CN1148589A

CN1148589A - Oxalate synthesis catalyst

Info

Publication number: CN1148589A
Application number: CN 95116136
Authority: CN
Inventors: 张炳楷; 郭廷煌; 黄存平; 王金木
Original assignee: Fujian Institute of Research on the Structure of Matter of CAS
Current assignee: Tongliao Gold Coal Chemical Co., Ltd.
Priority date: 1995-10-20
Filing date: 1995-10-20
Publication date: 1997-04-30
Anticipated expiration: 2015-10-20
Also published as: CN1066070C

Abstract

A new type Pd-Zr/Al2O3 catalyst for synthesizing oxalate is developed by using Zr as adjuvant and adopting pickling process. Said invention adopts a fixed-bed reactor, and uses said catalyst in gas-phase catalytic synthesis reaction of oxalate by using carbonic oxide and nitrous acid ester. In the course of carbon monoxide catalytic coupling reaction to synthesize dimethyl oxalate and diethyl oxalate said catalyst possesses highest reactive activity, and can operate for a long period, and its reaction property is stable.

Description

Oxalate synthesizing catalyst

The invention belongs to the research of a catalyst for synthesizing oxalate.

Oxalates are important chemical raw materials and intermediates useful in the manufacture of oxalic acid, oxamides, ethylene glycol and certain drugs and dyes. The oxalate synthesized by the catalysis of carbon monoxide and nitrous acid ester opens up C₁A new important way for chemically producing oxalate. The progress of oxalate synthesis research is continuously reported at home and abroad in the eighties. JP8242.656 patent publication first reports a process for synthesizing dimethyl oxalate from CO and methyl nitrite using a platinum group metal-supported catalyst, wherein the space-time yield of the catalyst is 432g/l-h, and the yield is not decreased by a continuous reaction for 480 hours. Subsequently, there are many patents which successively report addition of Mo, Ni, Ti, Fe,Ga and Cu, Na, respectively, to the catalyst components₂O、SiO₂The catalyst composed of the auxiliary agents is applied to the process for synthesizing dimethyl oxalate, diethyl oxalate and diisopropyl oxalate by CO and nitrous acid, but the space-time yield is still low, for example: Pd-Mo/Al reported in US4,384,433₂O₃And Pd-Ni/Al₂O₃Catalyst at normal pressure, 110 deg.C and space velocity of 2000h^-1The raw material gas composition is as follows: CH (CH)₃ONO：15％、CO：20％、CH₃OH: 15%, NO: 3% and N₂: the reaction is carried out under the condition of 47 percent (volume concentration, all gas concentrations are volume concentrations), the space-time yield of the dimethyl oxalate is about 400g/l-h, and the product is prepared from CH₃The selectivity of ONO to dimethyl oxalate is 95 percent; synthesis of diethyl oxalate, Pd-Mo/Al₂O₃The catalyst is maintained at normal pressure, 120 ℃ and space velocity of 3900h^-1The raw material gas composition is as follows: c₂H₅ONO: 8%, CO: 60% and N₂: under 32% reaction condition, the space-time yield of diethyl oxalate is 550g/1-h, and the product is prepared from C₂H₅The selectivity of ONO to diethyl oxalate was 90.5%. Pd-Ti/Al reported in US4,507,494₂O₃Catalyst under a pressure of 2.5kg/cm²、115-120℃And airspeed 3000h-¹And initial feed gas composition: CH (CH)₃ONO：10％、CO：20％、CH₃OH: 4%, NO: 3% and N₂: 63 percent, etc., the continuous reaction lasts for 950 hours, the space-time yield of the dimethyl oxalate is 429-462g/l-h, and the selectivity of generating the dimethyl oxalate by CO can reach more than 95 percent.

In order to raise the action efficiency of catalyst and develop oxalate synthetic catalyst meeting the national condition of China, the invention selects Zr as adjuvant, and improves the preparation process of catalyst to develop new Pd-Zr/Al₂O₃A catalyst. Experiments prove that the catalyst has extremely high reaction activity and stable reaction performance in the process of synthesizing dimethyl oxalate and diethyl oxalate by CO catalytic coupling, and can operate for a long time.

Pd-Zr/Al₂O₃The catalyst is prepared by an impregnation method. According to the loading amount of active metal components and auxiliary agents of the catalyst, nitrate, sulfate, halide, acetate or oxalate of Pd and Zr are selected to prepare impregnation liquid. In order to prevent the metal ions from hydrolyzing to form hydroxide or oxide precipitates, a small amount of an acid corresponding to the anion of the metal salt is generally added to the impregnation solution. Then adding inert carrier Al with porous structure₂O₃Soaking for 2-12 hr, absorbing, separating out soaked solid, drying at 600 deg.C and 3 deg.CThe catalyst can be prepared by roasting for-8 hours and reducing at 100 ℃ and 250 ℃ for 1-5 hours. In addition, chlorine and sulfur interfere with the synthesis of oxalate and therefore, should be removed as much as possible during the catalyst preparation process to make the content below 100 PPM.

The reaction formula for synthesizing oxalate by gas phase catalysis of carbon monoxide and nitrite is as follows: wherein: r is alkyl.

This reaction, in addition to the primary oxalate product, also produces by-product nitric oxide, NO, in equimolar amounts to the consumed nitrite. NO must be recycled in continuous production. The nitrous acid ester can be prepared by reacting nitrous acid with alcohol or NO, O₂And alcohol. Wherein the alcohol can be any saturated aliphatic alcohol containing 1-8 carbon atoms, and methanol and ethanol are most commonly used. The feed gas is usually N₂Or CO₂And diluting with inert gas.

The oxalate synthesis reaction adopts a fixed bed reaction device. The synthesis process comprises the following steps: feed gas CO and dilution gas N₂Or CO₂After deoxidization, water removal and metering, the mixture enters a reactor. The reaction tube adopts a hard glass tube or a stainless steel tube with the inner diameter of 20-30mm and the length of 300-500mm, and 10-200ml of catalyst is filled in the reaction tube. The top of the catalyst layer is additionally provided with glass beads with the diameter of 3mm and the thickness of 100m for preheating reaction gas. The reaction tube was heated in a tube furnace, and the temperature control and measurement were continuously recorded using an IWT-702 type temperature controller and a WZB glass platinum resistance thermometer with an XQC-300 type automatic balance recorder, respectively. Each reaction time is 4-6 hours, RONO, CO and NO are respectively analyzed by a GDX-103 type chromatograph, and a 5A molecular sieve is used as a chromatographic column.

The catalyst needs to be reduced before reaction, the reduction temperature is 180 ℃ and 220 ℃, and the reduction time is 2-5 hours. After the catalyst is reduced, raw material gas CO and RONO are introduced, and the contact time of the raw material gas and the catalyst is 0.2-4 seconds. Because water affects the synthesis reaction of oxalate, the water content in raw material gas must be less than 2%, and the reaction is carried out under normal pressure condition without liquid phase in reaction zone. The reaction temperature is controlled at 100 ℃ and 150 ℃, and the temperature is easy to fly when the temperature is over 160 ℃, so that the reaction is out of control. The lower the reaction temperature, the less side reactions. The CO and RONO contents in the raw material gas can be changed in a wide range, the former is 10-70%, and the latter is 5-20%. The reaction product is separated after condensation.

The invention prepares the novel Pd-Zr/Al by improving the preparation method of the catalyst and adding the novel auxiliary agent₂0₃The catalyst has good effect in the reaction of synthesizing dimethyl oxalate and diethyl oxalate by CO and RONO. The cyclic reaction observation of 435-hour continuous synthesis of diethyl oxalate proves that Pd-Zr/Al₂O₃The catalyst has high reaction activity and selectivity, and is stable in reaction and easy to control. Even if the catalyst is deactivated due to accidental oxygen accidents, the catalyst can quickly recover the reaction performance through on-site regeneration, so that the catalyst can run for a long time, and the method has obvious industrial prospect.

Example 1 Pd/Al₂O₃The catalyst is prepared by respectively adopting a traditional method and a modified method.

Taking PdCl₂1.0 part of HCl solution (30%) 0.3 part and H₂Al is added to 23.4 parts of mixed solution₂O₃(diameter 3mm, length 4mm, specific surface 6-7M²G)29.3 parts, soaking for 10 hours, heating in a rotary evaporator, exhausting air, drying, roasting at 500 ℃ for 5 hours, and finally reducing at 200 ℃ for 2 hours. The traditional preparation method of the catalyst still adopts the process, and finally uses H₂The reduction and improvement rules change certain process conditions and adopt CO reduction. The obtained catalyst is respectively Pd/Al₂O₃(TRANS) AND Pd/Al₂O₃The results are shown in Table 1.

Example 2 Pd-Zr/Al₂O₃(modified) catalyst

Taking PdCl₂1.0 part of HCl solution (30%) 0.3 part and H₂O21.0 parts of mixed solution, and then ZrCl is added₄0.22 portion, and soaking Al in the solution according to the improved method sequence after the solution is clear and transparent₂O₃29.3 portions of the mixture are dried for 10 hours, then roasted at 500 ℃, and finally, 10 percent of CO to 90 percent of N are adopted₂The mixed gas is reduced for 2 hours at 200 ℃.

The reaction gas composition is as follows under normal pressure and 140 ℃:N₂∶CO∶CH₃ONO (oxide-nitride-oxide) ratio of 5: 3: 2 and space velocity of 3000h^-1Under the same conditions, the main results of the catalysts of examples 1 and 2 are shown in Table 1 when CO is reacted with methyl nitrite to synthesize dimethyl oxalate.

TABLE 1

Catalyst (COOCH)₃)₂Yield CH₃ONO conversion rate (COOCH)₃)₂Selectivity is

(g/l-h) (%) (%) example 1 Pd/Al₂O₃64541.8>95

Pd/Al₂O₃84154.2>95 examples 2 Pd-Zr/Al₂O₃99963.9>95

Under the same Pd loading and reaction conditions, the improved catalyst promotes the conversion of nitrite ester, so that the generation amount of oxalic acid dimethyl ketone is obviously increased. The Zr-added catalyst further promotes the improvement of the reaction activity.

Example 3 Pd/Al₂O₃Catalyst and process for preparing same

Get H₂2.2 parts of O/HCl 1: 1 solution and 22.0 parts of H₂Mixing O, adding PdCl₂1.0 part, loading Pd on 29.4 parts of Al by a micro-wet impregnation method after dissolution₂O₃Soaking for 10 hr, drying, roasting at 500 deg.C for 5 hr, and adding 50% CO-N₂The mixed gas is reduced for 2 hours at 200 ℃. The Pd loading of the catalyst was 1.97%.

Example 4 Pd-Zr/Al₂O₃Catalyst and process for preparing same

Taking HCl: H₂2.0 parts of solution O1: 1 and H₂O21.2 parts, adding PdCl₂1.0 part by weight of Zr/Pd 1/3 (weight ratio), ZrCl was added after dissolution₄After the solution is clear and transparent, Pd and Zr components are loaded on the solution by a micro-wet impregnation method27.3 parts of Al₂O₃Then, drying, calcination and reduction were carried out under the same conditions as in example 3. The Pd and Zr loadings of the catalyst were 1.86% and 0.61%, respectively.

Example 5 Pd-Zr/Al₂O₃Catalyst and process for preparing same

Taking HCl: H₂2.0 parts of solution O1: 1 and H₂O22.0 parts, adding PdCl₂1.0 part by weight of Zr/Pd 1/3 (weight ratio), ZrCl was added after dissolution₄Then adding Al₂O₃27.3 parts of the resultant was immersed for 10 hours, dried and calcined under the same conditions as in example 3, followed by immersing in 60.6 parts of 2.0% NaOH aqueous solution at 50 ℃ for 4 hours, and then washing with distilled water until it was free of Cl^-Drying at 200 deg.C for 3 hr, and adding 50% CO-N₂The mixed gas is reduced for 3 hours at 200 ℃, and the load amounts of Pd and Zr of the catalyst are respectively 1.77 percent and 0.35 percent.

At normal pressure, the composition of the reaction gas is as follows: n is a radical of₂∶CO∶C₂H₅ONO (32: 50: 18) and 3000h^-1The main results of the synthesis of diethyl oxalate with the catalysts of examples 3, 4 and 5 under the same conditions are shown in Table 2.

TABLE 2 catalyst reaction temperature (COOC)₂B₅)₂Yield CO Selectivity

(° c) (g/l-h) (%) example 3 Pd/Al₂O₃13098695 example 4 Pd-Zr/Al₂O₃130104495 example 5 Pd-Zr/Al₂O₃120 1079 96

Although the catalyst of example 5, which was subjected to dechlorination treatment, had a slight decrease in the reaction temperature and a slight decrease in the Pd loading, the reaction activity was still increased, indicating that Cl was present^-Has interference effect on the synthesis reaction of the oxalate.

The catalyst of example 5 was also used in a continuous reaction for diethyl oxalate synthesis. Adopts a fixed bed connected withThe reaction device was continuously circulated, and the reactor was a stainless steel tube having an inner diameter of 25.4mm and containing 200ml of the catalyst. At 130 deg.C under normal pressureAnd reaction gas composition: c₂H₅ONO7-12％，CO45％，NO10％，N₂10% and C₂H₅OH is less than 6 percent and the space velocity is 3800h^-1And under the same conditions, performing continuous cyclic reaction of CO and ethyl nitrite to synthesize diethyl oxalate. The product is separated off by condensation. NO, N₂、CO₂And unreacted CO, C₂H₅Non-condensed gases such as ONO enter an oxidizer and an esterifier for respectively carrying out NO and O₂And C₂H₅Oxidation and esterification of OH:

the regenerated nitrite can be recycledto the reactor to continuously participate in the reaction for synthesizing the oxalate. Therefore, only CO and C are consumed in the total reaction result₂H₅OH and O₂So that diethyl oxalate can be produced. The cycling reaction was continued for 435 hours with the main results listed in table 3.

TABLE 3 reaction time (h) 104140191C₂H₅ONO average content (%) 7.29.911.2 (COOC)₂H₅)₂Average yield 558730787

(g/l-h) CO Selectivity (%) 91.593.494.6 average space-time yield of diethyl oxalate 717 g/l-h. The data in the table also show that the yield of oxalate increases with increasing nitrite content in the feed gas. C₂H₅The ONO content is sequentially increased from 7.2 percent to 11.2 percent, the average yield of the oxalate can be increased from 558g/l-h to 787g/l-h, wherein the average yield exceeds 800g/l-h within about 50 hours and reaches up to 825g/l-h, the reaction is smooth, and the reactivity and the selectivity of the catalyst are kept unchanged before stopping the test.

Claims

1. The catalyst for synthesizing oxalate is characterized in that Zr is selected as an auxiliary agent and prepared by an impregnation method, and the preparation process comprises the following steps: according to the loading quantity of the active metal component and the auxiliary agent of the catalyst, the catalyst is selectedPreparing halide of Pd and Zr into impregnation liquid; a small amount of acid corresponding to the metal salt anion is generally added into the impregnation solution; then adding inert carrier Al with porous structure₂O₃Soaking for 2-12 hours, and separating out soaked solids after sufficient absorption; then drying the solid, roasting at 300-600 ℃ for 3-8 hours and reducing at 100-250 ℃ for 1-5 hours to obtain Pd-Zr/Al₂O₃A catalyst.

2. The catalyst of claim 1, wherein the halide of Pd or Zr is replaced by sulfate, nitrate, acetate or oxalate of Pd or Zr.

3. The synthetic reaction of oxalate is characterized in that the oxalate is synthesized in Pd-Zr/Al₂O₃Under the action of the catalyst, carbon monoxide and nitrite are catalyzed to synthesize oxalate, and the reaction formula is as follows:

wherein R is an alkyl group

The reaction adopts a fixed bed reaction device, a reaction tube is a hard glass tube or a stainless steel tube with the inner diameter of 20-30mm and the length of 300-500mm, 10-200ml of catalyst is filled in the reaction tube, a glass ball with the diameter of 3mm is additionally arranged at the top of a catalyst layer and the thickness of 100mm, the reaction tube is heated by adopting a tube furnace, and the reaction process is as follows: firstly, the catalyst is reduced for 1-5 hours at the temperature of 100 ℃ and 250 ℃, and then raw material gas CO and diluent gas N are used₂Deoxidizing, removing water, metering and mixing; then introducing the raw material gas CO and RONO into the reactor, so that the contact time of the raw material gas and the catalyst is 0.2-4 seconds, the reaction temperature is controlled at 100-150 ℃, and the reaction product is separated after condensation.

4. A reaction according to claim 3, wherein the diluent gas used is CO₂。

5. The oxalate synthesis reaction of claim 3, wherein the water content in the feed gas is less than 2% (v/v).

6. The oxalate synthesis reaction of claim 3, wherein the contents of CO and RONO can be varied within a wide range, the former being 10-70% and the latter being 5-20%.

7. The reaction of claim 3, wherein the reaction is carried out under atmospheric pressure without the presence of a liquid phase in the reaction zone.