Yongli Sun

Transesterification of dimethyl oxalate with phenol over TS-1 catalyst

Abstract The transesterification of dimethyl oxalate with phenol to produce methyphenyl oxalate and diphenyl oxalate was carried out in liquid phase using a heterogeneous catalyst. The evaluation results showed that TS-1 had better activity and excellent selectivity to target products compared with many conventional ester exchange catalysts tested. Two hours as the duration of the reaction was appropriate. Under the catalytic reaction conditions, framework IR and the reaction results jointly proved that the best calcination temperature was 823 K at which the amount of acid sites measured by IR of adsorbed pyridine reached a maximum. X-ray diffraction of TS-1 did not show much variation with changing calcination temperatures from 723 to 923 K. The characterization of the catalyst, by means of IR of adsorbed pyridine and NH 3 -TPD indicated that the desired catalytic activity of TS-1 could be ascribed to its weak Lewis acidity. Tin modified TS-1 showed a better performance in activity and selectivity. The conversion of dimethyl oxalate was improved up to 50.3% when Sn loading was 2, while the selectivity was above 99% over all Tin modified TS-1 molecular sieves.

CHARACTERIZATION OF PVA-BASED MAGNETIC AFFINITY SUPPORT FOR PROTEIN ADSORPTION

A magnetic fluid was prepared by an oxidization-precipitation with FeCl2 and H2O2 in polyvinyl alcohol (PVA) solution. Cross-linked directly with glutaraldehyde, a magnetic support with magnetic particles entrapped by cross-linked PVA gel was produced. Cibacron blue 3GA (CB) was immobilized to the magnetic support to prepare the magnetic affinity support (MAS). The MAS was characterized by transmission electron microscopy (TEM) and infrared spectrum analysis. The TEM showed that the MAS ranged from 1 to 10 μm and consisted of nanometer-sized colloidal magnetite particles. It was determined that the MAS had a saturation magnetization of 1.16 × 103 A/m and showed no hysteresis in an external magnetic field of up to 5.6 × 105 A/m. The adsorption kinetics and equilibrium of bovine serum albumin (BSA) confirmed rapid adsorption and large capacity of the MAS. BSA adsorption reached equilibrium in 5 min. At a CB coupling density of 23 μmol/g, the adsorption capacity of the MAS was 35 mg/g at an aqueous phase concentration of 0.1 mg/mL. The possibility of repetitive uses of the MAS was also demonstrated, indicating the stability of the magnetic support for protein adsorption.

Heterogeneous oxidative desulfurization of diesel fuel catalyzed by mesoporous polyoxometallate-based polymeric hybrid

In this work, the simple preparation of novel polymer supported polyoxometallates (POMs) catalysts has been reported. Soluble task-specific cross-linked poly (ionic liquid) (PIL) was prepared with N,​N-​dimethyl-​dodecyl-​(4-​vinylbenzyl) ammonium chloride and divinylbenzene as co-monomers. The as-prepared cationic PILs were assembled with different commercial POMs to form the interlinked mesoporous catalysts, and the formation mechanism was provided. The catalytic oxidation activities of the catalysts were closely related to the formation pathway of their corresponding peroxide active species. The catalyst with H2W12O4210- as counterion, which exhibited the best activity in the oxidation of benzothiophene (BT) and dibenzothiophene (DBT) to sulfones in model oil with hydrogen peroxide (H2O2, 30wt%) as oxidant, was characterized by different techniques and systematically studied for its sulfur removal performance. As for the oxidative desulfurization of a real diesel, it was observed that almost all of the original sulfur compounds could be completely converted, and the catalyst could be reused for at least eight cycles without noticeable changes in both catalytic activity and chemical structure. In the end, a catalytic mechanism was put forward with the assistant of Raman analysis.

Experimental Study of Precision-Woven Fabrics for Oil-In-Water Emulsion Coalescence: Operating Conditions and Oil Saturation

Fabrics have the advantage of having high mechanical strength and low environmental sensitivity. The Kozeny–Carman equation and its modified form can be used to predict permeability, pressure drop, porosity, and oil saturation, as well as to help find optimum pore size. Experiments were conducted under a wide range of flow velocity, oil concentration, bed length, and pore size. Under optimal conditions, more than 90% of surfactant-stabilized emulsified oil could be removed. Relating the pressure drop and oil saturation with separation efficiency aids in a clearer understanding of emulsion transport in fibrous media and finding the optimum medium and operating conditions.

Synthesis of chlorostannate(II) ionic liquids and their novel application in the preparation of high-quality L-lactide

Polylactic acid (PLA) is a representative biodegradable polymer, which is expected to be a promising replacement for some petroleum-based materials. Noticeably, the properties of PLA products depend strongly on the quality of the lactide monomer, a crucial precursor of PLA production. In this work, a large range of different chlorostannate(II) ionic liquids (ILs), prepared by mixing 1-butyl-3-methyl-imidazolium chloride and tin(II) chloride in various molar ratios, xSnCl2, were firstly applied for the preparation of L-lactide of high chemical and optical purity. The cation–anion interaction, the thermal stability and the acidity of imidazolium-based chlorostannate(II) ionic liquids were experimentally determined and systematically analyzed. Compared with the conventional SnCl2 catalyst, the depolymerization of oligomeric poly(L-lactic acid) catalyzed by chlorostannate(II) ionic liquids occurred in a moderate yield. Interestingly, using [Bmim]Cl–SnCl2 (xSnCl2 = 0.63) as a catalyst, L-lactide of 99.9% optical purity was obtained, simultaneously leaving a high-Mw oligomeric residue with high isotacticity (99.1%). Furthermore, the effects of various reaction parameters were investigated in order to obtain the highest possible yield of lactide. A plausible reaction mechanism was suggested and discussed. Finally, owing to the reutilization of PLLA residue of high isotacticity, a reiterative lactide synthesis was realized. The recycled catalyst showed no notable loss of activity. By combining this chlorostannate(II)-based IL (xSnCl2 = 0.63) catalyst technology with the cyclic resynthesis process, high-quality L-lactide could be selectively produced in high yield (>80%, based on L-lactic acid replenished).

Novel Protic Ionic Liquid Composite Membranes with Fast and Selective Gas Transport Nanochannels for Ethylene/Ethane Separation

Protic ionic liquids (PILs) were utilized for the fabrication of composite membranes containing silver salt as the C2H4 transport carrier to perform C2H4/C2H6 separation for the first time. The intrinsic nanostructures of PILs were adopted to construct fast and selective C2H4 transport nanochannels. The investigation of structure-performance relationships of composite membranes suggested that transport nanochannels (polar domains of PILs) could be tuned by the sizes of cations, which greatly manipulated activity of the carrier and determined the separation performances of membranes. The role of different carriers in the facilitated transport was studied, which revealed that the PILs were good solvents for dissolution and activation of the carrier due to their hydrogen bond networks and waterlike properties. The operating conditions of separation process were investigated systemically and optimized, confirming C2H4/C2H6 selectivity was enhanced with the increase of silver salt concentration, the flow rate of sweep gas, and the feed ratio of C2H4 to C2H6, as well as the decrease of the transmembrane pressure and operating temperature. Furthermore, the composite membranes exhibited long-term stability and obtained very competitive separation performances compared with other results. In summary, PIL composite membranes, which possess good long-term stability, high C2H4/C2H6 selectivity, and excellent C2H4 permeability, may have a good perspective in industrial C2H4/C2H6 separation.

Preparation of poly(L-lactic acid) membrane from solvent mixture via immersion precipitation

ABSTRACT Poly (L-lactic acid) (PLLA) membranes were fabricated through immersion precipitation method. 1, 4-dioxane (DX), N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-dimethyl-acetamide (DMAc), and DX/NMP, DX/DMF and DX/DMAc were used as solvents severally. With a focus on the PLLA/DX/NMP/H2O system, the effect of solvent mixture on PLLA membrane was investigated by altering the ratio of DX/NMP. Various membrane morphologies were obtained, which were further correlated by mean of solubility parameter and viscosity of casting solution. It was found that the membrane cast with DX/NMP (1/1) exhibited ideal structure and better performance compared with membranes cast with same concentration of PLLA.