Decomposition behavior of CaSO4 during potassium extraction from a potash feldspar-CaSO4 binary system by calcination

The extraction of potassium from a tablet mixture of K-feldspar ore and CaSO_4by roasting was studied with a focus on the effects of the decomposition behavior of CaSO_4on the potassium extraction process.The roasted slags were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy,and thermogravimetric(TG)analysis.The XRD analysis revealed that hydrosoluble mischcrystal K_2Ca_2(SO_4)_3was obtained by ion exchange of Ca~(2+)in CaSO_4and K~+in KAlSi_3O_8.Meanwhile,the intermediate product,SiO_2,separated from KAl Si_3O_8and reacted with CaSO_4to decompose CaSO_4.The SEM results showed that some blowholes emerged on the surface of the CaSO_4particles when they reacted with SiO_2at 1200°C,which indicates that SO_2and O_2gases were released from CaSO_4.The TG curves displayed that pure CaSO_4could not be decomposed below 1200°C,while the mixture of K-feldspar ore and CaSO_4began to lose weight at 1000°C.The extraction rate of potassium and decomposition rate of CaSO_4were 62%and 44%,respectively,at a mass ratio of CaSO_4to K-feldspar ore of 3:1,temperature of 1200°C,tablet-forming pressure of6 MPa,and roasting time of 2 h.The decomposition of CaSO_4reduced the potassium extraction rate;therefore,the required amount of CaSO_4was more than the theoretical amount.However,excess CaSO_4was also undesirable for the potassium extraction reaction because a massive amount of SO_2and O_2gas were derived from the decomposition of CaSO_4,which provided poor contact between the reactants.The SO_2released from CaSO_4decomposition can be effectively recycled.     

Production of biodiesel from waste vegetable oil using impregnated diatomite as heterogeneous catalyst

In this study, biodiesel was produced from waste vegetable oil using a heterogeneous base catalyst synthesized by impregnating potassium hydroxide (KOH) onto diatomite. Response surface methodology based on a central composite design was used to optimize four transesterification variables:temperature (30–120 °C), reaction time (2–6 h), methanol to oil mass ratio (10%–50%) and catalyst to oil mass ratio (2.1%–7.9%). A quadratic poly-nomial equation was obtained to correlate biodiesel yield to the transesterification variables. The diatomite–KOH catalyst was characterized using X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR) and a scanning electron microscope (SEM) equipped with an energy dispersive X-ray detector (EDS). A maximum biodiesel yield of 90%(by mass) was obtained. The reaction conditions were as follows:methanol to oil mass ratio 30%, catalyst to oil mass ratio 5%, reaction time 4 h, and reaction temperature 75 °C. The XRD, FTIR and SEM (EDS) results confirm that the addition of KOH modifies the structure of diatomite. During impregnation and calcination of the diatomite catalyst the K2O phase forms in the diatomite structural matrix and the active basicity of this compound facilitates the transesterification process. It is possible to recycle the diatomite–KOH catalyst up to three times. The crucial biodiesel properties from waste vegetable oil are within the American Stan-dard Test Method specifications.     

The influence mechanism of solvent on the hydrogenation of dimethyl oxalate

The hydrogenation of dimethyl oxalate(DMO) for the producing of C2-C4 alcohols with methanol as solvent was researched at the temperature of 270 °C to 310 °C. Ethylene glycol(EG) was the main product at low temperature and the selectivity of which was 61.9% at 230 °C. However, EG selectivity decreased sharply with the increase of temperature while ethanol became the main liquid products with the selectivity of 43.5% at 270 °C. It can be ascribed to a thorough hydrogenation of DMO at a high temperature. In addition, the promotion of Guerbet reaction led to the production of propanol and butanol. Simultaneously, the amount of gas products including CO, CO_2 and dimethyl ether(DME) also increased, which became a competition factor in the conversion of DMO to liquid products including C2-C4 alcohols. The blank test was carried out with pure methanol as feedstock with and without Cu/SiO_2 catalyst, which revealed that methanol was involved in the formation of gas products and higher alcohols on Cu-based catalyst, and the main gas product was CO.     

Study on reactions of gaseous P2O5 with Ca3(PO4)2 and SiO2 during a rotary kiln process for phosphoric acid production

In a rotary kiln process for phosphoric acid production,the reaction between gaseous phosphorus pentoxide(P_2O_5)and phosphate ore and silica contained in feed balls(the so-called P_2O_5"absorption")not only reduces phosphorous recovery but also generates a large amount of low melting-point side products.The products may give rise to formation of kiln ring,which interferes with kiln operation performance.In this study,the reactions of gaseous P_2O_5with solid calcium phosphate(Ca_3(PO_4)_2),silica(SiO_2)and their mixture,respectively,were investigated via combined chemical analysis and various characterizations comprised of X-ray diffraction(XRD),Fourier-transform infrared(FT-IR)spectroscopy,thermogravimetric analysis and differential scanning calorimeter(TGDSC),and scanning electron microscopy and energy dispersive spectrometer(SEMEDS).Attentions were focused on apparent morphology,phase transformation and thermal stability of the products of the P_2O_5"absorption"at different temperatures.The results show that the temperature significantly affected the"absorption".The reaction between pure Ca_3(PO_4)_2 and P_2O_5 occurred at 500°C.Calcium metaphosphate(Ca(PO_3)_2)was the primary product at the temperatures≤900°C with its melting point≤900°C while calcium pyrophosphate(Ca_2P_2O_7)was obtained over 1000°C,which has a melting point≤1200°C.The"absorption"by pure SiO_2 started at 800°C and the most significant reaction occurred at 1000°C with formation of silicon pyrophosphate(SiP_2O_7)product of melting point≤1000°C.Using mixed Ca_3(PO_4)_2and SiO_2as raw material,the"absorption"by Ca_3(PO_4)_2 was enhanced due to existence of silica.At 600–700°C,silica was inert to P_2O_5and thus formed a porous structure in the raw material,which accelerated diffusion of gaseous P_2O_5inside the mixture.At higher temperatures,the combined"absorption"by calcium phosphate and reaction between silicon dioxide and the"absorption"product calcium pyrophosphate,reinforced the"absorption"by the mixture.Besides,it was found that both Ca(PO_3)_2and SiP_2O_7were unstable at high temperatures and would decompose to Ca_2P_2O_7and SiO_2,respectively,at over 1000°C and 1100°C with the release of gaseous P_2O_5at the same time.     

2，4–二氟苯甲醛的合成

2,4-Difluorobenzaldehyde was synthesized from 1,3-difluorobenzene and carbon monoxide with AlCl3 and HCl as catalyst in CO atmosphere at a pressure in the range of 1.5MPa. Effects on the converting ratio and yield were investigated. The results showed that the optimum technological conditions should be that n(1,3-difluorobenzene):n(AlCl3)=1.0:1.0, the reaction temperature was 60℃, amount of HCl was 1.0% of total mass of reation mixture, and the reation time was 20 hours. The selectivity of 2,4-difluorobenzaldehyde from 1,3-difluorobenzene was up to the purity of the refined product ω(2,4-difluorobenzaldehyde)≥98.81%.     

An efficient methodology for utilization of K-feldspar and phosphogypsum with reduced energy consumption and CO2 emissions

The issues of reducing CO2 emissions, sustainably utilizing natural mineral resources, and dealing with industrial waste offer challenges for sustainable development in energy and the environment. We propose an efficient methodology via the co-reaction of K-feldspar and phosphogypsum for the extraction of soluble potassium salts and recovery of SO2 with reduced CO2 emission and energy consumption. The results of characterization and reactivity evaluation indicated that the partial melting of K-feldspar and phosphogypsum in the high-temperature co-reaction significantly facilitated the reduction of phosphogypsum to SO2 and the exchange of K+(K-feldspar) with Ca2+(CaSO4 in phosphogypsum). The reaction parameters were systematical y investigat-ed with the highest sulfur recovery ratio of~60%and K extraction ratio of~87.7%. This novel methodology possesses an energy consumption reduction of~28%and CO2 emission reduction of~55%comparing with the present typical commercial technologies for utilization of K-feldspar and the treatment of phosphogypsum.     

垂直管式反应器中超临界甲醇连续制备生物柴油I:相含率及反应中间产物的轴向分布(英文)

Production of biodiesel with supercritical methanol is a green synthesis process.A study was carried out in a vertical tubular reactor with a length of 3700 mm and a diameter of 20 mm at 275-375°C,15 MPa,and molar ratio of methanol to soybean oil of 40︰1.The phase holdup,intermediate product,yield and axial distribution of methyl ester(ME) were investigated.Methanol and oil were mixed non-uniformly due to the formation of biodiesel and difference in their densities,even when the reaction system was in the supercritical state.From top to bottom,the phase holdup of methanol increased and that of oil decreased.As temperature increased,the concentrations of monoglyceride and diglyceride decreased gradually and the ME yield increased.When the temperature reached 300°C,the critical temperature of the system,the ME yield was 50%.Further increase in temperature led to a sharp in-crease of ME yield.However,at 375°C after 1200 s of reaction time,the decomposition rate of ME was greater than its formation rate,reducing the ME yield.     

固体超强酸催化剂SO2-4/TiO2-MoO3的制备及其催化合成缩醛（酮）

SO4^2-/TiO2-MoO3, a novel solid superacid, has been prepared and its catalytic activity at different synthetic conditions was examined with esterification of n-butanoic acid and n-butyl alcohol as probing reaction.The optimum conditions were also found, that is, the mass ratio of MoO3 used in the compound is 25%, the calcination temperature 450℃, and the soaked consistency of H2SO4 is 0.5mol.L^-1. Then it was applied in the catalytic synthesis of six similar important ketals and acetals as catalyst and revealed high catalytic activity. Under the condition that the molar ratio of aldehyde/ketone to glycol was 1:1.5, the mass ratio of the catalyst to the reactants was 0.5% and the reaction time 1.0 h, the yield of ketals and acetals reached up to 63.2%. The catalyst can be easily recovered and reused.     

蠕虫形管状镧铝复合介孔材料的合成及表征

The lanthanum aluminum mesoporous materials were synthesized using sodium dodecyl sulfate as a template agent by ultrasonic hydrothermal method.The resulting samples were characterized by low angle X-ray diffraction(XRD),N2 adsorption-desorption studies,transmission electron microscopy(TEM)and surface morphology analysis(SEM),surface acid(NH3-TPD),reducibility properties(TPR),X-ray energy dispersive spectrometer(EDS)and thermogravimetric analysis(TG/DTG).A l/La composite mesoporous material were synthesized with n(Al)︰n(La)=70︰1.0,80°C of reaction temperature,20 h of reaction time,12 h of crystallization time,650°C of calcination temperature.The specific surface area of the sample is 273.90 m 2 ·g ?1 ,with the average diameter 5.642 nm and pore volume 0.2354 cm 3 ·g ?1 .The samples have mesoporous structure and its particles are similar to a worm-shaped tubular structure.The influence of calcination temperature on the surface physical and chemical properties of Al/La composited mesoporous materials was examined,and the results showed that the acid strength was increased but the amount of acidic sites is decreased as the calcination temperature increased.It was found that the sample calcined at 650°C had appropriate acid content,acid strength and better reducibility.     

Continuous production of biodiesel from cottonseed oil and methanol using a column reactor packed with calcined sodium silicate base catalyst☆

Sodium silicate and that calcined at 400 °C for 2 h were used to catalyze the transesterification of cottonseed oil with methanol. Calcined sodium silicate(CSS) catalyst exhibited much higher catalytic activity and stability. A maximum biodiesel yield of 98.9% was achieved at methanol/oil mole ratio of 12:1, reaction temperature65 °C, reaction time 3.0 h, and CSS/oil mass ratio of 2 wt%. After 7 consecutive reactions without any treatment,biodiesel yield reduced to 82.5%. Considering technological and economic feasibility, CSS base catalyst supported on θ rings was prepared for continuous transesterification. The maximum yield was 99.1% under optimum conditions(reaction temperature 55 °C, methanol velocity 1 ml·min-1, oil velocity 3 ml·min-1, and 5 tower sections). These results indicate that this new continuous biodiesel production process and apparatus present a great potential for industrial application in biodiesel.     

添加NaCl-CaCO3混合助剂焙烧难溶性钾矿提取氯化钾的实验研究

为综合利用我国难溶性钾矿提取氯化钾,采用石盐和石灰石作为焙烧难溶性钾矿的混合助剂,研究了钠钾摩尔比、石灰石加入量、焙烧温度与时间、钾钠挥发等因素对钾提取率的影响.钠钾摩尔比为4,石灰石加入量为12.5wt%的配料在900 ℃焙烧90 min的条件下,混合助剂实现了钾提取率84.6%.通过X射线衍射仪(XRD)对焙烧产物水浸后的滤渣进行了矿物组成分析,探讨了NaCl和CaCO3作为混合助剂分解钾长石的机理.石盐和石灰石组成的混合助剂与难溶性钾矿的质量比为0.73,与其它体系相比,助剂用量大大降低.     

The extraction of potassium from K-feldspar ore by low temperature molten salt method

The low temperature molten salt method was used to extract potassium from K-feldspar ore, and some related factors including mass ratio between NaNO₃, NaOH, H₂O and K-feldspar ore, particle size of K-feldspar ore, reaction temperature and time were investigated, respectively. In addition, the optimum condition for this method was determined by a series of condition experiments. What was more, the K-feldspar ore and the leach residue after reaction based on the above optimum condition were analyzed by XRD, SEM and EDS, separately. The results of which indicated that the mechanism of extraction of potassium for this method was according to the ion exchange reaction between sodium ion and potassium ion, and the extraction ratio of potassium had an obvious improvement than that of traditional methods, which could reach up to 96.25%. Therefore, this method can be a feasible solution to extract potassium from K-feldspar ore for its low energy consumption and high efficiency.     

绢云母的焙烧提钾实验研究

以CaCl2、CaSO4、CaCO3、NaCl和NaOH为助熔剂对四川地区的绢云母矿进行了焙烧提钾试验,结果表明:助剂CaCl2、NaCl及NaOH用量与绢云母矿质量比为0.3∶1时,钾的浸出率分别高达45.46％、54.51％和66.70％;以CaCl2为助剂,进一步研究焙烧温度、添加剂用量、焙烧时间以及矿粉粒度等条件对提钾效果的影响,并通过正交实验确定了最佳提钾条件:绢云母矿粉与助剂质量比为1∶1.2,焙烧温度为900℃,焙烧时间为40 min.在最佳条件下焙烧后,熟料经过水浸,钾的浸出率为81.86％.通过对焙烧前后样品及水浸后的不溶物的XRD分析,初步确定了焙烧过程中的主要物相变化及反应机理.     

CaCl2-NaCl混合助剂分解钾长石提取钾的实验研究

CaCl2和NaCl按一定比例混合作助剂焙烧分解钾长石提钾,对产物的物相组成及分解反应过程进行了研究. 结果表明,混合助剂能缩短分解反应达到平衡的时间,在较低的焙烧温度和较短的焙烧时间下获得较高的提取率,且温度越低或时间越短效果越明显,在焙烧温度800℃、焙烧时间60 min的条件下,混合助剂的钾提取率为93.65%,比CaCl2高22.57%,比NaCl高39.56%. 超过700℃后,体系进入快速反应阶段,混合助剂有效降低了分解反应温度,适宜的焙烧温度为800~890℃.     

微波协同条件下钾长石低温提钾工艺研究

探讨了微波协同条件下钾长石低温提钾工艺过程。在微波消解仪中使用化学试剂与钾长石反应,分析各影响因素对钾溶出率的影响。研究结果表明：钾长石粒径越小,钾的溶出率越高;硫酸质量分数增大,溶出率逐步增大;溶出率随反应温度的上升而增加,在反应温度达到160 ℃时,钾提取率趋于稳定。利用响应面分析法对钾长石提取工艺条件进行优化,最终确定最佳实验条件：硫酸质量分数为70%,钾长石与磷矿质量比为0.8∶1,氟化钙与磷酸钙质量比为3∶1,温度为160 ℃,钾提取率达到83%以上。     

N-(2-(5-溴-1H-吲唑-1-基)苯基)-2-氯烟酰胺的合成工艺研究

采用单因素试验法对N-(2-(5-溴-1H-吲唑-1-基)苯基)-2-氯烟酰胺合成反应的反应条件进行了优化和研究,对关键步骤中间体I的合成确定了各个因素的最佳取值:反应时间为22h;物料配比应为5-溴吲唑:邻硝基氯苯:碳酸钾=1:0.85:1.15;反应温度为120℃;碱为碳酸铯。大大的提高了目标产物的总收率,为以后的大批量生产提供了有效途径。     

钾长石在熔盐和熔碱体系中钾的熔出研究

CaCl2-NaCl混熔盐体系和NaOH-NaCl混熔碱体系与钾长石反应均可以熔出钾离子,然后用水浸取得含钾溶液用于生产钾肥.当采用CaCl2-NaCl混熔盐体系为熔剂、以1#钾长石为原料,CaCl2/NaCl的质量比为1.00时,正交试验得出的钾(以K0计)的最佳熔出条件为:反应温度900℃,反应时间1.0h,混熔盐...     

贵州省钾长石提钾工艺初步研究

在高温条件下,利用熔融浸渍法,对贵州万山地区钾长石进行提钾工艺研究,全面探讨助熔剂的阴离子及阳离子对钾提取率的影响,最终选定NaCl为最佳助熔剂。正交实验数据表明,钾长石提钾的较佳工艺条件为:焙烧温度900℃、焙烧时间120 min、m(钾长石)∶m(NaCl)=1.5,钾的提取率为87.97%。     

氯化钙和氯化钠分解钾长石提钾的动力学实验

采用焙烧法对添加氯化钙和氯化钠混合助剂的钾长石体系进行动力学实验,结果表明,改变反应温度、助剂用量和钾长石粒度,分解反应过程符合Ginstling-Brundshtein动力学方程,根据Arrhenius经验公式,求得分解反应表观活化能为58.6 kJ/mol,比氯化钙体系降低68.34 kJ/mol,比氯化钠体系降低...     

钾长石与氯化钙在磷酸体系中的反应过程探讨

基于低温水热反应理论,以钾长石和无水氯化钙为反应物,在磷酸体系中研究温度、时间和钾长石粒径对钾、铝溶出率的影响。通过正交试验得出比较理想的反应条件：温度200℃;65％的磷酸用量2．23mL／（g钾长石）;配料比m（氯化钙）：m（钾长石）=1．5：1,此时,钾长石中K2O溶出率可达75％以上,Al2O,溶出率可达95％以上。