| During the 1980', ZSM-22 was identified with MObile corporation USA. ZSM-22 is a microporous, high silica aluminosilicate zeolite, having a TON structural. Compared with ZSM-5(5.6×5.4(?), 5.5×5.3(?)), the structure of ZSM-22 consists solely of 5-, 6-, and 10-rings. The one-dimensional, nonintersecting channel system has 5.5×4.5(?) with 10-membered ring openings, provide special shape-selective that have specific importance in isomerization of normal alkanes. So far the synthesis of SiO2/Al2O3 ratio range is from 20 to 90, that restrict the application of ZSM-22 to a certian extent.Zeolite ZSM-22 was prepared under the static hydrothermal condition with potassium hydroxide as alkali source, silica sol as silica source and 1, 6-diaminohexane as template. The crystallization temperature, crystallization time and material ratio were studied. Pure zeolite ZSM-22 samples with different SiO2/Al2O3 ratio and grain size were obtained. N-hepatane reacting conditions(reaction temperature, WHSV, the molar ratio of H2/C7, exchange concentration) over HZSM-22 were studied. Then, the isomerization of n-hepatane was carried out over different SiO2/Al2O3 ratio and grain size HZSM-22 samples in a fix-bed flow reactor. According to the study, we found out:1.The synthesis of pure zeolite ZSM-22 was successfully achieved under the condition: crystallization temperature was 150-170℃, crystallization time was 12-72h, n(DAH)/ n(SiO2) was 0.2-0.4, n(H2O)/n(SiO) was 20-40, seed contents was 1500-l0000ppm. The best synthesis conditions were: crystallization temperature was 160℃, crystallization time was 48h, seed contents was 1500ppm, material ratio was 1.3K2O: 3DAH: 0.11Al2O3: 10SiO2: 400H2O.2. From above synthesis condition, different SiO2/Al2O3 ratio ZSM-22 was synthesized. When SiO2/Al2O3 ratio≤40, there wasn't produced ZSM-22; when SiO2/Al2O3 ratio≥130, there was produced ZSM-22 with great amount crstobalite impurity. Through changing the alkalinity(n(K2O)/n(SiO2)为0.03-0.07), pure zeolite ZSM-22 samples with varied SiO2/Al2O3ratio (40-130) was obtained.3. Different grain size ZSM-22 was synthesized SiO2/Al2O3 ratio at 130. The stirring time and the n(NaCl)/n(Al2O3) ratio were studied. Zeolite ZSM-22 with 3μm,2.8μm,1.6μm and 700nm were synthesized. 4. The experiments showed that the best reaction conditions were: reaction temperature was 400℃, WHSV was 10h-1, the molar ratio of H2/C7 was 2:1, exchange concentration was 1mol/L, atmospheric pressure. Under this condition, on the sample of SiO2/Al2O3 ratio at 130 and grain size at 700nm, the convertion and the selectivity reached 16.57% and 91.5%, respectively. |
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