Dry Reforming Of Biogas Research Articles

Evaluating the performance of non-precious metal based catalysts for sulfur-tolerance during the dry reforming of biogas

A portfolio of catalysts with a nominal composition 15wt.%Ni+(0/5wt.%)Co/MaOx–NaOx–Al2O3 (where M=Mg, Ca, La, Y, Gd; N=Al, Zr) were synthesized and evaluated for biogas reforming application. Structure activity relations (SARs) were designed to help explain the significant difference in activity observed among the catalysts containing monometallic (Ni) and bimetallic species (Ni–Co) and among the bimetallic catalysts impregnated by altering the sequence of impregnation. The order of activity observed among the various catalyst formulations was: bi-metallic (reverse stepwise Co→Ni)>bi-metallic (simultaneous Ni+Co)>mono-metallic>bi-metallic (stepwise Ni→Co). From SARs it is established that high pore volume to surface area ratio, high metal dispersion, high reducibility and high support basicity are the essential traits of an active and stable catalyst. Analysis of variability (ANOVA) was performed to identify the main and interaction effects of various factors on both catalyst activity and catalyst textural properties. Impregnation sequence and promoter composition are found to have significant effects on both catalysts activity and its textural properties. Also, an empirical model equation that establishes a statistical relationship between the factors and the response variable was developed. In addition, a sensitivity analysis was performed to study the effect of surfactant to metal ratio, CH4-to-CO2 ratio, operating temperature, H2S concentration, cobalt amount, and support basicity on catalyst performance.

Pressurization effect on dry reforming of biogas in kilohertz spark-discharge plasma

To produce high-concentration syngas (CO+H2) from biogas, the effect of pressurization on dry reforming of biogas (CH4/CO2=60%/40%) in kilohertz spark-discharge plasma was reported for the first time by elevating the pressure from 1 bar to 2 bar. It was found that elevating the pressure could not only increase the reactant conversions, but also reduce energy cost and increase fuel-production efficiency at the same specific energy input (SEI). In particular, pressurization exhibited a significantly positive effect on increasing CO2 conversion and decreasing energy cost for converting CO2. Syngas concentration as high as 83% (H2/CO=1.4) was achieved with a ratio of the flow rates of product gas (dry basis) to feeding gas, 1.7, at 2 bar and SEI=753kJ/mol. The by-product, H2O, was produced with only about 5% of hydrogen-based selectivity in this work. At 2 bar, the effect of SEI was investigated by varying the power and flow rate, respectively. Compared with those at 1 bar, with the increase in SEI, reactants conversion increased fast, energy cost rose slowly and fuel-production efficiency decreased slowly at 2 bar.

The role of carbon deposition on precious metal catalyst activity during dry reforming of biogas

A preliminary investigation into the dry reforming (synthesis gas production) of landfill gas (LFG) was performed using precious metal catalysts. Thermogravimetric analysis work was performed on the dry reforming reaction over 0.5% Pt/γ-Al 2O 3 catalysts. Variables such as reforming temperature, CO 2 concentration, and the effect of pre-reduction have been studied. It was found that reforming at 900 °C with pre-reduction gave the most H 2 production for reactant gas concentrations similar to LFG. However, at this high temperature there was significant weight gain measured. EDX analysis and follow up oxidation tests confirmed that it was due to carbon deposition on the catalyst surface. Yet, this weight gain, up to 24% in some cases, did not coincide with a decrease in catalyst activity as was the case for the lower temperature tests. One possible mechanism for this is the onset of the carbon gasification (Boudouard) reaction at high temperatures. For increased CO 2 concentrations, the activity of the catalyst at high temperatures was maintained (high production of syngas) despite significant carbon deposition.