High yield of monoacylglycerols production through low‐temperature chemical and enzymatic glycerolysis

The present study aimed to produce MAG through low‐temperature chemical glycerolysis. Over 80% MAG yield with 97% TAG conversion was obtained within short reaction times at temperature of 35–55°C, when tert‐butanol (TB) or tert‐pentanol (TP) was used as reaction medium and sodium hydroxide (NaOH) as catalyst. TB gave a faster reaction rate than TP. Catalysts were important for the low‐temperature chemical glycerolysis reaction. Of the eight common base catalysts evaluated, only NaOH and potassium hydroxide (KOH) were effective, and NaOH was better than KOH. Reaction parameters were studied and optimized. The optimum conditions were TB dosage 3:1 (TB to oil in weight ratio), NaOH concentration 0.45 wt% based on oil, molar ratio of glycerol to oil 5:1. Under these conditions, similar MAG yield and TAG conversion was also observed by Novozym 435 catalyzed glycerolysis, however, a 4 h reaction was required. Practical applications: The process of NaOH catalyzed chemical glycerolysis for MAG production in TB solvent system described in this study provides several advantages including short reaction time and high product yield, which is potential for industrial considerations.     

Low‐temperature photopolymerization and post‐cure characteristics of acrylates

Near‐infrared spectroscopy was used to investigate the post‐cure characteristics of acrylates polymerized from ? 75 °C up to room temperature. The results obtained showed that the double bond conversion increased with increasing initiator concentration. Post‐cure was much more striking for samples cured at lower temperatures. The chemical structure of monomer and photoinitiator had a great effect on the post‐cure process. The greater the functionality, the lower the final double bond conversion and the more distinct the post‐cure effect. Copyright © 2006 Society of Chemical Industry Society of Chemical Industry     

新型低汽气比低变催化剂B207的工业应用

B2 0 7在有效提高催化剂活性和稳定性的同时 ,提高了选择性。在一段转化水碳比低 ,低变炉的汽 /气比值为 0 .3的变换反应中 ,可发挥低汽气比低变催化剂低能耗的性能 ,从而达到合成氨系统节能降耗的要求。B2 0 7具有较宽的操作温区 ,稳定的活性 ,适宜各种中串低流程的操作要求     

Low‐Temperature Pretreatment of Lignocellulosic Biomass for Enhanced Biogas Production

Readily available lignocellulosic biomass as substrate for biogas plants is gaining popularity amongst biogas plant operators. Results of low‐temperature pretreatment (light cooking) of wheat straw to remove waxes and prepare the biomass for microbial action are described. Benefits of light cooking are low thermal energy demand and low investment cost compared to conventional techniques such as steam explosion. The novelty lies in utilizing the low temperature range 25–100 °C for pre‐soaking the biomass. Two different types of wheat straws were pretreated at varying temperatures and sizes. The results were compared with Buswell's equation for theoretical maximum biomethane yield. Compared to untreated straw, pre‐soaking leads to a significantly higher methane yield. Size reduction combined with light‐cooking does not affect the methane yield in the same manner as pre‐soaking of the biomass.     

Low‐Temperature Oxidation of Catocene and Its Influence on the Mechanical Sensitivities of a Fine‐AP/Catocene Mixture

High burning‐rate composite solid propellants with fine ammonium perchlorate (fine‐AP) and catocene have high mechanical sensitivities. The products of fine‐AP and catocene mixtures after low‐temperature exothermic reactions at about 173 °C were analyzed by X‐ray photoelectron spectroscopy (XPS). The result showed that FeO, Fe₂O₃, or FeCl_x were generated during the oxidation of catocene in the fine‐AP/catocene mixture. The mixture of fine‐AP and catocene has high impact and friction sensitivities, whereas the impact sensitivity of the after‐heated fine‐AP/catocene mixture reduced from 88 to 18 % and the friction sensitivity also decreased from 80 to 66 %. The low‐temperature oxidation of catocene is one important incentive for the high mechanical sensitivity of fine‐AP/catocene mixtures.     

Synthesis of novel optically active pyrrolidine‐containing polyaniline: A new heterogeneous organo polymeric‐base catalyst for direct Aldol reaction

An optically active pyrrolidine containing polyaniline, poly‐(2‐anilinomethylpyrrolidine) (PANiMp) is synthesized for the first time. PANiMp material is synthesized by simple one‐pot synthetic route and is characterized by circular dichroism, NMR, FTIR, and electronic absoroption spectral techniques. This novel polyaniline base is evaluated as new heterogeneous organo polymeric‐base catalyst for direct Aldol reaction in water medium. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Low‐temperature synthesis of ultrafine TiB2 nanopowders by molten‐salt assisted borothermal reduction

The synthesis of TiB₂ nanopowders arouses considerable interests due to its importance for implementing the extensive applications of TiB₂ ceramic. Herein, the high‐purity ultrafine TiB₂ nanopowders were successfully synthesized via a molten salt assisted borothermal reduction technique at a relatively low temperature of 1173 K using TiO₂ and B powders as precursors within a KCl/NaCl salt. The results showed that the as‐obtained TiB₂ nanopowders possessed a polycrystallinity structure, and their specific surface area and equivalent average particle size were 33.18 m²/g and 40 nm, respectively. This study provides a new low temperature synthesis technique of TiB₂ nanopowders.     

Heterogeneous Catalytic Epoxidation: High Limonene Oxide Yields by Surface Silylation of Ti‐MCM‐41

Limonene oxide is an intermediate getting growing attention in industrial chemistry. A series of Ti‐MCM‐41 heterogeneous catalysts with different hydrophilic/hydrophobic character, prepared by post‐synthesis silylation with hexamethyldisilazane (HMDS), were studied in the liquid‐phase epoxidation of limonene with tert‐butylhydroperoxide (TBHP). A maximum yield of 84 % in limonene oxide was obtained over a partially silylated catalyst with a surface coverage of 55 %.     

Technological Aspects of Nanoemulsion Formation of Low‐Fat Foods Enriched with Vitamin E by High‐Pressure Homogenization

Formation of a low‐fat oil‐in‐water (O/W) nanoemulsion enriched with vitamin E using the nonionic surfactant Tween 40 is studied by means of a high‐pressure homogenizer. The effect of different process variables of the emulsification process, including pressure, temperature, and concentration of the emulsifying agent, is evaluated. The relation between pressure and the obtained mean droplet diameter is derived and described by an equation which can be taken as a basis of any process design. The droplet size can be decreased by increasing the vitamin E concentration. A higher fat content slightly affects the droplet size distribution and the mean droplet diameter of the nanoemulsion, so it is recommended to use preparations of nanoemulsions with low fat contents enriched with vitamin E for dietary supplement.     

Low‐Temperature Rapid Synthesis of Rod‐Like ZrB2 Powders by Molten‐Salt and Microwave Co‐Assisted Carbothermal Reduction

A novel molten‐salt and microwave coassisted carbothermal reduction (termed as MSM‐CTR) method was developed to prepare ZrB₂ powders from raw materials of ZrO₂, B₄C, and amorphous carbon. The results indicated that the carbothermal reduction reaction for synthesizing ZrB₂ was initiated at the temperature as low as 1150°C, and phase pure ZrB₂ powders were obtained after only 20 min at 1200°C, which were significantly milder than that of the conventional CTR method as well as the modified CTR method even using active metal as additional reducing agents. More interestingly, the as‐obtained ZrB₂ powders consisted of well‐defined single‐crystalline nanorods, which had diameters of 40–80 nm and high aspect ratios of >10. These results demonstrated that the MSM‐CTR is a simple and efficient route for preparation of high‐quality ZrB₂ powders.     

Low‐temperature synthesis of Mg(OH)2 nanoparticles from MgO as halogen‐free flame retardant for polypropylene

Mg(OH)₂ (MH) nanoparticles were synthesized by hydration of the light‐burned MgO at low temperature (70°C). Effects of additives, such as magnesium nitrate and magnesium acetate, on the size, morphology and agglomeration of MH particles were investigated. MH nanoparticles have platelet‐like structure and approximately 20–40 nm in thicknesses. The supersaturation degree plays an important role in magnesia hydration and is defined. When magnesium acetate was used as the additive, the hydroxyl ion can be homogeneously introduced into the solution. The size and morphology of MH nanoparticles are more homogeneous. Modified by titanate coupling agent, MH nanoparticles were used as the flame retardant for polypropylene (PP). The combustibility, mechanical properties and thermal behaviors of the PP/MH composites were characterized. The mechanical properties of PP/MH composites are not seriously deteriorated with increasing MH content. When the amount of MH fraction reached 65, the limiting oxygen index (LOI) value and UL 94 testing result of MH65 are 33.8 and V‐0 grading, respectively. The onset temperature (T_10%) and the maximum thermal decomposition temperature (T_max) of MH65 separately increased by approximately 100°C and 77°C than those of neat PP. Copyright © 2012 John Wiley & Sons, Ltd.