酸化油固定床酶法合成生物柴油研究

酸化油是油脂工业中以皂脚、油脚经酸化处理得到的产品。它的主要成分是游离脂肪酸及中性油，是生产脂肪酸的重要原料，但生产过程中有水解废水的产生，若将其直接排放，既污染了环境又浪费了资源。生物柴油的主要成分是脂肪酸甲酯（fatty acid methyl ester，FAME）。它具有原料丰富而且可再生、可生物降解、无毒、不含芳香烃、二氧化硫等污染物、燃烧排放低、闪点高、运输储存安全等特点。作为石化柴油的潜在替代能源，生物柴油因其独特的优越性和现实的需求越来越受到关注。利用酸化油生产生物柴油不仅可以缓解生物柴油原料不足问题，还可解决酸化油所带来的环境问题。

The convertion of acid oil to biodiesel by use of immobilized Candida lipase absorbed on textile cloth was studied in a fixed bed reactor, which can not only reduce the environmental pollution of acid oil, but also produce a substitute for petroleum diesel. The acid oil mixed with methanol was pumped into three fixed bed reactors in series, and the methanol was added with the molar flow rate same as the acid oil in each reactor. The effects of enzyme content, solvent content, water content, flow rate of reactant and temperature on the enzymatic reaction were analyzed. The result of orthogonal experiments indicates that the optimal transesterification can be performed under the following conditions： immobilized lipase content in acid oil, 20% ; hexane content in acid oil, 10% ; water content in acid oil, 10%, reaction temperature, 50 ℃ ; and flow rate of reactant, 0.08 g/rain. Under these conditions, the FAME content of 90.18% in the product is obtained. The immobilized lipase can be reused with relatively stable activity after glycerol being removed from the surface. By refining, most of the chemical and physical properties of biodiesel will meet the American and Germany biodiesel standards and exceed the Chinese standard of 0^# petroleum diesel except for carbon residue, density and kinematic viscosity.

酸化油固定床酶法合成生物柴油研究

以固定化的假丝酵母酶为催化剂，在三段式固定床反应器内，醇油摩尔比为1：1，采用分级流加甲醇的方式，将高酸值的酸化油转化为生物柴油，探讨了酶量、溶剂量、水量、温度、反应液流速等与产物中甲酯含量的关系。正交实验结果表明，反应的最适条件为酶用量、溶剂量、水量分别为油重的15％、10％、10％，反应液流速为0.8g·min^-1，温度为45℃，在此条件下，产物中甲酯含量达到了90．18％。

Optimization of biodiesel production from trap grease via acid catalysis

As a kind of waste collected from restaurants, trap grease is a chemically challenging feedstock for biodiesel production for its high free fatty acid (FFA) content. A central composite design was used to evaluate the effect of methanol quantity, acid concentration and reaction time on the synthesis of biodiesel from the trap grease with 50% free fatty acid, while the reaction temperature was selected at 95 degrees C. Using response surface methodology, a quadratic polynomial equation was obtained for ester content by multiple regression analysis. Verification experiments confirmed the validity of the predicted model. To achieve the highest ester content of crude biodiesel (89.67%), the critical values of the three variables were 35.00 (methanol-to-oil molar ratio), 11.27 wt% (catalyst concentration based on trap grease) and 4.59 h (reaction time). The crude biodiesel could be purified by a second distillation to meet the requirement of biodiesel specification of Korea.

Novel biodiesel production technology from soybean soapstock

This paper describes an attractive method to make biodiesel from soybean soapstock (SS). A novel recovery technology of acid oil (AO) from SS has been developed with only sulfuric acid solution under the ambient temperature (25 +/- 2 degrees C). After drying, AO contained 50.0% FFA, 15.5% TAG 6.9% DAG 3.1% MAG 0.8% water and other inert materials. The recovery yield of AO was about 97% (w/w) based on the total fatty acids of the SS. The acid oil could be directly converted into biodiesel at 95 degrees C in a pressurized reactor within 5 hours. Optimal esterification conditions were determined to be a weight ratio of 1 : 1.5 : 0.1 of AO/methanol/sulfuric acid. Higher reaction temperature helps to shorten the reaction time and requires less catalyst and methanol. Ester content of the biodiesel derived from AO through one-step acid catalyzed reaction is around 92%. After distillation, the purity of the biodiesel produced from AO is 97.6% which meets the Biodiesel Specification of Korea. The yield of purified biodiesel was 94% (w/w) based on the total fatty acids of the soapstock.

应用负载型纳米铁去除饮用水中砷的研究

砷是毒性最强的元素之一，水体中砷的污染己经引起人们广泛的关注。我国的新疆、内蒙、山西和台湾等省和地区地下水砷含量严重超标。全球共有5,000多万人遭受高砷饮用水的威胁，其中中国有1,500多万，是饮用水砷污染最严重的国家之一。WHO推荐饮用水砷的最高允许浓度从原来的50 µg•L-1已降至10 µg•L-1。更为严格的砷卫生标准的颁布，对作为饮用水源的地下水中的砷去除工艺提出了更高的要求。吸附法除砷比膜法、混凝法和离子交换法更安全、简便，是砷去除工艺中最有效的方法之一。 首先，本研究通过优化制备条件（包括炭种类的选择、炭的粒径大小、还原剂的浓度及滴定速率、反应温度、铁盐的种类及浓度、分散剂的比例及浓度），制备了负载型纳米铁。考虑到砷的去除效率、工程应用的可行性以及经济性，最优的制备条件如下：选用粒径为20~40目煤质炭，在室温、一定的分散剂比例及浓度，0.2 M KBH4滴速为20 d•min-1时所制备的Fe/炭为82.0 mg•g-1；纳米铁在活性炭孔内呈针状，其直径为30~500 nm，长度为1,000~2,000 nm。绝大多数的铁都负载到活性炭内部，这在处理水时铁不流失很重要。 其次，利用制备的负载型纳米铁作吸附载体，进行了饮用水中As(Ⅴ)的吸附去除实验。研究了该吸附剂对As(Ⅴ)的吸附等温线、动力学以及影响动力学的各种因素（包括As(Ⅴ)的不同初始浓度、吸附剂用量、pH值、共存离子和不同温度）、pH值、共存离子等环境条件对As(Ⅴ)去除的影响；以及吸附剂的再生及再生后的吸附效率等。研究发现在前12 h内吸附较快，72 h时达到了平衡。用Langmuir 吸附等温式估算出As(Ⅴ)的吸附量为12.0 mg•g-1。该吸附剂在pH 6.5， (25±2)℃， As(Ⅴ)初始浓度为2 mg•L-1，吸附剂用量为1.0 g•L-1时，As(Ⅴ)的去除率为75.2%；当把吸附剂的用量增加到1.5 g•L-1时，As(Ⅴ)的去除率可达99.9%以上。吸附剂可以用0.1M的NaOH浸泡12 h后即可再生，再生效率较高。常见的阴离子中PO43-、SiO32-对As(Ⅲ)的去除抑制较大，而SO42-、CO32-、C2O42-等离子对砷的去除影响较小。Fe2+对As(Ⅲ)的吸附抑制作用较大而其它阳离子影响不大。吸附剂可用0.1 M NaOH 有效再生，并且具有良好的机械性能。实验室初步实验数据表明，该吸附剂对饮用水除砷具有较好的应用前景。 第三，利用实验室制备的负载型纳米铁对饮用水中As(Ⅲ)的吸附去除也进行了研究。考察了吸附等温线、动力学以及影响动力学的各种因素、pH值、共存离子等环境条件对As(Ⅲ)去除的影响；以及吸附剂的再生及再生后的吸附效率等。研究发现，该吸附剂在pH 6.5， (25±2)℃， As(Ⅲ)初始浓度为2 mg•L-1，吸附剂用量为1.0 g•L-1时， 对As(Ⅲ)的去除率为99.8%；其吸附容量为1.996mg•g-1。吸附过程中部分As(Ⅲ)被氧化。与As(Ⅴ)的吸附相比，该吸附剂对As(Ⅲ)的效率比较高-而常见的其它除砷吸附剂如载铁纤维棉等，对As(Ⅴ)的效率比As(Ⅲ)高，为有效去除As(Ⅲ)，常常需要专门加上氧化这一过程。 最后，利用负载型纳米铁对饮用水中As(Ⅲ) 的氧化性能进行考察，发现该吸附剂不但能够有效吸附去除饮用水中的砷，而且还能把As(Ⅲ)有效地氧化为As(Ⅴ)。经过对吸附剂的构成组分分析发现，活性炭表面因富含多种官能团而对三价砷的氧化作用最大；其次是纳米铁也能把As(Ⅲ)氧化为As(Ⅴ)。

Coking kinetics on the catalyst during alkylation of fcc off-gas with benzene to ethylbenzene

The production of ethylbenzene from the alkylation of dilute ethylene in fee off-gases with benzene has been commercialized in China over a newly developed catalyst composed of ZSM-5/ZSM-11 co-crystallized zeolite. The duration of an operation cycle of the commercial catalyst could be as long as 180 days. The conversion of ethylene could attain higher than 95%, while the amount of coke deposited on the catalyst was only about 10 wt.%. Thermogravimetry (TG) was used to study the coking behavior of the catalyst during the alkylation of fee off-gas with benzene to ethylbenzene. Based on effects of reaction time, reaction temperature, reactants and products on coking during the alkylation process, it is found that the coking rate during the alkylation procedure follows the order: ethylbenzene > ethylene > propylene > benzene for single component, and benzene-ethylene > benzene-propylene for bi-components under the same reaction condition. Furthermore, the coking kinetic equations for benzene-ethylene, benzene-propylene and ethylbenzene were established. (C) 2003 Elsevier B.V. All rights reserved.

Methanol synthesis from CO2 using a silicone rubber/ceramic composite membrane reactor

A one-dimensional isothermal pseudo-homogeneous parallel flow model was developed for the methanol synthesis from CO2 in a silicone rubber/ceramic composite membrane reactor. The fourth-order Runge-Kutta method was adopted to simulate the process behaviors in the membrane reactor. How those parameters affect the reaction behaviors in the membrane reactor, such as Damkohler number Da, pressure ratio p(r), reaction temperature T, membrane separation factor alpha, membrane permeation parameter phi , as well as the non-uniform parameter of membrane permeation L-1, were discussed in detail. Parts of the theoretical results were tested and verified; the experimental results showed that the conversion of the main reaction in the membrane reactor increased by 22% against traditional fixed bed reactor, and the optimal non-uniform parameter of membrane permeation rate, L-1.opt ,does exist. (C) 2003 Elsevier B.V All rights reserved.

Effect of acid strength distribution on conversion of FCC gasoline over a ZSM-5 zeolite catalyst

Acid strength distribution and the distribution of aromatics formed in the FCC gasoline conversion reaction on a ZSM-5 zeolite with different Na contents have been studied. With increasing Na content in the ZSM-5 zeolite, the acid sites determined by NH3-TPD technique, especially the strong acid sites, clearly decrease. When used as catalyst for the aromatization reaction, the transformation of olefins in the FCC gasoline into aromatics is governed directly by the strong acid sites on the ZSM-5 catalyst. Only under the conditions that a ZSM-5 catalyst possesses suitable strong acid sites is reaction temperature favorable for the aromatics formed.

Reduction of NO by CH4 with microwave heating

The reduction of NO by CH4 in the presence of excess O-2 over Co/HZSM-5, Ni/HZSM-5 and Mn/HZSM-5 catalysts with microwave heating was studied. By comparing the activities of the catalysts in the microwave heating mode with that in the conventional reaction mode, it was demonstrated that microwave heating could greatly reduce the reaction temperature, and could clearly expand the temperature window of the catalysts. Especially for the Co/HZSM-5 catalyst, the maximum conversion of NO to N-2 in the conventional reaction mode was consistent with that in the microwave heating mode. However, the temperature window for the maximum conversion in the microwave heating mode was from 260 to 360degreesC instead of a temperature of 420degreesC in the conventional reaction mode. The results suggest that microwave heating has a novel effect in the reduction of NO.

Epoxidation of propylene over Ag-CuCl catalysts using air as the oxidant

Ag-CuCl catalysts were found to be active and selective for the epoxidation of propylene using air as the oxidant. Ag catalyst gives a propylene conversion of 31.6%, with a propylene oxide (PO) selectivity of 0.42% at a reaction temperature of 350 degreesC after 220 min of reaction. Addition of CuCl significantly improves the selectivity to PO, and suppresses the conversion of propylene. The Ag-CuCl (1/0.6) catalyst gives propylene conversion of about 3% and a PO selectivity of about 30% at a reaction temperature of 350 degreesC after 500 min of reaction. The activity of the Ag-CuCl catalyst increases with the reaction time and the selectivity to PO is very stable for this catalyst. It is found that AgCl and CuO phases formed during the catalyst preparation are beneficial to the epoxidation of propylene.

Quantified MS analysis applied to combinatorial heterogeneous catalyst libraries

A high-throughput screening system for secondary catalyst libraries has been developed by incorporation of an 80-pass reactor and a quantified multistream mass spectrometer screening (MSMSS) technique. With a low-melting alloy as the heating medium, a uniform reaction temperature could be obtained in the multistream reactor (maximum temperature differences are less than 1 K at 673 K). Quantification of the results was realized by combination of a gas chromatogram with the MSMSS, which could provide the product selectivities of each catalyst in a heterogeneous catalyst library. Because the catalyst loading of each reaction tube is comparable to that of the conventional microreaction system and because the parallel reactions could be operated under identical conditions (homogeneous temperature, same pressure and WHSV), the reaction results of a promising catalyst selected from the library could be reasonably applied to the further scale-up of the system. The aldol condensation of acetone, with obvious differences in the product distribution over different kind of catalysts, was selected as a model reaction to validate the screening system.

Influence of iron promoter on catalytic properties of Rh-Mn-Li/SiO2 for CO hydrogenation

The effect of iron promoter on the catalytic properties of Rh-Mn-Li/SiO2 catalyst in the synthesis Of C-2 oxygenates from syngas was investigated by means of the following techniques: CO hydrogenation reaction, temperature-programmed reduction (TPR), temperature-programmed desorption and reaction of adsorbed CO (CO-TPD and TPSR) and pulse adsorption of CO. The results showed that the addition of iron promoter could improve the activity of the catalysts. Unexpectedly, the yield of C-2 oxygenates increased greatly from 331.6 up to 457.5 g/(kg h) when 0.05% Fe was added into Rh-Mn-Li/SiO2 catalyst, while no change in the selectivity to C-2 oxygenates was observed. However, the activity and selectivity Of C-2 oxygenates were greatly decreased if the Fe amount exceeded 1.0%. The existence of a little iron decreased the reducibility of Rh precursor, while the reduction of Fe component itself became easier. CO uptake decreased with increasing the quantity of Fe addition. This phenomenon was further confirmed by CO-TPD results. The CO-TPD and TPSR results showed that only the strongly adsorbed CO could be hydrogenated, while the weakly adsorbed CO was desorbed. We propose that Fe is highly dispersed and in close contact with Rh and Mn; such arrangements were responsible for the high yield Of C-2 oxygenates. (C) 2002 Elsevier Science B.V. All rights reserved.

SbOx/SiO2 catalysts for the selective oxidation of methane to formaldehyde using molecular oxygen as oxidant

SbOx and SbOx/SiO2 catalysts were prepared and investigated for methane selective oxidation to HCHO. HCHO selectivity up to 41% can be obtained on Sb2O5/SiO2 catalyst at 873 K and just drop gently to 18% with temperature up to 923 K. HCHO selectivity for SbOx/SiO2 catalysts decreases gently with reaction temperature, so considerable value of HCHO selectivity can still be obtained at high temperatures.

The experimental research for production of hydrogen from n-octane through partially oxidizing and steam reforming method

The reaction of producing hydrogen for fuel cell which used normal octane as gasoline or diesel oil reactant through catalytic partial oxidizing and steam reforming method has been researched in the fixed-bed reactor. A series of catalysts that mainly used nickel supported on Al2O3 have been studied. It showed that the activity of the catalyst was increased with the content of nickel by using only nickel supported on Al2O3. However, its activity was not obviously increased when the content of nickel was over 5 wt%. The conversion ratio of normal octane and hydrogen selectivity were higher at higher reaction temperature. The single noble catalyst of palladium had better stability compared with that of platinum catalyst although their activity and selectivity were similar during the experimental reaction temperature. The prepared bimetallic catalyst consisted mainly of nickel and little noble metal of palladium supported on Al2O3. It showed that this catalyst had higher activity and selectivity, especially at lower or higher reaction temperatures compared with single nickel or palladium catalyst, and better stability. ((C) 2001 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.