The Technique Of Microcalorimetric Adsorption And Its Application In Studying Several Acid/Base Materials

Microcalorimetric adsorption technique is a method of mensurating the relation between adsorbed capacity and heat when the adsorbate was adsorbed in the sorbent suface. The differential heat means the adsorbed strength of the adsorbed center and the adsorbate coverage means the quantity of the adsorbed center with microcaloric adsorption, consequently obtaining the adsorbed strength distribution.Microcalorimetric adsorption technique can reflect excellently the actual status for the catalyst of gas reaction comparing the titration method of indicator in the non-water solution, and its precision is much better. And with the small molecule NH3 as the probe molecule, this method can resolve the problem of diffuse control in the zeolite with small or resistant pore. Microcalorimetric adsorption technique can character the comparative accurate acid/base strength distribution comparing the TPD method which can only give the average acid/base strength with gas adsorbed dynamic methods. But there is still some localization. Combining the other investigating methods for example the FT-IR spectrum, Mossbaur and so on, it can also gain the information relative to the character of the adsorbed center in the surface. If we choose the proper acid/base probe molecule, the calorimetric adsorption technique is a very effective quantitative analysis method of the acid/base catalysis materials.In this paper we have ourselves built a microcalorimetric adsorption system and used the microcalorimetric adsorption technique combining with some other mensuration to see the adsorption performance of five kinds of acid/base materials, and we can gain these primary conclusions as follow: (1)In this paper, alkalescent aminopropyl-functionalized SBA-15 materials are synthesized by postgrafting method. To synthesize NH₂-SBA-15 with the best efficiency of the flavanone, we have seen about the synthesized condition of the NH2-SBA-15 with the microcalorimetric CO₂ adsorption technique of getting the alkali strength and quantity at the same time, and changed the temperature and the time of baking SBA-15, and adjusted the amount of aminopropyl-triethoxysilane. We have found a conclusion via the calorimetric adsorption data of CO₂ in 150℃: the SBA-15(550,6,1.5)whose the initial adsorption heat is 228 kJ /mol and the saturation cover degree is 68.7μmol/g is a type of solid alkali catalyst which have the uniform mesopore distribution, the bigger alkali quantity, complete aminopropyl-functionalization, and which have the big pore, the thick bore wall and good water-heat stability and so on. We realize optimizing synthesized condition of NH2-SBA-15 with microcalorimetric adsorption technique of CO₂: high-temperature baking SBA-15 6 hours in 550℃, the mass ratio is 1:5 between aminopropyl-triethoxysilane and SBA-15. We can also know that microcalorimetric adsorption technique is a good method of basicity quantity and strength, and it can be used to watch and measure the change of the catalyst in synthesis.(2)The MCM-22 family zeolite, include MCM-22,MCM-36,MCM-49 and MCM-56, those all have the MWW framework and independent 10MR and 12MR pore at the same time, shows the favorable catalysis performance in the reaction of isomerization, alkylation, cracking, alkyl translation into alkene or aromatic hydrocarbon and so on. It is a typical microporous solid acid catalyst. The acidity of these solid acid catalysts influences the catalytic activity and the selectivity intensively, so we used calorimetric adsorption technique with NH3 to study the acid strength and quantity of MCM-22,MCM-36,MCM-49å’ŒMCM-56 zeolite, combining the FT-IR spectrum of pyridine adsorption. The result shows: HMCM-49,HMCM-56,HMCM-22 and HMCM-36 are all have two kinds of acidity strength centers, the overall acidity quantity of these four zeolites is 1.106mmol/g,1.123mmol/g,0.382mmol/g and 0.357mmol/g. The four acidity zeolites all have B and L acidity, the acid quantity of HMCM-49 is bigger and the most is B acid; HMCM-56 has big acid quantity and close to HMCM-49, but more L acidity; The acid quantity of HMCM-22 and HMCM-36 is close and small, HMCM-22 has more B acid; The proportion of B acid and L acid of HMCM-36 is close, and the B acidity is more.(3) As the absorbent of carbon dioxide, solid-state amine resin has a large of advantages. The physical and chemical character of solid-state amine resin is good. And it has light density, fine regeneration capability, long life, nontoxic and no the second pollution. So the solid-state amine resin is an applied cleaning carbon dioxide absorbent with high efficiency in the sealed circumstance. For explaining the carbon dioxide adsorption capability of solid-state amine resin which we synthesized, we used the homemade calorimetric adsorption system to determine the carbon dioxide adsorption efficiency. We can conclude those conclusions: carbon dioxide adsorption capacity of solid-state amine resin decreases with the increase of surrounding temperature in the anhydrous condition; As the absorbent of carbon dioxide, the solid-state amine resin I and II can be repeated adsorption under the anhydrous condition; When solid-state amine resin I adsorbed trace water, the initial differential heat of adsorption increases remarkably, and the adsorption capacity for carbon dioxide is boosted up; And solid-state amine resin II is a better carbon dioxide adsorbent than solid-state amine resin I with uniform basic strength distribution.(4)HMCM-49 zeolite is a typical acidic material, its acidity corresponds to the acidity of HZSM-5 and HMCM-22, and it displays excellent catalysis performance. In this paper we eliminate the aluminum atoms from the HMCM-49 zeolite effectively with the nitric acid washing-up method. The calorimetric adsorption of NH3 shows that washing-up the aluminum atoms by nitric acid can change the acidity of the HMCM-49 zeolite with two kinds of acid strength. The degree of eliminating aluminum increases with the increase of the time and temperature of the nitric acid washing-up. From the curve of NH3 heat of adsorption vs the coverage, we can see that acid strength was not modified and the two kinds of acid quantity decreased at low-grade comparing HMCM-49; The dealumination samples not only decreased the two kinds of acid strength but also reduced the acid quantity in strong-grade. The dealumination sample is eliminated the strong L acid and the B acid at low-grade and strong-grade. From the catalytic activity and the selective data of the HMCM-49 zeolite dealumination sample on the liquid-phase alkylation of benzene with propylene reaction, we can see that the catalytic activity of the dealumination sample decreased, but selectivity of the cymene increased. (5)Amorphous mesoporous aluminophosphates (AlPO) is a non-silicon group mesoporous material. There is big BET surface area, uniform mesopore, and the pore diameter which can be adjusted in a certain range in the AlPO. The task group where the teacher Zhang wenxiang and Jia mingjun work synthesized the mesoporous aluminophosphates(AlPO) which have uniform mesopore by using the citric acid (CA) route successfully first. The heat stability of this AlPO material is high, and the P/Al ratio can be easy to control. The investigation shows that the change of P/Al ratio can influence the composing, structure, the heat stability and numbers of acidic and basic sites on the surface of the catalyst of AlPO. In this paper we investigated the acidity and the alkalescence of AlPO material with microcalorimetric adsorption technique. The result shows that there are weak acidity and basicity in the AlPO material with different P/Al ratio, and acidic P-OH's are likely to active sites in the vapor phase selective O-methylation of catechol with methanol reaction, and the acidic-basic property probably influences the selective of guaiacol.