DE69804783T2 - METHOD FOR PRODUCING ALLYL HALIDES AND DEVICE USED THEREFOR - Google Patents

Description

The invention relates to a process for producing allyl halide (allyl halides) and to a reactor which can be suitably used in such a process. In particular, the invention relates to the production of allyl halide by chlorinating propene at high temperature in the gaseous phase.

Allyl halides, and in particular allyl chloride, are important intermediates for the production of epihalohydrin and in particular epichlorohydrin, which in turn has been a key chemical for the production of epoxy resins.

US Patent Application No. 5,504,266 describes a two-step process for producing allyl halide, comprising:

(a) introducing propene and halogen in a molar ratio of at least 2.5:1, and suitably less than 5:1, into a continuously stirred tank reactor;

(b) allowing propene and halogen to partially react in the continuously stirred tank reactor at a temperature in the range of 400 to 525ºC for partial conversion;

(c) feeding effluent from the continuously stirred tank reactor into a Tubular reactor, where the reaction continues in ideal flow at a temperature in the range of 400 to 525ºC; and

(d) Removing the reaction product from the tubular reactor.

The continuously stirred tank reactor has the shape of a sphere, an oval or an egg.

US Patent Application No. 5,367,105 describes a process for producing allyl halide comprising: feeding substantially parallel streams of gaseous propene and gaseous chlorine in a molar ratio of 3:1 to 5:1 into a reactor, and removing the reaction product from the reactor.

The reactor used in the process described above has a cylindrical housing with a conical upper section and an inverted conical lower section, with the reactants being injected into the conical upper section.

It has been found that the known processes have disadvantages in that they either give a relatively low yield or that a considerable amount of by-products are formed which cause putrefaction. In addition, the volume expansion of the known processes has proven difficult.

As allyl halides become increasingly valuable, there is an incentive to improve yields and reduce the generation of by-products.

As a result of intensive research, an improved process has been found which suffers less from the disadvantages of the known processes.

Accordingly, the process for producing allyl halide from gaseous propene and a gaseous halogen according to the present invention comprises:

(a) feeding propene into a tubular ring line reactor through an inlet nozzle;

(b) feeding gaseous halogen into the loop reactor through a plurality of axially spaced groups of radially placed inlet openings arranged in the wall of the tubular loop reactor;

(c) allowing the reaction of propene and halogen;

(d) removing reaction medium from the tubular loop reactor through an outlet port, wherein the concentration of halogen in any reactor volume element is maintained below 3% by mass, based on the total gas mixture, and wherein the linear gas velocity of the propene in the inlet nozzle is at least sufficient to maintain uninterrupted circulation in the tubular loop reactor.

The halide concentration in the gaseous reaction mixture in each reactor volume element is preferably kept in the range of 0.5 to 1.5% w/w.

In the description and in the claims, the term "reactor volume element" is used to mean an element defined by the inner surface of the reactor and two axially spaced planes perpendicular to the direction of fluid flow through the reactor, the element having a small thickness compared to the inner diameter of the reactor.

The halogenation reaction is exothermic and an advantage of the process of the present invention is that the continuous circulation provides a uniform temperature distribution throughout the reactor. In addition, the recirculation rate can be regulated to improve temperature control.

A preferred embodiment of the method of the present invention further comprises:

(e) feeding the reaction medium removed in step (d) into the inlet end of a tubular reactor;

(f) feeding gaseous halogen into the tubular reactor through a plurality of axially spaced groups of radially placed inlet openings arranged in the wall of the tubular reactor and allowing the reaction of halogen and propene; and

(g) Discharge the reaction product from the outlet end of the tubular reactor.

Preferably the halogen gas is chlorine gas.

The invention further relates to a reactor, comprising a reactor with at least one inlet nozzle, several axially spaced groups of radially arranged inlet openings arranged in the wall of the tubular ring line reactor, and an outlet opening.

The invention will now be described in more detail using an embodiment with reference to the accompanying drawings. In the drawings:

Fig. 1a, 1b and 1c schematically show three extended sections of reactor examples which can be suitably used in the process according to the invention;

Fig. 2 shows schematically a longitudinal section of an improved embodiment of the reactor; and

Fig. 3 shows schematically a longitudinal section of a part of the tubular ring line reactor on a larger scale than in Fig. 1a to 1c.

Reference is now made to Figs. 1a to 1c. The reactor 1 comprises a tubular ring line reactor 2.

The tubular ring line reactor 2 may have an elongated shape (as shown in Fig. 1a), a circular shape (as shown in Fig. 1b) or an elliptical shape (as shown in Fig. 1c).

The tubular ring reactor 2 has at least one inlet nozzle 3 and a plurality of inlet openings 4 arranged in the wall 5 of the tubular ring reactor 2. The inlet openings 4 are arranged in a plurality of axially spaced groups 6, and in each group the inlet openings are placed radially, i.e. distributed along the circumference of the tubular ring reactor 2. For reasons of clarity, not all inlet nozzles and not all groups are provided with reference numerals.

The tubular ring reactor is further provided with an outlet opening 9 arranged near the inlet nozzle 3. Suitably, the outlet opening 9 is located at the downstream end of the tubular ring reactor 2, downstream of the inlet nozzle 3.

During normal operation, propene is introduced into the tubular ring reactor 2 through the inlet nozzle 3 and gaseous halogen is introduced into the tubular ring reactor 2 through the plurality of inlet openings 4. The reaction mixture is passed through the tubular ring reactor 2 in the direction of the arrows 12. Reaction medium is discharged from the tubular ring reactor 2 through the outlet opening 9 and from there the reaction medium is fed to a reactor (not shown) for isolating the desired allyl halide by methods known per se. recovery plant. The rest of the reaction medium circulates through the tubular ring line reactor 2. The recycle ratio (R) is defined as the mass ratio of the recirculated amount of reaction mixture to the amount of propene injected through the injection nozzle 3.

The conditions are selected so that the halide concentration in a reactor volume element 13 is kept below 3 mass/%, based on the total gas mixture, and the linear gas velocity of the propene leaving the inlet nozzle 3 is at least sufficient to maintain a continuous circulation within the tubular ring line reactor 2.

The linear gas velocity (UPropen) of the propene leaving the inlet nozzle(s) must be sufficient to

(a) to achieve an average velocity (Uloop) in each cross-section of the tubular ring reactor above 20 m/s, preferably 40 m/s; and

b) to achieve a recycle ratio (R) which ensures the minimum temperature in the ring line reactor above 400ºC, preferably above 430ºC. The maximum temperature in the ring line reactor must below 520ºC, preferably below 500ºC.

Suitable values for the recycle ratio (R) are greater than 2 and preferably more than 3.

The Applicant had found that with such a selection of conditions, allyl halide, and preferably allyl chloride, can be produced with good selective efficiency. Due to the significant reduction of by-products, and in particular 1,5-hexadiene, which is the main precursor for heavy chloroethers in the medium, the allyl chloride obtained is less colored.

The number of groups 6 of inlet openings 4 is suitably in the range from 2 to 15, and preferably from 6 to 12, and the number of inlet openings 4 per group is in the range from 2 to 8.

The number of radially placed halide inlet openings per group in a cross-section is normally in the range from 2 to 15, and preferably from 4 to 12.

Preferably, more than one injection nozzle 3 is used, which are axially spaced along the tubular ring line reactor 2. To determine the recycle ratio, the total amount of propene is taken from all injection nozzles.

Reference is now made to Fig. 2. The reactor 1 shown in this figure further comprises a tubular reactor 15 having an inlet end 17 which is in fluid communication with the outlet opening 9 of the tubular ring line reactor.

The tubular reactor 15 is provided with several axially spaced groups 19 of radially placed inlet openings 20, which are located in the wall 21 of the tubular reactor 15.

The tubular reactor 15 has an outlet end 25 for discharging the reaction product from the reactor 1.

During normal operation, the reaction medium removed from the outlet line 9 is fed into the inlet end 17 of the tubular reactor 15, gaseous halogen is fed into the tubular reactor 15 through the axially spaced groups 19 of radially placed inlet openings 20 located in the wall of the tubular reactor. The halogen is allowed to react with unreacted propene and the reaction product is discharged from the outlet end 25 of the tubular reactor 15, and from there the reaction product is fed to a recovery plant (not shown) to separate the desired allyl halide by methods known per se.

Referring now to Fig. 3, the inlet nozzle used in this embodiment is an ejector 30 and a portion of the propene charge can be supplied through the auxiliary inlet 35 so that the recycle ratio can be reduced by controlling the amounts of propene supplied through the ejector 30 and through the auxiliary inlet 35. As shown in Fig. 3, the rear part of the ejector 30 is tapered and the half top angle 37 is about 2°. Furthermore, the end of the ejector 30 is supported by support rods 40, of which there are preferably three.

If, according to a preferred embodiment of the process according to the invention, a combination of a ring reactor and a tubular reactor connected thereto is used, the molar ratio of the halogen fed into the tubular ring reactor is relative to the total amount of halogen fed into both the tubular ring reactor and the tubular reactor, in the range of 60 to 100%, and preferably 70 to 90%.

The inlet temperature of the halogen charge, and preferably of the chlorine charge, is in the range from 50 to 150ºC, and preferably from 60 to 110ºC, and more preferably from 80 to 110ºC, while the temperature of the halogen introduced through each respective inlet may be the same or different.

Preferably, the temperature of the halogen, and preferably of the chlorine gas fed into the tubular ring reactor, will be approximately the same, and the temperature of the halogen gas fed into the optional tubular reactor can also be kept at the same value, although the corresponding temperatures of the halogen fed into the ring reactor on the one hand and the halogen fed into the optional tubular reactor on the other hand can be different. The propene fed will have a temperature in the range of 200 to 400°C, and preferably of 230 to 360°C. Other reaction temperatures can be used in other cross sections of the ring reactor or the optional tubular reactor, and in particular different temperature zones can prevail in the tubular reactor sections.

Typically, the residence time (τloop) in the loop reactor is on average 0.5 s to 3 s, and the residence time in the tube reactor (τpipe) is 0.2 s to 1 s.

In general, the inner diameter (in m) of the tubular ring reactor is determined by the following equation: Dloop = A·(R/τloop )·(U2Propene/U3loop)·d2, where A is an empirical, depending on the surface property of the reactor material (-); R is the recycle ratio (-); τloop is the residence time in the ring reactor (in s); UPropen is the linear velocity of the propene leaving the nozzle (in m/s); Uloop is the linear velocity in the tubular ring reactor (in m/s); and d is the inner diameter of the propene nozzle (in m).

Under practical conditions, A will have a value in the range from 20 to 40, and preferably from 25 to 35.

The number of groups of inlet openings along the tubular ring reactor is selected according to the critical concentration requirement mentioned above. Preferably, the groups are distributed at equal distances from each other along the tubular ring reactor.

The inner diameter of the tubular reactor is selected so that the linear velocity in the tubular reactor is between 20 and 80 m/s. The number of groups of inlet openings and their positions are determined in the same way as for the tubular ring line reactor.

According to a preferred embodiment in which a combination of ring line reactor and tube reactor is used, the volume of the ring line reactor is relatively large compared to the volume of the tube reactor.

It should be noted that the invention also relates to a specific reactor arrangement in which the method specified above is carried out.

It should be noted that preferably this tubular reactor is formed by a straight pipe connected to the ring line reactor via the outlet opening, but other alternatives can also be used, wherein the straight tubular reactor is connected to the ring line reactor via one or more bent pipe parts.

Preferably, the ratio of the inner diameter of the ring line reactor and the inner diameter of the tubular reactor is in the range of 4:1 to 3:2, and the volume ratio of the tubular ring line reactor, relative to the volume of the tubular reactor, is in the range of 6 to 9.

In a reactor arrangement - as described in Fig. 2 - the ratio of the outer maximum length of the ring reactor relative to the diameter of the tube forming the ring reactor is in the range of 30 to 50, while the ratio of the outer width of the tubular ring reactor relative to the diameter is in the range of 3 to 5.

A more preferred ratio of the outer maximum length of the tubular ring line reactor relative to the inner diameter of the ring line reactor is in the range of 35 to 45.

The invention is further explained by the following example, but without restricting its scope to this embodiment.

example 1

In a reactor as shown in Fig. 2, propene was converted with chlorine under the following conditions:

Propene preheated (ºC): 340

Chlorine preheated (ºC): 70

Propene/chlorine molar ratio: 4.2

Reactor outlet temperature (ºC): 505

Propene batch quantity (kg/h): 6300

Chlorine batch quantity (kg/h): 2536

Reaction pressure (bara): 3.2

Residence time in the ring line reactor, τloop(s): 1.8

Residence time in the tubular reactor, τloop(s): 0.2

Linear velocity of the propene ejector, UPropen(m/s): 355

Gas velocity in the ring line reactor, Uloop(m/s): 40

Inner diameter of the ring line reactor, Dloop(m): 0.3

Inner diameter of the tube reactor, Dpipe(m): 0.15

Diameter of the propene ejector, d (m): 0.055

Number of chlorine inlet groups in the ring line reactor: 7

Number of chlorine inlet groups in the tubular reactor: 3

Recycle ratio: 3

Yield based on propene moles converted (mol%):

Allyl chloride: 89.37

2-Chloropropene: 2.81

1,2-Dichloropropane: 1.38

Cis-1,3-dichloropropene: 1.95

Trans-1,3-dichloropropene: 1.76

Other: 2.73

Claims (14)

1. A process for producing allyl halide from gaseous propene and a gaseous halogen, the process comprising: (a) feeding propene into a tubular ring line reactor through an inlet nozzle; (b) feeding gaseous halogen into the loop reactor through a plurality of axially spaced groups of radially placed inlet openings arranged in the wall of the tubular loop reactor; (c) allowing the reaction of propene and halogen; (d) removing reaction medium from the tubular ring reactor through an outlet port, wherein the concentration of halogen in any reactor volume element is maintained below 3% by mass based on the total gas mixture, and wherein the linear gas velocity of the propene in the inlet nozzle is at least sufficient to produce a to maintain uninterrupted circulation in the tubular ring line reactor. 2. The process of claim 1, wherein the reaction medium is discharged from the tubular ring line reactor through an outlet opening located near the inlet nozzle. 3. A process according to claim 1 or 2, wherein the reaction in step (c) is carried out at a temperature in the range of 430 to 520°C. 4. A process according to claim 1 to 3, wherein the halogen concentration in the gaseous reaction mixture in each reactor volume element is maintained in a range of 0.5 to 1.5% by mass. 5. A process according to claims 1 to 4, wherein the inlet temperature of the halogen feed is in the range of 80 to 110°C. 6. The method according to any one of claims 1 to 5, further comprising: (e) feeding the reaction medium removed in step (d) into the inlet end of a tubular reactor; (f) feeding gaseous halogen into the tubular reactor through a plurality of axially spaced groups of radially placed inlet openings formed in the wall of the tubular reactor and allowing the reaction of halogen and propene; and (g) Discharge the reaction product from the outlet end of the tubular reactor. 7. Process according to claims 1 to 6, wherein the propene feed has a temperature in the range of 200 to 400°C. 8. Process according to one of claims 1 to 7, wherein the residence time in the ring line reactor (τloop) is in the range from 0.5 to 3 s. 9. Process according to one of claims 6 to 8, wherein the residence time in the tubular reactor (τpipe) is in the range of 0.2 s to 1 s. 10. A process according to any one of claims 1 to 9, wherein the halogen is chlorine. 11. A reactor comprising a tubular ring reactor equipped with at least one inlet nozzle, a plurality of axially spaced groups of radially placed inlet openings arranged in the wall of the tubular ring reactor, and an outlet opening. 12. Reactor according to claim 11, wherein the number of groups is in the range of 2 to 15, and preferably from 6 to 12. 13. A reactor according to claim 11 or 12, further comprising: an open-ended tubular reactor having an inlet end in fluid communication with the outlet port. 14. Reactor according to claim 13, wherein the ratio of the inner diameter of the ring line reactor and the inner diameter of the tubular reactor is in the range of 4:1 to 3:2, and the ratio of the volume of the tubular ring line reactor, relative to the volume of the tubular reactor, is in the range of 6 to 9.