CN1408696A - Method for producing camphor by sulfuric acid catalyzed camphene hydration - Google Patents

Abstract

Available step from camphene to isoborneol in camphor production has several demerits. In the camphor producing process of the present invention, camphene is acidified into isoburneol directly is water solution of sulfuric acid and isoborneol is separated timelty. The dilute acid solution may be reused and thus there is no effluent. Available esterification reactor may be used in acidification and hydration and the said process may result in high economic utility.

Description

Method for preparing camphor by catalyzing hydration of camphene with sulfuric acid

The camphor is previously extracted from Lauraceae plants. The xylonite can be used as cardiotonic, analgesic, algefacient and skin irritant in medicine, can be used for preparing xylonite and polyvinyl chloride for increasing plasticity, is used as a stabilizer of smokeless powder in military industry, and is a substance with wide application range.

At present, the synthesis capacity of camphor in China reaches more than ten thousand tons, and pinene in turpentine is used as a raw material for preparation. The process is long, and the requirements of each operation link are higher, so that the method is a fine chemical product.

The production flow of each camphor factory in China is the same at present: extracting pinene from turpentine, isomerizing pinene into camphene with titanium catalyst, reacting camphene with acetate with sulfuric acid or ionic membrane to obtain isoborneol acetate, alkaline hydrolyzing isoborneol acetate to obtain isoborneol, and dehydrogenating isoborneol with copper catalyst to obtain camphor.

For a long time, a great deal of research work has been done by technologists on the step from camphene to isoborneol, and particularly the requirement on environmental protection is higher and higher, and the defect that the step from camphene to isoborneol consumes a great deal of acetic acid and generates a great deal of waste water is felt to be intolerable. In order to change the situation of passive pollution control, scientists have conducted various studies seeking other methods, and it has been practical to use an ionic membrane instead of sulfuric acid as an esterification catalyst. This reduces the discharge of waste acid water, but still does not alter the major disadvantages of the esterification process. The leading research is to hydrate camphene into isoborneol by using acidic synthetic resin, and if the method is only from the aspect of yield, the method has been successfully exemplified by (1), and some methods have been tried even in factories, for example, Jiangxi Jian camphor factory adopts equipment of hydration process when the factory is built, but the method is found not to be economically beneficial after the operation. The reason for this is that the technical solution is complicated in equipment, expensive in cost, short in the lifetime of the used resin and long in the time of the hydration process, so that the desired benefits are all offset one by one. Since then, there have been no attempts by the industry to do so again.

In fact, to apply the method of synthesizing isoborneol from camphene water to camphor in the industrial production of camphor, the chemical process and essence of synthesizing isoborneol from camphene water must be made clear, and only on the basis, the optimal application scheme can be selected.

If a comprehensive analysis is made on the various scientific and technological achievements related to the above, the conclusion should be drawn that: regardless of which catalyst is used to promote camphene hydration, the true catalytic factor is that acidic hydrogen ions play a role. The following reversible reaction equation has been found to exist in practice.

In the formula (II)⁺The ions can be obtained from any acidic species, e.g., sulfuric acid, oxalic acid, strongly acidic cationic resins, etc., which provide H⁺The ions come from the ion source to the ion source,this can be fully verified from experiments in which: a500 ml three-mouth (ground) spherical glass flask is provided with a stirring device with good sealing property at the middle mouth, a ground glass straight tube condenser at the left mouth is provided with a ground glass straight tube condenser, materials in the flask are condensed into liquid to flow back to the flask after boiling and gasification, a ground glass plug with good sealing property is arranged at the right mouth, and feeding and analysis sampling are carried out through the mouth. A500 watt electric furnace is arranged at the bottom of the three-mouth glass flask.

120 ml of 11.5% -12% aqueous sulfuric acid, 120 g of industrial camphene and 36 ml of isooctanol were added to the flask. The right opening is closed by a plug, then the electric heating is carried out, and the stirring is started at the same time. The stirring speed is based on the condition that the layering phenomenon of materials in the bottle disappears and the materials are completely changed into an opaque state, and the stirring speed is higher, so that the stirring speed is beneficial and harmless to the reaction.

After the contents of the flask were boiled and refluxed, samples were taken every hour, and this was continued for 4 times. The sample is first neutralized with alkali solution, washed with distilled water to neutrality, dewatered in high speed centrifuge and gas chromatographic analysis in a sample injection machine.

Practice proves that after 3 hours, the product isoborneol and a small amount of hydrated camphene cannot be increased continuously, the amount of camphene is not reduced any more, and the ratio of isoborneol to camphene is 15.4%. It is worth mentioning that the increase in isoborneol is not linearly proportional to the reaction time, but is substantially close to the apex after less than two hours. The chromatogram of FIG. 1 is the result of sampling analysis when the reaction proceeded for two hours. The names of the materials represented by the main peaks in each time period in the figure are listed as follows:

0.9-membered tricyclene

1.2 parts camphene

3.5 min isooctanol

6.41 part hydrated camphene

7.54 fen Bian Longnao

Tricyclenes and camphene are considered as equivalent raw materials in industrial production and have been included when calculating camphene content. The numerical calculation of camphene and isoborneol in theatlas shows that the ratio of isoborneol to camphene is 14.8%, namely is very similar to 15%, and the isoborneol content is 13% of the total material at this time except the value of isooctanol which does not participate in change.

To further examine the relationship between them, the experiment was not reversed, i.e., 120 g of isoborneol was put into the flask, and the remaining amounts of dilute sulfuric acid solution and isooctanol were still unchanged, thus reversing the chemical reaction. After the operation for a short time, camphene appears in the materials, and the operation is continued until the camphene is not increased any more and chemical equilibrium appears. The time taken was longer than in the previous experiment, but the final isoborneol to camphene ratio was still 15.4%.

This is evidence of a reversible reaction. The equilibrium relationship here appears to be very similar to the well-known Happo-Bosch reaction, i.e., the equilibrium of nitrogen and hydrogen synthesis into ammonia, and the equilibrium pattern of both is very similar (2). in the reaction for synthesizing ammonia, there are no other unrelated substances except hydrogen and nitrogen, but in this practice, isooctyl alcohol which does not react with camphene, isoborneol and dilute acid is added, just to make the experiment proceed smoothly, and it does not affect the equilibrium result of the final chemical reaction.

It must also be noted that the equilibrium relationship of 15.4% is already within the optimal equilibrium region for the conversion of camphene to isoborneol. It is self-understood that the conversion of camphene to isoborneol in acid solutions of different concentrations at a certain temperature will have a corresponding series of equilibrium relations with the change of the acid solution concentration, and the ratio of one section of the acid solution is higher, which is the optimal area that we needfor improving the technology.

Then, the experiment of converting camphene into isoborneol is used for discussing. If the parts of camphene and isooctanol are always fixed, the concentration of the sulfuric acid solution is only increased from 1% gradually, the equilibrium ratio is gradually increased, and the reaction time for reaching equilibrium is also gradually shortened. However, when the acid concentration exceeds a specific limit, the time consumed for equilibrium is still shortened, but the ratio when equilibrium is reached is reduced. A peak occurs at the intersection of the gradual increase and decrease. This peak has two important implications, one is that its equilibrium ratio is the largest in the overall system, and the corresponding acid concentration with which it acts is the optimal formulation.

It is also known from experiments that the concentrations of aqueous solutions prepared from various sulfuric acids from different sources are different when the peak value is reached, but the concentrations are about 12%; the peak values of the two are slightly different and are mostly between 15.4% and 16%. From a practical point of view, the practical ratio of each batch of concentrated sulfuric acid raw material is determined by practical effect without carrying out a set of experiments with the concentration of 10% -14%. The experiment is very simple and easy, and the experiment is more practical when the experiment is carried out once and then is applied to industrial production. There is also a problem of great importance in industrial production, that is, the index of processing man-hour, if it is time-consuming to reach the peak value, it can be selected at a concentration slightly higher than the index, so as to obtain the maximum economic benefit.

After the above basic situation has been elucidated, no further theoretical considerations are to be considered, since H⁺Is a substance which really plays a catalytic role, so that the selection of strong acid is most economical and reasonable, and single monoacid is better. However, it is not preferable to use hydrochloric acid and nitric acid because they are not preferred because they are relatively useless, but they are inferior because they have a lower acid strength than sulfuric acid. This strongly argues that the catalytic nature of this reversible reaction is H⁺The function is played.

The choice of reaction temperature, room temperature and low temperature is not preferred because the ionization degree of water and the ionization degree of acid are high at high temperature, which not only accelerates the reaction rate and reaches the equilibrium position as early as possible, but also suppresses the appearance of other by-products, which means that the application in industrial production saves time and improves the yield. In order to simplify the production equipment, it is not suitable to adopt the measures of increasing pressure by higher temperature, and the heating is subject to the dilute acid boiling in the material under normal pressure.

However, in order to apply the principle to the actual work of synthesizing isoborneol by camphene hydration, a post-treatment process must be added and is carried out in a step-by-step connection mode in production, wherein in the first step, camphene must be converted to isoborneol in a dilute solution of sulfuric acid and is balanced until the equilibrium point is reached; the second step is to separate out the dilute sulfuric acid, and then to separate out the camphene by utilizing the characteristic difference that the boiling point of the camphene is lower than that of isoborneol by about 50 ℃. The separated camphene returns to the first step for reprocessing. The process principle is a process with a few cycles as shown in figure 2.

After the process principle is ascertained and determined, specific equipment and operating conditions must also be determined in order to enable industrial production.

In order to improve the heating and operating efficiency of the whole set of equipment, the fractionating kettle stops receiving the balance mixture transferred from the first step when the inventory of isoborneol in the fractionating kettle is close to or reaches half of the volume of the fractionating kettle, then the camphene is evaporated completely, and the inventory of isoborneol in the fractionating kettle is discharged.

The specific arrangement of the apparatus can be arranged in the manner of fig. 3:

1. acidifying the porcelain expanding kettle: the kettle cover is provided with a matched mechanical seal stirring device, a paddle type stirring shaft runs in the kettle, the rotating speed is as high as more than 80 revolutions per minute, and materials in the kettle are in an opaque state. A sight glass and a liquid dividing valve are arranged behind the discharge valve at the bottom of the kettle. The acidification process of camphene is performed here.

2. A graphite condenser: it receives the gas from 1 boiling, after condensation, it flows back to 1 through the lower liquid-sealed tube.

3. Washing out the barrel: a simple stirring device is arranged on a common container made of carbon steel. The material discharged from 1 is washed away from the acid solution. The cleaned material enters the chamber 4 through the lower sight glass and the discharge valve.

4. A fractionating kettle: the charge amount was the same as 1, and the vessel was made of plain carbon steel. The lower half contains a close-packed heater tube assembly to ensure that the amount of evaporated camphene (with a small amount of hexanol and isooctanol) reaches more than half of its charge in two hours. 4 receiving the material with camphene and isoborneol basically balanced, and discharging the isoborneol with camphene evaporated. (with a minor amount of isooctyl alcohol in addition).

5. A fractionating tower: stainless steel corrugated net packing is filled in the device, and the number of tower plates of the device can ensure that camphene and isoborneol can be separated. Camphene is distilled out, and isoborneol is naturally left in the lower fractionating kettle.

6. A dephlegmator: this is necessary to ensure that the isoborneol does not boil off with the camphene, and the upper outlet pipe is provided with a dew point thermometer at the top.

7. A camphene condenser: the camphene gas is here condensed into a liquid and then flows to 8 or 9.

8. 9, a camphene reservoir; the upper part is provided with a feed valve, a material circulating valve, a vacuum valve and an emptying valve, and the side surface is provided with a liquid level pipe. It is charged by only half 1. This design is to allow for just 1 full load after it is mixed with dilute sulfuric acid. The lower device discharge valve opens directly into 1. Two tanks alternately introduce the material in the circulation under vacuum, so that one of them is full and is at normal pressure, ready for the transfer of material to 1.

10. A mechanically reciprocating vacuum pump.

11. An exhaust gas catcher. The cavity at the front end is connected with the exhaust port of the valve 10, and the rear part is provided with a water seal to separate the cavity from the atmosphere. The gas exhausted by the vacuum pump is firstly diffused in the front cavity and then enters the atmosphere after passing through the water seal part.

12. A dilute sulfuric acid storage tank. It can be made of polypropylene, and the dilute sulfuric acid solution separated from 1 is flowed into it and stored, and the regulation by adding water is also implemented in it.

13. An acid liquor delivery pump. And selecting a common plastic pump. The reservoir in 12 is pumped back to 1 via this pump.

The use of the whole set of equipment has several important aspects to be mastered: one is to take into account that the concentration of the aqueous sulfuric acid solution increases gradually as a result of the hydration reaction, and to ensure that the acidification hydration is close to the optimum equilibrium within 2 hours, without forgetting to supply a certain amount of tap water to 12 each time before returning the dilute acid to 1. Secondly, when the inventory of isoborneol in 4 reaches half of the charging amount, the material is not received from 3 any more.

The process of 4 in which the inventory of isoborneol has reached half the charge can be estimated as follows: initially, 4 is empty and therefore receives a second balanced blend from 3, each time considered as an 8 or 9 flow, and its mass is determined as a after metering. 4 after receiving two mixed materials of A, one A camphene can be steamed out, and then six mixed materials of A and six camphenes are received and steamed out, so that after seven times of steaming out, a little of four A isoborneol is left in 4. If the loss rate of each wind consumption is one percent, seven losses are totally lost for seven times, and the total yield can still reach ninety-three percent. However, to meet this requirement, the condensation area of 7 should be large enough, and the cavity of 11 associated therewith must not be too small.

In addition, since only 13% of the content can be obtained by equilibrium operation once in two hours, about one A isoborneol is accumulated, and eight times of equilibrium processes are needed, so that the time of photochemical reaction on acidification is as much as sixteen hours, if the auxiliary operation time is added for each time for half an hour, eight times are four hours, and the gold process reaches twenty hours, which is comparable with the working hours of the existing esterification working procedure. Therefore, the liquid separation and discharging in two hours each time must be carried out in time, and the subsequent isoborneol increment process cannot be retained. Knowing that the increment after two hours is small, lingering it will lose its size.

Only by mastering and coordinating the above-mentioned various requirements, it is possible for camphor-producing enterprises to accept and benefit for a long time. The inherent disadvantage of this method of increasing the amount of material remaining on the production line is ignored just as the blemishes on white jade.

Finally, the most concerned economic benefit problem is mentioned, which is the conclusion that the past hydration method cannot be popularized, so that the method is not available.

From the chromatographic analysis data in fig. 1, the selectivity of the dilute sulfuric acid catalytic reaction is very high, the reaction products are only two, more than 93% are isoborneol, the hydration camphene is less than 7%, while the esterification efficiency of the esterification method is only 85% (3), and compared with the method, the color is not increased.

The hydrated camphene is mostly remained in the mother liquor in the process of the isoborneol being separated out from the isooctanol, so that the quality of the camphor is not endangered. In the esterification process, by-products are also produced in the reaction.

The density of 12% dilute sulfuric acid solution is much higher than that of material, and it is not dissolved mutually, so that it is very quick in layering and separation, and itseconomic property for cyclic use is close to zero cost. Such an improvement is most suitable for the companies that are currently using esterification because the existing esterification enamel tanks are being used for the acid hydration of camphene.

The existing esterification method for producing one ton of camphor consumes about 0.6 ton of acetic acid and 0.45 ton of sodium hydroxide, and the camphor factory generally does not recover sodium acetate by itself, but the residual liquid of sodium acetate is sold to a nearby small factory at a low price, and the recovery value only accounts for a very small part. The method does not consume acetic acid and caustic soda any more, and only the saving value equivalent to half ton of acetic acid is remained after deducting the recovery value of the sodium acetate residual liquid compared with the esterification method, so that a camphor factory producing two thousand tons of acetic acid every year can save one thousand tons of acetic acid in one year, and the cost can be reduced for the factory by more than four million yuan according to the calculation of the current market price.

Because the method has low requirements on equipment and is simple and easy to assemble and install, the technical improvement is easy to carry out, and the cost for the technical improvement is negligible compared with the later benefits. And because the equipment modification does not need to take more days, the technical modification investment can be recovered in the same year, and a large amount of surplus can be obtained. Reference documents:

[1]studies on the catalysis of camphene hydration reaction by cation exchange resins such as Caosulin, et al, Linn chemical&Industrial 1995(9)25-29

[2]Published by the encumbrancy P75-P77 chemical industry Press of Daxixianzhi exploring catalyst.

[3]The Nanjing Lin industry academy of academic sciences master edition college of university: the natural resin production technology P264-P265 Chinese forestry press.

Claims (5)

1. A method for producing camphor comprises: the method is that after pinene is isomerized into camphene, camphene is directly hydrated into isoborneol by using a sulfuric acid water solution, and finally the isoborneol is dehydrogenated into camphor by using a copper catalyst.

2. The concentration of the sulfuric acid aqueous solution for hydrating camphene into isoborneol is between 10 and 14 percent.

3. Isooctanol and hexanol were used as solvents for camphene.

4. The temperature for hydrating camphene into isoborneol is based on the boiling of dilute acid solution in the material under normal pressure, and the stirring speed is based on the disappearance of the boundary of two liquid phases with different densities and the appearance of the mixture as an integral body.

5. When the acidification hydration reaction is carried out until the ratio of isoborneol to camphene is close to 15 percent, the acidification is stopped, then the reaction product is transferred to subsequent equipment for fractionation, the camphene is evaporated out for acidification, and the operation is circulated until the reaction is complete; the corresponding main equipment for completing the production work is formed by connecting and combining an acidified enamel kettle, a washing barrel, a fractionating kettle, a fractionating tower, a dephlegmator, an camphene condenser and an camphene storage tank in series to form a material circulating processing ring; when the volume of isoborneol is increased to half of the volume of fractionating still, it can be discharged from its bottom valve, and the camphene can be added from feeding hole of camphene storage tank, so that the whole equipment possesses the functions of whole opening and internal circulation.

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