And Solid acid The properties that have an important relationship with the catalytic behavior are acid center, acid strength and acidity. ① The acid centers on the surface can be divided into B-acid and L-acid (see Acid base catalyst ）And sometimes there are alkali centers at the same time. The formation of acid centers on the surface of alumina can be schematically represented by the following formula: 
solid acid catalyst infrared spectrum The research shows that γ - Al calcined at 800 ℃ two O three There can be five types of hydroxyl groups on the surface, corresponding to five acid centers with different acid strengths. Acid centers appear on the surface of mixed oxides, mostly due to the metal ion Have different Valence Or different coordination number Formed. SiO two -Al two O three The acid center model of (see figure) has many modes.
solid acid catalyst ② Acid strength, Hamet acid can be used Strength function H zero To represent Solid acid The smaller the value is, the higher the acid strength is. ③ Acidity, in unit weight or unit Surface area The number of upper acid centers or millimoles is called acidity. There are usually multiple types on the same solid surface Acid strength different Acid center , and the quantity is different, so acid intensity distribution It is also one of the important properties. By some Solid acid The range of acid strength of SiO two -Al two O three 、B two O three -Al two O three It is strongly acidic, and its acid strength is equivalent to the acid strength of sulfuric acid aqueous solution with a concentration of more than 90%. different catalytic reaction There are often certain requirements for the acid strength of the catalyst, such as sulfate Go up aldehyde Aggregation propylene Aggregation Paraldehyde Depolymerization Propylene hydration The acid strength range of effective catalyst is H zero ≤3.3, H zero ≤1.5， H zero ≤-3，-3< H zero <+1.5。 Conduct the same operation on the same type of catalyst Reaction time , catalytic activity It is related to the acidity of catalyst, such as SiO two -Al two O three upper Cumene The catalytic activity is similar to the acidity of the catalyst linear relationship 。 Solid catalyst Most of them are porous materials. In addition to the acid function of their surface, the effect of pore structure on reactant Diffusion and Heat transfer process Impact. For example, for Hydrocarbons Reactions are designed with many regular pore structure The solid acid catalyst, such as molecular sieve catalyst with tubular and cage like pores, has a layered structure Hemicrystalline state Aluminium silicate Or silicate catalyst. There are many kinds of solid acid catalysts with different manufacturing methods. Examples are as follows: ① Manufacture of natural clay catalyst. In the early stage, natural clay was used to manufacture oil catalytic cracking catalyst acid treatment And then washed and dried. Acid treatment is used to remove metals Impurity ion , exposed silicon aluminum framework structure, and used Hydrogen ion Replace the original sodium, calcium, etc cation 。② Manufacture of synthetic mixed oxides. Most Representativeness Amorphous aluminum silicate catalyst used for oil catalytic cracking can be prepared by stepwise precipitation method Coprecipitation method or Hybrid method manufacture. industrial production Multi step precipitation method water glass Add H to the solution two SO four Made into SiO two hydrogel The slurry is aged into a gel structure suitable for serving as a catalyst skeleton. Then add Al to the slurry two (SO four ) three Solution, reuse ammonia Make aluminum deposit on SiO two Hydrogel. Filtering, filter cake Add water to make slurry, spray drying become Microsphere And then repeatedly wash to remove Na two SO four And finally dry. ③ Manufacture of molecular sieve catalyst. stay Amorphous silicon -Aluminium Mucilage Liquid incorporation rare earth Y-type after exchange molecular sieve , spray drying, washing and re drying to obtain molecular sieve cracking catalyst (see molecular sieve catalyst). ④ Manufacture of semi synthetic catalyst. Add a part of the molecular sieve catalyst kaolin And Silicon aluminum gel As a carrier, the catalyst is called semi synthetic catalyst. Change to use in recent years Silica sol 、 Aluminium sol As Binder , rare earth- Y-type molecular sieve Kaolin clay has been bonded into a new generation of Semi synthetic cracking catalyst 。⑤ Manufacture of solid acid catalyst for lubrication. Set H three PO four Aqueous solution and diatomite After mixing, drying, grinding, kneading and drying, the finished product can be used for alkylation of benzene ethylbenzene 、 Cumene , can also be used for olefin Superposition hydration Etc. 
