Effect of Mo Dispersion on the Catalytic Properties and Stability of Mo-Fe Catalysts for the Partial Oxidation of Methanol.

Mo-Fe catalysts with different Mo dispersions were synthesized with fast (Cat-FS, 600 r·min-1) or slow stirring speed (Cat-SS, 30 r·min-1) by the coprecipitation method. Improving the stirring speed strengthened the mixing of the solution and increased the dispersion of particles in the catalyst, which exhibited favorable activity and selectivity. The byproduct (dimethyl ether (DME)) selectivity increased from 2.3% to 2.8% with Cat-SS, while it remained unchanged with Cat-FS in a stability test. The aggregation of particles and thin Mo-enriched surface layer decreased the catalyst surface area and slowed down the reoxidation of reduced active sites with Cat-SS, leaving more oxygen vacancies which promoted the formation of DME by the nonoxidative channel.

Supported Ni Catalyst for Liquid Phase Hydrogenation of Adiponitrile to 6-Aminocapronitrile and Hexamethyenediamine.

Supported Ni catalysts prepared under different conditions, for liquid phase hydrogenation of adiponitrile (ADN) to 6-aminocapronitrile (ACN) and hexamethyenediamine (HMD), were investigated. The highly reactive imine intermediate can form condensation byproducts with primary amine products (ACN and HMD), which decreased the yield coefficient of primary amines. The catalysts support, condition of catalyst preparation and dosage of additive were studied to improve the yield. A highly dispersed Ni/SiO2 catalyst prepared by the direct reduction of Ni(NO3)2/SiO2 suppressed the condensation reactions by promoting the hydrogenation of adsorbed imines, and it gave the improved hydrogenation activity of 0.63 mol·kgcat-1·min-1 and primary amine selectivity of 94% when NaOH was added into the reactor.

Elucidating the deactivation mechanism of beta zeolite catalyzed linear alkylbenzene production with oxygenated organic compound contaminated feedstocks.

Zeolite catalyzed alkylation of benzene with long-chain α-olefins is a promising method for the detergent industry. Considering the long-chain α-olefins from Fischer-Tropsch synthesis always contain some oxygenated organic compounds, the effect of which on the alkylation of benzene with 1-dodecene was comprehensively investigated over beta zeolite herein. n-heptanol, n-heptaldehyde and n-heptanoic acid were selected as the model oxygenated organic compounds, and it was revealed that an obvious decrease of lifetime occurred when only trace amount of oxygenated organic compounds were added into the feedstocks. The deactivated catalyst was difficult to regenerate by extraction with hot benzene or coke-burning. A series of characterization tests complementary with DFT calculations revealed that the deactivation was mainly caused by the firm adsorption of oxygenated organic compounds on the acid sites. Further, comparison with the open-framework MWW zeolite revealed a similar effect of oxygenated organic compounds and deactivation mechanism for both beta and MWW, but beta is less sensitive to the oxygenated organic compounds. The main reason lies in the three-dimensional framework of beta, wherein the much higher adsorption energy of 1-dodecene makes it difficult to be replaced by oxygenated organic compounds. Additionally, beta could be regenerated more easily by extraction with hot benzene compared with MWW. But coke-burning caused a sharp decrease of its lifetime, which is mainly due to the decreased acid sites after calcination.

Effect of surface silicon modification of H-beta zeolites for alkylation of benzene with 1-dodecene.

H-beta zeolites of 100-200 nm (named BEA-L) and 20-30 nm (named BEA-S) were treated by chemical liquid deposition (CLD) of tetraethyl orthosilicate (TEOS) to improve the selectivity of 2-phenyl linear alkylbenzene (2-LAB) from benzene alkylation with 1-dodecene. The results indicate that H-beta zeolite with a smaller crystal size has a longer lifetime due to shorter channels and less diffusion limitation. The deposited SiO2 layers passivated the external surface acid sites of the zeolite and made the pores narrower. BEA-L lost more external Brønsted acid sites than BEA-S with the same added amount of TEOS, which was due to the severe aggregation of BEA-S grains. This increased passivation gave BEA-L increased 2-LAB selectivity. And when the added amount of SiO2 was 7.20 wt% of the parent zeolite, the selectivity of 2-LAB over BEA-L significantly increased from 41.9% to 54.7% while that of BEA-S only increased by 2%.

Effect of synthesis pH on the structure and catalytic properties of FeMo catalysts.

The effect of pH on polynuclear molybdenum species (isopolymolybdates) synthesis was investigated by Raman spectroscopy. As the pH decreased from 6.0 to 1.0, the main isopolymolybdates changed from MoO4 2- to Mo7O24 6- to Mo8O24 6- to Mo36O116 8-. They began to aggregate and their solubility decreased with decreasing pH. The FeMo catalysts comprised particle- and plate-like structures, which were Fe2(MoO4)3 and MoO3, respectively. When a low pH value was used in the catalyst preparation, there was severe aggregation of the particles which have a high Mo/Fe mole ratio and Mo enrichment on the surface layer, which decreased the activity and selectivity of the FeMo catalyst.

[Studies on IR spectroscopy and quantum chemical calculation of chloroaluminate ionic liquids acidity].

The acidity of chloroaluminate ionic liquids and the interaction mechanism of Lewis acid site Al2Cl7(-) of chloroaluminate ionic liquid and pyridine were experimentally investigated by IR characterization by using pyridine as molecular probe and increasing pyridine adsorption, and theoretically confirmed by quantum chemical calculations at density functional theory (DFT) and ab initio levels. It was found that the anions, Al2Cl7(-) and AlCl4(-), which could withdraw lone pair electrons of pyridine, were characteristic of Lewis acid. Therefore, they displayed pyridine coordinated to Lewis acidic site using pyridine as probe. The acidity of Al2Cl7(-) was found stronger than that of AlCl4(-) by analyzing IR absorption frequency, bond length and charge distribution. The mechanism of forming and evolvement of the Lewis acid site Al2Cl7(-) of chloroaluminate ionic liquid was proposed. When the amount of pyridine is small, only the adsorption state of Py-Al2Cl7(-) exists. The highly Lewis acidic adsorption state of Py-Al2Cl7(-) complex was converted into Py-AlCl4(-) complex and Py-AlCl3 complex with increasing pyridine contents, leading to the changes in IR absorption spectra.

Carbon nanotube-alumina strips as robust, rapid, reversible adsorbents of organics.

Developing nanostructured adsorbents of organics is crucial for environmental protection with low energy consumption, but care needs to be taken to prevent the loss of nanomaterials because of their small size. This paper reports the fabrication of carbon nanotube (CNT)-alumina strips (CASs) with a high surface area, sufficient mesopores and strongly interacted structure. Use of CASs allowed the rapid and reversible adsorption-desorption of para-xylene, when compared to pristine powders of CNT and activated carbon. Use of CASs is promising for the practical use when packed in a scaled adsorption tower.

[Synthesis and characterization of novel brønsted acidic ionic liquids].

Several water-stable Brønsted-acidic ionic liquids with an alkane sulfonic acid group were synthesized, and were characterized by nuclear magnetic resonance (NMR), infrared spectrum (IR), electrospray ionization mass spectrum (ESI-MS) and thermogravimetry (TG.). It was found that their structures were consistent with the designed one and all of their purities were more than 95%. These ionic liquids possess high thermal stability and wide liquid range, and their decomposition temperatures are higher than 300 degrees C by analyzing TG. In addition, they were found to have four kinds of ionic form, in which hydrogen ion can exist independently by analyzing ESI-MS. Moreover, the solubility of these ionic liquids was studied in some common solvents. All the ionic liquids are miscible with water and methanol, but are insoluble in ether, toluene and ethyl acetate.

[Studies on acidity of chloroaluminate ionic liquids and its catalytic performance for alkylation of benzene with long-chain alkenes].

The acidity of chloroaluminate ionic liquids (ILs) was determined by using pyridine and acetonitrile as IR spectroscopic probes. Based on the characterization method of acidity of solid acid, IR vCCN absorption frequencies of pyridine in ionic liquids were assigned. By using the pyridine probe, it was found that when the anion molar composition x of ionic liquid varies within 0.4-0.5, ionic liquids exhibit weak Lewis acidity. Strongly basic molecular pyridine can be used as a probe to measure the acidity of ionic liquids whether their acidity is strong or weak, while weakly basic molecular acetonitrile is only fit for strong acid. In addition, the Lewis acidity-activity correlation for the chloroaluminate ionic liquids catalyst in the alkylation reaction was studied. The weakly acidic ILs with x < or = 0.5 does not exhibit any catalytic activity in the alkylation reaction. When the anion molar composition x is more than 0.55, the activity of ionic liquids is greatly enhanced due to the increase in the strength of the strong Lewis acidic species Al2Cl7-. But with the increase in alkenes conversion, the selectivity of 2-alkylbenzene is slightly reduced.

Preparation of biodiesel from waste oils catalyzed by a Brønsted acidic ionic liquid.

Preparation of biodiesel from waste oils catalyzed by a novel Brønsted acidic ionic liquid with an alkane sulfonic acid group was investigated. The acidity and the activity of the ionic liquid were very low at lower temperature when the ionic liquid was crystalloid; they recovered at higher temperature when the crystallized ionic liquid was liquefied. When methanol:oils:catalyst molar ratios were 12:1:0.06, the yield of fatty acid methyl esters can reach 93.5% after the reaction of acidic oil with methanol had taken place at 170 degrees C for 4h. In addition, the ionic liquid had a good reusability and can be easily separated from the biodiesel by simple decantation.