Grantee Research Project Results

Final Report: Sulfur Tolerant Catalysts for Biomass Tar Removal

EPA Contract Number: EPD13025
Title: Sulfur Tolerant Catalysts for Biomass Tar Removal
Investigators: Long, Richard
Small Business: NexTech Materials
EPA Contact: Richards, April
Phase: I
Project Period: May 15, 2013 through November 14, 2013
Project Amount: $80,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2013) RFA Text |  Recipients Lists
Research Category: SBIR - Sustainabile Utilization of Biomass , Small Business Innovation Research (SBIR)

Description:

As renewable energy, biomass conversion has gained more interest in recent years. Biomass provides a carbon dioxide (CO₂)-neutral alternative over a wide spectrum of uses that fossil fuels now fill. It has been suggested that the annual production of 1.3 billion tons of biomass in the United States could be used to displace more than 33 percent of the domestic demand for transportations fuels. The process of converting biomass into energy begins with gasification at high temperatures, producing hydrogen gas (H₂), carbon monoxide (CO), CO₂, water, methane (CH₄) and a lot of wastes, such as sulfur, ammonia and tar. The tar is a complex mixture of condensable hydrocarbons, including single-ring to five-ring aromatic compounds along with other oxygen-containing hydrocarbons and complex polycyclic aromatic hydrocarbons. Due to its high boiling point, the tar will condense or polymerize into more complex structures in exit pipes, in heat exchangers, or on particulate filters, leading to choking and attrition, which results in a decrease of total efficiency and an increase in the cost of the process. A major challenge to utilization of biomass gasification technology is cost-effective and efficient removal of tar from the product stream.

Summary/Accomplishments (Outputs/Outcomes):

In this SBIR Phase I program, NexTech has developed a catalytic reforming approach for removing waste tar from gasified biomass. As compared to a conventional liquid scrubbing approach, this catalytic reforming method not only eliminates the process of liquid waste disposal and enhances overall energy efficiency, but also converts tar and light hydrocarbons to useful syngas (CO and H₂), increasing the fuel value. In particular, the base metal-based catalysts are stable in the presence of hydrogen sulfide (H₂S) and ammonia (NH₃), two impurities in gasified biomass. Also, the operation temperature can be decreased from 900°C to 800°C by adding a small amount of promoters, improving energy efficiency and reducing operation cost.

Conclusions:

Nearly 100 percent tar conversion has been achieved at ≥ 800°C during reforming of oak wood gasification product. The reforming activity did not change in at least 600–900 hours on stream in the presence of sulfur. Moreover, unlike other conventional nickel (Ni)-based reforming catalysts, NexTech’s catalysts do not need pre-reduction process and can be self-activated in flowing biomass gasification gas at 700–850°C prior to operation. Therefore, the sulfur-tolerant catalysts can be loaded downstream of biomass gasifiers to eliminate tar. This catalytic approach is expected to overcome a significant barrier for commercializing biomass gasification process with low cost and enable efficient use of biomass to produce power, liquid fuels and valuable chemicals. In addition, the catalysts also are very active in reforming light hydrocarbons to syngas, which could extend their applications to other fuel industries.

Supplemental Keywords:

biomass gasification technology, biomass tar removal, waste tar, liquid scrubbing, catalytic reforming method, alternative fuel, sulfur-tolerant catalyst