Preparative conditions, SAPO

Table 15.3 Preparative conditions for SAPO-34 in Table 15.4. All samples were stirred during crystallization. DPA = di-n-propylamine.

Methanol to Ethylene. Methanol to ethylene economics track the economics of methane to ethylene. Methanol to gasoline has been flilly developed and, during this development, specific catalysts to produce ethylene were discovered. The economics of this process have been discussed, and a catalyst (Ni/SAPO 34) with almost 95% selectivity to ethylene has been claimed (99). Methanol is converted to dimethyl ether, which decomposes to ethylene and water the method of preparation of the catalyst rather than the active ingredient of the catalyst has made the significant improvement in yield (100). By optimizing the catalyst and process conditions, it is claimed that yields of ethylene, propylene, or both are maximized. This is still in the bench-scale stage. 

The cracking catalysts were prepared by diluting SAPO-37 samples in a silica matrix. The cracking experiments were carried out in a quartz fixed bed tubular reactor after "in situ" activation. The activation was performed by increasing the temperature up to 823 K at 2K.min ", under N2 flow (240 ml.min"" ). These conditions were maintained for 4 hours, and then N2 was changed to dry air (240 ml.min"" ) for 1 hour. At this point, the temperature was raised (2K.min 1) up to 923 K and maintained overnight. After this treatment all the organic template was removed from SAPO crystals. 

The preparation of a solution of soap by the reaction of fat with water in the presence of base was probably one of the earliest chemical processes discovered by humans. Although the details of this discovery are lost in antiquity, we can imagine early humans finding that water that had been in contact with wood ashes from the campfire could be used to remove grease from hands and other objects and that this water became a more effective cleaning agent as it was used. The water leaches some alkaline compounds from the ashes, and this basic water hydrolyzes the esters of the fat or grease to alcohols and soap. This is why the hydrolysis of esters under basic conditions is called saponification (the Latin word for soap is sapo). 

In addition to demonstrating that discrete acid sites are formed upon substitution into the AIPO-5 framework, we made two other important observations. First, the calcination conditions used for preparing all of the materials was critical. This had been reported previously for CoAPO-5 [6], but we found that it was equally true for SAPO-5. Second, materials prepared with high concentrations of either Co+2 or Mg+2 tended to have many defects. These materials exhibited reasonable pore volumes as measured by 62 uptakes however, larger molecules were unable to enter the structure. 

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