Question: A type of zeolite used to convert alcohols directly into gasoline is: A. Zeolite A B. Zeolite L ...

Question

A type of zeolite used to convert alcohols directly into gasoline is:
A. Zeolite A
B. Zeolite L
C. Zeolite Beta
D. ZSM-5

Answer 1

Solution

The type of zeolite which is used to convert alcohols directly into gasoline belongs to the pentasil family of zeolite. Also it is an aluminosilicate zeolite. It has a general chemical formula as $N{a_n}A{l_n}S{i_{96 - n}}{O_{192}}$ . It is widely used in the petroleum industry as a heterogeneous catalyst during isomerization.

Complete step by step answer:
ZSM-5 is used as a catalyst in the conversion of alcohol such as ethanol and methanol to gasoline. This conversion takes place in the presence of ZSM-5 at ${300^0} - {400^0}C$ temperature.
It belongs to the pentasil family of zeolite. Also it is an aluminosilicate zeolite. It has a general chemical formula as $N{a_n}A{l_n}S{i_{96 - n}}{O_{192}}$ . For hydrocarbon isomerization, ZSM-5 is used as a heterogeneous catalyst in the petroleum industry.
ZSM-5 is a synthetic zeolite and it can be prepared by combining an aqueous solution of silica, sodium hydroxide, sodium aluminate and tetrapropylammonium bromide together in appropriate ratios.
The reaction takes place as:
$Si{O_2}\; + {\text{ }}NaAl{O_2}\; + {\text{ }}NaOH{\text{ }} + {\text{ }}N{(C{H_2}C{H_2}C{H_3})_4}Br{\text{ }} + {\text{ }}{H_2}O{\text{ }} \to {\text{ }}ZSM - 5{\text{ }} + \;analcime\; + {\text{ }}alpha - quartz$
ZSM-5 is prepared in Teflon-coated autoclave and at a very high temperature and high pressure. It can also be prepared by using different ratio of silicon oxide and aluminium.
Hence, option D is correct.

Note:
ZSM-5 is mainly used as a catalyst. In a case, copper gets deposited on the zeolite and after that a stream of ethanol is passed through at temperatures of ${240^0}$ to ${320^0}C$ as a vapour stream. Due to this the ethanol gets oxidized to acetaldehyde. And two hydrogen get lost by the ethanol in the form of hydrogen gas. It appears that the specific pore size of ZSM-5 is of benefit to this process, which also functions for other alcohols and oxidations.