A Novel Production Route for Nylon‐6: Aspects of Microwave‐Enhanced Catalysis

Abstract

Summary: Microwave irradiation was used for the amidation of a nitrile with an amine with a freshly prepared zirconium-based heterogeneous catalyst. Microwave irradiation selectively heats the catalyst which enhances its activity as compared to conventional heating. The difference between microwave heating and conventional heating disappears when Zr(OH) 4 is used instead of ZrO 2 , indicating a microwaveinduced shift in the hydrolysis equilibrium, i.e. the distribution of ZrO 2 , ZrO(OH) 2 and Zr(OH) 4 , of the zirconium-based catalyst. The catalyst efficiently catalyzes the amidation of valeronitrile with n-hexylamine with conventional as well as with microwave heating. Zr(OH) 4 was also used for the polymerization of 6-aminocapronitrile using conventional and microwave heating. With both heating methods a relatively low molecular weight polymer with a M n of 4000 g/mol was obtained in a sealed vessel, due to the presence of water and ammonia. A post-polymerization step under microwave irradiation, with active removal of water and ammonia shifts M n to 10000 g/mol. Pressure decrease to facilitate water removal resulted in products with higher molecular weights. A pressure reduction to 50 Pa and operation in an argon atmosphere at 230 8C resulted in nylon-6 with a M n of 65000 in rather short reaction times. Lower pressures led to end-biting and evaporation of the volatile e-caprolactam at 230 8C. As a consequence the resulting product has than a much lower molecular weight. The combination of a heterogeneous zirconium based catalyst and microwave heating is promising for process intensification for nylon-6 production.

Phenol (CAS 108-95-2)

“…20,21 A caprolactama obtida é a matéria prima utilizada nas reações de polimerização que levam a formação do nylon 6 (Esquema 12). 22 A nitração do fenol pela metodologia clássica é eficaz, entretanto pouco seletiva, devido a isso há inúmeras metodologias descritas relatando aumento de regioseletividade: catálise via zeólitas, ativação por microondas, uso de ácido nítrico diluído sob catalisadores de transferência de fase entre outros. 26,27 Nitrofenóis podem ser utilizados na síntese de diversos azo compostos.…”

Microwave‐Assisted RAFT Polymerization

“…For many years, microwave heating has been employed to accelerate organic reactions involving small molecules while often simultaneously leading to a reduced occurrence of side reactions 21. Recently, the adoption of microwave heating techniques in polymer chemistry has facilitated rapid polymer synthesis22–27 and post‐polymerization modification 28–31. However, microwave‐irradiation has had somewhat limited application in CRP, and the results often appear inconsistent as a result of widely varying reaction setups.…”

Modelling and Comparative Assessment of Polyamide-6 Manufacturing towards a Sustainable Chemical Industry

“…An example of a possible alternative route is the production of polyamide-6 using 1,3-butadiene and hydrogen cyanide. e initial process description was patented by BASF and further examined by Koning and Meuldijk (56) (92). e process consists of three consecutive steps: hydrocyanation of 1,3-butadiene to adiponitrile, hydrogenation of adiponitrile to 6-aminocapronitrile, and polymerization of 6-aminocapronitrile to polyamide-6, see Figure 4-1.…”