Stereoselective hydrogenation of tert-butylphenols over charcoal-supported rhodium catalyst in supercritical carbon dioxide solvent (original) (raw)
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Industrial & Engineering Chemistry Research, 1988
T h e kinetics of the stereoselective liquid-phase hydrogenation of 2-tert-butylphenol to cis-and trans-2-tert-butylcyclohexanol were investigated over nickel, cobalt, and ruthenium catalysts in the hydrogen pressure rarige of 10-100 bar and at temperatures up to 200 "C. Time-conversion diagrams show a consecutive competitive reaction behavior with a pressure-dependent selectivity of intermediate 2-tert-butylcyclohexanone. At temperatures below 200 O C , with increasing H2 pressure, an increasing fraction of 2-tert-butylcyclohexanol is formed, apparently direct from the phenol omitting the ketone step (shunt reaction). A modified Langmuir-Hinshelwood-type model is presented based on nonequilibrium adsorption of the ketone. The pressure-dependent ketone selectivity, the extent of the shunt hydrogenations, and the kinetics of establishing the isomeric equilibrium for 2-tert-butylcyclohexanol can be described quantitatively. Since the model includes the thermodynamical restrictions of the reaction system, it can also be used under reversible conditions. Most of the characteristic features of the catalytic hydrogenation of alkylphenols over a large number of catalysts (nickel, cobalt,
Stereoselective hydrogenation of p-tert-butylphenol over supported rhodium catalyst
Journal of Molecular Catalysis A: Chemical, 2002
p-tert-Butylcyclohexanol is used as an intermediate for manufacturing esters with lower carboxylic acids, which are important in perfumery, soap and detergents manufacturing. Stereoselective hydrogenation of p-tert-butylphenol (PTBP) to cis and trans-p-tert-butylcyclohexanol (PTBCH) has been carried out by using supported metal catalysts such as rhodium supported on carbon (2% Rh/C), Raney nickel, nickel supported on silica (20% Ni/SiO 2), and palladium supported on carbon (5% Pd/C). Among the variety of catalysts used 2% Rh/C exhibited 100% conversion of PTBP and 100% selectivity of the cis-isomer of PTBCH when methanesulphonic acid was used as the co-catalyst. The reaction was 100% selective towards the product. The effects of various parameters on the rates of reaction were studied systematically and a kinetic model was built. The reaction was found to be kinetically controlled. The formation of cis-isomer was explained theoretically.
Catalysis Communications, 2009
Hydrogenation of 4-alkylphenols was studied over a carbon-supported rhodium catalyst in supercritical carbon dioxide (scCO 2) solvent, and the results were compared with those in 2-propanol. Higher selectivities to cis-4-alkylcyclohexanols were obtained in scCO 2 than in 2-propanol for the hydrogenation of all 4alkylphenols tested. In addition, the formation of alkylcyclohexane (dehydroxylated product) was suppressed in scCO 2. Stereoselectivities to cis forms were further improved in the presence of hydrochloric acid.
Hydrogenation of 2- tert -butylphenol over Ni catalyst
1999
The hydrogenation of 2-tert-butylphenol was studied in regard to possibilities of influencing selectivity, namely the ratio of c/s-and trans-isomers of 2-tertbutylcyolohexanol in the final reaction mixture. The hydrogenation reactions were carried out using the catalyst Ni/AI20~ During the hydrogenations, a higher content of the eis-isomer was attained, when simultaneously the final reaction mixture contained 2-tert-butylcyclohexanone. The content of this intermediate, which primarily hydrogenated to the cis-isomer, increased with a decreased pressure and after the addition of acetic acid into the reaction mixture.
Gas-phase hydrogenation of 4-tert-butylphenol over Pt/SiO2
Journal of Catalysis, 2004
Gas-phase hydrogenation of 4-tert-butylphenol (4-TBP) over 1% Pt/SiO2 to cis and trans 4-tert-butylcyclohexanol (4-TBCHOL), via the intermediate 4-tert-butylcyclohexanone, was studied in a differential reactor at atmospheric pressure and at temperatures between 127 and 227 °C. The formation of by-products due to hydrogenolysis played an important role in the reaction at temperatures over 200 °C. The rates of 4-t-butylcyclohexanol and 4-t-butylcyclohexanone formation passed
Journal of Molecular Catalysis, 1986
The solvated ion pair [(CsHi7)sNCH3]+[RhClJ, formed from aqueous rhodium trichloride and Aliquat@-336 in a two-phase liquid system, was shown to hydrogenate a&unsaturated ketones and esters selectively at the CC double bonds. The reduction of benzylideneacetophenone was found to follow first-order kinetics in the substrate only below 0.2 M, and to approach second-order in HZ at partial pressures of <0.12 atm. The catalysis also proved to depend on the nature of the solvent, the phase transfer catalyst and the stirring rate. The observed activation energy E, = 12.4 kcal mol-l suggests that the process is both chemically and diffusion controlled.
An Updated Comprehensive Literature Review of Phenol Hydrogenation Studies
Catalysis Letters, 2021
Cyclohexanone is an important industrial intermediate to produce nylons. The main industrial routes for cyclohexanone manufacture used cyclohexane and phenol as feedstock. The selective hydrogenation of phenol to cyclohexanone comprises one-step and two-step processes. This review presents a detailed analysis of the research findings available in the open literature for phenol hydrogenation to produce cyclohexanone and cyclohexanol and covers the research conducted during 2014-2020 using conventional and modern catalysts. This review aims to disseminate the knowledge of the current research conducted for phenol hydrogenation and provide a comprehensive resource for researchers working in this field. This review has included and discussed both methods of thermocatalytic and electrocatalytic hydrogenation of phenol. Most of the studies have used carbon or carbon-nitrogen supported catalysts loaded with Pd. The carbon and carbon-nitrogen materials were derived from different sources including polymers, activated carbon, and MOF. Oxygen treatment was found to produce highly active and stable catalysts. The high performance was found associated with the high surface area of the catalyst and uniformly dispersed metal nanoparticles. The acidic conditions exhibited an increase in catalyst performance. Alkali-promoted precious metal-loaded catalysts performed better than un-promoted catalysts.
Catalytic Hydrogenation of 2-Butyne-1,4-diol: Activity, Selectivity and Kinetics Studies
Journal of the Japan Petroleum Institute, 2008
The reaction pathway for hydrogenation of 2-butyne-1,4-diol involves parallel and consecutive isomerization as well as hydrogenation reactions forming other side products along with cis-2-butene-1,4-diol and butane-1,4-diol. Hence, achieving the highest selectivity to butene-and/or butanediol is critical from industrial point of view. Hydrogenation of butynediol is also of fundamental significance, due to its adsorption characteristics leading to the formation of active species and their role in determining the product distribution. Studies on designing various catalyst systems including colloidal as well supported palladium nanoparticles for the hydrogenation of butynediol, role of additives, catalyst pretreatment, kinetic studies carried out in our group has been presented in this review. Interestingly, almost complete selectivity to the intermediate olefinic diol was achieved with 1％ Pd/CaCO3 _ NH3 catalyst system. This could be due to the competitive adsorption of ammonia on the palladium surface along with the substrate 2-butyne-1,4-diol. Studies on catalyst pretreatment and kinetics using palladium catalyst have also been presented here. Nanostructure palladium both colloidal as well as supported catalysts showed a very high catalytic activity (10-40 times more) in the hydrogenation 2-butyne-1,4-diol to cis-2-butene-1,4-diol compared with the corresponding conventional Pd catalysts. For platinum based catalysts, formation of side products was completely eliminated in the hydrogenation of butyne diol. The increase in the basic strength of alkali metal doped Pt catalysts measured by CO2-TPD, led to the increase in electron density of Pt hence, faster desorption and higher selectivity to butenediol. In the case of continuous hydrogenation, the selectivity pattern was completely different from that found in the case of batch slurry reactor and by varying the contact time, the selectivity to both butene-and butanediols could be varied over a wide range of conditions.
Selective Hydrogenation of 2-Butenal Using Cluster of Clusters-Based Catalysts
Journal of Catalysis, 1996
Complex cobalt-carbonyl ligand clusters of clusters are used as well defined molecular precursors for self-supported single metal or bimetallic catalysts. These precursors incorporate two metals: an outer layer formed from the complex cobalt cluster carbonyl ligands [(CO) 9 Co 3 CCO 2 ] and an inner core of the metal carboxylate cores. Two types of precursor structures are used: one with two metal atoms in the core (designated as M 2 Co 12 , where M = Co, Cu, and Mo) and the other with four metal atoms in the core bonded to a centering oxygen atom (designated as M 4 Co 18 , where M = Co and Zn). The catalysts are prepared in situ by partial thermolysis (LT catalysts) or complete thermolysis (HT catalysts) of the cluster of clusters precursors. The catalysts derived from Co 4 Co 18 , Zn 4 Co 18 , Co 2 Co 12 , Mo 2 Co 12 , and Cu 2 Co 12 precursors are used in the selective hydrogenation reaction of 2-butenal. The desired product of the reaction is the thermodynamically less favored unsaturated alcohol (2-butenol). The highest 2-butenol selectivity observed was 100% over HT-Co 2 Co 12 catalyst at 373 K. The highest 2-butenol yield observed in our experiments was ≈ 28% using HT-Co 4 Co 18 at 423 K. The activity and selectivity behavior of HT-Co 4 Co 18 was stable over at least 50 h of operation. The factors affecting 2-butenol selectivity and yield during 2-butenal hydrogenation using these catalysts are discussed.