A novel method for producing benzene polycarboxylic acids by electrochemical oxidation of Zhaotong lignite in aqueous NaCl solution

The development of a coal-based synthetic route to produce benzene polycarboxylic acids(BPCAs)is of great importance for the highly efficient utilization of lignites.In this paper,aqueous NaCl^(-)electrolytic system was used to oxidize Zhaotong lignite to prepare BPCAs.The electrochemical oxidation of lignite in aqueous NaCl solution could produce more BPCAs than that in aqueous NaOH solution.The aqueous NaCl electrolytic system could in-suit produce a stable OCl^(-),which was synthesized by the combination reaction between Cl_(2)and OHgenerated in the anode or cathode,respectively.The in-suit produced OCl^(-)would degrade the organic structures of the lignite dispersing in the electrolyte to generate BPCAs.The formation of BPCAs could be greatly affected by current density,electrolysis time and the addition amount of NaCl in the electrolytic system,which resulted from that the factors played an important role in the generation of OCl^(-).The coal related model compounds including anthracene and phenanthrene were used to investigate the electrochemical oxidation mechanism of the lignite.The results indicated that the aromatic ring structures in the lignite were attacked by O_(2)•^(-)from the OCl^(-)to afford BPCAs.

Differentiation of qualified tea beverages from spoiled ones by the LC-MS-based analysis of their polycarboxylic acids

Polycarboxylic acids(PACs)are important metabolic products in almost all living bodies,yet current analytical methods for detection of PACs in tea beverages are still unsatisfactory due to the complex matrix and physicochemical properties of PACs.In this work,a rapid method was developed for the simultaneous determination of 7 PACs,including tartaric acid,α-ketoglutaric acid,malic acid,malonic acid,cis-aconitic acid,succinic acid,and fumaric acid,in beverages,based on selective removal of the matrix in combination with liquid chromatography–mass spectrometry(LC-MS)analysis.By stirring with activated carbon and the Na2CO3 solution,the matrix in beverages was selectively removed,and PACs were almost retained in the supernatant of diluted Na2CO3 solution.Under optimized parameters,the limit of quantitation for the PACs was in the range of 1–50 ng/mL,and the content of the PACs in 8 beverages was determined with the recovery range of 72.2%–122.5%.The contents of malic acid,malonic acid,and succinic acid in tea beverages were found to be greater than those in non-tea beverages.Moreover,the concentration of these PACs in beverages was found to be multiplied many times in their deterioration period,especially for fumaric acid andα-ketoglutaric acid.These results indicated that PACs can be selected as a criterion to differentiate qualified tea beverages from spoiled beverages.

Molecular Weight Distributions of Cotton Cellulose Treated with a Polycarboxylic Acid at Different pH

In last paper, the average molecular weight of a control cotton fabric and cotton fabrics treated with the polycarboxylic acid at different pH were measured. The result doesnt support the hypothesis that the pH of the finishing bath can affect the depolymerization of the finished cotton fabric. In order to understand more about it, the molecular weight distributions of the control and finished cotton fabrics were measured and the reason was fund. From the ratio and the molecular weight of the low molecular part one can see that the pH of the finishing bath can affect the depolymerization of the finished cotton fabrics. The phenomenon that the average molecular weights of the cotton fabric crosslinked with BTCA at different pH are almost same is attributed to that the crosslinks are not broken completely when treated with 0.5 M NaOH solution at 50℃ for 144 h.

Influence of Different Organic Carboxylate Anions on the Crystal Structure of Silver(Ⅰ)Coordination Polymers

The reaction of AgNO3 , 4,4′-bipyridine （bpy） and 2,2′-bipyridine-3,3′-dicarboxylic acid （H2bpdc）/2,2′-biquinoline-4,4′-dicarboxylic acid （H2bqdc）/1,3-benzenedicarboxylic acid （H2bdc） gave rise to block-like crystals of [Ag4（bpy）2（bpdc）2]·13H2O（1）, [Ag2（bpy）（bqdc）（H2O）]·4.5H2O（2） and [Ag2（bpy）2（H2O）2]（bdc）·3H2O（3） by slow evaporation. All the three complexes contain sandwich-like crystal structures, in which anionic sheets built up from different anions （bpdc2- , bqdc2- and bdc2- ） and lattice water molecules via rich hydrogen-bonding interactions are inserted between the cationic silver complex layers, and the abundant Ag···Ag, Ag···N and π-π stacking interactions further strengthen the 3D frameworks. The lattice water molecules are situated among the framework of crystal structure and stabilized by rich hydrogen-bonding interactions, and lattice water molecules may play a role in the orientation of organic anions in the crystal packing. Additionally, the thermal properties of 1, 2 and 3 were also discussed in detail.

Research Progress of Metal-Organic Frameworks Based on Aromatic Polycarboxylic Acid

Metal-organic frameworks （MOFs） have attracted tremendous attention due to their fascinating structure types and extensive application prospect in many fields. In the process of synthesis, aromatic polycarboxylic acid as ligand plays an important role in constructing functional MOFs. In this review, we have summarized the research progress on the synthesis and structures analysis of MOFs based on aromatic polycarboxylic acids as well as their potential applications in magnetism, gas adsorption, separation, photodegradation, catalysis and emission.

Synthesis and dyeing performance of a novel polycarboxylic acid azo dye

A novel reactive polycarboxylic acid dye was synthesized by the reaction of polymaleic anhydride（PMA） with 3-methyl-1-（4- sulfonylphenyl）-4-（4-aminophenylazo）-2-pyrazoline-5-one.The structure of the novel dye was characterized by FTIR,UV-vis and ^（13）C NMR spectra.The dyeing properties of dye on cotton were tested,and the novel dye possessed high fixation and good fastness.

Effect of pyrolysis on Zhaotong lignite oxidation with aqueous sodium hypochlorite

The pyrolysis treatment of lignites could remove thermal-unstable aliphatic structures but enrich aromatic structures in resulting pyrolysis residues,which would facilitate producing benzene polycarboxylic acids(BPCAs).Herein,the demineralized Zhaotong lignite(DZL)was pyrolyzed at 250-550℃ to afford the corresponding pyrolysis residues.Subsequently,DZL and its pyrolysis residues were subjected to oxidation with aqueous sodium hypochlorite.By XRD,FTIR,and element analyses,it was found that the content and polycondensation degree of aromatic structures simultaneously increased with increasing pyrolysis temperature.Furthermore,the yield and selectivity of BPCAs both increased along with raising pyrolysis temperature in resulting products from fully oxidation of DZL and its pyrolysis residues.Based on the distribution of BPCAs,peri-condensed aromatic structures were dominant in DZL and its DPRs,and obviously increased with increasing pyrolysis temperature.More interestingly,good correlation was found between the yield of BPCAs and aromaticity parameters.Meanwhile,the yield of benzenepentacrboxylic acid was well associated with polycondensation degree parameters.