Synthesis of High-Stability Acidic β/Al-MCM-41 and the Catalytic Performance for the Esterification of Oleic Acid

β/Al-MCM-41 molecular sieve was synthesized and used to catalyze the esterification of oleic acid with short chain alcohols such as methanol, ethanol, isopropanol and isobutanol to obtain biodiesel. The results indicated that β/Al-MCM-41 exhibited the excellent catalytic activity and stability, which was obviously superior to traditional Al-MCM-41. The relationship between acidity and catalytic activity was in detail examined by NH3-TPD and Py-FTIR. Moreover, the kinetics of esterification of oleic acid with methanol showed that the average reaction order n was 1.97 and that activation energy was 50.01 kJ/mol.

Chitosan-based carbon dots with multi-color-emissive tunable fluorescence and visible light catalytic enhancement properties

Carbon quantum dots(CQDs)are receiving increasing attention for their excellent photostability,low toxicity,and tunable fluorescence performance,but it is still challenging to prepare full-spectrum CQDs using only one single set of precursor and solvent.In this study,P and N co-doped carbon dots(N,PR-CQDs)with multi-color-emissive tunable fluorescence from blue to green and orange were synthesized from bio-based chitosan,employing phosphoric acid as solvent and dopant.The introduction of phosphoric acid successfully shortens the manufacturing reaction time,and the heteratomic functional groups of P–O/P=O on surface of carbon dots enrich the surface defect states,promoting n–π*transition,and therefore changing their electron structure/energy level to reduce the band gap,thus facilitating emission at long wavelength.Specifically,increasing phosphoric acid concentration leads to characteristic excitation peaks red shift from 320 to 420 nm with the characteristic emission peaks red shift from 406 to 503 nm.A new emission peak at 610 nm appears,enabling N,PR-CQDs exhibit double emission peaks with fluorescence color from green to yellow to orange.After compositing with carbon nitride(g-C3N4),N,PR-CQDs work as photosensitizer and effectively narrow the energy gap(Eg)of g-C3N4 from 2.75 to 2.40 eV,endowing the photocatalyst higher visible light capture ability and broader light response region.The photocatalytic degradation rate of rhodamine B(RhB)under visible light irradiation reaches up to 98.39%within 60 min using N,P20%-CQDs/g-C3N4 as catalyst,which is 1.4 times that of pure g-C3N4,and it is demonstrated that·O2−is the major active substance contributing for RhB degradation by de-ethyl and aromatic ring breakage.

Profiles of and variations in aluminum species in PAC-MC used for the removal of blooming microalgae

Polyaluminum chloride modified clay(PAC-MC)is a safe and efficient red tide control agent that has been studied and applied worldwide.Although it is well known that the distribution of hydrolytic aluminum species in PAC affects its flocculation,little is known about the influence of particulars aluminum species on the microalgae removal efficiency of PAC-MC;this lack of knowledge creates a bottleneck in the development of more efficient MCs based on aluminum salts.The ferron method was used in this study to quantitatively analyze the distributions of and variations in different hydrolytic aluminum species during the process of microalgae removal by PAC-MC.The results showed that Ala,which made up 5%–20%of the total aluminum,and Alp,which made up 15%–55%of the total aluminum,significantly affected microalgae removal,with Pearson’s correlation coefficients of 0.83 and 0.89,respectively.Most of the aluminum in the PAC-MC sank rapidly into the sediments,but the rate and velocity of settlement were affected by the dose of modified clay.The optimal dose of PAC-MC for precipitating microalgae was determined based on its aluminum profile.These results provide guidance for the precise application of PAC-MC in the control of harmful algal blooms.

Synthesis and property of imidazolium oxidative-thermoregulated ionic liquids

A series of novel imidazolium oxidative-thermoregulated bifunctional ionic liquids(ILs) have been synthesized by introducing the thermoregulated structural unit into imidazolium cation and using heteropolyanion as the anion of ILs. The structures of these new type of taskspecific ionic liquids(TSILs) are characterized by FT-IR and1 H NMR. The thermostability of ILs is analyzed by thermogravimetry. The thermoregulated properties of ILs in aqueous and organic solvents are mainly investigated.These ILs have the corresponding cloud points(CPs) in aqueous. The effects of IL concentration, polymerization degree, inorganic additives and organic additives on the CP are studied. IL/DMF/n-heptane or n-octane biphasic system has the corresponding critical solution temperature(CST),and has the feature of ‘‘homogeneous at high temperature,heterogeneous at low temperature''. The effects of IL dosage and polymerization degree on the CST are given.IL/DMF/n-octane thermoregulated biphasic system has been successfully applied for catalytic oxidative desulfurization of model fuels. This study opens up a new way for catalytic oxidation to achieve an integration of homogeneous catalysis and heterogeneous separation.