Engineering topics

Joseph, Babu

Publications and source records attributed to Joseph, Babu.

6 records

DOE OSTI2024

Intensified biogas to liquid (IBGTL) Process: Experimental validation and modeling analysis

The Intensified Biogas to Liquid (IBGTL) process aims to overcome traditional economy-of-scale barriers in biogas-to-liquid fuel production by integrating bi-reforming and Fischer-Tropsch synthesis (FTS) in a single IBGTL reactor. This reactor operates at uniform pressure with different optimized temperatures across two zones for efficient conversion, utilizing multifunctional bi-reforming catalysts and high-temperature FTS catalysts. Bench scale experiments were carried out using landfill gas (LFG) in a single pass process, and the yield data from these experiments were fed into process scale-up design and techno-economic analysis (TEA) across four scenarios: (1) a single pass process, (2) a process with material recycling, (3) a process with liquefied petroleum gas (LPG) co-product recovery, and (4) a process with electricity generation from the fuel gas produced. TEA identified Scenario 2 as the most cost-effective, achieving a Minimum Fuel Selling Price (MFSP) of $\$4.59$ per gallon, competitive with the current national diesel price of $\$4.7$ per gallon. However, comparison with the conventional two-reactor system highlights the need for catalyst performance improvements. Sensitivity analysis emphasized the importance of manufacturing cost, liquid fuel yield, and biogas flow rate. Further analysis determined that the IBGTL process must achieve a diesel mass yield beyond 11.7% to surpass the economic viability of the conventional TriFTS (Tri-reforming followed by Fischer-Tropsch Synthesis) process. If the IBGTL process attains the TriFTS yield of up to 17%, the resulting MFSP could be approximately 31% lower than the current TriFTS MFSP. Furthermore, renewable energy credits and carbon credits can further enhance the economic viability of BGTL processes.

09 BIOMASS FUELS↗

DOE OSTI2024

High-Temperature Fe-Based Fischer–Tropsch Synthesis: Experimentally Validated Kinetic Models Implemented at Pellet and Reactor Scales

Pellet- and reactor-scale models for Fischer–Tropsch synthesis (FTS) with a Fe–K/silica catalyst were developed to investigate the sensitivity of the hydrocarbon products and carbon dioxide selectivity to process conditions and feed composition at high temperature (350–400 °C), moderate pressure (1–10 bar), and a range of H 2 /CO ratios (3–1). The major objective of this paper is to develop, validate, and evaluate a high-temperature FTS model that is then used to assess the feasibility of process integration with syngas production. Since there is limited kinetic data available, in literature at these conditions, bench-scale reactor tests were conducted to obtain operational data for parameter fitting of kinetic expressions used in the model. This resulting kinetic model demonstrated agreement with the experimental data with an R 2 of 0.97 to the testing data set and, thus, was feasible to apply at pellet and reactor scales. Here, multiple pellet sizes were modeled to detail the role of transport limitations as the sphere’s diameter approached and exceeded 1 mm. Application of the reactor model indicated that hydrocarbon selectivity depended strongly on temperature, whereas the ratio of olefin to paraffin products decreased with increasing temperature, pressure, and H 2 /CO ratio. Product selectivity was not sensitive to the conversion of carbon monoxide. Furthermore, the roles of the pressure and H 2 /CO ratio were closely coupled. At a H 2 /CO ratio of 3, only slight variations in selectivity occurred over a pressure range of 1–20 bar, whereas at a ratio of 1, selectivity could vary by as much as 30% over the same pressure range. At pressures below 5 bar and temperatures above 350 °C, minimal selectivity to heavy hydrocarbons (C 12+ ) is obtained, and selectivity to midrange products (C 5–11 ) rapidly declined as pressure dropped below 5 bar, which indicated that an operational pressure of at least 5 bar is needed to achieve reasonable yields in this temperature range. These results, while tentative, provide guidelines for further experimentation and evaluation of integrated FTS processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Enhancing Low-Temperature Syngas Production via Surface Tailoring of Supported Intermetallic Nanocatalysts

An active and coke-resistant silica-encapsulated intermetallic Ni 3 Zn nanoparticle catalyst was developed for low-temperature (450 °C) dry reforming of methane (DRM). The catalyst exhibited a remarkable 4-fold increase in activity (4.5 s –1 ) with over 99% CO selectivity and 3 orders of magnitude less carbonaceous species and demonstrated remarkable stability (70 h) compared to that of a monometallic Ni catalyst. Here, the key is the combined effect of surface ensemble structure and electronic interaction modulation through the surface composition tailoring achieved by off-stoichiometric Ni and Zn loading in controlling surface chemistry for achieving different activities and H 2 /CO ratios. Characterized by ion spectroscopy, X-ray photoelectron spectroscopy, and the neutron pair distribution function, it was revealed that paired Ni δ – –Zn δ+ active sites are crucial for DRM. Transient infrared spectroscopy and isotopic analysis uncovered the synergistic effect of Ni δ – –Zn δ+ sites in activating C–H bonds and dissociating CO 2 to prevent coke formation under low-temperature conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Low temperature dry reforming of methane using Ru-Ni-Mg/ceria-zirconia catalysts: Effect of Ru loading and reduction temperature

Dry reforming catalysts, especially those with activity at moderate temperatures, have been intensely investigated to enhance the conversion of biogas. Here, Ru is evaluated as a promoter for Ni-Mg based catalysts. Catalysts based on 1.4 wt%Ni-1.0 wt%Mg-Ce 0.6 Zr 0.4 O 2 with Ru (0.02–0.32 wt%) were prepared using incipient wetness. The reducibility of the catalysts and conversions increased with increasing Ru content. Increases in conversions with increasing Ru loading was attributed to the additional active sites and synergistic effect between Ru and Ni, which weakened Ni-Mg interactions. Samples showed dry reforming activity at low temperatures (450–510 °C). Reaction rates and activation energies of higher loading Ru samples (1.4 wt%Ni-1.0 wt%Mg/Ce 0.6 Zr 0.4 O 2 with 0.16 and 0.32 wt%Ru) decreased when the reduction temperature was raised from 300 to 400 °C. A 20 h TOS study showed stable catalytic activity with minimal coke deposition. Furthermore, the results suggest that Ru is an alternative to Pt in promoting low temperature dry reforming of methane.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Enhancing reactant selectivity for Ni/Mg reforming catalysts using silicalite-1 shells: A modeling study

The ability of a zeolite shell to enhance the selective conversion of hydrocarbons through diffusional limitations was investigated using a multi-scale model of a fixed-bed reactor. The impact of shell thickness and molecule/pore size on the catalytic performance of silicalite-1 zeolite encapsulated nickel catalyst pellets for steam reforming of C1-C7 hydrocarbons is reported. A reaction–diffusion model using kinetic expressions established in literature was employed. The model was verified through comparison with reported experimental results for steam reforming data over a temperature range of 748 – 1113 K and pressure of 1 – 10 bar. Comparisons are also made against experimental data for steam reforming in the presence of a zeolite shell. Evaluation of the Weisz-Prater criterion for both the core and encapsulated catalyst confirmed mass transfer limitation induced by the utilization of a zeolite shell. The model was used to suggest an optimal thickness that balances diffusional limitations imposed by the zeolite layer on methane versus that of the heavier hydrocarbons. The optimum thickness varied as a function of hydrocarbon size and shape which determined the diffusion rates. For toluene and heptane, a 50 nm thick shell was sufficient to wholly prevent reaction. Hydrocarbons like propane and butane required a shell 7.5 and 5 μm thick. Increasing the gas-hourly-space-velocity from 10,000 to 60,000 h –1 caused a decrease in the optimum shell thickness. Furthermore, this approach can be modified for application to other mixed hydrocarbon systems to predict optimal catalyst design.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Selective and Stable In-Promoted Fe Catalyst for Syngas Conversion to Light Olefins

A selective and stable alumina-supported In-promoted Fe catalyst (10 mol % In based on Fe) was discovered for converting syngas (2:1 H 2 /CO ratio) to olefins with high selectivity (45% with CO 2 included) and a remarkable stability (72 h run) at a CO conversion of 10% at 400 °C and 5 bar. The X-ray photoelectron spectroscopy results indicated that incorporating In into Fe catalysts changed the chemical bonding state of Fe and Fe/In composition near the surface layers, which affected the catalytic reactivity. Steady-state isotopic transient kinetic analysis showed that more stable CHx fragments are present on the catalyst surface when incorporating In into Fe, which can promote C–C coupling reaction toward olefins. Our study demonstrates that introducing In into Fe catalysts on Al 2 O 3 support can lower CO activation abilities. It has more impacts on lowering hydrogenation activity, which permits more C–C couplings and like of “ene” hydrogenation. Furthermore, weakening CO adsorption both in terms of sites and strength encouraged CO toward hydrocarbons rather than CO 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗