7 replies to this topic

[keeper]

Dear friends... I need you advise.
I am trying to simulate heterogeneous catalytic reaction in HYSYS. My main goal is to design reactor that will be a adequate model of my expiremental work. Namely, I engaged in ethanol dehydration over solid heterogeneous catalyst (Al2O3), temperature= 350-400 C, atm presure, PFR (reactor) fixed-bed catalyst. In hysys it is necessary to determine reaction rate. My questions:
1. It is necessary to determine reaction rate = numerator/denumerator (hetor. reaction). numerator = k*f(basis)-k`*f(basis), Hysys can calculate k and k` but I should specify parametrs of Arrhenius equation ( k=A*exp (-E/RT)*T^Z) for forward reaction andreverse reaction I should specify A and E. Therefore my problem is I do not know these parametrs, may be somebody could tell me literature or web site where I could find these data. If somebody has ChE books where I could find kinetics data (not only for ethanol dehydration, any other kinetic data will be very useful for me) I will highly appreciate if you could give me these books authors (Titles) or may be it will be possible for you to send me some chapters (electronic version).
2. Besides, for Denumerator I should specify K1 and K2, K1=A1*exp(-E1/RT)... so I can not see any differences between A1, E1 and these parametrs but for numerator. Could you explain me briefly?
3. In order to check reactor feasibility I specified A,E (for forward reaction) A,E (for reverse reaction), A1,E1 and A2, E2 randomly and tried to input these reaction set for PFR reactor.
But I faced some difficulties - "unknown dimensions" .
4. It is necessary to define Catalyst Data such as solid heat capacity. Could you tell me where I may find solid heat capacity for different catalysts (Al2O3, Zeolites...)

In general, the main aim of my message is to find people here who have some experiance in modeling heter. catalytic reactions in HYSYS. Any you suggestion will be very useful for me...

Thank you in advance

[Steve McGahey]

Dear friends... I need you advise.
I am trying to simulate heterogeneous catalytic reaction in HYSYS. My main goal is to design reactor that will be a adequate model of my expiremental work. Namely, I engaged in ethanol dehydration over solid heterogeneous catalyst (Al2O3), temperature= 350-400 C, atm presure, PFR (reactor) fixed-bed catalyst. In hysys it is necessary to determine reaction rate. My questions:
1. It is necessary to determine reaction rate = numerator/denumerator (hetor. reaction). numerator = k*f(basis)-k`*f(basis), Hysys can calculate k and k` but I should specify parametrs of Arrhenius equation ( k=A*exp (-E/RT)*T^Z) for forward reaction andreverse reaction I should specify A and E. Therefore my problem is I do not know these parametrs, may be somebody could tell me literature or web site where I could find these data. If somebody has ChE books where I could find kinetics data (not only for ethanol dehydration, any other kinetic data will be very useful for me) I will highly appreciate if you could give me these books authors (Titles) or may be it will be possible for you to send me some chapters (electronic version).

Information on reaction kinetic parameters is VERY hard to get your hands on. Normally, they would need to be found by experiment, since first principles prediction of reaction rates is (as I understand it) still a black (and largely erroneous) artform.

I'd suggest you set up a few simple experiments to determine the reaction rate parameters in your setup. If you've already been doing experimental work, then you might have the info you need in your results.

As a matter of fact, just what is your experiment trying to find out? Wouldn't determination of rate contstants be a useful thing to determine when you've got all the apparatus you need?

2. Besides, for Denumerator I should specify K1 and K2, K1=A1*exp(-E1/RT)... so I can not see any differences between A1, E1 and these parametrs but for numerator. Could you explain me briefly?

From the top of my head

E1 is the activation energy for the reaction.

A1 is a reaction-specific constant

R is the universal gas constant.

T is the temperature of the reaction in degrees Kelvin.

K1 and K2 are the first order reaction rate constants.

3. In order to check reactor feasibility I specified A,E (for forward reaction) A,E (for reverse reaction), A1,E1 and A2, E2 randomly and tried to input these reaction set for PFR reactor.
But I faced some difficulties - "unknown dimensions" .

The units of A1 and A2 will vary a lot depending on the reaction rate model you use. Your reaction rate equation (eg [reaction rate] = k1*[conc of first reactant]*[conc of second reactant]) should end up with the units of "1/second".

4. It is necessary to define Catalyst Data such as solid heat capacity. Could you tell me where I may find solid heat capacity for different catalysts (Al2O3, Zeolites...)

Again, experimental data will be the way to go. This is because the geometry of the catalysts will probably vary a lot from case to case. If you want to find someone elses's heat capacity, try looking in journal articles.

Hope this helps somewhat,
- Steve.

[keeper]

Dear Steve, First of all thank you so much for you answer. Let me to explain you the situation.
The main aim of my laboratory experiments is to find appropriate catalyst for ethanol dehydration into ethylene. But it is really difficult to find choose catalyst which will be selective toward ethylene. May be you know that the most part of ehylene is produced by pyrolysis. But ethanol might be very perspective. So my goal is process optimization, but be honest I want to determine kinetic equation (rate) for this reaction in future. For the time being I have not such possibilities because it requres perfect equipment. Besides, there are many problems that used to appear during kinetic investigation for heterogeneous catalysts. What is interesting, that recently I have found kinetic database (http://kinetics.nist...etics/index.jsp), may be it will be useful to know for ChE fellows about this website. In the same time my schedule does not contain HYSYS simulation tasks, it is my own interest and I just want to figure out all obstacles. Thank you for advise. It is really useful.

[perry]

Dear Steve, First of all thank you so much for you answer. Let me to explain you the situation.
The main aim of my laboratory experiments is to find appropriate catalyst for ethanol dehydration into ethylene. But it is really difficult to find choose catalyst which will be selective toward ethylene. May be you know that the most part of ehylene is produced by pyrolysis. But ethanol might be very perspective. So my goal is process optimization, but be honest I want to determine kinetic equation (rate) for this reaction in future. For the time being I have not such possibilities because it requres perfect equipment. Besides, there are many problems that used to appear during kinetic investigation for heterogeneous catalysts. What is interesting, that recently I have found kinetic database (http://kinetics.nist.gov/kinetics/index.jsp), may be it will be useful to know for ChE fellows about this website. In the same time my schedule does not contain HYSYS simulation tasks, it is my own interest and I just want to figure out all obstacles. Thank you for advise. It is really useful.

hi Keeper,
i been looking for the same answer for quite a few months, i am doing fuel reforming on ethanol and also looking for the missing data of activation energy. did u get much help from that web site?
hows yr progress?
looking forward to your update
per

[keeper]

Dear Steve, First of all thank you so much for you answer. Let me to explain you the situation.
The main aim of my laboratory experiments is to find appropriate catalyst for ethanol dehydration into ethylene. But it is really difficult to find choose catalyst which will be selective toward ethylene. May be you know that the most part of ehylene is produced by pyrolysis. But ethanol might be very perspective. So my goal is process optimization, but be honest I want to determine kinetic equation (rate) for this reaction in future. For the time being I have not such possibilities because it requres perfect equipment. Besides, there are many problems that used to appear during kinetic investigation for heterogeneous catalysts. What is interesting, that recently I have found kinetic database (http://kinetics.nist.gov/kinetics/index.jsp), may be it will be useful to know for ChE fellows about this website. In the same time my schedule does not contain HYSYS simulation tasks, it is my own interest and I just want to figure out all obstacles. Thank you for advise. It is really useful.

hi Keeper,
i been looking for the same answer for quite a few months, i am doing fuel reforming on ethanol and also looking for the missing data of activation energy. did u get much help from that web site?
hows yr progress?
looking forward to your update
per

Hi perry!
I`d like to inform you that I am angaging into ethanol reforming as well. Currently we are looking for appropriate catalysts for this reaction and moreover we are going to make some kinetic investigations. Be honest, I have not manage to find any materilas for that reaction and that is why I cant simulate heterogen. catalytic reaction. On web I mentioned above only some simple kinetics are represented and it was possible to find rate (equation) for ethanol dehydration. Maybe in the nearest time I`ll start thorough search on kinetics and I `ll be glad to share any information with you. As concerns to my progress it is very poor, I am just making first steps and some data seems me extremely complicated. Now I am going to use kinetics I` ve found to simulate ethylene production. Although I have 3 rate equation I`d want to use each of them and make sure that these rates are suitable.

Ethanol reforming is VERY interesting for me. Last night I had some experimets in University lab, but many questions are still unclear for me. Are you Chemical engineer? Why do you pursue research in ethanol reforming or it is you simulation task only? I am looking forward for you reply.

[Padmakar Katre]

Dear,
I have an operational experience of the Ethanol dehydration plant.First I would like to bring into your notice that the parameters which you have mentioned in your post are somewhat wrong.I have some details about the reaction kinetics are in the hard copies and I am currently not in my country so It will take time to scan and send you the mail.
Now the basic information what I have about the reaction is that the reaction is carried out over a 100 percent aluminium-oxide catalyst (it’s manufactured by Engel-Hardt) and conversion is almost 100 percent and is selective to the ethylene provided you maintain the required paramaters which are as below
- The reaction is an endothermic which needs an energy equal to 390 Kcal/kg of ethylene formed and the same is supplied in the form of the superheated steam directly fed along with the ethanol in the reactor as the recator condition should be adiabatic to avoid ethanol cracking and unselective reaction which will yield the acetaldehyde.
-the temperature at the reactor outlet is maintained say around 380 C and plus at a pressure of 4.5 Kg/cm2 to ensure the complete conversion of ethanol.
- as this reaction is reversible the equilibrium is favored by increase in temp (high conversion) and hindered by the pressure and water vapor in the reactor feed.

Any specific information you need please feel free to ask.(I will try to send the material ASAP just drop your mail id in my inbox)

Please could clear my doubt about your statement i.e. PFR (reactor) fixed bed of catalyst. PFR which I suppose is Plug flow reactor which is different than Fixed bed Reactors/Packed bed reactors.

[keeper]

Dear,
I have an operational experience of the Ethanol dehydration plant.First I would like to bring into your notice that the parameters which you have mentioned in your post are somewhat wrong.I have some details about the reaction kinetics are in the hard copies and I am currently not in my country so It will take time to scan and send you the mail.
Now the basic information what I have about the reaction is that the reaction is carried out over a 100 percent aluminium-oxide catalyst (it’s manufactured by Engel-Hardt) and conversion is almost 100 percent and is selective to the ethylene provided you maintain the required paramaters which are as below
- The reaction is an endothermic which needs an energy equal to 390 Kcal/kg of ethylene formed and the same is supplied in the form of the superheated steam directly fed along with the ethanol in the reactor as the recator condition should be adiabatic to avoid ethanol cracking and unselective reaction which will yield the acetaldehyde.
-the temperature at the reactor outlet is maintained say around 380 C and plus at a pressure of 4.5 Kg/cm2 to ensure the complete conversion of ethanol.
- as this reaction is reversible the equilibrium is favored by increase in temp (high conversion) and hindered by the pressure and water vapor in the reactor feed.

Any specific information you need please feel free to ask.(I will try to send the material ASAP just drop your mail id in my inbox)

Please could clear my doubt about your statement i.e. PFR (reactor) fixed bed of catalyst. PFR which I suppose is Plug flow reactor which is different than Fixed bed Reactors/Packed bed reactors.

Dear,

Thank you very much for you answer,

It is really difficult to find any information about processes that existed many years ago. So, ethanol dehydration was used to produce ethylene probably 50-60 years ago. In the same time as I know bioethanol can be very prospective for ethylene production in the nearest future. Could you be more specific about you experience ? It is extremily interesting for me, maybe you will be able to send me some more materials to artvityuk@yahoo.com.

Nevertheless, I still have some questions. First, you have mentioned that reaction is hindered by the pressure and water vapor in the reactor feed. But in the same time you said that you used to add some superheated steam directly fed along with the ethanol in the reactor. As I understood, it is no necessity to heat reactor by the fuel gas,other heat carrier... You just add some superheated steam directly to the reactor (as well as ethanol vapour). Secondly, you mentioned that acetaldehyde is the main byproduct, but according to my experiments diethyl ether remains the primary byproduct. It will be VERY interesting for me to get some more information about this process, it is marvelous that you have such experience. We use Fixed bed Reactor , excuse me for misunderstanding. I am looking forward for you reply,

Thank you

[Padmakar Katre]

Dear,

Thank you very much for you answer,

It is really difficult to find any information about processes that existed many years ago. So, ethanol dehydration was used to produce ethylene probably 50-60 years ago. In the same time as I know bioethanol can be very prospective for ethylene production in the nearest future. Could you be more specific about you experience ? It is extremily interesting for me, maybe you will be able to send me some more materials to artvityuk@yahoo.com.

Dear I am not aware about the inception of the process and its first commercial project. But still there are plants which produce ethylene from ethanol dehydration. There are 2 Mono-Ehtylene Glycol Plant in India which has the raw material ethanol for to get the Ethylene to react with Oxygen to Form Ethylene Oxide and subsequent reaction of the EO with water to form MEG. Anyways this is an additional information. Yes I do agree with your opinion that in coming future the Bioethanol to ethylene production will be of most important and profitable.
As far as my experience with this technology is concerned the licensor for this Technology is Petron Inc USA which uses the fixed bed reactor with a bed of activated alumina catalyst to produce ethylene.

Nevertheless, I still have some questions. First, you have mentioned that reaction is hindered by the pressure and water vapor in the reactor feed. But in the same time you said that you used to add some superheated steam directly fed along with the ethanol in the reactor. As I understood, it is no necessity to heat reactor by the fuel gas,other heat carrier... You just add some superheated steam directly to the reactor (as well as ethanol vapour). Secondly, you mentioned that acetaldehyde is the main byproduct, but according to my experiments diethyl ether remains the primary byproduct. It will be VERY interesting for me to get some more information about this process, it is marvelous that you have such experience. We use Fixed bed Reactor , excuse me for misunderstanding. I am looking forward for you reply,

As in my previous post I said that the reaction is reversible and equlibrium is disturbed by the parameters like temperature, pressure and the water vapor in the feed. Now I will explain about the reaction a bit. As the reaction is an endothermic one it requires the energy( which we call it as an activatation energy - the minimum energy the reactants should have to incept the reaction and which we normally give in the form of temperature - Catalyst never initiate the reaction it only speeds/retards the reaction rate).This energy required by the reaction is provided by the superheated steam which enters in the reactor with the ethanol vapor. This is one way of providing the energy to the reactants. Now as you told to heat the reactor by fuel gas ( in your case you will have the jacket around the reactor and will heat the reaction medium inside) is also one of the option to maintain the required temperature in the reactor. But what I have read in the articles is that indirect heating will crack the alcohol and will form acetaldehyde. As per you its diethyl ether which may be there but I don't know.
Now I will tell you how this parameters affect the chemical equilibrium. As per the Basic theory of Arrhenius 'the increase in temperature will increase the rate of reaction which is nothing but conversion' so increased temperature will have higher conversion but to a certain extent otherwise high temperature will crack the alcohol.
Now second one is the pressure which causes the equilibrium to shift towards left means the reversible reaction.( If you check for the partail pressures of the components over the reaction path)
And the last is the water vapor.Now the permissible water to ethanol ration in the feed is 3.5 : 1 which is again calculated based on the conditions (temp and pressure of both ethanol and water stream) in order to compensate the energy required.(The quantity of water is calculated base on energy balance)
Thats what if water vapor/ water conc goes up it will hinder the equlibrium.
Please bear with me that I can not send the related articles now as I am not in my country. In few days I will scan and send it to you.