PhysicoChemical Characteristics and Activity of Solid Acid Catalysts Jose Ortega1,2,3, Sagar Sarsani

1
Physico-Chemical Characteristics and Activity of
Solid Acid CatalystsJose Ortega1,2,3, Sagar
Sarsani2,3, Bala Subramaniam2,3 1Department of
Chemical Engineering, Kansas State University,
Manhattan, KS 665022Department of Chemical and
Petroleum Engineering, University of Kansas,
Lawrence, KS 660453Center for Environmentally
Beneficial Catalysis, University of Kansas,
Lawrence, KS 66044

Activity of the Catalysts
Conclusions
Table 2 Acid site density of catalysts
Introduction
Batch Reactor

• The acid site density of various batches of
  SAC-13 is similar
• The acid site density of supported Nafion
  catalysts is about 2 orders of magnitude lower
  than that of liquid acids like HF or H2SO4

Solid acid catalysts are being developed as
environmentally benign alternatives to replace
liquid acids (like HF, H2SO4) in various organic
transformations, for example in the alkylation of
isobutane with butenes to produce branched
octanes (gasoline). The enormous quantities of
the mineral acids used and the handling and
disposal problems associated with these liquid
acids has been driving the research for the use
of solid acid catalysts.

• The catalyst is grinded and sieved to the desired
  particle size and pretreated in a vacuum oven
  _at_150 C for 3 hours
• 25ml of 15 molar mixture of acetic anhydride and
  anisole is added to the reactor followed by the
  addition of pretreated catalyst

• The reactor is maintained at the desired
  temperature for the given amount of time and the
  products are collected after allowing it to cool
  to ambient.
• The mixture is filtered and analyzed by a GC.

Physical Characteristics
Figure 1 A zeolite catalyst
The activity and selectivity on the solid acid
catalysts depend on the physical and chemical
properties like strength of the acid site and the
size of the pores. The strength of the acid site
determine the selectivity towards the desired
reaction. The pore size determines the
diffusional limitations.
Brunauer Emmett Teller Analysis (BET)

• This was used to find the surface area, pore
  volume, and average pore diameter. The following
  procedure is used
• Grind and sieve 0.2 grams of the catalyst to the
  desired size
• Place the catalyst in sample tube and heat the
  catalyst to 150 C while under flowing nitrogen
  gas for 3 hours
• Place the sample tube with the catalyst into the
  analyzer and fill the dewar with liquid nitrogen
  and start analysis on the software (stardriver,
  Micromeritics)

Figure 3 Autoclave Reactor
Objectives
Table 4 Activity of the catalysts

• Characterize physical properties of solid acids,
  such as BET surface area, pore volume and the
  mean pore diameter
• Characterize chemical properties of solid acids,
  such as acid site density and strength of the
  acid site
• Testing the activity of various solid acid
  catalysts for acylation of anisole with acetic
  anhydride

Table 3 Physical characteristics of the catalysts
Catalyst Description
Table 1 Types of catalyst used
Conclusions

• Physical Chemical properties are important in
  determining the conversion and selectivity of the
  products
• The activity of a catalyst depends on the time
  and temperature at which it is used
• SAC 25 shows higher activity than SAC-13 at
  similar conditions as expected
• These mesoporous solid acid catalysts show
  promising activity for replacement with liquid
  acids like HF and H2SO4

Conclusions
Chemical Characteristics
Acid Site Density

• The surface area and pore size of both the
  supported Nafion catalysts and the supported
  heteropoly acids are typical of mesoporous
  catalysts
• Based on the results of alkylation, the
  mesoporous catalysts are less diffusion limited
  than that of microporous catalysts for e.g.,
  zeolites.

• The Acid site density titrations was used to
  find the acidity of a catalyst by measuring the
  Bronsted acid sties. The following is the
  procedure used
• Pretreat the catalyst in vacuum oven _at_ 150 for 3
  hours
• Add 2.0 g of catalyst, 7.0 g of NaCl, and 50ml of
  deionized water into a 100 ml beaker. Stir the
  solution for 3 hours.
• Filter the resin and wash the beaker and resin
  with deionized water 5 times with a total volume
  of 150 ml of water
• Titrate the filtrate with a 0.05 N NaOH solution
  using 2 drops of 1 phenolphthalein ethanol
  solution as indicator
• Calculate acidity using following formula
  HVNaOH CNaOH / 2.0 (meqH/g)

Acknowledgements

• Work supported by the National Science Foundation
  Engineering Research Centers Program, Grant
  EEC-0310689
• Dr. Bala Subramaniams research group

Figure 2 Gemini II 2370 used to find physical
characteristics of catalysts