Abstract
Polymerization of isobutylene (IB) for synthesizing highly reactive polyisobutylene (HRPIB) is characterized by a complicated fast intrinsic reaction rate; therefore, the features of its products exhibit a strong dependence on mixing efficiency. To provide uniform and efficient mixing, a rotating packed bed was employed as a reactor for polymerization of IB. The effects of operating parameters including polymerization temperature (T), rotating speed (N) and relative dosage of monomers and initiating systems ([M]0/[I]0) on number-average molecular weight (Mn) of HRPIB were studied. HRPIB with Mn of 2550 g·mol−1 and exo-olefin terminal content of 85 mol% were efficiently obtained at suitable conditions as T of 283 K, N of 1600 rpm and [M]0/[I]0 of 49. Moreover, the Mn can be regulated by changing T, N and [M]0/[I]0. Based on the presumptive-steady-state analysis method and the coalescence–redispersion model, a model for prediction of the Mn was developed and validated, and the calculated Mn values agreed well with experimental results, with a deviation of ±10%. The results demonstrate that RPB is a promising reactor for synthesizing HRPIB, and the given model for Mn can be applied for the design of RPB and process optimization.
Highlights
Polyisobutylene (PIB), the product of isobutylene (IB) polymerization, is an important organic polymer with excellent low gas permeability and high chemical stability, and it can be applied in many fields, such as oil additives, adhesive agents, sealants, paint and lubricants [1]
The difficulty lies in that the rate constants of propagation in the cationic polymerization of alkenes are similar for most systems with kp = 105±1 L·mol−1 ·s−1 [8,9], which means that the cationic polymerization of IB is featured with an extremely fast intrinsic reaction rate
Scribe the micromixing in rotating packed bed (RPB), a chain analysis method was used to develop a mathematThe molecular weight (Mn ) of the polymerization products was determined by the ical model for simulating the cationic polymerization process in RPB and predicting the Waters 5151–2410 GPC instrument equipped with three Styragel GPC columns
Summary
Polyisobutylene (PIB), the product of isobutylene (IB) polymerization, is an important organic polymer with excellent low gas permeability and high chemical stability, and it can be applied in many fields, such as oil additives, adhesive agents, sealants, paint and lubricants [1]. The rate of the mass transfer between gas and liquid in RPB is one to three orders of magnitude larger than that in a conventional packed bed reactor [22,23,24,25,26,27]. The value of tm in RPB is estimated as 0.01 to 0.1 ms [28], which corresponds to the t1/2 of the cationic polymerization In terms of these unique features, RPB has been successfully applied to efficiently obtain butyl rubber with Mn of 289,000 g·mol−1 via cationic copolymerization of isobutylene and isoprene, and the production capacity per unit equipment volume increases by two to three orders of magnitude [17,29]. A theoretical model for prediction of Mn was developed, and the theoretical values were compared with the experimental values
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