ZSM-5 Zeolite: Complete Notes for Competitive Exams

ZSM-5 (Zeolite Socony Mobil-5)

Most Important for GATE ▪ IIT-JAM ▪ CSIR-NET ▪ BARC ▪ ONGC ▪ IOCL ▪ UPSC (Geology/Chemistry) ▪ State PSCs

One-Liner to Remember:
ZSM-5 is a high-silica, medium-pore, pentasil zeolite (MFI framework) developed by Mobil Oil in 1972, world’s most widely used shape-selective catalyst in petroleum refining and petrochemical industry.

Key Data Table (Memorize Completely)

Property	Value / Fact
Developer	Mobil Oil Company (now ExxonMobil)
Year of invention	1972 (patented 1975)
IZA Structure Code	MFI (Mobil-Five)
Framework type	Pentasil (ZSM-5/ZSM-11 family)
Typical Si/Al ratio	10 – ∞ (can be fully siliceous → Silicalite-1)
Pore size	Medium pore: ~5.4–5.6 Å
Channel system	3D: Straight 10-ring (5.5×5.1 Å) + Sinusoidal 10-ring (5.3×5.6 Å)
Ring members	10-membered oxygen rings
Crystal system	Orthorhombic (Pnma)
Thermal stability	Up to ~1100 °C
Acidity	Strong Brønsted acid sites (high Si/Al → fewer but stronger sites)

Shape Selectivity (Most Asked Topic)

ZSM-5 exhibits all three types of shape selectivity:
1. Reactant selectivity – Only linear/paraxylene enters pores
2. Product selectivity – Only molecules ≤5.6 Å can exit (e.g., p-xylene preferred over o/m-xylene)
3. Transition-state selectivity – Bulky intermediates cannot form inside channels

Major Industrial Applications (Repeatedly Asked)

Process	Role of ZSM-5
Methanol-to-Gasoline (MTG)	100% conversion of methanol → gasoline-range hydrocarbons
Methanol-to-Olefins (MTO/MTP)	Ethylene & propylene production
Xylene isomerization	Selective production of para-xylene
Toluene disproportionation	Benzene + p-xylene
Ethylbenzene production	Benzene + ethylene → ethylbenzene
Dewaxing (MDDW)	Removes n-paraffins → improves pour point
Fluid Catalytic Cracking (FCC)	Octane booster additive
Beckmann rearrangement	Caprolactam production (nylon-6)

Frequently Asked MCQs (Actual Exam Level)

1. ZSM-5 zeolite belongs to which framework type?
Ans: MFI

2. The pore diameter of ZSM-5 is approximately
(A) 8 Å (B) 5.5 Å (C) 7.4 Å (D) 12 Å
Ans: (B) ~5.5 Å (medium pore)

3. Which company developed ZSM-5?
Ans: Mobil Oil (now ExxonMobil)

4. The first commercial process using ZSM-5 was
Ans: Methanol-to-Gasoline (MTG) – New Zealand plant, 1985

5. ZSM-5 is used for selective formation of which xylene isomer?
Ans: para-Xylene

6. Which zeolite is called “pentasil” zeolite?
Ans: ZSM-5 and ZSM-11

7. In Fluid Catalytic Cracking, ZSM-5 additive increases
Ans: Octane number (by producing more light olefins)

Quick Revision Points (1–2 Markers)

• Full form: Zeolite Socony Mobil – 5
• First synthetic zeolite with 10-membered ring channels
• Can be synthesized with TPA⁺ (tetrapropylammonium) as template
• H-ZSM-5 is the protonic (acidic) form used as catalyst
• Silicalite-1 = aluminium-free ZSM-5
• New Zealand’s MTG plant (1985–1997) was world’s only commercial gasoline-from-methanol plant

Previous Years’ Questions

GATE Chemistry 2022:

ame the zeolite used in MTG process

ZSM-5

CSIR-NET 2023:

Which zeolite shows shape-selective catalysis for para-xylene?

ZSM-5

ONGC 2024:

Pore size and framework code of ZSM-5

~5.5 Å, MFI

IIT-JAM 2023:

ZSM-5 is a ----- pore zeolite

Medium

GATE Chemistry 2024

The zeolite used as a catalyst for the conversion of methanol to gasoline (MTG process) is

ZSM-5

GATE Chemistry 2023

The framework type of ZSM-5 zeolite is

MFI

GATE Chemical Engg. 2023

ZSM-5 additive in FCC is primarily used to increase

Octane number / Propylene yield

GATE Chemistry 2022

The zeolite that exhibits shape-selective catalysis for para-xylene production is

ZSM-5

CSIR-NET Chemical Sciences Dec 2023

The template used for the synthesis of ZSM-5 is
(a) TPA⁺   (b) TMA⁺   (c) TEA⁺   (d) TBA⁺

(a) Tetrapropylammonium cation (TPA⁺)

CSIR-NET Chemical Sciences June 2022

The pore size of ZSM-5 falls in the category of

Medium pore (≈ 5.5 Å)

CSIR-NET 2021

Silicalite-1 is the aluminium-free analogue of

ZSM-5

IIT-JAM Chemistry 2024

The crystal system of ZSM-5 is

Orthorhombic

IIT-JAM Chemistry 2022

Which one of the following zeolites is a pentasil zeolite?

ZSM-5

ONGC GT Chemistry 2024

The commercial catalytic dewaxing process that employs ZSM-5 is known as

MDDW (Mobil Distillate Dewaxing)

ONGC GT 2023

The channel structure of ZSM-5 consists of

10-membered rings with straight and sinusoidal channels

BARC OCES/DGFS 2023

The company that invented ZSM-5 is

Mobil Oil

IOCL Refining Technologist 2023

In xylene isomerization, ZSM-5 is used for selective production of

para-Xylene

UPSC IFS Chemistry 2023

Name the zeolite used in Methanol-to-Olefins (MTO) process.

ZSM-5 (or SAPO-34, but ZSM-5 is accepted)

GATE Chemistry 2020

The acid form of the zeolite catalyst used in petroleum refining is denoted as

H-ZSM-5

CSIR-NET June 2019

Which of the following shows product shape selectivity?
(a) Zeolite A   (b) Zeolite Y   (c) ZSM-5   (d) Mordenite

(c) ZSM-5

GATE 2018 (Chemical)

The first large-scale commercial plant using ZSM-5 was located in

New Zealand (MTG plant, 1985–1997)

HPCL Engineer 2022

ZSM-5 catalyst is used in the production of caprolactam via

Vapour-phase Beckmann rearrangement of cyclohexanone oxime

GATE Chemistry 2017

The Si/Al ratio in ZSM-5 is usually

>10 (high silica zeolite)

NTPC ET 2023

Which zeolite is added in small amounts to FCC catalyst to boost gasoline octane rating?

ZSM-5

ISRO SC Chemistry 2022

The hydrocarbon pool mechanism is operative in

Methanol-to-hydrocarbons conversion over ZSM-5

BPCL Engineer 2024

Mobil’s selective toluene disproportionation process using modified ZSM-5 produces para-xylene with selectivity > --- %

90–95%

Must Read ZSM-5 PYQs