# Presentation: 561362

## High-Pressure Steam Reforming of Ethanol 

**Sheldon H.D. Lee, Rajesh Ahluwalia, and Shabbir Ahmed**** Argonne National Laboratory**
- Poster presented at 2005 Fuel Cell SeminarPalm Springs, CA, Nov. 13-17, 2005

## Objective

**Study the pressurized steam reforming of hydrated ethanol for H****2**** production for a refueling infrastructure**
**Study reforming equilibria and kinetics at elevated pressures**
**Evaluate high-pressure reforming options, e.g. membrane reactors**

## Advantages

**Ethanol fuel**
**Renewable liquid fuel**
**Easy to transport**
**High energy density (relative to compressed or liquefied gases)**
**Environmentally more benign (compared with petroleum-derived fuels)**
**High-pressure steam reforming**
**More options for H****2**** purification technique (membrane separation, PSA, etc.)**
**Energy cost saving for H****2**** compression**

## Process Challenges

**Unfavorable H****2**** yield at thermodynamic equilibrium **
**Higher tendency for coke formation**
**Choice of material for high-temperature/ high-pressure operation**

## Approach

**Study thermodynamic equilibria**
**Effects of temperature, pressure, and steam-to-C ratio**
**Evaluate system options with respect to efficiency and cost**
**Compare high-pressure reforming, compressing reformate, compressing high-purity hydrogen**
**Evaluate purification options with high-pressure reformate**
**Establish reforming kinetics through experiments and models**
**Set up a micro-reactor test facility for experimental testing**
**Use Chemcad to perform system modeling on efficiency and H****2**** yield associated with alternative process designs**

## Slide 6

## Approach

**Use membrane-reformer to shift the thermodynamic equilibrium back towards higher H****2**** yield**
**Use GCTool to perform system modeling on efficiency and H****2**** yield associated with alternative process designs **
**Conduct micro-reactor experiments to maximize H****2**** yield as a function of operating parameters: catalyst formulation, temperature, pressure, S/C molar ratio, and space velocity **
**Characterize potential membrane materials for their effectiveness, stabilities, and selectivities**

## 
Hydrogen compression represents a significant power loss

**Hydrogen compression represents a significant power loss**

**Background**

**Producing hydrogen at elevated pressures represents a**
**significant improvement in process efficiency. **

##   High pressure increases CH4 formation at the expense of H2     Ethanol steam reforming reaction:     C2H5OH (l) + 3H2O(l)  =  2CO2 + 6H2,   ΔH = +348 kJ    Eq. (1)

**Effect of pressure on the equilibrium product gas compositions from the steam reforming of ethanol.**

##  Tendency to form carbonaceous deposits (coke) increases     at higher pressures 

**COx selectivity as a function of pressure**

## Potential remedies for adverse pressure effect

**Remove H****2**** or CO****2**** to shift equilibrium **
**High temperature and high S/C molar ratio in the  feed increases H****2**** yield and reduces undesirable CH****4**** **

**Potential remedies for adverse pressure effect**

**Effect of temperature and steam-to-carbon ratio on the equilibrium product gas **
**composition from the steam reforming of ethanol.**

## System Modeling

**Reformer efficiency achieves 89% at stoichiometric**
**      ****S/C (= 1.5), followed by a linear decline at higher S/C**
***     ******η*****, % = [LHV of H****2**** produced per Eq. (1) – Heat of reaction of Eq.(1)] ******
**                     ****100/[LHV of Ethanol]**
-      where  *η *= efficiency
-                     LHV = lower heating value

**Effect of S/C molar ratio on the efficiency of an ideal reformer**

##  Simulated process efficiency approaches 70% at a S/C = 5

##   The total moles of H2 recovered are insensitive to reforming      pressure in a two-stage reforming/membrane separator system

**Effect of the system pressure on the efficiency of one- and **
**two-stage reformer-separator systems**

## Micro-reactor test facility

**Micro-reactor test facility**
**Test conditions:**
** ****600****o****-700****o****C**
** ****20-1000 psig**

**High-pressure ethanol steam-reforming experiments are**
**    ****conducted to maximize H****2**** yield with respect to temperature, **
**    ****pressure, S/C molar ratio, and space velocity **

**The ethanol-water mixture is prevaporized before entering the reactor**
**Sud-Chemie Ni catalyst in granules**

##  Ethanol decomposition as a function of temperature

**Gas composition of vaporized ethanol/water mixture from vaporizer**
**(Vaporizer temperatures = 390****o**** - 490****o****C)**

**At vaporizer temp. < 490****o****C, ethanol decomposed **
** ****< 12% for S/C = 12 & 20 and 1000 psig**
** ****< 3%   for S/C = 20 and 500 psig**

##  Partially decomposed ethanol feed effectively reformed by Ni    catalyst bed

**Product yields as a**
**function of time**
** ****Feed: S/C =20**
** ****Catalyst bed**
**  ****temp. = 620****o****-650****o****C**
** ****Pressure = 1000 psig**

** ****3 times more H****2**** and CO****2****   **
** ****Twice the CH****4**
** ****50% less CO, and undetectable ethane and ethylene**
**  ****100% carbon conversion was achieved **

**The catalyst bed converted the decomposition products into reformate**

##  Ni catalyst slowly degraded with time

**Product yields and**
**carbon conversion**
**as a function of time**
** ****Feed: S/C =12**
** ****GHSV = 85,600 h****-1**
** ****Catalyst bed**
**  ****temp. = 630****o****-660****o****C**
** ****Pressure = 1000 psig**

**Ni catalyst has been known********* to deactivate as a result of coke formation**
**The condensate collected from the test contained 4.53% ethanol, 0.84% acetaldehyde, and 0.06% acetic acid**
- *Agus Haryanto, Sandun Fernando, Naveen Murali, and Sushil Adhikari, “Current Status of Hydrogen
-   Production Techniques by Steam Reforming of Ethanol: A Review”, Energy & Fuel, 2005, 19, 2098-2106

##  Effect of pressure on product gas composition  

** ****Effect of pressure on product gas composition agrees with equilibrium **
**     ****predicted trend**

##  Effect of gas hourly space velocity on product yields

** ****Increasing GHSV decreases H****2****, CO****2****, and CO yields, **
**    ****but increases CH****4**** yield**

## Conclusions

**Steam reforming of ethanol at elevated pressures can lead to better process efficiencies**.
**Elevated pressure process presents challenges in unfavorable thermodynamic equilibrium, tendency for coke formation, and material choice.**
**Homogeneous decomposition of ethanol occurred at temperatures close to boiling point of ethanol-water solution at pressure.**
**High pressure increases CH****4**** formation at the expense of H****2**** yield**

## Future Work

**Study kinetics and define operating parameters for maximizing H****2**** yield**
**Evaluate system designs that take advantage of pressurized **
**     ****steam reforming**

## Acknowledgements

**This work is supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Hydrogen, Fuel Cells, & Infrastructure Technologies Program**

- Argonne National Laboratory is managed by The University of Chicago for the U.S. Department of Energy

- Argonne National Laboratory is managed by The University of Chicago for the U.S. Department of Energy

- The submitted manuscript has been created by the University of Chicago as Operator of Argonne National Laboratory (“Argonne”) under Contract No. W-31-109-ENG-38 with the U.S. Department of Energy. The U.S. Government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.