植物油加氫脫氧反應(yīng)路徑的探究

1、植物油加氫脫氧反應(yīng)路徑的探究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

2、 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 f

3、ind 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 a

4、rea in development.隨著世界經(jīng)濟(jì)的發(fā)展，全球性化石資源日益枯竭以及世界對全球氣候的關(guān)注，發(fā)展可再生環(huán)境友好型能源變得十分緊迫。生物燃料是一種新型、清潔的可再生能源。目前越來越人把節(jié)能減排的希望寄托在生物燃料方面。植物油燃料因可生物降解、能減少二氧化碳排放，對環(huán)境危害程度低，并可以從從可再生資源中獲取，受到了人們的廣泛關(guān)注。植物油燃料有望成為重要的石油產(chǎn)品的替代品1-3。Typical feedstocks for biofuels are vegetable oils with high energy contents.The major content in the veg

5、etable oils is Omega-3 fatty acids.The chain length of fatty acids concentrates in the range of C1224,植物油中的主要成分是脂肪酸甘油三酯，即一個(gè)甘油分子連接三個(gè)脂肪酸分子4。每個(gè)脂肪酸分子的鏈長度主要集中在C1224，且大多數(shù)是偶數(shù)碳。常見植物油的結(jié)構(gòu)如圖1所示。一般植物油含碳7678wt%，含氫11.512.5wt%，含氧911wt%，密度在0.9120.924kg/L之間，分子量在800960之間。氧含量高是植物油的一大特點(diǎn)，高的氧含量對燃料的熱值、安定性等都會(huì)產(chǎn)生很大的影響，植物油加氫脫

6、氧是制備生物燃料的一種重要步驟。圖2 棕櫚油中甘油三酯結(jié)構(gòu)圖Figure 2 The structure of triglyceride in palm oil植物油加氫脫氧過程包含了多個(gè)化學(xué)反應(yīng)，主要有加氫飽和反應(yīng)、加氫直接脫氧反應(yīng)、加氫脫羧基反應(yīng)、加氫脫羰基反應(yīng)，同時(shí)還包括異構(gòu)化、甲烷化等副反應(yīng)。加氫脫氧反應(yīng)主要包括加氫直接脫氧反應(yīng)、加氫脫羧基反應(yīng)和加氫脫羰基反應(yīng)三種反應(yīng)路徑。棕櫚油加氫反應(yīng)途徑如圖3所示5：The process of vegetable oil hydrodeoxygenation contains a number of reactions.,which includ

7、ing 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 d

8、eoxygenation、Hydrogenation decarboxylation and Decarbonylation reaction of hydrogenation.The palm oil hydrogenation reaction pathway is as illustrated in figure 3.圖3 棕櫚油加氫反應(yīng)途徑Figure 3 Hydrotreating reaction paths of palm oil注：R1，R2，R3為甘油三酯中脂肪酸端的長鏈烷基或自由脂肪酸的長鏈烷基。Note: R1，R2，R3 are the long-chain alkyl

9、 of one side of the fatty acid of triglycerides or free fatty acidss. 不同的反應(yīng)路徑，加氫反應(yīng)后的產(chǎn)物和氫耗都有很大的不同。加氫直接脫氧反應(yīng)，生成物主要是丙烷、水和C16、C18等偶碳數(shù)烴；加氫脫羧基反應(yīng)，生成物主要是丙烷、二氧化碳、和加氫脫羧基反應(yīng)，生成物主要是丙烷、二氧化碳、和C15、C17等奇碳數(shù)烴；等奇碳數(shù)烴；加氫脫羧基反應(yīng)生成物主要是丙烷、水、一氧化碳和和C15、C17等奇碳數(shù)烴。以棕櫚油為計(jì)算基礎(chǔ)，三種路線的化學(xué)氫耗、柴油收率、水收率和丙烷收率如表3。Different reaction paths lead t

10、o 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

11、 and odd carbon number hydrocarbons such as C15、C17 .Andthe 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

12、yield and the propane yield of the three reaction paths above can be figured out in Table 3 表3 不同脫氧路線的技術(shù)對比Table 3 The comparison with different paths of hydrodeoxygenation reaction反應(yīng)路徑化學(xué)氫耗/%柴油收率/%水收率/%丙烷收率/%加氫直接脫氧2.885.512.65.1加氫脫羰基1.480.66.35.1加氫脫羧基0.780.6-5.1隨著化石燃料的供應(yīng)日益緊張，以及環(huán)境保護(hù)的日益嚴(yán)格，以植物油做為燃料必須進(jìn)行脫

13、氧處理，加氫脫氧作為生產(chǎn)生物燃料的重要步驟，一直以來針對不同催化劑對模型化合物的加氫脫氧活性、選擇性以及路線有許多研究報(bào)道6-11。但在加氫直接脫氧、加氫脫羧基和脫羰基路線的反應(yīng)機(jī)理研究不多，對植物油加氫脫氧的認(rèn)識(shí)有待進(jìn)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 deoxygen

14、ated、Hydrodeoxygenation ，which as an important step in the production of bio fuels,and for the long run how the different catelysts impact on model compoundss Hydrodeoxygenation activity、selectivity and reaction route.However, we have little research on the reaction mechanism of hydrogenation deoxid

15、ation and hydrogenation decarboxylation route. The understanding of Hydrodeoxygenation for vegetable oils to be further deepen.實(shí)驗(yàn)采用癸酸甲酯和棕櫚油為原料，分別在小型固定床加氫裝置和中型固定床加氫裝置上探究在Ni-Mo/ Al2O3催化劑條件下植物油三種加氫脫氧反應(yīng)路徑的反應(yīng)化學(xué)。Our experiment takes acid methyl ester and palm oil as raw materials, to explore the three kin

16、ds of vegetable oil hydrogenation deoxygenation paths reaction chemistry respectively in small and medium-sized fixedbed hydrogenation plants under the catalysis of the Ni-Mo/AL2O3 catalyst .1實(shí)驗(yàn)部分1.Experimental section 1.1催化劑1.1catalyst 催化劑采用飽和浸漬法制備。將磷酸溶于去離子水，加熱至一定溫度，加入堿式碳酸鎳不斷攪拌，然后加入三氧化鉬并持續(xù)加熱攪拌至溶液澄清

17、。用此溶液飽和浸漬長嶺分公司提供的氧化鋁載體，飽和浸漬后的載體經(jīng)過干燥、焙燒制得成品催化劑。采用X射線熒光光譜儀測定催化劑元素組成及含量，其中NiO負(fù)載質(zhì)量分?jǐn)?shù)為3.6m%，MoO3負(fù)載質(zhì)量分?jǐn)?shù)為14.9m%。采用BET全分析測定的催化劑及載體的比表面積及總孔體積數(shù)據(jù)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

18、 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 catalyst.Useing X-ray fluorenscence spectrometer

19、determind catalysts elements and content,in which the mass fraction of NiO loading is 3.6m%, MoO3 loading 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1 BET分析結(jié)果Table1 BET analysis results of catalys

20、t and catalyst carrier分析項(xiàng)目載體催化劑BET比表面/（m2/g）249197總孔體積/（mL/g）0.8820.6261.2 棕櫚油的脂肪酸組成分析按照GB/T17376-1998方法，取0.5g棕櫚油，加入7mL濃度為0.5mol·L-1的NaOH甲醇溶液，在氮?dú)獾谋Ｗo(hù)下，回流20min，加入8mL14%的BF3甲醇溶液，繼續(xù)回流8min，加入5mL正庚烷，繼續(xù)回流2min，制得脂肪酸甲酯。冷卻后，采用色譜儀測定脂肪酸甲酯組成。According to GB/T17376-1998 method, we take 0.5g palm oil,add 7mL

21、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 chroma

22、tograph to set out the components of the Fatty acid methyl ester.表2列出了棕櫚油的脂肪酸組成，棕櫚油脂肪酸主要由軟脂酸、硬脂酸、油酸、亞油酸組成，且這5種脂肪酸組成之和占棕櫚油脂肪酸組成的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 thes

23、e five kinds of fatty acid accounts for 97.83% of palm oil fatty acid composition.表2 棕櫚油脂肪酸組成Table 2 Fatty acid distribution in palm oil脂肪酸組成C16:0C18:0C18:1C18:2合計(jì)質(zhì)量含量/%44.024.5439.1510.1297.831.4產(chǎn)物組成分析方法烴類沸點(diǎn)分布：采用GC/MS方法測定中間餾分各類烴的沸點(diǎn)分布。1.4 product composition analysis1.4反應(yīng)性能評價(jià)1.4 Reaction performance

24、 evaluation采用中型固定床加氫反應(yīng)器進(jìn)行棕櫚油加氫試驗(yàn)。首先在一定條件下將催化劑硫化，然后進(jìn)行反應(yīng)性能評價(jià)實(shí)驗(yàn)。反應(yīng)裝置如圖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液體產(chǎn)品氫氣原料油低分氣

25、高分氣圖1 加氫處理流程圖Figure 1 Hydrogenation processing flow chart高壓分離器反應(yīng)器穩(wěn)定塔2.試驗(yàn)結(jié)果與討論2.test results and discussion2.1中型實(shí)驗(yàn)結(jié)果與討論2.1medium-sized experiment result and discussion在反應(yīng)溫度為280，空速為2.0h-1，氫油比為1000的條件，考察了棕櫚油加氫反應(yīng)產(chǎn)物的組成分析，分析發(fā)現(xiàn)，反應(yīng)后的產(chǎn)物中含有物質(zhì)A和B，不含有物質(zhì)C。物質(zhì)A、 B、C的結(jié)構(gòu)如圖所示：When the reaction tempreture is 280,the s

26、pace velocity is 2.0h-1,the ratio of hydrogen to oil is 1000,we study the palm oilsproduct 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. 同時(shí)物質(zhì)B的含

27、量遠(yuǎn)遠(yuǎn)大于A的含量。這說明，在三脂肪酸甘油酯的轉(zhuǎn)化過程中，三脂肪酸甘油酯首先轉(zhuǎn)化為A，A再轉(zhuǎn)化為B。在反應(yīng)氫分壓為6.4MPa、空速為2.0h-1的條件下，考察了溫度對不同餾程餾分油的影響。試驗(yàn)結(jié)果見圖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,

28、 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.圖5 反應(yīng)溫度對餾分油的影響Figure 5 Effect of reaction

29、 temperature on the distillate oil通過對餾分油的餾程分布分析，原料棕櫚油的餾程主要集中在>500范圍內(nèi)，二脂肪酸甘油酯、單脂肪酸甘油酯等中間產(chǎn)物餾程主要在350500范圍內(nèi)，完全轉(zhuǎn)化后的正構(gòu)烷烴主要集中在180350范圍內(nèi)?？梢酝ㄟ^餾程分布表示原料轉(zhuǎn)化率的指標(biāo)。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 t

30、han 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 analysin

31、g the boiling range distribution.從圖5可以看出，隨著反應(yīng)溫度的提高，產(chǎn)品油中大于500的餾分油收率降低，柴油餾分油收率增加，中間餾分油先增加后降低；當(dāng)溫度高于320時(shí)，液體烴全部為柴油餾分；當(dāng)三脂肪酸甘油酯完全轉(zhuǎn)化，中間產(chǎn)物還未完全轉(zhuǎn)化。As can be seen from Figure 5,with the reaction temperature increased,the product oils distillate yield in which more than 500 would be reduction,the diesel distilla

32、te 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，綜上結(jié)果可以得到

33、，對于三脂肪酸甘油酯的完全轉(zhuǎn)化，單脂肪酸甘油酯的轉(zhuǎn)化是速控步驟。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 converted2.2小型實(shí)驗(yàn)結(jié)果與討論2.2small scale of experiment results and discussion分析了中型裝置的產(chǎn)品分布后，清楚了甘油三酯的轉(zhuǎn)化順序及控制

34、步驟。為了闡明加氫脫氧過程的基元步驟，探究反應(yīng)過程中的中間產(chǎn)物，以及指導(dǎo)催化劑設(shè)計(jì)促進(jìn)某一反應(yīng)的進(jìn)行，實(shí)驗(yàn)對三種脫氧路線的反應(yīng)機(jī)理進(jìn)行基礎(chǔ)研究，采用癸酸甲酯作為模型化合物，模擬探究植物油的加氫處理過程。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 routess deoxidation reaction mechanism of basic research and take acid methyl ester as a model c