Page 99 - Principles of Catalyst Development
P. 99

86                                                       CHAPTER  5

            5.2.1.  Stoichiometric Analysis

                Three tasks  are involved  in  this step.  First,  all  possible stoichiometric
            chemical equations are listed. These must be organized in a logical manner,
            for  example,  primary  reactant,  reactant  self  interactions,  reactant  cross
            interactions, reactant-products, and product-products. Only those involving
            chemically stable compounds are  included.
                Second, the thermodynamics for each reaction are calculated. The most
            useful property is tlG~. T  at a specified temperature or range of temperatures.
            Computation of tlH? T  is  also  of value  but not critical.
                Third, types of chemical bond changes are identified for each reaction.
            These should  be  indexed according to  some scheme,  for example

                Dehydrogenation       DH
                Hydrogenation         H
                Oxidation             0
                Oxygen insertion      0 I
                Dehydration           OW
                Group addition        A

            Appendix  5  is  an  extensive  compilation  of reaction  types  and  is  useful  in
            organizing  a  systematic  nomenclature.  For  methane  oxidation,  we  have,
            among others,  the  following  reactions:
                Primary  Reactions:

                                       CH 4  = none
                                         O 2  ==  none

                Self Interactions:





           2CH 4  = C 2 H 6  + H2            OH               8.5 kcal mole ..  1
                 =  C,H 4  + 2H2             DH              12.8
                                             DH              22.2
                 = C 2 H 2  + 3H 2
             20 2  =  hone

               Cross  Interactions:

           CH 4  + ~02 = CH:,OH              01             -20.6
                     ==  CH 20  + H2         OI,OH         -20.0
                     = CO + 2H]              OI,OH         -43.1
   94   95   96   97   98   99   100   101   102   103   104