397
• Homolytic where oxidation occurs outside the metal coordination sphere via a
radical chain mechanism
• Heterolytic in which activation of substrate or oxidizing reagent for the nucleophilic attack occurs by coordination to the metal clusters [13]
Recently researchers have been focusing on utilizing the exceptional separation
ability of MOFs in petroleum refineries to meet the environmental and governmental policies and regulations. MOFs’ tailored topology endures them to execute complex separations far more cheaply than standard oil-refining techniques. More
specifically in refineries, the MOFs are used as substances that are capable of separating individual hydrocarbons from various mixtures of organic molecules produced by refining processes. This separation of components from the soup of
organic molecules in an energy potent approach is the most challenging task in the
petrochemical and chemical industries. Although the refineries constitute various
complex operations and complex catalytic reactions, the high energy demand is
restraining their advance blooming. It is observed that the separation processes
solely account for approximately 40% of the total energy consumed by refineries.
Therefore the discovery of using MOFs in separation processes turns out to be a
quantum leap for refineries and petrochemical industries [22].
Propylene is one of the most important products obtained from the petrochemical
industry. Its production is a very energy-intensive process because it includes separation of propylene from other hydrocarbons. Presently this separation is achieved
by cryogenic distillation in which two gases are liquefied at sub-zero temperatures.
MOFs which are porous, crystalline polymers have emerged to be a promising alternative to this high energy demanding separation process. The higher surface area
and pore volume of MOFs enhances its capturing efficiency of desired molecules.
This attracted the interest of researchers toward the evolution of MOFs having various pore shapes and topology and making them the prime candidates in the carboncapture process. Thus MOFs-based membranes were developed. These are
considered to be the best material for separating the molecules with greater efficiency. For example, ZIF-8 MOF allows propylene to diffuse through its pore more
potently instead of propane at 30 °C [14].
3.4 Disadvantages of MOFs
There are many disadvantages with MOFs apart from their exceptional properties.
The major limitations related with the MOFs are:
• Lower framework density, as low as 0.13 g cm
−3
• Lower stability
• Lower selectivity and acid/base properties as compared to zeolites
Non-conventional Catalytic Materials for Refining and Petrochemicals
• Homolytic where oxidation occurs outside the metal coordination sphere via a
radical chain mechanism
• Heterolytic in which activation of substrate or oxidizing reagent for the nucleophilic attack occurs by coordination to the metal clusters [13]
Recently researchers have been focusing on utilizing the exceptional separation
ability of MOFs in petroleum refineries to meet the environmental and governmental policies and regulations. MOFs’ tailored topology endures them to execute complex separations far more cheaply than standard oil-refining techniques. More
specifically in refineries, the MOFs are used as substances that are capable of separating individual hydrocarbons from various mixtures of organic molecules produced by refining processes. This separation of components from the soup of
organic molecules in an energy potent approach is the most challenging task in the
petrochemical and chemical industries. Although the refineries constitute various
complex operations and complex catalytic reactions, the high energy demand is
restraining their advance blooming. It is observed that the separation processes
solely account for approximately 40% of the total energy consumed by refineries.
Therefore the discovery of using MOFs in separation processes turns out to be a
quantum leap for refineries and petrochemical industries [22].
Propylene is one of the most important products obtained from the petrochemical
industry. Its production is a very energy-intensive process because it includes separation of propylene from other hydrocarbons. Presently this separation is achieved
by cryogenic distillation in which two gases are liquefied at sub-zero temperatures.
MOFs which are porous, crystalline polymers have emerged to be a promising alternative to this high energy demanding separation process. The higher surface area
and pore volume of MOFs enhances its capturing efficiency of desired molecules.
This attracted the interest of researchers toward the evolution of MOFs having various pore shapes and topology and making them the prime candidates in the carboncapture process. Thus MOFs-based membranes were developed. These are
considered to be the best material for separating the molecules with greater efficiency. For example, ZIF-8 MOF allows propylene to diffuse through its pore more
potently instead of propane at 30 °C [14].
3.4 Disadvantages of MOFs
There are many disadvantages with MOFs apart from their exceptional properties.
The major limitations related with the MOFs are:
• Lower framework density, as low as 0.13 g cm
−3
• Lower stability
• Lower selectivity and acid/base properties as compared to zeolites
Non-conventional Catalytic Materials for Refining and Petrochemicals