(328e) Hastelloy As Hydrocarbon Reforming Catalyst for Hydrogen Production

for Hydrogen Production

de la Rama, S.R.^a, Kawai,S.^b, Hiroshi, Y.^c, and Tagawa, T.^d

Department of Chemical Engineering, Nagoya University, Nagoya, Japan

Introduction

Hydrogen produced from biomass gasification has the potential to provide renewable and clean energy for transportation and power.  At present, steam reforming and partial oxidation are being used to produce hydrogen from natural gas and heavy hydrocarbons, respectively.  Ni-based catalysts are commonly used for these processes since nickel is low cost and abundant.  However, this type of catalyst is known to be easily deactivated via excessive carbon deposition, sintering and poisoning.  Thus, novel catalyst design and engineering are needed to further improve the efficiency and cost of hydrogen production.  This report focused on the feasibility of surface oxidized Ni-containing tubular alloy as hydrocarbon reforming catalyst. It was hypothesized that upon calcination, metal oxides will be highly dispersed on the metal surface while maintaining a strong oxide-metal interaction rendering the catalyst resistant against sintering caused by tube-like carbon deposits [1,2].  To prevent carbon deposits from clogging the reactor, tubular configuration was used as a reactor [3].  Specifically, tetradecane and toluene were used as model compounds in evaluating the activity of surface oxidized Hastelloy C276 in steam reforming, dry reforming and partial oxidation for hydrogen production. 

Experimental Procedures 

The apparatus used for calcination and reforming reaction was consists of an evaporator, a quartz tube, an electrically heated furnace and a temperature control system.  The alloy tube (φ: 1/4in, 1in; L: 35cm) was inserted into the quartz tube and placed in the middle of the heated furnace.  The upper end of the quartz tube was connected to the feed inlet while the lower end was connected to a gas sampling valve and a condenser.  Surface calcination of Hastelloy C276 was conducted with oxygen at 1000°C for 2 hours.  Tetradecane and toluene were fed into the reactor at a rate of 1.06x10^-6 mol/s and 2.09x10^-6 mol/s, respectively.  Steam reforming, dry reforming and partial oxidation were conducted at 730°C; steam, CO₂ and O₂ were respectively fed at 1.40x10^-5 mol/s, 71.0x10 ^-6mol/s, and 7.5x10^-6 mol/s.  All reforming reactions were conducted for 3 days if catalyst deactivation did not occur.  X-ray diffractometer (Shimadzu XRD-6100) was utilized to confirm the presence of metal oxides on the surface of the alloy tubes; while, GC-TCD (GL Sciences GC-3200) was used to quantify H₂, CO₂, CO and CH₄in the product gas.

Results and Discussion

Surface oxidized Hastelloy C276 generally exhibited good reforming activity using Tetradecane and Toluene (Table 1).  Specifically, good and stable catalytic activity was observed during tetradecane and toluene steam reforming.  On the other hand, surface oxidized Hastelloy C276 exhibited very low activity towards hydrocarbon dry reforming.  Excessive amount of carbon was also deposited on the alloy surface after 2 days when toluene was used as feedstock which caused the gas production rate to be unstable.  Conversely, stable activity was noted when toluene was partially oxidized despite the large amount of carbon deposited on the alloy’s surface.  Further, the opposite was observed when tetradecane was partially oxidized.

             Table 1. Catalytic activity of surface oxidized Hastelloy C276 after 2 hours

In general, an increase in the amount of carbon deposit was observed during toluene reforming.  In some cases, the amount of carbon deposit has little effect on the production rate; this observation suggests that different types of carbon were formed on the alloy surface depending on the type of reaction and feedstock involved.  Lastly, catalytic activity was deduced to be an effect of the oxide species formed on the surface of Hastelloy C276 after surface calcination.

References

[1] M. Itoh, T.Tagawa, S. Goto, Appl. Catal., A General, 177,15 (1993)

[2] A. Takano, T. Tagawa, S. Goto, J. Ceram. Soc., Japan, 104,444  (1996)

[3] N. Chikamatsu, T. Tagawa, S. Goto, J. Materials Sci., 30, 1367 (1995)

Acknowledgement

Financial support was provided by the Ministry of Environment (K2106)

E-mail address: ^asrdelarama@yahoo.com, ^bsinkawataroi@yahoo.co.jp,^cyamada@nuce.nagoya-u.ac.jp, ^dtagawa@nuce.nagoya-u.ac.jp