Process Optimization Study on the Purification of Citral from Litsea Cubeba Oil Using Molecular Distillation Technology
Abstract
This study uses Litsea cubeba oil with an 80.9% citral content as raw material to systematically investigate the effects of molecular distillation process parameters on citral purification. A gas chromatography-mass spectrometry (GC-MS) quantitative analysis method was established using vanillin as an internal standard, yielding a linear regression equation y=0.2243x+0.0545 (r²=0.9994), demonstrating good linearity within a concentration range of 1-7.86 mg/mL. Experimental results indicate that under conditions of scraper film speed at 400 r/min, feed amount at 1 L, material flow rate at 8 mL/min, and cooling water temperature at 10℃, the optimal distillation temperature is set at 55℃ and pressure at 0.18 kPa; under these conditions, citral purity can reach up to 97.2%, with a yield of 77.4%. Further pilot-scale experiments (with a feed amount of 20 L) confirmed the stability of this process, achieving a citral purity of 97.1% and yield of 78%. This research provides reliable technical support for the industrial high-value utilization of Litsea cubeba oil.
Introduction
Litsea cubeba is an important aromatic plant resource in China, widely distributed in regions south of the Yangtze River such as Sichuan, Hunan, Fujian, and Guangxi provinces. The essential oil extracted from its fruits through steam distillation contains rich amounts of citral typically ranging between 60%-80%, with some high-quality materials exceeding over 90%. As an important flavoring compound composed mainly by cis-citral (neral) and trans-citral (geranial), it has extensive applications in food products, pharmaceuticals, and daily chemicals. In food industry applications, high-purity citral serves not only as a natural flavor enhancer for candies, baked goods, and seasonings but also acts as a natural preservative due to its significant antibacterial activity against various foodborne pathogens and spoilage bacteria—effectively extending shelf life. In medicine, citral is crucial for synthesizing key drugs like vitamins A and E. Moreover, it serves as foundational raw material for producing high-value fragrances such as violet ketone or methyl violet ketone in fragrance industries. Traditional separation methods like steam distillation or solvent extraction face challenges including high energy consumption, solvent residues, and low product purity levels.Molecular distillation represents new short-path distillation technology characterized by low operating temperatures, a brief heating duration, and high separation efficiency—especially suitable for separating heat-sensitive substances.This study systematically optimizes molecular distillation parameters, establishing an efficient, green purification process for extracting citral from Litsea cubeba oil while providing technical references for related industrial production processes.
Materials and Methods
Experimental Materials The raw material used was sourced from Jiangxi Xuesong Natural Medicinal Oil Co., Ltd., which upon GC-MS analysis revealed that its citral content stood at approximately (80 .9%). Standard samples were procured: pure vanillin ((≥99 .2%)) came from Dr.Ehrenstorfer GmbH Germany; analytical-grade acetone was obtained via Nanjing Chemical Reagent Co., Ltd.; other reagents were supplied by Tianjin Kemiou Chemical Reagents Co.Ltd.. nMain Instruments & Equipment the main instruments utilized included Agilent's7820A Gas Chromatography coupled with5975 Mass Spectrometer(American Agilent Technologies Inc.),moleculardistillationsetup(Wuxi Haiyuan Biochemical Equipment Co.Ltd.),FA2004 electronic balance(sensitivity(0 .0001g))(Shanghai Yuping Scientific Instrument Co.Ltd.)and100μL pipette tips(Agilent Technologies). n Analytical Method Establishment n Selection & Validation Of Internal Standards n By comparing chromatographic behaviors among potential internal standards,the final choice settled uponvanillin.AGC-MS analyses indicatedvanillin peaks appeared distinctly around14 .871min awayfrom major components presentinLitseacubebaoilwhile retaining close retention times relative tocitrals twoisomericpeaks(8 .929min&9 .960min).Vanillin exhibits stable chemical properties without reacting adversely towardcitronellalthus meetingbasicrequirementsforinternalstandards' selection criteria."... [Content truncated] ...