Functionalized oligoesters from poly(3-hydroxyalkanoate)s containing reactive end group for click chemistry: Application to novel copolymer synthesis with poly(2-methyl-2-oxazoline)

Well defined poly(3-hydroxyalkanoates) PHAs containing an alkyne end group were prepared in a one step reaction by direct alcoholysis from natural polyesters using propargyl alcohol. The reactions were allowed to proceed with dibutyltin dilaurate as catalyst at different concentrations from 0.5 up to 24% mol/mol of the alcohol. Oligoesters were obtained with molar masses ranging from 44,500 to 2700 g mol⁻¹. Analysis of the MALDI-TOF mass spectra of the obtained oligomers has revealed the presence of alkyne group on one side and hydroxyl end group on the other side when the reaction was conducted in dried chloroform. The reaction rate of oligomer formation was depending on the nature of the PHAs and decreased with the length of the side chains. The Huisgen 1,3-dipolar cycloaddition has been investigated between the alkyne group of PHAs and 2-azido-2-deoxy-d-glucose or azido-poly(2-methyl-2-oxazoline) (N₃-POXZ). The click reaction allowed the preparation of novel diblock copolymer PHA-b-POXZ soluble in water.     

超临界CO2中脂肪酶催化酯交换反应

建立了一套超临界ＣＯ２中酶催化反应装置，实现了脂肪酶催化苯甲醇与乙酸丁酯的酯交换反应，并分别探讨了压力、水含量、温度和脂肪酶用量对反应速度和转化率的影响以及酶的稳定性。     

Transesterification of tributyrin with methanol over calcium oxide catalysts prepared from various precursors

Calcium oxide catalysts were prepared by calcining various precursors such as calcium acetate, carbonate, hydroxide, nitrate and oxalate and their catalytic activities were examined in the transesterification of tributyrin with methanol. The prepared calcium oxide catalysts were characterized using thermogravimetry (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), N₂ adsorption and temperature programmed desorption (TPD) of CO₂. The calcium oxide catalyst obtained by calcining calcium hydroxide at 600–800 °C showed the highest tributyrin conversion and methyl butyrate yield. The large desorption peak of CO₂ TPD confirmed that its numerous basic sites were responsible for its high activity. The low-temperature decomposition of calcium hydroxide provided many nano-sized pores with strong basic sites. Although the activity of the calcium oxide catalyst prepared from calcium hydroxide was high, its activity was one order of magnitude less than that of sodium hydroxide catalyst. The dissolution of calcium oxide catalysts in products and their repeated uses were also investigated to discuss their advantages as heterogeneous catalysts in the production of biodiesel.     

关于控制PET／PEN共混物酯交换反应的研究

通过在聚对苯二甲酸乙二酯和聚二甲酸乙二酯的共混体系中加入不同种类,不同含量的热稳定剂或酯交换阻止剂,在300℃左右,经不同时间的熔融共混后取样,再经DSC、NMR测试观察,发现所使用的化学试剂不能阻酯交换反应的发生,酯交换反应程度与所加化学试剂的种类、含量基本夫关,而随熔融共混时间的缩短而受到抑制。     

Intensified production of biodiesel using a spinning disk reactor

This work achieves continuous transesterification of soybean oil and methanol in a spinning disk reactor. The effects of the methanol-to-oil molar ratio, catalyst type, catalyst concentration, reaction temperature, flow rate, and rotational speed were investigated. Optimal yield of 96.9% was obtained with a residence time of 2–3 s at a molar ratio of 6, potassium hydroxide concentration of 1.5 wt%, temperature of 60 °C, flow rate of 773 mL/min, and rotational speed of 2400 rpm. The production rate of 1.86 mol/min was high compared to that of other reactors for continuous transesterification process, indicating that a spinning disk reactor is a promising alternative method for continuous biodiesel production.     

Synthesis of biodiesel from soybean oil using supercritical methanol in a one-step catalyst-free process in batch reactor

The transesterification of soybean oil with supercritical methanol in a batch reactor with no added catalyst was investigated, studying the evolution of intermediate products (monoglycerides and diglycerides) as well as the conversion of triglycerides and the yield of fatty acid methyl esters and glycerol. Experiments were carried out in a temperature range of 250–350 °C (12–43 MPa) at reaction times of between 15 and 90 min for a methanol-to-oil molar ratio of 43:1. The best reaction conditions in this one-step supercritical process (325 °C/35 MPa and 60 min), in which triglyceride conversion was practically total, led to a maximum yield of fatty acid methyl esters of 84%. In these conditions an 8.1 wt% of monoglycerides and diglycerides remained in the medium. Although the use of more severe reaction conditions (longer reaction times and higher temperatures) reduced the content of these glycerides, the yield of methyl esters decreased due to their thermal decomposition.     

Artificial Neural Network based prediction of performance and emission characteristics of a variable compression ratio CI engine using WCO as a biodiesel at different injection timings

Due to the increasing demand for fossil fuels and environmental threat due to pollution a number renewable sources of energy have been studied worldwide. In the present investigation influence of injection timing on the performance and emissions of a single cylinder, four stroke stationary, variable compression ratio, diesel engine was studied using waste cooking oil (WCO) as the biodiesel blended with diesel. The tests were performed at three different injection timings (24°, 27°, 30° CA BTDC) by changing the thickness of the advance shim. The experimental results showed that brake thermal efficiency for the advanced as well as the retarded injection timing was lesser than that for the normal injection timing (27° BTDC) for all sets of compression ratios. Smoke, un-burnt hydrocarbon (UBHC) emissions were reduced for advanced injection timings where as NO_x emissions increased. Artificial Neural Networks (ANN) was used to predict the engine performance and emission characteristics of the engine. Separate models were developed for performance parameters as well as emission characteristics. To train the network, compression ratio, injection timing, blend percentage, percentage load, were used as the input parameters where as engine performance parameters like brake thermal efficiency (BTE), brake specific energy consumption (BSEC), exhaust gas temperature (T_exh) were used as the output parameters for the performance model and engine exhaust emissions such as NO_x, smoke and (UBHC) values were used as the output parameters for the emission model. ANN results showed that there is a good correlation between the ANN predicted values and the experimental values for various engine performance parameters and exhaust emission characteristics and the relative mean error values (MRE) were within 8%, which is acceptable.     

Kapok oil methyl esters

The increased need for biodiesel feedstocks has caused various vegetable oils to be examined for this purpose. In the present work, the methyl esters of kapok (Ceiba pentandra) oil were prepared. The essential fuel properties were comprehensively determined and evaluated in comparison to specifications in biodiesel standards and some prior results. The kinematic viscosity of kapok oil methyl esters was greater than expected, an observation traced to the elevated amounts of methyl esters with cyclic moieties. Overall, kapok oil is a potential biodiesel feedstock. The ¹H and ¹³C NMR spectra of kapok methyl esters are reported.     

Obtaining and characterization of biodiesel from jupati (Raphia taedigera Mart.) oil

The search for alternative triglyceride sources for biodiesel production is a widely discussed issue in Brazil because of the initiation of the Brazilian biofuel program. The viability of biodiesel production from the oil of Raphia taedigeraMart., commonly known as jupati, is studied in this work. This paper presents the obtention and characterization of biodiesel from jupati using an ethylic route with a methane sulfonic acid reaction catalyst. The alcohol:oil molar ratio was 9:1, and the catalyst concentration was 2% of the oil mass. The yield of the process was 92% by mass, and the oil conversion into jupati ethylic biodiesel was 99.6%. The physical and chemical parameters of jupati ethylic biodiesel were within the limits set by the National Agency of Petroleum, Natural Gas and Biofuels (ANP).