植物油加氢脱氧反应路径的探究

植物油加氢脱氧反应路径的探究
Oil scarcity,non-renewable resource,unpredictable prices and increasing environmental issues involved with petroleum-based fuels lead to the need for alternative sources to fulfill fuel needs. Industry and transportation, especially air trans-portation, play crucial roles in increasing the emission of greenhouse gases, which cause global warming. Therefore, it is necessary to develop an alternative fuel source that can replace non-renewable fossil fuels. The use of biomass-derived fuels in place of conventional fuels is an emerging field of interest, and studies are on-going to find a solution to avoid a future energy crisis. Hydrodeoxygenation, which converts biofeed to hydrocarbon fuels that have all the qualities of conventional fossil fuels, is one of the most interesting and promising techniques in this field. The hydrodeoxygenation of vegetable oils to biofuel is an area in development.随着世界经济的发展，全球性化石资源日益枯竭以及世界对全球气候的关注，发展可再生环境友好型能源变得十分紧迫。

生物燃料是一种新型、清洁的可再生能源。

目前越来越人把节能减排的希望寄托在生物燃料方面。

植物油燃料因可生物降解、能减少二氧化碳排放，对环境危害程度低，并可以从从可再生资源中获取，受到了人们的广泛关注。

植物油燃料有望成为重要的石油产品的替代品[1-3]。

Typical feedstocks for biofuels are vegetable oils with high energy contents.The major content in the vegetable oils is Omega-3 fatty acids.The chain length of fatty acids concentrates in the range of C12~24,植物油中的主要成分是脂肪酸甘油三酯，即一个甘油分子连接三个脂肪酸分子[4]。

每个脂肪酸分子的链长度主要集中在C12~24，且大多数是偶数碳。

常见植物油的结构如图1所示。

一般植物油含碳76~78wt%，含氢11.5~12.5wt%，含氧9~11wt%，密度在0.912~0.924kg/L 之间，分子量在800~960之间。

氧含量高是植物油的一大特点，高的氧含量对燃料的热值、安定性等都会产生很大的影响，植物油加氢脱氧是制备生物燃料的一种
重要步骤。

R 2O
O
R
1
R 3
O
O
O
O
图2 棕榈油中甘油三酯结构图
Figure 2 The structure of triglyceride in palm oil
植物油加氢脱氧过程包含了多个化学反应，主要有加氢饱和反应、加氢直接脱氧反应、加氢脱羧基反应、加氢脱羰基反应，同时还包括异构化、甲烷化等副反应。

加氢脱氧反应主要包括加氢直接脱氧反应、加氢脱羧基反应和加氢脱羰基反应三种反应路径。

棕榈油加氢反应途径如图3所示[5]：
The process of vegetable oil hydrodeoxygenation contains a number of reactions.,which including Hydrogenation Saturated reaction、Direct Hydrogenation deoxygenation、Hydrogenation decarboxylation、Decarbonlation reaction of hydrogenation，also included side effects like Isomerization and Methanation. Hydrodeoxygenation reaction is made up of three kinds of reaction route:Direct hydrogenation deoxygenation、Hydrogenation decarboxylation and Decarbonylation reaction of hydrogenation.The palm oil hydrogenation reaction pathway is as illustrated in figure 3.
图3棕榈油加氢反应途径
Figure 3 Hydrotreating reaction paths of palm oil
注：R1，R2，R3为甘油三酯中脂肪酸端的长链烷基或自由脂肪酸的长链烷基。

Note: R1，R2，R3 are the long-chain alkyl of one side of the fatty acid of triglycerides or free fatty acids’s.
不同的反应路径，加氢反应后的产物和氢耗都有很大的不同。

加氢直接脱氧反应，生成物主要是丙烷、水和C16、C18等偶碳数烃；加氢脱羧基反应，生成物主要是丙烷、二氧化碳、和加氢脱羧基反应，生成物主要是丙烷、二氧化碳、和C15、C17等奇碳数烃；等奇碳数烃；加氢脱羧基反应生成物主要是丙烷、水、一氧化碳和和C15、C17等奇碳数烃。

以棕榈油为计算基础，三种路线的化学氢耗、柴油收率、水收率和丙烷收率如表3。

Different reaction paths lead to different products and hydrogen consumption when the hydrogenation is completed.The products of Deoxy direct hydrogenation reaction are mainly propane、water and even carbon number hydrocarbons such as C16、C18 .The products of Hydrogenation decarboxylation reaction are mainly propane、carbon dioxide and odd carbon number hydrocarbons such as C15、C17 .And the main product of Hydrogenation decarboxylation are pronane、water、carbon monoxide and other odd carbon number hydrocarbons such as C15、C17 .Base on the caculation of the palm oil ,the chemical hydrogen consumption 、the diesel yield、the water yield and the propane yield of the three reaction paths above can be figured out in Table 3
表3不同脱氧路线的技术对比
Table 3 The comparison with different paths of hydrodeoxygenation reaction
反应路径化学氢耗
/% 柴油收率/% 水收率/% 丙烷收率
/%
加氢直接
脱氧
2.8 85.5 12.6 5.1 加氢脱羰 1.4 80.6 6.3 5.1
基
加氢脱羧
0.7 80.6 -- 5.1
基
随着化石燃料的供应日益紧张，以及环境保护的日益严格，以植物油做为燃料必须进行脱氧处理，加氢脱氧作为生产生物燃料的重要步骤，一直以来针对不同催化剂对模型化合物的加氢脱氧活性、选择性以及路线有许多研究报道[6-11]。

但在加氢直接脱氧、加氢脱羧基和脱羰基路线的反应机理研究不多，对植物油加氢脱氧的认识有待进一步深化。

With the increasingly tight supply of fossil fuels ,as well as increasingly stringent environmental protection,there are many reports about vegetable oil，which as fuel must be deoxygenated、Hydrodeoxygenation ，which as an important step in the production of bio fuels,and for the long run how the different catelysts impact on model compounds’s Hydrodeoxygenation activity、selectivity and reaction route.However, we have little research on the reaction mechanism of hydrogenation deoxidation and hydrogenation decarboxylation route. The understanding of Hydrodeoxygenation for vegetable oils to be further deepen.
实验采用癸酸甲酯和棕榈油为原料，分别在小型固定床加氢装置和中型固定床加氢装置上探究在Ni-Mo/ Al2O3催化剂条件下植物油三种加氢脱氧反应路径的反应化学。

Our experiment takes acid methyl ester and palm oil as raw materials, to explore the three kinds of vegetable oil hydrogenation deoxygenation path’s reaction chemistry respectively in small and medium-sized fixedbed hydrogenation plants under the catalysis of the Ni-Mo/AL2O3 catalyst .
1实验部分
1.Experimental section
1.1催化剂
1.1catalyst
催化剂采用饱和浸渍法制备。

将磷酸溶于去离子水，加热至一定温度，加入碱式碳酸镍不断搅拌，然后加入三氧化钼并持续加热搅拌至溶液澄清。

用此溶液饱和浸渍长岭分公司提供的氧化铝载体，饱和浸渍后的载体经过干燥、焙烧制得成品催化剂。

采用X射线荧光光谱仪测定催化剂元素组成及含量，其中NiO负载质量分数为3.6m%，MoO3负载质量分数为14.9m%。

采用BET全分析测定的催化剂及载体的比表面积及总孔体积数据如表2所示。

The catalysts were prepared by saturated impregnation method. We dissoved phosphoric acid in deionized water,then heated it to a certain tempreture,adding basic nickle carbonate with stirring,and then adding the molybdenum trioxide .continued heating until a clear solution was stirred.The alumina suppport comes from dipped and saturated solution,which through drying and baking process we can obtain finished eing X-ray fluorenscence spectrometer determind catalyst’s elements and content,in which the mass fraction of NiO loading is 3.6m%, MoO3loading mass fraction is 14.9m%.the data of catalyst and carrier surface area and total pore volume which beasured by BET analysis of is shown in Table 2.
表1BET分析结果
Table1 BET analysis results of catalyst and catalyst carrier 分析项目载体催化剂
BET比表面/（m2/g）249 197
总孔体积/（mL/g）0.882 0.626
1.2 棕榈油的脂肪酸组成分析
按照GB/T17376-1998方法，取0.5g棕榈油，加入7mL浓度为0.5mol·L-1的NaOH甲醇溶液，在氮气的保护下，回流20min，加入8mL14%的BF3甲醇溶液，继续回流8min，加入5mL正庚烷，继续回流2min，制得脂肪酸甲酯。

冷却后，采用色谱仪测定脂肪酸甲酯组成。

According to GB/T17376-1998 method, we take 0.5g palm oil,add 7mL concentration of 0.5mol·L-1 of NaOH solution in methanol in ,refux them for 20minutes under the protection of nitrogen,then add 8mL14% methanol solution of BF3, adding 5ml n-heptane ,refluxing was continued for 2 minutes.Finally, fatty acid methylester was obtained .After cooling ,we use chromatograph to set out the components of the Fatty acid methyl ester.
表2列出了棕榈油的脂肪酸组成，棕榈油脂肪酸主要由软脂酸、硬脂酸、油酸、亚油酸组成，且这5种脂肪酸组成之和占棕榈油脂肪酸组成的97.83%。

Table 2 lists the component of fatty acids of palm oil, palm oil fatty acids mainly consists of palmitic acid 、stearic acid/oleic acid /linoleic acid .The sum of these five kinds of fatty acid accounts for 97.83% of palm oil fatty acid composition.
表2棕榈油脂肪酸组成
Table 2 Fatty acid distribution in palm oil
脂肪酸组成C16:0C18:0C18:1C18:2合计质量含量/% 44.02 4.54 39.15 10.12 97.83 1.4产物组成分析方法
烃类沸点分布：采用GC/MS方法测定中间馏分各类烃的沸点分布。

1.4 product composition analysis
1.4反应性能评价
1.4 Reaction performance evaluation
采用中型固定床加氢反应器进行棕榈油加氢试验。

首先在一定条件下将催化剂硫化，然后进行反应性能评价实验。

反应装置如图1。

Doing palm oil hydrogenation experiment with a medium-sized fixed-bed.. At first we vulcanize the catalyst under certain conditions ,then doing reaction perfomance evaluation experiment ,the facility is shown in Figure 1
2.试验结果与讨论
2.test results and discussion 2.1中型实验结果与讨论
2.1medium-sized experiment result and discussion
在反应温度为280℃，空速为2.0h -1，氢油比为1000的条件，考察了棕榈油加氢反应产物的组成分析，分析发现，反应后的产物中含有物质A 和B ，不含有物质C 。

物质A 、 B 、C 的结构如图所示： When the reaction tempreture is 280℃,the space velocity is 2.0h -1,the ratio of hydrogen to oil is 1000,we study the palm oil ’sproduct composition of the hydrogenation reaction.Analysis finds that after the reaction ,the product contains substance A and B,but not substance C. the structure of the substance A 、B 、C is as shown in figure.
R 1
R 3O
O
O
O
R 3
O
O
高分气
图1 加氢处理流程图
Figure 1 Hydrogenation processing flow chart
高压分离器 反应器 稳定塔
R 2O
O R 3O
O
同时物质B 的含量远远大于A 的含量。

这说明，在三脂肪酸甘油酯的转化过程中，三脂肪酸甘油酯首先转化为A ，A 再转化为B 。

在反应氢分压为6.4MPa 、空速为2.0h -1的条件下，考察了温度对不同馏程馏分油的影响。

试验结果见图5。

While the content of substance B is far more greater than A content,which indicated that in the transformation process of three fatty acid glycerides ,it itself transforms to substance A,hereafter, substance A is converted into substance B.
We study the influence of temperature on different kinds of distillate boilling range under the circumstance of reaction hydrogen pressure 6.4Mpa, space velocity 2.0h -1.The experimental results are shown in Figure 5.
020
40
60
80
100
P e r c e n t a g e c o n t e n t /%
Temperature /℃
图5反应温度对馏分油的影响
Figure 5 Effect of reaction temperature on the distillate oil 通过对馏分油的馏程分布分析，原料棕榈油的馏程主要集中在>500℃范围内，二脂肪酸甘油酯、单脂肪酸甘油酯等中间产物馏程主要在350~500℃范围内，完全转化后的正构烷烃主要集中在180~350℃范围内。

可以通过馏程分布表示原料转化率的指标。

By analysing the boiling range distribution of distillate ,we can see that the boiling range of the raw material palm oil is in the range of higher than 500℃,the boiling range of the intermediate as Two fatty acid glycerides and fatty acid monoglyceride are in the range of 350℃ to 500℃,the complete conversion of n-alkanes are mainly concentrated in the range of 180℃ to 350℃,we can figure out the conversion of the feedstock index by means of analysing the boiling range distribution.
从图5可以看出，随着反应温度的提高，产品油中大于500℃的馏分油收率降低，柴油馏分油收率增加，中间馏分油先增加后降低；当温度高于320℃时，液体烃全部为柴油馏分；当三脂肪酸甘油酯完全转化，中间产物还未完全转化。

As can be seen from Figure 5,with the reaction temperature increased,the product oil’s distillate yield in which more than 500℃ would be reduction,the diesel distillate yield would be increased,the intermidiate distillate would be increased and then decreased.When the temperature is higher than 320℃,all of the liquid hydrocarbon are oil fraction,When the three fatty acid glycerides are complete converted,the intermediate product is not fully converted.
因此，综上结果可以得到，对于三脂肪酸甘油酯的完全转化，单脂肪酸甘油酯的转化是速控步骤。

Therefore, the results above can be obtained on : fatty acid monoglyceride ‘s conversion is the rate-controlling step if the three fatty acid glycerides are completely converted
2.2小型实验结果与讨论
2.2small scale of experiment results and discussion
分析了中型装置的产品分布后，清楚了甘油三酯的转化顺序及控制步骤。

为了阐明加氢脱氧过程的基元步骤，探究反应过程中的中间产物，以及指导催化剂设计促进某一反应的进行，实验对三种脱氧路线的反应机理进行基础研究，采用癸酸甲酯作为模型化合物，模拟探究植物油的加氢处理过程。

After analysing of the distribution of products in the pilot plant,we understand the conversion sequence and the control steps of the triglycerides. For the sake of explain the elementary step of the hydrodeoxygenation ,to explore what the intermidiate would be in the reaction process,and to guidance catalyst designed to promote for a reaction,the experiment take place on three routes’s deoxidation reaction mechanism of basic research and take acid methyl ester as a model compound to make a stimulation inquiry to the process of vegetable hydrotreating .
在反应温度为260℃，反应氢分压为 4.0MPa、空速为24.0h-1的条件下，考察了癸酸甲酯加氢反应产物的组成分析。

通过色质联用检测到液态产品中除了原料癸酸甲酯外，还含有甲醇、n-C9H20、n-C10H22、环癸烷、癸酸、癸醛、1-癸醇、1-癸烯、癸酸癸酯、10-十九酮以及相应的10-十九烯和十九烷等，在反应后的尾气中，检测到CO2、CO以及甲烷的存在。

这些产品验证了上述三种脱氧路线的存在。

通过反应产物的组成，推断出癸酸甲酯的反应路线机理如下图所示：
We analysed the acid methyl ester’s hydrogenation reaction product’s composition, under the condition of reaction temperature :260℃, reaction of hydrogen partial pressure 24.0h-1 .By using a GC-MS we detected that in the liquid product. Besides the raw material--Acid methyl ester there are also Methanol, n-C9H20, n-C10H22, cyclodecane, capric acid, capric aldehyde, 1 - decanol, 1 - decene, capric acid decyl ester, 05 - XIX one and the corresponding 10 - nonadecene and X nine alkyl, etc, we detected the exhaust gas after reaction and found the presence of CO2、CO and methane. These products demonstrate the existence of the three dexy route.
C 9H 19-C-O-CH 3O C 9H 199H 29H 19-CH
2OH 9H 18=CH 2
C 9H +H +C 9H
19COOH,-CO 2,-H 2O C 9H 19-C-C 9H 19O
9H 19-CH-C 9H OH 9H 19=CH-C 9H 18
221940+C H CH OH C 9H 19-C-O-CH 2-C 9H 19O
2+H 29H 18=CH -H 2O
在反应后的产物中，发现醛和烯烃的含量较高癸醛和1-癸烯的含量较高，可以推断，癸醛的加氢反应以及1-癸烯的烯烃饱和反应似乎是反应的速控步骤。

3.结论
（1）植物油加氢处理过程中，三脂肪酸甘油酯的转化顺序为：原料
A B 。

C 物质难以生成。

（2）对于三脂肪酸甘油酯的完全转化，单脂肪酸甘油酯的转化是速控步骤。

（3）证实了三种脱氧路线的存在，并推断出三种脱氧路线的具体反应路径。

（4）加氢脱氧过程中，醛的加氢反应和烯烃的饱和反应是速控步骤。