氧化铝-硫酸固体酸催化剂催化油酸与甲醇酯化反应及其动力学研究

以氯仿为溶剂,通过氧化铝和氯磺酸反应制备了氧化铝-硫酸（ ASA）固体酸催化剂,以油酸转化率为指标,考察了ASA催化剂在油酸与甲醇酯化反应中反应时间、醇酸摩尔比、催化剂用量及氯磺酸负载量对酯化反应的影响。得到的最佳酯化反应条件为：氯磺酸负载量4.1 mmol/g,反应时间6 h,反应温度68℃,醇酸摩尔比8∶1,催化剂用量为油酸质量的5%。在最佳酯化反应条件下,油酸转化率达到93.1%,ASA催化剂重复使用5次,油酸转化率仍在80%以上。在303~333 K范围内,油酸和甲醇的酯化反应符合准二级动力学方程,表观活化能为54.34 kJ/mol,指前因子为2.91×109 L/（mol·h）。

CaO-Al_2O_3-BaSO_4系统物相形成及其动力学初探

研究了CaO -Al2 O3-BaSO4系统物相形成变化关系 ,对该系统仅存三元化合物 3CA·BaSO4的形成动力学进行了初步研究 .研究表明 ,该系统可能出现的主要固相包括CA ,C1 2 A7,BA ,3CA·BaSO4,气相有SO2 和O2 等 .其中 ,固相CA ,C1 2 A7,BA有两种形成机制 .温度低于13 5 0℃时 ,这些矿相因原料的组分之间发生反应而形成 ;而温度高于 13 60℃的条件下 ,这些矿物是由 3CA·BaSO4分解形成的 .矿物 3CA·BaSO4的形成可能表现为吸热效应 .在温度 115 0℃和 13 0 0℃范围内 ,三元化合物 3CA·BaSO4的形成受界面化学反应控制 ,符合动力学方程f(α) =1-(1-α) 1

Sulfur phase and sulfur removal in high sulfur-containing bauxite

The sulfur phase in high sulfur-containing bauxite was studied by an X-ray diffraction analysis and a chemistry quantitative analysis.The methods for the removal of different shaped sulfur were also discussed.The results show that sulfur phases in high sulfur-containing bauxites exist in the main form of sulfide sulfur （pyrite） or sulfate sulfur,and the main sulfur forms of bauxites from different regions are not the same.Through a combination of an X-ray diffraction analysis and a chemistry quantitative analysis,the sulfur phases of high sulfur-containing bauxite could be accurately investigated.Deciding the main sulfur form of high sulfur-containing bauxite could provide theoretical instruction for choosing methods for the removal of sulfur from bauxite,and an oxidizing-roasting process is an effective way to remove sulfide sulfur from high sulfur-containing bauxite,the content of S^2-in crude ore in the digestion liquor is above 1.7 g/L,but in the roasted ore digestion liquor,it is below 0.18 g/L.Using the sodium carbonate solution washing technology to wash bauxite can effectively remove sulfate sulfur,the content of the total sulfur in ore is lowered to below 0.2% and can meet the production requirements for the sulfur content.

La/Ni改性SO_4^(2-)/ZrO_2-Al_2O_3催化正丁烷异构化反应性能研究

利用浸渍法和共沉淀法得到La-Ni改性的硫酸化氧化锆催化剂,并对其在正丁烷异构化反应的性能进行考察。结果表明:改性方法对其催化异构化反应性能具有显著影响;用共沉淀法制得的催化剂在不降低异丁烷收率的前提下,通过减少副反应的发生来提高异丁烷选择性;而用浸渍法得到的催化剂表现出很高的异丁烷选择性,但正丁烷转化率显著降低,造成异丁烷收率也明显降低。利用Py-FTIR、低温氮气吸附-脱附、红外硫碳分析等表征,发现La-Ni改性处理对正丁烷在催化剂表面氧化脱氢能力影响不大,但对质子活化途径影响较大。共沉淀得到的催化剂表面超强B酸位密度的适度降低有利于提高单分子异构化途径所占的比例,而浸渍法所得催化剂表面B酸密度的显著降低导致其正丁烷转化受阻。

Effect of x-alumina addition on H_2S oxidation properties of pure and modified y-alumina

The influence of the textural and acidic properties ofγ‐Al2O3,(γ+χ)‐Al2O3,and?‐Al2O3on the catalytic activity,selectivity,and stability of direct H2S oxidation has been studied.A comparison of the H2S‐to‐S conversion effectiveness of aluminas with their acidic properties(identified by Fourier transform infrared spectroscopy and temperature programmed desorption of NH3)shows that H2S adsorption occurs predominantly on weak Lewis acid sites(LAS).γ‐Alumina samples containing aχ‐phase and/or modified Mg2+ions have a greater concentration of weak LAS and exhibit greater catalytic activity.When alumina is treated with a sulfuric acid solution,strong LAS appear and the number of LAS decreases significantly.Modification of alumina with hydrochloric acid has a limited effect on LAS strength.Weak LAS are retained and double in number compared to that present in the unmodified alumina,but the treated sample has Al?Cl bonds.Alumina samples modified by sulfate and chloride anions exhibit poor catalytic activity in H2S oxidation.

Extraction of alumina from fly ash by ammonium hydrogen sulfate roasting technology

NH4HSO4 roasting technology was used for preparing Al2O3 from fly ash. First, Al and Fe were extracted from fly ash by NH4HSO4 roasting and deionized water leaching. Then, the Al and Fe in the leached liquid were precipitated by adding NH4HCO3 solution. After the mixed precipitations of Al（OH）3 and Fe（OH）3 were leached by NaOH solution, the NaAl（OH）4 solution was decomposed by carbonation. Finally, the pure Al（OH）3 was calcined to α-Al2O3. The optimal conditions of the whole technology were determined by experiments. The quality ofa-Al2O3 product is up to the technical indicator of YS/T 274-1998 standard.

Influence of oxidation heat on hard anodic film of aluminum alloy

The special experimental device and sulfuric acid electrolyte were adopted to study the influence of anodic oxidation heat on hard anodic film for 2024 aluminum alloy. Compared with the oxidation heat transferred to the electrolyte through anodic film, the heat transferred to the coolant through aluminum substrate is more beneficial to the growth of anodic film. The film forming speed, film thickness, density and hardness are significantly increased as the degree of undercooling of the coolant increases. The degree of undercooling of the coolant, which is necessary for the growth of anodic film, is related to the degree of undercooling of the electrolyte, thickness of aluminum substrate, thickness of anodic film, natural parameters of bubble covering and current density. The microstructure and performance of the oxidation film could be controlled by the temperature of the coolant.

Comparative study on simultaneous removal of calcium and sulfate ions from flotation recycling water by aluminum hydroxide

Due to the environmental policies and economic reasons,the water used in some flotation operations of complex sulfide ores is recirculated,causing the ion concentration of some species to increase over time,affecting the flotation of the minerals of interest.In this work,an experimental and thermodynamic analysis of the synthetic solutions was presented with a high content of calcium and sulfate ions.The study focused on evaluating the use of two aluminum compounds for the precipitation of Ca^(2+)and SO_(4)^(2−)in the form of ettringite.The amorphous aluminum hydroxide was found to be more efficient than the crystalline one,giving rise to 83%calcium and 91%sulfate removal.The XRD analysis of the solids showed the main reaction product of ettringite,accompanied by small amounts of calcite,due to the absorption of atmospheric carbon dioxide.The final solution after the chemical treatment showed residual calcium and sulfate concentrations below 200 mg/L.Finally,the kinetics of calcium removal appeared to correspond to a second order reaction with respect to calcium concentration,with an apparent activation energy of 53.48 kJ/mol,which may suggest that the ettringite precipitation process is governed by the chemical reaction.

Chemical dissolution resistance of anodic oxide layers formed on aluminum

Chemically resistant anodic oxide layers were formed on pure aluminum substrates in oxalic acid-sulphuric acid bath.Acid dissolution tests of the obtained anodic layers were achieved in accordance with the ASTM B 680-80 specifications：35mL/L 85% H3PO4＋20g/L CrO3 at 38℃.Influence of oxalic acid concentration,bath temperature and anodic current density on dissolution rate and coating ratio was examined,when the sulphuric acid concentration was maintained at 160g/L.It was found that chemically resistant and compact oxide layers were produced under low operational temperature （5℃） and high current densities （3A/dm^2）.A beneficial effect was observed concerning the addition of oxalic acid （18g/L）.The morphology and the composition of the anodic oxide layer were examined by scanning electron microscopy （SEM）,atomic force microscopy （AFM） and glow-discharge optical emission spectroscopy （GDOES）.

Comparison of deep desulfurization methods in alumina production process

Several methods of deep desulfurization in alumina production process were studied, and the costs of these methods were compared. It is found that most of the S2- in sodium aluminate solution can be removed by adding sodium nitrate or hydrogen peroxide in digestion process, and in this way the effect of S2- on alumina product quality is eliminated. However, the removal efficiency of 2?32OS in sodium aluminate solution is very low by this method. Both S2- and 2?32OS in sodium aluminate solution can be removed completely by wet oxidation method in digestion process. The cost of desulfurization by wet oxidation is lower than by adding sodium nitrate or hydrogen peroxide. The results of this research reveal that wet oxidation is an economical and feasible method for the removal of sulfur in alumina production process to improve alumina quality, and provide valuable guidelines for alumina production by high-sulfur bauxite.

Synthesis and alumina leaching mechanism of calcium sulphoaluminate

Calcium sulphoaluminate(3CaO·3Al2O3·CaSO4,abbreviated as C4A3S)was synthesized by sintering at1375°C for2h with analytically pure carbonate calcium,alumina and dihydrate calcium sulfate.The crystal structure of C4A3S was characterized by XRD,SEM and TEM.Alumina leaching properties in Na2CO3solution were studied,and the leaching mechanism was investigated by means of Raman spectrum and XRD.The results show that C4A3S has porous morphology.The polycrystallines and single crystals coexist in C4A3S and grow along different directions.The alumina leaching rate of C4A3S is98.41%,which is higher than that of12CaO·7Al2O3under the optimal condition.The aluminum and sulfur elements exist in the leaching solution in the form of Al(OH)4and24SO,respectively,and the calcium exists as CaCO3in the leaching residues.

磷酸丁辛酯的合成实验研究

以磷酸、丁辛醇为原料,在催化剂存在下合成了用途广泛并可作为新型结焦抑制剂中间体的磷酸酯,实现了磷酸的直接酯化。试验结果表明:在磷酸酯的合成中反应温度、时间、催化剂用量、原料配比等因素对合成都有影响。最佳工艺条件为:醇酸物质的量比2.3∶1,反应时间4 h,反应温度控制在140℃,催化剂加入量为反应物总物质的量数的2.0%,且采用硫酸氢钠-氧化铝复合体系(其中硫酸氢钠含量为75%)效果最好,其产率为75.67%。

Efficient synthesis of thiohydantoin derivatives from amino acid esters and isothiocyanates in alkaline Al_2O_3

Various amino acid esters were reacted with different isothiocyanates in alkaline Al2O3 at room temperature for 1 h affording thiohydantoins in moderate to excellent yields.