原油中环烷酸催化酯化前后的高分辨质谱分析

原油中的环烷酸可通过酯化反应转化为环烷酸酯，从而降低原油酸值。本文利用Zn-Al水滑石作为酯化反应催化剂，乙二醇作为反应物。对催化酯化前后的原油采用ESI FT-ICR MS进行分析，从中鉴定出了O2、O1、N1、N2、N1O1及N1O2六种类型的杂原子非烃化合物，其中O2的丰度最高。酯化前原油中O2的丰度远高于其它组分，酯化后O2的丰度显著降低。酯化前后的原油样品中，丰度较高的环烷酸的DBE值均为5，碳数均基本分布在C30-C34。研究结果表明，原油中的环烷酸可被有效酯化从而显著降低原油酸值，酯化前后环烷酸的碳数和DBE值分布均基本接近，这主要是由于酯化过程中各类环烷酸的酯化效率基本相同。

Tracking catalytic esterification of naphthenic acids in a crude oil by ESI FT-ICR MS

The catalytic esterification reaction was used to decrease total acid number (TAN) of crude oil by converting naphthenic acids to naphthenic esters in the presence of Zn-Al hydrotalcite as catalyst and glycol as reactant. The crude oil and its corresponding esterified oil were characterized by negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Six acidic class species, O2, O1, N1, N2, N1O1 and N1O2 were assigned in the negative-ion spectrum both in crude oil and its esterified oil. Among the identified acidic compounds, the O2 class was dominant. The relative abundance of O2 class species was much higher than other acidic class species in crude oil, while it was significantly decreased after esterification. The most abundant O2 class species had carbon numbers of 30-34 and DBE value of 5 before and after esterification. It could be concluded that the naphthenic acids in crude oil can be esterified to lower its TAN value, and each of them seems exhibited identical esterification efficiency approximately due to the similar DBE versus carbon number distribution before and after esterification.