CN1057079C - Catalystic rectification and hydrolization technology and equipment for methyl acetate - Google Patents

Abstract

The invention discloses a methyl acetate catalytic rectification hydrolysis process and its equipment. The hydrolysis process is to carry out a catalytic hydrolysis reaction in a reaction zone filled with a cation exchange resin in a metered ratio of water and methyl acetate; the non-hydrolysis reaction The product is condensed and then metered and proportioned, and then flows back into the reaction zone, and the product hydrolyzate is drawn out from the bottom still; At least five catalyst structural units formed in bundled packages are vertically staggered, so the present invention can obtain any required ester decomposition rate within the range of 35-98.5%.

Description

Methyl acetate catalytic rectification hydrolysis process and its equipment

The invention relates to a heterogeneous catalytic rectification hydrolysis process for methyl acetate and catalytic rectification equipment used in the hydrolysis process.

There are various hydrolysis methods for methyl acetate, such as alkaline hydrolysis, acid hydrolysis and cation exchange resin catalyzed hydrolysis. At present, in the production process of polyethanol at home and abroad, the hydrolysis of methyl acetate all adopts the catalytic hydrolysis method of cation exchange resin. There are two processes for this hydrolysis method: one is the cation exchange resin fixed bed hydrolysis process, which is a traditional hydrolysis method currently at home and abroad; the other is the cation exchange resin heterogeneous catalytic rectification hydrolysis method, which is currently being studied A new hydrolysis process. The topmost shortcoming of traditional technique: the decomposition rate of methyl acetate is low, and when its water-ester ratio is 0.95/1.0 (mol), it is generally about 23-25%, and the concentration of acetic acid in the hydrolyzate is about 14% this moment, The ratio of acid to water weight is about 1.3; due to the low hydrolysis rate, a large amount of unhydrolyzed methyl acetate needs to be recycled, so the equipment is huge and the energy consumption is high; there is azeotrope in the hydrolyzate, and the separation device is complicated.

Existing Japanese published patent (8207,259 and JP 5-212290) and Japanese document (CA, 96164550n) report, Japan's methyl acetate catalytic rectification hydrolysis is still in laboratory research stage, and its cationic exchange resin catalyst is in the tower There are two filling methods: one is to make the ion exchange resin into fibers and wrap it on the plastic rod, and then fill it in the tower; the other is to mold the ion exchange resin and high-density polyethylene into a cylinder under heating and melting. Then fill in the tower. These two methods are cumbersome to make, and it is difficult to replace and recycle the catalyst, especially the latter will fall off and lose the catalyst after long-term use, causing losses. Its hydrolysis process adopts high water-to-ester ratio (mole) and high reflux ratio (Kg top steam condensation reflux flow/Kg methyl acetate feed rate) to reach the purpose of high decomposition rate, high energy consumption, difficult to popularize and apply. U.S. Patent [US.Pat4215011(1980)/US.Pat4302356(1981)/US.Pat4242530(1980)] discloses a different catalyst filling method from Japan, but the catalyst filling method in the United States is not in the catalytic rectification of methyl acetate Application in hydrolysis process; this filling method is referred to as "bundle bag method", that is, the catalyst is filled in the reaction zone of the tower in the form of bundle bag.

The object of the present invention is to provide a kind of methyl acetate to carry out heterogeneous catalytic rectification hydrolysis process and the equipment used for this process under cation exchange resin as catalyzer.

The object of the present invention is achieved like this, and described technological method is characterized in that the methyl acetate of metering enters the bottom that is filled with the catalytic rectification tower reaction zone of hydrolysis catalyst gel-type cation exchange resin after preheating, after metering ratio The water is preheated and added from the top of the reaction zone at the same time, methyl acetate and water undergo hydrolysis reaction in the reaction zone, and the unhydrolyzed methyl acetate and water form the lowest azeotrope, which is condensed and then metered and then returned to the tower. In the zone, the product hydrolyzate is extracted from the still under the tower; the above process conditions are; the hydrolysis temperature is 55-56 °C; the molar ratio of water and methyl acetate is 1-6:1; The volume ratio is 1-9.5:1; the superficial velocity is 0.23-0.25 cubic meters per cubic meter of catalyst per hour.

The above reaction conditions can be selected arbitrarily according to the requirements of process, equipment, etc., so as to obtain any required ester decomposition rate within the range of 35-98.5%.

The equipment used for the hydrolysis process described in the object of the present invention is a catalytic rectification tower. Its structural characteristics are to be appropriately improved after referring to the U.S. patent. The specific structure is: it includes a cylindrical tower body, and the tower body is a reactive distillation tower. Section and stripping section, the sieve plate in the reactive distillation section is filled with gel-type cation exchange resin catalyst to form a reaction zone, and the reaction zone is formed by at least five structural units filled with cation exchange resin vertically interlaced in the tower. The structural unit described above is cylindrical, and its outer diameter matches the inner diameter of the reactive distillation section of the column. The cylindrical structural unit is formed by connecting small bags filled with cation exchange resin with a length and width of 40-80×8-16 mm side by side. The corrugated body and the corrugated 60-80 mesh stainless steel wire mesh of the same size pressed into a tooth shape angle of 60-120 degrees are stacked together and rolled into a layer of small bags and a layer of stainless steel wire mesh. Each tooth-shaped corrugation on the stainless steel wire mesh Form an inclination angle of 30-75 degrees with the screen edge.

In addition, the small bag wrapped with cation exchange resin in the reaction zone of the tower is made of silk cloth, nylon cloth or polyester cloth, and the stainless steel wire mesh used in the tower is molybdenum-titanium stainless steel wire mesh. Height, the height of the cation exchange resin catalyst filled in the pouch is 0.6-0.8 times the length of the pouch.

In the present invention, because the catalyzer that methyl acetate catalytic rectification hydrolysis adopts is packed in the reaction zone of the reaction rectification section of catalytic rectification tower with the form of similar binding bag, thereby the advantage of the present invention is that reaction is in the range of described process conditions The corresponding ester decomposition rate varies within a wide range of 35%-98.5%, so the user can choose the ester decomposition process requirements required for any decomposition rate of ester according to specific equipment, energy consumption and operating conditions.

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is the schematic diagram of hydrolysis process flow equipment of the present invention.

Fig. 2 is a schematic diagram of structural units in the catalytic rectification tower of the present invention.

FIG. 3 is a schematic cross-sectional view of the structural unit in FIG. 2 .

Fig. 4 is the plan view that the spun silk cloth that constitutes the structural unit is sewn into several side-by-side small bags.

Fig. 5 is a schematic plan view of the arrangement of tooth-shaped corrugations of the stainless steel wire mesh constituting the structural unit.

FIG. 6 is a schematic structural diagram of each tooth-shaped corrugation in FIG. 5 .

As shown in Fig. 1, Fig. 2, Fig. 3, Fig. 4 and Fig. 5 and Fig. 6, the structure of the catalytic rectification tower is as follows: the upper section is the reactive distillation section 15, and the lower section is the stripping section 16. Reactive distillation section: the material is heat-resistant glass, the tower diameter is 25mm, the tower height is 900mm, filled with a certain number of structural units 17 filled with gel-type cation exchange resin, and the height is 460-690mm. Stripping section 16: the material is heat-resistant glass; the tower diameter is 25mm, the tower height is 840mm, and the tower is filled with 2.5×2.50 ring fillers made of molybdenum-titanium stainless steel wire mesh (wire diameter 0.15mm, 60 mesh). 243-486mm high.

The small bag in the catalyst structural unit in the tower is made of silk cloth, nylon cloth or polyester cloth, and the tooth-shaped corrugated stainless steel wire mesh that acts as a support and a gas channel is 0.15 wire diameter and 60 mesh molybdenum-titanium stainless steel wire mesh; Used catalyzer is a gel-type cation exchange resin, adopts SK-IA type in the example of the present invention, and its specific structure of the reaction zone of the used catalytic rectification tower of the example of the present invention is made as follows: sewed into with spun silk cloth Nine small bags 18 with a length of 55mm and a width of 12mm are filled with an appropriate amount of gel-type cation exchange resin, and the nine small bags are connected into one piece to form a corrugated body 19, which is pressed into a peak height of 4.3mm with the same size. The tooth profile angle is 81 Waste corrugated molybdenum-titanium stainless steel wire mesh 22 is rolled together into a cylinder of one layer of cloth bag and one layer of wire mesh. The outer diameter of the cylinder is the same as the inner diameter of tower 8, which is 25mm. 45 degree slope. Each cylinder is a structural unit 17, and the reaction zone of the reactive distillation section 15 in the tower is formed by vertically interlaced overlapping of 12 structural units, and the length of the reaction zone is 660 mm, so that the corrugated wire mesh in the upper and lower adjacent cylindrical structural units The tooth-shaped corrugations are staggered to increase the turbulence of the gas-liquid fluid and make the gas-liquid fully contact.

Examples 1-9 of the present invention all adopt the following process in the reaction in the above-mentioned catalytic rectification tower; 13 is added from the top of the reaction zone after preheating, the unhydrolyzed methyl acetate and water form the lowest azeotrope and enter the top condenser 7, and all the condensate flows back into the tower after metering. The hydrolyzate is extracted from the still, and this still adopts a 250mm three-necked flask 10 with a thermometer, heated with an electric heating mantle, and the composition of the hydrolyzate and the decomposition rate of the ester are tested by a Shimadzu gas chromatograph. The hydrolysis temperature is 55-56 degrees. Concrete water-to-ester ratio, superficial velocity, reflux ratio and the decomposition product and the yield of the ester and the decomposition rate of the ester are detailed in the following table:

Experimental example instance number Water/Ester (mol) Superficial velocity m ³ ester/hm ³ catalyst Reflux ratio L/Fml reflux liquid/ml feed ester Hydrolyzate composition (wt%) Ester decomposition rate ester alcohol water acetic acid % 1 1.44 0.23 3.92 45.646 12.556 13.962 19.375 40.2 2 2.10 0.23 3.35 23.485 20.4354 23.516 32.5629 63.8 3 3.00 0.23 3.55 14.9677 18.8657 31.5949 34.4395 73.8 4 4.53 0.23 4.78 4.2554 20.2226 40.7473 34.7645 90.9 5 6.00 0.23 5.05 0.6917 17.6987 49.627 31.992 98.5 6 2.50 0.23 7.27 15.552 21.319 25.703 37.425 74.4 7 2.00 0.345 3.30 28.3167 17.8244 24.3466 29.5121 56.9 8 2.00 0.407 4.49 28.0215 18.4594 22.5138 31.004 59.4 9 2.10 0.532 3.47 15.823 21.5867 25.9864 36.6038 56.5

Claims (3)

1, a kind of methyl acetate catalytic rectification hydrolysis process, it is characterized in that metered methyl acetate enters the bottom of the catalytic rectification tower reaction zone that is filled with hydrolysis catalyst gel-type cation exchange resin after preheating, after metering ratio The water is preheated and added from the top of the reaction zone at the same time, methyl acetate and water undergo hydrolysis reaction in the reaction zone, and the unhydrolyzed methyl acetate and water form the lowest azeotrope, which is condensed and then metered and then returned to the tower. In the zone, the product hydrolyzate is extracted from the still under the tower; the above process conditions are: the hydrolysis temperature is 55-56 ° C, the molar ratio of water and methyl acetate is 1-6:1; the volume ratio of reflux liquid and feed ester 1-9.5:1; the superficial velocity is 0.23-0.55 cubic meters per cubic catalyst per hour. 2. A catalytic rectification tower for the method of claim 1, comprising a cylindrical tower body (8), the tower is divided into a reactive rectification section (15) and a stripping section (16), and the sieve in the reactive rectification section The plate is filled with gel-type cation exchange resin to form a reaction zone, which is characterized in that the reaction zone is formed by at least five structural units (17) filled with cation exchange resin vertically interlaced in the tower, and the structural units are cylinders Body shape, the outer diameter matches the inner diameter of the column reaction rectification section, and this cylindrical structural unit is connected side by side into a corrugated body (19) by the small bag (18) filled with cation exchange resin in the length and width of 40-80 * 8-16 mm ) and the corrugated 60-80 mesh stainless steel wire mesh (22) that is pressed into the tooth shape angle of 60-120 degree with the same size are stacked together and rolled into a layer of pouch and constituted by a layer of stainless mesh wire mesh, each wire mesh on the stainless steel wire mesh The tooth-shaped corrugation (23) forms an inclination of 30-75 degrees with the screen edge. 3. The catalytic rectification tower according to claim 2, characterized in that the material of the small bag wrapped with cation exchange resin in the reaction zone of the tower is silk cloth or nylon cloth or polyester cloth, and the stainless steel wire mesh used in the tower is molybdenum Titanium stainless steel wire mesh, the length of the small bag is the height of the cylindrical structural unit, and the height of the cationic exchange resin catalyst filled in the small bag is 0.6-0.8 times of the length of the small bag.

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