing them to zeolite from the oil fraction in the vapor phase, followed by blowing the zeolite with a blowing agent with a low molecular weight alkane, to obtain an intermediate fraction and desorbing the zeolite, to obtain a mixture of higher H-alkanes and desorbent, fed to the rectifier, with the release of the target product and desorbent and recirculation of the latter into the process, characterized in that, in order to increase the purity and yield of the target product, the purge process is carried out in two stages, This intermediate fraction and the first stage purge podgtsot on rektifika9. 76 together with a mixture of desorbent and fleHopManKsara, followed by a second purge stage or isolated higher H-alkanes or a low molecular weight alkane containing 5-75 wt.% Higher n-alkanes for JL / 6-1 / 3 duration of the entire spinning, with the production of purge products recycled to the feedstock. 708010 Sources of information, which are taken into account in the examination of i US Patent 3291725, Jo-ZU, published. 1966. -, -j п,, t "..,", r 2. US patent 3422005, 20,8-310, publ. 1969. 3. U.S. Patent 3,342,725, incl. 208-310, published. 1968 (prototype).