PtSnLi/Al_2O_3催化剂在丙烷脱氢过程中的氢气选择氧化性能

采用浸渍法制备氧化铝负载三元Pt-Sn-Li催化剂(PtSnLi/A_2O_3),采用X射线衍射(XRD)、透射电镜(TEM)和物理吸附(BET)等手段对催化剂进行表征,并在固定床反应器中评价了该催化剂在丙烷脱氢过程中对氢气选择氧化性能。结果表明,PtSnLi/Al_2O_3催化剂对氢气具有良好的选择氧化性,组分Sn和Li的加入能有效提高Pt基催化剂活性和选择性。PtSnLi/Al_2O_3催化剂在常压、550℃和质量空速为1.45 h~(-1)的条件下,氢气的选择氧化性为80%,氧气转化率大于98%,烃类损耗量0.2%。与PtSn/Al_2O_3相比,氧气转化率基本相同,氢气的选择氧化增加了29.2%,烃损耗率降低了0.9%。     

Ce对Pt-Sn/Al_2O_3催化剂在H_2/O_2体系中丙烷催化脱氢的影响

提出在丙烷临氢催化脱氢过程中引入少量氧,让氧和氢燃烧提供催化脱氢过程所需热量,同时使反应向脱氢方向移动的脱氢过程.脱氢测试表明,在H_2/O_2体系中催化剂的稳定性最为关键.以Pt-Sn/Ce-γ-Al_2O_3为催化剂,氧的引入可以显著提高丙烷的转化率、消除积碳、提高催化剂活性和补偿反应所需的部分热量,并获得较高的丙烯收率.积碳定量分析,氢脉冲吸附的测试表明,Ce的存在是维持催化剂稳定性的关键因素,它的存在可以增强Pt粒子抗烧结的能力和稳定催化剂的表面结构,同时还可以通过参与反应提高丙烷脱氢反应速率.     

锡组分状态对Pt/Al2O3丙烷脱氢性能的影响

采用浸溃法制备了不同Sn组分含量以及一定量的金属钠组分的Pt-Sn/Al2O3催化剂,并采用程序升温还原(TPR),光电子能谱(XPS)和程序升温氧化(TPO)等手段对催化剂进行了表征.研究表明,Sn组分状态与Sn组分以及Na组分的相对含量有关,在Sn与Pt物质的量之比小于5(Pt质量负载量0.4%)时,Sn组分在催化剂表面以氧化态的形式存在.此种催化剂用量为0.32 g时,在常压、550℃、丙烷质量空速3.4 h-1的条件下,反应6.5 h丙烷转化率达43.1%,丙烯选择性达98.0%.若Sn含量更高,将导致Sn被还原析出,形成Sn与Pt合金.当Sn与Pt物质的量之比为1时,引入1.2%的NaCl不会影响Sn组分状态;当Sn与Pt物质的量之比为5,引入相同量的NaCl,导致催化剂表面的Sn组分容易被氢气还原.     

镧对PtSnNa/Al2O3催化剂丙烷脱氢反应性能的影响

制备了镧改性的PtSnNa/La/Al2O3催化剂,用于丙烷脱氢反应研究.结果表明镧的添加对PtSnNa//Al2O3催化剂的丙烷脱氢反应性能影响明显,当镧添加量(质量分数)为0.7%时,PtSnNa(0.3)/La/Al2O3催化剂的丙烯收率最大,而过量镧的加入不利于脱氢反应的进行.Na+和La+的协同调变作用可以明显抑制催化剂表面的积炭.     

Sn掺杂量对Pt/Sn-MFI催化剂的丙烷脱氢性能影响

随着对丙烯需求的日渐增加,由丙烷催化脱氢制丙烯来实现对丙烯的增产,已成为增产丙烯的重要手段之一。利用水热法制备一系列不同Sn掺杂量的Sn-MFI载体,采用等体积浸渍法制备相同Pt负载量的Pt/Sn-MFI催化剂,通过XRD、N2吸附-脱附、FT-IR和H2-TPR等表征考察不同Sn掺杂量的催化剂对丙烷催化脱氢性能的影响。结果表明,Pt/Sn1. 3%-MFI催化剂具有最高的催化丙烷脱氢活性和稳定性,丙烷初始转化率为43. 3%,丙烯选择性为98. 9%。反应360 min后,丙烷转化率为25. 1%,选择性保持不变。     

CrOx/Ti-Al2O3催化剂结构及其催化丙烷脱氢性能

以模板法制备的Ti改性Al₂O₃为载体制备了CrO _x /nTi-Al₂O₃催化剂,考察了Ti含量对催化剂的结构及其催化丙烷脱氢性能的影响。采用X射线衍射（XRD）、N₂吸附-脱附、透射电子显微镜（TEM）、傅里叶变换红外光谱（FTIR）、拉曼光谱、X射线光电子能谱（XPS）、氨气程序升温脱附（NH₃-TPD）、吡啶红外吸附（Py-IR）等方法对催化剂的结构进行了表征。结果表明,CrO _x /nTi-Al₂O₃催化剂具有均匀的泡沫状介孔结构并含有少量微孔,表面积在180~195m²/g;铬主要以Cr⁶⁺和Cr³⁺形式存在,其中Cr⁶⁺主要以单铬酸盐和双铬酸盐形式存在,Cr³⁺以α-Cr₂O₃晶体和高分散Cr₂O₃形式存在,Ti的加入降低了催化剂表面Cr⁶⁺含量,增加了孔道内高分散Cr³⁺含量;Ti的加入降低了弱酸的强度,生成了少量中强酸,并使催化剂中B酸和L酸中心数量明显减少。少量的Ti（0.5%~1.0%TiO₂,质量分数）可明显提高丙烷转化率和丙烯收率,但过多的Ti（>2%TiO₂）则明显降低丙烯选择性而使丙烯收率降低。CrO _x /nTi-Al₂O₃催化剂表面Cr⁶⁺物种可催化丙烷氧化脱氢,本身还原成Cr³⁺后继续催化丙烷直接脱氢,孔道内部的高分散Cr³⁺可催化丙烷直接脱氢反应,二者结合使催化剂保持了较高的催化活性和较好的稳定性。     

助剂Zn对PtSn/Al2O3催化剂丙烷脱氢性能的影响

以羰基铂锡化合物为前体,采用浸渍法将其负载于Zn改性Al₂O₃载体上制备了PtSn/xZn-Al₂O₃催化剂,考察了Zn的添加对催化剂丙烷脱氢性能的影响。采用N₂吸附-脱附、X射线衍射（XRD）、吡啶红外吸附（Py-IR）、氨气程序升温脱附（NH₃-TPD）、透射电子显微镜（TEM）等手段对催化剂的孔结构、表面酸性以及积炭行为进行了分析。结果表明,PtSn/xZn-Al₂O₃催化剂孔道以介孔为主,孔径集中分布于8～10nm;Zn助剂的添加,在催化剂表面会形成ZnO物种,可使PtSn/Al₂O₃催化剂上的金属颗粒粒径减小、分散更加均匀;Zn的加入能有效降低催化剂表面酸量,主要表现为L中强/强酸中心的降低,随着Zn含量的增加,催化剂表面酸量先减少后增加。少量Zn的存在可使PtSn/Al₂O₃丙烯选择性和稳定性显著提高,但过量Zn的加入会降低催化剂的脱氢活性,适宜Zn的质量分数为0.75%～1.0%。反应后催化剂表面积炭主要表现为烯烃性质和芳香烃性质,Zn的添加可有效抑制积炭的形成,提高催化剂稳定性。     

MoO3/ZrO2催化剂的丙烷氧化脱氢制丙烯催化性能

以十六烷基三甲基溴化铵为表面活性剂,采用溶剂热法制备系列MoO_3/ZrO_2催化剂,采用H2-TPR、N_2吸附-脱附、X射线衍射等对其进行表征,并评价MoO_3/ZrO_2催化剂的丙烷氧化脱氢制丙烯催化性能。结果表明,MoO_3负载于ZrO_2载体上制备的催化剂催化活性增加,MoO_3负载质量分数为20%的MoO_3/ZrO_2催化剂,在反应温度为600℃时,丙烷转化率27.45%,丙烯选择性44.78%,丙稀收率12.29%。     

柱撑型钒基催化剂的制备及其丙烷氧化脱氢催化性能

以人工合成的3种不同层板组成的层状双羟基金属氢氧化物MgAl-CO₃-LDHs、CoAl-CO₃-LDHs和NiCr-CO₃-LDHs为载体,以偏钒酸钠NaVO₃为柱撑剂和钒前体,采用离子交换法制备了钒柱撑的催化剂样品（MgAlVO、CoAlVO和NiCrVO）,通过XRD、FTIR、XPS和Raman等手段表征了样品的物相、钒物种的存在形态以及钒的价态,以丙烷氧化脱氢制丙烯为模型反应,表征了所制备的催化剂样品的催化性能,着重探讨了LDHs载体的层板组成以及钒的含量对催化剂样品中的钒氧物种存在形态及其丙烷氧化脱氢催化性能的影响。结果表明：以20%理论含量的钒柱撑MgAl-CO₃-LDHs所制备的催化剂样品20%MgAlVO对丙烷氧化脱氢反应的催化性能较好,当反应温度为560℃时,丙烯收率可以达到11.3%,Raman光谱显示该催化剂样品中的钒以Mg₃V₂O₈和α-Mg₂V₂O₇两种形式共存,且晶格氧O^2-和吸附氧O^-所占的比例较为均衡,有利于获得较好的丙烷氧化脱氢催化性能,而在同样条件下制备的催化剂样品20%CoAlVO和20%NiCrVO中的钒物种只观察到分别以Co₃V₂O₈和Ni₃V₂O₈存在的正钒酸盐,前者对丙烯的收率不到8%,后者甚至完全得不到丙烯。     

丙烷在La_2O_3－V_2O_5及La_2O_3－MoO_3催化剂上的氧化脱氢

研究了Ｌａ_２Ｏ_３－Ｖ_２Ｏ_５及Ｌａ_２Ｏ_３－ＭＯＯ_３两个催化体系对丙烷氧化脱氢反应的活性以及反应体系中加入ＣＯ_２对Ｃ_３Ｈ_６选择性及其产率的影响；并对这二个催化体系进行了比较。     

Propane Dehydrogenation over a Commercial Pt-Sn/Al2O3 Catalyst for Isobutane Dehydrogenation: Optimization of Reaction Conditions

The applicability of a commercial Pt-Sn/Al₂O₃ isobutane dehydrogenation catalyst in dehydrogenation of propane was studied. Catalyst performance tests were carried out in a fixed-bed quartz reactor under different operating conditions. Generally, as the factors improving propane conversion decrease the propylene selectivity, the optimal operating condition to maximize propylene yield is expected. The optimal condition was obtained by the experimental design method. The investigated parameters were temperature, hydrogen/hydrocarbon (H₂/HC) ratio and space velocity, being changed in three levels. Constrains such as the susceptibility of the catalyst components to sintering or phase transformation were also taken into account. Activity, selectivity and stability of the catalyst were considered as the measured response factors, while the space-time-yield (STY) was considered as the variable to be optimized due to its commercial interest. A STY of 16 mol·kg^-1·h^-1 was achieved under the optimal conditions of T 620℃, H₂/HC 0.6 and, weight hourly space velocity (WHSV) 2.2 h^-1. Single carbon-carbon bond rupture was found to be the main route for the formation of lower hydrocarbon byproducts.     

Dehydrogenation of Propane on Pt or PtSn Catalysts with Al2O3 or SBA-15 Support

Dehydrogenation of propane on Pt or PtSn catalyst over Al2O3 or SBA-15 support was investigated. The catalysts were characterized by CO-pulse chemisorption, thermogravimetry, temperature-programmed-red...     

Dehydrogenation of Propane on Pt or PtSn Catalysts with Al2O3 or SBA-15 Support

Dehydrogenation of propane on Pt or PtSn catalyst over Al₂O₃ or SBA-15 support was investigated. The catalysts were characterized by CO-pulse chemisorption, thermogravimetry, temperature-programmed-reduction of H₂, and diffuse reflectance infrared Fourier transform spectroscopy of absorbed CO. The results show that the platinum species is in oxidation state in the catalyst on Al₂O₃ support, so the catalyst must be reduced in H₂ before dehydrogenation reaction. Addition of Sn improves the Pt dispersion, but the catalyst deactivates rapidly because of the coke formation. The interaction of Pt and Al₂O₃ is strong. On SBA-15 support, the platinum species is completely reduced to Pt⁰ in the calcination process, so the reduction is not needed. Addition of Sn improves the activity and selectivity of the catalyst. The interaction of Pt and SBA-15 is weak, so it is easy for Pt particles to sinter.     

Oxidative Dehydrogenation of Propane on V2O5/ZrO2 Catalyst

The performance of zirconia supported vanadia catalyst has been investigated for the oxidative dehydrogenation of propane. Vanadia loading was varied from 1.6 to 22.7 wt%, both below and well above monolayer coverage. The turnover frequency was highest for the catalyst with a vanadia surface density of 5 VO _x /nm². The effect of vanadia loading on the redox behavior of the catalysts was investigated by temperature-programmed reduction and temperature-programmed oxidation. The specific activity increased with ease of reducibility of the catalyst. The extent of reduction and ease of reoxidizability of the catalysts were also found to depend on the surface vanadia structure and to influence the catalytic activity. The effect of vanadia loading on the basicity of the catalysts was also investigated.     

Pt/Al_2O_3-TiO_2催化剂催化氯代硝基苯选择加氢活性探究

氯代苯胺(CAN)是染料、杀虫剂和医药等生产过程中的一种重要中间体,在化学工业、医药等行业有着广泛的应用。因此,研发合成氯代苯胺催化剂成为该领域的研究热点。采用浸渍-还原法制备了Pt基催化剂,以氯代硝基苯(CNB)为反应底物,在30℃、常压下系统考察了载体组成、载体焙烧温度、添加不同的水量等因素对催化剂加氢性能的影响,并运用XRD对复合氧化物载体进行表征。     

乙苯脱氢-氢选择性氧化催化剂失活机理的研究

考察和分析了Pt/Al2O3体系的乙苯脱氢-氢选择性氧化催化剂的失活原因。研究结果表明,该催化剂的失活主要是由于长期在高温和水蒸气条件下运行,造成Pt晶粒团聚导致的;另外,来自前段脱氢催化剂的铁元素,由于非选择性氧化活性较高也会在一定程度上使催化剂中毒失活;而表面积炭对催化性能的影响不大。     

重整重芳烃选择加氢Ni-M/Al_2O_3催化剂性能

为提高镍基催化剂对萘系化合物的加氢活性和单环芳烃的收率,本研究以Al_2O_3为载体采用浸渍法制备了不同金属助剂修饰的系列Ni-M/Al_2O_3加氢催化剂,对催化剂的物性结构和形貌进行了表征,并考察了其在重整重芳烃中萘系化合物的加氢反应性能。结果表明,含Cu助剂的催化剂具有较佳的织构性能,金属活性组分高度分散,在C_(10)~+重芳烃加氢中具有良好的反应选择性和活性。在反应温度为140℃,压力为1.5 MPa,氢油体积比为300,新鲜油体积空速为1.0 h~(-1)的条件下,萘的转化率和四氢萘的选择性分别达到98%和99%,反应1 000 h稳定性良好。     

Observations on the Aging Environment Dependent NO Oxidation Activity of Model Pt/Al2O3 Diesel Oxidation Catalyst

The influence of aging environment of model diesel oxidation catalyst Pt/Al₂O₃ on the NO oxidation activity is studied. The fresh catalyst Pt/Al/F (calcined in air at 500 °C) is aged with or without phosphorus (P) poisoning (7.5 wt%) at 800 °C either in air (P/Pt/Al/O or Pt/Al/O) or in simulated diesel exhaust (P/Pt/Al/R or Pt/Al/R). Catalyst aged under diesel exhaust environment (Pt/Al/R) surprisingly presents the best NO oxidation activity under excess of O₂ followed by the fresh (Pt/Al/F) and thermally aged (Pt/Al/O) catalysts. The activity difference between the catalysts is quite large, especially between Pt/Al/R and Pt/Al/O that are aged at the same temperatures but under different environments suggesting the importance of the aging environment for the catalytic activity. The NO oxidation activity of P poisoned catalysts P/Pt/Al/R and P/Pt/Al/O is minute as compared to their P free counter parts indicating that chemical aging is more detrimental for catalytic efficiency than thermal aging.