Ionic liquid-assisted preparation of hydroxyapatite and its catalytic performance for decarboxylation of itaconic acid

The synthesis of methacrylic acid from biomass-derived itaconic acid is a green route,for it can get rid of the dependence on fossil resource.In order to solve the problems on this route such as use of a preciousmetal catalyst and a corrosive homogeneous alkali,we prepared a series of hydroxyapatite catalysts by an ionic liquid-assisted hydrothermal method and evaluated their catalytic performance.The results showed that the ionic liquid[Bmim]BF_(4) can affect the crystal growth of hydroxyapatite,provide fluoride ion for fluorination of hydroxyapatite,and adjust the surface acidity and basicity,morphology,textural properties,crystallinity,and composition of hydroxyapatite.The[Bmim]BF4 dosage and hydrothermal temperature can affect the fluoride ion concentration in the hydrothermal system,thus changing the degree of fluoridation of hydroxyapatite.High fluoride-ion concentration can lead to the formation of CaF_(2) and thus significantly decrease the catalytic performance of hydroxyapatite.The hydrothermal time mainly affects the growth of hydroxyapatite crystals on the c axis,leading to different catalytic performance.The suitable conditions for the preparation of this fluoridized hydroxyapatite are as follows:a mass ratio of[Bmim]BF4 to calcium salt=0.2:1,a hydrothermal time of 12 h,and a hydrothermal temperature of 130℃.A maximal methacrylic acid yield of 54.7%was obtained using the fluoridized hydroxyapatite under relatively mild reaction conditions(250℃ and 2 MPa of N_(2))in the absence of a precious-metal catalyst and a corrosive homogeneous alkali.

Synthesis and kinetics of 2,5-dicyanofuran in the presence of hydroxylamine ionic liquid salts

2,5-Dicyanofuran(DCF)is an important biomass-derived platform compound primarily used to prepare bio-based adiponitrile,which is the key precursor for the synthesis of nylon 66 and 1,6-hexanediisocyanate(HDI).In this study,one-pot,green and safe synthesis of DCF from 2,5-diformylfuran(DFF)and hydroxylamine ionic liquid salts was proposed.Eco-friendly hydroxylamine ionic liquid salts were used as the nitrogen source.Ionic liquid exhibited three-fold function of cosolvent,catalysis and phase separation.The conversion of DFF and yield of DCF reached 100%under the following optimum reaction conditions:temperature of 120℃ for 70 min,volume ratio of paraxylene:[HSO_(3)-b-Py]
HSO4 of 2:1,and molar ratio of DFF:(NH_(2)OH)_(2)
[HSO_(3)-b-Py]
HSO4 of 1:1.5.The reaction mechanism for the synthesis of DCF was proposed,and the kinetic model was established.The reaction order with respect to DFF and intermediate product 2,5-diformylfuran dioxime(DFFD)was 1.06 and 0.16,and the reaction activation energy was 64.07 kJ·mol^(-1) and 59.37 kJ·mol^(-1) respectively.After the reaction,the ionic liquid was easy to separate,recover and recycle.

Influence of Ca/P ratio on the catalytic performance of hydroxyapatite for decarboxylation of itaconic acid to methacrylic acid

Methacrylic acid,an important organic chemical,is commercially manufactured starting from fossil feedstock.The decarboxylation of itaconic acid derived for biomass is a green route to the synthesis of methacrylic acid.In view of the problems existing in the researches on this route such as use of noble metal catalyst,harsh reaction conditions and low desired-product yield,we prepared a series of hydroxyapatite catalysts with different Ca/P molar ratios and evaluated their catalytic performance.The results showed that the hydroxyapatite catalyst with a Ca/P molar ratio of 1.58 had the best catalytic activity.The highest yield of MAA up to 61.2%was achieved with basically complete conversion of itaconic acid under the suitable reaction conditions of 1 equivalent of NaOH,2 MPa of N_(2),250℃,and 2 h.On this basis,a reaction network for the decarboxylation of itaconic acid to methacrylic acid catalyzed by hydroxyapatite was established.With the aid of catalyst characterization using X-ray powder diffraction,NH3/CO2 temperature-programmed desorption,N_(2)physisorption,inductively coupled plasma optical emission spectrometry,and scanning electron microscopy,we found that the distribution of surface acid sites and basic sites,crystal growth orientation,texture properties and morphology of hydroxyapatite varied with the Ca/P molar ratio.Furthermore,the change of the crystal growth orientation and its influence on the surface acidity and alkalinity were clarified.

Preparation and characterization of H_4SiW_(12)O_(40)@MIL-100(Fe) and its catalytic performance for synthesis of 4,4'-MDA

The catalytic performance of commonly used heteropoly acids(H_3 PW_(12)O_(40). H_4 SiW_(12)O_(40) and H_3 PMo_(12)O_(40)) for the synthesis of 4,4'-methylenedianiline(4.4'-MDA) from aniline and formaldehyde was evaluated and the result showed that H_4 SiW_(12)O_(40) with moderate acid strength exhibited the best catalytic performance. Then H_4 SiW_(12)O_(40)@MIL-100(Fe) was prepared by encapsulating H_4 SiW_(12)O_(40) within the pores of MIL-100(Fe) to facilitate its recovery and reuse. The prepared H_4 SiW_(12)O_(40)@MIL-100(Fe) was characterized by means of FT-IR, N_2 adsorption-desorption, XRD, TG and then the catalytic performance was evaluated. The result showed that H_4 SiW_(12)O_(40) was highly dispersed in the pores of MIL-100(Fe), and both the Keggin structure of H_4 SiW_(12)O_(40)and the crystal skeleton structure of MIL-100(Fe) could be effectively preserved. Furthermore. H_4 SiW_(12)O_(40)@MIL-100(Fe) showed excellent catalytic performance under the following reaction conditions: a molar ratio of aniline to formaldehyde = 5, a mass ratio of catalyst to formaldehyde = 1.2, a reaction temperature of 120 ℃and a reaction time of 6 h. Under the above reaction conditions, the conversion of aniline was 41.1%, and the yield and selectivity of 4.4'-MDA were 81.6% and 79.2%, respectively. Unfortunately, an appreciable loss in the catalytic activity of the recovered H_4 SiW_(12)O_(40)@MIL-100(Fe) was observed because of the blocking of the pores and the change of the acidity resulted from the adsorption of alkaline organics such as aniline and 4,4'-MDA.The adsorbed alkaline organics could be cleaned up when the recovered catalyst was washed by methanol and DMF. Then the catalyst was effectively reused up to three cycles without much loss in its activity.

Investigation on the deactivation cause of lead-zinc double oxide for the synthesis of diphenyl carbonate by transesterification

The deactivation cause of lead-zinc double oxide for synthesis of diphenyl carbonate （DPC） by transesterification of dimethyl carbonate （DMC） with phenol has been investigated. X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, infrared spectroscopy （IR）, thermogravimetry analysis （TG）, atomic absorption spectroscopy and elementary analysis are employed for the catalyst characterization. The results show that, the formation of Pb4O（OC6H5）6 through the reaction of phenol and lead species in the catalyst leads to the crystal phase change of active component and serious leaching of lead, which is the cause of the catalyst deactivation. In addition, the composition of the leached lead is ascertained to be a mixture of Pb4O（OC6H5）6 and PbO with the weight percentage of 62.7% and 37.3%, respectively.

A core–shell Ni/SiO_(2)@TiO_(2) catalyst for highly selective one-step synthesis of 2-propylheptanol from n-pentanal

One-step synthesis of 2-propylheptanol(2-PH)from n-pentanal via a reaction integration of n-pentanal self-condensation and successive hydrogenation is of great significance for it can simplify process flow and reduce energy consumption.The key to promotion of 2-PH selectivity is to enhance the competitiveness of n-pentanal self-condensation with respect to its direct hydrogenation.For this purpose,a core–shell structured Ni/SiO_(2)@TiO_(2) catalyst was designed and prepared.With the precise architecture of this core–shell structured catalyst,n-pentanal can be firstly in contact with TiO_(2) to 2-propyl-2-heptenal(2-PHEA)while the direct hydrogenation to n-pentanol can be effectively inhibited,and then 2-PHEA diffuses into the core of Ni/SiO_(2) and is hydrogenated to 2-PH.The spatial threshold of the core–shell catalyst significantly enhanced its catalytic performance;a 2-PH selectivity of 77.9%was reached with a 100%npentanal conversion.The 2-PH selectivity is much higher than that obtained by employing Ni/TiO_(2) catalyst.Furthermore,the reaction kinetics of one-step synthesis of 2-PH from n-pentanal catalyzed by Ni/SiO_(2)@TiO_(2) was studied and its kinetic model was established which is useful for reactor design and scale-up.

Chitosan-catalyzed n-butyraldehyde self-condensation reaction mechanism and kinetics

The chitosan was found to possess an excellent catalytic performance in n-butyraldehyde selfcondensation to 2 E2 H.Under suitable conditions,the conversion of n-butyraldehyde,the yield and selectivity of 2 E2 H separately attained 96.0%,86.0%and 89.6%.The chitosan catalyst could be recovered and used for 5 times without a significant deactivation after being treated with ammonium hydroxide.In order to elucidate the reaction mechanism,the adsorption and desorption of n-butyraldehyde on the surface of chitosan were studied using in situ FT-IR spectroscopy analysis.The result showed that n-butyraldehyde interacts with\\NH2 group of chitosan to form an intermediate species with an enamine structure.Then the reaction process of n-butyraldehyde self-condensation was monitored by React-IR technique and it was found that n-butyraldehyde self-condensation to 2-ethyl-3-hydroxyhexanal followed by a dehydration reaction to 2-ethyl-2-hexenal.On this basis,chitosan-catalyzed n-butyraldehyde self-condensation reaction mechanism was speculated and its reaction kinetics was investigated.The self-condensation reaction follows auto-catalytic reaction characteristics and then the corresponding kinetic model was established.

Synthesis and Characterization of Novel Bronsted-Lewis Acidic Ionic Liquids

To meet the demands of some kinds of reactions catalyzed simultaneously by Br?nsted acid and Lewis acid catalyst, two novel Br?nsted-Lewis acidic ionic liquids, 1-carboxyethylene-3-(4-zinc acetate sulfobutyl) imidazolium chloride ([CH3COO-Zn-O3S-bim-CH2CH2COOH]Cl) and 1-(1,2-dicarboxy) ethylene-3-(4-zinc acetate sulfobutyl) imidazolium chloride ([CH3COO-Zn-O3S-bim-C4H5O4]Cl) were synthesized, in which both Br?nsted and Lewis acidic sites existed in the cation. The structures of the ionic liquids were determined by means of FT-IR, 1H NMR and elemental analysis. The results of Py-IR analysis indicated that the two novel ionic liquids have both Br?nsted and Lewis acid properties. The acid strength values (H0) of the ionic liquids were measured utilizing the UV-visible spectroscopy combined with Hammett indicator method, and the acid amount of them was determined by acid-base titration.

Synthesis of bifunctional Pt/MgAPO-5 catalysts and their catalytic performance in the hydrogenation of nitrobenzene to p-aminophenol

MgAPO-5 molecular sieves have been synthesized using diethylaminoethanol as the templating agent in a wide range of the MgO/Al2O3 ratio.The samples were characterized by XRD,SEM,solid state NMR,FT-IR and NH3-TPD.Using MgAPO-5 as acidic supports,bifunctional Pt/MgAPO-5 catalysts were prepared for hydrogenation of nitrobenzene to p-aminophenol (PAP).The results showed that the MgO/Al2O3 ratios influenced the Mg content and the acidity of MgAPO-5 samples,thereby greatly affecting the catalytic performance of Pt/MgAPO-5 catalysts.The selectivity to PAP over Pt/MgAPO-5 was dependent on the amount of strong acid sites of MgAPO-5.When the MgO/Al2O3 molar ratio was 0.5,the synthesized MgAPO-5 sample exhibited the largest amount of strong acid and a highest PAP yield of 41.1% was achieved over Pt/MgAPO-5 catalyst.

Synthesis of magnetic Pb/Fe_(3)O_(4)/SiO_(2) and its catalytic activity for propylene carbonate synthesis via urea and 1,2-propylene glycol

To facilitate the recovery of Pb/SiO_(2) catalyst,magnetic Pb/Fe_(3)O_(4)/SiO_(2) samples were prepared separately by emulsification,sol-gel and incipient impregnation methods.The catalyst samples were characterized by means of X-ray diffraction and N_(2) adsorption-desorption,and their catalytic activity was investigated in the reaction for synthesizing propylene carbonate from urea and 1,2-propylene glycol.When the gelatin was applied in the preparation of Fe_(3)O_(4) at 60℃ and the pH value was controlled at 4 in the preparation of Fe_(3)O_(4)/SiO_(2),the Pb/Fe_(3)O_(4)/SiO_(2) sample shows good catalytic activity and magnetism.Under the reaction conditions of a reaction temperature of 180℃,reaction time of 2h,catalyst percentage of 1.7 wt-% and a molar ratio of urea to PG of 1∶4,the yield of propylene carbonate attained was 87.7%.