5-Methyl-3-vinyl-2-oxazolidinone–Investigations of a New Monomer for Kinetic Hydrate Inhibitor Polymers

Malcolm A. Kelland,Hiroharu Ajiro,Erik G. Dirdal,Radhakanta Ghosh

doi:10.1021/acs.energyfuels.1c04417

Abstract

Kinetic hydrate inhibitors (KHIs) are polymers used in a chemical method to prevent gas hydrate plugging of oil and gas production flow lines. The main ingredient in a KHI formulation is one or more water-soluble amphiphilic polymers. Several classes of KHI polymers contain pendant heterocyclic 5-rings including poly(N-vinylpyrrolidone) (PVP) and poly(2-isopropenyl-2-oxazoline) (PiPOx). Here, we present a KHI performance study on polymers based on the 5-ring vinylic monomer 5-methyl-3-vinyl-2-oxazolidinone (VMOX), which has only recently been manufactured in large quantities. Low molecular weight PVMOX homopolymers were produced in quantitative yield using radical polymerization, with or without a chain transfer agent. For example, PVMOX-2.4k (Mn = 2400 g/mol) had a cloud point at 2500 ppm of 73 °C in deionized water. The polymers were screened for KHI performance using slow constant cooling tests (1.0 °C/h) in high-pressure rocking cells with a synthetic natural gas blend. At 2500 ppm, PVMOX-2.4k gave a better performance than PVP or PiPOx at a similar molecular weight but not as good as poly(N-vinylcaprolactam) (PVCap). Isobutyl glycol ether was shown to enhance the KHI performance of PVMOX. PVMOX gave improved performance with increasing concentration but not as steep of an improvement as some of the best amide-based KHI polymers. A 1:1 copolymer of VMOX with N-vinylcaprolactam gave improved performance compared to the PVMOX homopolymer.

Highlights

Gas hydrate plugging of flow lines from gas or oil fields is one of the most serious production issues to manage.[1−5] There are several chemical methods to use to avoid this problem, and one of them is the deployment of kinetic hydrate inhibitors (KHIs) which are a subgroup of low dosage hydrate inhibitors (LDHIs).[6−17] KHIs delay particle growth whether as subcritical size particles or as crystal growth inhibition.[18]
We carried out the same reaction but with added chain transfer agent (CTA) 3-mercaptopropionic acid to give a lower molecular homopolymer (PMVOX-2.4k) that analyzed as Mn = 2400 g/mol (PDI = 2.9)
The cloud point in varying sodium chloride salinities was investigated for PVMOX-2.4k (Figure 8)

Summary

■ INTRODUCTION

Gas hydrate plugging of flow lines from gas or oil fields is one of the most serious production issues to manage.[1−5] There are several chemical methods to use to avoid this problem, and one of them is the deployment of kinetic hydrate inhibitors (KHIs) which are a subgroup of low dosage hydrate inhibitors (LDHIs).[6−17] KHIs delay particle growth whether as subcritical size particles (nucleation inhibition) or as crystal growth inhibition.[18]. We report the first KHI performance study on the PVMOX homopolymer as well as the VMOX statistical copolymer with VCap. These were carried out in five parallel high-pressure rocking cells placed in a thermally controlled water bath, part of a rig supplied by PSL Systemtechnik, Germany (Figure 5).[23−25] A synthetic natural gas (SNG) blend was used (Table 1). The t test is a well-known statistical method to evaluate if there is a significant difference between two sets of data, which, in our case, can help rank the KHIs.[27] A p-value is calculated, usually by software A p-value of less than 0.05, between two sets of To values, indicates a 95% confidence that the performance of one KHI is better than another

■ RESULTS AND DISCUSSION

15 VMOX:VCap

■ CONCLUSION

■ REFERENCES