Mesoporous Catalysis

Ben Lehtovaara1

Andrew Finkle1

1Department of Chemical Engineering (Nanotechnology), University of Waterloo,

Waterloo, Ontario, Canada

Outline

– Recap of Mesoporous Material Synthesis

– Introduction to Petroleum Refining

– Introduction to Biofuel Refining

– Zeolites vs. Mesoporous Materials

– Biofuel Refining Using Mesoporous/Zeolite Composites

MCM - 41

Introduction to Petroleum Refining• Crude Oil Contains

o methane, ethane, propane, aromatics, cycloalkanes, alkenes, and alkynes

• Crude oil is refined to smaller distillates and/or liquefied petroleum gas (LPG; varying ratios of propane/butane)

• Hydrocracking creates smaller distillates with high temperatures and partial pressure of H2

• Mild Hydrocracking uses lower temperatures and pressures to create smaller distillates

• Hydrocracking uses noble metals supported on mesoporous material, aluminosilicates, or zeolites. Each with their own advantages / disadvantages.

• Our Focus: Mesoporous Catalysis

R=catalyst (i.e. noble metal)

Mesoporous Materials Synthesis

– Mesoporous (~2-50nm pores) require surfactants as templating material to achieve desired structure

– Formation of Micelles via Surfactant Self Assembly– Controled pore size

• Surfactant chain length• Surfactant to Silica ratio• Swelling by organic additives

Effects of Surfactant Parameters• Changes micelle dimensions and pore sizes

o Surfactant/Si Ratio changes phase (e.g. cubic)

MCM-41 Hex. Structure

Swelling Agent

“Rod-like micelles”

Other factors:-Temperature-pH-nature of surfactant

• Sol-gel chemistry• Hydrolysis to create

hydroxymetallates• Acidic catalyst such as NaF

effective

• Condensation to creation oxolated bridges between an inorganic framework

Mesoporous Materials Synthesis

Cracking of Gas Oil

• Hydrocracking involves creating smaller distillates under high T,P

• Activity is greatest for Zeolite material (USY-1), followed by Mesoporous MCM-41, and Amorphous Silica Aluminosilicates (ASA)

• High Activity is a result of the higher SA of the zeolite material (pore=~2-5nm)

• Zeolites are currently the industry choice for hydrocracking

• At high T, P: most mesoporous materials collapse

Mild Hydrocarbon Cracking• Mild conditions (lower T, P) are more advantageous to mesoporous

material activity due to a decrease in pore collapse at high T,P (more SA)• This leads to increased MCM-41 desirability due to:

• Larger exposed surface area• Increased dispersion of catalytic sites

• Removal of heteroatoms to reduce emission of sulfur dioxide nitrous oxides which are detrimental to the environment

Biofuel Refining• Biomass Refining: Refine

to bio-oil that is catalytically upgraded to standard fuels

• Leaves, shoots, fronds of oil palm tree

• Palm Oil Refining: Palm oil is converted to methyl/ ethyl esters (biodiesel) by transesterification

Palm Biomass Refining• Leaves, Shoots, and Fronds of Oil Palm Tree• Pyrolysis: decomposition in absence of oxygen

o produces gaseous hydrocarbons, coke, and bio-oilo Nickel on mesoporous materials improves bio-oil yield

• Gasification: temperatures higher than 720 degrees celsiuso produces CO, H2, CO2, and methaneo Fischer Tropsch Synthesis converts CO and H2 into liquid

hydrocarbons such as Liquid Petrolium Gas (LPG)

• Catalytic upgrading on mesoporous materials produces transportation fuels from both palm biomass and bio-oil

Palm Oil Refining

Effect of Si/Al ratio on Palm Oil Cracking• Incorporation of some Aluminum hetero atoms through exchange

with Si atoms results in a stronger Lewis Acid due to interaction with noble metal (NiMo)

• Catalyst materials synthesized via sol-gel, hydrothermal, ion-exchange and grafting methods

• Optimal Si/Al ratio around 20:1

• Linear hydrocarbon production is proportional to pore size• Catalytic activity is proportional to surface area• Palm kernel oil had a higher conversion rate then palm olein oil

Effects of Pore Size on Palm Oil Cracking

Increase pore size

Mesoporous / Zeolite Composite as Hydrocarbon cracking catalyst

• MCM-41 / ZSM-5 Composite for biofuel applicationso MCM-41 selective to C5+ olefin

products (diesel gasoline)o MCM-41 lacks in catalytic activity,

incorporate ZSM-5o Composite named CMZo Mesoporous structure synthesized on

surface of ZSM-5 particles• Microporous structure is combined with a

mesoporous material.

 

Zeolite: ZSM-5

Mesostructure:MCM-41

Composite Zeo/Meso:CMZ (0.2,0)

CMZ NitrogenIsotherms

• Increased SA of composite• Decreased SA with increased

Aluminumo Due to Loss of Crystallinity

Catalytic Activity and Selectivity

• CMZ(0.2,0.05) had highest yield and selectivity

• More liquid fewer gas products • desirable

ConclusionsThere are distinct advantages of mesoporous materials over traditional zeolites• Larger pores facilitate mass transport and selectivity for C5+

products• More versatile synthesis techniques that require lower T and

P and shorter periods of time (Zeolites take weeks, mesoporous take days/hours)

• Versatility in the incorporation of other materials (heteroatoms for catalysts) into their active sites (Al3+, Ti4+)

• Currently not as effective as zeolites in fuel refining activity• Composite Zeo/Meso materials do improve performance

• Mesoporous materials have the most distinct advantages in the realm mild hydrocarbon cracking

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