Rong-Hsien Lin

A continuous-flow biodiesel production process using a rotating packed bed

The continuous-flow transesterification of soybean oil with methanol using a rotating packed bed (RPB) for the production of fatty acid methyl esters (biodiesel) is presented herein. The RPB, which provides high centrifugal force and has an adjustable rotational speed, is employed as a novel transesterification reactor. In this study, biodiesel is synthesized via the methanolysis of soybean oil using potassium hydroxide as the catalyst. The following variables were investigated for their effects on transesterification efficiency: the methanol-oil molar ratio, the estimated hydraulic retention time, the rotational speed of the packed-bed rotator, the reaction temperature, and the catalyst dosage. The yield of the fatty acid methyl esters (Y(FAME)) in the RPB system depends significantly on the experimental conditions, which influence the residence time distribution, the transesterification reaction rate, and the micromixing intensity. Due to its excellent micromixing characteristics, the RPB system shows satisfactory transesterification efficiency. The values of Y(FAME), productivity of FAMEs (P(FAME)), and P(FAME) per unit reactor volume (P(FAME)/V(R)) in the RPB are used to evaluate the performance for biodiesel production and allow for further comparison with other continuous transesterification reactors. Consequently, a RPB is considered a practical transesterification reactor with high transesterification efficiency.

Melting behavior and identification of polymorphic crystals in syndiotactic polystyrene

Abstract Melting peaks and resulted crystal forms in syndiotactic polystyrene (s-PS) subjected to various thermal treatments were thoroughly investigated using DSC and X-ray diffraction. This study concluded that the four major crystal forms were individually generated and no transformation occurred between α′, α″, β′ and β″ forms during thermal treatments. Thickening of these crystals, however, was likely during either slower heating scan (i.e. dynamic annealing) or extended isothermal annealing at relatively high temperatures. Different polymorphs were found to dominate the observed multiple melting endotherms of a thermally treated s-PS sample, which was erased of the thermal history in advance. Through cross-reference between the thermograms and X-ray crystallographs, each of the multiple melting peaks in DSC thermograms of s-PS was individually assigned and associated with the identified crystal forms. The melting peak of β-form is always located at lower temperature than those of α-form. Meanwhile, β-form is less thermally stable than α-form.

Photocatalytic degradation of p-phenylenediamine with TiO2-coated magnetic PMMA microspheres in an aqueous solution

This study investigates the photocatalytic degradation of p-phenylenediamine (PPD) with titanium dioxide-coated magnetic poly(methyl methacrylate) (TiO2/mPMMA) microspheres. The TiO2/mPMMA microspheres are employed as novel photocatalysts with the advantages of high photocatalytic activity, magnetic separability, and good durability. The scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and transmission electron microscopy (TEM) images of the TiO2/mPMMA microspheres are used to characterize the morphology, element content, and distribution patterns of magnetite and TiO2 nanoparticles. The BET-specific surface area and saturation magnetization of the TiO2/mPMMA microspheres are observed as 2.21 m(2)/g and 4.81 emu/g, respectively. The photocatalytic degradation of PPD are performed under various experimental conditions to examine the effects of initial PPD concentration, TiO2/mPMMA microsphere dosage, and illumination condition on the eliminations of PPD and chemical oxygen demand (COD) concentrations. Good repeatability of photocatalytic performance with the use of the TiO2/mPMMA microspheres has been demonstrated in the multi-run experiments. The photocatalytic kinetics for the reductions of PPD and COD associated with the initial PPD concentration, UV radiation intensity, and TiO2/mPMMA microsphere dosage are proposed. The relationships between the reduction percentages of COD and PPD are clearly presented.

Kinetics of polycyclotrimerization of 4,4′-thiodiphenylcyanate

Abstract Polycyclotrimerization of 4,4′-thiodiphenylcyanate was studied by means of differential scanning calorimetry. Samples of different impurity levels or different catalyst loadings (n-nonylphenol (NP), 1 to 10 phr) were studied. In the absence of added catalyst, the sample with higher impurity level (most likely residual water) underwent polycyclotrimerization at a lower temperature range than the sample of comparatively higher purity, although both samples shared the same apparent activation energy (Ea = 93 kJ mol−1) and exhibited similar autocatalysed first-order characteristics. The lowering of the reaction temperature range was more significant in the presence of NP. Interestingly, kinetic features in this case were quite different from the uncatalysed counterpart: in addition to the expected decrease in the apparent activation energy (Ea = 75 kJ mol−1, independent of the catalyst concentration), the cure reaction followed an autocatalysed second-order kinetics. These observations are explained in terms of a mechanistic scheme in which the competition between hydroxyl-catalysed and autocatalytic paths is considered. In particular, formation of NP aggregates ((NP)m, where m ≈ 7) is proposed to account for the less-than-additive catalytic capacity with increasing NP level.

Tri-substituted s-Triazines as Mesogenic Cores

Abstract Two series of equivalently- and inequivalently-tri-substituted s-triazines (as ESTs and ISTs, respectively) were synthesized and characterized in this study. More than one mesogenic biphenyl substituent were required to display mesomorphic properties, and two or three biphenyl substituents resulted in liquid crystalline textures under polarizing light. The mesophase transition temperatures for both IST and EST series are quite close despite their molecular weight difference. With longer sidechains, s-triazine for IST series formed a columnar hexagonal disordered mesophase (D hd); while for the analogous compound in EST series, a perfectly aligned layered structure was found to be co-existed with the D hd phase. With shorter sidechains, the s-triazines exhibited nematic mesomorphism.

Effect of intramolecular cycles on the formation of rigid polycyanate networks

Abstract On the basis of the recursive method of Macosko and Miller ( Macromolecules , 1976, 9 , 199), a theoretical scheme with due considerations on the formation of intramolecular cycles is developed for polycyanate networks. Experimental observations on gelation behaviour of a typical aromatic dicyanate, 2,2-bis(4-cyanatophenyl)propane, are compared with the theoretical predictions. Results indicate that deviations from the classical behaviour (including the sluggish molecular weight build-up during the pre-gelation regime, the delayed gelation, and the steeper increase of gel fraction in the post-gelation stage) can be explained in terms of effects of intramolecular cyclisation, which is negligible in the early stage of curing, becomes more important with increasing conversion, and is then counterbalanced (presumably by loop-interlocking) in the post gelation regime.

Effect of Intramolecular Cycles on the Polycyclotrimerization of Aromatic Dicyanates

The gel conversions (agel) for the polycyclotrimerization of aromatic dicy- anates are significantly higher than the classical mean-field value of 0.5. The reasons for the higher gel conversion, which is consistent with all experimental results of different structures of monomers, were inductively attributed to the accessibility effect of the functional group and the substitution effect, as well as the effect of the intramo- lecular cyclization. Nevertheless, the former two effects on the gel conversion can be quantitatively represented in terms of the extent of the intramolecular cyclization. Some theoretical expressions (including gel conversion and crosslink density with respect to the conversion) were derived by use of the recursive method with due consideration of the intramolecular cyclization. These expressions (with only one ex- perimental parameter, agel) were found to be effective in describing gel fraction- conversion data for various polycyanurates. A dramatic change in the product value of DCp z Tg was also found in the vicinity of the gel point for all different structures of aromatic dicyanate systems. The dramatic change in DCp z Tg occurs at the gel point rather than the expected mean-field gel conversion of 0.5, presumably due to the intramolecular cyclization.