mesoporous catalysis
DESCRIPTION
Mesoporous Catalysis for petroleum and biofuel production.TRANSCRIPT
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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