Production of hydrogen by cyclic sorption enhanced reaction process

Kinetic analysis for cyclic CO2 capture using lithium orthosilicate sorbents derived from different silicon precursors

The illustration of the CO₂ sorption process in Li₄SiO₄.

Thermodynamic Modeling of Propane Reforming Processes to Quantify Hydrogen and Syngas Production with and without Product Removal

The present study aims to explore the possibility of promoting hydrogen and syngas production capacity and quality by steam (SRP) and oxidative steam (OSRP) reforming of propane with and without H2 and CO2 removal. Conditions studied are temperature range of 600–1,100 K under atmospheric pressure with steam to propane feed ratio (WPR) of 1–18, oxygen to propane feed ratio (OPR) and fractional removal of H2 and CO2 (f) ranging from 0–0.99. The results indicate that SRP with 99% H2 removal produces high H2 yield of 9.93 moles close to theoretical value of 10 moles at relatively low temperature (750 K) than SRP (950 K). Approximately identical results are achieved at 950 K with 99% CO2 removal at same conditions of WPR (12), pressure (1 atm), and complete conversion of propane. Thus, SRP with H2 removal is more energy saving process. In OSRP, lower OPR, higher WPR minimize CO and CH4 production but at the expense of H2 production. However, OSPR process is the most suitable process to provide most favourable H2/CO ratio in syngas. Molar H2/CO ratio in syngas in the range of 1–3 are found at T≥1,000 K, WPR≤6 in SRP, SRP with H2 removal (f=0.4–0.99) and OSRP (OPR=0.2–2). Thermal efficiency is higher than 80% in both SRP with H2 or CO2 removal than SRP(69.39%). The thermal efficiency in OSRP is less than 69%. Hence, propane reforming process in hydrogen selective membrane reactor, provides high quality of hydrogen at relatively lower energy utilization.

Progress on sorption-enhanced reaction process for hydrogen production

Concerns about the environment and fossil fuel depletion led to the concept of “hydrogen economy”, where hydrogen is used as an energy carrier. Nowadays, hydrogen is mostly produced from fossil fuel resources by natural gas reforming, coal gasification, as well as the water-gas-shift (WGS) reaction involved in these processes. Alternatively, bioethanol, glucose, glycerol, bio-oil, and other renewable biomass-derived feedstocks can also be employed for hydrogen production via steam reforming process. The combination of steam reforming and/or WGS reaction with

Monitoring solid oxide CO2 capture sorbents in action

The separation, capture, and storage of CO2 , the major greenhouse gas, from industrial gas streams has received considerable attention in recent years because of concerns about environmental effects of increasing CO2 concentration in the atmosphere. An emerging area of research utilizes reversible CO2 sorbents to increase conversion and rate of forward reactions for equilibrium-controlled reactions (sorption-enhanced reactions). Little fundamental information, however, is known about the nature of the sorbent surface sites, sorbent surface-CO2 complexes, and the CO2 adsorption/desorption mechanisms. The present study directly spectroscopically monitors Na2 O/Al2 O3 sorbent-CO2 surface complexes during adsorption/desorption with simultaneous analysis of desorbed CO2 gas, allowing establishment of molecular level structure-sorption relationships between individual surface carbonate complexes and the CO2 working capacity of sorbents at different temperatures.

Chemisorption of carbon dioxide on potassium-carbonate-promoted hydrotalcite

New equilibrium and column dynamic data for chemisorption of carbon dioxide from inert nitrogen at 400 and 520 degrees C were measured on a sample of potassium-carbonate-promoted hydrotalcite, which was a reversible chemisorbent for CO(2). The equilibrium chemisorption isotherms were Langmuirian in the low-pressure region (p(CO(2)) < 0.2 atm) with a large gas-solid interaction parameter. The isotherms deviated from Langmuirian behavior in the higher pressure region. A new analytical model that simultaneously accounted for Langmuirian chemisorption of CO(2) on the adsorbent surface and additional reaction between the gaseous and sorbed CO(2) molecules was proposed to describe the measured equilibrium data. The model was also capable of describing the unique loading dependence of the isosteric heat of chemisorption of CO(2) reported in the literature. The column breakthrough curves for CO(2) sorption from inert N(2) on the chemisorbent could be described by the linear driving force (LDF) model in conjunction with the new sorption isotherm. The CO(2) mass-transfer coefficients were (i) independent of feed gas CO(2) concentration in the range of the data at a given temperature and (ii) a weak function of temperature. The ratio of the mass-transfer zone length to the column length was very low due to highly favorable CO(2) sorption equilibrium.