Taiseki Kunugi

Hydrogenation of adsorbed carbon monoxide on supported platinum group metals

Hydrogenation of adsorbed carbon monoxide on supported platinum group metals was studied by in situ ir spectroscopy and reactive temperature-programmed desorption (RTD) methods using hydrogen as a carrier gas. The main product of the hydrogenation was methane. The RTD gave spectra for methane formation which showed peaks between 423 and 650 K depending on the metals. On alumina-supported metals the temperature of maximum methane formation was in the following order: Ru(420K) approx. = Rh(420K) < Pd(490 K) < Pt(560 K) < Ir (600 K). It agreed well with the order of catalytic activity for the hydrogenation of carbon monoxide, which had been referenced elsewhere. The ir spectra of the bridge, linear, and twin types of adsorbed CO were observed on Rh/Al/sub 2/O/sub 3/ or Ru/Al/sub 2/O/sub 3/. On both samples the bridge CO was hydrogenated at lower temperature than the linear CO to form hydrocarbons consisting mainly of methane. The twin CO on Rh/Al/sub 2/O/sub 3/ desorbed without being hydrogenated. Some adsorbed hydrocarbon species were observed on Ru/Al/sub 2/O/sub 3/ during hydrogenation. Adsorbed CO reacted easily with H/sub 2/O in the gas phase to form CO/sub 2/. 8 figures, 2 tables.

Oxychlorination of propylene on supported palladium and other platinum group metal catalysts

Oxychlorination of propylene was studied on platinum groups metal catalysts. Main product was allyl chloride on all catalysts studied. The catalylic activity was in the following order: Rh > Pd > Pt > Ir . Ru. Details of the reaction were studied on palladium catalysts. By-products were isopropyl chloride, 1,2-dichloropropane, chloropropenes and carbon dioxide. Isopropyl chloride and 1,2-dichloropropane were formed parallel to allyl chloride and major part of carbon dioxide was formed successively from allyl chloride. Among others active charcoal was the best support for the palladium catalyst. The high efficiency of active charcoal support is explained by its catalytic action for palladium oxidation. Hydrogen chloride was chemically adsorbed on the catalyst in the presence of oxygen and a significant amount of palladium chloride was formed during the reaction. The concentration of palladium chloride under working conditions was measured by a novel method. The PdCl 2 concentration reached a steady state, which was controlled by the feed composition. On a fully chlorinated palladium catalyst little allyl chloride was formed and 1,2-dichloropropane was formed instead. Allyl chloride was considered to be formed through a reaction of π-allyl species of propylene on the reduced palladium with the chlorides of palladium.

Selective decomposition of isobutylaldehyde to propene, carbon monoxide and hydrogen

Abstract Supported palladium modified with sodium sulphide was an excellent catalyst for the selective decomposition of iso-butylaldehyde (IBA) to its feed stocks, propene and oxo gas. The catalyst gave about 90% conversion and 99% propene selectivity at 350°C and under atmospheric pressure. The sulphide ion suppressed propene hydrogenation and promoted CO desorption from the catalyst.

Oxidation of olefins with mercuric salts-active charcoal catalysts

Abstract Catalytic reactions of olefins with mercuric salts supported on active charcoal in the presence of oxygen and steam yield unsaturated carbonyl compounds as major products. For proceeding the reaction catalytically, the active charcoal treated with nitric acid was essential as a carrier. The comparison with homogeneous oxymercuration on the kinetics, product distributions and reactivities of olefins suggested that the heterogeneous reactions proceed through each σ-complex and σ-allyl complex.

Effect of Transition Metal lons on Cyclohexene Formation over Zeolite Catalyst

Oxidative dehydrogenation of cyclohexane was investigated at 180. v2900C over several kinds of X, Y and mordenite type zeolites of which Na were ion exchanged with transition metal ions. The: metal ions employed in this study were Cr(III), Cr(III), Fe(III), Co(III), Cu(1), Cu(III)and Tl(1). This reaction was observed over Na and Cq type Y zeolite catalysts, but carbon. dioxide was fermed in preference to cyclohexene or benzene. Oxidative dehydrogenation was.., . accelerated by exchange with the transition metal ions, especially by Fe(III), which were found to adsorb oxygen. The catalysts exchanged with the other metal ions showed a similar catalytic action as of Na type Y zeolite with rather lower activity. A pretty good selectivity with respect to partial dehydrogenatfon of cyclohexane to cyclohexene was obtained, in the presence of steam, over X and Y type zeolites exchanged with Fe(III)io s. Mordenite catalysts showed no catalytic activity for this reaction. The Fe(II)X catalyst was the most excellent of all catalysts used in this study, and the selectivity for dehydrogenation of cyclohexane to cyclohexene and benzene was increased with an increase in the degree of ion exchange, while combustion reaction was decreased.

Oxidation of Palladium during the Olefin Oxidation over Palladium Salts-Active Charcoal Catalysts

Oxidation of reduced palladium on active charcoal during the ethylene oxidation over palladium salts-active charcoal catalysts was studied. Effect of oxygen pressure on the reaction rate was determined from the rate of oxygen adsorption using the apparatus with constant volume and constant pressure equipment. Effect of oxygen pressure became evident only when its value was very little.If we assume that the over-all reaction rate is determined in terms of the dynamic equilibrium between the oxidation of ethylene by palladium salts and the re-oxidation of reduced palladium compounds by oxygen, the conclusion, that the rate of re-oxidation is represented by the equation (01), can be derived from the analysis of experimental results, where K is the dissociative adsorption constant of oxygen. This suggests that the reduced palladium is oxidized by oxygen which is dissociatively adsorbed on active charcoal.In the equation (01), κ2√K which is the measure of the re-oxidation activity, was found to vary with temperature, ethylene pressure and anions. The order of re-oxidation activity of palladium salts was Pd(NO3)2>PdCl2>PdSO4 under the same reaction condition.

Catalytic Synthesis of Vinyl Acetate with Palladium Salt-Active Charcoal Catalysts.

活性炭に吸着させたパラジウム塩を触媒とし,気相でエチレン,酸素および酢酸から酢酸ビニルの合成反応を行なった。銅塩等の助触媒が存在しなくても活性種はパラジウム塩であった。これはアセトキシ化反応により還元されたパラジウムが活性炭の触媒作用により酸素で再び酸化されるためと考えた。反応活性はPd(NO3)2>PdCl2>Pd(OAc)2>PdSO4の順であったが酢酸ビニルの選択性はPd(OAc)2>Pd(NO3)2>PdCl2>PdSO4の順であった。パラジウムに換算して1wt%を担持したPd(OAc)2-AC触媒についてつぎの結果を得た。135℃,接触時間:100(g-cat・hr/mol),モル比C2H4 5:O2 2:AcOH5でエチレン反応率19%酢酸ビニル選択率53%,アセトアルデヒド選択率39%。アセトアルデヒドは酢酸ビニルから逐次的に生成した。アセトキシ化反応のみかけ活性化エネルギーは10～15kcal/mol,二酸化炭素生成のそれは25kcal/molであった。

Hydrogenation of Carbon Monoxide with Iron Catalyst in the Slurry Phase

重量比で100Fe:0.3Cu:0.6K2CO3なる組成の沈殿鉄触媒を1μ程度の微粒子として重質フィッシャー合成油中に懸濁せしめ,200～250℃,3～10kg/cm2・GでCO/H2モル比1.3～1.5の合成ガスを吹き込んで気液固流動床を構成し,一酸化炭素の水素化重合による炭化水素の合成を行なった。同じ触媒を用い固定床で反応を行なった場合と違って,気液固流動床では反応初期の活性低下がなく,しかも活性は固定床の初期活性に近い値を持続する。また見掛け活性化エネルギーは5～7kcal/molと固定床での約20kcal/molに比して小さく,またメタンの生成率も非常に少なかった。このような差異は両反応形式における律速段階の違いと触媒層の局部過熱の多少にもとづくものと推論される。すなわち,固定床では表面反応律速として反応が進むのに対し,気液固流動床では一酸化炭素が触媒表面に吸着するまでの過程が律速であり,触媒表面の一酸化炭素濃度が小さいので触媒は炭化されずに高活性を持続し,また微粒の触媒が油中に懸濁していて局部過熱が少ないのでメタンの生成率が小さくなるものと考えらる。

Radical Copolymerization of Ethylene and Carbon Monoxide

エチレンと一酸化炭素のラジカル共重合を,オートクレーブ中でシクロヘキサンを溶媒とし,過酸化ジ-tert-ブチルを開始剤として,135～170℃,120～265kg/cm2,CO/(CO+C2H4)モル比0.10～0.68で行なった。重合物は一般式〓(C2H4)m-C=O〓nであらわされ,“ポリケトン”とよばれている。CO/(CO+C2H4)モル比であらわした重合物の組成はすべて0.5以下であった。アゼオトロープ組成は135℃,150～200kg/cm2では約0.42,160℃,150～200kg/cm2では約0.32であった。反応機構として従来提出されているCoffmanらの説およびBarbの説を,重合物の組成の点から検討した結果,エチレン-一酸化炭素モル比1:1の中間体を仮定するBarbの説を支持する結果が得られた。また各重合物のNMRスペクトルから,-C=O-基に対しα位,β位,またはγ位以上の各炭素原子に結合する水素原子の量比が求まり,これから“ポリケトン”の一般式におけるmの値の分布を求めることができた。