New Products from FischerTropsch

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New Products from Fischer-Tropsch

• M. Miller, Y. Zhang, J.W. Tierney and I.
  WenderChemical and Petroleum Engineering
  DepartmentUniversity of Pittsburgh
• Lexington, KY
• July 29-August 1, 2007

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Objectives

• To change the product slate in the FT synthesis
  from essentially only straight chain hydrocarbons
  so as to incorporate new properties in the
  products. Obtain a range of new and potentially
  useful products.
• To gain information as to the mechanism of chain
  initiation in the FT synthesis.

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Introduction

• Recent work in this lab has discovered a unique
  way of incorporating controlled amounts of
  oxygenates, naphthenes or aromatics as
  chain-initiating molecules or as molecules placed
  in the middle of the FT chain.
• This is made possible by the addition of suitable
  triply-bonded compounds to the FT synthesis.

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Introduction contd

• The added molecules are effective because they
  are adsorbed on the surface of the FT catalyst
  more strongly than carbon monoxide.
• The alkyne adsorbs more strongly onto the
  catalyst surface and is hydrogenated into an
  olefin which is incorporated into the FT chain.
• The additives serve only as chain initiators
  they do not appear twice in the same chain.

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Illustration

• Addition of CH3CO2CH2CCH (from HCCCH2OH and
  CH3COOH) to the FT reaction would yield a series
  of long chain products resembling biodiesel.
• It is likely that addition of only small amounts
  of additive will influence the nature of the FT
  product significantly.
• Biodiesel is a molecule similar to diesel in
  viscosity and molecular weight. Biodiesel is in
  the C12-C18 range with an ester group, i.e.
  RCOOCH3

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Uses of new products

• Potential biodiesel-like products
  CH3COOCH2CH2CH2-(CH2)n-CH3
• Used in several different ways
• 1 to 2 with FT products can act as a lubricity
  additive to jet/diesel fuel (particularly for low
  sulfur fuel)
• 20 in FT products (as seen in B-20 in diesel/jet
  fuel)
• Whole FT products used in jet/diesel fuel
  (biodiesel is used as 100 with diesel engines)

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Alternative initiators

• Cyclopentylacetylene
• 1-phenyl-1-propyne
• 4-phenyl-1-butyne
• Dipropargyl ether
• 1,4-Diethynylbenzene
• Ethyl propiolate

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How alkynes react

• Rank of adsorption strength to catalyst
• gt CO gt CC
• Alkynes are adsorbed more strongly than CO and
  are then hydrogenated to alkenes on the catalyst
  surface.
• Olefins formed on the catalyst surface
  participate directly in chain lengthening.
• Alkenes added to the ongoing FT participate only
  to a limited extent in chain formation since CO
  is more strongly adsorbed the catalyst surface.

HCCH
H2, CO
H2, CO
RCH2-CH2-CH2-
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Experimental

• Fixed-bed reactor
• Catalysts 20Co/80Al2O3, Fe100/Si5.1/Cu2.0/K2O5.0
• T 180220oC
• P 300 psi
• H2CO21
• Initiators dissolved in cyclohexane (5/10 by
  volume) pumped into the reactor
• GC online analysis and GC-MS offline analysis

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reactor
Automatic FT Reaction System
CO
MFC
vent
oven
H2
MFC
Ar
MFC
CO,CO2 H2, Ar, CH4
Evaporator
saturator
Interface
C1-C5
wax
Keithley 500
PAYNE
controller
Oil water
Temperature Pressure Sampling
Chemstation
Controlling
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Markers distinguish normal FT products from those
initiated by additives

• Typical FT distributions contain alkanes,
  alkenes, and small amounts of oxygenates
• Initiators used have unique functional groups
  such as naphthenes, esters, ethers or aromatics
• These characteristics make initiated products
  distinguishable from normal FT products

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GC-MS chromatogram of FT products over a cobalt
with 4-phenyl-1-butyne addition
(4-phenyl-1-butyne)
T220oC, P100psi, H2/CO2, flow rate of
4-phenyl-1-butyne(10) in pentane is 2ml/hour 10
hours after addition of the probe
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GC-MS chromatogram of FT products over a cobalt
catalyst with 1-phenyl-1-propyne addition
(1-phenyl-1-propyne)
Normal FT
T220oC, P100psi, H2/CO2. Sample was
hydrogenated before GC-MS analysis.
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GC-MS chromatogram of FT products over a cobalt
catalyst with ethylpropiolate addition
C3COOEt
C5COOEt
C4COOEt
C10
C2COOEt
C9
C8
C6COOEt
C4COOEt
C3COOEt
C5COOEt
C9COOEt
C7COOEt
C10COOEt
C8COOEt
C7 C8 C9 C10
C11 C12 C13 C14 C15 C16
C17 C18 C19 C20 C21 C22 C23 C24 T200C
P300psi H2/CO2 10 ethylpropiolate in
cylcohexane flow2ml/h
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GC-MS chromatogram of FT products over an iron
catalyst with cyclopentylacetylene addition
C3OH
C9
C10 C11 C12 C13
C14 C15 C16 C17 T200C
P300psi H2/CO2 10 cyclopentylacetylene in
cylcohexane flow2ml/h
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Conclusions

• Use of certain alkynes as additives can alter the
  product slate of the FT.
• Lubricity properties of the FT product may be
  improved.
• Incorporation of phenyl or naphthenic groups
  increases the energy content of the products.
• The FT product slate will vary depending on the
  amount and type of initiator molecule added, the
  catalyst, the temperature and the pressure.
• Products may be used as fuel additives or stand
  alone.

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Future Work

• Obtain an understanding of the nature of chain
  initiation within the FT reaction.
• Obtain insights as to the type and range of
  products from initiators at varying conditions.

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• Questions?