Construction of a Bronsted-Lewis solid acid catalyst La-PW-SiO_(2)/SWCNTs based on electron withdrawing effect of La(Ⅲ)onπbond of SWCNTs for biodiesel synthesis from esterification of oleic acid and methanol

A novel solid Bronsted-Lewis acid catalyst La-PW-SiO_(2)/SWCNTs(single-wall carbon nanotubes)was synthesized from the synergistic modification of H_(3)PW_(12)O_(40)(HPW)by single-walled carbon nanotubes functionalized with sidewall hydroxyl groups(SWCNTs–OH)and La^(3+) via sol–gel method.The freshly prepared catalyst was characterized by several methods,and the catalytic activity and stability of it were studied from the esterification of oleic acid and methanol.Results showed that the highest conversion of oleic acid was 93.1%(mass)and maintained as high as 88.7%(mass)after six cycles of La-PW-SiO_(2)/SWCNTs.The high catalytic activity and stability of La-PW-SiO_(2)/SWCNTs can be attributed to the strong electron withdrawing effect of La^(3+) on π bond of SWCNTs,because it can facilitate the formation of a large number of strong Lewis acid sites.Therefore,the reduction of catalytic activity of a solid acid catalyst due to the fact that hydration reaction of its Bronsted acid sites can be effectively reduced.La-PW-SiO_(2)/SWCNTs can be an efficient and economical catalyst,because it shows good catalytic activity and stability.

In situ[2+3] cycloaddition synthesis,crystal structures,strong SHG responses and fluorescence properties of three novel Zn coordination polymers

We report on the synthesis of two acentric and one centrosymmetric Zn metal-organic complexes with 3-tetrazolenethyl pyridine spacers obtained in situ by hydrothermal routes.X-ray diffraction structural analysis reveals that they have the same equivalent nodes but with dissimilar topologies.The two acentric frameworks[Zn(Tzmp)Cl]n(1)and([Zn(Tzmp)Br]n(2),HTzmp=3-tetrazolemethyl pyridine)are isomorphism which exhibit an acentric 3D framework with(10,3)-b net called"ths",while the centro symmetric complex([Zn(Tzmp)N3]n(3))features a distinctive 2D sheet with Shubnikov hexagonal plane net.Photo-luminescent studies suggest the ligand-field strength of coordinated negative ions(Cl^->Br^->N3^-)has ordered adjusting effects on the emission redshift.The second harmonic generation(SHG)measurement shows that compounds 1 and 2 are nonlinear optically active,with SHG responses being 2/3 and half of the standard potassium dihvdrogen phosphate(KDP),respectively.