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Leolynn Cauthron
What are the major differences between the concept of catalyst...
Rick, I deliberately referred to your statements on the basis of partial negation to trigger further discussion. Each statement can be taken literally, but it does not have to be. However, I added that both inhibition and deactivation can be considered from the point of view of various criteria. There is the approach of J.B. Butt, there is the approach of G. Froment, there is the approach of B.W. Wojciechowski, but there are also a number of other approaches including Japanese scientists. One can also mention parallel deactivation, consecutive deactivation as well as consecutive-competing one. Moreover, the phenomena of deactivation (in case of enzymes - inactivation) or inhibition can not be separated from specific chemical processes. Another approach concerns the oil refinery (you mention a few processes), other ammonia production and still other organic synthesis. Once, I tried to find a universal division, but I did not succeed. There was no consensus on different types of deactivation and, in my opinion, it will never be. Regards,
Rick, I deliberately referred to your statements on the basis of partial negation to trigger further discussion. Each statement can be taken literally, but it does not have to be. However, I added that both inhibition and deactivation can be considered from the point of view of various criteria. There is the approach of J.B. Butt, there is the approach of G. Froment, there is the approach of B.W. Wojciechowski, but there are also a number of other approaches including Japanese scientists. One can also mention parallel deactivation, consecutive deactivation as well as consecutive-competing one. Moreover, the phenomena of deactivation (in case of enzymes - inactivation) or inhibition can not be separated from specific chemical processes. Another approach concerns the oil refinery (you mention a few processes), other ammonia production and still other organic synthesis. Once, I tried to find a universal division, but I did not succeed. There was no consensus on different types of deactivation and, in my opinion, it will never be. Regards,
Inhibitors curb the catalyzing powers of a catalyst but do not react with any of the reactants but Poisons react with the catalyst and the reaction is irreversible.
Inhibitors curb the catalyzing powers of a catalyst but do not react with any of the reactants but Poisons react with the catalyst and the reaction is irreversible.
This is what IUPAC says: " Traces of impurities in the fluid to which the catalystis exposed can adsorb at the active sites and reduce oreliminate catalytic activity. This is called poisoning andthe effective impurity is called a poison. If adsorption ofpoison is strong and not readily reversed, the poisoning iscalled permanent. If the adsorption of the poison isweaker and reversible, removal of the poison from thefluid phase results in restoration of the original catalyticactivity. Such poisoning is called temporary. If adsorptionof the poison is still weaker and not greatly preferred toadsorption of reactant, the reduction in rate occasionedby the poison may be called competitive inhibition orinhibition. Here, of course, the poison may be present inmuch larger than trace amounts. There are, of course, nosharp boundaries in the sequence permanent poisoning,temporary poisoning, competitive inhibition." It can be consulted at: http://publications.iupac.org/pac/pdf/1976/pdf/4601x0071.pdf
This is what IUPAC says: " Traces of impurities in the fluid to which the catalystis exposed can adsorb at the active sites and reduce oreliminate catalytic activity. This is called poisoning andthe effective impurity is called a poison. If adsorption ofpoison is strong and not readily reversed, the poisoning iscalled permanent. If the adsorption of the poison isweaker and reversible, removal of the poison from thefluid phase results in restoration of the original catalyticactivity. Such poisoning is called temporary. If adsorptionof the poison is still weaker and not greatly preferred toadsorption of reactant, the reduction in rate occasionedby the poison may be called competitive inhibition orinhibition. Here, of course, the poison may be present inmuch larger than trace amounts. There are, of course, nosharp boundaries in the sequence permanent poisoning,temporary poisoning, competitive inhibition." It can be consulted at: http://publications.iupac.org/pac/pdf/1976/pdf/4601x0071.pdf
Inhibition is when a substance (feed, product, or inert/other) occupies the catalyst site to such a great extent that it prevents reactants from getting to the site and therefore "inhibits the reaction. Poisons usually permanently block the sites but sometimes they can be removed during a regeneration (usually a burn with air or O2). Tthe most common true poisons are arsenic, lead and cyanides -substances most people recognize as toxins/poisons.
Inhibition is when a substance (feed, product, or inert/other) occupies the catalyst site to such a great extent that it prevents reactants from getting to the site and therefore "inhibits the reaction. Poisons usually permanently block the sites but sometimes they can be removed during a regeneration (usually a burn with air or O2). Tthe most common true poisons are arsenic, lead and cyanides -substances most people recognize as toxins/poisons.
Everything depends on the criteria. Poisoning is regarded as deactivation of the catalyst, and inhibition is not. The inhibition may be a slowdown of the chemical reaction in a heterogeneous gas-solid system due to an excessive amount of the product. And this is not deactivation. It is easier to explain the inhibition by referring to enzymatic reactions. But here one can also distinguish several behaviors that differ from each other. Regards,
Everything depends on the criteria. Poisoning is regarded as deactivation of the catalyst, and inhibition is not. The inhibition may be a slowdown of the chemical reaction in a heterogeneous gas-solid system due to an excessive amount of the product. And this is not deactivation. It is easier to explain the inhibition by referring to enzymatic reactions. But here one can also distinguish several behaviors that differ from each other. Regards,
Catalyst poisoning deactivate the catalyst reaction. Catalyst inhibition prevent the reaction of the catalyst. This varies depending on the type of medium and the state of the catalyst in question.
Catalyst poisoning deactivate the catalyst reaction. Catalyst inhibition prevent the reaction of the catalyst. This varies depending on the type of medium and the state of the catalyst in question.
Are you sure?. And what about inhibitors in enzymatic reactions? The enzyme is also a catalyst. Many textbooks also mention reversible poisoning in case of solid catalyst. There is no clarity and will not be here. Regards,
Are you sure?. And what about inhibitors in enzymatic reactions? The enzyme is also a catalyst. Many textbooks also mention reversible poisoning in case of solid catalyst. There is no clarity and will not be here. Regards,
One is to prevent the activity of the catalyst, and the other is the deactivation of the activity of the catalyst; the equivalent of one is that the activity is unfavorable and the other is that the activity is required.
One is to prevent the activity of the catalyst, and the other is the deactivation of the activity of the catalyst; the equivalent of one is that the activity is unfavorable and the other is that the activity is required.
I think of fouling as a blockages that cause maldistribution. A burn will sometimes remove a blockage (e.g. if it is coke blocking a pore) but sometimes it will not and dumping and reloading catalyst is often necessary, especially if he blockage is caused by scale/metals instead of hydocarbons.
Coking/carbon disposition is the most common way for commercial Hydrotreating, Catalytic Cracking and Hydrocracking catalyst to lose actiity. Historically these catalyst were :regenerated" with a burn but recently the trend has been to dump catalyst and send it to an offsite regeneration facitity for screnning and coke burning. Arsenic and lead are posons that will permanently deactivate most catalyst and cause them to be unregenerable via burn.
I think of an inhibitor as a material that competes with reactant for catalyst sites inhibition is reversable. If the inhibitor is removed from the feed the rate of the desired reaction will increase. An inhibitor may also increase the rate of coking. If the calayst site is coked up it will usually require a burn(with air or O2) to remove the coke. that has closed up catalysyt pores and/or blocked active sites . Poisoning and coking are forms of catalyst deactivation that usually require a stoppage either for regeneration or catalyst replacement.You seem to disagree with the comment it can sometimesbe removed during a regeneration (usually a burn with air or O2). I agree it is not really a "poison" if you can remove it with air/ burn.
All catalyst can be "regenerated" if you take extreme enough measures. For my purposes - in the refining indusrty- catalyst is not regenerable if activity can not be recovered with a simple burn or other relatively minor procedures like a wash with a solvent.
However even then the active metals can be reclamed and used to make new catalyst.
I think of fouling as a blockages that cause maldistribution. A burn will sometimes remove a blockage (e.g. if it is coke blocking a pore) but sometimes it will not and dumping and reloading catalyst is often necessary, especially if he blockage is caused by scale/metals instead of hydocarbons.
Coking/carbon disposition is the most common way for commercial Hydrotreating, Catalytic Cracking and Hydrocracking catalyst to lose actiity. Historically these catalyst were :regenerated" with a burn but recently the trend has been to dump catalyst and send it to an offsite regeneration facitity for screnning and coke burning. Arsenic and lead are posons that will permanently deactivate most catalyst and cause them to be unregenerable via burn.
I think of an inhibitor as a material that competes with reactant for catalyst sites inhibition is reversable. If the inhibitor is removed from the feed the rate of the desired reaction will increase. An inhibitor may also increase the rate of coking. If the calayst site is coked up it will usually require a burn(with air or O2) to remove the coke. that has closed up catalysyt pores and/or blocked active sites . Poisoning and coking are forms of catalyst deactivation that usually require a stoppage either for regeneration or catalyst replacement.You seem to disagree with the comment it can sometimesbe removed during a regeneration (usually a burn with air or O2). I agree it is not really a "poison" if you can remove it with air/ burn.
All catalyst can be "regenerated" if you take extreme enough measures. For my purposes - in the refining indusrty- catalyst is not regenerable if activity can not be recovered with a simple burn or other relatively minor procedures like a wash with a solvent.
However even then the active metals can be reclamed and used to make new catalyst.
Dear Rick, This time I can not agree with you, because the description you provided is more like fouling and in particular coking ("usually a burn with air or O2") than inhibition or poisoning. Moreover, the inhibition (slow down in reaction rate} in the case of solid catalysts, excluding porous bodies with immobilized enzymes, is often caused by transport phenomena. But as I wrote above, there are many different criteria for deactivation and inhibition. There is, of course, a number of catalyst poisons, at which even a low concentration, the catalyst is completely and irreversibly poisoned. This applies to metal catalysts but not only. Regards,
Dear Rick, This time I can not agree with you, because the description you provided is more like fouling and in particular coking ("usually a burn with air or O2") than inhibition or poisoning. Moreover, the inhibition (slow down in reaction rate} in the case of solid catalysts, excluding porous bodies with immobilized enzymes, is often caused by transport phenomena. But as I wrote above, there are many different criteria for deactivation and inhibition. There is, of course, a number of catalyst poisons, at which even a low concentration, the catalyst is completely and irreversibly poisoned. This applies to metal catalysts but not only. Regards,
Rick,
I deliberately referred to your statements on the basis of partial negation to trigger further discussion. Each statement can be taken literally, but it does not have to be.
However, I added that both inhibition and deactivation can be considered from the point of view of various criteria. There is the approach of J.B. Butt, there is the approach of G. Froment, there is the approach of B.W. Wojciechowski, but there are also a number of other approaches including Japanese scientists. One can also mention parallel deactivation, consecutive deactivation as well as consecutive-competing one. Moreover, the phenomena of deactivation (in case of enzymes - inactivation) or inhibition can not be separated from specific chemical processes. Another approach concerns the oil refinery (you mention a few processes), other ammonia production and still other organic synthesis. Once, I tried to find a universal division, but I did not succeed. There was no consensus on different types of deactivation and, in my opinion, it will never be. Regards,
Rick,
I deliberately referred to your statements on the basis of partial negation to trigger further discussion. Each statement can be taken literally, but it does not have to be.
However, I added that both inhibition and deactivation can be considered from the point of view of various criteria. There is the approach of J.B. Butt, there is the approach of G. Froment, there is the approach of B.W. Wojciechowski, but there are also a number of other approaches including Japanese scientists. One can also mention parallel deactivation, consecutive deactivation as well as consecutive-competing one. Moreover, the phenomena of deactivation (in case of enzymes - inactivation) or inhibition can not be separated from specific chemical processes. Another approach concerns the oil refinery (you mention a few processes), other ammonia production and still other organic synthesis. Once, I tried to find a universal division, but I did not succeed. There was no consensus on different types of deactivation and, in my opinion, it will never be. Regards,
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VOTE
Inhibitors curb the catalyzing powers of a catalyst but do not react with any of the reactants but Poisons react with the catalyst and the reaction is irreversible.
Inhibitors curb the catalyzing powers of a catalyst but do not react with any of the reactants but Poisons react with the catalyst and the reaction is irreversible.
More
VOTE
This is what IUPAC says:
" Traces of impurities in the fluid to which the catalystis exposed can adsorb at the active sites and reduce oreliminate catalytic activity. This is called poisoning andthe effective impurity is called a poison. If adsorption ofpoison is strong and not readily reversed, the poisoning iscalled permanent. If the adsorption of the poison isweaker and reversible, removal of the poison from thefluid phase results in restoration of the original catalyticactivity. Such poisoning is called temporary. If adsorptionof the poison is still weaker and not greatly preferred toadsorption of reactant, the reduction in rate occasionedby the poison may be called competitive inhibition orinhibition. Here, of course, the poison may be present inmuch larger than trace amounts. There are, of course, nosharp boundaries in the sequence permanent poisoning,temporary poisoning, competitive inhibition."
It can be consulted at:
http://publications.iupac.org/pac/pdf/1976/pdf/4601x0071.pdf
This is what IUPAC says:
" Traces of impurities in the fluid to which the catalystis exposed can adsorb at the active sites and reduce oreliminate catalytic activity. This is called poisoning andthe effective impurity is called a poison. If adsorption ofpoison is strong and not readily reversed, the poisoning iscalled permanent. If the adsorption of the poison isweaker and reversible, removal of the poison from thefluid phase results in restoration of the original catalyticactivity. Such poisoning is called temporary. If adsorptionof the poison is still weaker and not greatly preferred toadsorption of reactant, the reduction in rate occasionedby the poison may be called competitive inhibition orinhibition. Here, of course, the poison may be present inmuch larger than trace amounts. There are, of course, nosharp boundaries in the sequence permanent poisoning,temporary poisoning, competitive inhibition."
It can be consulted at:
http://publications.iupac.org/pac/pdf/1976/pdf/4601x0071.pdf
More
VOTE
Inhibition is when a substance (feed, product, or inert/other) occupies the catalyst site to such a great extent that it prevents reactants from getting to the site and therefore "inhibits the reaction.
Poisons usually permanently block the sites but sometimes they can be removed during a regeneration (usually a burn with air or O2).
Tthe most common true poisons are arsenic, lead and cyanides -substances most people recognize as toxins/poisons.
Inhibition is when a substance (feed, product, or inert/other) occupies the catalyst site to such a great extent that it prevents reactants from getting to the site and therefore "inhibits the reaction.
Poisons usually permanently block the sites but sometimes they can be removed during a regeneration (usually a burn with air or O2).
Tthe most common true poisons are arsenic, lead and cyanides -substances most people recognize as toxins/poisons.
More
VOTE
Everything depends on the criteria. Poisoning is regarded as deactivation of the catalyst, and inhibition is not. The inhibition may be a slowdown of the chemical reaction in a heterogeneous gas-solid system due to an excessive amount of the product. And this is not deactivation. It is easier to explain the inhibition by referring to enzymatic reactions. But here one can also distinguish several behaviors that differ from each other. Regards,
Everything depends on the criteria. Poisoning is regarded as deactivation of the catalyst, and inhibition is not. The inhibition may be a slowdown of the chemical reaction in a heterogeneous gas-solid system due to an excessive amount of the product. And this is not deactivation. It is easier to explain the inhibition by referring to enzymatic reactions. But here one can also distinguish several behaviors that differ from each other. Regards,
More
VOTE
Catalyst poisoning deactivate the catalyst reaction. Catalyst inhibition prevent the reaction of the catalyst. This varies depending on the type of medium and the state of the catalyst in question.
Catalyst poisoning deactivate the catalyst reaction. Catalyst inhibition prevent the reaction of the catalyst. This varies depending on the type of medium and the state of the catalyst in question.
More
VOTE
Are you sure?. And what about inhibitors in enzymatic reactions? The enzyme is also a catalyst. Many textbooks also mention reversible poisoning in case of solid catalyst. There is no clarity and will not be here. Regards,
Are you sure?. And what about inhibitors in enzymatic reactions? The enzyme is also a catalyst. Many textbooks also mention reversible poisoning in case of solid catalyst. There is no clarity and will not be here. Regards,
More
VOTE
One is to prevent the activity of the catalyst, and the other is the deactivation of the activity of the catalyst; the equivalent of one is that the activity is unfavorable and the other is that the activity is required.
One is to prevent the activity of the catalyst, and the other is the deactivation of the activity of the catalyst; the equivalent of one is that the activity is unfavorable and the other is that the activity is required.
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VOTE
Miroslaw,
I think of fouling as a blockages that cause maldistribution. A burn will sometimes remove a blockage (e.g. if it is coke blocking a pore) but sometimes it will not and dumping and reloading catalyst is often necessary, especially if he blockage is caused by scale/metals instead of hydocarbons.
Coking/carbon disposition is the most common way for commercial Hydrotreating, Catalytic Cracking and Hydrocracking catalyst to lose actiity. Historically these catalyst were :regenerated" with a burn but recently the trend has been to dump catalyst and send it to an offsite regeneration facitity for screnning and coke burning. Arsenic and lead are posons that will permanently deactivate most catalyst and cause them to be unregenerable via burn.
I think of an inhibitor as a material that competes with reactant for catalyst sites inhibition is reversable. If the inhibitor is removed from the feed the rate of the desired reaction will increase. An inhibitor may also increase the rate of coking. If the calayst site is coked up it will usually require a burn(with air or O2) to remove the coke. that has closed up catalysyt pores and/or blocked active sites
.
Poisoning and coking are forms of catalyst deactivation that usually require a stoppage either for regeneration or catalyst replacement.You seem to disagree with the comment it can sometimesbe removed during a regeneration (usually a burn with air or O2). I agree it is not really a "poison" if you can remove it with air/ burn.
All catalyst can be "regenerated" if you take extreme enough measures.
For my purposes - in the refining indusrty- catalyst is not regenerable if activity can not be recovered with a simple burn or other relatively minor procedures like a wash with a solvent.
However even then the active metals can be reclamed and used to make new catalyst.
Miroslaw,
I think of fouling as a blockages that cause maldistribution. A burn will sometimes remove a blockage (e.g. if it is coke blocking a pore) but sometimes it will not and dumping and reloading catalyst is often necessary, especially if he blockage is caused by scale/metals instead of hydocarbons.
Coking/carbon disposition is the most common way for commercial Hydrotreating, Catalytic Cracking and Hydrocracking catalyst to lose actiity. Historically these catalyst were :regenerated" with a burn but recently the trend has been to dump catalyst and send it to an offsite regeneration facitity for screnning and coke burning. Arsenic and lead are posons that will permanently deactivate most catalyst and cause them to be unregenerable via burn.
I think of an inhibitor as a material that competes with reactant for catalyst sites inhibition is reversable. If the inhibitor is removed from the feed the rate of the desired reaction will increase. An inhibitor may also increase the rate of coking. If the calayst site is coked up it will usually require a burn(with air or O2) to remove the coke. that has closed up catalysyt pores and/or blocked active sites
.
Poisoning and coking are forms of catalyst deactivation that usually require a stoppage either for regeneration or catalyst replacement.You seem to disagree with the comment it can sometimesbe removed during a regeneration (usually a burn with air or O2). I agree it is not really a "poison" if you can remove it with air/ burn.
All catalyst can be "regenerated" if you take extreme enough measures.
For my purposes - in the refining indusrty- catalyst is not regenerable if activity can not be recovered with a simple burn or other relatively minor procedures like a wash with a solvent.
However even then the active metals can be reclamed and used to make new catalyst.
More
VOTE
Dear Rick, This time I can not agree with you, because the description you provided is more like fouling and in particular coking ("usually a burn with air or O2") than inhibition or poisoning. Moreover, the inhibition (slow down in reaction rate} in the case of solid catalysts, excluding porous bodies with immobilized enzymes, is often caused by transport phenomena. But as I wrote above, there are many different criteria for deactivation and inhibition.
There is, of course, a number of catalyst poisons, at which even a low concentration, the catalyst is completely and irreversibly poisoned. This applies to metal catalysts but not only. Regards,
Dear Rick, This time I can not agree with you, because the description you provided is more like fouling and in particular coking ("usually a burn with air or O2") than inhibition or poisoning. Moreover, the inhibition (slow down in reaction rate} in the case of solid catalysts, excluding porous bodies with immobilized enzymes, is often caused by transport phenomena. But as I wrote above, there are many different criteria for deactivation and inhibition.
There is, of course, a number of catalyst poisons, at which even a low concentration, the catalyst is completely and irreversibly poisoned. This applies to metal catalysts but not only. Regards,
More
VOTE