DD249380A3 - PROCESS FOR THE PRODUCTION OF LIGHT ALKYLATE - Google Patents

Abstract

The invention relates to an improved process for obtaining high-octane alkylates with the aim of using them for the production of low-lead and lead-free super-fuel. According to the invention, in a multi-section column belonging to the HF alkylation plant from the lowest column section on the 5th floor below the intermediate heater, the superfuel component is taken from the liquid flow flowing from the bed above it.

Description

For this 1 page drawing

Field of application of the invention

The invention relates to a process for obtaining particularly high-octane alkylate fractions with a strongly shortened boiling point j

and thus creates the conditions for the production of low-lead and unleaded super-fuel. I

, ι

Characteristic of the known technical solutions

It is known that the production of high-octane carburetor fuels, a number of mixing components are necessary, which contribute in different ways to comply with the standardized standards and are thus placed on the very specific requirements. Very important criteria are the octane number and the boiling behavior of the individual mixing components. So z. B. known that reformate gas is used in large quantities for fuel production, as far as the leaded varieties "Normal" and "Extra" relates.

At significantly higher octane level, as z. For example, the high-lead grade "Super" and is particularly necessary for unleaded super-fuel, the conventional reformate quality is no longer sufficient.Also the well-known sharp reforming, which has an octane increase, solves the problem because of too high a boiling point and missing easier Even the FCC gasoline known to be used for significant proportions for the production of fuel, as a "super" component by a too low octane level and too high sensitivity, has significant shortcomings that can not be eliminated even by fractionation. Furthermore, it is known that the obtained from lower olefins and preferably isobutane by acid catalysis alkylates equipped with a relatively high octane level and thus, also because of other benefits such. As nitrogen and extensive freedom from sulfur, as Vergaserkraftstoffmischkomponenten are particularly sought after, which among other things the current Weltalkylaterzeugung of about 43 million t / a sustainably underlines (Chem.Techn 35, Issue 1, [1983], pp 1-7). It is also known in this context that the alkylate is separated in modern HF alkylation in just one multi-section column by stripping of its accompanying components Kreislaufisobutan, normal butane, propane and hydrogen fluoride, but not fractionated itself (US Pat 3 502 547). It is also known that special solutions have been developed for the economic design of these separation operations and that different separation sections in the multi-section column have been materially and structurally linked to one another (US Pat. No. 3,713,615). It is to be noted as a disadvantage that the alkylate is removed in the wide boiling range of about 40 ⁰ C to about 200 ⁰ C as the bottom product of the multi-section column.

The advantage of an integrated design of the separation unit is paid for by a treatment which is insufficient for the production of supermix components. It does not succeed according to the known methods to release quality reserves, which has the alkylate, and make it usable. So it is z. B. unfavorable that the alkylate produced by known means at 200 ° C has a relatively high boiling point, which also makes the use of up to a boiling point of about 125 ⁰ C existing higher octane levels of up to 2 units compared to normal impossible.

To overcome this deficiency, one can distill the alkylate in a separate fractionation, as it is also known from older methods ago

 (Chem. Techn. 35, Issue 3 [1983] p. 117-123)

But since such a solution is technology and energy-intensive and thus expensive, the development was very soon towards integrated separation apparatus, which also includes today's conventional multi-section column. Finally, for the preparation of lighter alkylates it is also known to use propene or propene-butene mixtures as olefinic starting products for the alkylation reaction (US Pat. No. 3,787,518, Hyd. Proc. 47 [9] [1968] 245-247). In this way, although the proportion of low-boiling components in the alkylate can be significantly increased, the rising end of boiling and a decrease in the octane number are unfavorable. In addition, propane is a high-quality synthetic raw material that can be used only occasionally for the Alkylaterzeugung when it comes to reduce surpluses.

Object of the invention

The aim of the invention is an economical process for obtaining particularly hochoktaniger alkylate fractions with greatly reduced boiling point, which are to be used for the production of low-lead and unleaded premium gasoline.

Explanation of the essence of the invention

The production of low-lead and lead-free fuel grades requires the use of hydrocarbon fractions characterized by a high octane level and low boiling end, because their use provides the opportunity to incorporate even those components in these fuel mixtures, the lower octane and / or a higher, have above the standard boiling point.

As pure isoparaffine mixtures with a relatively high octane level, alkylates are principally suitable mixing components for this purpose. Disadvantage, however, affect their relatively broad boiling position of about 40 ⁰ C to about 200 ⁰ C and an associated octane loss, which can be eliminated by shortening the boiling point. The invention is therefore based on the object Entwickein, the recovery of a higher than the conventional octane level alkylate fraction with greatly reduced boiling point at a boiling ratio to 100 ⁰ C of at least 50 vol .-%, and thus the production of low-lead and lead-free Super fuel allows. The object is achieved in that first by an HF-catalyzed alkylation of butene fractions or butene-propene mixtures with isobutane at a temperature of 30-40 ⁰ C, a pressure of 1-2 MPa, a molar isobutane-olefin ratio of 10-20, an acid to hydrocarbon volume ratio of 1-2, an acid strength of 85-95 wt% titratable hydrogen fluoride, and an acid-hydrocarbon contact time of 2-10 min produces an isoparaffing mixture. This Isoparaffingemisch is then separated in a multi-section column, with propane and hydrogen fluoride in the top column, isobutane and normal butane from the stripping column, under which a laterally inserted into the column intermediate heater is withdrawn, and the alkylate is thermally stabilized in the sump section by means of a Sumpfaufheizers ,

According to the invention a Teilverdampfungsgrad between 30 and 70% is set in the bottom product, the total specific heat to be supplied to the column reduced by 20 kJ per kg column feed, wherein liquid and vapor flow ratios of 1.1 to 1.4 are realized, and from the lowest column section on the 5th floor below the intermediate heater, the liquid flow discharging from the overlying floor through its downcomer in the direction of the column sump with a mass fraction of 10% over a vertically downwards over the length of 1.5 times the ground clearance through the adjoining column internals with a gradient of 2% to the column wall outwardly guided exhaust pipe whose free cross section to the shaft cross section has an area ratio of 0.06: 1, the super fuel component is taken as the target product.

embodiment

With reference to the following examples listed in Table 1, the present invention will be explained in more detail:

Table 1

Parameter Dimension Example 1 Example 2

(old Verf.) (new Verf.)

process conditions ^m olefin (Kg / h) 9,560 '9 700 - Reactor- mic ₄ (Kg / h) 9,940 10 100 11,800 section iC ₄ : Olefin (Mol / mol) 16 16 8,000 Sre: KWS (V / v) 2.0 1.8 47 · 10 ⁶ ChF (Wt .-%) 92.3 91.9 280 Tr ( ⁰ C) 32 31 224 ^m A-normal (Kg / h) 19,500 226 mA slightly (Kg / h) - 45 1 ^m A-sch. Ver (Kg / h) - 125 process conditions Qn (KJ / h) 50- 10 ⁶ 75.9 separating q _N (KJ / kg) 300 12.0 section ts ( ⁰ C) 201 82.1 Tha ( ⁰ C) 210 96.1 Quality SA (X) 68 697 characteristic values SE ( ⁰ C) 192 of the target product ΣΤΜΡ (Wt .-%) 71.0 TMP: DMH (Mummy.) 5.2 ROZ 100 (Wt .-%) 80.6 RON 94.4 (kg / m ³ ) 703

Explanation of the parameter symbols used in Table 1

m _o i _afi "= input product throughput based on the pure olefin content

m _iC4 = input product throughput based on the pure isobutane content

iC ₄ : olefin · = molar isobutane / olefin ratio in the reactor under consideration

the circulation isobutane stream

Sre: KWS. = Acid-hydrocarbon volume ratio

C _HF = titratable hydrofluoric acid content in the acid phase

T _R = reaction temperature

m _{A. norma} i = amount of alkylate normal

rh _A. | _oak , = amount of alkylate readily produced

riiA-heavy ⁼ Generated amount of alkylate-heavy

Q _n = above the intermediate heater and bottom product heater

supplied useful heat

q _N = specific useful heat per kg total use

T _s = column bottom temperature

T _HA = initial temperature of the bottoms product booster

SA = boiling start of the target product

SE = boiling point of the target product

£ TMP = sum of trimethylpentane content contained in the target product

TMP: DMH = mass ratio of trimethylpentanes to dimethylhexanes in

target product

RON 100 = component fraction with a research octane number above

= Density of the target product

The results presented in Examples 1 and 2 were under approximately the same, i. H. obtained comparable process conditions in a large-scale HF alkylation.

Example 1 characterizes the prior art and shows the average quality achievable by the conventional method for the alkyl.

With an octane number of 94.4 and a boiling point of 68-192 ° C, the product thus obtained satisfies the requirements for a mixed component for the fuel types "normal" and "extra" to a sufficient extent.

However, only to a very limited extent can such an alkylate be used for the production of low-lead or lead-free super-fuel.

For this purpose, a clear improvement of the mentioned quality characteristics is required.

This is z. B. from the summarized in Table 3 results of extensive mixing experiments with typical VK components of a refinery even with further variation of the mixing ratios clearly visible, as it succeeded in any case, specification-compliant VK96 unleaded or VK98 with 0.15 g Pb / I, too produce, if is dispensed with the admixture of valuable aromatics.

In contrast, with the VK blending component according to the invention produced according to Example 2, specification-compliant VK96 unleaded or VK98 with 0.15 g Pb / I could be prepared in each blending test without admixing high-grade aromatics.

As the data in Table 4 show, this could be achieved even with a relatively wide variation of the mixing proportions. Thus, the solution according to the invention ensures a high degree of flexibility for the production of VK that is justifiable for changing product requirements and component availabilities.

On the quality data listed in Example 2 it becomes clear why a further increase in octane number is possible by changing the alkylate decomposition to an already high level. It is essential in addition to an increase in the content of trimethylpentanes, especially the particularly greatly increased ratio of trimethylpentanes to dimethylhexanes. Herein, the shift in the alkylate composition is expressed in favor of the higher octane components.

Decisive for the "quality advantage of the new VK component is the inventive circuit of the lowest column section, which loses the function of a stabilizing column and instead serves the separation of the heavy alkylate components and a strong enrichment of trimethylpentanes in the light alkylate cut This separation process is particularly effective in output columns of Rectification can be realized, since here mass flow ratios F / D from 1.1 to 1.6 can be set.

In contrast, in rectification column rectification columns only F / D values of <1.0 are achievable even at very high reflux ratios.

F / D values of 1.0 mean decrease in separation efficiency by reducing the liquid content of the two-phase dispersion on the mass transfer trays. In the column section 1 2 F / D values of 1.1 to 1.4 are achieved to achieve a high Leichtalkylatschnittqualität by setting different Teilverdampfungsgrade of 30 to 70 wt .-% in the bottom product. The bottom product 3 of the multi-section column is recirculated through the bottom product heater 2 to the column and part of it is discharged as heavy alkylate.

Due to the removal of low-boiling alkylate constituents taking place in the rectification zone 8 of the bottom section located between the bottom of the column and the bottom for the light alkylate section 4, the boiling point of the circulating stream 5 is concentrated so much that a significant reduction in the temperature difference between inlet and outlet of the bottom product booster 2 of FIG 9 K to 2 K is recorded. The proportion of latent heat required for the heating of the part of the circulation stream 5 which remains liquid after the partial evaporation is thereby reduced to about % and utilized for the evaporation of the low-boiling alkylate constituents from the useful heat of the bottom product boiler 2.

The changed Siedelage the circulation stream 5 further leads to the shift of the vapor-liquid equilibria of the volatile component key 2.2.4-trimethylpentane to the heavier-boiling components and to increase the mass ratio of trimethylpentanes to dimethylhexanes from 5.2: 1 to 12: 1 in the target product.

The removal of the Leichtalkylatschnittes 6 as target product takes place in the lowest column section from the liquid phase of the 4th

For reasons of convenience, the liquid product is removed from the downcomer of the bottom, discharged by means of pipe 7 of 300 mm diameter down into the rectification zone 8 and then laterally through the column wall from the column. The high temperature gradient in the rectification zone 8 of 15 to 20 K per soil in the discharge pipe 7 leads to a slight overheating of the liquid-boiling product and to a Nachstabilisierung, ie thermal cleavage of about 1 Ma .-% C ₄ hydrocarbons the light alkylate cut. By sufficient dimensioning of the perpendicular over the length of 1.5 times the ground distance guided removal pipe 7 with flow rates of <0.12 m / s, the degassing of the stabilized Leichtalkylatschnittes 6 is possible. In order to improve the degassing effect, the horizontal part of the removal pipeline 7 lying inside the column is laid with a gradient of 2%.

The removal of the Q hydrocarbons to proportions of smaller Ma.% From the unstabilized alkylate gasoline 4 leaving the liquid overflow 10 of the intermediate heater 9 takes place beforehand in the stabilization zone of the lowermost column section between the bottom 61 and the intermediate heater 9.

Table 2

Quality Data of Common VK Mixed Components and VK Mixed Component According to the Invention Reformate FCC Gasoline Conventional Invention

Alkylate

VK-blending component

ROZ clear 98.0 92.5 94.4 96.1 MOZ clear 88.1 80.2 92.5 ' 94.3 Density at 15 ⁰ C, g / cm ³ 0.802 0,750 0.706 0.696 distillation ⁰ C 5% 84 67 92 88 50% 142 101 106 99 95% 182 202 177 107 SE 199 212 204 121

t.

Table 3

Results of the VK mixing experiments with conventional alkylate (target a) VK96 unleaded

b) VK98 with 0.15 g lead per liter)

Shares of reformate 30 50 70 40 50 35 50 components conventional in% alkylate 70 50 30 40 20 15 30 FCC gasoline - - - 20 30 50 20 Quality to be achieved reference number End Product quality ROZcI. min 96.0 95.4 * 96.2 96.9 95.5 * 95.6 * 94.7 * 95.8 * MOZcI. min 86.0 91.1 90.3 89.3 88.2 86.5 84.7 * 87.7 ROZ + 0.15 GPB / l min 98.0 100.0 100.1 100 99.2 98.8 97.8 * 99.2 MOZ +0.15 g Pb / I min 88.0 96.0 94.3 92.6 91.7 89.2 87.0 * 90.9 % Boiling share up 100 ⁰ C 40-65 22 * 21 * 23 * 28 * 30 * 36 * 28 * Density at 0,740- 15 ⁰ C g / cm ³ 0,790 0,735 * 0.754 0.773 0.753 0.766 0,762 0.763

* Non-compliance with the standard values

Table 4

Results of the VK mixing experiments with VK mixed component according to the invention (objective a) VK% unleaded

b) VK98 with 0.15 g lead per liter)

components

reformate 50 40 50 50 35 Invention VK component 50 40 20 30 20

FCC gasoline - 20 30 20

Quality to be achieved

Reference number end product

quality

ROZcI. min 96.0 97.1 96.3 96.1 96.4

MOZcI. min 86.0 91.1 88.8 86.9 88.2

% Boiling shares up to

100 ⁰ C 40-65

Density at

15 ° C, g / cm ³ 0.740-0.790

ROZ + 0.15

g Pb / I min 98.0

MOZ + 0.15 g Pb / I 'min 88.0

44 45 40 41 44 0.749 0,750 0.764 0.761 0.757 101.3 100.1 99.3 100.0 98.6 95.4 92.6 89.7 91.6 88.3

Claims (1)

Invention claim: A process for obtaining a hochoktanigen Alkylatfraktion with strongly shortened boiling end at a boiling range to 100 ⁰ C of at least 50 vol .-% for the production of low-lead and unleaded super-fuel by HF-catalyzed alkylation of butene fractions or butene-sample mixtures with isobutane at a temperature 30-40 ⁰ C, a pressure of 1-2 MPa, a molar isobutane to olefin ratio of 10-20, an acid-hydrocarbon volume ratio of 1-2, an acid strength of 85-95 wt .-% titratable hydrogen fluoride and an acid-hydrocarbon contact time in the reaction zone of 2-10.min, wherein in a multi-section column, the separation of the reaction product mixture in such a way that propane and hydrogen fluoride in the top column by Isobutanstrippung aborted, circulatory isobutane and normal butane from the stripping column, under the a laterally inserted into the column intermediate heater is removed, and the alkylate in d the sump section can be thermally stabilized by means of a sump production heater, characterized in that a partial evaporation degree is set between 30 and 70% in the bottom product heater (2) and 20 kJ per kg column feed and flow ratios of liquid and liquid are added to the specific useful heat to be supplied to the column Vapor from 1.1 to 1.4 from the lowest column section on the 5th floor the liquid flow flowing from the overlying floor through the downcomer in the direction of the column bottom a mass fraction of 10% over a vertically downwards over the length of 1.5 times the ground clearance through the subsequent column internals with a gradient of 2% to the column wall outwardly guided sampling tube (7) whose free cross-section to the shaft cross section has an area ratio of 0.06: 1, the super fuel component is taken as the target product.