Adsorption/Desorption Rate constants

[xenhua]

I am using a in-house built micro kinetics code for my Catalytic reaction mechanism.
I am using pMutt to calculate the rate constants for various surface elementary reactions with the help of a code snippet like the one below:

reactions_data = read_excel(io=excel_path, sheet_name='reactions')
reactions_list = []
for reaction_data in reactions_data:
    reaction = ChemkinReaction.from_string(species=species_dict, **reaction_data)
    print('-------------------------------------------------------------------')
    print(reaction_data)

    # Calculate forward reaction preexponential factor
    A_rxn_fwd = reaction.get_A(use_q=True, T=923.15)
    print('forward reaction preexponential factor A1_fwd(T = 923.15 K) = {:.3e}'.format(A_rxn_fwd))

    # Calculate reverse reaction preexponential factor
    A_rxn_rev = reaction.get_A(use_q=True, T=923.15, rev=True)
    print('reverse reaction preexponential factor A1_rev(T = 923.15 K) = {:.3e}'.format(A_rxn_rev))

    # Calculate forward Arrhenius energy of activation
    E_rxn_fwd = reaction.get_E_act(units='J/mol', T=923.15, del_m=0)
    print('forward Arrhenius energy of activation E1_fwd(T = 923.15 K) = {:.3f} J/mol'.format(E_rxn_fwd))

    # Calculate reverse Arrhenius energy of activation
    E_rxn_rev = reaction.get_E_act(units='J/mol', T=923.15, rev=True, del_m=0)
    print('reverse Arrhenius energy of activation E1_rev(T = 923.15 K) = {:.3f} J/mol'.format(E_rxn_rev))


    reactions_list.append(reaction)

reactions = Reactions(reactions=reactions_list)

I am wondering on how to use pMutt to calculate the rate constants for adsorption and desorption processes.
In general, Collision Theory (Hertz-Knudsen Equation) is used to describe the adsorption process.
How can i use pMutt to calculate the rate constants for adsorption and desorption.

[jonlym]

Thank you for your patience.

Currently, pMuTT cannot calculate the rate constants for adsorption/desorption. Until an appropriate class is developed (it's unclear how long this will take), you can create a child class of ChemkinReaction. A template of how to do so is shown below.

from pmutt.reaction import ChemkinReaction

class AdsReaction(ChemkinReaction):
    """Model adsorption and desorption using Hertz-Knudsen kinetics

    Attributes
    ----------
        <<Insert relevant attributes for documentation>>

    """

    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        """<<Insert relevant data to initialize variables>>"""
        pass

    def get_A(self, T, P):
        """<<Insert relevant equations to calculate pre-exponential factors>>"""
        pass

[xenhua]

Thank you Jon for the clarification and suggestion!

[jonlym]

Thank you for bringing it up. I have been thinking about creating a new object for this so hopefully, I can find some time to implement it.

[xenhua]

Thank you!

That would be a great addition to pMuTT. The rate constant for adsorption calculated by Hertz-Knudsen equation and its corresponding reverse rate (rate constant for desorption) calculated from the Gas-phase reaction Equilibrium constant, K_ads = k_ads/k_des, to maintain the thermodynamic consistency.