Polymer-alumina dually supported palladium catalysts (PVP-Pd/Al2O3, PVP = poly(N-vinyl-2-pyrrolidone); PPPO-Pd/ Al2O3, PPPO = phosphinated poly(phenylene oxide)) were used to catalyze the carbonylation of allyl halides to form butenoic acid under the mild conditions of 40C and 0.1 MPa. These catalysts exhibit high activity and stability towards the carbonylation of allyl halides. The maximum turnovers (mol CO/mol Pd) of PPPO-Pd/Al2O3 are up to 8.2×105 and 4.6×105 for the carbonylation of allyl bromide and allyl chloride respectively in an aqueous NaOH/benzene medium. 相似文献
Vapor phase carbonylation of ethanol with Ni/C and Ni-Zn/C catalyst was investigatedunder atmospheric pressure.Ni-Zn/C was found to have a significantly higher activity andselectivity than Ni/C.Effects of Zn and Ni loading on ethanol conversion and productdistributions were also investigated,and the sequence of metal loading was compared.The cata-lyst was characterized by XRD(X-ray diffraction)and SEM-EDS.The spectra of XRDdemonstrated that the catalyst structure was changed from crystalline to non-crystalline in theprocess of carbonylation.Stable iodide compound was formed due to the interaction betweenC_2H_5I and active metals.The authors believe that the active phase of carbonylation might havebeen non-crystalline. 相似文献
Carbonylation of 1‐(4‐isobutylphenyl)ethanol has been studied using a homogeneous catalyst system consisting of PdCl2(PPh3)2/ TsOH/ LiCl. Higher reaction rates with TOF up to 1200 h−1 and ibuprofen selectivity >95% have been achieved at 388 K under a CO partial pressure of 5.4 MPa. The reaction proceeds through the formation of 4‐isobutylstyrene and 1‐(4‐isobutylphenyl)ethyl chloride as intermediates. The same catalyst system is shown to be effective for carbonylation of various α-arylethanols, vinyl aromatics and corresponding chloro derivatives. This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
Pd complexes with diimine ligands were investigated as novel Pd catalysts for direct synthesis of diphenyl carbonate by oxidative carbonylation of phenol using carbon monoxide and air. Best efficiency was obtained by using a PdCl2(ArN=CH–)2 or PdCl2(ArN=CMe–)2/Mn(TMHD)3/(Ph3P=)2NBr system where TOF reached 8.08 and 8.00 mol-DPC/mol-Pd h, respectively. The efficiency was increased with increases in the CO pressure. 相似文献
The epoxidation of β-ionone over the Pt/MCM-41 catalyst using molecular oxygen in the liquid phase had been studied. The results
indicated that the β-ionone was catalytically oxidized to 5,6-epoxy-β-ionone, 4-oxo-β-ionone, 4-hydroxy-β-ionone and dihydroactinidiolide
using molecular oxygen as the sole oxidant. The effects of solvent, content of Pt, reaction temperature and time on the catalytic
activity and product selectivity had also been investigated in detail. 相似文献
An efficient palladium nanoparticles-catalyzed N-arylation of sulfonamides and sulfonyl azides is described. This procedure serves as an active protocol for intermolecular C–N bond formation using Pd(OAc)2 in PEG-400 under air. Aryl bromides and triflates react at 35°C, while aryl chlorides require heating to 50°C and give the desired products only in low yields. This reaction proceeds smoothly in acceptable yields using low catalyst loading. 相似文献
The nickel on active carbon (Ni/A.C.) catalysts prepared by a simple chemical vapor deposition (CVD) method showed comparable catalytic activities for the vapor phase carbonylation of methanol to those of the catalysts prepared by impregnating A.C. with nickel nitrate and activating by hydrogen treatment. The CVD method was successfully applied to the in situ catalyst preparation. 相似文献
Aryl α‐diimine derivatives have been used, for the first time, as efficient new ligands for the palladium‐catalyzed oxidative bis‐alkoxycarbonylation reaction of olefins. The most active catalyst was formed in situ from bis(9‐anthryl)‐2,3‐dimethyl‐1,4‐diazabutadiene and palladium(II) trifluoroacetate [Pd(TFA)2]. This catalytic system was able to selectively convert olefins into succinic diesters in good yields (up to 97%) and low catalyst loading (up to 0.5 mol%) under mild reaction conditions [4 bar of carbon monoxide (CO) at 20 °C in the presence of p‐toluenesulphonic acid as additive and p‐benzoquinone as oxidant]. The optimized conditions could be successfully applied to both aromatic and aliphatic olefins, by using methanol, benzyl alcohol or isopropyl alcohol as nucleophiles.
The straightforward in situ synthesized bis(2,6‐diisopropyl)acenaphthenequinonediimine palladium triflate catalyst was generally employed for both the mono‐alkoxycarbonylation of terminal alkynes, and the bis‐alkoxycarbonylation of 1,2‐disubstituted alkynes by using mild reaction conditions [carbon monoxide pressure (PCO)=4 bar, temperature=20 °C]. Utilizing low catalyst loading (down to 0.5 mol%), a variety of propiolic esters were synthesized with good to excellent isolated yields. Most importantly the system was very efficient not only with methanol but also with a range of different alcohols, starting from the less hindered benzyl alcohol to the most hindered ones, such as isopropyl alcohol and tert‐butyl alcohol. In addition, aromatic and aliphatic 1,2‐disubstituted alkynes were converted into maleic acid derivatives, together with an acid‐catalyzed isomerization reaction, showing modest to good selectivity and excellent combined yields. In particular 3‐hexyne showed a satisfactory degree of selectivity for the maleic diesters of methanol and benzyl alcohol, obtaining the corresponding products with good isolated yields.
Various carbonyl compounds have been protected as dithioacetals in very good yields using silica sulfuric acid as a mild, chemoselective catalyst under solvent-free conditions. 相似文献
A direct synthesis of thiolester from carboxylic acids and thiols under mild conditions using cyanuric chloride as an inexpensive and readily available reagent is described. 相似文献
Ni/AC catalysts promoted with or without CeO2 for vapor phase carbonylation of ethanol to propionic acid were tested and investigated by CO chemisorption, XRD and H2-TPR techniques. The catalytic test results showed that the proper amount of CeO2 addition could remarkably enhance the activity and stability of Ni/AC catalyst. The characterization results indicated that CeO2 added can improve the dispersion and metal area of Ni on the catalyst, suppress the sintering of Ni crystallite and benefit the reduction of Ni, which are closely related to high performance of the Ni/AC catalyst promoted with CeO2. 相似文献
By doping of polyaniline (PANI) in PdCl2 aqueous and ethanol solutions the catalysts containing crystalline and colloidal Pd particles of different sizes were prepared. The size of palladium particles present in Pd/PANI catalysts (characterised by SEM and XRD methods) influenced the course of 2‐ethylanthraquinone (eAQ) hydrogenation, a key step in the industrial production of H2O2. The presence of large palladium particles promotes reactions leading to the formation of the so‐termed “degradation products” not capable of hydrogen peroxide formation. This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
The isomerization of 2‐methyl‐2‐pentene has been studied on boron phosphate (BP) catalysts with P/B ratios from 0.8 to 1.6 and at various reaction temperatures and contact times. Double‐bond shift occurs on the compositions with P/B of 1.0 and less, while methyl shifts occur on samples with P/B of 1.2–1.6, demonstrating the presence of strong acidity on the latter solids. Ammonia chemisorption and proton MAS NMR is employed to provide supplementary evidence of the variation in acidity with composition. Although BP of P/B < 1 contains predominantly Lewis acid sites, 2‐methyl‐2‐pentene isomerizes through carbocations, which are formed on the strong Brønsted acid sites on BP with P/B > 1. 相似文献