梅州金柚柚子皮的真空冷冻干燥工艺研究

目的以梅州金柚柚子皮为原料,研究柚皮真空冷冻干燥工艺技术,确定最佳工艺参数和加工工艺,为柚皮综合利用提供参考依据。方法通过单因素实验和正交实验设计,以冻干速率作为考察指标,研究了压力(真空度)、加热温度、物料厚度对真空冷冻干燥速率的影响。结果实验表明,对冻干柚皮干燥速率的影响主次顺序为加热温度、压力(真空度)、物料厚度,最佳工艺条件分别为:加热温度50℃、压力(真空度)40 Pa、物料厚度5 mm,在此干燥工艺条件下,产品在色泽等方面保持较好。结论该正交试验筛选出的工艺稳定可行。     

PVB流延膜干燥工艺研究

采用溶液流延法制备了一系列聚乙烯醇缩丁醛(PVB)膜材料,以热板干燥方式进行干燥,考察了干燥温度、初始料层厚度、溶液浓度和填充粒子含量对PVB流延膜干燥速率的影响。结果表明,这4种因素对流延膜的干燥速率均有重要影响,其中,较高的干燥温度、较薄的初始料层厚度以及较低的溶液浓度均有利于干燥速率的提高。     

粘胶短纤维的热风干燥特性研究

利用自行研制的热风干燥实验装置研究了热风温度、纤维层厚度、热风速度、纤维层含水率等对粘胶短纤维干燥特性的影响规律。结果表明:粘胶短纤维的热风干燥过程可依次分为4个阶段,即蒸发预热段、表面自由水分干燥段、纤维内部自由水分干燥段和纤维内部结合水分干燥段;热风温度对纤维第2阶段干燥速率的影响很大,100~140℃的含水率相差37.3%,对后面阶段的干燥速率影响较小,最佳热风温度为120℃;纤维层厚度对粘胶短纤维的第3阶段干燥速率略有影响,纤维层厚度以12 cm为宜;热风速度对短纤维干燥速率的影响很大,热风速度以2.0 m/s为宜,纤维层含水率对第2和第3阶段的干燥速率影响较大,应尽量减少纤维层的表面含水率。     

反应过程中升华型催化剂的物性变化(Ⅱ) X—射线衍射结果

对衰化程度不同的升华型催化剂进行了 X—射线衍射测定。发现在使用过程中催化剂比表面迅速减小,但氯化汞-活性炭催化剂的新旧样品中,氯化汞均保持单层分散。但即将废弃的醋酸锌-活性炭催化剂上,醋酸锌的单层分散情况受到破坏,出现了醋酸锌晶相峰。晶相峰的出现可能与后期使用温度偏高引起烧结有关。晶相峰的出现会降低催化活性,使之不得不被废弃。     

Zn(OAc)_2/C-Al_2O_3催化乙炔气相法合成醋酸乙烯初探

考察了多种活性炭和γ-氧化铝作为醋酸锌载体在乙炔气相法合成醋酸乙烯中的催化效果,筛选出活性高的活性炭和γ-氧化铝载体并制备出基于活性炭-γ-氧化铝复合载体的醋酸锌催化剂。实验结果表明,在210℃,C2H2/HAc摩尔比为6:1,空速360h-1的条件下,复合催化剂F2合成醋酸乙烯的时空收率达到2.7g/(dmL),与相同条件下的醋酸锌/4#活性炭催化剂相比,时空收率提高了约13%,且催化剂的寿命明显提高;与醋酸锌/WHA-201B-γ-氧化铝相比,反应温度降低了30℃。     

膜蒸馏-结晶耦合技术在卤水镁盐分离过程中的应用研究

采用膜蒸馏-结晶耦合技术处理盐水,可在高效、经济、环保地回收淡水的同时结晶分离出无机盐晶体。利用聚四氟乙烯平板膜进行了氯化镁溶液的直接接触式膜蒸馏-结晶(DCMDC)和真空膜蒸馏-结晶(VMDC)实验,研究了料液进口温度、循环速率、浓度以及真空度对水的膜透过量和盐截率等的影响。结果表明:在DCMDC处理氯化镁溶液过程中,水的膜透过量随着料液进口温度的升高、料液循环速率的提高而增大,随着料液浓度的增加而降低;在VMDC处理氯化镁溶液过程中,除了料液进口温度、循环速率、浓度对水的膜透过量有影响外,透过液侧的真空度对实验结果也有明显的影响,透过液侧的真空度增大水的透过速率增加,而且浓缩后的原料液在室温下冷却结晶,得到了形貌均一的六水合氯化镁晶体。在DCMDC和VMDC实验过程中,虽然盐截率随着实验的进行有所下降,但是不同的料液进口温度、循环速率、浓度以及真空度对盐截率的影响不显著。     

氯硅烷歧化反应催化剂干燥特性及催化性能

研究了氯硅烷歧化反应催化剂Amberlyst 21和改性后树脂B的干燥特性,考察了供热温度和料层厚度对催化剂干燥规律的影响,并建立了干燥曲线的半经验关联式。此外,还通过滴定法测量了树脂活性官能团含量,最终通过实验检验催化效果。结果表明:树脂B和Amberlyst 21的干燥规律基本类似,得到最优的干燥温度及物料层厚度分别为70℃和3 cm,含水质量分数降至5%时干燥时间分别为23.3,20.0 h。在最优干燥条件下,树脂B的胺基含量略高于Amberlyst 21,2种树脂均可作为三氯氢硅歧化反应的催化剂,且树脂B的催化效果优于Amberlyst 21,反应转化率可达23.42%。     

超声波浸渍制备醋酸锌-活性炭催化剂

采用浸渍法制备醋酸锌-活性炭催化剂,研究了普通浸渍和超声波浸渍制备醋酸锌-活性炭催化剂,通过优化实验,得出超声波浸渍的适宜条件是:浸渍时间30 min,超声波频率28 MHz,浸渍温度45℃.在此条件下制得的催化剂较普通浸渍制得的催化剂醋酸锌含量提高了7%,比表面积提高了约30%.活性测试结果表明,超声波浸渍制备的催化剂活性较普通浸渍制得的催化剂活性显著提高,其中在180℃时活性提高了约34.54%.     

合成醋酸乙烯催化剂制备条件的研究

采用过量浸渍法制备乙炔气相法合成醋酸乙烯催化剂醋酸锌/活性炭,对制备条件进行了研究.结果表明,较合适的浸渍条件为醋酸锌浓度0.8mol/L,平衡时间60min,浸渍温度55℃.120℃下干燥30min水分就完全烘干,而90℃下干燥70min催化剂才达到恒重.由比表面积分析可知,随着干燥温度的升高,中孔被堵塞,催化剂的平均孔半径减小;干燥温度高于110℃后,比表面积和平均孔半径变化不明显.由SEM可以看出,催化剂表面明显存在醋酸锌晶体.     

明胶热风干燥特性的实验研究

采用静态法研究了明胶的平衡含湿质量分数,得到了20℃下吸湿和解吸等温线,结果表明,当空气相对湿度在16%—39%,存在吸湿滞后现象。在对流干燥实验台上进行了明胶干燥特性的实验,以不同厚度的明胶块为实验对象研究了热风温度、风速、湿度对干燥过程的影响。实验结果表明:明胶的干燥过程只有降速阶段,提高热风温度、加大风速均可以在前期提高干燥速率,但在干燥后期干燥速率反而降低;明胶块中心温度受胶块厚度、热风温度影响较大,而在实验范围内空气相对湿度的变化对明胶中心温度影响甚微;明胶的相对含湿质量分数随时间呈指数规律下降,提高风温、加大风速后明胶含湿质量分数在开始阶段下降较快,但最终含湿质量分数反而偏高。     

Continuous preparation of activated carbon supported zinc acetate catalyst and industrial synthesis of vinyl acetate from acetylene

A continuous manufacturing method of an activated carbon supported zinc acetate catalyst has been established. Based on the dipping of a crushed activated palm carbon into a zinc acetate aqueous solution, the catalyst is prepared for the synthesis of vinyl acetate from acetylene in an industrial fluidized reaction vessel. The relationship between the supported amount of zinc acetate and various factors has been studied. Based on these results, an empirical formula was developed. Using this formula, the continuous manufacturing apparatus was designed and constructed for the purpose of preparing the optimum supported fluidized catalyst. To minimize the activated carbon loss due to crushing and wearing, a vibrating conveyor system was employed. This continuous manufacturing process produced a uniform catalyst with an activated carbon feed rate of 0.25 m³ h^?1. Using this catalyst, a series of operational tests of the vinyl acetate synthesis was performed for investigating the optimum reaction conditions. These operational tests were carried out using an industrial fluidized reaction vessel of 3.28 m diameter and 50 tons day^?1 vinyl acetate production capacity. Based on these test results, the reaction rate constant and the deterioration rate constant were newly introduced, and the optimum operation conditions were then determined.     

醋酸锌/炭小球催化剂的制备及其催化合成醋酸乙烯性能

以炭小球(SAC)为载体,采用过量浸渍法制备了不同醋酸锌负载量的醋酸锌/炭小球催化剂,在常压固定床反应器上,考察了醋酸锌负载量、反应温度、乙炔和醋酸摩尔比、空速等因素对乙炔合成醋酸乙烯的影响。采用SEM,BET,XRD等表征手段研究了催化剂活性降低的机理。研究表明,活性组分的流失和反应过程中形成的少量积炭是催化剂活性下降的2个重要原因。当催化剂中醋酸锌负载量(质量分数)为32.05%,常压,反应温度220℃,C2H2/HAc摩尔比为3∶1,乙炔体积空速为500 h-1,反应110 h后,醋酸的单程转化率为24.20%,醋酸乙烯选择性为98.50%,醋酸锌/炭小球催化剂催化合成醋酸乙烯的生产能力可达2.95 g/(mL.d),比高比表面活性炭催化剂的生产能力高35.32%,且该催化剂具有良好的催化活性、醋酸乙烯选择性和反应稳定性。     

活性炭烟气脱硫中影响脱硫效率因素的实验研究

对活性炭法烟气脱硫进行了实验研究,探讨了活性炭的干燥程度、空塔速度、床层高度等因素对活性炭吸附二氧化硫效果的影响。结果显示,上述因素对活性炭脱硫效果影响显著。经干燥箱120℃高温均匀干燥0.5 h后,脱硫效果远远优于静置和吹扫;空塔速度为0.15 m/s时,脱硫效率较为理想;随着床层高度的增大,活性炭的脱硫效率明显提高。     

Biodiesel production from waste cooking palm oil using calcium oxide supported on activated carbon as catalyst in a fixed bed reactor

A reactor has been developed to produce high quality fatty acid methyl esters (FAME) from waste cooking palm oil (WCO). Continuous transesterification of free fatty acids (FFA) from acidified oil with methanol was carried out using a calcium oxide supported on activated carbon (CaO/AC) as a heterogeneous solid-base catalyst. CaO/AC was prepared according to the conventional incipient-wetness impregnation of aqueous solutions of calcium nitrate (Ca(NO₃)₂·4H₂O) precursors on an activated carbon support from palm shell in a fixed bed reactor with an external diameter of 60 mm and a height of 345 mm. Methanol/oil molar ratio, feed flow rate, catalyst bed height and reaction temperature were evaluated to obtain optimum reaction conditions. The results showed that the FFA conversion increased with increases in alcohol/oil molar ratio, catalyst bed height and temperature, whereas decreased with flow rate and initial water content in feedstock increase. The yield of FAME achieved 94% at the reaction temperature 60 °C, methanol/oil molar ratio of 25: 1 and residence time of 8 h. The physical and chemical properties of the produced methyl ester were determined and compared with the standard specifications. The characteristics of the product under the optimum condition were within the ASTM standard. High quality waste cooking palm oil methyl ester was produced by combination of heterogeneous alkali transesterification and separation processes in a fixed bed reactor. In sum, activated carbon shows potential for transesterification of FFA.     

Catalyzing the carbonylation of methanol using a heterogeneous vapor phase catalyst

Nickel supported on activated carbon has been shown to be active for the carbonylation of methanol. Methyl acetate was the major and primary product; acetic acid was formed as a minor product. The greatest yield of methyl acetate was approximately 0.21 at a reaction temperature of approximately 225°C. The effect of reduction temperature and nickel loading on the performance of catalyst is reported. The catalyst was mostly stable at temperatures near 225°C but deactivated irreversibly at elevated temperature. The results are consistent with a competitive reaction between the nickel catalyst and the activated carbon support, to produce an inactive nickel carbide product.     

醋酸乙烯共聚物碱醇解研究

本文以氢氧化钠 NaOH 为催化剂,甲醇为溶剂进行醋酸乙烯(VAC)——不饱和二元羧酸共聚物的醇解反应,研究了各种因素对醇解反应速率的影响,得到了宏观动力学规律,为制备共聚改性聚乙烯系列高分子表面活性剂工艺配方的确定,以及醇解度的控制提供了基础数据。     

二氧化碳再生乙酸乙烯合成用触媒载体活性炭

提出用二氧化碳活化法再生乙酸乙烯合成用触媒载体活性炭工艺。研究了活化温度、活化时间和二氧化碳流量对活性炭吸附性能和得率的影响。确定最佳工艺条件为活化温度1 273 K,活化时间100 m in,二氧化碳流量0.5 L/m in,在此条件下得到的活性炭碘吸附值为1 091.33 mg/g,乙酸吸附值为518.30 mg/g,强度为72%,活化得率为80.33%,并对制得的活性炭做了比表面积测定和孔结构分析。再生后的活性炭强度和乙酸吸附值均达到标准,符合乙酸乙烯合成用触媒载体活性炭的要求。     

活性炭吸附法脱除双酚A反应液中残留催化剂

采用活性炭吸附法脱除双酚A反应液中的残留催化剂,用丙酮对活性炭进行再生。考察了活性炭的粒径、吸附温度、空速等对双酚A反应液中残留催化剂脱除效果的影响。结果表明,最佳操作条件为:10～20目活性炭,床层体积5 cm3,吸附温度65℃,空速1.0 h-1。在此条件下,对酸度为0.014 mmol/L的双酚A反应液进行了连续脱除残留催化剂处理,双酚A反应液的酸度能符合要求(≤0.001 mmol/L)。该方法具有不引入碱性杂质、不影响产品质量、操作简单的优点。     

回收PET醇解催化剂的研究及机理分析

采用回收PET制备不饱和聚酯,探讨了不同催化体系中最佳醇解条件。当控制醇解产物分子量在600左右时,在相同温度(185℃),相同丙二醇/PET摩尔比(1.6)和相同催化剂用量(0.5%,质量比)的情况下,在乙酸锌催化体系中,乙酸锌/二环己胺为0.4(摩尔比),反应2h;在乙酸锰催化体系中,乙酸锰/环己胺为0.2(摩尔比),反应4h。