Unbounding the Future: Designing NiAl-based Catalysts for Dry Reforming of Methane.

Dry reforming of methane (DRM), the catalytic conversion of CH4 and CO2 into syngas (H2 + CO), is an important process closely correlated to the environment and chemical industry. NiAl-based catalysts have been reported to exhibit excellent activity, low cost, and environmental friendliness. At the same time, the rapid deactivation caused by carbon deposition, Ni sintering, and phase transformation exerts great challenges for its large-scale applications. This review summarizes the recent advances in NiAl-based catalysts for DRM, particularly focusing on the strategies to construct efficient and stable NiAl-based catalysts. Firstly, the thermodynamics and elementary steps of DRM, including the activation of reactants and coke formation and elimination, are summarized. The roles of Al2O3 and its mixed oxides as the support, and the influences of the promoters employed in NiAl-based catalysts over the DRM performance, are then illustrated. Finally, the design of anti-coking and anti-sintering NiAl-based catalysts for DRM is suggested as feasible and promising by tailoring the structure and states of Ni and the modification of Al-based supports including small Ni size, high Ni dispersion, proper basicity, strong metal-support interaction (SMSI), active oxygen species as well as high phase stability.

Facile synthesis of ordered mesoporous zinc alumina catalysts and their dehydrogenation behavior.

Ordered mesoporous Zn/Al2O3 materials with varying Zn content were simply prepared via an evaporation-induced self-assembly (EISA) method. Dehydrogenation of isobutane to isobutene was carried out on these materials; an isobutane conversion of 45.0% and isobutene yield of 39.0% were obtained over the 10%Zn/Al2O3 catalyst at 580 °C with 300 h-1 GHSV. The obtained materials with Zn content up to 10% possess large specific surface area and big pore volume and zinc species can be highly dispersed on the surface or incorporated into the framework. The acidity of these catalysts was changed by the introduction of Zn, the decrease of strong acid sites is conducive to the promotion of isobutene selectivity and the weak and medium acidic sites played an important role in isobutane conversion. In addition, these catalysts exhibited good catalytic stability, due to the effective inhibition of coke formation by the ordered mesoporous structure.

Mesoporous Mn-Zr composite oxides with a crystalline wall: synthesis, characterization and application.

Mesoporous Mn-Zr composite oxides (M-MnZr) with a crystalline wall were designed and achieved by a facile one-pot evaporation-induced self-assembly (EISA) strategy. As proved by XRD, HRTEM and SAED characterization, the wall of the obtained mesoporous materials exhibited a typical tetragonal phase of ZrO2. In addition, the introduced manganese species were homogeneously dispersed in the mesoporous skeleton. N2-physisorption and TEM results showed that all the final materials possessed an obvious mesoporous structure accompanied by a large specific surface area (∼120 m(2) g(-1)), big pore volume (∼0.2 cm(3) g(-1)) and uniform pore size (∼4.9 nm). In addition, the liquid phase oxidation was chosen as the test reaction and the excellent catalytic performance of M-MnZr demonstrated their potential applications in oxidation reactions.

Hydrolysis of cellulose in SO3H-functionalized ionic liquids.

Influence of acidity and structure of ionic liquids on microcrystalline cellulose (MCC) hydrolysis was investigated. MnCl2-containing ionic liquids (ILs) were efficient catalysts and achieved MCC conversion rates of 91.2% and selectivities for 5-hydroxymethyl furfural (HMF), furfural and levulinic acid (LA) of 45.7%, 26.2% and 10.5%, respectively. X-ray diffractometry indicated that catalytic hydrolysis of MCC in ionic liquids resulted in the changes to MCC crystallinity and transformation of cellulose I into cellulose II. SO3H-functionalized ionic liquids showed higher activities than non-functionalized ILs. The simplicity of the chemical transformation of cellulose provides a new approach for the use this polymer as raw material for renewable energy and chemical industries.

Catalytic conversion of cellulose to chemicals in ionic liquid.

A simple and effective route for the production of 5-hydroxymethyl furfural (HMF) and furfural from microcrystalline cellulose (MCC) has been developed. CoSO(4) in an ionic liquid, 1-(4-sulfonic acid) butyl-3-methylimidazolium hydrogen sulfate (IL-1), was found to be an efficient catalyst for the hydrolysis of cellulose at 150°C, which led to 84% conversion of MCC after 300min reaction time. In the presence of a catalytic amount of CoSO(4), the yields of HMF and furfural were up to 24% and 17%, respectively; a small amount of levulinic acid (LA) and reducing sugars (8% and 4%, respectively) were also generated. Dimers of furan compounds were detected as the main by-products through HPLC-MS, and with the help of mass spectrometric analysis, the components of gas products were methane, ethane, CO, CO(2,) and H(2). A mechanism for the CoSO(4)-IL-1 hydrolysis system was proposed and IL-1 was recycled for the first time, which exhibited favorable catalytic activity over five repeated runs. This catalytic system may be valuable to facilitate energy-efficient and cost-effective conversion of biomass into biofuels and platform chemicals.

Hydrolysis of cellulose by using catalytic amounts of FeCl2 in ionic liquids.

Microcrystalline cellulose (MCC) is hydrolyzed to an appreciable extent (70 %) by using 1-(4-sulfonic acid) butyl-3-methylimidazolium hydrogen sulfate (IL-1) as effective catalyst. Valuable chemicals, such as 5-hydroxymethyl furfural (HMF) and furfural, are obtained in relatively high yields (15 % and 7 %, respectively). Interestingly, the introduction of FeCl2 as catalyst into IL-1 further enhances the catalytic activity, as proved by the higher conversion of MCC (84 %) and higher yields of HMF and furfural (34 % and 19 %, respectively) under the same experimental conditions, although small amounts of levulinic acid (LA) and total reducing sugars (TRS) were also found. The hydrolysis of MCC scarcely proceeded, or showed a lower efficiency, in the absence of catalyst (4 %) or with Al2O3 (7 %), inorganic acids (≤65 %), or several other ionic liquids (≤24 %) as catalyst. Dimers of furan compounds were detected as the main byproducts, as analyzed by HPLC-MS; from the mass spectrometry analysis, the components of the gas-phase products were determined to be methane, ethane, CO, CO2, and H2. A mechanism to explain the high activity of FeCl2 in the IL-1 system is proposed. Recycling of the IL-1 catalyst showed an almost constant activity during five successive trials. The simple and effective catalyst system may prove valuable in facilitating the energy-efficient and cost-effective conversion of biomass into biofuels and platform chemicals.