Xinying Liu

High-surface-area activated red mud for efficient removal of methylene blue from wastewater

Red mud was activated by a digestion–precipitation method, resulting in a mesostructure with high surface area, and the activated red mud was further used as the adsorbent for methylene blue removal. The physicochemical properties of the resultant samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry analysis, and nitrogen sorption techniques. Batch studies were measured to investigate the influence factors including adsorbent dosage, contact time, pH, and initial concentration. It was revealed that the activated red mud was highly efficient for removal of methylene blue. Adsorption experiments were found to be better achieved in faintly acidic and alkaline conditions, where the adsorption capacity of activated red mud and activated red mud-200 reached 232 and 274 mg/g at pH 7.0, respectively. Langmuir, Freundlich, Temkin isotherms, and pseudo-second-order kinetic model fitted the experimental data well, demonstrating an electrostatic interaction mechanism.

Cobalt hybrid catalysts in Fischer-Tropsch synthesis

Abstract Currently, cobalt and zeolites are used in Fischer-Tropsch synthesis (FTS) to produce gasoline-range hydrocarbons (GRHs) that constitute clean and environmentally friendly fuels. This technology has earned a great deal of attention from researchers across the world, as it provides a substitute for fuel derived from fossil crudes, which have hitherto been the sole source of the petrol and diesel required by the industry. However, owing to the depletion of the earth’s oil and coal reserves and the unfavourable environmental impact of conventional fuel production, an alternative source of fuel is needed. This article provides a critical review of the technological challenges involved in producing middle isoparaffins and olefins (gasoline hydrocarbons) by FTS. These involve combining cobalt-based catalysts and zeolites to form hybrid catalysts. In this review, we address most of these by setting out each method of creating cobalt and zeolite hybrid catalysts in turn, so that researchers can identify which applications are most effective for producing GRHs.

Desulphurization of diesel fuels using intermediate Lewis acids loaded on activated charcoal and alumina

Abstract According to Pearson’s hard/soft (Lewis) acids/bases concept, sulfur compounds in diesel will prefer to interact with intermediate or soft Lewis acid sites since they are soft to intermediate bases. In this work, intermediate Lewis metal oxides (MO) acids were loaded on activated carbon (AC) and alumina (Al2O3) to desulfurize diesel using adsorption. For carbon-loaded MO, NiO showed the highest desulfurization activity of 89% and 50% when using both model diesel and conventional diesel, respectively. The activity of Al2O3 and Al2O3 supported MO was approximately four times less than that of AC for model diesel desulphurization. It is suggested that the low activity of Al2O3 is due to lower surface area, pore distribution, and the strong acidity nature of Al2O3 since the adsorbates are soft to intermediate Lewis bases. Lower activity, 2–4 times, was observed when treating conventional diesel compared to model diesel. This lower activity is due to competitive adsorption with compounds such as naphthalene and indole. Despite this difference, the activity trends were generally maintained suggesting that the use of model diesel is not a bad technique for screening adsorbents. Selectivity on AC was observed to decrease in this order: 4-MDBT > 1,4,6-TMDBT > 4,6-DMDBTZ ∼ 4E,6-MDBT ∼ 2,4,6-TMDBT. This suggests that steric hindrances dominate selectivity for these high-molecular weight molecules. Finally, it was observed that the challenge with regeneration of adsorbent (AC) that treated conventional diesel using solvent extraction is competitive desorption of hydrocarbons and sulfur compounds.

Carbon efficiency targets for methanol production from a hybrid solar-carbonaceous feedstocks process

The carbon efficiency of a methanol production process that utilises concentrated solar power has been determined using basic process synthesis tools. The relationship between the hydrogen and oxygen content of the carbonaceous feed material and the carbon efficiency as well as the energy requirements has been explored. The target carbon efficiency of gasification-based methanol production from carbonaceous materials can be increased by 10-20 % by employing concentrated solar power (CSP) depending on the hydrogen and oxygen content of the feed material. Further improvement in carbon efficiency can be attained by considering process that may not be gasification-based, but rather employ a novel overall mass balance.The carbon efficiency of a methanol production process that utilises concentrated solar power has been determined using basic process synthesis tools. The relationship between the hydrogen and oxygen content of the carbonaceous feed material and the carbon efficiency as well as the energy requirements has been explored. The target carbon efficiency of gasification-based methanol production from carbonaceous materials can be increased by 10-20 % by employing concentrated solar power (CSP) depending on the hydrogen and oxygen content of the feed material. Further improvement in carbon efficiency can be attained by considering process that may not be gasification-based, but rather employ a novel overall mass balance.

Synthesis of a Biomass-to-Liquids (BTL) Process using a Hybrid Pyrolysis-Gasification System

Abstract Biomass is a promising feedstock for the production of energy and products (fuels, chemicals and materials). Thermochemical conversion technologies such as pyrolysis and gasification are attractive conversion techniques to transform biomass into a variety of products. Systematic techniques are required to synthesise and evaluate biomass conversion processes. In this work, the synthesis of Biomass-to-Liquids (BTL) systems are considered. By utilising atomic species balances and the first law of thermodynamics, various overall process configurations are developed and evaluated in terms of carbon efficiency and atom economy. Gasification, Pyrolysis and Fischer-Tropsch (FT) synthesis is utilised to attain the overall process configurations. The level of mass and energy integration required is determined. The carbon efficiency and raw material requirements for both the integrated and unintegrated processes are determined.

Analysis of the Carbon Efficiency of a Hybrid XTL-CSP process

Abstract The carbon efficiency of XTL (X- Coal, Natural gas, Biomass etc.) processes depends on the feedstock composition, especially the H content in the feedstock, and the energy requirements of the process. Low H: C ratios and high energy requirements requires extra feedstock to balance the material flows or to provide energy by combustion. This lowers the carbon efficiency, and increase the CO 2 emission of the process. The target carbon efficiency of XTL process is normally determined by the gasification process, which is highly endothermic. By employing Concentrated Solar Power (CSP) to supply the energy required for the gasification process the target carbon efficiency can be significantly improved. In the case of CTL, the carbon efficiency can be improved from around 50% to 66%, and for BTL, the carbon efficiency can be improved from around 60% to 70%. Furthermore, by changing the overall mass balance of XTL processes that employ CSP, a carbon efficiency of 100% can be achieved. One such possible process mass balance is: C H x O y + 1 − x / 2 H 2 O → C H 2 + 1 + y − x / 2 / 2 O 2