硫酸催化柠檬皮水热转化制取平台化合物研究

Preparation of platform compounds by hydrothermal conversion of lemon peel under the catalysis of sulfuric acid

果皮作为水果加工业的典型含碳固废,其高效回收和资源化利用对开发可再生液体燃料和提升水果加工业经济效益均具有重要意义。柠檬皮含有的柠檬酸被证明是一种可有效促进生物质及其衍生物水热转化制取高附加值呋喃产物的弱酸。因此,本研究利用柠檬皮经硫酸催化水解制取乙酰丙酸(LA)和糠醛(FF)等重要液体燃料前驱物,并探究常见金属盐对硫酸催化柠檬皮水解过程的促进作用。研究发现,柠檬皮本身含有的柠檬酸对水解过程有一定促进作用,联合硫酸催化,可在170℃/90 min的温和水解工况下获得产率为22.6%的LA。KCl的加入能够有效抑制柠檬皮水解过程的副反应,并提升硫酸与柠檬皮的相互作用。相比于AlCl_(3)和FeCl_(3),KCl的促进作用更为明显,可将LA产率提升至27.9%。葡萄糖和FF的制取工况相对LA更为温和,温度升高、反应时间延长以及酸性提升都会导致葡萄糖和FF的产率明显下降。

Lemon peel,as a typical carbon solid waste in fruit processing industry,of which efficient recycling and resource utilization contribute to the development of renewable liquid fuel and economic benefits.Citric acid contained in lemon peel has been proved to be a weak acid that can effectively promote the hydrothermal conversion of biomass and its derivatives to produce high value-added furan products.Therefore,sulfuric acid is used to catalyze the hydrolysis of lemon peel to produce precursor of important liquid fuel,such as levulinic acid(LA)and furfural(FF).The promotion effect of common metal salt on catalysis of sulfuric acid to the hydrolysis process of lemon peel is explored.The citric acid contained in lemon peel promotes the hydrolysis process.Combined with catalysis of sulfuric acid,the LA yield as 22.6%can be obtained under the mild hydrolysis conditions of 170℃and 90 min,and the addition of the KCl can effectively inhibit the secondary reaction of the decomposition process of the lemon peel and enhance the interaction of the sulfuric acid and the lemon peel.Compared with AlCl_(3) and FeCl_(3),the LA yield is increased to 27.9%by the addition of KCl.Preparing conditions of glucose and FF are milder than that of LA.Enhancement of temperature and acidic concentration,and prolonging reaction time all lead to significant decrease in glucose and FF yield.