Ionic liquids-SBA-15 hybrid catalysts for highly efficient and solvent-free synthesis of diphenyl carbonate

Diphenyl carbonate(DPC)is one of the versatile carbonates,and is often used for the production of polycarbonates.In recent years,the catalytic synthesis of DPC has become an important topic but the development of a highly active metal-free catalyst is a great challenge.Herein,a series of ionic liquids-SBA-15 hybrid catalysts with different functional groups have been developed for the synthesis of DPC under solventfree condition,which are effective and clean instead of the metal-containing catalysts.It is found that in the presence of[SBA-15-IL-OH]Br catalyst,methyl phenyl carbonate(MPC)conversion of 80.5%along with 99.6%DPC selectivity is achieved,the TOF value is thrice higher than the best value reported by using transition metal-based catalysts.Moreover,the catalyst displays remarkable stability and recyclability.This work provides a new idea to design and prepare eco-friendly catalysts in a broad range of applications for the green synthesis of carbonates.

Molybdosphoric Acid Mixed with Titania Used as a Catalyst to Synthesize Diphenyl Carbonate via Transesterification of Dimethyl Carbonate and Phenol

The 12-molybdosphoric acid mixed with titania （MPA-TiO2） was found to be a novel and efficient catalyst for the synthesis of diphenyl carbonate （DPC） via transesterification of dimethyl carbonate （DMC） and phenol. The X-ray diffraction （XRD） and infrared （IR） techniques were employed to characterize the prepared catalysts. The effect of the weight ratio of the 12-molybdosphoric acid to titania on the transesterification was investigated. A 13.1% yield of DPC and an 11.6% yield of methyl phenyl carbonate （MPC） were obtained over MPA-TiO2 with the weight ratio of MPA to TiO2 as 5：1.

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.

Preparation of CuO-CoO-MnO/SiO_2 Nanocomposite Aerogels as Catalyst Carriers and Their Application in the Synthesis of Diphenyl Carbonate

CuO-CoO-MnO/SiO2 nanocomposite aerogels were prepared by using tetraethyl orthosilicate （TEOS） as Si source, and aqueous solution of Cu, Co and Mn acetates as transition metal sources via sol-gel process and supercritical drying （SCD） technique. The effect of synthesis conditions on gelation was investigated. Moreover, the composition of the CuO-CoO-MnO/SiO2 nanocomposite aerogels was characterized by electron dispersive spectroscopy （EDS） and X-ray photoelectron spectroscopy （XPS）, and the specific surface area of the nanocomposite aerogels was determined by the Brunauer-Emmett-Teller （BET） method. Diphenyl carbonate （DPC） as the product was analyzed by gas chromatography （GC）. The experimental results show that the range of optimal temperature for gelation is 30-45 ℃, and the pH is 3.0-4.5. CuO-CoO-MnO/SiO2 nanocomposite aerogels are porous with a specific surface area of 384.9-700.6 m2/g. Compared to CO2 SCD, ethanol SCD is even favorable to the formation of aerogel with high specific surface area. The transition metals content in the nanocomposite aerogels can be controlled to be 0.71at%-13.77at%. With CuO-CoO-MnO/SiO2 nanocomposite aerogels as catalyst carrier, the yield of DPC is in direct proportion to the atomic fraction of transition metals in the nanocomposite aerogels, and it is up to 26.31 mass%, which is much higher than that via other porous carriers.

Kinetic model of transesterification of diphenyl carbonate and 1,4-butyldiol

The transesterification of diphenyl carbonate （DPC） with 1,4-butyldiol （BD） was kinetically investigated in the presence of lithium acetate catalyst at 465 K.The reaction was followed by the measurement of the quantity of phenol which was distilled from the reactor.The experiments supported the assumption that the phenyl ester groups in DPC and phenyl hdroxybutyl carbonate （PHBH） had the same reactivity,and the transesterification obeyed first-order kinetics with respect to DPC and BD,and a rate equation was derived.The reaction rate was found to be first order with respect to the catalyst concentration as well.When those data were incorporated in the rate equation,excellent agreement between calculated values and the observed ones was recognized over a wide range.

High Selectivity to Diphenyl Carbonate Synthesized via Transesterification Between Dimethyl Carbonate and Phenol with C60-doped TiO2

An environmentally friendly heterogeneous catalyst, C60-doped TiO2（denoted as C60-TiO2）, was prepared and firstly used to catalyze the synthesis of diphenyl carbonate（DPC） via the transesterification of phenol and dime- thyl carbonate（DMC）. The characterization results of FTIR, XRD, XPS, SEM, TEM and digital optical micro- scope（MIC） show that C60 promotes the dispersion of TiO2 and the prepared conditions affect the dispersion and the electron density of Ti species. The C60-TiO2-8[n（Ti）：n（C60）=8：1] prepared with toluene and calcined at 200 ℃ exhi- bits the best catalytic performance. The DPC selectivity of 86.5% attained over C60-TiO2-8 was much higher than that（about 50%） attained over Ti-based catalysts reported, which was originated from the electronic effect of C60 and the efficient dispersion of Ti species by C60. The phenol conversion slowly decreased from 34.4% to 26.7% after four consecutive runs due to the leach of Ti species. It also suggested that the C60 could relieve the leach of Ti species compared with other Ti-based catalysts reported. Moreover, C60-TiO：-8 exhibited excellent catalytic behavior for disproportionation of methyl phenyl carbonate（MPC） with high DPC selectivity.

Direct synthesis of diphenyl carbonate over heterogeneous catalyst: effects of structure of substituted perovskite carrier on the catalyst activities

The perovskite-type compound LaMnO_(3) was substituted for the part of La in position A and for the part of Mn in position B by citrate method.The phases were detected by X-ray diffraction.Powder morphologies were scanned by scanning electron microscopy.The valence of atoms was determined by X-ray photoelectron spectroscopy.It was found that the perovskite can form crystal defect and increase the proportion of high valence B element by doping.Active component Pd was loaded on various perovskite supports for synthesis of diphenyl carbonate.The results showed that the activities of catalysts in which supports have crystal defect by substitution were higher.It can be concluded that perovskite with defect structure by doping could lead to the formation of oxygen vacancy where the lattice oxygen became exchangeable with the oxygen gas.Also,this improved the redox process of the carrier by transferring electrons and activities of catalysts.

Synthesis of Mg_5(CO_3)_4(OH)_2·4H_2O with Flower-like Micro-structure and Its Catalytic Activity for Transesterification of Dimethyl Carbonate with Phenol

A novel flower-like hydrated magnesium carbonate hydroxide, Mg5 （CO3 ）4 （OH）2·4H2O, with micro-structure composed of individual thin nano-sheets was synthesized using a facile solution route without the use of template or organic surfactant. Reaction time has an important effect on the final morphology of the product. The micro-structure and morphology of Mg5 （CO3）4 （OH）2·4H2O were characterized by means of X-ray diffractometry （XRD）, fieldemission scanning electron microscopy（FE-SEM）. Brunauer-Emmett-Teller（BET） surface areas of the samples were also measured. The probable formation mechanism of flower-like micro-structure was discussed. It was found that Mg5 （CO3）4（ OH）2·4H2O with flower-like micro-structure was a novel and efficient catalyst for the synthesis of diphenyl carbonate （DPC） by transesterification of dimethyl carbonate （DMC） with phenol.

Polyoxometalates Pillared Hydrotalcite:Synthesis and Catalysis in Transesterification of Dimethyl Carbonate and Phenol

The salts of para-tungstic and para-molybdic were heterogenized for their effective use as solid catalysts in the transesterification reaction of dimethyl carbonate and phenol by inserting them between the layers of Mg2Al-hydrotalcite. These catalysts were characterized by FT-IR spectra and X-ray powder diffraction. Polyoxometalates （POMs） clusters were intercalated into the interlayer of layered double hydroxide （LDH） via anion exchange with organic acid precursor in Mg2Al-LDH, and the integrity of the clusters [W7O24 ]^6- and [Mo7O24 ]^6- was maintained. The intercalated para-molybdic cluster showed high catalytic activity and reusability in the transesterification under mild reaction conditions. When the reaction was carried out at 180 ℃, with a molar ratio of phenol to DMC of 1 ： 1, a reaction time 10 h, and a catalyst amount 1% （wt）, the conversion of phenol was 10.0 %, the selectivities of diphenyl carbonate and methyl phenyl carbonate were 10.7 % and 86.1%, respectively.

Facile Synthesis of 2PbCO_3·Pb(OH)_2 Microcrystals and Its Catalytic Behavior for Transesterification of Dimethyl Carbonate with Phenol

Polyhedron lead hydroxide carbonate （2PbCO3·Pb（OH）2 ） microcrystals have been prepared in solution phase via a facile method in the presence of surfactant cetyltrimethylammonium bromide （CTAB）. All the samples were characterized by powder X-ray diffraction ,pattern （XRD）, field-emission scanning electron mi- croscopy （FE-SEM）, high-resolution transmission electron microscopy （HRTEM）, and selected area electron diffraction （SAED）. The possible growth mechanism was discussed. 2PbCO3·Pb（OH）2 microcrystals were found to be a novel and efficient catalyst for the synthesis of diphenyl carbonate （DPC） by transesterification of dimethyl carbonate （DMC） with phenol. Compared with some other catalysts, such as AlCl3, ZnCl2, and Mg5（CO3）4（OH）2, 2PbCO3·Pb（OH）2 microcrystals are stable and show relatively high activity at low catalyst amount. When the reaction was carried out at 180 12, with a molar ratio of phenol to DMC of 2：1, a reaction time 14 h, and a catalyst amount 0.2% （molar ratio to phenol）, the selectivity of DPC and methyl phenyl carbonate （MPC） was 14.7% and 78.8%, respectively.

Effect of Zr-doping on Pd/CexZr1-xO2 catalysts for oxidative carbonylation of phenol

Ce–Zr solid solution(CexZr1-xO2,CZO)was prepared by the citric acid sol–gel method.The CZO was then used as a support for Pd/CZO catalysts for the oxidative carbonylation of phenol to diphenyl carbonate.The Pd/CZO catalyst showed enhanced activity and diphenyl carbonate selectivity compared with the Pd/CeO2 catalyst.The catalytic performance of Pd/CZO was influenced by the calcination temperature of the CZO support.X-ray diffraction,scanning electron microscopy,N2 adsorption–desorption measurements,X-ray photoelectron spectroscopy and H2 temperature-programmed reduction measurements were used to investigate the effects of Zr doping and calcination temperature.The catalytic performance of Pd/CZO and Pd/CeO2 for the oxidative carbonylation of phenol was affected by several factors,including the specific surface area,Ce^3+and/or oxygen vacancy content,oxygen species type and Pd(II)content of the catalyst.All these properties were influenced by Zr doping and the calcination temperature of the CZO support.

Magnesium Acetate Used as an Effective Catalyst for Synthesizing Aliphatic Polycarbonates via Melt Transesterification Process

High-molecular-weight aliphatic polycarbonates（APCs） were synthesized through a two-step transesterification process under solvent-free conditions. Oligomers with equal numbers of hydroxyl and phenyl carbonate terminal groups could be easily controlled by using equimolar amounts of diphenyl carbonate（DPC） and aliphatic diols as feedstocks in the first step. In the second step, the high-molecular-weight APCs can be obtained by connecting -OH with -OC（O）OC6H5 end-group upon removing the generated phenol at reduced pressure. Mg（OAc）2 was found to be the best catalyst for this process among the screened catalysts, which gave the poly（l,4-butylene carbonate）（PBC） a weight-average molecular weight（Mw） of 148600 and a yield of 84.8% under its suitable reaction conditions. In addition, based on the results of X-ray diffraction（XRD）, scanning electron microscopy（SEM） and fourier transform infrared spectroscopy（FTIR）, a possible reaction mechanism over Mg（OAe）2 was proposed for APCs synthesis.

Structure-Activity Correlations of Calcined Mg-Al Hydrocalcites for Aliphatic Polycarbonate Synthesis via Transesterification Process

Mg-A1 mixed oxides with different Mg/A1 molar ratio were prepared by thermal decomposition of hydrotalcite- like precursors at 500 ℃ for 5.0 h and used as catalysts for the transesterification of diphenyl carbonate with 1,4-butanediol to synthesize high-molecular-weight poly（butylene carbonate） （PBC）. The structure-activity correlations of these catalysts in this transesterification process were discussed by means of various characterization techniques. It was found that the chain growth for the formation of PBC can only be obtained through connecting -OH and -OC（C）OC6H5 end-group upon removing the generated phenol, and the sample with Mg/A1 molar ratio of 4.0 exhibited the best catalytic performance, giving PBC with Mw of 1.64 × 105 g/mol at 210℃ for 3.0 h. This excellent activity depended mainly on the specific surface area and basicity rather than pore structure or crystallite size of MgO.

Synthesis of Poly(isosorbide carbonate) via Melt Polycondensation Catalyzed by Ca/SBA-15 Solid Base

Ca/SBA-15 solid bases with different Ca/Si atomic ratios were prepared by a one-pot route and employed as catalysts for the production of poly（isosorbide carbonate） （PIC） from diphenyl carbonate and isosorbide via a transesterification polymerization process. The relationship between physicochemical properties and catalytic performance for Ca/SBA-15 in this melt process was investigated by means of various characterization techniques. It was found that basic site amount and strength were responsible for this transesterification process; the weak and medium basic sites inclined to promote polycondensation reaction. It was worth noting that strong basic sites could favor the decomposition of the resultant P/C, resulting in the decrease of weight-average molecular weight （Mw） and yield, and the sample with Ca/Si atomic ratio of 0.4 exhibited the best catalytic performance, giving PIC with Mw of 4.88 × 10^4 g/mol and Tg of 169 ℃ at the optimal conditions. This excellent activity can be ascribed to the presence of rich basic sites and specific basic strength on the surface of 0.4Ca/SBA-15.