Browsing by Author "Ji, Guozhao"

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    Enhanced hydrogen production from thermochemical processes
    (Royal Society of Chemistry, 2018-07-24) Ji, Guozhao; Yao, Joseph G.; Clough, Peter T.; Diniz da Costa, João C.; Anthony, Edward J.; Fennell, Paul S.; Wang, Wei; Zhao, Ming
    To alleviate the pressing problem of greenhouse gas emissions, the development and deployment of sustainable energy technologies is necessary. One potentially viable approach for replacing fossil fuels is the development of a H2 economy. Not only can H2 be used to produce heat and electricity, it is also utilised in ammonia synthesis and hydrocracking. H2 is traditionally generated from thermochemical processes such as steam reforming of hydrocarbons and the water-gas-shift (WGS) reaction. However, these processes suffer from low H2 yields owing to their reversible nature. Removing H2 with membranes and/or extracting CO2 with solid sorbents in situ can overcome these issues by shifting the component equilibrium towards enhanced H2 production via Le Chatelier's principle. This can potentially result in reduced energy consumption, smaller reactor sizes and, therefore, lower capital costs. In light of this, a significant amount of work has been conducted over the past few decades to refine these processes through the development of novel materials and complex models. Here, we critically review the most recent developments in these studies, identify possible research gaps, and offer recommendations for future research.
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    Kinetics of catalytic biomass pyrolysis using Ni-based functional materials
    (Elsevier, 2019-07-12) Yang, Hang; Ji, Guozhao; Clough, Peter T.
    The pyrolysis behaviors of three types of biomass (cellulose, sawdust and straw) in three cases (no catalyst, Ni-CaO-Ca2SiO4 and Ni-Ca2SiO4) were investigated by non-isothermal thermogravimetric analysis. The non-isothermal pyrolysis was implemented with four different heating rates: 20, 30, 40 and 50 °C/min and the yield rates of the produced gases were measured by TG-MS. For kinetic analysis, the activation energy was obtained using four isoconversional analysis methods (Flynn-Wall-Ozawa (FWO) method, Kissinger-Akahira-Sunose (KAS) method, Starink method, and the Miura distributed activation energy model (DAEM)). Ni-CaO-Ca2SiO4 and Ni-Ca2SiO4 was found to intensify the decomposition of biomass to produce more H2 and CO. The correlation R2, of all fitting lines in all cases, was above 0.9 which demonstrated that FWO, KAS, Starink methods and DAEM were suitable for calculating the activation energy of the biomass catalytic pyrolysis. Ni-CaO-Ca2SiO4 showed the obvious catalytic effects in the decrease of activation energy of biomass pyrolysis to produce additional H2 and CO from the breakage of light organic molecules.
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    Mesoporous MgO promoted with NaNO3/NaNO2 for rapid and high-capacity CO2 capture at moderate temperatures
    (Elsevier, 2017-09-12) Zhao, Xiao; Ji, Guozhao; Liu, Wen; He, Xu; Anthony, Edward J.; Zhao, Ming
    A series of mesoporous MgO samples with different morphologies were synthesized through a simple hydrothermal treatment and NaNO3/NaNO2 were used as promoters to enhance CO2 capture capacity at an intermediate temperature range (200–400 °C). The effects of hydrothermal solution pH and content of promoters were examined to determine the optimal synthesis conditions. The influence of operational temperatures, CO2 partial pressure, and performance over repeated cycles was investigated and the reaction mechanism was discussed. The mesoporous MgO promoted by NaNO3/NaNO2 exhibited a CO2 capture capacity as high as 19.8 mmol g−1 at 350 °C in the presence of 0.85 bar of CO2 within only 50 min. A “three-stage” reaction process was proposed based on a detailed sorption kinetics study, namely Stage I: initiating interactions between CO2 and exposed MgO; Stage II: generation and accumulation of Mg2+ and CO32−; and Stage III: fast carbonation. Gradual deterioration of sorbents was found over the first 5 cycles followed by stable regenerability in the 5−15th cycles. A kinetic study of the 15th cycle suggests that the deactivation of sorbents inhibited the accumulation of Mg2+ and CO32− in Stage II and suppressed the carbonation in Stage III. A range of characterizations were undertaken revealing the morphology and structure of both fresh and regenerated sorbents. The results confirmed that, other than the sintering effect due to phase transition, the transformation of MgO skeleton is also an important contributor to the gradual deactivation of the sorbents over the first 5 cycles. More severe sintering effect under harsh decarbonation conditions suppressed the stability of the sorbents over cycles.