Advances in Fine Petrochemical Industry LIU Weiqiao1, XU Jingfeng1, SUN Guida2, WU Yizhi3, ZHANG Jinyuan4(1. College of Petrochemical Engineering, Liaoning Shihua University, Fushun 113001, China; 2 Beijing Institute of Petrochemical Technology, Beijing 102600, China 3. PetroChina Fushun Petrochemical Company, No. 3 Oil Plant, Fushun 113001; 4. Petroleum No.1 Plant, PetroChina Fushun Petrochemical Company, Fushun 113008) Selectivity, thermal stability, and damp-heat stability. The synthesis and application of various zeolite molecular sieves developed rapidly after SAPO developed synthetic zeolite molecular sieves. In 1982, the company developed a new type of molecular sieve with non-silicon and aluminum skeletons, namely AlPO 4 series molecular sieves [1. However, because the molecular sieve of this molecular sieve is electrically neutral, it does not have ion exchange property, and the surface acidity is weak. Therefore, it is limited in application. In 1984, Lok et al. [2] introduced Si into AlPO4 series molecular sieves to synthesize a series of silicoaluminophosphate (SAPO) molecular sieves, which are the third generation of molecular sieves following the synthesis of molecular sieves represented by natural zeolites and ZSM*5. The molecular sieve is a three-dimensional framework structure composed of three tetrahedral units of AlO4, PO4 and SiO4, and its skeleton is negatively charged and has protonic acidity. The different pore sizes determine the structure of the SAPO series of molecular sieves. SAPO *11 is a member of the SAPO series molecular sieves, and its structure type is similar to that of AlPO4-11, belonging to orthorhombic system, with a medium pore size structure, and its physicochemical properties are similar to aluminosilicate zeolites, and at the same time have certain aluminophosphate molecular sieves. The characteristics can be used as adsorbent, catalyst or catalyst carrier, and has its wide application prospects. In recent years, the review on the acidic nature of SAPO and its catalytic applications in chemical industry has been reviewed.

Synthesis of 1 SAPO-11 Molecular Sieve 1.1 General Synthetic Methods At present, rice hydrothermal crystallization is generally used to synthesize SAPO or pseudoboehmite), phosphorus source (orthophosphoric acid), and template (R)-generally di-n-propylamine (DPA) or Diisopropylamine (DIPA). The reactant condensate is added to a mixture of orthophosphoric acid and water, and the silica sol and the templating agent are separately added after stirring. Stir at room temperature into a gel, into a stainless steel autoclave sealed, crystallized at 140 ~ 200 * C constant temperature. After the crystallization is complete, the product is filtered, washed with 80*C distilled water until the pH value is unchanged, and dried in 100*C air, namely, the SAPO-11 molecular sieve original powder is synthesized.

1.2 Factors Affecting the Synthesis of SAPO-11 Molecular Sieve 1.2.1 Influence of Different Template Agents Template agents are substances that play a structural role in the crystal formation process. Its main effects are electronic and spatial effects. According to 〔4 reported for SAPO amines. In the synthetic SAPO 5~1.50 range, the templating agent is preferably diisopropylamine. When n(Si2)/n(Ak3) is less than 0.5, di-n-propylamine is preferable, and n(P2O5)/n(Ah3)>1 is the best among the reactants. The main miscellaneous crystal of SAPO*11 molecular sieve is SAPO*5. The molar ratio of diisopropylamine to P2O5 should be greater than 1. If the amount of diisopropylamine is small, the resulting SAPO-5 heterocrystallites will be added.

There are also [5] reports that, through energy calculations, it is shown that diethylamine is more conducive to the synthesis of high silica content SAPO-11 molecular sieves than dipropylamine, and is synthesized using diethylamine as a template at higher temperatures under hydrothermal conditions. For SAPO-11 samples with different silicon-aluminum atomic ratios, the ratio of Si to Al increased, the crystallinity decreased, and the grains became smaller.

1.2.2 Influence of silicon content Liu Weiqiao et al. The SAPO-11 molecular sieve and its application in the chemical industry only made the relationship between the number of acid sites of the SAPO 5 molecular sieve and its Si content, and found that when the mass fraction of Si is less than 1%, one Si atom produces an acid center, followed by With the increase in the mass fraction of Si, the number of acid sites rapidly decreases. He believes that this is due to the fact that Si has a different mechanism for replacing the AIPO4-5 backbone atoms at different Si contents. Therefore, it can be considered that due to the presence of different Si content, the mechanism of Si substitution for A1PO4*11 is also different, which leads to the influence of different reaction media of SAPO 1.2.3. The SAPO ~ 1.0 obtained by crystallization of diisopropylamine as a template agent in an acidic medium In the alkaline medium, the crystallized SAPO-11 product is gathered from single crystals into rectangular or spherical aggregates. The grain size is generally 6~7m. Di-n-propylamine is used as the template agent, and most of the spherical aggregates are obtained in the acidic medium. The body size is generally 2~3 rtn. In the alkaline medium, all the spherical aggregates are obtained, and the grain size is 5 11 molecular sieves. It is stable when roasted at 750*C. Studies have shown that fluoride ions also play a structural guiding role in the synthesis process of molecular sieves, as with the templating agent, and play a stabilizing role in the molecular sieve structure.

1.2.4 Effect of crystallization conditions The crystallization temperature and crystallization time are two important parameters for the synthesis of molecular sieves and have a significant influence on the crystallization process. As the crystallization temperature increases, the induction period shortens and the crystal nucleus accelerates. At 200°C, the crystals were directly crystallized from amorphous colloids to SAPO 170*C, and the amorphous colloids were first converted to intermediate transitional crystalline phases and formed.

By controlling the appropriate crystallization conditions, the crystallization time can be greatly shortened and rapid synthesis can be achieved. Sinha [8 using dipropylamine as a template agent, using rapid synthesis of SAPO-11 molecular sieve, the temperature of the gel from room temperature to 1.5C/min to 200C, constant temperature crystallization 4h, the synthesis of the catalyst has a relatively high acidity, Compared with the traditional method, the formed sample particle size and morphology are more uniform.

The Structure and Properties of 2SAPO-11 Molecular Sieve The elements of SAPO-11 molecular sieve are Si, P, Al and O4 elements, and the anhydrous form of molecular sieve is mR: made from a pair of chair-type 4-member rings and a pair of ship models. Elemental ring composition. The main channel is a 10-ring oval. The pore size is (4.4X6.7) X1010m, the wall of the pore is 6-membered ring, and the pore size is 2.6X1010m [9. See the structure of SAPO*11 molecular sieve.

(a) Two boat-shaped 4-membered ring connection methods (b) Two chairs-shaped 6-membered ring connection method *11 The ten-membered ring main pores SAPO-11 molecular sieve molecular sieve surface acidity infrared spectrum study found [10, SAPO- 11 The development of fine petrochemicals on molecular sieves*11 The acid strength and number of acid sites of molecular sieves were calculated. The activation energy of desorption was obtained by the rectangular method. It was concluded that SAPO-11 is a molecular sieve with medium acidity, which is caused by the introduction of Si into molecular sieves. Aluminum phosphate molecular sieve AlPO4 *11 is formed by connecting Al4 tetrahedron and PO4 tetrahedron strictly according to the ratio of 1:1. The net charge of the skeleton is zero, and the acidity is very weak. After the Si atom is formed in the aluminum phosphate skeleton to form the SAPO-11 molecular sieve, The skeleton is composed of three tetrahedrons of Al4, PO4 and Si4. The negative net charge of the skeleton exists in the interval of Si-O*Al, making the SAPO-11 molecular sieve possess protonic acidity.

Sex *C, respectively, heated to 600 * Q still maintain its crystal structure.

The SAPO-11 catalyst is suitable for the conversion of light olefins. During the conversion of light olefins to gasoline products, the SAPO-11 molecular sieve is highly active and highly selective due to its mild acidity and unique pore structure. The catalyst. For example, in the process of low molecular weight polymerization of propylene to produce liquid gasoline products, it exhibits very high low-molecular-weight polymerization activity and excellent shape-selective catalytic ability for liquid products, with good selectivity and high yield. At a temperature of 371 and a pressure of 25 kPa, the conversion of propylene can reach 83.6%, and the selectivity of the liquid product can reach 77. The process of synthesizing gasoline with coal or natural gas as raw material is an important way to obtain vehicle fuel. Syngas can be converted to gasoline using the Fischer-Tropsch (F*T) process, but process selectivity and gasoline quality are poor. Coughlin et al. [12] combined Fe- or Co-containing catalysts with SAPO*11 molecular sieves to form a bifunctional catalyst for the conversion of synthesis gas into a C5 or higher gasoline component, which can improve process selectivity and product quality.

Isobutylene is mainly used for the production of methyl tert-butyl ether (MTBE) and methyl methacrylate. Global excess n-butene, environmental protection law also prohibits its direct use of gasoline, so the conversion of n-butene into a practical significance. SAPO studies have shown that isomerization reactions are favored at low temperatures.

The study of active centers showed that the medium-strong B acid center is the active site of the isomerization reaction, and the strong B acid center easily induces side reactions such as dimerization and cleavage. In the presence of 10-membered ring-channel molecular sieves SAPO-11, isobutylene is difficult to dimerize, and the carbon deposition associated with the isomerization of n-butene has little effect on the yield of isobutylene, but it is a low-temperature dimerization reaction of isobutylene. There is a clear inhibitory effect, and the dimerization reaction proceeds only on the outer surface of SAPO-11, while the isomerization of n-butene is mainly carried out inside the 10-membered ring channel of the molecular sieve, so that the yield of isobutene can be increased. . Yang SzeMing et al. [13] studied the isomerization of n-butene on mesoporous molecular sieves. At a reaction temperature of 300*C, pressure of 0.01 MPa, and an airspeed of adsorption of 1.11, the conversion was 55.5%. For 645%, the isobutylene yield is 38.5%. Para-xylene is an important chemical raw material for producing polyester fibers. In the xylene isomers obtained from reformed gasoline, pyrolysis gasoline and toluene disproportionation, the content of meta-xylene is as high as More than 50%, but the use is very little, it is necessary to isomerization of meta-xylene to paraxylene. In recent years, the application of molecular sieves in the meta-xylene isomerization process has been studied at home and abroad. Sinha [8 et al. used the rapid crystallization method to synthesize mesoporous SAPO-11 molecular sieves. Compared with the conventional method, the particle size and morphology were more uniform, more acid sites could be formed, and the mesitylene isomerization had higher activity. . The meta-xylene isomerization reaction was carried out at a reaction temperature of 350*C, an adsorption space velocity of 3 h, and a reaction time of 3 h, and compared with the conventionally produced SAPO-11 molecular sieve. The results are shown in Table 1 [14. The SAPO-11 molecular sieve synthesized by the rapid crystallization method was also used for the toluene alkylation, but also had a higher para-selectivity [14. At 350 * C, the adsorption rate of space 3h1, toluene conversion was 36.58%, The yield of xylene is 30.71%, and the paraxylene content in xylene is 57%. Table 1 Conversion of m-xylene over SAPO catalyst, %'product yield, % toluene xylene (o- and p-position) trimethylbenzene 4 Conclusion Currently The n-butene isomerization catalyst has the most potential for development. In the framework of thermal 11 molecular sieves, the structure and properties of Pan Gan Liu Weiqiao et al. SAPO-11 Molecular Sieve and Its Application in Chemical Industry SAPO*11 New Molecular Sieve, such as MAPSO*11 or ELPSO-11 Molecular Sieve [15. Basic research, modification and application of SAPO*11 molecular sieve still needs further exploration and development .