The method of separation of the contact gas dehydrogenation butanebutylene mixtures

 

(57) Abstract:

Usage: in the petrochemical industry. The essence of the invention: method of separation of the contact gas dehydrogenation of butane-butylene mixtures enables selection of a butane-butylene-butadiene fraction, its extractive distillation in the presence of acetonitrile to obtain nextdaysomany butane-butylene fraction returned in the dehydrogenation process, and the extract containing butadiene, rectification extract with obtaining butadiene raw, clear rectification to obtain the desired butadiene and VAT residue. Moreover, the VAT residue clear rectification return in column a clear rectification in the reflux line of the latter, without prior washing. 2 Il.

The invention relates to the petrochemical industry, namely to obtain butadiene by extracting gas from the contact dehydrogenation of butane-butyl mixtures.

A known method of producing butadiene extraction of the contact gas dehydrogenation, consisting in the allocation of butane-butylene-butadiene fraction in the column pre-rectification, submitting it to the extractive rectification, the return nextpage the rigid rectification and submission of VAT residue water washing from the extractant with further, washed from the extractant in the supply line of the column pre-rectification [1] Method allows you to retrieve up to 93 wt. butadiene gas from the contact, which is not enough.

The goal of the proposed method increases the degree of extraction of butadiene from the contact gas dehydrogenation of butane-butylene mixtures.

The objective is achieved by changing the process technology division contact gas by separating the butane-butylene-butadiene fraction (BBF) in the column pre-rectification, feed her on extractive rectification, return nextdaysomany faction in the dehydrogenation process, the selection of the extract butadiene raw, clear rectification and submission of VAT residue in the reflux line of the column pre-rectification.

A distinctive feature of the proposed method is the exclusion from the scheme of the column of water washing VAT residue clear distillation of butadiene raw and the return of the VAT residue in the reflux line of the column pre-rectification, and not in her power (see schemes 1 and 2 in Fig. 1 and 2).

Example 1 (the prototype). Setup subjected to dehydrogenation dehydrogenation mixture fresh is 1) composition, wt. H21,2; total hydrocarbons1-C36,1; isobutylene + isobutane 1,2; n-butylene 26,5; butadiene 13,0); the amount of hydrocarbons WITH5and above 2.0; n-butane else.

Received contact the gas is subjected to separation according to scheme 1 by rectification in CT-2 emitting 168,2 t/h butane-butylene butylene fraction (stream 2) composition, wt. hydrocarbons WITH2-C30,04; isobutane + isobutylene 1,25; n-butylene 29,07; butadiene 13,73; hydrocarbons5and up to 0.12; n-butane else.

Received BBBF served on extractive rectification in CT 20/1; not extracted butane-butylene fraction washed with water from acetonitrile in the CT-150 and returned to the dehydrogenation (stream 3) number 138 t/h composition, wt. isobutane-isobutylene 1,61; n-butylene 32,96; butadiene 0,16; the amount of the hydrocarbon WITH5and up to 0.03; n-butane else.

From the extractant in CT-20/P-30 produce butadiene raw, put it first distillation cleared from the lungs in CT-50, then storable in CT 56 hydrocarbons and get 23,0 t/HR of butadiene concentrate with a content of butadiene to 99.5 wt. the rest of the butylenes.

VAT product of the distillation of butadiene from high-boiling hydrocarbons washed with water in CT a and the number is rasaut in the power of the column pre-rectification CT-2.

The degree of extraction of butadiene from the contact strip of 93.5 wt.

Example 2. At the same dehydrogenation as in example 1, is subjected to dehydrogenation mixture of fresh n-butane (52 t/h) and recycle butane-butylene fraction (138 t/h).

Get 1 88 t/h contact gas (stream 1), wt. H21.3; total hydrocarbons1-C36,3; isobutylene + isobutane 1,1; n-butylene 27,5; butadiene 13,6); the amount of hydrocarbon, C5and up to 1.9; n-butane else.

Received contact the gas is subjected to separation according to scheme 2 by rectification in the column 2 with the release 169,0 t/h BBBF (stream 2) composition, wt. hydrocarbons, C2-C30.05; isobutane + isobutylene 1.27mm; n-butylene 29,85; butadiene 14,98; hydrocarbons5and above 1,14; acetonitrile 0,26; n-butane else.

Received BBBF served on the extractive rectification column 3, nextdaytramadol butane-butylene fraction washed with water in column 7 and return to the dehydrogenation (stream 3) number 138 t/h composition, wt. isobutylene+isobutane 1.55V; n-butylene 3,69; butadiene 0,12; hydrocarbons WITH5and above 0,04 n-butane else.

From the extractant in column 4 produce butadiene raw, put it first distillation purification from l content of butadiene to 99.5 wt. the rest of the butylenes.

VAT product of the distillation of butadiene from high-boiling hydrocarbons in the amount of 2.0 t/h composition, wt. n-butylene 72,5; butadiene 2,5; hydrocarbons WITH5and higher than 3.0; acetonitrile 22,0 return in the reflux line of the column 2.

The degree of extraction of butadiene from the contact gas is 96.5 wt.

Thus, the proposed method of separation of the contact gas butane-butyl mixtures can increase the degree of extraction of butadiene from 93.5 wt. to 96.5 wt. In this case, also, removed the butane-butylene fraction in the same quantities as in the known method. The dehydrogenation extracted butane-butylene fraction in the mixture with fresh butane allows you to contact the gas with a content of butadiene is not less than the known method.

The method of separation of the contact gas dehydrogenation of butane-butylene mixtures, including the allocation of butane-butylene-butadiene fraction in the pre-column distillation, extractive distillation of the butane-butylene-butadiene fraction in the presence as a solvent of acetonitrile with getting nextdaysomany butane-butylene fraction returned to the dehydrogenation process, and extract, sod target butadiene and VAT residue, refund of VAT residue clear rectification in the column pre-rectification, characterized in that the return VAT residue clear rectification directly served in the reflux line of the column pre-rectification.

 

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SUBSTANCE: 1,3-butadiene is obtained via catalytic dehydrogenation of n-butylenes at 580-640°C and essentially atmospheric pressure while diluting butylenes with water steam at molar ratio 1:(10-12) and supplying butylenes at space velocity 500-750 h-1. Catalyst is composed of, wt %: K2O 10-20, rare-earth elements (on conversion to CeO2) 2-6, CaO and/or MgO 5-10. MoO3 0.5-5, Co2O3 0.01-0.1, V2O5 0.01-0.1, and F2O3 the balance. Once steady condition is attained, dehydrogenation is carried out continuously during all service period of catalyst.

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