Zeolites, crystalline aluminosilicates, have been widely used as unique catalysts in many petrochemical processes. The first key to their activity is that the proton or multivalent cation-exchanged zeolites usually show extremely strong Brönsted acidity, which is essential for promoting many kinds of organic reactions of hydrocarbons, e, g. dehydration, polymerization, isomerization, alkylation, cracking and so on. The second key is that the anhydrous crystal has a large, regular pore structure, which lets it function efficiently as molecular sieves to sort out molecules, reactants and/or products. This aspect is called the shape selectivity in catalysis, for which the effective sige of pore opening is important. In 1976, MTG (Methanol To Gasoline) process was reported on HZSM-5, which is very strong in Brönted acidity, and has a zigzag pore channel of uniform size. This invention affords us the most typical shape selective reaction. Further extension of the idea is desired in the field of C
1 chemistry to produce ethylene or propylene selectively from methanol.
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