p-Methoxystyrene, a crucial monomer for producing advanced polystyrene resins that resist chemical corrosion, finds extensive applications in the information industry and other sectors requiring durable polymers. Traditional synthesis methods have faced significant challenges, including high costs from expensive reagents like formaldehyde and complex purification steps, as well as prolonged reaction times that hinder large-scale manufacturing. Published techniques, such as those relying on Wittig reactions or multi-step esterifications in batch reactors, not only consume excessive resources but also risk impurity accumulation and unintended polymerization during processing. This has limited commercial viability despite the compound's value as an anti-corrosion material in electronics and coatings.

To address these issues, a revolutionary three-step synthesis process has been developed, focusing on cost-efficiency, scalability, and environmental benefits. The method eliminates common pitfalls by minimizing solvent dependency and introducing a tubular reactor for seamless conversion. In the initial stage, a mixture of p-methoxyacetophenone, alcohol (typically ethanol or propanol), and water undergoes reduction. A selected reducing agent, such as sodium borohydride or potassium borohydride, is added at temperatures of 60-80°C for 4-6 hours to form compound I (α-methyl-p-methoxyphenyl carbinol), achieving yields above 95% with purity exceeding 99% in gas chromatography tests. Molar ratios are optimized to 3-4 moles of p-methoxyacetophenone per mole of reducing agent, 2.5-2.7 moles of alcohol, and 8-9 moles of water, reducing raw material expenses while simplifying purification.

The second phase involves esterification, where compound I reacts with a weak acid catalyst like potassium bisulfate or ammonium bisulfate. This step is conducted at 60-80°C for 1.5-2.5 hours, without additional solvents, to generate a mixture of compounds II and III (ester derivatives). Catalyst addition is carefully controlled at 4-6% by mass of compound I to ensure high conversion rates. Crucially, this intermediate mixture serves as a solvent-free precursor, streamlining the transition to the final synthetic stage and demonstrating a purity of approximately 97% post-processing based on experimental data.

The core innovation lies in step three, where the ester mixture flows at 1.4-2.5 g/min into a tubular reactor—constructed from glass or stainless steel with a tube diameter of 24-50 mm and length of 800-1300 mm. Under vacuum conditions of 4-8 mmHg and heating at 180-200°C, the mixture undergoes thermal elimination in a continuous flow system. This generates p-methoxystyrene (compound IV) while recycling sulfuric acid as a catalyst from the ester decomposition. The tubular design enables non-stop operation and scalability via parallel reactors, overcoming issues like vessel clogging and batch polymerization. Experimental trials confirm yields up to 71.9% with purity levels exceeding 95%, significantly outperforming traditional batch methods.

Key advantages of this process include reduced capital costs by over 30% through elimination of solvents in most steps and higher throughput. For instance, the tubular reactor facilitates direct industrial implementation without downtime, allowing for modular expansion that can boost output exponentially compared to fixed-volume batch tools. Additionally, the method minimizes waste, as catalyst reuse lowers disposal needs and water washing is limited to the reduction phase. Safety enhancements stem from vacuum environments that mitigate spill risks and prevent impurity accumulation. Overall, this sustainable approach paves the way for broader adoption in polymer manufacturing, where p-methoxystyrene is increasingly in demand for next-generation materials.

Robust validation comes from ten experimental cases: variations in reagents, temperatures, and flow rates consistently achieved optimal results, such as a 99.5% purity in compound I and elimination rates above 60% under mild conditions. For example, higher flow rates and reactor dimensions improved yield efficiency without compromising product quality. These findings underscore the method's adaptability for diverse industrial settings and its potential to drive innovation across the chemicals sector.