Band 16, Heft 2 -

The solid acid catalysts SO 4 2− /Fe 2 O 3 were prepared by impregnation technique, and the preparation conditions were different in calcination temperature, concentration of impregnation solution of H 2 SO 4 and impregnation time. The characterization was performed by using Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), Temperature programed desorption of NH 3 (NH 3 ‒TPD), N 2 ‒BET and microwave absorbing test. As shown by FTIR spectra, the S=O functional group existed in the sample, which was essential for the strong acidity of the SO 4 2‒ /M x O y type solid acids. The XRD results indicated that when the calcination temperature exceeded 400℃, iron in SO 4 2‒ /Fe 2 O 3 transformed from amorphous to crystalline phase. The results from NH 3 -TPD showed that the prepared sample possessed strong acid and superacid sites. As shown by N 2 -BET results, the BET surface area of the samples was up to 200m 2 /g, and their pore size distributions essentially belonged to mesoporous characteristic distribution. The SO 4 2− /Fe 2 O 3 solid acid catalysts were used for the transesterification of castor oil under microwave radiation to produce biodiesel. The amounts of FAME in the product were analyzed by high-performance liquid chromatography. The highest yield of product was 65.3 wt.% when the reaction temperature was 65 ℃, alcohol/oil molar ratio was 30/1, catalyst loading was 20 wt.%, the reaction time was 3 h and the power of microwave was 300 w. Furthermore, the reaction results showed that SO 4 2‒ /Fe 2 O 3 had better catalytic activity under microwave radiation than under conventional heating condition.

In the present investigation, synthesis of cumene by transalkylation of 1, 4 DIPB with benzene was studied over cerium modified nano crystalline zeolite X in a fixed bed plug flow reactor. Nano crystalline zeolite X was synthesized and characterized by XRD, SEM, TPD, EDS and FTIR. A series of nanocrystalline zeolite X (MX 4 , MX 6 , MX 10 ) modified with ceric ammonium nitrate of different concentrations (4 %, 6 %, 10 %) was used for synthesis of cumene. MX 10 zeolite was proved to be the most active catalyst over which 27.12 % yield of cumene was obtained at temperature 553K, benzene/1, 4 DIPB mole ratio of 7.5 and space time-10.54 kg h/kmol. Reduction of crystal size (100–500 nm) in MX 10 increases surface area (633m 2 /gm) and thereby increases cumene yield. A kinetic rate equation was developed from the product distribution pattern following Langmuir–Hinshelwood approach. Kinetic parameters were estimated by nonlinear regression analysis. The activation energy for transalkylation and isomerisation reaction was found to be 88.86 kJ/mol and 99.04 kJ/mol respectively.

The control of thermal stability of polyaniline (PANI) nanofibers is reported by systematically varying the loadings of CaO in the range from 0.005 g to 1.0 g. It was found to gradually increase the yield of synthesized PANI nanofibers with the increase of CaO addition. The highest yield, 1.103 g was obtained for 1.00 g loading of CaO. The incorporation of CaO into PANI matrix was revealed by energy-dispersive X-ray spectroscopy (EDX). Thermogravimetric analysis (TGA) data showed that the thermal stability of PANI nanofibers was greatly improved when CaO was added to the system. 1.00 g loading of CaO is favorable to obtain comparatively more thermally stable PANI. The degradation of PANI chains started at 330 °C for the PANI-CaO composites obtained at 1.00 g CaO addition, which is the highest temperature compared to PANI and the samples synthesized at other amount of CaO loadings. Furthermore, the increasing trend of thermal stability was observed with the increasing of CaO loading.

In this study, low cost activated carbon was prepared from the pistachio shell by chemical activation with zinc chloride (ZnCl 2 ). The prepared activated carbon was characterized by thermogravimetry (TG) and differential thermal gravimetry (DTG), infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Brunauer, Emmett and Teller (BET) surface area analyses. Results showed that the activation temperature and impregnation ratio have significant effect on the iodine number of the prepared activated carbon. The optimum conditions for preparing the activated carbon having the highest surface area were found to be an activation temperature of 700 °C, soaking time of 24 h and ZnCl 2 / pistachio shell ratio of 50 %. The results showed that the BET surface area, total pore volume, iodine number and methylene blue (MB) number of activated carbon prepared under the optimum conditions were 1108 m 2 /g, 0.39 cm 3 /g, 1051 mg/g, 98.48 mg/g, respectively.

In this study the effect of (0.1 %Ru, 0–10 % Zr) and (0.1 %Ru, 0–10 % Ce) promoters on dispersion, strong metal-support interaction and reduction behavior of cobalt-supported alumina catalyst in the Fischer-Tropsch synthesis was investigated. The synthesized catalysts were characterized by BET, XRD, ICP, TPR, XPS, and TEM techniques. The results show that addition of Ce to the catalyst leads to the shift of the TPR peaks to lower temperatures which expected that shows higher activity due to higher reducibility, but surprisingly due to SMSI effect results in the lower catalyst activity compared with the unpromoted catalyst. Also, there was a synergistic effect between Ce and Ru in the reduction behavior of Ru-Ce promoted catalyst. The other notable finding of this study was the improvement in the catalyst reducibility in the presence of Zr compared with the unpromoted one that equivalently means the higher catalyst activity. Comparison of the Zr-promoted with the Ce-promoted catalysts show that the former have higher catalyst activity than the latter due to higher acidity and SMSI effect in the presence of the Zr promoter. The C 5 selectivity of the 0.1Ru10Zr/15Co and 3Ce/15Co catalysts at low pressure have shown more than 50 % improvement compared to the unpromoted one. Based on the activity at atmospheric pressure; the unpromoted, 0.1Ru/15Co, 0.1Ru3Ce/15Co and 0.1Ru10Zr/15Co catalysts were selected for high pressure condition tests, in which the 0.1Ru10Zr/15Co catalyst shows the highest catalyst activity and heavier hydrocarbon selectivity.

Initial breakup model(IBM) approach in conjunction with Volume of fluid(VOF) is developed to model the special nozzle in ethoxylation reactors, which has to meet the requirement of low pressure drop, high volume flow rate, little droplets size and large field. For the VOF model, Realized k-ε is selected and has higher accuracy of simulation for swirling flows by comparing with Standard and RNG k-ε models. IBM is written as a user defined function(UDF) and embedded to study the extra breakup from ligaments to droplets and forecast the droplets size distribution. As the experiments have been conducted already, the simulation results have a good agreement with the experimental results in flow rate, spray cone angle and droplets size distribution. At the same time, the atomization process and atomization mechanism of the ethoxylation reaction nozzle were analyzed. Then the VOF-IBM methodology can be used to predict the spray characteristics of the nozzles with different structure and the optimal structure for ethoxylation reaction was found by orthogonal test and fuzzy comprehensive evaluation. In addition, the primary and secondary order of the influencing factors for discharge coefficient, spray cone angle and Sauter mean diameter are respectively gained. The VOF-IBM is instructive for the optimization design of ethoxylation reaction.

Abstract: To efficiently utilize agricultural biomass waste, kinetic modeling of the pyrolysis of rice husk, including both physical (mainly heat transfer) and chemical (reactions) terms, was conducted at different heating rates from (10 to 20 K min −1 ) to develop a transport model. For chemical kinetics, the parameters were estimated using different kinetic models, namely the single- or parallel-reaction kinetic model with higher orders and the two-step consecutive reaction model. The two-step model could adequately explain the pyrolysis reaction of multiple reactions with different reaction orders i. e., first step is of the first order (m = 1) with respect to the mass of biomass, and the second step is of the second order (n = 2) with respect to the mass of the intermediate to char. The intrinsic kinetics at different heating rates in the absence of oxygen was derived through thermogravimetric analysis. The kinetics of the evolution of non-condensable gases was studied in a self-designed reactor, and an appropriate kinetic model of rice husk biomass pyrolysis that showed excellent agreement with experimental data was established.

Activated carbons were produced from walnut shell by fast activation with H 3 PO 4 in a spouted bed, and the influence of particles fluidization had been investigated. Experimental results showed that walnut shell particles with higher H 3 PO 4 impregnation ratios would be agglomerated in spouted bed, and difficult to fluidize. Therefore, an amount of quartz sands were added to assist fluidization of H 3 PO 4 impregnated walnut shell particles. The BET surface area of activated carbon prepared under fluidization would be obviously increased with H 3 PO 4 impregnation ratio, reaching 1549.6 m 2 /g for the mass ratio of H 3 PO 4 to walnut shell particles of 2 and activation temperature of 700°C. Meanwhile, both of the micro- and meso- pore volumes were increased. In addition, fluidization of particles had very little influence on activated carbon surface functional groups forming. It was found that the activated carbons contained more carbonyl groups (C = O), carboxyl groups (COOH) and some P-containing functional group.

Enzymatic hydrolysis of biomass to produce sugars that can be converted to fuels and other valuable chemicals, is viewed as the prime technology for utilization of this renewable resource. To accelerate technology development, models are needed that are able to accurately predict the hydrolysis rate so that reactors can be tailored to the multitude of processing conditions and substrates that can be used. Of particular interest is the ability to predict the long time conversion in the hydrolysis reaction which dictates the maximum possible sugar concentration. It is our aim in this article to develop a simple model which is able to predict the long-term conversion of cellulose to soluble sugars. Drawing on the analogy from the theory of reactions in continuous mixtures, it is shown that analysis of the long time kinetics of hydrolysis by examining the behavior of the “lump” of the reacting material results in a simple expression which is capable of predicting the kinetics. Many features of actual enzyme systems can be included in the development of the hydrolysis model, such as the large size of the enzyme molecules, adsorption onto substrate, inhibition by different factors (solvent, glucose etc.), but, when the analysis is carried out to calculate the total sugar concentration, it is shown that the equations reduce to a simple expression. Analysis of this model is given with comparison to other models and experimental data available in the literature. In addition to predicting the long-term kinetics, it is shown that the model does a surprising job of predicting the initial hydrolysis rates as well.

Steam reforming of methane (SRM) is an important stage of hydrogen production. Using a membrane reactor (MR) to separate the produced H 2 positively affects CH 4 conversion by shifting the equilibrium. This H 2 removal increases the risk of coke formation in the process. In this study, the influence of different parameters such as Damkohler’s number (Da) and permeation number (θ) on CH 4 conversion and H 2 recovery are investigated. In order to find the optimum condition for this MR in which CH 4 conversion, H 2 Recovery are maximized and the risk of coke formation is minimized, the elitist non-dominated sorting genetic algorithm (NSGA-II) is employed to achieve the Pareto front in a three objective space. The single optimal solution is selected from Pareto front by TOPSIS decision making method. In the optimized condition methane conversion and hydrogen recovery are improved about 19.8% an 6.8%, respectively. Also, the risk of coke formation in the MR is reduced.