A method for preparing a long-life solid phosphoric acid catalyst

Abstract

The present invention relates to the technical field of solid phosphoric acid catalysts, and in particular to a method for preparing a long-life solid phosphoric acid catalyst; comprising: impregnating a phosphoric acid solution and silica gel under vacuum conditions for a first time, draining after the impregnation, and then calcining for a first time to obtain a catalyst after the first calcination; cooling the catalyst after the first calcination to room temperature, impregnating for a second time under vacuum conditions, draining after the impregnation, and then calcining for a second time to obtain a catalyst after the second calcination; cooling the catalyst after the second calcination to room temperature, impregnating for a third time under vacuum conditions, draining after the impregnation, draining after the impregnation, and then calcining for a third time to obtain a solid phosphoric acid catalyst. The preparation method provided by the present invention adopts a vacuum multiple impregnation and calcination technology, which can make the prepared catalyst have good catalytic activity, and at the same time have the characteristics of strong pressure resistance, high selectivity, good thermal stability and long service life.

Description

Technical Field

[0001] The present invention relates to the technical field of solid phosphoric acid catalysts, in particular to a method for preparing a long-life solid phosphoric acid catalyst. Background Art

[0002] Low carbon number olefin superposition is a chemical reaction that superposes monomer olefins to form a compound containing one or more units repeatedly connected. 12 High-carbon-number olefins are used as raw materials for fine chemicals such as resins, detergents, surfactants, and lubricant additives, offering excellent economic benefits. It is well known that the non-selective superposition process (UOP process) both domestically and internationally still uses diatomaceous earth phosphate catalysts. As described in patents such as US3112350 and US3132109, this catalyst uses diatomaceous earth as a carrier. During the preparation process, the diatomaceous earth and phosphoric acid react to form silicon phosphate through calcination. Because the phosphoric acid is supported on the diatomaceous earth surface, this phosphoric acid is generally considered non-volatile. Furthermore, compared to liquid acid catalysts, the acid on the catalyst surface is less likely to be lost, resulting in excellent catalytic activity. However, the major drawback of this catalyst is that water vapor activation during the reaction softens the silicon phosphate, reducing its mechanical strength. To improve the catalyst's mechanical strength during the reaction, the All-Soviet Petroleum Research Institute developed a "double-skeleton" carrier in the 1970s. During the preparation process, the carrier activated carbon is first impregnated with sodium silicate and then neutralized with silicic acid, leaving the silica gel within the activated carbon framework. This dual-skeleton carrier combines the advantages of both diatomaceous earth and activated carbon: excellent mechanical strength, resistance to muddling, and acid loss. But this catalyst preparation process is too complicated and does not carry out industrialized production. In addition, Chinese patent CN1151104C discloses a kind of light olefins superposition or superposition solid phosphoric acid catalyst, its catalyst composition is SiBaXb(P2O5)c(H2O)d, this catalyst is at first 78~88% polyphosphoric acid and contains oxide compound, hydroxide or corresponding salt of B and X at 150~240 ℃ of stirring reactions down, then reaction mass and diatomaceous earth or silica gel are kneaded into shape in a kneader, make phosphoric acid diatomaceous earth catalyst through drying, roasting, activation again, at 180~220 ℃, raw material space velocity is 1~4h-1, reaction pressure is under 3.0~6.0Mpa condition, the highest conversion rate of this catalyst is 78%, nonene selectivity is 65.4%, and dodecene selectivity is 20.1%. As can be seen from this catalyst evaluation result, the mechanical strength of solid phosphoric acid catalyst improves to some extent, is 580 N / cm2, but conversion rate, nonene and dodecene selectivity are lower. Even though the catalytic activity and anti-sludging ability of the catalyst have been greatly improved, it has not yet met the requirements of high activity, high strength and high selectivity of solid phosphoric acid catalysts.

[0003] In summary, the solid phosphoric acid catalyst prepared in the prior art has the following defects:

[0004] 1. Solid phosphoric acid catalysts have the disadvantages of low mechanical strength, poor anti-sludge ability and short service life;

[0005] 2. Solid phosphoric acid catalysts cannot have the defects of high activity, high strength and high selectivity at the same time.

[0006] To this end, the present invention provides a method for preparing a long-life solid phosphoric acid catalyst. The preparation method adopts vacuum multiple impregnation and roasting technology, so that the prepared catalyst has good catalytic activity, strong pressure resistance, high selectivity, good thermal stability and long service life. Summary of the Invention

[0007] In view of the above-mentioned deficiencies in the prior art, the present invention aims to provide a method for preparing a long-life solid phosphoric acid catalyst to solve the problems that the existing solid phosphoric acid catalyst has low mechanical strength and cannot simultaneously have high activity, high strength and high selectivity.

[0008] In order to achieve the above object, the technical solution of the present invention is as follows:

[0009] A method for preparing a long-life solid phosphoric acid catalyst comprises the following steps:

[0010] First, the phosphoric acid solution and silica gel are impregnated for the first time under vacuum conditions, and after the impregnation is completed, they are drained and then calcined for the first time to obtain a catalyst after the first calcination;

[0011] The catalyst after the first calcination is cooled to room temperature, and is impregnated for the second time under vacuum conditions. After the impregnation is completed, it is drained and then calcined for the second time to obtain a catalyst after the second calcination;

[0012] The catalyst after the second calcination is cooled to room temperature, and is impregnated for the third time under vacuum conditions. After the impregnation is completed, the catalyst is drained and then calcined for the third time to obtain a solid phosphoric acid catalyst.

[0013] Furthermore, the phosphoric acid concentration of the first impregnation is 40-70%, the impregnation time is 8-14 hours, and the vacuum degree is -0.08-0.09 MPa.

[0014] Furthermore, the first calcination temperature is 300-450° C., and the calcination time is 10-15 hours.

[0015] Furthermore, the phosphoric acid concentration of the second impregnation is 40-70%, the impregnation time is 10-16 hours, and the vacuum degree is -0.09-0.095 MPa.

[0016] Furthermore, the second calcination temperature is 250-350° C., and the calcination time is 15-22 hours.

[0017] Furthermore, the phosphoric acid concentration of the third impregnation is 40-70%, the impregnation time is 15-20 hours, and the vacuum degree is -0.09-0.099 MPa.

[0018] Furthermore, the third calcination temperature is 200-300° C., and the calcination time is 20-28 hours.

[0019] As a general technical concept, the present invention also provides a long-life solid phosphoric acid catalyst prepared based on the above preparation method, and the chemical formula of the solid catalyst in terms of molar ratio is as follows:

[0020] SiA a (P2O5) b (H2O) C , where boron, titanium, aluminum or a mixture thereof is selected, a value is 0.1 to 0.5, b is 0.9 to 1.9, c is 0.7 to 1.4, and a, b, and c are the molar numbers of the corresponding elements when Si=1.

[0021] The advantages and beneficial effects of the present invention are:

[0022] The present invention provides a method for preparing a long-life solid phosphoric acid catalyst. The preparation method adopts a three-step vacuum impregnation and roasting technology, which can enable the prepared catalyst to have high crushing strength. At the same time, the catalyst has the advantages of strong anti-slitting ability, good stability and high product yield. In addition, the activity of the catalyst does not show a downward trend after long-term operation, and has the advantage of a long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention provides a flow chart of a method for preparing a long-life solid phosphoric acid catalyst. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0026] Reference Attachment Figure 1 The present invention provides a method for preparing a long-life solid phosphoric acid catalyst, comprising the following steps:

[0027] S101, firstly, performing a first impregnation of phosphoric acid solution and silica gel under vacuum conditions, draining after the impregnation, and then performing a first calcination to obtain a catalyst after the first calcination.

[0028] In this embodiment, the phosphoric acid concentration of the first impregnation is 40-70%, the impregnation time is 8-14 hours, and the vacuum degree is -0.08-0.09 MPa; the roasting temperature of the first roasting is 300-450° C., and the roasting time is 10-15 hours.

[0029] S102, cooling the catalyst after the first calcination to room temperature, performing a second impregnation under vacuum conditions, draining after the impregnation, and then performing a second calcination to obtain a catalyst after the second calcination.

[0030] In this embodiment, the phosphoric acid concentration of the second impregnation is 40-70%, the impregnation time is 10-16 hours, and the vacuum degree is -0.09-0.095 MPa; the roasting temperature of the second roasting is 250-350° C., and the roasting time is 15-22 hours.

[0031] S103, cooling the catalyst after the second calcination to room temperature, performing a third impregnation under vacuum conditions, draining after the impregnation, draining after the impregnation, and then performing a third calcination to obtain a solid phosphoric acid catalyst.

[0032] In this embodiment, the phosphoric acid concentration of the third impregnation is 40-70%, the impregnation time is 15-20 hours, and the vacuum degree is -0.09-0.099 MPa; the roasting temperature of the third calcination is 200-300° C., and the roasting time is 20-28 hours.

[0033] In this embodiment, the present invention further provides a long-life solid phosphoric acid catalyst prepared based on the above-mentioned preparation method. The chemical formula of the solid catalyst in terms of molar ratio is as follows:

[0034] SiA a (P2O5) b (H2O) C , where boron, titanium, aluminum or a mixture thereof is selected, a value is 0.1 to 0.5, b is 0.9 to 1.9, c is 0.7 to 1.4, and a, b, and c are the molar numbers of the corresponding elements when Si=1.

[0035] Description of the detection method:

[0036] The present invention uses a DL-III particle strength tester to test the catalyst crushing strength. The measured catalyst crushing strength is the axial crushing force that can be sustained per unit area, and the unit is Newton.

[0037] The present invention uses an acid-base titration indicator method to test the phosphoric acid leakage of a catalyst. The catalyst sample is heated in a neutral aqueous solution to decompose it into phosphoric acid, which is then titrated with an alkaline solution. The measured phosphoric acid leakage is measured as a percentage of phosphoric acid (P2O5).

[0038] The present invention adopts SH / T 0958 test method to test the bulk density of the catalyst. The unit of the measured bulk density of the catalyst is g / cm 3 .

[0039] The performance evaluation of the catalyst product of the present invention was carried out in a fixed bed reactor. The reactor was a stainless steel tubular reactor with an inner diameter of 16 mm and a catalyst loading of 30 mL. Olefins (C3 and / or C4 olefins) were used as the reaction raw materials. The reaction temperature was 180-240°C, the reaction pressure was 3-6 MPa, and the liquid space velocity was 0.5-3 h -1 Under the process conditions, the raw propylene is brought into contact with the catalyst to initiate a propylene polymerization reaction. The reaction products, including liquid and gaseous products, pass through a gas-liquid separator. The liquid product enters a liquid collector, where it is regularly sampled and analyzed for hydrocarbon composition. The gaseous product, or unreacted tail gas, is periodically fed to a gas chromatograph for analysis.

[0040] The analysis and calculation method in the above reaction process is to take samples of the reaction raw materials and tail gas after 12 hours of stable reaction, analyze the mass percentage of olefins in the raw materials and tail gas, and calculate the olefin conversion rate; sample and analyze the hydrocarbon composition of the liquid phase product to calculate the product selectivity. The olefin conversion rate and product selectivity are defined as follows:

[0041]

[0042]

[0043]

[0044] To further illustrate the present invention, the following detailed description of a method for preparing a long-life solid phosphoric acid catalyst provided by the present invention is provided in conjunction with examples. However, it should be understood that these examples are implemented based on the technical solutions of the present invention, and detailed implementation methods and specific operating procedures are provided only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention. The scope of protection of the present invention is not limited to the following examples.

[0045] Example 1

[0046] In this embodiment, a method for preparing a long-life solid phosphoric acid catalyst is provided. Specifically, silica gel is immersed in a phosphoric acid solution having a concentration of 50%, a vacuum degree of -0.085 MPa, and an immersion time of 10 hours. After the immersion is completed, the silica gel is drained and the dried catalyst is heated and calcined at a temperature of 380°C for 15 hours, and then cooled to room temperature after the calcination. The catalyst has a compressive strength of 30 Newtons.

[0047] The catalyst was used in the propylene polymerization reaction for evaluation and analysis. The evaluation process conditions were: reaction temperature 200 ° C, pressure 5 MPa, liquid mass space velocity 2.0 h -1 , the raw material propylene concentration is 99.5%, and the evaluation results of the catalyst are: propylene conversion rate is 80.4%, nonene selectivity is 70.7%, dodecene selectivity is 14.5%, and the total selectivity of nonene and dodecene is 85.2%.

[0048] Example 2

[0049] This example provides a method for preparing a long-life solid phosphoric acid catalyst. Specifically, the catalyst prepared in Example 1 is subjected to a second impregnation, drying, and calcination. The phosphoric acid solution has a concentration of 50%, a vacuum degree of -0.092 MPa, an impregnation time of 15 hours, a calcination temperature of 300°C, a calcination time of 18 hours, and the temperature is then cooled to room temperature. The catalyst has a compressive strength of 58 Newtons.

[0050] The catalyst was used in the propylene polymerization reaction for evaluation and analysis. The evaluation process conditions were: reaction temperature 200 ° C, pressure 5 MPa, liquid mass space velocity 0.7 h -1 , the raw material propylene concentration is 99.5%, and the evaluation results of the catalyst are: propylene conversion rate is 91.8%, nonene selectivity is 71.5%, dodecene selectivity is 17.9%, and the total selectivity of nonene and dodecene is 89.4%.

[0051] Example 3

[0052] This example provides a method for preparing a long-life solid phosphoric acid catalyst. Specifically, the catalyst prepared in Example 2 is subjected to a third impregnation, drying, and calcination. The phosphoric acid solution has a concentration of 50%, a vacuum of -0.096 MPa, an impregnation time of 18 hours, a calcination temperature of 250°C, a calcination time of 25 hours, and the temperature is then cooled to room temperature. The catalyst has a compressive strength of 80 Newtons.

[0053] The catalyst was used in the propylene polymerization reaction for evaluation and analysis. The evaluation process conditions were: reaction temperature 200 ° C, pressure 5 MPa, liquid mass space velocity 0.7 h -1, the raw material propylene concentration is 99.5%, and the catalyst evaluation results are: propylene conversion rate is 99.2%, nonene selectivity is 71.8%, dodecene selectivity is 21.6%, and the total selectivity of nonene and dodecene is 93.4%.

[0054] Comparative Example 1

[0055] In this comparative example, according to the preparation methods of Examples 1, 2 and 3, except that vacuum impregnation was changed to atmospheric pressure impregnation, other conditions remained unchanged, and the compressive strength of the prepared phosphoric acid-silica gel catalyst was 42 Newtons.

[0056] The catalyst was used in the propylene polymerization reaction for evaluation and analysis. The evaluation process conditions were: reaction temperature 200 ° C, pressure 5 MPa, liquid mass space velocity 0.7 h -1 , the raw material propylene concentration is 99.5%, and the evaluation results of the catalyst are: propylene conversion rate is 84.6%, nonene selectivity is 71.4%, dodecene selectivity is 18.7%, and the total selectivity of nonene and dodecene is 90.1%.

[0057] Comparative Example 2

[0058] In this comparative example, a catalyst was prepared according to the solid phosphoric acid catalyst preparation method provided in CN1155547C, and the catalyst was used in a propylene polymerization reaction for evaluation and analysis. The evaluation process conditions were: reaction temperature 200°C, pressure 5 MPa, liquid mass space velocity 2.0 h -1 , the raw material propylene concentration is 99.5%, and the evaluation results of the catalyst are: propylene conversion rate is 83.5%, nonene selectivity is 65.4%, dodecene selectivity is 20.1%, and the total selectivity of nonene and dodecene is 85.5%.

[0059] With reference to the above-mentioned corresponding detection methods, the physical and chemical properties of the solid phosphoric acid catalysts prepared in Examples 1-3 of the present invention and Comparative Examples 1-2 were analyzed. The results are shown in Tables 1-3.

[0060] Table 1 Results of multiple impregnation particle strength and phosphoric acid leakage

[0061] Catalyst batch Total phosphoric acid leakage / % Particle strength / Newton <![CDATA[Bulk density / (g / cm 3 )]]> Olefin conversion rate (cycle) / % Example 1 36.7 30 670.1 80.4 Example 2 47.5 58 944.5 91.8 Example 3 62.4 80 982.2 99.2 Comparative Example 1 42.7 42 789.5 84.6

[0062] As can be seen from the measurement results in Table 1, by comparing Example 3 with Comparative Example 1, it was found that the total phosphoric acid loading, bulk density and particle strength of the catalyst were increased after multiple vacuum impregnation and calcination, and at the same time, the catalytic activity of the catalyst was changed; in particular, the catalytic activity of the catalyst obtained after three vacuum impregnation and calcination was the best, indicating that the vacuum multiple impregnation and calcination process can effectively change the catalytic activity of the catalyst.

[0063] Table 2 Catalyst activity and product composition test results

[0064]

[0065] From the measurement results in Table 2, it can be seen that the catalyst of Example 3 obtained by three vacuum impregnation and calcination conditions is compared with the catalyst of Comparative Example 2. It is found that the catalyst obtained by multiple vacuum impregnation and calcination has better catalytic activity, and the content of nonene and dodecene in the product is relatively high, indicating that multiple vacuum impregnation and calcination can improve the selectivity of the catalyst for nonene and dodecene.

[0066] Table 3 Measurement results of catalyst service life

[0067]

[0068] From the stability test results in Table 3, it can be seen that the catalyst of Example 3 obtained by three vacuum impregnation and calcination methods still has high catalytic activity after 240 days of reaction, and the selectivity for nonene and dodecene is also relatively stable. This shows that the silica gel phosphate catalyst prepared by the multiple impregnation and calcination method has the characteristics of high activity, long service life and good stability.

[0069] In summary, the above test results show that the solid phosphoric acid catalyst prepared by the present invention can be used for the polymerization and polymerization reaction of low-carbon olefins to prepare C5-C 12 High carbon number olefins, especially suitable for propylene polymerization to produce nonene and dodecene, have good catalytic activity, and have the advantages of strong pressure resistance, high selectivity, good thermal stability and long service life.

[0070] The above content is a further detailed description of the present invention in conjunction with specific embodiments, and the specific implementation of the present invention cannot be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing a long-life solid phosphoric acid catalyst, characterized in that: The following steps are involved: First, the phosphoric acid solution and silica gel are impregnated for the first time under vacuum conditions, and after the impregnation is completed, they are drained and then calcined for the first time to obtain a catalyst after the first calcination; The phosphoric acid concentration of the first impregnation is 40-70%, the impregnation time is 8-14 hours, and the vacuum degree is -0.08-0.09 MPa; the roasting temperature of the first roasting is 300-450°C, and the roasting time is 10-15 hours; The catalyst after the first calcination is cooled to room temperature, and is impregnated for the second time under vacuum conditions. After the impregnation is completed, it is drained and then calcined for the second time to obtain a catalyst after the second calcination; The phosphoric acid concentration of the second impregnation is 40-70%, the impregnation time is 10-16 hours, and the vacuum degree is -0.09-0.095 MPa; the roasting temperature of the second roasting is 250-350°C, and the roasting time is 15-22 hours; The catalyst after the second calcination is cooled to room temperature, impregnated for a third time under vacuum conditions, drained after the impregnation, and then calcined for a third time to obtain a solid phosphoric acid catalyst; the phosphoric acid concentration of the third impregnation is 40-70%, the impregnation time is 15-20 hours, and the vacuum degree is -0.09-0.099 MPa; the calcination temperature of the third calcination is 200-300°C, and the calcination time is 20-28 hours.

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