2012 Spring Meeting & 8th Global Congress on Process Safety

A Novel Catalyst for Partial Oxidation of Natural Gas

Author

Xu, N. - Presenter, Dason Technology

A Novel Catalyst for Partial Oxidation of Natural Gas

Nicholas Xu* Dason Technology Inc., Naperville, 60565, USA

Yu Wu Chongqing Chemical Industry Research Institute, Chongqing, 400023, China

*nick.xu@dasontechnology.com

Introduction

Many people have worked on CPOX research. The main barrier in the area was catalyst lifespan being insufficient to meet industrial requirements. We developed a novel catalyst for partial oxidation of natural gas (CPOX) to synthesis gas. The experiment was carried out in the lab and pilot plant at 10-20 bar pressure. The feed consisted of a mixture of natural gas and oxygen at a ratio of C:O2 of about 2:1. The natural gas conversion and CO selectivity are at 95% and H2 selectivity is about 90%. The catalyst was continuously running for about a year without deactivation.

Experimental

The experiments were carried out in an adiabatic stainless steel reactor with a Rh and Ni catalyst system. The lab reactor size is 20 mm in diameter and the pilot plant capacity is 1000 ton/yr. There is inert material at the bottom and the top of the catalyst.

The feed was heated to a range from 150 oC to 300 oC in an electric heater. There is a thermocouple at the top of the catalyst bed and another thermocouple at the bottom of the inert material below the catalyst bed. The experiments were performed between 10-20 bar pressure. A gas sample was taken from the reactor inlet and outlet. A GC was used for the gas sample analysis.

Results and discussion

Our catalyst was running for about a year under 10 – 20 bar condition without deactivation. The pilot plant results are in the figure below.

CPOX is compared to steam reforming and ATR technology in the following table.

 

Technology

Advantages

Disadvantages

Steam Reforming (SMR)

  • Mature, proven
  • Most commonly use for large scale operations

 

  • Large reactor size, highest CAPEX and OPEX
  • Reaction requires heat (endothermic) and steam
  • Large CO2 emissions from furnace
  • High CO2 in syngas

Autothermal Reforming (ATR)

  • Smaller reactor size, lower CAPEX and OPEX than SMR
  • Less CO2 in syngas product than SMR
  • Part of NG is burned in the reactor to supply heat for reforming, internal burning has higher efficiency than SMR furnace
  • Requires 20% more oxygen than reaction required (CH4:O2=1:0.6)
  • Must add steam to reduce soot (CH4:H2O=1:0.4-0.7)

 

Catalytic Partial Oxidation (CPOX)

  • Smallest reactor size, lowest CAPEX and OPEX
  • Highest carbon efficiency
  • Idea oxygen consumption (20% less than ATR)
  • Lowest CO2 in syngas product
  • Don’t need steam
  • Low catalyst lifespan before Dason’s invention
  • Need oxygen but less than ATR

CPOX carbon efficiency is at least 15% higher than ATR as demonstrated in this chart.

 

CH4

CO

CO2

H2

CH4 Conv.

CO sel

H2 Sel

CPOX

1.68

33.0

1.23

62.4

95.3

96.4

89.0

ATR

1.0

24.5

7.62

66.9

96.98

76.28

100.2

CPOX data above is our pilot plant typical data. The ATR data is from V. Palma et al. (2010) and is a calculated results using GasEq software at the equilibrium condition.

The carbon efficiency for CPOX is calculated as

32.2/(1.68+33.0+1.23) = 91.9%,

and for ATR is

24.5/(1+24.5+7.62) = 74%.

For a large plant, the feed stock consumption difference at about 18% makes a huge difference in operating costs.

Reference

1.   D. A. Hickman and L. D. Schmidt, "Syngas Formation by Direct Catalytic Oxidation of Methane", Science 259, 343-346 (1993).

2.   Rostrup-Nielsen, "Syngas in perspective", Catalysis Today 71 (2002), pp. 243-247