CN1299801A

CN1299801A - Multiple-section water circulation resin process of preparing para-butanol

Info

Publication number: CN1299801A
Application number: CN 99122620
Authority: CN
Inventors: 孙业茂
Original assignee: Yang Binming
Current assignee: Yang Binming
Priority date: 1999-12-13
Filing date: 1999-12-13
Publication date: 2001-06-20
Anticipated expiration: 2019-12-13
Also published as: CN1101799C

Abstract

The present invention is characterized by using normal butylene as raw material and using strong acid type ion exchange resin as catalyst, and placing said catalyst in a multi-stage reactor. The n-butylene can be passed through all the reaction stages from first reaction stage, the circulating water can be respectively fed into every reaction stage, and the product of every reaction stage is passed through gas-liquid separator to make gas-liquid separation, and the discharged liquids of all the reaction stages are collected, and fed into distillation tower to make product undergo the processes of dewatering and purification to obtain the invented refined sec-butyl alcohol.

Description

Process for preparing sec-butyl alcohol by multi-stage water circulation resin method

The invention belongs to the technical field of sec-butyl alcohol preparation by a resin method, and particularly relates to a process for preparing sec-butyl alcohol by a multi-stage water circulation resin method.

Sec-butanol (second butanol, C-C-COH-C) is mainly used for producing methyl ethyl ketone, and other purposes are few. Nowadays, the production of sec-butanol in the world is mainly the sulfation method started decades ago, and due to the important defects of equipment corrosion, concentration and recovery of dilute sulfuric acid, high production cost and the like, people are always seeking a production method without sulfuric acid for many years, but the development is not fast, and only until the eighties of the twentieth century, the heteropoly acid method (Japan) and the resin method (Germany) in which n-butene is directly hydrated are put into industrial application.

The direct hydration reaction formula of n-butene is as follows:

the commercial process for producing sec-butyl alcohol by German resin method uses strong acid type ion exchange resin as catalyst, and fixed bed reaction, and its main characteristics are that the water consumption is small (close to theoretical quantity), and the reaction product is circularly carried out in the reaction system by using a large quantity of excess hydrocarbon (n-butene material, about ten times of theoretical quantity) (so it can be called "hydrocarbon circulating resin method"). The reaction of the method is strongly influenced by chemical equilibrium, high-concentration n-butene material which is more than or equal to 92 percent needs to be used, or the conversion rate is too low. The largest n-butene resource is petroleum refinery, but the high-concentration n-butene can notbe directly produced by oil refining process, and can be obtained only by using special processing method such as extractive distillation, which increases the trouble of providing qualified methyl ethyl ketone raw material for oil refiners and increases the cost of n-butene material. In the reaction of the method, di-sec-butyl ether is generated, the separation of the di-sec-butyl ether from sec-butyl alcohol is difficult, the number of equipment is increased, and the flow is increased.

The invention aims to provide a process for preparing sec-butyl alcohol by a multi-stage water circulation resin method, which has the advantages of simple process, wide raw material source, high n-butyl conversion rate, no generation of di-sec-butyl ether and low cost.

The technical solution of the present invention can be implemented as follows:

the invention divides a large reactor into a plurality of independent small reaction sections (reactors) to be used in series, n-butene material enters (can enter at multiple points) from the upper part of the front first reaction section and passes through each reaction section sequentially, tail hydrocarbon is discharged from the last reaction section, each section enters fresh deionized water according to the specified water space velocity, and water produced by each reaction section is directly received (does not enter the next reaction section) and is converged to carry out product separation and purification; the invention is characterized in that: n-butene is used as raw material, a strong acid type ion exchange resin is used as catalyst, and the catalyst is loaded into a multi-stage reactor for reactionEach reaction section of the reactor forms an independent reaction unit; the n-butene enters from the first reaction section and sequentially passes through the reaction sections; circulating water enters each reaction section through a shunt circuit; the product of each reaction section is subjected to gas-liquid separation through a gas-liquid separator; collecting the produced water in each section, feeding the water into a distillation tower to separate the product, and dehydrating and purifying the product to obtain refined sec-butyl alcohol; the dealcoholized water of the distillation tower is pumped by a pump and returned to each reaction section; before returning the dealcoholized water to the reactor, adjusting the temperature to carry out anion and cation removal treatment; the temperature of the n-butene and the circulating water can be 140-170 ℃; the pressure is 3-8 MPa; the water inlet airspeed is 0.5-10 h^-1. The temperature of the n-butene and the circulating water is preferably as follows: the temperature is 150-160 ℃, the pressure is preferably 4-5MPa, and the space velocity of water inflow is preferably 3-6 h^-1。

The n-butene material enters from the foremost reaction section of the reactor once and sequentially passes through each reaction section until reaching the last reaction section. Fresh water is fed into each reaction section, and the water produced in each reaction section is collected into an alcohol recovery system and does not enter the next reaction section. And washing and discharging tail hydrocarbon produced in the last stage. Very high n-butene conversions, e.g., 70-95% (depending on the initial feedstock concentration and the number of reaction stages) can be achieved with one feed.

The invention has simple process and lower raw material cost, and delays the arrival of reaction balance because the generated alcohol can be dissolved in excessive water in the reaction. In the process, the conversion rate of n-butene is high, and di-sec-butyl ether is not generated.

The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings:

FIG. 1 is a block diagram of a process flow of the present invention;

FIG. 2 is a schematic view of a multi-stage reactor according to the present invention;

a process for preparing sec-butyl alcohol by a multi-section water circulation resin method is characterized by comprising the following steps: n-butene is taken as a raw material, strong acid type ion exchange resin is taken as a catalyst, the catalyst is loaded into a multi-section reactor 1, and each reaction section of the reactor forms an independent reaction unit;the n-butene enters from the first reaction section and sequentially passes through the reaction sections; circulating water enters each reaction section through a shunt circuit; the product of each reaction section is subjected to gas-liquid separation by a gas-liquid separator 2; collecting the produced water in each section, feeding the water into a distillation tower to separate the product, and dehydrating and purifying the product to obtain refined sec-butyl alcohol; the dealcoholized water at the bottom of the distillation tower is pumped by a pump and returns to each reaction section; before returning the dealcoholized water to the reactor 1, the temperature should be adjusted to carry out anion and cation removal treatment; the temperature of the n-butene and the circulating water is 140-170 ℃; the pressure is 3-8 MPa; the air speed is 0.5-10 h^-1。

N-butene and circulating water (deionized water) enter from the upper part of a reactor filled with a strong acid type ion exchange resin catalyst at the temperature of about 155 ℃ and the pressure of 4.5MPa, and part of the n-butene is subjected to hydration reaction through a catalyst bedto generate sec-butyl alcohol and is dissolved in excessive water. And condensing and washing unreacted tail hydrocarbon out of the reactor, recovering a small amount of sec-butyl alcohol dissolved in the unreacted tail hydrocarbon, and discharging the sec-butyl alcohol serving as a liquefied gas component. And (3) sending reaction product water containing about 1% of sec-butyl alcohol to be distilled out, wherein the sec-butyl alcohol is distilled out in a water azeotrope form, and the refined sec-butyl alcohol suitable for preparing methyl ethyl ketone by dehydrogenation is obtained through dehydration and purification. The dealcoholized water is pumped by a pump and returned to the reaction system for recycling. The process principle is as in figure 1.

The n-butene material used in the reaction has reasonable concentration more than or equal to 70 percent, low concentration and poor process benefit. The method for synthesizing sec-butyl alcohol by using n-butene to hydrate has high selectivity and hardly generates impurities. The value of the tert-butyl alcohol generated by the hydration of the raw material containing isobutene is low and should be reduced as much as possible, and the best value is less than or equal to 1 percent. The polyhydric alcohol and higher alcohol generated in the hydration of butadiene and five-carbon olefin cannot be completely distilled out from the reaction produced water under the operation condition, the regeneration ratio of circulating water is increased, and the lower the content is, the better the content is. When the butadiene content is too high, polymer formation is observed, which affects the smooth progress of the hydration process.

Feeding airspeed: high conversion rate can be obtained only by little feeding in the first-stage reaction, and the hydrocarbon feeding is approximately equal to 0.1h^-1Is reasonable; in the multi-stage reaction, the number of reaction stages has an influence on the conversion rate, the feeding airspeed is aimed at reaching the specified conversion rate, and the process model is usedAnd (5) determining. Hydration catalyst: in principle, various strong acid ion exchange resins were available, and a commercial resin with the designation D72 was selected for this study, with good reactivity and a working life of about 3 months under reasonable operating conditions.

In the first stage of reaction, all the catalyst is loaded into a reactor, n-butene and water are heated, pressurized and discharged, and the hydration reaction process is completed through a resin agent bed under the reaction condition. Is suitable for the condition that a large amount of cheap and moderate n-butene material with moderate concentration is available and high conversion rate is not required. However, this process has many disadvantages, including low n-butene conversion, high bed water line speed, high circulating water deacidification load, short resin life, etc.

In one stage of reaction, when the diameter of the resin bed (or reactor) is constant, the water passing through the resin in the high section per unit bed (hydrocarbon is gas phase and water is liquid phase under the reaction condition, only the liquid phase water with larger scouring action on the resin is looked at here) is the total water quantity calculated according to the total dosage of the bed and the specified water space velocity, such as the total bed packing agent RM³The water airspeed is Wh^-1The amount of water passing through the bed is RW M³H is used as the reference value. However, if a long reactor is divided into N small segments, and each segment individually constitutes an independent small reactor (segment), although the hydrocarbon enters the first small reaction segment once and passes through the small reaction segments sequentially, the feed water (fresh deionized water without alcohol) to eachsmall reaction segment is calculated only according to the loading amount of each segment and the specified water space velocity (each small reaction segment)The produced water of the section goes to a recovery system and does not enter the next section), namely the resin in the high section of the unit bed bears the RW/N M water quantity at the moment³The bed water line speed decreased N times compared to the reaction in only one stage (test results show that the decrease in bed water line speed slightly adversely affects the reaction, but not greatly).

When the water line speed of the reaction bed is too high, the bed pressure is greatly reduced, and the PH of the produced water is greatly reduced (sometimes approximately equal to 4) during initial transportation, which indicates that the resin agent cannot bear the scouring action of high-line-speed water under the reaction condition, and the sulfonic group is obviously lost; sometimes, the produced water is slightly mixed, and a small amount of lime yellow fine powder can be seen to precipitate after sampling and placing, which indicates that the resin matrix is crushed. Sometimes, it is found that the amount of discharged waste resin is considerably reduced from the original amount after one cycle. The resin has fast activity reduction and short service life in operation. Meanwhile, the deacidification load of the circulating water has to be increased to avoid the accumulation of acid generated by the circulating water.

From the reaction equilibrium, although the use of excess water in the reaction considerably reduces its effect on the reaction depth, its presence cannot be eliminated. During the first stage of reaction, the reaction water encountered by the end agent of the bed must be dissolved in more alcohol, and the continuous reaction of n-butene must be retarded, i.e. the end agent cannot fully exert its alcohol-producing capacity. In the multi-stagereaction, fresh water is fed into each stage, even if the last reaction stage is faced with n-butene whose concentration is greatly reduced, the water fed into said stage does not contain alcohol, and still has a large reaction driving force, and the resin agent still can fully produce its alcohol-producing capacity.

If one considers that the entire hydrocarbon feed to the system from the first stage only results in a large pressure drop across the bed due to the large gas volume. It is also possible to introduce a small fraction of hydrocarbons from a stage subsequent to the first stage, i.e. multipoint feeds are also contemplated.

The more reactor stages, the lower the bed water line speed, but the more staged reactors are troublesome to manufacture, and it is considered herein that, only from the bed water line speed, it is a reasonable limit when it is so small as to constitute a trickle bed reaction bed type. At this time, the gas phase n-butene in the reaction bed is the continuous phase, and the water flows down along the surface of the agent particles mainly by gravity in a film shape. The pressure drop of the reaction bed is small, even no pressure drop.

The reaction produced clear water with pH approximately 6 in the multi-stage reaction experiments, which is believed to be very advantageous in keeping the active centers of the agent from being washed away by water (increasing the resin life) during the reaction. Further reduction of the bed water line speed should not be of greater significance. The water velocity value of the trickle bed can be determined by tests.

The water passing through any section of the bed in the first stage of reaction is the water passing through the whole bed layer, the diameter of the reactor (operating at 4-5 MPa) cannot be very large, the loading quantity is increased along with the increase of the scale of the device, the space velocity of water inlet cannot be reduced too much, and the water velocity of the bed can reach a very large value which cannot be accepted. This is one of the reasons why one-stage reaction cannot be designed into a large-scale industrial production apparatus, and this problem can be solved well by adopting a multistage reaction.

The adoption of low water line speed or trickle bed of the reaction bed can reduce the falling of a sulfonic group at the active center of the reaction resin, but can not completely prevent the occurrence of the sulfonic group, the pH value of the circulating water can still be continuously reduced in the use process, and in order to prevent the accumulation of acid and the corrosion of equipment, an anion exchange resin bed is arranged in the circulating water system to deacidify the circulating water, so that the pH value is more than or equal to 5.5. The anion resin is not resistant to temperature, and water can pass through the anion resin only after being cooled to about 70 ℃ through heat exchange. Due to the heat exchange temperature difference, the energy consumption is increased. The anion bed can remove various kinds of mixed anions in water. An anion bed and a cation exchange resin bed are arranged simultaneously to remove various mixed cations, especially Fe, entering the water⁺³. The quality of the treated water needs to be carefully monitored, and a corresponding instrument such as an online PH instrument or a conductivity meter can be arranged. The anion bed and the cation bed are provided with a double-set system capable of switching operation so as to switch use and regeneration at proper time. The resin used in the cation resin bed can be used as the returned reaction catalyst after regeneration treatment.

The content of sec-butyl alcohol in the water produced by the reaction is only about 1 percent, and the concentration is very low, but the actual operation provesthat the water is easy to remove and recover. The distillation column used does not have to exceed 15 theoretical stages. The alcohol produced is distilled off from the column as an alcohol-water azeotrope (small amounts of hydrocarbons originally dissolved in the circulating water are also recovered dissolved in the dry azeotrope when the distillation column is operated under pressure). Dehydration of alcohol-water azeotropesBy azeotropic distillation, optionally with an appropriate azeotropic dehydrating agent, e.g. benzene, but it is recommended to use C as the internal system₄Hydrocarbons (both the raw n-butenes and the tail hydrocarbons) are used as dehydrating agents. If the raw material n-butene is used, a small amount of n-butene originally dissolved in the circulating water can be conveniently recovered at the same time. The operating pressure of the distillation column is chosen so that it is reasonable that the bottom water has the same temperature as the reaction (about 0.55 Ma).

If di-sec-butyl ether is produced during the reaction, it is difficult to separate it, and therefore, several fractionating columns are required. Di-sec-butyl ether is formed by two sec-butyl alcohol molecules reacting on a catalyst under water-deficient conditions to remove one molecule of water. The reaction uses a large amount of excess water and water to have excellent wettability on the surface of the resin particles, the agent particles must be always surrounded by water in the reaction, the generated alcohol can be immediately dissolved in the excess water, and the water-deficient environment can not occur. Long-term test detection shows that the di-sec-butyl ether does not exist in the product. That is, this product is not produced in the reaction of this method.

The reactor of the method is preferably made of high acid-resistant steel, and is made of 316-L steel (foreign brand). However, when a trickle bed is adoptedand the deacidification monitoring of circulating water is enhanced to ensure that the pH of water is more than or equal to 5.5, 1Cr18Ni9Ti is used by observation; the steel is possible, the reaction coupon still has metallic luster for two months, and the accounting corrosion speed is less than 0.05 mm/a.

The equipment contacted with the circulating water is made of 1Cr18Ni9Ti steel, so that ordinary carbon steel cannot be used, otherwise, the equipment is seriously corroded, and the risk of catalyst poisoning is increased. The technological process after the dehydration of the alcohol-water azeotrope is non-corrosive, and carbon steel equipment can be used.

Modeling test of multi-stage process: although different operating conditions can theoretically be adopted in each stage in the multistage reaction, the obtained synergy is not reasonable compared with the added trouble, so that the same operating conditions, namely the temperature, the pressure, the loading amount and the water inlet airspeed, are recommended to be adopted in each stage of the multistage reaction. The raw material hydrocarbon continuously reacts in the movement from the front section to the rear section, the quantity is not reduced, the n-butene concentration is reduced continuously, the feeding concentration and the feeding space velocity of the rear section are smaller than those of the front section, the corresponding alcohol production is less, namely the parameters are continuously changed in the reaction, and the change rule is found out in the experimental work. In order to make the actual test more accurate and simple, one reactor is still used for preparing a plurality of n-butene materials with different concentrations, a plurality of different feeding airspeeds are arranged, the test result of each condition combination is obtained, and then the relation among the feeding concentration, the feeding airspeed and the alcohol yield (converted into the alcohol space-time yield) is found through mathematical processing, namely a statistical model of a multi-stage process is obtained, so that the multi-stage process can be simulated.

Four concentrations of n-butene material were used for the experiments: 46%, 70%, 82% and 97%, the test space velocity specified for each material being 0.1h^-1、0.26h^-1、0.62h^-1、1.0h^-1And 1.2h^-1Total five airspeedsValue, 20 trials (full trials) were done. The arrangement and results of four of these tests are listed below (see table 1).

TABLE 1

D72 agent, water space velocity 5h^-1,155℃,4.5 Mpa

Test No	Starting material n-butene Concentration (%)	Feed airspeed h^-1	Alcohol space-time yield g/(l,h)
1 7 14 20	46 70 82 97	0.1 0.26 1.0 1.2	16.58 28.84 46.79 56.96

Statistical processing of the 20 sets of data gives a process model of the form:

y=f(x₁,x₂) The space-time yield of the y-alcohol in the formula, g/(1. h);

x₁-feed n-butene concentration,%;

x₂-space velocity of feed, h^-1。

Description of process simulation:

the process simulation is to obtain reasonable reaction segment number and corresponding segment parameters according to given process conditions (mainly including initial concentration of n-butene raw material and yield to be achieved by the process). The method is carried out on a computer.

When the design task is determined (including production scale, raw material concentration and process yield), and the catalyst is selected, the n-butene concentration (x) can be determined according to the raw material₁) The feeding amount and the total loading amount are determined according to the average alcohol production capacity (average alcohol space-time yield) of the catalyst, and the n-butene concentration which the tail hydrocarbon discharged from the tail section should have is calculated according to the specified process yield and is used as the criterion for searching the number of the process sections.

The simulation begins by assuming a smaller number of reaction stages, and calculating the loading of each small reaction stage to obtain the airspeed x of hydrocarbon entering from the first stage₂Then according to model y = f (x)₁,x₂) And calculating the first alcohol production data. The amount of tail hydrocarbon produced in the first stage and its concentration can be simply calculated from the hydrocarbon feed amount and the alcohol production amount and used as the feed parameters of the second stage. The calculation method of the second and subsequent sections is completely the same as that of the first section. When the concentration of the tail hydrocarbon produced at the end section is not less than the concentration of the tail hydrocarbon calculated according to the process yield specified by the task after the calculation according to the number of the assumed sections, the number of the original assumed sections is insufficient, and the tail hydrocarbon is usedAdd a segment back from scratch. This operation is repeated until the requirements are met (all automatically). The number of the currently assumed stages is now taken as a reasonable number of reaction stages.

When the required n-butene yield is high when the required concentration of the n-butene is low or the catalyst is saved by using high catalyst space-time yield, the number of reaction stages is too large to be accepted, and the required process yield or catalyst space-time yield is reduced properly. From the results of the experiments, when it is desired to control the number of reaction stages to about 15 stages, the reasonable alcohol space-time yield and process yield using D72 reagent according tothe concentration of the raw material are approximately as follows

(Table 2)

TABLE 2

Initial n-butenes Raw material concentration (%)	Reagent alcohol space-time yield g/(1.h)	Reasonable process yield ％
70 85 95	35 37 41	70-73 80-84 91-95

Claims

1. A process for preparing sec-butyl alcohol by a multi-section water circulation resin method is characterized by comprising the following steps: n-butene is taken as a raw material, strong acid type ion exchange resin is taken as a catalyst, the catalyst is loaded into a multi-section reactor (1), and each reaction section of the reactor (1) forms an independent reaction unit; the n-butene enters from the first reaction section and sequentially passes through the reaction sections; circulating water enters each reaction section through a shunt circuit; the product of each reaction section is subjected to gas-liquid separation by a gas-liquid separator (2); collecting the produced water of each section, feeding the collected water into a distillation tower to separate products, and dehydrating and purifying the products to obtain refined sec-butyl alcohol; the dealcoholized water at the bottom of the distillation tower is pumped by a pump and returns to each reaction section; before the dealcoholized water returns to the reactor (1), the temperature is adjusted to carry out anion and cation removal treatment; the temperature of the n-butene and the circulating water is 140-170 ℃; the pressure is 3-8 MPa; the water inlet airspeed is 0.5-10 h^-1。

2. The process for preparing sec-butyl alcohol by the multi-stage water circulation resin method according to claim 1, wherein the process comprises the following steps: the temperature of the n-butene and the circulating water is as follows: 150-160 ℃, 4-5MPa of pressure and 3-6 h of water inlet airspeed^-1。