STUDY ON THE ELECTROCHEMICAL BEHAVIOR OF ION EXCHANGE MEMBRANE IN PREPARING POTASSIUM CARBONATE

This investigation describes the one step preparation of potassium carbonate by electrolysis of potas-sium chloride solution in electrolyzers with various Nation membranes.Potassium bicarbonate solution wasfed to the cathode compartment,where it was converted into carbonate by reaction with the hydroxideformed at cathode.Because of the low OH^- concentration in the cathode compartment,the back migrationof OH^- through the membrane was almost negligible,resulting in a higher current efficiency,say 90% or more.In this study,electroconductivity,mass transfer,current efficiency and cell voltage were measured.Thefeasibility of the process was discussed and the optimal conditions examined.

Synthesis of Dimethyl Carbonate from CO_2, Methanol, and Epoxides Using Re(CO)_5Cl/K_2CO_3 as Catalyst System

Over the past few years, dimethyl carbonate （DMC） has been proven to be an efficient methylating, methoxylating, and methoxycarbonylating agent in organic syntheses, in which DMC is used to replace the toxic methyl halides, dimethyl sulfate or carbon monoxide, and so forth. Furthermore, DMC has been used in the syntheses of polycarbonates and polyurethane to develop the nonphosgene routes Therefore, DMC has become one of the most important compounds in the development of green synthetic chemistry.

A novel method to produce potassium chromate from carbon ferrochrome

The oxidizing roasting of carbon ferrochrome in the presence of potassium carbonate and air was investigated. The effects of reaction temperature, reaction time, ratio of alkali-to-ore were studied, together with a discussion of the thermodynamics and macro kinetics. It is observed that the reaction temperature and reaction time have significant influence on the roasting reaction. The reaction mechanism changes greatly as the temperature varies. A two-stage roasting process is favorable for the roasting reaction, and a recovery ratio of 96.51% is obtained through this two-stage roasting method. The chromium residue yielded from this method is quite little, only one third of the product. Moreover, the component of Fe in the residue is as high as 54.28%. Therefore, it can be easily recovered to produce sponge iron, realizing zero-emission of chromium residue.

NO adsorption and temperature programmed desorption on K_2CO_3 modified activated carbons

Fuel cell stacks as the automotive power source can be severely poisoned by a trace amount of NOx in atmosphere,which makes it necessary to provide clean air for fuel cell vehicles.In this work,activating commercial activated carbons with K2CO3 for the large enhancement of NO capture was studied.K2CO3 modified activated carbons(K2CO3 ACs)were prepared by impregnating activate carbons in K2CO3 solution under ultrasound treatment,followed by temperature programmed baking at 800 oC.The dynamic NO flow tests on K2CO3 ACs at room temperature indicated that NO adsorption capacity reached the maximum(96 mg/g)when K2CO3 loading was 19.5 wt%,which corresponded to a specific surface area of 1196.1 m2/g and total pore volume of 0.70 cm3/g.The ten-fold enhancement of NO adsorption on K2CO3 ACs compared to the unimpregnated activated carbon was mainly attributed to the formation of potassium nitrite,which was confirmed by FTIR and temperature programmed desorption measurements.Regeneration tests of NO adsorption on the optimum sample revealed that 76%of the NO adsorption capacity could be remained after the fourth cycle.

Operating limits and features of direct air capture on K_(2)CO_(3)/ZrO_(2) composite sorbent

Potassium carbonate-based sorbents are prospective materials for direct air capture(DAC).In the present study,we examined and revealed the influence of the temperature swing adsorption(TSA)cycle conditions on the CO_(2) sorption properties of a novel aerogel-based K_(2)CO_(3)/ZrO_(2) sorbent in a DAC process.It was shown that the humidity and temperature drastically affect the sorption dynamic and sorption capacity of the sorbent.When a temperature at the sorption stage was 29℃ and a water vapor pressure P_(H2O) in the feed air was 5.2 mbar(1 bar=105 Pa),the composite material demonstrated a stable CO_(2) sorption capacity of 3.4%(mass).An increase in sorption temperature leads to a continuous decrease in the CO_(2) absorption capacity reaching a value of 0.7%(mass)at T=80℃.The material showed the retention of a stable CO_(2) sorption capacity for many cycles at each temperature in the range.Increasing PH2O in the inlet air from 5.2 to 6.8 mbar leads to instability of CO_(2) sorption capacity which decreases in the course of 3 consecutive TSA cycles from 1.7%to 0.8%(mass)at T=29℃.A further increase in air humidity only facilitates the deterioration of the CO_(2) sorption capacity of the material.A possible explanation for this phenomenon could be the filling of the porous system of the sorbent with solid reaction products and an aqueous solution of potassium salts,which leads to a significant slowdown in the CO_(2) diffusion in the composite sorbent grain.To investigate the regeneration step of the TSA cycle in situ,the macro ATRFTIR(attenuated total reflection Fourier-transform infrared)spectroscopic imaging was applied for the first time.It was shown that the migration of carbonate-containing species over the surface of sorbent occurs during the thermal regeneration stage of the TSA cycle.The movement of the active component in the porous matrix of the sorbent can affect the sorption characteristics of the composite material.The revealed features make it possible to formulate the requirements and limitations that need to be taken into account for the practical implementation of the DAC process using the K_(2)CO_(3)/ZrO_(2) composite sorbent.

Preparation of K_2CO_3 Using Potassic Syenite from East Qinling Mountains

1 Introduction Songxian at East Qinling mountains in China possesses more than 100 million tons potassic syenite with the average K2O content of 13%and the main mineral phase of K-feldspar which is a kind of potential potassium

Fabrication of K-promoted iron/carbon nanotubes composite catalysts for the Fischer–Tropsch synthesis of lower olefins

K-promoted iron/carbon nanotubes composite（i.e., Fe K-OX） was prepared by a redox reaction between carbon nanotubes and K2FeO4followed by thermal treatments on a purpose as the Fischer–Tropsch catalyst for the direct conversion of syngas to lower olefins. Its catalytic behaviors were compared with those of the other two Fe-IM and Fe K-IM catalysts prepared by impregnation method followed by thermal treatments. The novel Fe K-OX composite catalyst is found to exhibit higher hydrocarbon selectivity,lower olefins selectivity and chain growth probability as well as better stability. The catalyst structureperformance relationship has been established using multiple techniques including XRD, Raman, TEM and EDS elemental mapping. In addition, effects of additional potassium into the Fe K-OX composite catalyst on the FTO performance were also investigated and discussed. Additional potassium promoters further endow the catalysts with higher yield of lower olefins. These results demonstrated that the introduction method of promoters and iron species plays a crucial role in the design and fabrication of highly active,selective and stable iron-based composite catalysts for the FTO reaction.

Preparation and modification of activated carbon for benzene adsorption by steam activation in the presence of KOH

A series of activated carbons from Taixi anthracite were prepared by steam activation in the presence of KOH and then they were modified by different methods. The regulation of porosity and the modification of surface chemistry were carried out with the aim to improve the benzene adsorption capacity of activated carbon. The influences of KOH and activation process parameters including activation temperature, activation time and steam flow rate on porosity of activated carbon were evaluated, and the effect of modification methods on surface chemistry was investigated. Also, the relationship between benzene adsorption capacity and porosity and surface chemistry was analyzed. Results show that activation temperature is the dominant factor in the activation process; the introduction of KOH into the raw material can enhance the reactivity of char in activation process, meanwhile it shows a negative effect on the porosity development, especially on the mesopore development. Results of FTIR analysis indicate that anthracite-based activated carbon with condensed aromatics and chemically inert oxygen does not present the nature to be surface modified. Besides, benzene adsorption capacity has an approximate linear relationship with surface area and in our preparation, benzene adsorption capacity and surface area of activated carbon are up to 1210 m 2 /g and 423 mg/g, respectively.

A Computational Study on the Mechanism for the K_2CO_3-catalyzed Reaction of Carbon Dioxide and 1-Chlo-2-propanol

The microcosmic reaction mechanism of K2CO3-catalyzed 1-chlo-2-propanol and carbon dioxide has been investigated by density functional theory（DFT） at the GGA/PW91/DNP level.We optimize the geometric configurations of reactants,intermediates,transition states,and products.The energy analysis calculation approves the authenticity of intermediates and transition states.According to our calculations,four feasible reaction pathways are found.The main pathway of the reaction is ReA → IMA1 → TSA1 → IMA2 → IMA5 → TSA5 → P.Besides,we also in-vestigate the reaction mechanism of 1-chlo-2-propanol and carbon dioxide without K2CO3-catalyzation by the same theory and level.The computational results indicate that the activation barrier with K2CO3-catalyzed is smaller than the activation barrier without K2CO3-catalyzed.That is to say,K2CO3 can promote the reaction to give the product in a high yield,which is in agreement with the experimental results.

Free-standing N-doped hollow carbon fibers as high-performance anode for potassium ion batteries

A novel hierarchical architecture—N-doped hollow carbon fibers decorated with N-doped carbon clusters(NHCF@NCC)—was synthesized for high-performance anode material of potassium ion batteries(PIBs).The material is formulated with porous N-doped hollow carbon fibers as the backbone,which effectively shortens the diffusion length of potassium ion and increases the interface between the electrode and electrolyte.In addition,the N-doped carbon clusters attached on the hollow carbon fibers can provide abundant reactive sites.Specially,NHCF@NCC could form a freestanding electrode with a three dimensional interconnected conductive network owing to the ultrahigh aspect ratio.In this way,NHCF@NCC delivers an excellent electrochemical performance as free-standing anode materials of PIBs,exhibiting a high reversible capacity of 310 mA h g^−1 at a current density of 100 mA g^−1,a long cycling stability of 1000 cycles with negligible degradation,and a superior rate performance of 153 mA h g^−1 at a large current density of 2000 mA g^−1.

Facile synthesis of indoles by K2CO3 catalyzed cyclization reaction of 2-ethynylanilines in water

The cyclization reaction of 2-ethynyl-N-sulfonylanilides proceeded efficiently in water with the presence of a catalytic amount of K2CO3 under transition metal-free condition to give indoles in high yields.The recovery and reusability of the present catalytic system were investigated.