Amination of alcohols, using Cu/Ni-based colloidal catalyst, for consecutive reaction system

Animation of dodecyl alcohol and monomethylamine (MMA, di-functional) using Cu/Ni-based colloidal catalyst stabilized by barium stearate, and its kinetic study were performed to effectively synthesize didodecylmethylamine (DDMA). For the initial 3–4 h when MMA/dodecyl alcohol mole ratio was less than 1, the amination reaction proceeded very fast (72 mole-alcohol h^-1 mole-Cu at 200 °) by zero-order kinetics to directly produce DDMA (85%), with complete consumption of MMA, without liberation of the intermediate, momomethyldodecylamine (MMDA) at all. Then, immediately after the mole ratio exceeded 1, the amination proceeded very slowly (3.4 mole-alcohol h^-1 mole-Cu) by consecutive mechanism (second order) with liberation of MMDA. Aldolization of dodecyl aldehyde, formed by dehydrogenation of dodecyl alcohol, was found to be catalyzed by methylamines. Maintaining the zero-order kinetics by continuous control of MMA/alcohol mole ratio at less than 1 through out the amination is essential to obtain a highest DDMA yield by preventing the unwanted aldolization and transalkylation of MMA leading to various byproducts. Catalytic activity of the colloidal catalyst was sevenfold active than that of corresponding solid ones. Amination of 1,6-hexanediol and dimethylamine, using the colloidal catalyst and liquid paraffin as a solvent, was proceeded by consecutive mechanism to form N,N,N,N-tetramethyl-l,6-hexamethylenediamine with an yield of 80%.     

脂肪醇制备叔胺的新型催化剂的最新进展

对采用脂肪醇和二甲胺一步胺化制备(得率100%)相应的叔胺(烷基二甲基叔胺)的新型催化剂的最新进展进行了论述,对高活性Cu/Ni/Ca/Ba-St胶体催化剂(Cu0/Ni0/Ca0的比为5∶1∶1)和不含镍的Cu/La2O3进行了讨论。由此得出结论:要达到定量制备的关键因素是,通过结合还原钙或更活泼的促进剂,如Ce0和La0,尽可能地增加催化体系的氢解活性,由此形成金属氢化物,在铜/镍的作用下产生活性氢的“自供体系”。这一就地形成金属氢化物的基本功能将可极大地减少催化剂的用量,使铜质量分数减少到2×10-3%,从而极大地降低二甲胺的歧化,增加目的叔胺的选择性。总的来说,观察到在铜/镍固体催化剂以及胶体催化剂作用下,活性氢自供体系的基本功能使充入的大量氢一点都不被消耗掉。     

Cu/Ni colloidal dispersions stabilised by calcium and barium stearates for the amination of oxo-alcohols

Bimetallic Cu/Ni colloidal dispersions (the core catalyst) stabilised by a combination of calcium and barium stearates as protective colloids (catalyst C) showed a remarkable catalytic activity-several times higher than that of the core catalyst stabilised by barium stearate only (catalyst A) for the amination reaction of low reactive oxo-alcohols, having steric hindrance by branched alkyls, with dimethylamine to prepare N,N-dimethyl tertiary amines. Application of the catalyst C for the same amination reaction of dodecyl alcohol could be performed at a lower catalyst concentration of even 100 ppm based on copper at 220° C with a tertiary amine yield of 92% in a three hours' reaction. The reaction mixture containing catalyst C formed a gel at room temperature and formed a stable homogeneous solution with acetone as a polar solvent. It is postulated that water-repellency of calcium stearate and further incorporation of barium stearate as a second promoter yields a doubly stabilised structure for the core catalyst resulting in a remarkable increase in catalytic activity.     

Evidence for the migration of ZnOx in a Cu/ZnO methanol synthesis catalyst

The behavior and role of ZnO in Cu/ZnO catalysts for the hydrogenations of CO and CO₂ were studied using XRD, TEM coupled with EDX, TPD and FT-IR. As the reduction temperature increased, the specific activity for the hydrogenation of CO₂ increased, whereas the activity for the hydrogenation of CO decreased. The EDX and XRD results definitely showed that ZnO _x (x = 0–1) moieties migrate onto the Cu surface and dissolve into the Cu particle forming a Cu-Zn alloy when the Cu/ZnO catalysts were reduced at high temperatures above 600 K. The content of Zn dissolved in the Cu particles increased with reduction temperature and reached 18% at a reduction temperature of 723 K. The CO-TPD and FT-IR results suggested the presence of Cu⁺ sites formed in the vicinity of ZnO _x on the Cu surface, where the Cu⁺ species were regarded as an active catalytic component for methanol synthesis.     

Ni/ADM: a high activity and selectivity to C2+OH catalyst for catalytic conversion of synthesis gas to C1-C5 mixed alcohols

In the present paper alkali-doped molybdenum sulfide (ADM) catalysts modified by Ni were prepared and Ni promoter showed an effective promotion on the activity and C₂₊OH selectivity. At Ni:Mo molar ratio of 0.5, the percentage of methanol decreased sharply from 53(C-atom) to 11(C-atom) and the ratio of C₂₊OH/C₁OH reached the maximum (8.75), which was about 10 times compared with that of traditional ADM catalyst (0.87). Calculation revealed that the additions of Ni caused the apparent activation energies for C_1–3 alcohols decreased, especially for ethanol. The great deviation of methanol from the linear A-S-F distribution indicated a different reaction route which might caused by the bi-functionality of nickel, namely, the formation of corresponding precursor of alcohol (CH_x) and the strong ability of CO insertion. Characterization suggested that such a promotion was closely related to the structure of nickel of the catalyst, the simultaneous presences of aggregated particles and high-dispersed Ni.