WO1995016740A1

WO1995016740A1 - Hydrogen fluoride composition

Info

Publication number: WO1995016740A1
Application number: PCT/US1994/008157
Authority: WO
Inventors: Kenneth J. Del Rossi; Albin Huss, Jr.; Michael E. Landis; Roland Bernard Saeger; Jeffrey C. Trewella
Original assignee: Mobil Oil Corporation
Priority date: 1993-12-16
Filing date: 1994-07-20
Publication date: 1995-06-22
Also published as: AU7367794A

Abstract

A composition comprising HF and a viscoelastic polymer having an average molecular weight of at least about 100,000 is useful in isoparaffin/olefin alkylation as a substitute for concentrated HF catalyst.

Description

HYDROGEN FLUORIDE COMPOSITION The present invention relates to a composition which contains hydrogen fluoride and which avoids many of the safety and environmental concerns associated with concentrated hydrofluoric acid but which is substantially interchangable with concentrated hydrofluoric acid in many industrial applications.

Hydrogen fluoride, or hydrofluoric acid (HF) is highly toxic and corrosive, but is useful as a catalyst in a variety of isomerization, condensation, polymerization and hydrolysis reactions. As used herein, the term

"concentrated hydrofluoric acid" refers to an essentially anhydrous liquid containing at least about 85 weight percent HF. The petroleum industry uses anhydrous hydrogen fluoride primarily as a liquid catalyst for alkylation of olefinic hydrocarbons to produce alkylate for increasing the octane number of gasoline. Years of experience in its manufacture and use have shown that HF can be handled safely, provided the hazards are recognized and precautions taken. Alkylation is a reaction which adds an alkyl group to an organic molecule. Thus an isoparaffin can be reacted with an olefin to provide an isoparaffin of higher molecular weight. The principal alkylation reaction of interest in petroleum refining reacts a C₂ to C₅ olefin with isobutane in the presence of an acidic catalyst producing a so-called alkylate. This alkylate is a valuable blending component in the manufacture of gasolines due not only to its high octane rating but also to its compatibility with octane-enhancing additives such as ethers. Given the many and varied uses for HF, it would be desirable to provide a safer HF composition which may eadily be substituted for concentrated HF in commercial applications such as isoparaffin/olefin alkylation.

Accordingly, this invention provides a composition comprising HF and a viscoelastic polymer having a molecular weight of at least about 100,000. The concentration of the viscoelastic polymer additive typically ranges from 1 to 5000 ppm, preferably from 5 to 2000 ppm, more preferably from 10 to 1500 ppm. The composition of the invention is typically characterized by extensional viscosities within the range of from 10 to 10,000 cP, preferably from 100 to 10,000 cP, and more preferably from 1000 to 10,000 cP. The composition preferably contains no added metal halide. The composition may optionally contain other components, for example, water or other solvents which are miscible with HF.

The composition of this invention is useful as an isoparaffin/olefin alkylation catalyst in accordance with the disclosures of U.S. Patents 5,196,628 to Del Rossi and Huss, and 5,202,518 to Del Rossi. The viscoelastic polymer employed in the composition of the invention is not a surfactant. As used herein, the term surfactant is intended to indicate a compound which satisfies many of the six fundamental characteristics which are generally understood to be associated with surfactants: solubility in at least one phase of a liquid system, an amphiphatic structure, the tendency to form oriented monolayers at phase interfaces, preferential equilibrium concentration at a phase interface as compared to the bulk of a solution, micelle formation, and the posession of some combination of the functional properties of surfactants, such as detergency, foaming, wetting, emulsifying, solubilizing, and dispersing. For a general discussion of surfactant properties, see 22 Kirk-Othmer Encyclopedia of Chemical Technology 332 (2nd ed. , 1969) . The viscoelastic polymer of this invention may comprise more than one monomer and may comprise a random copolymer. Block copolymers which function as surfactants are not preferred for use in the present invention, and the composition of the invention preferably excludes block copolymers.

The invention further comprises a method for rendering a liquid hydrofluoric acid composition less susceptible to forming a tenaceous vapor cloud, said method comprising adding a viscoelastic polymer to said composition in an amount sufficient to increase the extensional viscosity of said composition.

For a discussion of other additives useful for mitigating the tenacity of HF vapor clouds, see U.S. Patent 4,938,935 to Audeh et al.

The invention still further comprises a process for alkylating an isoparaffin with an olefin comprising contacting said isoparaffin and said olefin in the presence of the composition of the invention to produce alkylate. Solvents

The composition of this invention comprises HF and a viscoelastic polymer having a molecular weight of at least about 100,000. The composition may optionally comprise a solvent which is not deleterious to the viscoelastic behavior of the mixture. Solvents which may be added to the mixture of HF and viscoelastic polymer in accordance with the invention include, but are not limited to, those solvents characterized by a Donor Number of less than about 40.

The term "donicity" describes the propensity of a solvent to donate electron pairs to acceptor solutes. The term "Donor Number" (DN) as used herein is a measure of donicity, and is defined as the negative of the enthalpy change, measured in Kcal-mol^"1, for the reaction of the solvent with SbCl₅ to form a 1:1 adduct, where both reactants are in dilute solution in 1,2-dichloroethane (DCE) . For a discussion of donicity and Donor Numbers, see Y. Marcus, "The Effectivity of Solvents as Electron Pair Donors", 13 Journal of Solution Chemistry 599 (1984) . Table 1 below reports donor numbers listed in the Marcus article for various solvents. Solvents useful in the present invention include nitroalkanes, carbonates, perhalogenated alkaneε, halogenated alcohols, sulfonic acids, sulfones, acetyl halides, benzoyl halides, phosphorous oxychloride, alkyl sulfites, anhydrides, esters, and sulfuryl halides. Non- limiting examples of these additives include nitromethane, 1-nitropropane, propylene carbonate, perfluorodecalin, 2,2,2-trifluoroethanol, methanesulfonic acid, a low donicity solvent, acetyl chloride, benzoyl fluoride, methyl propionate, sulfuryl chloride, and sulfuryl chloride fluoride.

Table 1

Solvent DN Solvent DN

1,2-dichloroethane (0) Methyl-t-butylketone 17.0

Acetyl Chloride 0.7 Diethyl Ether 19.2

Benzoyl Chloride 2.3 Tetrahydrofuran 20.0

Sulfuryl Chloride 0.1 Triethylamine 30.5

Thionyl Chloride 0.4 Pyridine 33.1

Selenoyl Chloride 12.2 Acetonitrile 14.1

Phosphoryl Chloride 11.7 Propanonitrile 16.1

Tetrachloroethylene Butanonitrile 16.6

Carbonate 0.8 Isobutanonitrile 15.4

Dichloroethylene Benzyl Cyanide 15.1

Carbonate 2.7 Benzonitrile 11.9

Nitromethane 2.7 N,N-DimethyIformamide 26.6

Nitrobenzene 4.4 N,N-Diethylformamide 30.9

Acetic Anhydride 10.5 N,N-Dimethylacetamide 27.8

Methyl Acetate 16.4 N,N-Diethylacetamide 32.2

Ethyl Acetate 17.1 Tetramethyl Urea 29.6

2-Propyl Acetate 17.5 Hexamethyl Phosphoric

Ethyl Propanoate 17.1 Triamide 38.8

Ethyl Butanoate 16.8 Ethylene Sulfite 15.3

Ethyl Isobutanoate 16.4 Dimethylsulfoxide 29.8

Ethyl t-Pentanoate 12.9 Tetramethylene Sulfone 14.8

Diethylcarbonate 16.0 Phenyldifluorophosphine

Ethylene Carbonate 16.4 Oxide 16.4

1,2-Propylene Phenyldichlorophosphine

Carbonate 15.1 Oxide 18.5

Acetone 17.0 Diphenylchlorophosphine

Oxide 22.4

2-Butanone 17.4 Methylisopropyl-ketone 17.1

Trimethyl Phosphate 23.0 Tri-n-butyl Phosphate 23.7 Viscoelastic Polymer

The viscoelastic polymers useful in the invention generally range in molecular weight from 10⁵ to 3xl0⁷, preferably from 10⁶ to 3xl0⁷, and more preferably from 10⁷ to 3xl0⁷. The viscoelastic polymers may comprise one or more monomers. Random copolymers are useful in the invention, and while some block copolymers are useful, block copolymers which function as surfactants are not preferred for the present invention. Thus the viscoelastic polymers of the invention preferably exclude block copolymers.

Viscoelastic polymers useful in this invention include polymers having the following structures:

wherein X and Z are selected from H, alkyl groups, alkenyl groups, halogens, substituted and unsubstituted phenyl groups, CONH₂, CONHR, CONR'R, COOR, and C≡N; wherein Y is selected from O, NR, and NX; wherein R and R' are selected from hydrogen and alkyl groups.

Examples of useful viscoelastic polymer additives are disclosed in the following U.S. Patents.

U.S. Patent 4,089,804 to Falk discloses alkeneoxyalkenes and alkyleneiminoalkenes of 2 to 12 carbon atoms at column 1, line 64, through column 2 at line 10.

U.S. Patent 4,257,903 to Kucera et al. discloses useful viscoelastic polymers at column 1, line 61, through column 2, line 24.

U.S. Patent 4,363,886 to Lipowski et al. discloses monomers which can be polymerized by convention means to produce polyacrylamides usefulin the present invention. See column 3, lines 4-64.

U.S. Patent 4,505,828 and 4,552,670 to Lipowski et al. similarly disclose monomers which can be polymerized by known methods to produce polyacrylamides useful in the present invention.

U.S. Patent 4,599,372 to Bardoliwalla et al. discloses useful viscoelastic polymers at column 5, line 33 through column 6 at line 29. U.S. Patent 4,646,834 to Bannister discloses useful viscoelastic polymers at column 2, lines 3-38.

U.S. Patent 4,796,703 to Gabel et al. discloses polymeric flocculating agents (which include viscoelastic polymers useful in the present invention) at column 2, lines 15-63.

U.S. Patent 4,847,342 to Peiffer discloses polyacrylamide polymers at column 3, lines 10-26, and at column 4, lines 3-59.

U.S. Patent 4,913,585 to Thompson et al. discloses useful polyacrylamide polymers at column 3, line 57, through column 4 at line 34.

U.S. Patent 5,071,934 to Peiffer discloses useful viscoelastic polymers at column 2, lines 52-69. U.S. Patent 5,132,284 to Tsai discloses useful viscoelastic polymers at column 1, line 66, through column 3, line 56.

U.S. Patent 5,132,285 to Tsai discloses useful viscoelastic polymers at column 1, line 67, through column 3, line 56. Feedstocks Feedstocks useful in the alkylation process of the invention include at least one isoparaffin and at least one olefin. The isoparaffin reactant used in the present alkylation process has from 4 to 8 carbon atoms. Representative examples of such isoparaffins include isobutane, isopentane, 3-methylhexane, 2-methylhexane, 2,3- dimethylbutane and 2,4-dimethylhexane. The olefin component of the feedstock includes at least one olefin having from 2 to 12 carbon atoms. Representative examples of such olefins include butene-2, isobutylene, butene-1, propylene, ethylene, hexene, octene, and heptene. The preferred olefins include the C. olefins, for example, butene-1, butene-2, isobutylene, or a mixture of one or more of these C. olefins, with butene-2 being the most preferred. Suitable feedstocks for the process of the present invention are described in U.S. Patent 3,862,258 to Huang et al. at column 3, lines 44-56.

The molar ratio of isoparaffin to olefin is generally from 1:1 to 100:1, preferably from 1:1 to 50:1, and more preferably from 5:1 to 20:1. Process Conditions The composition of the present invention may be readily substituted for the concentrated hydrofluoric acid catalyst in an existing hydrofluoric acid alkylation process unit, for example, a riser reactor alkylation process unit, without substantial equipment modifications. Accordingly, the conversion conditions for the process of the present invention resemble those of typical commercial hydrofluoric acid alkylation processes.

The present alkylation process is suitably conducted at temperatures of from -18 to 66°C (0 to 150°F) , preferably from 10 to 66°C (50 to 150°F) , and more preferably from 21 to 43°C (70 to 110°F). Pressure is maintained to ensure a liquid phase in the alkylation reaction zone and typically ranges from 240 to 8375 kPa (20 to 1200 psig) , preferably from 445 to 3550 (50 to 500 psig) . The reaction zone is preferably free from added hydrogen. Olefin feed rates generally range from 0.01 to 50 HSV and more preferably from 0.5 to 20 HSV. The mixed isoparaffin-olefin reactants may be contacted with the catalyst composition of the invention in any suitable reaction vessel, examples of which include stirred-tank reactors as well as riser-type reactors. Contact time for the mixed isoparaffin-olefin feed and the catalyst composition of the invention typically are within the range of from 0.1 second to 50 seconds, and are preferably from 8 seconds to 25 seconds. The relative amounts of catalyst and reactants are defined herein by the acid-to-oil ratio. The volumetric acid-to-oil ratio (as used herein) is the ratio of the sum of the volumes of ASO (acid soluble oil) , acid, a suitable solvent (if present) , and the viscoelastic polymer to the total isoparaffin and olefin reactor feed. The volumetric acid-to-oil ratio typically falls within the range of 0.1:1 to 10:1, preferably from 0.1:1 to 5:1.

The viscoelastic polymer may be added by injection directly into the alkylation process unit, or may be mixed with the hydrocarbon charge, or may be mixed with the fresh and/or the circulating acid catalyst component, or with a stream of mixed acid/additive catalyst. Downstream from the alkylation reaction zone, the viscoelastic polymer may be separated from the alkylate product stream, mixed with fresh and/or circulating acid and/or circulating acid/additive catalyst mixture, and recycled to the alkylation reaction zone. Alternatively, the viscoelastic polymer may be used in a concentration which is sufficiently low (i.e. -50 ppm) to eliminate the economic incentive for recovering and recycling the viscoelastic polymer.

The invention will now be more particularly described with reference to accompanying drawings, in which:

Figure 1 is a simplified schematic diagram showing a ductless siphon apparatus useful for measuring the viscoelasticity (expressed in terms of extensional viscosity, μ_e) for catalysts of the present invention.

Figure 2 is a plot of ductless siphon height (the y-axis, mm) as a function of ionic strength (the x-axis, mol/£) for the solutions of Examples 1-7.

Figure 3 is a plot of ductless siphon height (the y-axis, mm) as a function of polymer concentration (the x- axis, ppm) for the solutions of Examples 8-11.

Figure 4 is a plot of ductless siphon height (the y-axis, mm) as a function of polyacrylamide additive molecular weight for the solutions of Example 12. Examples 1-7

Referring now to Figures 1 and 2, the ductless siphon as schematically illustrated provides a direct measurement of polymer/solvent system's viscoelastisity. See, e.g., G. Astarita, et al., "Extensional Flow Behaviour of Polymer Solutions" 1 Chem. Eng. J. 57 (1970) . In this apparatus, an applied pressure to the free surface of the polymer/solvent in a reservoir 11 generates a free-standing column of fluid 12 when a nozzle 13 is withdrawn from the polymer/solvent. The height, h, of the fluid column (or siphon) at snap-off, when column self-weight balances the elastic forces generated within the fluid, measures the polymer/solvent system's anti-misting tendencies. See, e.g., K.K. Chao, et al. "Antimisting Action of Polymeric Additives in Jet Fuels", 30 AIChE J. Ill (1984). Thus the siphon height, h, measured when polymer is added to the HF/sulfolane or HF/solvent mixture indicates the degree of potential rainout-improvement. For a given flowrate, Q, and a given nozzle diameter, (and thus a given upward fluid velocity v_x) the siphon breakage height, h, is proportional to (M_e/M_s)^*5, where μ_e is extensional viscosity and μ_s is the shear viscosity.

Examples 1 and 2 examined the behavior of polyethylene oxide (5,000,000 mw) in aqueous HC1 at polymer concentrations of 1000 ppm (Example 1) and 100 ppm (Example 2) as a function of ionic strength in solution. The effectiveness of the polyethylene oxide (PEO) additive decreased with increasing ionic strength.

Example 3 examined the behavior of polyethylene oxide (5,000,000 mw) in NaCl at polymer concentration of 100 ppm as a function of ionic strength in solution. The effectiveness of the polyethylene oxide (PEO) additive decreased with increasing ionic strength.

Examples 4 and 5 examined the behavior of polyacrylamide (5,000,000 mw) in aqueous HC1 at polymer concentrations of 1000 ppm (Example 4) and 100 ppm (Example 5) as a function of ionic strength in solution. The effectiveness of the polyacrylamide (PAM) additive surprisingly increased with increasing ionic strength in solution. Example 6 examined the behavior of polyacrylamide

(PAM) (5,000,000 mw) in NaCl at polymer concentration of 100 ppm as a function of ionic strength in solution. The effectiveness of the polyethylene oxide (PEO) additive surprisingly increased with increasing ionic strength. Example 7 examined the behavior of polyethylene oxide (5,000,000 mw) in a solution of HF and sulfolane (49/49/2 wt/wt/wt HF/sulfolane/PEO) . The effectiveness of the polyethylene oxide (PEO) additive decreased with increasing ionic strength. Examples 8-11

Referring now to Figure 3, Examples 8-11 demonstrate the effect of polymer concentration (x-axis, ppm) on ductless siphon height (y-axiε, mm) . Increasing polymer concentration improved ductless siphon height for solutions of PEO or PAM (5,000,000 m.w.) with water or aqueous (9.2 M) HC1. Example 12

Figure 4 (Example 12) shows the effect of polyacrylamide (PAM) polymer molecular weight (x-axis) on ductless siphon height (y-axis, mm) . Higher molecular weight viscoelastic additives are preferred for use in accordance with the present invention. Examples 13-25

Examples 13-25 show the ductless siphon heights for HF/sulfolane/water mixtures. Examples 13-16 show the ductless siphon heights for HF/sulfolane/water mixtures with the addition of PEO, while Examples 17-25 show the ductless siphon heights for HF/sulfolane/water mixtures with the addition of PAM.

Table 2

Ductless Siphon Heights

Example Solvent Polymer Polymer siphon No. cone. , height, mm ppm

13 water PEO 100 12

14 water PEO 500 17

15 water PEO 1000 25

16 HF/sulfolane/ PEO 1000 1-2 water 49/49/2 (weight)

17 HF/sulfolane/ Nalco 100 5 water 9905 49/49/2 (weight)

18 HF/sulfolane/ Nalco 100 3 water 9905 69/29/2 (weight)

19 HF/sulfolane/ Nalco 1000 15 water 9905 69/29/2 (weight)

20 HF/sulfolane/ Nalco 1000 23 water 9905 84/14/2 (weight) Example Solvent Polymer Polymer siphon

No. cone. , height, mm ppm

21 HF/sulfolane/ Magnafloc 100 7 water 905N 69/29/2 (weight)

22 HF/sulfolane/ Magnafloc 1000 15 water 905N

69/29/2

(weight)

23 HF/sulfolane/ Magnafloc 100 2 water 496C

69/29/2

(weight)

24 HF/sulfolane/ Magnafloc 1000 16 water 496C

69/29/2

(weight)

25 HF/sulfolane/ Magnafloc 100 27 water 866A

69/29/2

(weight) Table 3 Polymer Properties

Polymer Description Supplier Molecular

Weight, millions

PEO polyethylene Aldrich 3-5 oxide

Nalco 9905 cationic Nalco >1 polyacrylamide

Magnofloc 866A anionic American 16-19 polyacrylamide Cyanimid

Magnafloc 905N nonionic American 14-17 polyacrylamide Cyanimid

Magnafloc 496C cationic American 3-5 polyacrylamide Cyanimid

Claims

Claims :

1. A composition comprising HF and a viscoelastic polymer having an average molecular weight of at least 100,000.

2. A composition as claimed in claim 1 including 1 to 5000 ppm of said viscoelastic polymer.

3. A composition as claimed in claim 1 including 10 to 1500 ppm of said viscoelastic polymer.

4. A composition as claimed in any preceding claim wherein said viscoelastic polymer has a structure selected from:

wherein X and Z are selected from the group consisting of H, alkyl groups, alkenyl groups, Br, Cl, I, F, substituted and unsubstituted phenyl groups, C0NH₂, CONHR, CONR'R, COOR, and C≡N; wherein Y is selected from the group consisting of O, NR, and NX; wherein R and R' are the same or different, and are selected from the group consisting of hydrogen and alkyl groups.

5. A composition as claimed in claim 4 wherein said viscoelastic polymer has the structure

6. A composition as claimed in claim 4 or claim 5 wherein X is CONH₂.

7. A composition as claimed in any one of claims 4 to 6 wherein n is at least about 10,000.

8. A composition as claimed in any preceding claim wherein said viscoelastic polymer has a molecular weight of at least about 10⁶.

9. A composition as claimed in claim 8 wherein said viscoelastic polymer has a molecular weight of from 10⁷ to 3xl0⁷.

10. A composition as claimed in any preceding claim further comprising a solvent having a Donor Number of less than about 40.

11. A composition as claimed in any preceding claim further comprising sulfolane.

12. A method for rendering a liquid hydrofluoric acid composition less susceptible to forming a tenaceous vapor cloud, said method comprising adding to said composition a viscoelastic polymer having an average molecular weight of at least 100,000 in an amount sufficient to increase the extensional viscosity of said composition.

13. A process for alkylating an isoparaffin with an olefin comprising reacting said isoparaffin with said olefin in the presence of an alkylation catalyst comprising HF and a viscoelastic polymer having an average molecular weight of at least about 100,000 wherein said viscoelastic polymer is present in an amount sufficient to enhance the extensional viscosity of the composition.